JPH0976926A - Motor-driven power steering gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor-driven power steering gear capable of giving a stable steering feeling even if the set condition of a steering wheel is changed over to the high speed steering of the steering handle. SOLUTION: A control means is provided with a limit means 30 consisting of a symbol reversal detecting means 31, rotational speed comparing means 32, integration value comparing means 33, logic product calculating means 34, level holding means 35, limit factor generating means 36 and limit stop controlling means 37.

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 system for reducing the steering force of a driver by causing the power of an electric motor to act on a steering system as a steering assist force, and more particularly, the driver steers the steering wheel fast to steer the steering system. The present invention relates to an electric power steering apparatus that improves a reduction in steering feeling due to a response delay in control of a steering system when switching back from the vehicle.

[0002]

2. Description of the Related Art In a conventional electric power steering apparatus, a steering torque sensor detects a steering torque generated by a driver's operation of a steering wheel, and the detected steering torque signal is converted into a target current signal for driving a motor. A signal obtained by performing PI (proportional / integral) or PID (proportional / integral / differential) control on the deviation signal between the current signal and the motor current signal corresponding to the motor current actually flowing in the motor is generated, and based on this signal It is known that a generated electric motor control signal (for example, a PWM signal) is used to drive an electric motor to apply a steering assist force to a steering system.

In such a conventional electric power steering apparatus, the deviation signal is quickly controlled to zero because the electric current signal is fed back (negatively fed back) to the target current signal for PI control or PID control. , The electric motor current converges to a value set by the target current signal to drive the electric motor, and a steering assist force corresponding to the steering torque signal is obtained.

FIG. 7 shows a block diagram of a main part of a conventional electric power steering apparatus. In addition, in FIG.
An example in which I (proportional / integral) control is performed will be shown. In FIG. 7, the electric power steering device 50 includes a steering torque sensor 12, a vehicle speed sensor 14, a control unit 51, an electric motor drive unit 16, an electric motor current detection unit 18, and an electric motor 10.

The control means 51 is basically composed of a microprocessor and comprises various calculation means, comparison / processing means, memory, etc., a target current setting means 52, a deviation calculation means 53, a proportional
The integration control means 54 and the control signal generation means 55 are provided.

The steering torque sensor 12 detects the steering torque generated in response to the driver's operation of the steering wheel as an analog electric signal, and the steering torque signal T _S is supplied to the target current setting means 52. The vehicle speed sensor 14 detects an electric pulse signal having a frequency corresponding to the vehicle speed, and the vehicle speed signal V _S is supplied to the target current setting means 52.

The target current setting means 52 converts the steering torque signal T _S supplied from the steering torque sensor 12 into a digital steering torque signal T _D , and this steering torque signal T _D
And based on the vehicle speed signal V _S supplied from the vehicle speed sensor 14 is converted to the target current signal I _MS which is set in advance, the vehicle speed _{V S (V L, V M} , V H) steering torque signal T and the a parameter configured to output the target current signal I _MS to the deviation computing means 53 for _D.

[0008] steering torque signal and vehicle speed as a parameter in FIG. 8 (T _D) - showing the target current signal (I _MS) characteristic diagram (the table 1). 8, the vehicle speed V _L, V _M and V _H are the low vehicle speed region respectively, show the middle vehicle speed range and the high vehicle speed region, even in the steering torque signal T _D is the same, increases the vehicle speed V _S is (V _L → It is preset such that the target current signal _IMS decreases as V _M → V _H ).

As described above, the target current setting means 52 sets the target current signal I to the electric motor 10 in the low vehicle speed region (V _S = V _L ).
It is configured so that a sufficiently large steering assist force can be obtained by driving with a large electric motor current I _M corresponding to _MS , while in the high vehicle speed region (V _S = V _H ) the electric motor 10 is small corresponding to the target current signal I _MS. It is configured to be driven by the electric motor current I _M to suppress the steering assist force and to obtain steering stability.

The deviation calculating means 53 is provided with a target current signal I
And _{the MS,} and it is detected by the motor current detecting means 18, to correspond to the motor current I _M to calculate the deviation (= I _MS -I _MO) with the motor current signal I _MO converted into a digital signal, proportional deviation signal ΔI Provided to the integral control means 54.

The proportional / integral control means 54 has a deviation signal ΔI.
A proportional sensitivity K _P multiplying a proportional element, the deviation signal [Delta] I (= I
_MS- I _MO ) is connected in parallel to perform integral control of the integral gain K _I , the deviation signal ΔI is subjected to proportional / integral calculation, and the proportional / integral signal I _PI is supplied to the control signal generating means 55. It The proportional / integral signal I _PI is expressed by Equation 1 using the proportional sensitivity K _P and the integral gain K _I.

[0012]

## EQU1 ## I _PI = K _P * ΔI + (K _I / p) * ΔI where p is the Heaviside operator

By setting the proportional sensitivity K _P and the integral gain K _I to large values, the motor current signal I
_MO (corresponding to the motor current I _M )
_{The MS} can converge (deviation signal ΔI = 0).

The control signal generating means 55 includes a PWM (pulse width modulation) signal generating means, and the PWM signal V _PWM corresponding to the magnitude and direction of the proportional / integral signal I _PI is supplied to the motor driving means 16 as the motor control signal V _O. Supplied and electric motor 10
It is driven by the motor voltage V _M to be supplied from the motor driving means 16.

Further, the motor 1 is controlled by the motor control signal V _O.
0 is driven and the motor current I _M flows, but the motor current detection means 18 detects the motor current I _M , and the motor current I _M
The electric motor current signal I _MO corresponding to is fed back to the deviation calculation means 53.

As described above, the conventional electric power steering apparatus 50 feeds back the target current signal I _MS with the motor current signal I _MO corresponding to the motor current I _M (negative feedback).
And the proportional / integral control is performed on the deviation signal ΔI, so that the motor current signal _IMO can be quickly converted to the target current signal IMO.
_By converging to _MS , electric motor power corresponding to the steering torque can be obtained, and a desired responsive steering assist force can be applied to the steering system.

Further, since the conventional electric power steering apparatus 50 is configured to perform integral control on the deviation signal ΔI, the motor current signal I _MO corresponding to the motor current I _M is made to coincide with the target current signal I _MS, and the offset is adjusted. The value can be set to 0.

[0018]

In the conventional electric power steering apparatus 50, when the steering assist force is large and the rotation speed of the electric motor 10 is high, such as steering when the steering wheel is stationary or running at low speed, the electric motor 10 is not operated. The counter electromotive force induced in the inductance component of the armature winding increases, the motor current I _M flowing in the motor 10 decreases, and the deviation signal ΔI (= I _MS
-I _MO ) tends to have a large value.

In the case where the steering wheel is turned back for a quick steering from such a steering wheel stationary state, the second number of the equation 1
The integral value (K _I / p) * ΔI of the integral term expressed by the term is large, and the sign of the target current signal I _MS is the integral value (K _I / p).
* The sign of the target current signal I _MS forming the deviation signal ΔI (= I _MS −I _MO ) of ΔI is opposite, and the delay time until the integrated value once converges to 0 is long and the direction opposite to the steering direction of the driver. Since the steering assist force of is applied to the steering system,
There is a problem in that the steering feel of the driver is drastically changed and the steering feeling is significantly reduced.

The present invention has been made to solve the above problems, and an object thereof is to provide an electric power steering apparatus capable of obtaining an optimum steering feeling even when the steering wheel is turned back for a fast steering from the steering wheel stationary state. To provide.

[0021]

In order to solve the above-mentioned problems, the electric power steering apparatus according to the present invention is characterized in that the control means is provided with a limiting means for limiting the signal output from the integrating element.

Since the control means is provided with the limiting means to limit the signal output from the integral element, even if the steering wheel is turned back quickly from the steering wheel stationary state, the response delay of the signal due to the integral element is compensated. You can

Further, the limiting means of the electric power steering apparatus according to the present invention comprises a sign reversal detecting means for detecting reversal of the steering direction and an integral value comparing means for comparing the integral value of the integral element with a preset reference value. And limiting the signal output from the integration element based on the signals output from the sign inversion detection means and the integrated value comparison means.

Since the limiting means is provided with the sign inversion detecting means and the integral value comparing means, since the steering wheel turning back of the fast steering from the steering wheel stationary state is surely detected and the signal outputted from the integrating element is limited, The response delay of the signal due to the integration element can be compensated.

[0025]

Embodiments of the present invention will be described below with reference to the accompanying drawings. According to the present invention, the signal output from the integral element of PI (proportional / integral) control forming the control system is limited when the steering wheel is steered from the steering wheel stationary state, and the response delay of the signal by the integral element is limited. Is compensated so that the optimum steering feeling is 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 steering shaft 2 integrally formed with a steering wheel 17 and a universal joint 3 attached to a steering shaft 2.
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.

A rack shaft 7 provided with rack teeth 7a meshing with the pinion 5a and reciprocating by these meshes.
The left and right front wheels 9 as steering wheels are connected to both ends of the vehicle through tie rods 8.

In this way, 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).

In the steering gear box 4, a steering torque sensor 12 for detecting the direction and magnitude of the driver's manual steering torque, and a steering rotation for detecting the direction and magnitude of the steering rotation speed of the steering wheel 17 operated by the driver. The speed sensor 13 is arranged, and the steering torque signal T _S of the analog electric signal corresponding to the steering torque detected by the steering torque sensor 12 and the steering rotation speed of the analog electric signal corresponding to the steering rotation speed detected by the steering rotation speed sensor 13 are arranged. Each of the signals N _S is provided to the control means 15. Also,
The vehicle speed sensor 14 detects the vehicle speed signal V _S as an electric pulse signal having a frequency corresponding to the vehicle speed, and controls the vehicle speed signal V _S.
5 provided.

An electric motor rotation speed sensor is provided instead of the steering rotation speed sensor 13, and the steering rotation speed N _S
Can also be calculated.

[0032]

## EQU2 ## N _S = K ₁ (N _M −dT _S / dt) where K ₁ is a constant, N _M is the motor rotation speed, and dT _S / dt is the differential value of the steering torque T _S.

The electric motor rotation speed N _S can also be estimated from the equation 3 by using the electric motor voltage V _M , the electric motor current I _M , the induced voltage coefficient K _M of the electric motor and the electric motor internal resistance R _M.

[0034]

[Number 3] _{N S = (V M -R M} * I M) / K M

The control unit 15 various arithmetic unit microprocessor-base, processing means, signal generating means, constituted by a memory or the like, the motor control signal V _O corresponding to the steering torque signal T _S (e.g., an ON signal and a PWM signal To generate a mixed signal of (1) to drive and control the motor driving means 16.

Further, the control means 15 is provided with a proportional / integral control means and a limiting means for limiting a signal output from an integral element of the proportional / integral control means, and integrates when the steering wheel is turned back from a steering wheel stationary state. The signal from the element is limited to compensate for the response delay of the signal due to the integrating element.

The electric motor driving means 16 is constituted by a bridge circuit composed of, for example, four power FET (field effect transistor) switching elements, and outputs the electric motor voltage V _M based on the electric motor control signal V _O to output the electric motor 10. To drive.

The electric motor current detecting means 18 detects the electric motor current I _M actually flowing in the electric motor 10 and feeds back (negative feedback) the electric motor current signal I _MO corresponding to the electric motor current I _M to the control means 15.

FIG. 2 is a block diagram of the essential parts 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, and a control signal generation unit 2.
7. The limiting means 30 is provided.

The target current setting means 21, the deviation calculating means 22 and the control signal generating means 27 have the same structure and function as the target current setting means 52, the deviation calculating means 53 and the control signal generating means 55 shown in FIG. 7, respectively. Therefore, the description is omitted.

The proportional / integral control means 23 determines the proportional sensitivity K _P
The generated error signal ΔI (= I _MS -I _MO) and proportional element 24 proportional control, integral element integrates controls the integral gain K _I of occurring deviation signal _{ΔI (= I MS -I MO)} 25 When,
The multiplication means 28 for multiplying the output signal from the integration element 25 by the limiting coefficient K _L and the addition means 26 for adding the output signals of the proportional element 24 and the multiplication means 28 are provided.

Integral element 2 connected in series with multiplication means 28
5 is connected in parallel with the proportional element 24. Proportional element 24 supplies a proportional signal I _P obtained by multiplying a proportional sensitivity K _P the deviation signal ΔI to the adding means 26. The integration element 25 is an integration signal (integral value) obtained by performing integration processing on the deviation signal ΔI with the integration gain K _I.
I _I is provided to the multiplying means 28, and the integral limiting signal I _L (= I _I × K _L ) obtained by multiplying the limiting coefficient K _L by the multiplying means 28 is supplied to the adding means 26.

The adding means 26 adds the proportional signal I _P and the integral limiting signal I _L (= I _I × K _L ) to obtain the proportional / integral signal I
_PI (= I _P + I _L ) is output to the control signal generating means 27.

The limiting means 30 is provided with a sign inversion detecting means, a rotation speed comparing means, an integral value comparing means, a limiting coefficient generating means, etc., and is supplied from the steering rotation speed signal N _S detected by the steering rotation speed sensor 13 and the integrating element 25. Based on the integrated signal (integrated value) I _I , the steering state at the time of turning the steering wheel in the fast steering from the steering wheel stationary state is detected, and the limiting coefficient K _L is supplied to the multiplying means 28.

In addition, the multiplication signal (integral value) is obtained by the multiplication means 28.
By multiplying processes I _I and restriction coefficient K _L, the integrated signal (integrated value) I limit _I coefficient K _L integration limit signal restricted with I
_L (= I _I × K _L ), for example, the limiting coefficient K _L can be set to a value smaller than 1 (0 ≦ K _L <1) to improve the response delay associated with the integral control of the integral element 25. it can.

The adding means 26 proportional-integration signal output from the _{I PI (= I P + I} L) is corresponding to the magnitude and direction of the proportional-integral signal _{I PI (= I P + I} L) in the control signal generating means 27 Is converted into a PWM signal V _PWM , and the PWM signal V _PWM is supplied as a motor control signal V _O to the motor driving means 16 to drive the motor 10 with the generated motor voltage V _M ,
The power of the electric motor 10 acts on the steering system as a steering assist force.

As described above, in the electric power steering apparatus 1 according to the present invention, the control means 15 is provided with the limiting means 30 and the integral signal (integral value) I output from the integrating element 25.
_{Since I} is limited by the limiting coefficient K _L , even if the steering wheel is turned back for a fast steering from the steering wheel stationary state, the proportional element 2
The proportional signal I _P output from No. 4 becomes dominant and the response delay of the signal by the integral element 25 can be compensated.

FIG. 3 is a block diagram of the essential parts of the limiting means according to the present invention. The limiting means 30 includes a sign inversion detecting means 31, a rotation speed comparing means 32, an integral value comparing means 33, a logical product calculating means 34, a level holding means 35, a limiting coefficient generating means 36, a limiting stop control means 37, and a steering rotation. The steering rotation speed signal N _S detected by the speed sensor 13 and FIG.
Integrated signal (integral value) supplied from the integration element 25 shown in
Based on I _I , the steering wheel turning state of fast turning is detected from the steering wheel stationary state, and the integrated signal (integrated value) I _I
A limiting coefficient K _L that attenuates is generated.

The sign reversal detection means 31 rises the polarity of the steering rotation speed signal N _S (for example, a polarity determination means (not shown), which is detected by a binary signal of H level in the right direction of the steering wheel and L level in the left direction of the steering wheel). Alternatively, when the polarity inversion is detected by using the falling edge as a trigger and the polarity inversion is detected, for example, H
Polarity inversion signal H _O consisting of one-shot pulse of level
Is provided to the logical product calculating means 34.

FIG. 4 is a block diagram showing the essential parts of one embodiment of the code inversion detecting means according to the present invention. In FIG.
The sign inversion detection means 31 includes a positive polarity inversion detection means 31A,
The negative polarity inversion detection means 31B and the OR operation means 31C are provided.

The positive polarity reversal detection means 31A and the negative polarity reversal detection means 31B are composed of, for example, retriggerable monomultivibrators, and the steering rotation speed signals N _S are respectively provided.
The positive polarity detection signal Pτ ₊ and the negative polarity detection signal Pτ _−, which are one-shot pulses (H level, for example) of a predetermined time T _M , are supplied to the logical sum operation means 31C by using the rising and falling of the polarity of the above as a trigger.

The OR operation means 31C has an OR gate or OR operation function, and has a positive polarity detection signal Pτ ₊ supplied from the positive polarity inversion detection means 31A and a negative polarity supplied from the negative polarity inversion detection means 31B. sex detection signal Ptau _- calculates a logical sum of the outputs of the polarity inversion signal H _O (one-shot pulse at the H level for a predetermined time T _M).

The rotation speed comparison means 32 includes a memory such as a ROM and a comparison means, compares the reference rotation speed N _K set in the memory with the steering rotation speed signal N _S , and the steering rotation speed signal N _S is the reference rotation speed. When it exceeds the speed N _K (N _S > N _K ), for example, an H level rotation speed determination signal N _O is provided to the AND operation unit 34. The rotation speed comparison means 32
Can be omitted.

In this way, the sign reversal detection means 31 detects the turning of the steering wheel by detecting the polarity of the steering rotation speed signal N _S , and the rotation speed detection means 32 the steering rotation speed signal N _S and the reference rotation speed N _S. Since it is possible to detect a sudden turning operation of the steering wheel from the result of comparison with _K , the turning operation from the fast turning of the steering wheel performed by the driver is detected from the logical product of the polarity inversion signal H _O and the rotation speed determination signal N _O. can do.

The integrated value comparison means 33 is a memory such as a ROM,
A reference integral value I _K which is provided with a comparison means and is preset in the memory
And the integrated signal (integrated value) I _I are compared, and when the integrated signal (integrated value) I _I exceeds the reference integrated value I _K (I _I > I _K ), for example, an H-level integrated value determination signal I _O is provided to the logical product operation means 34.

As described above, by setting the reference integrated value I _K corresponding to the vicinity of the steering wheel steering wheel and detecting the integrated value determination signal I _O , the steering wheel steering wheel operation of the driver can be detected.

The logical product calculation means 34 has a 3-input logical product gate or a logical product calculation function, and calculates a logical product of the polarity inversion signal H _O , the rotation speed determination signal N _O and the integrated value determination signal I _O , For example, the polarity inversion signal H _O and the rotation speed determination signal N _O
And when all of the integrated value determination signals I _O are H level,
The logical product data D _O of H level is provided to the level holding means 35.

Therefore, when the logical product data D _O output from the logical product calculating means 34 is at the H level, it is possible to detect the steering wheel from the stationary steering state to the fast steering state.

The level holding means 35 has a latch function,
Holds logical data D _O supplied from the AND operation unit 34, to provide for example a retention signal L _O of the H level to the limiting coefficient generator 36.

The level holding means 35 has a latch release function, releases the latch based on the stop control signal S _C supplied from the limit stop control means 37, and supplies the hold signal L _O to the limit coefficient generating means 36. To stop.

The limiting coefficient generating means 36 is composed of a memory such as a ROM and a selecting means, and a plurality of limiting coefficients K _L (for example, 1 and 0) preset in the memory are stored in the level holding means 3.
5 selected based on the hold signal L _O supplied from, provide restriction coefficient K _L selected to multiplying means 28 shown in FIG.

For example, when the holding signal L _O is at H level, the limiting coefficient K _L (= 0) is selected and output, while
Hold signal L _O is prohibited (for example, hold signal L _O is at L level)
In the case of, the limiting coefficient K _L (= 1) is selected and output.

FIG. 5 shows a characteristic diagram of the limiting coefficient K _L of the limiting coefficient generating means according to the present invention. In FIG. 5, time t1
In the region before and after the time t2, the limiting coefficient K _L is set to 1 (K _L = 1) corresponding to the normal steering state,
The integral signal (integral value) I _I output from the integral element 25 is added as an integral limiting signal I _L (= I _I ) having the same value, and the adding means 26 is provided.
Is output to

On the other hand, in the region from time t1 to time t2,
The limiting coefficient K _L is set to 0 (K _L = 0) corresponding to the steering state where the steering wheel is switched from the steering wheel stationary state to the fast steering state, and the integral signal (integral value) I _I output from the integrating element 25 is The integral limiting signal I limited to the limiting coefficient K _{L
The signal} is output as _L (= 0) to the adding means 26, and the response delay of the signal due to the integral element 25 of the steering assist force acting on the steering system can be compensated.

The limit stop control means 37 has a comparator or a comparison function, compares the integrated signal (integrated value) I _I with a preset reference value I _X, and the integrated signal (integrated value) I _I becomes the reference value I _X. When it is less than (I _I <I _X ), for example, the H level stop control signal S _C is provided to the level holding means 35,
Logical product data D _O held in the level holding means 35
Control to release the latch of.

[0066] Incidentally, as an embodiment of the present application, but the restriction coefficient K _L a steering state of the steering wheel crosscut fast steered from the state-away laid handle been described as being set to 0, only the restriction coefficient K _L 0 Limit coefficient K _L
Can be set to a predetermined value below 1 (0 <K _L <1) and the integration limit signal I _L can be set to a constant value other than 0 (0 <I _L <1).

Further, as a simpler embodiment of the present application, an integrating element 25 and an adding means 26 are used in place of the steering rotation speed sensor 13, the limiting means 30, and the multiplying means 28 shown in FIG.
The limiting means 41 between the provided integrated signal I _I is the case exceeds a predetermined value I _Y set in advance (I _I> I _Y), the integrated signal I _I a is limited to a predetermined value I _Y adding means 26 may be provided.

FIG. 6 is a block diagram showing the main part of another embodiment of the proportional / integral control means according to the present invention. In FIG. 6, the proportional / integral control means 40 differs from the proportional / integral control means 23 shown in FIG. 2 in that a limiting means 41 is provided between the integrating element 25 and the adding means 26 instead of the multiplying means 28.

The limiting means 41 has a memory for storing a predetermined value I _Y of a preset integral value and a comparison function, and has an integral signal (integral value) I _I supplied from the integrating element 25 and a predetermined value I _Y.
When the integrated signal (integrated value) I _I is less than or equal to the predetermined value I _Y (I _I ≦ I _Y ), the integrated signal (integrated value) I _I is used as it is as the integral limiting signal I _L in the adding means 26. When the integrated signal (integrated value) I _I exceeds a predetermined value I _Y (I _I
> I _Y ), the integral signal (integral value) I _I is limited to a predetermined value I _Y and is output to the adding means 26 as the integral limiting signal I _L.

As described above, in the electric power steering apparatus 1 according to the present invention according to the present invention, the limiting means 30 is provided with
Since the sign reversal detection means 31, the rotation speed comparison means 32, the integral value comparison means 33, and the limiting coefficient generation means 36 are provided, the steering wheel turning of the fast steering from the steering wheel stationary state is surely detected to generate the limiting coefficient. Since the signal output from the integral element is corrected by the limiting coefficient, the response delay of the signal due to the integral element can be compensated.

Further, the limiting coefficient generating means 36 of the electric power steering system 1 according to the present invention can generate a predetermined limiting coefficient and reduce the signal output from the integrating element 25 to a constant value. Integral element 25
It is possible to compensate the signal response delay due to.

[0072]

As described above, in the electric power steering apparatus according to the present invention, the control means is provided with the limiting means to limit the signal output from the integrating element. Even if the steering wheel is turned back, it is possible to improve the response delay of the signal due to the integral element and to compensate for the abrupt change of the steering characteristic.

In the electric power steering apparatus according to the present invention, the limiting means is provided with the sign reversal detecting means and the integral value comparing means, and the steering wheel turning-back is surely detected from the steering wheel stationary state and output from the integrating element. Since the signal is limited, the response delay of the signal due to the integral element can be compensated to ensure the optimum steering feeling.

Therefore, it is possible to provide the electric power steering apparatus which can obtain a stable steering feeling even when the steering wheel is turned back for a quick steering from the steering wheel stationary state.

[Brief description of 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 limiting means according to the present invention.

FIG. 4 is a block configuration diagram of a main part of an embodiment of a code inversion detection means according to the present invention

FIG. 5: Limiting coefficient K of limiting coefficient generating means according to the present invention
Characteristic diagram of L

FIG. 6 is a block diagram of the main part of another embodiment of the proportional / integral control means according to the present invention.

FIG. 7 is a block diagram of a main part of a conventional electric power steering device.

[8] the steering torque signal and vehicle speed as a parameter (T _D) - target current signal (I _MS) characteristic diagram (Table 1)

[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, 12 ... Steering torque sensor, 13 ... Steering rotation speed sensor, 15 ... Control means, 16 ... Electric motor drive means, 17 ... Steering wheel, 18 ... Electric motor current detection means, 21 ... Target current setting means, 22 ... Deviation calculation means, 23, 40 ... Proportional / integral control means , 24 ... proportional element, 25 ... integral element, 26 ... adding means, 27 ... control signal generating means, 28 ... multiplying means, 3
0, 41 ... Limiting means, 31 ... Sign inversion detecting means, 31A
... Positive polarity inversion detection means, 31B ... Negative polarity inversion detection means,
31C ... OR operation means, 32 ... Rotation speed comparison means, 3
3 ... integrated value comparing means, 34 ... AND operation unit, 35 ... level holding means, 36 ... restriction coefficient generating means, 37 ... limiting stop control unit, D _O ... logical data, H _O ... polarity inversion signal,
I _I ... Integral signal (integral value), I _K ... Reference integral value, I _L ... Integral limit signal, I _M ... Motor current, I _MO ... Motor current signal, I _MS ... Target current signal, I _O ... Integral value judgment Signal, I _P ...
Proportional signal, I _PI ... Proportional / integral signal, ΔI (= I _MS −
I _MO ) ... Deviation signal, K _I ... Integral gain, K _L ... Limiting coefficient,
K _P ... proportional sensitivity, L _O ... holding signal, N _K ... reference rotation speed,
N _O ... Rotational speed determination signal, N _S ... Steering rotational speed signal, Pτ
₊ ... positive polarity detection signal, Pτ _- ... negative polarity detection signal, S _C ... stop control signal, T _S ... steering torque signal, V _PWM ... PWM signal, V _M ... motor voltage, V _O ... motor control signal.

Claims (2)

[Claims] 1. A motor for applying a steering assist force to a steering system, target current setting means for determining a target current signal for driving the motor based on a steering torque signal from a steering torque sensor, and target current setting means. From the target current signal from the motor current detection means and the motor current signal from the motor current detection means, the electric motor is controlled based on the deviation, and a control means including a proportional / integral control means including at least a proportional element and an integral element. In the electric power steering device, the control means includes a limiting means for limiting a signal output from the integrating element. 2. The limiting means includes a sign reversal detecting means for detecting reversal of the steering direction, and an integral value comparing means for comparing an integral value of the integrating element with a preset reference value, and the sign reversing means. 2. The electric power steering apparatus according to claim 1, wherein the signal output from the integration element is limited based on the signals output from the detection means and the integrated value comparison means.