JPH11208492A - Control method for electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent steep change in the steering torque in the event of failure in an abnormal vehicle behavior sensing means in an arrangement where a control to suppress abnormal behavior is conducted by an electric power steering device. SOLUTION: When abnormality in vehicle behavior is sensed by a vehicle behavior sensing means to sense the behavior of a vehicle, a steering reaction force is generated so as to suppress the abnormality in behavior by a motor which is to generate an assist force for driving the steering vehicle wheel in compliance with the turning angle of a steering wheel. In this electric power steering device, the steering reaction force is decreased gradually in case any failure in the vehicle behavior sensing means is detected. This leaves the component of assist force to allow suppressing a steep change in the steering torque, and it is possible to suppress change in the feeling in the steering operation before and after occurrence of failure as much as practicable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for an electric power steering apparatus which generates an auxiliary reaction torque by an electric motor so as to suppress an abnormality in vehicle behavior when an abnormality in vehicle behavior is detected. It is.

[0002]

2. Description of the Related Art Conventionally, various techniques have been applied to improve the running performance of a vehicle. For example, the steering force of a driver when steering to steer a steered wheel is reduced to improve the steering performance. There is an electric power steering device that generates an auxiliary steering torque by an electric motor, but also detects abnormal vehicle behavior when external disturbance such as crosswind or rut travel is applied, and suppresses the abnormal vehicle behavior In some cases, an auxiliary reaction torque is generated by an electric motor. FIG. 3 shows an example of such an electric power steering apparatus.

[0003] The device shown in FIG. 3 includes a pinion 4 connected to a steering shaft 2 integrally connected to a steering wheel 1 via a connecting shaft 3 having a universal joint, and meshes with the pinion 4 to reciprocate in the vehicle width direction. The rack and pinion mechanism comprises a rack shaft 8 having both ends connected to knuckle arms 7 of left and right front wheels 6 as steered wheels via tie rods 5 while being movable. Further, an electric motor 9 is coaxially arranged at an intermediate portion of the rack shaft 8 so as to generate an auxiliary steering torque for reducing a manual steering force via the rack and pinion.

Further, a steering torque sensor 11 for detecting a steering torque acting on the pinion 4, a steering wheel angular velocity sensor 12 for detecting a rotational angular speed of the steering wheel 1 by a rack and pinion mechanism, and A vehicle speed sensor 13 for outputting a vehicle speed signal corresponding to the traveling speed, and a control unit 14 for controlling the assisting force of the electric motor 9 based on these detected values are provided.

[0005] Further, the vehicle acceleration abnormality detected by the lateral acceleration sensor 15 and the yaw rate sensor 16 when an external disturbance such as a cross wind or a rut is applied is detected by an electric power steering. It is generated by the device.

FIG. 4 shows a control block diagram of such an electric power steering apparatus. As shown in FIG.
The control unit 14 includes an auxiliary steering torque determining means 19 to which detection signals of steering torque, vehicle speed, and steering wheel angular speed are input, and an auxiliary steering torque determining means 19 to which detection signals of vehicle speed, steering wheel angular speed, lateral angular speed, yaw rate, and steering wheel angle are input. Adder 21 for adding output signals of force torque determining means 20, auxiliary steering torque determining means 19 and auxiliary reaction torque determining means 20
And a target current determining means 22 to which the result of the adder 21 is input, and a driving circuit 18 based on the target current signal calculated by the target current determining means 22 and considering a feedback current signal from the driving circuit 18. Output current control means 23 for calculating an output current to be controlled is provided. An abnormality in the behavior of the vehicle can be determined from each of the detection signal values, and when it is determined that the behavior is abnormal, an auxiliary reaction torque is generated by the electric motor 9 to perform control for suppressing the abnormality in the behavior of the vehicle. It can be carried out.

Next, an example of control based on the control block of FIG. 4 will be described below with reference to a control flow chart of FIG.
In FIG. 5, in an eleventh step ST11, the yaw rate sensor failure flag FY is set (= 1) or not (=
0), and if normal (FY = 0), a twelfth step ST1 in which assist control of normal auxiliary steering torque is performed.
The control of the second to fifteenth steps ST15 is performed.

In the twelfth step ST12, an assist component is calculated, in the next thirteenth step ST13, an active steering reaction (ARS) component is calculated, and in the next fourteenth step ST14, the above components are added to obtain an assist torque. calculate. Then, in a fifteenth step ST15, a target motor current is determined based on the assist torque, and an active steering reaction force control by the electric power steering device is performed according to the target motor current in a control routine (not shown).

In this conventional control system, for example, when it is detected that the yaw rate sensor has failed, a yaw rate sensor failure flag FY is set, and if it is determined in the eleventh step ST11, the assist control and the active steering reaction force are determined. Without performing the control, the 16th step ST16
Proceed to. In the sixteenth step ST16, a warning lamp is turned on to notify the driver of the failure.

[0010]

However, in the above-described fault processing control, for example, if the fault occurs during cornering, the assist control and the active steering reaction force control are not performed. This causes a sudden change in the driver's response, which causes a problem of discomfort.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problem, the steering torque suddenly changes when a failure occurs in the vehicle behavior abnormality detecting means in a case where the electric power steering device performs control for suppressing the vehicle behavior abnormality. In order to realize the prevention, in the present invention, an electric motor for generating an assist force when driving the steered wheels according to the steering wheel steering torque, and a vehicle behavior detecting means for detecting the behavior of the vehicle, A control method for an electric power steering device, comprising: generating an auxiliary reaction torque by the electric motor so as to suppress the abnormality of the vehicle behavior when the abnormality of the vehicle behavior is detected by the vehicle behavior detection means. Detecting the failure of the vehicle behavior detection means, and gradually reducing the auxiliary reaction force torque when the failure is detected. It was assumed to have a process.

In this way, when the vehicle behavior detecting means breaks down, control is performed to gradually reduce only the auxiliary reaction force torque related to the vehicle behavior detecting means, so that a steering reaction force is generated. Since the assist force for assisting the normal steering force can be generated even if the control is not performed, the control can be shifted to the control using only the component of the assist force.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to specific examples shown in the accompanying drawings.

FIG. 1 is a flowchart showing control to which the present invention is applied. In FIG. 1, a first step ST1 to a fifth step ST5 are the same as the control in the eleventh step ST11 to the fifteenth step ST15 shown in the conventional example. The vehicle behavior detecting means will also be described using a yaw rate sensor. However, any means used for detecting vehicle behavior may be used.
Judgment can also be made based on sensors and the results obtained by combining them.

As shown in FIG. 1, a first step ST
In step 1, it is determined whether or not the yaw rate sensor failure flag FY is set. If it is normal (FY = 0), the assist component is calculated in the second step ST2, and the third step ST2 is performed.
The active steering reaction force (AR
S) A component is calculated, and the above components are added in a fourth step ST4 to calculate an assist torque.
At 5, the target motor current is determined based on the assist torque. Then, in a control routine (not shown), active steering reaction force control by the electric power steering device is performed according to the target motor current.

If the yaw rate sensor fails, a yaw rate failure flag FY is set (FY =
1) In that case, the process proceeds from the first step ST1 to the sixth step ST6. In the sixth step ST6, the value of the assist component in the control cycle immediately before the failure (previous time) is read.

In the next seventh step ST7, the previous A
Assuming that the RS component value is 100%, the ARS component is reduced at the timing of the control cycle until it becomes 0% based on a counter provided in the control flow. That is, the counter decreases every time the control cycle passes, and the ARS component ratio that decreases based on the counter is obtained for each control cycle as shown by the solid line in the component ratio of FIG. The value is multiplied to calculate the ARS component value in the control cycle.

In the next eighth step ST8, similarly to the eighteenth step ST18 of the conventional example, a warning lamp is turned on to notify the driver of the failure, and the process proceeds to a fourth step ST4. In the fourth step ST4, since the assist torque is calculated by adding the components as described above, for example, the ARS obtained by multiplying the assist component which may be maintained at the value immediately before the failure by the component ratio is obtained. The ARS component is reduced for each control cycle as described above, and the assist torque calculated in the fourth step ST4 is represented by an imaginary line in the component ratio of FIG. As shown, it decreases with decreasing ARS component.

As described above, every time the control cycle proceeds, the ARS (auxiliary reaction torque) component, which is one of the components added to calculate the assist torque, fades out. Does not change suddenly. Then, when the ARS component ratio becomes 0%, the fade-out processing ends, and the control shifts to the fault response control in which the control is performed with the ARS component set to 0 (see FIG. 2).

[0020]

As described above, according to the present invention, when the vehicle behavior detecting means fails, only the auxiliary reaction torque for suppressing the abnormal vehicle behavior is gradually reduced to leave the component of the assist force. Therefore, it is possible to suppress a sudden change in the steering torque and suppress a change in the feeling of the steering operation before and after the occurrence of the failure as much as possible.

[Brief description of the drawings]

FIG. 1 is a flowchart showing control to which the present invention is applied.

FIG. 2 is a diagram showing a change in control based on the present invention.

FIG. 3 is a diagram showing a schematic configuration of a conventional electric power steering device.

FIG. 4 is a diagram showing a conventional control block.

FIG. 5 is a flowchart showing conventional control.

[Explanation of symbols]

 Reference Signs List 1 handle 2 steering shaft 3 connecting shaft 4 pinion 5 tie rod 6 front wheel 7 knuckle arm 8 rack shaft 9 electric motor 11 steering torque sensor 12 handle angular velocity sensor 13 vehicle speed sensor 14 control unit 15 lateral acceleration sensor 16 yaw rate sensor 18 drive circuit 19 auxiliary steering torque Determining means 20 auxiliary reaction torque determining means 21 adder 22 target current determining means 23 output current controlling means

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B62D 137: 00 (72) Inventor Kazushige Sumatama 1-4-1 Chuo, Wako-shi, Saitama Pref. 72) Inventor Hiroyuki Kawagoe 1-4-1, Chuo, Wako-shi, Saitama Pref.Honda R & D Co., Ltd. (72) Inventor Tatsuya Nishikawa 1-4-1, Chuo, Wako-shi, Saitama Pref.Honda R & D Co., Ltd.

Claims (1)

[Claims] 1. An electric motor for generating an assist force for driving a steered wheel in accordance with a steering torque of a steering wheel, and a vehicle behavior detecting means for detecting a behavior of the vehicle. In a control method of an electric power steering device, wherein an auxiliary reaction torque is generated by the electric motor so as to suppress the abnormality of the vehicle behavior when the abnormality of the behavior is detected, a failure of the vehicle behavior detection means is detected. And a step of gradually reducing the auxiliary reaction torque when the failure is detected.