JP4668776B2 - MOTOR TORQUE RIPPLE MEASUREMENT METHOD, MEASUREMENT DEVICE, TORQUE RIPPLE SUPPRESSION METHOD, AND MOTOR DRIVE DEVICE USING THE SUPPRESSION METHOD - Google Patents

Description

  The present invention relates to a technique for easily measuring torque ripple generated due to operation of a motor in a device driven by a motor such as a servo motor and suppressing the torque ripple.

Servo motors, particularly permanent magnet motors, have a phenomenon in which the torque varies with rotation called torque ripple due to cogging torque, magnetic saturation, and the like. This torque ripple causes problems such as lowering the operation accuracy of the device and generating noise due to mechanical resonance with the device at a specific frequency. Therefore, it is desirable to accurately measure this torque ripple and compensate by control.
As a method for measuring this torque ripple, there is usually a device called a torque meter that detects a displacement in the torsional direction of a shaft and measures it as a force. However, in order to increase the accuracy of the torque meter, it is necessary to reduce the torsional rigidity of the shaft and increase the displacement with respect to the torque to some extent on the principle of operation. However, since the torque meter is arranged between the rotor of the motor and the load device, a torque pulsation (torque ripple) component exceeding several tens of Hz is caused by the influence of both the rotational inertia and the mechanical resonance generated by the torsion spring of the shaft. Its accurate measurement becomes difficult.
In addition, many expensive devices such as frequency analyzers are required, and for example, it is unsuitable for simple adjustment in a remote place such as adjustment work at the site of machine assembly.

  As a conventional technique for this, as a method for adjusting torque ripple at the time of assembling the apparatus without using a torque meter, for example, Patent Document 1 discloses a method for estimating torque ripple using sensor information of the apparatus.

Japanese Patent Laid-Open No. 7-210221 (see paragraph 0008, FIGS. 1 and 2)

  As described above, in the prior art, when the torque ripple is estimated using the measurement information of the displacement of the driven part generated as a result of the torque ripple, when the driven part having a relatively large inertia is driven, The displacement that occurs is extremely small, and in order to measure this with high accuracy, a position sensor with extremely high resolution is required, which is not practical.

  The present invention has been made in order to solve the above-described problems, and a torque ripple measurement method that can easily and easily measure torque ripple of a motor without requiring a highly accurate position sensor or torque meter. An object of the present invention is to provide a measuring device, a torque ripple suppressing method for suppressing the torque ripple, and a motor driving device to which the torque ripple suppressing method is applied.

A torque ripple measuring method for a motor according to the present invention is a method for measuring torque ripple generated by a motor driving a load,
A resonator having a characteristic that makes the rotation speed of the motor variable and resonates at a single frequency in the moving direction of the load, and a displacement detector that detects the displacement due to the vibration of the resonator. Prepared,
The frequency of torque ripple is obtained by calculation based on the rotational speed at resonance, which is the rotational speed of the motor when the resonator resonates.

  A motor torque ripple measuring apparatus according to the present invention includes the above-described resonator and displacement detector.

A torque ripple measuring method for a motor according to the present invention is a method for measuring torque ripple generated by a motor driving a load,
Input to a resonator attached to the load and having a characteristic of resonating at a single frequency in the moving direction of the load, a displacement detector for detecting a displacement due to the vibration of the resonator, and a driving means for driving the motor A torque ripple command superimposing means for superimposing the torque ripple command on the torque command;
The motor is driven at a resonance speed corresponding to the frequency of the torque ripple generated by the motor so that the resonator resonates, and a signal having the torque ripple frequency is superimposed on the torque command by the torque ripple command superimposing means as a torque ripple command. When the phase difference of the torque ripple command with respect to the predetermined reference phase is varied within a predetermined range, the extreme value phase difference when the output of the displacement detector becomes the minimum or maximum, and the amplitude of the torque ripple command at the extreme value phase difference Obtaining the extreme amplitude when the output of the displacement detector becomes the minimum when fluctuating within a specified range, and obtaining the phase difference and amplitude of the torque ripple at that frequency based on the extreme phase difference and the extreme amplitude It is.

  A motor torque ripple measuring apparatus according to the present invention includes the above-described resonator, displacement detector, and torque ripple command superimposing means.

  In addition, the torque ripple suppression method for a motor according to the present invention includes a torque ripple having a frequency having a phase difference and an amplitude obtained by the above measurement method by shifting the phase by 180 ° and superimposing it on the torque command as a torque ripple command. The torque ripple generated when the superposition is not performed is canceled out and suppressed.

  The motor driving apparatus according to the present invention includes the above-described resonator, displacement amount detector, and torque ripple command superimposing means.

  The presence and generation amount of the torque ripple of the specific frequency can be grasped by the above-described resonator, so that the torque ripple of the motor can be easily and easily measured without requiring a highly accurate position sensor or torque meter. Further, the frequency of the torque ripple of the motor and the amplitude and phase difference of the torque ripple can be obtained easily and easily. Furthermore, torque ripple can be easily and easily suppressed.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration of a mechanical device to which a motor torque ripple measuring device according to Embodiment 1 of the present invention is attached. In the machine apparatus of FIG. 1, a servo motor 1 is attached to one end of a fixed object 6, and a linear mechanism 5 using a ball screw is coupled to a rotating shaft of the servo motor 1, and further formed through a load 2. The male screw of the linear mechanism 5 is screwed into the female screw thus formed.
When the servo motor 1 is rotated, the linear mechanism 5 is rotated accordingly, and the load 2 that is screwed with the linear mechanism 5 is moved up and down in the paper surface.

  FIG. 2 is a block diagram showing a drive device for the servo motor 1. The servo amplifier 12 inputs the rotational speed command and torque command from the host mechanism, calculates the motor energization current by feeding back the motor rotational speed from the position detector 11, and gives the servo motor 1 a predetermined frequency and voltage. Supply.

Next, returning to FIG. 1, the resonator 4, the vibration displacement sensor 3, and the displacement amount measuring device 7 constituting the torque ripple measuring device, which is a main part of the present invention, will be described. First, the resonator 4 has one end attached to and fixed to the load 2 and the other end having a single vibration in the direction in which the load 2 moves, and thus when the servo motor 1 generates torque ripple, the torque ripple acts. Resonance with numbers. The resonator 4 may simply be a rod-like spring element with a weight attached thereto.
The vibration displacement sensor 3 detects vibration at the tip of the resonator 4 and can be easily obtained as an optical type or a magnetic type. The displacement amount measuring device 7 measures the displacement amount detected by the vibration displacement sensor 3, and the vibration displacement sensor 4 and the displacement amount measuring device 7 constitute a displacement amount detector referred to in the claims of the present application.

  By the way, when the rotational speed of the motor is r1 [r / min] and the number of pole pairs of the motor rotor is Pn, the frequency f1 of the torque ripple of the motor at the rotational speed r1 can be expressed by equation (1). .

  Here, n is a value obtained by dividing the number of torque ripples generated per rotation of the motor by the number of pole pairs Pn. In the present specification, this is referred to as a generated harmonic order of torque ripple, and the target motor When n and the motor speed r1 are determined, the torque ripple frequency f1 is uniquely determined from the equation (1). Hereinafter, a torque ripple command that suppresses the resonance of the resonator is obtained, and the torque ripple at the frequency f1 is measured from the torque ripple command.

m represents the number of torque ripples generated per one rotation of the motor. In the following, a torque ripple command of a sine wave pulsating m times per rotation of the motor is created and superimposed on the torque command to obtain a torque ripple command that suppresses resonance of the resonator.

  In the mechanical device incorporating the servo motor 1, the final purpose of grasping the torque ripple of the motor by measurement is to suppress the generated torque ripple based on the grasped data. In this case, since the frequency of the torque ripple is actually known in many cases, the torque ripple measuring apparatus shown in FIG. 1 shows the amplitude and phase difference of the torque ripple when the motor is actually incorporated in the mechanical device. Next, a method for measuring using the motor and a method for suppressing torque ripple generated from the motor using the measurement result will be described. Note that the frequency of torque ripple is not known, and a measurement method for obtaining this will be described in the second embodiment.

  FIG. 3 shows each waveform when a torque ripple occurs and the torque of the motor pulsates even though a constant value is given as the torque command. In the figure, the solid line is the torque command, and the dotted line is the output torque of the motor. The torque ripple component of amplitude a1 is superimposed on the value of the constant torque command. The solid-line sine wave is a fundamental wave component of the motor current exemplified for the reference phase, and when this motor current fundamental wave component is the reference phase, in this example, the torque ripple has a phase difference of b1.

  FIG. 4 shows a circuit for measuring the amplitude and phase difference of torque ripple, and a torque ripple command superimposing circuit 13 and an adder 14 as torque ripple command superimposing means are added to the circuit of FIG. The torque ripple command superimposing circuit 13 inputs torque ripple frequency, amplitude, and phase difference information to create a torque ripple command, and the adder 14 superimposes the torque ripple command on the torque command.

Next, a procedure for measuring the amplitude and phase difference of torque ripple will be described. First, the rotation speed of the servo motor 1 is set to a resonance rotation speed corresponding to the harmonic order n of the torque ripple to be measured so that the resonator 4 is in a resonance state, and the servo motor 1 is driven. .
Here, since the frequency of the torque ripple (the generated harmonic order n) is known, the resonance speed r2 [r / min] is expressed by the equation (2) when the resonance frequency of the resonator 4 is F1. .

Then, the torque ripple command superimposing circuit 13 generates a torque ripple command having a frequency of the generated order n with an arbitrary amplitude and phase difference, and superimposes it on the torque command by the adder 14, and outputs the displacement amount measuring device 7. The amplitude of the resonator is monitored.
First, as shown in FIG. 5, the phase difference of the torque ripple command is gradually changed within a predetermined range to obtain the extreme value phase difference β at which the amplitude of the resonator is minimized. In FIG. 5, the extreme value phase difference β is obtained from the point where the amplitude of the resonator is minimized, but the same extreme value phase difference β can also be obtained from the point where the amplitude of the resonator is maximized.

Next, the phase difference is fixed to the above-mentioned extreme value phase difference β, and the amplitude of the torque ripple command is gradually varied within a predetermined range as shown in FIG. Find α.
Based on the extreme value amplitude α and the extreme value phase difference β obtained above, obtain the amplitude and phase difference of the torque ripple of the harmonic order to be measured through necessary conversion taking into account the measurement conditions such as the load size. Can do.
As a matter of course, the waveform of the torque ripple command superimposed on the torque command and finally adjusted as the point where the amplitude of the resonator is minimized is obtained by reversing the polarity of the actually generated torque ripple waveform.

  If there are a plurality of frequencies of torque ripple of the motor, the amplitude and phase difference of the torque ripple may be measured by rotating the motor at the resonance speed at which the resonator 4 resonates for each frequency.

  As can be easily understood from the measurement principle described above, torque ripple generated during actual motor operation can be suppressed using the above measurement results. The torque ripple command superimposing means 13 and 14 described with reference to FIG. 4 have the same configuration, and the torque ripple command superimposed here is that the phase of the torque ripple obtained in the previous measurement is shifted by 180 °. In other words, it is equivalent to the torque ripple command superimposed during the previous measurement. In this sense, the torque ripple suppression method according to the present invention does not reliably grasp the amplitude and phase difference of torque ripple by measurement, and outputs a torque ripple command superimposed when the amplitude of the resonator is minimized during the previous measurement during motor operation. This includes the case where torque ripple is suppressed by superimposing.

  FIG. 7 shows each waveform when the above torque ripple suppression method is implemented. That is, as shown by the solid pulsation waveform, the torque command is obtained by superimposing the torque ripple command for canceling the generated torque ripple on the constant original torque command value shown in FIG. Torque ripple is suppressed, and the output torque of the motor has a constant value as shown by the dotted line.

  When a torque ripple command with multiple frequencies is superimposed on the torque command, there is interference between different harmonics, but the amplitude of the torque ripple command is sufficiently smaller than the torque command value of the motor. The optimum amplitude and phase data measured at the harmonics and frequencies may be superimposed.

Incidentally, the torque ripple of the motor changes according to the load 2. Therefore, when using a motor under various load conditions, it is necessary to grasp the load dependency. FIG. 8 shows the relationship between the average torque value (the torque ripple component is removed by taking the average value) and the torque ripple amplitude. In the figure, the torque ripple amplitude identified at two torque average values is indicated by a straight line, and the actually measured value is indicated by ▲. As shown in the figure, the torque ripple in the case of other torque values can be identified by linear interpolation from two different torque values.
The relationship obtained in FIG. 8 is directly the relationship between the amplitude of the torque ripple command to be superimposed and the load. Therefore, if the amplitude of the torque ripple command to be superimposed is controlled according to this relationship characteristic, the load fluctuated. Even in this case, a stable operating characteristic in which torque ripple is always suppressed can be obtained.

  In the above description, the torque ripple in the case of another torque value is identified by linear interpolation from two different torque values. However, when the torque value is 0, the torque ripple is almost 0. Amplitude is calculated, and torque ripples at other torque values can be identified by linear interpolation from the data at the torque value 0 and the measured torque value at one point.

  As described above, in the first embodiment of the present invention, the presence and generation amount of the torque ripple of the specific frequency can be grasped by monitoring the resonance state of the resonator 4, so that a highly accurate position sensor or torque meter is provided. The torque ripple of the motor can be measured easily and easily without the need. Further, the amplitude and phase difference of the torque ripple of the motor can be obtained simply and easily. Furthermore, torque ripple can be easily and easily suppressed.

More specifically, a servo motor is actually used by being attached to a machine. In a conventional system, when a torque ripple of a motor has conventionally occurred, the servo amplifier torque command value is adjusted. Torque pulsation of the motor is suppressed. In this case, in order to measure the torque ripple of the servo motor alone, it is necessary to remove the motor and attach the torque meter to the drive motor to measure the torque ripple of the motor. Further, when there is no torque meter, torque ripple is estimated from sensor information as in Patent Document 1, and therefore, adjustment of the servo amplifier requires equipment such as an FFT analyzer and an acceleration sensor, and the adjustment time takes several days. As a result, the necessary costs were high.
On the other hand, when the first embodiment of the present invention is applied, the torque ripple can be measured by monitoring the resonance of the resonator attached to the load without changing the local system. The required torque ripple can be measured over time.

Embodiment 2. FIG.
In the second embodiment, a method of obtaining the torque ripple frequency using the measuring apparatus described in FIGS. The rotational speed at resonance, which is the rotational speed at which the resonator 4 resonates, is obtained by making the rotational speed of the servo motor 1 variable.
In this case, if the resonance frequency F1 of the resonator 4 is known, assuming that the calculated rotation speed at resonance is r2 [r / min], the frequency of the torque ripple (occurrence is generated using the relationship of the above equation (2). The harmonic order n) can be determined.
When there are multiple torque ripple frequencies, if the motor rotation speed is changed over a wide range, multiple resonance rotation speeds corresponding to each frequency can be obtained. You can ask for. Here, even when Pn shown in the above equation (1) is not known, the number of torque ripples generated per one rotation of the motor can be easily obtained. Therefore, the frequency of the torque ripple can be obtained even when the number of pole pairs and the generated harmonic order are not known, and the torque ripple can be obtained by performing the following procedure.

  Here, if a plurality of resonators having different resonance frequencies are prepared, when obtaining a plurality of torque ripple frequencies, the range of change in the number of rotations of the motor necessary for creating the resonance state of the resonator is narrowed accordingly. Since it is possible to avoid driving in extremely high speed ranges and low speed ranges, there is an advantage that restrictions on the measurement range due to the ability of the motor itself and devices such as an inverter for controlling the motor speed are relaxed. .

  In addition, a plurality of resonators having different resonance frequencies set corresponding to the ratio of each frequency of torque ripple that can be generated by the motor are provided, and resonance of the motor when at least one of these resonators resonates. If the rotational speed of the motor is obtained and the frequency of the torque ripple is obtained by calculation from the resonant frequency of the resonator that resonates at the same time, it can be assumed that the rotational speed of the motor is set to the rotational speed of the resonance once. There is an advantage that it is possible to simultaneously determine which frequency of the torque ripple is generated among the types of frequencies.

In the first place, the generated harmonic order n that determines the frequency of the torque ripple is an integer, and for example, n = 2, 6, 12, etc., and can generally be predicted by the motor type, rating, etc. Although it is assumed that the resonance frequency of the resonator 4 is known, there is a possibility that the frequency can be estimated even when the resonance frequency has a characteristic of resonating at a single frequency but the resonance frequency is not necessarily known.
FIG. 9 is a plot of the vibration amount of the same resonator when the number of rotations of the motor is varied within a predetermined range. Resonance occurs at a plurality of resonance points, that is, three locations in the example of this figure. You can see that it has occurred. Since the ratio of the rotational speed at resonance at these three locations matches the ratio of the three harmonic orders at which torque ripple is generated, these frequencies can be estimated based on this constraint condition.
Further, when the expected range of the torque ripple frequency can be set narrow, the frequency can be estimated more easily.

  As described above, in the second embodiment of the present invention, the presence and generation amount of the torque ripple of the specific frequency can be grasped by monitoring the resonance state of the resonator 4, so that a highly accurate position sensor or torque meter is provided. The torque ripple frequency of the motor can be easily and easily obtained without requiring it.

Embodiment 3 FIG.
FIG. 10 is a diagram showing a torque ripple measuring apparatus according to Embodiment 3 of the present invention. Here, the linear mechanism 5 is coupled to the rotating shaft of the servo motor 1 via the speed reducer 8. Assuming that the reduction ratio of the speed reducer 8 is 1: s (s is an integer), the frequency component of the torque ripple of the motor is observed by being multiplied by s in the load 2 portion. Therefore, when the resonance frequency of the resonator 4 is F2, the resonance speed r3 [r / min] is expressed by the equation (3).

  That is, when measuring the torque ripple of the same frequency by connecting the speed reducer 8, the rotational speed at resonance of the motor is reduced by (1 / s) times compared to the case of directly connecting, and in particular, higher order There is an advantage that it is easy to execute when measuring the torque ripple.

Embodiment 4 FIG.
In each of the above embodiments, as shown in FIG. 1, the case where the rotation of the servo motor 1 is transmitted to the linear mechanism 5 and applied to a mechanical device that drives the load 2 in the linear direction has been described. As shown in FIG. 11, it can also be applied to a device that transmits the rotational power of the servo motor 1 to the load 2 through a rotational power transmission mechanism such as a gear. However, in this case, as shown in the figure, the resonator 4 attached to the load 2 resonates at a predetermined frequency in the rotational direction of the load 2 which is the direction in which the load moves due to the rotational force of the motor. The displacement sensor 3 detects the displacement of the resonator 4 in the resonance direction.
As a result, even in a mechanical device in which the load rotates, the existence and generation amount of the frequency torque ripple can be ascertained by monitoring the resonance state of the resonator 4 in exactly the same manner as the previous embodiments. The torque ripple of the motor can be measured easily and easily without the need for a highly accurate position sensor or torque meter. Further, the frequency of the torque ripple of the motor and the amplitude and phase difference of the torque ripple can be obtained easily and easily. Furthermore, torque ripple can be easily and easily suppressed.

In the above description, the resonator 4 and the vibration displacement sensor 3 are configured as independent separate bodies. However, the sensor is configured by using an acceleration sensor or a strain gauge having a resonator function. Also good.
In the above description, the case where the present invention is applied to a mechanical device using a servo motor has been described. However, the present invention can be widely applied to devices using other types of rotary motors, and provides the same effect.
Further, in a linear motor that is driven linearly, by attaching a resonator to the moving system, it is possible to easily and easily measure the thrust ripple of the linear motor based on the same principle as described above.

  In each modification of the present invention, the torque ripple frequency is obtained from the rotation speed at resonance and the resonance frequency of the resonator by calculation, so that the torque ripple frequency can be obtained easily and reliably.

  In addition, since a plurality of resonators having different resonance frequencies are provided, the necessary range of change in the rotational speed of the motor can be narrowed, and the burden on the motor drive system is reduced.

  In addition, the frequency of the torque ripple is calculated based on the number of rotations at resonance when the number of rotations of the motor fluctuates within a predetermined range and the resonators resonate at a plurality of different rotations. Even if the frequency is not known, the frequency can be estimated.

  The motor includes a plurality of resonators having different resonance frequencies set corresponding to the ratio of each frequency of torque ripple that can be generated by the motor, and the motor rotation speed at resonance when at least one of the resonators resonates. Since the torque ripple frequency is calculated from the resonance frequency of the resonator that resonates simultaneously with at least one resonating resonator, a plurality of types of torque ripple frequencies can be obtained simply by setting the motor rotation speed to the resonance rotation speed once. Can be obtained.

  In addition, when the load fluctuates, the amplitude of the superimposed torque ripple command is varied following the load variation, so that torque ripple is always suppressed even when the load varies.

  In addition, since the relationship characteristic that specifies the relationship between the load and the amplitude of the torque ripple command is determined by calculation from the relationship between the load and the amplitude of the torque ripple command measured at at least one point of the load by the previous measurement method, It becomes easy to obtain a relational characteristic that specifies the relation between the load and the amplitude of the torque ripple command, which is necessary for the follow-up control to the load fluctuation.

It is a figure which shows the structure of the mechanical apparatus which attached the torque ripple measuring apparatus of the motor in Embodiment 1 of this invention. 1 is a block diagram showing a drive device for a servo motor 1. FIG. It is a figure which shows each waveform before implementing a torque ripple suppression method. It is a block diagram which shows the structure which added the torque ripple instruction | command superimposition means to the circuit of FIG. It is a characteristic view showing a change in the amplitude of the resonator when the phase of the torque ripple command is changed. It is a characteristic view showing a change in the amplitude of the resonator when the amplitude of the torque ripple command is changed. It is a figure which shows each waveform at the time of implementing the torque ripple suppression method. It is a characteristic view showing the relationship between the average value of torque and the amplitude of torque ripple. In Embodiment 2 of this invention, it is a characteristic view which shows the change of the vibration amount of the resonator at the time of changing the rotation speed of a motor. It is a figure which shows the structure of the mechanical apparatus which attached the torque ripple measuring apparatus of the motor in Embodiment 3 of this invention. It is a figure which shows the structure of the mechanical apparatus which attached the torque ripple measuring apparatus of the motor in Embodiment 4 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Servo motor, 2 Load, 3 Vibration displacement sensor, 4 Resonator, 7 Displacement measuring device, 12 Servo amplifier, 13 Torque ripple command superimposition circuit, 14 Adder.

Claims (12)

A method for measuring torque ripple generated by a motor driving a load,
A resonator having a variable speed of the motor and having a characteristic of resonating at a single frequency in the moving direction of the load, and a displacement amount for detecting a displacement amount due to the vibration of the resonator Equipped with a detector,
A method for measuring torque ripple of a motor, wherein the frequency of the torque ripple is obtained by calculation based on a rotational speed at resonance which is a rotational speed of the motor when the resonator resonates . 2. The method of measuring torque ripple of a motor according to claim 1, wherein the frequency of the torque ripple is obtained by calculation from the rotation speed at resonance and the resonance frequency of the resonator . The method for measuring torque ripple of a motor according to claim 2, comprising a plurality of resonators having different resonance frequencies . The frequency of the torque ripple is obtained by calculation based on the plurality of resonance rotation speeds when the rotation speed of the motor is varied within a predetermined range and the resonator resonates at a plurality of rotation speeds different from each other. Item 5. A torque ripple measuring method for a motor according to Item 1 . A plurality of resonators having different resonance frequencies set corresponding to the ratio of each frequency of torque ripple that can be generated by the motor;
The frequency of the torque ripple is obtained by calculation from the number of revolutions of the motor at the time of resonance when at least one of the resonators resonates and the resonance frequency of the resonator that resonates simultaneously with the at least one resonator. The method for measuring torque ripple of a motor according to claim 1 . A method for measuring torque ripple generated by a motor driving a load,
A resonator attached to the load and having a characteristic of resonating at a single frequency in the moving direction of the load, a displacement detector for detecting a displacement due to the vibration of the resonator, and a driving means for driving the motor Torque ripple command superimposing means for superimposing the torque ripple command on the input torque command,
The motor is driven at a resonance speed corresponding to the frequency of torque ripple generated by the motor so that the resonator resonates, and a signal having the frequency of torque ripple is used as the torque ripple command by the torque ripple command superimposing means. When the phase difference of the torque ripple command with respect to a predetermined reference phase is varied within a predetermined range, superimposed on the torque command, the extreme phase difference when the output of the displacement detector becomes minimum or maximum, and the pole When the amplitude of the torque ripple command is varied within a predetermined range in the value phase difference, an extreme value amplitude is obtained when the output of the displacement detector is minimized, and the value is calculated based on the extreme value phase difference and the extreme value amplitude. A method for measuring torque ripple of a motor, comprising: obtaining a phase difference and an amplitude of torque ripple at a frequency . The torque ripple of the frequency having the phase difference and the amplitude obtained by the measurement method according to claim 6 is generated when the phase is shifted by 180 ° and superimposed on the torque command as a torque ripple command. A torque ripple suppression method for a motor, wherein torque ripple is canceled and suppressed. 8. The method of suppressing torque ripple of a motor according to claim 7, wherein, when the load fluctuates, the amplitude of the superimposed torque ripple command is varied following the load variation . The relation characteristic for specifying the relation between the load and the amplitude of the torque ripple command is calculated from the relationship between the load measured at at least one point of the load and the amplitude of the torque ripple command by the measurement method according to claim 7. 9. The motor torque ripple suppression method according to claim 8, wherein the torque ripple suppression method is determined. 6. A torque ripple measuring device for a motor comprising the resonator according to claim 1 and a displacement detector. A torque ripple measuring device for a motor comprising the resonator according to claim 6, a displacement detector, and a torque ripple command superimposing means . A motor drive device comprising the resonator according to claim 7, a displacement detector, and a torque ripple command superimposing unit.

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