JPH11291926A - Electric power steering device - Google Patents

Abstract

(57) [Problem] To detect a current actually supplied to a motor for generating steering assist torque and perform feedback control of the current supplied to the motor. Provided is an electric power steering device capable of preventing an excessive motor current. SOLUTION: An electric motor 10 for applying an auxiliary torque to a steering system, a steering torque detector 12 for detecting a steering torque Tp of the steering system, an electric motor current detector 14 for detecting an electric motor current IM, and at least a steering torque Tp.
A target current setting unit 30 that sets a target current IT to be supplied to the motor 10 based on the target current IT, and a motor drive unit 40 that performs feedback control on the current supplied to the motor 10 based on a deviation between the target current IT and the motor current IM. Current limiter 51 that limits the amount of change in target current IT per unit time
Is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus for reducing the steering force of a driver by applying the power of an electric motor to a steering system, and more particularly, to detecting a current actually supplied to the electric motor. The present invention relates to an electric power steering device that performs feedback control of a current supplied to an electric motor and prevents an excessive increase in electric motor current due to a response delay of the feedback control.

[0002]

2. Description of the Related Art FIG. 1 is a schematic structural view of an electric power steering apparatus. The electric power steering device 1 includes an electric motor 10 in a steering system, and controls the power supplied from the electric motor 10 by using the control device 20 to reduce the steering force of the driver.

[0003] A steering shaft 3 integrally provided on a steering wheel (handle) 2 includes a universal joint 4.
The rack & pinion mechanism 5 is connected to a pinion 6 via a connection shaft 4 having a and b. The rack shaft 7 includes rack teeth 7a that mesh with the pinion 6. The rack and pinion mechanism 5 converts the rotation of the pinion 6 into a reciprocating motion of the rack 7 in the axial direction. Left and right front wheels 9 as rolling wheels are connected to both ends of the rack shaft 7 via tie rods 8. When the steering wheel 2 is steered, the front wheels 9 swing through the rack and pinion mechanism 5 and the tie rods 8. Thereby, the direction of the vehicle can be changed.

In order to reduce the steering force, a motor 10 for supplying a steering assist torque (assist torque) is connected to a rack shaft 7.
The rotation output of the electric motor 10 is converted into a thrust through a ball screw mechanism 11 provided substantially parallel to the rack shaft 7 so as to act on the rack shaft 7. Electric motor 1
The drive side helical gear 10a is provided integrally with the rotor 0. The helical gear 11b and the drive-side helical gear 10a provided integrally with the shaft end of the screw shaft 11a of the ball screw mechanism 11 are meshed. The nut 11c of the ball screw mechanism 11 is connected to the rack shaft 7.

A steering torque detector 12 provided on a steering box (not shown) detects a manual steering torque acting on the pinion 6 and supplies a steering torque signal Tp corresponding to the detected steering torque to the control device 20. I have. The control device 20 controls the output power (steering assist torque) of the electric motor 10 by operating the electric motor 10 with the steering torque signal Tp as a main signal.

FIG. 2 is a block diagram of a conventional electric power steering apparatus. The conventional control device 20J includes a target current setting unit 30 and a motor driving unit 40. The motor drive unit 40 includes a high-frequency component removal unit 41, a deviation calculation unit 42, a PID control unit 43, and a PWM signal generation unit 44.
, A gate drive circuit section 45, and a motor drive circuit 46 in which four power field effect transistors Q1 to Q4 are connected in an H-type bridge. Reference numeral 12 denotes a steering torque detector,
Reference numeral 13 is a vehicle speed detector, reference numeral 14 is a motor current detector,
Reference numeral 19 denotes a battery power supply. Steering torque detector 12
Outputs a steering torque signal Tp related to the direction and magnitude of the manual steering torque. The vehicle speed detector 13 outputs a vehicle speed signal VS relating to the speed of the vehicle. The motor current detector 14 outputs a motor current signal (hereinafter referred to as “motor current”) IM related to the direction and magnitude of the current flowing through the motor 10.

The target current setting unit 30 supplies a basic steering torque to the electric motor 10 based on the steering torque signal Tp output from the steering torque detector 12 so that the electric motor 10 generates a steering assist torque corresponding to the steering torque. The current value is obtained, the basic current value is corrected according to the vehicle speed detected by the vehicle speed detector 13, and the corrected current value is output as a target current signal (hereinafter, referred to as a target current) IT. In the vehicle speed correction, the target current is set smaller as the vehicle speed becomes higher. The target current IT is the motor drive unit 4
0.

The high-frequency component removing section 41 removes high-frequency components of the motor current IM detected by the motor current detector 14 and outputs a motor current 41a from which high-frequency components have been removed. The steering assist torque supplied from the motor 10 is controlled by performing the PWM (pulse width modulation) operation of the motor 10. For this reason, the motor current IM detected by the motor current detector 14 contains a high-frequency component accompanying the switching control of the motor current. When feedback control is performed using the motor current IM including the high-frequency component,
Since the feedback control is not performed correctly, the high-frequency component removing unit 41 removes the high-frequency component.

The deviation calculator 42 calculates a deviation between the target current IT and the motor current 41a from which high-frequency components have been removed, and outputs a deviation signal 42a. The PID control unit 43 outputs the deviation signal 4
A drive control signal 43a for controlling the current supplied to the electric motor 10 so that the deviation approaches zero by performing processes such as proportional, integral, and derivative with respect to 2a is generated and output. PW
The M signal generation unit 44 generates and outputs a PWM (pulse width modulation) signal 44a for performing the PWM operation of the electric motor 10 based on the drive control signal 43a. The gate drive circuit unit 45 drives the gates of the field effect transistors Q1 to Q4 based on the PWM signal 44a to drive the field effect transistors Q1 to Q4.

With the above configuration, the conventional control device 20
J performs PWM control of the electric power supplied from the battery power supply 19 to the electric motor 10 based on the steering torque Tp detected by the steering torque detector 12, and controls the output power (steering assist torque) of the electric motor 10.

[0011]

The conventional control device 20J shown in FIG. 2 feeds back the current supplied to the motor 10 so that the deviation between the target current IT and the motor current 41a from which high-frequency components have been removed approaches zero. Controlling. When an operation of turning the steering wheel is performed quickly and the target current changes greatly in a short time, the motor current changes greatly in response to the change in the target current. Even if the motor current IM detected by the motor current detector 14 changes greatly in a short time, the motor current signal 41a from which the high-frequency component has been removed is supplied to the deviation calculation unit 42 via the high-frequency component removal unit 41. Then, a time delay occurs in the motor current signal 41a supplied to the deviation calculation unit 42 with respect to the change in the motor current IM.

When the control device 20J is configured using a microcomputer system, the motor current IM detected by the motor current detector 14 is taken in as digital data via an A / D converter. In this case, the motor current IM is set to A /
The motor current data is obtained by D-conversion, and the obtained motor current data is subjected to digital filter processing to remove high-frequency components. A time delay occurs in the supplied motor current signal 41a.

For this reason, when a steering operation for increasing the target current IT in a short time is performed, the motor current IM actually supplied to the motor 10 has reached a current value corresponding to the target current IT. In some cases, the feedback current value supplied to the deviation calculation unit 42 may be delayed in time. In this case, the deviation calculation unit 42 outputs the deviation signal 42a for further increasing the motor current, so that the current supplied to the motor 10 may temporarily become excessively large. If the motor current temporarily becomes excessive, the characteristics of the electric field effect transistors Q1 to Q4 constituting the electric motor 10 and the electric motor drive circuit 46 may deteriorate, which is not desirable.

The present invention has been made to solve such a problem. Even when a steering operation for increasing the motor current in a short time is performed, the current that actually flows through the motor due to time delay or hunting of the feedback control system. It is an object of the present invention to provide an electric power steering device that can prevent the power from becoming excessive.

[0015]

An electric power steering apparatus according to a first aspect of the present invention sets a target current to be supplied to an electric motor based on at least a steering torque detected by a steering torque detector. In an electric power steering apparatus including a target current setting unit and a motor drive unit that feedback-controls a current supplied to the motor based on a deviation between the target current and the motor current detected by the motor current detector, a target current unit A target current change amount limiting unit that limits the amount of change per unit time is provided.

An electric power steering apparatus according to a second aspect of the present invention is characterized in that the electric power steering apparatus further comprises a target current limiting section for correcting the target current to decrease when the target current exceeds a predetermined value.

According to a third aspect of the present invention, the electric power steering apparatus further comprises a target current limiting section for reducing and correcting the target current when the motor current detected by the motor current detector exceeds a predetermined value. It is characterized by.

According to a fourth aspect of the present invention, there is provided an electric power steering apparatus, wherein a motor speed detecting section for detecting a rotational speed of the motor, and a target when the rotational speed detected by the motor speed detecting section exceeds a predetermined value set in advance. A target current limiting section for reducing and correcting the current.

According to a fifth aspect of the present invention, the electric power steering apparatus further comprises a target current limiting section for correcting the target current to decrease when the target current change per unit time exceeds a predetermined allowable change. It is characterized by.

According to a sixth aspect of the present invention, when the variation per unit time of the motor current detected by the motor current detector exceeds a predetermined allowable variation, the target current is reduced and corrected. A target current limiting unit is provided.

According to a seventh aspect of the present invention, in the electric power steering apparatus, the target current exceeds a predetermined value, and a change amount of the target current per unit time exceeds a predetermined allowable change amount. Is provided with a target current limiter for reducing and correcting the target current.

According to an eighth aspect of the present invention, in the electric power steering apparatus, the motor current detected by the motor current detector exceeds a predetermined value, and the amount of change in the motor current per unit time is set in advance. A target current limiter is provided for reducing and correcting the target current when the allowable change amount is exceeded.

The electric power steering apparatus according to the first aspect of the present invention includes the target current change amount limiting unit that limits the amount of change in the target current per unit time. Can be limited to a predetermined value or less. By limiting the amount of change in the target current per unit time to a value corresponding to the response time of the feedback control, it is possible to prevent the current that actually flows through the motor from becoming excessively large. Deterioration of characteristics of the effect transistor can be prevented.

In the electric power steering apparatus according to the second aspect, the target current is reduced and corrected when the target current exceeds a predetermined value. Therefore, the target current approaches the maximum rated current of the motor. In this case (when the target current is, for example, about 80 to 90% of the maximum rated current of the motor), the target current can be reduced to prevent the current actually flowing through the motor from becoming excessive. In the range where the target current is small, even if the amount of change in the target current per unit time is large, no limitation is imposed on the target current, so that steering responsiveness does not decrease.

According to a third aspect of the present invention, when the motor current detected by the motor current detector exceeds a predetermined value (for example, about 80 to 90% of the maximum rated current of the motor). In addition, since the target current is reduced and corrected, it is possible to prevent the motor current from becoming excessively large even when the feedback control system has a response delay.

According to a fourth aspect of the present invention, the electric power steering apparatus is configured such that the target current is reduced and corrected when the rotational speed of the electric motor detected by the electric motor speed detector exceeds a predetermined value. Even if there is a response delay in the current feedback control system, it is possible to prevent the motor current from becoming excessive. In order to input the motor current that is being subjected to switching control by the PWM operation to the feedback control system, it is necessary to remove a high-frequency component accompanying the switching operation, which causes a time delay in the motor current detection operation. Since the rotation speed of the motor corresponds to the motor current, the motor current can be detected without time delay based on the rotation speed of the motor, and if there is a possibility that the motor current may become overcurrent, the target current is reduced and corrected. By doing so, overcurrent can be prevented.

In the electric power steering apparatus according to the fifth aspect, the target current is reduced and corrected when the change amount of the target current per unit time exceeds a predetermined allowable change amount. Only when the amount of change per unit time exceeds the permissible amount of change, the target current is reduced and corrected, thereby preventing the motor current from becoming excessive. The target current decrease correction is performed only when the change amount of the target current per unit time exceeds the allowable change amount.Otherwise, the target current decrease correction is not performed, so that the steering response deteriorates. There is no.

In the electric power steering apparatus according to the present invention, the target current is reduced and corrected when the variation of the motor current per unit time exceeds a predetermined allowable variation. Only when the variation per unit time exceeds the permissible variation, the target current is corrected to decrease. This prevents the motor current from becoming excessive. If the change amount of the motor current per unit time is less than the allowable change amount, the reduction correction of the target current is not performed, so that the steering response does not decrease.

The electric power steering apparatus according to claim 7 is configured so as to reduce and correct the target current only when the target current is large (for example, about 80 to 90% of the rated current of the motor) and the amount of change in the target current is large. Therefore, in the range where the target current is not large, the steering responsiveness does not decrease even if the steering is performed sharply. When the target current is large and the change amount is large, it is possible to prevent the motor current from becoming excessive.

In the electric power steering apparatus according to the present invention, the motor current exceeds a predetermined value (for example, about 80 to 90% of the rated current of the motor) and the motor current per unit time. Since the target current is reduced and corrected when the change amount exceeds a preset allowable change amount, it is possible to prevent the motor current from becoming excessive. If the motor current is less than the predetermined value, the target current is not corrected to decrease even if the change amount is large, so that the steering response does not decrease.

[0031]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 3 is a block diagram of a control device of the electric power steering device according to the first embodiment. The control device 20A shown in FIG.
Target current variation limiting section 51 between the motor and motor driving section 40
Is that the conventional control device 20 shown in FIG.
Different from J.

The target current IT output from the target current setting unit 30 designates the turning direction of the motor 10 (left and right directions of the steering assist torque) by positive and negative polarities, and sets the target motor current value (right and left directions) by its absolute value. Target current value).

The target current variation limiting section 51 outputs the target current I
The amount of change per unit time is monitored with respect to the change in which the absolute value of T increases, and if the amount of change per unit time is less than a preset allowable amount of change, the target output from the target current setting unit 30 The current IT is supplied to the deviation calculation unit 42 as it is. When the amount of change per unit time exceeds a predetermined allowable change amount, the target current change amount limiting unit 51 limits the target current so that the amount of change per unit time does not exceed the allowable change amount, The restricted target current 51a is calculated by the deviation calculating unit 42.
Supply to

FIG. 4 is an explanatory diagram showing the operation of the target current change amount limiting section. Here, the allowable change amount per unit time is set to 10 amps per millisecond (10 A / 1 mS). If the amount of change in the target current IT is within 10 amps per millisecond, even if overshoot or undershoot occurs in the current actually flowing through the motor 10 due to a response delay of the feedback control system, the target current and It is assumed that the current actually flowing through the motor 10 does not become an overcurrent even when the difference from the current actually flowing through the motor 10 falls within a predetermined value and the target current reaches the maximum value.

In FIG. 4, the vertical axis represents the absolute value of the target current, and the horizontal axis represents the passage of time. The alternate long and short dash line indicates a change characteristic of the target current IT output from the target current setting unit 30. The solid line indicates the change characteristic of the target current (the target current whose change amount per unit time is limited) output from the target current change amount limiting unit 51. From time 0 to 4 milliseconds, the amount of change in the target current IT per unit time is less than the permissible change (10 amps per millisecond), so the target current IT is output from the target current change amount limiting unit 51 as it is. You. Since the amount of change in the target current IT per unit time exceeds the permissible amount of change (10 amps per millisecond) during the time period of 4 to 6 milliseconds, the target current output from the target current change amount limiting section 51 is output. 51a is limited so that the variation per unit time does not exceed the allowable variation (10 amps per millisecond).

Therefore, even when the target current IT set by the target current setting unit 30 increases in a short time due to a sudden steering operation or the like, the target current limited by the target current change amount limiting unit 51 is limited. 51a, and
Since the generated target current 51a is supplied to the motor drive unit 40, the current feedback control by the motor drive unit 40 is stabilized. Therefore, even when the steering operation for rapidly increasing the manual steering torque is performed, it is possible to prevent the overcurrent from being supplied to the electric motor 10.

In FIG. 3, the target current change amount limiting section 51
Are provided independently, but the target current setting unit 30 may have a function of the target current change amount unit 51.

FIG. 5 is a block diagram of a control device of the electric power steering apparatus according to the second aspect. The control device 20B shown in FIG. 5 differs from the conventional control device 20J shown in FIG. 2 in that a target current limiter 52 is interposed between the target current setting unit 30 and the motor drive unit 40. When the absolute value of the target current IT output from the target current setting unit 30 is smaller than a predetermined value set in advance, the target current limiting unit 52 outputs the target current I output from the target current setting unit 30.
T is supplied to the deviation calculation unit 42 as it is. When the absolute value of the target current IT output from the target current setting unit 30 exceeds a predetermined value set in advance, the target current limiting unit 52 outputs a current 52a obtained by reducing the target current IT.

FIG. 6 is an explanatory diagram showing an operation example of the target current limiting section. In FIG. 6, the vertical axis represents the absolute value of the target current, and the horizontal axis represents the passage of time. The alternate long and short dash line indicates a change characteristic of the target current IT output from the target current setting unit 30. The solid line indicates a change characteristic of the target current (the target current whose upper limit is limited) output from the target current limiter 52. FIG. 6 shows an example in which the maximum value of the maximum rated current of the motor and the maximum value of the target current IT are set to 100 amps, and the limit start current of the target current IT is set to 90 amps.

The target current limiter 52 sets the upper limit of the target current 52a to be supplied to the deviation calculator 42 for a predetermined time (for example, 4 milliseconds) from the time when the target current IT exceeds 90 amps, which is the limit start current. The value is limited to 90 amps and for the next predetermined time (4 to 8
Milliseconds) limits the upper limit to 91 amps. In this way, the target current limiter 52 gradually increases the upper limit of the target current 52a to be supplied to the deviation calculator 42 in accordance with the elapsed time from when the target current IT exceeds the limit start current. Go. Therefore, even when the target current IT changes to the maximum value of 100 amps in a short time, the current 52a supplied to the motor drive unit 40 increases stepwise with the passage of time from 90 amps, which is the limit start current value. Become. Therefore, even when the steering operation for rapidly increasing the manual steering torque is performed, the upper limit value of the current 52a supplied to the motor drive unit 40 is limited stepwise from the time when the target current IT exceeds the limit start current. The current feedback control by the drive unit 40 is stably performed. Therefore, even if the steering operation for rapidly increasing the manual steering torque is performed,
It is possible to prevent an overcurrent from being supplied to the electric motor 10.

The target current limiting section 52 outputs the target current I
When T is the limit start current, for example, when it exceeds 80 amps, a value of 1/2 of the value exceeding 80 amps is set to 8
A value added to 0 amps is output, and at the next time, the difference between the target current IT and the previously output value is, for example, １ ／.
The target current IT may be reduced and corrected by sequentially repeating outputting a value obtained by adding the value multiplied by the value to the previously output value.

FIG. 7 is a block diagram of a control device of the electric power steering apparatus according to the third aspect. The control device 20C shown in FIG. 7 includes a target current limiting unit 53 interposed between the target current setting unit 30 and the motor driving unit 40. When the motor current 41a from which the high-frequency component has been removed exceeds the maximum rated current, for example, 80%, the target current limiting unit 53 sets the target current supplied to the motor driving unit 40 to exceed the maximum rated current, for example, 85%. The limit condition is gradually raised toward 100% over time. Therefore, even if the target current IT is a large value substantially corresponding to the rated current value, the upper limit value of the current value supplied to the motor drive unit 40 is gradually limited in accordance with the above-described limiting condition. As a result, the current feedback control by the motor drive unit 40 is stably performed. Therefore, even when a steering operation for rapidly increasing the manual steering torque is performed, it is possible to prevent the overcurrent from being supplied to the electric motor 10. The motor current signal before removing the high-frequency component may be used as the motor current signal.

FIG. 8 is a block diagram of a control device for an electric power steering apparatus according to a fourth aspect. Claim 4
The electric power steering device according to the present invention detects the rotation speed of the electric motor 10 and detects the electric motor speed signal (hereinafter referred to as the electric motor speed S).
M) is provided. The motor speed detection unit 15 includes a power generation mechanism or the like, and may output a voltage corresponding to the rotation speed of the motor 10 or output a pulse signal each time the output shaft of the motor rotates a predetermined angle. . The motor speed detector 15
Alternatively, the motor voltage VM supplied to the motor 10 may be detected by a voltage detector, and the estimated motor speed SM may be obtained by calculation based on the motor voltage VM and the motor current IM.

The estimated motor speed SM can be obtained by the following equation. SM = (VM−IM · RM) / Kp Here, RM is a resistance value of the motor, and Kp is an induced voltage coefficient.

When the motor speed SM is less than a predetermined value, the target current limiter 54 supplies the target current IT to the motor driver 40 as it is. Target current limiter 5
When the motor speed SM exceeds a predetermined value, the correction target current 5 is a correction target current obtained by reducing the target current IT.
4a is supplied to the motor drive unit 40. Since the motor speed SM corresponds to the current flowing through the motor, the motor speed S
By correcting the target current IT to decrease when M exceeds a predetermined value, it is possible to prevent an overcurrent from flowing through the electric motor 10.

FIG. 9 is a block diagram of a control device of the electric power steering apparatus according to the fifth aspect. The control device 20E shown in FIG. 9 includes a target current limiting unit 55 interposed between the target current setting unit 30 and the motor driving unit 40. The target current limiting unit 55 monitors the amount of change in the target current IT per unit time from the target current setting unit 30. If the amount of change per unit time is less than the preset allowable amount of change,
The target current IT output from the target current setting unit 30 is supplied to the motor drive unit 40 as it is. Target current limiter 55
When the change amount per unit time exceeds a preset allowable change amount, the correction target current 55a obtained by reducing the target current IT is supplied to the motor drive unit 40. The target current limiter 55 increases the decrease correction amount as the change amount per unit time increases.

FIG. 10 is an explanatory diagram showing an example of the operation of the target current limiting section shown in FIG. The target current limiter 55
If the amount of change in the target current IT per unit time is, for example, less than 5 amps / millisecond, the target current IT is output as it is by multiplying the target current IT by the correction coefficient 1. The correction coefficient is set to 1 until the amount of change in the target current IT per unit time is, for example, 5 amps / 1 millisecond. When the amount of change per unit time is, for example, between 5 amps / 1 millisecond and 10 amps / 1 millisecond, the correction coefficient is increased from 1 to 0 in accordance with the increase in the amount of change per unit time.
It is set to sequentially smaller values to 5. When the variation per unit time is 10 amps / 1 millisecond or more, the correction coefficient is set to 0.
5 is set.

Therefore, the amount of change in the target current IT per unit time due to sudden steering operation or the like is, for example, 5 amps / 1.
If the time exceeds milliseconds, the target current (corrected target current) 55a supplied to the motor drive unit 40 is reduced and corrected in accordance with the amount of change in the target current IT per unit time.
Thus, even when a steering operation for rapidly increasing the manual steering torque is performed, it is possible to prevent an overcurrent from being supplied to the electric motor 10.

FIG. 11 is a block diagram of a control device for an electric power steering device according to claim 6. FIG.
The control device 20 </ b> F shown in FIG. 1 has a target current limiting unit 56 interposed between the target current setting unit 30 and the motor driving unit 40. The target current limiter 56 monitors the amount of change per unit time of the motor current 41a from which high-frequency components have been removed,
If the amount of change per unit time is less than a preset allowable amount of change, the target current I output from the target current setting unit 30 is output.
T is supplied to the motor drive unit 40 as it is. When the amount of change per unit time exceeds a preset allowable amount of change, the target current limiter 56 supplies the motor drive unit 40 with a corrected target current 56a obtained by reducing the target current IT.
The target current limiting section 56 increases the decrease correction amount as the change amount per unit time increases.

FIG. 12 is an explanatory diagram showing an operation example of the target current limiting section shown in FIG. Target current limiter 56
If the amount of change in the motor current IM per unit time is, for example, less than 5 amps / 1 millisecond, the target current I
By multiplying T by the correction coefficient 1, the target current IT is output as it is. The correction coefficient is set to 1 until the amount of change in the motor current IM per unit time is, for example, 5 amps / 1 millisecond. When the amount of change per unit time is, for example, 5 amps / 1 millisecond to 10 amps / 1 millisecond, the correction coefficient is sequentially increased from 1 to 0.5 in accordance with the increase in the amount of change per unit time. It is set to a small value. When the amount of change per unit time is 10 amps / 1 millisecond or more, the correction coefficient is set to 0.5.

Therefore, if the amount of change in the motor current IM per unit time exceeds, for example, 5 amps / 1 millisecond due to a sudden steering operation or the like, the amount of change in the motor current IM per unit time corresponds to the amount of change. Then, the target current (corrected target current) 56a supplied to the motor drive unit 40 is reduced and corrected. Thus, even when a steering operation for rapidly increasing the manual steering torque is performed, it is possible to prevent an overcurrent from being supplied to the electric motor 10. The motor current signal before removing the high-frequency component may be used as the motor current signal.

FIG. 13 is a block diagram of a control device of the electric power steering apparatus according to claim 7. FIG.
The control device 20G includes a target current limiting unit 57 interposed between the target current setting unit 30 and the motor driving unit 40. The target current limiting unit 57 monitors the absolute value of the target current IT output from the target current setting unit 30 and the amount of change in the target current IT per unit time. Target current limiter 57
When the target current IT is less than a preset limit start current (for example, 80 amps), the target current IT output from the target current setting unit 30 is supplied to the motor drive unit 40 as it is. The target current limiter 57 outputs the target current I
If T exceeds a preset limit start current (for example, 80 amperes), a correction current 57a obtained by reducing the target current IT in accordance with the amount of change per unit time of the target current IT is supplied to the motor drive unit 40. Supply to

Even if the target current IT exceeds a preset limit start current (for example, 80 amps), the target current limiter 57 determines that the amount of increase in the target current IT per unit time is, for example, 20 amps / 1. If it is less than milliseconds,
The target current IT output from the target current setting unit 30 is supplied to the motor drive unit 40 as it is. Target current limiter 57
If the target current IT exceeds a preset limit start current (for example, 80 amps) and the amount of change in the target current IT per unit time is, for example, 20 amps / 1 millisecond or more, the motor The amount by which the correction target current 57a supplied to the drive unit 40 is increased per unit time is limited so as not to exceed, for example, 20 amps / 1 millisecond.

FIG. 14 is an explanatory diagram showing an operation example of the target current limiting section shown in FIG. The target current limiter 57
When the target current IT exceeds the limit start current, the amount of change in the target current per unit time increases by a predetermined amount (for example, 20
Ampere per millisecond). Therefore, even when the target current IT increases in a short time due to a sudden steering operation or the like, the amount of increase in the target current per unit time after the limit start current is exceeded by a predetermined amount (for example, 20 amps / (1 millisecond). As a result, the current feedback control by the motor drive unit 40 is stably performed. Therefore, even when the steering operation for rapidly increasing the manual steering torque is performed, it is possible to prevent the overcurrent from being supplied to the electric motor 10.

The target current limiting section 57 outputs the target current I
If T exceeds the limit start current, for example, 80 amperes, and if the amount of increase in the target current IT per unit time exceeds the permissible amount, for example, the excess of 80 amperes, for example, A value obtained by adding a value of 1/4 to 80 amps is output. At the next time point, a value obtained by multiplying the difference between the target current IT and the previously output value by, for example, 1/4 is output first. The target current IT may be corrected to decrease by sequentially repeating outputting the value added to the target current IT.
Further, as the amount of increase in the target current IT per unit time increases, the coefficient by which the amount exceeding 80 amps is multiplied is set to be gradually smaller, such as 1/2, 1/4, 1/8. You may.

FIG. 15 is a block diagram of a control device of the electric power steering apparatus according to the eighth aspect. FIG.
The control device 20H shown in FIG. 1 has a target current limiter 58 interposed between the target current setting unit 30 and the motor drive unit 40. The target current limiter 58 monitors the absolute value of the motor current 41a from which high-frequency components have been removed and the amount of change per unit time of the motor current 41a. The target current limiting unit 58 determines that the motor current IM has a preset limit start current (for example, 8
0 ampere), the target current IT output from the target current setting unit 30 is
Supply to When the motor current IM exceeds a preset limit start current (for example, 80 amps), the target current limiting unit 58 decreases and corrects the target current IT according to the amount of change in the motor current IM per unit time. Correction current 58
is supplied to the motor drive unit 40.

Even if the motor current IM exceeds a preset limit start current (for example, 80 amps), the target current limiter 58 can increase the motor current IM per unit time by, for example, 10 amps / 1. If the time is less than the millisecond, the target current IT output from the target current setting unit 30 is supplied to the motor drive unit 40 as it is. The target current limiter 58 determines that the motor current IM has exceeded a preset limit start current (for example, 80 amps) and that the target current IT
Is, for example, 10 amps /
If it is 1 millisecond or more, the amount of increase in the correction target current 58a supplied to the motor drive unit 40 per unit time is:
For example, it is limited so as not to exceed 10 amps / 1 millisecond.

In the target current limiting section 58, the motor current IM exceeds the limit start current, for example, 80 amperes, and the amount of increase in the motor current IM per unit time exceeds the allowable amount. In this case, a value obtained by adding a value of, for example, 1/4 that exceeds 80 amps to 80 amps is output, and at the next time point, the difference between the target current IT and the previously output value is calculated, for example. The target current IT may be reduced and corrected by sequentially repeating outputting a value obtained by adding the value multiplied by ４ to the previously output value. Further, as the amount of increase in the target current IT per unit time increases, the coefficient by which the amount exceeding 80 amps is multiplied is set to be gradually smaller, such as 1/2, 1/4, 1/8. You may.

The target current limiting section 58 determines that the motor current IM exceeds the limit start current, for example, 80 amperes, and that the amount of increase in the motor current IM per unit time exceeds the allowable amount. In this case, the target current IT is reduced and corrected by multiplying the target current IT by a correction coefficient (a value smaller than 1) set in advance corresponding to the amount of change per unit time of the motor current IM. 58a may be supplied to the motor drive unit 40. The motor current signal before removing the high-frequency component may be used as the motor current signal.

FIG. 16 is an explanatory view showing an overcurrent preventing effect in the electric power steering apparatus according to the eighth aspect. The vertical axis indicates the current value, and the horizontal axis indicates time. FIG.
Is that the operation of turning the steering (handle) to the left is performed in a short time from the state where the steering (handle) is turned to the right and a large manual steering torque is applied, and the steering (handle) is turned to the left; FIG. 9 shows a change in the target current IT and a change in the motor current IM when the state in which the manual steering torque is large is shown.

In a conventional electric power steering device,
Since the target current IT is set in accordance with the manual steering torque, when the steering operation is performed from right to left, the target current IT is quickly changed to the final target current value as indicated by a chain line. Change. Due to the response delay of the current feedback control system, in the conventional electric power steering device,
The motor current actually flowing through the motor greatly exceeds the final target current value as shown by a two-dot chain line. Therefore, when the final target current value is close to the rated current value of the motor, an overcurrent state may occur in which the motor current actually flowing through the motor exceeds the rated current value of the motor.

In the electric power steering apparatus according to the present invention, the target current change limiter 51 and the target current limiter 5
Since the target current is reduced and corrected by the steps 2 to 58 so as not to cause an overcurrent state, the motor current actually flowing through the motor does not greatly deviate from the target current as shown by the dotted line. In this manner, by correcting the target current to decrease, it is possible to suppress overshoot due to a control delay element. Therefore, it is possible to prevent an overcurrent from flowing through the electric motor and each of the field effect transistors constituting the electric motor drive circuit.

[0063]

As described above, the first aspect of the present invention is as follows.
The electric power steering device described in (1) includes a target current change amount limiting unit that limits the amount of change in the target current per unit time, so that even when sudden steering is performed, the amount of change in the target current per unit time is determined. It can be restricted below the value. By limiting the amount of change in the target current per unit time to a value corresponding to the response time of the feedback control, it is possible to prevent the current that actually flows through the motor from becoming excessively large. Deterioration of characteristics of the effect transistor can be prevented.

In the electric power steering apparatus according to the present invention, the target current is reduced and corrected when the target current exceeds a predetermined value, so that the target current approaches the maximum rated current of the motor. In this case (when the target current is, for example, about 80 to 90% of the maximum rated current of the motor), the target current can be reduced to prevent the current actually flowing through the motor from becoming excessive. In the range where the target current is small, even if the amount of change in the target current per unit time is large, no limitation is imposed on the target current, so that steering responsiveness does not decrease.

In the electric power steering apparatus according to the third aspect, the motor current detected by the motor current detector exceeds a predetermined value (for example, about 80 to 90% of the maximum rated current of the motor). In case,
Since the target current is reduced and corrected, it is possible to prevent the motor current from becoming excessively large even when the feedback control system has a response delay.

In the electric power steering apparatus according to the present invention, the target current is reduced and corrected when the rotation speed of the motor detected by the motor speed detector exceeds a predetermined value. Even if there is a response delay in the motor current feedback control system, it is possible to prevent the motor current from becoming excessive. In order to input the motor current that is being subjected to switching control by the PWM operation to the feedback control system, it is necessary to remove a high-frequency component accompanying the switching operation, which causes a time delay in the motor current detection operation. Since the rotation speed of the motor corresponds to the motor current, the motor current can be detected without time delay based on the rotation speed of the motor, and if there is a possibility that the motor current may become overcurrent, the target current is reduced and corrected. By doing so, overcurrent can be prevented.

In the electric power steering apparatus according to the present invention, the target current is reduced and corrected when the change amount of the target current per unit time exceeds a preset allowable change amount. The target current is reduced and corrected only when the change amount per unit time exceeds the allowable change amount, so that the motor current can be prevented from becoming excessive. The correction of the target current is reduced only when the steering speed is extremely high, but otherwise the reduction of the target current is not corrected, so that the steering response is not reduced.

In the electric power steering apparatus according to the present invention, the target current is reduced and corrected when the variation of the motor current per unit time exceeds a predetermined allowable variation. The target current is corrected to decrease only when the variation per unit time exceeds the allowable variation. This prevents the motor current from becoming excessive. If the change amount of the motor current per unit time is less than the allowable change amount, the decrease correction of the target current is not performed.
Steering responsiveness does not decrease.

In the electric power steering apparatus according to the present invention, the target current is reduced and corrected only when the target current is large (for example, about 80 to 90% of the rated current of the motor) and the change amount of the target current is large. With this configuration, the steering responsiveness does not decrease even if the driver steers sharply in a range where the target current is not large. When the target current is large and the change amount is large, it is possible to prevent the motor current from becoming excessive.

In the electric power steering apparatus according to the present invention, the motor current exceeds a predetermined value (for example, about 80 to 90% of the rated current of the motor) and the motor current per unit time. The target current is reduced and corrected when the amount of change exceeds the preset allowable amount of change, so that the motor current can be prevented from becoming excessive. If the motor current is less than the predetermined value, the target current is not corrected to decrease even if the change amount is large, so that the steering response does not decrease.

[Brief description of the drawings]

FIG. 1 is a schematic structural view of an electric power steering device.

FIG. 2 is a block diagram of a conventional electric power steering device.

FIG. 3 is a block diagram of a control device of the electric power steering device according to claim 1;

FIG. 4 is an explanatory diagram showing an operation of a target current change amount limiting unit.

FIG. 5 is a block diagram of a control device of the electric power steering device according to claim 2;

FIG. 6 is an explanatory diagram showing an operation example of a target current limiting unit.

FIG. 7 is a block diagram of a control device for an electric power steering device according to claim 3;

FIG. 8 is a block diagram of a control device for an electric power steering device according to claim 4.

FIG. 9 is a block diagram of a control device of the electric power steering device according to claim 5;

FIG. 10 is an explanatory diagram showing an operation example of the target current limiting section shown in FIG. 9;

FIG. 11 is a block diagram of a control device for an electric power steering device according to claim 6;

FIG. 12 is an explanatory diagram showing an operation example of the target current limiting section shown in FIG. 11;

FIG. 13 is a block diagram of a control device of the electric power steering device according to claim 7;

FIG. 14 is an explanatory diagram showing an operation example of the target current limiting unit shown in FIG.

FIG. 15 is a block diagram of a control device for an electric power steering device according to claim 8;

FIG. 16 is an explanatory diagram showing an overcurrent prevention effect in the electric power steering device according to claim 8;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electric power steering device, 2 ... Steering wheel (handle), 10 ... Electric motor, 12 ... Steering torque detector, 13 ... Vehicle speed detector, 14 ... Electric motor current detector,
15 ... motor speed detecting section, 20A-20H ... control device
Reference numeral 30: target current setting unit, 40: motor drive unit, 41: high frequency component removal unit, 42: deviation calculation unit, 43: PID control unit, 44: PWM signal generation unit, 45: gate drive circuit unit, 46: motor drive Circuits, 51: target current change limiter, 52 to 58: target current limiter, Q1 to Q4: field effect transistors.

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[Procedure amendment]

[Submission date] June 10, 1999

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Document Name] Statement

[Title of the Invention] Electric power steering device

[Claims]

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus for reducing the steering force of a driver by applying the power of an electric motor to a steering system, and more particularly, to detecting a current actually supplied to the electric motor. The present invention relates to an electric power steering device that performs feedback control of a current supplied to an electric motor and prevents an excessive increase in electric motor current due to a response delay of the feedback control.

[0002]

2. Description of the Related Art FIG. 1 is a schematic structural view of an electric power steering apparatus. The electric power steering device 1 includes an electric motor 10 in a steering system, and controls the power supplied from the electric motor 10 by using the control device 20 to reduce the steering force of the driver.

[0003] A steering shaft 3 integrally provided on a steering wheel (handle) 2 includes a universal joint 4.
The rack & pinion mechanism 5 is connected to a pinion 6 via a connection shaft 4 having a and b. The rack shaft 7 includes rack teeth 7a that mesh with the pinion 6. The rack and pinion mechanism 5 converts the rotation of the pinion 6 into a reciprocating motion of the rack 7 in the axial direction. Left and right front wheels 9 as rolling wheels are connected to both ends of the rack shaft 7 via tie rods 8. When the steering wheel 2 is steered, the front wheels 9 swing through the rack and pinion mechanism 5 and the tie rods 8. Thereby, the direction of the vehicle can be changed.

In order to reduce the steering force, a motor 10 for supplying a steering assist torque (assist torque) is connected to a rack shaft 7.
The rotation output of the electric motor 10 is converted into a thrust through a ball screw mechanism 11 provided substantially parallel to the rack shaft 7 so as to act on the rack shaft 7. Electric motor 1
The drive side helical gear 10a is provided integrally with the rotor 0. The helical gear 11b and the drive-side helical gear 10a provided integrally with the shaft end of the screw shaft 11a of the ball screw mechanism 11 are meshed. The nut 11c of the ball screw mechanism 11 is connected to the rack shaft 7.

A steering torque detector 12 provided on a steering box (not shown) detects a manual steering torque acting on the pinion 6 and supplies a steering torque signal Tp corresponding to the detected steering torque to the control device 20. I have. The control device 20 controls the output power (steering assist torque) of the electric motor 10 by operating the electric motor 10 with the steering torque signal Tp as a main signal.

FIG. 2 is a block diagram of a conventional electric power steering apparatus. The conventional control device 20J includes a target current setting unit 30 and a motor driving unit 40. The motor drive unit 40 includes a high-frequency component removal unit 41, a deviation calculation unit 42, a PID control unit 43, and a PWM signal generation unit 44.
, A gate drive circuit section 45, and a motor drive circuit 46 in which four power field effect transistors Q1 to Q4 are connected in an H-type bridge. Reference numeral 12 denotes a steering torque detector,
Reference numeral 13 is a vehicle speed detector, reference numeral 14 is a motor current detector,
Reference numeral 19 denotes a battery power supply. Steering torque detector 12
Outputs a steering torque signal Tp related to the direction and magnitude of the manual steering torque. The vehicle speed detector 13 outputs a vehicle speed signal VS relating to the speed of the vehicle. The motor current detector 14 outputs a motor current signal (hereinafter referred to as “motor current”) IM related to the direction and magnitude of the current flowing through the motor 10.

The target current setting unit 30 supplies a basic steering torque to the electric motor 10 based on the steering torque signal Tp output from the steering torque detector 12 so that the electric motor 10 generates a steering assist torque corresponding to the steering torque. The current value is obtained, the basic current value is corrected according to the vehicle speed detected by the vehicle speed detector 13, and the corrected current value is output as a target current signal (hereinafter, referred to as a target current) IT. In the vehicle speed correction, the target current is set smaller as the vehicle speed becomes higher. The target current IT is the motor drive unit 4
0.

The high-frequency component removing section 41 removes high-frequency components of the motor current IM detected by the motor current detector 14 and outputs a motor current 41a from which high-frequency components have been removed. The steering assist torque supplied from the motor 10 is controlled by performing the PWM (pulse width modulation) operation of the motor 10. For this reason, the motor current IM detected by the motor current detector 14 contains a high-frequency component accompanying the switching control of the motor current. When feedback control is performed using the motor current IM including the high-frequency component,
Since the feedback control is not performed correctly, the high-frequency component removing unit 41 removes the high-frequency component.

The deviation calculator 42 calculates a deviation between the target current IT and the motor current 41a from which high-frequency components have been removed, and outputs a deviation signal 42a. The PID control unit 43 outputs the deviation signal 4
A drive control signal 43a for controlling the current supplied to the electric motor 10 so that the deviation approaches zero by performing processes such as proportional, integral, and derivative with respect to 2a is generated and output. PW
The M signal generation unit 44 generates and outputs a PWM (pulse width modulation) signal 44a for performing the PWM operation of the electric motor 10 based on the drive control signal 43a. The gate drive circuit unit 45 drives the gates of the field effect transistors Q1 to Q4 based on the PWM signal 44a to drive the field effect transistors Q1 to Q4.

With the above configuration, the conventional control device 20
J performs PWM control of the electric power supplied from the battery power supply 19 to the electric motor 10 based on the steering torque Tp detected by the steering torque detector 12, and controls the output power (steering assist torque) of the electric motor 10.

[0011]

The conventional control device 20J shown in FIG. 2 feeds back the current supplied to the motor 10 so that the deviation between the target current IT and the motor current 41a from which high-frequency components have been removed approaches zero. Controlling. When an operation of turning the steering wheel is performed quickly and the target current changes greatly in a short time, the motor current changes greatly in response to the change in the target current. Even if the motor current IM detected by the motor current detector 14 changes greatly in a short time, the motor current signal 41a from which the high-frequency component has been removed is supplied to the deviation calculation unit 42 via the high-frequency component removal unit 41. Then, a time delay occurs in the motor current signal 41a supplied to the deviation calculation unit 42 with respect to the change in the motor current IM.

When the control device 20J is configured using a microcomputer system, the motor current IM detected by the motor current detector 14 is taken in as digital data via an A / D converter. In this case, the motor current IM is set to A /
The motor current data is obtained by D-conversion, and the obtained motor current data is subjected to digital filter processing to remove high-frequency components. A time delay occurs in the supplied motor current signal 41a.

For this reason, when a steering operation for increasing the target current IT in a short time is performed, the motor current IM actually supplied to the motor 10 has reached a current value corresponding to the target current IT. In some cases, the feedback current value supplied to the deviation calculation unit 42 may be delayed in time. In this case, the deviation calculation unit 42 outputs the deviation signal 42a for further increasing the motor current, so that the current supplied to the motor 10 may temporarily become excessively large. If the motor current temporarily becomes excessive, the characteristics of the electric field effect transistors Q1 to Q4 constituting the electric motor 10 and the electric motor drive circuit 46 may deteriorate, which is not desirable.

The present invention has been made to solve such a problem. Even when a steering operation for increasing the motor current in a short time is performed, the current that actually flows through the motor due to time delay or hunting of the feedback control system. It is an object of the present invention to provide an electric power steering device that can prevent the power from becoming excessive.

[0015]

[MEANS FOR SOLVING THE PROBLEMS]
An electric power steering device according to the present invention includes a target current setting unit that sets a target current to be supplied to an electric motor based on at least a steering torque detected by a steering torque detector, and a target current that is detected by the target current and the electric motor current detector. An electric power steering device including a motor drive unit that feedback-controls a current supplied to the motor based on a deviation from the motor current, including a target current change limit unit that limits a change amount of a target current per unit time. It is characterized by having.

The electric power steering apparatus according to the present invention is provided with a target current limiter for decreasing and correcting the target current when the motor current detected by the motor current detector exceeds a predetermined value. Features.

The electric power steering apparatus according to the present invention is provided with a target current limiter for decreasing and correcting the target current when a change amount of the target current per unit time exceeds a preset allowable change amount. Features.

The electric power steering apparatus according to the present invention has a target for decreasing and correcting the target current when the change per unit time of the motor current detected by the motor current detector exceeds a predetermined allowable change. It is characterized by including a current limiting section.

In the electric power steering apparatus according to the present invention , when the target current exceeds a predetermined value and the amount of change of the target current per unit time exceeds an allowable change set in advance. A target current limiting section for reducing and correcting the target current is provided.

In the electric power steering apparatus according to the present invention , the motor current detected by the motor current detector exceeds a predetermined value, and a change amount of the motor current per unit time is set to a predetermined allowable value. When the amount of change is exceeded, a target current limiter for reducing and correcting the target current is provided.

Since the electric power steering apparatus according to the present invention includes the target current change amount limiting section for limiting the change amount of the target current per unit time, even when the steering operation is suddenly performed, the target current per unit time is increased. The amount of change can be limited to a predetermined value or less. By limiting the amount of change in the target current per unit time to a value corresponding to the response time of the feedback control, it is possible to prevent the current that actually flows through the motor from becoming excessively large. Deterioration of characteristics of the effect transistor can be prevented.

The electric power steering apparatus according to the present invention is provided when the motor current detected by the motor current detector exceeds a predetermined value (for example, about 80 to 90% of the maximum rated current of the motor). Since the target current is reduced and corrected, it is possible to prevent the motor current from becoming excessively large even when the feedback control system has a response delay.

The electric power steering apparatus according to the present invention is configured such that the target current is reduced and corrected when the change amount of the target current per unit time exceeds a preset allowable change amount. Only when the amount of change per time exceeds the allowable amount of change, the target current is reduced and corrected, so that the motor current can be prevented from becoming excessive. The target current decrease correction is performed only when the change amount of the target current per unit time exceeds the allowable change amount.Otherwise, the target current decrease correction is not performed, so that the steering response deteriorates. There is no.

In the electric power steering apparatus according to the present invention , the target current is reduced and corrected when the variation of the motor current per unit time exceeds a predetermined allowable variation. Only when the variation per time exceeds the permissible variation, the target current is corrected to decrease. This prevents the motor current from becoming excessive. If the change amount of the motor current per unit time is less than the allowable change amount, the reduction correction of the target current is not performed, so that the steering response does not decrease.

The electric power steering apparatus according to the present invention has a configuration in which the target current is reduced and corrected only when the target current is large (for example, about 80 to 90% of the rated current of the motor) and the change amount of the target current is large. Therefore, in the range where the target current is not large, the steering responsiveness does not decrease even if the steering is performed sharply. When the target current is large and the change amount is large, it is possible to prevent the motor current from becoming excessive.

In the electric power steering apparatus according to the present invention , the motor current exceeds a predetermined value (for example, about 80 to 90% of the rated current of the motor) and the change in the motor current per unit time. Since the target current is reduced and corrected when the amount exceeds a predetermined allowable change amount, it is possible to prevent the motor current from becoming excessive. If the motor current is less than the predetermined value, the target current is not corrected to decrease even if the change amount is large, so that the steering response does not decrease.

[0027]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 3 is a block diagram of a control device of the electric power steering device according to the present invention. The control device 20A shown in FIG.
Target current variation limiting section 51 between the motor and motor driving section 40
Is that the conventional control device 20 shown in FIG.
Different from J.

The target current IT output from the target current setting section 30 specifies the direction of rotation of the motor 10 (left and right directions of the steering assist torque) by positive and negative polarities, and sets the target motor current value (left and right) by its absolute value. Target current value).

The target current variation limiting section 51 outputs the target current I
The amount of change per unit time is monitored with respect to the change in which the absolute value of T increases, and if the amount of change per unit time is less than a preset allowable amount of change, the target output from the target current setting unit 30 The current IT is supplied to the deviation calculation unit 42 as it is. When the amount of change per unit time exceeds a predetermined allowable change amount, the target current change amount limiting unit 51 limits the target current so that the amount of change per unit time does not exceed the allowable change amount, The restricted target current 51a is calculated by the deviation calculating unit 42.
Supply to

FIG . 4 is an explanatory diagram showing the operation of the target current change amount limiting section. Here, the allowable change amount per unit time is set to 10 amps per millisecond (10 A / 1 mS). If the amount of change in the target current IT is within 10 amps per millisecond, even if overshoot or undershoot occurs in the current actually flowing through the motor 10 due to a response delay of the feedback control system, the target current and It is assumed that the current actually flowing through the motor 10 does not become an overcurrent even when the difference from the current actually flowing through the motor 10 falls within a predetermined value and the target current reaches the maximum value.

In FIG . 4, the vertical axis represents the absolute value of the target current, and the horizontal axis represents the passage of time. The alternate long and short dash line indicates a change characteristic of the target current IT output from the target current setting unit 30. The solid line indicates the change characteristic of the target current (the target current whose change amount per unit time is limited) output from the target current change amount limiting unit 51. From time 0 to 4 milliseconds, the amount of change in the target current IT per unit time is less than the permissible change (10 amps per millisecond), so the target current IT is output from the target current change amount limiting unit 51 as it is. You. Since the amount of change in the target current IT per unit time exceeds the permissible amount of change (10 amps per millisecond) during the time period of 4 to 6 milliseconds, the target current output from the target current change amount limiting section 51 is output. 51a is limited so that the variation per unit time does not exceed the allowable variation (10 amps per millisecond).

[0032] Therefore, even when the target current IT which is set by the target current setting unit 30 by the abrupt steering operation or the like is increased in a short time, the target current limiting the amount of change per unit time by the target amount of current change limiting section 51 51a, and
Since the generated target current 51a is supplied to the motor drive unit 40, the current feedback control by the motor drive unit 40 is stabilized. Therefore, even when the steering operation for rapidly increasing the manual steering torque is performed, it is possible to prevent the overcurrent from being supplied to the electric motor 10.

In FIG. 3, the target current variation limiting section 51
Are provided independently, but the target current setting unit 30 may have a function of the target current change amount unit 51.

FIG . 5 is a block diagram of a control device of the electric power steering device according to the present invention . The control device 20B shown in FIG. 5 differs from the conventional control device 20J shown in FIG. 2 in that a target current limiter 52 is interposed between the target current setting unit 30 and the motor drive unit 40. When the absolute value of the target current IT output from the target current setting unit 30 is smaller than a predetermined value set in advance, the target current limiting unit 52 outputs the target current I output from the target current setting unit 30.
T is supplied to the deviation calculation unit 42 as it is. When the absolute value of the target current IT output from the target current setting unit 30 exceeds a predetermined value set in advance, the target current limiting unit 52 outputs a current 52a obtained by reducing the target current IT.

FIG . 6 is an explanatory diagram showing an operation example of the target current limiting section. In FIG. 6, the vertical axis represents the absolute value of the target current, and the horizontal axis represents the passage of time. The alternate long and short dash line indicates a change characteristic of the target current IT output from the target current setting unit 30. The solid line indicates a change characteristic of the target current (the target current whose upper limit is limited) output from the target current limiter 52. FIG. 6 shows an example in which the maximum value of the maximum rated current of the motor and the maximum value of the target current IT are set to 100 amps, and the limit start current of the target current IT is set to 90 amps.

The target current limiter 52 sets the upper limit of the target current 52a to be supplied to the deviation calculator 42 for a predetermined time (for example, 4 milliseconds) from the time when the target current IT exceeds 90 amps, which is the limit start current. The value is limited to 90 amps and for the next predetermined time (4 to 8
Milliseconds) limits the upper limit to 91 amps. In this way, the target current limiter 52 gradually increases the upper limit of the target current 52a to be supplied to the deviation calculator 42 in accordance with the elapsed time from when the target current IT exceeds the limit start current. Go. Therefore, even when the target current IT changes to the maximum value of 100 amps in a short time, the current 52a supplied to the motor drive unit 40 increases stepwise with the passage of time from 90 amps, which is the limit start current value. Become. Therefore, even when the steering operation for rapidly increasing the manual steering torque is performed, the upper limit value of the current 52a supplied to the motor drive unit 40 is limited stepwise from the time when the target current IT exceeds the limit start current. The current feedback control by the drive unit 40 is stably performed. Therefore, even if the steering operation for rapidly increasing the manual steering torque is performed,
It is possible to prevent an overcurrent from being supplied to the electric motor 10.

The target current limiting section 52 outputs the target current I
When T is the limit start current, for example, when it exceeds 80 amps, a value of 1/2 of the value exceeding 80 amps is set to 8
A value added to 0 amps is output, and at the next time, the difference between the target current IT and the previously output value is, for example, １ ／.
The target current IT may be reduced and corrected by sequentially repeating outputting a value obtained by adding the value multiplied by the value to the previously output value.

FIG . 7 is a block diagram of a control device of the electric power steering device according to the present invention . The control device 20C shown in FIG. 7 includes a target current limiting unit 53 interposed between the target current setting unit 30 and the motor driving unit 40. When the motor current 41a from which the high-frequency component has been removed exceeds the maximum rated current, for example, 80%, the target current limiting unit 53 sets the target current supplied to the motor driving unit 40 to exceed the maximum rated current, for example, 85%. The limit condition is gradually raised toward 100% over time. Therefore, even if the target current IT is a large value substantially corresponding to the rated current value, the upper limit value of the current value supplied to the motor drive unit 40 is gradually limited in accordance with the above-described limiting condition. As a result, the current feedback control by the motor drive unit 40 is stably performed. Therefore, even when a steering operation for rapidly increasing the manual steering torque is performed, it is possible to prevent the overcurrent from being supplied to the electric motor 10. The motor current signal before removing the high-frequency component may be used as the motor current signal.

FIG . 8 is a block diagram of a control device of the electric power steering device according to the present invention . The electric power steering apparatus according to the present invention detects a rotation speed of the electric motor 10 and detects an electric motor speed signal (hereinafter referred to as an electric motor speed S).
M) is provided. The motor speed detection unit 15 includes a power generation mechanism or the like, and may output a voltage corresponding to the rotation speed of the motor 10 or output a pulse signal each time the output shaft of the motor rotates a predetermined angle. . The motor speed detector 15
Alternatively, the motor voltage VM supplied to the motor 10 may be detected by a voltage detector, and the estimated motor speed SM may be obtained by calculation based on the motor voltage VM and the motor current IM.

The estimated motor speed SM can be obtained by the following equation. SM = (VM−IM · RM) / Kp Here, RM is a resistance value of the motor, and Kp is an induced voltage coefficient.

When the motor speed SM is less than a predetermined value, the target current limiting section 54 supplies the target current IT to the motor drive section 40 as it is. Target current limiter 5
When the motor speed SM exceeds a predetermined value, the correction target current 5 is a correction target current obtained by reducing the target current IT.
4a is supplied to the motor drive unit 40. Since the motor speed SM corresponds to the current flowing through the motor, the motor speed S
By correcting the target current IT to decrease when M exceeds a predetermined value, it is possible to prevent an overcurrent from flowing through the electric motor 10.

FIG . 9 is a block diagram of the control device of the electric power steering device according to the present invention . The control device 20E shown in FIG. 9 includes a target current limiting unit 55 interposed between the target current setting unit 30 and the motor driving unit 40. The target current limiting unit 55 monitors the amount of change in the target current IT per unit time from the target current setting unit 30. If the amount of change per unit time is less than the preset allowable amount of change,
The target current IT output from the target current setting unit 30 is supplied to the motor drive unit 40 as it is. Target current limiter 55
When the change amount per unit time exceeds a preset allowable change amount, the correction target current 55a obtained by reducing the target current IT is supplied to the motor drive unit 40. The target current limiter 55 increases the decrease correction amount as the change amount per unit time increases.

FIG . 10 is an explanatory diagram showing an example of the operation of the target current limiting section shown in FIG. The target current limiter 55
If the amount of change in the target current IT per unit time is, for example, less than 5 amps / millisecond, the target current IT is output as it is by multiplying the target current IT by the correction coefficient 1. The correction coefficient is set to 1 until the amount of change in the target current IT per unit time is, for example, 5 amps / 1 millisecond. When the amount of change per unit time is, for example, between 5 amps / 1 millisecond and 10 amps / 1 millisecond, the correction coefficient is increased from 1 to 0 in accordance with the increase in the amount of change per unit time.
It is set to sequentially smaller values to 5. When the variation per unit time is 10 amps / 1 millisecond or more, the correction coefficient is set to 0.
5 is set.

[0044] Thus, the amount of change per unit of the target current IT time by abrupt steering operation or the like for example, 5 amps / 1
If the time exceeds milliseconds, the target current (corrected target current) 55a supplied to the motor drive unit 40 is reduced and corrected in accordance with the amount of change in the target current IT per unit time.
Thus, even when a steering operation for rapidly increasing the manual steering torque is performed, it is possible to prevent an overcurrent from being supplied to the electric motor 10.

FIG . 11 is a block diagram of a control device of the electric power steering device according to the present invention . FIG.
The control device 20 </ b> F shown in FIG. 1 has a target current limiting unit 56 interposed between the target current setting unit 30 and the motor driving unit 40. The target current limiter 56 monitors the amount of change per unit time of the motor current 41a from which high-frequency components have been removed,
If the amount of change per unit time is less than a preset allowable amount of change, the target current I output from the target current setting unit 30 is output.
T is supplied to the motor drive unit 40 as it is. When the amount of change per unit time exceeds a preset allowable amount of change, the target current limiter 56 supplies the motor drive unit 40 with a corrected target current 56a obtained by reducing the target current IT.
The target current limiting section 56 increases the decrease correction amount as the change amount per unit time increases.

FIG . 12 is an explanatory diagram showing an example of the operation of the target current limiting section shown in FIG. Target current limiter 56
If the amount of change in the motor current IM per unit time is, for example, less than 5 amps / 1 millisecond, the target current I
By multiplying T by the correction coefficient 1, the target current IT is output as it is. The correction coefficient is set to 1 until the amount of change in the motor current IM per unit time is, for example, 5 amps / 1 millisecond. When the amount of change per unit time is, for example, 5 amps / 1 millisecond to 10 amps / 1 millisecond, the correction coefficient is sequentially increased from 1 to 0.5 in accordance with the increase in the amount of change per unit time. It is set to a small value. When the amount of change per unit time is 10 amps / 1 millisecond or more, the correction coefficient is set to 0.5.

[0047] Thus, the amount of change per unit time of the motor current IM by abrupt steering operation or the like, for example, if it exceeds 5 amps / millisecond, corresponds to the size to the amount of change per unit time of the motor current IM Then, the target current (corrected target current) 56a supplied to the motor drive unit 40 is reduced and corrected. Thus, even when a steering operation for rapidly increasing the manual steering torque is performed, it is possible to prevent an overcurrent from being supplied to the electric motor 10. The motor current signal before removing the high-frequency component may be used as the motor current signal.

FIG . 13 is a block diagram of a control device of the electric power steering device according to the present invention . FIG.
The control device 20G includes a target current limiting unit 57 interposed between the target current setting unit 30 and the motor driving unit 40. The target current limiting unit 57 monitors the absolute value of the target current IT output from the target current setting unit 30 and the amount of change in the target current IT per unit time. Target current limiter 57
When the target current IT is less than a preset limit start current (for example, 80 amps), the target current IT output from the target current setting unit 30 is supplied to the motor drive unit 40 as it is. The target current limiter 57 outputs the target current I
If T exceeds a preset limit start current (for example, 80 amperes), a correction current 57a obtained by reducing the target current IT in accordance with the amount of change per unit time of the target current IT is supplied to the motor drive unit 40. Supply to

Even if the target current IT exceeds a preset limit start current (eg, 80 amps), the target current limiter 57 determines that the amount of increase / decrease of the target current IT per unit time is, for example, 20 amps / 1. If it is less than milliseconds,
The target current IT output from the target current setting unit 30 is supplied to the motor drive unit 40 as it is. Target current limiter 57
If the target current IT exceeds a preset limit start current (for example, 80 amps) and the amount of change in the target current IT per unit time is, for example, 20 amps / 1 millisecond or more, the motor The amount by which the correction target current 57a supplied to the drive unit 40 is increased per unit time is limited so as not to exceed, for example, 20 amps / 1 millisecond.

FIG . 14 is an explanatory diagram showing an operation example of the target current limiting section shown in FIG. The target current limiter 57
When the target current IT exceeds the limit start current, the amount of change in the target current per unit time increases by a predetermined amount (for example, 20
Ampere per millisecond). Therefore, even when the target current IT increases in a short time due to a sudden steering operation or the like, the amount of increase in the target current per unit time after the limit start current is exceeded by a predetermined amount (for example, 20 amps / (1 millisecond). As a result, the current feedback control by the motor drive unit 40 is stably performed. Therefore, even when the steering operation for rapidly increasing the manual steering torque is performed, it is possible to prevent the overcurrent from being supplied to the electric motor 10.

The target current limiting section 57 outputs the target current I
If T exceeds the limit start current, for example, 80 amperes, and if the amount of increase in the target current IT per unit time exceeds the permissible amount, for example, the excess of 80 amperes, for example, A value obtained by adding a value of 1/4 to 80 amps is output. At the next time point, a value obtained by multiplying the difference between the target current IT and the previously output value by, for example, 1/4 is output first. The target current IT may be corrected to decrease by sequentially repeating outputting the value added to the target current IT.
Further, as the amount of increase in the target current IT per unit time increases, the coefficient by which the amount exceeding 80 amps is multiplied is set to be gradually smaller, such as 1/2, 1/4, 1/8. You may.

FIG . 15 is a block diagram of a control device of the electric power steering device according to the present invention . FIG.
The control device 20H shown in FIG. 1 has a target current limiter 58 interposed between the target current setting unit 30 and the motor drive unit 40. The target current limiter 58 monitors the absolute value of the motor current 41a from which high-frequency components have been removed and the amount of change per unit time of the motor current 41a. The target current limiting unit 58 determines that the motor current IM has a preset limit start current (for example, 8
0 ampere), the target current IT output from the target current setting unit 30 is
Supply to When the motor current IM exceeds a preset limit start current (for example, 80 amps), the target current limiting unit 58 decreases and corrects the target current IT according to the amount of change in the motor current IM per unit time. Correction current 58
is supplied to the motor drive unit 40.

Even if the motor current IM exceeds a preset limit start current (for example, 80 amps), the target current limiting section 58 can increase the motor current IM per unit time by, for example, 10 amps / 1. If the time is less than the millisecond, the target current IT output from the target current setting unit 30 is supplied to the motor drive unit 40 as it is. The target current limiter 58 determines that the motor current IM has exceeded a preset limit start current (for example, 80 amps) and that the target current IT
Is, for example, 10 amps /
If it is 1 millisecond or more, the amount of increase in the correction target current 58a supplied to the motor drive unit 40 per unit time is:
For example, it is limited so as not to exceed 10 amps / 1 millisecond.

In the target current limiting section 58, the motor current IM exceeds the limit start current, for example, 80 amperes, and the amount of increase in the motor current IM per unit time exceeds the allowable amount. In this case, a value obtained by adding a value of, for example, 1/4 that exceeds 80 amps to 80 amps is output, and at the next time point, the difference between the target current IT and the previously output value is calculated, for example. The target current IT may be reduced and corrected by sequentially repeating outputting a value obtained by adding the value multiplied by ４ to the previously output value. Further, as the amount of increase in the target current IT per unit time increases, the coefficient by which the amount exceeding 80 amps is multiplied is set to be gradually smaller, such as 1/2, 1/4, 1/8. You may.

Further , the target current limiting section 58 determines that the motor current IM exceeds the limit start current, for example, 80 amperes, and that the amount of increase in the motor current IM per unit time exceeds the allowable amount. In this case, the target current IT is reduced and corrected by multiplying the target current IT by a correction coefficient (a value smaller than 1) set in advance corresponding to the amount of change per unit time of the motor current IM. 58a may be supplied to the motor drive unit 40. The motor current signal before removing the high-frequency component may be used as the motor current signal.

FIG . 16 is an explanatory diagram showing an overcurrent preventing effect in the electric power steering apparatus according to the present invention . The vertical axis indicates the current value, and the horizontal axis indicates time. FIG.
Is that the operation of turning the steering (handle) to the left is performed in a short time from the state where the steering (handle) is turned to the right and a large manual steering torque is applied, and the steering (handle) is turned to the left; FIG. 9 shows a change in the target current IT and a change in the motor current IM when the state in which the manual steering torque is large is shown.

In a conventional electric power steering device,
Since the target current IT is set in accordance with the manual steering torque, when the steering operation is performed from right to left, the target current IT is quickly changed to the final target current value as indicated by a chain line. Change. Due to the response delay of the current feedback control system, in the conventional electric power steering device,
The motor current actually flowing through the motor greatly exceeds the final target current value as shown by a two-dot chain line. Therefore, when the final target current value is close to the rated current value of the motor, an overcurrent state may occur in which the motor current actually flowing through the motor exceeds the rated current value of the motor.

In the electric power steering apparatus according to the present invention, the target current change limiter 51 and the target current limiter 5
Since the target current is reduced and corrected by the steps 2 to 58 so as not to cause an overcurrent state, the motor current actually flowing through the motor does not greatly deviate from the target current as shown by the dotted line. In this manner, by correcting the target current to decrease, it is possible to suppress overshoot due to a control delay element. Therefore, it is possible to prevent an overcurrent from flowing through the electric motor and each of the field effect transistors constituting the electric motor drive circuit.

[0059]

As described above, the electric power steering apparatus according to the present invention is provided with the target current change amount limiter for limiting the change amount of the target current per unit time.
Even when sudden steering is performed, the amount of change in the target current per unit time can be limited to a predetermined value or less. By limiting the amount of change in the target current per unit time to a value corresponding to the response time of the feedback control, it is possible to prevent the current that actually flows through the motor from becoming excessively large. Deterioration of characteristics of the effect transistor can be prevented.

The electric power steering apparatus according to the present invention is designed so that the motor current detected by the motor current detector exceeds a predetermined value (for example, about 80 to 90% of the maximum rated current of the motor). Since the target current is reduced and corrected, it is possible to prevent the motor current from becoming excessively large even when the feedback control system has a response delay.

The electric power steering apparatus according to the present invention is configured such that the target current is reduced and corrected when the change amount of the target current per unit time exceeds a preset allowable change amount. Only when the amount of change per time exceeds the allowable amount of change, the target current is reduced and corrected, so that the motor current can be prevented from becoming excessive. The correction of the target current is reduced only when the steering speed is extremely high, but otherwise the reduction of the target current is not corrected, so that the steering response is not reduced.

The electric power steering apparatus according to the present invention is configured such that the target current is reduced and corrected when the change amount of the motor current per unit time exceeds a preset allowable change amount. Only when the variation per time exceeds the permissible variation, the target current is corrected to decrease. This prevents the motor current from becoming excessive. If the change amount of the motor current per unit time is less than the allowable change amount, the reduction correction of the target current is not performed, so that the steering response does not decrease.

The electric power steering apparatus according to the present invention has a configuration in which the target current is decreased and corrected only when the target current is large (for example, about 80 to 90% of the rated current of the motor) and the amount of change in the target current is large. Therefore, in the range where the target current is not large, the steering responsiveness does not decrease even if the steering is performed sharply. When the target current is large and the change amount is large, it is possible to prevent the motor current from becoming excessive.

In the electric power steering apparatus according to the present invention , the motor current exceeds a predetermined value (for example, about 80 to 90% of the rated current of the motor) and the change in the motor current per unit time. Since the target current is reduced and corrected when the amount exceeds a predetermined allowable change amount, it is possible to prevent the motor current from becoming excessive. If the motor current is less than the predetermined value, the target current is not corrected to decrease even if the change amount is large, so that the steering response does not decrease.

[Brief description of the drawings]

FIG. 1 is a schematic structural view of an electric power steering device.

FIG. 2 is a block diagram of a conventional electric power steering device.

FIG. 3 is a block diagram of a control device of the electric power steering device according to the present invention .

FIG. 4 is an explanatory diagram showing an operation of a target current change amount limiting unit.

FIG. 5 is a block diagram of a control device of the electric power steering device according to the present invention .

FIG. 6 is an explanatory diagram showing an operation example of a target current limiting unit.

FIG. 7 is a block diagram of a control device of the electric power steering device according to the present invention .

FIG. 8 is a block diagram of a control device of the electric power steering device according to the present invention .

FIG. 9 is a block diagram of a control device of the electric power steering device according to the present invention .

FIG. 10 is an explanatory diagram showing an operation example of the target current limiting section shown in FIG. 9;

FIG. 11 is a block diagram of a control device of the electric power steering device according to the present invention .

FIG. 12 is an explanatory diagram showing an operation example of the target current limiting section shown in FIG. 11;

FIG. 13 is a block diagram of a control device of the electric power steering device according to the present invention .

FIG. 14 is an explanatory diagram showing an operation example of the target current limiting unit shown in FIG.

FIG. 15 is a block diagram of a control device of the electric power steering device according to the present invention .

FIG. 16 is an explanatory diagram showing an overcurrent prevention effect in the electric power steering device according to the present invention .

[Description of Signs] 1 ... Electric power steering device, 2 ... Steering wheel (handle), 10 ... Electric motor, 12 ... Steering torque detector, 13 ... Vehicle speed detector, 14 ... Electric motor current detector,
15 ... motor speed detecting section, 20A-20H ... control device
Reference numeral 30: target current setting unit, 40: motor drive unit, 41: high frequency component removal unit, 42: deviation calculation unit, 43: PID control unit, 44: PWM signal generation unit, 45: gate drive circuit unit, 46: motor drive Circuits, 51: target current change limiter, 52 to 58: target current limiter, Q1 to Q4: field effect transistors.

Claims (8)

[Claims] An electric motor for applying an auxiliary torque to a steering system; a steering torque detector for detecting a steering torque of the steering system; an electric motor current detector for detecting a current flowing through the electric motor; A target current setting unit that sets a target current to be supplied to the motor based on the steering torque detected by the motor; and a controller that controls the motor based on a deviation between the target current and the motor current detected by the motor current detector. An electric power steering apparatus comprising: a motor drive section that performs feedback control of a supplied current; and an electric power steering apparatus including a target current change amount restriction section that restricts a change amount of a target current per unit time. 2. An electric motor for applying an auxiliary torque to a steering system, a steering torque detector for detecting a steering torque of the steering system, a motor current detector for detecting a current flowing in the electric motor, and at least the steering torque detection. A target current setting unit that sets a target current to be supplied to the motor based on the steering torque detected by the motor; and a controller that controls the motor based on a deviation between the target current and the motor current detected by the motor current detector. An electric power steering device comprising: a motor drive unit that performs feedback control of a supplied current, wherein an electric power steering device includes a target current limiting unit that corrects a decrease in the target current when the target current exceeds a predetermined value set in advance. Electric power steering device. 3. An electric motor for applying an auxiliary torque to a steering system, a steering torque detector for detecting a steering torque of the steering system, a motor current detector for detecting a current flowing through the electric motor, and at least the steering torque detection. A target current setting unit that sets a target current to be supplied to the motor based on the steering torque detected by the motor; and a controller that controls the motor based on a deviation between the target current and the motor current detected by the motor current detector. An electric power steering device comprising: a motor drive unit that performs feedback control of a supplied current; a target current that decreases and corrects the target current when the motor current detected by the motor current detector exceeds a predetermined value set in advance. An electric power steering device comprising a restriction unit. 4. An electric motor for applying an auxiliary torque to a steering system, a steering torque detector for detecting a steering torque of the steering system, a motor current detector for detecting a current flowing through the electric motor, and at least the steering torque detection. A target current setting unit that sets a target current to be supplied to the motor based on the steering torque detected by the motor; and a controller that controls the motor based on a deviation between the target current and the motor current detected by the motor current detector. An electric power steering device comprising: a motor drive unit that performs feedback control of a supplied current; a motor speed detection unit that detects a rotation speed of the motor; and a rotation speed detected by the motor speed detection unit is a predetermined value set in advance. And a target current limiter for reducing and correcting the target current when exceeding the target current. War steering device. 5. A motor for applying an auxiliary torque to a steering system, a steering torque detector for detecting a steering torque of the steering system, a motor current detector for detecting a current flowing through the motor, and at least the steering torque detection. A target current setting unit that sets a target current to be supplied to the motor based on the steering torque detected by the motor; and a controller that controls the motor based on a deviation between the target current and the motor current detected by the motor current detector. In an electric power steering apparatus including a motor drive unit that performs feedback control of a supplied current, a target current limit for reducing and correcting the target current when a change amount per unit time of a target current exceeds a preset allowable change amount. An electric power steering apparatus comprising: 6. A motor for applying an auxiliary torque to a steering system, a steering torque detector for detecting a steering torque of the steering system, a motor current detector for detecting a current flowing in the motor, and at least the steering torque detection. A target current setting unit that sets a target current to be supplied to the motor based on the steering torque detected by the motor; and a controller that controls the motor based on a deviation between the target current and the motor current detected by the motor current detector. An electric power steering apparatus comprising: a motor drive unit that performs feedback control of a supplied current.If the amount of change per unit time of the motor current detected by the motor current detector exceeds a predetermined allowable change amount, An electric power steering apparatus, comprising: a target current limiter that reduces and corrects a target current. 7. A motor for applying an auxiliary torque to a steering system, a steering torque detector for detecting a steering torque of the steering system, a motor current detector for detecting a current flowing through the motor, and at least the steering torque detection. A target current setting unit that sets a target current to be supplied to the motor based on the steering torque detected by the motor; and a controller that controls the motor based on a deviation between the target current and the motor current detected by the motor current detector. An electric power steering apparatus comprising: a motor drive unit that feedback-controls a supplied current; wherein a target current exceeds a predetermined value, and a change amount of the target current per unit time is a predetermined allowable change amount. An electric power steering device comprising a target current limiter for reducing and correcting the target current when the power supply exceeds the target current. Packaging equipment. 8. A motor for applying an auxiliary torque to a steering system, a steering torque detector for detecting a steering torque of the steering system, a motor current detector for detecting a current flowing in the motor, and at least the steering torque detection. A target current setting unit that sets a target current to be supplied to the motor based on the steering torque detected by the motor; and a controller that controls the motor based on a deviation between the target current and the motor current detected by the motor current detector. An electric power steering apparatus comprising: a motor drive unit that performs feedback control of a supplied current; wherein the motor current detected by the motor current detector exceeds a predetermined value set in advance, and is detected by the motor current detector. If the change in the motor current per unit time exceeds the allowable change set in advance, the target current Decrease correction electric power steering apparatus comprising the target current limiting section for.