JP5235822B2 - Current control device for electric power steering device - Google Patents

Description

  The present invention relates to a current control device for an electric power steering device that suppresses vibration generated by a disturbance voltage having a specific frequency.

  A current control device for a conventional electric power steering device that suppresses vibration generated by a disturbance voltage is detected by, for example, a control input estimator configured by the inverse characteristics of a model corresponding to a control target as shown in Patent Document 1. By inputting the detected current signal that is the output of the controlled object, an estimated input voltage value to the controlled object is obtained, and the difference between the actual controlled input voltage value and the estimated input voltage value is calculated. A disturbance observer that estimates the disturbance voltage estimated value through a low-pass filter as the disturbance voltage estimated value, and the disturbance voltage estimated value by this disturbance observer is used as the disturbance voltage compensation amount as it is, and main control for target current tracking such as feedforward and feedback It is configured to be superimposed on the quantity.

  Here, as described in Non-Patent Document 1, the above-described low-pass filter is indispensable for stabilizing the control system. At this time, the target disturbance voltage is a counter electromotive voltage of the motor proportional to the rudder angular speed and can be compensated for because the frequency is low. However, a high-frequency power supply voltage of 100 Hz or more as shown in Non-Patent Document 2 is used. The disturbance voltage due to the fluctuation could not be suppressed.

  Further, as described in Non-Patent Document 3, the electric power steering first calculates a target current that is substantially proportional to the steering torque of the driver, and secondly performs current control so as to match the target current as much as possible. Thus, the auxiliary torque that is substantially proportional to the steering torque is generated, and the steering torque of the driver is reduced. That is, current control is a local controller that performs local control of the system.

  The electric power steering system simply calculates the target current that is approximately proportional to the steering torque, and even if the target current and the detected current completely match, the phase margin and gain margin are around the crossover frequency that is approximately 100 Hz or less. Oscillates because it cannot be secured sufficiently. Therefore, a phase compensator or the like provides a phase margin and a gain margin to ensure stability.

  However, if it does not match the target current at approximately 100 Hz or less, the phase margin and gain margin of the electric power steering system may decrease and oscillation may occur. Therefore, the current control characteristics are set so that the phase deviation and the gain margin of the entire electric power steering system are set to a level that does not impair the stability when the gain is deviated from 1 and the phase is deviated from 0 deg. It is necessary to keep.

  Also, for example, as shown in Patent Document 2, a notch filter is passed through the detected current signal in order to reduce the influence of torque ripple generated in electromagnetic characteristics corresponding to the electrical angle of the brushless motor on current feedback as disturbance. For example, as in Patent Document 3, there is an example in which a notch filter is passed after the PID controller in order to reduce the influence of the resonance characteristics of the motor on the current feedback. None of these consider the influence of the disturbance voltage applied between the coils from the target current, and the added compensator is a notch filter whose peak frequency gain is smaller than the DC gain. It cannot be suppressed.

JP-A-8-310417 JP 2008-296877 A JP 11-313497 A

Bank, Harashima, Motion Control (1993), pp. 100-101, Corona Kurishige, M., Fukusumi, K., Inoue, N., Kifuku, T. and Otagaki, S., “A New Electric Current Control Strategy for EPS Motors”, SAE 2001− 01− 0484. (2001) Kurishige K., Kifuku T., Inoue, N., Zeniya S. and Otagaki, S., “A Control Strategy to Reduce Steering Torque for Stationary Vehicles Equipped with EPS”, SAE 1999-01−0403 (1999)

  A conventional electric power steering current control device that suppresses vibrations generated by a disturbance voltage is detected by a control input estimator configured with a reverse characteristic of a model corresponding to a control target, as shown in Patent Document 1, for example. By inputting the detected current signal that is the output of the controlled object, the input estimated value for the controlled object is obtained, and the difference between the actual controlled input value and the input estimated value is calculated, and this is used as a low-pass filter. The disturbance observer estimates the disturbance voltage estimated value as the disturbance voltage estimated value, and the disturbance voltage estimated value by the disturbance observer is directly used as the disturbance voltage compensation amount and is superimposed on the main control amount for target value tracking such as feedforward and feedback. It is the composition which makes it.

  Further, as described in Non-Patent Document 1, this low-pass filter is essential for stabilizing the control system. At this time, the target disturbance voltage is a counter electromotive voltage of the motor proportional to the rudder angular velocity and can be compensated for because the frequency is low. For example, the disturbance voltage due to high-frequency voltage fluctuations of 100 Hz or higher is suppressed. I could not.

  Also, for example, as shown in Patent Document 2, a notch filter is passed through the detected current signal in order to reduce the influence of torque ripple generated in electromagnetic characteristics corresponding to the electrical angle of the brushless motor on current feedback as disturbance. For example, as in Patent Document 3, there is an example in which a notch filter is passed after the PID controller in order to reduce the influence of the resonance characteristics of the motor on the current feedback. None of these consider the influence of the disturbance voltage applied between the coils from the target current, and the added compensator is a notch filter whose peak frequency gain is smaller than the DC gain. It cannot be suppressed.

  The present invention has been made to solve the above-described problems, and suppresses vibrations caused by high-frequency disturbance voltages, and also follows the characteristics of the current flowing from the target current to the motor, which is the purpose of current control. It is an object of the present invention to obtain a current control device for an electric power steering device that can sufficiently reduce the influence on the phase and gain margin of the entire electric power steering system and reduce the stability to a level that does not lose stability.

A current control device for an electric power steering device according to the present invention is a current control device for an electric power steering device that suppresses vibrations caused by a disturbance voltage, and is in a feedback loop that causes a current detection value to follow a target current value. In addition, the transfer characteristic of the loop from the disturbance voltage to the determination of the current flowing to the motor is obtained by ω _d √ (1−ζ _d ² ) on both the denominator side and the numerator side so that the frequency of the disturbance voltage and the notch frequency coincide. It is characterized in that a compensator having a notch filter characteristic with a set frequency is inserted.

  According to the present invention, the feedback type current control for causing the current detection value to follow the target current value is performed, and the transfer characteristic of the loop from the disturbance voltage to the current flowing through the motor is determined by the disturbance voltage frequency and the notch frequency. By inserting a compensator with matching notch filter characteristics in the feedback loop, gain fluctuations and phase delays in the frequency characteristics of current control from the target current to the current flowing to the motor can be reduced in the entire electric power steering system. The level can be reduced to a level that can sufficiently secure a phase margin and a gain margin suitable for the loop transfer function. For this reason, there is an unprecedented effect that current fluctuation due to disturbance voltage can be suppressed without impairing the stability of the entire electric power steering system.

It is a block which shows the structure of the electric current control apparatus of the electric power steering apparatus by Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the electric current control apparatus of the electric power steering apparatus by Embodiment 1 of this invention. It is a figure which shows the frequency characteristic of the resonance type phase compensator 2 in Embodiment 1 and 2 of this invention. It is a figure which shows the frequency characteristic of the loop until it determines the electric current which flows into the motor from the disturbance voltage of Embodiment 1 of this invention. It is a figure which shows the frequency characteristic of the loop until it determines the electric current which flows into the motor from the target electric current of Embodiment 1 of this invention. It is a block which shows the structure of the electric current steering apparatus of the electric power steering apparatus by Embodiment 2 of this invention. It is a flowchart which shows operation | movement of the electric current control apparatus of the electric power steering apparatus by Embodiment 2 of this invention. It is a figure which shows the frequency characteristic until it determines the electric current which flows into the motor from the disturbance voltage of Embodiment 2 of this invention. It is a figure which shows the frequency characteristic of the loop until it determines the electric current which flows into the motor from the target electric current of Embodiment 2 of this invention.

Embodiment 1 FIG.
1 is a block diagram showing a configuration of a current control device of an electric power steering apparatus according to Embodiment 1 of the present invention. The first embodiment shown in FIG. 1 is applied to current control of a torque control device such as an electric power steering device. Based on the target current I _ref calculated by a target current calculator (not shown) and the detected current signal I _act detected by the current detector 5 based on the target current I _ref that is detected by the current detector 5, the target feedback voltage V _{ref — fb} is Calculated.

Feedback controller 1, the target current I _ref and the detection current signal I _act current error calculator 1a for calculating an error, the current error calculator proportional controller 1b that performs the output of 1a operations for multiplying a gain K _p, the current error calculator 1a integrator controller 1c for multiplying the gain K _I with integrating an output of, from PI adder 1d which adds the output of the output of the proportional controller 1b integral controller 1c calculates the target feedback voltage V _{Ref_fb} Composed.

In addition, a resonance type phase compensator 2 that inputs the output of the feedback controller 1 and matches the resonance frequency with the disturbance frequency is disposed. The output of the resonance type phase compensator 2 is input to the voltage driving unit 3, and the voltage driving unit 3 generates a driving voltage _Vdr . The voltage driving unit 3 drives the battery voltage V _{dr on} average to match the target voltage V _ref by turning on and off the battery voltage by, for example, a high frequency PWM method. The drive voltage V _dr is applied to the terminal of the motor 4. At this time, the inter-terminal voltage V _t may fluctuate with respect to the drive voltage V _dr due to a disturbance voltage V _w due to, for example, battery voltage fluctuation. Further, the current I _m flowing through the motor 4 is determined according to the impedance characteristics of the coil 4a with respect to the coil application voltage V _c obtained by subtracting the counter electromotive voltage V _e which is proportional to the rotational speed of the motor terminal voltage of the motor 4 It generates torque T _m which is proportional to the current I _m at the torque generating unit 4b.

Next, the operation will be described with reference to the flowchart shown in FIG. First, in step S101, the target current _Iref is read and stored in the memory. In step S102, the detected current signal I _act is read and stored in the memory. In step S103, the current error calculator 1a calculates the current deviation ΔI = I _ref −I _act and stores it in the memory. In step S104, the proportional controller 1b multiplies the current deviation ΔI by the proportional gain K _P and stores it in the memory. . Step S105 The current deviation △ I in integral controller 1c in the integral calculated and stored in the memory by multiplying the gain K _I. In step S106, the PI adder 1d adds the output of the proportional controller 1b and the output of the integral controller 1c, and stores them in the memory as V _{ref_fb} . In step S107, V _{ref_fb} is input to the resonance type phase compensator 2, and the target voltage V _ref is calculated and stored in the memory. In step S108, the target voltage _Vref is output to the voltage driver 3.

The voltage drive unit 3 drives the motor 4 so that the drive voltage V _dr is equal to the target voltage V _ref on average by turning on and off the battery voltage by, for example, a high frequency PWM method.

  At this time, the input / output characteristics of the resonant phase compensator 2 are:

And then, to match the set resonance frequency omega _d disturbance voltage frequency. The set anti-resonance frequency ω _n is made to coincide with ω _d . The set anti-resonance damping coefficient ζ _n is set to a value larger than the set resonance damping coefficient ζ _d , and the frequency characteristic of the resonance type phase compensator 2 peaks at the set resonance frequency ω _d (= 500 Hz) as shown in FIG. The gain is set to have a characteristic that becomes higher than the DC gain. In addition, s in Formula (1) is a frequency transfer function and is a Laplace operator generally used.

Before describing the effects of the disturbance voltage V _w, it describes specifications of the current controller in the electric power steering. The current controller in the electric power steering is a local controller for the entire electric power steering system. For example, according to Non-Patent Document 3 above, even if the electric current I _m which to target current flowing through the motor 4 completely match, an appropriate phase margin and gain margin in the open loop transfer function of the entire system of the electric power steering It is necessary to ensure system stability by giving. Further, the phase and gain of the open loop transfer function of the entire system, including current characteristic, the phase and gain when the current I _m flowing through the motor 4 relative to the target current of the above-mentioned completely match, the current control target current each as overlapped with the phase and gain of the tracking frequency characteristic of the current I _m for. Therefore, the current control characteristic is set to a level at which the phase deviation and gain margin of the entire electric power steering system do not impair the stability when the gain deviation from 1 and the phase deviation from 0 deg. It is necessary to keep.

In the first embodiment, the configuration as shown in FIG. 1 increases the feedback gain of the disturbance voltage frequency. 4, for example, the bandwidth gain by PI control is reduced 3dB and 2 kHz, and the disturbance voltage frequency is assumed that the 500 Hz, the current flowing through the set resonance frequency omega _d to the motor 4 from the disturbance voltage _{V w} as 500 Hz _{I m} It is the result of calculating the transfer function of the loop until it is determined. A solid line indicates the frequency characteristic of the present invention, and a broken line indicates the frequency characteristic of PI control. Setting the resonant frequency omega _d As can be seen from FIG. 4 is a characteristic that the gain becomes the notch frequency is decreased, it is possible to suppress the influence of the disturbance voltage.

Further, as shown in FIG. 5 does not affect the stability of the entire electric power steering system because the target current characteristics of the loop to determine the current I _m flowing through the motor 4 is hardly changed at all range of frequencies.

In the first embodiment, ω _n is matched with ω _d , but for example, the resonance frequency in the equation (1) is strictly ω _d √ (1−ζ _d ² ), so that the damping coefficients ζ _d and ζ _When the difference of _n is large, ω _n may be set to a value different from ω _{d in} order to match the actual resonance frequency and the anti-resonance frequency in Equation (1).

  As described above, according to the first embodiment, during the feedback loop that causes the current detection value to follow the target current value, the transfer characteristic of the loop until the current flowing from the disturbance voltage to the motor 4 is determined is the disturbance voltage. Since a compensator having a notch filter characteristic with the same frequency and the notch frequency is inserted, the output characteristic with respect to the disturbance voltage has a notch filter characteristic, and the notch frequency coincides with the disturbance frequency, and the disturbance suppressing effect is enhanced.

  The compensator is inserted in a loop from the feedback controller 1 that calculates the target feedback voltage based on the error between the target current value and the current detection value to the position where the disturbance voltage and the drive voltage are superimposed. Since the resonance type phase compensator 2 has a set resonance frequency that matches the frequency and has a characteristic that the gain at the set resonance frequency is higher than the DC gain, the characteristics from the target current to the current flowing through the motor 4 are almost all. The disturbance voltage can be suppressed without being changed.

Embodiment 2. FIG.
FIG. 6 is a diagram showing a configuration of a current control device for an electric power steering device according to Embodiment 2 of the present invention. In the second embodiment shown in FIG. 6, torque is applied to the current control of the control device such as an electric power steering device. Target current computing unit signal detection current signal I _act detected by the current detector 5 the current I _m flowing through the target current I _ref calculated by (not shown) and the motor 4 through the resonance type phase compensator 2 I _The target voltage V _ref is calculated by the feedback controller 1 based on _{act_res} .

The feedback controller 1 calculates the error between the target current I _ref and the signal I _{act_res} that has passed through the resonance type phase compensator 2, and _{performs an} operation of multiplying the output of the current error calculator 1 a by the gain K _p. proportional controller 1b that performs gain K multiplied by the _I integral controller 1c with integrating the output of the current error calculator 1a, a target voltage V _ref and the output by adding the output and integral controller 1c of proportional controller 1b It is composed of a PI adder 1d for calculation.

The target voltage V _ref is input to the voltage driver 3 to generate a drive voltage V _dr . The voltage driving unit 3 drives the battery voltage V _{dr on} average to match the target voltage V _ref by turning on and off the battery voltage by, for example, a high frequency PWM method. The drive voltage V _dr is applied to the terminal of the motor 4. At this time, the inter-terminal voltage V _t may fluctuate with respect to the drive voltage V _dr due to a disturbance voltage V _w due to, for example, battery voltage fluctuation. The current flowing through the motor 4 in accordance with the impedance characteristics of the coil 4a with respect to the coil application voltage V _c obtained by subtracting the counter electromotive voltage V _e which is proportional to the rotational speed of the motor 4 to the terminal voltage V _t of the motor 4 I _m It generates torque T _m which is proportional to the current I _m flowing through the motor 4 by the torque generating unit 4b together is determined.

Next, the operation will be described with reference to the flowchart of FIG. First, in step S201, the target current _Iref is read and stored in the memory. In step S202, the detected current signal I _act is read and stored in the memory. In step S203, the detected current signal I _act is input to the resonance type phase compensator 2, and I _{act_res} is calculated and stored in the memory. In step S204, the current deviation _ΔI = I _ref −I _{act_res} is calculated by the current error calculator 1a and stored in the memory, and in step S205, _ΔI is multiplied by the proportional gain K _P and stored in the memory by the proportional controller 1b. Step S206 The △ I with integral controller 1c in the integral calculated and stored in the memory by multiplying the gain K _I. In step S207, the output of the proportional controller 1b and the output of the integral controller 1c are added by the PI adder 1d and stored in the memory as the target voltage _Vref . In step S208, the target voltage _Vref is output to the voltage driver 3.

The voltage drive unit 3 drives the motor 4 so that the drive voltage V _dr is equal to the target voltage V _ref on average by turning on and off the battery voltage by, for example, a high frequency PWM method.

In the second embodiment, such a configuration increases the ratio of disturbance frequency components included in the feedback component. As a result, for example, the disturbance voltage frequency on the assumption that the 500Hz, the result of calculation of the transfer function of the loop to determine the current I _m flowing from disturbance voltage V _w the set resonance frequency omega _d as 500Hz to the motor 4, FIG. as shown in 8, it is possible to set the resonance frequency omega _d is a characteristic in which the gain becomes the notch frequency is decreased to suppress the influence of the disturbance voltage.

Further, as shown in FIG. 9, the whole the characteristics of the loop until determining the current I _m flowing from the target current to the motor 4 is changed can be suppressed small in the non-set resonant frequency ω _{d (=} 500Hz) in the electric power steering system When the frequency is sufficiently higher than the crossover frequency, the resonance frequency ω _d does not affect the stability of the entire system.

Also in the second embodiment, in the case as described in the first embodiment, ω _n does not have to be completely matched with ω _d .

In the second embodiment, the resonance type phase compensator 2 is processed by a microcomputer. However, since the resonance type phase compensator 2 is arranged at the subsequent stage of the current detector 5, an analog circuit configuration is also possible. If you have an analog circuit, rather than the detection current signal I _act in step S202, step S203 is unnecessary since read were processed detection current signal I _act in the resonance type phase compensator 2 output. When configured with an analog circuit, the output of the resonant phase compensator is not affected by the current control sampling frequency, particularly when the frequency of the disturbance voltage is high.

  As described above, according to the second embodiment, as the compensator, the current detector 5 that detects the current flowing through the motor 4 and the feedback that calculates the target feedback voltage based on the error between the target current value and the current detection value. The resonance type phase compensator 2 is inserted into a loop between the controller 1 and has a set resonance frequency that matches the disturbance frequency and has a characteristic that the gain at the set resonance frequency is higher than the DC gain. Therefore, the disturbance voltage can be suppressed without changing the characteristics of the loop from the target current to the current flowing through the motor 4 except in the vicinity of the disturbance frequency. Further, since it is arranged at the subsequent stage of the current detector 5, an analog circuit configuration is possible, so that the output of the resonance type phase compensator is not affected by the current control sampling frequency particularly when the frequency of the disturbance voltage is high.

  DESCRIPTION OF SYMBOLS 1 Feedback controller, 1a Current error calculator, 1b Proportional controller, 1c Integration controller, 1d PI adder, 2 Resonance type phase compensator, 3 Voltage drive part, 4 Motor, 5 Current detector.

Claims (3)

A current control device for an electric power steering device that suppresses vibration generated by a disturbance voltage,
During the feedback loop that follows the current detection value with respect to the target current value, the transfer characteristics of the loop from the disturbance voltage to the determination of the current flowing to the motor are such that the frequency of the disturbance voltage matches the notch frequency. A current control device for an electric power steering apparatus, wherein a compensator having a notch filter characteristic in which a frequency setting obtained by ω _d √ (1−ζ _d ² ) is provided on both numerator sides is inserted. In the electric current steering device of the electric power steering device according to claim 1,
The compensator is inserted into a loop from a feedback controller that calculates a target feedback voltage based on an error between the target current value and the detected current value to a position where the disturbance voltage and the drive voltage are superimposed. A current control device for an electric power steering device, wherein the current control device is a resonance type phase compensator having a resonance frequency that matches the frequency and having a characteristic that a gain at the resonance frequency is higher than a DC gain. In the electric current steering device of the electric power steering device according to claim 1,
The compensator is inserted in a loop between a current detector that detects a current flowing through the motor and a feedback controller that calculates a target feedback voltage based on an error between the target current value and the current detection value. And a resonance type phase compensator having a resonance frequency that matches the disturbance frequency and having a gain at the resonance frequency higher than the DC gain.

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