JPH0939809A - Control device for electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect the state of steering wheel-return by detecting the state of the steering wheel-return based on how frequently the differentiated value of motor-current detected within a specified time exceeds a preset specified value when the motor-current becomes oscillating current at the time of steering wheel-return. SOLUTION: An electronic control circuit 13 containing a structure of detecting the state of steering wheel-return receives signals from a torque sensor 3, a speed sensor 12 to calculate a command-current value, and to detect the duty ratio of a PWM signal and motor-current. Then, an estimate value of motor-angular velocity is calculated based on the motor-current and the duty ratio of the PWM signal, and further a differentiated value of the motor-current is calculated. Next, how frequently the differentiated value of the motor-current exceeds a specified value, is counted, and whether the count-value computed when a specified time has elapsed exceeds a preset, specified frequency or not, is judged. In this case, when the specified frequency is exceeded, it is judged that a handle is in the state of steering wheel-return.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an electric power steering device.

[0002]

2. Description of the Related Art An electric power steering apparatus for a vehicle detects a steering torque or the like generated in a steering shaft by operating a steering wheel, and based on the detection signal, a current which is a control target value of a motor. Calculate the command value,
In the current feedback control circuit, the difference between the current command value, which is the above-mentioned control target value, and the current actually flowing in the motor is obtained as a current control value, and the motor is controlled by the current control value for steering. There is something that assists the steering force of the steering wheel.

In such an electric power steering apparatus, as shown in FIG. 10, four field effect transistors FET1 to FET4 are connected to a bridge and two first and second arms are provided. A motor drive circuit is used in which an H-bridge circuit is formed, a power supply is connected between the input terminals of the H-bridge circuit, and a motor M is connected between the output terminals.

The operation thereof will be briefly described. The FE of the first arm of the H-bridge circuit which constitutes the motor drive circuit.
The magnitude of the motor current is controlled by driving T1 (or the FET2 of the second arm) with a PWM signal (pulse width modulation signal) having a duty ratio D determined based on the current control value. To be done.

Further, based on the sign of the current control value, the FET 3 of the second arm is turned on and the FET 4 of the first arm is turned on.
The rotation direction of the motor M is controlled by turning off FF (or turning off the FET 3 of the second arm and turning on the FET 4 of the first arm).

On the other hand, in general, the steering mechanism, when the steering handle is rotated during traveling and then released from the steering handle (hereinafter referred to as "handle return"),
The self-aligning torque due to the reaction force from the tire exerts a force to return the steering mechanism to the neutral position, and the steering mechanism automatically returns to the straight traveling position (neutral position).

Looking at the above-mentioned steering wheel return state in the electric power steering apparatus, since the motor for driving the steering mechanism has inertia, the steering wheel does not return well at low speeds and the neutral position at high speeds. Vibration occurs that swings back and forth on the other side across the distance.
In addition, when traveling at high speed, there are inconveniences such as occurrence of vibration of the steering mechanism due to backlash from the road surface and poor convergence of the yaw angular velocity of the automobile.

Therefore, in the conventional electric power steering apparatus, the steering mechanism is controlled so that the steering handle can be easily returned when traveling at a low speed, and the steering mechanism is controlled so as to suppress the vibration of the steering mechanism during traveling at a high speed. Is proposed.

In order to perform such control, it is necessary to detect whether or not the steering mechanism is in the steering wheel returning state. A conventional electric power steering device is provided with a sensor for detecting a motor angular velocity, and when the steering torque is a predetermined value or less and the detected motor angular velocity is a predetermined value or more, the steering wheel is returned. There has been proposed a method which adopts a means for determining that there is (Japanese Patent Laid-Open No. 62-62160).
(See JP-A-244761).

In order to detect such a steering wheel return state, a current sensor for controlling the electric power steering apparatus is not provided without a sensor for detecting the motor angular velocity.
Whether or not the steering wheel is returned based on the estimated motor angular velocity and the steering torque by estimating the motor angular velocity from the motor current detected in the feedback control circuit and the voltage between the motor terminals. It has been proposed to employ a means for determining (see Japanese Patent Application Laid-Open No. 3-182874).

[0011]

However, in the above-mentioned means for detecting the return state of the handlebar, the above-mentioned means is used.
Since a sensor for detecting the angular velocity is required, the number of components increases, resulting in an increase in manufacturing cost. Also,
The latter means for detecting the state of returning the steering wheel is advantageous in that it does not require a sensor for detecting the motor angular velocity, but has the following problems.

That is, the PWM signal (pulse width modulation signal) having the duty ratio D and the motor current i in the motor drive circuit are
In the normal state, that is, when the motor angular velocity ω = 0, the duty ratio D is as shown in FIG.
And the motor current i exhibit linear characteristics.

However, when the steering wheel is returned, the steering torque is almost 0, and the motor rotates in the opposite direction due to the self-alignment torque.
The motor angular velocity ω becomes ω <0 or ω> 0, and FIG.
As shown in the line (b) or the line (c) of FIG. 3, the duty ratio D = is shifted up or down by the amount corresponding to the counter electromotive force of the motor.
A non-linear characteristic having a discontinuity in the motor current i occurs near zero.

When the steering wheel is returned, the motor current i of the current feedback control circuit becomes an oscillating current because it passes through this non-linear characteristic. Since an error occurs in the motor angular velocity estimated from the oscillating current, the motor current,
There is an inconvenience that the state of returning the steering wheel cannot be accurately detected. An object of the present invention is to solve the above problems.

[0015]

SUMMARY OF THE INVENTION The present invention is to solve the above problems, and the invention of claim 1 is to detect a current command value calculated based on at least a steering torque signal and a vehicle speed signal generated in a steering shaft. In a controller for an electric power steering apparatus having a feedback control means for controlling the output of a motor for applying a steering assisting force to a steering mechanism based on a current control value calculated from the motor current value A motor drive circuit in which a power source is connected between the input terminals of the bridge circuit formed by connecting four semiconductor elements to the H bridge and the motor is connected between the output terminals, and a motor detected within a predetermined time. Steering wheel return detecting means for detecting a steering wheel return state based on the frequency at which the differential value of the steering current exceeds a preset predetermined value, and when the steering wheel return state is detected, Characterized by comprising a correction means for correcting the current command value by a handle return compensation value is set in accordance with the order speed.

Further, a PWM current signal for driving the semiconductor element of the H-bridge circuit and the detected value of the motor current are also used.
A motor angular velocity estimating means for estimating the motor angular velocity based on the Tay ratio, and a second steering wheel return detecting means for detecting a steering wheel returning state based on the detected steering torque and the estimated motor angular velocity value. When either one of the two steering wheel return detecting means detects the steering wheel returning state, it is determined that the steering wheel returning state is detected, and the steering wheel returning correction value preset according to the vehicle speed is used. You may make it operate | move the correction | amendment means which correct | amends a current command value.

According to a third aspect of the present invention, at least the current command value calculated based on the steering torque signal generated in the steering shaft and the vehicle speed signal and the current control value calculated from the detected motor current value. In a controller for an electric power steering apparatus having a feedback control means for controlling an output of a motor for giving a steering assist force to a steering mechanism, a bridge circuit of four semiconductor elements is connected to an H bridge. A motor drive circuit having a power supply connected between the input terminals and the motor connected between the output terminals, and a motor drive circuit.
A motor angular velocity estimation means for calculating an estimated motor angular velocity value based on the duty ratio of the PWM signal for driving the semiconductor element of the H-bridge circuit and the motor detected within a predetermined time. Steering wheel return detection means for detecting the state of steering wheel return based on the frequency at which the differential value of the estimated motor angular velocity calculated based on the detected motor current value and the duty ratio exceeds a preset predetermined value, When a steering wheel return state is detected, a correction means for correcting the current command value with the steering wheel return correction value set in advance according to the vehicle speed is provided.

Further, there is provided a second steering wheel return detecting means for detecting the steering wheel returning state based on the detected steering torque and the estimated motor angular velocity value, and one of the two steering wheel returning detection means is provided for steering wheel returning. When the state of the steering wheel return is detected, it is determined that the state of the steering wheel return has been detected, and the correction means for correcting the current command value by the steering wheel return correction value set in advance according to the vehicle speed may be operated. Good.

[0019]

According to the first aspect of the present invention, when the handle is returned, the motor current i near the duty ratio D = 0.
Even if the motor current becomes an oscillating current due to the discontinuity characteristic of the handlebar, the handle return is performed based on the frequency at which the differential value of the motor current detected within a predetermined time exceeds a preset predetermined value. Since the state is detected, the state of the handle return can be accurately detected.

Further, in the third aspect of the invention, when the handle is returned, the motor current becomes an oscillating current due to the discontinuous characteristic of the motor current i in the vicinity of the duty ratio D = 0. However, the steering wheel is manipulated based on the frequency at which the differential value of the estimated motor angular velocity calculated based on the detected motor current value and the duty ratio detected within the predetermined time exceeds the preset predetermined value. Since the return state is detected, the handle return state can be accurately detected.

[0021]

Embodiments of the present invention will be described below.
First, an outline of an electric power steering apparatus suitable for carrying out the present invention will be described with reference to FIGS. 1 to 3. FIG.
Is a diagram for explaining the outline of the configuration of the electric power steering device. The shaft 2 of the steering handle 1 is connected to the steering wheel 8 of the steering wheel through the reduction gear 4, the universal joints 5a, 5b, and the pinion rack mechanism 7. Has been done. The shaft 2 is provided with a torque sensor 3 for detecting the steering torque of the steering handle 1, and a motor 10 for assisting the steering force is connected to the shaft 2 via a clutch 9 and a reduction gear 4. I have.

The electronic control circuit 13 for controlling the power steering device is supplied from the battery 14 to the ignition key-1.
Power is supplied through a relay that is turned on / off at 1. The electronic control circuit 13 calculates a current command value based on the steering torque detected by the torque sensor 3 and the vehicle speed detected by the vehicle speed sensor 12, and supplies the current command value to the motor 10 based on the calculated current command value. Control the current.

The clutch 9 is controlled by an electronic control circuit 13. The clutch 9 is engaged in a normal operation state, and is disconnected when the electronic control circuit 13 determines that the power steering device has failed and when the power is off.

FIG. 2 is a block diagram showing the configuration of the electronic control circuit 13. In this embodiment, the electronic control circuit 13 is mainly composed of a CPU, but the functions executed by a program inside the CPU are shown here.
For example, the stabilization compensator 21 does not show the stabilization compensator 21 as an independent hardware, but shows the stabilization compensation function executed by the CPU.

Hereinafter, functions and operations of the electronic control circuit 13 will be described. The steering torque signal input from the torque sensor 3 is phase-compensated by the stabilization compensator 21 in order to enhance the stability of the steering system, and is input to the current command value calculator 22. The vehicle speed signal detected by the vehicle speed sensor 12 is input to the current command value calculator 22 after the vehicle speed calculator 23 calculates the vehicle speed.

The current command value memory 24 is a memory that stores a map indicating the current command value corresponding to the steering torque in the normal state (the state where the steering wheel is not returned), and the vehicle speed correction memory 25 is the normal state (the steering wheel is not returned). It is a memory that stores a map indicating a correction value corresponding to the vehicle speed in the (state).

The current command value calculator 22 obtains a current command value by referring to the current command value memory 24 based on the input steering torque, and also refers to the vehicle speed correction memory 25 based on the input vehicle speed. Then, the current command value is corrected to output the current command value I0 in the normal state corresponding to the steering torque and the vehicle speed.

Reference numeral 27 denotes an adder, which is a current control target value of the current supplied to the motor 10 by adding the current command value I0 and a correction value Is for correcting the damping of the steering mechanism in the steering wheel returning state described later. The command value I is output.

The circuit composed of the comparator 28, the differential compensator 29, the proportional calculator 30, the integral calculator 31, and the adder 32 ensures that the actual motor current value i matches the current command value I. This is a circuit for performing feedback control.

In the comparator 28, the current command value I which is the control target value of the motor output from the adder 27 and the actual motor current value detected by the motor current detector 35 which will be described later. i is compared, and the signal of the difference is output.

The proportional calculator 30 outputs a proportional value proportional to the difference between the current command value I and the actual motor current value i. Further, the differential compensator 29 outputs a value proportional to the differential value of the current command value I in order to increase the response speed of the motor current value i actually flowing to the motor with respect to the current command value I. The integration calculator 31 performs integration in order to improve the characteristics of the feedback system, and outputs a value proportional to the integrated value.

The differential value of the current command value I output from the differential compensator 29, the proportional value output from the proportional calculator 30 and the integrated value output from the integral calculator 31 are added and calculated in the adder 32, and calculated. The resulting current control value E is output to the motor control circuit 33, and the motor 10 is driven via the motor drive circuit 34. The motor current i is detected by the motor current detector 35.

The motor angular velocity estimator 41 has information on the duty ratio D of the PWM signal for driving the motor 10, the motor current i detected by the motor current detector 35, and the battery voltage. An estimated value of the motor angular velocity ω is calculated based on Vb. The calculation of the estimated value of the motor angular velocity ω will be described later in detail.

The handle return detector 42 obtains the differential value of the detected motor current, counts the number of times the differential value exceeds a preset predetermined value within a predetermined time, and the number of times the preset value exceeds the predetermined value is preset. A first configuration for determining that the steering wheel is returned when the number of times is equal to or greater than a set number of times, and a differential value of a motor angular velocity estimated value is obtained, and the differential value within a predetermined time is a predetermined value set in advance. Count the number of times
There is a second configuration in which it is determined that the steering wheel is returned when the number of times exceeding a predetermined value is a preset number of times or more. Regarding these, there is a flow chart of FIGS. 6 to 9. It will be described in detail later. It is shown as a handle return detector 42 on the electronic control circuit 13 shown in FIG.

Further, the steering wheel return detector 42 is provided with a configuration for detecting the steering wheel return state based on the estimated motor angular velocity ω and the steering torque in addition to the first and second configurations. There is. This will also be described later in detail with reference to the flowcharts of FIGS.

The damping correction memory 44 is a memory in which a map indicating the damping correction value Is of the steering mechanism according to the vehicle speed calculated by the vehicle speed calculator 23 is stored. The map indicating the damping correction value is a damping correction value Is that improves the slowness of the steering wheel return that occurs when the vehicle speed is low and the steering wheel returns when the vehicle speed is low, and the vibration of the steering wheel that occurs when the vehicle speed is high. , The damping correction value Is that improves the instability of the steering wheel return is recorded.

When a signal indicating the steering wheel return state is input from the steering wheel return detector 42, the damping correction controller 43 refers to the vehicle speed calculated by the vehicle speed calculator 23, and from the damping correction memory 44, the current vehicle speed. Then, a damping correction value Is of the steering mechanism corresponding to the above is calculated and output to the adder 27.

FIG. 3 shows an example of the configuration of the motor control circuit 33, the motor drive circuit 34, and the motor current detector 35. The motor control circuit 33 controls the PW of the duty ratio D determined on the basis of the current control value E input from the adder 32.
A PWM circuit 331 that generates a M signal and outputs a rotation direction signal that determines the rotation direction of the motor based on the sign of the current control value E, and FET1 to FE of the H bridge circuit
It is composed of a gate drive circuit 332 for driving the gate of T4.

The motor driving circuit 34 is an H-bridge circuit having two first and second arms by connecting four field-effect transistors FET1 to FET4 to the bridge, and its input terminal. The battery 14 is supplied with electric power of the voltage Vb from the battery 14 through a relay operated by the ignition key 11, and the motor 10 is connected between the output terminals.

The gates of FET1 and FET2 are turned ON / OFF based on the PWM signal of the duty ratio D determined based on the current control value E, and the magnitude of the current i flowing through the motor is determined. Controlled. Also, FET3 and FET4
The gate is turned on / off by the rotation direction signal determined based on the sign of the current control value E.

When the FET3 is in a conducting state, a current flows through the FET1, the motor 10, the FET3 and the resistor R1 and a forward current flows through the motor 10. In addition, FET
When 4 is conducting, the current is FET2, motor 1
0, FET4, and resistor R2, and a negative current flows through the motor 10.

The motor current detector 35 detects the voltage drop across the resistor R1 inserted in the downstream side of the FET3, the resistor R2 inserted in the downstream side of the FET4, the resistor R1 and the resistor R2, and the motor current detector 35 detects the voltage drop. It is composed of a current detection circuit 351 for detecting the input current. The detected motor current i is fed back to the comparator 28 of the feed back control system, and the
Is input to the angular velocity estimator 41.

Next, the calculation of the estimated value of the motor angular velocity ω in the motor angular velocity estimator 41 will be described.

When a voltage is applied between the terminals of the motor, the motor rotates, but when the motor rotates, a counter electromotive force is generated in proportion to the number of rotations, and the counter electromotive force is added to the voltage applied to the motor. It

The relationship between the motor applied voltage and the back electromotive force of the motor can be expressed by the following equation (1).

Vm = (Ls + R) i + K _T ω (1) where Vm is the motor applied voltage, L is the motor inductance s is the Laplace operator, R: resistance between terminals of motor i: motor current _KT : counter electromotive force constant of motor ω: angular velocity of motor When the equation (1) is solved by ω, the angular velocity ω of the motor is , Can be expressed by the following equation (2).

Ω = {Vm- (Ls + R) i} / K _T (2) As described above, the current control value E output from the feedback control system is In the motor control circuit 33 and the motor drive circuit 34, the PWM signals having the duty ratio D are converted to drive the gates of FET1 to FET4 of the H-bridge circuit. For this reason, the motor has a duty ratio D of P
Since the battery voltage Vb is applied only while the WM signal is ON, the motor applied voltage Vm is (Vb.
It can be represented by D). The motor current i is detected by the motor current detector 35.

Therefore, the model of the motor (L is determined by the inductance L of the motor and the resistance R between the terminals of the motor).
s + R) and the back electromotive force constant K _T of the motor,
The angular velocity ω of the data can be estimated.

In order to distinguish the angular velocity of the motor and its estimated value, if the estimated value is ω1, the estimated angular velocity of the motor ω
1 can be represented by the following formula (3).

Ω1 = {Vm− (Ls + R) i} / K _T = {(Vb · D) − (Ls + R) i} / K _T (3) In order to calculate this by the program in the CPU,
Since the term of (Ls + R) cannot be calculated, a known discretization means is used, for example, s = 2 / h. (Z-1) / (z + 1) is set, and da '(s) = (Ls +
R) i (s), da ′ (k) = b1i (k) + b2i (k
-1) -a1 · da '(k-1), which allows calculation. Here, (k) shows the sample at the present time, and (k-1) shows the sample at the previous time.

The estimated angular velocity .omega.1 of the motor can be expressed by the following equation (4) and can be described in the program.

Ω1 (k) = (Vb (k) · D (k) / K _T ) − (i (k) · da ′ (k) / K _T ) ... (4) where , Vb (k) represent samples of the current battery voltage.

Next, the detection of the steering wheel return state will be described. The steering wheel return state is detected when the steering torque is 0 (or almost 0) and the motor is rotating, that is, when the motor angular velocity has a finite value, it is determined that the steering wheel is returning. can do.

However, as described above with reference to FIG. 11 in the problem to be solved by the invention,
The relationship between the PWM signal of the duty ratio D and the motor current i in the motor drive circuit is that the duty ratio D is 0 as shown in the line (b) or the line (c) of FIG. In the vicinity, a discontinuity occurs in the motor current i.

In the state where the steering wheel is returned (eg, ω <0), the current command value Iret is given in the direction in which the steering wheel is prevented from being returned due to the inertia of the steering mechanism including the motor. The current feedback control system uses this current command value I
Although the control is performed so as to follow ret, the duty ratio D corresponding to Iret does not exist because the current command value Iret is in the portion A of FIG. Therefore, when the steering wheel is returned, the motor current i of the current feedback control circuit is reduced.
Is an oscillating current, the use of the detected motor current i cannot accurately estimate the angular velocity of the motor, and as a result, the steering wheel return state cannot be detected.

Therefore, according to the first structure for detecting the state of the handle return of the present invention, the differential value of the detected motor current is obtained, and the amplitude of the differential value within a predetermined time is set to a predetermined value. The number of times (frequency) of exceeding is counted, and when the number of times exceeding a predetermined value is equal to or more than a predetermined number set in advance, it is determined that the steering wheel is returned.

That is, FIG. 4 is an example showing the state of fluctuation of the motor current i. In the normal steering state, as shown in the area (a), the motor current i is gentle in response to the steering wheel operation. However, when the handle is returned, an oscillating current is generated as shown in the area (b).

Generally, since the differential value of a signal indicates the rate of change of the signal, the waveform obtained by differentiating the oscillating current has a larger amplitude than the waveform of the oscillating current before the differentiating. In the normal steering state, the differential value of the motor current i does not fluctuate largely as shown in the area (a) of FIG. 5, but in the steering wheel returning state, as shown in the area (b), -Current i
The differential value of fluctuates greatly. Therefore, the number of times (frequency) that the differential value of the motor current i exceeds a preset predetermined value is counted, and when the number of times the preset value exceeds the preset value appears more than a preset number of times, the steering wheel is returned. Can be determined.

FIGS. 6 and 7 are flow charts for explaining the control operation of the electronic control circuit 13 including the first construction for detecting the handle return state according to the present invention. First, the signals from the torque sensor and the vehicle speed sensor are input, and the current command value I0 is calculated (steps P1, P2, P3). PWM
The duty ratio D of the signal and the motor current i are detected (steps P4 and P5).

Based on the motor current i and the duty ratio D of the PWM signal, the estimated angular velocity value ω1 of the motor is calculated (step P6), and the differential value of the motor current i is calculated (step P6). P7).

It is judged whether or not the differential value of the motor current i exceeds a predetermined value set in advance (step P8), and when it exceeds the predetermined value, the number of times exceeding the predetermined value is counted (step P9).

The elapse of a predetermined time is judged (step P1
0) When the predetermined time has elapsed, it is judged whether or not the count value counted in step P9 exceeds a preset predetermined number of times (step P11). When it exceeds the predetermined number of times, it can be determined that the steering wheel is returned.

When it is determined in step P10 that the predetermined time has not elapsed and when the determination in step P11 does not exceed the predetermined number of times, the steering torque exceeds the predetermined value and the motor angular velocity estimated value is further exceeded. Is above the predetermined value (steps P12 and P13), and when the steering torque exceeds the predetermined value and the estimated motor angular velocity exceeds the predetermined value, it is determined that the steering wheel is returned. . This supplements the determination of the steering wheel return state under the condition that the differential value of the motor current i exceeding the preset predetermined value, which is executed in the processing from steps P8 to P11, appears over the predetermined number of times, This is to ensure the determination of the handle return state.

The vehicle speed is determined, the correction value Is corresponding to the vehicle speed is read from the damping correction memory, and the current command value I is corrected (steps P14, P15, P16). That is, if the vehicle speed is low, the correction value Is for improving the steering wheel return is added to the current command value I0. If the vehicle speed is high, the current command value I0 is added.
The correction value Is for improving the convergence is added to 0, the current control value E is obtained based on the corrected current command value I, and the duty ratio D of the PWM signal is determined based on the current control value E. Motor control is performed (step P17), and step P1
Return to

Next, the second configuration for detecting the handle return state of the present invention will be described. The first configuration for detecting the state of the handle return is to obtain the differential value of the detected motor current, count the number of times the differential value exceeds a preset predetermined value within a predetermined time, and set the predetermined value. When the number of times exceeds the predetermined number of times appears more than a preset number of times, it is determined that the steering wheel is in the return state. In the second configuration, after estimating the motor angular velocity, the motor angular velocity estimated value is Obtain the differential value, count the number of times the amplitude of the differential value exceeds a preset predetermined value within a predetermined time, and when the number of times the predetermined value exceeds the preset number of times appears,
It is determined that the steering wheel is returned.

8 and 9 are flow charts for explaining the control operation of the electronic control circuit 13 including the second structure for detecting the return state of the handle according to the present invention. First, the signals from the torque sensor and the vehicle speed sensor are input, and the current command value I0 is calculated (steps P21, P22, P23).
The duty ratio D of the PWM signal and the motor current i are detected (steps P24 and P25).

Based on the motor current i and the duty ratio D of the PWM signal, the estimated motor angular velocity .omega.1 is calculated (step P26), and the differential value of the estimated motor angular velocity .omega.1 is calculated. (Step P27).

It is determined whether or not the differential value of the estimated motor angular velocity .omega.1 exceeds a preset predetermined value (step P2).
8) If it exceeds the predetermined value, the number of times the predetermined value is exceeded is counted (step P29).

The elapse of a predetermined time is judged (step P3
0) When the predetermined time has elapsed, it is determined whether the count value counted in step P29 has exceeded a preset predetermined number of times (step P31). When it exceeds the predetermined number of times, it can be determined that the steering wheel is returned.

When it is determined in step P30 that the predetermined time has not elapsed, and when the determination in step P31 has not exceeded the predetermined number of times, the steering torque exceeds the predetermined value and the motor angular velocity estimated value is further exceeded. Is above the predetermined value (steps P32 and P33), and when the steering torque exceeds the predetermined value and the estimated motor angular velocity exceeds the predetermined value, it is determined that the steering wheel is returned. . This supplements the determination of the steering wheel return state under the condition that the differential value of the estimated motor angular velocity value exceeding the preset predetermined value, which is executed in the processing from steps P28 to P31, appears over the predetermined number of times. This is to ensure the determination of the steering wheel return state.

The vehicle speed is determined, the correction value Is corresponding to the vehicle speed is read from the damping correction memory, and the current command value I is corrected (steps P34, P35, P36). That is, if the vehicle speed is low, the correction value Is for improving the steering wheel return is added to the current command value I0. If the vehicle speed is high, the current command value I0 is added.
The correction value Is for improving the convergence is added to 0, the current control value E is obtained based on the corrected current command value I, and the duty ratio D of the PWM signal is determined based on the current control value E. Motor control is performed (step P37), and step P2
Return to 1.

[0072]

As described above, the control device for the electric power steering apparatus of the present invention is caused by the discontinuous characteristic of the motor current i in the vicinity of the duty ratio D = 0 when the steering wheel is returned. Even if the motor current becomes an oscillating current, the handle return state is detected based on the frequency at which the differential value of the motor current detected within a predetermined time exceeds a preset predetermined value, or Detecting the steering wheel return state based on the frequency at which the estimated motor angular velocity calculated based on the detected motor current value and duty ratio detected within a predetermined time exceeds a preset predetermined value. Therefore, the state of returning the handle can be accurately detected. Further, it is possible to obtain a remarkable action and effect such that a sensor for detecting the motor angular velocity is not required and the manufacturing cost is not increased.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an outline of a configuration of an electric power steering device.

FIG. 2 is a block diagram of an electronic control circuit of the electric power steering device.

FIG. 3 is a block diagram of a motor control circuit, a motor drive circuit, and a motor current detection circuit.

FIG. 4 is a diagram showing an example of a variation state of a motor current.

FIG. 5 is a diagram illustrating extraction of a motor current.

FIG. 6 is a flow chart (No. 1) for explaining the control operation of the electronic control circuit 13 including the detection of the steering wheel return state.

FIG. 7 is a flowchart (part 2) for explaining the control operation of the electronic control circuit 13 including the detection of the steering wheel return state.

FIG. 8 is a flowchart (No. 1) for explaining the second control operation of the electronic control circuit 13 including the detection of the steering wheel return state.

FIG. 9 is a flowchart (No. 2) for explaining the second control operation of the electronic control circuit 13 including the detection of the steering wheel return state.

FIG. 10 is a block diagram of a motor drive circuit including an H-bridge circuit composed of FET1.

FIG. 11 is a diagram for explaining a relationship among a motor angular velocity, a motor current, and a duty ratio.

[Explanation of symbols]

 3 torque sensor 10 motor 12 vehicle speed sensor 13 electronic control circuit 21 stabilization compensator 22 current command value calculator 23 vehicle speed calculator 24 static characteristic command value memory 25 static characteristic vehicle speed correction memory 27 adder 28 comparator 29 differential compensation 30 Proportional calculator 31 Integral calculator 32 Adder 33 Motor control circuit 34 Motor drive circuit 35 Motor current detection circuit 41 Motor angular velocity estimator 42 Handle return detector 43 Damping correction controller 44 Damping Correction memory

Claims (4)

[Claims] 1. A steering assist force for a steering mechanism based on a current command value calculated from at least a steering torque signal generated in a steering shaft and a vehicle speed signal and a current control value calculated from a detected motor current value. In a control device for an electric power steering apparatus having a feedback control means for controlling the output of a motor, a power source is output between input terminals of a bridge circuit constituted by connecting a semiconductor element to an H bridge. A motor drive circuit in which the motor is connected between terminals, and the handle return state is detected based on the frequency at which the differential value of the motor current detected within a predetermined time exceeds a preset predetermined value. When the steering wheel return detection means and the steering wheel return state are detected, the current command value is corrected by the steering wheel return correction value set in advance according to the vehicle speed. A controller for an electric power steering apparatus, comprising: 2. A controller for an electric power steering apparatus according to claim 1, further comprising a motor current detection value and a duty ratio of a PWM signal for driving a semiconductor element of the H-bridge circuit. A motor wheel angular velocity estimating means for estimating the motor angular velocity; and a second steering wheel returning detecting means for detecting a steering wheel returning state based on the detected steering torque and the estimated motor angular velocity value. When any one of the detecting means detects the steering wheel return state, it is determined that the steering wheel return state is detected, and the current instruction value is corrected by the steering wheel return correction value set in advance according to the vehicle speed. A control device for an electric power steering device, characterized in that the control device operates. 3. A steering assist force is applied to a steering mechanism based on a current command value calculated from at least a steering torque signal generated in a steering shaft and a vehicle speed signal and a current control value calculated from a detected motor current value. In a control device for an electric power steering apparatus having a feedback control means for controlling the output of a motor, a power source is output between input terminals of a bridge circuit constituted by connecting a semiconductor element to an H bridge. A motor drive circuit in which the motor is connected between terminals, and a motor angular velocity estimated value is obtained based on a motor current detection value and a duty ratio of a PWM signal for driving a semiconductor element of the H-bridge circuit. The motor angular velocity estimating means for calculating and the differential value of the motor angular velocity estimated value calculated based on the detected motor current value and the duty ratio within a predetermined time are previously calculated. When the steering wheel return state is detected, the steering wheel return detection means detects the steering wheel return state based on the frequency of exceeding the set predetermined value. A controller for an electric power steering apparatus, comprising: 4. The control device for an electric power steering system according to claim 3, further comprising a second steering wheel return detection for detecting a steering wheel return state based on the detected steering torque and the estimated motor angular velocity value. When either one of the two steering wheel return detecting means detects the steering wheel return state, it is determined that the steering wheel return state is detected, and the steering wheel return correction value set in advance according to the vehicle speed. A control device for an electric power steering apparatus, characterized in that a correction means for correcting the current command value is operated by means of.