JP2001310750A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device easily detecting an abnormal condition of a motor controlling means for securing a comfortable steering property. SOLUTION: An abnormal condition is detected by comparing a motor voltage Vm with a voltage command value Vo.

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 Conventionally, an input member and an output member provided in a steering system, a motor for applying an assist torque to the output member, and a steering torque detecting means such as a torque sensor for detecting the steering torque input to the input member. 2. Description of the Related Art There is known an electric power steering apparatus including: a motor control unit that controls a motor based on at least a steering torque.

In addition, the motor control means often has a vehicle speed detection means such as a vehicle speed sensor for detecting the vehicle speed. In this case, the motor control means controls the motor based on the steering torque and the vehicle speed. Become.

Further, in order to obtain the steering wheel return at the time of cornering, the motor terminal voltage of the motor is detected by the motor voltage detecting means, and the steering wheel return can be compensated by a compensation torque based on the motor terminal voltage.

That is, in the conventional electric power steering apparatus, as shown in FIG. 5, an input shaft 2 as an input member provided at an axis of the handle 1 is connected to an output shaft 4 as an output member via a torsion bar 3. Is connected to A pinion is provided at the tip of the output shaft 4, and this pinion is engaged with the rack 5. Further, a motor M capable of applying an assist torque via a speed reducer 6 is connected to the output shaft 4 or the rack 5. This motor M is ECU
The ECU 10 is connected to a torque sensor 11 and a vehicle speed sensor 12 having the torsion bar 3 integrally. Here, the ECU 10, a motor drive circuit 15 described later, and the like are motor control means.

In this electric power steering apparatus, when the driver steers the steering wheel 1, the input shaft 2 rotates, and the output shaft 4 rotates via the torsion bar 3. And
The rotation of the output shaft 4 is converted into the axial movement of the rack shaft 5 to steer a tire (not shown). At this time, the ECU 10 rotationally drives the motor M based on the steering torque input from the torque sensor 11 and the vehicle speed input from the vehicle speed sensor 12, and the motor M applies assist torque to the output shaft 4 via the speed reducer 6. .

As shown in FIG. 6, a torque sensor 11 for detecting a steering torque input to the input shaft 2 is connected to an ECU 10 via an interface 13a and an A / D converter 14a.
It is connected to the. A vehicle speed sensor 1 for detecting a vehicle speed
2 is also connected to the ECU 10 via the interface 13b and the timer 14b.

The ECU 10 includes a phase compensator 21, an assist commander 22, an adder 23, a PI controller 24, a PWM calculator 25, a steering wheel angular velocity estimator 28, and a steering wheel return compensator 27. The steering wheel angular velocity estimating unit 28 has subtraction circuits 28a and 28b. This ECU 10
The PWM drive unit 25 includes a motor drive circuit 15 composed of an H-bridge circuit having FETs 15a to 15d.
Are connected, and the motor drive circuit 15 is connected to the motor M.

A steering angular velocity estimating section 28 of the ECU 10 is connected to each terminal of the motor M via interfaces 13d and 13e and A / D converters 14d and 14e. Further, the ECU 10 is connected to one terminal of the motor M via the interface 13c and the A / D converter 14c.
Of the steering wheel angular velocity estimation unit 28 and the PI control unit 24 are connected.

The steering torque signal detected by the torque sensor 11 is transmitted to an interface 13a and an A / D converter 14
The signal is input to the phase compensator 21 of the ECU 10 via a, the phase is advanced to compensate for the mechanical delay, and is output to the assist command value calculator 22. The vehicle speed sensor 12
Is output to the assist command value calculation unit 22 of the ECU 10 via the interface 13b and the timer 14b, and the assist current command value corresponding to the assist torque is obtained based on the phase-compensated torque signal and the vehicle speed signal. To determine.

Then, the assist current command value is input to the PI control unit 24 via the adding circuit 23, and a corresponding voltage command value is generated. This voltage command value 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. As a result, the motor M is driven.

At this time, the FETs 15a and 15d are
When T15a is ON, FET15d is OFF and F15
ON / OFF control is performed so that the FET 15d is turned on when the ET 15a is turned off. Further, the FET 15b,
ON / OFF control of 15c is also performed so that the FET 15b and the FET 15c are in the opposite states.

The motor current flowing through the motor M is fed back to the PI control unit 24 of the ECU 10 via the interface 13c and the A / D converter 14c.
The PI control unit 24 controls the voltage command value so that the current command value matches the detected value of the motor current.

On the other hand, when the driver stops steering and releases his / her hand while traveling, that is, when the output value of the torque sensor 11 is zero or less than a predetermined value close to it, The motor angular velocity at the time when the motor M is rotated toward the neutral position is calculated by the action of so-called self-aligning torque, which causes the tire to return to the straight running direction by the reaction force.

That is, the back electromotive force constant of the motor M is Ke,
Assuming that the inductance is L and the resistance between terminals (hereinafter, referred to as motor resistance) is R, the motor terminal voltage (hereinafter, referred to as motor voltage) Vm is obtained by Expression 1, and the motor angular velocity ω
m is obtained by solving Equation 1 by using ωm.

[0016]

Vm = (LS + R) Im + Ke · ωm

[0017]

Ωm = {Vm− (LS + R) Im} / Ke where S = d / dt.

Thus, the motor angular velocity ωm is obtained from the motor voltage Vm and the motor current Im. For this reason,
The motor voltage Vm is input to the steering wheel angular velocity estimating unit 28 via the interfaces 13d and 13e and the A / D converters 14d and 14e, and the motor current Im is received via the interface 13c and the A / D converter 14c. 28.

As disclosed in, for example, Japanese Patent Laid-Open No. Hei 4-8190, the motor angular velocity ω
m includes a transient term due to the inductance L when the motor M is driven by PWM. Also, the motor current I
Since the rising time constant of m is sufficiently small and has little effect on the motor angular velocity ωm, the inductance L is ignored, and the motor angular velocity ωm is calculated by Expression 3.

[0020]

Ωm = (Vm−R · Im) / Ke

In this way, the steering wheel angular velocity is obtained by multiplying the motor angular velocity ωm obtained by Equation 3 by the reduction ratio.

Based on the steering angular velocity calculated by the steering angular velocity estimating section 28 and the output signal of the vehicle speed sensor 12, the steering wheel return compensating section 27 issues a compensation current command for restoring the steering wheel to a neutral position by driving the motor. The value is determined, and the compensation current command value is sent to the addition circuit 23. Here, in a low-speed range where the self-aligning torque is small, the compensation torque for returning the steering wheel to the neutral position increases, and it is possible to overcome the frictional force and return the steering wheel to the neutral position. Further, in a high-speed range where the self-aligning torque is large, the compensation torque is small, so that the sense of stability of the steering is increased.

[0023]

However, in the above-described conventional electric power steering apparatus, if an abnormality occurs in the PWM operation unit 25, the motor drive circuit 15, the interfaces 13d and 13e, and the A / D converters 14d and 14e,
The value of the motor voltage Vm input to the ECU 10 shifts from the normal value, and an error occurs in the calculation result of the motor angular distance ωm in the steering wheel angular velocity estimating unit 28. As a result, an error also occurs in the compensation current command value calculated by the steering wheel return compensation unit 27, and comfortable steering performance cannot be secured. Thus, if an abnormality occurs in these motor control means, an optimum assist torque will not be generated accurately, and more comfortable steering will not be ensured.

The present invention has been made in view of the above-mentioned conventional circumstances, and provides an electric power steering apparatus capable of easily finding an abnormality in a motor control means and ensuring comfortable steering. Is an issue to be solved.

[0025]

SUMMARY OF THE INVENTION An electric power steering apparatus according to the present invention includes an input member and an output member provided in a steering system, a motor for applying an assist torque to the output member, and a motor input to the input member. An electric power steering apparatus comprising: a steering torque detecting unit that detects a steering torque; and a motor control unit that controls the motor based on at least the steering torque. In the electric power steering device, the motor control unit includes the assist based on at least the steering torque. Assist command calculating means for determining an assist current command value corresponding to the torque; motor voltage detecting means for detecting a motor terminal voltage of the motor; and determining a compensation current command value corresponding to a compensation torque based on the motor terminal voltage. Compensation command calculation means, and a voltage finger corresponding to the assist current command value and the compensation current command value. Voltage command generating means for generating a value, motor driving means for driving the motor according to the voltage command value, and abnormality detecting means for detecting an abnormality by comparing the motor terminal voltage with the voltage command value. It is characterized by the following.

In this electric power steering apparatus, since the abnormality detecting means for comparing the motor terminal voltage with the voltage command value to detect the abnormality is provided, the abnormality of the motor control means can be easily detected. Therefore, the abnormality processing can be performed at an early stage, and comfortable steering performance can be secured. As the abnormality processing, it is conceivable to turn on a warning lamp to call the driver's attention.

An abnormality can also be detected by comparing the motor terminal voltage with the voltage command value for each motor terminal. Thus, since an abnormality can be detected for each terminal, the location where the abnormality has occurred can be specified to some extent.

It is desirable to have a security means for stopping the operation of the motor when the abnormality detection means detects an abnormality. In this case, the assist by the motor is stopped,
Reliable steering in an emergency can be secured.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 and 2 embodying the present invention will be described below with reference to the drawings. (Embodiment 1) The electrical configuration of the electric power steering apparatus of Embodiment 1 is shown in FIG. The main mechanical configuration of the steering system of this electric power steering device is the same as that of FIG. 5, and the same reference numerals are used for the same components as those of the conventional electric power steering device shown in FIG. The description is omitted.

In this electric power steering apparatus, E
The CU 10 includes a PI control unit 24 and a steering wheel angular velocity estimation unit 28
And a comparison circuit 32 connected to the subtraction circuit 31. The phase compensator 21 and the assist commander 22 are assist command calculators that determine an assist current command value corresponding to the assist torque based on the steering torque and the vehicle speed. The interfaces 13d and 13e and the A / D converters 14d and 14e are motor voltage detecting means for detecting the motor terminal voltage of the motor M. Further, the steering wheel angular velocity estimating unit 28 and the steering wheel return compensating unit 27 are compensation command calculating means for determining a compensation current command value corresponding to a compensation torque based on the motor terminal voltage. Further, the addition circuit 23, the PI control unit 24, and the PWM
The calculation unit 25 is a voltage command generation unit that generates a voltage command value corresponding to the assist current command value and the compensation current command value. Further, the motor drive circuit 15 is a motor drive unit that drives the motor M according to the voltage command value. And E
The CU 10, the motor drive circuit 15, and the like are motor control means.

The PI control unit 24 and the steering wheel angular velocity estimating unit 2
8 is connected to a comparison circuit 32 via a subtraction circuit 31, and the comparison circuit 32
Is connected to a power supply relay RL. Further, the motor drive circuit 15 is connected to a power supply via a contact of a power supply relay RL. The subtraction circuit 31 and the comparison circuit 32 are abnormality detection means for comparing the motor terminal voltage with the voltage command value to detect an abnormality. Further, the interface 33 and the power relay RL are security means for stopping the operation of the motor M.

In such an electric power steering apparatus, the PWM operation unit 25, the motor drive circuit 15, the interfaces 13d and 13e, and the A / D converter 14d
Means for detecting and processing an abnormality such as 14e will be described.

As shown in FIG. 2, first, in step S10
In step (1), a current command value corresponding to the assist torque is calculated by the assist command value calculation unit 22 based on the steering torque signal and the vehicle speed signal, and a voltage command value Vo for driving the motor M is output by the PI control unit 24. You.

Next, in step S11, the PWM
The arithmetic unit 25 outputs a motor drive signal generated based on the voltage command value Vo to the motor drive circuit 15. That is, the PWM command unit 25 converts the voltage command value Vo into a corresponding duty ratio, and outputs a pulse signal corresponding to the duty ratio to the motor drive circuit 15,
Drive the motor M.

Then, in step S12, the motor voltage Vm is input. Specifically, the voltage of each terminal of the motor M is divided by the interfaces 13d and 13e so that the voltage can be input to the ECU 10, and the voltage is divided by the A / D converters 14d and 14e.
e is digitally converted. And these are ECU
10 and passed through a subtraction circuit 28a to obtain a motor voltage Vm.

Further, in step S13, the PWM
Arithmetic unit 25, motor drive circuit 15, interface 1
The abnormality of 3d, 13e and A / D converters 14d, 14e is checked. That is, first, the voltage command value Vo output from the PI control unit 24 and the motor voltage Vm obtained by the subtraction circuit 28a are input to the subtraction circuit 31. Then, the comparison circuit 32 compares | Vo−Vm |, which is the result of the subtraction by the subtraction circuit 31, with the threshold value Vt. as a result,
If | Vo−Vm | <Vt (YES), it is determined to be normal, the process returns to step S10, and the same steps as described above are repeated. If | Vo−Vm | ≧ Vt, (N
O), it is determined to be abnormal and step S14 is executed.

In step S14, the comparison circuit 32
An abnormal signal is output to the power supply relay RL via the interface 33. As a result, the contact of the power supply relay RL is opened, and the power to the motor drive circuit 15 is cut off. Therefore, the application of the assist torque to the output shaft 4 (see FIG. 5) by the motor M is stopped. At this time, a warning lamp (not shown) is turned on to notify the driver of the abnormality.

Therefore, according to the electric power steering apparatus of the present embodiment, the abnormality in the PWM operation section 25, the motor drive circuit 15, the interfaces 13d and 13e, the A / D converters 14d and 14e, etc. can be easily detected, Since the application of the assist torque to the output shaft 4 by the M is stopped and the warning lamp can be turned on to notify the driver of the abnormality, comfortable steering performance can be ensured.

(Embodiment 2) FIG. 3 shows an electric configuration of an electric power steering apparatus according to Embodiment 2. The main mechanical configuration of the steering system of this electric power steering device is also the same as that of FIG. 5, and the same components as those of the conventional electric power steering device shown in FIG. The description is omitted.

In this electric power steering device, E
The CU 10 has a distributor 35, and the PI control unit 24 is connected to the distributor 35. The distributor 35 is a PWM operation unit 25
Within the PWM operation unit (L) 25a and the PWM operation unit (R)
25b. And a PWM operation unit (L)
Reference numeral 25a is connected to the FETs 15a and 15d of the motor drive circuit 15, and the PWM operation unit (R) 25b is connected to the FETs 15b and 15c of the motor drive circuit 15. Also,
The distributor 35 is connected to subtraction circuits 36 and 38 together with the A / D converters 14d and 14e. And the subtraction circuit 3
6 and 38 are connected to comparison circuits 37 and 39, respectively.
7 and 39 are connected to an OR circuit 40. OR circuit 4
0 is connected to the power supply relay RL via the interface 41. Further, the motor drive circuit 15 is connected to a power supply via a contact of a power supply relay RL. Subtraction circuit 3
6, 38, comparison circuits 37 and 39, and an OR circuit 40 are abnormality detection means for comparing the motor terminal voltage with the voltage command value to detect an abnormality. In addition, the interface 41 and the power supply relay RL are means for ensuring that the operation of the motor M is stopped.

In such an electric power steering apparatus, the PWM operation unit 25, the motor drive circuit 15, the interfaces 13d and 13e, and the A / D converter 14d
Means for detecting and processing an abnormality such as 14e will be described.

As shown in FIG. 4, first, at step S20
In, voltage command values Vol and Vor for driving the motor M are output from the distributor. The voltage command values Vol and Vor are generated as follows. First, an assist command value calculation unit 22 calculates a current command value corresponding to the assist torque based on the steering torque signal and the vehicle speed signal. A voltage command value corresponding to the current command value is generated by the PI control unit 24, and further, the voltage command values Vol and Vor are generated by the distributor 35 based on the voltage command value.

Next, in step S21, the PWM
The calculation unit 25 outputs a motor drive signal generated based on the voltage command values Vol and Vor to the motor drive circuit 15. That is, the PWM command unit 25 converts the voltage command values Vol and Vor into corresponding duty ratios, and outputs a pulse signal corresponding to the duty ratio to the motor drive circuit 15 to drive the motor M.

Then, in step S22, the terminal voltages Vml and Vmr of the motor M are input. Specifically, the voltage of each terminal of the motor M is divided by the interfaces 13d and 13e so that the voltage can be input to the ECU 10, and A
Digitally converted by the / D converters 14d and 14e,
The terminal voltages Vml and Vmr are obtained.

Further, in step S23, the voltage of one terminal of the motor M is checked to determine the PWM.
Arithmetic unit 25, motor drive circuit 15, interface 1
The abnormality of 3d, 13e and A / D converters 14d, 14e is checked. That is, first, the voltage command value Vol output from the distributor 35 and the terminal voltage Vml obtained by the A / D converter 14d are input to the subtraction circuit 36, and the subtraction circuit 36 outputs the subtraction result to the comparison circuit 37. Output. And
In comparison circuit 37, the result of subtraction in subtraction circuit 36 is |
Vol−Vml | is compared with the threshold value Vt. as a result,
If | Vol−Vml | <Vt (YES), it is determined to be normal and the process proceeds to step S24. Also, | Vol-Vm
If l | ≧ Vt (NO), it is determined to be abnormal and step S25 is executed.

In step S24, the other terminal voltage of the motor M is checked, so that the PWM operation unit 25, the motor drive circuit 15, the interfaces 13d and 13e, and the A / D converter 14d are checked as in step S23. , 14e, etc. are checked. That is,
First, the voltage command value Vor output from the distributor 35,
The terminal voltage Vmr obtained by the A / D converter 14e is input to the subtraction circuit 38, and the subtraction circuit 38 outputs the result of the subtraction to the comparison circuit 39. In the comparison circuit 39, | Vor−Vmr | which is the result of the subtraction in the subtraction circuit 38 and the threshold value Vt
Compare with As a result, if | Vor−Vmr | <Vt (YES), it is determined to be normal, the process returns to step S20, and the same steps as described above are repeated. Also, | Vor
If −Vmr | ≧ Vt (NO), it is determined that there is an abnormality, and step S25 is executed.

In step S25, the comparison circuit 37
Alternatively, an abnormal signal is output from the comparison circuit 38 to the power supply relay RL via the OR circuit 40 and the interface 41. As a result, the contact of the power supply relay RL is opened, and the power to the motor drive circuit 15 is cut off. Therefore, the application of the assist torque to the output shaft 4 (see FIG. 5) by the motor M is stopped. At this time, a warning lamp (not shown) is turned on to notify the driver of the abnormality.

Therefore, the same effects as in the first embodiment can be obtained by the electric power steering device of the present embodiment. Further, according to the electric power steering device of the present embodiment, it is possible to determine which of the terminals of the motor M has an abnormality.

In each of the embodiments, the example in which the steering wheel angular velocity is used for the steering wheel return compensation has been described.
Various compensation controls based on the steering wheel angular velocity can be applied.

[0050]

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a main electrical configuration of an electric power steering device according to a first embodiment.

FIG. 2 is a flowchart illustrating abnormality detection processing of the electric power steering device according to the first embodiment.

FIG. 3 is a block diagram illustrating a main electric configuration of an electric power steering device according to a second embodiment.

FIG. 4 is a flowchart illustrating an abnormality detection process of the electric power steering device according to the second embodiment.

FIG. 5 is a schematic diagram showing a mechanical configuration of the electric power steering device.

FIG. 6 is a block diagram showing a main electric configuration of a conventional electric power steering device.

[Explanation of symbols]

2 ... input member (input shaft) 4 ... output member (output shaft) M ... motor 11 ... steering torque detecting means (torque sensor) 10, 15 ... motor control means (10 ... ECU, 15 ... motor drive circuit) 21, 22 ... Assist command calculation means (21 ... Phase compensator, 22 ... Assist command section) 13d, 13e, 14d, 14e ... Motor voltage detection means (13d, 13e ... Interface, 14d, 14e)
... A / D converters 28,27 ... Compensation command calculation means (28 ... Handle angular velocity estimating unit, 27 ... Handle return compensation unit) 23,24,25 ... Voltage command generation means (23 ... Addition circuit, 24 ... PI control) Unit, 25: PWM operation unit 15: Motor drive means (motor drive circuit) 31, 32, 36, 37, 38, 39, 40 ... Abnormality detection means (31, 36, 38 ... subtraction circuits, 32, 37, 39)
... comparison circuit, 40 ... OR circuit)

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) B62D 119: 00 B62D 119: 00 (72) Inventor Yasutani Shintani 1-1-1 Asahicho, Kariya-shi, Aichi Pref. F term (reference) 3D032 CC34 CC39 CC40 DA15 DA23 DA65 DC01 DC02 DC17 DD10 DD17 EA01 EC24 GG01 3D033 CA03 CA13 CA16 CA20 CA21 CA28 CA33 5H571 AA03 BB10 CC04 EE02 EE03 GG04 GG05 HA09 HB01 HD02 JJ03 LL24 LL29

Claims (3)

[Claims] An input member and an output member provided in a steering system, a motor for applying an assist torque to the output member,
An electric power steering apparatus including: a steering torque detecting unit configured to detect a steering torque input to the input member; and a motor control unit configured to control the motor based on at least the steering torque. Assist command calculation means for determining an assist current command value corresponding to the assist torque based on the steering torque, motor voltage detection means for detecting a motor terminal voltage of the motor, and a compensation torque based on the motor terminal voltage Compensation command operation means for determining a compensation current command value, voltage command generation means for generating a voltage command value corresponding to the assist current command value and the compensation current command value, and a motor for driving the motor according to the voltage command value Driving means, abnormality detection for detecting an abnormality by comparing the motor terminal voltage with the voltage command value And an electric power steering apparatus. 2. The electric power steering apparatus according to claim 1, wherein the abnormality detecting means compares a motor terminal voltage with a voltage command value for each motor terminal. 3. The electric power steering apparatus according to claim 1, further comprising a security means for stopping the operation of the motor when the abnormality detection means detects an abnormality.