JP2014189096A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology capable of suppressing noise and vibration while inhibiting deterioration of steering feeling.SOLUTION: An electric power steering device comprises: an electric motor for applying auxiliary force to an operation of a steering wheel of a vehicle; a torque sensor for detecting steering torque of the steering wheel; a vehicle speed sensor 170 for detecting vehicle speed; a motor current detection part 33 for detecting an actual current actually supplied to the electric motor; a target current calculation part 20 for setting a target current to the electric motor on the basis of the steering torque detected by the torque sensor; a steering torque correction part 44 for calculating corrected steering torque Tc by correcting the steering torque detected by the torque sensor in accordance with the vehicle speed detected by the vehicle speed sensor 170; and a feedback processing part 42 for performing feedback processing with current responsiveness in accordance with the corrected steering torque Tc calculated by the steering torque correction part 44 so that the target current It set by the target current calculation part 20 and the actual current Im detected by the motor current detection part 33 coincide with each other.

Description

  The present invention relates to an electric power steering apparatus.

In recent years, there has been proposed an electric power steering device that includes an electric motor in a steering system of a vehicle and assists a driver's steering force with the power of the electric motor.
For example, the electric power steering device described in Patent Document 1 is controlled by a control device. In order to control the drive of the electric motor, the control device first sets a target current to be supplied to the electric motor according to the steering torque, the vehicle speed, and the like. Then, feedback control is performed so that the deviation between the target current and the actual current becomes zero so that the set target current and the actual current that actually flows through the electric motor match.

JP 2001-315657 A

When the drive torque of the electric motor that is the feedback control target increases, the sound and vibration generated from the steering device increase. Therefore, it is preferable that the current response is small from the viewpoint of suppressing the sound and vibration. On the other hand, when current responsiveness is reduced in feedback control, phase delay and output current attenuation occur, making it difficult for the assist force to follow the steering wheel operation, resulting in a deterioration in steering feeling.
An object of the present invention is to provide an electric power steering apparatus that can suppress noise and vibration while suppressing deterioration of steering feeling.

  For this purpose, the present invention provides an electric motor that gives an assisting force to the operation of a steering wheel of a vehicle, a torque detection means that detects a steering torque of the steering wheel, and a vehicle speed that is a moving speed of the vehicle. A vehicle speed detecting means for detecting; a current detecting means for detecting an actual current actually supplied to the electric motor; and a target for setting a target current to the electric motor based on the steering torque detected by the torque detecting means. Current setting means; correction means for calculating a corrected steering torque obtained by correcting the steering torque detected by the torque detection means according to the vehicle speed detected by the vehicle speed detection means; and a target set by the target current setting means The current response corresponding to the post-correction steering torque calculated by the correction means so that the current and the actual current detected by the current detection means match. A feedback processing means for performing a feedback process in sex, an electric power steering apparatus comprising: a.

Here, the feedback processing means may reduce the current responsiveness when the corrected steering torque is greater than a predetermined reference value than when it is equal to or less than the reference value.
The correction means may change the reference value of the corrected steering torque that causes the feedback processing means to reduce the current responsiveness in accordance with the vehicle speed.
The correction means may make the reference value smaller when the vehicle speed is greater than zero than when the vehicle speed is zero.

  According to the present invention, it is possible to suppress sound and vibration while suppressing deterioration of steering feeling.

It is a figure showing the schematic structure of the electric power steering device concerning an embodiment. It is a schematic block diagram of a control apparatus. It is the schematic of the control map which shows a response | compatibility with steering torque, vehicle speed, and base current. It is a schematic block diagram of a feedback control part. It is a figure which illustrates the control map which shows a response | compatibility with a vehicle speed and a torque correction coefficient. It is a figure which illustrates the control map which shows a response | compatibility with the steering torque after correction | amendment, and a gain correction coefficient. It is a figure which shows the output characteristic of the electric motor feedback-controlled by the feedback control part which concerns on this Embodiment.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a diagram illustrating a schematic configuration of an electric power steering apparatus 100 according to an embodiment.
Electric power steering device 100 (hereinafter, also simply referred to as “steering device 100”) is a steering device for arbitrarily changing the traveling direction of a vehicle, and in this embodiment, an automobile as an example of the vehicle. The structure applied to is illustrated.

  The steering apparatus 100 includes a wheel-like steering wheel 101 that is operated by a driver to change the traveling direction of the automobile, and a steering shaft 102 that is provided integrally with the steering wheel 101. . The steering device 100 includes an upper connecting shaft 103 connected to the steering shaft 102 via a universal joint 103a, and a lower connecting shaft 108 connected to the upper connecting shaft 103 via a universal joint 103b. . The lower connecting shaft 108 rotates in conjunction with the rotation of the steering wheel 101.

  Steering device 100 includes tie rods 104 connected to left and right front wheels 150 as rolling wheels, and rack shaft 105 connected to tie rods 104. Further, the steering device 100 includes a pinion shaft 106 on which a pinion 106 a that constitutes a rack and pinion mechanism is formed together with rack teeth 105 a formed on the rack shaft 105.

  The steering device 100 also has a steering gear box 107 that houses a part of the pinion shaft 106. The pinion shaft 106 is connected to the lower connection shaft 108 via a torsion bar (not shown) in the steering gear box 107. Inside the steering gear box 107, a torque sensor 109 is provided as an example of torque detecting means for detecting the steering torque T of the steering wheel 101 based on the relative angle between the lower connecting shaft 108 and the pinion shaft 106.

  The steering device 100 includes an electric motor 110 supported by the steering gear box 107, and a speed reducing mechanism 111 that decelerates the driving force of the electric motor 110 and transmits it to the pinion shaft 106. Electric motor 110 according to the present embodiment is a three-phase brushless motor. The reduction mechanism 111 includes, for example, a worm wheel (not shown) fixed to the pinion shaft 106, a worm gear (not shown) connected to the output shaft of the electric motor 110, and the like.

  In addition, the steering device 100 includes a control device 10 that controls the operation of the electric motor 110. An output signal from the torque sensor 109 described above is input to the control device 10. In addition, the control device 10 includes vehicle speed detection means for detecting a vehicle speed Vc, which is a moving speed of the vehicle, via a network (CAN) that performs communication for sending signals for controlling various devices mounted on the vehicle. An output signal from a vehicle speed sensor 170 as an example is input.

  The steering device 100 configured as described above detects the steering torque T applied to the steering wheel 101 by the torque sensor 109, drives the electric motor 110 in accordance with the detected torque, and generates torque generated by the electric motor 110. Is transmitted to the pinion shaft 106. Thereby, the torque generated by the electric motor 110 assists the driver's steering force applied to the steering wheel 101.

Next, the control device 10 will be described.
FIG. 2 is a schematic configuration diagram of the control device 10.
The control device 10 is an arithmetic and logic circuit composed of a CPU, ROM, RAM, backup RAM, and the like.
The control device 10 includes a torque signal Td obtained by converting the steering torque T detected by the torque sensor 109 described above into an output signal, and a vehicle speed signal obtained by converting the vehicle speed Vc detected by the vehicle speed sensor 170 into an output signal. v or the like is input.

  Then, the control device 10 calculates a target auxiliary torque based on the torque signal Td and the vehicle speed signal v, and calculates a target current It necessary for the electric motor 110 to supply the target auxiliary torque. As an example, and a control unit 30 that performs feedback control and the like based on the target current It calculated by the target current calculation unit 20.

First, the target current calculation unit 20 will be described in detail.
The target current calculation unit 20 includes a base current calculation unit 21 that calculates a base current Ib that serves as a reference for setting the target current, and an inertia compensation current calculation unit 22 that calculates a current for canceling the inertia moment of the electric motor 110. And a damper compensation current calculation unit 23 for calculating a current for limiting the rotation of the motor. The target current calculation unit 20 includes a target current determination unit 25 that determines the target current It based on values calculated by the base current calculation unit 21, the inertia compensation current calculation unit 22, and the damper compensation current calculation unit 23. ing. In addition, the target current calculation unit 20 includes a phase compensation unit 26 that compensates for the phase of the steering torque T detected by the torque sensor 109.

  The target current calculation unit 20 receives a torque signal Td, a vehicle speed signal v, a rotation speed signal Nms obtained by converting the rotation speed Nm of the electric motor 110 into an output signal, and the like. The rotational speed signal Nms is, for example, a sensor configured to detect a rotational position of a rotor (rotor) of the electric motor 110 that is a three-phase brushless motor (for example, a rotor configured by a resolver, a rotary encoder, or the like that detects the rotational position of the rotor) It can be exemplified that the value obtained by differentiating the rotation angle of the electric motor 110 detected by the position detection circuit) is converted into an output signal.

FIG. 3 is a schematic diagram of a control map showing the correspondence between the steering torque T, the vehicle speed Vc, and the base current Ib.
The base current calculation unit 21 calculates a base current Ib based on the torque signal Ts obtained by phase compensation of the torque signal Td by the phase compensation unit 26 and the vehicle speed signal v from the vehicle speed sensor 170. That is, the base current calculation unit 21 calculates the base current Ib according to the phase-compensated steering torque T and the vehicle speed Vc. The base current calculation unit 21 is, for example, a phase-compensated steering torque T (torque signal Ts), vehicle speed Vc (vehicle speed signal v), and base current that are created in advance based on empirical rules and stored in the ROM. The base current Ib is calculated by substituting the steering torque T (torque signal Ts) and the vehicle speed Vc (vehicle speed signal v) into the control map or calculation formula illustrated in FIG. 3 showing the correspondence with Ib.

  The inertia compensation current calculation unit 22 calculates an inertia compensation current Is for canceling the moment of inertia of the electric motor 110 and the system based on the torque signal Ts and the vehicle speed signal v. That is, the inertia compensation current calculation unit 22 calculates the inertia compensation current Is according to the steering torque T (torque signal Ts) and the vehicle speed Vc (vehicle speed signal v). Note that the inertia compensation current calculation unit 22 generates, for example, the steering torque T (torque signal Ts), the vehicle speed Vc (vehicle speed signal v), and the inertia compensation current Is, which are previously created based on empirical rules and stored in the ROM. The inertia compensation current Is is calculated by substituting the steering torque T (torque signal Ts) and the vehicle speed Vc (vehicle speed signal v) into a control map or a calculation formula indicating the correspondence between the two.

  The damper compensation current calculation unit 23 calculates a damper compensation current Id for limiting the rotation of the electric motor 110 based on the torque signal Ts, the vehicle speed signal v, and the rotation speed signal Nms of the electric motor 110. That is, the damper compensation current calculation unit 23 calculates the damper compensation current Id according to the steering torque T (torque signal Ts), the vehicle speed Vc (vehicle speed signal v), and the rotational speed Nm (rotational speed signal Nms) of the electric motor 110. calculate. For example, the damper compensation current calculation unit 23 is prepared based on an empirical rule and stored in the ROM in advance, such as steering torque T (torque signal Ts), vehicle speed Vc (vehicle speed signal v), and rotation speed Nm (rotation). The steering torque T (torque signal Ts), the vehicle speed Vc (vehicle speed signal v), and the rotational speed Nm (rotational speed signal Nms) are substituted into a control map or calculation formula indicating the correspondence between the speed signal Nms) and the damper compensation current Id. Thus, the damper compensation current Id is calculated.

  The target current determination unit 25 includes the base current Ib calculated by the base current calculation unit 21, the inertia compensation current Is calculated by the inertia compensation current calculation unit 22, and the damper compensation calculated by the damper compensation current calculation unit 23. A target current It is determined based on the current Id. For example, the target current determination unit 25 determines the current obtained by adding the inertia compensation current Is to the base current Ib and subtracting the damper compensation current Id as the target current It.

Next, the control unit 30 will be described in detail.
As shown in FIG. 2, the control unit 30 includes a motor drive control unit 31 that controls the operation of the electric motor 110, a motor drive unit 32 that drives the electric motor 110, and an actual current Im that actually flows through the electric motor 110. And a motor current detection unit 33 as an example of current detection means to detect.

The motor drive control unit 31 performs feedback control based on a deviation between the target current It determined by the target current calculation unit 20 and the actual current Im supplied to the electric motor 110 detected by the motor current detection unit 33. A feedback (F / B) control unit 40 that performs the above and a PWM signal generation unit 60 that generates a PWM (pulse width modulation) signal for PWM driving the electric motor 110.
The feedback control unit 40 will be described in detail later.
The PWM signal generation unit 60 generates a PWM signal for driving the electric motor 110 by PWM (pulse width modulation) based on the output value from the feedback control unit 40, and outputs the generated PWM signal.

The motor drive unit 32 is a so-called inverter, and includes, for example, six independent transistors (FETs) as switching elements. Three of the six transistors are a positive line of a power source, an electric coil of each phase, The other three transistors are connected to the electric coil of each phase and the negative side (ground) line of the power source. Then, the driving of the electric motor 110 is controlled by driving the gates of two transistors selected from the six and switching the transistors.
The motor current detection unit 33 detects the value of the actual current Im flowing through the electric motor 110 from the voltage generated at both ends of the shunt resistor connected to the motor drive unit 32.

Next, the feedback control unit 40 will be described in detail.
When the output of the electric motor 110 that is a feedback control target (current supplied to the electric motor 110) increases, sound and vibration generated from the steering device 100 increase. As shown in the control map illustrated in FIG. 3, the base current Ib increases as the steering torque T increases. Therefore, the target current It supplied to the electric motor 110 also increases as the steering torque T increases. . Therefore, as the steering torque T increases, sound and vibration generated from the steering device 100 increase.
Further, when the current supplied to the electric motor 110 increases, the ripple generated in the electric motor 110 also increases. Therefore, if the current responsiveness of the feedback control is high, this ripple also easily follows, so that the sound and vibration generated from the steering device 100 become larger than when the current responsiveness is low.
Therefore, in the feedback control unit 40 according to the present embodiment, when the steering torque T is large, the current response is made smaller than when the steering torque T is small.

However, how much the sound or vibration increases the steering torque T has an adverse effect on the vehicle on which the steering device 100 is mounted (such as difficulty in steering due to vibration or sound being uncomfortable). It depends on the characteristics of the vehicle.
On the other hand, when current responsiveness is reduced in feedback control, phase delay and output current attenuation occur, so that it becomes difficult for the assist force to follow the operation of the steering wheel 101 and the steering feeling deteriorates. Therefore, it is preferable to increase the current response as much as possible in a region where noise and vibration are not so large as to adversely affect the steering feeling of the driver.
In view of the above, the feedback control unit 40 according to the present embodiment is configured as follows.

FIG. 4 is a schematic configuration diagram of the feedback control unit 40.
The feedback control unit 40 includes a deviation calculating unit 41 that calculates a deviation between the target current It calculated by the target current calculating unit 20 and the actual current Im detected by the motor current detecting unit 33, and the deviation calculating unit 41 calculates the deviation. A feedback (F / B) processing unit 42 as an example of feedback processing means for performing feedback processing so that the deviation becomes zero. The F / B processing unit 42 sets a current to be supplied to the electric motor 110 that is a control target based on the deviation obtained by the deviation calculating unit 41 and the feedback gain G. For example, the F / B processing unit 42 sets a value obtained by multiplying the deviation obtained by the deviation calculating unit 41 by the feedback gain G as a current supplied to the electric motor 110. Further, the F / B processing unit 42 multiplies a predetermined feedback constant K by the gain correction coefficient αg calculated by the gain correction coefficient calculation unit 45 as a feedback gain G (= K × αg). Use. Therefore, the gain correction coefficient αg functions as a coefficient that determines the current response of the feedback control system performed by the feedback control unit 40.

  The feedback control unit 40 also includes a torque correction coefficient calculating unit 43 that calculates a torque correction coefficient αt used to correct the steering torque T (torque signal Ts) based on the vehicle speed Vc (vehicle speed signal v), and a torque correction. And a steering torque correction unit 44 as an example of a correction unit that corrects the steering torque T (torque signal Ts) using the coefficient αt. Further, the feedback control unit 40 calculates a gain correction coefficient αg for correcting a feedback gain G used by the F / B processing unit 42 based on the steering torque T corrected by the steering torque correction unit 44. A portion 45 is provided.

For example, the torque correction coefficient calculation unit 43 creates a control map or calculation formula indicating the correspondence between the vehicle speed Vc (vehicle speed signal v) and the torque correction coefficient αt, which is created based on the vehicle characteristics and stored in the ROM in advance. The torque correction coefficient αt is calculated by substituting the vehicle speed Vc (vehicle speed signal v).
FIG. 5 is a diagram illustrating a control map showing the correspondence between the vehicle speed Vc and the torque correction coefficient αt. In the present embodiment, as shown in FIG. 5, when the vehicle speed Vc is zero, the torque correction coefficient αt is 1, and when the vehicle speed Vc is greater than zero and equal to or less than a predetermined speed V0, the vehicle speed Vc is large. As the torque correction coefficient αt gradually increases from 1 to a predetermined value αt0 and the vehicle speed Vc is higher than the predetermined speed V0, the control map is created so that the torque correction coefficient αt becomes the predetermined value αt0. It can be exemplified that the predetermined speed V0 is 15 km / h and the predetermined value αt0 is 1.5.
The steering torque correction unit 44 corrects the steering torque T by multiplying the phase-compensated steering torque T (torque signal Ts) by the torque correction coefficient αt calculated by the torque correction coefficient calculation unit 43, and the corrected steering torque. The corrected steering torque Tc (= T × αt), which is T, is output to the gain correction coefficient calculation unit 45.

For example, the gain correction coefficient calculation unit 45 creates a control map or a calculation formula indicating the correspondence between the corrected steering torque Tc and the gain correction coefficient αg, which is previously created based on the vehicle characteristics and stored in the ROM. The gain correction coefficient αg is calculated by substituting the steering torque Tc.
FIG. 6 is a diagram illustrating a control map showing the correspondence between the corrected steering torque Tc and the gain correction coefficient αg. In the present embodiment, as shown in FIG. 6, when the corrected steering torque Tc is zero to a predetermined torque value T0 or less, the gain correction coefficient αg is 1, and the corrected steering torque Tc is a predetermined torque value T0. If it is larger, the gain correction coefficient αg gradually decreases from 1 as the corrected steering torque Tc increases.

  Note that the control map shown in FIG. 6 can be exemplified as a control map showing the correspondence between the corrected steering torque Tc and the gain correction coefficient αg when the vehicle speed Vc is zero. Then, when the vehicle speed Vc is zero, the steering torque T that becomes so large that sound or vibration adversely affects the vehicle is set to a predetermined torque value T0. For example, the predetermined torque value T0 is 5 N · m.

  In the feedback control unit 40 configured as described above, when the vehicle speed Vc is zero, the torque correction coefficient calculation unit 43 calculates the torque correction coefficient αt as 1 based on the control map illustrated in FIG. In this case, the steering torque correction unit 44 corrects the corrected steering torque Tc (= T × 1), which is a value obtained by multiplying the phase-compensated steering torque T by the torque correction coefficient αt = 1 calculated by the torque correction coefficient calculation unit 43. ) Is output to the gain correction coefficient calculation unit 45. Then, the gain correction coefficient calculation unit 45 calculates the gain correction coefficient αg based on the control map illustrated in FIG. In the control map illustrated in FIG. 6, when the corrected steering torque Tc (= steering torque T) is equal to or less than the predetermined torque value T0, the gain correction coefficient αg is 1, and the corrected steering torque Tc (= steering torque T) is When it is larger than the predetermined torque value T0, the gain correction coefficient αg gradually decreases from 1 as the corrected steering torque Tc increases.

Then, the F / B processing unit 42 performs feedback processing using a value obtained by multiplying the feedback constant K by the gain correction coefficient αg as a feedback gain G (= K × αg).
As a result, when the corrected steering torque Tc (= steering torque T) at which the sound or vibration does not adversely affect the vehicle is equal to or less than the predetermined torque value T0, the F / B processing unit 42 sets the gain correction coefficient αg to the feedback constant K. Since feedback processing is performed with a feedback gain G (= K × 1) multiplied by (= 1), responsiveness can be improved. On the other hand, when the corrected steering torque Tc (= steering torque T) is greater than the predetermined torque value T0, the F / B processing unit 42 multiplies the feedback constant K by the gain correction coefficient αg (<1). Since the feedback process is performed at, the current responsiveness is lower than when the gain correction coefficient αg = 1. That is, when the corrected steering torque Tc is larger than a predetermined torque value T0 as an example of a predetermined reference value, the F / B processing unit 42 has a linear current response as compared with a case where the corrected torque is smaller than the predetermined torque value T0. To lower.
As a result, in a region where the corrected steering torque Tc (= steering torque T) is so large that the sound and vibration adversely affect the vehicle, the current responsiveness is linearly reduced, so that the generated sound and vibration are applied to the vehicle. It is possible to suppress adverse effects.

  FIG. 7 is a diagram illustrating output characteristics of the electric motor 110 that is feedback-controlled by the feedback control unit 40 according to the present embodiment. In FIG. 7, the vertical axis represents the output of the electric motor 110, and the horizontal axis represents time. As described above, when the output of the electric motor 110 (current supplied to the electric motor 110) increases, sound and vibration generated from the steering device 100 increase. FIG. 7 shows a region where sound and vibration measures need to have a sound and vibration adversely affecting the vehicle, and a region where sound and vibration measures are unnecessary.

  In the electric motor 110 that is feedback-controlled by the feedback control unit 40 according to the present embodiment, when the corrected steering torque Tc is equal to or less than the predetermined torque value T0, that is, in a region where noise and vibration countermeasures are unnecessary, the F / B Since the processing unit 42 performs the feedback process with the feedback gain G (= K × (αg = 1)), the current response can be improved. On the other hand, when the corrected steering torque Tc is larger than the predetermined torque value T0, that is, in a region where noise and vibration countermeasures are required, the F / B processing unit 42 sets the feedback gain G (= K × (αg <1)). Therefore, the current response is lower than that when the gain correction coefficient αg = 1. Thereby, in the area | region where a sound and vibration countermeasure are required, the generated sound and vibration are reduced and suppressed.

When the vehicle speed Vc is the predetermined speed V0, the torque correction coefficient calculation unit 43 calculates the torque correction coefficient αt as αt0 (for example, 1.5) based on the control map illustrated in FIG. In this case, the steering torque correction unit 44 corrects the corrected steering torque Tc (= T × αt0> T), which is a value obtained by multiplying the phase-compensated steering torque T by the torque correction coefficient αt0 calculated by the torque correction coefficient calculation unit 43. ) Is output to the gain correction coefficient calculation unit 45. Then, the gain correction coefficient calculation unit 45 calculates the gain correction coefficient αg based on the control map illustrated in FIG. In the control map illustrated in FIG. 6, when the corrected steering torque Tc (= T × αt0) is equal to or smaller than the predetermined torque value T0, the gain correction coefficient αg is 1, and the corrected steering torque Tc (= T × αt0) is When it is larger than the predetermined torque value T0, the gain correction coefficient αg gradually decreases from 1 as the corrected steering torque Tc increases. That is, when αt0 = 1.5, the gain correction coefficient αg becomes 1 when the steering torque T is equal to or smaller than the predetermined torque value T0 / αt0 = T0 × 2/3, and the steering torque T is T0 × 2/3. If it is larger, the gain correction coefficient αg gradually decreases from 1 as the steering torque T increases. As a result, when the vehicle speed Vc is the predetermined speed V0, the current responsiveness becomes lower from the stage where the steering torque T is smaller than when the vehicle speed Vc is zero, and sound and vibration are reduced.
Thus, the steering torque correction unit 44 changes the reference value (the predetermined torque value T0 in FIG. 6) of the corrected steering torque Tc that causes the F / B processing unit 42 to reduce the current response in accordance with the vehicle speed Vc. Even if the vehicle requires different sound and vibration measures for each vehicle speed Vc, the current response is reduced according to the vehicle speed.
Therefore, according to the feedback control unit 40 according to the present embodiment, it is possible to suppress deterioration in steering feeling due to deterioration in responsiveness to steering while suppressing sound and vibration.

Note that the control map showing the correspondence between the vehicle speed Vc and the torque correction coefficient αt shown in FIG. 5, the control map showing the correspondence between the corrected steering torque Tc and the gain correction coefficient αg shown in FIG. 6, the predetermined speed V0 and the predetermined speed. By arbitrarily setting the torque value T0 according to the specification of the vehicle, it is possible to suppress deterioration of steering feeling and deterioration of steering response in any vehicle while suppressing sound and vibration.
For example, in the control map showing the correspondence between the vehicle speed Vc and the torque correction coefficient αt illustrated in FIG. 5, when the vehicle speed Vc is greater than zero, the torque correction coefficient αt when the vehicle speed Vc is zero is used. However, it may be smaller than the torque correction coefficient αt = 1 when the vehicle speed Vc is zero. It may be set according to how the sound and vibration change depending on the vehicle speed Vc depending on the characteristics of the vehicle.

  A control map showing the correspondence between the corrected steering torque Tc and the gain correction coefficient αg shown in FIG. 6 is a control map when the vehicle speed Vc is zero, and the vehicle speed Vc and the torque correction coefficient αt shown in FIG. In the control map showing the correspondence with the above, the torque correction coefficient αt is set to 1 when the vehicle speed Vc is zero, but it is not particularly limited to such a mode. For example, a control map showing the correspondence between the corrected steering torque Tc and the gain correction coefficient αg when the vehicle speed Vc is not zero is created, and the control showing the correspondence between the vehicle speed Vc and the torque correction coefficient αt according to the control map. Create a map.

  Further, for example, the feedback control unit 40 performs a proportional process with a proportional element on the deviation calculated by the deviation calculation unit 41, an integration process with an integral element, and adds these values by an addition calculation unit. In some cases, the gain correction coefficient calculation unit 45 may calculate a correction coefficient for correcting the feedback gain used for the proportional process and a correction coefficient for correcting the feedback gain used for the integration process. Also in this case, both correction coefficients are 1 when the corrected steering torque Tc is from zero to a predetermined torque value T0 or less, and when the corrected steering torque Tc is greater than the predetermined torque value T0, the corrected steering torque Tc. It is preferable to calculate so that the value gradually decreases from 1 as the value increases. Thereby, it can suppress that a steering feeling deteriorates resulting from the responsiveness with respect to steering falling, suppressing a sound and vibration.

DESCRIPTION OF SYMBOLS 10 ... Control apparatus, 20 ... Target electric current calculation part, 30 ... Control part, 40 ... Feedback control part, 41 ... Deviation calculation part, 42 ... Feedback (F / B) processing part, 43 ... Torque correction coefficient calculation part, 44 ... Steering torque correction unit 45 ... Gain correction coefficient calculation unit 100 ... Electric power steering device 110 ... Electric motor

Claims (4)

An electric motor for providing an assisting force to the operation of the steering wheel of the vehicle;
Torque detecting means for detecting a steering torque of the steering wheel;
Vehicle speed detecting means for detecting a vehicle speed which is a moving speed of the vehicle;
Current detection means for detecting an actual current actually supplied to the electric motor;
Target current setting means for setting a target current to the electric motor based on the steering torque detected by the torque detection means;
Correction means for calculating a corrected steering torque obtained by correcting the steering torque detected by the torque detection means according to the vehicle speed detected by the vehicle speed detection means;
Feedback processing is performed with current responsiveness according to the corrected steering torque calculated by the correction means so that the target current set by the target current setting means matches the actual current detected by the current detection means. Feedback processing means;
An electric power steering apparatus comprising:   2. The feedback processing unit according to claim 1, wherein when the corrected steering torque is larger than a predetermined reference value, the current response is reduced as compared with a case where the corrected steering torque is equal to or smaller than the reference value. Electric power steering device.   3. The electric power steering apparatus according to claim 2, wherein the correction unit changes the reference value of the corrected steering torque that causes the feedback processing unit to reduce the current response according to the vehicle speed.   4. The electric power steering apparatus according to claim 3, wherein the correction means makes the reference value smaller when the vehicle speed is greater than zero than when the vehicle speed is zero.

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