JP6288330B1 - Electric motor control device and electric motor control method - Google Patents

Abstract

When suppressing the speed fluctuation of an electric motor, the rate of suppressing the speed fluctuation is accurately controlled to suppress a decrease in control device efficiency. A motor control device includes a speed controller that outputs a torque command based on a speed command, a compensation coefficient setting unit that sets an arbitrary value of 0 to 1 as a compensation coefficient K, and a rotational speed of the motor. The torque compensation value ΔT that suppresses periodic fluctuations of the torque is multiplied by the compensation coefficient K and added to the torque command to obtain a post-compensation torque command, and output to the motor based on the post-compensation torque command A current controller for controlling the current. [Selection] Figure 1

Description

  The present invention relates to an electric motor control device and an electric motor control method.

  When speed control of an electric motor is performed using an electric motor control device such as an inverter, control for causing the rotational speed of the electric motor to follow a command speed is generally performed by feedback control. At this time, if the motor is used for a purpose such as a compressor in which the load fluctuates periodically, the speed fluctuation of the motor periodically occurs with the load fluctuation, which causes vibration and noise.

  In Patent Document 1, a compensation voltage pattern in accordance with a change in load torque is obtained in advance for each predetermined rotation angle of the electric motor, stored in the internal memory of the control means, and an addition read from the internal memory for each predetermined rotation angle. An electric motor control method is described in which a value obtained by adding data to a reference voltage is used as an applied voltage of an electric motor, thereby changing an output torque of the electric motor to suppress fluctuations in rotational speed during one rotation.

  In Patent Document 2, when the primary component of the speed fluctuation of the motor is suppressed by torque control, a hysteresis characteristic is given according to the average magnitude of the speed fluctuation, and the input to the primary component compensation unit and It describes switching control of the signal model in the first-order component compensator and keeping the speed fluctuation in the vicinity of a predetermined value.

JP 2002-247878 A Japanese Patent Laid-Open No. 10-174488

  An object of the present invention is to accurately control the rate of speed fluctuation suppression when suppressing the speed fluctuation of the electric motor, and to suppress a decrease in the efficiency of the control device.

  An electric motor control device according to an aspect of the present invention includes a speed controller that outputs a torque command based on a speed command, a compensation coefficient setting unit that sets an arbitrary value of 0 to 1 as a compensation coefficient K, and an electric motor A torque compensation value ΔT that suppresses periodic fluctuations in the rotational speed of the motor is multiplied by the compensation coefficient K and added to the torque command to obtain a post-compensation torque command, and an electric motor based on the post-compensation torque command And a current controller for controlling a current to be output.

  An electric motor control device according to another aspect of the present invention provides a speed compensation based on a remaining torque compensation value (1-K) ΔT obtained by multiplying the torque compensation value ΔT by (1-K). A torque-speed conversion unit for obtaining a value may be provided, and the speed controller may further output a torque command based on the speed compensation value.

  The motor control device according to another aspect of the present invention may limit addition to the torque command when a product of the torque compensation value ΔT and the compensation coefficient K is smaller than a preset value.

  The motor control device according to another aspect of the present invention restricts addition to the torque command when the product of the torque compensation value ΔT and the compensation coefficient K is smaller than a preset value, and the torque The speed compensation value may be obtained using the compensation value ΔT as the remainder of the torque compensation value.

  In the electric motor control device according to another aspect of the present invention, the correction coefficient K may be changed based on conditions relating to at least one of time, electric motor rotation speed, load, and external command.

  The motor control method according to one aspect of the present invention calculates a torque command based on a speed command, sets an arbitrary value from 0 to 1 as a compensation coefficient K, and periodically varies the rotational speed of the motor. Is multiplied by the compensation coefficient K to be added to the torque command to obtain a compensated torque command, and the current output to the motor is controlled based on the compensated torque command.

  An electric motor control method according to another aspect of the present invention provides a speed compensation based on a remaining torque compensation value (1-K) ΔT obtained by multiplying the torque compensation value ΔT by (1-K). A torque command may be calculated based on the speed compensation value.

  According to another aspect of the present invention, there is provided a motor control method that measures a torque command for the motor when the compensation coefficient K is 0 or a load torque generated in the motor, and sets the compensation coefficient K to 0. In order to obtain the speed compensation value based on the measured torque command or the load torque and the peak of the cyclic fluctuation of the rotational speed. May be calculated.

1 is a block diagram illustrating a configuration of an electric motor control device according to an embodiment of the present invention, and an electric motor control system including an electric motor and a load. It is a flowchart which shows an example of the operation | movement which suppresses noise and vibration in the electric motor control apparatus which consists of an electric motor control apparatus which concerns on one Embodiment of this invention, and an electric motor and load. It is a figure which shows an example which provided the limiter in order not to perform suppression of the periodic fluctuation | variation of the rotational speed of an electric motor when the value of K (DELTA) T is smaller than a fixed value. It is a figure which shows another example which provided the limiter in order not to perform suppression of the periodic fluctuation | variation of the rotational speed of an electric motor, when the value of K (DELTA) T is smaller than fixed.

  FIG. 1 is a block diagram showing the configuration of an electric motor control device 1 according to an embodiment of the present invention, an electric motor control system including an electric motor 2 and a load 3.

The motor control device 1 is a device that supplies electric power so that the motor 2 rotates at a desired speed based on an input speed command ωr ^* . Here, the motor control device 1 is a so-called inverter control device, but is not necessarily limited thereto, and may be a control device such as a servo control device or a cycloconverter. The electric motor 2 is an AC electric motor, but the form thereof is not particularly limited, and may be various induction machines or synchronous machines. Here, the motor 2 is a three-phase permanent magnet synchronous motor as an example. The load 3 is a mechanism that receives power from the electric motor 2 and operates. The load 3 is not particularly limited, but here, a compressor is exemplified as a mechanism having a large torque fluctuation during one rotation of the electric motor 2.

The basic configuration of the motor control device 1 is that a speed deviation Δω ^* , which is the difference between the speed command ωr ^* and the rotational speed ωr of the motor 2 estimated by the speed estimator 14, is input to the speed controller 10 and the torque command T ^{Get *} . The current controller 11 obtains a current command Iq ^* (torque component current command) from the torque command T ^* and a current command Id ^* (excitation current command) (not shown), and a current Iq (torque component current) described later. ) And Id (excitation current), voltage commands vq ^* (torque voltage command) and vd ^* (excitation voltage command value) in the dq coordinate are obtained. The voltage commands vq ^* and vd ^* are coordinate-converted from the dq coordinate system to the uvw coordinate system by the coordinate converter 12 (reverse dq conversion), and the voltage commands vu ^{* for the} u-phase, v-phase, and w-phase, respectively ^. , Vv ^* , vw ^* .

Inverter 13 applies power from power supply 14 to each of the three phases of electric motor 2 in accordance with voltage commands vu ^* , vv ^* , and vw ^* , and drives load 3.

  Further, the current value output from the inverter 13 to the electric motor 2 is input to the coordinate converter 15, coordinate-converted from the uvw coordinate system to the dq coordinate system (dq conversion), and the currents Iq and Id Converted to.

Further, the voltage commands vq ^* and vd ^* and the currents Iq and Id are input to the speed estimator 16 and are used for estimating the rotor position θ and the rotational speed ωr of the electric motor 2. The position θ is input to the coordinate converter 12 and the coordinate converter 15 and used for inverse dq conversion and dq conversion, and the rotational speed ωr constitutes a so-called speed feedback that is subtracted from the speed command ωr ^*. Yes.

In the description so far, any known configuration may be used as the specific configuration of the speed controller 10, the current controller 11, and the speed estimator 16. In this embodiment, the position θ and the rotational speed ωr are estimated by the speed estimator 16 from the voltage commands vq ^* and vd ^* and the currents Iq and Id. A rotational position detection sensor such as an encoder or a resolver may be provided, and the rotational position θ may be directly measured, and the rotational speed ωr may be obtained from the obtained rotational position θ. Alternatively, another method that can estimate the rotational position θ and the rotational speed ωr may be used.

In the configuration described above, the speed compensation within the range of the tracking performance of the speed controller 10 is performed for the torque fluctuation of the electric motor 2 caused by the characteristics of the load 3 and the like. However, if there is a detection delay or an estimation delay in the feedback value due to speed detection or speed estimation, compensation by the speed controller 10 is effective for steady speed fluctuations, but is effective for steep torque fluctuations. It is known that there may be no or even increased fluctuations. For this reason, when a steep and periodic torque fluctuation occurs, a periodic fluctuation occurs in the rotational speed ωr of the electric motor 2 and causes vibration and noise. Therefore, in the present embodiment, a feedforward compensation is further performed on the torque command T ^* input to the current controller 11 to suppress periodic fluctuations in the rotational speed ωr of the electric motor 2.

  The torque compensation value ΔT used for the feedforward compensation is given according to the rotational speed ωr and the rotational position θ of the electric motor 2. The method for obtaining the torque compensation value ΔT is not particularly limited, and any known method may be used. For example, the torque compensation value ΔT is determined in advance as a table in accordance with the rotational speed ωr and the rotational position θ of the electric motor 2 in the same manner as described in Patent Document 1 described above, and torque compensation is performed with reference to the table. The value ΔT may be obtained. Alternatively, the torque compensation value ΔT may be obtained from the model of the electric motor 2 and the load 3 in the same manner as described in Patent Document 2 described above, or may be obtained by another method.

In the present embodiment, the torque compensation value ΔT is multiplied by the compensation coefficient K in block 17 and added to the torque command T ^* . Thus, what is actually input to the current controller 11, the torque command T ^* not itself, the torque command T ^* to the compensated torque command obtained by adding the product KΔT torque compensation value ΔT and the compensation coefficient K Tc ^* .

The compensation coefficient K is set to an appropriate value by the compensation coefficient setting unit 21 as an arbitrary value in the range of 0 to 1. The compensation coefficient setting unit 21 may set the compensation coefficient K by an operator's operation, or may be configured to automatically set the compensation coefficient K as will be described later. Then, by setting the compensation coefficient K to an appropriate value, it is possible to arbitrarily set how much the periodic fluctuation of the rotational speed ωr is suppressed. That is, when the torque compensation value ΔT is simply added to the torque command T ^* , the rotation speed ωr is set to a value that can substantially eliminate the periodic fluctuation of the rotation speed ωr. The periodic variation can be made substantially zero, and if K = 0.5, the periodic variation of the rotational speed ωr can be suppressed to 50%. When K = 0, periodic fluctuations in the rotational speed ωr are not suppressed.

  The compensation coefficient K may be set as an arbitrary value depending on conditions when the electric motor 2 is operated. For example, when torque compensation (feed forward compensation) is performed, the current value applied to the motor increases, and the efficiency of the motor control device 1 decreases. The compensation coefficient K may be set to an appropriate value in order to suppress a decrease in efficiency, that is, an increase in current value. Alternatively, the compensation coefficient K is set to a high value close to 1 under conditions where noise and vibration are to be suppressed such as at night, and power prices are low, and noise and vibration of the motor 2 are suppressed, and noise and vibration such as during the daytime are suppressed. Under a condition that is allowed to some extent or a condition that the power price is high, the compensation coefficient K can be set to a low value close to 0, and the current consumption can be suppressed while allowing noise and vibration to some extent.

By the way, simply adding KΔT to the torque command T ^* cannot accurately control how much the periodic fluctuation of the rotational speed ωr is suppressed. This is because the rotational speed ωr of the electric motor 2 that has fluctuated due to the post-compensation torque command Tc ^* is fed back to the speed controller 10 and the influence of feedback control by the speed controller 10 is reflected in the torque command T ^* .

Therefore, the present embodiment has a configuration for removing the influence of KΔT from the speed deviation Δω ^* input to the speed controller 10. That is, KΔT is multiplied by (1−K) / K in block 18 to obtain a residual torque compensation value (1−K) ΔT that was not used for torque compensation (feedforward compensation). Further, the torque-speed conversion 19 converts the torque compensation value remainder (1-K) ΔT into a speed compensation value Δω, which is the speed that would have been generated by the remainder.

The post-compensation speed command ωc ^{* that} is finally input to the speed controller is compensated based on the speed compensation value Δω in addition to the speed command ωr ^* . Specifically, a speed compensation value Δω is subtracted in advance from the speed command ωr ^* , and converted to a post-compensation speed command ωc ^* . Therefore, in this embodiment, the speed deviation Δω ^* is not the difference between the speed command ωr ^* and the rotational speed ωr, but actually the difference between the compensated speed command ωc ^* and the rotational speed ωr.

By doing so, the speed controller 10 is apparently inputted with the speed deviation Δω ^* as if torque compensation by KΔT was applied to the torque command T ^* . As a result, the speed controller 10 eliminates the effect that the fluctuation amount of the rotational speed ωr of the electric motor 2 caused by the remaining torque compensation value (1-K) ΔT is fed back, and the periodic fluctuation of the rotational speed ωr. Can be accurately determined by the compensation coefficient K.

Note that the configuration for compensating the speed command ωr ^* based on the speed compensation value Δω is not limited to the configuration in which the speed compensation value Δω is directly subtracted from the speed command ωr ^* as described above. In other words, the post-compensation speed command ωc ^* may be obtained as a value obtained by subtracting the speed compensation value Δω from the speed command ωr ^* . As such another configuration, for example, there is a configuration in which the speed compensation value Δω is subtracted from the difference between the speed command ωr ^* and the rotational speed ωr. Alternatively, a configuration in which a speed compensation value Δω is added to the rotation speed ωr and the sum is subtracted from the speed command ωr ^* may be used.

  FIG. 2 is a flowchart showing an example of an operation that is performed while suppressing noise and vibration in the motor control system 1 including the motor control apparatus 1 according to the present embodiment, the motor 2 and the load 3. In the flowchart, steps ST1 to ST4 are pre-operation preparation operations, and steps ST5 to ST8 are operation operations.

First, in step ST1, the torque command T ^{* for} the motor 2 or the load torque generated in the motor 2 when the periodic fluctuation of the rotational speed ωr of the motor 2 is not suppressed is measured. The load torque may be measured directly by attaching an appropriate measuring device to the electric motor 2 or may be obtained from the output of a disturbance torque observer. The case where the periodic fluctuation of the rotational speed ωr of the electric motor 2 is not suppressed is nothing but the case where the compensation coefficient K is 0. Therefore, this measurement may be performed at K = 0. The pulsation component obtained by removing the steady component that does not depend on the position of the rotor of the electric motor 2 from the obtained torque command T ^* or the load torque corresponds to the torque compensation value ΔT. A table is created in advance by setting according to the rotational position θ. This is (A).

  Further, in step ST2, the peak of the periodic fluctuation is measured when the periodic fluctuation of the rotational speed ωr of the electric motor 2 is not suppressed. This measurement may also be performed directly by attaching an appropriate measuring device to the electric motor 2 or may be obtained from the rotational speed ωr output from the speed estimator 16. However, when there is a delay in speed detection by the speed estimator 16, it is not preferable to use the output of the speed estimator 16 for measurement of periodic fluctuations in the rotational speed ωr. When the electric motor 2 has a rotational position detection sensor such as a rotary encoder, measurement may be performed from the output. Let this be (B).

  Next, in step ST3, from the torque compensation value ΔT obtained in step ST1 and the periodic fluctuation peak obtained in step ST2, a conversion count between torque and speed is obtained by (A) / (B). Calculate.

  The above steps ST1 to ST3 are procedures that should be performed in advance as a preparatory stage before the motor control system is operated while suppressing periodic fluctuations in the rotational speed ωr of the motor 2, and are scheduled to be used. The torque compensation value ΔT corresponding to each rotation speed, the peak of periodic fluctuation, and the conversion count between torque and speed are obtained in advance for each of the various rotation speeds of the motor 2.

  Further, in step ST4, an appropriate compensation coefficient K is set in light of the operation status of the electric motor 2. This completes the pre-operation preparation.

In step ST5, KΔT is obtained from the torque guarantee value ΔT obtained in step ST1 and the compensation coefficient K set in step ST4, and is added to the torque command T ^* . Thereby, the periodic fluctuation of the rotational speed ωr of the electric motor 2 is suppressed by a ratio equal to the guarantee coefficient K.

  Further, in step ST6, the remainder (1-K) ΔT of the torque compensation value is divided by the conversion factor obtained in step ST3, and torque-speed conversion is performed to derive a speed compensation value Δω.

In step ST7, the speed compensation value Δω is subtracted from the speed command ωr ^* to obtain a post-compensation speed command ωc ^* . As a result, the influence due to the feedback of the rotational speed ωr of the electric motor 2 that has fluctuated due to the compensated torque command Tc ^* to the speed controller 10 is eliminated.

The removal of the influence of the post-compensation torque command Tc ^* in steps ST6 and ST7 may use another method, not the method of subtracting the speed compensation value Δω from the speed command ωr ^* . As another method, for example, the influence of the post-compensation torque command Tc ^{* is} caused to suppress periodic fluctuations in the rotational speed ωr of the electric motor 2, so that the influence is exerted on the rotational speed ωr of the electric motor 2. It is considered that they are generated with substantially the same period, and frequency components having a period substantially equal to the rotational speed ωr from the output from the speed controller 10 and the output from the speed estimator 14 by an appropriate frequency filter, for example, a low pass filter or a band pass filter. The method of cutting is mentioned.

  Further, when the operation of the electric motor 2 is continued in step ST8 (ST8: Y), the process returns to step ST5, the periodic fluctuation of the rotational speed ωr of the electric motor 2 is continuously suppressed, and the operation of the electric motor 2 is not continued. In the case (ST8: N), the operation is terminated.

When the value of KΔT to be added to the torque command T ^* is smaller than a certain value, the magnitude of noise / vibration is small in the first place and there is little need for compensation. Therefore, the value of KΔT is smaller than a certain value. In addition, the periodic fluctuation of the rotational speed ωr of the electric motor 2 may not be suppressed. That is, there is a practical error in the torque compensation value ΔT or the detected value. Based on the estimated value including this error, the periodic fluctuation of the rotational speed ωr of the motor 2 is reduced to 0 or a level close to 0. This is because there is a possibility that the fluctuation will be increased when trying to suppress it.

  FIG. 3 is a diagram showing an example in which a limiter is provided so as not to suppress periodic fluctuations in the rotational speed ωr of the electric motor 2 when the value of KΔT is smaller than a certain value. FIG. 3 constitutes a part of the block diagram shown in FIG.

As shown in FIG. 3, the limiter 18 is provided from the block 15 until KΔT is added to the torque command T ^* . The limiter 20 outputs KΔT as it is when KΔT is equal to or greater than the threshold torque Tth, and the output is 0 when KΔT is less than the threshold torque Tth. As a result, when the value of KΔT is less than the threshold torque Tth, the value added to the torque command T ^* is 0 as in the case of K = 0, and the rotational speed ωr of the electric motor 2 varies periodically. There is no suppression.

  FIG. 4 is a diagram showing another example in which a limiter 20 is provided so as not to suppress periodic fluctuations in the rotational speed ωr of the electric motor 2 when the value of KΔT is smaller than a certain value. FIG. 4 also forms part of the block diagram shown in FIG.

In the example of FIG. 4, the torque compensation value ΔT is input to the block 15, and KΔT output from the block 17 is input to the limiter 20. The operation of the limiter 20 is the same as in the previous example. When KΔT is equal to or greater than the threshold torque Tth, KΔT is output as it is, and when KΔT is less than the threshold torque Tth, the output is zero. Since this KΔT or 0 is added to the torque command T ^* , when the value of KΔT is less than the threshold torque Tth, it is the same as when K = 0, and the rotation speed ωr of the electric motor 2 is periodically changed. Suppressing fluctuations is not performed.

  Further, in this example, KΔT or 0 output from the limiter 20 is subtracted from the torque compensation value ΔT and input to the torque-speed conversion 19. Here, when KΔT is equal to or greater than the threshold value Tth and KΔT is output from the limiter 20, ΔT−KΔT = (1−K) ΔT is input to the torque-speed conversion 19 and is shown in FIG. The result is equivalent to

  When KΔT is less than the threshold value Tth and 0 is output from the limiter 20, ΔT−0 = ΔT is output to the torque-speed conversion 19. Therefore, in this example, the same result as that obtained when K = 0 is obtained in the case shown in FIG.

  Further, the value of K used in the block 17 and the block 18 may be changed during the operation of the electric motor 2. As described above, the change may be set in advance by the operator in accordance with the conditions for operating the electric motor 2, but the electric motor control device 1 itself detects such conditions and sets them automatically. You may make it do. By doing in this way, suppression of the noise and vibration of the electric motor 2 can be finely controlled as necessary.

  Various conditions can be cited as such conditions. Examples thereof are shown below.

  (1) The compensation coefficient K is changed according to the time. For example, noise / vibration suppression is not performed during the day or the suppression ratio is low, and noise / vibration suppression is strengthened at night.

  (2) The compensation coefficient K is changed according to the rotational speed ωr of the electric motor 2. For example, the resonance frequency of the vibration system composed of the electric motor 2 and the load 3 is measured in advance, and at a rotational speed ωr that is equal to or near the resonance frequency, the compensation coefficient K is set to 1 or a large value close to 1. For other rotational speeds ωr, the value is smaller than that. Alternatively, generally, since the vibration tends to increase when the rotation speed ωr of the electric motor 2 is small, the compensation coefficient K is increased as the rotation speed ωr decreases.

  (3) The compensation coefficient K is changed according to the load of the inverter 13 or the electric motor 2. For example, an overload of the inverter 13 or the electric motor 2 is expected such that the peak current value of the current output from the inverter 13 to the electric motor 2 exceeds a predetermined value, or the electric power output from the inverter 13 to the electric motor 2 exceeds a predetermined value. In such a case, the compensation coefficient K is changed to a small value to prevent in advance failure or abnormal stop due to overload. Alternatively, an event caused by the load of the inverter 13 or the electric motor 2 may be detected. For example, when the temperature of the inverter 13 itself, the switching element used for the inverter 13, or the temperature of the electric motor 2 exceeds a predetermined value, the overloading of the inverter 13 or the electric motor 2 is expected, and the compensation coefficient K is set to a small value You may change it.

  (4) The compensation coefficient K is changed according to an external command. The command from the outside includes, for example, an operation mode instruction by the operator. That is, when the operator operates an appropriate operation terminal to instruct the motor controller 1 to operate in a low noise (low vibration) mode, the compensation coefficient K is set to 1 or a large value close to 1, and the energy saving mode is instructed. In this case, the compensation coefficient K is set to 0 or a small value close to 0. This intermediate mode may be provided, and an intermediate value between the low noise (low vibration) operation mode and the energy saving mode may be set as the compensation coefficient K.

  Furthermore, the conditions raised in (1) to (4) above may be used in any combination. When combining, the compensation coefficient K may be set by giving priority to each condition, or the product of the compensation coefficient K derived from each condition may be used as the value of the compensation coefficient K that is finally used.

  The configuration of the embodiment described above is shown as a specific example, and the invention disclosed in this specification is not intended to be limited to the configuration of the specific example itself. Those skilled in the art may make various modifications to these disclosed embodiments, and the control shown in the flowchart may be replaced with another control that has an equivalent function. It should be understood that the technical scope of the invention disclosed herein includes such modifications.

  DESCRIPTION OF SYMBOLS 1 Motor controller, 2 Motor, 3 Load, 10 Speed controller, 11 Current controller, 12 Coordinate converter, 13 Inverter, 14 Power supply, 15 Coordinate converter, 16 Speed estimator, 17 block, 18 block, 19 Torque -Speed conversion, 20 limiter, 21 compensation coefficient setting unit.

Claims (6)

A speed controller that outputs a torque command based on the speed command;
A compensation coefficient setting unit that sets an arbitrary value of 0 to 1 as the compensation coefficient K;
A configuration for obtaining a post-compensation torque command by multiplying the torque compensation value ΔT that suppresses periodic fluctuations in the rotational speed of the electric motor by the compensation coefficient K and adding it to the torque command;
A current controller for controlling a current output to the electric motor based on the post-compensation torque command;
I have a,
A torque-speed converter that obtains a speed compensation value based on a torque compensation value remainder (1-K) ΔT obtained by multiplying the torque compensation value ΔT by (1-K);
The speed controller further outputs a torque command based on the speed compensation value;
Electric motor control device. If the product of the torque compensation value ΔT and the compensation coefficient K is smaller than the preset value, the motor control device according to claim 1 which limits the addition to the torque command. When the product of the torque compensation value ΔT and the compensation coefficient K is smaller than a preset value, the addition to the torque command is restricted, and the torque compensation value ΔT is regarded as the remainder of the torque compensation value. The motor control device according to claim 1 , wherein a value is obtained. The motor control device according to any one of claims 1 to 3 , wherein the correction coefficient K is changed based on a condition regarding at least one of time, a rotation speed of the motor, a load, and a command from the outside. Calculate the torque command based on the speed command,
Set any value from 0 to 1 as the compensation coefficient K,
A torque compensation value ΔT that suppresses periodic fluctuations in the rotational speed of the motor is multiplied by the compensation coefficient K and added to the torque command to obtain a compensated torque command;
Based on the post-compensation torque command, control the current output to the motor ,
Based on the torque compensation value remainder (1-K) ΔT obtained by multiplying the torque compensation value ΔT by (1-K), a speed compensation value is obtained,
Further, a torque command is calculated based on the speed compensation value.
Electric motor control method. A torque command for the motor when the compensation coefficient K is 0, or a load torque generated in the motor,
Measure the peak of periodic fluctuations in the rotational speed of the motor when the compensation coefficient K is 0,
Based on the measured torque command or the load torque and the peak of the periodic fluctuation of the rotational speed, a conversion count for obtaining the speed compensation value is calculated.
The electric motor control method according to claim 5 .

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