Steering device

i

STEERING DEVICE

The present invention relates to an automatic steering device and method for use in an automatically controlled vehicle, for performing a parking maneuver, for example, without requiring the steering control of a vehicle driver.

A steering device disclosed in Japanese Patent Publication No. 4205505 enables the driver of the vehicle to easily perform a steering control action during the automatic steering control operation by simultaneously generating an automatic steering torque and a steering torque. power steering control. The automatic steering device reduces the excess steering torque in the automatic steering mode, using the steering assist torque. When the operator of the vehicle intends to perform steering operation according to the automatic steering mode, the steering control torque is reduced so as to help the driver of the vehicle to easily perform the steering control operation.

When the driver of the vehicle performs a steering control operation in the automatic steering mode, the steering mode is switched to the manual steering mode by canceling the automatic steering mode. According to the technology described in the publication mentioned above, the automatic mode can be gradually switched to the manual steering mode. Since the automatic steering device produced before the introduction of the above-mentioned technology does not generate assist torque from the power steering in the automatic steering mode, the automatic steering torque is largely lost. The assist torque, in turn, is generated largely in the opposite direction to that of the automatic steering torque, resulting in a sharp change in the steering reaction force. On the other hand, the technology described in the above-mentioned publication prevents a sudden change in steering reaction by reducing the steering torque in excess of the automatic steering torque. Therefore, the steering mode can gradually change from manual steering mode to automatic steering mode.

The technology for switching from automatic steering mode to manual steering mode in response to the vehicle driver's steering control operation is disclosed in JP-A-11-198839. In this technology, it is determined whether the steering control operation has been performed by the driver of the vehicle based on the measured values ​​of the steering torque measured by the steering torque sensor.

WHlRSCH6 \ PATENTS \ Patents \ 19800 \ 19807.doc - September 9, 2002 - 1/13

With the automatic steering device simultaneously generating the automatic steering torque and the assist torque of the power steering control, the driver of the vehicle can realize the steering control operation even if the automatic steering mode is at one. reduced steering torque. The steering torque which has been kept low to assist the driver of the vehicle may, in turn, make it difficult to determine whether the steering control operation has been performed based on the measured values ​​of the torque. turning point. The threshold value of the steering torque measurement values ​​must be decreased so as to determine the steering control operation of the driver of the vehicle. In this case, however, it is difficult to distinguish the steering torque generated by the steering control operation of the driver of the vehicle from an inertia torque of the steering wheel itself, as the parasitic noise. As a result, the steering control operation cannot be accurately measured.

According to one embodiment of the present invention, an automatic steering device applies a steering torque, in an automatic steering mode, to a steering shaft of a steering control mechanism which rotates a wheel of a vehicle. corresponding to the rotation of the steering shaft connected to a steering wheel. The automatic steering device includes a controller which calculates an automatic steering torque value and an assist torque setpoint value, and an actuator which is controlled by the controller to apply a torque corresponding to the sum of the torque value. of automatic steering and of the steering shaft assist torque setpoint. The controller calculates the assist torque setpoint by multiplying the assist torque gain by a steering torque applied by the driver of the vehicle from the steering wheel to the steering shaft. The controller adjusts the assist torque gain in the automatic steering mode to a value less than the assist torque gain in the non-automatic steering mode.

As the assist torque gain in the automatic steering mode becomes smaller than in the non-automatic (manual) steering mode, the steering torque generated by the steering control operation in the automatic steering control mode is increased to a certain value. This makes it possible to set the threshold value of the steering torque for the detection of the steering control operation to a relatively large value. Therefore, the steering torque can easily be distinguished from the steering wheel inertia torque. The steering control operation performed by the driver of the vehicle can be accurately determined based on the value

WHlRSCH6 \ PATENTS \ Brevets \ 19800 \ l9807.doc - September 9, 2002 - 2/13 measured steering torque and the automatic steering control operation can therefore be accurately switched to manual steering mode.

Although the steering torque in the automatic steering mode is increased to a certain amount, the steering control operation in the automatic mode can easily be performed in comparison with the case where no assist torque is generated. This makes it possible to suppress the abrupt reduction in the steering torque generated by the operation of engaging the automatic control towards the manual control by a steering control operation performed by the driver of the vehicle.

The actuator includes an electric motor that applies torque to the steering shaft. The controller controls the electric motor so that the torque applied to the steering shaft is the sum of the assist torque setpoint value and the automatic steering torque value.

The actuator may simply consist of the electric motor serving to supply the steering shaft with the automatic steering torque and the assist torque.

According to another embodiment of the invention, the controller detects a steering operation performed by the driver of the vehicle by determining whether the steering torque is greater than a threshold value and whether the steering torque is maintained at a greater value. at the threshold value for at least a predetermined time. At least one threshold value and at least one predetermined time are used to detect the steering operation performed by the driver of the vehicle. After detecting the steering operation performed by the driver of the vehicle, the controller stops the automatic steering mode and switches to the non-automatic steering mode.

In general, the invention relates to a steering device applying a steering torque according to one of a non-automatic steering mode and an automatic steering mode to a steering shaft of a steering mechanism which rotates a wheel of a vehicle corresponding to the rotation of the steering shaft connected to a steering wheel, the steering device generating an assistance torque added to the steering torque generated in the non-automatic steering mode, device in which the assistance torque in the automatic mode is made less than the assistance torque generated in the non-automatic mode .

Other aims, advantages and characteristics will appear on reading the description of an embodiment of the invention, given by way of non-limiting example and with reference to the appended drawing in which:

\\ HIRSCH6 \ PATENTS \ Patents \ 19800 \ 19807.doc - September 9, 2002 - 3/13

FIG. 1 is a schematic view of the structure of an automatic steering device according to one embodiment of the invention;

FIGS. 2A and 2B show timing diagrams showing a relationship between the steering angle and the steering torque compared with the moment of inertia;

Fig. 3 is a flowchart of a control routine or subroutine for determining the manual steering control operation; and

Figs. 4A to 4D show timing diagrams each showing the variation over time of the steering torque values ​​measured according to the embodiment of the invention compared to general types of automatic steering control apparatus.

Fig. 1 is a schematic view showing an automatic steering device according to a preferred embodiment of the invention and a steering control mechanism to which the automatic steering device is applied. The automatic steering device comprises an electric control unit (ECU) 10 for automatic control, an electric control unit (ECU) 12 for the EMPS (Electric Motor Steering Assistance), a steering torque sensorel4 and an EMPS actuator 20 (actuator) as a combination of an electric motor 16 and the gear wheels 18a, 18b.

The ECUs 10 and 12 constitute a controller 11 of the automatic steering device. A steering shaft 24 is provided with the steering torque sensorel4 which is directly connected to a steering wheel 22. The steering torque sensorel4 measures a steering torque applied by the steering wheel 22 to the steering shaft 24. The wheel gear 18a attached to steering shaft 24 meshes with gear wheel 18b attached to electric motor shaft 16.

The continuity of the steering shaft 24 is provided at a predetermined position by a universal joint or Cardan 26. One end of the steering shaft 24 is connected to a side rod 30 via a housing d. gears 28 such as a rack and pinion steering gear case.

The controller 11 calculates an actuation torque setpoint value and controls the actuator 20 so as to apply a torque equal to the actuation torque setpoint value to the steering shaft 24.

The actuating torque setpoint value corresponds to the sum of the assistance torque setpoint value and the automatic steering torque value. The assist torque setpoint is calculated by the ECU 12 based on the measured value of the steering torque measured by the steering torque sensor.

WHIRSCH6 \ PATENTS \ Patents \ 19800 \ 19807.doc - September 9, 2002 - 4/13

The value of the automatic steering torque is calculated by the ECU 10 and sent to the ECU 12 which calculates the set value of the actuating torque by adding the value of the automatic steering torque sent by the ECU 10 to the assist torque setpoint value.

Due to the fact that the value of the automatic steering torque is zero in the manual steering mode, that is to say the non-automatic mode, the setpoint value of the actuating torque becomes equal to the setpoint value of the torque d 'assistance. ECU 12 calculates the assist torque setpoint based on the steering torque value measurement by the steering torque sensorel4 in the non-automatic steering mode. The actuator 20 is thus controlled to generate the assistance torque corresponding to the reference value of the assistance torque. ECU 12 calculates the assist torque setpoint by multiplying the assist torque gain by the steering torque measurement value measured by the steering torque sensor 14.

In the automatic steering mode, the ECU 12 calculates the actuating torque setpoint by adding the assist torque setpoint to the steering torque value determined by the ECU 10. ECU UNIT 12 controls the actuator 20 to generate the torque corresponding to the set value of the actuating torque.

In the automatic steering mode, the measured value of the steering torque measured by the steering torque sensor 14 is kept equal to zero except at the start and end of the automatic steering operation until the driver of the vehicle performs a steering steering operation. Therefore, the setpoint value of the actuating torque becomes equal to the value of the automatic steering torque.

At the start and end of the automatic steering operation, the inertia torque is generated instantaneously in the direction opposite to that of the automatic steering force due to the inertia of the steering wheel 22. The steering torque sensorel4 can measure the moment of inertia as a parasite that interferes with the measurement of the steering torque.

FIG. 2A is a timing diagram of a steering angle and FIG. 2B is a timing diagram of a steering torque measurement value. In these figures, the steering operation in the automatic steering mode starts at a time t1 and ends at a time t2, that is, the steering operation in the automatic steering mode is performed between times tl and t2. During the time when the automatic steering operation is performed, the measured steering torque values ​​form a waveform pulse profile, indicating the inertia torque caused by the inertia of the flywheel 22.

\\ HlRSCH6 \ PATENTS \ BrevetsM9800 \ 19807.doc - September 9, 2002 - 5/13

The operation of the steering device as having the above structure will be described with reference to the diagram shown in Fig. 3.

In step S1, it is determined whether the vehicle is operating in the automatic steering mode. If the answer is YES, the vehicle is running in automatic steering mode, the process goes to step S2 where the assist torque gain is reduced by the ECU 12.

The assist torque gain in automatic steering mode is reduced to a lower value than in manual steering mode. Assuming that the assist torque gain in the manual steering mode is adjusted so that the ratio of the steering torque to the assist torque becomes 1:15, the value of the assist torque gain is adjusted to be reduced so that the ratio of the steering torque to the assist torque in the manual steering mode becomes 1: 3.

Then, in step S3, the ECU 10 calculates the value of the automatic steering torque. The process goes to step S4 where the steering torque is measured by the steering torque sensor 14. Based on the measured steering torque, the ECU 12 calculates the power assist torque setpoint value. 'steps.

In step S6, the assist torque setpoint calculated in step S5 is added to the automatic steering torque value calculated in step S3 and the actuator 20 is controlled to return the torque to the actuator 20 equal to the set value of the actuating torque.

If the answer NO is obtained in step S1, it means that the vehicle is not in automatic steering mode, the process goes directly to step S4.

The process proceeds to step S 7 where it is determined whether the vehicle is operating in the automatic steering mode. If the answer is YES, that is, the vehicle is operating in automatic steering mode, the process goes to step S8. In step S8, it is determined whether the vehicle is operating in the non-automatic steering mode (manual steering mode) based on the torque measurement value measured by the steering torque sensorel4. If the answer is NO in step S7, that is, the vehicle is operating in the non-automatic steering mode, the check routine ends.

Referring to Figs. 4A to 4D, the determination regarding the manual steering mode in step S8 of the check routine shown in Fig. 3 will be described. Figure 4A is a timing diagram of the steering angle. Each of Figs. 4B to 4C is a timing diagram of the steering torque detection value of the automatic steering device of the above-mentioned types and of the embodiment of the invention respectively. In these figures, the automatic steering operation starts at a time t1 and a signal indicating the steering operation.

WHlRSCH6 \ PATENTS \ Brevets \ 19800 \ l9807.doc - September 9, 2002 - 6/13 manual steering is received (the steering operation is performed by the driver of the vehicle) at time t2. At a time t3, the manual steering operation is no longer measured and, at a time t4, the automatic steering operation ends. The automatic steering operation according to the value of the automatic steering torque is carried out between the times t1 and t4. Between times t2 and t3, the steering torque is generated by the manual steering operation of the driver of the vehicle so as to prevent the steering angle from changing with respect to the automatic steering operation.

FIG. 4B shows a chronological modification of the measurement values ​​of the steering torque of an automatic steering device generally employed and which does not fulfill the function of assistance in the automatic steering mode. FIG. 4C shows a chronological modification of the measurement values ​​of the steering torque of another type of automatic steering device generally employed. In the automatic steering device of this case, the assist function is used in the automatic steering mode and the gain of the assist torque obtained is made equal to that of the non-automatic steering mode. FIG. 4D shows a chronological modification of the measurement values ​​of the steering torque of the steering device generally employed according to the embodiment of the invention.

In the case where the assistance is not performed during the steering operation of the driver of the vehicle in the automatic steering mode as shown in Fig. 4A, the steering torque in the direction opposite to that of the steering operation. direction (negative direction) as represented by T1 in Figure 4B, should be applied.

Meanwhile, in another type of automatic steering device providing assistance with an assist torque gain equal to that used in manual steering operation, a reduced steering torque is applied in the opposite direction ( negative) as represented by the value of the torque T2 in FIG. 4C. The steering angle can thus be maintained despite the automatic steering operation. In the case mentioned above, the difference between the torque values ​​T1 and T2 can be compensated by the assist torque . This type of automatic steering device enables the driver of the vehicle to easily perform steering operations in the automatic steering mode. However, since the steering torque is small, it is difficult to detect the steering operation in the manual mode based on the measurement values ​​of the steering torque sensor.

In the automatic steering device according to the invention, the gain of the assist torque during the automatic steering operation is controlled so as to be \\ HlRSCH6 \ PATENTS \ Patents \ l9800 \ I9807.doc - September 9, 2002 - 7 / 13 lower than that used during non-automatic steering operation. The steering torque measurement values ​​measured based on the steering operation in the automatic steering mode form a wavy curve with a certain amplitude and a certain width as shown by the torque value T3 in Fig. 4D. The wavy curve shown in Fig. 4D is clearly different from the wave pulse of the steering torque measurement values ​​due to the inertia torque. This makes it possible to detect the steering operation based on the width and amplitude of the wave by distinguishing the change in the steering torque measurement values ​​obtained due to the steering operation from the change in the values. for measuring the steering torque due to the moment of inertia.

The steering steering device according to the invention allows the driver of the vehicle to easily perform the power-assisted steering operation, even in automatic steering mode. The automatic steering device can further detect the automatic steering operation performed by the driver of the vehicle accurately.

As shown in Fig. 4A to 4D, the automatic steering operation is maintained even after the steering operation is terminated. In fact, when detecting the steering operation (manual steering operation) in the automatic steering mode, the automatic steering device is used to switch the steering mode to manual mode by stopping the automatic steering operation. . In fact, the steering device adjusts the value of the automatic steering torque when detecting the automatic steering operation.

In the general type of steering device not providing assistance during the automatic steering operation as shown in Fig. 4B, the steering torque reaction force may decrease very quickly when the automatic steering torque becomes zero due to a significant steering torque. The driver of the vehicle is thus subjected to an uncomfortable sensation at the time of the steering operation.

The automatic steering device according to the embodiment of the invention activates the assist function in the automatic steering operation so as to reduce the steering torque. This eliminates the sharp decrease in the reaction force relative to the steering torque generated when switching from steering mode to automatic steering mode to manual steering mode.

The steering operation is measured by determining whether the steering torque measurement value is greater than the threshold value and whether the time that the state where the steering torque measurement value is held during a hold reaction predetermined. At least one threshold value Th of the value of \\ HIRSCH6 \ PATENTS \ Patents \ 19800 \ 19807.doc - September 9, 2002 - 8/13 steering torque measurement can be combined with at least one predetermined holding time S.

Several threshold values ​​Th of the steering torque measurement values ​​can be combined with several holding times S. It is accepted that three kinds of threshold values ​​Th1, Th2, and Th3 are adjusted and three kinds of predetermined holding times SI, S2 and S3 are adjusted. It can be determined that the steering operation has been performed by the driver of the vehicle when the following conditions are met:

(1) the steering torque measurement value is greater than or equal to Thl which is maintained for a period greater than or equal to SI;

(2) the steering torque measurement value is greater than or equal to Th2, which is maintained for a period greater than or equal to S2; and the steering torque measurement value is greater than or equal to Th3, which is maintained for a period greater than or equal to S3.

With the conditions under which the steering operation performed by the driver of the vehicle is determined, the automatic steering mode can be terminated for a short time when the driver of the vehicle applies a large steering torque. When the driver of the vehicle applies a small steering torque, the automatic steering operation may be stopped after a short period of time has elapsed.

In this embodiment of the invention, a single actuator unit 20 is used, and is controlled such that the output torque becomes equal to the sum of the value of the assist torque and the value of the torque of automatic steering. However, the automatic steering device can be structured to have one actuator for automatic steering operation and another for assistance, separately. The output torque of the actuator for automatic steering is made equal to the torque value in the automatic steering mode and the output torque of the actuator for the assistance can be made equal to the set value of the steering torque. If each function of the actuators for applying the automatic steering torque and for applying the assist torque is combined into a simple function performed by a single electric motor, the structure of the automatic steering device can be further simplified.

The automatic steering device according to the invention controls the assistance gain to a value lower than that which is used during the non-automatic operation (manual operation). The steering torque is increased to a certain extent when the driver of the vehicle performs the steering operation. The steering torque can thus be clearly distinguished from the flywheel momentum.

WHIRSCH6 \ PATENTS \ Patents \ 19800 \ 19807.doc - September 9, 2002 - 9/13 ίο steering and it can be determined whether the steering operation has been performed on the basis of the steering torque measurement values. Therefore, the automatic steering operation can accurately switch to the manual steering mode based on the final results.

In the illustrated embodiment, the apparatus is controlled by the controller 11 (one or more electrical control units ECU which is implemented in the form of a general purpose programmed computer. It will be appreciated by those skilled in the art that the controller can be realized using a single special purpose integrated circuit (eg, an ASIC) having a main or central processor part for general control at the system level and parts. dedicated to performing various calculations, functions and other specific processes under the control of the central processor part. The controller 11 may consist of several dedicated separately or programmable integrated circuits or other electronic circuits or assemblies (for example hard-wired or logic electronic circuits such as discrete circuit elements or programmable logic devices such as PLDs, PLAs, etc. PAL or others). The controller 11 may be implemented using a suitably programmed general purpose computer, for example a microprocessor, microcontroller or other processor assembly (CPU or MPU), either alone or in combination with one or more data processors. and signals (eg integrated circuit). In general, any member or set of members having solid state circuits capable of performing the procedures described herein can be used as a controller 11. A distributed processing architecture can be used to achieve capacitance and speed. maximum data / signal processing.

Of course, the invention is not limited to the embodiments described and shown above, from which it is possible to provide other embodiments and other embodiments, without thereby departing from the scope of the invention.

WHIRSCH6 \ PATENTS \ Patents \ 19800 \ 19807.doc - September 9, 2002 - 10/13