JP2006296100A - Motor drive system and motor drive method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the peak level of radiated noise as a time average. <P>SOLUTION: A control device 5 comprises a rotational speed detection means 8 that detects the rotational speed of a motor 1, a speed-command control means 9 that generates a speed command signal using the detected signal of the rotational speed and a target rotational speed inputted from a target rotational speed input means 10, a carrier signal generation means 7 that generates a carrier signal, and a pulse width modulation signal generation means 6 that generates a pulse signal for driving a switch portion 2. The frequency of the speed command signal is set higher than that of rotational speed detection signal and lower than that of a carrier signal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a motor driving system and a motor driving method for driving a motor by pulse width modulation (PWM) control.

  Currently, a stepping motor driving method that is widely used is a configuration in which a stepping motor is rotated forward or backward by sequentially controlling on / off of switching elements having an H-bridge configuration in accordance with a predetermined sequence. . In this configuration, by performing PWM control on the driving pulse of the stepping motor, the average driving current can be increased / decreased to control the speed of the stepping motor.

  However, when the stepping motor is driven by PWM control in this way, switching noise of the fundamental frequency of the current waveform of the PWM control signal and its harmonic frequency is generated. This switching noise affects the operation of a radio or communication device that is being used in the vicinity of the stepping motor, and there is a problem of causing annoying noise or malfunctioning of these devices.

  As a noise component suppression method for preventing the problem due to the switching noise, there is a method shown in Patent Document 1 below. That is, the frequency of the carrier signal for driving the stepping motor is frequency-modulated by PWM control so as to change in a sine wave shape within a predetermined frequency range. Thereby, the spectrum structure including the fundamental frequency of PWM control changes with time, and the noise level due to switching noise is reduced as a time average.

JP-A-7-99795

  However, even if the fundamental frequency of the current waveform of the PWM control signal is periodically changed in a sinusoidal manner as described above, the radiation noise to the outside cannot always be sufficiently reduced depending on the conditions. That is, when the fundamental frequency of the current waveform of the PWM control signal is changed in a sine wave shape within a predetermined frequency range, the spectrum of the radiation noise changes in time because the fundamental frequency changes in a sine wave shape within the predetermined frequency range. The noise level can be reduced as a time average, but the spectrum of radiated noise includes not only harmonic noise at the fundamental frequency but also the peak of radiated noise that depends on the rotation of the motor. Exists. The peak of the radiation noise depending on the rotation of the motor still occurs even when the fundamental level of the carrier signal, which is the conventional technique described above, is changed to a sine wave shape and the noise level is reduced as a time average.

  The present invention has been made in order to solve the above-described problem. By suppressing the peak level of radiation noise depending on the rotation of the motor, the motor drive capable of reducing the peak level of radiation noise as a time average. It is an object to provide a system and a motor driving method.

  In order to achieve this object, in the present invention, in the control device, a rotational speed detecting means for detecting the rotational speed of the motor, and a speed command for generating a speed command signal using the rotational speed of the motor and the input target rotational speed. A control means; a carrier signal generating means for generating a carrier signal; and a pulse width modulation signal generating means for generating a pulse signal using the speed command signal and the carrier signal. The speed command signal is a rotational speed detection signal. The frequency is higher than the frequency of the carrier signal and lower than the frequency of the carrier signal.

  In the motor drive system according to the present invention, the speed command signal from the speed command control means changes at a frequency higher than the frequency of the detection signal of the rotational speed of the motor and lower than the frequency of the carrier signal. The peak of the noise spectrum caused by the signal changes with time, the peak level of the radiation noise depending on the rotation of the motor can be suppressed, and the peak level of the radiation noise can be reduced as a time average.

First Embodiment FIG. 1 is a basic configuration diagram of a motor drive system according to a first embodiment. DESCRIPTION OF SYMBOLS 1 is a motor to be controlled, 2 has a switching element, controls a drive current, a switch unit that drives the motor 1, 3 a battery that supplies power to the switch unit 2, and 4 a drive that drives the switch unit 2 Reference numerals 5 and 5 are control devices for controlling the operation of the switch section 2, and 10 is a target rotational speed input means for inputting a target rotational speed of the motor 1. Here, the control device 5 includes a pulse width modulation signal generation unit 6 that generates a pulse signal for driving the switch unit 2, a carrier signal generation unit 7 that generates a carrier signal, and a rotation speed that detects the rotation speed of the motor 1. The detection means 8 has speed command control means 9 for generating a speed command signal using the rotation speed and the target rotation speed.

  Next, a series of operations for driving the motor 1 in the present embodiment will be described. First, the speed command control means 9 for generating a rotational speed command to the motor 1 is a rotational speed detection means 8 for directly detecting the target rotational speed signal inputted from the target rotational speed input means 10 and the rotational speed of the motor 1. Is used to generate a speed command signal for rotating the motor 1.

  Next, the pulse width modulation signal generation means 6 uses the speed command signal from the speed command control means 9 and the carrier signal from the carrier signal generation means 7 to generate a PWM signal for turning on / off the switching element of the switch unit 2. Generated and output to the drive unit 4. The drive unit 4 amplifies the PWM signal input from the pulse width modulation signal generating means 6 to drive the switching element in the switch unit 2, and outputs the amplified PWM signal to the switch unit 2. The switch unit 2 controls the drive current to the motor 1 by turning on / off the switching element according to the PWM signal input from the drive unit 4, and drives the motor 1 at a predetermined rotational speed.

  Next, the motor rotation speed detection means 8 detects again the rotation speed of the motor 1 and outputs a rotation speed detection signal to the speed command control means 9. In the stage of repeating the above series of operations, the difference between the rotational speed at which the motor 1 is actually rotating and the rotational speed command is compensated by performing PID (Proportional Integral Differential) control, and always matches the target rotational speed. The motor 1 is driven.

  Next, how to change the speed command signal of the motor 1 will be described with reference to FIGS. FIGS. 2A and 2B are diagrams showing waveforms of speed command signals to the motor 1 generated by the speed command control means 9. When the waveform of the speed command signal is a sine wave shown in FIG. 2A, the motor speed command signal I (t) is described by the following equation.

I (t) = A · sin (2π · fo · t)
(Fo is constant frequency, A is amplitude)
In the present embodiment, the waveform of the speed command signal to the motor 1 is changed with time as shown in FIG. In such a case, the speed command signal I (t) is described by the following equation.

I (t) = A · sin {2π · f (t) · t}
(F (t) is the time-varying frequency and A is the amplitude)
Here, f (t) is as follows when it changes in a triangular wave shape as shown in FIG.

f (t) = fo + Δf (t) (Δf is a triangular wave)
The following equation is established so that the average rotation speed of the motor 1 becomes a desired constant rotation speed.

Time average of I (t) = A · sin {2π · fo · t}
The PWM signal generation means 6 generates a signal for turning on / off the switching element of the switch unit 2 by using the speed command signal from the speed command control means 9 and the carrier signal from the carrier signal generation means 7, Output to part 4.

  Next, a noise spectrum of radiation noise generated from the motor drive system will be described with reference to FIGS. FIG. 3A shows a noise spectrum of radiation noise when the waveform of the speed command signal is a sine wave (FIG. 2A). The peak of the radiation noise shows a characteristic that changes with time in a sine wave shape that follows the velocity command waveform of the sine wave.

  On the other hand, FIG. 3B shows the characteristics when the waveform of the speed command signal is that of FIG. 2B, and the speed command signal changes at a speed faster than the rotational speed detection signal of the motor. It can be seen that the peak of the radiation noise caused by the rotation speed of the noise changes with time, the time average of the noise spectrum of the radiation noise becomes a substantially uniform value, and the peak of the radiation noise can be reduced as compared with FIG.

  Here, as a condition for reducing the peak of the radiation noise, for example, when the frequency of the detection signal of the rotational speed of the motor 1 is about several hundred Hz and the frequency of the carrier signal from the carrier signal generating means is several tens of kHz, The speed command signal from the command control means 9 may determine the modulation rate (Δf / fo) and the modulation frequency (in the above example, the triangular wave frequency) so that the frequency is changed at about several kHz.

  Next, a motor driving method that is an operation of the motor driving system of the present embodiment will be described. That is, the target rotational speed input means 10 inputs the target rotational speed of the motor 1, the control device 5 controls the switch section 2 via the drive section 4 in accordance with the target rotational speed, and the drive section 4 controls the switch section 2 In the motor driving method of driving, supplying power to the switch unit 2 with the battery 3, driving a switching element for flowing a predetermined drive current to the motor 1 with the switch unit 2, and controlling the motor 1, the control device 5 includes: The rotation speed detection means 8 detects the rotation speed of the motor 1, the carrier signal generation means 7 generates a carrier signal, and the speed command control means 9 determines the rotation speed from the frequency of the rotation speed detection signal and the target rotation speed. A speed command signal having a frequency higher than the frequency of the detection signal and lower than the frequency of the carrier signal is generated, and the pulse width modulation signal generating means 6 uses the speed command signal and the carrier signal. A motor driving method of generating a pulse signal for driving the switching unit 2.

  As described above, in the present embodiment, the control device 5 includes the rotation speed detection means 8 that detects the rotation speed of the motor 1 and the speed command control that generates a speed command signal using the rotation speed and the target rotation speed. Means 9, carrier signal generating means 7 for generating a carrier signal, and pulse width modulation signal generating means 6 for generating a pulse signal using the speed command signal and the carrier signal. The speed command signal is changed at a frequency higher than the frequency of the detection signal of the rotational speed of the motor 1 and lower than the frequency of the carrier signal of the carrier signal generating means 7, and the peak of the noise spectrum caused by the speed command signal Changes with time, and the peak level of radiation noise can be reduced as a time average.

Second Embodiment FIG. 4 is a basic configuration diagram of a motor drive system according to a second embodiment. The speed command control means 9 generates a speed command signal by using the rotational speed signal output from the rotational speed detection means 8 and the target rotational speed signal output from the target rotational speed input means 10. Means 11 and modulation means 12 for modulating the speed command signal.

  That is, the speed command generation means 11 generates a speed command signal from the rotation speed signal and the target rotation speed signal and outputs the speed command signal to the modulation means 12. The modulation means 12 modulates the speed command signal from the speed command generation means 11 and outputs it to the pulse width modulation signal generation means 6. For this reason, the speed command signal can be changed at a frequency higher than the frequency of the rotational speed detection signal. Subsequent processing is the same as that in the first embodiment, and therefore will be omitted.

  With such a configuration, for example, the output signal from the speed command generation means 11 has a sine wave shape as shown in FIG. 5A, but the output signal from the modulation means 12 as shown in FIG. 5B. The speed command signal has a higher frequency. As a result, the speed command signal (FIG. 5B), which is the output from the modulation means 12, can be changed in a time faster than the detection signal detected by the rotational speed detection means 8 of the motor 1.

  As described above, in the present embodiment, the speed command control means 5 includes the speed command generation means 11 and the modulation means 12, and the speed command generation means 11 includes the target rotational speed input means 10 and the motor 1. Since the speed command signal is generated from the rotation speed detection means 8 and the speed command signal is modulated by the modulation means 12, the speed command signal is not dependent on the type of the rotation speed detection signal 8, and the speed command signal is the motor rotation speed detection signal. Can be changed at a frequency higher than the frequency of the carrier signal and lower than the frequency of the carrier signal. The peak of the noise spectrum caused by the speed command changes with time, and the peak level of noise can be reduced as a time average. .

Third Embodiment FIG. 6 is a basic configuration diagram of a motor drive system according to a third embodiment. The speed command control means 9 includes a target rotational speed diffusion means 13 for diffusing the target rotational speed signal input from the target rotational speed input means 10, a target rotational speed signal diffused by the target rotational speed diffusion means 13, and a rotational speed. Speed command generating means 14 for generating a speed command signal using the rotational speed signal output from the detection signal 8.

  Here, the target rotational speed diffusing means 13 is composed of, for example, a function generator, and generates a signal that periodically changes in the positive and negative directions with the input signal from the target rotational speed input means 10 as the center, and the speed command generating means 14 Output to. The speed command generating means 14 generates a speed command signal from the target rotational speed signal whose input signal is periodically changed by the target rotational speed diffusion means 13 and the rotational speed signal output from the rotational speed detection signal 8. It outputs to the pulse width modulation signal generation means 6.

  The target rotation speed signal diffused by the target rotation speed diffusion means 13 is a triangular wave. As an example, FIG. 7 shows an output waveform when the target rotational speed input is changed to a triangular wave shape.

  With this configuration, the target rotational speed signal from the target rotational speed command 10 can be easily and periodically changed by the target rotational speed diffusion means 13. As a result of driving the motor 1 by performing pulse width modulation using such a signal, the speed command signal can be changed in a time faster than the detection signal of the rotational speed of the motor.

  As described above, in the present embodiment, the speed command control means 9 has the speed command generation means 14 and the target rotation speed diffusion means 13, and the speed command generation means 14 receives from the target rotation speed input means 13. Since the speed command signal is generated from the diffused target rotational speed signal and the rotational speed signal from the rotational speed detection means 8, the target rotational speed signal can be easily changed, and noise caused by the speed command is generated. The peak of the spectrum changes with time, and the peak level of radiation noise can be reduced as a time average.

Fourth Embodiment FIG. 8 is a basic configuration diagram of a motor drive system according to a fourth embodiment. The speed command control means 9 changes the frequency of the rotational speed signal from the rotational speed detection means 8, that is, periodically changes the frequency variable means 15, the changed rotational speed signal and the target rotational speed input means 10. Speed command generating means 16 for generating a speed command signal using the input target rotational speed signal.

  Here, the frequency varying means 15 periodically changes the frequency of the rotational speed signal of the motor 1 from the rotational speed detecting means 8 and outputs the frequency to the speed command generating means 16. The speed command generation means 16 generates a speed command signal using the periodically changed rotational speed signal and the target rotational speed signal, and outputs them to the pulse width modulation signal generation means 6. As a result, the speed command signal from the speed command generating means 16 can be changed in a time faster than the rotation speed detection signal of the motor 1.

  As described above, in the present embodiment, the speed command control means 9 has the frequency variable means 15 for changing the frequency of the rotation speed detection signal and the speed command generation means 16, and the speed command generation means 16 is Since the speed command signal is generated from the signal obtained by periodically changing the frequency of the signal from the rotational speed detection means 8 by the frequency variable means 15 and the signal from the target rotational speed input means 10, the target rotational speed input Regardless of the type, the speed command signal can be changed at a frequency higher than the frequency of the rotation speed detection signal of the motor 1 and lower than the frequency of the carrier signal. Therefore, the peak of the noise spectrum due to the speed command changes with time, and the peak level of the radiation noise can be reduced as a time average.

Fifth Embodiment FIG. 9 is a basic configuration diagram of a motor drive system in a fifth embodiment. The control device 5 includes frequency changing means 20 that changes the frequency of the carrier signal of the carrier signal generating means 7. Here, the frequency changing unit 20 is, for example, a frequency changing unit that changes a predetermined frequency range in a sine wave shape.

  With such a configuration, the rotation speed command from the rotation speed control means 9 and the carrier signal from the carrier signal generation means 7 can be independently and periodically changed.

  FIG. 10 shows an example of a radiation noise spectrum in the present embodiment. The horizontal axis represents frequency and the vertical axis represents electric field strength. The characteristic (A) is a characteristic when both the basic frequency of the carrier signal and the command signal for the rotational speed of the motor 1 are constant, and the characteristic (B) is the basic frequency of the carrier signal and the rotational speed of the motor 1. This is a characteristic when both signals of the command signal are periodically changed. Compared with the case of the characteristic (A), in the case of the characteristic (B), the electric field strength is low in all frequency bands, and an effect of reducing the noise peak of the harmonics is seen.

  As described above, in the present embodiment, the control device 5 has the frequency changing means 20 for changing the frequency of the carrier signal generating means 7, so that the carrier obtained when the carrier signal is changed periodically. Noise peak reduction effect of signal harmonics and noise peak caused by speed command signal obtained when speed command signal from speed command control means 9 is changed in a time faster than detection signal of rotation speed of motor 1 Both reduction effects can be obtained simultaneously.

It is a basic lineblock diagram of the motor drive system in a 1st embodiment. It is a figure which shows the command waveform of the rotational speed in 1st Embodiment. It is a figure which shows the noise spectrum of the radiation noise in 1st Embodiment. It is a basic lineblock diagram of the motor drive system in a 2nd embodiment. It is a figure which shows the command waveform of the rotational speed in 2nd Embodiment. It is a basic lineblock diagram of the motor drive system in a 3rd embodiment. It is a figure which shows the command waveform of the rotational speed in 3rd Embodiment. It is a basic lineblock diagram of the motor drive system in a 4th embodiment. It is a basic lineblock diagram of the motor drive system in a 5th embodiment. It is a figure which shows the noise spectrum of the radiation noise in 5th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Motor 2 ... Switch part 3 ... Battery 4 ... Drive part 5 ... Control apparatus 6 ... PWM comparison means 7 ... Carrier signal generation means 8 ... Rotational speed detection means 9 ... Speed command control means 10 ... Target rotational speed input means 11 ... Speed command generating means 12 ... Modulating means 13 ... Target rotational speed diffusing means 14 ... Speed command generating means 15 ... Frequency variable means 16 ... Speed command generating means 20 ... Frequency changing means

Claims (7)

A motor, a switch unit for controlling the drive current to drive the motor, a battery for supplying power to the switch unit, a drive unit for driving the switch unit, and a target rotational speed for inputting a target rotational speed of the motor In a motor drive system having input means and a control device that controls the switch unit via the drive unit according to the target rotational speed,
The control device includes: a rotation speed detection unit that detects a rotation speed of the motor; a speed command control unit that generates a speed command signal using the rotation speed and the target rotation speed; and a carrier signal generation that generates a carrier signal. Means, and a pulse width modulation signal generating means for generating a pulse signal using the speed command signal and the carrier signal,
The motor drive system according to claim 1, wherein the speed command signal has a frequency higher than a frequency of the rotation speed detection signal and lower than a frequency of the carrier signal.   2. The speed command control means includes speed command generation means for generating a speed command signal using the rotation speed and the target rotation speed, and modulation means for modulating the speed command signal. The motor drive system described in 1.   The speed command control means includes a target rotational speed diffusion means for diffusing the target rotational speed signal to generate a rotational speed diffusion signal, and a speed command for generating a speed command signal using the rotational speed diffusion signal and the rotational speed. The motor drive system according to claim 1, further comprising generating means.   The motor drive system according to claim 3, wherein the rotation speed spread signal is a triangular wave.   The speed command control means includes a frequency variable means for changing the frequency of the rotational speed detection signal, a speed command generation means for generating a speed command signal using the rotational speed whose frequency has been changed and the target rotational speed. The motor drive system according to claim 1, comprising:   6. The motor drive system according to claim 1, wherein the control device includes frequency changing means for changing a frequency of a carrier signal of the carrier signal generating means. The target rotational speed of the motor is input by the target rotational speed input means, the control unit controls the switch unit via the drive unit according to the target rotational speed, the drive unit drives the switch unit, and the battery uses the switch unit. In a motor driving method for supplying electric power to and driving the motor by controlling a driving current with a switch unit,
The control device detects a rotation speed of the motor by a rotation speed detection means, generates a carrier signal by a carrier signal generation means, and detects the rotation speed detection signal from the rotation speed and the target rotation speed by a speed command control means. A speed command signal having a frequency higher than the frequency of the carrier signal and lower than the frequency of the carrier signal is generated, and a pulse signal for driving the switch unit using the speed command signal and the carrier signal is generated by the pulse width modulation signal generating means A motor driving method characterized by:

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