Model based diagnostics based on traction model

MODEL BASED DIAGNOSTICS BASED ON TRACTION MODEL

TECHNICAL FIELD

The present invention relates generally to diagnostics of a materials handling vehicle, and, more particularly, to utilizing a traction model to perform diagnostics.

BACKGROUND ART

Forklifts and other types of industrial vehicles are expected to operate under a variety of different conditions. Further, such vehicles typically include a number of different functional systems such as a traction system to control a travelling speed of the vehicle and a steering system to control a direction in which the vehicle travels.

For diagnostic purposes, it may be beneficial to monitor different attributes of one or more of toe different functional systems while the vehicle is being operated.

DISCLOSURE OF INVENTION

One aspect of toe present invention relates to a method that includes receiving, by a traction application executing on a vehicle control module of a vehicle, a traction speed control input to control a traction wheel of toe vehicle; and based on the traction speed control input, determining, by the traction application, a first setpoint value of a control attribute related to the traction wheel. The method also includes receiving, by a first diagnostic supervisor: a) a measured value of toe control attribute related to toe traction wheel, and b) the first setpoint value from toe traction application; wherein the first diagnostic supervisor comprises a first model of a traction system of toe vehicle. Based on toe first setpoint value and the first model, the first diagnostic supervisor calculates a first virtual value of the control attribute related to the traction wheel; and determines a first operating condition of the traction system of toe vehicle based on the first virtual value and the measured value of the control attribute related to the traction wheel. The traction system may include a traction control module and a traction motor and toe traction application may transmit toe first setpoint value to toe traction control module.

Also, the method may include generating, by the traction application, a second setpoint value of toe control attribute related to the traction wheel. There may also be a second diagnostic supervisor which receives a) the second setpoint value, from the traction application, and b) toe measured value of toe control attribute related to the traction wheel, from toe traction control module; wherein toe second diagnostic supervisor comprises a

Date Reçue/Date Received 2023-06-06 second model of die traction system of the vehicle. Based on at least the second setpoint value and the second model, the second diagnostic supervisor calculates a second virtual value of the control attribute related to the traction wheel; and determines a second operating condition of die traction system of the vehicle based on the second virtual value and die measured value of the control attribute.

In particular, the control attribute related to the traction wheel may be one of a speed of the traction wheel, or a speed of a traction motor coupled with the traction wheel of the vehicle.

In some embodiments, a steering application executing on die vehicle control module receives a) a steering control input to control a steered wheel of the vehicle; b) a measured value of a control attribute related to the steered wheel; and c) die measured value of the control attribute related to the traction wheel of the vehicle. Based on the steering control input, the measured value of the control attribute related to the steered wheel and the measured value of the control attribute related to the traction wheel, the steering application determines a setpoint value of the control attribute related to the steered wheel. Also, based on the steering control input, the measured value of the control attribute related to the steered wheel and the measured value of the control attribute related to the traction wheel, the steering application may determine a target steering angle. Additionally, the steering application may calculate a wheel angle command based on the steering control input.

In addition to the steps described above, in some embodiments, the steering application, determines a traction speed limit based on the wheel angle command; and determines that the measured value of the control attribute related to the traction wheel of the vehicle is less than the traction speed limit. Afterwards, the steering application may set the setpoint value of the control attribute related to the steered wheel to equal the wheel angle command; and set the target stewing angle to equal: a) the wheel angle command, when the wheel angle command is greater than the measured value of the control attribute related to the steered wheel, and b) the measured value of the control attribute related to the steered wheel, when the wheel angle command is less than or equal to the measured value of the control attribute related to the steered wheel.

Alternatively, in other embodiments the steering application determines a) a traction speed limit based on the wheel angle command; b) a wheel angle limit based on the measured value of the control attribute related to the traction wheel; and c) that the measured value of the control attribute related to the traction wheel of the vehicle is more than or equal to the traction speed limit. Afterwards, the steering application may set the target steering angle to

Date Reçue/Date Received 2023-06-06 equal the wheel angle command; and set the setpoint value of the control attribute related to the steered wheel to equal one of: a) the wheel angle limit, when the wheel angle limit is between the measured value of the control attribute related to the steered wheel and the wheel angle command; b) the measured value of Ae control attribute related to Ae steered wheel, when Ae wheel angle limit is: i) not between Ae measured value of Ae control attribute related to Ae steered wheel and Ae wheel angle command; and ii) closer to Ae measured value of Ae control attribute related to Ae steered wheel Aan to Ae wheel angle command, and c) Ae wheel angle command, when Ae wheel angle limit is: i) not between Ae measured value of Ae control attribute related to Ae steered wheel and Ae wheel angle command; and ii) closer to Ae wheel angle command Aan to Ae measured value of Ae control attribute related to Ae steered wheel.

In some embodiments of Ae invention, Ae traction application generating a second setpoint value of Ae control attribute related to Ae traction wheel, based on Ae first setpoint value; and a second A agnostic supervisor which receives a) Ae second setpoint value, from Ae traction application, and b) Ae measured value of Ae control attribute related to Ae traction wheel, from Ae traction control module; wherein Ae second diagnostic supervisor comprises a second model of Ae traction system of Ae vehicle. Based on Ae second setpoint value, a vehicle battery voltage, Ae measured value of Ae control attribute related to Ae traction wheel and Ae second model, Ae second diagnostic supervisor calculates a second virtual value of Ae control attribute related to Ae traction wheel; and determines, based on Ae second virtual value and Ae measured value of Ae control attribute related to Ae traction wheel, a second operating conAtion of Ae traction system of Ae vehicle.

AnoAer aspect of Ae present invention relates to a system Aat includes a first controller comprising: a first memory storing code executable by Ae first controller, and a first input configured to receive a traction speed control input to control a traction wheel of Ae vehicle. The executable code includes a traction application configured to, based on Ae traction speed control input, determine a first setpoint value of a control attribute related to Ae traction wheel. The executable code also includes a first Aagnostic supervisor configured to receive a measured value of Ae control attribute related to Ae traction wheel, and Ae first setpoint value, from Ae traction application; wherein Ae first Aagnostic supervisor comprises a first model of a traction system of Ae vehicle. The first Aagnostic supervisor is also configured to calculate, based on Ae first setpoint value and Ae first model, a first virtual value of the control attribute related to Ae traction wheel; and determine, based on the first virtual value and Ae measured value of Ae control attribute related to Ae traction wheel,

Date Reçue/Date Received 2023-06-06 a first operating condition of the traction system of the vehicle.

Any features described in relation to the method of the first aspect of the invention may be included in embodiments of the system according to this aspect of die invention.

Yet another aspect of the present invention relates to a method that includes receiving, by a steering application executing on a vehicle control module a steering control input to control a steered wheel of a vehicle; and based on the steering control input, determining, by the steering application a traction threshold value associated with a traction control attribute related to a traction wheel of the vehicle. The method also includes receiving by a first diagnostic supervisor executing on the vehicle control module a) a measured value of the traction control attribute; and b) the traction threshold value. When the measured value of the traction control attribute exceeds the traction threshold value, the first diagnostic supervisor repeatedly calculates a respective difference between the traction threshold value and the measured value of the traction control attribute; to generate a set comprising a plurality of the respective differences. Based on the plurality of respective differences, the first diagnostic supervisor can determine a first operating condition of a traction system of the vehicle. In embodiments, the first diagnostic supervisor, for each respective difference, determines if the difference is greater than a difference threshold; and when the difference is greater than the difference threshold, increments a first counter value; and when the difference is less than or equal to the difference threshold, resets the first counter to a first initial value. The method may additionally include determining a fault condition of the traction system has occurred when the first counter value is greater than a first counter threshold. The traction threshold value may, for example, include a traction speed limit.

In a particular embodiment, the first counter threshold and the difference threshold are based on response characteristics of the traction system to at least one operational input received by the vehicle.

Also, the method may include, for each respective difference: a) determining if the difference is greater than a difference threshold; and when the difference is greater than the difference threshold, incrementing a first counter value, and when the difference is less than or equal to the difference threshold, resetting the first counter to a first initial value; and b) determining if the difference is greater than an immediately preceding difference in the set of respective differences; and when the difference is greater than the immediately preceding difference, incrementing a second counter value; when the difference is less than or equal to the immediately preceding difference, resetting the second counter value to a second initial value. Thus, the method may additionally include determining a fault condition of the

Date Reçue/Date Received 2023-06-06 traction system has occurred when either the first counter value is greater than a first counter threshold or the second counter value is greater than a second counter threshold.

In one particular embodiment the first counter threshold, the second counter threshold and the difference threshold are based on response characteristics of the traction system to at least one operational input received by the vehicle.

In other embodiments, the method includes, for each respective difference: a) determining if the difference is greater than a first difference threshold; when the difference is greater than the first difference threshold, incrementing a first counter value; and when the difference is less than or equal to the first difference threshold, resetting the first counter to a first initial value; and b) determining if the difference is greater than a second difference threshold; when the difference is greater than the second difference threshold, incrementing a second counter value; and when the difference is less than or equal to the second difference threshold, resetting the second counter to a second initial value. In particular, the method may additionally include determining a fault condition of the traction system has occurred when either the first counter value is greater than a first counter threshold or the second counter value is greater than a second counter threshold.

Furthermore, the first counter threshold, die second counter threshold, the first difference threshold, and the second difference threshold may be based on response characteristics of the traction system to at least one operational input received by the vehicle.

One further aspect of the present invention relates to a vehicle control system that includes a controller that has a) a first input configured to receive a steering control input to control a steered wheel of a vehicle; b) a second input configured to receive a measured value of a traction control attribute related to a traction wheel of the vehicle; c) a third input configured to receive a traction speed control input to control the traction wheel of the vehicle; and d) a memory coupled with the controller and storing code executable by the controller. The executable code includes a steering application configured to receive a steering control input to control a steered wheel of a vehicle; and determine, based on the steering control input, a traction threshold value associated with a traction control attribute related to a traction wheel of the vehicle. The executable code also includes a diagnostic supervisor configured to a) receive a measured value of the traction control attribute, and the traction threshold value; b) repeatedly calculate, when the measured value of the traction control attribute exceeds the traction threshold value, and a respective difference between the traction threshold value and the measured value of the traction control attribute, to generate a set comprising a plurality of the respective differences; and c) determine, based on the

Date Reçue/Date Received 2023-06-06 plurality of respective differences, a first operating condition of a traction system of the vehicle. Any features described in relation to the method of the further aspect of the invention described above may be included in embodiments of the vehicle control system according to this aspect of the invention.

Still a further aspect of the present invention relates to a method that includes iteratively performing the following steps: a) receiving, by a steering application executing on a vehicle control module a steering control input to control a steered wheel of a vehicle; a measured value of a steering control attribute related to the steered wheel; and a measured value of a traction control attribute related to a traction wheel of the vehicle; b) based on the steering control input, the measured value of the steering control attribute and the measured value of the traction control attribute, determining, by die steering application a first setpoint value of the steering control attribute related to the steered wheel and a target steering angle of the steered wheel of the vehicle; c) receiving, by a traction application executing on the vehicle control module of the vehicle, a traction speed control input to control the traction wheel of the vehicle, and the target steering angle, from the steering application; and d) based on the traction speed control input and the target steering angle, determining, by the traction application a second setpoint value of die traction control attribute.

In particular, the steering control attribute may include a steered wheel angle or an angular velocity of a steering motor coupled with the steered wheel of the vehicle. The traction control attribute may, for example, comprise one of a speed of the traction wheel, a linear speed of the vehicle or a speed of a traction motor coupled with the traction wheel of the vehicle.

The method may also include the steering application calculating a wheel angle command based on the steering control input. The method may also include determining a traction speed limit based on the wheel angle command, and determining that the measured value of the traction control attribute related to the traction wheel of the vehicle is less than the traction speed limit. The steering application may then set the first setpoint value to equal the wheel angle command; and set the target steering angle to equal a) the wheel angle command, when the wheel angle command is greater than the measured value of the steering control attribute, and b) the measured value of the steering control attribute, when the wheel angle command is less than or equal to the measured value of the first control attribute.

Alternatively, the method may include the steering application determining a) a traction speed limit based on the wheel angle command; b) awheel angle limit based on the measured value of the traction control attribute related to the traction wheel; and c) that the

Date Reçue/Date Received 2023-06-06 measured value of the traction control attribute related to the traction wheel of the vehicle is more than or equal to the traction speed limit. The steering application may then set the target steering angle to equal the wheel angle command; and set the first setpoint value to equal one of: a) the wheel angle limit, when the wheel angle limit is between the measured value of the steering control attribute and the wheel angle command; b) the measured value of the steering control attribute, when the wheel angle limit is i) not between the measured value of the steering control attribute and the wheel angle command; and ii) closer to the measured value of the steering control attribute than to the wheel angle command, and c) the wheel angle command, when the wheel angle limit is i) not between the measured value of the steering control attribute and the wheel angle command; and ii) closer to the wheel angle command than to the measured value of the steering control attribute.

A further aspect of the present invention relates to a system that includes a controller which comprises a) a first input configured to receive a steering control input to control a steered wheel of a vehicle; b) a second input configured to receive a measured value of a steering control attribute related to the steered wheel; c) a third input configured to receive a measured value of a traction control attribute related to a traction wheel of the vehicle; and d) a fourth input configured to receive a traction speed control input to control the traction wheel of the vehicle. The controller also includes a memory coupled with the controller and storing code executable by the controller. The executable code includes a steering application and a traction application that iteratively perform: a) based on the steering control input, the measured value of the steering control attribute and the measured value of the traction control attribute, determining, by the steering application a first setpoint value of a steering control attribute related to the steered wheel of the vehicle and a target steering angle of the steered wheel of the vehicle; b) receiving, by the traction application a traction speed control input to control fee traction wheel of the vehicle, and the target steering angle, from the steering application; and c) based on fee traction speed control input and the target steering angle, determining, by the traction application a second setpoint value of foe traction control attribute. Any features described in relation to foe method of the still further aspect of foe invention described above may be included in embodiments of foe system according to this aspect of foe invention.

The invention also encompasses vehicles, such as materials handling vehicles (e.g. fork lift trucks) comprising foe vehicle control systems of foe invention.

Date Reçue/Date Received 2023-06-06

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 is a perspective view of a materials handling vehicle according to an aspect of the present invention.

Fig. 2A depicts a computing environment for providing control logic in a vehicle control module (VCM) of the vehicle of Fig. 1.

Fig. 2B schematically illustrates selected features of a vehicle and an example vehicle control module that are helpful in describing model-based diagnostic techniques that utilize a traction model in accordance with the principles of aspects of the present invention.

Fig. 3 depicts a flowchart of an example algorithm for performing model-based diagnostics of a vehicle traction system in accordance with the principles of aspects of the present invention.

Fig. 4A - Fig. 4D illustrate a flowchart of an example control algorithm of a steering application and traction application in accordance with the principles of aspects of the present invention.

Fig. 5 graphically depicts an example of how a vehicle traction system can react to a step input.

Fig. 6 illustrates an example look up table for an empirically based traction model utilized in accordance with the principles of aspects of the present invention.

Fig. 7A - Fig. 7C illustrate different look up tables that can be used to calculate values for traction wheels and steered wheels in accordance with the principles of aspects of the present invention.

Figs. 8A and 8B illustrate a frame of reference for measuring or calculating a value related to a steered wheel angle in accordance with the principles of aspects of the present invention.

Fig. 9 is a flowchart of an example method of utilizing an empirically based model in accordance with the principles of aspects of the present invention.

Fig. 1OA is an example of a response of an actual vehicle traction system to a changing speed setpoint.

Fig. 1 OB is a flowchart of an example method of determining whether a vehicle traction system is in a fault condition in accordance with the principles of aspects of the present invention.

Fig. 11 schematically illustrates selected features of a vehicle and an example vehicle control module that are helpful in describing other model-based diagnostic techniques that utilize an alternative traction model in accordance with the principles of aspects of the present invention.

Date Reçue/Date Received 2023-06-06

BEST MODE FOR CARRYING OUT THE INVENTION

In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, and not by way of limitation, specific preferred embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and that changes may be made without departing from the spirit and scope of the present invention.

Referring now to Fig. 1, a materials handling vehicle 10 (hereinafter “vehicle”) is shown. While the present invention is described herein with reference to the illustrated vehicle 10, which comprises a forklift truck, it will be apparent to those skilled in the art that the present invention may be used in a variety of other types of materials handling vehicles.

The vehicle 10 includes a main body or power unit 12, which includes a frame 14 defining a main structural component of the vehicle 10 and which houses a battery 15. The vehicle 10 further comprises a pair of fork-side support wheels 16 coupled to first and second outriggers 18, a driven and steered wheel 20 mounted near a first comer at a rear 12A of the power unit 12, and a caster wheel (not shown) mounted to a second comer at the rear 12A of the power unit 12. The wheels 16,20 allow the vehicle 10 to move across a floor surface.

An operator’s compartment 22 is located within the power unit 12 for receiving an operator driving the vehicle 10. A tiller knob 24 is provided within the operator’s compartment 22 for controlling steering of the vehicle 10. The speed and direction of movement (forward or reverse) of the vehicle 10 are controlled by the operator via a multifunction control handle 26 provided adjacent to an operator seat 28, which control handle 26 may control one or more other vehicle functions as will be appreciated by those having ordinary skill in the art. The vehicle 10 further includes an overhead guard 30 including a vertical support structure 32 affixed to the vehicle frame 14.

A load handling assembly 40 of the vehicle 10 includes, generally, a mast assembly 42 and a carriage assembly 44, which is movable vertically along the mast assembly 42. The mast assembly 42 is positioned between the outriggers 18 and includes a fixed mast member 46 affixed to the frame 14, and nested first and second movable mast members 48,50. It is noted that the mast assembly 42 may include additional or fewer movable mast members than the two shown in Fig. 1, i.e., the first and second movable mast members 48,50. The carriage assembly 44 includes conventional structure including a reach assembly 52, a fork carriage 54, and fork structure comprising a pair of forks 56A, 56B. A movable assembly 47

Date Reçue/Date Received 2023-06-06 as defined herein includes the lower and upper movable mast members 48,50 and the carriage assembly 44. The mast assembly 42 may be configured as the monomast described in U.S. Patent No. 8,714,311 to Steven C. Billger et al., granted on May 6,2014.

The vehicle 10 of Fig. 1 is provided by way of example and many different types of materials handling trucks are contemplated within the scope of the present invention. As described in detail below, aspects of a vehicle control module are provided which allow a number of identical components to be utilized on various vehicles even though die vehicles may be of different types.

Fig. 2A depicts a block-level view of a computing environment for providing control logic and software applications in a vehicle control module (VCM) 200, according to one or more embodiments shown and described herein. The vehicle control module 200 and die way it interfaces with various operator controls and other functional systems of the vehicle 10 may be similar to control structure disclosed in U.S. Patent Publication Nos. 2010/0228428 and 2014/0188324. The VCM may comprise one of a number of cooperating modules, such as a traction control module (TCM) or a steering control module (SCM), that cooperatively control operation of the vehicle 10.

In the illustrated embodiment, the VCM 200 includes one or more processors or microcontrollers 216, input/output hardware 218, network interface hardware 220, a data storage component 222, and a memory component 202. The data storage component 222 and the memory component 202 may each be configured as volatile and/or nonvolatile memory and as such, may include random access memory (including SRAM, DRAM, and/or other types of RAM), flash memory, secure digital (SD) memory, registers, compact discs (CD), digital versatile discs (DVD™), and/or other types of non-transitory computer-readable mediums. Any stored information that is intended to be available after the vehicle 10 is shutdown and restarted may beneficially be stored in non-volatile memory. Also, depending on the particular embodiment, the non-transitory computer-readable medium, mentioned above, may reside within the VCM 200 and/or external to the VCM 200.

Additionally, the memory component 202 may store software or applications that can be executed (i.e., using executable code) by the one or more processors or microcontrollers 216. Thus the memory component 202 may store an operating application or logic 204, a traction application or logic 208, a steering application or logic 206, a hoist application or logic 210, and accessory application(s) or logic 212. The operating logic 204 may include an operating system and other software such as, for example, diagnostic-related applications for managing components of the VCM 200. The traction application or logic 208 may be

Date Reçue/Date Received 2023-06-06 configured with one or more algorithms and parameters for facilitating optimal traction control for the vehicle 10. The steering application or logic 206 may be configured with one or more algorithms and parameters for facilitating optimal steering control of the vehicle 10. The hoist application or logic 210 may include one or more algorithms and parameters for facilitating optimal hoist control of the vehicle 10, which acts as the primary load handling assembly system used to raise and lower the movable assembly 47 of the vehicle 10. Additionally, the accessory application or logic 212 may include one or more algorithms and parameters for providing control of accessories of the vehicle 10 such as an auxiliary load handling assembly system, which performs additional tasks such as tilt and sideshift of the carriage assembly 44. A local communication interface 214 is also included in FIG. 2A and may be implemented as a bus or other communication interface to facilitate communication among the components of the VCM 200.

The one or more processors or microcontrollers 216 may include any processing component operable to receive and execute instructions (such as from the data storage component 222 and/or the memory component 202). The processors or microcontrollers 216 may comprise any kind of a device which receives input data, processes that data through computer instructions, and generates output data. Such a processor can be a microcontroller, a hand-held device, laptop or notebook computer, desktop computer, microcomputer, digital signal processor (DSP), mainframe, server, cell phone, personal digital assistant, other programmable computer devices, or any combination thereof. Such processors can also be implemented using programmable logic devices such as field programmable gate arrays (FPGAs) or, alternatively, realized as application specific integrated circuits (ASICs) or similar devices. Ihe term “processor” is also intended to encompass a combination of two or more of the above recited devices, e.g., two or more microcontrollers.

The input/output hardware 218 may include and/or be configured to interface with a monitor, positioning system, keyboard, touch screen, mouse, printer, image capture device, microphone, speaker, gyroscope, compass, and/or other device for receiving, sending, and/or presenting data. The network interface hardware 220 may include and/or be configured for communicating with any wired or wireless networking hardware, including an antenna, a modem, LAN port, wireless fidelity (Wi-Fi) card, WiMax card, mobile communications hardware, and/or other hardware for communicating with other networks and/or devices. From this connection, communication may be facilitated between the VCM 200 and other computing devices including other components coupled with a CAN bus or similar network: on the vehicle 10.

Date Reçue/Date Received 2023-06-06

It should be understood that the components illustrated in FIG. 2A are merely exemplary and are not intended to limit the scope of this disclosure. While the components in FIG. 2A are illustrated as residing within die VCM 200, this is merely an example. In some embodiments, one or more of the components may reside external to the VCM 200. It should also be understood that while the VCM 200 in FIG. 2A is illustrated as a single device; this is also merely an example. In some embodiments, the traction application 208, the steering application 206, the hoist application 210, and/or the accessory application 212 may reside on different devices. Additionally, while the VCM 200 is illustrated with the traction application 208, die steering application 206, the hoist application 210, and the accessory application 212 as separate logical components, this is also an example. In some embodiments, a single, composite software application may cause die VCM 200 to provide the described functionality.

It also should be understood that the VCM 200 may communicate with various sensors and other control circuitry of the vehicle 10 to coordinate the various conditions of manual operation and automatic operation of the vehicle 10.

In the description below, the following terms are used and are intended to convey the following definitions:

steering control input sensor output signal values from the operator steering mechanism.

WheelAngleCmà. a value generated by the steering application and is a transformation of a digitized value of the steering control input into units that reflect an angle/angular velocity value.

Wheel^AngleTarget, or target steering angle Or. based on the operator's input, this is a value generated by the steering application and provided to the traction application in order to calculate a second Trx_Speed_Limit2. Depending on the current operation of a vehicle its value can be one of either the Wheel_Angle_Cmd or a Wheel_Angle.

Wheel Angle Limit: a highest allowable steered wheel angle, generated by the steering application based on the measured value of the traction wheel/motor speed and can be used to modify the Wheel_Angle_Setpoint in order to stay within a desired Wheel Angleto-Traction Speed relationship.

WheelAngleSetpoint, or steering setpoint ωι or Θγ. a value generated by the steering application, based on the operator's input, but modified based on traction speed, this is the input sent to the steering control module to effect a change in the steered wheel angle/angular velocity.

Date Reçue/Date Received 2023-06-06

Steering feedback (ω2 or Θ2), or Wheel Angle: a measured value of foe steered wheel angle/angular velocity, generated by the steering control module.

traction speed control input', a value received from a sensor/actuator that the operator manipulates.

TrxSpeedCmd. a value generated by the traction application and is a transformation of the digitized voltage reading of the traction speed control input into units that reflect a speed.

First Trx Speed Limiti'. a highest allowable traction wheel/motor speed for a particular wheel angle value, based on a desired wheel angle - to - traction speed relationship such as defined by the graph in Fig. 7A. The first Trx_Speed_Limiti is generated by the steering application and uses a WheelAngleCmd as a particular wheel angle value, see Fig. 7A. The first TrxSpeedJLimiti is used by the steering application to determine the Wheel_Angle_Target and the Wheel_Angle_Setpoint.

Second Trx_SpeedJL,imit2: The second Trx_Speed_Limit2 is generated by the traction application and uses Wheel_Angle_Target as the particular wheel angle value, see Fig. 7A. The second Trx_Speed_Limit2 is used by the traction system to slow down the vehicle if necessary to stay within a desired Wheel Angle-to-Traction Speed relationship.

traction speed setting ex: a value generated by the traction application, based on the operator's input, but modified based on the Trx_Speed_Limit2; this velocity value will eventually be converted to a torque value by the traction application.

traction setpoint, τι: a torque value based on the traction speed setting and the current speed of the vehicle, and is generated by the traction application.

TrxSpeed, or speed feedback, 03: is a measured value of the traction wheel/motor speed, generated by the traction control module.

Fig. 2B schematically illustrates selected features of a vehicle 10 and an example vehicle control module 200 that are helpful in describing model-based diagnostic techniques that utilize a traction model. The other features of the vehicle 10 and the VCM 200 desaribed with respect to Fig. 1 and Fig. 2A are omitted from Fig. 2B so as not to obscure aspects of the example model-based diagnostics described herein.

Referring to Fig. 2B, the VCM 200 includes a master microcontroller 216A that includes the steering application 206, the traction application 208 and a first diagnostic supervisor 250. The VCM 200 also includes a slave microcontroller 216B on which a second diagnostic supervisor 252 executes. A first simulation model 254 is contained in the first diagnostic supervisor 250 and a second simulation model 256 is contained within the second

Date Reçue/Date Received 2023-06-06 diagnostic supervisor 252.

In Fig. 2B, an operator-controlled steering control input sensor 276 forming part of a steering device comprising the tiller knob 24 of the vehicle 10 set out in Fig. 1, provides sensor output signal values defining a steering control input or steering control input signal 278 (e.g., an analog voltage) to the vehicle control module (VCM) 200. The steering control input sensor 276 may also form part of another steering device comprising a steering wheel, a control handle, a steering tiller or like steering element The steering control input signal 278 may be adjusted or otherwise conditioned and may, for example, be provided to an input pin of a master microcontroller 216A within the VCM 200. That signal may be further conditioned and supplied as an input value to the steering application 206 that is being executed by the master microcontroller 216A. The voltage, for example, of the steering control input signal 278, or the rate of change of that voltage, can vary based on the position and the rate of change of position of the steering control input sensor 276 associated with the steering device, i.e., the tiller knob 24 in the illustrated embodiment. Based on the input signal the steering application 206 receives that corresponds to the steering control input signal 278, the steering application 206 determines a setpoint for a control attribute related to the steered wheel 20 of the vehicle. For example, a voltage value may be used along with a lookup table to correlate the voltage value to a particular wheel angle value for a steering setpoint or the rate of change of the voltage may be multiplied by a predetermined scaling factor to convert that rate of change into the setpoint that changes a steering motor angular velocity. Hence, the control attribute may, for example, be a steered wheel angle or an angular velocity of a steering motor 274 and, therefore, a value of the setpoint may be a steered wheel angle θι or a steering motor angular velocity eh. The steering setpoint ωι or 0i can be provided to a steering control module (SCM) 272. The SCM 272 uses the setpoint ωι or θι for controlling a steering motor 274 which positions the steered wheel 20 to conform to a desired position as indicated by die operator's manipulation of die steering control input sensor 276. The SCM 272 also provides a feedback value 02 or ©2 of the control attribute related to the steered wheel. In particular, the feedback value is a measured, or actual, steered wheel angle 02 of the steered wheel 20 or is a measured, or actual, angular velocity ω2 of the steering motor 274. The SCM 272 provides the feedback value 02 or ¢02 to the steering application 206.

The steering application 206 additionally produces the target steering angle θτ or Wheel_Angle_Target which is provided to the traction application 208. As discussed below, with respect to Figs. 4A -4D, awheel angle/traction speed limiting process is performed by

Date Reçue/Date Received 2023-06-06

Ae steering application 206 and the traction application 208 wherein an output of Ae steering application 206 includes boA:

a) Ae steering setpoint, or Wheel_Angle_Setpoint, on or θι and

b) Ae target steering angle, or Wheel Angle Target, θτ.

The target steering angle θτ received at Ae traction application 208 from Ae steering application 206 serves as a limiting constraint Aat is converted by Ae traction application 208 to a traction control speed limit via a predetermined desired speed-to-wheel-angle relationship and is used in Ae determination of Ae desired traction speed setting ©4 and Ae traction setpoint τι, comprising a torque value. The traction wheel speed, or a traction motor speed, may be considered a control attribute related to Ae traction wheel or driven wheel 20 of Ae vehicle 10 and Ae desired traction speed setting ©4, for eiAer a traction motor 264 or Ae traction wheel 20, and Ae traction setpoint τι, for Ae traction motor, may be considered to be respective setpoints for Ais control attribute related to Ae traction wheel.

The TCM 258 monitors Ae traction motor 264 and provides a traction feedback speed ©3 to Ae traction application 208, Ae steering application 206 and Ae two Aagnostic supervisors 250,252. Since Ae steering setpoint (θι or ωι) is partly dependent on Ae actual traction wheel or motor speed, i.e., speed feedback ©3, Ae Aagnostic supervisors 250,252 can verify Aat the actual traction speed ω3 is responding correctly to Ae traction setpoint τι. The traction speed, or speed feedback, ©3 may also be converted to an actual linear speed of Ae vehicle 10 by Ae traction application 208. If, for example, Ae speed feedback ©3 is an angular speed of Ae traction motor 264, Aen Ae traction application 208 may scale Aat value to an actual linear speed, V3, of Ae vehicle 10 based on a) a gearing ratio between Ae traction motor 264 and the driven wheel 20 and b) Ae circumference of Ae driven wheel 20. Alternatively, if Ae speed feedback ©3 is an angular speed of Ae driven wheel 20, Aen Ae traction application 208 may scale Aat value to an actual linear speed, V3, of the vehicle 10 based on Ae circumference of Ae driven wheel 20. The linear speed of Ae vehicle equals Ae linear speed of Ae driven wheel 20, presuming there is no slip at the driven wheel. As explained more fully below, in some embodiments Ae traction application 208 provides Ae value of Ae actual linear speed, or linear speed feedback, V3 to Ae Aagnostic supervisors 250,252. Providing the linear speed feedback V3 to the Aagnostic supervisors 250,252 may be performed as an alternative to, or in addition to, Ae TCM 258 providing Ae speed feedback ©3, as shown in Fig. 2B.

The first simulation model 254 is configured to compute a virtual response ©5 of Ae vehicle speed, i.e., traction wheel speed or traction motor speed, under various conditions

Date Reçue/Date Received 2023-06-06 while under control of the traction control module (TCM) 258 via the traction setpoint τι. In instances where the linear speed feedback V3, rather than the angular speed feedback (03, is provided to the first diagnostic supervisor 250, the virtual response (whether it represents a traction wheel speed or a traction motor speed) may also be scaled to a virtual linear speed response vs by the first diagnostic supervisor 250. The traction setpoint τι is determined by the traction application 208 using a Trx Speed Cmd which is generated by the traction application 208 and is based on a traction speed control input or traction speed control input signal 260 received from an operator controlled traction speed control input sensor 262, such as the multi-function control handle 26 of the vehicle 10, and the target steering angle Ot output from the steering application 206. The traction setpoint τι is output from the traction application 208 to the TCM 258 as a torque value which results in a corresponding speed of a traction motor 264 under the control of die TCM 258.

Based on the virtual response os provided by the first model 254 and the speed feedback 003 from the TCM 258, the first diagnostic supervisor 250 may perform a correlation computation to determine the degree of similarity of the predicted, or virtual, traction speed os to the actual traction speed os. Alternatively, the first diagnostic supervisor 250 may perform a correlation computation to determine the degree of similarity of die predicted, or virtual, linear speed vs of the driven wheel and vehicle to the actual linear speed V3. The first diagnostic supervisor 250 executes so as to provide the first model 254 with the setpoint τι value, a present voltage of the vehicle battery 15, and the speed feedback ¢1)3 value as inputs in order to generate, or calculate, the virtual response œs as an output. The first model 254 is designed to accurately reflect or predict the behavior of the traction system, which traction system includes the traction control module 258, the traction motor 264 and a load that represents a reactive force of the traction or driven wheel 20 of the vehicle 10 whose speed is being changed by the traction motor 264. Hence, the virtual response cos should closely reflect the intended or desired speed of the traction wheel 20 or the traction motor 264 which is a result of the setpoint τι and other vehicle operating conditions being provided to the traction control module 258 of the presently operated vehicle. If the virtual response ω$ and the actual speed of the traction wheel 20 or the traction motor 264 differ significantly, then this is an indication that there may be a problem with the traction control module 258, the traction motor 264, and/or the determination of the setpoint values, τι or ou.

Accordingly, the first diagnostic supervisor 250 can compare the feedback value 03 with the virtual response os. As explained below, the first model 254 may be an empiricallybased model that produces a predicted result based on the operating conditions of the vehicle

Date Reçue/Date Received 2023-06-06

10. The virtual response os can be compared to the measured, or feedback, value 03 for verification of proper operation of the vehicle's traction system. In embodiments, if the comparison indicates that the two values differ by more than a predetermined threshold, then the first diagnostic supervisor 250 may generate a fault signal, indicating a fault condition is occurring. The VCM 200 may, in response to the fault signal, stop movement of the vehicle 10.

The second simulation model 256 is configured to compute a virtual response ωβ of the traction motor or driven wheel speed under various conditions while under control of the traction control module (TCM) 258 via a traction setpoint τι. A traction speed setting or setpoint ûm is determined by the traction application 208 using the input signal 260 received from die operator controlled traction speed control input sensor 262 and the taiget steering angle θτ output from the steering application 206. The traction speed setting ω4 is also used by the traction application 208 along with a current or actual traction speed 03 or Trx Speed to calculate the traction setpoint τι, as discussed below, which results in a corresponding speed of a traction motor 264 under the control of the TCM 258. The second model 256 can be a virtual traction system cominising the TCM 258, die traction motor 264, and a load that represents a reactive force of the traction wheel of the vehicle 10 whose speed is being changed by the traction motor 264.

While one example type of model is described in more detail below, the second model 256 may be of any type that simulates the behavior of the isolated traction system such that the model provides a predicted result of how the control attribute of the traction system should reacL i.e., what its speed should equal, if the traction control module 258 is provided with a particular setpoint τι (or equivalently gm).

The second diagnostic supervisor 252 executes so as to provide the model 256 with the traction speed setpoint ou value as an input in order to generate, or calculate, the virtual response ωβ as an output. Assuming that the model 256 accurately reflects the behavior of the isolated traction system, the virtual response ωβ should closely reflect the actual speed of the traction wheel 20 or the traction motor 264 (i.e, the speed feedback ω3) which is a result of the traction speed setpoint ω4 being used to calculate the setpoint τι that is provided to the traction control module 258 of the presently operated vehicle, presuming the traction system is operating properly.

Accordingly, the second diagnostic supervisor 252 can compare the feedback value ω3 with the virtual response ωβ. As mentioned, the second model 256 is essentially a virtual traction system that produces a simulated response (i.e., the virtual response ωβ) of the

Date Reçue/Date Received 2023-06-06 vehicle's traction system. The virtual response ωβ can be compared to the measured, or feedback, value ¢03 for verification of proper operation of the vehicle's traction system. If the comparison indicates that the two values differ by more than a predetermined threshold, then the second diagnostic supervisor 252 may generate a fault signal, indicating a fault condition is occurring. In embodiments, the VCM 200 may, in response to the fault signal, stop movement of the vehicle. As described above with respect to the virtual response os, the output of the second model 256, i.e., the virtual response ωβ, may be converted to a virtual linear speed response ve for comparison to die actual linear speed V3 of the vehicle 20, when appropriate.

One of ordinary skill will recognize that the first model 254 and the second model 256 may be different types of models, as described above, or they may be the same type of model. In either case, a redundant diagnostic system is provided that monitors the operating conditions of the traction system of the vehicle 10. While the description below focuses on the second diagnostic supervisor 252 and the second model 256, similar techniques may be utilized with the first diagnostic supervisor 250 and the first model 254.

Fig. 3 depicts a flowchart of an example algorithm for performing steering application calculations, traction application calculations, and model-based diagnostics of a vehicle traction system in accordance with the principles of the present invention.

In step 302, the steering application 206, which is executing on the vehicle control module, receives a steering control input signal 278 to control a steered wheel of a vehicle and a measured, feedback value 62, (02 of a first control attribute related to the steered wheel, such as a steered wheel angle or a steering motor angular velocity. The steering application also receives a measured, feedback value ου of a second control attribute related to a traction wheel of the vehicle, such as a traction wheel speed or a traction motor speed.

Then, based on the steering control input signal, the measured value of the first control attribute and the measured value of the second control attribute, the steering application determines, in step 304, a first setpoint value θι, ωι of the first control attribute related to the steered wheel, and a target steering angle θτ of the steered wheel.

In step 306, the traction application 208, which is executing on the vehicle control module, receives a traction speed control input signal 260 to control the traction wheel of the vehicle, the measured value 03 of the second control attribute and the target steering angle θτ, from the steering application. Based on the traction speed control input signal, the measured value 0)3 of the second control attribute, and the target steering angle, the traction application determines, in step 308, a second setpoint value τι or eu of the second control attribute.

Date Reçue/Date Received 2023-06-06

There is also a first diagnostic supervisor 250 executing on the VCM and it receives, in step 310, the measured value on of the second control attribute, and the second setpoint value (τι or 014); wherein the first diagnostic supervisor comprises a first model 254 of the traction system of the vehicle.

In step 312, based on the second setpoint value and the first model, the first diagnostic supervisor calculates a first virtual value βκ or ©6 of the second control attribute related to the traction wheel and, in step 314, based on the first virtual value and the measured value of the second control attribute, the first diagnostic supervisor determines a first operating condition of the traction system of the vehicle.

In step 316 the traction application may generate a third setpoint value (ou or τι) of the second control attribute. A second diagnostic supervisor 252 may also be executing on the VCM and receives, in step 318, the third setpoint value and the measured value ω₃ of the second control attribute; wherein the second diagnostic supervisor comprises a second model 256 of the traction system of the vehicle

In step 320, based on the third setpoint value and the second model, the second diagnostic supervisor calculates a second virtual value cue or o»5 of the second control attribute and, in step 322, based on the second virtual value and the measured value of the second control attribute, determines a second operating condition of the traction system of the vehicle.

As mentioned earlier, the steering application 206 and the traction application 208 operate in conjunction with one another to control a steered wheel angle and traction speed of the vehicle 10. A steering control input sensor 276 associated with a steering wheel or tiller knob may generate a steering control input signal 276 that varies according to an operator's manipulation of the apparatus. This signal may than be converted to a digital value which can be scaled and adjusted to represent a value that has units appropriate for either a steered wheel angle (e.g., units of degrees) or an angular velocity of the steering motor (e.g., units of RPM ). For instance, such a value can be referred to as a WheelAngleCmd and represents the operator’s desired wheel position or steering motor angular velocity. One priority of a steering system comprising the steering control input sensor 276, the steering application 206, the SCM 272, the steering motor 274 and the steered wheel 20 is to position the steered wheel to the desired operator setting indicated by the Wheel_Angle_Cmd. Because the Wheel_Angle can be adjusted very quickly by the steering system, this rapid positional change may produce operator instability. Therefore, it is desirable that the steering application 206 produces control that will achieve the Wheel Angle Cmd as quickly as

Date Reçue/Date Received 2023-06-06 possible and without significant delay while also, in appropriate circumstances, reducing the traction speed so as to achieve a desired Wheel Angle - to - Traction Speed relationship (one example of which is depicted in Fig. 7Â) to maintain operator stability. Using the WheelAngleCmd and a current TixSpeed, the steering application 206 may determine two limiting constraints: a first Tix_Speed_Limiti and a Wheel_Angle_Limit. Using these four values and the current WheelAngle, the steering application 206 determines the steering setpoint (WheelAngleSetpoint) and the WheelAngleTarget. The Wheel_Angle_Setpoint is the value (i.e., ωι or θι) communicated to foe SCM 272 for wheel angle position adjustment. The WheelAngleTarget is the target steering angle θτ communicated to the traction application 208 for determination of the second Trx_Speed_Limit2 value.

Even though the operator's input may result in a Wheel_Angle_Cmd indicating that the operator desires the steered wheel to have an angle x, the steering system can position the steered wheel per the operator command as quickly as possible without operator perceived delay, but in order to maintain operator stability, the steering application 206 of the VCM 200 may not immediately issue the new command x to the SCM 272 based on the traction wheel/motor speed feedback or Tix Speed but rather in smooth incremental changes as the traction speed reduces. For instance, while a vehicle is traveling relatively fast, there may be a greater likelihood that a sharp steering change can cause control or stability issues as compared to when the vehicle is traveling relatively slowly. Accordingly, a current measured value of the traction speed or Tix Speed of the vehicle may be used to determine a maximum allowable angle to which the steered wheel can be changed so as to stay within a desired Wheel Angle-to-Traction Speed relationship maintaining operator stability, such as shown in Fig. 7B. This traction speed dépendant maximum allowable angle can be referred to as the WheelAngleLimit.

Also, the Wheel Angle Target may be used by the traction application 208 to determine a maximum allowable traction speed at which the vehicle can be traveling at a wheel angle equal to the Wheel Angle Target so as to maintain a desired Wheel Angle- toTraction Speed relationship, such as shown in Fig. 7A. This maximum allowable traction speed can be referred to as the second Tix_Speed_Limit2, or the traction speed to which die vehicle shall be reduced while also adjusting the steered wheel angle to the Wheel Angle Cmd. Because of the quick response of the traction system to reduce the speed of the vehicle, the steering system is able to achieve the operator desired steering adjustment without perceivable delay as mentioned above.

Date Reçue/Date Received 2023-06-06

An example control algorithm, or process, for the steering application 206 of the VCM 200, is illustrated in Fig. 4A and Fig. 4B. The traction application 208 communicates with and works in conjunction with the steering application 206 to ensure that a TrxSpeed and a Wheel_Angle remain at a value that allows for safe control and stability defined by desired Wheel Angle-to-Traction Speed relationships, see Figs. 7A and 7B. Fig. 4C illustrates an example algorithm of a portion of the traction application that generates a traction setpoint τι and/or a traction speed setting ω4.

In Fig. 4A, in step 402, a Wheel_Angle_Cmd and the traction motor speed feedback ω3, defining a measured traction wheel or motor speed (i.e., Trx Speed), are received so that, in step 404, a first Trx_Speed_Limiti and WheelAngleLimit can be calculated. A lookup table 700 constructed from a graph 706 in Fig. 7A in the illustrated embodiment may be used to determine a Tix Speed Limiti based on the WheelAngleCmd. In particular, the x-axis of the table 700 refers to an absolute value of a wheel angle amount 704 that can be between 0 and 90 degrees, wherein 0 degrees corresponds to a wheel angle when the vehicle is traveling in a straight line. The y-axis of the table 700 corresponds to a velocity value 702 of the traction wheel or traction motor, i.e., die first Trx_Speed_Limiti. The graph 706 in Fig. 7A depicts a Wheel Angle-to-Traction Speed relationship between a wheel angle value on the x-axis 704 and a maximum traction speed value or limit on the y-axis. The steering application 206 uses the Wheel Angle Cmd as the x-axis value 707 and locates file corresponding y-axis value 708 on the graph 706. The y-axis value 708 is determined to be the first Trx_Speed_Limiti for the steering application.

Referring to Fig. 7B, a lookup table 710 constructed from the graph in Fig. 7B in the illustrated embodiment may be used to determine a WheelAngleLimit based on the Trx Speed. In particular, the x-axis of the table 710 refers to a measured velocity value 714 of the traction wheel or traction wheel motor, i.e., the Trx Speed. The y-axis of the table 710 refers to an absolute value of a wheel angle amount 712 that can be between 0 and 90 degrees, wherein 0 degrees corresponds to a wheel angle when the vehicle is traveling in a straight line. The graph 716 in Fig. 7B depicts a Wheel Angle-to-Traction Speed relationship between a maximum wheel angle value on the y-axis 712 and a traction speed value on the xaxis 714. The steering application 206 uses the Trx Speed as the x-axis value 717 and locates the corresponding y-axis value 718 on the graph 716. The y-axis value 718 is determined to be the Wheel Angle Limit.

The steering application 206 may also receive the measured steered wheel angle θ2 of the steered wheel 20 or the measured angular velocity ©2 of tire steering motor 274, i.e., a

Date Reçue/Date Received 2023-06-06 measured WheelAngle, that has a value indicative of the present angle of the vehicle’s steered wheel or angular velocity of the steering motor. In step 406, a determination is made as to whether the vehicle’s current traction speed, TrxSpeed, is less than the first Trx_Speed_Limiti. If it is not, then the traction speed of the vehicle is reduced by die traction application 208 while the steering application 206 adjusts the Wheel_Angle to equal the WheelAngleCmd. As shown by block 410 in the embodiment of Fig. 4A, the control logic of the steering application 206 continues at step 424 of Fig. 4B where a determination is made as to whether the WheelAngleLimit is between the Wheel Angle and the Wheel Angle Cmd. As long as the Wheel Angle Limit is between the current Wheel_Angle and the Wheel Angle Cmd, the Wheel_Angle_Setpoint is set to the Wheel_Angle_Limit in step 426. Otherwise a determination is made in step 428 whether the Wheel Angle Limit is closer to the Wheel Angle or the Wheel Angle Cmd. The Wheel Angle Setpoint is set equal to the value closer to the Wheel_Angle_Limit: the WheelAngle or the WheelAngleCmd in steps 430 or 432, respectively. In any of these cases (i.e., step 426,430, or 432), the WheeI_Angle_Target is set equal to the Wheel Angle Cmd. In the illustrated embodiment, when the Trx_Speed is equal to or greater than the first Trx_Speed_Limiti, the traction application 208 may quickly reduce the traction wheel or motor speed, i.e., the Trx Speed, to the second Trx_Speed_Limit2, in the manner discussed below with regards to Fig. 7C, wherein the second Tix_Speed_Limit2 is based on the Wheel_Angle_Tatget, and, as noted above, in steps 426,430 and 432, the Wheel_Angle_Target is set equal to the Wheel Angle Cmd. In step 434 control returns to step 402 so that another iteration of these steps just described can be performed.

Fig. 4C illustrates an example algorithm of how the traction application 208 can produce a traction setpoint such that, in appropriate circumstances, the vehicle's traction speed, Trx Speed is reduced. Referring to Fig. 7A, the lookup table 700 may be used to determine a second Trx Speed Limitz based on the Wheel Angle Target in the same manner that the steering application 206 determines a Trx_Speed_Limiti based on the Wheel Angle Cmd. In this manner, the traction application 208 can be made aware of a future Wheel Angle, i.e., the Wheel_Angle_Target, and adjust the traction speed accordingly even before the current Wheel_Angle has reached that commanded angle, i.e., the Wheel_Angle_T arget.

Returning to step 406, if the vehicle's traction speed, however, is below the first Trx Speed Limiti, then the traction wheel or motor speed or the Trx_Speed requires no reduction to meet the Wheel Angle-to-Traction Speed relation, such as illustrated in Fig. 7A

Date Reçue/Date Received 2023-06-06 at a Wheel_Angle equal to WheelAngleCmd. Therefore the WheelAngleSetpoint can be set to WheelAngCmd in step 412 of Fig. 4A. Again to maintain operator stability, the WheelAngleTarget is set equal to the larger of the Wheel Angle Cmd or the Wheel_Angle in steps 418 or 420, respectively, based on a comparison between the Wheel Angle Cmd and the Wheel_Angle performed in step 416. In either case, in step 422, control returns to step 402 so that another iteration of these steps just described can be performed.

According to an example algorithm depicted in Fig. 4C, foe traction application 208 may calculate a traction speed setpoint ω4 or a traction setpoint τι, such that, in appropriate circumstances, the traction wheel or motor speed, i.e., foe TrxSpeed, of the vehicle 10 is reduced. The traction application receives, in step 450, a traction speed control input signal 260 received from an operator controlled traction speed control input sensor 262 so as to determine a traction speed command. The traction speed control input signal 260 may be adjusted or otherwise conditioned and may, for example, be provided to an input pin of the master microcontroller 216A within foe VCM 200. That signal may be further conditioned and used by the traction application 208 that is being executed by the master microcontroller 216A to calculate the traction speed command, Trx_Speed_Cmd. As described above, foe traction application 208 also receives the target steering angle θτ or foe Wheel_Angle_Target from foe steering application 206. In step 452, a look-up table or similar model may be accessed to calculate a maximum traction speed (i.e., the second Trx Speed Limit?) corresponding to a vehicle 10 being steered at the Wheel_Angle_Target.

Referring back to Fig. 7A, the same lookup table 700 used by foe steering application 206 to determine a first Tix Speed Limiti based on the Wheel Angle Cmd may be used by foe traction application 208 to determine a second Trx_Speed_Limit2 based on foe Wheel_Angle_Target. In particular, foe x-axis of the table 700 may refer to an absolute value of a wheel angle amount 704 that can be between 0 and 90 degrees, wherein 0 degrees corresponds to a wheel angle when the vehicle is traveling in a straight line. The y-axis of foe table 700 corresponds to a velocity value 702 of the traction wheel or traction wheel motor. The graph 706 depicts a predetermined Wheel Angle-to-Traction Speed relation between a wheel angle value on the x-axis 704 and a maximum traction speed value on the yaxis. The traction application 208 may use the Wheel Angle Target as the x-axis value 707 and locate the corresponding y-axis value 708 on the graph 706. The y-axis value 708 may then be determined to be the second Trx_Speed_Limit2 for the traction application 208.

The Trx_Speed_Cmd reflects a vehicle speed that the operator desires to reach. In step 454, the traction application 208 may use the second Tix_Speed_Limit2 to reduce the

Date Reçue/Date Received 2023-06-06

TrxSpeedCmd in order to calculate an allowable Trx_Speed_Setting, ©4.

For example, a lookup table 720 constructed from a graph 724 in Fig. 7C in Ae illustrated embodiment can be used to limit a Trx Speed Cmd. BoA Ae x-axis 722 and the y-axis 726 represent a speed value of ei Aer Ae traction wheel or Ae traction motor and Ae graph 724 defines a relationship between values on Ae x-axis and corresponding values on Ae y-axis. These speed values can be eiAer positive or negative so a positive limit and a negative limit are shown in Fig. 7C; however, an example is described below Aat is based on only a positive traction speed value. The traction application uses Ae Tix_Speed_Cmd as Ae speed value, e.g., a value 727, for Ae x-axis 722 and locates Ae conresponAng speed value, e.g., a value 728 conresponAng to Ae value 727, on Ae y axis of Ae graph 724. This corresponAng value 728 is output by Ae traction application 208 as Ae Trx_Speed_Setting, ©4. Presuming Ae graph 724 is a 45 degree line between 0 and Ae value 728, which equals Ae value of Ae current second Trx_SpeedLimit2, Aen Ae speed value along Ae y-axis will equal Ae speed value along Ae x-axis in Ais range. However, once Ae speed value along Ae x-axis exceeds Ae speed value 727, which value 727 equals Ae speed value 728 and Ae current second Trx_Speed_Limit2, Ae graph 724 has a y-value limited to Ae value 728, which again equals Ae current value of Ae second Trx_Speed_Limit2. AccorAngly, if Ae traction application 208 sets Ae speed value 728, i.e., Ae maximum value of Ae graph 724 in Ae y direction, to equal the current second Trx_Speed_Limit2, Aen Ae Tix_Speed_Cmd received by Ae traction application will not result in a Trx_Speed_Setting, ©4 that exceeds Ae second Tix_Speed_Limit2.

When Ae TrxSpeed is equal to or greater than Ae first TrxSpeedLimiti in step 406 in Fig. 4A, Ae Wheel_Angle_Target is set equal to Ae Wheel_Angle_Cmd. The traction application 208 uses Ae WheelAngleTarget equal to Ae WheelAngleCmd to determine a second TrxSpeedLimit2, which, because Ae first Trx Speed Limiti is also determined from Ae WheelAngleCmd, Ae first TrxSpeedLimiti equals Ae second Tix_Speed_Limit2 in Ais scenario. The traction application 208 Aen uses Ae Trx_Speed_Cmd as an input into Ae lookup table 720 based on Ae graph 724 in Fig. 7C and receives an output. Presuming Ae Trx Speed is generally equal to Ae Trx Speed Cmd and since Ae Trx Speed is greater Aan the first Trx_Speed_Limiti, Ae output from Ae lookup table 720 typically equals Ae second Trx_Speed_Limit2. Hence, Ae traction application 208 outputs as Ae Trx_Speed_Setting, ©4 Ae second Trx_Speed_Limit2. The TCM 258 Aen quickly reduces the traction wheel or motor speed, i.e., Ae Tix_Speed, to the second TrxSpeed_Limit2.

Date Reçue/Date Received 2023-06-06

The traction setpoint may be a traction speed setpoint ω* defined by the Trx_Speed_Setting ω*, or the traction setpoint may be a traction setpoint τι that can be calculated based on the TrxSpeedSetting and a current Trx_Speed of the vehicle. As one example and as known to those skilled in the prior art, a proportional-integral-derivative (PID) controller may be used that receives, as an input, a difference value between the Trx_Speed_Setting and the TixSpeed and calculates, as output, the traction setpoint τι. Thus, in step 456, the traction application 208 calculates the traction setpoint τι which the TCM 258 will use to control operation of the traction motor 264. Ihe traction setpoint τι is calculated so as to control the traction motor speed, e.g, to reduce toe Tix Speed of the vehicle when the Trx_Speed is equal to or greater than the first Trx_Speed_Limiti in step 406 in Fig. 4A, to arrive at the Tix_Speed_Limit2 while toe Wheel_Angle is also being adjusted to arrive at the Wheel Angle Cmd.

Figs. 4A and 4B relate to operation of the steering application 206 and Fig. 4C relates to operation of the traction application 208. Fig. 4D is a flowchart of a conceptual view of how both the steering application 206 and the traction application 208 may operate together. In step 470, the steering application receives toe steering control input and a present value of the vehicle's traction speed ω3, Tix Speed. As mentioned above, the steering application can then determine in step 472 a first setpoint for the steered wheel (i.e., steering setpoint ωι or Oi). As described above, this first setpoint value can be affected by toe present traction speed of the vehicle, ω?, because the steering application uses the table of Fig. 7B to determine a maximum allowable steering setpoint ωι or Oi. The steering control module 272 can then control the steering motor 274 based on this first setpoint to effect a change in an actual angle of the steered wheel.

In step 472, the steering application also determines a value of toe target steering angle θτ. Independent of the logical flow of toe steering application, the traction application executes in order to determine a second, traction setpoint (i.e., τι or on). In particular, in step 474, toe traction application receives the taiget steering angle θτ and a traction speed control input. In stqp 476, toe traction application uses the Wheel_Angle_Target or target steering angle θτ and the graph of Fig. 7A to determine the second Tix_Speed_Limit2 which, as described above, can be used to limit a value of toe traction setpoint (i.e., τι or om) generated by toe traction application. The traction control module 274 can then control the traction motor 264 based on this second setpoint to effect a change in an actual speed of toe traction wheel.

The logical flow of the flowchart of Fig. 4D returns from step 476 to step 470 in order

Date Reçue/Date Received 2023-06-06 to repeatedly iterate through the steps, such that in each successive iteration through the four steps 470 -476, updated values for the vehicle traction speed ©3 and, thus, the target steering angle θτ are utilized. In this manner, when the Trx_Speed is equal to or greater than the first Tix_Speed_Limiti in step 406 in Fig. 4A, the steering application and the traction application cooperate to reduce the Trx Speed, ©3, of the vehicle to arrive at the TrxSpeed_Limit₂ while the Wheel Angle, ©2 or 02, is also being adjusted to eventually arrive at the WheelAngleCmd.

The steered wheel 20 of at least some vehicles can be turned in a complete circle (i.e., 360 degrees) from a position pointing straight ahead (i.e., 0 degrees) to a position pointing straight behind (i.e., 180 degrees). Also, the steered wheel 20 can also be turned to the right and turned to the left. Therefore, the steered wheel 20 can be located in any one of first, second, third and fourth quadrants 810, 811,812, and 813 shown in Figs. 8A and 8B and travel between adjacent quadrants in the course of a turn. Similarly, the Wheel_Angle_Cmd and the WheelAngleLimit can, for example, refer to values in any of the four quadrants 810,811,812, and 813. In Fig. 8A, a value 802 related to a wheel angle amount can be measured so as to be between 0 and +/- 90 degrees. When measured this way for quadrants 810 and 811, a larger absolute value of the value 802, represents a sharper turn. Similarly, in Fig. 8B, the value 802 related to a wheel angle amount can be measured so as to vary between 0 and +/- 90 degrees. As before, when measured this way for quadrants 812 and 813, a larger absolute value of the value 802 represents a sharper turn.

Regardless of which quadrant 810,811,812,813 the Wheel_Angle_Cmd value is actually in, it may be measured as shown in Figs. 8A and 8B and its absolute value may then be used, by the steering application 206, as the value 707 in the lookup table 700 of Fig. 7A to identify a maximum traction speed value 708 on the y-axis, i.e., a first Trx Speed Limiti. Similarly, regardless of which quadrant 810, 811,812,813 the WheelAngleTarget value is actually in, it can be measured as shown in Figs. 8A and 8B and its absolute value may then be used, by the traction application 208, as the value 707 in the lookup table 700 to identify a maximum traction speed value 708 on the y-axis, i.e., a second Trx_Speed_Limit₂.

With respect to the table 710 of Fig. 7B, the Trx_Speed value 717 may be used to identify a Wheel_Angle_Limit 718 that has a value that varies between some minimum value 719 and 90 degrees. As discussed above, this Wheel Angle Limit can be used by the steering application 206 to limit a steering setpoint value in any of the four quadrants 810, 811, 812, 813 of Figs. 8A and 8B.

Additionally, the flowcharts of Figs. 4A -4C discussed above involve a number of

Date Reçue/Date Received 2023-06-06 quantities related to a steered wheel angle: Wheel_Angle_Target, Wheel_Angle_Cmd, WheelAngleLimit, Wheel Angle Setpoint, and Wheel Angle. When these quantities are measured (or calculated) using the frame of reference shown in Figs. 8A and 8B, then the absolute value of that quantity can be used in the comparative steps of Figs. 4A - 4C to provide the appropriate logical flow control. The measured value of the steered wheel is in the range of-180 to +180 degrees. In order to use the look-up-tables, both the steering and traction applications convert the wheel angle to a value between -90 and +90 degrees. For measured wheel angles between -90 and +90 degrees, both applications take the absolute value of the measured wheel angle. For measured wheel angles between 90 and 180 degrees or -90 and -180 degrees, both applications take the absolute value of the measured wheel angle and convert and subtract it from 180 degrees. In this manner, angles between 90 and 180 degrees are converted to angles between 90 and 0 degrees.

Correlation example of a diagnostic comparison:

Because of the way microcontrollers and other digital hardware of the vehicle handle signals and values of signals, the feedback value gm, for example, may be an array of values that results from a continuous signal being sampled at a periodic rate (e.g., every 10 ms). Similarly, the second model 256 may be provided with the respective setpoint or traction speed setting gm every 10 ms (for example) so that a new virtual value gm is calculated every 10 ms. While it would be possible to compare each individual feedback value gm with a single, corresponding virtual value gm, that comparison may not accurately reveal whether or not the traction system of the vehicle is malfunctioning. However, comparing the last predefined number, e.g., 100, feedback values ω3 with the predefined number, e.g., 100, of most recently generated virtual values gm would likely provide a much more accurate indication of whether or not the vehicle's traction system is malfunctioning. Thus, the virtual value gm may comprise a first array of individually valued elements and the measured value gm may comprise a second array of corresponding individually valued elements so that the similarity between the measured value gm and the virtual value gm may be determined based on a computed correlation between the first array and the second array.

In general, the more samples of feedback values gm and the more calculations of the virtual values ωβ that are used for a comparison to one another, the more accurate of a result will be produced. However, accumulating more samples of these values reflect a longer time period which might allow a malfunction to occur for an extended period of time before that condition is detected. Accordingly, there is typically some operational upper limit to the amount of time used to collect values before a comparison is made between the feedback

Date Reçue/Date Received 2023-06-06 value ©3 and the virtual value ©6. For example, there may be operational constraints that require detection and/or mitigating action be initiated within, for example, 100 ms of a malfunction occurring. Or for instance, there may be a maximum allowable deviation between the setpoint ©4 and the actual speed ©3 to keep the system under proper control which would potentially decrease or increase the diagnostic evaluation time.

For example, if the sample period of the feedback value ©3 is 10 ms, then 10 samples can be collected and used for the comparison between die feedback value ©3 and the virtual value ©6 using a lOmS response time. The 10 samples of the feedback value ©3 can be considered a first random variable, X, comprising an array of 10 actual responses (e.g., xi xio) to 10 input values (i.e., setpoint values ©4) and the virtual value ©6 can be considered a second random variable, Y, comprising 10 simulated model responses (e.g., yi - y 10) to those same 10 input values. One measure of similarity of two random variables is known as a correlation coefficient, P. The correlation coefficient of two variables, sometimes simply called their correlation, is the covariance of the two variables divided by the product of their individual standard deviations. It is a normalized measurement of how the two variables are linearly related. However, one of ordinary skill will recognize that there are many other techniques for measuring similarity between two arrays of values, which may be used in the context of the invention.

Using well understood techniques, the respective average, ~X, ~Y , of the variables X, Y can be computed and then each respective variance o_x², oy² can be computed as well. The square root of the variances provide a respective standard deviation σχ, ay for each variable. The covariance C_xy of the two variables can be also be calculated according to:

^ = ^(2,=1((^-7)^,-7)) which allows the correlation coefficient to be calculated according to:

p _ ^c*y OxOy

When two variables or signals exactly correlate P = 1 and for exactly uncorrelated signals, P = 0. Thus, a predetermined threshold value may be identified which is used to determine that when the P value is below that threshold, the feedback value ©3 and the virtual value ©6 are not similar to one another. In die example where 10 samples are used to calculate P, then a value for P of around 0.5 to around 0.8 likely indicates that the feedback value ©3 and the virtual value ©6 are similar enough that a traction system malfunction is unlikely. If a P value is calculated below 0.5, then a malfunction of the traction system of the vehicle is likely occurring. Because of unexpected noise or other anomalies, the occurrence

Date Reçue/Date Received 2023-06-06 of a single P value below that threshold may occasionally occur even in the absence of a malfunction. Thus, the second diagnostic supervisor 252 may increment a counter each time a P value is calculated below the predetermined threshold and decrement the counter each time a P value is calculated above the predetermined threshold. If the value of that counter ever reaches a maximum allowable number (e.g., 5), then the second diagnostic supervisor 252 may alert the VCM 200 that a fault condition has occurred.

Indépendant of the second diagnostic supervisor 252, the first diagnostic supervisor 250 may also calculate how similar the virtual value ω$ from the first model 254 is to the feedback value ©3. While the first diagnostic supervisor 250 may employ a model 254 different than the second model 256, a different sampling period, or a different similarity measurement technique, the first diagnostic supervisor 250 may also be configured substantially similar to the second diagnostic supervisor 252 so that it operates in almost an identical way. Thus, the first model 254 and the second model 256 may both be the same model and a similar correlation coefficient and counter may be used by the first diagnostic supervisor 250 to generate its own diagnostic signal alerting the VCM 200 of a fault condition of ihe vehicle's traction system. In order to utilize the above correlation technique, the diagnostic traction model may generate the required simulated response sequence. There are various ways to model or simulate systems similar to the isolated traction system of the vehicle described above. Any of these known modeling techniques may be used without departing from the scope of the present invention. However, one example type of model that can be used for either the model 254 or 256 is a transfer function model calculated based on observed responses of an actual isolated traction system to a plurality of différant operating conditions.

Generally, a transfer function (and analogous terms system function and netwoik fonction) refers to a mathematical representation to describe a relationship between the inputs and outputs of a system. In particular, the relationship is described using a ratio of polynomials where the roots of the denominator polynomial are referred to as the system poles and the roots of the numerator polynomial are referred to as the system zeros.

A transfer function for a system can be developed by providing the systom with welldefined input values and collecting the resulting output values. For example, an isolated vehicle traction system as described above that includes a controller, a traction motor, and a load on the motor can be provided with input values and then observed in order to measure the resulting output. Fig. 5 graphically depicts an example of how a vehicle traction system can react to a step input.

Date Reçue/Date Received 2023-06-06

In Fig. 5, the y-axis represents both an input value for a control attribute related to the vehicle traction wheel and an output value of that control attribute which results. The x-axis represents time. The step input 1402 may, for example, reflect the vehicle traction system receiving an operator input, at time 1405, that corresponds to a desired traction wheel or traction motor speed 1403. The output signal 1404 reflects an actual response of the isolated traction system components to the input 1402.

The output signal 1404 can include a number of characteristic attributes. The point 1406 corresponds to when the output signal 1404 first shows a response to the step input 1402; the point 1408 corresponds to when the output signal 1404 reaches the value 1403; the point 1410 corresponds to the peak value 1411 of the output signal 1404; and the point 1412 corresponds to when the output signal 1404 settles (i.e., reaches steady state) at the desired traction wheel or traction motor speed value 1403. These different points help define a delay time ta between points 405 and 406, a peak time tpk between points 1405 and 1410, a settling time Let between points 1405 and 1412, and a rise time L between points 1406 and 1408. The output signal 1404 also includes an overshoot value related to the steady state value 1403 and the peak value 1411. The output signal’s overshoot is typically referred to as “percentage overshoot” and calculated according to: _n/ , . peak value-steady state value % overshoot = -------------— -----.

steady state value

The oscillating portion of the output signal 1404 before it settles to its steady state value includes an oscillating period τ that defines a natural frequency fn (i.e., l/τ) which, in terms of radians, is ®n= 2πί_η. Also, a damping coefficient ζ can be calculated according to:

<=—— tsefton

The input signal 1402 can be considered a time-based continuous signal x(t) and the output signal 1404 can also be considered a time-based signal u(t) such that the Laplace transform of each signal is X(s) and U(s). The transfer function, H(s) for the isolated traction system is therefore generically defined as U(s) = H(s)X(s). More specifically, a system that produces the output signal 1404 of Fig 5 based on receiving the step input signal 1402 can be represented by a second order transfer function H(s) according to:

3² + 2ζω_η3 + ω²

As described above, however, the microcontrollers and diagnostic supervisors operate with discrete time-sampled values and not with continuous signals. Thus, the transfer function H(s) may be transformed into a discrete transfer function H(z) by a variety of

Date Reçue/Date Received 2023-06-06 different methods. One method, known as a bilinear transfer transforms H(s) to H(z) by making the substitution of: s = (“) (θ where ts is the sampling time (e.g., 10ms) used to measure values of the input and output signals.

There are, however, automated methods for calculating a discrete transfer function that are available as alternatives to the methods just described. For example, MATLAB™ includes a function “c2d” that automates this process. If, for example, the input signal 1402 and the output signal 1404 reveal an initial transfer function of:

H(_s)=——--— s² + 3s + 10 then the commands:

h = tf(10, [1 3 10]);

hd = c2d(h, 0.01) will first define the continuous transfer function “h” and transform it to a discrete transform function “hd” using a sampling time of “0.01” seconds. The MATLAB™ command “hd =” will print out the discrete transform function as:

_ 0.01187Z² + 0.06408Z + 0.009721 ” z² - 1.655Z + 0.7408

Such a transfer function H(z) may be used by the first and second diagnostic supervisors 250, 252 to produce virtual values for the control attribute related to the traction wheel or traction motor of the vehicle. In particular, when a setpoint value is received by a diagnostic supervisor (250,252) it may be transformed by the transfer function H(z) to a virtual value. Thus, a stream of discrete samples of the setpoint value (e.g., traction speed setting or setpoint gm) produces a corresponding stream of virtual values (e.g., gm). These virtual values may then be compared with the feedback values gm to determine an operating condition of the traction system of the vehicle.

For example, if k is used as an index to refer to a particular sample x[k] in the stream of discrete samples of the setpoint value gm, then a corresponding virtual value y[k] (i.e., gm) can be calculated according to the above transfer function using:

(ox[k] + bx[k -1] + cx[k - 2] - ey[k - 1] - fy[k - 2]) --d--------------------where, for this particular example transfer function: a = 0.01187,

Date Reçue/Date Received 2023-06-06 b = 0.06408, c = 0.009721, d=l, e = -1.655, and f= 0.7408.

MATLAB™ also provides tools to fine-tune this initial transfer function H(z). For example, the transfer function H(z) can be modeled in SIMULINK™ which includes an OPTIMIZATION TOOLBOX™. The OPTIMIZATION TOOLBOX™ includes a tool for model parameter estimation. In the example transfer function H(z) above, the numerator coefficients are [0.01187 0.06408 0.009721] and the denominator coefficients are [1 1.655 0.7408]. The parameter estimation function of the OPTIMIZATION TOOLBOX™ can be provided with a set of input data, a set of output data and the transfer function. For example, the parameter estimation tool can be provided with data representing the input signal 1402, the output signal 1404 and the transfer function H(z). The parameter estimation function will use the input data and the transfer function H(z) to calculate a simulated set of output data. Based on a comparison between the actual output signal 1404 and the simulated output data, the parameter estimation function will fine-tune the numerator and denominator coefficients to more closely match the simulated data to the actual output data signal 1404.

To further refine die transfer function H(z), other actual input and output data can be provided to the parameter estimation function of the SIMULINK™ OPTIMIZATION TOOLBOX™. For example, a sinusoidal input and its resulting output can be provided and a ramp input and its resulting output can be provided. As a result, a transfer function H(z) can be developed that is calculated based on observed responses of a vehicle traction system to a plurality of different operating conditions.

A second type of model that may be used by one or both of the diagnostic supervisors 250,252 is an empirically-based model that includes the lookup table depicted in Fig. 6. Similar to developing the transfer function model, an isolated traction system can be tested and characterized under a plurality of operating conditions by controlling inputs, such as battery voltage and load, and recording the corresponding outputs, such as current, torque and speed. A look up table(s) LUT(s) can then be filled with the test data to provide die proper input-to-output relationship such that the traction command is used as the LUT input and the output is the resulting motor speed or torque. While such a technique is possible for collecting all the data for all the various possible operating conditions of interest, other more practical techniques are presently known to one of ordinary skill in this technology field,

Date Reçue/Date Received 2023-06-06 which may be used to develop a third alternative. The motor characterization, discussed above, allows for the estimation of motor resistance, inductance and flux linkage properties. Various simulation and estimation techniques, e.g., MATLAB™, can be used to develop 5parameter or 7-parameter models, (see “Modem Power Electronics and AC Drives,” by Bimal K. Bose, published Jan. 1,2015) for example, of a particular three phase induction motor. The resulting model represents the interrelationships between the different parameters of the motor in operation. The model is used to compute a predicted motor response to a plurality of input conditions to verify previous collected test data or used in whole as a traction motor model. The verified data can then be used to construct look-up-tables (LUT) from which a three-dimensional lookup table 600 of Fig. 6 is constructed and which forms part of the first model 254 in die illustrated embodiment.

The inputs to the lookup table 600 are the operating vehicle battery voltage, a motor speed feedback value an, and a traction command or traction setpoint τι value. The output of the lookup table 600 is an applied torque value. The battery voltage can be measured in volts and range between a voltage (e.g., 32V) below a nominal battery voltage (e.g., 36V) of a vehicle to a voltage (e.g., 40V) above that nominal voltage. The speed feedback value can be either a speed of the traction motor (e.g., RPMs) or the speed of the traction wheel (e.g., m/sec) and range from 0% of a maximum speed to 100% of the maximum speed. The traction command or traction setpoint, as well as the applied torque value, may be a torque value measured in N m and range from 0 to an amount that will stall the traction motor. The applied torque value is an amount of modeled torque realized by the traction motor that is applied to the traction wheel/load under a particular set of battery voltage, speed, and traction setpoint values.

As mentioned above, the collected or modeled data may be arranged in a threedimensional lookup table 600 of Fig. 6. Each particular cell 608 of the table 600 is addressable by a first coordinate on the traction setpoint axis 602, a second coordinate on the battery voltage axis 604, and a third coordinate of the speed feedback axis 606. A diagnostic supervisor may use, for instance, the lookup table 600 which defines part of the first model 254 in the illustrated embodiment, the present actual truck values for a traction setpoint τι, the speed feedback ©3, and a battery voltage to identify one cell 608 of the lookup table 600. The output value of that cell 608 is one of the output torque values collected during empirical testing or modeled applied torque values for an amount of torque which should be presently being applied by the traction motor 264 to the traction wheel for a particular set of coordinate values (i.e., traction setpoint, battery voltage, and speed). As described more fully below,

Date Reçue/Date Received 2023-06-06 this applied torque value selected from the lookup table of Fig. 6, if applied to an actual vehicle's traction wheel should produce a vehicle speed, which in Fig. 2B is the virtual speed value ωβ output by the first model 254. As discussed above, a comparison between the virtual speed value ωβ and the speed feedback value ω3 may be used by the first diagnostic supervisor 250 to determine if the traction system of the vehicle is in a fault condition.

In summary, the traction system models described herein may be represented as a transfer function (TF), a lookup table, or a 5,7 parameter model (ParModel). In any of these, the model represents an input to output relationship where the inputs are values such as, for example, the traction setpoint τι, battery voltage, and a current traction speed while the output is a virtual, or expected, traction speed value. Thus, in general, any one of the three traction model implementations discussed above may be selected when evaluating a current operating condition of the track. Input values appropriate for the selected model are first determined. For example, for the first model 254, the traction setpoint τι, the operating vehicle batteiy voltage, and the motor speed feedback value gm may be used as inputs. For the second model 256, the traction speed setting 04 from the traction application 208 can be used as the input to a transfer function. Regardless of the model implementation selected, the output of the model is a virtual response (e.g., ωβ or ωβ) that can be compared with the speed feedback value ω3 to determine if the traction system of the vehicle is in a fault condition

Fig. 9 is a flowchart of an example method of utilizing an empirically based model, such as the LUT of Fig. 6, in accordance with the principles of the present invention. In step 902, a vehicle is being operated and the first diagnostic supervisor 250, for example, receives, in step 904, from various sensors and other components of the vehicle the traction setpoint τι, the vehicle’s present battery voltage, and the vehicle present’s Trx_Speed or speed feedback ω3. These values can then be used, in step 906, to identify or compute the output of a traction module such as identifying one of the cells of the three-dimensional lookup table of Fig. 6. The speed feedback value gm could, for example, be a traction wheel speed measured in m/s or a traction motor rotational speed measured in RPMs. As noted above, the traction wheel speed and traction motor rotational speed are related by a scaling factor that relates to the gearing ratio of mechanical linkages between the traction motor and the traction wheel of the vehicle and the circumference of the traction wheel. The output from the traction model, such as the one particular cell identified from the lookup table of Fig. 6, provides a value that represents an expected “torque applied” value that would be applied by the traction motor to drive the traction wheel of the vehicle.

In step 908, this “torque applied” value is then used to determine an expected, or

Date Reçue/Date Received 2023-06-06 virtual, speed that would result if applied by the traction motor to the traction wheel of a vehicle in which the VCM 200 is incorporated. In particular and in accordance with one embodiment of the present invention, the operation of such a vehicle may be modeled by the equation:

dw₃“^applied 1 4 4 ^load where:

^applied is the modeled torque applied by the traction motor to the traction wheel and equals the “torque applied” value from the lookup table (or traction model);

is the change in the speed feedback ©3 of the traction motor or traction wheel and can be calculated by the traction application from a sequence of recent values of the speed feedback ©3;

I is an inertia value of all elements of the vehicle and load that are being accelerated, and is a fixed value for a particular vehicle;

©s is a virtual rotational speed (e.g., in RPMs) of the traction motor;

B is a rolling resistance or friction of the vehicle and can be determined, for example, from a lookup table that provided a resistance value based on a weight of the vehicle and the speed of the vehicle and represents friction loss such as that caused by bearings, various couplings, the floor and vehicle tire(s); and rioad represents the weight in torque units of the operator, the vehicle and the load on its forks.

The above equation forms part of the first model 254 in a first embodiment and can be solved for speed ©5 in order to determine an expected, or virtual value, of rotational speed of the traction motor or traction wheel that is expected to result if the torque applied value from the lookup table (or traction model) were applied to the traction wheel.

The above equation is in terms of torques and angular velocities but could also be converted to an equivalent equation in terms of linear velocities and linearly-applied forces. The conversion of a torque to a linearly applied force can be accomplished by scaling the torque value based on a) a gear ratio between the traction motor and the traction, or driven, wheel and b) a diameter of the traction, or driven, wheel.

Hence, in accordance with another embodiment of the present invention, the operation of the vehicle in which the VCM is incorporated may be modeled by an equation scaled from the above torque-based equation (e.g., Nm) to a linear-based force equation (e.g., N or -^7-)

Date Reçue/Date Received 2023-06-06 such that:

^applied =Acc ‘m + V_SB + F_load which can be solved for a linear vehicle speed “vs” resulting from an applied force and the value “vs” is the virtual linear speed calculated by the first diagnostic supervisor 250 in Fig.

2B.

In the above equation, which forms part of the first model 254 in a second embodiment:

FappEed is a linearly applied force determined by scaling the modeled torque applied value replied from the lookup table 600 based on a) a gear ratio between the traction motor and the traction, or driven, wheel and b) a diameter of the traction, or driven, wheel;

Acc is a linear acceleration equal to the change in the linear velocity of die traction wheel and is equivalent to d©3/dt scaled by a) a gear ratio between the traction motor and the traction, or driven, wheel and b) a diameter of the traction, or driven, wheel;

m is the mass of all elements of the vehicle and load that are being accelerated;

B is a rolling resistance or friction of the vehicle and can be determined, for example, from a lookup table that provides a resistance value based on a weight of the vehicle and the speed of the vehicle; and

Fioad is the weight of the vehicle, the load on its forks and the operator.

Thus, in step 910, the virtual value ©s or virtual linear speed value vs, is compared with an actual vehicle speed ©3, or actual linear speed V3, so that an operating condition of the vehicle can be determined in step 912.

In another example, one or more diagnostic comparisons may be performed by a model that utilizes timing constraints and signal thresholds for comparison to the actual response from the TCM 258. Such a model, for example, is depicted in Fig. 11 as a third model 1254 used by the first diagnostic supervisor 250 in place of the first model 254. Inputs to the third model 1254 and/or the first diagnostic supervisor 250 may include the speed feedback ©3 and the Trx_Speed_Limiti, 1202 provided by the steering application 206. For instance such a model may rely on known or measured attributes of the response of an actual traction system of a vehicle such as is shown in Fig. 10A. The x-axis, in Fig. 10A represents time and the y-axis is a speed (e.g., m/s). In response to a traction speed setting ©4,1004 defining a traction setpoint provided by the traction application 208 to the TCM 258, a measured response of the traction wheel or traction motor speed of the vehicle is shown by

Date Reçue/Date Received 2023-06-06 the graph 1002. By analyzing the two signals 1002,1004, a determination may be made, for example, about how long it takes the actual traction speed 1002 to reach the traction speed setting 1004. Additionally, the two signals 1002,1004 reveal that a difference between the actual traction wheel speed 1002 and the traction speed setting never exceeds some threshold amount. As explained below with respect to Fig. 10B, these characteristics of the traction system response to one or more operational inputs received by the vehicle can be relied upon to construct a number of cross-checks that may indicate whether the traction system of an operating vehicle is in a fault condition. Two example operational inputs that may be received by the vehicle are shown in Fig. 2B as the steering control input signal 278 and the traction speed control input signal 260 which are directly, or indirectly, used by the VCM 200 to generate the traction speed setting ©4Fig. 10B is a flowchart of an example method of determining whether a vehicle traction system is in a fault condition in accordance with the principles of aspects of the present invention. In the embodiment illustrated in Fig. 11, the first diagnostic supervisor 250 receives the Trx_Speed (i.e., speed feedback 03) and the Trx_Speed_Limiti, which Trx_Speed_Limiti is calculated and provided by the steering application 206 to the diagnostic supervisor 250. In the example embodiment of Fig. 11, the first supervisor 250 includes this third model 1254 as defined by the flowchart in Fig. 10B. In step 1009, an initial determination is made if the present Trx_Speed is greater than the Trx_Speed_Limiti. If so, then the remaining diagnostic steps of Fig. 10B are performed. If not, then none of the steps are performed and the steps of Fig. 10B are skipped until the VCM 200 operates to once again perform step 1009. In step 1010, a TrxSpeedJErr is calculated that is the absolute difference between the TrxjSpeed_Limiti from the steering application and the present Trx_Speed of the vehicle. In particular, the steps in the flowchart of Fig. 10B may be executed within die first supervisor 250 of Fig. 11 as part of a looping software application such that step 1010 may, for example, be repeated every 10 ms. Thus, the TrxSpeedJErr as shown in Fig. 10B is labeled as Trx Speed Err[i] to indicate that it is the Trx Speed Err value for a current iteration of the method of Fig. 10B. In step 1012, a determination is made whether or not the Trx_Speed Err[i] is greater than some first “difference threshold” amount. For example, that threshold may be 0.1 m/s. If this is the case, then this indicates that the Tix_Speed is greater than the Trx Speed Limiti by an amount that may raise concerns regarding operation of the vehicle’s traction system, i.e., the first threshold amount. There may be a counter associated with this condition labeled the Above Command counter. When the determination in step 1012 is true, die Above Command counter is incremented

Date Reçue/Date Received 2023-06-06 in step 1014. If the determination in step 1012 is not true, then the Above Command counter is reset to, or remain at, 0 in step 1016.

In step 1018 a determination is made whether the present iteration Trx_Speed_Err[i] value is greater than or equal to the previous iteration's Tix_Speed_Enr[i-l]. If fois condition is true, then the Trx Speed is greater than foe TrxSpeedLimiti and, furthermore, diverging from the Trx_Speed_Limiti. A No Response counter can be associated with this condition such that whenever foe determination in step 1018 is true, foe No Response counter is incremented in step 1020. If either the determination in step 1012 or foe determination in step 1018 is not true, then foe No Response counter is set to, or remains at, 0 in step 1022.

In step 1024, a determination is made whether or not the Trx_Speed_Err[i] is greater than a second, larger “difference threshold” amount such as, for example, 0.8 m/s. A Large Error counter may be associated with this condition and incremented, in step 1026, when the determination in step 1024 is true. When the determination in step 1024 is not true, then foe Large Error counter is set to, or remain at, 0 in step 1028.

Each of the Above Command”, No Response, and Large Error counters may have an associated counter limit, or “counter threshold” that is reflective of how long each of the three conditions described above are allowed to exist before the diagnostic supervisor determines that the vehicle's traction system is likely in a fault condition. Thus, after each of the three counters are adjusted during a current iteration of the method of Fig. 10B, the counters may be compared to their respective counter limit or threshold. The combination of repeatedly calculating a difference value in step 1010 and comparing each of the three counters to a respective counter threshold value results in the determination of a fault condition being made based on a plurality, or a set, of foe different difference values rather than a single instance of a present difference value.

For example, the Above Command counter threshold may be 300 and if, as assumed above, foe flowchart of Fig. 10B repeats about every 10 ms, then the limit of300 is analogous to a time period of about 3 seconds. The Large Error counter threshold may be a lower amount than 300 such as, for example, 170 so that the time period associated with that condition is smaller, e.g., 1.7 seconds. The No Response counter threshold may be smaller yet such as, for example, 50.

In step 1030 a determination is made whether any of foe three counters exceed their respective counter threshold. If foe determination in step 1030 is true, then a status flag is set, in step 1032, to a first value (e.g., 1). If the determination in step 1030 indicates that all

Date Reçue/Date Received 2023-06-06 three counters are at or below their respective counter threshold, then Ae status flag is set, in step 1034, to a second value (e.g., 0). If Ae status flag is set to Ae first value, Aen Ae diagnostic supervisor may determine Aat the operating condition of Ae vehicle traction system is in a fault conAtion. If Ae status flag is set to Ae second value, then Ae Aagnostic supervisor may determine Aat Ae operating conAtion of Ae vehicle traction system is not in a fault conAtion.

The predetermined values such as 0.1 m/s in step 1012,0.8 m/s in step 1024 and Ae counter thresholds in step 1030 may be based on Ae actual response 1002 of an operating vehicle to an operator’s input. Fig. 5 illustrated a hypoAetical response of a vehicle traction system Aat was useful for developing a transfer function model of Aat system. As mentioned above, Fig. 10A illustrates data collected from an actual vehicle Aat characterizes its response 1002 to an operator’s input. The signal 1004 represents a traction speed setpoint ©4 and Ae signal 1002 represents Ae traction speed ©3 of Ae vehicle. Based on a Wheel Angle Cmd, Aere may also be a Trx Speed Limiti value. The response signal 1002 is Aat of a property functioning vehicle and does not clearly show any anomalies or malfunctions of Ae vehicle's traction system. AccorAngly, a hypoAetical signal 1002' is shown in phantom Aat illustrates at least some of Ae determinations Ascussed wiA respect to Fig. 10B.

Analysis of Ae Afferent signals of Fig. 10A reveals Aere is a time period timei Aat begins when Ae response signal 1002’ exceeds Ae Trx_Speed_Limiti plus an example “Afference threshold” of 0.1 m/s. In Fig. 10A, Ae hypoAetical response signal 1002’ reveals Aat Ae time period timei is about 0.7 second before Ae signal 1002’ settles to a value substantially equal to Ae Trx_Speed_Limiti, i.e., within 0.1 m/s, Ae “difference threshold” of step 1012. A maximum allowable lengA of Ae time period timei corresponds to Ae counter threshold value “300” for Ae “Above Command” counter. If Aat counter were to reach 300, which would correspond to Ae period timei reaching 3 seconds, for example, Aen Ae diagnostic supervisor would determine Aat Ae vehicle’s traction system was malfunctioning.

One example malfunction Aat might lead to Ae Above Command counter reaching 300 is if communication between Ae traction application 208 and Ae TCM 258 is not occumng. As explained above wiA respect to Figs. 4A - 4D, if Ae steering application 206 determines a lower Trx_Speed_Limiti is appropriate given a vehicle’s current operating conAtions, Aen traction application 208 may also provide a traction setpoint τι which is intended to slow Ae vehicle. If communication is broken between Ae traction application 208 and Ae TCM 258, Aen Ae vehicle speed may not decrease and may exceed Ae

Date Reçue/Date Received 2023-06-06

Trx_Speed_Limiti by at least 0.1 m/s for a period of time that allows the Above Command counter to reach 300.

A second time period time2 represents a period of time in which the response signal 1002 is greater than the TrxSpeedLimiti by the example threshold amount of 0.1 m/s and is increasing. These conditions exist when step 1018 in Fig. 10B is true. A maximum allowable length of the time period times corresponds to the threshold value “50” for the “No Response” counter. If that counter were to reach 50 which would correspond to the period times reaching 0.5 seconds for example, then the diagnostic supervisor would determine that the vehicle’s traction system was malfunctioning.

As mentioned, the response signal 1002 of Fig. 10A is that of a properly functioning vehicle traction system. Ihus, the signal 1002 does not exceed the “large Error” threshold value of 0.8 m/s that is tested in step 1024 of Fig. 10B. However, the “Large Error” counter threshold of “170” would correspond to a maximum time period (not shown) that the signal 1002 could exceed the TrxSpeedLimiti by that second example threshold amount of 0.8 m/s before the diagnostic supervisor would, in step 1032, indicate that the vehicle’s traction system was in a fault condition.

Thus, the values 0.1 m/s and 0.8 m/s for the “Above Command” and “Large Error” determination, respectively, may be based on a vehicle’s traction system response to an operator’s input. For example, the actual response signal 1002 may be tested and observed for a statistically significant number of examples (e.g., one or more examples) to determine that it typically settles within about 0.1 m/s of the Trx Speed Limiti for a particular vehicle's traction system. Also, analysis of those examples of the response signal 1002 may reveal that while overshoot is very likely to occur, overshoot that exceeded 0.8 m/s rarely happened and could empirically be linked to a traction system failure. Similarly, the threshold values for the counters (e.g., 300,170, 50) may also be based on the actual response of a vehicle’s traction system to an operator’s input. One of ordinary skill will recognize that these values are provided by way of example and other specific values would be appropriate for different and varying vehicles. The 300 can be used in conjunction with a processing loop speed (e.g., every 10 ms) so that the threshold corresponds to a time period. For example, if an operating condition is tested every 10 ms and a true result increments a counter, then that counter reaching 300 corresponds to the operating condition being true for the previous 3 seconds. Thus, instead of any of the conditions tested in steps 1012,1018 or 1024 immediately resulting in a determination of a fault condition, the threshold values may represent how long a respective one of the conditions may last before a fault condition is

Date Reçue/Date Received 2023-06-06 determined. Analysis of a statistically significant number examples (e.g., one or more examples) of actual response signal 1002 can reveal that the time taken for the signal 1002 to settle within 0.1 m/s of the Trx_Speed_Limiti rarely if ever exceeds 3 seconds. One of ordinary skill will recognize that these values are provided by way of example and other specific values would be appropriate for different and varying vehicles.

While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.

Date Reçue/Date Received 2023-06-06