JPH09175414A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a smooth steering feeling by controlling a changeover in the regular and the reverse directions of a driving signal fed to an electric motor driving means, depending on a control signal, in the system controlling the electric motor driving means depending on the control signal by the deflection between an object current signal and an electric motor current signal. SOLUTION: In the system in which a current signal IMO corresponding to an electric motor current IM is fed back to an object current signal IMS depending on a steering torque signal TS, and the proportion and integration control of a deflection signal ▵I is carried out, a driving signal generating means 24 is provided. In this case, a PWM signal corresponding to a control signal IPI fed from a proportion and integration control means 23 is produced as a driving signal V0 , and fed to an electric motor driving means 16, and an electric motor voltage VM is given to an electric motor 10. Depending on a discriminating signal DO from a driving direction discriminating means 25, the PWM signal is switched in the rotating direction of the electric motor 10 corresponding to the direction to operate a steering auxiliary force, and it is fed to the driving means 16 as the driving signal VO.

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 in which the power of an electric motor is directly applied to a steering system as a steering assist force to reduce a driver's steering force. The present invention relates to an electric power steering device that can obtain a smooth and stable steering feeling even when performing the following.

[0002]

2. Description of the Related Art In a conventional electric power steering apparatus, a steering torque generated by operating a steering wheel is detected by a steering torque sensor, and the detected steering torque signal is converted into a target current signal for driving an electric motor. The difference signal between the signal and the motor current signal corresponding to the motor current actually flowing through the motor is represented by PI (proportional / integral) or PID.
A control signal is generated by performing (proportional / integral / differential) control calculations, and a drive signal (for example, a PWM signal) generated based on the control signal drives the electric motor to apply a steering assist force to the steering system. Such is known.

In such a conventional electric power steering apparatus, since the motor current signal is fed back (negative feedback) to the target current signal to perform PI control or PID control, control is performed so that the deviation signal quickly becomes zero. Then, the motor is driven so that the motor current converges on the value set by the target current signal, and a steering assist force corresponding to the steering torque signal is obtained.

FIG. 6 shows a block diagram of a main part of a conventional electric power steering apparatus. FIG. 6 shows the control system as P
An example in which I control is performed will be described. 6, the electric power steering device 50 includes a steering torque sensor 12, a control unit 51, a motor driving unit 16, a motor current detecting unit 18,
It is composed of an electric motor 10.

The control means 51 is composed of various arithmetic means, comparison / processing means, signal generation means, memory, etc. based on a microprocessor, or is an analog signal processor or arithmetic unit mainly composed of an operational amplifier. The system includes a target current setting unit 52, a deviation calculation unit 53, a proportional / integral control unit 54, a drive signal generation unit 55, and a steering direction determination unit 56.

The steering torque sensor 12 detects a steering torque generated in response to a driver's steering operation as an analog electric signal, and supplies the analog electric signal to the target current setting means 52 as a steering torque signal T _{S in} both left and right directions.

The target current setting means 52 is constituted by a memory such as a ROM, and has a steering torque (T
It reads the target current signal I _MS from characteristic table of the target current (I _MS) corresponding to the steering torque signal T _S for _S) configured to provide to the deviation computing means 53.

The deviation calculating means 53 outputs the target current signal I
_MS and is detected by a motor current detecting means 18, a deviation between the motor current signal I _MO corresponding to the motor current I _M (= I _MS -
I _MO ) to generate a deviation signal ΔI and provide it to the proportional / integral control means 54.

The proportional / integral control means 54 outputs the deviation signal ΔI
A proportional sensitivity K _P multiplying the proportional element and the deviation signal ΔI (= I _MS
−I _MO ) is connected in parallel with an integral element that performs integral control with an integral gain K _I , performs a proportional / integral operation on the deviation signal ΔI to generate a control signal I _PI , provide.

[0010] Incidentally, by setting a large value for the proportional sensitivity K _P and the integral gain K _I, the motor current signal I
_MO (corresponding to the motor current I _M )
_{The MS} can converge (deviation signal ΔI = 0).

The drive signal generating means 55 includes a PWM (pulse width modulation) signal generating means and a switching means, and includes a control signal I _PI
The magnitude PWM signal corresponding to the Is is supplied to the motor drive unit 16 as a drive signal V _O, the motor 10 is driven by the motor voltage V _M to be supplied from the motor driving means 16.

The drive signal generating means 55 generates a motor 1 corresponding to a direction in which a steering assist force is applied, based on the steering direction determination signal _SD supplied from the steering direction determination means 56.
0, the PWM signal is switched to the rotational drive direction, and the drive signal V
_It is provided to the motor drive means 16 as _O.

[0013] electric motor 10 is driven forward and reverse rotation via the motor driving unit 16 by the drive signal V _O is the motor current I _M flows, the motor current detector 18 detects this motor current I _M, the motor current The motor current signal I _MO corresponding to I _M is fed back to the deviation calculating means 53.

The steering direction discriminating means 56 has a comparator, generates a steering torque discriminating signal _SD based on the steering torque signal T _S supplied from the steering torque sensor 12, and supplies it to the drive signal generating means 55.

The steering direction discriminating means 56 compares the value of the steering torque signal T _S with a predetermined reference value, and when the value of the steering torque signal T _S exceeds the reference value, the steering direction of the steering wheel is changed to the right. It is determined that the steering torque is due to the steering, and if the torque is below the reference value, it is determined that the steering is to the left and a steering direction determination signal _SD is generated.

As described above, the conventional electric power steering apparatus 50 converts the motor current signal I _M corresponding to the motor current I _M to the target current signal I _MS based on the steering torque signal T _S.
The motor is fed back (negative feedback) to perform proportional / integral control on the deviation signal ΔI, and the rotational drive direction of the electric motor 10 is switched according to the operation of the left and right steering wheels, so that the electric motor current signal _IMO is quickly changed. target current signal I _MS motor power corresponding to the steering torque is converged to obtain, it is possible to act the desired steering assist force good responsiveness to the steering system.

[0017]

In [Problems that the Invention is to Solve conventional electric power steering apparatus 50, for determination of the rotational driving direction of the motor 10 in the motor control system is performed based on the polarity of the steering torque signal T _S, the handle Utatehebi When a quick return from the vehicle is performed, the control signal I _{PI in the} steered direction is
Drive signal V _O is the motor 10 which has been driven directly crosscut direction of the drive signal V _O, and the to the steering direction based on the
Is driven in the direction opposite to the steering direction (turning direction).

In the motor control system after the quick switching, the smoothness of the steering assist force obtained from the motor 10 is remarkably deteriorated due to the discontinuous control operation, and the steering feeling of the steering wheel is distracted or sensed. And a problem that magnetostrictive noise is generated from the electric motor 10.

FIG. 7 is an explanatory diagram of the operation of the control means for the steering torque signal (T _S ) of the conventional electric power steering apparatus. FIG. 7A shows a change in the control amount of the control signal _IPI or the drive signal V _O with respect to the steering torque signal T _S when the steering wheel is turned to the left in a short time from turning to the right. I have. FIG. 7B shows changes in the proportional term (P) and the integral term (I) of the proportional / integral control means 54.

The steering torque signal T since the motor current signal I _MO is fed back to the target current signal I _MS supplied from the target current setting unit 52 in accordance with the _S, handle Kirikaesa is the steering torque signal T _S Is inverted from right to left and the direction of the target current signal _IMS is also inverted from right to left, and if the drive signal V _O is delayed due to a delay element such as an integral term of the proportional / integral control means 54, it will be abrupt. The reversal of the rotation driving direction occurs.

When the steering wheel is turned back, the steering torque signal T
_{When S} changes from the right direction to the left direction (motor drive direction switching point), the drive signal V _O according to the control amount A _R in the steering direction (right) is the control amount A _{L in the} turning direction (left). the driving signal V _O corresponding to.

As shown in FIG. 3A, the drive signal V _O changes discontinuously due to the quick turning steering from the turning of the steering wheel, and the electric motor 10 is forced to make a rapid switching of the rotational driving direction and a rapid rising. Therefore, the smoothness of the steering assist force acting on the steering system is significantly deteriorated.

Switching of the rotational driving direction of the electric motor 10 is performed as follows.
The steering direction is determined by a steering direction determination signal _SD generated by the steering direction determination means 56 based on the polarity of the steering torque signal T _S ,
The delay of the drive signal V _O with respect to the point of time when the rotational drive direction is switched is not limited to the delay due to the delay element of the control calculation such as the integral term of the proportional / integral control means 54, or when the control means 51 is constructed based on a microprocessor Even if there is no delay element in the control calculation with only the proportional term as the calculation, for example, if the target current setting means 52 has a delay in signal processing, the drive signal V _O will be delayed.

In order to suppress the discontinuity of the electric motor control due to the timing mismatch between the switching operation of the rotational driving direction of the electric motor 10 and the operation of the electric motor control system, the hysteresis of the steering torque sensor 12 and other electric motor control systems are used. There is a problem that the control for correcting the influences of various steering force transmission elements in the interior and adjusting the timing is required, and the number of control processes increases and the computer capacity must be increased.

The present invention has been made to solve such a problem, and an object of the present invention is to continuously and smoothly switch the rotational driving direction of the motor while ensuring the continuity of the motor control operation. It is an object of the present invention to provide an electric power steering device that generates a steering assist force and can obtain a smooth and stable steering feeling even when a quick turn from a steering wheel is turned.

[0026]

In order to solve the above-mentioned problems, an electric power steering apparatus according to the present invention has a control means for switching the forward / reverse rotation direction of a drive signal supplied to an electric motor drive means. It is characterized by comprising a drive direction discriminating means for controlling on the basis of.

The control means is provided with drive direction discriminating means for controlling switching between forward and reverse rotation directions of the drive signal supplied to the electric motor drive means based on the value of the control signal, and the electric motor is driven through the electric motor drive means. Since the drive signal can be switched according to the value of the control signal to control the switching of the rotational drive direction of the electric motor, the rotational drive direction of the electric motor can be smoothly switched while ensuring continuity of the motor control operation.

[0028]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the present invention, the switching of the rotational driving direction of the motor is performed based on a control signal supplied from the proportional / integral control means, and continuity of the motor control operation is ensured so that a smooth steering assist force can be obtained even when the motor is switched. To be obtained.

FIG. 1 is an overall configuration diagram of an electric power steering apparatus according to the present invention. In FIG. 1, an electric power steering apparatus 1 includes a universal joint 3 on a steering shaft 2 provided integrally with a steering wheel 17.
a manual steering force generating means 6 which is connected to a pinion 5a of a rack & pinion mechanism 5 provided in a steering gear box 4 via a connecting shaft 3 provided with a and a 3b.

The rack shaft 7 is provided with rack teeth 7a meshing with the pinion 5a, and reciprocates by these meshing.
The left and right front wheels 9 as steering wheels are connected to both ends thereof via tie rods 8.

Thus, the steering wheel 1
At the time of steering, the front wheels 9 are rolled by manual steering via a normal rack and pinion type manual steering force generating means 6 to change the direction of the vehicle.

In order to reduce the steering force by the manual steering force generating means 6, a motor 10 for supplying a steering assist force is arranged coaxially with the rack shaft 7, and a ball screw mechanism 11 provided coaxially with the rack shaft 7. Converted to thrust through the rack shaft 7
(Ball screw shaft 11a).

A steering torque sensor 12 for detecting the direction and magnitude of a driver's manual steering torque is disposed in the steering gear box 4.
Provides the control means 15 with a steering torque signal T _S of an analog electric signal corresponding to the detected steering torque.

The control means 15 is composed of various arithmetic means, comparison / processing means, signal generation means, memory and the like based on a microprocessor, or is composed of various analog signal processors and arithmetic units mainly composed of operational amplifiers. Then, the drive signal V _O corresponding to the steering torque signal T _S (for example, the ON signal and P
A hybrid signal of the WM signal is generated to drive and control the motor driving means 16.

The control means 15 is a control operation means for performing control operations such as proportional, integral, and derivative, a drive direction judgment means for generating a judgment signal based on a control signal supplied from the control operation means, and the electric motor 10. Drive signal generating means for controlling the driving of the steering wheel, the left and right driving directions are determined based on a change in the control signal accompanying the steering of the steering wheel, and the driving signal V _O for controlling the rotating direction and the driving force of the electric motor 10 is transmitted to the electric motor driving means 16. provide.

The motor drive unit 16, for example constituted by a bridge circuit composed of switching elements of four power FET (field effect transistor), driving the electric motor 10 outputs a motor voltage V _M based on the driving signal V _O I do.

The motor current detector 18 detects the motor current I _M actually flowing through the electric motor 10, to the feedback (negative feedback) the motor current I _M motor current signal I _MO control means 15 corresponding to.

FIG. 2 is a block diagram of a main part of the electric power steering apparatus according to the present invention. In FIG.
The control unit 15 includes a target current setting unit 21, a deviation calculation unit 22, a proportional / integral control unit 23, a drive signal generation unit 24, and a drive direction determination unit 25. For convenience of explanation, the control unit 15 is shown as being constituted by various analog signal processors and arithmetic units mainly composed of operational amplifiers.

Target current setting means 21, deviation calculating means 22
The proportional / integral control means 23 and the target current setting means 52, the deviation calculating means 53 and the proportional / integral control means 23 shown in FIG. 6, respectively.
Since the configuration and operation are the same as those of the integral control means 54, the description thereof will be omitted. The control calculation performed by the proportional / integral control means 23 is not limited to PI (proportional / integral).
The control operation may be only (proportional) control operation or PID (proportional / integral / derivative) control operation.

The drive signal generating unit 24 based on the control signal I _PI supplied from the proportional-integral control unit 23 generates and electric motor driving a PWM signal corresponding to the magnitude of the control signal I _PI as a drive signal V _O Means 16 and the motor 10
It is driven by the motor voltage V _M to be supplied from the motor driving means 16.

Further, the drive signal generating means 24, based on the determination signal D _O supplied from the drive direction discrimination means 25, switching the PWM signal to the rotational drive direction of the motor 10 which corresponds to the direction that applies a steering assist force, It is provided to the motor drive means 16 as a drive signal V _O.

FIG. 3 is a block diagram of the essential parts of the drive signal generating means and drive direction determining means according to the present invention. In FIG. 3, the drive signal generating means 24 includes a converting means 24a.
, A triangular wave generating unit 24b, and a switching unit 24c, and the conversion unit 24a and the triangular wave generating unit 24b are configured to generate a PWM (pulse width modulation) signal corresponding to the magnitude of the control signal _IPI . The switching means 24c is configured to switch the PWM signal.

The conversion means 24a is a proportional / integral control means 2
A control signal I _PI supplied from 3, the triangle wave generating means 24
b based on the triangular wave oscillation signal S _R supplied from
A control signal I _PWM is generated and provided to the switching means 24c.

The conversion means 24a includes a signal comparison functions such as a comparator, a triangular wave oscillation signal S _R is a triangular wave of a predetermined frequency by comparing the magnitude of the control signal I _PI to the reference, large as the pulse of the control signal I _PI The width is long and the control signal I _PI
PWM control signal I whose pulse width changes according to the magnitude of
Generate _PWM .

The triangular wave oscillating means 24b includes, for example, an oscillating circuit for oscillating a rectangular wave and an integrating circuit for integrating the rectangular wave, and generates a triangular wave having a predetermined frequency (for example, about 20 KHz) and a constant amplitude. providing the converting means 24a as triangular wave oscillation signal S _R.

The switching means 24c has a switch function of software control. For example, a switch is configured to turn off at L level and turn on at H level, and the right direction discrimination signal D _OR supplied from the driving direction discrimination unit 25 is provided. In the case of the H level, a predetermined switch is turned on, and the PWM control signal I _PWM supplied from the conversion means 24a is output as the right drive signal V _OR ,
On the other hand, when the left direction discrimination signal D _OL is at the H level, a predetermined switch is turned on, and the PWM control signal I _PWM is output as the left drive signal V _OL .

Note that the right drive signal V _OR and the left drive signal V
_OL is determined so that the steering direction of the steering wheel and the direction of action of the steering assist force by the electric motor 10 correspond to each other. For example, the right drive signal _VOR drives the electric motor 10 in a forward rotation when the steering wheel is steered to the right. Then, the steering assist force is applied, and the left drive signal _VOL is configured to apply the steering assist force by driving the electric motor 10 in reverse rotation when the steering wheel is steered to the left.

The right drive signal V _OR and the left drive signal V
_{The OL} is supplied to the electric motor drive means 16 as a drive signal V _O ,
The drive control of the motor 10 in forward and reverse rotations is performed via the motor drive means 16.

The drive direction discriminating means 25 generates a discrimination signal D _O based on the control signal I _PI supplied from the proportional / integral control means 23 and supplies it to the drive signal generating means 24. In FIG. 3, the driving direction determining unit 25 includes a right direction determining unit 25a and a left direction determining unit 25b having a signal comparison function such as a comparator.

Right direction determining means 25a and left direction determining means 2
Equivalently constitute the 5b, right direction discrimination means 25a is, for example, when the value of the control signal I _PI exceeds a preset reference value for comparison, it is determined that the right driven by the control signal I _PI An H level, if lower, an L level right direction discrimination signal _DOR is output.

The left direction determining means 25b is, for example,
When the value of the control signal _IPI is lower than a preset comparison reference value, the control signal _IPI determines that the driving is the left direction, and when the value exceeds the L level, the L level left discrimination signal _DOL is determined. Output.

[0052] Control signal comparison reference value serving as a reference for determining the value of I _PI, the direction determination unit 25a, with 25b are provided dead zone between them so as not to output a determination signal D _O of the H level at the same time, the comparison reference value Hysteresis is provided.

The right direction discrimination signal D _OR and the left direction discrimination signal D _OL are respectively supplied to the switching means 24c provided in the drive signal generating means 24, and control the switching function provided in the switching means 24c. For example, the right direction discrimination signal D _OR
Is at the H level (the left direction discrimination signal D _OL is at the L level).
Turns on the switch so as to output the PWM control signal I _PWM as the right drive signal V _OR .

FIG. 4 is a circuit diagram and a waveform diagram of the drive direction determining means of the electric power steering apparatus according to the present invention. In FIG. 4A, a right direction discriminating unit 25a and a left direction discriminating unit 25b include a comparator and a resistor to constitute a voltage comparison circuit having a hysteresis characteristic.

The right direction determining means 25a is provided with a constant voltage power supply E _1.
The comparison reference voltage I _REF to the voltage produced by two series resistors divided, and supplied to the negative input terminal of the comparator COMP1, to be compared via a connection to the input resistance of the feedback resistor and the input resistor to the positive input terminal A control signal _IPI , which is a signal, is supplied, and a feedback resistor and an input resistor constitute a hysteresis circuit.

[0056] FIG. 4 (b) is a waveform diagram of the right judgment signal D _OR explaining the operation of the right direction discrimination means 25a. The right direction determining means 25a compares the control signal I _PI with the comparison reference voltage I _REF.
If the control signal _IPI exceeds the comparison reference voltage _IREF , an H level right direction determination signal _DOR is output.

[0057] When the control signal I _PI exceeds the value of _RH I increased from a small value below the value of _RH I, right direction discriminating signal D _OR
Changes from the L level to the H level, and the control signal I _PI
When the value decreases from a large value exceeding the value of I _RH and falls below the value of I _RL , the right direction discrimination signal D _OR changes from H level to L level. Incidentally, I _RL, the value of _RH I is set to a value greater than comparison reference voltage I _REF, the value between I _RL and I _RH is hysteresis width.

[0058] The control signal I _PI left discrimination means 25b is the comparison signal, is supplied to the minus input terminal of the comparator COMP2, the positive input terminal of two series resistors divide the voltage of the constant voltage source E ₁ Generated reference voltage I
_REF is supplied, and a hysteresis circuit is formed by the feedback resistor and the parallel resistance of the two divided resistors.

[0059] Figure 4 (c) is a waveform diagram of the left-direction discrimination signal D _OL for explaining the operation of the left direction discrimination means 25b. The left direction discriminating means 25b receives the comparison reference voltage I _REF and the control signal I _PI
Comparing the door, the control signal I _PI is the case below the comparison reference voltage I _REF outputs the leftward determination signal D _{O L} of H level.

The operation of the left direction discriminating means 25b is the reverse operation of the right direction discriminating means 25a described above, and a description thereof will be omitted. The value of I _LL, I _LH is set to a value lower than the comparison reference voltage I _REF, the value between I _LL and I _LH is hysteresis width.

FIG. 5 is an explanatory diagram of the operation of the control means for the steering torque signal (T _S ) of the electric power steering apparatus according to the present invention. The operation of the control means in response to the steering torque signal T _S when the steering wheel is turned from the right to the left in a short time is represented by the control signal _IPI .

In FIG. 5, the rotational drive direction of the motor 10 is switched not at the time when the steering torque signal T _S switches from right to left but at the time when the value of the control signal I _PI switches ( (Motor drive direction switching point).

The control signal _IPI or the drive signal V _O changes smoothly and continuously in the direction in which the motor 10 is driven in reverse even if the steering wheel is rapidly turned from the turning of the steering wheel, so that the continuity of the control operation of the motor control system is improved. The motor 10 is held, and the motor 10 is smoothly rotated in the turning direction without requiring a rapid rise from a sudden reversal.

As described above, the electric power steering apparatus 1 according to the present invention allows the control means 15 to switch the forward / reverse rotation of the drive signal V _O supplied to the motor drive means 16 to the value of the control signal I _PI . Driving direction discriminating means 25 for controlling the motor 1 based on the electric motor 1
Since 0 can be a switched according to the value of the driving signal V _O control signal I _PI for driving for switching control of the rotational driving direction of the motor 10, the rotation of the motor 10 while ensuring the continuity of the motor control operation The driving direction can be switched smoothly.

Although the control means 15 includes the proportional / integral control means 23 and employs the PI (proportional / integral / derivative) control operation, the same applies to the PID (proportional / integral / derivative) control operation. Function and effect can be obtained.

Further, even when the control calculation is constituted only by P (proportional) control and the control system does not include a delay element, for example,
When the control means 15 is basically composed of a microprocessor, it is unavoidable that a delay in the signal processing occurs in the target current setting means 21 and the like, causing a delay in the drive signal V _O. The same operation and effect as those obtained by the above can be obtained.

[0067]

As described above, in the electric power steering apparatus according to the present invention, the control means controls the switching between the forward and reverse rotation directions of the drive signal supplied to the motor drive means based on the value of the control signal. A driving direction discriminating means for controlling the rotation direction of the motor by switching a driving signal for driving the motor via the motor driving means in accordance with the value of the control signal. The rotation direction of the motor can be switched smoothly while ensuring the smoothness of the motor, so even if a quick turn from the steering wheel is performed, the motor generates a continuous and smooth steering assist force and provides smooth and stable steering. It is possible to provide an electric power steering device that provides a feeling.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an electric power steering device according to the present invention.

FIG. 2 is a block diagram of a main part of an electric power steering apparatus according to the present invention.

FIG. 3 is a block diagram of a main part of a drive signal generation unit and a drive direction determination unit of the electric power steering device according to the present invention.

FIG. 4 is a circuit diagram and a waveform diagram of a driving direction determining unit of the electric power steering device according to the present invention.

FIG. 5 is an explanatory diagram of the operation of the control means for the steering torque signal (T _S ) of the electric power steering apparatus according to the present invention.

FIG. 6 is a block diagram of a main part of a conventional electric power steering device.

FIG. 7 is an operation explanatory diagram of a control means for a steering torque signal (T _S ) of the conventional electric power steering device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electric power steering device, 2 ... Steering shaft, 3 ... Connection shaft, 3a, 3b ... Universal joint, 4 ... Steering gear box, 5 ... Rack & pinion mechanism, 5
a: pinion, 6: manual steering force generating means, 7: rack shaft, 7a: rack teeth, 8: tie rods, 9: left and right front wheels, 10: electric motor, 11: ball screw mechanism, 11a: ball screw shaft, 11b ... Driven helical gear, 12 steering torque sensor, 15 control means, 16 motor drive means, 17 steering wheel, 18 motor current detection means, 21 target current setting means, 22 deviation calculation means, 23 ... Proportional / integral control means 24 drive signal generating means 24a converting means 24b triangular wave generating means 24
c: switching means, 25: driving direction discriminating means, 25a: right direction discriminating means, 25b: left direction discriminating means, A _R , _AL : control amount, D _O : discrimination signal, D _OL : left direction discrimination signal, D _OR : right direction discrimination signal, E ₁ : constant voltage power supply, I _M : motor current, I
_MO : motor current signal, I _MS : target current signal, I _PI : control signal, I _PWM : PWM control signal, I _REF : comparison reference voltage,
S _D : steering direction determination signal, S _R : triangular wave oscillation signal, T _S :
Steering torque signal, V _M ... motor voltage, V _O ... drive signal, V
_OL : Left drive signal, V _OR : Right drive signal, ΔI (= I _MS −I
_MO ): Deviation signal.

Claims (1)

[Claims] 1. A motor for driving a steering system to apply left and right steering assist force by forward / reverse rotation driving by a motor driving means having a switching element forming a bridge circuit, and a steering torque for detecting a steering torque of the steering system. A target current signal for driving the electric motor is generated from the steering torque signal from the sensor, and a control calculation is performed based on the deviation between the target current signal and the electric motor current signal from the electric motor current detection means for detecting the current flowing in the electric motor. And a control means for generating a control signal, switching the drive signal composed of a mixed signal of the pulse width modulation signal and the ON signal generated based on the control signal to the forward / reverse rotation direction and providing the motor drive means, In the electric power steering apparatus having the above-mentioned, the control means controls the forward / reverse rotation direction of a drive signal supplied to the electric motor drive means. An electric power steering apparatus characterized by comprising driving direction discrimination means for controlling on the basis of switching the control signal.