JPH11342859A - Control device for motor power steering - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect directional abnormalities in circuit using a monitor signal independently of detection for abnormalities by means of comparison of a control signal with the monitor signal in an motor power steering control device, enhance the reliability of control, diagnose a directional abnormality detection circuit itself at the time of starting the device, and thereby enhance the reliability of a directional abnormality detecting function. SOLUTION: The output of a torque sensor not used for the control of a motor 6 is made to be a monitoring signal so as to use it as input to a right and a left rotational direction abnormality detecting circuit 31R and 31L. Each direction abnormality detecting circuit has a threshold, when it directs an output command opposite to its normal one because of abnormalities of a torque sensor or a CPU 15, an abnormality detection signal is outputted while the monitoring signal exceeds its threshold, and the current flowing into the motor 6 is prohibited, so that the occurrence of erroneous auxiliary steering torque is thereby prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering control device which assists a steering force with an output of an electric motor.

[0002]

2. Description of the Related Art Conventionally, a control device for an electric power steering is provided with a torque sensor for steering torque control.
The motor generates an auxiliary torque corresponding to the steering torque detected by the torque sensor, transmits the auxiliary torque to the steering shaft, and reduces the steering wheel steering force of the driver.

It is inconvenient if the auxiliary torque acts in a direction different from the direction the driver intends to steer due to some failure of the control device. Therefore, as a workaround, a direction signal corresponding to the torque sensor input and a control device The direction abnormality is detected by the AND circuit with the direction signal output by the CPU of
A method of stopping the steering assist when an abnormality is detected is known.

Further, in order to improve the reliability of the torque sensor, the input of the torque sensor is made a double system, and a torque sensor used for motor control is compared with a torque sensor not used for motor control.
A monitoring torque sensor is provided, and one of the torque sensor signals is compared with the other torque sensor signal so that even if one of the torque sensors fails, it can be detected. .

[0005]

However, even in the conventional control apparatus as described above, even if the input of the torque sensor is normal, the CPU controlling the control causes some trouble and the output direction of the steering assist torque is determined. In the event of a failure that makes it impossible to perform steering, there is a risk that steering assist may be performed in a direction unrelated to the driver's will. Further, even if the torque sensor input is a double system, if the torque sensor used as the control input fails, the steering assist is performed in a direction irrelevant to the driver's intention. Conventionally, there has been a tendency to rely too much on abnormality detection by comparison between the control signal and the monitoring signal by the CPU as described above, and there is still no direction abnormality detection technology capable of coping with both of the failure modes as described above. Not proposed. Further, a technique for judging an abnormality of the abnormality detection circuit itself as described above has not been proposed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. The monitoring signal is independent of the abnormality detection by comparing the control signal and the monitoring signal depending on the CPU constituting the control means. To improve the reliability of the control by detecting the direction abnormality in a circuit by using, and to improve the reliability of the direction abnormality detection function by performing the failure diagnosis of the direction abnormality detection circuit itself at the start of this device. An object of the present invention is to provide an electric power steering control device.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is directed to an electric motor connected to a steering system for generating a steering assist torque, and a motor for controlling the electric motor by detecting a steering torque of the steering system. A control signal to be used, a torque sensor that is independent of the control signal, and outputs a monitoring signal for monitoring the signal, and a command to drive the electric motor based on each signal output from the torque sensor. An electric power steering control device comprising: a control unit for generating a right rotation direction signal and a left rotation direction signal based on a monitoring signal output from a torque sensor; and a right rotation direction signal. A right rotation direction abnormality detection circuit having a certain threshold value, and a left rotation direction abnormality detection circuit having a certain threshold value having a left rotation direction signal input,
The right rotation direction abnormality detection circuit generates an abnormality detection signal when the right rotation direction signal exceeds the threshold value, stops driving the motor in the right rotation direction by the control means, and the left rotation direction abnormality detection circuit When the rotation direction signal exceeds a threshold value, an abnormality detection signal is generated, and the control means stops driving the motor in the left rotation direction.

In this configuration, the control means drives the motor based on the control signal of the torque sensor output to generate a steering assist torque, and uses the output of the torque sensor not used for controlling the motor as a monitoring signal. This monitoring signal is input to the right rotation direction abnormality detection circuit and the left rotation direction abnormality detection circuit. Each direction abnormality detection circuit has a certain threshold value, and when the control unit issues an output command in a direction opposite to the original direction due to abnormality of the torque sensor or the control unit, the monitoring signal is generated in each direction abnormality detection circuit. As a result of exceeding the threshold value, an abnormality detection signal is output, the current flowing through the electric motor is blocked, and the generation of erroneous steering assist torque is prevented.

Further, the invention of claim 2 provides an electric motor connected to a steering system for generating a steering assist torque, a control signal for detecting the steering torque of the steering system and used for controlling the electric motor, and a control signal based on the control signal. An electric power steering system comprising: a torque sensor that independently outputs a monitoring signal for monitoring the signal; and a control unit that outputs a command to drive an electric motor based on each signal output from the torque sensor. Means for generating a right rotation direction signal and a left rotation direction signal based on the monitoring signal output from the torque sensor, and a right rotation direction having a threshold value to which the right rotation direction signal is input. An abnormality detection circuit, comprising a left rotation direction abnormality detection circuit having a certain threshold value to which the left rotation direction signal is input, the right rotation direction abnormality detection circuit, the right rotation direction signal is the When the predetermined threshold is exceeded, an abnormality detection signal is output, and the left rotation direction abnormality detection circuit outputs an abnormality detection signal when the left rotation direction signal exceeds the set threshold, The control means forcibly generates an abnormal state by changing the respective thresholds of the right rotation direction abnormality detection circuit and the left rotation direction abnormality detection circuit when the electric power steering control device is started. At the same time, the motor is driven in this state to check the motor current, thereby performing self-diagnosis of each abnormality detection circuit.

In this configuration, the threshold value of each rotation direction abnormality detection circuit is forcibly changed by an output command from the control means when the control device is started, and an abnormal state is generated. To check the motor current. If the motor current flows at this time, it is considered that the respective rotation direction abnormality detection circuits are abnormal. Thus, the self-diagnosis of the rotation direction abnormality detection circuit can be performed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the electric power steering apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 shows the overall configuration of the electric power steering device. The steering wheel 1 (handle) is connected to a tie rod 3 via a column gear 7 and a rack and pinion 2 interposed in a column shaft constituting a steering system, and a wheel 4 is connected to the tie rod 3. . The control device 5 (ECU) of the power steering device is based on detection signals from a steering torque sensor 11 for detecting a steering torque of the steering system (here, a twist of the shaft of the column gear 7) and a vehicle speed sensor 12 for detecting the vehicle speed. , And controls the driving of a motor 6 which is connected to a steering system and generates a steering assist torque. The control device 5 drives the motor 6 to apply a steering assist torque at the column gear 7 with the operation of the driver rotating the steering wheel 1 to switch the steering angle of the wheels 4 via the steering system. The control device 5 is supplied with power from a battery 8.

FIG. 2 shows the relationship between the detected value of the steering torque sensor 11 and the motor drive current (steering assist torque) controlled by the control device 5. For the same steering torque, the lower the vehicle speed Vs, the greater the motor drive current to increase the steering assist.

FIG. 3 shows a specific circuit of the control device 5 (ECU). The control device 5 has a CPU 15 that performs self-diagnosis control such as power steering control and fail-safe control. The CPU 15 has various peripheral circuits as described below. Ignition power supply 1
6 receives power from the battery 8 when the ignition 17 is turned on, and supplies power to the CPU power supply 18. CP
The U voltage monitoring circuit 18 monitors the voltage of the CPU power supply 18. The watchdog timer (WDT) circuit 20 is for detecting runaway of the CPU 15,
The CPU 15 stops the refresh pulse of the watchdog timer circuit 20 when the apparatus is started, thereby
A self-diagnosis is made that the resetting of the resetting 15 operates normally (the details will be described later).

Also, the control circuit 25 (control means)
The motor drive circuit 26 is controlled based on a command from U15, and includes a logic output circuit 27 and an FET drive circuit (gate drive circuit) 28. Motor drive circuit 2
Reference numeral 6 denotes an FET H-type bridge circuit for controlling driving of the motor 6. The power supply for driving the motor is controlled by the motor drive circuit 26 from the battery 8 via a fail-safe power relay circuit 29 (hereinafter, referred to as a relay circuit). The relay circuit 29 is driven via a power relay drive circuit 30 according to an instruction from the CPU 15.
At startup, the CPU forcibly drives the motor drive circuit 26 in each of the ON / OFF states of the relay circuit 29, thereby making a self-diagnosis that the welding failure or the open failure has not occurred in the relay circuit 29. The direction abnormality detection circuit 31 is configured to output the sub torque signal of the steering torque sensor 11 and C
Based on a command from the PU 15, it is determined whether or not the assist steering direction is abnormal, and when the assist steering direction is abnormal, the assist steering operation is prohibited. The details will be described later.

The motor current detection circuit 32 detects the motor current for control / fail-safe use.
15 self-diagnoses that the motor current detection circuit 32 operates normally by forcibly driving the motor drive circuit 26 at the time of starting. The overcurrent detection circuit 33 detects an overcurrent of the motor drive current.
At startup, the CPU 15 injects an overcurrent level voltage from the CPU 15 into the overcurrent detection circuit 33 so that the overcurrent detection circuit 33
Self-diagnose that the system operates normally.

The torque input amplifier circuit 40 is for inputting a torque detection value from the steering torque sensor 11 to the CPU 15 for control / fail-safe use.
It includes a main torque input amplifier circuit 41 (double), a main torque input amplifier circuit 42 (differential), and a sub torque input amplifier 43. When these torque input amplifier circuits 40 are to be operated for fail-safe use, the CPU 15 checks the offset voltage of the output of the torque input amplifier circuit 40 at the time of starting, so that the torque input amplifier circuit 40
Make a self-diagnosis that there is no abnormality. Note that the CPU 15 has a built-in A / D converter.

FIG. 4 shows a main circuit configuration for detecting a direction abnormality, and FIG. 5 shows a configuration of a direction abnormality detection circuit. The above-described direction abnormality detection circuit 31 includes a clockwise rotation direction abnormality detection circuit 31R.
And a left rotation direction abnormality detection circuit 31L. CPU
Reference numeral 15 denotes a main torque detection signal of the steering torque sensor 11 which is a main torque input amplifier circuit 41 or 42 (FIG. 3).
, And a sub torque detection signal of the steering torque sensor 11 is input to each of the abnormality detection circuits 31R and 31L via a sub torque input amplifier 43 (FIG. 3). C
The PU 15 outputs a rightward command or a leftward command to the gate drive circuit 28 according to the main torque detection signal. The gate drive circuit 28 controls the voltage applied to the gates G1 to G4 of the H-bridge connected FETs in the motor drive circuit 26 to control the conduction of the FETs. Apply current. Each direction abnormality detection circuit 3
Output terminals of 1R and 31L are connected to gates G3 and G4, respectively, to prevent conduction of the FET when an abnormality is detected, thereby preventing an erroneous current from flowing through the motor 6. In the bridge-structure FET of the motor drive circuit 26, an element through which a current flows when the motor 6 is driven to rotate in the left direction is indicated by SW, and the other elements are indicated by X. Gate G3, G
Reference numeral 4 denotes a gate of the FET on the ground side.

The main torque detection signal from the main torque input amplifier circuit 41 or 42 is a control signal used for controlling the motor, and the sub torque detection signal from the sub torque input amplifier 43 is independent of the control signal. And a monitoring signal for monitoring the signal. The monitoring sub-torque detection signal includes a right rotation direction signal or a left rotation direction signal. The right rotation direction abnormality detection circuit 31R receives the right rotation direction signal as an input, has a predetermined threshold value, and generates an abnormality detection signal when the right rotation direction signal exceeds the threshold value. Regardless of the command, the right rotation direction drive of the motor is stopped. The left rotation direction abnormality detection circuit 31R receives the left rotation direction signal as an input, has a predetermined threshold value, and generates an abnormality detection signal when the left rotation direction signal exceeds the threshold value.
Regardless of the output command from U15, the motor stops driving in the left rotation direction.

In the normal operation, when the CPU 15 issues a right rotation direction command, the right rotation direction abnormality detection circuit 31R outputs a high impedance output, the left rotation direction abnormality detection circuit 31L outputs a low output, and in the abnormal operation, each output is inverted. It is configured as follows. Further, when the CPU 15 issues a left rotation direction command in a normal operation, the left rotation direction abnormality detection circuit 31L has a high impedance output, the right rotation direction abnormality detection circuit 31R has a low output, and the outputs are inverted during abnormal operation. Have been.

Further, the CPU 15 forcibly changes the threshold values of the right rotation direction abnormality detection circuit 31R and the left rotation direction abnormality detection circuit 31L when the electric power steering control device is started. An abnormal state is generated, and the motor is driven in that state to check the motor current, thereby performing a self-diagnosis of each abnormality detecting circuit. As shown in FIGS. 5A and 5B, each of the abnormality detection circuits 31R and 31L is composed of a non-inverting comparator and an inverting comparator using an operational amplifier. The PA4 allows the circuit to be changed between the normal time and the self-diagnosis.

FIG. 6 shows the CPU 1 during normal operation and during self-diagnosis.
5 shows the state of signals PA5 and PA4. FIG.
(A) shows the relationship between the sub torque detection value and the steering torque, (b) shows the output (G3) of the right rotation direction abnormality detection circuit 31R with respect to the steering torque, and (c) shows the left rotation direction with respect to the steering torque. The output (G4) of the abnormality detection circuit 31L is shown. When the output is in a high impedance state, it works so that the motor current can flow.

Next, a description will be given of a direction abnormality detecting operation in the above configuration. FIG. 4 shows a normal / abnormal operation when the CPU 15 outputs the left rotation direction command. First,
In a normal state, when the CPU 15 issues an output command in the left rotation direction in response to the main torque input, the output of the left rotation direction abnormality detection circuit 31L becomes high impedance (Z) due to the sub torque input, and the output of the right rotation direction abnormality detection circuit 31R The output is at a low level (L). Therefore, the gate drive of the H-type bridge operates as instructed by the CPU 15, and the motor current in the left rotation direction flows. At the time of abnormality, when an output command is issued in the opposite direction (that is, rightward) due to the main torque detection signal or the abnormality of the CPU 15, the output of the left rotation direction abnormality detection circuit 31L becomes low level (L) and the right rotation direction abnormality due to the sub torque input. The output of the detection circuit 31R becomes high impedance (Z). Therefore, all the gate driving of the H-type bridge is turned off, and no motor current flows. Note that the operation when the right rotation direction command is output is the same, and a description thereof will be omitted.

Next, the self-diagnosis operation at startup by the CPU 15 will be described with reference to the flowchart of FIG. When the control device of the electric power steering is started, the CPU 15 determines signals PA5 and PA4 for determining respective threshold values of the right rotation direction abnormality detection circuit 31R (right side circuit) and the left rotation direction abnormality detection circuit 31L (left side circuit). (Corresponding to the diagnosis output) is changed to HIGH, L as in the self-diagnosis shown in FIG.
OW is set (# 1, # 2), thereby forcibly bringing the output of the abnormality detection circuit into an abnormal state. In this state, the motor is rotated rightward (# 3), and the motor current is detected (# 3).
4). At this time, when the motor current is detected, it is determined that the abnormality detection circuit is abnormal (# 11). If the motor current is not detected, the motor is rotated leftward (# 5), and the motor current is detected (# 6). At this time, when the motor current is detected, it is determined that the abnormality detection circuit is abnormal (# 11). If the motor current is not detected, each abnormality detection circuit is determined to be normal (# 7), the drive is terminated (# 8), and the right circuit diagnosis output is set to L in order to return to normal.
OW (# 9), the output for left side circuit diagnosis is set to HIGH (#
10) End the self-diagnosis.

The present invention is not limited to the configuration of the above-described embodiment, but can be variously modified. For example, the circuit configurations of the right rotation direction abnormality detection circuit 31R and the left rotation direction abnormality detection circuit 31L are appropriately changed. Can be adopted.

[0025]

As described above, according to the first aspect of the present invention,
When the torque sensor signal used for control is abnormal, or when the CPU constituting the control means loses the output direction discriminating function of the auxiliary steering torque due to some abnormality, the rotational direction abnormality detecting circuit detects the direction abnormality, and Driving can be prohibited and serious failure modes can be avoided. Further, according to the invention of claim 2, since the failure detection of the rotation direction abnormality detection circuit itself is performed at the time of starting the control device, the reliability can be further improved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an electric power steering device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a motor drive current and a detection value of a steering torque sensor.

FIG. 3 is a diagram showing a specific circuit of the control device.

FIG. 4 is a main part circuit configuration diagram for detecting a direction abnormality.

FIG. 5 is a diagram showing a configuration of a direction abnormality detection circuit.

FIG. 6 is a diagram showing states of signals from a CPU in a normal state and in a self-diagnosis.

7A is a diagram showing a relationship between a detected sub-torque value and a steering torque, FIG. 7B is a diagram showing an output of a right rotation direction abnormality detection circuit with respect to the steering torque, and FIG. 7C is a left rotation direction abnormality detection circuit with respect to the steering torque. FIG.

FIG. 8 is a flowchart for a self-diagnosis operation at the time of starting.

[Explanation of symbols]

 Reference Signs List 5 control device 11 steering torque sensor 15 CPU (control means) 26 motor drive circuit 31R rightward abnormality detection circuit 31L leftward abnormality detection circuit 41 main torque input amplifier 42 main torque input amplifier 43 sub torque input amplifier

Claims (2)

[Claims] An electric motor connected to a steering system for generating a steering assist torque; a control signal for detecting the steering torque of the steering system and used for controlling the electric motor; and a control signal independent of the control signal. A control device for an electric power steering, comprising: a torque sensor that outputs a monitoring signal for monitoring a signal; and control means that outputs a command to drive the electric motor based on each signal output from the torque sensor. A means for generating a right rotation direction signal and a left rotation direction signal based on a monitoring signal output from the torque sensor; and a right rotation direction abnormality detection having a certain threshold value to which the right rotation direction signal is input. A left rotation direction abnormality detection circuit having a certain threshold value to which the left rotation direction signal is input, wherein the right rotation direction abnormality detection circuit includes the right rotation direction signal. If but exceeding the threshold value, and generates an abnormality detection signal,
Stopping the motor in the right rotation direction by the control means, the left rotation direction abnormality detection circuit, when the left rotation direction signal exceeds the threshold value, generates an abnormality detection signal,
A control device for an electric power steering, wherein the control unit stops driving the motor in the left rotation direction. 2. An electric motor connected to a steering system for generating a steering assist torque, a control signal for detecting the steering torque of the steering system and used for controlling the electric motor, and a signal independent of the control signal. And a control unit for outputting a command to drive the electric motor based on each signal output from the torque sensor. Means for generating a right rotation direction signal and a left rotation direction signal based on the monitoring signal output from the torque sensor; and a right rotation direction abnormality detection having a certain threshold to which the right rotation direction signal is input. A left rotation direction abnormality detection circuit having a certain threshold value to which the left rotation direction signal is input, wherein the right rotation direction abnormality detection circuit includes the right rotation direction signal. Outputs an abnormality detection signal when the value exceeds the set threshold value, and outputs an abnormality detection signal when the left rotation direction signal exceeds the set threshold value. The control means forcibly changes the threshold values of the right rotation direction abnormality detection circuit and the left rotation direction abnormality detection circuit when the control device for the electric power steering is started. A self-diagnosis of each of the abnormality detection circuits by generating an abnormal state and driving the electric motor in that state to check the electric current of the electric motor.