JP5265410B2 - ELECTRIC POWER STEERING DEVICE, ITS CONTROL METHOD, AND PROGRAM - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology of improving responsiveness, while suppressing an adverse influence on a stationary characteristic of an electric motor. <P>SOLUTION: An electric power steering device includes a torque sensor for detecting steering torque of a steering wheel, the electric motor for applying steering assist force to the steering wheel, a motor current detecting part for detecting actual current supplied actually to the electric motor, a target current calculating part for setting target current to be supplied to the electric motor based on the steering torque detected by the torque sensor, a feedback control part 40 performing a feedback control so that the target current set by the target current calculating part and the actual current detected by the motor current detecting part may coincide with each other, and a feedforward control part 50 performing a feedforward control to increase actual current detected by the motor current detecting part when the target current is increased and having a band pass filter 52 reducing amount of increase in the actual current as a frequency of a variation in the target current is lower. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an electric power steering apparatus, a control method thereof, and a program.

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.
This electric power steering device 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.

  However, the feedback control alone is not necessarily sufficient in response to changes in the current flowing through the electric motor. For this reason, in addition to feedback control, a method has been proposed in which feedforward control for increasing a motor drive signal in accordance with a target current is executed to improve steering response (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 10-100914

  Responsiveness is improved by performing feedforward control in addition to feedback control. However, the adder that adds the feedback control output and the feedforward control output adds the feedback control output and the feedforward control output even in the steady state. There will be a difference between Therefore, simply adding feedforward control to an existing feedback control system may significantly affect the steady state characteristics of the electric motor. Therefore, a new system including the existing feedback control is required to add the feedforward control without affecting the steady-state characteristics of the electric motor.

  For this purpose, the present invention detects a steering torque detecting means for detecting the steering torque of the steering wheel, an electric motor for giving a steering assist force to the steering wheel, and an actual current actually supplied to the electric motor. Current detection means for setting, target current setting means for setting a target current to be supplied to the electric motor based on the steering torque detected by the steering torque detection means, target current set by the target current setting means and the current detection Feedback control means for performing feedback control so that the actual current detected by the means matches, and feedforward control for increasing the actual current detected by the current detection means when the target current increases, and the target current A feed having frequency compensation means for decreasing the increase amount of the actual current as the frequency of fluctuation of the signal is lower And Owado control unit, an electric power steering apparatus comprising: a.

Here, it is preferable that the feedforward control unit further includes a weighting processing unit that increases or decreases the increase amount of the actual current by multiplying a predetermined weighting factor.
The feedforward control means sets the weighting coefficient to set the weighting coefficient according to at least either the vehicle speed of the vehicle on which the electric power steering device is mounted or the amount of change in the steering torque detected by the steering torque detecting means. It is preferable to further have means.
The weighting factor setting means preferably increases the weighting factor as the vehicle speed decreases.
Further, it is preferable that the weighting factor setting means increases the weighting factor as the change amount of the steering torque is smaller.
Here, it is preferable that the frequency compensation means is a bandpass filter that passes only a predetermined frequency.

  From another point of view, the present invention detects the steering torque of the steering wheel, detects the actual current actually supplied to the electric motor that gives the steering assist force to the steering wheel, and based on the detected steering torque. Set a target current to be supplied to the electric motor, perform feedback control so that the target current and the actual current match, perform feedforward control to increase the actual current when the target current increases, In the feedforward control, the control method for the electric power steering apparatus is characterized in that the amount of increase in the actual current is reduced as the frequency of the target current fluctuation is lower.

  From another point of view, the present invention provides a computer with a function of detecting a steering torque of a steering wheel and a function of detecting an actual current actually supplied to an electric motor that applies a steering assist force to the steering wheel. And a function for setting a target current for driving the electric motor based on a steering torque detected by the function for detecting the steering torque, and a function for setting the target current to detect the target current and the actual current set. The function of performing feedback control so that the actual current detected by the function matches, and the feedforward control for increasing the actual current detected by the current detection means when the target current increases, and the fluctuation of the target current This is a program for realizing a function of reducing the increase amount of the actual current as the frequency of is lower.

  According to the present invention, it is possible to improve responsiveness while suppressing adverse effects on steady characteristics of an electric motor without redesigning existing feedback control.

It is a figure showing the schematic structure of the electric power steering device concerning an embodiment. It is a schematic block diagram of the control apparatus of an electric power steering apparatus. It is a schematic block diagram of a target current calculation part. It is a schematic block diagram of a control part. It is a block diagram of a feedback control part and a feedforward control part. It is a figure which shows the characteristic of the band pass filter used by this Embodiment. It is a figure which shows the relationship between weighting coefficient (alpha) and a vehicle speed. It is a figure which shows the relationship between the weighting coefficient (alpha) and the torque variation | change_quantity of a steering wheel. It is a figure which shows the comparison of a step response.

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.
An 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. In the present embodiment, the configuration applied to an automobile is used. Illustrated.

  The steering device 100 includes a wheel-like steering wheel (handle) 101 operated by a driver, and a steering shaft 102 provided integrally with the steering wheel 101. The steering shaft 102 and the upper connection shaft 103 are connected via a universal joint 103a, and the upper connection shaft 103 and the lower connection shaft 108 are connected via a universal joint 103b.

  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 106 a that constitutes a rack and pinion mechanism together with rack teeth 105 a formed on the rack shaft 105. The pinion 106 a is formed at the lower end portion of the pinion shaft 106.

  The steering device 100 also has a steering gear box 107 that houses 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 a steering torque detection unit that detects the steering torque 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.
In addition, the steering device 100 includes a motor current detection unit 33 (see FIG. 4) as an example of a current detection unit that detects the magnitude and direction of the actual current that actually flows through the electric motor 110, and the voltage between the terminals of the electric motor 110. Has a motor voltage detection unit 160 for detecting.

  The steering device 100 includes a control device 10 that controls the operation of the electric motor 110. The control device 10 receives the output value of the torque sensor 109, the output value of the vehicle speed sensor 170 that detects the vehicle speed of the vehicle, the output value of the motor current detection unit 33, and the output value of the motor voltage detection unit 160.

  The electric power steering apparatus 100 configured as described above detects the steering torque applied to the steering wheel 101 by the torque sensor 109, drives the electric motor 110 according to the detected torque, and generates the electric motor 110. Torque 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.
The control device 10 is an arithmetic and logic circuit composed of a CPU, ROM, RAM, backup RAM, and the like.
FIG. 2 is a schematic configuration diagram of the control device 10 of the electric power steering device 100.
The control device 10 includes a torque signal Td in which the steering torque detected by the torque sensor 109 described above is converted into an output signal, and a vehicle speed signal v in which the vehicle speed detected by the vehicle speed sensor 170 is converted into an output signal. Is entered.

Further, the control device 10 converts the motor current signal Im obtained by converting the actual current detected by the motor current detector 33 into an output signal and the voltage detected by the motor voltage detector 160 into an output signal. The motor terminal voltage signal Vm is input.
Since the detection signal from the torque sensor 109 or the like is input as an analog signal, the control device 10 converts the analog signal into a digital signal by an A / D conversion unit (not shown) and takes it into the CPU.

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

Next, the target current calculation unit 20 will be described in detail. FIG. 3 is a schematic configuration diagram of the target current calculation unit 20.
The target current calculation unit 20 includes a base current calculation unit 21 that calculates a base current that serves as a reference for setting the target current, an inertia compensation current calculation unit 22 that calculates a current for canceling the inertia moment of the electric motor 110, and It has. The target current calculation unit 20 calculates the rotation speed of the electric motor 110 based on the damper compensation current calculation unit 23 that calculates a current that limits the rotation of the motor, the motor current signal Im, and the voltage signal Vm between the motor terminals. And a motor rotation speed calculation unit 24. Further, the target current calculation unit 20 includes a final target current determination unit 25 that determines a final target current based on outputs from the base current calculation unit 21, the inertia compensation current calculation unit 22, the damper compensation current calculation unit 23, and the like. I have.

  The base current calculation unit 21 calculates a base current 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, and information on the base current is obtained. The base current signal Ims including it is output. Note that the base current calculation unit 21, for example, displays a map indicating the correspondence between the torque signal Ts and the vehicle speed signal v and the base current, which is created in advance based on empirical rules and stored in the ROM, and the torque signal Ts and the vehicle speed. The base current is calculated by substituting the signal v.

  The inertia compensation current calculation unit 22 calculates an inertia compensation current for canceling out the moment of inertia of the electric motor 110 and the system based on the torque signal Td and the vehicle speed signal v, and generates an inertia compensation current signal Is including information on this current. Output. For example, the base current calculation unit 21 creates a map showing the correspondence between the torque signal Td and the vehicle speed signal v and the inertia compensation current, which is previously created based on an empirical rule and stored in the ROM. The inertia compensation current is calculated by substituting the vehicle speed signal v.

  The damper compensation current calculation unit 23 calculates a damper compensation current for limiting the rotation of the electric motor 110 based on the torque signal Td, the vehicle speed signal v, and the rotation speed signal Nm of the electric motor 110, and information on this current A damper compensation current signal Id including is output. The damper compensation current calculation unit 23 indicates the correspondence between the torque compensation signal Td, the vehicle speed signal v, the rotation speed signal Nm, and the damper compensation current, which are previously created based on empirical rules and stored in the ROM, for example. The damper compensation current is calculated by substituting the torque signal Td, the vehicle speed signal v, and the rotational speed signal Nm into the map.

The final target current determination unit 25 includes the base current signal Ims output from the base current calculation unit 21, the inertia compensation current signal Is output from the inertia compensation current calculation unit 22, and the damper compensation output from the damper compensation current calculation unit 23. A final target current is determined based on the current signal Id, and a target current signal IT including information on this current is output. For example, the final target current determination unit 25 previously created a compensation current obtained by adding the inertia compensation current to the base current and subtracting the damper compensation current based on an empirical rule, and stored it in the ROM. The final target current is calculated by substituting it into a map indicating the correspondence between the compensation current and the final target current.
As described above, the target current calculation unit 20 functions as an example of a target current setting unit that sets a target current to be supplied to the electric motor 110 based on the steering torque detected by the torque sensor 109.

Next, the control unit 30 will be described in detail. FIG. 4 is a schematic configuration diagram of the control unit 30.
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 a motor current detection unit 33 that detects the actual current that actually flows through the electric motor 110. have.

  The motor drive control unit 31 performs feedback control based on the deviation between the target current calculated by the target current calculation unit 20 and the actual current supplied to the electric motor 110 detected by the motor current detection unit 33. A feedback (F / B) control unit 40 as an example of feedback control means is provided. Further, the motor drive control unit 31 includes a feed forward (F / F) control unit 50 as an example of a feed forward control unit that performs feed forward control based on the target current calculated by the target current calculation unit 20. ing. The feedback (F / B) control unit 40 and the feedforward (F / F) control unit 50 will be described in detail later.

  Further, the motor drive control unit 31 includes a PWM signal generation unit 60 that generates a PWM (pulse width modulation) signal for PWM driving the electric motor 110. The PWM signal generation unit 60 generates a PWM signal 60a based on the output values from the feedforward (F / F) control unit 50 and the feedback (F / B) control unit 40, and the generated PWM signal 60a is used as a motor drive unit. 32.

  The motor drive unit 32 drives a motor drive circuit 70 in which four power field effect transistors are connected in an H-type bridge circuit configuration, and drives the gates of two field effect transistors selected from the four. And a gate drive circuit unit 80 for switching the field effect transistor. The gate drive circuit unit 80 selects two field effect transistors according to the steering direction of the steering wheel 101 based on the drive control signal (PWM signal) 60a output from the PWM signal generation unit 60, and selects the selected 2 The field effect transistors are switched.

  The motor current detection unit 33 detects the value of the motor current (armature current) flowing through the electric motor 110 from the voltage generated at both ends of the shunt resistor 71 connected in series with the motor drive circuit 70, and outputs the motor current signal Im. To do.

Next, the feedback control unit 40 and the feedforward control unit 50 will be described.
FIG. 5 is a block diagram of the feedback (F / B) control unit 40 and the feedforward (F / F) control unit 50.
The feedback control unit 40 includes a deviation calculating unit 41 for obtaining a deviation between the target current calculated by the target current calculating unit 20 and the actual current detected by the motor current detecting unit 33, and the deviation becomes zero. And a feedback (F / B) processing unit 42 for performing feedback processing.

The deviation calculation unit 41 outputs a deviation value between the output value IT from the target current calculation unit 20 and the output value Im from the motor current detection unit 33 as a deviation signal 41a.
The feedback (F / B) processing unit 42 performs feedback control so that the target current and the actual current match. For example, the input deviation signal 41a is proportionally processed by a proportional element. A signal obtained by the integration processing by the integration element is output, and the addition calculation unit adds these signals to generate and output a feedback processing signal 42a.

The feedforward control unit 50 is provided in order to improve the followability to the target current calculated by the target current calculation unit 20, and basically outputs an output value corresponding to the variation of the target current.
The feedforward control unit 50 includes a feedforward (F / F) processing unit 51 that performs a feedforward process on the target current calculated by the target current calculation unit 20, and a feedforward (F / F) processing unit 51. A band pass filter (BPF) 52 as an example of a frequency compensation means for changing the feedforward effect according to the frequency of the output signal.

Further, the feedforward control unit 50 includes a weighting processing unit 53 as an example of a weighting processing unit that performs weighting on an output value from the bandpass filter 52, and a weighting coefficient used when the weighting processing unit 53 performs processing. and a weighting factor setting unit 54 as an example of a weighting factor setting unit for setting α.
Further, the feedforward control unit 50 includes an adder 55 that adds the output value 53 a from the weighting processing unit 53 and the output value 42 a from the feedback control unit 40 and outputs the value 50 a to the PWM signal generation unit 60. doing.

The feed forward (F / F) processing unit 51 is a process in which the transfer function is given as an inverse function of the transfer function of the electric motor 110. That is, when the transfer function of the electric motor 110 is G (s), the transfer function H (s) of the feedforward processing unit 51 is H (s) = 1 / G (s). For example, when the transfer function G (s) is expressed by the following equation (1), where Jm is the motor shaft inertia, Kt is the motor torque constant, and Ke is the induced voltage constant, the feedforward processing unit The transfer function H (s) 51 is expressed by the following equation (2).
G (s) = Jm × s / (Jm × L × s ² + Jm × R × s + Ke × Kt) (1)
H (s) = (Jm × L × s ² + Jm × R × s + Ke × Kt) / (Jm × s) (2)
Note that s is a Laplace transform operator.

The band-pass filter (BPF) 52 is a filter that passes only frequencies in a necessary range and does not pass (attenuates) other frequencies. FIG. 6 is a diagram showing the characteristics of the bandpass filter 52 used in the present embodiment. As shown in FIG. 6, the bandpass filter 52 according to the present embodiment sets the passing frequency region to f1 to f2 and attenuates other frequencies not to pass. Therefore, in the low frequency region lower than f1, the value output from the feedforward processing unit 51 is attenuated as the frequency decreases. In the high frequency region higher than f2, the value output from the feedforward processing unit 51 is attenuated as the frequency increases.
It can be exemplified that f1 is 5 Hz and f2 is 100 Hz. By setting f2 to 100 Hz, even when noise is mixed in the torque signal Td or the like, it is possible to suppress adverse effects on the steering feeling of the steering wheel 101 due to the influence of the noise component. Instead of the band pass filter (BPF) 52, a low pass filter (LPF) and / or a high pass filter (HPF) may be provided as appropriate.

The weighting processing unit 53 is a process of multiplying the output value from the bandpass filter 52 by the weighting factor α set by the weighting factor setting unit 54.
The weighting factor setting unit 54 calculates the weighting factor α based on the vehicle speed signal v. FIG. 7 is a diagram showing the relationship between the weighting factor α and the vehicle speed. Based on empirical rules, an optimum weighting factor α corresponding to the vehicle speed is derived in advance as shown in FIG. Then, the weighting factor setting unit 54 adds the vehicle speed signal to a map indicating the correspondence between the vehicle speed signal v and the weighting factor α, or a relational expression between the vehicle speed signal v and the weighting factor α, which has been created and stored in the ROM. The weighting factor α is calculated and set by substituting v.

  Further, the weighting factor setting unit 54 may calculate the weighting factor α based on the torque signal Td. FIG. 8 is a diagram illustrating the relationship between the weighting factor α and the torque change amount of the steering wheel 101. Based on an empirical rule, an optimal weighting factor α corresponding to the amount of torque change of the steering wheel 101 is previously derived as shown in FIG. Then, the weight coefficient setting unit 54 substitutes the torque change amount derived from the torque signal Td into a map that is created in advance and stored in the ROM and indicating the correspondence between the torque change amount of the steering wheel 101 and the weight coefficient α. As a result, the weighting coefficient α is calculated. Alternatively, the weight coefficient α may be calculated by substituting the torque change amount into a relational expression between the torque change amount and the weight coefficient α created in advance. A differential value of the torque signal Td may be calculated as the torque change amount.

  It is also preferable that the weighting factor setting unit 54 calculates the weighting factor α based on the vehicle speed signal v and the torque signal Td. Even in such a case, the relationship between the vehicle speed signal v and the torque change amount of the steering wheel 101 and the optimum weighting factor α is previously derived based on empirical rules. A map showing these correspondences is created in advance and stored in the ROM, and the weighting factor setting unit 54 calculates the weighting factor α by substituting the vehicle speed signal v and the torque change amount into this map. Alternatively, the weighting factor α may be calculated by substituting the vehicle speed signal v and the torque fluctuation into a relational expression between the vehicle speed signal v and the torque change amount and the weighting factor α created in advance.

Below, the effect | action of the electric power steering apparatus 100 comprised as mentioned above is demonstrated.
FIG. 9 is a diagram showing a comparison of step responses.
In FIG. 9, when the target current calculated by the target current calculation unit 20 is a step function, the feedforward control unit 50 and the feedback (F / B) control unit 40 of the control unit 30 of the present embodiment The step response of the output value 50a is indicated by a solid line. Further, the step response of the output value 50a in the system (first comparison system) in which the band-pass filter 52, the weighting processing unit 53, and the weighting coefficient setting unit 54 are excluded from the feedforward control unit 50 of the present embodiment is one point. Shown with a chain line. Further, the feedforward control unit 50 is excluded from the control unit 30 of the present embodiment, that is, the step response of the output value from the feedback control unit 40 in a system (second comparison system) in which only the feedback control unit 40 is provided is a broken line. Is shown. These step responses are compared with the step response of the target current indicated by a thick solid line (thick line).

  As shown in FIG. 9, since the control unit 30 of the present embodiment is provided with the feedforward control unit 50, the responsiveness is better than the second comparison system provided with only the feedback control unit 40. Further, the feedforward control unit 50 of the control unit 30 of the present embodiment is closer to the target current than the first comparison system in the steady state. This is because the output value on the low frequency side is canceled or attenuated by the band pass filter 52, so that the feedforward effect is also canceled or attenuated. In other words, it is because the increase amount of the actual current by the feedforward control unit 50 is reduced by the band pass filter 52 as the frequency of fluctuation of the target current is lower.

  Therefore, for example, when the steering wheel 101 is rotated from a state where it is held (steered) at a fixed position, the output value from the feedforward control unit 50 varies in the output value IT from the target current calculation unit 20. Fluctuates to follow. Therefore, the value input to the PWM signal generation unit 60 is larger than that of the system in which only the feedback control unit 40 is provided without providing the feedforward control unit 50, and the response to the operation of the steering wheel 101 is improved.

Further, by determining the weighting coefficient α according to the vehicle speed as shown in FIG. 7, the responsiveness to the operation of the steering wheel 101 is improved at a low speed such as when entering the garage. On the other hand, since the responsiveness is reduced at high speed, the operation of the steering wheel 101 is stabilized.
Further, as shown in FIG. 8, by determining the weighting coefficient α according to the torque fluctuation, the responsiveness is improved when the steering wheel 101 is operated relatively gently such as when entering the garage. On the other hand, the responsiveness is eased at the time of a sudden handle, which is safe.

  On the other hand, for example, when the steering wheel 101 is held (steered) at a fixed position or operated slowly, the feedforward effect is canceled or attenuated by the bandpass filter 52. In other words, the increase amount of the actual current by the feedforward control unit 50 is reduced by the band pass filter 52 as the frequency of the target current fluctuation is lower. Therefore, the value input to the PWM signal generation unit 60 is the same as the system in which only the feedback control unit 40 is provided without providing the feedforward control unit 50, or even if it is increased, it does not increase greatly and is stable. .

  As described above, in the electric power steering apparatus 100 according to the present embodiment, it is possible to improve the responsiveness while suppressing the adverse effect on the steady characteristics of the electric motor 110. Further, by adding the feedforward control unit 50 according to the present embodiment to a control device provided with only the feedback control unit 40, the above-described effects can be obtained without redesigning the feedback control unit 40.

DESCRIPTION OF SYMBOLS 10 ... Control apparatus, 20 ... Target electric current calculation part, 30 ... Control part, 33 ... Motor current detection part, 40 ... Feedback control part, 50 ... Feed forward control part, 51 ... Feed forward processing part, 52 ... Band pass filter, DESCRIPTION OF SYMBOLS 53 ... Weighting process part, 54 ... Weight coefficient setting part, 55 ... Adder, 100 ... Electric power steering apparatus, 101 ... Steering wheel, 102 ... Steering shaft, 109 ... Torque sensor, 110 ... Electric motor, 160 ... Motor voltage detection Part, 170 ... vehicle speed sensor

Claims (8)

Steering torque detecting means for detecting steering torque of the steering wheel;
An electric motor for providing a steering assist force to the steering wheel;
Current detection means for detecting an actual current actually supplied to the electric motor;
Target current setting means for setting a target current to be supplied to the electric motor based on the steering torque detected by the steering torque detection means;
Feedback control means for performing feedback control so that the target current set by the target current setting means matches the actual current detected by the current detection means;
A feedforward control for increasing the actual current detected by the current detection means when the target current increases, and a frequency compensation means for decreasing the increase amount of the actual current as the frequency of fluctuation of the target current is lower Feedforward control means;
An electric power steering apparatus comprising:   2. The electric power steering apparatus according to claim 1, wherein the feedforward control means further includes weighting processing means for increasing or decreasing the increase amount of the actual current by multiplying a predetermined weighting factor.   The feedforward control means includes weight coefficient setting means for setting the weight coefficient according to at least a vehicle speed of a vehicle on which the electric power steering apparatus is mounted or a change amount of the steering torque detected by the steering torque detection means. The electric power steering apparatus according to claim 1, further comprising:   The electric power steering apparatus according to claim 3, wherein the weighting factor setting unit increases the weighting factor as the vehicle speed decreases.   5. The electric power steering apparatus according to claim 3, wherein the weighting factor setting unit increases the weighting factor as the amount of change in the steering torque decreases.   The electric power steering apparatus according to any one of claims 1 to 5, wherein the frequency compensation means is a band-pass filter that passes only a predetermined frequency.   The steering torque of the steering wheel is detected, the actual current actually supplied to the electric motor that gives steering assist force to the steering wheel is detected, and the target current to be supplied to the electric motor is set based on the detected steering torque. Feedback control is performed so that the target current matches the actual current, and when the target current increases, feedforward control is performed to increase the actual current, and when the feedforward control is performed, the target A control method for an electric power steering apparatus, wherein the amount of increase in the actual current is reduced as the frequency of current fluctuation is lower. On the computer,
A function to detect the steering torque of the steering wheel;
A function of detecting an actual current actually supplied to the electric motor that applies a steering assist force to the steering wheel;
A function of setting a target current for driving the electric motor based on the steering torque detected by the function of detecting the steering torque;
A function of performing feedback control so that the target current set by the function of setting the target current matches the actual current detected by the function of detecting the actual current;
When the target current increases, feed-forward control is performed to increase the actual current detected by the current detection means, and a function of decreasing the increase amount of the actual current as the frequency of the target current fluctuation is lower is realized. Program for.

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