JPWO2016051740A1 - Motor control device, motor control method, and motor control system - Google Patents

Abstract

This motor control device has a plurality of motor control units that control one axis based on an operation command from a host device, and controls two or more motors in synchronization. Each of the motor control units includes a control unit that performs motor operation control, a command signal generation unit that generates a command signal, a PWM signal generation unit that generates a PWM control signal that is pulse-width modulated based on the command signal, and a PWM And an inverter that generates a drive signal by switching the switching element according to the control signal. Each of the PWM signal generation units includes a superimposition signal generation unit that generates a superposition signal to be superimposed on the command signal, a carrier signal generation unit that generates a carrier signal that is a triangular wave, and an addition that adds the command signal and the superposition signal. And a comparator that compares the post-superimposition command signal output from the adder with the carrier signal to generate a PWM control signal. The superimposed signal is a signal that differs for each axis controlled by the plurality of motor control units.

Description

  The present invention relates to a motor control device, a motor control method, and a motor control system that apply a voltage for PWM control to a winding of a motor and control a plurality of axes synchronously, and in particular, a function of controlling the switching timing of an inverter for each axis. The present invention relates to a motor control device, a motor control method, and a motor control system.

  In a servo motor used in FA (FACTORY AUTOMATATION), the position, speed, and torque of the motor are controlled so as to follow a drive command (position command) from a host device (host controller). Digital control using a microcomputer is widely used as the control arithmetic unit. In the PWM (PULSE WIDTH MODULATION) control method generally used for controlling the motor torque, the current flowing through each phase (U phase, V phase, W phase) of the motor is controlled in a sine wave form in a pseudo manner. The torque output from the motor can be freely controlled.

  However, in the PWM control method, since the voltage applied to the motor is controlled by switching of the inverter, a large voltage fluctuation of the output voltage of the inverter and a leakage current in amperes occur at the moment of switching. Due to these effects, a large current instantaneously flows in the power supply, the potential of the power supply itself fluctuates, and conduction noise occurs. This amount of noise is regulated by CISPR (International Radio Interference Special Committee) and the like, and reduction is required.

  In addition, a phenomenon in which high-frequency radiation noise is generated from a power cable, a motor cable, a wiring pattern, etc. at the timing of switching has also been confirmed, which is also regarded as a problem.

  For this reason, conventionally, there has been proposed a technique for spreading a spectrum of radiation noise and superimposing a superimposed signal having a predetermined waveform on a drive command signal to reduce peak intensity (for example, Patent Document 1). FIG. 10 is a configuration diagram of a PWM signal generation unit in such a conventional power converter. The conventional PWM signal generation unit superimposes the command signal Sd generated by the command signal generation unit 100 and the alternating superimposed signal Sm generated by the superimposed signal generation unit 102 in each of the U phase, the V phase, and the W phase. The addition unit 104 adds the values. Then, the superposed command signal Sdm after addition and the carrier signal Sc generated by the carrier signal generation unit 106 are compared by the comparison unit 108, and the PWM duty ratio is modulated to generate the PWM control signal Pw. The inverter 110 is pulse-driven. This conventional PWM signal generation unit suppresses the noise by diffusing the spectrum of the radiation noise by the configuration in which the superposition signal Sm is superposed.

  However, noise caused by switching in the inverter as described above is particularly affected during non-rotation (servo lock), low-speed rotation, and low-torque operation where the switching timings of the phases tend to overlap. And in the conventional method of superimposing an AC superposition signal on the command signal, there is a solution to the phenomenon that a large noise is generated because the switching timing of the U to W phases overlaps at the time of servo lock, low speed rotation, and low torque operation. There is a problem of not becoming.

  Here, in order to explain such a problem, first, a PWM control signal at the time of U to W-phase servo lock in the case where the superimposed signal Sm is not superimposed on the command signal Sd in the configuration of FIG. 10 will be described. . When the servo is locked, the command signal Sd is set to 0, and the motor is stopped by controlling so that no current flows between the phases U to W. In such a case, since the command signal Sd is 0 in both the U to W phases, and the superimposed signal Sm is not superimposed, the post-superimposition command signal Sdm is also 0. FIG. 11 shows how the PWM control signal is generated in such a case. Since the post-superimposition command signal Sdm is 0 when all the U to W phases are servo-locked, in FIG. 11, they are collectively described as one post-superimposition command signal Sdm. As shown in FIG. 11, each of the U to W phases of the PWM control signal Pw generated by comparing the post-superimposition command signal Sdm with the carrier signal Sc becomes the same signal (rectangular wave with a duty of 50%), and U to W It can be seen that the switching timings of the phase inverters 110 overlap. That is, each of the U to W phases of the PWM control signal Pw, which is a pulse signal, is in a state where the rising timing of the pulse (for example, time tr in FIG. 11) and the falling timing (for example, time tf) are aligned. . Then, the levels of conduction noise and radiation noise are mutually emphasized at those timings.

  Next, the U to W phase PWM control signal Pw at the time of servo lock when the superimposed signal Sm is superimposed on the command signal Sd will be described. Since the command signal Sd is 0 for all the U to W phases and the superimposed signal Sm is a common signal for the U to W phases, the post-superimposition command signal Sdm is the same signal as the superimposed signal Sm in any phase. FIG. 12 shows how the PWM control signal is generated in such a case. As in FIG. 11, the post-superimposition command signal Sdm for the U to W phases is described as one. Each PWM control signal Pw generated by comparing the post-superimposition command signal Sdm and the carrier signal Sc is modulated in duty. With this effect, the spectrum is dispersed and the peak intensity of the radiation noise can be reduced. However, as is apparent from FIG. 12, the switching timing of the U to W phases overlaps with each other in the same manner as in FIG. 11, for example, the rising timing tr and the falling timing tf in FIG. A large conduction noise and radiation noise are generated at each moment.

  This problem is further affected particularly when synchronous control of a plurality of axes is performed. In general, since carrier signals Sc for all axes are synchronized during synchronous control, the U to W phase PWM control signals Pw for all axes have the same waveform, and the switching timing of the U to W phase inverters for all axes This is because large noise is generated.

JP 2011-111777 A

  The motor control device according to the present invention includes a plurality of motor control units that control one axis based on an operation command from a host device, and controls two or more motors in synchronization. Each of the motor control units includes a control unit that performs motor operation control, a command signal generation unit that generates a command signal for commanding motor operation based on the operation control of the control unit, and pulse width modulation based on the command signal A PWM signal generation unit that generates the PWM control signal, and an inverter that generates a drive signal for driving the motor by switching the switching element using the PWM control signal. Each of the PWM signal generation units includes a superimposition signal generation unit that generates a superimposition signal to be superimposed on the command signal, a carrier signal generation unit that generates a carrier signal that is a triangular wave, and an addition unit that adds the command signal and the superposition signal. A comparison unit that compares the post-superimposition command signal output from the addition unit with the carrier signal to generate a PWM control signal. The superimposed signal is configured to be different for each axis controlled by the plurality of motor control units.

  A motor control system according to the present invention includes the motor control device according to the present invention, a host device that transmits an operation command to the motor control device, and a motor having two or more axes controlled by the motor control device. It is.

  Further, the motor control method according to the present invention generates a command signal for instructing motor operation based on an operation command from a host device, generates a pulse width modulated PWM control signal based on the command signal, It has a plurality of motor control units that control one axis by applying a drive voltage generated by switching the switching element of the inverter with a control signal to the motor, and the motors of two or more axes are synchronized by the plurality of motor control units. This is a motor control method of a motor control device that controls the motor. In this motor control method, the step of determining whether the motor is in a low drive state smaller than a predetermined drive amount and the command signal differed between the motor control units when determined to be in the low drive state. A PWM control signal is generated by superimposing a superimposition signal, which is a signal, a post-superimposition command signal that is a signal obtained by superimposing the superimposition signal on the command signal, and a triangular wave carrier signal synchronized between the motor control units. And steps.

  According to the present invention, when synchronously controlling a multi-axis motor, when the U to W phases during servo lock, low speed rotation, and low torque operation are switched at substantially the same timing, the carrier signal remains synchronized, The switching timing of the PWM control signal can be shifted for each axis. For this reason, it is possible to avoid an increase in conduction noise and radiation noise when the U to W phases of a plurality of axes are simultaneously switched. Further, if an AC signal is superimposed, radiation noise due to duty modulation can be reduced.

FIG. 1 is a configuration diagram of a motor control system including a motor control device according to an embodiment of the present invention. FIG. 2 is a waveform diagram in the case of superimposing AC signals having only different frequencies for each axis in the motor control device. FIG. 3 is a waveform diagram in the case of superimposing AC signals having different phases only for each axis in the motor control apparatus. FIG. 4 is a waveform diagram in the case where an AC signal having only different amplitudes for each axis is superimposed in the motor control apparatus. FIG. 5 is a waveform diagram in the case of superimposing AC signals that differ only in DC potential for each axis in the motor control device. FIG. 6 is a waveform diagram when a different DC signal is superimposed for each axis in the motor control device. FIG. 7 is a flowchart showing an example of the procedure of the motor driving method according to the embodiment of the present invention. FIG. 8 is an explanatory diagram of a configuration in which the superimposed signals are not crossed at the peak and valley of the carrier signal in the motor control device. FIG. 9 is a superimposed waveform diagram when the superimposed signals are not crossed at the peak and valley of the carrier signal in the motor control device. FIG. 10 is a configuration diagram of a conventional PWM signal generation unit. FIG. 11 is a waveform diagram of a PWM control signal when a superimposed signal is not superimposed in the conventional example. FIG. 12 is a waveform diagram of a PWM control signal when a superimposed signal is superimposed in the conventional example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

  In the following, it is assumed that the servo is locked as the most severe noise state.

(Embodiment)
FIG. 1 is a configuration diagram of a motor control system including a motor control device according to an embodiment of the present invention. In FIG. 1, as an example of such a system, a configuration of a multi-axis motor control motor control system 50 including a motor control device 30 that controls a plurality of motors 21 is illustrated. In addition, FIG. 1 shows an example in which two motors 21 as two axes are provided as multi-axis. The motor control system 50 further includes a host device 40 using, for example, a personal computer in order to control the motor control device 30 by a command or the like. The host device 40 and the motor control device 30 are communicatively connected via a control bus line or the like. A command from the host device 40 is transmitted to the motor control device 30 and information from the motor control device 30 is received from the host device. 40.

  Next, the motor control device 30 is configured to include a motor control unit (hereinafter, appropriately referred to as a control unit) 31 for each of the motors 21 in order to control the motors 21 for two axes. In FIG. 1, the control unit 31 </ b> A that is the first control unit 31 controls the motor 21 </ b> A that is the first motor 21, and the control unit 31 </ b> B that is the second control unit 31 is the second motor 21. The structural example which controls the motor 21B is shown. The control unit 31 is supplied with the power supply voltage Vdc from the power supply 32 in common. Each control unit 31 uses this power supply voltage to operate the circuit in the unit and to drive the motor 21 via the inverter 20. In the present embodiment, the control unit 31 is configured to include digital processing, and the timing signal Tm generated by the timing generation unit 33 is also supplied to each control unit 31. The timing signal Tm is a clock signal for digital processing and a signal for indicating other timing.

  Each of the control units 31 includes a control unit 19, a command signal generation unit 11, a PWM signal generation unit 10, and an inverter 20. In FIG. 1, as the PWM signal generation unit 10, a control unit 31A includes a PWM signal generation unit 10A, and the control unit 31B includes a PWM signal generation unit 10B.

  As shown in FIG. 1, in the control unit 31, the control unit 19 is communicatively connected to a host device 40. Command information for instructing position, speed, torque, and the like is transmitted from the host device 40 to the control unit 19. In addition, the control unit 19 transmits information of the control unit 31 and the like to the higher-level device 40. The control unit 19 controls each part in the control unit 31 such as the command signal generation unit 11 and the PWM signal generation unit 10 together with such a communication function, and controls the operation so that the motor performs a predetermined motion such as a speed and a position. I do.

  Further, in the present embodiment, the control unit 19 includes a function for determining the driving state of the motor 21. That is, the control unit 19 determines that the motor 21 is in a low drive state such as a servo lock state, a low-speed rotation or a low torque operation state, and the determination result is used as an operation determination signal Cs for PWM. The signal generation unit 10 is notified.

  More specifically, for example, the following function may be included in the control unit 19 for determining such a low drive state. First, the control unit 19 stores a predetermined drive amount that is set in advance in order to determine the low drive state. Then, the control unit 19 determines whether or not the command drive amount is smaller than the predetermined drive amount. When the command drive amount is smaller than the predetermined drive amount for determination, the control unit 19 is in a low drive state. Is output. Further, as the command drive amount at this time, an operation command to the command signal generation unit 11 described below or the amplitude of the command signal Sd output from the command signal generation unit 11 may be used as the drive amount.

  Next, the command signal generation unit 11 generates a command signal Sd based on an operation command for commanding the position, speed, torque, and the like from the control unit 19 and supplies the command signal Sd to the PWM signal generation unit 10. More specifically, this command signal Sd is generated for three phases of U, V, and W phases, and sine waves that are shifted from each other by 120 ° in accordance with the rotational speed and torque amount required for the motor 21. This is a signal having a waveform. As described above, since the rotation of the motor 21 is stopped when the servo is locked, the amplitude of the command signal Sd at this time becomes zero.

  Next, the PWM signal generation unit 10 includes a superimposition signal generation unit 12, a superimposition signal addition unit 14, a carrier signal generation unit 16, and a comparison unit 18. Note that the PWM signal generation unit 10 has, specifically, the superposition signal addition unit 14 and the comparison unit 18 in three phases of U phase, V phase, and W phase, similarly to the configuration shown in FIG. It has corresponding components. In FIG. 1, since each phase has the same configuration, and when the servo is locked, the command value is 0 and the same signal is used, so only one phase (for example, U phase) is shown as a representative.

  In the PWM signal generation unit 10, the control unit 19 notifies the superimposed signal generation unit 12 of an operation determination signal Cs indicating whether or not the low drive state is set. For example, the superimposed signal generation unit 12 generates an alternating superimposed signal Sm, and supplies the superimposed signal Sm to the superimposed signal adding unit 14 in accordance with the operation determination signal Cs. Specifically, the superimposed signal generation unit 12 supplies the generated superimposed signal Sm only when the operation determination signal Cs indicates a low drive state, and otherwise supplies the superimposed signal Sm set to 0 level. .

  The superimposition signal adding unit 14 is supplied with the command signal Sd from the command signal generating unit 11. The superimposition signal adding unit 14 adds the supplied command signal Sd and the superimposition signal Sm, and outputs the sum as a post-superimposition command signal Sdm after the addition. That is, when the motor is driven at a low drive such as when the servo is locked, the superimposition signal adding unit 14 superimposes the superimposition signal Sm on the command signal Sd, so that the post-superimposition command signal Sdm becomes the command signal Sd Is a signal obtained by superimposing the superimposition signal Sm on the signal. Such a post-superimposition command signal Sdm is supplied to the comparison unit 18.

  The carrier signal generator 16 generates a triangular wave carrier signal Sc for generating a pulse-width modulated signal. When synchronizing with a plurality of axes, the carrier signals Sc between the control units 31 are generally synchronized in order to ensure synchronization accuracy. In the present embodiment, the common timing signal Tm is distributed from the timing generation unit 33 to each control unit 31, and the carrier signal generation unit 16 of each control unit 31 generates the carrier signal Sc using the common timing signal Tm. It has a simple structure. With such a configuration, the carrier signals Sc are synchronized between the control units 31. In addition, the timing generator 33 may generate the carrier signal Sc and distribute the carrier signal Sc to each control unit 31. That is, as a matter of course, instead of synchronization, the same carrier signal Sc may be supplied to each control unit 31 as long as the phases of the respective carrier signals Sc match.

  Such a carrier signal Sc is supplied to the comparison unit 18. Then, the comparison unit 18 generates the PWM control signal Pw by comparing the levels of the post-superimposition command signal Sdm and the carrier signal Sc, and outputs the PWM control signal Pw to the inverter 20. Here, the PWM control signal Pw generated in this way is composed of a pulse train whose pulse width is modulated in accordance with the level of the post-superimposition command signal Sdm. Although omitted in FIG. 1, the PWM control signal Pw includes a reverse-phase inversion signal provided with an on-delay in addition to a normal-phase signal, and two control lines for both forward and reverse phases. Are output to the upper arm and the lower arm of the inverter 20, respectively.

  The PWM signal generation unit 10 generates the PWM control signal Pw that is pulse-width modulated based on the command signal Sd with the above configuration.

  In the control unit 31, the PWM control signal Pw generated in this way by the PWM signal generation unit 10 is supplied to the inverter 20. The inverter 20 receives the PWM control signal Pw from the PWM signal generation unit 10 and generates a drive voltage Vd by switching the voltage supplied from the power supply 32 according to the PWM control signal Pw using a switching element. The inverter 20 applies the generated drive voltage Vd to the motor 21 via the U-phase, V-phase, and W-phase motor wires. The inverter 20 includes a switching element such as an IGBT (INSULATED GATE BIPOLAR TRANSISTOR) and a power element such as a diode. Recently, an IPM (INTELLIGENT POWER MODEL) incorporating a pre-drive circuit for driving a power element is often used. Although only one pair of inverters is shown in FIG. 1, actually, three pairs of inverters are used to drive the motor in three phases of U phase, V phase, and W phase.

  As described above, each control unit 31 generates a drive voltage Vd for driving the motor 21 based on a command from the host device 40, and applies the generated drive voltage Vd to the motor 21 to cause the motor 21 to operate. Driving.

  As the motor 21, a three-phase brushless motor in which a magnet is arranged on a rotor is widely used from the viewpoint of efficiency and controllability. That is, as a specific configuration example of the motor 21, a three-phase brushless motor including a stator having a winding wound around a stator core and a rotor having a permanent magnet is applied, and a driving voltage Vd is applied to each phase winding. What is necessary is just to make it the structure which does.

  Next, a more detailed configuration of the present embodiment will be described. In particular, the present embodiment is characterized in that the superimposed signal Sm generated by the superimposed signal generation unit 12 of the control unit 31 is a different signal between the control units 31.

  That is, as shown in FIG. 1, in the first control unit 31A, the superimposed signal adding unit 14 superimposes the superimposed signal SmA having the first waveform generated by the superimposed signal generating unit 12A on the command signal SdA, The superposed command signal SdmA is supplied to the comparison unit 18. On the other hand, in the second control unit 31B, the superimposed signal adding unit 14 superimposes the superimposed signal SmB of the second waveform generated by the superimposed signal generating unit 12B on the command signal SdB, and compares the command signal SdmB after superposition. It supplies to the part 18. As described above, in the present embodiment, in order to obtain the effect, it is necessary that the superimposed signal SmA of the first control unit 31A and the superimposed signal SmB of the second control unit 31B are different signals. .

  In addition, a different signal is a signal from which at least any one of a frequency, a phase, an amplitude, and a direct current potential differs. In consideration of ease of control and circuit scale, a method of parameterizing one of frequency, phase, amplitude, and DC potential and controlling from the host device 40 via the control unit 19 is desirable. You may make it controllable. Further, the frequency of the superimposed signal Sm is not particularly limited and may be set freely. Further, the amplitude and DC potential of the superimposed signal Sm may be freely set within a range in which the amplitude of the post-superimposition command signal Sdm does not exceed the amplitude of the carrier signal Sc. Further, when the servo is locked, the command signal Sd becomes 0 level, while the operation determination signal Cs from the control unit 19 indicates a low drive state, so that the superimposed signal Sm has a predetermined frequency and phase as described above. , An amplitude, or a non-zero signal having a DC potential. Since the command signal Sd is at the 0 level, the superimposed signal Sm and the post-superimposition command signal Sdm are the same signal.

  In recent years, the PWM signal generation unit 10 is often configured by a DSP (DIGITAL SIGNAL PROCESSOR), microcomputer software, ASIC (APPLICATION SPECIFIC INTEGRATED CIRCUIT), or FPGA (FIELD PROGRAMMABLE GATE ARRAY) logic circuits. In this case, a signal to be processed such as the superimposed signal Sm is generally updated when the carrier signals 17A and 17B have peaks (maximum value) and valleys (minimum value) because of digital processing. That is, since each signal is digitally processed, the carrier signal Sc is also generated based on the sampling clock, and the processed signal such as the post-superimposition command signal Sdm is also time-series data sampled in accordance with the sampling clock. It is configured. As a result, when the value of the signal to be processed is updated at a timing other than the timing when the carrier signal Sc has a peak (maximum value) and a valley (minimum value), the PWM switching timing and the update timing overlap, and the PWM control signal Pw May cause chattering. Therefore, when the carrier signal Sc is a peak (maximum value) or a valley (minimum value), the sampling timing may be set so as to update the value of the signal to be processed. When the value is updated at the peaks and valleys of the carrier signal Sc, the frequency of the superimposition signal Sm can be set only below the frequency of the carrier signal Sc by the sampling theorem.

  Next, the operation of the above embodiment will be described with reference to several examples of the superimposed signal Sm, using the waveform diagrams of the different superimposed signals described above.

  First, FIG. 2 shows a case in which the superimposed signal SmA of the first control unit 31A and the superimposed signal SmB of the second control unit 31B are AC signals, and further, only the frequencies are different from each other as the above different signals. It is a wave form diagram which shows each of these waveforms. That is, FIG. 2 shows a case where the first-axis superimposed signal SmA and the second-axis superimposed signal SmB at the time of servo lock are AC signals that differ only in frequency. As described above, when the servo is locked, the command signal Sd is set to 0, and the motor is stopped by performing control so that no current flows between the phases U to W. For this reason, the post-superimposition command signal Sdm is the same signal as the superimposition signal Sm in any phase. That is, the post-superimposition command signal SdmA of the first control unit 31A and the post-superimposition command signal SdmB of the second control unit 31B are AC signals that differ only in frequency. In FIG. 2, the post-superimposition command signal SdmB is a signal having a frequency that is twice that of the post-superimposition command signal SdmA (that is, the superposition signal SmB is twice the superposition signal SmA).

  Note that this embodiment is at the time of servo lock, and since the superimposition signals SmA and SmB are the same signals as the post-superimposition command signals SdmA and SdmB, respectively, not the superimposition signals SmA and SmB but as shown in the figure. The post-superimposition command signals SdmA and SdmB, which are input signals of the comparison unit 18, will be described. Furthermore, as shown in FIG. 2, in the present embodiment, the carrier signals Sc of the first axis and the second axis are synchronized, that is, the phases match. Further, since the U to W phases have the same waveform at the time of servo lock, in FIG. 2, the post-superimposition command signals SdmA and SdmB and the PWM control signals PwA and PwB of the U to W phases in the control units 31A and 31B are One phase is shown as a representative.

  In the present embodiment, by comparing the post-superimposition command signals SdmA and SdmB as shown in FIG. 2 with the carrier signal Sc, PWM control signals PwA and PwB composed of pulse trains as shown in FIG. 2 are generated. The Here, as shown in FIG. 2, since the superimposed signal SmA and the superimposed signal SmB have different frequencies, even if the carrier signal Sc is synchronized, the rising timing tra of the PWM control signal PwA and the PWM control signal PwB The timing is different from the rising timing trb. Similarly, the falling timing tfa of the PWM control signal PwA and the falling timing tfb of the PWM control signal PwB are different timings. Therefore, according to the present embodiment, the switching timings of the inverters between the plurality of axes do not overlap at the time of servo lock in the configuration in which the plurality of axes are synchronously controlled. For this reason, the levels of conduction noise and radiation noise are not mutually emphasized among a plurality of axes, and an increase in conduction noise and radiation noise in a multi-axis motor control device can be suppressed.

  Next, FIG. 3 shows the PWM control signal PwA when the superimposed signal SmA of the first control unit 31A and the superimposed signal SmB of the second control unit 31B are alternating signals that differ only in phase as the different signals described above. It is a wave form diagram which shows each waveform including the waveform of PwB. In FIG. 3, the post-superimposition command signal SdmB is a signal obtained by inverting the post-superimposition command signal SdmA by shifting the phase by 180 °.

  Next, FIG. 4 shows that when the superposition signal SmA of the first control unit 31A and the superposition signal SmB of the second control unit 31B are alternating signals that differ only in amplitude, the PWM control signal PwA, It is a wave form diagram which shows each waveform including the waveform of PwB. In FIG. 4, the post-superimposition command signal SdmB is a signal having half the amplitude of the post-superimposition command signal SdmA.

  Next, FIG. 5 shows the PWM control signal PwA when the superimposed signal SmA of the first control unit 31A and the superimposed signal SmB of the second control unit 31B are AC signals that differ only in DC potential as the different signals described above. FIG. 4 is a waveform diagram showing each waveform including a waveform of PwB. In FIG. 5, the post-superimposition command signal SdmA and the post-superimposition command signal SdmB are signals obtained by superimposing DC potentials in the positive and negative directions on the AC signal.

  Next, FIG. 6 shows the waveforms of the PWM control signals PwA and PwB when the superimposed signals SmA of the first control unit 31A and the superimposed signals SmB of the second control unit 31B are different DC signals as the above-mentioned different signals. It is a wave form diagram which shows each waveform including this. In FIG. 6, the post-superimposition command signal SdmA and the post-superimposition command signal SdmB are DC potential signals having different voltages. In the case of this configuration, although the effect of reducing the peak intensity of radiation noise when an AC signal is superimposed cannot be obtained, this configuration can be easily realized. That is, it is not necessary to provide a complicated configuration for superimposing the AC signal, and it is only necessary to provide a configuration for adding a DC potential and to have different DC potential information for each axis.

  As described above, as shown in FIGS. 3 to 6, in the superimposed signal SmA and the superimposed signal SmB, any one of the phase of the AC signal, the amplitude of the AC signal, the DC potential of the AC signal, and the voltage of the DC signal is mutually Even when configured differently, the rise timing tra of the PWM control signal PwA and the rise timing trb of the PWM control signal PwB are different timings. Similarly, the falling timing tfa of the PWM control signal PwA and the falling timing tfb of the PWM control signal PwB are different timings.

  As described above, in any of the configurations of FIGS. 2 to 6, the timing of switching between the PWM control signal PwA and the PWM control signal PwB is deviated at the time of servo lock in the configuration in which a plurality of axes are synchronously controlled. The effect of preventing an increase in noise due to simultaneous switching of a plurality of axes can be obtained.

  In the above description, the example in which the control unit 31 is configured by the above functional blocks has been described. However, for example, the control unit 31 may be realized by the above-described DSP or microcomputer software. That is, a configuration in which processing is performed based on a processing procedure such as a program may be used. In this case, more specifically, the functions of the control unit 19, the command signal generation unit 11 and the PWM signal generation unit 10 in FIG. 1 are stored as programs in a memory or the like, and the control unit 19 is embodied by a DSP or a microcomputer. What is necessary is just to set it as the structure which performs the program and to perform the motor drive method based on the program.

  FIG. 7 is a flowchart showing an example of the procedure of the motor driving method in the present embodiment. Here, an example will be described in which the control unit 19 also realizes the functions of the command signal generation unit 11 and the PWM signal generation unit 10.

  In FIG. 7, when the process of this motor driving method is started, the control unit 19 determines whether or not the motor is in a low driving state smaller than a predetermined driving amount (step S70).

  Next, if the control part 19 determines with it being in the low drive state (YES), the superimposition signal Sm which is a signal different from the other control unit 31 will be superimposed on the command signal Sd (step S72). That is, as described above, for example, the control unit 31A superimposes the superimposed signal SmA different from the superimposed signal SmB superimposed on the control unit 31B on the command signal Sd.

  Conversely, when the control unit 19 determines that the low drive state is not set (NO), the control unit 19 superimposes a zero superimposition signal Sm on the command signal Sd (step S74). As a matter of course, instead of superimposing the zero superimposition signal Sm, a procedure of skipping the superimposing step and proceeding to step S76 may be used.

  Next, the control unit 19 generates a PWM control signal Pw by comparing the post-superimposition command signal Sdm obtained by superimposing the superposition signal Sm on the command signal Sd and the triangular wave carrier signal Sc synchronized between the control units 31. (Step S76). The generated PWM control signal Pw is output to the inverter 20.

  Next, the control unit 19 determines whether or not to end the process. If the process is not ended, the process returns to step S70, and if the process is not ended, the process ends (step S78).

  Even when the control unit 31 is configured to include a DSP or a microcomputer that executes the motor driving method as described above, at the time of servo lock in a configuration in which multiple axes are synchronously controlled, the inverters between the multiple axes can be controlled. Switching timing does not overlap. For this reason, increase in conduction noise and radiation noise in the multi-axis motor control device can be suppressed. In the motor control method, a more detailed configuration may be the same as the configuration described based on FIG. For example, as the superimposed signal Sm in step S72, any one of the frequency of the AC signal, the phase of the AC signal, the amplitude of the AC signal, the DC potential of the AC signal, and the voltage of the DC signal is different between the motor control units 31. A simple signal.

  2 to 6, only one frequency, phase, amplitude, and direct current potential are changed, but it goes without saying that the same effect can be obtained even if a plurality of changes are made simultaneously.

  By the way, when setting different superimposed signals Sm for each axis, if these signals are set with sufficient consideration in advance, it is possible to completely shift the switching timing of a plurality of axes. That is, the superimposed signal Sm may be an AC signal in which a frequency, a phase, an amplitude, and a DC potential are set, or a signal that is a DC signal so that the switching timings of a plurality of axes do not overlap.

  In principle, the multiple axes do not switch at the same time if they can be set so that the post-superimposition command signal Sdm does not have the same value at any timing. As shown in FIGS. 5 and 6, the simplest method is to largely shift the DC potential between the post-superimposition command signal SdmA and the post-superimposition command signal SdmB. According to this means, the post-superimposition command signal SdmA and the post-superimposition command signal SdmB can be prevented from intersecting at any timing.

  Further, the superimposed signal Sm may be an AC signal in which frequency, phase, amplitude, and DC potential are set, or a signal that is a DC signal so that the switching timings of a plurality of axes do not overlap.

  In addition, the following configuration may be adopted in which an AC signal in which a frequency, a phase, an amplitude, and a DC potential are set is set so that the command signal Sdm after superimposing a plurality of axes does not have the same value at any timing. That is, a method of synchronizing the carrier signal Sc and the post-superimposition command signal Sdm is also conceivable. As described above, when the post-superimposition command signal Sdm is generated by the microcomputer, each signal is digitally processed, so that the value is not continuously changed, but the value is updated at the peak and valley timings of the carrier signal Sc. Often to do.

  Utilizing this fact, the command signal Sdm after superimposing a plurality of axes is prevented from crossing at the peaks and valleys of the carrier signal Sc. An example is shown in FIG. As in FIG. 2, the post-superimposition command signal SdmB is a signal having a frequency twice that of the post-superimposition command signal SdmA, the timing at which the post-superimposition command signal SdmA and the post-superimposition command signal SdmB intersect, and the peaks and valleys of the carrier signal Sc The position is shifted. FIG. 9 shows waveforms of post-superimposition command signals SdmA and SdmB actually set by the microcomputer. It can be seen that the post-superimposition command signal SdmA and the post-superimposition command signal SdmB are not the same value at any timing.

  Further, as another means for not making the post-superimposition command signal SdmA and the post-superimposition command signal SdmB the same value, the superposed value is monitored by the host device 40, and if the post-superimposition command signal Sdm has the same value for a plurality of axes, the value is set. Means such as shifting a small amount are also conceivable.

  As described above, the above embodiment has been described assuming that the servo is locked. However, the present invention is not limited to the servo lock. It can also be applied when the U to W phases are switched at substantially the same timing during low-speed rotation or low torque operation.

  In the above embodiment, the case where the waveform of the superimposition signal Sm (post-superimposition command signal Sdm) generated by the superimposition signal generation unit 12 is a sine wave has been described. However, the present invention is not limited to this. Alternatively, a rectangular wave or a sawtooth wave may be used. Even in this case, the effect of shifting the switching timing can be generated if the signals are different for each axis.

  In the above embodiment, the two-axis synchronous control has been described. However, the same concept can be applied to three-axis or more synchronous control.

  In the above-described embodiment, the case where the PWM signal generation unit 10 is applied to the motor control device has been described. However, the present invention is not limited to this, and other arbitrary inverters are PWM controlled to synchronize a plurality of axes. It is also possible to apply the present invention to a device to be controlled.

  According to the present invention, the switching timing of a plurality of axes can be shifted with no particular demerit, an increase in noise can be suppressed, and the effect of reducing the peak intensity of radiation noise by duty modulation can be obtained at the same time. Therefore, the present invention is particularly useful in a device that performs PWM control in synchronization with a plurality of inverters, particularly in a motor control device in which there is a state in which the switching timings of the U to W axes, such as servo lock, completely overlap.

10, 10A, 10B PWM signal generation unit 11, 100 Command signal generation unit 12, 12A, 12B, 102 Superimposition signal generation unit 14, 104 Superimposition signal addition unit 16, 106 Carrier signal generation unit 18, 108 Comparison unit 19 Control unit 20 , 110 Inverter 21, 21A, 21B Motor 30 Motor control device 31, 31A, 31B Motor control unit 32 Power source 33 Timing generator 40 Host device 50 Motor control system

  The present invention relates to a motor control device, a motor control method, and a motor control system that apply a voltage for PWM control to a winding of a motor and control a plurality of axes synchronously, and in particular, a function of controlling the switching timing of an inverter for each axis. The present invention relates to a motor control device, a motor control method, and a motor control system.

  In a servo motor used in FA (FACTORY AUTOMATATION), the position, speed, and torque of the motor are controlled so as to follow a drive command (position command) from a host device (host controller). Digital control using a microcomputer is widely used as the control arithmetic unit. In the PWM (PULSE WIDTH MODULATION) control method generally used for controlling the motor torque, the current flowing through each phase (U phase, V phase, W phase) of the motor is controlled in a sine wave form in a pseudo manner. The torque output from the motor can be freely controlled.

  However, in the PWM control method, since the voltage applied to the motor is controlled by switching of the inverter, a large voltage fluctuation of the output voltage of the inverter and a leakage current in amperes occur at the moment of switching. Due to these effects, a large current instantaneously flows in the power supply, the potential of the power supply itself fluctuates, and conduction noise occurs. This amount of noise is regulated by CISPR (International Radio Interference Special Committee) and the like, and reduction is required.

  In addition, a phenomenon in which high-frequency radiation noise is generated from a power cable, a motor cable, a wiring pattern, etc. at the timing of switching has also been confirmed, which is also regarded as a problem.

  For this reason, conventionally, there has been proposed a technique for spreading a spectrum of radiation noise and superimposing a superimposed signal having a predetermined waveform on a drive command signal to reduce peak intensity (for example, Patent Document 1). FIG. 10 is a configuration diagram of a PWM signal generation unit in such a conventional power converter. The conventional PWM signal generation unit superimposes the command signal Sd generated by the command signal generation unit 100 and the alternating superimposed signal Sm generated by the superimposed signal generation unit 102 in each of the U phase, the V phase, and the W phase. The addition unit 104 adds the values. Then, the superposed command signal Sdm after addition and the carrier signal Sc generated by the carrier signal generation unit 106 are compared by the comparison unit 108, and the PWM duty ratio is modulated to generate the PWM control signal Pw. The inverter 110 is pulse-driven. This conventional PWM signal generation unit suppresses the noise by diffusing the spectrum of the radiation noise by the configuration in which the superposition signal Sm is superposed.

  However, noise caused by switching in the inverter as described above is particularly affected during non-rotation (servo lock), low-speed rotation, and low-torque operation where the switching timings of the phases tend to overlap. And in the conventional method of superimposing an AC superposition signal on the command signal, there is a solution to the phenomenon that a large noise is generated because the switching timing of the U to W phases overlaps at the time of servo lock, low speed rotation, and low torque operation. There is a problem of not becoming.

  Here, in order to explain such a problem, first, a PWM control signal at the time of U to W-phase servo lock in the case where the superimposed signal Sm is not superimposed on the command signal Sd in the configuration of FIG. 10 will be described. . When the servo is locked, the command signal Sd is set to 0, and the motor is stopped by controlling so that no current flows between the phases U to W. In such a case, since the command signal Sd is 0 in both the U to W phases, and the superimposed signal Sm is not superimposed, the post-superimposition command signal Sdm is also 0. FIG. 11 shows how the PWM control signal is generated in such a case. Since the post-superimposition command signal Sdm is 0 when all the U to W phases are servo-locked, in FIG. 11, they are collectively described as one post-superimposition command signal Sdm. As shown in FIG. 11, each of the U to W phases of the PWM control signal Pw generated by comparing the post-superimposition command signal Sdm with the carrier signal Sc becomes the same signal (rectangular wave with a duty of 50%), and U to W It can be seen that the switching timings of the phase inverters 110 overlap. That is, each of the U to W phases of the PWM control signal Pw, which is a pulse signal, is in a state where the rising timing of the pulse (for example, time tr in FIG. 11) and the falling timing (for example, time tf) are aligned. . Then, the levels of conduction noise and radiation noise are mutually emphasized at those timings.

  Next, the U to W phase PWM control signal Pw at the time of servo lock when the superimposed signal Sm is superimposed on the command signal Sd will be described. Since the command signal Sd is 0 for all the U to W phases and the superimposed signal Sm is a common signal for the U to W phases, the post-superimposition command signal Sdm is the same signal as the superimposed signal Sm in any phase. FIG. 12 shows how the PWM control signal is generated in such a case. As in FIG. 11, the post-superimposition command signal Sdm for the U to W phases is described as one. Each PWM control signal Pw generated by comparing the post-superimposition command signal Sdm and the carrier signal Sc is modulated in duty. With this effect, the spectrum is dispersed and the peak intensity of the radiation noise can be reduced. However, as is apparent from FIG. 12, the switching timing of the U to W phases overlaps with each other in the same manner as in FIG. 11, for example, the rising timing tr and the falling timing tf in FIG. A large conduction noise and radiation noise are generated at each moment.

  This problem is further affected particularly when synchronous control of a plurality of axes is performed. In general, since carrier signals Sc for all axes are synchronized during synchronous control, the U to W phase PWM control signals Pw for all axes have the same waveform, and the switching timing of the U to W phase inverters for all axes This is because large noise is generated.

JP 2011-111777 A

  The motor control device according to the present invention includes a plurality of motor control units that control one axis based on an operation command from a host device, and controls two or more motors in synchronization. Each of the motor control units includes a control unit that performs motor operation control, a command signal generation unit that generates a command signal for commanding motor operation based on the operation control of the control unit, and pulse width modulation based on the command signal A PWM signal generation unit that generates the PWM control signal, and an inverter that generates a drive signal for driving the motor by switching the switching element using the PWM control signal. Each of the PWM signal generation units includes a superimposition signal generation unit that generates a superimposition signal to be superimposed on the command signal, a carrier signal generation unit that generates a carrier signal that is a triangular wave, and an addition unit that adds the command signal and the superposition signal. A comparison unit that compares the post-superimposition command signal output from the addition unit with the carrier signal to generate a PWM control signal. The superimposed signal is configured to be different for each axis controlled by the plurality of motor control units.

  A motor control system according to the present invention includes the motor control device according to the present invention, a host device that transmits an operation command to the motor control device, and a motor having two or more axes controlled by the motor control device. It is.

  Further, the motor control method according to the present invention generates a command signal for instructing motor operation based on an operation command from a host device, generates a pulse width modulated PWM control signal based on the command signal, It has a plurality of motor control units that control one axis by applying a drive voltage generated by switching the switching element of the inverter with a control signal to the motor, and the motors of two or more axes are synchronized by the plurality of motor control units. This is a motor control method of a motor control device that controls the motor. In this motor control method, the step of determining whether the motor is in a low drive state smaller than a predetermined drive amount and the command signal differed between the motor control units when determined to be in the low drive state. A PWM control signal is generated by superimposing a superimposition signal, which is a signal, a post-superimposition command signal that is a signal obtained by superimposing the superimposition signal on the command signal, and a triangular wave carrier signal synchronized between the motor control units. And steps.

  According to the present invention, when synchronously controlling a multi-axis motor, when the U to W phases during servo lock, low speed rotation, and low torque operation are switched at substantially the same timing, the carrier signal remains synchronized, The switching timing of the PWM control signal can be shifted for each axis. For this reason, it is possible to avoid an increase in conduction noise and radiation noise when the U to W phases of a plurality of axes are simultaneously switched. Further, if an AC signal is superimposed, radiation noise due to duty modulation can be reduced.

FIG. 1 is a configuration diagram of a motor control system including a motor control device according to an embodiment of the present invention. FIG. 2 is a waveform diagram in the case of superimposing AC signals having only different frequencies for each axis in the motor control device. FIG. 3 is a waveform diagram in the case of superimposing AC signals having different phases only for each axis in the motor control apparatus. FIG. 4 is a waveform diagram in the case where an AC signal having only different amplitudes for each axis is superimposed in the motor control apparatus. FIG. 5 is a waveform diagram in the case of superimposing AC signals that differ only in DC potential for each axis in the motor control device. FIG. 6 is a waveform diagram when a different DC signal is superimposed for each axis in the motor control device. FIG. 7 is a flowchart showing an example of the procedure of the motor driving method according to the embodiment of the present invention. FIG. 8 is an explanatory diagram of a configuration in which the superimposed signals are not crossed at the peak and valley of the carrier signal in the motor control device. FIG. 9 is a superimposed waveform diagram when the superimposed signals are not crossed at the peak and valley of the carrier signal in the motor control device. FIG. 10 is a configuration diagram of a conventional PWM signal generation unit. FIG. 11 is a waveform diagram of a PWM control signal when a superimposed signal is not superimposed in the conventional example. FIG. 12 is a waveform diagram of a PWM control signal when a superimposed signal is superimposed in the conventional example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

  In the following, it is assumed that the servo is locked as the most severe noise state.

(Embodiment)
FIG. 1 is a configuration diagram of a motor control system including a motor control device according to an embodiment of the present invention. In FIG. 1, as an example of such a system, a configuration of a multi-axis motor control motor control system 50 including a motor control device 30 that controls a plurality of motors 21 is illustrated. In addition, FIG. 1 shows an example in which two motors 21 as two axes are provided as multi-axis. The motor control system 50 further includes a host device 40 using, for example, a personal computer in order to control the motor control device 30 by a command or the like. The host device 40 and the motor control device 30 are communicatively connected via a control bus line or the like. A command from the host device 40 is transmitted to the motor control device 30 and information from the motor control device 30 is received from the host device. 40.

  Next, the motor control device 30 is configured to include a motor control unit (hereinafter, appropriately referred to as a control unit) 31 for each of the motors 21 in order to control the motors 21 for two axes. In FIG. 1, the control unit 31 </ b> A that is the first control unit 31 controls the motor 21 </ b> A that is the first motor 21, and the control unit 31 </ b> B that is the second control unit 31 is the second motor 21. The structural example which controls the motor 21B is shown. The control unit 31 is supplied with the power supply voltage Vdc from the power supply 32 in common. Each control unit 31 uses this power supply voltage to operate the circuit in the unit and to drive the motor 21 via the inverter 20. In the present embodiment, the control unit 31 is configured to include digital processing, and the timing signal Tm generated by the timing generation unit 33 is also supplied to each control unit 31. The timing signal Tm is a clock signal for digital processing and a signal for indicating other timing.

  Each of the control units 31 includes a control unit 19, a command signal generation unit 11, a PWM signal generation unit 10, and an inverter 20. In FIG. 1, as the PWM signal generation unit 10, a control unit 31A includes a PWM signal generation unit 10A, and the control unit 31B includes a PWM signal generation unit 10B.

  As shown in FIG. 1, in the control unit 31, the control unit 19 is communicatively connected to a host device 40. Command information for instructing position, speed, torque, and the like is transmitted from the host device 40 to the control unit 19. In addition, the control unit 19 transmits information of the control unit 31 and the like to the higher-level device 40. The control unit 19 controls each part in the control unit 31 such as the command signal generation unit 11 and the PWM signal generation unit 10 together with such a communication function, and controls the operation so that the motor performs a predetermined motion such as a speed and a position. I do.

  Further, in the present embodiment, the control unit 19 includes a function for determining the driving state of the motor 21. That is, the control unit 19 determines that the motor 21 is in a low drive state such as a servo lock state, a low-speed rotation or a low torque operation state, and the determination result is used as an operation determination signal Cs for PWM. The signal generation unit 10 is notified.

  More specifically, for example, the following function may be included in the control unit 19 for determining such a low drive state. First, the control unit 19 stores a predetermined drive amount that is set in advance in order to determine the low drive state. Then, the control unit 19 determines whether or not the command drive amount is smaller than the predetermined drive amount. When the command drive amount is smaller than the predetermined drive amount for determination, the control unit 19 is in a low drive state. Is output. Further, as the command drive amount at this time, an operation command to the command signal generation unit 11 described below or the amplitude of the command signal Sd output from the command signal generation unit 11 may be used as the drive amount.

  Next, the command signal generation unit 11 generates a command signal Sd based on an operation command for commanding the position, speed, torque, and the like from the control unit 19 and supplies the command signal Sd to the PWM signal generation unit 10. More specifically, this command signal Sd is generated for three phases of U, V, and W phases, and sine waves that are shifted from each other by 120 ° in accordance with the rotational speed and torque amount required for the motor 21. This is a signal having a waveform. As described above, since the rotation of the motor 21 is stopped when the servo is locked, the amplitude of the command signal Sd at this time becomes zero.

  Next, the PWM signal generation unit 10 includes a superimposition signal generation unit 12, a superimposition signal addition unit 14, a carrier signal generation unit 16, and a comparison unit 18. Note that the PWM signal generation unit 10 has, specifically, the superposition signal addition unit 14 and the comparison unit 18 in three phases of U phase, V phase, and W phase, similarly to the configuration shown in FIG. It has corresponding components. In FIG. 1, since each phase has the same configuration, and when the servo is locked, the command value is 0 and the same signal is used, so only one phase (for example, U phase) is shown as a representative.

  In the PWM signal generation unit 10, the control unit 19 notifies the superimposed signal generation unit 12 of an operation determination signal Cs indicating whether or not the low drive state is set. For example, the superimposed signal generation unit 12 generates an alternating superimposed signal Sm, and supplies the superimposed signal Sm to the superimposed signal adding unit 14 in accordance with the operation determination signal Cs. Specifically, the superimposed signal generation unit 12 supplies the generated superimposed signal Sm only when the operation determination signal Cs indicates a low drive state, and otherwise supplies the superimposed signal Sm set to 0 level. .

  The superimposition signal adding unit 14 is supplied with the command signal Sd from the command signal generating unit 11. The superimposition signal adding unit 14 adds the supplied command signal Sd and the superimposition signal Sm, and outputs the sum as a post-superimposition command signal Sdm after the addition. That is, when the motor is driven at a low drive such as when the servo is locked, the superimposition signal adding unit 14 superimposes the superimposition signal Sm on the command signal Sd, so that the post-superimposition command signal Sdm becomes the command signal Sd. Is a signal obtained by superimposing the superimposition signal Sm on the signal. Such a post-superimposition command signal Sdm is supplied to the comparison unit 18.

  The carrier signal generator 16 generates a triangular wave carrier signal Sc for generating a pulse-width modulated signal. When synchronizing with a plurality of axes, the carrier signals Sc between the control units 31 are generally synchronized in order to ensure synchronization accuracy. In the present embodiment, the common timing signal Tm is distributed from the timing generation unit 33 to each control unit 31, and the carrier signal generation unit 16 of each control unit 31 generates the carrier signal Sc using the common timing signal Tm. It has a simple structure. With such a configuration, the carrier signals Sc are synchronized between the control units 31. In addition, the timing generator 33 may generate the carrier signal Sc and distribute the carrier signal Sc to each control unit 31. That is, as a matter of course, instead of synchronization, the same carrier signal Sc may be supplied to each control unit 31 as long as the phases of the respective carrier signals Sc match.

  Such a carrier signal Sc is supplied to the comparison unit 18. Then, the comparison unit 18 generates the PWM control signal Pw by comparing the levels of the post-superimposition command signal Sdm and the carrier signal Sc, and outputs the PWM control signal Pw to the inverter 20. Here, the PWM control signal Pw generated in this way is composed of a pulse train whose pulse width is modulated in accordance with the level of the post-superimposition command signal Sdm. Although omitted in FIG. 1, the PWM control signal Pw includes a reverse-phase inversion signal provided with an on-delay in addition to a normal-phase signal, and two control lines for both forward and reverse phases. Are output to the upper arm and the lower arm of the inverter 20, respectively.

  The PWM signal generation unit 10 generates the PWM control signal Pw that is pulse-width modulated based on the command signal Sd with the above configuration.

  In the control unit 31, the PWM control signal Pw generated in this way by the PWM signal generation unit 10 is supplied to the inverter 20. The inverter 20 receives the PWM control signal Pw from the PWM signal generation unit 10 and generates a drive voltage Vd by switching the voltage supplied from the power supply 32 according to the PWM control signal Pw using a switching element. The inverter 20 applies the generated drive voltage Vd to the motor 21 via the U-phase, V-phase, and W-phase motor wires. The inverter 20 includes a switching element such as an IGBT (INSULATED GATE BIPOLAR TRANSISTOR) and a power element such as a diode. Recently, an IPM (INTELLIGENT POWER MODEL) incorporating a pre-drive circuit for driving a power element is often used. Although only one pair of inverters is shown in FIG. 1, actually, three pairs of inverters are used to drive the motor in three phases of U phase, V phase, and W phase.

  As described above, each control unit 31 generates a drive voltage Vd for driving the motor 21 based on a command from the host device 40, and applies the generated drive voltage Vd to the motor 21 to cause the motor 21 to operate. Driving.

  As the motor 21, a three-phase brushless motor in which a magnet is arranged on a rotor is widely used from the viewpoint of efficiency and controllability. That is, as a specific configuration example of the motor 21, a three-phase brushless motor including a stator having a winding wound around a stator core and a rotor having a permanent magnet is applied, and a driving voltage Vd is applied to each phase winding. What is necessary is just to make it the structure which does.

  Next, a more detailed configuration of the present embodiment will be described. In particular, the present embodiment is characterized in that the superimposed signal Sm generated by the superimposed signal generation unit 12 of the control unit 31 is a different signal between the control units 31.

  That is, as shown in FIG. 1, in the first control unit 31A, the superimposed signal adding unit 14 superimposes the superimposed signal SmA having the first waveform generated by the superimposed signal generating unit 12A on the command signal SdA, The superposed command signal SdmA is supplied to the comparison unit 18. On the other hand, in the second control unit 31B, the superimposed signal adding unit 14 superimposes the superimposed signal SmB of the second waveform generated by the superimposed signal generating unit 12B on the command signal SdB, and compares the command signal SdmB after superposition. It supplies to the part 18. As described above, in the present embodiment, in order to obtain the effect, it is necessary that the superimposed signal SmA of the first control unit 31A and the superimposed signal SmB of the second control unit 31B are different signals. .

  In addition, a different signal is a signal from which at least any one of a frequency, a phase, an amplitude, and a direct current potential differs. In consideration of ease of control and circuit scale, a method of parameterizing one of frequency, phase, amplitude, and DC potential and controlling from the host device 40 via the control unit 19 is desirable. You may make it controllable. Further, the frequency of the superimposed signal Sm is not particularly limited and may be set freely. Further, the amplitude and DC potential of the superimposed signal Sm may be freely set within a range in which the amplitude of the post-superimposition command signal Sdm does not exceed the amplitude of the carrier signal Sc. Further, when the servo is locked, the command signal Sd becomes 0 level, while the operation determination signal Cs from the control unit 19 indicates a low drive state, so that the superimposed signal Sm has a predetermined frequency and phase as described above. , An amplitude, or a non-zero signal having a DC potential. Since the command signal Sd is at the 0 level, the superimposed signal Sm and the post-superimposition command signal Sdm are the same signal.

  In recent years, the PWM signal generation unit 10 is often configured by a DSP (DIGITAL SIGNAL PROCESSOR), microcomputer software, ASIC (APPLICATION SPECIFIC INTEGRATED CIRCUIT), or FPGA (FIELD PROGRAMMABLE GATE ARRAY) logic circuits. In this case, a signal to be processed such as the superimposed signal Sm is generally updated when the carrier signals 17A and 17B have peaks (maximum value) and valleys (minimum value) because of digital processing. That is, since each signal is digitally processed, the carrier signal Sc is also generated based on the sampling clock, and the processed signal such as the post-superimposition command signal Sdm is also time-series data sampled in accordance with the sampling clock. It is configured. As a result, when the value of the signal to be processed is updated at a timing other than the timing when the carrier signal Sc has a peak (maximum value) and a valley (minimum value), the PWM switching timing and the update timing overlap, and the PWM control signal Pw May cause chattering. Therefore, when the carrier signal Sc is a peak (maximum value) or a valley (minimum value), the sampling timing may be set so as to update the value of the signal to be processed. When the value is updated at the peaks and valleys of the carrier signal Sc, the frequency of the superimposition signal Sm can be set only below the frequency of the carrier signal Sc by the sampling theorem.

  Next, the operation of the above embodiment will be described with reference to several examples of the superimposed signal Sm, using the waveform diagrams of the different superimposed signals described above.

  First, FIG. 2 shows a case in which the superimposed signal SmA of the first control unit 31A and the superimposed signal SmB of the second control unit 31B are AC signals, and further, only the frequencies are different from each other as the above different signals. It is a wave form diagram which shows each of these waveforms. That is, FIG. 2 shows a case where the first-axis superimposed signal SmA and the second-axis superimposed signal SmB at the time of servo lock are AC signals that differ only in frequency. As described above, when the servo is locked, the command signal Sd is set to 0, and the motor is stopped by performing control so that no current flows between the phases U to W. For this reason, the post-superimposition command signal Sdm is the same signal as the superimposition signal Sm in any phase. That is, the post-superimposition command signal SdmA of the first control unit 31A and the post-superimposition command signal SdmB of the second control unit 31B are AC signals that differ only in frequency. In FIG. 2, the post-superimposition command signal SdmB is a signal having a frequency that is twice that of the post-superimposition command signal SdmA (that is, the superposition signal SmB is twice the superposition signal SmA).

  Note that this embodiment is at the time of servo lock, and since the superimposition signals SmA and SmB are the same signals as the post-superimposition command signals SdmA and SdmB, respectively, not the superimposition signals SmA and SmB but as shown in the figure. The post-superimposition command signals SdmA and SdmB, which are input signals of the comparison unit 18, will be described. Furthermore, as shown in FIG. 2, in the present embodiment, the carrier signals Sc of the first axis and the second axis are synchronized, that is, the phases match. Further, since the U to W phases have the same waveform at the time of servo lock, in FIG. 2, the post-superimposition command signals SdmA and SdmB and the PWM control signals PwA and PwB of the U to W phases in the control units 31A and 31B are One phase is shown as a representative.

  In the present embodiment, by comparing the post-superimposition command signals SdmA and SdmB as shown in FIG. 2 with the carrier signal Sc, PWM control signals PwA and PwB composed of pulse trains as shown in FIG. 2 are generated. The Here, as shown in FIG. 2, since the superimposed signal SmA and the superimposed signal SmB have different frequencies, even if the carrier signal Sc is synchronized, the rising timing tra of the PWM control signal PwA and the PWM control signal PwB The timing is different from the rising timing trb. Similarly, the falling timing tfa of the PWM control signal PwA and the falling timing tfb of the PWM control signal PwB are different timings. Therefore, according to the present embodiment, the switching timings of the inverters between the plurality of axes do not overlap at the time of servo lock in the configuration in which the plurality of axes are synchronously controlled. For this reason, the levels of conduction noise and radiation noise are not mutually emphasized among a plurality of axes, and an increase in conduction noise and radiation noise in a multi-axis motor control device can be suppressed.

  Next, FIG. 3 shows the PWM control signal PwA when the superimposed signal SmA of the first control unit 31A and the superimposed signal SmB of the second control unit 31B are alternating signals that differ only in phase as the different signals described above. It is a wave form diagram which shows each waveform including the waveform of PwB. In FIG. 3, the post-superimposition command signal SdmB is a signal obtained by inverting the post-superimposition command signal SdmA by shifting the phase by 180 °.

  Next, FIG. 4 shows that when the superposition signal SmA of the first control unit 31A and the superposition signal SmB of the second control unit 31B are alternating signals that differ only in amplitude, the PWM control signal PwA, It is a wave form diagram which shows each waveform including the waveform of PwB. In FIG. 4, the post-superimposition command signal SdmB is a signal having half the amplitude of the post-superimposition command signal SdmA.

  Next, FIG. 5 shows the PWM control signal PwA when the superimposed signal SmA of the first control unit 31A and the superimposed signal SmB of the second control unit 31B are AC signals that differ only in DC potential as the different signals described above. FIG. 4 is a waveform diagram showing each waveform including a waveform of PwB. In FIG. 5, the post-superimposition command signal SdmA and the post-superimposition command signal SdmB are signals obtained by superimposing DC potentials in the positive and negative directions on the AC signal.

  Next, FIG. 6 shows the waveforms of the PWM control signals PwA and PwB when the superimposed signals SmA of the first control unit 31A and the superimposed signals SmB of the second control unit 31B are different DC signals as the above-mentioned different signals. It is a wave form diagram which shows each waveform including this. In FIG. 6, the post-superimposition command signal SdmA and the post-superimposition command signal SdmB are DC potential signals having different voltages. In the case of this configuration, although the effect of reducing the peak intensity of radiation noise when an AC signal is superimposed cannot be obtained, this configuration can be easily realized. That is, it is not necessary to provide a complicated configuration for superimposing the AC signal, and it is only necessary to provide a configuration for adding a DC potential and to have different DC potential information for each axis.

  As described above, as shown in FIGS. 3 to 6, in the superimposed signal SmA and the superimposed signal SmB, any one of the phase of the AC signal, the amplitude of the AC signal, the DC potential of the AC signal, and the voltage of the DC signal is mutually Even when configured differently, the rise timing tra of the PWM control signal PwA and the rise timing trb of the PWM control signal PwB are different timings. Similarly, the falling timing tfa of the PWM control signal PwA and the falling timing tfb of the PWM control signal PwB are different timings.

  As described above, in any of the configurations of FIGS. 2 to 6, the timing of switching between the PWM control signal PwA and the PWM control signal PwB is deviated at the time of servo lock in the configuration in which a plurality of axes are synchronously controlled. The effect of preventing an increase in noise due to simultaneous switching of a plurality of axes can be obtained.

  In the above description, the example in which the control unit 31 is configured by the above functional blocks has been described. However, for example, the control unit 31 may be realized by the above-described DSP or microcomputer software. That is, a configuration in which processing is performed based on a processing procedure such as a program may be used. In this case, more specifically, the functions of the control unit 19, the command signal generation unit 11 and the PWM signal generation unit 10 in FIG. 1 are stored as programs in a memory or the like, and the control unit 19 is embodied by a DSP or a microcomputer. What is necessary is just to set it as the structure which performs the program and to perform the motor drive method based on the program.

  FIG. 7 is a flowchart showing an example of the procedure of the motor driving method in the present embodiment. Here, an example will be described in which the control unit 19 also realizes the functions of the command signal generation unit 11 and the PWM signal generation unit 10.

  In FIG. 7, when the process of this motor driving method is started, the control unit 19 determines whether or not the motor is in a low driving state smaller than a predetermined driving amount (step S70).

  Next, if the control part 19 determines with it being in the low drive state (YES), the superimposition signal Sm which is a signal different from the other control unit 31 will be superimposed on the command signal Sd (step S72). That is, as described above, for example, the control unit 31A superimposes the superimposed signal SmA different from the superimposed signal SmB superimposed on the control unit 31B on the command signal Sd.

  Conversely, when the control unit 19 determines that the low drive state is not set (NO), the control unit 19 superimposes a zero superimposition signal Sm on the command signal Sd (step S74). As a matter of course, instead of superimposing the zero superimposition signal Sm, a procedure of skipping the superimposing step and proceeding to step S76 may be used.

  Next, the control unit 19 generates a PWM control signal Pw by comparing the post-superimposition command signal Sdm obtained by superimposing the superposition signal Sm on the command signal Sd and the triangular wave carrier signal Sc synchronized between the control units 31. (Step S76). The generated PWM control signal Pw is output to the inverter 20.

  Next, the control unit 19 determines whether or not to end the process. If the process is not ended, the process returns to step S70, and if the process is not ended, the process ends (step S78).

  Even when the control unit 31 is configured to include a DSP or a microcomputer that executes the motor driving method as described above, at the time of servo lock in a configuration in which multiple axes are synchronously controlled, the inverters between the multiple axes can be controlled. Switching timing does not overlap. For this reason, increase in conduction noise and radiation noise in the multi-axis motor control device can be suppressed. In the motor control method, a more detailed configuration may be the same as the configuration described based on FIG. For example, as the superimposed signal Sm in step S72, any one of the frequency of the AC signal, the phase of the AC signal, the amplitude of the AC signal, the DC potential of the AC signal, and the voltage of the DC signal is different between the motor control units 31. A simple signal.

  2 to 6, only one frequency, phase, amplitude, and direct current potential are changed, but it goes without saying that the same effect can be obtained even if a plurality of changes are made simultaneously.

  By the way, when setting different superimposed signals Sm for each axis, if these signals are set with sufficient consideration in advance, it is possible to completely shift the switching timing of a plurality of axes. That is, the superimposed signal Sm may be an AC signal in which a frequency, a phase, an amplitude, and a DC potential are set, or a signal that is a DC signal so that the switching timings of a plurality of axes do not overlap.

  In principle, the multiple axes do not switch at the same time if they can be set so that the post-superimposition command signal Sdm does not have the same value at any timing. As shown in FIGS. 5 and 6, the simplest method is to largely shift the DC potential between the post-superimposition command signal SdmA and the post-superimposition command signal SdmB. According to this means, the post-superimposition command signal SdmA and the post-superimposition command signal SdmB can be prevented from intersecting at any timing.

  Further, the superimposed signal Sm may be an AC signal in which frequency, phase, amplitude, and DC potential are set, or a signal that is a DC signal so that the switching timings of a plurality of axes do not overlap.

  In addition, the following configuration may be adopted in which an AC signal in which a frequency, a phase, an amplitude, and a DC potential are set is set so that the command signal Sdm after superimposing a plurality of axes does not have the same value at any timing. That is, a method of synchronizing the carrier signal Sc and the post-superimposition command signal Sdm is also conceivable. As described above, when the post-superimposition command signal Sdm is generated by the microcomputer, each signal is digitally processed, so that the value is not continuously changed, but the value is updated at the peak and valley timings of the carrier signal Sc. Often to do.

  Utilizing this fact, the command signal Sdm after superimposing a plurality of axes is prevented from crossing at the peaks and valleys of the carrier signal Sc. An example is shown in FIG. As in FIG. 2, the post-superimposition command signal SdmB is a signal having a frequency twice that of the post-superimposition command signal SdmA, the timing at which the post-superimposition command signal SdmA and the post-superimposition command signal SdmB intersect, and the peaks and valleys of the carrier signal Sc The position is shifted. FIG. 9 shows waveforms of post-superimposition command signals SdmA and SdmB actually set by the microcomputer. It can be seen that the post-superimposition command signal SdmA and the post-superimposition command signal SdmB are not the same value at any timing.

  Further, as another means for not making the post-superimposition command signal SdmA and the post-superimposition command signal SdmB the same value, the superposed value is monitored by the host device 40, and if the post-superimposition command signal Sdm has the same value for a plurality of axes, the value is set. Means such as shifting a small amount are also conceivable.

  As described above, the above embodiment has been described assuming that the servo is locked. However, the present invention is not limited to the servo lock. It can also be applied when the U to W phases are switched at substantially the same timing during low-speed rotation or low torque operation.

  In the above embodiment, the case where the waveform of the superimposition signal Sm (post-superimposition command signal Sdm) generated by the superimposition signal generation unit 12 is a sine wave has been described. However, the present invention is not limited to this. Alternatively, a rectangular wave or a sawtooth wave may be used. Even in this case, the effect of shifting the switching timing can be generated if the signals are different for each axis.

  In the above embodiment, the two-axis synchronous control has been described. However, the same concept can be applied to three-axis or more synchronous control.

  In the above-described embodiment, the case where the PWM signal generation unit 10 is applied to the motor control device has been described. However, the present invention is not limited to this, and other arbitrary inverters are PWM controlled to synchronize a plurality of axes. It is also possible to apply the present invention to a device to be controlled.

  According to the present invention, the switching timing of a plurality of axes can be shifted with no particular demerit, an increase in noise can be suppressed, and the effect of reducing the peak intensity of radiation noise by duty modulation can be obtained at the same time. Therefore, the present invention is particularly useful in a device that performs PWM control in synchronization with a plurality of inverters, particularly in a motor control device in which there is a state in which the switching timings of the U to W axes, such as servo lock, completely overlap.

10, 10A, 10B PWM signal generation unit 11, 100 Command signal generation unit 12, 12A, 12B, 102 Superimposition signal generation unit 14, 104 Superimposition signal addition unit 16, 106 Carrier signal generation unit 18, 108 Comparison unit 19 Control unit 20 , 110 Inverter 21, 21A, 21B Motor 30 Motor control device 31, 31A, 31B Motor control unit 32 Power source 33 Timing generator 40 Host device 50 Motor control system

Claims (9)

A motor control device that has a plurality of motor control units that control one axis based on an operation command from a host device, and controls two or more motors in synchronization with the plurality of motor control units,
Each of the motor control units is
A control unit for controlling the operation of the motor;
A command signal generating unit that generates a command signal for commanding the operation of the motor based on the operation control of the control unit;
A PWM signal generator that generates a PWM control signal that is pulse-width modulated based on the command signal;
An inverter that generates a driving voltage for driving the motor by switching a switching element according to the PWM control signal;
Each of the PWM signal generators is
A superimposition signal generation unit that generates a superimposition signal to be superimposed on the command signal;
A carrier signal generator for generating a carrier signal that is a triangular wave;
An adder for adding the command signal and the superimposed signal;
A comparison unit that compares the post-superimposition command signal output from the addition unit and the carrier signal to generate the PWM control signal;
The motor control apparatus, wherein the superimposed signal is a signal that is different for each axis controlled by the plurality of motor control units. The superimposed signal is
AC signals having different frequencies for each axis, AC signals having different phases for each axis, AC signals having different amplitudes for each axis, AC signals having different DC potentials for each axis, and DC signals different for each axis The motor control device according to claim 1, wherein the signal is at least one of the following signals. 3. The motor control device according to claim 2, wherein the superimposed signal is a signal in which at least one of frequency, phase, amplitude, and DC potential is set so that switching timings of a plurality of axes do not overlap. . The superimposed signal is a signal in which at least one of a frequency, a phase, an amplitude, and a direct current potential is set so that switching timings of a plurality of axes do not overlap at a specific position of the carrier signal. The motor control device according to claim 2. The specific position of the carrier signal is any one of a timing at which the carrier signal takes a maximum value, a timing at which the carrier signal takes a minimum value, and a timing at which either the maximum value or the minimum value is taken. 3. The motor control device according to 3. The control unit determines whether or not the motor is in a low drive state, and outputs an operation determination signal indicating a result of the determination to the superimposed signal generation unit,
2. The motor control device according to claim 1, wherein the superimposition signal generation unit outputs the superimposition signal to the addition unit when the motor is in a low drive state based on the operation determination signal. . The motor control device according to claim 1, wherein carrier signals generated by each of the motor control units are synchronized with each other. The motor control device according to any one of claims 1 to 7,
The host device for transmitting the operation command to the motor control device;
A motor control system comprising two or more motors controlled by the motor control device. Generates a command signal for commanding the motor operation based on the operation command from the host device, generates a PWM control signal that is pulse width modulated based on the command signal, and switches the switching element of the inverter by the PWM control signal A plurality of motor control units that control one axis by applying the drive voltage generated in this way to the motor, and the motor of the motor control apparatus that controls two or more axes of motors synchronously with the plurality of motor control units A control method,
Determining whether the motor is in a low drive state smaller than a predetermined drive amount;
Superimposing a superposition signal that is a different signal between the motor control units on the command signal when it is determined that the low drive state;
Generating the PWM control signal from a post-superimposition command signal, which is a signal obtained by superimposing the superposition signal on the command signal, and a triangular wave carrier signal synchronized between the motor control units. A motor control method.

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