JP2014064424A - Dc motor controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor controller which can perform feedback control properly on the basis of motor current even when the motor current contains ripples.SOLUTION: A motor controller 100 has: a current detection section 7 for detecting current flowing to a DC motor 200; a low pass filter 8 for removing ripples from the current detected by the current detection section 7; a speed detection section 30 for extracting the ripples from the current detected by the current detection section 7 and detecting rotation speed of the DC motor 200 on the basis of the ripples; a speed controller 2 for outputting a current instruction value on the basis of the comparison result between the speed instruction value and the detection speed; a current controller 3 for outputting a voltage instruction value on the basis of the comparison result between the current instruction value and the detection current outputted from the low pass filter 8; and a motor driving section 20 for driving the DC motor 200 on the basis of the voltage instruction value.

Description

  The present invention relates to a DC motor control apparatus that performs feedback control by detecting a current flowing through a motor.

  A technique for controlling the rotation of a motor by feedback control has been well known. For example, when controlling the rotation speed of the motor by controlling the current flowing through the motor (motor current), a current detection circuit for detecting the motor current is provided. Then, the current value of the motor current detected by the current detection circuit is compared with the command value, and feedback control is performed so that a current that matches the command value flows to the motor. Patent Documents 1 and 2 describe a motor control device based on such feedback control.

  In the motor control device of Patent Document 1, a current detection unit that detects a current flowing through the motor and an AC component having a frequency equal to or higher than the first cutoff frequency are removed from the current detected by the current detection unit to obtain a motor current. The first filter means for output and the current detected by the current detection means remove the AC component equal to or higher than the second cutoff frequency lower than the first cutoff frequency, and output it as the rotational torque of the motor. 2 filter means. The first filter means secures the responsiveness of position control, and the second filter means increases the accuracy of torque control.

  In the motor control device of Patent Document 2, a current detection unit that detects a motor current, a current ripple detection unit that detects a current ripple included in the motor current and outputs a pulse signal synchronized with the rotation of the motor, and a pulse signal And a motor control unit for controlling the motor based on the motor control unit. When the current value detected by the current detecting means is larger than the predetermined value and the pulse signal is not detected continuously for a predetermined time, it is determined that the motor is in a locked state and the motor is stopped. Yes.

  In Patent Document 1, detection means such as a rotary encoder is provided to control the rotation position (rotation amount) and rotation speed of a motor. On the other hand, in Patent Document 2, a ripple of a motor current is detected, and control is performed by acquiring information on the rotational position and rotational speed of the motor based on the ripple.

JP-A-7-231687 JP 2000-166275 A

  The motor control device disclosed in Patent Document 1 requires a detecting means such as a rotary encoder, which increases the number of parts. On the other hand, according to the motor control device of Patent Document 2, a rotary encoder or the like is not required by using the ripple of the motor current. However, as in Patent Document 2, it is actually difficult to control the rotational position and rotational speed of the motor based on the ripple of the motor current. The reason is as follows.

  FIG. 11 shows an example of a conventional motor control apparatus 300 that performs feedback control by detecting a current flowing through the motor. The position control unit 1 outputs a speed command value based on the comparison result between the target position and the detected position. The speed control unit 2 outputs a current command value based on the comparison result between the speed command value and the detected speed. The current control unit 3 outputs a voltage command value based on the comparison result between the current command value and the detected current. The duty calculator 4 calculates the duty of a PWM (Pulse Width Modulation) signal based on the voltage command value and the voltage value of the power supply B. The PWM circuit 5 generates and outputs a PWM signal corresponding to the duty. The inverter circuit 6 performs a switching operation based on the PWM signal and drives the motor 200. The current detection unit 7 detects the value of the current flowing through the motor 200 based on the voltage generated at both ends of the current detection resistor R.

  The output of the current detection unit 7 is fed back to the current control unit 3 as a detection current. The output of the current detection unit 7 is fed back to the speed control unit 2 as a detection speed via the bandpass filter 9, the pulse generation circuit 10, and the speed calculation unit 11. Further, the output of the current detection unit 7 is fed back to the position control unit 1 as a detection position via the band pass filter 9, the pulse generation circuit 10, and the position calculation unit 12.

  In FIG. 11, the motor current detected by the current detection unit 7 is fed back to the current control unit 3 as it is. However, if this is done, the current control unit 3 outputs the voltage command value so as to cancel the fluctuation of the ripple included in the motor current, so that a current without ripple flows in the motor 200 as a result of the feedback control. That is, the current detected by the current detector 7 is a current that does not include ripples (broken lines) as shown in FIG. For this reason, also in the band pass filter 9, the output becomes a constant value as shown in FIG. 12B, and the ripple (broken line) is not extracted. Therefore, the pulse generation circuit 10 does not generate a pulse synchronized with the ripple, and the pulse output becomes zero as shown in FIG. As a result, the speed calculation unit 11 cannot acquire information on the rotation speed of the motor 200 from the pulse cycle, and the position calculation unit 12 obtains information on the rotation position (rotation amount) of the motor 200 from the number of pulses. Since it cannot be acquired, motor control cannot be performed properly.

  The subject of this invention is providing the control apparatus of the direct current motor which can perform feedback control appropriately based on a motor current, even if a motor current contains a ripple.

  A control device for a DC motor according to the present invention is detected by a current detection unit that detects a current flowing through the DC motor, a first filter that removes a ripple from the current detected by the current detection unit, and a current detection unit. Ripple is extracted from the detected current, and the speed detection unit that detects the rotational speed of the DC motor based on the ripple is compared with the current based on the comparison result between the speed command value and the rotation speed value detected by the speed detection unit. A first control unit that outputs a command value; a second control unit that outputs a voltage command value based on a comparison result between the current command value and the current value output from the first filter; And a motor drive unit that drives the DC motor based on the voltage command value output from the control unit 2.

  If it does in this way, the ripple of the motor current detected by the current detection part will be removed by the 1st filter, and the detection current without a ripple will be inputted into the 2nd control part. Accordingly, since the second control unit does not output a command value that cancels the fluctuation of the ripple, a current including the ripple flows in the motor. For this reason, it is possible to acquire information on the rotational position and rotational speed of the motor from the ripple of the motor current, thereby enabling proper motor control.

  In the present invention, the speed detection unit includes a second filter that extracts a ripple from the current detected by the current detection unit, a pulse generation circuit that generates a pulse from the ripple extracted by the second filter, and the pulse generation A speed calculation unit that calculates the rotational speed of the DC motor based on the pulse generated by the circuit may be used.

  In the present invention, based on the comparison result between the position calculation unit that calculates the rotational position of the DC motor based on the pulse generated by the pulse generation circuit, and the rotational position calculated by the target position and the position calculation unit, A third control unit that outputs a speed command value to one control unit may be further provided.

  In the present invention, it is preferable that the first filter is constituted by a low-pass filter and the second filter is constituted by a band-pass filter.

  In this invention, you may further provide the filter control part which controls the 1st and 2nd filter. In this case, the filter control unit changes the signal pass bands of the first and second filters from the low frequency side to the high frequency side in conjunction with the speed of the DC motor from low to high.

  ADVANTAGE OF THE INVENTION According to this invention, even if motor current contains a ripple, the control apparatus of the DC motor which can perform feedback control appropriately based on motor current can be provided.

It is a block diagram showing an embodiment of the present invention. It is the figure which showed the specific structure of the position control part of FIG. 1, a speed control part, a current control part, and a duty calculation part. It is the figure which showed the specific structure of the inverter circuit and current detection part of FIG. It is the figure which showed the electric current path | route in an inverter circuit. It is the figure which showed the characteristic of the low-pass filter (LPF) and the band pass filter (BPF). It is the figure which showed the signal waveform in each part of FIG. It is the block diagram which showed other embodiment of this invention. It is a figure explaining control of the filter in the embodiment of FIG. It is the block diagram which showed other embodiment of this invention. It is the block diagram which showed other embodiment of this invention. It is the block diagram which showed the conventional motor control apparatus. It is the figure which showed the signal waveform in each part of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, the same reference numerals are given to the same or corresponding parts.

  First, the configuration of a DC motor control device (hereinafter referred to as “motor control device”) according to an embodiment of the present invention will be described with reference to FIG. Here, a motor control device used for a vehicle power window device is taken as an example. However, the present invention can also be applied to a motor control device used to open and close an electric parking brake of a vehicle, a sliding door, or a sunroof.

  In FIG. 1, a motor control apparatus 100 controls a DC motor (hereinafter simply referred to as “motor”) 200 for opening and closing a window, and includes blocks indicated by reference numerals 1 to 12.

  The position control unit 1 outputs a speed command value based on a comparison result between a target position (target value of a window position) input from the outside and a detection position input from a position calculation unit 12 described later.

  The speed control unit 2 outputs a current command value based on a comparison result between a speed command value input from the position control unit 1 and a detected speed input from a speed calculation unit 11 described later.

  The current control unit 3 outputs a voltage command value based on a comparison result between a current command value input from the speed control unit 2 and a detected current input from a low-pass filter 8 described later.

  The duty calculation unit 4 performs a predetermined calculation based on the voltage command value input from the current control unit 3 and the voltage value of the power source B, and PWM (Pulse Width Modulation) for driving the motor 200 ) Calculate the duty of the signal.

  The PWM circuit 5 generates a PWM signal corresponding to the duty calculated by the duty calculator 4 and outputs the PWM signal to the inverter circuit 6. Further, the PWM circuit 5 outputs information representing normal rotation / reverse rotation of the motor 200 to the current detection unit 7 described later as a code.

  The inverter circuit 6 performs a switching operation by the PWM signal supplied from the PWM circuit 5, supplies current from the power supply B to the motor 200, and drives the motor 200. A current detection resistor R for detecting a current (motor current) flowing through the motor 200 is connected between the inverter circuit 6 and the ground.

  The motor 200 is formed of a direct current motor including a brush and a commutator, and rotates forward or backward depending on the direction of a flowing current to open and close a vehicle window. While the motor 200 is being driven, a ripple occurs in the motor current each time the commutator that is in sliding contact with the brush is switched. As will be described later, based on this ripple, the rotational speed of the motor 200 (= window opening / closing speed) and the rotational position (= window opening / closing position) can be detected.

  The current detection unit 7 detects the value of the current flowing through the motor 200 based on the voltage generated at both ends of the current detection resistor R. The current detection unit 7 determines the direction of the current flowing through the motor 200 based on the code input from the PWM circuit 5. The output (signal at point a) of the current detector 7 is a signal including ripples as shown in FIG.

  The low-pass filter 8 (first filter) has a filter characteristic like the LPF (solid line) shown in FIG. 5 and removes ripples from the motor current detected by the current detection unit 7. The output of the low-pass filter 8 (signal at point b) is a DC signal as shown by the solid line in FIG. 6B, and is supplied to the current control unit 3 as a detection current (current value).

  The bandpass filter 9 (second filter) has a filter characteristic like the BPF (broken line) shown in FIG. 5 and is included in a specific frequency band from the motor current detected by the current detector 7. Extract ripples. The output of the bandpass filter 9 (the signal at point c) has a constant ripple as shown in FIG. 6C and is given to the pulse generation circuit 10.

  The pulse generation circuit 10 generates a pulse based on the ripple input from the band pass filter 9. For example, a pulse that is high in the positive half-wave section of the ripple waveform and low in the negative half-wave section is generated. The output (signal at point d) of the pulse generation circuit 10 is a pulse (cycle = T) synchronized with the ripple as shown in FIG. 6D, and is given to the speed calculation unit 11 and the position calculation unit 12.

  The speed calculation unit 11 measures the period T of the pulse input from the pulse generation circuit 10 and calculates the current rotation speed of the motor 200, that is, the opening / closing speed of the window, from the period T. Since the frequency of the ripple output from the bandpass filter 9 is proportional to the rotational speed of the motor 200, the cycle T of the pulse generated by the pulse generation circuit 10 is inversely proportional to the rotational speed of the motor 200. Therefore, the rotation speed Vm of the motor 200 can be obtained by the calculation of Vm = 1 / T. The output (speed value) of the speed calculation unit 11 is given to the speed control unit 2 as a detected speed.

  As shown in FIG. 6E, the position calculation unit 12 counts the number of pulses input from the pulse generation circuit 10, and from this counted value, the current rotation position (rotation amount) of the motor 200, that is, the window position. Calculate the position. The output (pulse count value) of the position calculation unit 12 is given to the position control unit 1 as a detection position.

  In the above, the duty calculation unit 4, the PWM circuit 5, and the inverter circuit 6 constitute a motor drive unit 20. The bandpass filter 9, the pulse generation circuit 10, and the speed calculation unit 11 constitute a speed detection unit 30. The bandpass filter 9, the pulse generation circuit 10, and the position calculation unit 12 constitute a position detection unit 40. The speed controller 2 constitutes a “first controller” in the present invention, the current controller 3 constitutes a “second controller” in the present invention, and the position controller 1 corresponds to the present invention. The “third control unit” in FIG.

  A specific configuration of the position control unit 1, the speed control unit 2, the current control unit 3, and the duty calculation unit 4 of FIG. 1 is shown in FIG.

  The position control unit 1 includes a calculator 1a that calculates a deviation between the target position and the detected position, and differential (S, D), proportional calculation (P), and integral (1 / S, I) for the deviation. And a controller 1b for calculating and outputting a speed command value based on the calculation.

  The speed control unit 2 includes a calculator 2a that calculates a deviation between the speed command value and the detected speed, and a controller 2b that performs a proportional calculation (P) on the deviation and outputs a current command value. .

  The current control unit 3 calculates a deviation between the current command value and the detected current, performs proportional calculation (P) and integral (1 / S, I) on the deviation, And a controller 3b that calculates and outputs a voltage command value based on the controller 3b.

  The duty calculation unit 4 includes a calculator 4a that calculates the ratio of the voltage command value to the voltage value of the power supply voltage B, and a controller 4b that calculates the duty by multiplying the calculation result by 100%.

  Specific configurations of the inverter circuit 6 and the current detection unit 7 of FIG. 1 are shown in FIG.

  The inverter circuit 6 includes an H bridge circuit in which four switching elements Q1 to Q4 are bridge-connected. The switching elements Q1 to Q4 are made of, for example, a MOS type FET. The PWM circuit 5 generates four PWM signals (PWM1 to PWM4) based on the duty calculated by the duty calculator 4, and outputs each PWM signal to each gate of the switching elements Q1 to Q4. Switching elements Q <b> 1 to Q <b> 4 perform an on / off switching operation based on the PWM signal, and supply current from power supply B to motor 200.

  The current detection unit 7 includes an operational amplifier 7a and a multiplier 7b. The operational amplifier 7a takes in a voltage generated at both ends of the resistor R due to the motor current flowing through the current detection resistor R, and multiplies it by a predetermined gain to convert it into a current value. The multiplier 7b multiplies the output of the operational amplifier 7a by a sign (1 or -1) given from the PWM circuit 5 and outputs a detected current value having a positive or negative sign.

  The above sign is determined by the direction of the current flowing through the motor 200. As shown in FIG. 4A, when Q1 of the switching elements is in the on state, Q2 and Q3 are in the off state, and Q4 is performing the switching operation by the PWM signal, the current flows to the motor 200 through the path of the arrow. Flows and the motor 200 rotates forward. In this case, a code “1” representing normal rotation of the motor is output from the PWM circuit 5 to the current detection unit 7. As the motor 200 rotates forward, the window closes.

  On the other hand, as shown in FIG. 4B, when Q3 among the switching elements is in the on state, Q1 and Q4 are in the off state, and Q2 is performing the switching operation by the PWM signal, the motor 200 is routed by the arrow. Current flows, and the motor 200 reverses. In this case, the code “−1” representing the reverse rotation of the motor is output from the PWM circuit 5 to the current detection unit 7. As the motor 200 reverses, the window opens.

  In the motor control device 100 having the above configuration, the output of the current detection unit 7 is not directly fed back to the current control unit 3 but is fed back to the current control unit 3 through the low-pass filter 8. It is a feature.

  As described above, when the output of the current detection unit 7 is directly fed back to the current control unit 3, the output of the current detection unit 7 includes a ripple as shown in FIG. The control unit 3 outputs a voltage command value that suppresses the fluctuation of the ripple. For this reason, the current flowing through the motor 200, that is, the current flowing through the current detection resistor R is a current without ripple. As a result, no ripple appears in the output of the current detection unit 7, so no ripple is extracted in the band pass filter 9. Therefore, the speed calculation unit 11 and the position calculation unit 12 cannot calculate the rotation speed and rotation position of the motor 200 from the ripple.

  However, according to the above-described embodiment, the ripple included in the output of the current detection unit 7 is removed by the low-pass filter 8 and then the output is fed back to the current control unit 3. The voltage command value that suppresses is not output. For this reason, a motor current including a ripple flows in the current detection resistor R, and a ripple appears in the output of the current detection unit 7. Therefore, the ripple is extracted by the band pass filter 9 and converted into a pulse by the pulse generation circuit 10, so that the speed calculation unit 11 and the position calculation unit 12 can rotate the rotation speed of the motor 200 from the ripple (= window opening / closing speed). And the rotation position (= opening / closing position of the window) can be calculated. As a result, appropriate feedback control for the motor 200 can be performed based on accurate rotational speed and rotational position information.

  Next, another embodiment of the present invention will be described with reference to FIG. In the motor control device 101 of FIG. 7, a filter control unit 13 is added to the configuration of FIG. Since other configurations are the same as those in FIG. 1, the description of the same parts as those in FIG. 1 is omitted.

  In the present embodiment, the low-pass filter 8 and the band-pass filter 9 are composed of digital filters, and the characteristics of the filters 8 and 9 are controlled by the filter control unit 13 according to the rotation speed of the motor 200. Details will be described below.

  In the initial state, each of the filters 8 and 9 has a signal pass band set on the low frequency side as shown in FIG. When the motor 200 rotates, the filter control unit 13 converts the waveform of the current output from the current detection unit 7 into a frequency spectrum by Fast Fourier Transform (FFT), and analyzes the frequency spectrum to thereby calculate the frequency of the ripple. To extract.

  When the motor 200 rotates at a low speed, the ripple frequency is low, and when the motor 200 rotates at a high speed, the ripple frequency is high. Therefore, the filter control unit 13 monitors the temporal change in the ripple frequency, and as the speed of the motor 200 increases from a low speed to a high speed, the signal passbands of the filters 8 and 9 are shown in FIG. As shown in c), the low frequency side is changed to the high frequency side in conjunction with each other.

  In this way, when the rotation speed of the motor 200 is low, the ripples at the low speed rotation are removed or extracted by the filters 8 and 9 set on the low frequency side, and when the rotation speed of the motor 200 is high The ripples at the time of high-speed rotation can be removed or extracted by the filters 8 and 9 set on the high frequency side. That is, a ripple having a frequency corresponding to the rotation speed of the motor 200 is accurately removed and extracted.

  Here, the filter control unit 13 monitors the rotational speed of the motor 200 by performing a fast Fourier transform on the current waveform output from the current detection unit 7 and extracting the ripple frequency, The characteristics of the filters 8 and 9 were changed. Instead, as in the motor control device 102 shown in FIG. 9, the filter control unit 13 acquires the rotation speed from the speed calculation unit 11 and changes the characteristics of the filters 8 and 9 according to the rotation speed. You may do it.

  In the present invention, various embodiments other than those described above can be adopted. For example, in the above embodiment, the motor control devices 100 to 102 including the position control unit 1 are taken as an example, but as shown in FIG. 10, the motor control does not include the position control unit 1 (does not perform position control). The present invention can also be applied to the apparatus 103. In addition, in FIG. 10, it cannot be overemphasized that the filter control part 13 of FIG. 7, FIG. 9 may be provided.

  In the above embodiment, the switching elements Q1 to Q4 are driven by the PWM signal. However, the switching elements Q1 to Q4 may be driven by a pulse signal other than the PWM signal.

  In the above-described embodiment, a DC motor including a brush and a commutator has been described as an example of the motor 200. However, the present invention can also be applied to devices that control other DC motors. .

  In the above embodiment, the motor control device used for the power window device of the vehicle is taken as an example. However, as described above, the present invention is applicable to the electric parking brake of the vehicle, the opening / closing of the slide door or sunroof, etc. The present invention can also be applied to a motor control device used, and can also be applied to a motor control device used for purposes other than vehicles.

1 Position control unit (third control unit)
2 Speed controller (first controller)
3 Current control unit (second control unit)
4 Duty calculator 5 PWM circuit 6 Inverter circuit 7 Current detector 8 Low-pass filter (first filter)
9 Bandpass filter (second filter)
DESCRIPTION OF SYMBOLS 10 Pulse generation circuit 11 Speed calculation part 12 Position calculation part 13 Filter control part 20 Motor drive part 30 Speed detection part 40 Position detection part 100-103 DC motor control apparatus 200 DC motor

Claims (5)

A current detector for detecting the current flowing through the DC motor;
A first filter that removes ripples from the current detected by the current detector;
A speed detection unit that extracts a ripple from the current detected by the current detection unit and detects a rotation speed of the DC motor based on the ripple;
A first control unit that outputs a current command value based on a comparison result between a speed command value and a rotation speed value detected by the speed detection unit;
A second control unit that outputs a voltage command value based on a comparison result between the current command value and a current value output from the first filter;
A motor drive unit that drives the DC motor based on a voltage command value output from the second control unit;
A control apparatus for a DC motor, comprising: In the control apparatus of the DC motor according to claim 1,
The speed detector
A second filter for extracting ripples from the current detected by the current detection unit;
A pulse generation circuit for generating a pulse from the ripple extracted by the second filter;
Based on the pulse generated by the pulse generation circuit, a speed calculator that calculates the rotational speed of the DC motor;
A control apparatus for a direct current motor, characterized by comprising: In the control device for a DC motor according to claim 2,
A position calculation unit that calculates a rotational position of the DC motor based on the pulse generated by the pulse generation circuit;
A third control unit that outputs the speed command value to the first control unit based on a comparison result between a target position and the rotational position calculated by the position calculation unit;
A control apparatus for a DC motor, further comprising: In the control apparatus for a DC motor according to claim 2 or 3,
The DC motor control apparatus, wherein the first filter is a low-pass filter, and the second filter is a band-pass filter. In the control apparatus of the DC motor according to any one of claims 2 to 4,
A filter control unit for controlling the first and second filters;
The filter control unit is configured to change each signal pass band of the first and second filters from the low frequency side to the high frequency side in conjunction with the speed of the DC motor from low to high. DC motor control device.

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