JP2001354152A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device for obtaining a stable steering feeling even if a steering wheel of quick steering is turned back from a stationary steering state of the steering wheel. SOLUTION: This electric power steering device has a limiting means 30 composed of a sign reversal detecting means 31, a rotating speed comparing means 32, an integral value comparing means 33, a theoretical product operation means 34 and a limitation stopping control means 37 in a control means 15.

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 applied to a steering system as a steering assist force to reduce a driver's steering force. TECHNICAL FIELD The present invention relates to an electric power steering device which improves a reduction in steering feeling caused by a response delay in control of a steering system when performing a return from a steering.

[0002]

2. Description of the Related Art In a conventional electric power steering apparatus, a steering torque generated by a driver 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. A signal is obtained by performing PI (proportional / integral) or PID (proportional / integral / differential) control on a deviation signal between the current signal and the motor current signal corresponding to the motor current actually flowing through the motor. It is known that a motor is driven by a generated motor control signal (for example, a PWM signal) to apply a steering assist force to a steering system.

In such a conventional electric power steering apparatus, since the motor current signal is fed back (negatively fed back) to the target current signal to perform PI control or PID control, the electric power steering apparatus is controlled so that the deviation signal quickly becomes zero. The motor current converges on the value set by the target current signal to drive the 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. Note that FIG.
An example in which I (proportional / integral) control is performed will be described. 7, the electric power steering apparatus 50 includes a steering torque sensor 12, a vehicle speed sensor 14, a control unit 51, a motor driving unit 16, a motor current detecting unit 18, and the motor 10.

The control means 51 is composed of various arithmetic means, comparison / processing means, memory, etc. based on a microprocessor. The target current setting means 52, deviation calculation means 53,
An integration control unit 54 and a control signal generation unit 55 are provided.

The steering torque sensor 12 detects a steering torque generated in response to a driver's operation of a steering wheel as an analog electric signal, and a steering torque signal TS is supplied to a target current setting means 52. The vehicle speed sensor 14 detects an electric pulse signal having a frequency corresponding to the speed of the vehicle, and the vehicle speed signal VS is supplied to the target current setting means 52.

[0007] The target current setting means 52 converts the steering torque signal TS supplied from the steering torque sensor 12 into a digital steering torque signal TD, and this steering torque signal TD
Is converted into a preset target current signal IMS based on the vehicle speed signal VS supplied from the vehicle speed sensor 14, and a target current signal IMS corresponding to the steering torque signal TD using the vehicle speed VS (VL, VM, VH) as a parameter. It is configured to output to the deviation calculating means 53.

FIG. 8 shows a steering torque signal (TD) -target current signal (IMS) characteristic diagram (Table 1) using the vehicle speed as a parameter. In FIG. 8, vehicle speeds VL, VM, and VH indicate a low vehicle speed region, a medium vehicle speed region, and a high vehicle speed region, respectively. Even when the steering torque signal TD is the same, the vehicle speed VS increases (VL → VM → VH). Accordingly, the target current signal IMS is preset so as to decrease.

As described above, the target current setting means 52 controls the motor 10 to output the target current signal I in the low vehicle speed region (VS = VL).
The motor 10 is driven by a large motor current IM corresponding to MS to obtain a sufficiently large steering assist force. On the other hand, in a high vehicle speed region (VS = VH), the motor 10 is driven by a small motor current IM corresponding to the target current signal IMS. It is configured such that the steering assist force is suppressed by driving to obtain steering stability.

The deviation calculating means 53 has a target current signal IMS.
Is detected by the motor current detecting means 18 and the motor current I
A deviation (= IMS−IMO) from the motor current signal IMO converted into a digital signal corresponding to M is calculated, and the deviation signal Δ
I is provided to the proportional / integral control means 54.

The proportional / integral control means 54 generates a deviation signal ΔI
Is proportional to the proportional sensitivity KP and the deviation signal ΔI (= IM
S-IMO is integrated in parallel with an integral gain KI to perform a proportional / integral operation on the deviation signal ΔI, and the proportional / integral signal IPI is supplied to the control signal generating means 55. The proportional / integral signal IPI is expressed by Equation 1 using the proportional sensitivity KP and the integral gain KI.

[0012]

IPI = KP * ΔI + (KI / p) * ΔI where p is a Heaviside operator

By increasing the values of the proportional sensitivity KP and the integral gain KI, the motor current signal IMO
(Corresponding to the motor current IM) quickly to the target current signal IMS
(The deviation signal ΔI = 0).

The control signal generating means 55 includes a PWM (pulse width modulation) signal generating means, and a PWM signal VPWM corresponding to the magnitude and direction of the proportional / integral signal IPI is supplied to the motor driving means 16 as a motor control signal VO. Electric motor 10
Are driven by the motor voltage VM supplied from the motor driving means 16.

Further, the motor 1 is controlled by the motor control signal VO.
0 is driven and the motor current IM flows, but the motor current detection means 18 detects the motor current IM and outputs the motor current IM.
Are fed back to the deviation calculating means 53.

As described above, in the conventional electric power steering apparatus 50, the motor current signal IMO corresponding to the motor current IM is fed back (negative feedback) to the target current signal IMS.
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 is obtained, and a desired steering assist force with good responsiveness can be applied to the steering system.

Further, since the conventional electric power steering device 50 is configured to perform integral control on the deviation signal ΔI, the motor current signal IMO corresponding to the motor current IM is made to coincide with the target current signal IMS, and the offset value is set to 0. Can be set to

[0018]

The conventional electric power steering apparatus 50 has a large steering assist force such as a steering operation when the steering wheel is stationary or running at a low speed, and when the rotation speed of the motor 10 is high, the motor 10 The back electromotive force induced in the inductance component of the armature winding of the motor 10 increases, the motor current IM flowing through the motor 10 decreases, and the deviation signal ΔI (= IMS
−IMO) tends to be large.

In the case where the steering wheel is turned back for fast turning from such a steering wheel stationary state, the second equation (1) is obtained.
The integral value of the integral term expressed by the term (KI / p) * ΔI is large, and the sign of the target current signal IMS is the integral value (KI / p)
* The sign of the target current signal IMS that constitutes the deviation signal ΔI (= IMS−IMO) of ΔI is opposite, the delay time until the integral value once converges to 0 is long, and the steering assist in the direction opposite to the steering direction of the driver is performed. Because the force acts on the steering system,
There is a problem that a sudden change is exerted on the steering force of the driver and the steering feeling is remarkably reduced.

An object of the present invention is to solve such a problem, and an object of the present invention is to provide an electric power steering apparatus capable of obtaining an optimum steering feeling even when the steering wheel is turned quickly for turning from the steering wheel stationary state. Is to provide.

[0021]

In order to solve the above-mentioned problems, an electric power steering apparatus according to the present invention outputs to a control means, when a signal output from an integrating element is equal to or less than a predetermined value, the signal is output as it is. A limiting means for limiting the signal output from the controller to a predetermined value or less when the signal exceeds the predetermined value.

The control means includes limiting means for outputting the signal output from the integration element when the signal output from the integration element is less than a predetermined value, and limiting the signal output from the integration element to a predetermined value when the signal output from the integration element exceeds the predetermined value. Therefore, even if the steering wheel is turned back for fast turning from the steering wheel stationary state, the response delay of the signal by the integral element can be compensated.

The limiting means according to the present invention includes a sign inversion detecting means for detecting the 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. The signal output from the integration element is limited based on the signal output from the inversion detection means and the integration value comparison means.

The limiting means according to the present invention includes a sign reversal detecting means for detecting reversal of the steering direction, an integral value comparing means for comparing an integral value of the integral element with a preset reference value, and a sign reversal detecting means. Means and a signal output from the integration element based on the signal output from the integration value comparison means, so that the steering wheel turning of fast turning from the steering wheel stationary state is reliably detected and the response of the signal by the integration element is performed. The delay 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 constituting the control system is limited when the steering wheel is turned back from a stationary steering state to a fast steering, and the response delay of the signal by the integral element is restricted. In order to obtain an optimum steering feeling.

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.

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, an electric motor 10 for supplying a steering assist force is disposed coaxially with the rack shaft 7, and a ball screw mechanism 11 provided coaxially with the rack shaft 7. Is 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 and a steering rotation for detecting the direction and magnitude of the steering rotational speed of a steering wheel 17 operated by the driver are provided in the steering gear box 4. A speed sensor 13 is arranged, and a steering torque signal TS of an analog electric signal corresponding to the steering torque detected by the steering torque sensor 12 and a steering rotation speed signal of an analog electric signal corresponding to the steering rotation speed detected by the steering rotation speed sensor 13 are provided. Each of NS is provided to the control means 15. Also,
The vehicle speed sensor 14 detects a vehicle speed signal VS as an electric pulse signal having a frequency corresponding to the speed of the vehicle, and outputs a vehicle speed signal VS to the control unit 1.
5 provided.

A motor rotation speed sensor is provided in place of the steering rotation speed sensor 13, and the steering rotation speed NS
Can also be calculated.

[0032]

## EQU2 ## where NS = K1 (NM-dTS / dt) where K1 is a constant, NM is the motor rotation speed, and dTS / d.
t is a differential value of the steering torque TS.

The motor rotation speed NS can also be estimated from Equation 3 using the motor voltage VM, the motor current IM, the motor induced voltage coefficient KM, and the motor internal resistance RM.

[0034]

## EQU3 ## NS = (VM-RM * IM) / KM

The control means 15 is composed of various arithmetic means, processing means, signal generation means, memory and the like based on a microprocessor, and a motor control signal VO (for example, a hybrid of an ON signal and a PWM signal) corresponding to the steering torque signal TS. Signal) to drive and control the motor driving means 16.

The control means 15 includes a proportional / integral control means and a limiting means for limiting a signal output from an integral element of the proportional / integral control means. The signal from the element is limited to compensate for the response delay of the signal due to the integral element.

The motor driving means 16 comprises a bridge circuit comprising, for example, four power FETs (field effect transistors) switching elements, and outputs the motor voltage VM based on the motor control signal VO to drive the motor 10. .

The motor current detecting means 18 detects the motor current IM actually flowing through the motor 10, and feeds back (negative feedback) a motor current signal IMO corresponding to the motor current IM to the control means 15.

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 means 15 includes a target current setting means 21, a deviation calculation means 22, a proportional / integral control means 23, and a control signal generation means 2.
7. It has a limiting means 30.

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

The proportional / integral control means 23 has a proportional sensitivity K P
And an integral element 25 for proportionally controlling the deviation signal ΔI (= IMS−IMO) and an integral element 25 for generating an integral gain KI and integrating and controlling the deviation signal ΔI (= IMS−IMO).
Multiplication means 28 for multiplying the output signal from the integration element 25 by the limiting coefficient KL, and 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. The proportional element 24 supplies a proportional signal IP obtained by multiplying the deviation signal ΔI by the proportional sensitivity KP to the adding means 26. An integral element 25 is an integral signal (integral value) II obtained by subjecting the deviation signal ΔI to an integral process with an integral gain KI.
Is provided to the multiplying means 28, and the limiting coefficient KL
Is supplied to the adding means 26.

The adding means 26 adds the proportional signal IP and the integral limiting signal IL (= II × KL) to obtain a proportional / integral signal IP.
I (= IP + IL) is output to the control signal generating means 27.

The limiting means 30 includes sign inversion detecting means, rotational speed comparing means, integral value comparing means, limiting coefficient generating means, etc., and is supplied from the steering rotational speed signal NS detected by the steering rotational speed sensor 13 and the integral element 25. Based on the integral signal (integral value) II, the steering state at the time of turning the steering wheel from the steering wheel stationary state to the fast steering is detected, and the limiting coefficient KL is supplied to the multiplying means 28.

The integral signal (integral value) is multiplied by the multiplying means 28.
The integral limiting signal I obtained by multiplying the limiting signal KL with the limiting signal KL limits the integral signal (integral value) II with the limiting coefficient KL.
L (= II × KL) is obtained. For example, by setting the limiting coefficient KL to a value less than 1 (0 ≦ KL <1), it is possible to improve the response delay caused by the integration control of the integration element 25.

The proportional / integral signal IPI (= IP + IL) output from the adding means 26 is converted by the control signal generating means 27 into a PWM signal VPWM corresponding to the magnitude and direction of the proportional / integral signal IPI (= IP + IL). The PWM signal VPWM is supplied to the motor drive means 16 as the motor control signal VO, and the motor 10 is driven by the generated motor voltage VM,
The power of the electric motor 10 is applied to the steering system as a steering assist force.

As described above, the electric power steering apparatus 1 according to the present invention includes the limiting means 30 in the control means 15 and the integration signal (integral value) I output from the integration element 25.
Since I is limited by the limiting coefficient KL, even if the steering wheel is turned quickly for turning from the steering wheel stationary state, the proportional element 2
4 is dominant, and the response delay of the signal by the integration element 25 can be compensated.

FIG. 3 is a block diagram of a main part of the limiting means according to the present invention. The limiting means 30 includes a sign inversion detecting means 31, a rotational 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, and a limiting stop control means 37. The steering rotational speed signal NS detected by the speed sensor 13 and FIG.
(Integral value) supplied from the integration element 25 shown in FIG.
Based on II, the steering wheel turning state of fast turning from the steering wheel stationary state is detected, and an integral signal (integral value) II is detected.
KL is generated.

The sign inversion detecting means 31 detects the rising or falling of the polarity of the steering rotational speed signal NS (for example, a polarity judging means not shown, which is 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). The polarity inversion is detected using the falling edge as a trigger, and every time the polarity inversion is detected, for example, H
Polarity inversion signal H0 consisting of one-shot pulse of level
Is provided to the AND operation means 34.

FIG. 4 is a block diagram showing a main part of an embodiment of the sign inversion detecting means according to the present invention. In FIG.
The sign inversion detecting means 31 includes a positive polarity inversion detecting means 31A,
A negative polarity inversion detecting means 31B and a logical sum calculating means 31C are provided.

The positive polarity reversal detecting means 31A and the negative polarity reversing detecting means 31B are constituted by, for example, retriggerable mono-multi vibrators, each of which has a steering rotational speed signal NS.
The positive polarity detection signal Pτ + and the negative polarity detection signal Pτ-, each of which is a one-shot pulse (for example, H level) for a predetermined time period TM, are supplied to the logical sum operation means 31C with the rising and falling of the polarity as a trigger.

The OR operation means 31C has an OR gate or an OR operation function, and outputs a positive polarity detection signal Pτ + supplied from the positive polarity inversion detecting means 31A and a negative polarity supplied from the negative polarity inversion detecting means 31B. A logical sum of the sex detection signal Pτ- is calculated, and a polarity inversion signal HO (an H-level one-shot pulse for a predetermined time TM) is output.

The rotation speed comparison means 32 includes a memory such as a ROM and a comparison means, and compares the reference rotation speed NK preset in the memory with the steering rotation speed signal NS, and the steering rotation speed signal NS determines the reference rotation speed NK. In the case of exceeding (NS> NK), for example, an H level rotation speed determination signal NO is provided to the AND operation means 34. The rotation speed comparing means 32
Can be omitted.

As described above, the sign inversion detecting means 31 detects the turning of the steering wheel by detecting the polarity of the steering rotational speed signal NS, and the rotational speed detecting means 32 detects the steering rotational speed signal NS and the reference rotational speed NK. Since the sudden turning operation of the steering wheel can be detected from the comparison result, the turning operation of the steering wheel by the driver from fast turning can be detected from the logical product of the polarity reversal signal HO and the rotation speed determination signal NO.

The integration value comparison means 33 is a memory such as a ROM,
A comparison means, and a reference integral value IK preset in a memory.
Is compared with the integral signal (integral value) II. If the integral signal (integral value) II exceeds the reference integral value IK (II> IK), for example, the H-level integral value determination signal IO is used as a logical product operation means 34.

As described above, by setting the reference integral value IK in correspondence with the vicinity of the steering wheel being stationary, and detecting the integral value determination signal IO, it is possible to detect the steering wheel operation of the driver.

The AND operation means 34 has a three-input AND gate or an AND operation function, and performs an AND operation of the polarity reversal signal HO, the rotation speed judgment signal NO and the integral value judgment signal IO. Signal HO, rotation speed judgment signal NO
And when all of the integrated value determination signals IO are at the H level,
The logical product data DO of the H level is provided to the level holding unit 35.

Therefore, when the logical product data DO output from the logical product calculating means 34 is at the H level, it is possible to detect the turning-back state from the stationary steering state to the fast steering.

The level holding means 35 has a latch function,
The logical product data DO supplied from the logical product calculating means 34 is held, and a holding signal LO at H level, for example, is provided to the limiting coefficient generating means 36.

The level holding means 35 has a latch release function, releases the latch based on the stop control signal SC supplied from the limit stop control means 37, and stops the holding signal LO supplied to the limit coefficient generating means 36. I do.

The limiting coefficient generating means 36 comprises a memory such as a ROM and a selecting means and the like, and stores a plurality of limiting coefficients KL (for example, 1 and 0) preset in the memory in the level holding means 3.
5, and the selected limiting coefficient KL is provided to the multiplying means 28 shown in FIG.

For example, when the holding signal LO is at the H level, the limiting coefficient KL (= 0) is selected and output.
Holding signal L0 is prohibited (for example, holding signal L0 is at L level)
In this case, the limit coefficient KL (= 1) is selected and output.

FIG. 5 is a characteristic diagram of the limiting coefficient KL of the limiting coefficient generating means according to the present invention. In FIG. 5, time t1
Before and in the region after time t2, the limiting coefficient KL is set to 1 (KL = 1) corresponding to the normal steering state.
The integration signal (integral value) II output from the integration element 25 is added as an integration limiting signal IL (= II) of the same value to the adding means 26.
Is output to

On the other hand, in the region from time t1 to time t2,
The limiting coefficient KL is set to 0 (KL = 0) corresponding to the steering state in which the steering wheel is turned from a steering wheel stationary state to a quick steering, and an integral signal (integral value) II output from the integration element 25 is a limiting coefficient KL. Limited signal IL limited to
(= 0) is output to the adding means 26, and it is possible to compensate for a response delay of a signal caused by the integral element 25 of the steering assist force acting on the steering system.

The limit stop control means 37 has a comparator or a comparison function, compares the integral signal (integral value) I1 with a preset reference value IX, and the integral signal (integral value) I1 falls below the reference value IX (II1). <IX) In the case of, for example, an H level stop control signal SC is provided to the level holding means 35,
Logical product data DO held in the level holding means 35
Is controlled to release the latch.

As an embodiment of the present application, an example has been described in which the limiting coefficient KL for the steering state in which the steering wheel is turned quickly for turning the steering wheel from the stationary steering state is set to 0. However, the limiting coefficient KL is limited to 0. No limit coefficient KL
Can be set to a predetermined value below 0 (0 <KL <1), and the integration limit signal IL can be set to a constant value other than 0 (0 <IL <1).

Further, as a simpler embodiment of the present invention, an integral element 25 and an adding means 26 are used instead of the steering rotational speed sensor 13, the limiting means 30 and the multiplying means 28 in FIG.
And the limiting means 41 is provided between the first and second limiting means 41. When the integration signal II exceeds a predetermined value IY (II> IY), the integration signal II is limited to the predetermined value IY and supplied to the adding means 26. May be.

FIG. 6 is a block diagram showing a principal part of another embodiment of the proportional / integral control means according to the present invention. 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 IY of the preset integral value and a comparing function, and the integral signal (integral value) II supplied from the integrating element 25 and the predetermined value IY.
When the integrated signal (integrated value) II is equal to or less than the predetermined value IY (II ≦ IY), the integrated signal (integrated value) II is output as it is to the adding means 26 as the integration limiting signal IL. (Integral value) When II exceeds a predetermined value IY (II
> IY), the integration signal (integral value) II is limited to a predetermined value IY and is output to the adding means 26 as an integration limit signal IL.

As described above, the electric power steering apparatus 1 according to the present invention according to the present invention
Since the apparatus includes the sign inversion detecting means 31, the rotational speed comparing means 32, the integral value comparing means 33, and the limiting coefficient generating means 36, it is possible to reliably detect the turning of the steering wheel which is fast turning from the steering wheel stationary state and generate the limiting coefficient. Since the signal output from the integration element is corrected by the limiting coefficient, the response delay of the signal due to the integration element can be compensated.

The limit coefficient generating means 36 of the electric power steering apparatus 1 according to the present invention can generate a predetermined limit coefficient and reduce the signal output from the integration element 25 to a constant value. Even if the steering wheel is turned back quickly from the stationary state, the integral element 25
Can be compensated for the signal response delay due to

[0072]

As described above, the electric power steering apparatus according to the present invention includes the limiting means in the control means, and outputs the signal as it is when the signal output from the integrating element is equal to or less than a predetermined value. When the signal output from the steering wheel exceeds a predetermined value, the steering speed is limited to a predetermined value or less. Can be compensated for.

Further, the limiting means according to the present invention comprises a sign inversion detecting means for detecting the 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. Since the signal output from the integration element is limited based on the signal output from the inversion detection means and the integration value comparison means, the steering wheel turning of the fast steering is reliably detected from the steering wheel stationary state, and the signal by the integration element is detected. Optimum steering feeling can be ensured by compensating for the response delay.

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

[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 limiting unit according to the present invention.

FIG. 4 is a block diagram showing a main part of an embodiment of a sign inversion detecting means according to the present invention;

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

FIG. 6 is a block diagram showing a principal 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.

FIG. 8 shows a steering torque signal (T
D)-Target current signal (IMS) 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: motor drive means, 17: steering wheel, 18: 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 detecting means, 31B ... Negative polarity inversion detecting means,
31C: OR operation means, 32: Rotation speed comparison means, 3
3 ... Integrated value comparing means, 34 ... AND operation means, 35 ... Level holding means, 36 ... Limit coefficient generation means, 37 ... Limit stop control means, DO ... Logic product data, HO ... Polarity inversion signal,
II: integral signal (integral value), IK: reference integral value, IL: integral limiting signal, IM: motor current, IMO: motor current signal, IMS: target current signal, IO: integral value judgment signal, IP ...
Proportional signal, IPI ... proportional / integral signal, ΔI (= IMS−IM
O): Deviation signal, KI: Integral gain, KL: Limiting coefficient, KP
... Proportional sensitivity, LO ... Hold signal, NK ... Reference rotational speed, NO
... Rotation speed judgment signal, NS ... Steering rotation speed signal, Pτ + ...
Positive polarity detection signal, Pτ-: Negative polarity detection signal, SC: Stop control signal, TS: Steering torque signal, VPWM: PWM signal, V
M: motor voltage, VO: motor control signal.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Shinji Hironaka 1-4-1 Chuo, Wako-shi, Saitama F-term in Honda R & D Co., Ltd. (Reference) 3D032 CC08 DA09 DA15 DA23 DB20 DC01 DC02 DC07 DC09 DC28 DC33 DC34 DD02 EA01 EB11 EC23 GG01 3D033 CA13 CA16 CA19 CA21

Claims (2)

[Claims] An electric motor for applying a steering assist force to a steering system, a target current setting means for determining a target current signal for driving the electric motor based on a steering torque signal from a steering torque sensor, and the target current setting means A proportional / integral control means having at least a proportional element and an integral element for performing a proportional control and an integral control on a deviation between a target current signal from the motor and a motor current signal from the motor current detecting means; A motor driving means for driving the electric motor based on an output from the means, wherein the control means outputs the signal as it is when the signal output from the integration element is equal to or less than a predetermined value. And limiting means for limiting the signal output from the integration element to a predetermined value or less when the signal exceeds the predetermined value. Electric power steering system. 2. The control device according to claim 1, wherein the limiting unit includes a sign reversal detecting unit that detects reversal of the steering direction, and an integral value comparing unit that compares an integral value of the integral element with a preset reference value. The electric power steering apparatus according to claim 1, wherein a signal output from the integration element is limited based on a signal output from the detection unit and the integration value comparison unit.