JPH05155351A - Electromotive power steering device - Google Patents

Abstract

PURPOSE:To improve the operation feeling by providing a control means to correct the assist instruction value according to an inertia control signal and a inertia control signal, and to control the drive of an assisting motor. CONSTITUTION:A torque sensor signal process is applied so that a signal made by removing a vibration component from the output signal of a torque sensor 11 is used when an assist force is generated in case of steering a handle, while a signal including the vibration component to the output signal of the torque sensor 11 is used when a vibration owing to the rigidity of the torque sensor 11 is controlled. As a result, a phenomenon to generate a resonance owing to the rigidity of the torque sensor 11 between an assist motor 6 and a handle at both of the torque sensor is prevented, and by preventing the transmission of the resonance to the steering assist torque, a good steering feeling can be obtained, as well as a sufficient rigidity compensation can be given.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus suitable for use in a vehicle, and more particularly to a power steering apparatus which assists a steering force with a rotational output of a motor.

[0002]

2. Description of the Related Art In recent years, electric power steering systems using a motor instead of a hydraulic type have been used as a vehicle power steering device, and the motor has an increasing tendency in the future due to advantages such as small size and light weight as an actuator.

In the conventional power steering system, the torque sensor detects the steering torque of the steering system, the vehicle speed sensor detects the vehicle speed, and the drive of the motor connected to the steering system is controlled based on the detection results. , Power assist is done. Generally, it is a vehicle speed sensitive type, and the assist force is controlled according to the torque sensor input so that it is light in the low speed range and heavy in the high speed range.

[0004]

However, in such a conventional electric power steering apparatus,
When the positive feedback of acceleration that compensates the inertia moment of the assist motor is added by the compensation value created based on the rotational acceleration of the assist motor, if the acceleration positive feedback that sufficiently compensates the inertia of the assist motor is added, There is a problem in that the rigidity of the torque sensor provided between the motor drive unit and the motor drive unit adversely affects the assist motor and the steering wheel so that the assist motor and the handle resonate with each other across the torque sensor, resulting in instability.

Therefore, there is a drawback that the inertia of the assist motor cannot be sufficiently compensated when the rigidity of the torque sensor is low. Further, from such a situation, the steering wheel return time becomes short when the steering wheel is released, and the stability deteriorates, or the steering operation becomes too light and the operability deteriorates. Furthermore, since the resonance signal is transmitted to the assist command unit,
The operation feeling becomes poor.

Therefore, an object of the present invention is to provide an electric power steering apparatus capable of sufficiently compensating for the inertia of the assist motor even when the rigidity of the torque sensor portion is low and improving the operation feeling.

[0007]

In order to achieve the above object, an electric power steering apparatus according to the present invention detects an assist motor connected to a steering system to generate a steering assist torque and a steering torque of the steering system. Steering torque detecting means, steering angle detecting means for detecting the steering angle of the steering system,
Inertia control means for detecting a steering angular acceleration based on the output of the steering angle detection means, and generating an inertia control signal for compensating the inertia of the assist motor in accordance with the detected steering angular acceleration, and detected by the steering torque detection means. Viscosity control means for generating a viscosity control signal for controlling the viscosity of the steering torque detecting means in accordance with the differentiated steering torque, and resonance of the steering torque detected by the steering torque detecting means. And an assist command in response to the inertia control signal and the viscosity control signal, and an assist command means for setting an assist command value for driving the assist motor based on the output of the steering torque detecting means for removing the resonance component. Control means for correcting the value and controlling the drive of the assist motor.

Further, it is preferable that the assist commanding means removes the resonance component of the steering torque detected by the steering torque detecting means based on at least one of the running state and the driving state, for example, a low vehicle speed. Then, the damping rate of the resonance frequency component due to the rigidity of the steering torque detecting means is reduced, and at high vehicle speed, the damping rate is increased to remove the resonance frequency component.

[0009]

According to the present invention, the resonance frequency component due to the rigidity of the steering torque detecting means is removed according to the running state or the driving state, and the assist command value is created based on the output of the steering torque detecting means from which the resonance frequency component is removed. , The assist motor is driven. That is, when the assist force is generated, the signal obtained by removing the vibration component from the output signal of the steering torque detecting means is used, while when controlling the vibration due to the rigidity of the steering torque detecting means, the above-mentioned vibration is output to the steering torque detecting means. Signal processing is performed so that the signal containing the component is used. Therefore, the vibration due to the rigidity of the steering torque detecting means is reduced and the assist feeling is improved.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. 1 to 6 are views showing an embodiment of an electric power steering apparatus according to the present invention. FIG. 1 is a block diagram functionally showing the entire apparatus. FIG. 2 is a configuration diagram showing an example of a steering mechanical system to which the power steering device is applied.

First, the power steering mechanical system shown in FIG. 2 will be described. In FIG. 2, the rotational force of the steering wheel 1 is transmitted to the steering gear 2 including the pinion gear via the handle shaft, is transmitted to the rack shaft 3 by the pinion gear, and the wheels 4 are turned through the knuckle arm and the like. To be done. Further, the rotational force of the steering assist (auxiliary) motor (DC motor) 6 controlled and controlled by the control device 5 is transmitted to the rack shaft 3 by the meshing of the steering shaft 7 including the pinion gear and the rack shaft 3, and the steering wheel 1 is used. It will assist steering. The rotating shafts of the handle 1 and the motor 6 are mechanically connected by gears 2 and 7 and a rack shaft 3.

On the other hand, a steering torque sensor 11 (steering torque detecting means: see FIG. 1), which will be described later, detects a steering torque (return torque) Th, and a vehicle speed sensor 12 (see FIG. 1) detects a vehicle speed Vc. In addition, the steering angle P (steering angle detection means) 13 detects the steering angle P, and the current sensor 1
The armature current ia of the motor 6 is detected by 4. Then, the control device 5 controls the motor 6 based on the detected torque Th, the vehicle speed Vc, the steering angle P, and the armature current ia. The control device 5 and the motor 6 are supplied with operating power from a battery 8 mounted on the vehicle.

The control device 5 includes detectors such as a current detector and a voltage detector, a drive circuit for driving the motor 6, a computer (CPU, for example, a microprocessor) for controlling the overall control of the motor 6, a memory, and a computer. It is composed of an interface circuit with the input / output device.

Next, FIG. 1 is a block diagram showing various functions of a computer incorporated in the control device 5 for other input / output.
It is drawn together with blocks showing output devices and various circuits. In this figure, the assist command unit (assist command unit) 20 includes a detected torque Th of the torque sensor 11.
And the detected vehicle speed Vc of the vehicle speed sensor (vehicle speed detecting means) 12 are given.

The detected torque Th is given to the resonance signal removing section 28 in the assist command section 20, and the resonance signal removing section 28 removes the resonance frequency component due to the rigidity of the torque sensor from the detected torque Th. As the resonance signal removing unit 28, for example, a notch frequency filter or the like is used. Preferably,
It is desirable to change the low damping rate of the vibration component according to the running state and the driving state of the driver. For example, it is conceivable to detect the vehicle speed and reduce the damping rate at low vehicle speeds and increase the damping rate at high vehicle speeds so that the steering feel does not feel uncomfortable.

Therefore, the output of the vehicle speed sensor 12 is given to the damping rate function section 29, and the damping rate function section 29 detects the detected vehicle speed V.
Based on c, the resonance signal removing unit 28 outputs a command signal that decreases the damping rate at low vehicle speeds and increases the damping rate at high vehicle speeds.
Output to. The resonance signal removal unit 28 changes the low damping rate of the vibration component based on the command signal from the damping rate function unit 29 (that is, the damping rate is low at low vehicle speeds and high at high vehicle speeds). The output of the resonance signal removal unit 28 is given to the assist torque value instruction function unit 23.

The assist torque value instruction function unit 23 outputs a command value representing the assist torque to be generated by the motor 6 according to the detected torque Th. Further, the multiplication constant function unit 27 generates a constant according to the detected vehicle speed Vc, and this constant is multiplied in the multiplication calculation unit 25 by the assist torque command value. As a result, the assist torque value (or motor current command value) output from the multiplication calculator 25 becomes a value determined by the detected torque Th and the detected vehicle speed Vc, as shown in FIG.

In FIG. 3, according to the steering torque Th, a motor current almost proportional to the steering torque Th within a certain range flows (assist torque is generated), and beyond the above range, a certain constant value is obtained. The motor current (assist torque) is decreased when the vehicle speed Vc is high and the motor current (assist torque) is increased when the vehicle speed Vc is low, so that the motor current flows (the assist torque is generated). Thus, it indicates that an assist command for controlling the motor 6 is generated.

The assist torque value (or motor current command value) output from the multiplication calculator 25 is the assist command unit 2
The output of 0 (reference current command value) is supplied to the current control unit (control means) 30. In this case, the reference current command value includes the viscosity compensation value of the viscosity control unit 40 and the inertia control unit 5 which will be described later.
Inertia compensation value and torque sensor viscosity controller 60
After the torque-sensor viscosity compensation value of is added, it is given to the current controller 30 as a target current command value. The current control unit 30 may be entirely configured by a hardware circuit, or a part thereof may be implemented by computer software.

The current control section 30 is a PWM (Pulse) that follows the H-bridge drive method including, for example, four switching elements.
The motor 6 is driven and controlled by a chopper operation using a (Width Modulation) pulse, and current feedback control is performed. That is, the armature current sensor 14 detects the armature current ia of the motor 6, and the target current command value and the detected current ia given by the current deviation calculator 31 are detected.
The deviation from and is calculated. The absolute value of this deviation is obtained by the absolute value conversion unit 34, and the duty ratio of the PWM pulse is determined by the duty generation unit 35 based on this absolute value.

On the other hand, the polarity (positive or negative) of the deviation is discriminated by the positive / negative discriminating section 32, and the generated duty ratio and the discriminated polarity are given to the motor driving section 33, and the motor driving section 33 determines these values. Based on the above, the four switching elements wired in the H bridge type are controlled to be turned on / off to drive the motor 6.

The torque sensor viscosity control unit (viscosity control means) 60 is for compensating the viscosity of the portion where the torque sensor 11 is provided, and is likely to occur when inertia compensation by the inertia control unit 50, which will be described later, works. It suppresses the resonance between the assist torque 6 and the steering wheel 1 and stabilizes the system.
The detected torque Th of the torque sensor 11 is calculated by the differential value calculation unit 61.
Is differentiated by. The differential value ΔTh is converted into a torque / sensor part viscosity compensation value by being multiplied by a predetermined coefficient Kc in the torque / sensor part viscosity compensation value calculation part 62. This torque / sensor viscosity compensation value is added to the assist command value output from the assist command unit 20.

The coefficient Kc is preferably the vehicle speed Vc.
Is a value that changes according to. This coefficient Kc is, as shown in FIG. 4, an inertia compensation value calculation unit 5 of an inertia control unit 50 described later.
It changes in conjunction with the coefficient Ka used in 2 and has a proportional relationship with this. This coefficient Ka is, as shown in FIG.
It is a value that increases as c increases. Therefore, the coefficient Kc also increases as the vehicle speed Vc increases.

The viscosity control unit 40 basically produces a force for returning the steering angle to the neutral position, that is, a restoring force.
The detected steering angle P of the steering angle sensor 13 is given to the steering angular velocity detector 41 and differentiated to obtain the steering angular velocity v. The steering angular velocity v is given to the viscosity compensation value calculation unit 42, and the calculation unit 42 outputs, for example, a viscosity compensation value that produces a larger absolute value and reverse torque as the velocity v increases. This viscosity compensation value is added (actually subtracted) to the assist command value output from the assist command unit 20.

If necessary, the viscosity compensation value may be calculated in consideration of the vehicle speed Vc. For example, as the vehicle speed Vc is higher, a larger constant is multiplied to calculate the viscosity compensation value. By doing so, the output of the viscosity control unit 40 is the steering angular velocity v
Is larger, the output of the assist command unit 20 is further reduced. Further, the larger the vehicle speed Vc is, the larger the constant is multiplied and the larger the vehicle speed Vc becomes, and the larger the effect of viscous braking becomes. This suppresses the instability when returning to the vehicle, which tends to become unstable at higher vehicle speeds, and achieves a good steering feel. Further, at a low vehicle speed, the compensation that reduces the viscosity works, so that the viscous feeling of the steering wheel is reduced and a good steering wheel feeling is obtained. Needless to say, the viscosity control unit 40 may have another viscosity control function.

The inertia compensating section (inertia control means) 50 controls the motor 6 as if the rotor inertia of the motor 6 were reduced, and eliminates the weight caused by the fact that the motor 6 does not follow the rotation of the steering wheel during a sudden steering. It also acts to speed up the return speed when released.
The detected steering angle P of the steering angle sensor 13 is given to the steering angular acceleration detection unit 51, and the steering angular acceleration A is obtained by the second differentiation thereof. The steering angular acceleration A is given to the inertia compensation value calculation unit 52, and the inertia compensation value is calculated by being multiplied by the coefficient Ka described above. This inertia compensation value is the assist command unit 2
It is added to the assist command value of 0.

Preferably, the coefficient Ka is a value that changes according to the vehicle speed, as shown in FIG. Further, as the steering angular acceleration A, it is preferable to adopt a value after passing through the first-order lag element.

The steering angle sensor 13 and the steering angular velocity detection unit 4
An observer for estimating the steering angle, the steering angular velocity, and the steering angular acceleration may be provided instead of 1 and the steering angular acceleration detection unit 51. This observer selects one of the steering angle, the steering angular velocity, and the steering angular acceleration (rotational angular position of the motor, rotational speed, rotational acceleration) based on the voltage applied to the motor 6 and the armature current.
Estimate one, two or all.

FIG. 6 is a diagram showing an example of the output of the torque sensor 11 when the steering wheel 1 is steered. As is clear from this figure, an output signal corresponding to the twist of the handle shaft appears in the output of the torque sensor 11, and in addition to this, a resonance signal (vibration component) due to the resonance of the handle shaft is superimposed and added. ..

In this case, in this embodiment, the resonance frequency component due to the rigidity of the torque sensor 11 is removed by the resonance signal removing section 28 as described above, and the assist command value is obtained based on the output of the torque sensor 11 with the resonance frequency component removed. Is created and the assist motor 6 is driven. That is,
When the assist force is generated, a signal obtained by removing the vibration component from the output signal of the torque sensor 11 is used.
When controlling the vibration due to the rigidity of the torque sensor 11, the torque sensor signal processing is performed so that the output signal of the torque sensor 11 includes the above-mentioned vibration component.

Accordingly, the phenomenon that the assist motor 6 (lower part of the handle) and the handle 1 (corresponding to the upper part of the handle) cause resonance due to the rigidity of the torque sensor 11 while sandwiching the torque sensor 11 is prevented, and the resonance causes the steering assist torque. Therefore, sufficient rigidity compensation can be performed and at the same time a good steering feeling can be obtained.

In other words, vibration due to the rigidity of the torque sensor 11 can be reduced, and sufficient rigidity compensation can be performed. Moreover, since the resonance signal is not transmitted to the assist command value, the operation feeling can be improved. Further, since the vibration due to the rigidity of the torque sensor 11 can be reduced, the handle return time when the handle is released can be shortened, and the stability can be improved. Further, for the same reason, the handle operation becomes light and the operability is improved.

[0033]

According to the present invention, the vibration due to the rigidity of the steering torque detecting means can be reduced, and the rigidity can be sufficiently compensated. Moreover, since the resonance signal is not transmitted to the assist command value, the operation feeling can be improved. Further, since the vibration due to the rigidity of the steering torque detecting means can be reduced, the steering wheel return time when the steering wheel is released can be shortened, the stability can be improved, and the steering wheel operation becomes light and the operability can be improved. You can

[Brief description of drawings]

FIG. 1 is a functional block diagram of an embodiment of an electric power steering apparatus according to the present invention.

FIG. 2 is a diagram showing an example of a power steering mechanical system of the same embodiment.

FIG. 3 is a diagram showing characteristics of assist torque in the same example.

FIG. 4 is a graph showing that a coefficient Kc for calculating a torque sensor unit viscosity compensation value in the same embodiment is related to another coefficient Ka.

FIG. 5 is a coefficient K for calculating an inertia compensation value in the embodiment.
It is a graph which shows how a changes according to vehicle speed.

FIG. 6 is a graph showing output characteristics of the torque sensor of the example.

[Explanation of symbols]

 1 Steering Handle 6 Motor 11 Steering Torque Sensor (Steering Torque Detecting Means) 12 Vehicle Speed Sensor (Vehicle Speed Detecting Means) 20 Assist Command Unit (Assist Command Means) 28 Resonance Signal Removal Unit 29 Damping Factor Function Unit 30 Current Control Unit (Control Means) 40 Viscosity control unit 50 Inertia control unit (inertia control unit) 60 Torque sensor unit Viscosity control unit (Viscosity control unit)

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Claims (3)

[Claims] 1. An assist motor connected to a steering system for generating a steering assist torque, steering torque detecting means for detecting a steering torque of the steering system, steering angle detecting means for detecting a steering angle of the steering system, and steering. Inertia control means for detecting a steering angular acceleration based on the output of the angle detection means, and generating an inertia control signal for compensating the inertia of the assist motor in accordance with the detected steering angular acceleration; and the steering torque detection means. A viscosity control means for generating a differential value of the steering torque and generating a viscosity control signal for controlling the viscosity of the steering torque detecting means according to the differential value; and a resonance component of the steering torque detected by the steering torque detecting means. And an assist command value for driving the assist motor based on the output of the steering torque detecting means from which the resonance component is removed. Doo and command means, and corrects the assist command value in response to the inertia control signals and viscosity control signals, and control means for controlling the driving of the assist motor, an electric power steering apparatus characterized by comprising a. 2. The assist command means removes a resonance component of the steering torque detected by the steering torque detection means based on at least one of a running state and a driving state. Electric power steering device. 3. The assist command means reduces the attenuation rate of the resonance frequency component due to the rigidity of the steering torque detecting means at a low vehicle speed and increases the attenuation rate at a high vehicle speed to remove the resonance frequency component. The electric power steering device according to claim 2.