Method and arrangement for automated control of a vehicular drive train

SWEDEN (12) PATENT (13) C2 tu) 525 032 (19) SE (51)

International class ⁷B60K 28/16

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PATENT AND REGISTRATION (45) (41) (22) (24) (62) (86) (86)

Patent filed Application widely available The patent application was submitted on expiration date

Tribal application number

2004-11-16

2004-11-08

2003-05-07

2003-05-07 (21) Patent Application Number 0301334 9

Application received as:

(83)

International filing day

Filing date for European patent application Deposit of microorganism Swedish patent application completed international patent application with number □ converted European patent application with number (30) Priority information (73) (72) (74) (54) (56) (57)

PATENT HOLDER Volvo Trucks AB, 405 08 Gothenburg SE

INVENTOR Änders Eriksson, Gothenburg SE Marcus Steen, Angered SE AGENT Volvo Technology Corp

NAME Procedure and arrangement for automated control of a vehicle-drive system PUBLICATIONS QUOTED: - - SUMMARY:

Ingestion and arrangement of automated control of a transmission system (10) »a tendon vehicle for execution at ground level Breaggar which prevents the commencement or resumption of the Vehicle's Words, such as fixing on a solider's merit. The automated routine elicits a rocket movement in the vehicle intended to assist M with accessing the vehicle and painting the desired journey away from the area As an initial step of the routine, it is determined if such a ground condition exists. If this is the case, then the driving force, via the drive breath system (10) of the vehicle Ms driver foil (28,

30) excavates algae product Bv and train trains Btd the Br vehicle is established A reverse swing operation Measurement of an interruption of the driving force M The vehicle of the land vehicle (26, 30) With a predetermined choice of Br power consuming absorption exists. Optionally, baking power can be applied at this time. Otherwise, the driving force is applied to the drive wheel (28,30) for another attempt M progressing. Alpha these events control via an automated drive system tulin which performs the procedure typically in response to a driver information signal.

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The numbers in parentheses indicate the INID code.

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Summary

Method and arrangement for automated control of a driveline system (10) of a land vehicle for execution when ground conditions exist which impede the commencement or resumption of the vehicle's journey, such as jamming on loose or slippery ground. The automated routine induces a rocking motion in the vehicle designed to help release the vehicle and allow the desired vehicle away from the area. As an initial step of the routine, it is determined whether such a ground condition exists. If this is the case, driving force is applied, via a driveline system (10) of the vehicle, until the driving wheel (26, 30) buries or productive and continuous sheep is established for the vehicle. A reverse rocking motion is permitted by an interruption of the driving force to the land vehicle's drive wheel (26, 30) until a predetermined condition for power resumption exists. Optionally, reverse force can be applied at this time. In another case, driving force is reapplied on the drive wheel (26, 30) for another attempt at progress. All of these events are controlled via an automated drivetrain system control routine that performs the procedure, typically as

0 response to a driver-initiated signal.

(Fig. 2)

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Technical field of the invention

The present invention relates to systems and methods for controlling the start-up or take-off of a land vehicle, and in particular heavy-duty vehicles operating on unfavorable ground conditions, such as those typically found in terrain where runways may be littered with debris and eroded with holes and sinks, or consist of loose soil.

Technical background

Land vehicles, including motor vehicles, and in particular heavy trucks such as timber trucks and trucks used at construction sites, can be jammed when started or started under off-road and similar conditions, as the driving wheels experience reduced driving force to the ground. Experienced drivers have developed strategies to solve this problem, such as engaging a side differential latch, or engaging a longitudinal differential latch, or lifting a wheel pair to increase the weight of each remaining wheel. A more thoughtful method, known as rocking, involves periodically transferring power to the drive wheels. More specifically, the driver repeats a sequence in which the force transmitted to the drive wheels is first increased until the wheels spin, and then releases the accelerator pedal and steps out of the main clutch. An even more thoughtful version of the method involves alternately switching from a forward ratio to a reverse ratio.

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Several other ground conditions can present similar challenges. For example, if the vehicle will stop with one or more wheels in a lowering, trench or similar recess, then the engine power may be insufficient to get the vehicle out of the recess and into productive travel. If a log, ridge, hill or other obstacle is located in front of several of the vehicle's wheels before the start, similar difficulties can be experienced in getting the vehicle started. In a more general sense, these several start-up challenging states can be collectively referred to as obstacles or difficulties in starting or resuming the journey of the land vehicle.

Regarding the rocking methods described above to start the vehicle start, great skill and experience is required as the driver, sitting in the vehicle's cab, has little information about the actual wheel spin condition and must respond quickly to achieve the desired effects. For this reason, drivers who are beginners, at least with regard to these more difficult driving conditions, often have a disadvantage when compared to their more experienced colleagues. In addition, these methods are often found to be incompatible with power transmission and anti-spin systems (traction control systems) used in modern heavy goods vehicles.

Many semi-automatic power transmission systems include means for automatically selecting a predetermined starting gear when the vehicle is started from a stationary state. In US 6,383,116, however, it has been proposed to allow the operator to operate the selector lever to select a higher starting gear than the predetermined starting gear which would otherwise be automatically selected by the electronic actuator. This method may be suitable when the driving force is reduced on a non-deformable road surface, for example due to ice or a thin layer of snow. However, such a strategy is to little c η r Z ~ Ο

032 or no use when the ground surface is deformable, such as in the woods or at a construction site, since in these cases the drive wheels must have to eat through the deformable surface to find driving force on firmer, often underlying, ground.

Further, it has been proposed in WO 02/04242 to adapt a vehicle's anti-spinning system to operate on a deformable ground surface by increasing the amount of slip allowed by the anti-spinning system of the drive wheels, thereby allowing the wheels to eat through the deformable surface. The vehicle's anti-spin system is turned on when the drive wheel slip exceeds a predetermined slip threshold to reduce the amount of drive wheel slip by reducing the drive wheel speed. The anti-spinning system also monitors vehicle speed reduction. After detecting that the vehicle is slowing down and that the vehicle speed decrease has exceeded a speed reduction threshold, the anti-spinning system assesses that the vehicle has encountered a deformable surface such as mud or deep snow. After detecting entry on a deformable surface, the slip threshold is raised linearly over a period of time to increase the drive wheel speed. However, this control routine does not provide a method for starting from a standstill.

Brief description of the invention

It is an object of the present invention to provide both methods and / or devices adapted to control the commissioning of a vehicle, in particular a heavy load vehicle, when certain start-up ground conditions prevail, such as conditions with loose soil that are frequently encountered in the terrain, and which can be implemented by drivers who have insignificant experience and driving skills developed for such conditions. In accordance with a related aspect, it is preferred that the implemented systems and procedures utilize

525 032 signals and controls currently available in automatic or semi-automatic power transmission systems and / or vehicle anti-spin systems.

In a general sense, the present invention is designed to mimic the strategies that experienced drivers have developed to achieve vehicle start or start when anti-travel conditions are encountered as described above. These conditions include but are not limited to loose and muddy soil, and uneven terrain with recesses and depressions, and ridges and elevations that can be difficult for a heavy-duty truck to overcome when starting from a stationary position or slow operation. Because driveline systems in most land vehicles, and especially heavy goods vehicles, have at least semi-automated control systems, the present invention provides an automated control strategy that, when implemented, allows any operator, regardless of experience level, to maximize the ability of their vehicle to are driven out of jamming and other situations that otherwise make it difficult to get started.

The invention (s) can be characterized in the form of one or more embodiments. An embodiment is the method which, via drive-line system control, implements the described start-up or start-up strategy for a vehicle. Another embodiment is the systems and devices, either on board or standing in connection with the vehicle, through which these strategies are implemented.

As an important aspect of these control strategies is the fact that they can be automated on board the vehicle utilizing control processors and programmed computer-readable media, these programmable control systems constitute another embodiment of the invention. In connection with this, another embodiment is the executable

R o r. Η 7.9 the computer program itself as a product, which when run affects the execution of the established strategies.

In a first exemplary embodiment, the invention assumes the form of a method for automated control of a driveline system of a land vehicle for execution when ground conditions exist which impede the commencement of the vehicle's journey. The method includes (includes) determining that a ground condition exists that prevents the commencement of the land vehicle's journey. Examples of the various terrain opportunities that may present such obstacles are described here. The determination that such a relationship exists is preferably indicated by the driver, but can be derived automatically from the vehicle's operating and / or driving condition. Driving force is applied via a driveline system of the vehicle to one of the land vehicle's drive wheels in an attempt to achieve productive travel of the vehicle. The driving force application has been described as if it were on one of the land vehicle's drive wheels, but it must be understood that power can be applied to any number of drive wheels on any specific vehicle in question. Furthermore, productive travel should of course be defined as continuous travel over the ground, as long as the operator so requests, without excessive driving of the drive wheels or that insurmountable dead positions are found such as the recesses and ridges that have been described and which can prevent the vehicle in question from moving directly. The application of driving force continues until a predetermined condition for unproductive vehicle progress has been detected. This condition for unproductive vehicle progress has been established as a sensed condition which shows that the progress of the motor vehicle in relation to the ground one wishes to pass has fallen below a threshold. As has been suggested above, excessive driving of the drive wheel resulting in either an absolute interruption or almost an interruption of travel in relation to the ground is an example of such unproductive vehicle travel progress. The method also includes:

525 032 via an automated powertrain system control routine, controlling the execution of the propulsion application step on the drive wheel in an attempt to achieve productive travel of the vehicle in response to a driver-initiated signal. As defined by the invention in this exemplary embodiment, it must be understood that the driver may believe that sufficiently disadvantageous conditions exist that justify utilization of the take-off control and enable execution of the control routine, but the conditions are, in fact, such that starting directly into productive travel is possible. In this case, the automated powertrain system control routine has been initiated but startup is achieved without interruption of power delivery to the drive wheels.

In addition, in an improvement of the method described above, the invention may include suspending the driving force of the land vehicle's drive wheel until a predetermined condition for power resumption exists. Looking at the similarity of a driver-made rocking of the vehicle, the power to the drive wheels is interrupted once the vehicle's travel has slowed down, and the vehicle swings in a reverse direction. A condition for resumption of power exists when the reverse swing motion has either ended, or is almost complete. When the condition for power resumption exists, driving force is reapplied on the land vehicle's drive wheel for the purpose of continuing the land vehicle's productive motor drive. This step, on the other hand, can be likened to the next motor driven rocking in the desired direction of travel so that the vehicle continues motor driven in the desired direction. As indicated above, these additional steps can be incorporated to control, via the automated powertrain system control routine, the implementation of the application, interruption, and reapplication of propulsion on the land vehicle's drive wheel in response to the driver-initiated signal.

To make the above-defined procedures even more powerful, additional additions to the control routine can be achieved by, via the vehicle's

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drive line system, apply a driving force in the reverse direction to the land vehicle's drive wheel between the steps of interrupting and reapplying the driving force to the driving wheel. The application of driving force in the reverse direction continues until a predetermined condition for unproductive vehicle travel in the reverse direction has been detected. In a similar manner as defined above for unproductive forward moving forward, a condition for unproductive reverse moving forward is determined as a sensed condition showing that the motor vehicle's forward reverse travel, in relation to the ground that one wishes to pass, has fallen below a threshold. The conditions that characterize unproductive forward travel typically characterize unproductive backward travel in a similar way.

If the predetermined forward-backward propelled rocking routine thus established has not enabled the vehicle to start, the procedure proceeds optionally, after an initial application of thrust to the land vehicle's impeller, with a repetition of the steps of interrupting, reverse application, and reapplication of propulsion power to the ground vehicle. a predetermined condition for continued productive travel is established. Examples that may constitute signals for such a continued productive journey will be exemplified below. It should also be understood that the repetition process can also be implemented in embodiments that do not incorporate the aspect of reverse application of force, that is, if motor drive backward is not included, it is also conceivable that repeated motor-driven forward swinging, with unrestricted reverse retraction allowed between.

According to a further aspect, the operating mode for automated start-up control can be switched off when the predetermined condition for continued productive travel is detected. This step involves a voluntary feature of the inventive process which requires the operator to reinitiate the execution of the above defined startup process after

525 032 that a period of productive travel has occurred in an attempt to ensure that unintended implementation of the routine is avoided.

As has been suggested above, it is preferred that activation of the startup routine defined herein is dependent on driver initiation. In a related embodiment, execution of the routine is allowed only when the driver has manually selected an operating mode for automated pre-launch control for the vehicle's driveline system.

In one embodiment, the driver-initiated signal that initiates the automated powertrain system control routine is the depression of a gas pedal. In addition, the degree of depression of the accelerator pedal can either be ignored, or utilized as an input signal for a function that determines how much torque is delivered to the drive wheel during the various steps of the defined routines. In accordance with a related aspect, the execution of the routine and, for its part, the start attempt, can be halted on the basis of detecting that the accelerator pedal has been released by the driver, or at least released past a predetermined threshold accelerator position.

As an exemplary embodiment, the detection of a predetermined condition for unproductive vehicle travel may be based on at least one signal selected from the group consisting of: a speed signal for a driven wheel, a speed signal for a driving wheel, a speed signal for the driveline system, a torque signal for the driveline system, a vehicle speed signal, an acceleration signal for a detached body of the vehicle, and an acceleration signal for a non-driven vehicle. The selected signal is compared with a predetermined threshold value to control the execution of the automated drive line system control routine.

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In one embodiment, productive vehicle travel progress is distinguished from unproductive vehicle travel progress on the basis of a comparison of rotational speeds of the driven wheel with an unpowered wheel. In an alternative embodiment, the inventive method distinguishes productively from unproductive vehicle travel on the basis of a comparison between the rotational speed of the driven wheel and a measured speed of travel of the vehicle.

For example, the automated powertrain control system may be disconnected under any of the following conditions: up, depressing the accelerator pedal of the vehicle is released past a predetermined throttle position 15 threshold, and a pre-initiated disengagement command is received.

From a systems perspective, one embodiment of the invention assumes the form of a land vehicle propulsion system control device which includes a processor and readable medium configured and programmed to perform the above described methods. An alternative embodiment envisages incorporating the systems into a land vehicle.

Since the methods and devices for implementing these methods are preferably computer-based, further embodiments of the invention are considered to be computer-readable media with program code adapted to perform, upon execution, the described methods of the invention. A related embodiment assumes the form of a computer program product which includes program code, on a computer-readable medium, adapted to perform the inventive methods.

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The methods described herein can be implemented both for forward and reverse, depending on the driver's input. The vehicle's off-road operation mode can be determined on the basis of a manual input by the driver. Alternatively, it can also be determined automatically, for example on the basis of conditions established during previous operation of the vehicle, before the vehicle has come to a standstill. It can also be determined automatically after a first unsuccessful attempt to start the vehicle without implementing the procedure, based on measurements taken during this unsuccessful attempt. Advantageously, initiation of the terrain start-up mode will only be allowed if the vehicle is stationary or almost still.

In one embodiment, the step of transmitting power to a drive wheel includes at least one of the following steps: (1) inserting an gearbox of an automatic gearbox of the driveline system in the desired direction of travel, (2) controlling an engine of the driveline system to increase the engine torque, and / or (3) to "release" a main clutch of the driveline system. Advantageously the steering of the engine may include controlling the engine torque as a function of the degree of depression provided to the accelerator pedal by the driver. In this way, the driver can determine how much power is to be transmitted to the drive wheel (s). This feature also gives the operator a sense of control over the vehicle that could otherwise be lost through a completely independent control routine. This is particularly useful when the vehicle leaves the automated off-road procedure.

It is contemplated that a determination that the vehicle may be jammed can be obtained from the detection of one or more of the following signals: (1) a speed signal for a driven wheel, (2) a speed signal for a driving wheel, (3) a speed signal for the driveline system , (4) a torque signal for the ς ο ς η 7 ο driveline system, (5) a vehicle speed signal, (6) an acceleration signal for a sprung portion of the vehicle, and (7) an acceleration signal for a non-sprung portion of the vehicle. The final determination of the existence of a jamming state is based on a comparison of the sensed quantity against a predetermined quantity known to indicate a jamming state. The known magnitude can be expressed in the form of a threshold beyond which a jamming state is indicated.

The vehicle speed is most typically determined on the basis of the speed of rotation of an unpowered wheel. Alternatively, however, can be radar, optical (camera) or

Global Positioning System (GPS) signals provide a measure of the vehicle's speed relative to the ground, especially if all the wheels of the vehicle are driven. The vehicle acceleration can be derived from the vehicle speed signal, or measured directly by an accelerometer.

A jamming state is preferably determined on the basis of a function comparing a rotation speed signal for one or more drive wheels with a rotation speed signal for one or more driven wheels. Regarding the process steps of the invention, wheel spinning has been identified as a reliable indicator of when power should be interrupted to a sliding driving wheel. However, it must be understood that a certain degree of slip of the drive wheel should be allowed since the wheel should be allowed to eat through the deformable surface. However, too much wheel spin should be avoided. Advantageously, both (1) vehicle speed or acceleration and (2) wheel spin are used together, more wheel spin can be used.

5 thus allowed if it allows the vehicle to accelerate.

The amount of allowable spin can be a predetermined constant value. Permissible spin can also be determined as a function of a degree of operator depression of the accelerator pedal. In this way, the driver affects the amount of wheel spin allowed to thereby advantageously increase the driver's sense of

525 032 control as described previously. It is also envisaged that the degree of permissible spin can be automatically controlled (increased and / or decreased) via the control routine between each repeated attempt to release the vehicle and commence productive progress or gain.

The step of disabling or interrupting the transmission of power to the drive wheel includes one or more of the following steps: (1) controlling an engine of the drive line system to reduce engine torque, (2) "disengaging" a main clutch of the drive line system, (3) disengage an automatic transmission of the powertrain system.

After the power is interrupted and the vehicle is allowed to roll backwards, or is driven backwards, there is eventually a condition for power resumption as described above. Determining that power is to be resumed may advantageously, at least in part, be based on one or more of the following parameters: (1) a velocity signal for a driven wheel, (2) a vehicle velocity signal, (3) an acceleration signal for a resilient body of the vehicle, ( 4) an acceleration signal for a non-resilient portion of the vehicle. The measured parameter is typically mapped to a look-up table of the system, and on this basis force resumption is performed or not on the drive wheel.

If successful, the backward and forward swinging motion induced in the vehicle allows the vehicle to eventually achieve productive progress and move out of the obstructive relationship (s) in a desired predetermined direction. Therefore, it is important for the routine to recognize a run-off condition that shows that productive progress or travel has been achieved. Features that the control routine can evaluate in an attempt to establish that a run-off condition exists include: (1) detecting whether the vehicle has been operating more than a certain

525 032 travel distance, (2) sensing if the vehicle speed is above a vehicle speed threshold, (3) sensing if the brake pedal is depressed, (4) sensing if the accelerator pedal has been released, and / or (5) sensing if an operator signal has received at a driver interface of the system.

Preferably, several conditions can be monitored simultaneously, and one or more considerations in the control routine. Depending on the vehicle type, additional features can be incorporated into the routine to enhance the effects of the procedure.

Examples include turning on a side differential lock of the driveline system, activating an anti-spinning procedure controlling individual wheel brakes to reduce the difference between a right-hand drive speed and a left-hand drive speed, deactivating an anti-spinning procedure of the vehicle controlling individual wheel braking speeds, and individual wheel braking speeds. non-driven wheels, and to engage a longitudinal differential latch of the driveline system.

In terms of forward and reverse application of force, both forward and reverse swing or rocking motion of the vehicle is assisted, so that the amplification of the vehicle impulse is more effective. The method preferably determines whether the step of applying backward force is to be performed on the basis of a manual choice made by the driver. This can be an important feature since added reverse should only be implemented when backward travel is safe and doable. In addition, an independent initiation of

5 backward force become quite daunting for the driver.

As an alternative, the routine can reduce the force transmitted to the drive wheel to zero when a stop condition for reverse operating mode, or an indication that unproductive spin occurs, has been sensed. It is envisaged that this reverse condition for reverse operation mode may be based on such

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parameters such that (1) the vehicle has cut more a certain distance in the direction opposite to the desired direction of travel and / or (2) the vehicle speed is above a threshold for vehicle speed in the direction opposite to the desired direction of travel.

In most of the embodiments described, at least two parameters are taken into account to determine a jamming or start-up condition: a parameter representative of the vehicle's movement (speed sensor for driven wheel, vehicle speed sensor, accelerometer) and another parameter representative of the drive wheel. behavior (speed sensor for drive wheels, speed sensor for the output shaft of the transmission, drive line torque sensor).

Brief description of the drawings

Other advantages and features of the invention will become more apparent from the following description of an embodiment of the invention, given by way of non-limiting example only, and shown in the accompanying drawings, in which:

Figure 1 is a graphical representation of a driveline system with a driveline system controller in accordance with one aspect of the invention,

Figure 2 is a flowchart illustrating process logic of a routine for controlling a startup procedure in accordance with another aspect of the invention,

Figure 3 is a flowchart illustrating process logic of a subroutine of the routine of Figure 2, and

Figure 4 is a flowchart illustrating process logic of a subroutine of the routine of Figure 2.

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Detailed description

Referring to Figure 1, there is shown a driveline system 10 which includes an internal combustion engine 12 and a driveline 14 for transmitting engine power to a first and a second drive wheel pair. The drive line 14 includes (includes) an automatic gearbox 16, a main clutch 18 located between the engine 12 and the automatic gearbox 16, a PTO shaft 20 for transmitting power to a longitudinal torque distributor 22 which transmits power to a first lockable transverse differential 24 to distribute power. to the first pair of left and right drive wheels 26, and to a second lockable transverse differential 28 to distribute power to the second pair of left and right drive wheels 30. The longitudinal torque distributor is provided with a clutch or brake to interrupt power transmission to the first drive wheel pair 24. The torque distributor may also be equipped to continuously change the power distribution ratio between the first and second drive wheel pairs. The drive line 14 may also include power take-off, but has not been shown.

A drive-line system control system or arrangement according to the invention comprises an electronic control unit or controller 34 for controlling the output torque of the internal combustion engine 12, as well as the main clutch 18, gearbox 16, longitudinal torque distributor 22, and lockable differentials 24, 28. The electronic control unit 34 is connected to a driver interface 36 with sensors for detecting the position of a throttle pedal 38, of a brake pedal 40, of a selector lever 42, of a first selector 44, and of a second selector 46.

The electronic control unit 34 is also connected to a series of sensors for determining the movement of the vehicle. These sensors include one or more of the following: speed wheel speed sensors 50 for measuring one

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W «- \ J ii16 speed of the drive wheels 26, 30, speed sensors 52 for driven wheels for measuring a speed of driven wheels 54. The wheel speed sensors 50, 52 can be included in a lock-free brake system, but not shown. In addition, or alternatively, other sensors may be provided, such as a distance sensor 56 for measuring the longitudinal distance between a point fixed relative to a resilient portion of the vehicle, such as vehicle chassis or vehicle body 56a, and another point fixed relative to a non-resilient portion of the vehicle, such as a wheel axle 56b, one or more longitudinal and / or vertical acceleration meters 57 fixed on a resilient part of the vehicle and / or on the non-resilient part of the vehicle, a camera 58 or a radar 60. The camera and radar can be used either to measure the movement of the vehicle or to measuring the movement of the resilient portion of the vehicle relative to the non-resilient portion.

The electronic control unit is also connected to a series of sensors to determine the dynamic behavior of the drive line system 10 and the current state of the motor 12 and of the sub-units of the drive line 14, e.g. a speed sensor for the motor output shaft, a drive line speed sensor 62, a drive line torque sensor 64, and sensors for determining engagement state of the main clutch 18, of the longitudinal torque distributor 22, and of the lockable transverse differentials 24, 28.

It is to be understood that the signals of the various sensors can be integrated or differentiated by analog or digital means in the electronic control unit 34 to obtain new signals, e.g. the acceleration of the vehicle, the speed and / or the longitudinal acceleration of the chassis 56a relative to the wheel axle 56b, the speed of a propeller shaft. Furthermore, signals from different sensors can also be combined to obtain

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new signals, for example, the drivetrain torque signal and the drivetrain speed signal can be combined to obtain a drivetrain power signal. Inputs from multiple sensors are also necessary to determine a wheel spin of the vehicle's drive wheels. The wheel pin can be calculated as a difference between a speed of one or more of the drive wheels and a speed of one or more driven wheels. Alternatively, the wheel spin may be determined on the basis of a comparison of a vehicle speed signal determined on the basis of one of the sensors 56, 57, 58, 60 for detecting the movement of the vehicle, on the one hand, and a drive wheel speed signal or PTO shaft speed signal, on the other.

The electronic control unit comprises a motor control sub-unit 70 for controlling the engine power based on the position of the accelerator pedal 38, a main clutch control sub-unit 72 for controlling the main clutch 18, and a sub-unit for power transmission control 74 for controlling the transmission 16, the longitudinal torque distributor 22, and the lockable transverse differentials 24, 28.

The electronic control unit 34 also includes a read-only memory 76 for storing a routine for controlling the vehicle's start on soft surfaces. The electronic control unit 34 of the driveline system control system follows the instructions included in the routine each time the vehicle is stationary.

The routine 100 for controlling the start of the vehicle on soft surfaces is illustrated in Figure 2. First, it is decided or decided in decision block 102 whether a particular start-up mode should be applied. This decision is preferably made on the basis of the position of the voter 44. Alternatively or additionally, the electronic control unit 34 may automatically decide to run the routine based on the condition of an off-road flag set during the vehicle's previous operation, before the vehicle was stopped, and stored in a memory.

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Such a flag can be set, for example, when an anti-spinning device has determined that the vehicle has encountered a deformable surface such as clay or deep snow and has stopped on that surface. An exemplary method for detecting that a vehicle has encountered a deformable surface is described in WO

02/04242. For this reason, the contents of this publication are hereby expressly incorporated by reference into the specification of the present application.

Thereafter, the routine continues to function block 104 to determine a desired vehicle travel direction based on the position of the selector lever 42. The desired vehicle travel direction will be the forward direction always when the selector lever 42 indicates a forward gear range or a forward power transmission drive forward or forward forward position. Conversely, it will always be the reverse direction when the lever 42 indicates a reverse gear region.

The routine then proceeds to decision block 106 where the depression of the accelerator pedal 38 is detected. When the throttle pedal 38 is detected, the routine proceeds to function block 108 where a counter C:

reset. The routine continues to function block 110 to drive the power transmission to the drive wheels. In function block 110, the electronic control unit 34 activates the motor control sub-assembly 70 to determine the desired engine power on the basis of the position of the accelerator pedal 38, activates the power transmission control sub-assembly 74 to engage an gear ratio, and activates the main clutch control sub-assembly 72 to "release" the main clutch . The gear ratio may be the lowest gear ratio in the desired direction of travel. It can also be determined on the basis of the state of the counter C: and / or the position of the accelerator pedal 38 and / or the position of the lever 42. The routine continues

525 032 then to function block 120 where the counter is incremented on the basis of repeated repetitions of the motor drive step.

In decision block 122, the electronic control unit determines whether a jamming state has been detected. The condition for jamming is based on a comparison between a wheel spin value and a slip threshold.

If the wheel pin is smaller than the slime threshold, then the routine jumps to decision block 124. In decision block 124, the electronic control unit determines if a condition for run-out is met. For example, the condition for run-out is met if the counter C! is higher than a predetermined value, or if the vehicle speed is higher than a predetermined value, or if the vehicle has cut a predetermined distance in the desired direction of travel. In these cases, the routine ends. Otherwise, the routine jumps back to decision block 122.

If the wheel spin is greater than the slime threshold in decision block 122, then the condition for jamming is fulfilled and the routine jumps to function block 130, which calls a subroutine CANCEL to interrupt power transmission to the drive wheels 26, 30. The subroutine interrupt is illustrated in Figure 3. counter C₂. Thereafter, the subroutine moves to function block 134 to effect "uncoupling" of the main clutch while reducing the power of the motor. Then the interrupt counter in function block 136 is raised. The routine then proceeds to decision block 138 to detect if a resume condition is met.

Depending on the signals available, this condition for resumption of the interrupt counter value C is met₂ is higher than a predetermined value and / or if the vehicle speed is lower than a predetermined value and / or if the speed of the driven wheels has changed sign or is lower than a predetermined value, and / or if the speed in the longitudinal direction of the sprung part of the vehicle in relation to to the non-resilient part has changed characters. It will be appreciated that the condition for resumption may depend on whether the desired direction of travel is forward or reverse. If the resume condition is not met, the routine goes in a loop to the function block 136 to step up the interrupt counter C₂ and redo the test. If the condition for resumption is met in decision block 138, then the subroutine returns to the main routine, which proceeds to decision block 140 to decide whether to implement a reverse operation mode.

This condition is met if the corresponding selector 46 on the driver interface is switched on. If the condition is met, the routine goes to function block 150 to call a BACKA subroutine, which executes a reverse control operating mode and drives the power transmission to the drive wheels in the direction opposite to the desired direction of travel. Otherwise, the routine goes in a loop to function block 110.

The BACKA subroutine is illustrated in Figure 4. In function block 152, a counter C is reset₃. In function block 154, the electronic control unit activates the sub-unit for power transmission control 74 to enter an gear ratio in the direction opposite to the desired travel direction, said gear ratio being determined on the basis of the state of the counter and / or the position of the accelerator pedal. The subroutine proceeds to function block 156 to activate the motor control sub-unit 70 to determine the engine power on the basis of the position of the accelerator pedal 38, and activates the master clutch control sub-unit 72 to "release" the main clutch 18. The routine then proceeds to function block 158 to step up the counter C₃ and goes to decision block 160.

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In decision block 160, the electronic control unit 34 determines whether a jamming state has been detected in the direction opposite to the desired direction of travel. The test is very similar to the test at decision block 122. If the wheel spin is less than the threshold, the routine jumps to decision block 164.

In decision block 164, the electronic control unit determines if a condition for delivery is fulfilled. The condition for run-out is met if the counter C₃ value is higher than a predetermined value, or if the vehicle speed is higher than a predetermined value, or if the vehicle has traveled a distance greater than a predetermined limit value in the direction opposite to the desired direction of travel, or if the selector 46 has been turned off, or if the brake pedal has been pressed down, or if the accelerator pedal is released. In these cases, the subroutine ends. If the condition for run-out is not met, the subroutine jumps back to function block 158 to step up the counter.

If in decision block 160 the wheel spin is greater than a specified threshold, then the routine jumps to function block 162, where the sub-routine CANCEL is called to interrupt the transmission of power to the drive wheels. The interrupt subroutine has been described previously in connection with function block 130. However, it will be appreciated that the parameters of the interrupt subroutine may be different for the desired direction of travel and for the opposite direction. In particular, the predetermined values ​​used in decision blocks 138 may be different.

Although preferred embodiments of the invention have been described, it will be appreciated by those skilled in the art that the invention is, of course, not limited to these embodiments. Many variations are possible.

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For example, the vehicle speed or acceleration can also be used as parameters to determine a jamming condition of the vehicle. For example, the condition for jamming will be met if the vehicle speed is lower than a predetermined value. Vehicle speed or acceleration and wheel spin are advantageously used together, for example, more wheel spin can be allowed if it causes the vehicle to accelerate. The slip threshold can be a constant value, or it can be made depending on the position of an accelerometer, and / or a value of the counter Ci (how many times the motor drive step has been repeated).

In many cases, the vehicle will be equipped with an anti-spin system that automatically brakes individual wheels to limit slimming during acceleration. If this is the case, it may be advantageous to run the anti-spin system parallel to routine 100, especially if the transverse differentials are not lockable. Alternatively, it is also acceptable to automatically disengage the anti-spinning system while performing routine 100. It may also be advantageous to activate the latches of the lockable transverse differentials 24, 28 and / or a latch of the longitudinal torque distributor 22.

The BACKA subroutine is optional, therefore blocks 140 and 150 can be omitted and subroutine 130 can go directly in a loop to function block 110. Decision block 124 may be located before decision block 122.

An internal and / or external buzzer can be activated when the start-up operating mode is activated so that the driver and / or persons around the vehicle can be warned, especially when the reverse start-up procedure is implemented.

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The electronic control unit can be replaced by several control units, such as a motor control unit, a transmission control unit, a main clutch control unit and the like.

The gearbox may be a stepped gearbox or a continuously variable gearbox. The gearbox can be a manual gearbox as long as the main clutch 18 is operated automatically. In such a case, the reverse operation mode is not provided. The routine will be executed on the basis of the manually selected gear of the driver.

The invention can not only be incorporated in vehicles with an internal combustion engine, but also in vehicles with another type of engine or motors, such as electric motors or hybrid drive systems. The invention can also be incorporated into a vehicle with only one drive wheel, one drive wheel pair, or where all the wheels of the vehicle are driven.

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