JPH08107695A - Controller for power steering - Google Patents

Abstract

PURPOSE: To make it possible to detect a short-circuit of arms even before applying power to an H bridge circuit and also to stop power supply to the H bridge within a shorter time from the occurrence of anomaly by monitoring the conditions of a signal system between control means and the H bridge circuit. CONSTITUTION: Output signals g1 to g4 from each of gate drive circuits 51 to 54 are input to an anomaly detection circuit 66. Output signals g1 and g3 from the gate drive circuits 51 to 53 are input to an AND circuit AD5, output signals g2 and g4 from gate drive circuits 52 and 54 are input to AND circuit AD6, and the output signals from these AND circuits AD5 and AD6 are input to NOR circuit NR. Then, output signals from NOR circuit NR are input to AND circuits AD1 to AD4 and ADR and then to a microcomputer 21. Therefore, any anomaly in command signals from each of gate drive circuits 51 to 54 or in command signals from the microcomputer 21 can be detected before the H bridge circuit 40 becomes conductive.

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 system which applies a steering assist force by an electric motor to a steering system of a vehicle.

[0002]

2. Description of the Related Art Conventionally, as a control device for an electric power steering apparatus, a steering torque detector such as a torque sensor for detecting steering torque is attached to an input shaft to which a steering wheel is fixed, and steering detected by the steering torque detector is used. It is known that an assist torque corresponding to the torque is generated by an electric motor to assist the steering torque.

This electric motor is controlled by a controller, which controls the assist current based on the steering torque detection signal detected by the torque sensor and the vehicle speed of the vehicle detected by the vehicle speed sensor. Is supplied to the electric motor to assist the steering force of the steering wheel. This electric motor assists the steering operation, for example, during low-speed cornering or when entering the garage, and also during high-speed traveling. The feel of the wheel is obtained and running stability is ensured.

This conventional controller is constructed, for example, as shown in the block diagram of FIG. 8, and the controller 13 is based on a control circuit 20 formed by, for example, a microcomputer or the like, and a command from the control circuit 20. Motor drive circuit 3 for driving the motor 12 such as a DC motor
0, a current detection circuit 61, a clutch control circuit 62, a relay drive circuit 63, and a fail relay 64.

The control circuit 20 comprises a microcomputer 21, A / D converters 22, 23, 24, a phase compensator 25, and a counter 26. The microcomputer 21 receives the voltage signal from the torque sensor 3. The torque detection signal T _V is phase-compensated by the phase compensator 25 and further A / D converted by the A / D converter 22 to detect the torque detection value T _V.
And a vehicle speed detection signal V _P from a vehicle speed sensor 17 such as a rotation speed sensor, which is arranged on the output shaft of a transmission (not shown) and generates a pulse signal according to the rotation of the output shaft. The vehicle speed detection value V calculated from the number of pulses per unit time is input, and the left and right motor current detection signals I _L and I _R from the current detection circuit 61, which will be described later, are input to the A / D converter 23 and The motor current detection values i _L and i _{R in} the left-right direction are input via 24, and a command signal to the motor drive circuit 30 is formed according to a processing program stored in advance based on these input signals.

The motor drive circuit 30 has four FEs.
Each FE that drives the H bridge circuit 40 composed of T (field effect transistors) 41 to 44 and each of these FETs 41 to 44 based on a command signal from the control circuit 20.
The gate drive circuits 51 to 54 corresponding to T. The FETs 41 and 43 and the right direction current detection resistor R _R are connected in series, and the FETs 42 and 44 and the left direction current detection resistor R _L are connected in series. , And the series circuits thereof are connected in parallel so that the drain sides of the FETs 41 and 42 are connected to the battery 16 via the fail relay 64. The connection point between the FETs 41 and 43 and F
The motor 12 is connected between the connection points of the ETs 42 and 44, and the outputs of the gate drive circuits 51 to 54 corresponding to the FETs 41 to 44 are supplied. Then, the current value flowing in the motor 12 is detected by the current detection circuit 61 from the voltage generated at both ends of the right direction current detection resistor R _R and the left direction current detection resistor R _L , and this is detected as the motor current detection signal I in the left and right direction. Control circuit 20 as _L and I _R
Output to.

[0007] Then, right and left pulse width modulation signal PWM _R and PWM _L control circuit 20 drives the respective gate drive circuits 51 to 54 as a command signal, the left-right direction signal D _R and D _L
And outputs them, and the gate drive circuits 51 to 54 respond to these command signals by corresponding gate terminals G _{1 to} G of the FETs.
_By supplying a voltage to ₄ , a predetermined FET is turned on and the motor 12 is rotated forward or backward.

Further, the control circuit 20 detects whether or not an arm short circuit has occurred in the H bridge circuit 40. This arm short circuit is caused by, for example, FET 41 and FET.
43 is turned on and current flows through the H bridge circuit 40 without passing through the motor 12, and when an arm short circuit occurs, the ON resistance of the FETs 41 to 44 and the right and left current detection resistances R _R, R _{Since L} is small, an excessive current will flow in the H bridge circuit 40, which may cause a fire, and a failure due to a fire in a vehicle may lead to a serious accident. In addition, when the occurrence of arm short circuit is detected, it is necessary to immediately stop the energization.

In the control circuit 20, the detection of this arm short circuit is calculated based on the motor current detection signals I _R and I _L in the left and right directions from the current detection circuit 61.
Are performed based on _M, the motor current detection signal i _M
When the absolute value | i _M | of the above is larger than a preset predetermined value, it is determined that an excessive current is flowing in the H bridge circuit 40, and the command signals to the gate drive circuits 51 to 54 are turned off, The clutch 11 is disengaged by stopping the output of the clutch control signal S _C to the clutch control circuit 62, and the fail relay 64 is output by outputting the relay control signal S _R to the relay drive circuit 63 as “LOW”. Is activated to turn off the H bridge circuit 40 from the battery 16 and each gate drive circuit 51 to 54 stops supplying voltage to the corresponding FETs 41 to 44 to turn off each FET. By doing so, the FET, the harness, etc. are prevented from being burnt out.

[0010]

However, in the above-mentioned conventional control device for the electric power steering apparatus, the abnormality determination is performed based on the current actually flowing in the H bridge circuit 40 detected by the current detection circuit 61, and When it is determined as abnormal by the abnormality determination, the fail relay 64 or each of the gate drive circuits 51 to 54 is operated to activate each F
Since the ET is turned off, an arm short circuit occurs and a short circuit current occurs before the fail relay 6
4 or each of the gate drive circuits 51 to 54 takes a long time to operate, and during that time, the FETs 41 to 44, the substrate, the harness, etc. may be burned or stress may be applied to accelerate the deterioration. There are unresolved issues.

The cause of the arm short circuit is that each command signal PWM _R and PW due to an abnormality of the control circuit 20 or the like.
When the setting error of M _L , D _R, and D _L or the error occurs in the gate drive circuits 51 to 54 and each FET is activated regardless of the command signal from the control circuit 20, or FE
Although it is possible that T itself fails, in the conventional control circuit 20, the motor current detection value i _M calculated based on the left and right motor current detection signals I _R and I _L from the current detection circuit 61 is used. Since the abnormality determination is performed based on this, there is also a problem that the arm short circuit cannot be detected until after the H bridge circuit 40 is actually turned on.

Therefore, the present invention has been made by paying attention to the unsolved problem of the above-mentioned conventional example.
(EN) Provided is a control device for an electric power steering device, which can detect an arm short circuit even before energizing 0, and can stop energizing the H bridge circuit 40 in a shorter required time from the occurrence of an abnormality. Has an aim.

[0013]

In order to achieve the above object, a control device for an electric power steering apparatus according to the present invention includes a steering torque detecting means for detecting a steering torque of a steering system and a steering torque detecting means for the steering system. An electric motor that generates a steering assist force, a control unit that outputs a control signal that generates a steering assist force to the electric motor based on a torque detection value of at least the steering torque detection unit, and a control signal from the control unit. A control device for an electric power steering apparatus, comprising: an H bridge circuit for controlling a current supply direction and a current supply amount of the electric motor based on the control means and the H control circuit.
Abnormality detecting means for monitoring the state of the signal system between the bridge circuits and detecting an abnormal state of the energization path of the H bridge circuit;
And an energization interruption means for interrupting energization to the electric motor when the abnormality detection means detects an abnormality in the energization path of the H-bridge circuit.

[0014]

According to the present invention, the control means forms the control signal for driving the electric motor based on the steering torque detected by the steering torque detecting means, and the H bridge circuit operates based on the control signal to operate the electric motor. The direction of energization and the amount of energization are controlled, and at this time, the state of the signal system between the control means and the H bridge circuit is monitored by the abnormality detection means, and, for example, two switching elements connected in series are connected in parallel. Of the control signals for operating each switching element of the H-bridge circuit formed by four switching elements connected to each other, it is determined to be abnormal when each control signal for the switching elements connected in series is in the ON state. By detecting the abnormality of the energization path of the H bridge circuit, and the abnormality detection means detects the abnormality of the energization path of the H bridge circuit, By turning off the power to the electric motor by disconnection means, H-bridge circuit is prevented in advance that the current path abnormality.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing one embodiment of the present invention. In the figure, 1 is a steering wheel, and the steering force applied to the steering wheel 1 is the input shaft 2a.
And a steering shaft 2 composed of an output shaft 2b
Is transmitted to One end of the input shaft 2a is connected to the steering wheel 1, and the other end is connected to one end of the output shaft 2b via a torque sensor 3 as steering torque detecting means. Then, the steering force transmitted to the output shaft 2b is transmitted to the lower shaft 5 via the universal joint 4 and further transmitted to the pinion shaft 7 via the universal joint 6. The steering force is further transmitted to the tie rod 9 via the steering gear 8 to steer the steered wheels. The steering gear 8 is of a rack-and-pinion type having a pinion 8a and a rack 8b, and the rotary motion transmitted to the pinion 8a is converted into a linear motion by the rack 8b.

The output shaft 2b of the steering shaft 2 is connected to a reduction gear 10 for transmitting an auxiliary steering force (assist force) to the output shaft 2b. Output of a motor 12 as an electric motor configured to generate an auxiliary steering force, for example, via an electromagnetic clutch device 11 (hereinafter, referred to as a clutch) configured of an electromagnetic type, which is configured by a DC servo motor, for example. The shaft is connected. The clutch 11 has a solenoid, and an excitation current is supplied to the solenoid by a controller 13 as a control means which will be described later, so that the reduction gear 10 and the motor 12 are mechanically connected and disengaged when the excitation current is stopped. It

The torque sensor 3 is provided on the steering wheel 1 and detects the steering torque transmitted to the input shaft 2a. For example, the torsion torque is inserted between the input shaft 2a and the output shaft 2b. The torsion angle displacement of the bar is converted into a torsion angle displacement, and the torsion angle displacement is detected by a potentiometer.
By steering the steering shaft 2
The torque detection signal T _V, which is an analog voltage corresponding to the magnitude and direction of the twist that occurs in, is output. The torque sensor 3 outputs a predetermined neutral voltage V ₀ as the torque detection signal T _V when the steering wheel 1 is in the neutral state, as shown in FIG. Turning to the right turns the voltage that increases from the neutral voltage V ₀ according to the steering torque at that time, and turning to the left turns the neutral voltage V ₀ according to the steering torque at that time.
It is designed to output a voltage that decreases more.

Reference numeral 13 is a controller for controlling the drive of the motor 12 and for controlling the steering assist force to the steering system, which is operated by being supplied with power from the battery 16 mounted on the vehicle. The negative electrode of the battery 16 is grounded, and the positive electrode of the battery 16 is connected to the controller 13 via the ignition switch 14 and the fuse 15a for starting the engine and directly connected to the controller 13 via the fuse 15b. The power supplied via 15b is used, for example, for memory backup. Then, the controller 13 drives and controls the motor 12 based on the torque detection signal T _V from the torque sensor 3 and, for example, the vehicle speed detection signal V _P from the vehicle speed sensor 17 arranged on the output shaft of the transmission (not shown). At the same time, the clutch 11 is controlled so that the output shaft of the motor 12 and the reduction gear 10 are connected / disengaged.

FIG. 3 is a block diagram showing the configuration of the controller 13. The block diagram of the controller 13 is different from the block diagram of the controller 13 except that a gate circuit 65 as an energization interruption means and an abnormality detection circuit 66 as an abnormality detection means are added. 8 is similar to the conventional block diagram shown in FIG. 8, and the same reference numerals are given to the same parts. Then, the controller 13
For example, the control circuit 20, the motor drive circuit 30, the current detection circuit 61, the clutch control circuit 62, the relay drive circuit 6
3, a fail relay 64, a gate circuit 65, and an abnormality detection circuit 66.

The control circuit 20 is composed of a microcomputer 21, A / D converters 22, 23, 24, a phase compensator 25, and a counter 26. The microcomputer 21 includes at least an interface section for performing input / output processing with an externally connected device, a ROM, and a RAM.
And the like. Phase compensator 25
In order to stabilize the control system, for example, phase compensation processing such as advancing the phase with respect to the input signal is performed. Phase compensation is performed on the torque detection signal T _V from the torque sensor 3, The torque compensation signal T _P is output to the A / D converter 22, and the A / D converter 22 outputs the torque compensation signal T _P.
P is converted into a digital signal and output as a torque detection value T to the microcomputer 21.

Then, the microcomputer 21
The torque detection value T is input via the / D converter 22, and the rightward motor current detection signal I _R from the current detection circuit 61 is set as the rightward motor current detection value i _R via the A / D converter 24. Further, the leftward motor current detection signal I _L is input as the leftward motor current detection value i _L via the A / D converter 23, and further, the vehicle speed detection value V from the counter 26 is input.

Here, the counter 26 is provided on, for example, the output shaft of a transmission (not shown), and the vehicle speed sensor 1 such as a rotation speed sensor for generating a pulse signal according to the rotation of the output shaft.
The vehicle speed detection signal V _P, which is a pulse signal from 7, is input,
The number of pulses per unit time is integrated, and when the integrated value is read into the microcomputer 21, the count value is reset by the reset signal R _C from the microcomputer 21.

Then, in the microcomputer 21, based on these input signals, for example, PID control (proportional
The motor drive signal S _M supplied to the motor 12 is calculated by (integration / derivative), and P is calculated based on the motor drive signal S _M.
A WM (Pulse Width Modulation) signal is formed, and this P
A left pulse width modulation signal PWM _L , a right pulse width modulation signal PWM _R , a right direction signal D _R , and a left direction signal D _L are formed based on the WM signal, and these respective command signals PWM _L , PW are formed.
M _R, D _R, and outputs to the motor drive circuit 30 through the gate circuit 65 and D _L.

Further, the microcomputer 21 executes a predetermined failure detection process at the time of start-up, and when it is normal, the relay control signal S _R to the relay drive circuit 63.
Is output to the gate circuit 65 as “HIGH”,
The clutch control signal S _C that gradually increases to the clutch control circuit 62
Is output. Further, during drive control of the motor 12, abnormality monitoring processing is performed based on the motor current detection values i _R and i _L from the current detection circuit 61, and when abnormality is detected, the command signals PWM _L and PWM _R to the motor drive circuit 30 are detected. , D _R , D
_{After L} is output as "LOW", a clutch control signal S _C for disengaging the clutch 11 is formed and output, and then a relay control signal S _R for opening the fail relay 64 is formed and the relay drive circuit 63 is formed. And performs predetermined processing when an abnormality occurs, such as turning on an abnormality lamp.
Further, even when the abnormality detection signal S _A from the motor drive circuit 30 is input and the abnormality detection signal S _A is abnormal, similarly, each command signal is output as “LOW” and a predetermined value for the abnormality detection is output. The process of is executed. At the end, the clutch control signal S proportional to the motor angular velocity, for example, is used to absorb the elastic energy stored in the steering system.
_C is formed and output to the clutch control circuit 62, and control is performed so as to give a viscous load for a predetermined time.

The motor drive circuit 30 includes at least an H bridge circuit 40 having four switching elements, and gate drive circuits 51 to 51 for driving these switching elements.
And 54. And the H bridge circuit 4
0 is, for example, an enhanced N-channel MOS type F
Four FETs 41 such as ET (field effect transistor)
44, the FETs 41 and 43 are connected in series, and the FETs 42 and 44 are connected in series,
These series circuits are connected in parallel, and FETs 41 and 4 are connected.
The drain side of 3 is connected to the battery 16 via the fail relay 64. The motor 12 is connected between the connection point between the FETs 41 and 43 and the connection point between the FETs 42 and 44. Further, the source side of the FET 43 is grounded via the right direction current detection resistor R _R , and similarly, the FET 4
The source side of 4 is grounded via a leftward current detecting resistor R _L.

Of the gate terminals G _{1 to} G ₄ of these FETs 41 to 44, the gate terminal G ₁ is the gate drive circuit 51, the gate terminal G ₂ is the gate drive circuit 52, and the gate terminal G ₃ is the gate drive circuit. 53 and the gate terminal G ₄ are respectively connected to the gate drive circuit 54, and when a predetermined voltage is supplied from the gate drive circuits 51 to 54 to the gate terminals G _{1 to} G ₄ , the corresponding FETs 41 to 44 are turned on. When only the FETs 41 and 44 are turned on, the FET 41, the motor 12,
When the motor 44 is reversely rotated by energizing in the direction of the FET 44 and the left direction current detection resistor R _L , and only the FETs 42 and 43 are turned on, the FET 42, the motor 12 and the FET
43, the motor 12 is rotated forward by being energized in the direction of the rightward current detection resistor R _R.

A command signal from the control circuit 20 to each of the gate drive circuits 51 to 54 is output via the gate circuit 65. The gate circuit 65 includes AND circuits AD1 to AD4 and AD for calculating a logical product of input signals.
It is composed of a _R, left pulse width modulation signal PWM _L AND circuit AD1, right pulse-width modulation signal PWM _R AND circuit AD2, the right direction signal D _R is AND of the control circuit 20
The circuit AD3 and the leftward signal D _L are respectively input to one input terminal of the AND circuit AD4, and the other input terminal is
The abnormality detection signal S _A from the abnormality detection circuit 66 is input. The output signal D of each AND circuit AD1 to AD4
1 to D4, the output signal D1 to the gate drive circuit 51, the output signal D2 to the gate drive circuit 52, the output signal D3 to the gate drive circuit 53, the output signal D4 to the gate drive circuit 5
4 are input respectively.

Then, in the gate drive circuits 51 to 54,
Output signals D1 input from AND circuits AD1 to AD4
Based on D4, the voltage is supplied to the gate terminals G ₁ and G ₂ of the FETs 41 and 42 by a booster power source (not shown), and the battery voltage is supplied to the gate terminals G ₃ and G ₄ of the FETs 43 and 44, and the output signal Dn is A predetermined voltage is supplied to the gate terminal Gn while it is "HIGH", and the voltage supply to the gate terminal Gn is stopped while the output signal Dn is "LOW".

The output signals g1 to g4 from the respective gate drive circuits 51 to 54 are input to the abnormality detection circuit 66, and the abnormality detection circuit 66 performs abnormality detection based on these output signals g1 to g4 and outputs the abnormality detection signals. It is designed to output S _A. The abnormality detection circuit 66 includes an AND circuit AD5,
The output signals g1 and g3 from the gate drive circuits 51 and 53 are input to the AND circuit AD5, and the output signals g2 and g4 from the gate drive circuits 52 and 54 are input to the AND circuit AD6. The output signals from the AND circuits AD5 and AD6 are input to the NOR circuit NR.

The output signal from the NOR circuit NR serves as the abnormality detection signal S _A and AND circuits AD1 to AD4.
Is input to and AD _R, is adapted to be inputted to the microcomputer 21. On the other hand, the current detection circuit 61, for example, amplifies and removes the voltage generated at both ends of the right direction current detection resistor R _R and the left direction current detection resistor R _L , and outputs the right direction motor current detection signal I _R and the left direction motor. The current detection signal I _L is output to the control circuit 20.

Further, the clutch control circuit 62 is responsive to the clutch control signal S _C from the control circuit 20 to generate an exciting current i _C.
To output to the solenoid of the clutch 11 to form the motor 1
The output shaft 2 and the reduction gear 10 are controlled to be in a mechanically connected state / disengaged state. The relay drive circuit 63 controls ON / OFF of the fail relay 64 based on the output signal S _RR from the AND circuit AD _R of the gate circuit 65. The fail relay 64 has a normally open contact. The switch controls ON / OFF of the power supply of the battery 16 to the H-bridge circuit 40.

The AND circuit AD _R receives the relay control signal S _R from the control circuit 20 and the abnormality detection signal S _A from the NOR circuit NR of the abnormality detection circuit 66, calculates the logical product of these signals, and outputs the output signal. Relay drive circuit 63 as S _RR
The relay drive circuit 63 outputs the output signal S
_{When RR} is "HIGH", the coil 64L of the fail relay 64 is energized to close the relay contact 64a, and the power supply from the battery 16 to the H bridge circuit 40 is enabled, and the output signal S _RR is " When LOW ”, the coil 64L of the fail relay 64 is de-energized to open the relay contact 64a and the power supply from the battery 16 to the H-bridge circuit 40 is cut off.

Next, the processing procedure of the drive control processing of the motor 12 in the microcomputer 21 will be described based on the flowchart shown in FIG. The motor drive control process is performed by a timer interrupt at preset predetermined time intervals. The microcomputer 21 executes a predetermined failure detection process when the ignition switch 14 is turned on, and when no abnormality is detected, outputs a relay control signal S _R as “HIGH” and then outputs a clutch (not shown). A clutch control signal S _C that gradually increases based on the control process is generated and output, and each command signal to each gate drive circuit 51 to 54 is set to “LO” at the time of activation.
It shall be output as W ".

As a result, when the motor drive circuit 30 is normal, the abnormality detection signal S _A is output as "HIGH", and the output signal S _RR of the AND circuit AD _R is "H".
IGH ”, so that the relay drive circuit 63 energizes the coil 63L to cause the fail relay 6
4 is closed, and the H bridge circuit 40 is energized. In the clutch control circuit 62, the rotating shaft of the motor 12 and the reduction gear are gradually brought into a mechanically coupled state by supplying the exciting current i _C to the solenoid of the clutch 11 according to the clutch control signal S _C. .

Further, for example, the ignition switch 1
4 is turned off, a predetermined process at the time of termination set in advance is executed, and, for example, the clutch control signal S _C proportional to the motor angular velocity is absorbed in order to absorb the elastic energy stored in the steering system. Is output to the clutch control circuit 62 to control the viscous load for a predetermined time.

When the ignition switch 14 is turned on and the predetermined failure detection process is completed, the microcomputer 21 executes the motor drive control process, and first, in step S1, the A / D converter 22 is used to execute the motor drive control process. Torque sensor 3 with phase compensation performed by the phase compensator 25
The torque detection value T from is read. Then, step S
2, the calculation of T = T−V ₀ is performed, and the offset process is performed so that the torque detection value T at neutral is zero.

Then, the process proceeds to step S2a, the count value of the counter 26, that is, the vehicle speed detection value V is read, the reset signal _RC is output to the counter 26 to reset the counter value, and then the process proceeds to step S3. hand,
For example, referring to the characteristic diagram showing the correspondence between the steering torque, the vehicle speed, and the motor current shown in FIG. 5, the motor current corresponding to the torque detection value T and the vehicle speed detection value V is searched, and this is searched for as a motor current command. Set as the value S _I.

This characteristic diagram shows the steering shaft 2
The motor torque required to drive the motor 12 to generate an auxiliary steering force corresponding to the steering torque input to the motor 12, the steering torque, and the vehicle speed. Is smaller, the motor current command value is larger, and as the steering torque is larger, the motor current command value is larger.

Then, the process proceeds to step S4, and the motor current command value S _{I is} subjected to a predetermined differential processing or the like to be multiplied by a predetermined differential gain to obtain a differential processed value f _D, and then in step S5, right The motor current detection value i _{R in the} left direction and the motor current detection value i _L in the left direction are read, and the motor current detection value i _R in the right direction is set as a positive value and the motor current detection value i _L in the left direction is set as a negative value. Then, the motor current detection value i _M is calculated from the sum of these detection signals. That is, i _M = i
_{It is} calculated by _R- i _L.

Here, it is assumed that the current detection circuit 61 performs sufficient filtering on the respective signals so that the effective values of the motor current detection signals I _R and I _{L in} the left and right directions are obtained. Then, the process proceeds to step S5a,
For example, the abnormality monitoring process as shown in the flowchart of FIG. 6 is performed.

In this abnormality monitoring process, first, step S
At 21, it is determined whether the absolute value | i _M | of the motor current detection value i _M is smaller than a preset maximum current value I _MAX that the motor drive circuit 30 is considered to be operating normally.
The absolute value | i _M | of the detected motor current value i _M is the maximum current value I
When it is smaller than _MAX , the motor current detection value i _M is determined to be within the normal range, and the process returns to the motor drive control processing program.

On the other hand, as a result of the determination in step S21, | i
_{If M│} <I _MAX is not satisfied, it is determined that an excessive current is flowing in the H bridge circuit 40 and an abnormality has occurred, the process proceeds to step S22, and each command signal PWM _L to the gate drive circuits 51 to 54 is sent. , PWM _R , D _R , D _L to “LO
It is output as W ″, and the energization path of the H bridge circuit 40 is cut off by this.

[0043] Then, the process proceeds to step S23, by stopping the output of the clutch control signal S _C to the clutch control circuit 62, the motor 1 operates the clutch 11
The output shaft of 2 and the reduction gear 10 are disengaged, and then
In step S24, by outputting the relay control signal S _R to the relay drive circuit 63 as "LOW", the fail relay 64 is operated to cut off the energization from the battery 16 to the H bridge circuit 40, and Step S
At 25, for example, an abnormality notification is sent to the upper-level program such as the main processing program, and the abnormality monitoring processing is ended. Thereafter, the upper drive program does not execute the motor drive control process.

If no abnormality is detected in the motor drive current as a result of the abnormality monitoring processing in step S5a, the process proceeds to step S6. In this step S6,
The current deviation e _M is calculated from the difference between the motor current command value S _I set in step S3 and the motor current detection value i _M calculated in step S5, that is, e _M = S _I −i _M.

Next, at step S7, the current deviation e _M is multiplied by a predetermined proportional gain to obtain a proportional processed value f _P, and at step S8 the proportional processed value f _P is integrated and multiplied by a predetermined integral gain. Then, this is set as an integration processed value f _I. Then, in step S9, the differential processed value f _D , the proportional processed value f _P, and the integrated processed value f _I are added, and this is used as the motor drive signal S _M , and the process proceeds to step S10.

[0046] In step S10, the motor drive signal S _M is equal to or a S _M ≧ 0, when a S _M ≧ 0 and proceeds to step S11, the normal rotation of the rotation direction of the motor 12 Set the right direction signal D _R set to the direction to “HIG
H ", a duty ratio D for supplying a drive current corresponding to the motor drive signal S _M to the motor 12 is set, and this is output as a right pulse width modulation signal PWM _R to the corresponding AND circuits AD2 and AD3. Then, the left pulse width modulation signal PWM _L and the left direction signal D _L are set to “LOW” for the AND circuits AD1 and AD4, and the processing is ended and the process returns to the main program.

On the other hand, if S _M ≧ 0 is not satisfied in step S10, the process proceeds to step S12, and the left direction signal D _L for setting the rotation direction of the motor 12 to the reverse rotation direction is set to "HIG.
H ", a duty ratio D for supplying a drive current corresponding to the motor drive signal S _M to the motor 12 is set, and this is set as a left pulse width modulation signal PWM _L to the corresponding AND circuits AD1 and AD4. Output.
The right direction signal D _R and the right pulse width modulation signal PWM _R are “L
OW "is output to the AND circuits AD2 and AD3, respectively, and the process is terminated and the process returns to the main program.

Next, the operation of the above embodiment will be described. now,
Ignition switch 1 when the vehicle is stopped
When 4 is turned on, the power supply from the battery 16 is supplied to the controller 13 and the controller 13 starts operating. Then, the microcomputer 21 performs a predetermined failure monitoring process, and outputs the relay control signal S _R as “HIGH” to the AND circuit AD _R if there is no abnormality, and also outputs the command signals PWM _L and PW as initial values.
After outputting M _R , D _R , and D _L as “LOW”, a gradually increasing clutch control signal S _C is formed and output to the clutch control circuit 62.

As a result, since the command signals PWM _L , PWM _R , D _R , and D _L from the control circuit 20 are "LOW", the output signals g1 of the gate drive circuits 51 to 54 are obtained.
Since ~ g4 is "LOW", in the abnormality detection circuit 66, the output signals of the AND circuits AD5 and AD6 are "LO".
Since it becomes W ″, the output of the NOR circuit NR, that is,
The abnormality detection signal S _A becomes “HIGH”. Then, the abnormality detection signal S _A and the relay control signal S _R are both “HIG
H ", the output signal S _RR of the AND circuit AD _R
Becomes "HIGH", and in the relay drive circuit 63, the coil 64L is energized, and the fail relay 64 is closed to start energization of the H bridge circuit 40. Then, the clutch control circuit 62 supplies the exciting current i _C corresponding to the clutch control signal S _C to the solenoid of the clutch 11, so that the clutch 11 operates and the output shaft of the motor 12 and the reduction gear 10 gradually. It will be in a mechanically coupled state.

At this time, the command signal P from the control circuit 20
Despite that WM _L , PWM _R , D _R , and D _L are “LOW”, for example, the output signal g1 of the gate drive circuit 51
When is turned on, the output signal of the AND circuit AD5 becomes "LOW" and the output of the NOR circuit NR becomes "L".
Since the output signal S _RR of the AND circuit AD _R becomes “LOW”, the relay drive circuit 63 does not control the fail relay 64 to be in the closed state, so that the H bridge circuit 40 is supplied with power from the battery 16. No supply is made.
The outputs of the AND circuits AD1 to AD4 are "LOW" unless the abnormality detection signal S _A is "HIGH".
Therefore, after the abnormality is detected, the command signal P is output from the control circuit 20.
Even if WM _L , PWM _R , D _R , and D _L are output,
Since the gate drive circuits 51 to 54 are not driven, for example,
Even when the right direction signal D _R is output as “HIGH”, the gate drive circuit 53 does not operate, so that the output signal g3 is not turned on.
Since the FET 3 and the FET 3 are both turned on, an excessive current does not flow in the H bridge circuit 40. Further, in the control circuit 20, the abnormality detection signal S _A is “LOW”.
Therefore, it is recognized that the motor drive circuit 30 is abnormal, and, for example, the command signals PWM _L , PWM _R , D _R ,
The D _L "LOW", since the process when a predetermined abnormality detection such as setting to "LOW" the relay control signal S _R, excessive current does not flow through the H-bridge circuit 40.

While the controller 13 is in a normal state and the vehicle is in the running state from the stopped state, the torque detection value T from the torque sensor 3 is in the vicinity of the neutral voltage V ₀ while the vehicle is in the non-steering state. The motor current command value S _I is shown in Fig. 5.
The control circuit 20 outputs the command signals PWM _L , PWM _R , D _R , and D _L as “LOW”. Therefore, in the motor drive circuit 30, the control circuit 20 outputs the motor 1
2 is not drive controlled. At this time, for example, when an abnormality occurs in the FET and the FET is turned off and an excessive current flows in the H-bridge circuit 40, the current detection circuit 61 performs the operation in step S21 of the abnormality monitoring processing of FIG. It is determined whether or not the absolute value | i _M | of the detected motor current value i _M obtained from the detected motor current values i _R and i _{L in} the left-right direction is smaller than the maximum current value I _MAX . It is possible to detect that an excessive current is flowing through the H-bridge circuit 40, and the control circuit 20 causes the command signals PWM _L , PWM
_{Since R} , D _R , and D _L are output as “LOW”, the clutch control signal S _C is output as “LOW”, and the relay control signal S _R is output as “LOW”, the output S of the AND circuit AD _R is output. _RR becomes "LOW" and the fail relay 64 is opened to cut off the power supply to the H bridge circuit 40.

When the occupant steers to the right while traveling in this normal state, the control circuit 20 reads the detected torque value T, and the neutral position becomes zero by T = T-V _0. Based on the detected torque value T and the detected vehicle speed value V from the vehicle speed sensor 17, the corresponding motor current is searched with reference to the characteristic diagram shown in FIG. When the steering torque is large while the vehicle is traveling at a low speed, a large auxiliary steering force is required, so the motor current command value S _I is set to a large value. The motor current command value S _I is set to a small value in order to generate a small auxiliary steering force so that the wheel 1 feels responsive. Similarly, when the steering torque is small, sets the higher the vehicle speed is less large motor current command value S _I, to a small motor current instruction value S _I to be a responsive feeling of the steering wheel 1 as the vehicle speed increases Is set. At this time, since the right steering is performed, the offset torque detection value T has a positive value, and thus the motor current command value S _I set from FIG. 5 also has a positive value.

Then, a predetermined differential operation process is performed on the set motor current command value S _I to calculate a differential process value f _D. In addition, the motor current detection values i _R and i
Based on _L , the motor current detection value i _M is calculated as the current value flowing in the motor by i _M = i _R −i _L. Then, the motor current command value S _I and this motor current detection value i _M
If the current deviation e _M is calculated from the current deviation e _M , the abnormality monitoring processing is executed, and if it is determined to be normal, the current deviation e _{M is} subjected to a predetermined proportional calculation processing to calculate the proportional processing value f _P. Then, integral calculation processing is performed on the calculated proportional processing value f _P , and the differential processing value f _D , the proportional processing value f _P, and the integral processing value f _I are added to calculate the motor drive signal S _M.

Then, the current direction is judged based on the sign of the motor drive signal S _{M. In} this case, since S _M ≧ 0, the command signals PWM _L and D _L are output as “LOW”, and the command signal D _R is “HIGH”, and the command signal PWM _R is output as a pulse signal having a duty ratio D corresponding to the motor drive signal S _M. At this time, since it is in the normal state and the abnormality detection signal S _A is “HIGH”, the AND circuit AD
The output D3 of 3 becomes "HIGH" and the gate drive circuit 5
3 turns on the FET 43 by supplying a predetermined voltage, and the output D2 of the AND circuit AD2 is "HIGH".
During this period, the gate drive circuit 52 supplies a predetermined voltage to turn on / off the FET 42.

At this time, since the command signals PWM _L and D _L are "LOW", the gate drive circuits 51 and 54
Does not supply a predetermined voltage to the FETs 41 and 44, so that the FETs 41 and 44 remain off. Therefore, when the FET 42 is turned on, the battery 1
By the power supply from 6, the FET 42, the motor 12, the F
The motor 12 is positively rotated by being energized in the direction of the ET 43 and the right direction current detection resistor R _R , and the FET 42 is on / off controlled to supply a current according to the motor drive signal S _M to drive / control the motor 12. .

As a result, the rotational driving force of the motor 12 is transmitted to the steering shaft 2 via the reduction gear 10, and thus a predetermined steering assist force corresponding to the steering torque is transmitted and the vehicle is traveling at a low speed. When the steering torque is large, the motor current command value S _I is set to a large value, and a large steering assist force is transmitted from the motor 12 to the steering shaft 2. Therefore, for example, steering operation during garage entry or low speed cornering is performed. Further, when the vehicle is traveling at a high speed, a small steering assist force is transmitted from the motor 12 even when the steering torque is large, so that the steering wheel 1 can provide a feeling of response. .

When this right steering is performed, for example, AND circuits AD1 to AD6, gate drive circuits 51 to
54, abnormality occurs in any of the microcomputer 21, for example, command signal _{PWM L, PWM R, D R} , D L
Regardless of this, the gate drive circuits 51 and 53 stop the voltage supply to the FETs 41 and 43, and the gate drive circuits 52 and 54
When the predetermined voltage is supplied to the FETs 42 and 44, the FETs 42 and 44 are turned on to cause an excessive current to flow in the direction of the FETs 42 and 44. When the voltage is supplied, the output of the AND circuit AD5 becomes "LOW", and the output of the AD6 becomes "HIGH", so that the abnormality detection signal S _A becomes "LOW".
Since the output S _RR of the AND circuit AD _R becomes “LOW” and the relay drive circuit 64 opens the fail relay 64, the H bridge circuit 40 is immediately cut off from the current, and an excessive current flows through the H bridge circuit 40. This can be prevented immediately.

Further, since the abnormality detection signal S _A becomes "LOW", the output signals of the AND circuits AD1 to AD4 become "LOW", and the FETs 41 to 44 are turned off. Therefore, for example, the control circuit 20 fails. Even if the fail relay 64 does not open due to, for example,
It is possible to reliably prevent the H-bridge circuit 40 from being energized, and thus prevent an excessive current from flowing.

Further, for example, there is an abnormality on the side of the FETs 41 to 44, the FETs 42 and 44 are turned on regardless of the command of the command signals PWM _L , PWM _R , D _R , and D _L , and the FE is turned on.
If the T41,43 becomes the off state, the current detection resistor in the right-left direction R _R and from an excessive current flows through the R _L, the motor current detection value of the detected right and left by a current detecting circuit 61 i _R and i _Since the absolute value | i _M | of the motor current detection value i _M based on _L exceeds the maximum current value I _MAX , the control circuit 20 detects an abnormality by the abnormality monitoring process and sets the clutch control signal S _C to “LOW”. Since the relay control signal S _R is output as “LOW” after the output, the steering assist force by the motor 12 cannot be transmitted to the steering shaft 2, and the output S _RR of the AND circuit AD _R becomes “LOW”. When the relay drive circuit 63 opens the fail relay 64, the H bridge circuit 4
Power to 0 is immediately cut off.

Therefore, according to the above embodiment, the FET
The logical product of the output signals of the gate drive circuits 51 and 53 to 41 and 43 and the logical product of the output signals of the gate drive circuits 42 and 43 to the FETs 42 and 44 are input to the NOR circuit NR, and both FETs 41 and 43 are input. When the FETs 42 and 44 are turned on, or when the FETs 42 and 44 are turned on, the abnormality detection signal S _A from the NOR circuit NR becomes “LO”.
When it becomes W ″, the FETs 41 and 42, or F
By detecting that the voltage is simultaneously supplied to the ETs 42 and 44, the command signals PWM _L from the gate drive circuits 51 to 54 or the microcomputer 21,
It is possible to detect any abnormality of PWM _R , D _R , and D _L before the H bridge circuit 40 is energized.

Further, each command signal from the control circuit 20 is supplied through the gate circuit 65, and the gate drive circuits 51 to 5 are supplied.
4 is the abnormality detection signal S _A and each command signal PWM _L , PWM
_The relay drive circuit 63 operates based on the logical product of _R , D _R , and D _L, and the relay drive circuit 63 operates by the logical product of the abnormality detection signal S _A and the relay control signal S _R. These logical operations are performed by a logical operation circuit. By configuring to do, F
When the voltage is simultaneously supplied to the ETs 41 and 43 or the FETs 42 and 44, the abnormality detection signal S _A becomes “LOW”.
Accordingly, the output signals of the AND circuits AD1 to AD4 are immediately set to "LOW", whereby the gate drive circuits 51 to 54 operate and the FETs 41 to 44 are activated.
Is turned off, and the output signal S _RR of the AND circuit AD _R immediately becomes “LOW” to open the fail relay 64 in the relay drive circuit 63 to cut off the power supply to the H bridge circuit 40. Therefore, when an abnormality is detected, the gate circuit 65 is actuated to immediately stop the energization of the H bridge circuit 40 and the energization of the FETs by the gate drive circuits 51 to 54. Therefore, an excessive current flows in the H bridge circuit 40. This can be reliably prevented.

Therefore, the abnormality can be detected before the arm short circuit occurs, and when the abnormality is detected, it is possible to immediately take an abnormality countermeasure such as shutting off the power supply to the H-bridge circuit 40. ~ 44, the board, the harness, and the like can be prevented from being burnt, and the disaster due to the arm short circuit can be surely avoided. In the above embodiment, the case where the right steering is performed has been described, but the same effect as above can be obtained even when the left steering is performed.

Further, in the above embodiment, the case where the FET (field effect transistor) is used as the switching element of the H bridge circuit has been described, but the present invention is not limited to this.
It is also possible to apply other switching elements such as bipolar transistors. Further, in the above embodiment,
The case of detecting an abnormality in the abnormality detection circuit 66 based on the output signals of the gate drive circuits 51 to 54 has been described, but the present invention is not limited to this. For example, each command signal PWM _L , PWM _R , D from the control circuit 20 is used. It is also possible to detect an abnormality based on _R and D _L.

Further, in the above embodiment, the case where the drive control of the motor 12 is performed by the PID control has been described, but the present invention is not limited to this, and the control may be performed by PI control, P control, or the like. Further, in the above embodiment,
Although the case where the motor current command value is set based on the steering torque and the vehicle speed has been described, it is also possible to set the motor current command value based on only the steering torque, for example.

Further, in the above embodiment, the case where the control circuit 20 is formed by the microcomputer 21 has been described. However, the present invention is not limited to this, and may be configured by combining electronic circuits such as an arithmetic circuit, an addition circuit, and a logic circuit. It is possible. Further, in the above embodiment, the motor drive control for detecting the steering state based only on the detected torque value and generating the auxiliary steering torque according to the detected torque value has been described. When changing the driving lane, the steering state is detected according to the steering angular velocity and the steering angular acceleration of the steering wheel in addition to the steering torque, and the auxiliary torque corresponding to these values is generated to control the motor drive. It is also possible to do

FIG. 7 is a schematic block diagram showing an example of a control circuit for detecting the steering state based on the detected torque value, the steering angular velocity value and the steering angular acceleration value. This control circuit 20a
7, the current command calculator 32, the adder 37a, the proportional calculator 38, the integral calculator 39, the adder 37b, the steering angular velocity acceleration calculation circuit 102, and the damper coefficient circuit 103, as shown in FIG. And an inertia compensation coefficient circuit 104.

The detected torque value T is determined by the control circuit 20.
It is input to the current command calculator 32 of a, converted into a predetermined motor current command value S _I , and then supplied to the adder 37a. In addition to the motor current command value S _I , the adder 37a further includes a motor current detection value i _M , which is the output signal of each of the current detection circuit 91, the damper coefficient circuit 103, and the inertia compensation coefficient circuit 104, and a damper signal D _I. And the inertial signal K _I
Is supplied to the motor current command value S _I , and the motor current detection value i _M is subtracted, the damper signal D _I is subtracted, and the inertia signal K _I is added. In the proportional calculator 38 to which the output signal of the adder 37a is supplied, a predetermined proportional gain is multiplied, and the multiplication value is directly supplied to the adder 37b and via an integral calculator 39 that performs a predetermined integration process. And is supplied to the adder 37b. Then, the output signal from the adder 37b obtained by adding these input signals is supplied to the motor drive circuit 93b, and the motor drive circuit 93b outputs a pulse width modulation signal PWM having a predetermined pulse width based on this output signal. It is formed and supplied to the steering angular velocity acceleration calculation circuit 102, and the motor 12 is driven according to the formed pulse width modulation signal PWM.

Then, the detected motor current detection value i (i _R , i _L ) is output from the motor 12 to the steering angular velocity acceleration calculation circuit 102 and the current detection circuit 91. In the steering angular velocity acceleration calculation circuit 102, The steering angular velocity ω ₀ calculated based on the input pulse width modulation signal PWM and the detected motor current value i is output to the damper coefficient circuit 103, and the calculated steering angular acceleration ω ₁ is output to the inertia compensation coefficient circuit 104. .

Calculation of the steering angular velocity ω ₀ and the steering angular acceleration ω ₁ in the steering angular velocity acceleration calculation circuit 102 is performed as follows. Given that the duty ratio D of the pulse width modulation signal PWM and the power supply voltage V _BAT are the average voltage V supplied to the motor 12,
Is represented as follows. V = D · V _BAT (1) Further, the counter electromotive force is generated by the rotation of the motor 12, and the counter electromotive force constant is k _T , the counter electromotive voltage generated in the motor 12 is k _T · ω ₀ Therefore, the average voltage V supplied to the motor 12 having the coil resistance R is also expressed as follows.

[0070] _{V = k T · ω 0 +} R · i ... (2) Thus, from the equation (1) and (2), the steering angular velocity ω ₀ is obtained as follows. ω ₀ = (D · V _BAT −R · i) / k _T (3) The steering angular acceleration ω ₁ is calculated by differentiating the formula (3) with respect to the time t. The calculated steering angular velocity ω ₀ is multiplied by a predetermined damper coefficient K _{V in the} damper coefficient circuit 103,
This multiplied value is subtracted from the motor current command value S _I to execute the damper control, whereby an electric viscous resistance is given to the steering system and the stability of the vehicle is improved. Further, the calculated steering angular acceleration ω ₁ is multiplied by a predetermined inertia compensation coefficient K _{G in} the inertia compensation coefficient circuit 104, and the multiplication value and the motor current command value S _I are added to execute inertia compensation control. Thus, the delay in the response of the motor due to the motor inertia is compensated. Note that the steering angular acceleration ω ₁ may be directly detected by a sensor, or, for example, the steering angle speed ω ₀ is first obtained by differentiating the angle value detected by the angle sensor attached to the motor shaft with time t. Further, the steering angular acceleration ω ₁ may be obtained by differentiating again.

[0071]

As described above, according to the control device for the electric power steering apparatus of the present invention, the control means outputs the control signal for driving the electric motor based on the steering torque detected by the steering torque detecting means. The H bridge circuit operates based on this control signal to control the energizing direction and the energizing amount to the electric motor. At this time, the abnormality detecting means controls the state of the signal system between the control means and the H bridge circuit. By detecting the abnormality of the energizing path of the H bridge circuit by monitoring the electric current, and the abnormality detecting means detects the abnormality of the energizing path of the H bridge circuit, the energizing cutoff means cuts off the energization to the electric motor. It is possible to detect an abnormality before it becomes an energization path abnormality, and when the abnormality detection means detects an energization path abnormality, the electric motor is treated. By turning off the power, it can be avoided immediately be energized H-bridge circuit in a state of conduction path abnormality.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a steering torque and an output voltage of a torque sensor.

FIG. 3 is a block diagram of a controller.

FIG. 4 is a flowchart showing a processing procedure of motor drive control processing in a microcomputer.

FIG. 5 is a characteristic diagram showing a relationship between a steering torque and a motor current value with a vehicle speed as a parameter.

FIG. 6 is a flowchart showing a processing procedure of abnormality monitoring processing in a microcomputer.

FIG. 7 is a schematic block diagram of a control circuit that detects a steering state based on a detected torque value, a steering angular velocity value, and a steering angular acceleration value.

FIG. 8 is a block diagram of a conventional controller.

[Explanation of Codes] 1 Steering Wheel 3 Torque Sensor 11 Electromagnetic Clutch Device (Clutch) 12 Motor 13 Controller 16 Battery 17 Vehicle Speed Sensor 20 Control Circuit 21 Microcomputer 30 Motor Drive Circuit 40 H Bridge Circuit 41-44 FET (Field Effect Transistor) 51-55 Gate drive circuit 61 Current detection circuit 62 Clutch control circuit 63 Relay drive circuit 65 Gate circuit 66 Abnormality detection circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Kano 78 Toba-cho, Maebashi-shi, Gunma Nippon Seiko Co., Ltd.

Claims (1)

[Claims] 1. A steering torque detecting means for detecting a steering torque of a steering system, an electric motor for generating a steering assist force for the steering system, and the electric motor based on at least a torque detection value of the steering torque detecting means. An electric power steering apparatus including a control unit that outputs a control signal for generating a steering assist force to a motor, and an H bridge circuit that controls the energization direction and the energization amount of the electric motor based on the control signal from the control unit. In the control device of the above, the state of the signal system between the control means and the H bridge circuit is monitored and the H
An abnormality detecting means for detecting an abnormal state of the energization path of the bridge circuit, and an energization cutoff means for cutting off the energization of the electric motor when the abnormality detection means detects an abnormality of the energization path of the H bridge circuit. A control device for an electric power steering device.