JPH08142886A - Control device for motor-driven power steering - Google Patents

Abstract

PURPOSE: To prevent the accumulation of excess control quantity at the time of a motor driving current being saturated so as to prevent excessive control by providing a limiting means for imitating the saturated state of the motor driving current at the upper and lower limit value or the like, and a correcting means for correcting the integrated quantity in integrating operation. CONSTITUTION: A torque detection signal from a torque sensor 3 after being phase-compensated by a phase compensator 25, left-right direction motor current detection signals from a current detecting circuit 61, and the vehicle speed detection value from a counter 26 are inputted to a microcomputer 21. After computing the motor current command value serving as the steering assist force target value on the basis of these input signals, the microcomputer 21 computes a motor driving signal SM before limiting processing by PID control, for instance, also computes a motor driving signal SM' after limiting processing by imitating the saturation of the driving current of a motor 12 to limit the signal value within a specified range, and corrects the integrated quantity in integrating operation by the correction value based on the difference between both signals SM, SMM'.

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, and more particularly to a control device which is suitable for a sudden steering operation. The present invention relates to a control device capable of controlling.

[0002]

2. Description of the Related Art Conventionally, a control device for an electric power steering system has a torque detection signal detected by a torque sensor,
The assist current (motor drive current) is controlled based on the vehicle speed of the vehicle detected by the vehicle speed sensor, and the assist current is supplied to the electric motor to assist the steering force of the steering wheel. FIG. 8 shows a schematic block diagram thereof. This device has a torque detection value T
And a current command calculation process 18 for generating a motor current command value S _I as a target value of the assist current by a predetermined calculation based on the vehicle speed V, PID control as a control target of the motor current command value S _I (proportional-integral- PID control processing 19 for calculating the motor drive signal S _M by differentiation, and pulse signal etc. PWM _* of the duty ratio corresponding to the motor drive signal S _M
PWM circuit 29 for generating D _* and pulse signal PWM
A motor drive circuit 30 that supplies a drive current corresponding to _* , D _* to the electric motor 12, and a current value of the drive current by the motor drive circuit 30 is detected, and the detected current value i _M is determined by PID.
A current detection circuit 61 that feeds back to the control calculation 19 is provided.

As described above, the motor current command value S _I is generated based on the detected torque value T and the vehicle speed V and is used as the control target, so that the steering assist corresponding to the steering torque and the vehicle speed input to the steering shaft is generated. Force the motor 12
Has been raised. Further, the motor current command value S _M is calculated by performing feedback control calculation on the motor current command value S _I by the PID control calculation 19 using the motor drive current value i _M as a feedback signal. _It has better followability to changes in _I. That is, in addition to proportional control by proportional calculation,
Differential control is mainly performed by differential calculation for exhibiting quick response, and integral control is mainly performed by integral calculation for eliminating steady deviation.

Then, a drive current corresponding to the motor drive signal S _M calculated by such feedback control calculation is supplied to the electric motor 12 to follow the operation of the steering wheel by the driver of the vehicle. Since the steering assist force is generated, the driver can operate the steering wheel lightly.

[0005]

As described above, in the conventional controller for the electric power steering apparatus, the PID
Feedback control such as control is performed, and if it is a normal steering operation, the steering assist force follows this and a light operation can be performed. This is because the PID control or the like is control based on a linear model, but the electric motor or the like to be controlled can be approximated by the linear model within the range of normal steering operation.

[0006] However, when the normal operation range is exceeded, such as when the steering wheel is suddenly operated, a problem may occur. For example, there is a case where the steering wheel is suddenly and vigorously rotated and then immediately stopped. In such a case, the motor current command value S _I and the motor drive signal S _M become large in order to make the generation of the steering assist force follow a sudden operation of the steering wheel. There is a limit to the drive current that can be supplied to the motor. For example, in PWM control, the drive current of the motor saturates at a duty ratio of 100%, and a drive current that exceeds this cannot be supplied. Therefore, the motor drive signal S _M calculated by the feedback control operation exceeds the limit of the motor drive current, and if the motor drive signal S _M and the actual motor drive current do not correspond to each other, the control target It is far from the linear model, and as a result, proper control becomes difficult only by PID control.

In particular, when the feedback control includes an integral calculation, the control amount corresponding to the motor current command value S _{I and the} like is accumulated by the integral calculation, but the actual motor drive current is saturated. since the even control the amount of accumulation by the integral operation regardless this is done when gone, it limits the motor driving signal S _M is the motor drive current when the motor driving signal S _M has exceeded the limits of the motor drive current An extra control amount will be accumulated corresponding to the amount exceeding. Then, when the accumulated control amount is included in the motor drive signal S _M and output after a delay, excessive control is performed. In other words, if an attempt is made to immediately stop after a sudden rotation operation of the steering wheel, excessive control of the sudden rotation operation continues to generate steering assist force, and even if the steering wheel is stopped after the rotation operation, For a while, steering assist force is generated in the direction that assists the previous rotation operation. Therefore, despite trying to stop the steering wheel, on the contrary, the motor turns the steering wheel. As a result, the driver may experience a feeling of strangeness in steering operation, such as a large feeling of being caught,
There is an unsolved problem that unpleasant vibration may be felt in some cases.

In particular, such a phenomenon tends to occur frequently when PID control is combined with inertia compensation control. Inertial compensation control is added in order to allow the steering wheel to be operated more easily. As a control device for such an electric power steering device, for example, one disclosed in Japanese Patent Laid-Open No. 2-290773 is known. ing. The outline is shown in FIG. 10.
In the device shown in FIG. 9, the angular acceleration in the rotation of the motor is indirectly detected from the motor drive signal S _M and the motor drive current value i _M (71), and a predetermined gain K is added to this detected value.
A circuit (73) for adding a value (72) multiplied by a to the motor current command value S _I is added. By this inertia compensation control, the response delay due to the motor inertia is reduced, and the followability in motor control is improved.
However, since addition to the motor current command value S _I is performed based on the angular acceleration of the motor rotation,
There are more opportunities for the motor current command value S _I to become larger than when only PID control is performed. Therefore, while improving the followability of the motor control, a light steering operation can be performed in a normal operating state, while in the case of a sudden operation, the steering operation caused by the saturation of the motor drive current is rather adversely affected. It is likely to cause discomfort or uncomfortable vibration.

Therefore, the present invention has been made by paying attention to the unsolved problem of the above-mentioned conventional example, and even when a sudden steering operation is performed, a feeling of strangeness due to saturation of the motor drive current and An object of the present invention is to provide a control device for an electric power steering device that can perform accurate control in which vibration is unlikely to occur.

[0010]

In order to achieve the above object, a control device for an electric power steering system according to a first aspect of 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. And a steering assist force target value is calculated based on at least the torque detection value of the steering torque detecting means, and steering is performed by feedback control calculation including integration calculation from the steering assist force target value. Control of an electric power steering apparatus including a control means for calculating an assisting force command value and outputting the steering assisting force command value, and a driving means for supplying a drive current according to the output of the controlling means to the electric motor In the device, the steering assist force command value of the control means is limited to a predetermined range corresponding to the upper and lower limit values of the drive current of the electric motor, and is output to the drive means. And limiting means, in which a correction means for correcting the integrated amount of the integral calculation by the correction value based on the difference between the output value and the steering assist force command value of said restriction means.

[0011]

According to the first aspect of the present invention, the control device for the power steering device according to the present invention sets the steering assist force command value to a predetermined range corresponding to the upper and lower limit values of the drive current of the electric motor with respect to the steering assist force command value. A limiting unit that performs a limiting process is provided. The limiting process by this limiting means simulates a state in which the motor drive current is saturated at the upper and lower limit values, so the steering assist force command value after the limit process is set to a value that the motor drive current can actually take. It does not exceed the corresponding limit. Further, not the steering assist force command value before the limit process but the steering assist force command value after the limit process is output to the drive means, and the drive means that receives this outputs the drive force according to the steering assist force command value after the limit process. Current is supplied to the electric motor. As a result, even if the motor drive current is saturated and cannot accurately follow the steering assist force command value before the limit process, the steering assist force command value after the limit process is not corrected. The motor drive current can follow accurately. Therefore, the steering assist force command value after the limiting process and the motor drive current always have a fixed correspondence.

Further, the apparatus of the present invention comprises a correction means for correcting the integral amount in the integral calculation with a correction value based on the difference between the output value of the limiting means and the steering assist force command value of the control means. That is, the integral amount is corrected based on the difference between the steering assist force command value after the limit process and the steering assist force command value before the limit process. Here, when the motor drive current is not saturated and when it is saturated, the explanation will be made separately. First, when the motor drive current is not saturated, that is, when the steering assist force command value before the limiting process is within a predetermined range. Is equal to the steering assist force command value after the limit process and the steering assist force command value before the limit process, the correction value at this time is "0", and the correction of the integral amount in the integral calculation by the correction means is performed. It is equivalent to not doing anything. Therefore, when the motor drive current is not saturated, normal feedback control is properly performed,
As a result, a steering assist force that accurately follows the operation of the steering wheel is generated.

On the other hand, when the motor drive current is saturated, that is, when the steering assist force command value before the limiting process exceeds the predetermined range, the steering assist force command value after the limiting process and the steering assist force command before the limiting process are performed. Since the values do not match, the correction value at this time is not “0”, and the correction of the integration amount in the integration calculation by the correction means is effective. Specifically, since the steering assist force command value after the limit process corresponds to the actual motor drive current as described above, the steering assist force command value after the limit process and the steering assist force command before the limit process The correction value based on the difference from the value corresponds to the amount by which the steering assist force command value before the limiting process exceeds the actual motor drive current. Then, the integral amount in the integral calculation corrected by this correction value is actually the steering assist force command value before the limiting process as compared with the case where the feedback control including the integral calculation is normally performed on the steering assist force target value. The control amount accumulated in the integral calculation is reduced by the amount exceeding the motor drive current of. As a result, the storage of the extra control amount as in the conventional case is not performed. That is, conventionally, even when the motor drive current is saturated, the feedback control including the integral calculation is normally performed on the steering assist force target value (motor current command value S _I ). Steering assist force command value before limit processing (motor drive signal S _M )
However, in the present invention, the extra control amount is accumulated by the integral calculation by the amount that exceeds the actual motor drive current. The control amount accumulated in the is canceled by the correction value. Therefore, even when the motor drive current is saturated, an excessive amount of control is not accumulated, so excessive control is not performed.

Therefore, the control device for the electric power steering apparatus according to the present invention provides accurate control in which discomfort or vibration due to saturation of the motor drive current is unlikely to occur even when a sudden steering operation is performed. It can be done.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a control device for an electric power steering system according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram thereof. In the figure, reference numeral 1 denotes a steering wheel, and a steering force applied to the steering wheel 1 is transmitted to a steering shaft 2 composed of an input shaft 2a and an output shaft 2b. One end of the input shaft 2a is connected to the steering wheel 1, and the other end is a torque sensor 3 as steering torque detecting means.
Is connected to one end of the output shaft 2b. And
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 configured as a rack and pinion type having a pinion 8a and a rack 8b.
The rotational movement transmitted to the rack 8b is converted into a linear movement by the rack 8b.

The output shaft 2b of the steering shaft 2 is connected to a reduction gear 10 for transmitting a steering assist force (assist force) to the output shaft 2b. Further, the reduction gear 10 has an electromagnetic clutch device 1 for transmitting / disconnecting steering assist force.
An output shaft of a motor 12 as an electric motor that generates a steering assist force is connected via 1 (hereinafter referred to as a clutch). The clutch 11 is, for example, an electromagnetic type, and the motor 12 is, for example, a DC servo motor. Further, the clutch 11 has a solenoid, and this solenoid has a controller 13 as a control means described later.
When the exciting current is supplied by, the reduction gear 10 and the motor 12 are mechanically connected to each other, and are separated by stopping the exciting current.

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. It is configured to convert into a torsional angular displacement of the bar and detect the torsional angular displacement with a potentiometer. When the driver steers the steering wheel 1, a torque detection signal composed of an analog voltage corresponding to the magnitude and direction of the twist generated in the steering shaft 2 is output. That is, this torque detection signal is a signal having the detected value T _V of the steering torque as a value. The torque sensor 3 is, for example, as shown in FIG.
As shown in, when the steering wheel 1 is in a neutral state, the predetermined as the torque detection value T _V neutral voltage V
Outputs _0, when the right turn of the steering wheel 1 than this voltage to increase from the neutral voltage V ₀ in accordance with the steering torque at that time, decreased from the neutral voltage V ₀ in accordance with the steering torque when the Left cutting It is designed to output voltage.

Reference numeral 13 is a controller for controlling the driving of the motor 12 to control the steering assist force to the steering system, and 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 through the fuse 15b is used for memory backup, for example. Then, the controller 13 drives and controls the motor 12 based on the torque detection signal (T _V ) from the torque sensor 3 and the vehicle speed detection signal V _P from the vehicle speed sensor 17, and turns on / off the clutch 11 to control the motor 12. The output shaft and the reduction gear 10 are controlled to be coupled / disengaged.

FIG. 2 is a block diagram showing the circuit configuration of the controller 13. The controller 13 includes, for example, a control circuit 20, a motor drive circuit 30, a current detection circuit 61, a clutch control circuit 62, a relay drive circuit 63, and a fail relay 64. The control circuit 20 is composed of a microcomputer 21 (MPU), A / D converters 22, 23 and 24, peripheral circuits thereof, a phase compensator 25, and a counter 26.

The microcomputer 21 comprises at least an interface section for performing input / output processing with an externally connected device and a storage section such as ROM and RAM. In the microcomputer 21, the torque detection signal (T _V ) from the torque sensor 3 that has been phase-compensated for stabilizing the control system such as advancing the phase by the phase compensator 25 is transmitted via the A / D converter 22. The detected torque value T converted into a digital value is input. Similarly, the rightward motor current detection signal I _R from the current detection circuit 61 is input as the rightward motor current detection value i _R via the A / D converter 24, and the leftward motor current detection signal I _L is input. It is input as a leftward motor current detection value i _L via the A / D converter 23. 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,
When the number of pulses per unit time is integrated and the integrated value is read into the microcomputer 21 as the vehicle speed detection value V, the reset signal _RC from the microcomputer 21
The count value is reset by.

The microcomputer 21 calculates a signal for determining the drive current supplied to the motor 12 based on these input signals. That is, after the motor current command value S _I as the steering assist force target value is calculated based on these input signals, the motor drive as the steering assist force command value before the limiting process is performed by, for example, PID control (proportional / integral / derivative). The signal S _M is calculated, and the saturation of the motor drive current is simulated to limit the signal value to a predetermined range to calculate the motor drive signal S _{M ′} as the steering assist force command value after the limiting process. Then, a PWM (Pulse Width Modulation) signal is generated based on the motor drive signal S _{M ′} , and the left pulse width modulation signal PW is generated based on the PWM signal.
M _L , right pulse width modulation signal PWM _R , right direction signal D _R ,
Generate a leftward signal D _L. Then, this is output to the motor drive circuit 30.

Further, the microcomputer 21 executes a predetermined failure detection process at the time of start-up, outputs a relay control signal S _R to the relay drive circuit 63 as "HIGH" when it is normal, and outputs it to the clutch control circuit 62. The clutch control signal S _C that gradually increases 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 _L and the relay control signal S _R are output as “LOW”, the output of the clutch control signal S _C is stopped, and a predetermined process at the time of occurrence of an abnormality such as lighting an abnormality lamp is performed.

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 enhancement type N channel MOS
FETs 4 such as type FET (field effect transistor)
1 to 44, the FETs 41 and 43 are connected in series, the FETs 42 and 44 are connected in series, and the series circuits are connected in parallel so that the battery 16
To the fail relay 64. And F
The motor 12 is connected between the connection point between the ETs 41 and 43 and the connection point between the FETs 42 and 44. In addition, FET
The source side of 43 is grounded through the right direction current detection resistor R _R , and similarly, the source side of FET 44 is grounded through the left direction current detection resistor R _L.

The gate terminals G _{1 to} G ₄ of the FETs 41 to 44 are connected to the corresponding gate drive circuits 51 to 54, respectively, and when a predetermined voltage is supplied from the gate drive circuits 51 to 54, The FETs 41 to 44 are turned on, and the FETs 42 and 43 are turned on.
When only one is turned on, FET 42, motor 1
2, when the motor 12 is positively rotated by being energized in the direction of the FET 43 and the right direction current detection resistor R _R , and only the FETs 41 and 44 are turned on, the FET 41, the motor 12,
The motor 12 is reversely rotated by being energized in the direction of the FET 44 and the leftward current detecting resistor R _L.

On the other hand, the current detection circuit 61, for example, amplifies and eliminates the voltage generated at both ends of the rightward current detection resistor R _R and the leftward current detection resistor R _L , and outputs the rightward motor current detection signal I _R and It is output to the control circuit 20 as a leftward motor current detection signal I _L. The clutch control circuit 62 also generates an exciting current i _C according to the clutch control signal S _C from the control circuit 20 and outputs it to the solenoid of the clutch 11 to mechanically couple the output shaft of the motor 12 and the reduction gear 10. Control to the state / disengagement state.

The relay drive circuit 63 controls ON / OFF of the fail relay 64 based on the output signal S _R of the microcomputer 21. The fail relay 64 is a relay switch having a normally open contact and controls ON / OFF of the power supply of the battery 16 to the H bridge circuit 40. 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. This motor drive control process is performed by a timer interrupt at preset predetermined time intervals, and is executed, for example, every several msec.

The microcomputer 21 executes a predetermined failure detection process when the ignition switch 14 is turned on, and outputs the relay control signal S _R as "HIGH" when no abnormality is detected. In response to this, the relay drive circuit 63 energizes the coil of the fail relay 64 to close the fail relay 64 and energize the H bridge circuit 40. Further, the clutch control signal S _C that gradually increases is output to the clutch control circuit 62. This allows clutch 1
1 operates to gradually bring the rotating shaft of the motor 12 and the reduction gear 10 into a mechanically coupled state. Furthermore, each command signal to each gate drive circuit 51-54 is "LOW" at the time of starting.
Output as

Also, 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 following motor drive control process. In this process, first, in step S1, A /
Via the D converter 22, the torque detection value T from the torque sensor 3 which has been phase-compensated by the phase compensator 25 is read.
Further, the process proceeds to step S2, 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.

Next, in step S3, the count value of the counter 26, that is, the vehicle speed detection value V is read, and the reset signal _RC is output to the counter 26 to reset the count value. Then, the process proceeds to step S4,
Referring to the characteristic diagram showing the correspondence between the steering torque, the vehicle speed, and the motor current shown in FIG. 6, for example, 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, in step S5, the motor current command value S _{I is} differentiated and multiplied by a predetermined proportional gain to obtain the differentiated value f _D. Next, in step S6, the motor current detection value i _R in the right direction and the motor current detection value i _L in the left direction are read, the motor current detection value i _R in the right direction is a positive value, and the motor current detection value i _{L in the} left direction is read. Is set as a negative value, and the motor current detection value i _M is calculated from the sum of these detection signals. That is, i _M = i _R −i _L
It is calculated by:

Here, it is assumed that the current detection circuit 61 performs sufficient filter processing on each of the left and right motor current detection signals I _R and I _{L so that} the effective values thereof are obtained. Further, in the subsequent step S7, for example, abnormality monitoring processing as shown in the flowchart of FIG. 4 is performed. The details of the abnormality monitoring process will be described later.

Next, in step S8, the difference between the motor current command value S _I set in step S4 and the motor current detection value i _M calculated in step S6, that is, e _M
= S _I −i _M calculates the current deviation e _M. In a succeeding step S9, the current deviation e _M is multiplied by a predetermined proportional gain to obtain a proportional processed value f _P. Next step S10
Then, from the motor drive signal S _M calculated and stored in the immediately previous processing cycle and the motor drive signal S _{M ′} also calculated and stored in the immediately previous processing cycle, the difference dS between them is calculated by the formula dS = S. calculated by _M '-S _M. Then, in a succeeding step S11, a gain K _{C of a} predetermined value is added to this.
The correction value K _C × dS is calculated by multiplying by. Thereby, the correction value based on the difference between the motor drive signal S _{M ′} and the motor drive signal S _M is obtained. It should be noted that the value of the gain K _C may be “1” from the viewpoint of simply correcting the amount by which the motor drive signal S _{M ′} exceeds the predetermined range, but in reality, it may be a system responsiveness and stable operation. From the viewpoint of harmony, etc., it is set to a value of "1" or less obtained by analytically and experimentally adjusting in consideration of the dynamic characteristics and non-linearity of the control system.

Further, in the next step S12, the input value f _{P ′} of the integral calculation is calculated from the proportional processing value f _P and the correction value K _C × dS by the expression f _{P ′} = f _P + K _C × dS. Then, in a succeeding step S13, an integration process is performed on the value f _{P ′} and a predetermined proportional gain is multiplied, and this is integrated process value f _I
And Then, in step S14, the differential processed value f
_D , the proportional processed value f _P, and the integrated processed value f _I are added,
This is the motor drive signal S _M. The motor drive signal S _M has a new value in this processing cycle.

Next, the routine proceeds to step S15, where when the value of the new motor drive signal S _M is larger than the upper limit value S _{MAX, the} upper limit value S _M'is set as the value of the motor drive signal S _{M '.
MAX} is adopted, and the value of the motor drive signal S _M is the lower limit value −S
When the and below the upper limit value S _MAX above _MAX adopts the value of the motor drive signal S _M as the value of the motor drive signal S _{M ',}
Employing the lower limit value -S _MAX as the value of the motor drive signal S _{M 'when} the value of the motor drive signal S _M is smaller than the lower limit value -S _MAX. Here, the upper limit value S _MAX is the value of the motor drive signal S _M when the right pulse width modulation signal PWM _R has a duty ratio of 100%, and the lower limit value −S _MAX is the left pulse width modulation signal PWM _L. It is the value of the motor drive signal S _M when the duty ratio becomes 100%. That is, the upper limit value S
_MAX and the lower limit value −S _MAX are values corresponding to the upper and lower limit values of the drive current of the electric motor 12. Accordingly, operation in this step becomes a process of limiting the values in a predetermined range corresponding to the upper and lower limit values of the driving current of the electric motor 12, which motor drive signal S _{M 'from} the motor drive signal S _M by is calculated . The motor drive signal S _{M ′} is associated with the motor drive current even when the PWM signal has a duty ratio of 100% and the motor drive current is saturated.

[0038] Then, in step S16 after this, the motor drive signal S _{M 'is} S _M' determines whether ≧ 0, S
_{If M '} ≧ 0, it is determined that the steering wheel 1 has been steered to the right, and the process proceeds to step S17. Then, in step S17, the right direction signal D _R for setting the rotation direction of the motor 12 to the forward rotation direction is set to "HIGH",
In addition, a drive current corresponding to the motor drive signal S _{M ′} is supplied to the motor 1
2 is set to a duty ratio for supplying to the corresponding gate drive circuits 52 and 53 as right pulse width modulation signals PWM _R , and the gate drive circuits 51 and 54 are output.
The left pulse width modulation signal PWM _L and the left direction signal D _L are output as “LOW”. Then, this processing cycle is ended and the process returns to the calling program.

On the other hand, if S _{M '} ≧ 0 is not satisfied in step S16, it is determined that the steering wheel 1 is steered to the left, and the process proceeds to step S18. Then, in step 18, the leftward signal D _L for setting the rotation direction of the motor 12 to the reverse rotation direction is set to “HIGH”, and the drive current corresponding to the motor drive signal S _{M ′} is set to the motor 12.
To the corresponding gate drive circuits 51 and 54 as a left pulse width modulation signal PWM _L. The right direction signal D _R and the right pulse width modulation signal PWM _R are output to the gate drive circuits 51 and 54 as “LOW”, respectively. Then, the process is terminated and the process returns to the calling program. Thus, in steps S17 and S18, the PWM signal is generated based on the motor drive signal S _{M ′} . That is, the processing in step S17, S18 constitutes a part of the drive means, whereby driving current corresponding to the motor drive signal S _M instead motor drive signal S _{M 'is} supplied to the electric motor 12. The values of the motor drive signal S _M and the motor drive signal S _M'are stored for the correction value calculation in the next processing cycle. Then, one processing cycle of the motor drive control processing ends.

The abnormality monitoring process in step S7 will be described. In this processing, as shown in FIG. 4, first, in step S21, it is determined whether or not the absolute value of the motor current detection value i _M is smaller than the maximum current value I _MAX . Here, the maximum current value I _MAX is preset as a value at which the motor drive circuit 30 is considered to be operating normally. The absolute value of the motor current detection value i _M is the maximum current value I _MAX.
If it is smaller than this, it is determined to be normal, the processing here is terminated, and the process returns to the calling program.

On the other hand, in step S21, when the absolute value of the motor current detection value i _M is not smaller than the maximum current value I _MAX , an excessive current is flowing in the H bridge circuit 40,
When it is determined that an abnormality has occurred, the process proceeds to step S22. In step S22, the command signals PWM _L , PWM _R , D _R , and D _L to the gate drive circuits 51 to 54 are changed to “LO”.
W "is output, and the energization path of the H bridge circuit 40 is cut off by this. 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 clutch 11 is operated to bring the output shaft of the motor 12 and the reduction gear 10 into the disengaged state.
Further, the process proceeds to step S24, and the relay drive circuit 6
By outputting the relay control signal S _R to ₃ as "LOW", the fail relay 64 is operated and the energization from the battery 16 to the H bridge circuit 40 is cut off. Then, in step S25, for example, an abnormality is notified to a higher-level program such as the main processing program, and the process ends. After that, the motor drive control process is not executed by the upper program that has received the abnormality notification.

The operation of the control device for the electric power steering system of the first embodiment having the above construction will be described. Specifically, the operation when the driver performs a steering operation of immediately turning the steering wheel to the right while the vehicle is traveling straight after the start of the vehicle and then immediately returning the steering wheel to the original state will be described. It should be noted that FIG. 7 shows how the state changes when such an operation is performed, with the time axis t as the horizontal axis. In the figure, θ in (a) indicates the steering angle of the steering wheel, S _I indicated by the solid line in (b) is the motor current command value S _I , and i _{M ′} indicated by the solid line in (c) is the conventional device. The motor current detection value, i _M shown by the solid line in (d), is the motor current detection value i _M in the embodiment of the present invention. further,
I _{M *} indicated by broken lines in (b), (c) and (d) is
It is a virtual motor current detection value detected when it is assumed that the motor drive current can supply as much as ± i _MAX without being saturated.

If it is assumed that the vehicle is currently stopped and the ignition switch 14 is turned on from this state, the microcomputer 21 performs a predetermined failure monitoring process, and if there is no abnormality, The relay drive circuit 6 with the relay control signal S _{R set} to “HIGH”
3 and the clutch control signal S _C to the clutch control circuit 62 is gradually increased and output. As a result, the relay drive circuit 63 energizes the coil of the fail relay 64, so that the fail relay 64 is closed and the power supply of the battery 16 can be supplied to the H bridge circuit 40. Further, the clutch 11 gradually operates, the rotation shaft of the motor 12 and the reduction gear 10 are mechanically connected, and the rotational driving force of the motor 12 can be transmitted to the steering shaft 2.

Then, in the microcomputer 21,
After initializing variables and data areas, the motor drive control process is executed at a predetermined interrupt cycle. At this time, assuming that the occupant is not performing the steering operation, the torque detection signal T _V from the torque sensor 3 becomes the neutral voltage V ₀ ,
At this time, since the vehicle is stopped, the vehicle speed detection value V becomes zero, so in the motor drive control processing of FIG. 3, the motor current command value S _I becomes substantially zero from the characteristic diagram of FIG. Then, the motor drive signal S _M and the motor drive signal S _{M '}
Also becomes substantially zero and the motor current detection value i _M also becomes substantially zero, so that the motor 12 is not driven. Then, while the vehicle stops moving to the traveling state, the torque detection value T from the normal torque sensor 3 is in the vicinity of the neutral position V ₀ while the vehicle is traveling straight, that is, while the steering angle θ of the steering wheel is “0”. Therefore, similarly to the above, the motor current command value S _I , the motor drive signal S _M , the motor drive signal S _{M ′} , and the motor current detection value i _M become substantially zero, and the motor 12 is not driven (see FIG. 7). (Refer to the time t0 part).

When, for example, the occupant steers rightward steering during this traveling (see time t1 in FIG. 7), the torque sensor 3 detects the torque as the steering angle θ increases in the positive direction. The signal T _V has a voltage value larger than the neutral voltage V ₀ . The processing cycle of the motor drive control processing at this time will be described in detail. In the microcomputer 21, the detected torque value T input through the A / D converter 22 is detected.
Based on the above, offset processing is performed by T = T−V ₀ to calculate a torque detection value T at which the neutral point is zero. Further, based on the detected torque value T and the detected vehicle speed value V, the corresponding motor current command value S _I is set from the characteristic diagram of FIG. At this time, since the right steering is performed, the offset detected torque detection value T becomes a positive value, and therefore the motor current command value S
_I also has a positive value.

At this time, for example, when the vehicle is traveling at a low speed and the steering torque is large, a large steering assist force is required, so the motor current command value S _I is set to a large value and the vehicle is traveling at a high speed. In this case, the motor current command value S _I is set to a small value in order to generate a small steering assist force so that the steering 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. In any case, when a sudden steering operation is performed, the motor current command value S is promptly increased as the steering torque is rapidly increased.
_I has a positive value. However, it is assumed that the motor drive current is not yet saturated at this point. That is, the value of the motor drive signal S _M is between the lower limit value −S _MAX and the upper limit value S _MAX .

Then, a predetermined process such as a differential process is performed on the set motor current command value S _I to obtain a differential gain K _D
And the differential processed value f _D is calculated. In addition, based on the motor current detection values i _R and i _L in the left-right direction, i _M = i _R
The motor current detection value i _M is calculated as the current value flowing through the motor 12 by −i _L. Then, when the abnormality monitoring process is executed and it is determined to be normal, the current deviation e _M is calculated from the motor current command value S _I and the motor current detection value i _M. Then, to calculate the proportional processed value f _P by multiplying the proportional gain K _P read this current deviation e _M.

Further, the difference dS is calculated from the motor drive signal S _M and the motor drive signal S _{M ′} calculated in the immediately preceding processing cycle by the equation dS = S _{M ′} −S _M , and the predetermined gain K _The correction value K _C × dS is calculated by multiplying by _C. However, at this time, since the motor drive current is not yet saturated, the values of the motor drive signal S _M and the motor drive signal S _{M ′} match, and the difference dS and the correction value K _C × dS are “0”.
Is.

Next, the proportional processing value f _P and the correction value K _C × dS
The input value f _{P ′} of the integral operation is calculated from the equation f _{P ′} = f _P + K _C × dS, and the value f _{P ′ is} integrated and multiplied by a predetermined proportional gain to perform the integration process. Let the value f _I. At the time of this processing cycle, since the correction value K _C × dS is “0”, the input value f _{P ′} of the integral calculation matches the proportional processing value f _P.

[0050] Then, by multiplying the integral gain K _I to the integration process value to calculate the integral processing value f _I relative to the input value f _{P ',} the integration process and these differential processing value f _D the proportional processed value f _P The value f _I is added to calculate the motor drive signal S _M. At this time, since the input value f _{P ′} matches the proportional processing value f _P , the motor drive signal S _M matches the value without correction.

Next, the values are the lower limit value -S _MAX and the upper limit value S _MAX.
Between the motor drive signal S _M is the motor drive signal S _{M 'is} calculated, now the value of the motor drive signal S _M to the lower limit value -S _MAX and the upper limit value S _MAX by process of limiting between since there, the motor drive signal S _{M 'is} a motor drive signal S _M
Matches Therefore, the motor drive signal S _{M ′} matches the motor drive signal S _M when the motor drive current is not saturated and is not corrected at all.

[0052] Then, _'determines the current direction on the basis of the sign of the, in this case, the motor drive signal S _M' motor drive signal S _M ≧
Since it becomes 0, the command signals PWM _L and D _{L become} “LO
W ”, the command signal D _R is“ HIGH ”, and the command signal PWM _R is a pulse signal having a duty ratio D corresponding to the motor drive signal S _{M ′} . In response to this, the gate drive circuit 53 outputs a predetermined signal. Voltage is supplied to turn on the FET 43, and the command signal PWM _R 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 are
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, power is supplied from the battery 16 to the FET 42, the motor 12, and the FET.
43, the motor 12 is positively rotated by being energized in the direction of the right direction current detection resistor R _{R, and} the FET 42 is controlled to be turned on and off, whereby a drive current corresponding to the motor drive signal S _{M ′} is supplied to control the drive of the motor 12. Is done.

As described above, in this processing cycle, the motor current command value S _I becomes a positive value and the motor drive signal S _M'is also positive in response to a change in the steering angle θ of the steering wheel in the positive direction. Takes the value of. Then, according to this, the detection value of the drive current, that is, the motor current detection value i _M
Also increases in the positive direction slightly after the motor current command value S _I. That is, the motor current detection value i _M is delayed by the motor current command value S _I with a delay according to the electrical response of the motor 12.
(See FIG. 7B). At this time, since the motor driving signal S _{M 'matches} against those without any of correction a motor drive signal S _M when the motor driving current is not saturated as described above, the motor current detection value i _M and The motor current detection value i _{M ′} both match the motor current detection value i _{M *} on the assumption that the motor drive current is not saturated.

Therefore, the motor control state at this time is the same as the control for the operating state that can be approximated by the linear model, and is an appropriate state. Then, after the processing cycle in such a control state is repeated several times, when the detected torque value V and the motor current command value S _I increase with a rapid increase in the steering angle θ, the motor drive signal S _{M Will} exceed the upper limit value S _MAX (see the time t2 portion in FIG. 7). Thus, the motor drive signal S _M
Value exceeds the upper limit value S _MAX (time t2 in FIG. 7).
In the processing cycle from time t3 to time t3), the torque detection value T is read, the motor current command value S _I is set, the motor current detection value i _M and the current deviation e _M are calculated, and the proportional processing value f _P is calculated. The calculation is the same as described above, but the other processes are different in that the correction is effective.

That is, the difference is calculated by the expression dS = S _{M ′} −S _M , and the correction value K _C × dS is further calculated. At this time, the value of the motor drive signal S _M exceeds the upper limit S _MAX . Since S _{M ′} > S _M , the difference dS and the correction value K _C
× dS has a negative value. Then, the expression f _{P ′} = f _P + K _C ×
The input value f _{P ′} of the integral calculation calculated by dS becomes a value smaller than the input value f _P of the conventional integral calculation. Therefore,
Integral amount that is accumulated by the integration operation in the processing cycle of this time (see step S13 in FIG. 3), as compared with the conventional (S _M -S M _') by less. That is, the motor drive signal S _M becomes smaller than the conventional one by the amount that the upper limit S _MAX is exceeded. As a result, the integration amount in the integration calculation reflects the saturation state of the motor drive current.

Then, the integrated processing value f _I , the new motor drive signal S _M , and the motor drive signal S _{M ′} are calculated. At this time, since the value of the motor drive signal S _M exceeds the upper limit S _MAX , the motor drive signal S _{M ′} is limited to the upper limit S _MAX . That is, the PWM signal has a duty ratio of 100%.
And the drive current of the motor becomes saturated. Therefore,
The motor current detection value i _{M at} this time is different from the motor current detection value i _{M *} and is almost constant at the upper limit value i _MAX . Note that the same become almost constant by the motor current detection value i _{M 'is} an upper limit value i _MAX In the case of the conventional device.

Therefore, the motor control state at this time is an appropriate output state in that the motor drive current is controlled to the maximum supply possible. Also,
The saturation state of the motor drive current is reflected in the integral amount because the integral calculation is performed in consideration of the non-linear model correction corresponding to the saturation of the motor drive current. This point is different from the conventional control in which the saturated state of the motor drive current is not reflected in the integrated amount because the control is performed as a linear model.

After the processing cycle in such a control state is repeated several times, when the driver turns left to return the steering wheel, the steering angle θ is decreased by this operation. Becomes Then, when the detected torque value V and the motor current command value S _I also decrease as the steering angle θ decreases, the value of the motor drive signal S _M will eventually decrease to the upper limit S _MAX (Fig. 7 at time t3). Up to this point, the detected motor current value i _M is still equal to the detected motor current value i _{M ′ as} described above.
As above, the upper limit value i _MAX is almost constant,
The control state of the motor also externally matches the conventional one. However, when comparing the integration amount in the integration calculation, conventionally, the amount corresponding to the virtual motor current detection value i _{M *} is integrated, and even an amount more than the amount corresponding to the actual motor current detection value i _{M ′} is added. In contrast to the integration (see the region Y in FIG. 7C), the device of the present invention integrates only the amount corresponding to the actual motor current detection value i _M.

In this way, in the processing cycle after the value of the motor drive signal S _M becomes smaller than the upper limit value S _MAX (see the portion after the time t3 in FIG. 7), the torque detection is performed with the rapid decrease of the steering angle θ. The value V also rapidly decreases, and the motor current command value S _I calculated based on this also rapidly decreases. Then, the motor current detection value i _M , the current deviation e _M , the proportional processing value f _{P, and the} like, and the motor drive signal S _M and the motor drive signal S _{M ′} are also calculated according to the procedure described above. Since the value of the motor drive signal S _M is between the lower limit value −S _MAX and the upper limit value S _MAX , the motor drive signal S _{M ′} matches the motor drive signal S _M. That is, the motor drive signal S _{M ′} matches the motor drive signal S _M when the motor drive current is not saturated. Then, the correction regarding the input value f _{P ′} of the integral calculation in the feedback control is substantially stopped. Moreover, since the amount of integration in the integral calculation performed up to this time by the previous correction corresponds to the actual motor drive current as described above, the amount of integration at this time is the feedback based on the linear model. In control, it is almost equal to the integral amount when the motor drive current is not saturated. That is,
The influence of the saturation of the motor drive current no longer remains in the control state in the feedback control.

Therefore, the motor drive signal S _{M ′} corresponds to a motor drive signal when it is assumed that the motor drive current is not saturated and which is not corrected at all. Then, the motor current detection value i _M resulting from the control by the motor drive signal S _{M ′} substantially matches the motor current detection value i _{M *} when it is assumed that the motor drive current is not saturated ( See FIG. 7D). Therefore, the motor control state at this time is the same as the control for the operation state that can be approximated by the linear model, and is an appropriate state.

Comparing this point with the conventional example, in the conventional case, even if the motor current command value S _I decreases and the proportional processing value f _{P and the} like based on this decrease, the integral calculation in the feedback control is performed. since the integration process value f _I and the amount extra to the integral amount is left still maintaining a large value in the motor drive signal S _M also keep the large state value. Then, the motor drive signal S _M becomes equal to or less than the value S _{MAX for the} first time after the discharge of the excessive integrated amount is finished over a certain period of time (see the time t4 portion in FIG. 7C). For this reason, the motor current detection value i _{M ′} decreases with a delay from the motor current detection value i _{M *} when it is assumed that the motor drive current is not saturated. Further, such a delay sometimes causes excessive control in the opposite direction (see the time t5 portion in FIG. 7C). In contrast, the device of the present invention does not have such a delay in the conventional example.

In the apparatus of this embodiment, the motor drive control processing cycle is repeated several times, and when the driver returns the steering wheel to stop the operation, the motor drive signal S _{M is} promptly output. _' Is almost zero,
As a result, the detected motor current value i _M quickly becomes substantially zero (see the time t6 portion in FIG. 7). Moreover, this is more than the time when the conventional device having a delay in the change of the motor drive signal S _M reaches a similar state (time t in FIG. 7).
(See section 7), which will be achieved at an early point.

Therefore, the device of this embodiment does not respond to the operation of the steering wheel even when the driver performs a steering operation of steering the steering wheel to the right while the vehicle is traveling straight ahead and then immediately returning the steering wheel to the original position. It is possible to perform control to generate a steering assist force that accurately follows. A second embodiment of the control device for the electric power steering device of the present invention will be described. This is a combination of PID control and motor inertia compensation control, and its schematic configuration diagram is shown in FIG. This device is a calculation control circuit 2100 that calculates a motor drive signal S _{M ′} based on a torque detection value T and a vehicle speed detection value V.
A PWM circuit 29 for generating pulse signals such as PWM _* and D _* having a duty ratio corresponding to the motor drive signal S _{M ′} ,
Pulse signal or the like PWM _*, D _* and the motor drive circuit 30 supplies a drive current to the electric motor 12 in response to, and detects a current value of the drive current by the motor drive circuit 30 the detected current value i _M a PID control circuit And a current detection circuit 61 that feeds back to the.

Here, the arithmetic control circuit 2100 uses the motor current command value S _I as a command value for setting the motor drive current value based on the torque detection value T and the vehicle speed detection value V.
For generating a current command calculator 18 and a motor current command value S
Adder 19a constituting the PID control circuit for generating a motor drive signal S _M by the PID control as a control target _{I '}
, Differential calculator 19b, proportional calculator 19c, and integral calculator 1
And an adder 19e 9d, a limiter 2110 outputs a motor driving signal S _{M 'limits} the signal value of the motor drive signal S _M in the range of ± S _MAX, the adder 2121 and the proportional calculator 2
Correction circuit 212 including 122 and adder 2123
0. This portion is an electronic circuit substantially equivalent to the micro computer 21 in the first embodiment.

Further, the arithmetic control circuit 2100 has an angular acceleration detector 71 which indirectly detects the angular acceleration in the rotation of the motor from the motor drive signal S _{M ′} and the motor drive current value i _M, and a predetermined value for this detection value. Inertia compensation coefficient circuit 72 for calculating a compensation value by multiplying the inertia compensation coefficient K _G by the motor current instruction value S _I by adding the compensation value to the motor current instruction value S _I.
And an adder 73 for _{I '} . As a result, inertia compensation control for compensating for the response delay due to the motor inertia is also performed.

The inertia compensation control will be described in detail. The calculation of the motor angular acceleration ω _{1 by} the angular acceleration detector 71 is performed as follows. Duty ratio D of pulse width modulation signal PWM corresponding to motor drive signal S _{M ′} , power supply voltage V
_{Assuming BAT} (= battery voltage B), the average voltage V supplied to the motor 12 is expressed as follows. V _AV = D · V _BAT (1) On the other hand, when the motor 12 rotates, a counter electromotive force is generated in the motor 12 due to this rotation. At this time, the angular velocity in the motor rotation is ω ₀ , and the counter electromotive force constant is k _T
Then, the counter electromotive voltage generated in the motor 12 is k _T · ω ₀
Becomes From this, the motor 1 having the coil resistance R
The average voltage V _AV supplied to 2 is also expressed as follows.

V _AV = k _T · ω ₀ + R · i (2) Then, V _AV is deleted from the equations (1) and (2), and the motor angular velocity ω ₀ is obtained as follows. ω ₀ = (D · V _BAT −R · i) / k _T (3) Further, the angular acceleration ω ₁ in the motor rotation is calculated by differentiating both sides of this equation (3) with respect to time t.

The angular acceleration ω ₁ thus indirectly detected
Is multiplied by a predetermined inertia compensation coefficient K _{G in the} inertia compensation coefficient circuit 72 to obtain a compensation value for the motor current command value S _I. Then, this compensation value is added to the motor current command value S _I by the adder 73 to obtain the motor current command value S _{I '} . As a result, inertia compensation control is performed to compensate for a delay in motor responsiveness due to motor inertia.

The angular acceleration ω ₁ may be directly detected by a sensor. Alternatively, for example, the angular value detected by the angle sensor attached to the motor shaft is differentiated at time t to first obtain the angular velocity ω ₀ . , And again differentiate it to obtain angular acceleration ω ₁
May be requested. Alternatively, for example, the angular acceleration ω ₁ may be obtained by detecting the steering angle of the steering wheel with an angle sensor attached to the steering shaft 2 and using this as an approximate value of the angle of the motor shaft. In addition to inertia compensation control, although not shown,
In order to improve the stability of the vehicle by giving an electric viscous resistance to the steering system, a damper control is performed in which the angular velocity ω ₀ is multiplied by a predetermined damper coefficient K _V and the multiplied value is subtracted from the motor current command value S _I. You may break.

[0071] Operation of the control device for an electric power steering apparatus having such a configuration, except that the process of obtaining the motor current command value S _{I 'is} subjected to compensation by inertia compensation control on the motor current instruction value S _I is added Is almost the same as that of the first embodiment. Therefore, although the duplicate description is omitted, in the second embodiment, the motor current command value S
_{Since the} compensation value is added to _I , the motor current command value S _{I ′} becomes larger than the motor current command value S _I in the first embodiment even in the same steering operation. Tend. Therefore, like when a driver in running straight is subjected to steering operation undoing then immediately the steering wheel suddenly right turn the steering wheel, the motor current command value S _{I 'in} FIG. 7 (b) 7 is steeper and has a higher peak value than S _I , so that the region where the detected motor current value i _{M *} exceeds the upper limit value i _MAX is wider than the region Y in FIG. 7C. Alternatively,
Without inertia compensation control is the motor current detection value i _{M *} is the motor current detection value i _{M *} against the steering operation so as not to exceed the upper limit value i _MAX possible to exceed the upper limit i _MAX. However, in this device, since the correction is performed by the correction circuit 2120, even in such a case, the integral amount in the feedback control integral calculator 19d corresponds to the actual motor drive current. Then, the actual motor current detection value i _M quickly falls below the upper limit value i _{MAX at the} timing when the virtual motor current detection value i _{M *} falls below the upper limit value i _MAX . Therefore, it is possible to generate a steering assist force that accurately follows the operation of the steering wheel without causing discomfort or uncomfortable vibration in the steering operation.

Therefore, this device performs inertia compensation control in addition to PID control, but even when a sudden steering operation is performed, an uncomfortable feeling or vibration is generated due to saturation of the motor drive current. It is possible to perform precise control that is difficult to perform. In each of the above-described embodiments, 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.

In the above embodiment, the case where the motor drive control 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 or the like. Further, in the above embodiment, the case where the motor current command value is set based on the steering torque and the vehicle speed has been described, but for example, the motor current command value can be set based only on the steering torque. Is.

Further, in the above embodiment, the case where the motor drive circuit is constituted by the FET (field effect transistor) has been described, but the present invention is not limited to this, and it is also possible to apply other switching elements such as a bipolar transistor. is there.

[0075]

As described above, in the control device for the power steering device according to the present invention as defined in claim 1,
A limiting means is provided to simulate a state in which the motor drive current is saturated at its upper and lower limit values. In addition, a correction unit is provided to correct the integration amount in the integration calculation. As a result, even when the motor drive current is saturated, the storage of an extra control amount as in the conventional case is not performed, and excessive control is not performed.

Therefore, it is possible to provide a control device for an electric power steering device capable of performing accurate control in which discomfort or vibration due to saturation of a motor drive current is unlikely to occur even when a sudden steering operation is performed. You can

[Brief description of drawings]

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

FIG. 2 is a block diagram of a circuit configuration centering on a controller.

FIG. 3 is a flowchart showing a processing procedure of motor drive control processing by a microcomputer.

FIG. 4 is a flowchart showing a processing procedure in an abnormality monitoring processing for a motor drive control processing by a microcomputer.

FIG. 5 is a characteristic diagram showing a relationship between a steering torque and an output voltage of a torque sensor.

FIG. 6 is a characteristic diagram showing a relationship between a steering torque and a motor current value with a vehicle speed as a parameter.

FIG. 7 is a signal waveform diagram for explaining the operation of the device of the present invention.

FIG. 8 is a block diagram showing another embodiment of the present invention.

FIG. 9 is a block diagram of a conventional device.

FIG. 10 is a block diagram of another conventional device.

[Explanation of symbols]

 1 Steering Wheel 2 Steering Shaft 3 Torque Sensor 4 Universal Joint 5 Lower Shaft 7 Pinion Shaft 8 Steering Gear 9 Tie Rod 10 Reduction Gear 11 Clutch 12 Motor 13 Controller 14 Ignition Switch 15a, 15b Fuse 16 Battery 17 Vehicle Speed Sensor 18 Current Command Calculator 19 PID control circuit 19a Adder 19b Differential calculator 19c Proportional calculator 19d Integral calculator 19e Adder 20 Control circuit 21 Microcomputer (MPU) 22,23,24 A / D converter 25 Phase compensator 26 Counter 29 PWM circuit 30 Motor drive circuit 40 H bridge circuit 41-44 FET (field effect transistor) 51-54 Gate drive circuit 61 Current detection circuit 62 Clutch control Circuit 63 relay drive circuit 64 fail relay 71 angular acceleration detector 72 inertia compensation coefficient circuit 73 an adder 2100 arithmetic control circuit 2110 limiter 2120 correction circuit 2121 adder 2122 proportional calculator 2123 adder

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshinori Sugiyama 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 a steering assist based on at least a torque detection value of the steering torque detecting means. A control means for calculating a force target value, calculating a steering assist force command value from the steering assist force target value by calculation of feedback control including integration calculation, and outputting the steering assist force command value; and an output of the control means. In a control device for an electric power steering apparatus including a drive means for supplying a drive current corresponding to the electric motor, a steering assist force command value of the control means corresponds to upper and lower limit values of the drive current of the electric motor. The limiting means for limiting the output to the driving means and limiting the output to the driving means, and the correction value based on the difference between the output value of the limiting means and the steering assist force command value A control device for an electric power steering device, comprising: a correction unit that corrects an integration amount.