JPH08108858A - Control device of motor-driven power steering device - Google Patents

Abstract

PURPOSE: To surely prevent an electric motor from abnormal heating and the like by providing a limiting means limiting the maximum value of a control signal according to the integrating value of the absolute value of the control signal. CONSTITUTION: A control signal driving a motor 12 based on the steering torque detected by a torque sensor 3 is formed by means of a microcomputer 21, and an H bridge circuit 40 is operated based on this so as to control the current carrying direction and the current carrying quantity to the motor 12. Namely, by limiting the maximum value of the control signal according to the integrating value of the absolute value of the control signal to a motor drive circuit 30, for example, by limiting the control signal to be small in the case of the large integrating value of the absolute value of the control signal, or by enlarging the maximum value of the control signal reversely in the case of the small integrating value, the maximum value of the control signal is limited according to the integrating value of the control signal even in the case of the large steering torque and large current carrying to the motor 12. Consequently, generation of abnormality such as abnormal heating of the motor 12 following continuous large current flow can be surely prevented.

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 to assist torque with an electric motor.

This electric motor is controlled by a controller, and the controller controls an assist current based on a torque detection signal detected by a torque sensor and a vehicle speed detection signal from a vehicle speed sensor for detecting the vehicle speed. By supplying electric current to the electric motor,
It is designed to assist the steering force of the steering wheel.This electric motor assists the steering operation, for example, when cornering at low speed or when putting the car in the garage, and the feeling of the steering wheel can be felt at high speeds. It is designed to ensure running stability.

In the controller, when the steering wheel is held at the stroke end in the stationary state for a long time, or when a long time garage parking operation is repeated, a large current continues to the electric motor. The flow of electric current may cause abnormal heat generation of the motor, smoke generation, burnout, or the like, and in order to avoid this, the motor current supplied to the electric motor is limited. As described in Japanese Patent Laid-Open No. 1-186468, when current continuously flows through an electric motor for a predetermined time or longer, the electric current is supplied to the electric motor in accordance with the magnitude of the average current of the motor current for each predetermined time. There are known methods for limiting the motor current that is applied.

[0005]

However, in the conventional control device for the electric power steering system, the motor current is limited based on the motor current supplied to the electric motor. Since the motor current is likely to contain noise, a noise filter must be inserted in the motor current detection circuit that measures the motor current, which causes a problem that the stability of the entire control device is deteriorated. Further, when the steering wheel is cyclically steered to the left or right by a large steering force, the average current value for each predetermined time becomes small despite the fact that a large current actually flows, Therefore, there is an unsolved problem that the motor current is not limited.

Therefore, the present invention has been made by paying attention to the unsolved problem of the above-mentioned conventional example, and steers the steering wheel in the left-right direction periodically without lowering the stability of the control device. An object of the present invention is to provide a control device for an electric power steering device that can surely limit the current even in the case of doing so.

[0007]

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. In a control device for an electric power steering device including a motor drive circuit that controls the energization direction and the energization amount of the electric motor based on the above, a maximum value of the control signal is limited according to an integrated value of absolute values of the control signal. And a limiting means for

[0008]

According to the present invention, the control means forms a 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 drive the electric motor. By controlling the energization direction and the energization amount to the motor, at this time, by limiting the maximum value of the control signal according to the integrated value of the absolute value of the control signal to the motor drive circuit by the limiting means, for example, When the integrated value of absolute values is large, the control signal is limited to a small value, and when it is small, the maximum value of the control signal is increased to increase the steering torque and a large current flows through the electric motor. Since the maximum value of the control signal is limited by the limiting means according to the integrated value, a large current does not flow continuously to the electric motor.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention. In the figure, 1 is a steering wheel, and the steering force applied to this steering wheel 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.

A reduction gear 10 for transmitting an auxiliary steering force (assist force) to the output shaft 2b is connected to the output shaft 2b of the steering shaft 2, and the reduction gear 10 is used for transmitting / blocking the auxiliary steering force. For example, a motor 1 as an electric motor configured of, for example, a DC servo motor that generates an auxiliary steering force via an electromagnetic clutch device 11 (hereinafter, referred to as a clutch) configured of an electromagnetic type.
Two output shafts are connected. The clutch 11 has a solenoid, and this solenoid has a controller 13 to be described later.
By exciting current i _C is provided by a reduction gear 10 and the motor 12 is mechanically coupled, are detached by stopping supply of the exciting current i _C.

The torque sensor 3 is arranged 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 driving and controlling the motor 12 to control the steering assist force to the steering system, and is operated by being supplied with power from a vehicle-mounted battery 16. 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 detects the torque detection signal T _V from the torque sensor 3 and the vehicle speed detection signal V from the vehicle speed sensor 17 provided on the output shaft of the transmission, for example.
_The motor 12 is driven and controlled based on _P , and the clutch 11 is controlled to control the output shaft of the motor 12 and the reduction gear 10 to be in a coupled / disengaged state. FIG. 3 shows the controller 1
3 is a block diagram showing the configuration of the controller 3 of FIG.
Is, for example, a control circuit 20 as a control unit, a motor drive circuit 30, a current detection circuit 61, a clutch control circuit 6
2, a relay drive circuit 63 and a fail relay 64.

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. The A / D converter 22 is a phase compensator 25.
The torque compensation signal T _{P from} is input, converted into a digital value, and output to the microcomputer 21 as a torque detection value T.

The counter 26 is arranged on the output shaft of a transmission (not shown), for example, and detects a vehicle speed by a pulse signal from a vehicle speed sensor 17 such as a rotation speed sensor which generates a pulse signal according to the rotation of the output shaft. The signal V _P is input, the number of pulses per unit time is integrated, and the microcomputer 2
When the integrated value is read as 1, the count value is reset by the reset signal _RC from the microcomputer 21.

Then, the microcomputer 21 is
The torque detection value T from the D / D converter 22 and the vehicle speed detection value V from the counter 26 are input, and the current detection circuit 61
The rightward motor current detection signal I _R from the A / D converter 2
Input as the motor current detection value i _R via 4, and
The leftward motor current detection signal I _L is input as a motor current detection value i _L via the A / D converter 23, and based on these input signals, for example, PID (proportional / integral / derivative) control is applied to the motor 12. The motor drive signal S _M to be supplied is calculated, and PWM (Puls) is calculated based on this motor drive signal S _M.
e Width Modulation) signal is formed, and based on this PWM signal, a left pulse width modulation signal PWM _L , a right pulse width modulation signal PWM _R , a right direction signal D _R , a left direction signal D _L are formed, and each of these commands Signals PWM _L , PWM _R , D _R , D
_{The L} signal is output to the motor drive circuit 30.

In addition, the microcomputer 21 executes a predetermined failure detection process at the time of start-up, and outputs the relay control signal S _R to the relay drive circuit 63 as "HIGH" when it is normal, and then 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 in the left-right direction from the current detection circuit 61, and when abnormality is detected, each command signal PWM _L to the motor drive circuit 30 is detected. , PWM _R , D _R , D _L are output as “LOW” to form and output a clutch control signal S _C for disengaging the clutch 11, and then a relay control signal S _R for opening the fail relay 64. Is generated and output to the relay drive circuit 63, and predetermined processing is performed when an abnormality occurs, such as turning on an abnormal lamp. At the end, for example, a clutch control signal S _C proportional to the motor angular velocity is output to the clutch control circuit 62 in order to absorb the elastic energy stored in the steering system,
The control is performed so that a viscous load is applied 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)
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 drain sides of the FETs 41 and 42 are connected to the fail relay 64 and the ignition switch 14. Is connected to the battery 16 via. The connection point between the FETs 41 and 43 and the FET 42
The motor 12 is connected between the connection point of the motors 44 and 44. The source side of the FET 43 is grounded via the right direction current detection resistor R _R , and similarly, the source side of the FET 44 is grounded via the left direction current detection 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 connected to the gate drive circuit 54,
When a predetermined voltage is supplied from 54 to each of 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 is turned on. , Motor 12, FET4
4. When the motor 12 is reversely rotated by being energized in the direction of the leftward current detecting resistor R _L and only the FETs 42 and 43 are turned on, the direction of the FET 42, the motor 12, the FET 43, and the rightward current detecting resistor R _R Is energized to the motor 12
Is designed to rotate forward.

Then, the left pulse width modulation signal PWM _L from the control circuit 20 is output to the gate drive circuit 51, the right pulse width modulation signal PWM _R to the gate drive circuit 52, and the right direction signal D _R to the gate drive circuit 53. Then, the leftward signal D _L is output to the gate drive circuit 54, respectively. Then, in the gate drive circuits 51 to 54, the input command signals PW are input.
Based on M _L , PWM _R , D _R , and D _L , the gate terminals G ₁ and G of the FETs 41 and 42 are supplied by a boosting power source (not shown).
₂ performs voltage supply to, also, supplies the battery voltage to the gate terminal G ₃ and G ₄ of FET43 and 44, each command signal _{PWM L, PWM R, D R} , D L signal is "HIGH"
The predetermined voltage is supplied to the corresponding gate terminal during the period, and the voltage supply to the corresponding gate terminal is stopped while the command signal is “LOW”.

On the other hand, the current detection circuit 61, for example, amplifies 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 removes noise, and outputs the right direction motor current detection signal I. It outputs to the control circuit 20 as _R and the left motor current detection signal I _L. Further, the clutch control circuit 62 receives the clutch control signal S from the control circuit 20.
_An exciting current i _C is generated according to _C and is supplied to the solenoid of the clutch 11 to control the mechanical connection / disconnection state of the output shaft of the motor 12 and the reduction gear 10.

The relay drive circuit 63 controls ON / OFF of the fail relay 64 based on the relay control signal S _R from the control circuit 20, and the fail relay 64 has a normally open contact switch. a is, which controls ON / OFF the power supply of the battery 16 to the H-bridge circuit 40, the relay control signal S _R
Is "HIGH", the coil 6 of the fail relay 64
4 L is energized to close the relay contact 64a to enable power supply from the battery 16 to the H bridge circuit 40, and when the relay control signal S _R is "LOW", to the coil 64L of the fail relay 64. Is cut off 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 and the current limit value setting processing as the limiting means will be described based on the flowcharts shown in FIGS. The microcomputer 21 executes a predetermined failure detection process when the ignition switch 14 is turned on, and outputs a relay control signal S _R to the relay drive circuit 63 as “HIGH” when no abnormality is detected. After that, the clutch control signal S _C is gradually increased based on a clutch control process (not shown).
Is generated and output to the clutch control circuit 62. As a result, in the relay drive circuit 63, the coil 64L
To the H-bridge circuit 40, and the clutch control circuit 62 causes the clutch control circuit 62 to energize the solenoid of the clutch 11 according to the clutch control signal S _C. By supplying i _C , the rotation shaft of the motor 12 and the reduction gear 10
And are gradually brought into mechanical connection. Further, the microcomputer 21 starts each gate drive circuit 51 at startup.
Each command signal to 54 is output as "LOW".

FIG. 4 is a flow chart showing the processing procedure of the motor drive control processing, and this processing is performed by a timer interrupt at preset predetermined time intervals. In this motor drive control processing, first, in step S1, A /
The detected torque value T from the torque sensor 3 that has been phase-compensated by the phase compensator 25 is read via the D converter 22.

Then, the process proceeds to step S2, where T = T-
The calculation of V ₀ is performed, and the offset process is performed so that the torque detection value T at neutral is zero. Then, step S2a
Then, 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 reset the counter value, and then step S3
Move to

In step S3, the characteristic diagram showing the correspondence between the steering torque, the vehicle speed, and the motor current shown in FIG. 5 is referred to, and, for example, it corresponds to the torque detection value T and the vehicle speed detection value V that have been offset. The motor current is searched for, set as the motor current command value S _I , and updated and stored in a preset predetermined storage area. This characteristic diagram shows the motor current required to drive the motor 12 to generate an auxiliary steering force corresponding to the steering torque input to the steering shaft 2, the steering torque, and the vehicle speed. The motor current command value increases as the vehicle speed decreases, the motor current command value increases as the steering torque increases, and is set so that it does not increase beyond a certain value. .

Next, in step S3a, the current limit value I _LIM set by the current limit value setting process shown in FIG. 7 to be described later and stored in a predetermined storage area is read,
Based on this current limit value I _LIM and the absolute value of the motor current command value S _I set in step S3, | S _I | <I _LIM
If | S _I | <I _LIM , the process _proceeds to step S4 as it is, and | S _I | <I
If it is not _LIM , the process proceeds to step S3b, and the magnitude of the motor current command value S _I is changed and set to the current limit value I _LIM ( _{│S I} │ = I _LIM ). When the current command value S _I is a positive value, the motor current command value S _I = + I _LIM is set, and when the motor current command value S _I is a negative value, the motor current command value S _I =
-I _LIM, and the process _proceeds to step S4.

Then, in step S4, a value obtained by performing a predetermined process such as a differential process on the motor current command value S _{I is} set to
A predetermined differential gain K _D is multiplied and this is differentiated value f _D
Then, in step S5, 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, and the motor current detection value i _R in the right direction is set to a positive value, The motor current detection value i _L 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, it is calculated by i _M = i _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 can be 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.
When this absolute value | i _M | is smaller than the maximum current value I _MAX , it is determined that the motor current detection value i _M is within the normal range, and the process returns to the motor drive control processing program.

On the other hand, in step S21, | i _M | ≧ I
If it is _MAX, it is determined that an excessive current is flowing in the H-bridge circuit 40 and an abnormality has occurred, and it is determined in step S
22, the gate drive circuit 5 is operated at step S22.
Command signals PWM _L , PWM _R , D _R , D to 1 to 54
_L is output as "LOW", thereby cutting off the energization path of the H bridge circuit 40. Then, step S23
And the output of the clutch control signal S _{C to} the clutch control circuit 62 is stopped, the clutch control circuit 62 operates the clutch 11 to bring the output shaft of the motor 12 and the reduction gear 10 into the disengaged state. .

Then, in step S24, the relay control signal S _R to the relay drive circuit 63 is output as "LOW", thereby operating the fail relay 64 to transfer the battery 16 to the H bridge circuit 40. The power supply is cut off, and in step S25, for example, an upper-level program such as the main processing program is notified of an abnormality, 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,
Control goes to step S6. In this step S6, the motor current command value S _I set in step S3 and the step S6
The difference from the motor current detection value i _M calculated in 5, that is,
The current deviation e _M is calculated from e _M = S _I −i _M.

Next, in step S7, the current deviation e _M is multiplied by a predetermined proportional gain K _P , and this is multiplied by the proportional processed value f _P.
Further, in step S8, the proportional processing value f _P is integrated and multiplied by a predetermined integral gain K _I , and this is integrated processing value f _I
And 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 together, and this is used as the motor drive signal S _M. Then, the process proceeds to step S10.

[0035] 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 to the motor 12 according to the motor drive signal S _M is set, and this is set as a right pulse width modulation signal PWM _R to the corresponding gate drive circuits 52 and 53. Then, the left pulse width modulation signal PWM _L and the left direction signal D _L are output as “LOW” to the gate drive circuits 51 and 54, and the process ends 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 ″, and a duty ratio D for supplying a drive current to the motor 12 according to the motor drive signal S _M is set as a left pulse width modulation signal PWM _L , and the corresponding gate drive circuits 51 and 54 are provided. Output to
The right direction signal D _R and the right pulse width modulation signal PWM _R are “L
OW "is output to the gate drive circuits 52 and 53, respectively, and the process is terminated and the process returns to the main program.

Next, the processing procedure of the current limit value setting processing of FIG.
The flow chart showing is described. This process
A timer interrupt is executed every predetermined time set in advance.
Done. In this current limit value setting process,
First, in step S30, the motor drive control process of FIG.
Motor current command stored in the specified storage area
Value S_IIs read, and then in step S30a,
Seen motor current command value S _IAbsolute value of | S_ICalculate
I do. Then, the process proceeds to step S31, and this absolute value |
S_I| Is the integrated value I_SUMTo the new integrated value I
_SUMAnd (I_SUM= I_SUM+ | S_I|) And N = N
The cumulative number N is updated by +1 and the process proceeds to step S32.
You.

In step S32, it is determined whether the integrated number N is larger than a preset reference value Nα. If N> Nα, the process proceeds to step S33, and if N> Nα is not satisfied. In this case, this process is finished as it is. Then, in step S33, the integrated value I _SUM
Then, the average value I _AV of the absolute values | S _I | of the motor current command values is calculated by I _AV = I _SUM / N based on
Then, the process proceeds to step S34, the integrated value I _SUM and the addition number N are reset to I _SUM = 0, N = 0, and step S
Move to 35. In this step S35, the average value I _AV
, It is determined whether I _AV > Imax · 60%.
Here, Imax is the rated current value of the motor 12.

When I _AV > Imax60%, that is, the average value I _AV is 6 of the motor maximum current limit value.
If it is larger than 0%, it is determined that the current limit value I _LIM needs to be made small, and the process _proceeds to step S36. At step S36, the current limit value is decreased by 5% and the process proceeds to step S39. On the other hand, in step S35, I _AV > I
When it is not max.60%, that is, when the average value I _AV is smaller than 60% of the motor maximum current limit value, the process proceeds to step S37, and I _AV <Imax 30%, that is, the average value I _AV is the motor maximum current limit value of 3
It is determined whether it is smaller than 0%. And I _AV <I
If it is max · 30%, it is determined that the current limit value I _LIM needs to be increased, the process proceeds to step S38, the current limit value is increased by 5%, the process proceeds to step S38a, and the current limit value is increased by 5%. It is determined whether the current limit value I _LIM is smaller than the motor maximum current limit value Imax. If I _LIM <Imax, the process directly proceeds to step S39, and if I _LIM <Imax, the process proceeds to step S38b and the current limit value I _LIM =
After setting to Imax, the process proceeds to step S39.

Then, in step S39, the updated current limit value I _LIM is updated and stored in a predetermined storage area set in advance, and the process is terminated. Then, in step S37, I _AV
<Imax · If not 30%, current limit value I _LIM
Assuming that the change is not made, the process is terminated and the process returns to the main program.

Next, the operation of the first embodiment will be described.
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 control signal is output. S _R
Is output as "HIGH" to the relay drive circuit 63, 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
However, by energizing the coil 64L, 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, and the rotation shaft of the motor 12 and the reduction gear 1
0 becomes a mechanically coupled state, and the rotational driving force of the motor 12 can be transmitted to the steering shaft 2.

Then, the motor drive control process of FIG. 4 is performed at a predetermined interrupt cycle, and assuming that the occupant is not performing the steering operation at this time, the torque detection signal T _V from the torque sensor 3 is the neutral voltage V _0. Since the vehicle is stopped at this time, the vehicle speed detection value V becomes zero,
In the motor drive control process of FIG. 4, the motor current command value S _I becomes substantially zero from the characteristic diagram of FIG.
2 is not driven.

When the vehicle is brought into the running state from the stopped state, the torque detection signal T _V from the torque sensor 3 is in the vicinity of the neutral position V ₀ during the non-steering state. Moreover, since the motor current command value S _I becomes substantially zero, the motor 12 is not driven. During this traveling, for example, when the occupant makes a right steering, the torque detection signal T _V from the torque sensor 3 becomes a voltage value larger than the neutral voltage V ₀ because the right steering is performed, and the microcomputer 21 Then, based on the torque detection value T input via the A / D converter 22, offset processing is performed by T = T−V ₀ to calculate the torque detection value T at which the neutral point is zero.

Then, 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. 5 (step S3). At this time, for example, when the vehicle is traveling at a low speed and the steering torque is large, a large auxiliary steering force is required, so the motor current command value S _I is set large, and at this time, 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 auxiliary steering 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.

Whether or not the current limit value I _LIM set and stored by the current limit value setting process of FIG. 7 and the absolute value of the calculated motor current command value S _I are | S _I | <I _LIM If | S _I | <I _LIM , the motor current command value S _{I is} processed as it is. If | S _I | <I _LIM , the sign of the motor current command value S _I is determined. , The magnitude is changed and set to the current limit value I _LIM . In this case, since the right steering is performed and the motor current command value S _I is a positive value, the motor current command value S _I = +
I _LIM, and then the changed motor current command value S _I
Process.

[0046] Then, a differential processing such predetermined processing to the motor current command value S _I, to calculate a differential processing value f _D is multiplied by a derivative gain K _D (step S4). In addition, based on the motor current detection values i _R and i _L in the left-right direction, i _M
= I _R −i _L calculates the motor current detection value i _M as the value of the current flowing through the motor 12. Then, after executing the abnormality monitoring processing, the current deviation e _M is calculated from the motor current command value S _I and the motor current detection value i _M (step S6). Then, a proportional gain K is added to the calculated current deviation e _M.
By multiplying the _P calculates a proportional processed value f _P (step S
7), the proportional processed value a value obtained by integrating processing on f _P integral gain K _I multiplied by the calculated integration processing value f _I (step S8), and these differential processing value f _D the proportional processed value f _P
And the integrated processing value f _I are added to calculate the motor drive signal S _M (step S9).

[0047] Then, it is determined current direction on the basis of the sign of the motor drive signal S _M, in this case, the 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 and is output to the corresponding gate drive circuits 51 to 54 (step S11). ).

Therefore, the gate drive circuit 53 supplies a predetermined voltage to turn on the FET 43, and while the gate drive circuit 52 supplies the predetermined voltage while the command signal PWM _R is "HIGH", the FET 42 is turned on. Is controlled on and off. At this time, command signals PWM _L and D
_{Since L} is “LOW”, the gate drive circuit 51,
Since the FET 54 does not supply a predetermined voltage to the FETs 41 and 44, the FETs 41 and 44 remain off.

Therefore, when the FET 42 is turned on, the power is supplied from the battery 16 to the FET 4
2, motor 12, FET 43, right direction current detection resistor R _R
Is energized in the direction of the
Is controlled to be turned on and off so that the motor drive signal S _M
Is supplied to control the drive of 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. .

At this time, in the current limit value setting process in the first embodiment of FIG. 7, the process is performed by the timer interruption at every predetermined time, and the steering operation is performed from the state where the vehicle has the ignition switch 14 in the ON state. If not, since the torque detection signal T _V from the torque sensor 3 is in the vicinity of the neutral position V ₀ as described above, the motor current command value S _I set by the characteristic diagram of FIG. It becomes zero.

Therefore, in this case, the integrated number N is N
Even when> Nα, the integrated value I _SUM becomes substantially zero, so that steps S35 to S37 and S
38, and the current limit value I _LIM is increased by 5%. At this time, if it is assumed that the motor maximum current limit value Imax is set as the current limit value I _LIM at the time of startup, in step S38a, I _{Since LIM} <Imax is not satisfied, the current limit value I _LIM is not updated, and therefore the motor maximum current limit value Imax is set as the current limit value I _LIM.
Remains set.

From this state, a steering torque is generated on the steering shaft 2 by performing a steering operation or the like. At this time, for example, when the steering torque is large, such as when stationary steering is performed, the motor current command value is Since S _I is set to a large value, the average value I _AV of the absolute values of the motor current command values at this time becomes large, and for example, if it is larger than 60% of the motor maximum current limit value Imax, from step S35. The process proceeds to step S36, and the current current limit value, that is, the motor maximum current limit value Imax is set to 5%.
The reduced value is newly set as the current limit value I _LIM , and in the motor drive control process, the motor current command value S _I is limited to this current limit value I _LIM and output to the motor drive circuit 30. Then, when the average value I _AV again the motor current command value S _I at a current limit value setting process, when the average value I _AV is assumed greater than 60% of the maximum motor current limit value Imax, as described above In addition, the current limit value I
A value obtained by reducing _LIM by 5% is newly set as the current limit value I _LIM .

Thereafter, the average value I _AV of the motor current command value S _I is set every predetermined time, that is, every time the integrated number N becomes N> Nα.
Is greater than 60% of the motor maximum current limit value Imax, the current limit value I _LIM is decreased by 5%. Therefore, for example, when steering in the left-right direction is periodically performed, the motor current command value S _I Is large continuously, and the average value I _{AV for} each predetermined time is large, the current limit value I _LIM is gradually decreased by 5% at each elapse of the predetermined time, so that the motor 12 is controlled. It is possible to reliably prevent the continuous flow of a large current, and heat generation due to the large current and thermal destruction such as smoking will not occur.

Then, the current limit value I _LIM is gradually set to a small value, whereby the motor current command value S _I is limited, so that the average value I _AV becomes smaller, and the motor maximum current limit value Imax is 60. When smaller than%,
The process proceeds from step S35 to step S37, at which time the average value I _AV is 30 which is the motor maximum current limit value Imax.
If it is larger than%, the process is terminated as it is, and the current limit value I _LIM is not updated.

From this state, the steering torque decreases, and the motor current command value S _I decreases accordingly,
The average value I _AV is 30 which is the motor maximum current limit value Imax.
If it is smaller than%, the steps S37 to S37
38, this time the current limit value I _LIM is increased by 5%, and since the increased current limit value I _LIM is smaller than the motor maximum current limit value Imax, the process moves to step S39 and this current limit value is reached. I _LIM is updated and stored as a new current limit value.

Then, similarly to the above, this operation is repeated while the average value I _AV of the motor current command value S _I is small, so that the current limit value I _LIM gradually increases and the motor current command value S _I becomes small. Therefore, since the average value I _AV is small and no abnormality occurs in the motor drive circuit 30 or the motor 12 due to the excessive current, the current limit value I _LIM is gradually set in accordance with the average value I _AV. By
It is possible to efficiently limit the motor current command value S _I.

Therefore, according to the first embodiment described above, the average value I _AV per predetermined time is the maximum motor current limit value I
The current limit value I _LIM is gradually set smaller while it is larger than 60% of max, and conversely, the current limit value I _AV is gradually set large while the average value I _AV is smaller than 30% of the motor maximum current limit value Imax. The motor current command value S
_While the average value I _AV of I is small, the motor current command value S _I is not unnecessarily limited, and when the average value I _AV is large, the motor current command value S _I is limited to a small value.
The motor drive circuit 30 is driven by a large current flowing for a long time.
It is possible to reliably prevent abnormal heat generation, smoke generation, burnout, and the like.

Further, according to the first embodiment, the current limit value I _AV is set based on the average value I _AV calculated from the absolute value of the motor command current value S _{I in} the control circuit 20. Therefore, it is not necessary to provide an additional filter or the like as in the conventional case, so that the control system does not become unstable. Further, this average value I _AV is calculated based on the absolute value of the motor current command value S _I. By detecting the effective value of the motor current, steering in the left-right direction is performed as in the conventional case. Even when it is repeated, the current can be surely limited regardless of the energization direction.

Next, a second embodiment of the present invention will be described. The second embodiment is the same as the first embodiment except that the processing procedure of the current limit value setting processing in the microcomputer 21 is different. In the current limit value setting process in the second embodiment, as shown in FIG. 8, in the first embodiment, the current limit value I _LIM is increased or decreased by 5% in accordance with the average value I _AV . On the other hand, the rate of increase / decrease is changed according to the magnitude of the average value I _AV of the motor current command value S _I , and like the first embodiment, every preset predetermined time. Is executed by interruption.

Then, from step S30 to step S3
The process of No. 4 is the same as that of the first embodiment, the motor current command value S _I stored in a predetermined storage area is read, and the absolute value | S _I | N
The average value I _AV is calculated by integrating until reaching α. Then, the process proceeds to step S51, the calculated average value I _AV is multiplied by a preset coefficient K, and this is multiplied by the motor command current value S
And _I restriction degree dI, then proceeds to step S52, the average value I _AV is determined whether greater than a preset motor continuously operable current value Im, in the case of I _AV> Im is The process proceeds to step S53, and if I _AV > Im is not satisfied, the process proceeds to step S57.

Here, the current value Im for continuous motor operation is possible.
Is a current value at which the motor 12 does not become abnormal even when continuously energized. In step S53, a value obtained by subtracting the limit degree dI from the current limit value I _LIM and current limit value I _LIM, then in step S54, and the current limit I _LIM and the motor continuously operable current value Im,
It is determined whether the I _LIM <Im, in the case of I _LIM <Im, the current limit value and proceeds to step S55 as it is too much to decrease the current limit I _LIM I _LIM = I
Then, the process proceeds to step S56. And step S
If I _LIM <Im in 54, then step S is performed as it is.
Move to 56.

On the other hand, if I _AV > Im is not satisfied in step S52, the process proceeds to step S57, and in this step S57.
Now, the value obtained by adding the limit degree dI the current limit value I _LIM and the current limit value I _LIM, then in step S58, the and the current limit I _LIM and motor maximum current limit I _LMAX, I
It is determined whether the _LIM> I _LMAX, when a I _LIM> I _LMAX proceeds to step S59, I _LIM> I _LMAX
If not, the process proceeds directly to step S56.

Here, the motor maximum current limit value I _LMAX is
It is the maximum value that can be set as the current limit value I _LIM , and this represents the maximum value of the motor current command value S _{I that} can be set as the motor current command value S _I. And
In step S59, the current limit value I _LIM = I _LMAX is set, and then the process _proceeds to step S56.

Then, in step S56, the set current limit value I _LIM is updated and stored in a predetermined storage area as a new current limit value I _LIM , and the process returns to the main program. Next, the operation of the second embodiment will be described. Here, the operation based on the motor drive control processing of FIG. 4 in accordance with the steering torque and the vehicle speed is the same as that of the first embodiment, and therefore will be omitted here.

At this time, in the current limit value setting process in the second embodiment of FIG. 8, the process is performed by the timer interruption at every predetermined time, and the vehicle is in the stopped state or from the state in which the ignition switch is in the ON state. When the steering operation is not performed, the torque detection signal T _V from the torque sensor 3 is in the vicinity of the neutral position V ₀ .
The motor current command value S _I set by the characteristic curve of ₁ becomes substantially zero. Therefore, in this case, the integrated number N is N>
Even if it becomes Nα, the integrated value I _SUM becomes substantially zero. Therefore, the average value I _AV becomes zero and the limit degree dI becomes zero. At this time, since the average value I _AV is zero, the process proceeds from step S52 to step S57, and the limit degree dI is added to the current limit value I _LIM. Then, the current limit value I _LIM is updated. At this time, assuming that the motor maximum current limit value I _LMAX is set as the initial value of the current limit value I _LIM at start-up, in step S58, I _LIM Since> I _LMAX , I _LIM = I _LMAX is set in step S59, and thus the current limit value I _LIM is not updated.

From this state, a steering torque is generated in the steering shaft 2 by performing a steering operation or the like. At this time, for example, when the steering torque is large, such as when stationary steering is performed, the motor current command value is Since S _I is set to a large value, the average value I _AV of the motor current command values at this time becomes large. For example, if the average value I _AV is larger than the motor continuous operable current value Im, the process proceeds from step S52 to step S53. , Current limit value I _LIM to average value I
A value obtained by subtracting the limit degree dI according to _AV is newly set as the current limit value I _LIM , and in the motor drive control processing, the motor current command value S _I is limited to the current limit value I _LIM and the motor drive circuit 30 is controlled. Output.

As a result, when the current limit value processing is performed next time, the motor current command value S _I is changed to the current limit value I.
Since limited by _LIM, but the average value I _AV is smaller than the previous average value I _AV, for example, still, the average value when I _AV is made larger than the motor continuously operable current value Im, the step S52 To step S53, a value obtained by subtracting the limit degree dI according to the average value I _AV from the current limit value I _LIM is newly set as the current limit value I _LIM , and the motor current command value S for each predetermined time _When the average value I _AV of I is larger than the motor continuous operation possible current value Im, the current limit value I _LIM is decreased by the limit degree dI according to the average value I _AV .

[0069] Thus, for example, like the case of performing the left-right direction steering periodically, even when the motor current instruction value S _I becomes a large value in succession, the motor current command value S _I is larger, the predetermined When the average value I _{AV for} each time is large, the current limit value I _LIM is greatly reduced by the limit degree dI according to the average value I _AV , so the motor 12 or
In the motor drive circuit 30 such as the H-bridge circuit 40, heat generation due to excessive current, thermal destruction such as smoking does not occur.

Then, by gradually reducing the current limit value I _LIN , the motor current command value S _I is limited to a small value, so that the average value I _AV becomes small.
When I _AV > Im, the process proceeds from step S52 to step S57, and this time, by adding the limit degree dI set by dI = K · I _AV to the current limit value I _LIM , Since the limit value I _LIM is increased, the motor current command value S _I is no longer limited, and this operation is repeatedly performed while the average value I _AV of the motor current command values S _I is small, and the limit degree dI according to the average value I _AV is increased. Current limit value I
_{Since LIM} gradually increases, while the average value I _AV is small,
Motor drive circuit 3 due to large current or energization for a long time
0, or since there is no abnormality in the motor 12, the current limit value I is increased by the limit degree dI according to the average value I _AV.
By setting _LIM large, it is possible to efficiently limit the motor current command value S _I.

Therefore, according to the second embodiment, the current limit value I is maintained while the average value I _AV per predetermined time is large.
_By setting _LIM smaller by the limiting degree dI corresponding to the average value I _AV and conversely setting the current limiting value I _LIM larger by the limiting degree dI while the average value I _AV is smaller, a large current continues to flow. As a result, it is possible to reliably prevent abnormalities in the motor drive circuit 30, the motor 12, etc., such as abnormal heat generation and smoke generation.

Further, the average value I _{AV of the} motor current command value S _I
It is possible to increase or decrease the current limit I _LIM depending on, it is possible to effectively set according to the current limit value I _LIM to the average value I _AV, for example, the average value I _AV is small heat generation is Current limit value I _LIM when there is no possibility of occurrence
Can be set to a large value so that the motor current command value S _I is not limited, and the motor 12 can be effectively driven and controlled.

In the second embodiment, the control circuit 20
In this, the average value I _AV is calculated based on the motor current command value S _I , and the current limit value I _LIM is set based on this average value I _AV. Therefore, it is not necessary to provide the above, and therefore the control system does not become unstable. Further, since the average value I _AV is calculated based on the absolute value of the motor current command value S _I , and the current limit value I _LIM is set based on this average value I _AV , as in the conventional case, Even when the steering is repeatedly performed, the magnitude of the motor current can be reliably detected, and the current can be surely limited according to the average value I _AV .

In the first and second embodiments, the case where the right steering is performed has been described, but the same effect as the above can be obtained even when the left steering is performed. Also,
In the first and second embodiments, the case where the FET is used as the switching element of the H-bridge circuit has been described, but the present invention is not limited to this, and other switching elements such as a bipolar transistor can be applied.

In the first and second embodiments, the PI
Although the case where the drive control of the motor 12 is performed by the D control has been described, the control is not limited to this, and the control may be performed by the PI control, the P control, or the like. In addition, in the first and second embodiments, the case where the motor is drive-controlled based on the vehicle speed and the steering torque has been described, but the present invention is not limited to this, and the motor is drive-controlled based only on the steering torque, for example. It is also possible.

Furthermore, in the above-mentioned first and second embodiments, the case where the controller 13 is formed by using the micro computer 21 has been described, but the present invention is not limited to this, and an electronic circuit such as an arithmetic circuit, an addition circuit, a logic circuit or the like may be used. It is also possible to construct them in combination, and FIG. 9 shows an example thereof. To briefly describe FIG. 9, the controller 13 serves as, for example, a phase compensator 25, a counter 26, a current command calculator 32, a current feedback control circuit 33, a motor drive circuit 93, a current detection circuit 91, and a limiting unit. Of the limit value setting circuit 105, and the phase compensator 25, the counter 26, the current command calculator 32, and the current feedback control circuit 33 correspond to the control means.

Based on the torque compensation signal T _P from the phase compensator 25 and the vehicle speed detection value V from the counter 26, the current command calculator 32 sets the motor current command value S _I. The current command calculator 32 is formed by, for example, a function generator, selects a function based on the vehicle speed in the characteristic diagram of FIG. 5 described above, and calculates a required motor current command value S _I for the steering torque. This motor current command value S
_{When I} is larger than the current limit value I _LIM input from the limit value setting circuit 105 described later, the motor current command value S _I is limited to the current limit value I _LIM , and the motor command current value S I
_It is output as _I to the current feedback control circuit 33 and the limit value setting circuit 105.

Here, the limit value setting circuit 105 is composed of, for example, a counter, an adder, an arithmetic unit, etc., calculates the absolute value of the motor current command value S _I , adds it for a predetermined number of times, and adds the average value I. A motor protection detector 105a for calculating _AV ,
For example, it is composed of a computing unit such as a comparator, a multiplier, _an adder, etc., sets a current limit value I _LIM according to the average value I _AV from the motor protection detector 105 a, and outputs it to the current command computing unit 32. It is composed of a maximum current limiter 105b.

This current feedback control circuit 33 is
For example, the differential compensator 36, the adders 37a and 37b, the proportional calculator 38, and the integral calculator 39 are provided, and the motor current command value S _I from the current command calculator 32 is supplied to the differential compensator 36 and the adder 37a. In the differential compensator 36, the input motor current command value S _I is differentiated, and the differential processing value f _D proportional to the differential value is output to the adder 37b. The adder 37a outputs the motor current command value S _I , The difference from the motor current detection value i _M calculated based on the voltages across the left and right current detection resistors R _R and R _L from the current detection circuit 91 is calculated, and this difference is used as the current deviation e _M to calculate the proportional calculator 38. To the adder 37b and the integral calculator 39 as a proportional processed value f _P.

Then, the integral processing value f _I , the differential processing value f _D, and the proportional processing value f _p, which have been integrated by the integration calculator 39, are added by the adder 37b to the motor driving circuit 93 as the motor driving signal S _M. It is outputting. Then, in the motor drive circuit 93, the PWM is performed based on the motor drive signal S _M.
In the circuit 46a, left and right pulse width modulation signals PWM _L and P
WM _R and the left and right direction signals D _R and D _L are formed and output to the gate drive circuit 49, and the gate drive circuit 49 responds to each of the command signals PWM _L , PWM _R , D _R , and D _L by the FET 41. The currents corresponding to the motor drive signal S _M are supplied by controlling ON-OFF of the motors 44 to 44, and the motor 12 is drive-controlled.

Further, in the above-mentioned 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 during high-speed running, in addition to the steering torque, the steering state is detected according to the steering angular velocity and the steering angular acceleration of the steering wheel, and auxiliary torque is generated according to these values. It is also possible to perform motor drive control.

FIG. 10 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
10, the current command calculator 32, the adder 37a, the proportional calculator 38, the integral calculator 39, the adder 37b, the steering angular velocity acceleration calculator 102, and the damper coefficient circuit 103, as shown in FIG. And an inertia compensation coefficient circuit 104.

Then, 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. Then, the inertia signal K _I ′ is supplied, and the motor current command value S _I is subjected to processing of subtracting the motor current detection value i _M , subtracting the damper signal D _I , and adding the inertia signal K _I ′. Adder 37
In the proportional calculator 38 to which the output signal of a is supplied, a predetermined proportional gain is multiplied, and the multiplication value is directly supplied to the adder 37b and added via the integral calculator 39 which performs a predetermined integration process. It is supplied to the container 37b. The output signal from the adder 37b, which is the addition processing of these input signals, is supplied to the motor drive circuit 93b, and the motor drive circuit 9b
In 3b, a pulse width modulation signal PWM having a predetermined pulse width is formed based on this output signal and is 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. To drive.

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, and 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. .

The steering angular velocity ω ₀ and the steering angular acceleration ω ₁ are calculated by the steering angular velocity acceleration calculation circuit 102 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.

V = k _T · ω ₀ + R · i (2) Therefore, the steering angular velocity ω ₀ is calculated as follows from the equations (1) and (2). 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.

[0087]

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 energization direction and the energization amount to the electric motor. At this time, the limiting means controls the control signal according to the integrated value of the control signal to the motor drive circuit. By limiting the maximum value of, for example, the control signal is limited to a small value when the integrated value is large, and conversely, when the integrated value is small, the maximum value of the control signal is increased to increase the steering torque and increase the electric current of the electric motor. Even if the current flows, the maximum value of the control signal is limited by the limiting device according to the integrated value of the control signal, so that a large current flows continuously to the electric motor. Without therefore the abnormality occurrence of abnormal heat generation of the electric motor due to a large current flows can be reliably prevented.

[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 flowchart showing a processing procedure of a current limit value setting processing in the first embodiment of the present invention.

FIG. 8 is a flowchart showing a processing procedure of current limit value setting processing in the second embodiment of the present invention.

FIG. 9 is an example of a case where the controller 13 according to the present invention is configured by an electronic circuit.

FIG. 10 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.

[Explanation of symbols]

 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

 ─────────────────────────────────────────────────── ─── 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 a motor drive circuit that controls the energization direction and the energization amount of the electric motor based on the control signal from the control unit. 2. The control device for an electric power steering device according to claim 1, further comprising a limiting unit that limits a maximum value of the control signal according to an integrated value of absolute values of the control signal.