JP2004291815A - Electric power-steering apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power-steering apparatus which can prevent the lag of adding inertia compensation current to a steering torque. <P>SOLUTION: In a target current setting section 12 for setting a target value It of the electric current to be supplied to a motor, an angular acceleration signal Sa obtained by differentiating the angular velocity ω of the motor calculated from a detected value Vm of a motor voltage, etc. is supplied to a filter 1233. The filter 1233 has the frequency characteristic that a phase lead is zero in a DC range, and increases with the increase of frequency in the frequency range from 0 Hz to about 2 Hz, and becomes about 90° at 2 Hz, An inertia compensation control section 125 determines an inertia compensation current value Iic based on the angular acceleration signal Sb after passing through the filter 1233. An adder 127 calculates the target value It by adding the inertia compensation current value Iic to a reference assist current value Ia determined by an assist current setting section 121. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electric power steering device that applies a steering assist force to a steering mechanism of a vehicle by driving an electric motor in accordance with an operation for steering a vehicle, and more particularly, to a motor in an electric power steering device. Regarding compensation for inertia.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an electric power steering device that applies a steering assist force to a steering mechanism by driving an electric motor according to a steering torque applied to a steering wheel (steering wheel) by a driver has been used. In this electric power steering device, a torque sensor for detecting a steering torque applied to a steering wheel is provided, and a target value of a current to be supplied to the motor is set based on the steering torque and the like detected by the torque sensor. Then, based on the deviation between the target value and the current value actually flowing through the motor, a voltage command value to be given to the motor driving means is generated. The motor driving means includes, for example, a PWM signal generation circuit that generates a pulse width modulation signal (PWM signal) having a duty ratio according to the voltage command value, and a power transistor that turns on / off according to the duty ratio of the PWM signal And a voltage according to the duty ratio, that is, a voltage according to the voltage command value, is applied to the motor. The current flowing through the motor by the application of the voltage is detected by a current detector, and a difference between the current target value and the detected value is used as a deviation for generating the voltage command value. In the electric power steering apparatus, the feedback control is performed such that the current of the target value set based on the steering torque or the like flows through the motor.
[0003]
As described above, in the electric power steering apparatus, the target value of the current to be supplied to the motor as the drive source is determined based on the steering torque and the like. The current target value usually improves the operability of the steering operation. The compensation current value. That is, in order to secure the convergence of the inertia compensation current value for compensating the inertia of the motor and the vehicle behavior to the basic assist current value which is a current value determined according to the steering torque in order to generate the steering assist force. The target value of the current to be supplied to the motor is calculated by adding various compensation current values such as the above damping compensation current value. As described above, the feedback control is performed so that the current target values including the various compensation current values flow to the motor, so that the driver's load in operating the steering wheel is reduced while ensuring a good steering feeling.
[0004]
[Patent Document 1]
JP-A-6-247331
[Problems to be solved by the invention]
Of the various compensations described above, the inertia compensation is for canceling the motor inertia peculiar to the electric power steering device, and is usually an angular acceleration (this is a steering acceleration) which is a differential value of a motor angular velocity obtained from a motor terminal voltage or the like. ) Is added to the basic assist current to perform inertia compensation. However, the fact that the driver actually feels inertia often causes a phase shift in the rotation of the motor in response to the operation of the steering wheel, which means a phase shift of the motor angular acceleration with respect to the steering torque.
[0006]
When the steering frequency is low without sharp turning of the steering wheel, the phase shift of the motor angular acceleration with respect to the steering torque hardly occurs, and the turning point of the steering wheel almost coincides with the time point at which the inertia compensation current becomes maximum. However, since the motor is provided on the output side with respect to the steering wheel operated by the driver with the torsion bar interposed therebetween, when the steering frequency increases due to sudden turning of the steering wheel or the like, the torsion of the torsion bar increases, and A phase shift occurs between the steering torque based on the operation and the motor angular acceleration. As a result, in the configuration in which the inertia compensation current value is determined according to the angular acceleration of the motor, the addition of the inertia compensation current is delayed when the steering wheel that needs inertia compensation is turned back. Then, as shown in FIG. 7, the delay in adding the inertia compensation current when the steering wheel is turned back increases as the steering frequency increases (as the steeper turning operation is performed). FIG. 7 shows the change of the inertia compensation current value Iic after the steering wheel is turned back when the steering angle θ becomes θr or −θr, in three cases: when the steering frequency is low, medium, and high. The solid line indicates the change in the inertia compensation current value Iic when the steering frequency is low, the dotted line indicates the change in the inertia compensation current value Iic when the steering frequency is medium, and the one-dot chain line indicates the change in the steering frequency. The graph shows changes in the inertia compensation current value Iic when the value is high.
[0007]
As described above, when the steering frequency is increased, the addition of the inertia compensation current is delayed. Therefore, at the moment of turning the steering wheel, the sense of inertia, that is, the inertia force felt by the driver is not reduced, and as a result, sufficient inertia compensation cannot be performed. Further, after the turning of the steering wheel, when the sense of inertia decreases, the inertia compensation current increases, causing a phenomenon that the steering wheel suddenly becomes lighter (called "torque loss"), which may give the driver an uncomfortable feeling. .
[0008]
Therefore, an object of the present invention is to provide an electric power steering device that prevents a delay in adding an inertia compensation current to a steering torque and performs sufficient inertia compensation regardless of a steering frequency.
[0009]
Means for Solving the Problems and Effects of the Invention
A first invention is an electric power steering device that applies a steering assist force to a steering mechanism of a vehicle by driving an electric motor in accordance with an operation by an operation unit for steering a vehicle,
Torque detecting means for detecting a steering torque applied to the operating means,
A steering acceleration detecting unit that detects a value corresponding to the acceleration of the vehicle steering and outputs a steering acceleration signal indicating the detected value;
Target current setting means for determining a target value of a current to be supplied to the electric motor,
Drive control means for driving the electric motor so that the current of the target value flows through the electric motor,
The target current setting means,
Assist current setting means for determining a basic assist current value that is a value of a current to be supplied to the electric motor to generate the steering assist force based on the steering torque;
Inertia compensation current setting means for determining an inertia compensation current value for compensating for inertia of the electric motor based on the steering acceleration signal,
Adding means for calculating the target value by adding the inertia compensation current value to the basic assist current value,
The steering acceleration detecting means includes a filter means for reducing a phase difference between the steering torque and the steering acceleration signal.
[0010]
According to the first aspect, the inertia compensation current value is determined based on the steering acceleration signal in which the phase shift with respect to the steering torque is reduced by the filter means. Therefore, even if the steering frequency becomes high, the inertia compensation current value is determined. Addition delay is suppressed. Thereby, the inertia compensation current increases at a time when the inertia compensation is required, such as when the operation means for steering is turned back, and the inertia compensation can be sufficiently performed. In addition, the driver does not feel uncomfortable, such as torque loss, due to a delay in inertia compensation.
[0011]
In a second aspect, in the first aspect,
The filter means has a frequency characteristic such that the phase is advanced in a frequency range equal to or lower than a predetermined value, and the phase advance increases from 0 to the predetermined amount as the frequency increases from 0 to the predetermined value. And
[0012]
According to the second aspect, in a steering frequency range (a frequency range equal to or less than a predetermined value) required for practical use, the phase shift of the steering acceleration signal with respect to the steering torque can be eliminated or reduced by the filter means. The inertia compensation can be sufficiently performed by preventing the delay of the addition of the inertia compensation current.
[0013]
In a third aspect, in the second aspect,
The steering acceleration detecting means,
Angular velocity detecting means for detecting an angular velocity of the electric motor and outputting an angular velocity signal indicating the angular velocity;
Differentiating means for generating a value corresponding to the acceleration of the vehicle steering by differentiating the angular velocity signal,
The filter means,
It is arranged before or after the differentiating means or in the differentiating means,
It is characterized by having a frequency characteristic such that the phase lead amount increases from 0 to approximately 90 degrees as the frequency increases from 0 to a predetermined value.
[0014]
According to the third aspect, when the value corresponding to the steering acceleration is calculated based on the angular velocity of the electric motor and the inertia compensation is performed based on the calculated value, the range of the steering frequency that is practically necessary is provided. In the frequency range (0 to 3 Hz), the phase shift of the steering acceleration signal with respect to the steering torque can be reduced by the filter means, so that the delay of the addition of the inertia compensation current can be prevented and the inertia compensation can be sufficiently performed. Note that the predetermined value may be an upper limit (for example, 1.5 to 3 Hz) of a frequency that can be steered by a human.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
<1. Overall Configuration>
FIG. 1 is a schematic diagram showing a configuration of an electric power steering apparatus according to an embodiment of the present invention, together with a vehicle configuration related thereto. This electric power steering apparatus includes a steering shaft 102 having one end fixed to a steering wheel (steering wheel) 100 as an operating means for steering, a rack and pinion mechanism 104 connected to the other end of the steering shaft 102, 100, a torque sensor 3 for detecting a steering torque applied to a steering shaft 102, an electric motor 6 for generating a steering assist force for reducing a driver's load in operating the steering wheel, and a steering shaft for the steering assist force. An electronic control unit (ECU) that receives power from the reduction gear 7 transmitted to the motor 102 and the vehicle-mounted battery 8 via the ignition switch 9 and controls driving of the motor 6 based on sensor signals from the torque sensor 3 and the vehicle speed sensor 4. 5) . When a driver operates the steering wheel 100 in a vehicle equipped with such an electric power steering device, a steering torque due to the operation is detected by a torque sensor 3, and a steering torque signal Ts indicating the detected steering torque and a vehicle speed sensor 4 are provided. The motor 6 is driven by the ECU 5 based on the vehicle speed signal Vs indicating the vehicle speed detected by the ECU 5. As a result, the motor 6 generates a steering assist force, and the steering assist force is applied to the steering shaft 102 via the reduction gear 7, whereby the load on the driver in steering operation is reduced. That is, the sum of the steering torque applied by operating the steering wheel and the torque generated by the steering assist force generated by the motor 6 is given to the rack and pinion mechanism 104 via the steering shaft 102 as the output torque. As a result, when the pinion shaft rotates, the rotation is converted by the rack and pinion mechanism 104 into a reciprocating motion of the rack shaft. Both ends of the rack shaft are connected to wheels 108 via a connecting member 106 including a tie rod and a knuckle arm, and the direction of the wheels 108 changes according to the reciprocating motion of the rack shaft.
[0016]
In the above configuration, a torsion bar is interposed between a portion of the steering shaft 102 on the handle 100 side and a portion to which the steering assist force is applied via the reduction gear 7, and the torque sensor 3 is provided with a torsion bar. The steering torque is detected by detecting the twist. Therefore, as described above, when the steering frequency (steering speed) increases, the torsion of the torsion bar increases, and a phase shift occurs between the angular acceleration of the motor 6 and the steering torque based on the operation of the steering wheel 100. Occurs. Therefore, in the present embodiment, as described later, a filter for eliminating or reducing the phase shift is introduced.
[0017]
<2. Configuration and operation of control device>
FIG. 2 is a block diagram showing a configuration of the ECU 5 which is a control device in the electric power steering device. The ECU 5 includes a microcomputer (hereinafter, abbreviated as “microcomputer”) 10 and a pulse width modulation signal (PWM signal) having a duty ratio corresponding to a voltage command value Vd output from the microcomputer 10. A PWM signal generating circuit 18 for generating a voltage; a motor driving circuit 20 for applying a voltage corresponding to a duty ratio of the PWM signal to the motor 6; detecting a current flowing in the motor 6 and outputting the detection result as a current detection value Im And a voltage detector 22 that detects a voltage between the terminals of the motor 6 (motor voltage) and outputs the detection result as a voltage detection value Vm.
[0018]
The microcomputer 10 executes a predetermined program stored in an internal memory of the microcomputer 10 so that the target current setting unit 12, the subtractor 14, and the feedback control calculation unit (hereinafter, abbreviated as “FB control calculation unit”) 16 are executed. Function as a motor control unit. In the motor control unit 10, the target current setting unit 12 includes a steering torque signal Ts from the torque sensor 3, a vehicle speed signal Vs from the vehicle speed sensor 4, a voltage detection value Vm from the voltage detector 22, and a signal from the current detector 21. Based on the detected current value Im, the target value It of the current to be passed through the motor 6 is determined. The subtractor 14 calculates a deviation It-Im between the current target value It and the current detection value Im from the current detector 21. The FB control calculation unit 16 generates the voltage command value Vd for feedback control to be given to the PWM signal generation circuit 18 by a proportional integration control calculation based on the difference It-Im. The subtractor 14 and the FB control operation unit 16 in the motor control unit 10 constitute a drive control unit of the motor 6 together with the PWM signal generation circuit 18, the motor drive circuit 20, the current detector 21 and the voltage detector 22. .
[0019]
The PWM signal generation circuit 18 generates a pulse signal having a duty ratio according to the voltage command value Vd, that is, a PWM signal whose pulse width changes according to the voltage command value Vd. The motor drive circuit 20 is configured using a plurality of power transistors as switching elements, and these switching elements are turned on / off by the PWM signal generated by the PWM signal generation circuit 18. Thereby, the motor drive circuit 20 generates a voltage corresponding to the voltage command value Vd, and applies the generated voltage to the motor 6. The motor 6 generates a torque having a magnitude and a direction corresponding to a current flowing by applying the voltage.
[0020]
The configuration of the ECU 5 described above is merely an example, and the above-described configuration may be implemented as hardware or software. In the above description, components not directly related to the present invention, such as a phase compensation filter inserted between the torque sensor 3 and the target current setting unit 12, are omitted for convenience of explanation.
[0021]
FIG. 3 is a block diagram showing a functional configuration of the target current setting unit 12 in the motor control unit 10. The target current setting unit 12 includes an assist current setting unit 121 that determines a basic assist current value Ia that is a value of a current to be supplied to the motor 6 for assisting steering, and a steering acceleration that detects an angular acceleration corresponding to the steering acceleration. A detection unit 123, an inertia compensation control unit 125 that determines an inertia compensation current value Iic for compensating the inertia of the motor 6 according to the angular acceleration, and an addition that adds the inertia compensation current value Iic to the basic assist current value Ia And a vessel 127. The steering acceleration detector 123 has an angular velocity detector 1231, a differentiator 1232, and a filter 1233.
[0022]
In the motor control unit 10, the steering torque signal Ts output from the torque sensor 3 and the vehicle speed signal Vs output from the vehicle speed sensor 4 are input to the assist current setting unit 121. The assist current setting unit 121 determines a basic assist current value Ia based on the steering torque signal Ts and the vehicle speed signal Vs. Specifically, a table (referred to as an “assist table”) indicating the relationship between the value of the basic assist current to be supplied to the motor 6 and the steering torque in order to generate an appropriate steering assist force with the vehicle speed as a parameter is stored in advance in the microcomputer. The basic assist current value Ia is determined by referring to this assist table.
[0023]
On the other hand, the detected voltage value Vm output from the voltage detector 22 and the detected current value Im output from the current detector 21 are input to the steering acceleration detector 123. In the steering acceleration detector 123, first, the angular velocity detector 1231 calculates the motor angular velocity ω based on the detected voltage value Vm and the detected current value Im, and outputs a motor angular velocity signal Sω indicating the motor angular velocity ω. Specifically, the motor angular velocity ω is calculated by the following equation.
ω = (Vm−Im × R) / K (1)
Here, R indicates the motor resistance, and K indicates the back electromotive force constant. The angular velocity ω calculated in this way can be identified with the steering angular velocity except for the difference due to the reduction ratio of the reduction gear 7. Hereinafter, the motor angular velocity signal Sω and the steering angular velocity signal are simply referred to as “angular velocity signals” without distinction unless otherwise specified. This angular velocity signal Sω is input to the differentiator 1232. The differentiator 1232 differentiates the angular velocity signal Sω to generate a signal indicating the angular acceleration dω / dt (hereinafter, referred to as “angular acceleration signal” and represented by a sign “Sa”). The angular acceleration signal Sa is input to the filter 1233, and the angular acceleration signal Sb after passing through the filter 1233 (hereinafter, referred to as “filtered angular acceleration signal”) Sb is output as a signal corresponding to the steering acceleration.
[0024]
This filter 1233 is a phase lead / lag filter introduced to eliminate the phase shift of the angular acceleration with respect to the steering torque, and its transfer function G (s) is expressed by the following equation.
_{G (s) = (1 +} T 1 · s) / (1 + T 2 · s) ... (2)
Here, the parameters T ₁ and T ₂ in the above equation may be determined so that the phase shift of the angular acceleration with respect to the steering torque is eliminated (at least reduced). That is, the frequency characteristics of the steering angular velocity or the steering angular acceleration with respect to the steering torque may be examined by experiment, simulation, or the like, and the filter characteristics may be set according to the frequency characteristics so that the phase shift is eliminated or reduced. Hereinafter, a specific example of setting such filter characteristics will be described.
[0025]
FIG. 5 shows a frequency characteristic of the steering angular acceleration with respect to the steering torque. Note that the frequency characteristics shown in this figure are obtained when the steering angle is set to ± 25 degrees. Among the curves in this figure, the dotted curve shows the frequency characteristic of the angular acceleration with respect to the steering torque in the conventional case (when the above-described filter is not used). From the dotted curve in FIG. It can be seen that there is almost no phase shift near the steering frequency of 0, but the phase shift increases as the steering frequency increases, and a phase delay of about 90 degrees occurs when the steering frequency is 2 Hz. Therefore, in the DC domain (frequency 0), the phase lead is 0, and as the frequency becomes higher, the phase lead becomes larger, and the above equation is given so that the filter 1233 has a frequency characteristic such that the phase is advanced by about 90 degrees at 2 Hz. may be determined parameters _{T 1} and _{T 2} (2). However, in a high frequency range of 2 Hz or more, since the advance of the phase causes sound and vibration, it is preferable that the amount of the advance of the phase gradually approaches a constant value or the phase is delayed. FIG. 4 is a characteristic diagram (a gain curve (a) and a phase curve (b)) showing an example of the frequency characteristics of the filter determined in this way. When the filter 1233 (transfer function G (s)) has the frequency characteristic shown in FIG. 4, the frequency characteristic of angular acceleration with respect to steering torque, that is, the steering torque signal Ts is input, and the angular acceleration signal Sb after filtering is output. The frequency characteristic of the transfer element (transfer function) is as shown by the solid curve in FIG. According to this, the phase lag is extremely small until the steering frequency is around 2 Hz. By introducing the filter 1233 having such a frequency characteristic, the phase shift of the angular acceleration with respect to the steering torque in the frequency range of 0 to 2 Hz is substantially reduced. It turns out that it is canceled.
[0026]
The filtered angular acceleration signal Sb obtained as described above is input to the inertia compensation control unit 125. The inertia compensation control unit 125 determines an inertia compensation current value Iic based on the value of the angular acceleration signal Sb after the filtering. The method of determining the inertia compensation current value Iic is the same as the conventional method. Specifically, for example, a table (hereinafter, referred to as an “inertial compensation table”) indicating the relationship between the inertial compensation current value and the angular acceleration value to be added to the basic assist current value Ia in order to perform appropriate inertia compensation is stored in the microcomputer in advance. The inertia compensation current value Iic corresponding to the angular acceleration signal Sb after the filtering process may be obtained by referring to the inertia compensation table stored in a memory in the memory 10. If necessary, the inertia compensation table is created as a table indicating the relationship between the inertial compensation current value to be added to the basic assist current value Ia and the angular acceleration value as a parameter of the vehicle speed, and this inertia compensation table is referred to. Then, the inertia compensation current value Iic may be obtained based on the value of the angular acceleration signal Sb and the value of the vehicle speed signal Vs after the filtering process. Furthermore, instead of the inertia compensation table, a function indicating the relationship between the inertia compensation current value to be added to the basic assist current value Ia and the angular acceleration value or the like is set in advance, and the function is used to perform the filtering process. The inertia compensation current value Iic may be calculated based on the angular acceleration signal Sb and the like.
[0027]
The inertia compensation current value Iic determined by the inertia compensation control unit 125 is input to the adder 127. The adder 127 calculates a current target value It by adding the inertia compensation current value Iic to the basic assist current value Ia. In the actual target current setting section, various compensation current values such as a damping compensation current value for securing convergence of the vehicle behavior and the like are added in addition to the inertia compensation current value. Since these are not directly related to the present invention, the addition of these other compensation current values is omitted in this embodiment for convenience of explanation.
[0028]
The current target value It calculated as described above is input to the subtractor 14 and used for calculating the deviation It-Im for performing the feedback control on the motor 6 as described above.
[0029]
<3. Effect>
As described above, in the present embodiment, the inertia compensation current is calculated based on the angular acceleration signal Sb after the filtering process, that is, the angular acceleration signal Sb in which the phase shift with respect to the steering torque is substantially eliminated in the range of the steering frequency from about 0 to 2 Hz. The value Iic is determined (FIG. 5), and even if the steering frequency (steering speed) increases, the inertia compensation current value Iic hardly causes a phase shift with respect to the steering wheel operation. This means that the introduction of the filter 1233 allows the torsion bar to be regarded as a rigid body from the viewpoint of inertia compensation. Therefore, according to the present embodiment, unlike the related art in which the addition of the inertia compensation current (the increase in the absolute value of the inertia compensation current value Iic) is delayed as the steering frequency increases as shown in FIG. As shown in FIG. 6, the inertia compensation current is added with almost no delay when the steering wheel is turned back regardless of the steering frequency (the absolute value of the inertia compensation current value Iic increases). As a result, the inertia compensation current increases in a timely manner when the inertia compensation is required, such as when the steering wheel is turned back, so that the inertia compensation can be sufficiently performed. I will not give it to anyone.
[0030]
<4. Modification>
In the above embodiment, the angular velocity signal Sω is differentiated by the differentiator 1232 to calculate the angular acceleration signal Sa, and the angular acceleration signal Sa is filtered by the filter 1233. The angular acceleration signal Sb may be obtained by subjecting Sω to filter processing by the filter 1233 and then differentiating the differential processing by the differentiator 1232. That is, the filter 1233 may be arranged either before or after the differentiator 1232. Further, the differentiator 1232 and the filter 1233 may be integrated to be realized as one differential filter.
[0031]
In the above embodiment, the angular acceleration corresponding to the steering acceleration used to determine the inertia compensation current value Iic is calculated by differentiating the motor angular velocity ω obtained from the voltage detection value Vm or the like. Alternatively, a value corresponding to the steering acceleration obtained by another method may be used for determining the inertia compensation current value Iic. For example, when the vehicle equipped with the electric power steering device includes a steering angle sensor, the signal detected by the steering angle sensor is second-order differentiated to calculate the angular acceleration corresponding to the steering acceleration, The inertia compensation current value Iic may be determined based on this. Even in this case, the same effect as in the above embodiment can be obtained by introducing a filter that eliminates or reduces the phase difference between the obtained angular acceleration and the steering torque. Note that the angular acceleration obtained based on the signal from the steering angle sensor usually has a smaller phase shift with respect to the steering torque than the motor angular acceleration, so that the frequency characteristic of the filter to be introduced is also in accordance therewith.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a configuration of an electric power steering device according to an embodiment of the present invention, together with a vehicle configuration related thereto.
FIG. 2 is a block diagram showing a configuration of an ECU which is a control device in the electric power steering device according to the embodiment.
FIG. 3 is a block diagram showing a functional configuration of a target current setting unit in the embodiment.
FIG. 4 is a Bode diagram showing frequency characteristics of the filter in the embodiment.
FIG. 5 is a Bode diagram showing a frequency characteristic of angular acceleration after filtering with respect to a steering torque in the embodiment, together with a conventional frequency characteristic without filtering.
FIG. 6 is a diagram showing a change in inertia compensation current when the steering wheel is turned back in the electric power steering apparatus according to the embodiment.
FIG. 7 is a diagram showing a change in inertia compensation current when the steering wheel is turned back in the conventional electric power steering device.
[Explanation of symbols]
3 ... torque sensor 4 ... vehicle speed sensor 5 ... electronic control unit (ECU)
6 Motor 10 Microcomputer (motor control unit)
12 Target current setting unit 14 Subtractor 16 Feedback control calculation unit (FB control calculation unit)
18 PWM signal generation circuit 20 Motor drive circuit 21 Current detector 22 Voltage detector 121 Assist current setting unit 123 Steering acceleration detection unit 1231 Angular velocity detection unit 1232 Differentiator 1233 Filter 125 Inertial compensation control Unit 127 Adder Ts Steering torque signal Vs Vehicle speed signal Im Current detection value Vm Voltage detection value Ia Basic assist current value It Current target value Iic Inertial compensation current value Vd Voltage command value

Claims (3)

An electric power steering device that applies a steering assist force to a steering mechanism of the vehicle by driving an electric motor in accordance with an operation by an operation unit for steering a vehicle,
Torque detecting means for detecting a steering torque applied to the operating means,
A steering acceleration detecting unit that detects a value corresponding to the acceleration of the vehicle steering and outputs a steering acceleration signal indicating the detected value;
Target current setting means for determining a target value of a current to be supplied to the electric motor,
Drive control means for driving the electric motor so that the current of the target value flows through the electric motor,
The target current setting means,
Assist current setting means for determining a basic assist current value that is a value of a current to be supplied to the electric motor to generate the steering assist force based on the steering torque;
Inertia compensation current setting means for determining an inertia compensation current value for compensating for inertia of the electric motor based on the steering acceleration signal,
Adding means for calculating the target value by adding the inertia compensation current value to the basic assist current value,
The electric power steering apparatus according to claim 1, wherein the steering acceleration detection unit includes a filter unit that reduces a phase difference between the steering torque and the steering acceleration signal. The filter means has a frequency characteristic in which the phase is advanced in a frequency range equal to or lower than a predetermined value, and the amount of phase advance increases from 0 to a predetermined amount as the frequency increases from 0 to a predetermined value. The electric power steering device according to claim 1, wherein The steering acceleration detecting means,
Angular velocity detecting means for detecting an angular velocity of the electric motor and outputting an angular velocity signal indicating the angular velocity;
Differentiating means for generating a value corresponding to the acceleration of the vehicle steering by differentiating the angular velocity signal,
The filter means,
It is arranged before or after the differentiating means or in the differentiating means,
The electric power steering apparatus according to claim 2, wherein the electric power steering apparatus has a frequency characteristic such that the phase lead amount increases from 0 to approximately 90 degrees as the frequency increases from 0 to a predetermined value.

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