JP2010058571A - Control device for electric power steering - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an electric power steering giving suitable steering feeling according to the operation state of a vehicle behavior control device to a driver. <P>SOLUTION: Since determination of step S1 becomes No when an operation switch of VSA is turned OFF by a driver or when VSA is not operated by defect, EPS-ECU 21 makes a second gain G2 to 0 at step S2. Thereby, in the steering assist control, a value of a second steering reaction force base value Tab2 becomes 0 and a steering reaction force target value Trt is calculated only based on a first steering reaction force base value Tab1. Namely, even if behavior of the vehicle body is disturbed by non-operation of VSA and a yaw rate becomes large, relatively small steering reaction force according to a steering angle is given and the driver can perform driving according to the behavior of the vehicle and the road surface state. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for an electric power steering mounted on a four-wheel vehicle or the like, and relates to a technique for giving a driver a suitable steering feeling according to the operating state of a vehicle behavior control device.

  In an automobile, it is necessary to transmit a vehicle behavior and a road surface state to a driver as a steering reaction force in order to enable appropriate driving (steering and acceleration / deceleration). In the case of an automobile equipped with electric power steering (hereinafter referred to as EPS), the steering reaction force is set and steered based on various control parameters (steering wheel steering angle, yaw rate, vehicle speed, etc.). This is caused by reducing the assist torque in the direction. When the difference between the standard yaw rate calculated based on the vehicle speed and the steering angle and the actual yaw rate input from the yaw rate sensor exceeds a predetermined value, it is determined that the yaw rate sensor is broken and the steering reaction force control is stopped. The technique to do is known (refer patent document 1).

  On the other hand, in recent four-wheeled vehicles, ABS (Anti-lock Breaking System) that prevents the wheels from locking during braking, TCS (Traction Control System) that prevents the wheels from slipping during acceleration, as well as these during turning A vehicle behavior control device (Vehicle Stability Assist system: hereinafter referred to as VSA) to which a side slip suppression function or the like is added is adopted in part (see Patent Document 2). If a side slip occurs due to understeer or oversteer during turning, the vehicle deviates from a travel locus intended by the driver (hereinafter referred to as a target course). Therefore, the VSA returns the vehicle to the target course by, for example, braking one of the left and right wheels with an independent braking device at the stage of determining the deviation from the target course.

JP 2003-291842 A JP 2003-165431 A

  In a vehicle equipped with a VSA, if the driver turns off the VSA operation switch or the VSA stops operating due to failure, it is inevitable that the yaw rate will increase due to the disturbance of the vehicle body behavior. When the yaw rate increases, understeer, oversteer and the like due to tire slip occur, and the standard yaw rate and the actual yaw rate are likely to deviate. In such a situation, it is difficult to determine the failure of the yaw rate sensor described above, and appropriate steering reaction force control cannot be executed. Therefore, the conventional control device has stopped the steering reaction force control. However, when the steering reaction force disappears completely, it becomes difficult for the driver to recognize vehicle behavior and road surface information, which is not preferable from the viewpoint of steering stability and steering feeling.

  The present invention has been made in view of the above situation, and an object of the present invention is to provide an electric power steering control device that gives the driver an appropriate steering feeling according to the operating state of the vehicle behavior control device.

  A first invention is a control device provided in a vehicle on which an electric power steering and a vehicle behavior control device are mounted, and used for controlling the electric power steering, wherein at least a steering angle and a yaw rate are used as control parameters. And a steering reaction force setting means for setting a steering reaction force applied to the steering wheel, and an operation level detection means for detecting or determining an operation level of the vehicle behavior control device, wherein the steering reaction force setting means includes the vehicle When the operation level of the behavior control device is less than or equal to a predetermined value, the steering reaction force is set larger than 0 and smaller than when the operation level is larger than a predetermined value.

  According to a second aspect of the present invention, in the electric power steering control device according to the first aspect of the invention, the steering reaction force setting means sets the weight of the steering angle from the weight of the yaw rate when setting the steering reaction force. Is also made larger.

  According to a third aspect of the present invention, in the electric power steering control device according to the first aspect, the steering reaction force setting means sets the weight of the steering angle to the weight of the yaw rate as the vehicle speed of the vehicle increases. It is characterized by making it larger.

  According to the first invention, even when the operation level of the vehicle behavior control device is lowered, the driver can perform driving according to the vehicle behavior and the road surface condition by receiving a certain amount of steering reaction force. It becomes. Further, according to the second invention, even if the yaw rate is increased due to the disturbance of the vehicle body behavior, an excessive steering reaction force is not generated and the steering feeling is improved. Further, according to the third aspect of the present invention, even in a high vehicle speed region where the change in the yaw rate is large and the change in the steering angle is small, an excessive steering reaction force is not generated by increasing the weight of the steering angle. A feeling improves.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an electric power steering apparatus according to the embodiment, and FIG. 2 is a block diagram illustrating a schematic configuration of the EPS-ECU according to the embodiment.

<Electric power steering device>
As shown in FIG. 1, the electric power steering apparatus 1 includes a pinion 4 connected to a steering wheel 2 via a steering shaft 3 and a rack 5 that meshes with the pinion 4 and reciprocates in the vehicle width direction. Equipped with an and pinion mechanism. Both ends of the rack 5 are connected to the knuckle arms 8 on the left and right front wheels 7 via the tie rods 6, and the left and right front wheels 7 are steered according to the rotation operation of the steering wheel 2. A steering assist mechanism 9 including a motor, a gear, and the like is coaxially mounted on the rack 5, and the driver's steering force is reduced by the assist torque generated by the steering assist mechanism 9.

  The steering shaft 3 is provided with a steering angle sensor 11 for detecting the steering angle of the steering wheel 2, and a steering torque sensor 12 for detecting steering torque is provided in the vicinity of the pinion 4. A vehicle speed sensor 13 for detecting the vehicle speed, a yaw rate sensor 14 for detecting the actual yaw rate of the vehicle body, and a VSA-ECU 15 for controlling the VSA (not shown) are provided at appropriate positions of the vehicle body. The steering assist mechanism 9 is provided with a resolver 16 that detects a motor rotation angle.

  Output signals of these sensors 11 to 14 and 16 and the VSA-ECU 15 are input to a steering control device (EPS-ECU) 21. The EPS-ECU 21 controls the electric power steering apparatus 1 in an integrated manner, and includes a microcomputer, ROM, RAM, peripheral circuits, input / output interfaces, various drivers, and the like, and performs target control based on the output signals described above. The amount (target current) is determined and output to the drive circuit 22 of the steering assist mechanism 9. The drive circuit 22 is configured by an FET bridge or the like, and supplies power to the steering assist mechanism 9 based on the target control amount determined by the EPS-ECU 21, thereby controlling the assist torque to the rack 5 by the steering assist mechanism 9. Is done.

<EPS-ECU>
As shown in FIG. 2, the EPS-ECU 21 includes a steering direction determination unit 31, an angular velocity calculation unit 32, an assist torque setting unit 33, a damper compensation unit 34, a steering reaction force setting unit 35, and a target current setting. The part 36 is furnished.

  The steering direction determination unit 31 determines whether the steering direction is away from the neutral position or returns to the neutral position based on the output signals of the steering angle sensor 11 and the steering torque sensor 12, and the determination result is used as the assist torque setting unit 33. Output to. Further, the angular velocity calculation unit 32 calculates the angular velocity of the steering assist mechanism 9 based on the output signal of the resolver 16 and outputs the angular velocity signal to the damper compensation unit 34. The damper compensation unit 34 sets the attenuation correction value of the steering assist mechanism 9 based on the output signals of the steering angle sensor 11, the yaw rate sensor 14, and the angular velocity calculation unit 32, and outputs this to the assist torque setting unit 33.

  The assist torque setting unit 33 sets an assist torque target value based on input signals from the steering direction determination unit 31, the damper compensation unit 34, and the like in addition to the steering angle sensor 11 and the steering torque sensor 12, and sets the target target current value. To the unit 36.

  The steering reaction force setting unit 35 sets a steering reaction force target value based on the output signals of the angular velocity calculation unit 32 in addition to the output signals of the steering angle sensor 11, the steering torque sensor 12, the vehicle speed sensor 13, and the yaw rate sensor 14, Is output to the target current setting unit 36.

  The target current setting unit 36 sets a target current based on the assist torque target value input from the assist torque setting unit 33 and the target steering reaction force input from the steering reaction force setting unit 35, and outputs this to the drive circuit 22. To do.

<< Operation of Embodiment >>
When the automobile starts traveling, the EPS-ECU 21 repeatedly executes steering assist control at a predetermined control interval (for example, 10 ms). At this time, the EPS-ECU 21 calculates the assist torque target value Tat based on various driving information, and also calculates the steering reaction force target value Trt according to the following procedure. That is, the EPS-ECU 21 calculates the first steering reaction force base value Trb1 using a value obtained by multiplying the steering angle by the predetermined first gain G1, while calculating a value obtained by multiplying the yaw rate by the predetermined second gain G2. The second steering reaction force base value Trb2 is calculated, and the steering reaction force target value Trt is calculated by adding the two steering reaction force base values Trb1 and Trb2. After completing the calculation of the assist torque target value Tat and the steering reaction force target value Trt, the EPS-ECU 21 sets the target current It based on these.

<VSA adaptive control>
The EPS-ECU 21 repeatedly executes the VSA adaptive control whose procedure is shown in the flowchart of FIG. 3 at a predetermined control interval (for example, 10 ms) in parallel with the steering assist control described above. When the VSA adaptive control is started, the EPS-ECU 21 determines whether or not the VSA is in an operating state in step S1 of FIG. 3 based on an input signal from the VSA-ECU 15, and if this determination is Yes, no processing is performed. Return to the start without doing.

  If the driver turns off the operation switch of the VSA or the VSA does not operate due to a failure, the determination in step S1 is No. Therefore, the EPS-ECU 21 sets the second gain G2 to 0 in step S2. Thereby, in the steering assist control, the value of the second steering reaction force base value Tab2 becomes 0, and the steering reaction force target value Trt is calculated based only on the first steering reaction force base value Tab1. In other words, even if the vehicle behavior is disturbed due to the VSA not operating and the yaw rate is increased, a steering reaction force corresponding to the steering angle is applied although it is small, and the driver performs driving according to the vehicle behavior and the road surface condition. Is possible.

  Although description of specific embodiment is finished above, the aspect of the present invention is not limited to the above embodiment. For example, in the above-described embodiment, the second gain G2 (that is, the yaw rate weight) is set to 0 when the VSA is not operated, but is set to a sufficiently small value with respect to the first gain G1 (that is, the steering angle weight). It may be. Further, in the above embodiment, the weight of the yaw rate in the steering reaction force control is changed by the operation / non-operation of the VSA (in the embodiment, 0 is set to the non-operation of the VSA), but the operation level of the VSA is predetermined. When the value falls below the threshold, the yaw rate weight may be reduced, or the yaw rate weight may be gradually reduced according to the VSA operating level. In addition, the specific configuration of the electric power steering device and the EPS-ECU, the specific procedure of the control, and the like can be changed as appropriate without departing from the gist of the present invention.

1 is a schematic configuration diagram of an electric power steering apparatus according to an embodiment. It is a block diagram which shows schematic structure of EPS-ECU21 which concerns on embodiment. It is a flowchart which shows the procedure of the VSA adaptive control which concerns on embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric power steering apparatus 2 Steering wheel 7 Front wheel 9 Steering assist mechanism 11 Steering angle sensor 12 Steering torque sensor 13 Vehicle speed sensor 21 EPS-ECU (electric power steering control apparatus)
33 Assist torque setting unit 35 Steering reaction force setting unit 36 Target current setting unit

Claims (3)

A control device provided in a vehicle on which an electric power steering and a vehicle behavior control device are mounted and used for controlling the electric power steering,
Steering reaction force setting means for setting a steering reaction force applied to the steering wheel using at least the steering angle and the yaw rate as control parameters;
An operation level detection means for detecting or determining an operation level of the vehicle behavior control device,
The steering reaction force setting means sets the steering reaction force larger than 0 when the operation level of the vehicle behavior control device is less than or equal to a predetermined value and smaller than when the operation level is larger than a predetermined value. A control device for electric power steering.   2. The control device for an electric power steering according to claim 1, wherein the steering reaction force setting means sets the weight of the steering angle to be larger than the weight of the yaw rate when setting the steering reaction force. .   2. The electric power steering control device according to claim 1, wherein the steering reaction force setting unit increases the weight of the steering angle with respect to the weight of the yaw rate as the vehicle speed of the vehicle increases. .

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