JPH10278816A - Motor driven power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always balance steering characteristics corresponding to right and left steering torque even if a steering torque neutral point deviates from a reference value so as to improve steering feeling by correcting a steering torque signal in the ordinary steering state based on the steering torque reference value and the steering torque neutral point signal. SOLUTION: A torque correcting means 23 receives a specific signal JG transmitted from an external device 20, computes deviation between a steering torque reference value and a steering torque neutral point signal TO supplied from a steering torque detecting means 21 corresponding to the received signal JG, and provides this deviation to a reference value deviation adding means 22 as a torque correcting signal TH. The reference value deviation adding means 22 adds a torque detected signal TD supplied from the steering torque detecting means 21 to the torque correcting signal TH supplied from the torque correcting means 23, and supplies a steering torque correcting signal TX to a target current signal setting means 24.

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 the steering force of a driver, and in particular, to correct a center value deviation of a steering torque detection system. The present invention relates to an electric power steering apparatus capable of obtaining steering characteristics with a balanced right and left.

[0002]

2. Description of the Related Art In a conventional electric power steering apparatus, a steering torque sensor for detecting a steering torque of a driver is provided by an input shaft and an output of a steering mechanism, as disclosed by the present applicant in Japanese Utility Model Application Laid-Open No. 61-143039. A cylinder which is arranged around a connecting portion where the shaft is connected by a torsion bar, and which is provided so that a steering torque generated by a steering operation is displaced in an input / output axis direction according to a relative rotation angle difference of the input / output shaft. 2. Description of the Related Art There is known a movable iron core having a shape of a core and a differential transformer including a primary coil and two secondary coils fixed to an inner wall of a steering column.

[0003] The steering torque sensor configured as described above uses a movable iron core to control the steering torque acting on the steering wheel.
In the direction of the input / output axis of the differential transformer, and corresponding to this displacement, detection is performed by an electric signal generated differentially in two secondary coils of the differential transformer.

[0004] The number of turns of the two secondary coils is set so that the inductance is equal. When the handle is in the neutral position, the position of the movable iron core is also equidistant from the two secondary coils. And driving the primary coil with an AC drive signal (eg, a sine wave signal)
The differential output of the electric signal induced in the next coil is set to be zero.

The steering torque is detected by detecting the magnitude of the steering torque by the absolute value (signal level) of the differential output and the direction of the steering torque by the polarity of the differential output.

On the other hand, as disclosed in Japanese Utility Model Unexamined Publication No. 61-143039, deviation correction of a neutral point (zero point) position of a steering torque sensor due to manufacturing variation is performed by a steering column to which a differential transformer is fixed. Move in the axial direction,
By adjusting the relative positions of the two secondary coils and the movable iron core (core), the differential output of the electric signal induced in the two secondary coils is set to be zero.

The output of the steering torque sensor is supplied to a level shift circuit (for example, a level shift circuit constituting a steering torque detection circuit).
The center value is detected at 2.5 V using a +5 V single power supply driven differential amplifier with 2.5 V as a virtual ground point.
Leftward torque is less than 2.5V, rightward torque is 2.5V.
It is configured to detect at a value exceeding 5V.

As described above, the steering torque detecting means of the conventional electric power steering apparatus comprises the steering torque sensor using the differential transformer and the steering torque detecting circuit driven by a single power supply, and acts on the steering wheel. The steering torque is detected as an electric signal having a center value of 2.5V.

[0009]

A conventional electric power steering apparatus operates a steering wheel when one or both of a neutral point (zero point) of a steering torque sensor and a center value of a steering torque detection circuit are shifted. Even if the same steering torque is applied in the left-right direction, one of the steering assist forces of the electric power steering device is large, and the other is small, and there is a problem that the steering assist force is unbalanced and the steering feeling is deteriorated. .

FIG. 5 shows a characteristic diagram of the steering torque-sensor detection value of the steering torque sensor. In FIG. 5, G1 (shown by a solid line) shows the characteristic of the steering torque sensor in which the neutral point is corrected to the steering torque T (= 0), and G2 (shown by the broken line) deviates from the neutral point to the steering torque T (= Ta). 3 shows the characteristics of the steering torque sensor. The neutral point (zero point) of the steering torque sensor indicates a state in which the steering torque is 0 and the sensor detection value of the steering torque detection circuit becomes the center value V _C (2.5 V).

In the G1 characteristic, the sensor detection value is the center value V
Although the steering torque T becomes _C is set to 0, the G2 characteristic, the steering torque T sensor detection value becomes the center value V _C is in the state shifted by Ta to the right.

Accordingly, in the electric power steering apparatus equipped with the steering torque sensor with G1 properties, deviation (absolute value) from the center value V _C of the sensor detection value with respect to the steering torque T of the left and right sides the same size is equal to The steering assist force acting on the steering system is equal in both the left and right directions and is balanced. However, in the electric power steering device equipped with the steering torque sensor having the G2 characteristic, the neutral point of the steering torque sensor is shifted, so that the steering is performed. Torque T
There have sensor detection value becomes V _A value below the center value V _C to the state steering assist force of the left direction is already working at 0, this state is the steering of the right direction sensor detection value becomes the center value V _C It continues until the torque T (= Ta).

As described above, in the electric power steering device equipped with the steering torque sensor having the G2 characteristic, when the steering wheel is operated in the right direction, the steering assist force in the direction opposite to the manual steering force up to the steering torque Ta is obtained. When the steering wheel is heavy due to the operation and the steering wheel is operated in the left direction, a relatively large steering assist force in the same direction as the manual steering force acts from the beginning (steering torque T = 0), and the steering wheel is light, There is a problem that the steering characteristics are unbalanced and the steering feeling is reduced.

Similarly, even when the steering torque sensor is set at the neutral point (zero point), if the steering torque detection circuit has an offset, the sensor detection value is the center value V.
_Due to the deviation from _C , there is a problem similar to that described with reference to FIG.

Generally, the neutral point (zero point) of the steering torque sensor can be corrected by a sensor alone or a method in which the sensor is mounted on the electric power steering apparatus main body. However, there are the following problems. In the method using a single sensor, the neutral point (zero point) of the sensor is individually corrected before mounting it on the device. There is a problem that the time is required and the cost of the product increases.

[0016] On the other hand, a method performed in a state equipped with sensors in the apparatus, so that can process the sensor detection value V _A shifted from the center value V _C of the steering torque sensor shown in FIG. 5 as a center value in the control system of the apparatus e.g. However, the left and right steering characteristics corresponding to the steering torque T can be balanced to prevent a decrease in steering feeling. However, when the leftward steering torque T exceeds Tb (T> Tb), the sensor detection value is saturated. Therefore, there is a problem that the steering assist force in the left direction of the steering wheel operation is limited to a constant value.

In addition, the method of performing the operation with the sensor mounted on the apparatus includes a driving direction discriminating circuit for fail-safe purpose as disclosed in Japanese Patent Application Laid-Open No. 2-249762 by the applicant of the present invention. An electric steering device (electric power steering device) that controls the driving / stopping of the motor with a logical product signal of the driving direction signal of the motor based on the sensor detection value and the driving direction signal of the motor from the main processing unit. When it is assumed that a steering torque sensor shifted at a point (zero point) is mounted, the main arithmetic unit determines the shift (sensor detection value _VA ) of the neutral point (zero point) of the steering torque sensor shown in FIG. And outputs a driving direction signal corresponding to the steering torque T in the left and right direction. The driving direction discriminating circuit converts the driving direction signal of the motor from the sensor detection value. Constant, and the steering torque T is the right direction Ta
Up to this time, the driving direction signal in the left direction is generated, so that the motor is controlled to stop by the logical product signal and the steering torque in the right direction becomes zero.
There is a problem that the electric motor is not driven from Ta to Ta and no steering assist force is generated.

The present invention has been made to solve such a problem. An object of the present invention is to correct a deviation of a neutral point of a steering torque sensor and an offset of a steering torque detection circuit with a simple configuration, and to improve left and right steering characteristics. An object of the present invention is to provide an electric power steering device having a good steering feeling.

[0019]

In order to solve the above-mentioned problems, a control means of an electric power steering apparatus according to the present invention comprises: a steering torque reference value for defining a neutral point of a steering position;
In a state where the steering torque is considered to be zero, a torque correcting means for correcting a steering torque signal in a normal steering state based on a steering torque neutral point signal detected by the steering torque detecting means is provided.

The control means of the electric power steering apparatus according to the present invention includes a steering torque reference value defining a neutral point of the steering position and a steering torque neutral detected by the steering torque detecting means in a state where the steering torque is regarded as zero. Since the torque correction means for correcting the steering torque signal in the normal steering state based on the point signal is provided, the deviation of the detected steering torque value from the center value from the deviation between the steering torque reference value and the steering torque neutral point signal is determined. The center value can be corrected.

[0021] Further, the torque correction means according to the present invention comprises:
Torque reference value setting means for setting a steering torque reference value,
A reference value deviation calculating means for calculating a reference value deviation between the steering torque reference value and the steering torque neutral point signal, and a deviation storage means for storing the reference value deviation are provided.

The torque correcting means according to the present invention comprises: a torque reference value setting means for setting a steering torque reference value; and a reference value deviation calculating means for calculating a reference value deviation between the steering torque reference value and the steering torque neutral point signal. Since the steering signal is provided, the steering torque reference value of the steering torque signal in the normal steering state can be corrected as the center value based on the deviation signal.

Further, the torque correcting means according to the present invention includes a receiving means for receiving a specific signal transmitted from an external device.
It is characterized by receiving a specific signal.

The torque correcting means according to the present invention includes a receiving means for receiving a specific signal transmitted from an external device, and the state in which the steering torque is regarded as 0 is when the specific signal is received. The neutral point of the device can be easily detected by receiving the specific signal from the external device.

Further, the state in which the steering torque of the electric power steering apparatus according to the present invention is considered to be 0 is characterized in that the engine is started or the engine is stopped.

Since the state in which the steering torque of the electric power steering apparatus according to the present invention is considered to be 0 is defined as when the engine is started or stopped, the neutral point of the apparatus can be easily detected.

[0027]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In addition, the present invention corrects the deviation of the neutral point of the steering torque sensor and the offset of the steering torque detection circuit by the deviation signal between the steering torque reference value and the steering torque neutral point signal, and provides a steering feeling in which the left and right steering characteristics are balanced. It is to achieve improvement.

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 rolling 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 is disposed in the steering gear box 4, and the steering torque of an analog electric signal corresponding to the steering torque detected by the steering torque sensor 12 is provided. The signal T _S is provided to the control means 15.

The control means 15 is composed of various arithmetic means, processing means, signal generation means, memory and the like based on a microprocessor. The motor control signal V _O (for example, the ON signal and the PWM signal) corresponding to the steering torque signal T _S is provided. A control signal is generated to control the driving of the motor driving means 16.

Further, the control means 15 controls the external identification information J _G
A receiving means for receiving a specific signal (code code or DTMF signal) as a diagnostic signal supplied from an external failure diagnostic device, an ON signal of an ignition key, and an OFF signal, and a specific signal received by the receiving means. A torque reference value setting means for outputting a value, a steering torque reference value,
A deviation calculating means for calculating a deviation of the steering torque neutral point signal in a state where the steering torque is regarded as 0, a deviation storage means for storing the deviation, and the steering torque corresponding to the steering operation is calculated by the deviation stored in the deviation storage means. to correct.

The motor driving means 16 is constituted by, for example, a bridge circuit composed of switching elements of four power FETs (field effect transistors), and based on the motor control signal V _O , a pair of two diagonally opposite bridge circuits is provided. Power F
ET Each PWM (Pulse Width Modulation) driving, and outputs a drive motor voltage V _M to be turned on drive for driving the electric motor 10.

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 means 15 of the electric power steering apparatus 1 is composed of various arithmetic functions, processing functions, and memories based on a microprocessor, and includes a steering torque detecting means 21, a reference value deviation adding means 22, a torque correcting means 23, a target current signal setting. Means 24, deviation calculation means 25, and drive control means 26.

The steering torque detecting means 21 is, for example, 2.5
A differential amplifier driven by a single +5 V power supply with V as a virtual ground point, and a torque detection value (center value) corresponding to the steering torque 0 of the steering torque signal T _S of the electric differential signal detected by the steering torque sensor 12 Value) to 2.5V, left direction (for example,
(-Polarity) steering torque signal T _S is detected at a value lower than 2.5 V, and a rightward (for example, + polarity) steering torque T _S is detected at a value exceeding 2.5 V, and the torque detection signal T _D is deviated from a reference value deviation. It is supplied to the adding means 22.

Further, the steering torque detecting means 21 provides a steering torque neutral point signal T _O corresponding to the steering torque 0 to the torque correcting means 23.

When the steering torque sensor 12 is set at the neutral point and the steering torque detecting means 21 has no offset, the steering torque neutral point signal T _O outputs a center value of 2.5 V. If the neutral point has a deviation or has an offset, the center value fluctuates from 2.5 V.

The state in which the steering torque is regarded as 0 means when a specific signal is received from the failure diagnostic device, when the vehicle starts the engine (when the ignition switch is turned on), or when the vehicle stops the engine (ignition). (When the switch is turned off or when a predetermined time elapses after the switch is turned off).

As described above, the state in which the steering torque of the electric power steering apparatus according to the present invention is regarded as 0 is determined when the specific signal is received from the failure diagnostic device, or when the engine is started or stopped. Can be easily detected.

The reference value deviation adding unit 22, an addition function, the torque detection signal T _D supplied from the steering torque detection means 21, the torque correction signal T _H supplied from the torque correction unit 23 adds the steering Torque correction signal T _X (= T _D
+ _TH ) to the target current signal setting means 24.

The torque correcting means 23 includes a receiving means, a torque reference value setting means, a reference value deviation calculating means, and a deviation storing means, receives a specific signal J _G transmitted from the external device 20, and receives the received signal J _G. steering torque reference value corresponding to the _G and (T _K), calculates the steering torque neutral point signal T _O deviation supplied from the steering torque detection means 21, the reference value deviation adding the deviation as a torque correction signal T _H To the means 22.

As described above, the control means of the electric power steering apparatus according to the present invention detects the steering torque reference value defining the neutral point of the steering position and the steering torque detection means in a state where the steering torque is regarded as zero. A torque correction means for correcting the steering torque signal in the normal steering state based on the steering torque neutral point signal to be performed, so that the center value of the detected steering torque value is obtained from the deviation between the steering torque reference value and the steering torque neutral point signal. Can be detected, and the center value can be corrected.

FIG. 3 is a block diagram of a main part of the torque correcting means according to the present invention. In FIG. 3, the torque correction unit 23 includes a receiving unit 31, a torque reference value setting unit 32,
Reference value deviation calculating means 33 and deviation storage means 34 are provided.

The receiving means 31 is a receiving circuit, a decoding (decoding) means, or a DTMF (Dual Tone Multi Frequenc).
y) A receiver or the like is provided, receives a specific signal J _G transmitted from the external device 20 via a line, and converts, for example, a conversion signal C _O obtained by converting the specific signal J _G into an encoding (code) signal or a DTMF signal. It is provided to the torque reference value setting means 32.

The external device 20 is a failure diagnostic machine at a service factory, an ignition key mounted on a vehicle, or the like, which can generate a specific signal _JG such as an encoded (code) signal or a DTMF signal. I just need.

The torque reference value setting means 32 is composed of a memory such as a ROM, and stores a steering torque reference value (center value 2.
5V) When the data of T _K is set and the conversion signal C _O is supplied from the receiving means 31, the data of the steering torque reference value T _K is read from the conversion signal C _O , and the steering torque reference value signal T _K is read. It is supplied to the reference value deviation calculating means 33.

The reference value deviation calculating means 33 has a subtraction function, and includes a steering torque reference value signal T _K supplied from the torque reference value setting means 32 and a steering torque neutral point signal T _K supplied from the steering torque detecting means 21. Reference value deviation ΔT from _O
(= T _K -T _O ) and provides the reference value deviation signal ΔT to the deviation storage means 34.

The reference value deviation ΔT (= T _K −T _O ) is
The actual steering torque of the electric power steering device 1 is 0
In this state, the steering torque neutral point signal T _{O obtained} by combining the fluctuation of the neutral point of the steering torque sensor 12 and the offset of the steering torque detecting means 21 is equal to the preset steering torque reference value signal T _K (center value: 2). .5V).

The deviation storage means 34 has a rewritable EE
The reference value deviation calculating means 33 is constituted by a memory such as a PROM.
Storing the reference value deviation signal ΔT provided by and provides the reference value deviation signal ΔT to the reference value deviation adding unit 22 as the torque correction signal T _H.

As described above, the torque correction means according to the present invention comprises: a torque reference value setting means for setting a steering torque reference value; and a reference value deviation for calculating a reference value deviation between the steering torque reference value and the steering torque neutral point signal. With the calculation means,
Based on the deviation signal, the steering torque signal in the normal steering state can be corrected with the steering torque reference value as the center value.

Further, the torque correction means according to the present invention comprises:
Since there is provided receiving means for receiving a specific signal transmitted from an external device, and the steering torque reference value is output based on the specific signal, the neutral point of the device can be easily detected.

The target current signal setting means 24 is composed of a memory such as a ROM, and has a target current signal corresponding to a steering torque correction value T _X (= T _D + T _H ) set in advance based on experimental values or design values. set the data I _MS advance, the steering torque correction signal from the reference value deviation addition unit _{22 T X (= T D +} T H) is supplied, it reads the target current signal data I _MS corresponding target current signal I _MS is supplied to the deviation calculating means 25.

FIG. 4 is a characteristic diagram of the steering torque (T _S ) -target current signal ( _IMS ) of the control means according to the present invention. FIG.
In a state where the steering torque is assumed to be 0 due to the fluctuation of the neutral point of the steering torque sensor 12 and the offset of the steering torque detection means 21, the steering torque detection means 21
When the torque detection signal T _D of fluctuates up and down from the center value (2.5V), if there is no torque compensator 23, from the target current signal I _MS corresponding to the fluctuation torque detection signal T _D is 0 It varies the point P ₁ (+ ΔI _MS) or a point P ₂ (-ΔI _MS), the steering characteristics for the left and right of the steering torque T _S becomes unbalanced.

For such a state, the torque correction means 23 sets the steering torque reference value T _K of the center value (2.5 V) from the external device 20, and sets the steering torque reference value T _K and the steering torque neutral point. calculates the signal T _O deviation _{ΔT (= T K -T O)} , and outputs the deviation [Delta] T as the torque correction signal T _H,
Since correcting the torque detection signal T _D normal steering state in the torque correction signal T _H, when the steering torque T _S is 0, the offset fluctuation and the steering torque detection means 21 of the neutral point of the steering torque sensor 12 Irrespective of the target current signal _IMS.
Can be set to 0 (O point), so that the steering characteristics balanced with the left and right steering torques T _S can be compensated.

The deviation calculating means 25 has a subtraction function and the target current signal I supplied from the target current setting means 24.
A deviation ΔI (= I _MS −I _MO ) between _MS and the motor current signal I _MO supplied from the motor current detection unit 18 is calculated, and the deviation signal ΔI is provided to the drive control unit 26.

The drive control means 26 includes a PID controller, a motor control signal generation means, and the like.
P (proportional) control to the deviation signal ΔI supplied from
(Integral) control and D (differential) control are performed.
Based on the controlled signal, a motor control signal V _O including a PWM (pulse width modulation) signal V _PWM is supplied to the motor driving means 16 to control the deviation signal ΔI to become 0 quickly,
Desired steering assist force from the electric motor 10 and the motor current I _M is equal to the target current signal I _MS is controlled so as to act on the steering system.

[0060]

As described above, the control means of the electric power steering apparatus according to the present invention includes a steering torque reference value defining a neutral point of a steering position and a steering torque reference value in a state where the steering torque is regarded as zero. A torque correcting means for correcting a steering torque signal in a normal steering state based on the steering torque neutral point signal detected by the detecting means, and a steering torque detection value based on a deviation between the steering torque reference value and the steering torque neutral point signal. Since the fluctuation from the center value can be detected and the center value can be corrected, even if the steering torque neutral point signal deviates from the steering torque reference value, the steering characteristics corresponding to the left and right steering torques are always balanced. The steering feeling can be improved.

Further, the torque correction means according to the present invention comprises:
Torque reference value setting means for setting a steering torque reference value,
A reference value deviation calculating means for calculating a reference value deviation of the steering torque reference value and the steering torque neutral point signal, and correcting the steering torque reference value of the steering torque signal in a normal steering state as a center value based on the deviation signal; Therefore, even when the steering torque neutral point signal deviates from the reference value of the steering torque, the steering characteristics corresponding to the left and right steering torques are always balanced to improve the steering feeling.

Further, the torque correcting means according to the present invention includes a receiving means for receiving a specific signal transmitted from an external device.
When the specific signal is received, the neutral point of the device can be easily detected by receiving the specific signal from the external device, so that the troublesome work of correcting the neutral point of the steering torque sensor can be eliminated. it can.

Further, the state in which the steering torque of the electric power steering apparatus according to the present invention is regarded as 0 is defined as the time when the engine is started or stopped, and the neutral point of the apparatus can be easily detected. Can be simplified.

Accordingly, an electric power steering apparatus is provided which can simplify the operation of correcting the neutral point of the steering torque sensor and can always improve the steering feeling by balancing the steering characteristics corresponding to the left and right steering torques. can do.

[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 torque correction unit according to the present invention;

FIG. 4 shows the steering torque (T _S ) of the control means according to the present invention.
-Target current signal ( _IMS ) characteristic diagram

FIG. 5 is a characteristic diagram of a steering torque of a steering torque sensor and a detected value of the sensor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electric power steering device, 2 ... Steering shaft, 3 ... Connection shaft, 4 ... Steering gear box, 5
... Rack & pinion mechanism, 6 ... Manual steering force generating means, 7
... Rack shaft, 8 ... Tie rod, 9 ... Left and right front wheels, 10 ...
Electric motor, 11: ball screw mechanism, 12: steering torque sensor, 15: control means, 16: electric motor drive means, 17: steering wheel, 18: electric motor current detection means, 20
... external equipment, 21 ... steering torque detecting means, 22 ... reference value deviation adding means, 23 ... torque correcting means, 24 ... target current signal setting means, 25 ... deviation calculating means, 26 ... driving control means, 31 ... receiving means, 32: torque reference value setting means, 3
3: Reference value deviation calculating means, 34: Deviation storage means, C _O ...
Conversion signal, I _MO … motor current signal, I _M … motor current,
I _MS ... target current _{signal, ΔI (= I MS -I MO} ) ... deviation signal, J _G ... external specific information, T _S ... steering torque signal, T _D ...
Torque detection signal, T _O ... steering torque neutral point signal, T _H ... torque correction _{signal, T X (= T D +} T H) ... steering torque correction signal, T _K ... steering torque reference value, ΔT (= T _K -T _O) ... reference value deviation, V _M ... motor voltage, V _O ... motor control signal, V
_PWM ... PWM signal.

Claims (4)

[Claims] An electric motor for applying a steering assist force to a steering system; a steering torque sensor for detecting a steering torque;
Steering torque detecting means for converting a left-right steering torque detected by the steering torque sensor into an electric steering torque signal, and a target current signal for setting a target current signal corresponding to at least the steering torque signal from the steering torque detecting means A control means for generating a motor control signal based on a target current signal and having a drive control means for controlling the driving of the electric motor, wherein the control means comprises: A torque correction for correcting a steering torque signal in a normal steering state based on a steering torque reference value defining the following and a steering torque neutral point signal detected by the steering torque detection means when the steering torque is considered to be 0. An electric power steering apparatus comprising: 2. The torque correction means comprises: a torque reference value setting means for setting a steering torque reference value; a reference value deviation calculating means for calculating a reference value deviation between the steering torque reference value and a steering torque neutral point signal; 2. The electric power steering apparatus according to claim 1, further comprising: deviation storage means for storing a value deviation. 3. The method according to claim 2, wherein the torque correction unit includes a receiving unit that receives a specific signal transmitted from an external device, and the state in which the steering torque is regarded as 0 is when the specific signal is received. The electric power steering apparatus according to claim 1 or 2, wherein 4. The state in which the steering torque is considered to be 0,
2. The electric power steering device according to claim 1, wherein the engine is started or stopped.