JP2903176B2 - Control device for electric power steering device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control device for an electric power steering device.

2. Description of the Related Art A torque sensor for detecting a steering torque at the time of a steering operation is provided to reduce steering operation at the time of a steering operation, thereby converting the steering torque into an assist direction motor current command value. In an electric power steering device in which the output of an electric motor is variably controlled in accordance with a change in a motor current command value and power assist is performed in accordance with a steering torque, a return direction for returning to a straight traveling direction according to a turning angle. By controlling the motor current command value with an addition signal obtained by adding the motor current command value to the assist direction motor current command value, the electric motor is configured to cancel the resistance to the movement in the steering wheel return direction due to the inertia force of the electric motor and the friction of the speed reducer. Conventionally, various types of power steering devices have been developed and have already been disclosed, for example, in Japanese Patent Application Laid-Open No. 61-98670.

Also, in order to improve the kinematic performance of the vehicle body with respect to steering during steering operation, the rear wheels are configured to be able to rotate around the kingpin similarly to the front wheels, and the rear wheels are steered in conjunction with the steering of the front wheels. Various front and rear wheel steering devices have been developed in the past, and have been already disclosed in, for example, Japanese Patent Application Laid-Open No. 61-146681.

Problems to be Solved by the Invention The output of the electric motor is variably controlled based on the addition signal of the assist direction motor current command value and the return direction motor current command value as described above to reduce the steering force and the return force of the front wheels. In the case of an automobile equipped with an electric power steering device to be measured, when a front and rear wheel steering mechanism for turning the rear wheel in conjunction with the steering of the front wheel is further provided in order to further improve the exercise performance, the front and rear wheel steering mechanism is provided. Therefore, there is a problem that the resilience of the rudder changes depending on whether the direction of the turning angle of the rear wheel is in phase or opposite to the turning angle of the front wheel.

The present invention seeks to address such a problem.

Means for Solving the Problems The present invention returns the assist direction motor current command value of an assist command unit that issues an assist direction motor current command value according to the torsional torque of the steering shaft, and returns to the straight ahead direction according to the front wheel steering angle. An electric power steering apparatus for reducing a front wheel steering force by performing power assist control by an electric motor based on an addition signal of a restoring force command unit for issuing a predetermined returning motor current command value in the direction to the returning motor current command value. And a means for detecting a turning angle of the rear wheel in an automobile equipped with a rear wheel turning operating device for turning the rear wheel by actuation of a rear wheel steering actuator, and a returning direction issued by a restoring force command unit. The first feature is that a restoring force correction control unit that performs correction control based on the detected turning angle of the rear wheel based on the detected motor current command value is provided. A rear wheel state determination unit that determines the steering direction and the steering angle ratio of the front and rear wheels, and becomes 1 when the front and rear wheel steering angle ratio is 0, and becomes gradually smaller than 1 as the front and rear wheel steering angle ratio in the same phase direction increases. A multiplication coefficient setting unit for generating a correction multiplier that gradually increases from 1 as the front-rear wheel steering angle ratio in the opposite phase increases, and a return direction motor for generating the correction multiplier generated by the multiplication coefficient setting unit by the restoring force command unit A second feature is that the multiplication unit is configured to multiply the current command value.

Function As described above, when the rear wheel is steered in the opposite phase to the front wheel in order to improve small turning performance, the return direction motor current command value is increased to prevent deterioration of the rudder resilience, and steering stability is improved. When the rear wheels are steered in the same phase direction as the front wheels in order to improve the steering performance, the return motor current command value is reduced to prevent the steering from being excessively restored.

Embodiments The present invention will be described below with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 denotes an assist command unit. The assist command unit 1 detects a torsional torque of a steering shaft and outputs a torsional torque signal proportional to the torsional torque. And an output torque value indicating function unit 12 for issuing an assist direction motor current command value based on a function preset by the torsional torque signal.

Reference numeral 2 denotes a restoring force commanding unit. The restoring force commanding unit 2 detects a steering angle of a front wheel accompanying steering of a steering wheel, and issues a front wheel steering angle signal proportional to the steering angle of the front wheel. It comprises an angle sensor 21 and a return torque value indicating function unit 22 for issuing a return direction motor current command value based on a function preset by a front wheel steering angle signal of the front wheel steering angle sensor 21.

Reference numeral 3 denotes a restoring force correction control unit.
Is a rear wheel steering sensor 4 that detects a steering angle of a rear wheel steered by a rear wheel steering operating device (not shown) and generates a rear wheel steering angle signal proportional to the steering angle of the rear wheel. The steering angle ratio of the front and rear wheels is obtained from the angle signal and the front wheel steering angle signal of the front wheel steering angle sensor 21, and a positive sign is attached if the steering directions of the front and rear wheels are in phase, and a negative sign if the steering directions are opposite. A rear wheel state determination unit 31 that issues a front and rear wheel steering angle ratio signal with a sign attached thereto, and 1 when the front and rear wheel steering angle ratio signal of the rear wheel state determination unit 31 is 0, the positive value is large. , A multiplication coefficient setting unit 32 that generates a correction multiplier that gradually increases from 1 as the negative value increases, and increases as the negative value increases, and sets the correction multiplier of the multiplication coefficient setting unit 32 in the returning direction of the restoring force command unit 2. And a multiplication operation unit 33 for multiplying the motor current command value to generate a return direction motor current correction value.

5 is a motor current control unit, and the motor current control unit 5
The assist direction motor current command value of the assist command section 1 and the return direction motor current correction value of the restoring force correction control section 3 are added to obtain an assist torque command value, and the rotation direction of the motor 6 and the motor are determined based on the assist torque command value. The motor 6 is driven to rotate by controlling the current, and the assist torque according to the assist torque command value is applied to the steering system.

In the above description, the restoring force correction control unit 3 increases the value from 1 when the rear wheel steering operating device is operated and the rear wheel is steered in a direction opposite to that of the front wheel in order to improve small turning performance at low speed running. A large correction multiplier is issued, and the return motor current correction value is larger than the return motor current command value applied when the rear wheel is not steered, so that the rear wheel is steered in the opposite phase to the front wheel. The deterioration of the resilience of the rudder due to the operation can be completely prevented.

Conversely, when the rear wheel steering operating device is operated and the rear wheels are steered in the same phase as the front wheels in order to improve the steering stability during high-speed running, the restoring force correction control unit 3 sets 1 A smaller correction multiplier is issued, and the return direction motor current command value is smaller than the return direction motor current command value applied when the rear wheel is not steered, so that the rear wheel is steered in the same phase as the front wheel. It is possible to prevent the resilience of the rudder from becoming excessive due to the operation.

The rear wheel steering angle signal generated by the rear wheel steering angle sensor is used not only for controlling the rear wheel turning operation device but also for controlling the electric power steering device. Thus, fault detection can be performed twice.

Effect of the Invention As described above, according to the present invention, the assist direction motor current command value of the assist command unit that issues the assist direction motor current command value according to the torsional torque of the steering shaft, and the straight ahead direction according to the front wheel steering angle An electric power for reducing front wheel steering force by performing power assist control by an electric motor with a signal added to the return direction motor current command value of a restoring force command section that issues a predetermined direction return motor current command value in the direction to return to A rear wheel state determination unit that determines a steering direction and a steering angle ratio of front and rear wheels in an automobile including a steering device and a rear wheel steering operation device that steers rear wheels by operating a rear wheel steering actuator. When the front and rear wheel steering angle ratio is 0, it becomes 1 and becomes gradually smaller than 1 as the front and rear wheel steering angle ratio in the same phase direction increases, and becomes larger as the front and rear wheel steering angle ratio in the opposite phase direction increases. A multiplication coefficient setting unit for generating a correction multiplier that is gradually larger than 1, and a multiplication calculation unit for multiplying the return motor current command value generated by the restoring force command unit by the correction multiplier generated by the multiplication coefficient setting unit. By providing the restoring force correction control unit, when turning the rear wheel in the opposite phase to the front wheel in order to improve the small turning performance, the return direction motor current command value is increased to reduce the rudder resilience. When turning the rear wheels in the same phase as the front wheels to prevent and improve steering stability, not only can the return direction motor current command value be reduced to prevent excessive rudder resilience, Since the wheel steering angle sensor is used in both the electric power steering device and the rear wheel steering operating device, it can be double-checked by a failure detection unit which is usually provided independently in both devices. It is those that can lead to practical use on a great deal of effect I cooperation with the.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing a correction multiplier characteristic with respect to a front and rear wheel steering angle ratio. DESCRIPTION OF SYMBOLS 1 ... Assist command part, 2 ... restoring force command part, 3 ... restoring force correction control part, 31 ... rear wheel state determination part, 32 ... multiplication coefficient setting part
33: multiplication operation unit, 4: rear wheel steering angle sensor, 5: motor current control unit, 6: motor.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B62D 5/04

Claims (2)

(57) [Claims] An assist command section for issuing an assist direction motor current command value in accordance with a torsional torque of a steering shaft, and an assist command motor current command value for returning to a straight-forward direction in accordance with a front wheel steering angle. An electric power steering device that performs power assist control using an electric motor to reduce front wheel steering force with an addition signal of the restoring force command unit that generates a direction motor current command value and the return direction motor current command value; A vehicle equipped with a rear-wheel steering operating device that steers the rear wheel by actuation of the actuator, having means for detecting at least the steering angle of the rear wheel,
A control device for an electric power steering device, further comprising a restoring force correction control unit that performs correction control of a returning direction motor current command value generated by the restoring force command unit based on at least the detected steering angle of the rear wheel. And a rear wheel state determining unit for determining a steering direction and a steering angle ratio of the front and rear wheels. A multiplication coefficient setting unit that issues a correction multiplier that becomes 1 as the front and rear wheel steering angle ratio in the in-phase direction increases and becomes gradually smaller than 1 as the front and rear wheel steering angle ratio in the opposite phase direction increases. And a multiplying operation unit for multiplying a return direction motor current command value issued by the restoring force command unit by a correction multiplier issued by the multiplication coefficient setting unit.