JP2008043046A - Method for controlling servo motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive method which can reduce electromagnetic noises and enhance the reliability of a high-capacity servo motor that uses a plurality of inverters. <P>SOLUTION: In the drive method for controlling one AC motor 1 by a plurality of inverters 111, 112, 113, 114, the phase of a triangular wave generating section 29 that is a reference signal is changed for each inverter by a phase shift sections 281, 282, 283, 284, and respective signals are provided to PWM control units 271, 272, 273, 274 and signals for performing PWM control of the inverters are obtained. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control method for a large capacity servo motor, and more particularly to a control method for driving a large capacity servo motor by a plurality of inverters.

Large capacity servo motors are required in press machines and machine tools. In order to control these large-capacity servomotors, there is a method in which a plurality of armature windings are provided in one motor and these are driven by a plurality of inverters. FIG. 5 shows a conventional example in which four armature windings 1-1, 1-2, 1-3, and 1-4 are provided in one AC motor 1, and each winding is replaced by four inverters 111, respectively. , 112, 113, 114 are controlled by the control device 201. Since the armature winding current is controlled by four inverters, it is possible to realize large-capacity driving that is difficult to manufacture with one inverter.
JP 2005-86918 A JP-A-9-114504

In the above-described conventional example, a motor having a plurality of windings is driven by a plurality of inverters, so that a large capacity can be easily achieved. However, since a plurality of inverters are used, electromagnetic noise may increase or the reliability of the device may be reduced. In addition, there is a concern that harmonic current increases as the motor capacity increases, affecting peripheral devices.
The present invention has been made to solve the above problems, and an object of the present invention is to provide a control method for reducing electromagnetic noise and improving reliability of a large capacity servomotor using a plurality of inverters.

  According to a first aspect of the present invention, in the servo motor control method for controlling the winding current of one motor by a plurality of inverters, the phase of a reference signal for PWM control of each inverter of the plurality of inverters is set for each of the inverters. Instead, electromagnetic noise is reduced by PWM control of the inverter.

According to a second aspect of the present invention, the electromagnetic noise is reduced by PWM controlling the inverter according to the first aspect using the reference signal as a carrier wave for PWM control.
According to a third aspect of the present invention, the electromagnetic noise is reduced by performing PWM control of the inverter in the first aspect using the reference signal as a control period of PWM control.

  Furthermore, the invention of claim 4 is the servo motor control method according to any one of claims 1 to 3, wherein the number of the inverters is n, and one period of the reference signal applied to each inverter is 2π. When the phase of each reference signal applied to each inverter is shifted by 2π / n and the inverter is PWM controlled, electromagnetic noise is reduced.

According to a fifth aspect of the present invention, in the servo motor control method according to the first aspect, the drive current of the servo motor is shared by the operating inverter, and the plurality of inverters sharing the drive current of the servo motor are PWMed. By controlling, electromagnetic noise is reduced.
Further, the invention according to claim 6 is the servo motor control method according to claim 5, wherein the connection of the non-operating inverter to the armature winding of the servo motor is disconnected, and the operating inverter is controlled by PWM control. Reduce noise.

According to the first aspect of the present invention, in the servo motor control method for controlling the winding current of one motor by a plurality of inverters, the phase of the reference signal for PWM control of each inverter is changed for each inverter. Since the plurality of inverters are PWM-controlled, there is an effect of reducing electromagnetic noise.
According to the invention of claim 2, since the reference signal performs PWM control of the inverter as a carrier wave for PWM control in claim 1, there is an effect of reducing electromagnetic noise in PWM control of a system for comparing the carrier wave and the modulated wave.
According to the invention of claim 3, since the reference signal performs PWM control of the inverter as the control period of PWM control in claim 1, there is an effect of reducing electromagnetic noise in PWM control using no carrier wave such as space vector control.

According to a fourth aspect of the invention, in the servo motor control method according to any one of the first to third aspects, when the number of inverters is n and one period of a reference signal applied to each inverter is 2π, Since the inverter is PWM-controlled by making each reference signal phase different by 2π / n, there is an effect of easily reducing electromagnetic noise.
According to the fifth aspect of the present invention, in the servo motor control method according to the first aspect, the inverter which is operating and shares the motor driving current is PWM-controlled. Since it is driven by the inverters that are operating except those that do not operate, there is an effect of reducing electromagnetic noise while improving reliability.
According to a sixth aspect of the present invention, in the servo motor control method according to the fifth aspect, PWM control is performed for an inverter that is operating without being connected to an armature winding of the servo motor. Therefore, there is an effect of reducing electromagnetic noise while further improving the reliability.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows the configuration of a drive device for a large capacity servo motor to which the present invention is applied. Here, the example which comprised the permanent magnet alternating current motor 1 (henceforth AC motor 1) with the four armature winding 1-1, 1-2, 1-3, 1-4 is shown. Although not shown, a permanent magnet is attached to the rotor. Armature windings 1-1, 1-2, 1-3, and 1-4 are connected to inverters 111, 112, 113, and 114, respectively. In FIG. 1, the same reference numerals as those in FIG. The deviation between the speed command ω * and the detected value ω of the motor rotation speed (the detector is not shown) is amplified by the speed control unit 21 and output from the speed control unit 21 as the torque command τ * of the AC motor 1. Since AC motor 1 is driven by four inverters, torque command τ * from speed control unit 21 is reduced to ¼, and each inverter shares a quarter of the total torque.

  In other words, in the inverter 111, the torque command 1/4 is implemented by the torque command unit 221 and is output as d and q-axis current commands Id1 * and Iq1 * of the armature winding 1-1 corresponding to the torque command. d, q-axis current commands Id1 * and Iq1 * and the deviations between the currents Id1 and Iq1 obtained by converting the two-phase alternating currents iu1 and iv1 detected by the current detector 261 from stationary coordinates to rotating coordinates by the AC / DC converter 251. Deviation amplification is performed by the current control unit 231. This output is input to a DC / AC converter 241 that is a converter from rotating coordinates to stationary coordinates, and is output as AC output phase voltage commands vu1 *, vv1 *, and vw1 * of the inverter 111. These calculations from the torque command to the voltage command are well known as vector control of an AC motor, and will not be described in detail here. At this time, the DC / AC conversion unit 241 and the AC / DC conversion unit 251 perform coordinate conversion on the basis of the rotation phase of the rotation shaft of the AC motor 1, which is also well known.

The phase voltage commands vu1 *, vv1 *, vw1 * are input to the PWM control unit 271 where they are compared with a triangular wave that is a carrier wave to obtain a PWM signal. The inverter 111 is driven by the PWM signal from the PWM controller 271. The triangular wave is calculated by the triangular wave generator 29 and input to the PWM controller 271 via the phase shifter 281.
The control units of the inverters 112, 113, and 114 are configured in the same manner as that of the inverter 111 as shown in FIG. That is, the torque command τ * is calculated as a current command of the armature winding of each inverter by the torque command units 222, 223, 224, and after passing through the vector control unit (dotted line in FIG. 1) of each inverter, the PWM control units 272, 273 274 obtains a PWM signal for controlling each of the inverters 112, 113, and 114. Since the armature windings 1-1, 1-2, 1-3, and 1-4 of the motor 1 are electrically independent, there is no interference between the inverters 111, 112, 113, and 114, and the current is supplied. It can be controlled freely. In this way, each inverter is controlled to share a quarter of the total torque.

  The phase shift amount of the triangular wave in the phase shift units 281, 282, 283, and 284 is adjusted so that the electromagnetic noise is minimized by the operation of the inverters 111, 112, 113, and 114. For example, the phase is specifically shifted as follows. In this example, since the number of inverters is 4, the triangular wave phase applied to each PWM control unit 271, 272, 273, 274 is a phase in which one triangular wave period of the triangular wave generating unit 29 is 360 degrees, and 360/4 = 90 degrees. Each phase is shifted differently. That is, the phase shift of the triangular wave is 0 degree in the phase shift unit 281, the phase shift of the triangular wave is 90 degrees in the phase shift unit 282, the phase shift in the phase shift unit 283 is 180 degrees, and the phase shift in the phase shift unit 284 is 270. As a degree, it is input to the PWM controllers 271, 272, 273, 274, respectively. Since the phase of the triangular wave in the PWM control unit is different for each inverter, the probability of switching each inverter simultaneously is reduced, and electromagnetic noise can be reduced. In the above embodiment, the carrier wave applied to the PWM control unit is phase-shifted by the phase-shifting unit. However, each inverter has a triangular wave generation unit, and each phase is synchronized so that the phases are different as described above. You may control.

In the above embodiment, the PWM method for comparing the triangular wave as the carrier wave and the voltage command as the modulation wave has been described, but the same can be applied to the space vector PWM control. That is, in this case, the phase of the control reference period for performing the space vector control may be performed so that the phase of the control reference period of the other inverters is different from each other with reference to a certain inverter.
In addition, although the present Example showed about what drives one motor with four inverters, it can implement with two or more some inverters. If the number of inverters is n (n is an integer equal to or greater than 2), the phase of the carrier used by each inverter is different by 2π / n with respect to the electrical angle 2π of one cycle of the carrier.

  FIG. 2 shows another embodiment of the present invention. This is an example in which the armature windings 1-1, 1-2, 1-3, and 1-4 are well balanced, and the control system can be simplified. The current control unit is implemented by the control system of the inverter 111, and voltage commands to the other inverters 112, 113 and 114 are obtained from the voltage commands of the inverter 111. The PWM controllers 271, 272, 273, and 274 are implemented for each inverter. Even if it carries out like a present Example, the place which this invention intended can be implemented.

  As another embodiment, the following configuration may be adopted. That is, although there are four inverters 111, 112, 113, and 114, two armature windings may be provided, and two inverters may be connected in parallel to supply current to the same winding. Furthermore, the current may be supplied to one winding by four inverters with one armature winding. Thus, even when the number of inverters and the number of windings are not the same, the intention of the present invention can be implemented by controlling the phase of the carrier wave of each inverter.

  FIG. 3 shows still another embodiment. It is characterized by shifting the spatial phase of the armature winding. Assuming that one period of the spatial arrangement of the three-phase armature winding is 360 degrees, the winding 1-21 is 30 degrees, the winding 1-31 is 60 degrees, and the winding is based on the armature winding 1-11. 1-41 shifts the electrical angle phase in the space of the armature winding by 90 degrees. This has the effect of reducing torque ripple. At this time, since the induced voltage phase of each winding is also shifted, coordinate conversion performed by the DC / AC conversion unit 241 and the AC / DC conversion unit 251 is performed according to the phase of each winding. Even in this case, the phase shift amount of the carrier wave in the phase shift units 281, 282, 283, and 284 is set so that the electromagnetic noise is minimized. According to this embodiment, electromagnetic noise can be reduced while reducing torque ripple.

  FIG. 4 shows yet another embodiment of the present invention. Relays 121, 122, 123, and 124 are provided between the inverters 111, 112, 113, and 114 and the armature windings 1-1, 1-2, 1-3, and 1-4 connected to the respective inverters. The feature of this embodiment is that each inverter and each armature winding can be freely connected or disconnected. Here, for example, consider a case where the inverter 114 in FIG. 4 fails. In this case, the inverter 114 can be disconnected and the operation can be continued with the other three units. Therefore, the relays 121, 122, and 123 are connected and the relay 124 is disconnected.

  In this way, the same operation as in normal operation is performed even when three inverters are operated. Since the torque of the normal inverter bears 1/3 of the total, the coefficient values of the torque command units 221, 222, and 223 are set to 1/3. That is, the torque command unit 221 reduces the torque command τ * to 、, and outputs current commands Id1 * and Iq1 * corresponding to the torque command τ *. Similarly, the torque command τ * is reduced to で も in the other torque command units 222 and 223. In addition, since the inverter 114 disconnects from the armature winding 1-4, the coefficient of the torque command unit 224 is 0 (zero). In this way, three inverters perform the same operation as normal. In addition, since the operation is performed with three inverters, the phase shift unit is adjusted so that noise is minimized with three phase shift units. For example, if one period of a triangular wave signal that is a carrier wave is 360 degrees, the phase shift amount of the phase shift unit 281 is 0 degrees, the transfer amount of the phase shift unit 282 is 120 degrees, and the phase shift amount of the phase shift unit 283 is 240 degrees. In addition, the operation of the inverter 114 is stopped.

  In the above example, the groups 1-1, 1-2, 1-3, 1-4 of the armature windings are wound in balance in the respective groups themselves as shown in FIG. In some cases, the coefficient values of the torque command units 221, 222, and 223 when the inverter 114 has failed have been described. However, if the groups 1-1, 1-2, 1-3, 1-4 of the armature windings are not wound in a balanced manner in the stator, the torque coefficient is simply reduced to 1/3. In this case, the same magnitude of current flows in each of the armature winding groups 1-1, 1-2, and 1-3, so that there is a possibility that the balance of the magnetic flux distribution of the stator may be out of order. In this case, the coefficient values (including zero) of the torque command units 221, 222, and 223 are adjusted so that only the winding groups 1-1, 1-2, and 1-3 that can be operated can be balanced. Also in this case, the value of the torque command unit 224 for the winding 1-4 is 0 (zero).

  As described above, the coefficients of the torque command units 221, 222, 223, and 224 are changed depending on the location of the inverter that stops abnormally. Similarly, the phase shift amounts of the phase shift units 281, 282, 283, and 284 are also changed depending on the location of the inverter that stops abnormally. These changes may be made in the control device or by a command from a host system that grasps the abnormality. In the above description, the case where one inverter has failed and stopped has been described. However, even when two inverters have stopped by failure, the same concept can be applied. Furthermore, although the above has described the case where the armature winding group is four groups, it goes without saying that the present invention can be similarly implemented even in the case of two or more groups.

  In this way, if there is an abnormal inverter, the maximum torque is reduced (in the case of FIG. 4, it is reduced to 3/4), but up to this value can be operated as normal. In this way, if there is an abnormal inverter, it will be disconnected, the operation will continue with only the normal inverter, and the phase of the carrier will be shifted to reduce noise in a form suitable for the inverter being operated. It can be operated with low electromagnetic noise.

It is a figure which shows one Example of this invention. It is a figure which shows the other Example of this invention. It is a figure which shows the further another Example of this invention. It is a figure which shows another Example of this invention. It is a figure which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC motor 1-1, 1-2, 1-3, 1-4 Armature winding 1-11, 1-21, 1-31, 1-41 Armature winding 21 Speed control part 29 Triangular wave generation part 111 , 112, 113, 114 Inverter 121, 122, 123, 124 Relay 201 Control device 221, 222, 223, 224 Torque command unit 231 Current control unit 241 DC / AC conversion unit 251 AC / DC conversion unit 261 Current detector 271, 272, 273, 274 PWM control unit 281, 282, 283, 284 Phase shift unit ω * Speed command ω Motor rotation speed detection value τ * Torque command Id1 *, Iq1 * d, q-axis current command Id1, Iq1 Converted current iu1, iv1 Two-phase AC current Vu1 *, Vv1 *, Vw1 * Output phase voltage command for inverter 111

Claims (6)

In a servo motor control method for controlling a winding current of one motor by a plurality of inverters, a phase of a reference signal for PWM control of each inverter of the plurality of inverters is changed for each inverter, and the plurality of inverters A method for controlling a servo motor, wherein PWM control is performed. 2. The servo motor control method according to claim 1, wherein the reference signal is a PWM control carrier wave. 2. The servo motor control method according to claim 1, wherein the reference signal is a control cycle of PWM control. 4. The servo motor control method according to claim 1, wherein the number of the plurality of inverters is n, and one cycle of the reference signal applied to each inverter is 2π. A method of controlling a servo motor, wherein the phase of each of the reference signals applied to is different by 2π / n. 2. The servo motor control method according to claim 1, wherein a drive current of the servo motor is shared by an operating inverter among the plurality of inverters. 6. The servo motor control method according to claim 5, wherein a connection of an inverter that does not operate among the plurality of inverters is disconnected from an armature winding of the servo motor.

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