JPH11150976A - Control equipment of motor-operated power steering equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stop motor driving by surely detecting a failure of a motor driving system, in a control equipment of a motor-operated power steering equipment. SOLUTION: A control equipment is provided with a torque sensor 10 detecting the torque of a steering wheel, a motor 20 which assists to the steering shaft in energizing installed integrally with the wheel, and a control unit 30 driving the motor 20 in accordance with the steering torque. When a motor current command value is at most a specified value or when a motor current detection value is at most a specified value and the state that a voltage between motor terminals or the integrated value of duty ratio of PWM(pulse width modulation) is at most a specified value continues for a specified period, the control equipment judges that a failure exists in a motor driving system, and stops the driving of a motor 20.

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 which applies a steering assisting force by a motor to a steering system of an automobile or a vehicle, and more particularly to a control device for reliably detecting a failure in a motor drive system. The present invention relates to a control device for an electric power steering device that stops driving of a motor.

[0002]

2. Description of the Related Art An electric power steering apparatus for energizing a steering apparatus of an automobile or a vehicle with an auxiliary load by the rotational force of a motor uses a transmission mechanism such as a gear or a belt through a speed reducer to transmit the driving force of the motor to a steering shaft or the like. An auxiliary load is applied to the rack shaft.

FIG. 7 shows a configuration of a general electric power steering apparatus. A shaft 2 of a steering wheel 1 is driven through a reduction gear 3, universal joints 4a and 4b, a pinion rack mechanism 5, and a tie rod 6 of a steered wheel. Is joined to. The shaft 2 is provided with a torque sensor 10 for detecting a steering torque of the steering wheel 1. A motor 20 for assisting the steering force of the steering wheel 1 is coupled to the shaft 2 via a clutch 21 and a reduction gear 3. Have been. Power is supplied from the battery 14 to the control unit 30 that controls the power steering device via the ignition key 11.
The steering assist command value I of the assist command is calculated on the basis of the steering torque T detected at step S1 and the vehicle speed V detected by the vehicle speed sensor 12, and is supplied to the motor 20 based on the calculated steering assist command value I. Control the current. The clutch 21 is ON / OFF controlled by the control unit 30 and is ON (coupled) in a normal operation state. The clutch 21 is turned off (disengaged) when the control unit 30 determines that the power steering device has failed, and when the power of the battery 14 is turned off by the ignition key 11.

The control unit 30 is mainly composed of a CP
FIG. 8 shows a general function executed by a program inside the CPU.
For example, the phase compensator 31 does not indicate a phase compensator as independent hardware, but indicates a phase compensation function executed by the CPU. Control unit 3
It is also possible to configure each functional element with independent hardware instead of configuring CPU 0 with a CPU.

Here, general functions and operations of the control unit 30 will be described. The steering torque T detected and input by the torque sensor 10 is phase-compensated by a phase compensator 31 in order to enhance the stability of the steering system, and the phase-compensated steering torque TA is input to a steering assist command value calculator 32. Is done. The vehicle speed V detected by the vehicle speed sensor 12 is also input to the steering assist command value calculator 32. The steering assist command value calculator 32 determines a steering assist command value I which is a control target value of the current supplied to the motor 20 based on the input steering torque TA and the vehicle speed V. Is provided with a memory 33. The memory 33 stores a steering assist command value I corresponding to the steering torque using the vehicle speed V as a parameter.
Is used for calculating the steering assist command value I by the steering assist command value calculator 32. The steering assist command value (motor current command value) I is input to the subtractor 30A, and is also input to the feed-forward differential compensator 34 for increasing the response speed, and the deviation (I−
i) is input to the proportional calculator 35, and the proportional output is input to the adder 30B and also to the integration calculator 36 for improving the characteristics of the feedback system. The outputs of the differential compensator 34 and the integration compensator 36 are also added to the adder 30B, and the current control value E, which is the result of the addition in the adder 30B, is input to the motor drive circuit 37 as a motor drive signal. The motor current detection value i of the motor 20 is detected by the motor current detection circuit 38, and the motor current detection value i is input to the subtractor 30A and fed back.

An example of the configuration of the motor drive circuit 37 will be described with reference to FIG. 9. The motor drive circuit 37 uses a field effect transistor (FE) based on the current control value E from the adder 30B.
T) An FET gate drive circuit 371 for driving the gates of FET1 to FET4, an H bridge circuit composed of FET1 to FET4, a boost power supply 372 for driving the high side of FET1 and FET2, and the like. FET1 and FET2 are turned ON / OFF by a PWM (pulse width modulation) signal having a duty ratio D1 determined based on the current control value E.
It is turned off, and the magnitude of the current Ir actually flowing to the motor is controlled. FET3 and FET4 have a duty ratio D
In a small area of 1, the duty ratio D2 defined by a predetermined linear function expression (D2 = a.D1 + b where a and b are constants)
In the region where the duty ratio D1 is large, it is turned ON / OFF according to the rotation direction of the motor determined by the sign of the PWM signal. For example, when the FET 3 is in the conductive state, the current flows through the FET 1, the motor 20, the F
The current flows through the ET3 and the resistor R1, and a current flows in the motor 20 in the positive direction. When the FET 4 is in the conductive state, the current flows through the FET 2, the motor 20, the FET 4, and the resistor R2, and a negative current flows through the motor 20. Therefore, the current control value E from the adder 30B is also a PWM output. The motor current detection circuit 38 detects the magnitude of the positive current based on the voltage drop across the resistor R1, and detects the magnitude of the negative current based on the voltage drop across the resistor R2. The motor current detection value i detected by the motor current detection circuit 38 is input to the subtractor 30A and fed back.

In such a configuration, when a disconnection failure occurs between the motor 20 and the control unit 30, or when the FET or its drive circuit fails,
Although the motor drive signal is output from the motor drive circuit 37, no current flows through the motor 20 and the motor 20
Assist power cannot be generated. Therefore, the steering feels heavy at a low speed or at the time of stationary steering, so that it is necessary to notify the driver of the abnormality by displaying a warning. Further, when the motor current detection circuit 38 breaks down, the motor current detection value i cannot be detected, so that an excessive current is supplied to the motor, the assist becomes excessive, and the steering becomes unstable. When the motor line is grounded, almost no current flows through the motor current detection circuit 38, so that the current is further attempted to flow through the motor by feedback control.

[0008]

Conventionally, when detecting a failure of the motor drive system as described above, a motor current command value is compared with a motor current detection value, and when the difference is larger than a predetermined value. It was determined to have failed. FIG. 10 shows the configuration in correspondence with FIG. 8. The abnormality detection unit 39 includes a steering assist command value I from the steering assist command value calculator 32 and a motor current detection value i from the motor current detection circuit 38. When the difference is equal to or greater than a predetermined threshold, an abnormal signal AL is output, and the motor drive circuit 37 stops driving the motor 20.

However, a counter electromotive force is generated in the motor 20 when the steering wheel returns or when the steering wheel is suddenly steered, and the current may cause the motor current detection value i to become smaller than the normal value. In such a case, the above detection method has erroneously detected a failure in the motor drive system. In order to prevent such erroneous detection, conventionally, detection conditions (detection time and detection value) have been adjusted, but conversely, failures cannot be reliably detected.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a control device for an electric power steering apparatus which detects a failure in a motor drive system and stops the motor drive. Is to provide.

[0011]

According to the present invention, there is provided a torque sensor for detecting a steering torque of a steering wheel, a motor for urging a steering shaft integrally provided with the steering wheel to apply an auxiliary load, and a magnitude of the steering torque. The present invention relates to a control device for an electric power steering device, comprising: a control unit that drives the motor in accordance with a motor current command value that is equal to or less than a predetermined value, or the motor current detection value is a predetermined value. In the following, when a state in which the integrated value of the motor terminal voltage or the duty ratio of the PWM is equal to or more than a predetermined value continues for a predetermined time, it is achieved by determining that the motor driving system has failed and stopping the driving of the motor.

Further, when determining the detection value of the duty ratio of the PWM with respect to the motor current command value, the influence of the battery voltage may be considered. Further, when the motor current command value is equal to or less than a predetermined value or the motor current detection value is equal to or less than a predetermined value and the output of the integrator of the control unit is equal to or more than a predetermined value for a predetermined time, a failure of the motor drive system occurs. And stopping the driving of the motor.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A current value flowing through a motor of a power steering apparatus is kept constant by feedback control (for example, PI control) based on a motor current command value and a detected motor current value as described above. Is controlled. Then, for example, when a disconnection fault occurs between the motor and the control unit, the motor current detection value is zero despite the application of the motor current command value, so that the motor terminal voltage or the PWM duty ratio is reduced. It increases sharply and reaches a maximum value. Therefore, the output of the integrator for integrating the value of the motor terminal voltage or the duty ratio of the PWM or the output of the integrator of the PI controller is monitored, and the integrated value of the duty ratio assumed from the current command value in a normal state is monitored. If the state in which the difference is large continues for a predetermined time, it can be determined that the motor drive system is abnormal.
Similarly, when the motor current cannot be detected, that is, when the detected motor current value is zero, the voltage between the motor terminals or the PWM duty ratio is rapidly increased by the feedback control. In this case, it can be determined that a failure has occurred if the predetermined time has elapsed.

The comparison between the motor terminal voltage and the integrated value of the duty ratio may be performed based on the current detection value instead of the current command value. When the battery voltage fluctuates or the motor resistance changes due to a temperature change, the duty ratio of the PWM to the motor current command value changes. Therefore, the detected value is corrected by the battery voltage or the motor resistance value. This makes it possible to more reliably detect an abnormality in the motor drive system.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Embodiment 1: Detection of disconnection between motor and control unit> FIG. 1 is a block diagram showing this embodiment corresponding to FIG.
0 and an integrator 301 are provided. If the motor 20 and the control unit 30 are disconnected, the motor 2
Since no current flows through 0, the motor current detection value i becomes zero with respect to the motor current command value I. Since feedback control is performed on the motor current, when the detected motor current value i becomes zero, the motor terminal voltage Vm (or the PWM duty ratio) suddenly reaches a maximum value. The value of the motor terminal voltage Vm (or the duty of PWM) considering the fluctuation of the battery voltage is integrated by providing the integrator 301. FIG.
The connection relation for measuring the motor terminal voltage Vm is shown in correspondence with FIG. 9, and the resistances R3 and R4 are added to the predetermined voltage Vig.
Vm1 and Vm across the motor 20 connected via
m2. The integrator 301 integrates the input values during a predetermined time, and always replaces the latest input value with the input value after a lapse of the predetermined time. Then, a normal range of the integrated value of the motor terminal voltage Vm in consideration of the variation of the battery voltage with respect to the motor current command value I is determined in advance, and the integrated value of the motor terminal voltage Vm exceeding the range is determined. If it is detected for a predetermined time or more, the motor drive system or more detecting means 300 determines that the connection between the motor 20 and the control unit 30 has been disconnected, and outputs an abnormal signal AL. Thus, the motor drive circuit 37 stops driving the motor 20.

FIG. 3 shows an operation example of the motor drive system abnormality detecting means 300. First, a motor current command value I is read (step S1), and motor terminal voltages Vm1 and Vm2 from both ends of the motor 20 shown in FIG. (Step S
2). Then, the motor terminal voltage Vm is calculated according to the following equation (1).
Is calculated.

[0018]

Vm = | Vm1-Vm2 | Next, the obtained motor terminal voltage Vm is input to the integrator 301 (step S4), and the integrated output α of the integrator 301 is read (step S5). Motor current command value I
_Is read (step S6).

Upon reading the abnormality detection value α _err , the motor drive system abnormality detection means 300 compares the integrated output α from the integrator 301 with the following equation 2 (step S10).

[0020]

## EQU2 ## If α ≧ α _err number 2 does not hold, it is normal and the above step S
Returning to step 1, if the above equation 2 is satisfied, it is further determined whether or not a predetermined time (for example, several 100 milliseconds) has elapsed (step S11). If the predetermined time has not elapsed, the process returns to step S1 to repeat the above operation.
When the predetermined time has elapsed, it is determined that the motor drive system has failed (step S12), and an abnormal signal AL is input to the motor drive circuit 37 to stop driving the motor 20 (step S13).

<Embodiment 2: Detection of motor ground fault>
FIG. 11 is a configuration diagram corresponding to FIG. 10, showing a motor drive system abnormality detection unit 310 that uses the motor current command value I and the output of the integration calculator 36 as input signals. When the motor wire is grounded on the motor cold side, a current flows through the motor 20 due to the short-circuit portion, so that the motor current detection value i becomes zero with respect to the motor current command value I. Since feedback control is performed on the motor current, the output of the integration calculator 36 rapidly increases and reaches a maximum value. Therefore, a normal range of the output of the integration calculator 36 is predetermined with respect to the motor current command value I, and when an output of the integrator exceeding the range is detected for a predetermined time or more, the motor drive system abnormality is detected. The detecting means 300 outputs an abnormal signal AL upon judging that the motor wire has a ground fault. Thus, the motor drive circuit 37 stops driving the motor 20.

<Embodiment 3: Detection of disconnection between motor and control unit> FIG. 5 is a block diagram showing this embodiment in correspondence with FIG. 10, and shows the output of the integration calculator 36 and the motor current detection value i. A motor drive system abnormality detecting means 320 as an input signal is provided.

For example, as shown in FIG. 6, when the motor current command value I is input in a stepwise manner, the motor current detection value i gradually increases, and finally becomes equal to the motor current command value I by current feedback. Works. In the integration calculator 36 in this current loop, an amount proportional to the deviation between the motor current command value I and the motor current detection value i at the time of transition is accumulated, and the deviation becomes zero in a steady state. Keep a constant value. When a disconnection occurs between the motor 20 and the control unit 30 or when a failure occurs in the motor current detection circuit 38, the motor current detection value i becomes zero, and the deviation between the motor current command value I and the motor current detection value i becomes longer. Since the deviation itself is large even after the lapse of time and the deviation itself is large, the accumulated amount of the integral computing unit 36 rapidly increases with time, and the integral computing unit 36 is saturated in a short time.
Therefore, the integration calculator 36 is used for the motor current detection value i.
The normal range of the output of the motor drive system is determined in advance, and when the output of the integration calculator 36 that exceeds the range is detected for a predetermined time or more, the motor drive system abnormality detecting means 320
It is determined that the connection between the control unit 30 and the control unit 30 has been broken, and an abnormal signal AL is output. Thus, the motor drive circuit 37 stops driving the motor 20.

[0024]

As described above, according to the control apparatus for the electric power steering apparatus of the present invention, since the disconnection between the motor and the control unit and the detection of the motor ground fault are detected, the failure of the motor drive system can be reliably performed. Can be detected.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a connection diagram illustrating a measurement system of a voltage between motor terminals.

FIG. 3 is an abnormality detection flowchart showing an operation example of the first embodiment.

FIG. 4 is a block diagram showing a second embodiment of the present invention.

FIG. 5 is a block diagram showing a third embodiment of the present invention.

FIG. 6 is a characteristic diagram showing an operation example of the third embodiment of the present invention.

FIG. 7 is a block diagram illustrating an example of an electric power steering device.

FIG. 8 is a block diagram showing a general internal configuration of a control unit.

FIG. 9 is a connection diagram illustrating an example of a motor drive circuit.

FIG. 10 is a block diagram showing an example of a conventional apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steering handle 5 Pinion rack mechanism 10 Torque sensor 12 Vehicle speed sensor 20 Motor 30 Control unit 31 Phase compensator 37 Motor drive circuit 38 Motor current detection circuit 39 Abnormality detection unit 300, 310, 320 Motor drive system abnormality detection means

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B62D 119: 00

Claims (3)

[Claims] 1. A torque sensor for detecting a steering torque of a steering wheel, a motor for urging an auxiliary load on a steering shaft provided integrally with the steering wheel, and driving the motor in accordance with the magnitude of the steering torque. A control unit for the electric power steering apparatus, the control unit comprising: a motor current command value equal to or less than a predetermined value, or the motor current detection value equal to or less than a predetermined value, and a motor terminal voltage or an integrated value of a PWM duty ratio being predetermined. A control device for an electric power steering device, characterized in that when a state equal to or more than the value continues for a predetermined time, it is determined that the motor drive system has failed and the drive of the motor is stopped. 2. The control device for an electric power steering device according to claim 1, wherein when determining the detection value of the duty ratio of PWM with respect to the motor current command value, the influence of a battery voltage is considered. 3. A torque sensor for detecting steering torque of a steering wheel, a motor for urging an auxiliary load on a steering shaft provided integrally with the steering wheel, and driving the motor in accordance with the magnitude of the steering torque. A control device for an electric power steering device comprising a control unit, wherein a motor current command value is equal to or less than a predetermined value, or the motor current detection value is equal to or less than a predetermined value, and an output of the integrator of the control unit is equal to or more than a predetermined value. The control device for an electric power steering device is characterized in that, if a predetermined time has elapsed, it is determined that the motor drive system has failed and the drive of the motor is stopped.