JP2001171533A - Motor-driven power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an influence to control for steering wheel return compensation torque caused by contamination of a noise. SOLUTION: An angular velocity ωm of a motor is found by an expression shown by ωm=Vm/Ke, where Vm: motor voltage, Ke: counter-electromotive force constant, in this power steering device for conducting the control for the compensation torque based on the angular velocity ωm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an electric power steering apparatus.

[0002]

2. Description of the Related Art In a conventional electric power steering apparatus, an output signal of a torque sensor for detecting a steering torque,
The assist torque of the motor is controlled based on the output signal of the vehicle speed sensor that detects the vehicle speed. In such an electric power steering device, the steering wheel return compensation torque is controlled based on the motor angular velocity in order to compensate for the deterioration of the steering feeling due to friction in the motor and the speed reducer.

FIG. 9 is a block diagram showing the main electrical configuration of a conventional electric power steering apparatus. The torque signal output from the torque sensor 11 that detects the steering torque is input to the ECU 10 via the interface 13a and the A / D converter 14a, and
By 1, the phase is advanced to compensate for the mechanical delay with respect to the output of the torque sensor 11. The vehicle speed signal output from the vehicle speed sensor 12 for detecting the vehicle speed is transmitted to the EC via the interface 13b and the timer 14b.
It is input to U10. Subsequently, the assist command value calculation unit 2
2 is a phase-compensated torque signal and a vehicle speed sensor 1
A current command value corresponding to a torque (hereinafter referred to as an assist torque) generated in the motor M for assisting the steering force is determined based on the vehicle speed signal output from the second control signal.

A current command value is determined by an assist command value calculation unit 22, and a voltage command value corresponding to the current command value is generated by a PI control unit 24. This voltage command value is P
The signal is converted into a corresponding duty ratio by a WM (pulse width modulation) calculator 25, and a pulse signal corresponding to the duty ratio is output to the motor drive circuit 15 to drive the motor M. The motor current flowing through the motor M is supplied to the A / D converter 14 via the interface 13c.
c, and is input to the ECU 10,
It is fed back to the I control unit 24. Then, the PI control unit 24 controls the voltage command value so that the current command value matches the detected value of the motor current.

When the driver stops steering and releases his / her hand from the steering wheel during traveling, that is, when the output value of the torque sensor is zero or less than a predetermined value close to it, the steering wheel angular velocity estimating unit 28 detects the road surface reaction force. Calculates the motor angular velocity when the motor M is rotated toward the neutral position by the action of so-called self-aligning torque that causes the tire to return to the straight running direction.

[0006] The motor angular velocity can be obtained by detecting a motor terminal voltage (hereinafter referred to as motor voltage) Vm and a motor current Im when the motor M is rotated by the action of the self-aligning torque. That is, the motor M
If Ke is the back electromotive force constant, L is the inductance, and R is the resistance between terminals (hereinafter referred to as motor resistance), then the motor voltage Vm can be obtained by Equation 1, and the motor angular velocity ωm can be obtained by solving Equation 1 by ωm. Is given by Equation 2. (Equation 1) Vm = (LS + R) Im + Ke · ωm (Equation 2) ωm = {Vm− (LS + R) Im} / Ke, where S = d / dt.

The motor voltage Vm is supplied to A / D converters 14d and 14e via interfaces 13d and 13e.
The motor current Im is digitally converted by the A / D converter 14c and input to the steering wheel angular velocity estimating unit 28.

[0008] The motor angular velocity ωm obtained by equation 2 is
It includes a transient term due to the motor inductance L when the motor M is driven by PWM. Since the rise time constant of the current of the motor M is sufficiently small and has little effect on the motor angular velocity ωm, the motor angular velocity ωm is calculated by Expression 3 ignoring the motor inductance L.
(See, for example, Japanese Patent Application Laid-Open No. 4-8190) (Equation 3) ωm = (Vm−R · Im) / Ke The steering wheel angular velocity is obtained by multiplying the motor angular velocity ωm obtained by Equation 3 by the reduction ratio.

Then, a steering wheel return compensation current value calculation unit 2
7 determines a steering wheel return compensation current value for restoring the steering wheel to the neutral position by driving the motor based on the steering wheel angular velocity calculated by the steering wheel angular velocity estimating unit 28 and the output signal of the vehicle speed sensor. The return compensation current value is sent to the adder 23.

The steering wheel return compensation current value is determined based on the steering wheel angular velocity and the vehicle speed. Weighting is performed in accordance with the vehicle speed. The weighting is increased in a low speed range, and the weighting is reduced as the speed goes out of the low speed range. I do. As a result, in a low-speed range where the self-aligning torque is small, the steering wheel return torque for returning the steering wheel to the neutral position becomes large, the friction force can be overcome, and the steering wheel can be returned to the neutral position. In the range, the steering return torque is small, so that the sense of stability of the steering is increased.

[0011]

In the above prior art, when noise is mixed in the motor current detection circuit or the motor voltage detection circuit, a fluctuation component is added to the motor angular velocity and the steering wheel return compensation current value fluctuates. Noise and vibration may occur.

Accordingly, an object of the present invention is to provide an electric power steering apparatus capable of reducing the influence of noise in the steering wheel return compensation torque control and reliably restoring the steering wheel to a neutral position during traveling. I do.

[0013]

According to the present invention, in order to achieve the above object, an input member and an output member provided in a steering system in an electric power steering apparatus. And a motor that applies torque to the steering system, and a torque sensor that detects a steering torque input to the input member, wherein the motor has an assist torque that assists a steering force based on the steering torque. And a compensating torque for returning the steering wheel to the neutral position based on the angular velocity of the motor. The angular velocity of the motor is determined based on the voltage between the terminals of the motor.

According to the first aspect of the present invention, the angular velocity of the motor is obtained from the voltage between the terminals of the motor, and a compensation torque for returning the handle generated by the motor to the neutral position is controlled based on the obtained angular velocity of the motor. I have.

Therefore, the current flowing through the motor is not used to determine the angular velocity of the motor, so that the noise is reduced, and the motor is less likely to generate abnormal noise and vibration due to fluctuations in the compensation torque.

According to a second aspect of the present invention, in the electric power steering apparatus, an input member and an output member provided in a steering system, a motor for applying a torque to the steering system, and a steering input to the input member A torque sensor for detecting torque, wherein the motor has an assist torque for assisting a steering force based on the steering torque;
PWM control is performed in accordance with a duty ratio corresponding to a compensation torque for returning the steering wheel to the neutral position based on the angular speed of the motor, and the angular speed of the motor is calculated from the duty ratio and the power supply voltage. It was made to ask based on.

According to the second aspect of the invention, the motor voltage is calculated from the duty ratio and the power supply voltage applied to the motor, the angular velocity of the motor is determined from the voltage of the motor, and the motor angular velocity is determined based on the determined angular velocity of the motor. The compensation torque for returning the generated handle to the neutral position is controlled.

Therefore, the current flowing through the motor is not used to determine the angular velocity of the motor, so that noise is reduced, and the motor is less likely to generate abnormal noise and vibration due to fluctuations in the compensation torque. In addition, since the power supply voltage is originally input to the ECU for another purpose (for fail-safe processing), two interfaces and two A / D converters are required, compared with a configuration in which the voltage between the terminals of the motor is obtained. The noise can be reduced, the noise is further reduced, and the cost is reduced. Further, since the motor voltage is obtained from the duty ratio and the power supply voltage applied to the motor, the phase lag is smaller than that obtained by taking in the voltage between the terminals of the motor.

According to a third aspect of the present invention, in the electric power steering apparatus, an input member and an output member provided in a steering system, a motor for applying a torque to the steering system, and a steering input to the input member A torque sensor for detecting torque, wherein the motor has an assist torque for assisting a steering force based on the steering torque;
PWM control is performed in accordance with a duty ratio generated by a voltage command value corresponding to a compensation torque for returning the steering wheel to the neutral position based on the angular velocity of the motor, and the voltage command value is set to the voltage of the motor, The angular velocity was determined based on the voltage of the motor.

According to a third aspect of the present invention, a motor voltage is calculated from a voltage command value for generating a duty ratio applied to the motor, an angular velocity of the motor is determined from the voltage of the motor, and the angular velocity of the determined motor angular velocity is calculated. Based on this, the compensation torque for returning the handle generated by the motor to the neutral position is controlled.

Therefore, the current flowing through the motor is not used to determine the angular velocity of the motor, so that noise is reduced, and the motor is less likely to generate abnormal noise and vibration due to fluctuations in compensation torque. Further, as compared with the motor that takes in the voltage between the terminals of the motor, the number of interfaces and A / D converters can be reduced by two, thereby further reducing noise contamination and cost. Further, the time required for the A / D conversion of the motor voltage or the calculation processing time becomes unnecessary, and the time required for controlling the compensation torque is reduced.

According to a fourth aspect of the present invention, in the electric power steering apparatus according to any one of the first to third aspects, the angular velocity of the motor is ωm, the voltage of the motor is Vm, and the reverse of the motor is provided. Assuming that the electromotive force constant is Ke, the angular velocity of the motor is obtained from ωm = Vm / Ke.

According to the present invention, the angular velocity of the motor is obtained from the voltage of the motor and the back electromotive force constant of the motor.

Therefore, since the current flowing through the motor is not used to determine the angular velocity of the motor, the contamination of noise is reduced, and the occurrence of abnormal noise and vibration of the motor due to the fluctuation of the compensation torque is reduced. The calculation processing time is reduced.

According to a fifth aspect of the present invention, in the electric power steering apparatus according to any one of the first to fourth aspects, when the steering torque is equal to or more than a predetermined threshold, the compensation torque is set to zero. I made it.

According to the fifth aspect of the present invention, the current flowing through the motor is neglected in obtaining the angular velocity of the motor. Therefore, when a large current flows through the motor, the calculated value of the angular velocity of the motor and the actual value are calculated. Although offset occurs, if the steering torque is equal to or greater than a predetermined threshold, no compensation torque is generated in the motor.

Therefore, when the driver is holding the steering wheel, there is no effect of the offset between the actual motor angular velocity and the calculated motor angular velocity.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the electric power steering apparatus according to the present invention will be described below with reference to the drawings. In the following embodiments, an electric power steering device provided in a vehicle such as an automobile will be described as an example of the electric power steering device of the present invention. The same components as those of the conventional electric power steering device shown in FIG. 9 are denoted by the same reference numerals, and description thereof will be omitted.

First, a main mechanical configuration of a steering system constituting the electric power steering apparatus according to the first embodiment of the present invention will be described with reference to FIG. The driver is the steering wheel 1
Is steered, the input shaft 2 provided at the axis of the steering wheel 1
Rotates, and the output shaft 4 connected to the input shaft 2 via the torsion bar 3 rotates. The rotation of the output shaft 4 is converted into axial movement of a rack shaft 5 meshing at its tip with a rack and pinion gear mechanism, and steers a tire (not shown). A motor M is connected to the output shaft 4 via a speed reducer 6, and the motor M is driven to rotate by a command from the ECU 10. The ECU 10 includes a torque sensor 11 for detecting a driver's steering torque and a vehicle speed sensor 1 for detecting a vehicle speed of the vehicle.
2 is input. The torque sensor 1
Numeral 1 detects torque based on the amount of twist of the torsion bar 3, that is, the relative rotation angle between the input and output shafts 2 and 4.

Next, the electric configuration of the electric power steering apparatus is shown by blocks in FIGS.
This will be described with reference to FIG. As shown in FIG. 2, the output signal of the torque sensor 11 is supplied to A through the interface 13a.
Digitally converted by the / D converters 14a and 14b,
10 is input. The output signal of the vehicle speed sensor 12 counts a pulse cycle by a timer 14b via an interface 13b and is input to the ECU 10. EC
In U10, based on the input steering torque and vehicle speed, a PWM (pulse wi
dth modulation) Determine the command value. Motor drive circuit 1
5 outputs a drive current corresponding to the PWM command value sent from the ECU 10 to the motor M. And the motor M
Generates an assist torque to assist the steering force,
Alternatively, a steering wheel return compensation torque for restoring the steering wheel to the neutral position is generated.

An assist command current value IA is determined by the assist command value calculation unit 22, and a voltage command value Vn corresponding to the assist command current value IA is generated by the PI control unit 24. The voltage command value Vn is converted into a corresponding duty ratio by the PWM calculator 25, and a pulse signal corresponding to the duty ratio is output to the motor drive circuit 15 to drive the motor M. The motor current Im flowing to the motor M is fed back to the PI control unit 24, and the voltage command value Vn is controlled so that the assist command current value IA matches the detected value of the motor current Im. Note that this P
In the I control unit 24, a steering wheel return compensation current value I
For H, the same processing as the processing for the assist command current value IA is performed.

The motor drive circuit 15 is turned on by PWM.
FET15 as switching element to be controlled / off
a to H-bridge provided with FET 15d. The left FETs 15a and 15d are connected to the upper FET 15
a is ON, the lower FET 15d is OFF, and the upper F
ON / OFF control is performed so that the lower FET 15d is turned ON when the ET 15a is OFF. Right FET15
b, FET 15c are similarly ON / OF so that the upper FET 15b and the lower FET 15c are in the reverse state.
F control is performed. Then, the FETs 15a to 15d are connected to different duty ratios Da, Db, Dc (= 1−D
b), the motor M is controlled by turning on / off at Dd (= 1−Da).

The phase of the torque signal digitally converted by the A / D converter 14a is advanced by the phase compensator 21 to compensate for a mechanical delay with respect to the output of the torque sensor 11. This phase-compensated torque signal,
Based on the vehicle speed signal counted by the timer 14b, the assist command value calculation unit 22 determines a current command value IA corresponding to the assist torque generated in the motor M to assist the steering force.

Here, the processing in the assist command value calculation section 22 will be described with reference to FIG. The steering torque value compensated for advancing the phase by the phase compensator 21 is sent to the assist command value calculator 22. The assist command value calculation unit 22 has an assist current value Ia on the vertical axis.
Using the assist map 22a in which the steering torque is set on the horizontal axis, the assist current values Ial and Iah corresponding to the steering torque subjected to the phase compensation are determined, and the determined assist current values Ial and Iah are linearly interpolated. 22c
Send to

The assist command value calculation unit 22 determines the gain Ga corresponding to the vehicle speed sent from the vehicle speed sensor using the vehicle speed map 22b in which the vertical axis represents the gain Ga and the horizontal axis represents the vehicle speed. The determined gain Ga is sent to the linear interpolator 22c.

That is, the assist command value calculating section 22 uses the linear interpolator 22c to output the assist current values Ial and Ia.
h is a linear interpolation with gain Ga (Ial · Ga + Iah ·
(1−Ga) = IA), and determines the current command value IA to be sent from the assist command value calculation unit 22 to the adder 23.

On the other hand, when the driver turns the tire toward the neutral position by the self-aligning torque due to the road surface reaction force, such as when the driver releases the steering wheel 1, the rack shaft 5 pivots and the output shaft is rotated. 4 rotates, and the motor M also rotates.
During this regeneration, the motor current I generated in the motor M
m is input to the ECU 10 via the interface 13c, is digitally converted by the A / D converter 14c, and is fed back to the PI control unit 24. PI control unit 2
In (4), the voltage command value Vn sent to the PWM operation unit 25 is constantly controlled so that Equation 1 is satisfied.

At this time, the motor voltage Vm is supplied to the interface 1 so that it can be input to the ECU 10 from each terminal.
A / D converters 14d and 14e
Is converted into a digital signal, and is input to the ECU 10 and sent to the subtracter 28a of the steering wheel angular velocity estimating unit 28 to be detected. The steering wheel angular velocity ωh calculated from the motor voltage Vm is used as the steering wheel return compensation current value calculation unit 27.
Sent to

The steering wheel angular velocity estimating section 28 calculates the motor angular velocity ωm, and calculates the steering wheel angular velocity ωh based on this. Although the motor angular velocity ωm can be obtained by the above-mentioned formula 3, since the motor current Im due to regeneration is very small, this term is ignored and the motor electromotive force constant Ke and the motor voltage Vm are almost correctly calculated. (Equation 4). Also, the steering wheel angular velocity ωh
Is obtained by multiplying the motor angular velocity ωm by the reduction ratio 1 / G of the speed reducer 6 (Equation 5). (Equation 4) ωm = Vm / Ke (Equation 5) ωh = Vm / (G · Ke)

As shown in FIG. 4, the steering wheel return compensation current value calculation section 27 has a vertical axis representing the steering wheel return compensation current value Ih.
And a steering wheel angular velocity estimating unit 2 using a steering wheel return map 27a in which the steering axis velocity ωh is set on the horizontal axis.
The steering wheel return compensation current value Ih corresponding to the steering wheel angular velocity ωh output from 8 is determined, and the determined steering wheel return compensation current value Ih is sent to the multiplier 27c.

The steering wheel return compensation current value calculator 27
Selects the gain Gh corresponding to the vehicle speed transmitted from the vehicle speed sensor 12 using the vehicle speed map 27b in which the vertical axis represents the gain Gh and the horizontal axis represents the vehicle speed, and transmits the selected gain to the multiplier 27c. I do.

That is, the multiplying circuit 27c multiplies the steering wheel return compensation current value Ih by the gain Gh (Gh · Ih = I
h ′), and weights the steering wheel return compensation current value Ih in accordance with the vehicle speed.

The steering wheel return compensation current value Ih ′ determined by the steering wheel return compensation current value calculation section 27 is sent to the switching section 29. The switching unit 29 performs the determination by the steering-holding determination unit 30 that receives the phase-compensated torque signal,
The handle return compensation current value IH sent to the adder 23 is
It is determined to be either the value Ih 'determined by the steering wheel return compensation current value calculation unit 27 or zero. Then, the determined handle return compensation current value IH is subjected to a smoothing process by the low-pass filter unit 31 and sent to the adder 23.

Here, the determination in the steering-holding steering determination unit 30 will be described with reference to FIGS. FIG. 5 shows a state in which the driver holds the steering wheel 1 for one second and then releases it. The horizontal axis indicates time, and the vertical axis indicates the steering wheel angular velocity ωh.
(A), a steering wheel return compensation torque (b), and a steering-holding steering determination flag (c) are taken. FIG. 6 is a flowchart illustrating a flow of the determination in the steering-holding steering determination unit 30.

The steering wheel angular velocity ωh obtained by the equation (5) can be obtained almost correctly when the driver releases the steering wheel 1 because the motor current Im during regeneration is very small. However, when the driver is steering the steering wheel 1 at a constant steering angle, a large current flows through the motor M by the steering torque signal despite the actual steering wheel angular velocity ωh = 0, so that the motor current Im An offset as shown in FIG. 5A occurs in the calculated value of the steering wheel angular velocity ωh obtained by Expression 5 ignoring the term subtraction.

Therefore, the steering-holding steering determination unit 30 performs the processing shown in the flow chart of FIG. 6 to set the steering wheel return compensation torque of the motor M during steering to zero as shown in FIG. 5B. Handle return compensation current calculator 27
Then, the steering wheel return compensation current value Ih ′ is determined based on the input steering wheel angular velocity ωh (S301). Further, the phase-compensated steering torque is input to the steering-holding steering determination unit 30 (S302). Then, the value of the steering torque is compared with a predetermined threshold value TH0 (S303). S30
If the value of the steering torque is equal to or larger than the threshold value in step 3, it is determined that the driver is steering or maintaining the steering, and the steering maintenance determination flag is set to O.
N (see FIG. 5C), the steering wheel return compensation current value IH to be sent to the adder 23 becomes zero by the switching unit 29 (S304). When the value of the steering torque is less than the threshold value in S303, the steering-maintenance determining unit 30 determines that the driver has released the handle 1 and turns off the steering-maintenance determination flag (FIG. 5C). ), The handle return compensation current value IH sent to the adder 23 is the current value Ih 'determined by the switching unit 29 in S301 (S30).
5).

Then, as shown in FIG. 2, the assist current value IA determined by the assist command value calculation unit 22 and the steering wheel return compensation current value IH determined by the switching unit 29 are added by the adder 23, and PI The voltage command value Vn is generated by the control unit 24, the duty ratio corresponding to the voltage command value Vn is calculated by the PWM calculation unit 25, and a pulse signal corresponding to the duty ratio is sent to the motor drive circuit 15. Then, the motor M is rotated by a pulse signal given to the motor drive circuit 15, and generates an assist torque or a steering wheel return compensation torque in a direction opposite to the assist torque.

As described above, according to the first embodiment of the present invention, only the motor voltage Vm is used for estimation of the steering wheel angular velocity ωh (motor angular velocity ωm) (the motor current Im is not used). Therefore, the steering angular velocity estimating unit 2
8 is less likely to vary the steering wheel return compensation torque due to noise.

Also, during steering, the steering wheel angular velocity ω
The offset generated between the actual steering wheel angular velocity and the calculated value of the steering wheel angular velocity estimating unit 28 due to ignoring the motor current Im term in the estimation of h is the steering-holding steering determining unit 30
Since the steering wheel return compensation current value IH is set to zero by the determination of the above, there is no interference between the assist torque and the steering wheel return compensation torque.

Next, an electric power steering apparatus according to a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, only the method of extracting the motor voltage Vm is different from that of the first embodiment. Therefore, the same components as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. In the second embodiment, the motor voltage Vm is calculated from the duty ratio and the power supply voltage.

The PWM calculation unit 25 calculates a duty ratio corresponding to the voltage command value Vn generated by the PI control unit 24, outputs a pulse signal corresponding to the duty ratio to the motor drive circuit 15, M is controlled.

The motor drive circuit 15 includes FETs 15a to 15f
It is composed of an H-bridge with ET15d,
T15a to FET15d are on the left side (FET15a,
15d), the upper FET 15a and the lower FET 1
ON / OFF control is performed so that 5d is in the reverse state, and ON / OFF control is also performed on the right side (FET 15b, FET 15c) so that the upper FET 15b and the lower FET 15c are in reverse state.

Then, the PWM calculation unit 25 determines the FETs 15a to 15a based on the voltage command value Vn from the PI control unit 24.
Different duty ratios Da, Db, Dc for 5d
(= 1−Db) and Dd (= 1−Da), and the FETs 15 a to 15 d correspond to the duty ratios Da to Dd.
d is ON / OFF controlled. The motor current Im is determined based on the duty ratios Da to Dd by the FET 15a → the motor M
→ FET15c or FET15b → Motor M →
The current flows through the FET 15d, and the rotation of the motor M is controlled in both directions. Further, at the time of regeneration in which the motor is rotated by the self-aligning torque or the like, the motor current Im flows in the opposite direction.

On the other hand, the duty ratios Da to Dd generated by the PWM calculator 25 are sent to the motor drive circuit 15 and also sent to the steering wheel angular velocity estimator 28. The steering wheel angular velocity estimating unit 28 includes a motor voltage calculating unit 2
8a is provided, and the duty ratios Da to Dd are input here. The power supply voltage Vb is divided by the interface 13f into the motor voltage calculation unit 28a,
It is input to the ECU 10 via the D converter 14f. The interface 13f and the A / D converter 14f
Is originally provided for performing fail-safe processing such as stopping power supply to the electric power steering device when the power supply voltage Vb decreases.

The motor voltage calculator 28a calculates the motor voltage Vm based on the duty ratios Da to Dd and the power supply voltage Vb. The motor voltage Vm is such that the PWM pulse signal is sufficiently shorter than the electric time constant of the motor M, and the path of the motor current Im is the FET 15a, the motor M, and the FET1.
In the case of 5c, the power supply voltage Vb is multiplied by the duty ratios Da and Dc, and is approximately obtained by the difference (Equation 6). (Equation 6) Vm = Vb-Da-Vb-Dc = Vb {Da- (1-Db)} = Vb (Da + Db-1)

The path of the motor current Im is
Similarly, in the case of b, the motor M, and the FET 15d, it is also approximately obtained by Expression 6. This is the same at the time of regeneration.

In the steering wheel angular velocity estimating section 28, the motor voltage calculating section 28b calculates the motor voltage Vm according to Equation 6, and based on this motor voltage Vm, obtains the steering wheel angular velocity ωh according to Equation 5. Then, the calculated steering wheel angular velocity ωh is sent to the steering wheel return compensation current value calculation unit 27,
Thereafter, the same steering wheel return compensation torque control as in the first embodiment is performed.

In the electric power steering apparatus according to the second embodiment, the effects of the first embodiment can be obtained.
This has the effect of reducing costs by reducing the number of / D converters. That is, in the first embodiment, the motor M
Interface 1 to capture the terminal voltage Vm
3d and 13e and two A / D converters 14d and 14e were required respectively. However, in the second embodiment, the power supply voltage Vb already taken in the ECU 10 for fail-safe processing and the PWM calculation Since the motor voltage Vb is calculated from the duty ratios Da and Db obtained by the unit 25, the interfaces 13f and A
The number of / D converters 14f can be reduced by two. Further, the calculated phase delay of the steering wheel angular velocity ωh is smaller than that of the first embodiment in which the voltage Vm between the terminals of the motor M is taken.

Next, an electric power steering apparatus according to a third embodiment of the invention will be described with reference to FIG. In the electric power steering apparatus according to the third embodiment, the voltage command value Vn generated by the PI control unit 24 is sent to the steering wheel angular velocity estimation unit 28 as the motor voltage Vm. This eliminates the need for an interface for taking in the voltage between the terminals of the motor M and the A / D converter, and shortens the calculation time of the steering wheel angular velocity ωh. Note that the configuration is the same as that of the above-described first and second embodiments except for the acquisition of the motor voltage Vm, and a description of the same configuration will be omitted.

The assist current value IA determined by the assist command value calculation section 22 and the steering wheel return compensation current value IH determined by the switching section 29 are added by the adder 23 and input to the PI control section 24. In the PI control unit 24, a voltage command value Vn is generated, and the voltage command value Vn is sent to the PWM calculating unit 25 and also sent to the steering wheel angular velocity estimating unit 28. The steering angular velocity estimating unit 28 takes in the voltage command value Vn as the motor voltage Vm, and obtains the steering angular velocity ωh based on Equation 5. Then, the obtained steering wheel angular velocity ωh is sent to the steering wheel return compensation current calculator 27, and thereafter, the steering wheel return compensation torque control similar to that of the above-described first and second embodiments is performed.

As described above, according to the electric power steering apparatus of the third embodiment, the steering wheel angular velocity estimating section 28
Captures the voltage command value Vn generated by the PI control unit 24 as the motor voltage Vm. Therefore, similarly to the effect of the second embodiment, the interface for taking in the voltage between the terminals of the motor M and the A / D converter become unnecessary, and the cost can be reduced. Further, since the time for A / D conversion or the time for calculating the motor voltage Vm is not required, the processing time in the steering wheel return compensation control can be reduced, and the phase delay of the calculated steering wheel angular velocity is small.

In each of the above embodiments, the steering angular velocity ωh obtained by multiplying the motor angular velocity ωm by the reduction ratio 1 / G is used.
, The steering wheel return compensation torque control may be performed based on the motor angular velocity ωm.

As described above, according to the present invention, the motor angular velocity is calculated by taking in only the motor voltage. Mixing can be reduced, and the effect of noise can be reduced. Further, since the steering wheel angular velocity (motor angular velocity) is calculated only from the motor voltage, an offset occurs between the actual steering wheel angular velocity (motor angular velocity) during steering and the calculated steering wheel angular velocity (motor angular velocity). Since a steering determination unit is provided to determine that the steering is maintained when the steering torque is equal to or more than a predetermined threshold, the influence of the offset caused by ignoring the term of the motor current is completely eliminated.

Further, if the motor voltage is calculated from the power supply voltage and the duty ratio, the number of interfaces and A / D converters is reduced as compared with the case where the motor voltage is obtained from the voltage between the terminals of the motor M. As a result, the cost is reduced, and the phase delay of the calculated steering angular velocity is reduced.

If the voltage command value generated by the PI control unit is taken in as the motor voltage, the number of interfaces and A / D converters can be reduced, and the cost is reduced. In this case, the time required for the A / D conversion of the motor voltage or the calculation processing time is not required, and the time required for the steering wheel return compensation torque control is reduced.
The calculated phase lag of the steering wheel angular velocity is reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a mechanical configuration of an electric power steering device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing, in blocks, a main electrical configuration of the first embodiment of the present invention.

FIG. 3 is a detailed explanatory view of a part of FIG. 2;

FIG. 4 is a detailed explanatory view of a part of FIG. 2;

FIG. 5 is a diagram showing the respective time lapses of a steering wheel angular velocity, a steering wheel return compensation torque, and a steering-maintenance steering determination flag when the steering wheel is held for one second and then released.

FIG. 6 is a flowchart illustrating a flow of a process in a steering-maintenance determining unit.

FIG. 7 is an explanatory diagram showing, in blocks, a main electrical configuration of a second embodiment of the present invention.

FIG. 8 is an explanatory diagram showing, in blocks, a main electrical configuration of a third embodiment of the present invention.

FIG. 9 is an explanatory diagram showing the main electrical configuration of a conventional electric power steering device by blocks.

[Explanation of symbols]

 M Motor 10 ECU 11 Torque sensor 12 Vehicle speed sensor 15 Motor drive circuit 22 Assist command value calculation unit 24 PI control unit 25 PWM calculation unit 27 Handle return compensation current value calculation unit 28 Handle angular velocity estimation unit 29 Switching unit 30 Steering and steering determination unit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) B62D 137: 00 B62D 137: 00 (72) Inventor Yoshiaki Suzuki 1st Toyota Town, Toyota City, Aichi Prefecture Toyota Automobile Stock In-house (72) Inventor Takashi Iwasaki 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Toru Suzuki 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F-term (reference) 3D032 CC27 CC48 DA09 DA15 DA23 DA63 DA65 DC01 DC02 DC08 DC09 DC12 DC18 DC22 DC33 DD05 DD10 DD17 EA01 EB11 EC23 GG01 3D033 CA03 CA13 CA16 CA20 CA21 CA24

Claims (5)

[Claims] An input member and an output member provided in a steering system; a motor for applying a torque to the steering system; and a torque sensor for detecting a steering torque input to the input member. Is controlled to generate an assist torque for assisting a steering force based on the steering torque, and a compensation torque for returning a steering wheel to a neutral position based on the angular velocity of the motor. An electric power steering apparatus characterized in that the electric power steering apparatus is obtained based on a voltage between terminals. 2. The motor, comprising: an input member and an output member provided in a steering system; a motor that applies torque to the steering system; and a torque sensor that detects a steering torque input to the input member. PWM control is performed in accordance with a duty ratio corresponding to an assist torque for assisting a steering force based on the steering torque and a compensation torque for returning a steering wheel to a neutral position based on the angular speed of the motor. Is calculated based on the voltage of the motor calculated from the duty ratio and the power supply voltage. 3. An input member and an output member provided in a steering system, a motor for applying a torque to the steering system, and a torque sensor for detecting a steering torque input to the input member, wherein the motor Is determined according to a duty ratio generated by a voltage command value corresponding to an assist torque for assisting a steering force based on the steering torque and a compensation torque for returning a steering wheel to a neutral position based on the angular velocity of the motor.
An electric power steering apparatus which is subjected to WM control, wherein the voltage command value is a voltage of the motor, and an angular velocity of the motor is obtained based on the voltage of the motor. 4. An angular velocity of the motor is calculated from ωm = Vm / Ke, where ωm is the angular velocity of the motor, Vm is the voltage of the motor, and Ke is the back electromotive force constant of the motor. The electric power steering device according to any one of claims 1 to 3. 5. The electric power steering apparatus according to claim 1, wherein when the steering torque is equal to or more than a predetermined threshold, the compensation torque is set to zero.