JP7633111B2 - Motor control device and motor control method - Google Patents

Description

The present invention relates to a motor control device and a motor control method having an auto-tuning function.

When installing a servo motor in a target device such as a robot or machine tool, the gain of the servo amplifier must be adjusted according to the load inertia. Such servo amplifier gain adjustment is generally performed by a motor control device with an auto-tuning function.

In auto-tuning, multiple test operations are performed while changing the tuning parameters, and the next parameters to be set are determined based on the results of each test operation. In particular, to suppress oscillation on the motor side at the resonance point present in the target device, it is necessary to set a notch filter that can suppress the resonance peak, for example.

As an example of such autotuning, Patent Document 1 proposes an automatic adjustment method for a motor control device in which an encoding unit extracts and outputs only information on the sign of the internal state quantity, a limiter unit calculates and outputs information limiting the amplitude of the output of the notch filter unit, an adaptive update unit sequentially updates and outputs an estimated value of the notch frequency based on the multiplication of the output of the encoding unit and the output of the limiter unit, a notch filter unit adopts the estimated value as the notch frequency, a unit conversion unit converts the unit of the estimated value into Hertz and outputs this as an estimated value, and the estimated value is used to adaptively adjust the controller.

JP 2021-087276 A

In the automatic adjustment method for a motor control device described in Patent Document 1 above, the notch frequency of the notch filter is set near the frequency of the resonance point of the resonance frequency of the target device, which is thought to make it possible to attenuate the frequency level of the resonance point.

However, when there are multiple resonance points of the resonant frequency of the target device within a certain range, even if the notch frequency of the notch filter is set near the frequency of the resonance points, it is impossible to attenuate the frequency level of the resonance points within the certain range, and control may become unstable.

The present invention was made in consideration of these circumstances, and aims to provide a motor control device and a motor control method that can solve the above problems.

The motor control device of the present invention comprises a servo amplifier that adjusts the gain of a motor, and a torque adjustment unit having a notch filter, wherein the servo amplifier analyzes a feedback signal and determines the presence or absence of vibration above a certain reference level , and when it is recognized that the feedback signal has two vibration modes having different peak frequencies, the torque adjustment unit causes the notch frequency of the notch filter to correspond to only the peak frequency of one of the two vibration modes when the difference in peak frequencies between the two vibration modes is within a certain range, and attenuates the vibration of the two vibration modes by only adjusting the strength of the notch filter having a notch frequency set to correspond only to that peak frequency .
The motor control method of the present invention is characterized in that a feedback signal is analyzed by a servo amplifier that adjusts the gain of a motor, and the presence or absence of vibration above a certain reference level is determined. When a torque adjustment unit having a notch filter recognizes that the feedback signal has two vibration modes having different peak frequencies, when the difference in peak frequencies between the two vibration modes is within a certain range, the notch frequency of the notch filter is made to correspond to only the peak frequency of one of the two vibration modes, and the vibrations of the two vibration modes are damped simply by adjusting the strength of the notch filter, which has a notch frequency set to correspond only to that peak frequency .
In the motor control device and motor control method of the present invention, a servo amplifier that adjusts the gain of a motor analyzes a feedback signal and determines the presence or absence of vibration above a certain reference level . When a torque adjustment unit having a notch filter recognizes that the feedback signal has two vibration modes with different peak frequencies, when the difference in peak frequencies between the two vibration modes is within a certain range, the notch frequency of the notch filter is made to correspond to only the peak frequency of one of the two vibration modes, and the vibrations of the two vibration modes are damped simply by adjusting the strength of the notch filter, which has a notch frequency set to correspond only to that peak frequency .

The motor control device and motor control method of the present invention cover and attenuate the peak frequencies of vibrations within a certain range, preventing control from becoming unstable.

FIG. 1 is a diagram for explaining an embodiment of a motor control device of the present invention. FIG. 2A is a diagram for explaining torque adjustment by the servo amplifier of FIG. 1 for a vibration frequency exceeding a certain reference level, and is a diagram showing a case where a notch filter is set for one vibration. FIG. 2B is intended to explain torque adjustment by the servo amplifier of FIG. 1 for a vibration frequency that exceeds a certain reference level, and is a diagram showing a case in which a second vibration is present at a position that is away from the first vibration by a certain range or more. FIG. 2C is a diagram for explaining torque adjustment by the servo amplifier of FIG. 1 for a vibration frequency exceeding a certain reference level, and shows a case where a notch filter is set for the second vibration. FIG. 3A is a diagram for explaining torque adjustment by the servo amplifier of FIG. 1 for a vibration frequency exceeding a certain reference level, and shows the setting of a notch filter when the peak frequencies of adjacent vibrations are within a certain range. FIG. 3B is a diagram for explaining torque adjustment by the servo amplifier of FIG. 1 for a vibration frequency exceeding a certain reference level, and shows the setting of a notch filter when the peak frequencies of adjacent vibrations are within a certain range. FIG. 3C is a diagram for explaining torque adjustment by the servo amplifier of FIG. 1 for a vibration frequency exceeding a certain reference level, and shows the setting of a notch filter when the peak frequencies of adjacent vibrations are within a certain range. FIG. 4 is a flow chart for explaining auto-tuning by the servo amplifier of FIG.

Below, an embodiment of a motor control device of the present invention will be described with reference to Figures 1 to 4. Note that when performing auto-tuning, the motor control device M described below needs to adjust the gain of the servo amplifier 100 according to the load inertia, but for convenience of explanation, illustration and explanation of the load inertia will be omitted. Also, for convenience of explanation, the frequency values described below are set to values that are easy to explain.

The motor control device M is equipped with a servo amplifier 100 that has an auto-tuning function. The servo amplifier 100 performs FFT (Fast Fourier Transform) analysis of the encoder pulse, which is a feedback signal, and performs processing such as extracting the vibration frequency. In addition, the servo amplifier 100 determines that oscillation has occurred when the peak value of the extracted vibration frequency exceeds a certain reference level. Note that the reference numeral 300 indicates a motor, the reference numeral 150 indicates a subtractor, and the reference numeral 160 indicates an adder-subtractor.

The servo amplifier 100 has a position adjustment unit 110, a feedforward control unit 120, a feedback control unit 130, a torque adjustment unit 140, and a current control unit 170.

The position adjustment unit 110 outputs a position command according to the gain setting to the feedforward control unit 120 and the subtractor 150 based on a command indicating a target value including command values for position, speed, and torque from a controller (not shown).

Based on the position command from the position adjustment unit 110, the feedforward control unit 120 outputs a feedforward command (FF command) including a speed command and a torque command for controlling the speed and torque to the adder/subtractor 160.

Based on the feedback signal, the feedback control unit 130 outputs a feedback command (FB command) to the adder-subtractor 160 to set the deviation from the subtractor 150 to zero.

The torque adjustment unit 140 has a first and a second notch filter 141, 142. The torque adjustment unit 140 outputs an adjustment command to the current control unit 170, the adjustment command being attenuated by the notch filters 141 and/or 142 in response to the vibration contained in the torque command of the control command from the adder/subtractor 160.

The first and second notch filters 141, 142 are not limited to two as shown in the figure, and three or more may be provided. In addition, the first and second notch filters 141, 142 may be adaptive filters that can self-adapt a transfer function according to an optimization algorithm. Details of the settings of the first and second notch filters 141, 142 will be described later.

The subtractor 150 subtracts the position command corresponding to the gain setting from the position adjustment unit 110 from the position and velocity signals of the feedback signal, and outputs the deviation. The adder/subtractor 160 subtracts the feedforward command from the feedback command, and outputs a control command to make the deviation from the subtractor 150 zero.

The current control unit 170 controls the drive current of the motor 300 so that the torque indicated by the adjustment command from the torque adjustment unit 140 is generated.

When a command is output from a controller (not shown) in a motor control device configured in this manner, the motor 300 starts to drive based on a feedforward command (FF command) from the feedforward control unit 120.

When a feedback signal detected by an encoder (not shown) is output as the motor 300 is driven, a control command for making the deviation from the subtractor 150 zero is output from the adder-subtractor 160 in response to a feedback command (FB command) from the feedback control unit 130. Then, the current control unit 170 controls the drive current of the motor 300 so as to generate a torque indicated by the adjustment command from the torque adjustment unit 140 that has damped the vibration.

Next, the settings in the torque adjustment unit 140 will be described with reference to Figures 2A to 3C. For the sake of convenience, Figures 2A to 3C only show vibrations that exceed a certain reference level. The vertical axis indicates the vibration level and the depth of the first and second notch filters 141 and 142, and the horizontal axis indicates the frequency.

The first and second notch filters 141, 142 also have the characteristic that the phase lags on the low frequency side of the center frequency and leads on the high frequency side. Therefore, if the notch frequency of the first and second notch filters 141, 142 is matched to the peak frequency of the vibration, the phase lag on the low frequency side may cause the notch frequency and the peak frequency of the vibration to not match, which may cause the servo amplifier 100 to become unstable. For this reason, in this embodiment, the notch frequency of the first and second notch filters 141, 142 is set to, for example, 90% of the peak frequency of the vibration.

Note that 90% of the frequency means that, for example, when the peak frequency of the vibration is 400 Hz, the notch frequency is set to 360 Hz, as shown in FIG. 2A. This allows the phase of the notch frequency to match the peak frequency of the vibration after setting the first and second notch filters 141 and 142.

Figure 2A shows a case where the servo amplifier 100 has one vibration due to oscillation. In this case, the torque adjustment unit 140 sets the notch frequency of the first notch filter 141 to a frequency (360 Hz) that is 90% of the peak frequency of the vibration (400 Hz). As a result, after setting the first notch filter 141, the phase of the notch frequency can be matched to the peak frequency of the vibration, and the peak frequency of the vibration (400 Hz) can be attenuated as shown by the dotted line in Figure 2B.

Figure 2B shows a case where the servo amplifier 100 has two vibrations due to oscillation. In this case, when the peak frequency (800 Hz) of the second vibration is apart from the peak frequency (400 Hz) of the first vibration by a certain range or more, the torque adjustment unit 140 sets the notch frequency of the second notch filter 142 to a frequency (720 Hz) that is 90% of the peak frequency (800 Hz) of the vibration, as shown in Figure 2C. This makes it possible to attenuate the peak frequency (800 Hz) of the second vibration after setting the second notch filter 142. Here, being apart by a certain range or more means that the peak frequencies of the two vibrations are apart by more than twice the band of the notch frequency, for example.

In auto-tuning, after setting the first notch filter 141, the gain of the first notch filter 141 is increased and a test operation is performed. When it is confirmed that there is no vibration whose peak value in the FFT analysis result of the torque value obtained from the feedback signal exceeds a certain reference level, the tuning operation is completed. When the test operation of the first notch filter 141 is performed and there is a second vibration as shown in FIG. 2B, the second notch filter 142 is set to a frequency (720 Hz) that is 90% of the peak frequency (800 Hz) of the second vibration, and the gain of the second notch filter 142 is increased and a test operation is performed. When it is confirmed that there is no vibration whose peak value exceeds a certain reference level, the tuning operation is completed.

Next, FIG. 3A shows a case where the servo amplifier 100 has two vibrations due to oscillation, and the peak frequencies of the two vibrations are close to each other (within a certain range). Within a certain range means, for example, that the peak frequencies of the two vibrations are within the band of the notch frequency.

When the two vibration peak frequencies are close to each other as shown in FIG. 3A, the torque adjustment unit 140 sets the notch frequency of the first notch filter 141 to a frequency (360 Hz) that is 90% of the vibration peak frequency (400 Hz). As a result, after the first notch filter 141 is set, the vibration peak frequency (400 Hz) can be attenuated as shown by the dotted line in FIG. 3B.

Here, the gain of the first notch filter 141 is increased and a test operation is performed. Then, as shown in FIG. 3B, if the FFT analysis result of the torque value obtained from the feedback signal shows that the vibration close to the peak frequency (400 Hz) has not been attenuated, the torque adjustment unit 140 increases the strength of the first notch filter 141 from the initial setting, as shown in FIG. 3C. This makes it possible to cover and attenuate the peak frequency of vibration that is close (within a certain range) to the peak frequency of vibration (400 Hz) by deepening the depth of the notch frequency, as shown by the solid line in FIG. 3B.

When the peak frequencies of the two vibrations caused by the oscillation of the servo amplifier 100 are close to each other (within a certain range), it is also possible to set the notch frequency of the first notch filter 141 to the lower peak frequency of the vibration. However, if the first notch filter 141 is set to the lower peak frequency of the vibration, there is a risk that the notch frequency will not be able to cover the higher peak frequency of the vibration even if the depth of the notch frequency is increased. For this reason, it is preferable to align the first notch filter 141 with the higher peak frequency of the vibration.

Next, the auto-tuning process of the motor control device M will be described with reference to FIG. 4. Note that the following describes the case related to vibration reduction through torque adjustment.

(Step S101)
The servo amplifier 100 analyzes the vibration level.
In this case, the servo amplifier 100 performs, for example, FFT analysis on the feedback signal to extract the vibration frequency.

(Step S102)
The servo amplifier 100 judges whether or not there is vibration above a certain reference level.
In this case, if the peak value of the extracted vibration frequency does not exceed a certain reference level, the servo amplifier 100 determines that there is no vibration at or above the certain reference level (step S102: No), and ends the process.
In contrast, as shown in Figures 2A to 3C, if the peak value of the extracted vibration frequency exceeds a certain reference level, the servo amplifier 100 determines that there is vibration equal to or greater than the certain reference level (step S102: Yes), and proceeds to step S103.

(Step S103)
The servo amplifier 100 determines whether there are two or more vibrations.
In this case, if the servo amplifier 100 determines from the determination result of step S107 that there is one vibration as shown in FIG. 2A (step S103: No), the servo amplifier 100 proceeds to step S107.
On the other hand, if the servo amplifier 100 determines from the determination result of step S102 that there are two or more vibrations as shown in FIG. 2B (step S103: Yes), the servo amplifier 100 proceeds to step S104.

(Steps S104, S107)
The servo amplifier 100 sets the first notch filter 141 .
In this case, as shown in FIG. 2A, the torque adjustment unit 140 of the servo amplifier 100 sets the notch frequency of the first notch filter 141 to a frequency (360 Hz) that is 90% of the peak frequency (400 Hz) of the vibration.
Then, after setting the first notch filter 141, the gain of the first notch filter 141 is increased and a test operation is performed to check whether the vibration of the peak frequency (400 Hz) at which the first notch filter 141 is set has been attenuated.
It should be noted that, when the setting of the first notch filter 141 is completed in step S107 and it is confirmed that the vibration has been attenuated, the process ends.

(Step S105)
The servo amplifier 100 determines whether the peak frequency of the second vibration is within a certain range.
In this case, as shown in FIG. 3A, when the servo amplifier 100 determines that the peak frequency of the second vibration is within a certain range (close to) the peak frequency of the first vibration (400 Hz) (step S105: Yes), it proceeds to step S106.
In contrast, when the servo amplifier 100 determines that the peak frequency (800 Hz) of the second vibration is equal to or greater than a certain range relative to the peak frequency (400 Hz) of the first vibration (step S105: No), as shown in FIG. 2B, it proceeds to step S108.

(Step S106)
The servo amplifier 100 sets the second notch frequency.
In this case, as shown in FIG. 2C, the torque adjustment unit 140 of the servo amplifier 100 sets the notch frequency of the second notch filter 142 to a frequency (720 Hz) that is 90% of the peak frequency (800 Hz) of the second vibration.
Then, after setting the second notch filter 142, the gain of the second notch filter 142 is increased and a test operation is performed to check whether the vibration of the peak frequency (800 Hz) at which the second notch filter 142 is set has been attenuated.

(Step S108)
The servo amplifier 100 increases the strength of the first notch filter 141 .
In this case, the torque adjusting section 140 of the servo amplifier 100 makes the strength of the first notch filter 141 stronger than the initial setting, as shown in FIG. 3C.
As a result, the depth of the notch frequency of the first notch filter 141 becomes deeper, so that after setting the first notch filter 141, the notch frequency can cover and attenuate peak frequencies of vibration that are close (within a certain range) to the peak frequency of vibration (400 Hz).

(Step S109)
The servo amplifier 100 judges whether the setting is complete.
In this case, if the servo amplifier 100 cannot confirm in steps S104, S106, and S107 that the vibration of the peak frequency (400 Hz and 800 Hz, or 400 Hz) has been attenuated by setting the first and/or second notch filters 141, 142 (step S109: No), it determines that the setting is not complete.
In response to this, if the servo amplifier 100 can confirm in steps S104, S106, and S107 that the vibration of the peak frequency (400 Hz and 800 Hz, or 400 Hz) has been attenuated by setting the first and/or second notch filters 141, 142 (step S109: No), it determines that the setting is complete and terminates the process.

In the above description, the first and/or second notch filters 141, 142 are set in steps S104, S106, and S107, and the gain of the first and/or second notch filters 141, 142 is increased to perform the test operation, but this is not limited to the example. For example, after the first and/or second notch filters 141, 142 are set in steps S104, S106, and S107, the gain of the first and/or second notch filters 141, 142 is increased in step S109 to perform the test operation, and it may be determined whether the vibration of the peak frequency at which the first and/or second notch filters 141, 142 are set has attenuated, and whether the setting is complete.

In this manner, in this embodiment, when the servo amplifier 100, which adjusts the gain of the motor 300, analyzes the feedback signal and determines that there is vibration at or above a certain reference level, the torque adjustment unit 140 makes the strength of the notch filter 141 stronger than the initial setting when the peak frequencies of adjacent vibrations determined by the servo amplifier 100 are within a certain range, thereby covering and attenuating the peak frequencies of vibrations within the certain range. This makes it possible to prevent control from becoming unstable.

REFERENCE SIGNS LIST 100 Servo amplifier 110 Position adjustment section 120 Feedforward control section 130 Feedback control section 140 Torque adjustment section 141 First notch filter 142 Second notch filter 150 Subtractor 160 Adder/subtractor 170 Current control section 300 Motor M Motor control device

Claims (5)

A servo amplifier that adjusts the motor gain;
a torque adjusting unit having a notch filter,
The servo amplifier analyzes the feedback signal and determines whether or not there is vibration above a certain reference level,
a torque adjustment unit that, when it is recognized that the feedback signal has two vibration modes having different peak frequencies, and when the difference in peak frequencies between the two vibration modes is within a certain range, causes the notch frequency of the notch filter to correspond to only one of the peak frequencies of the two vibration modes, and attenuates vibrations of the two vibration modes by only adjusting the strength of the notch filter having a notch frequency set to correspond only to that peak frequency . 2. The motor control device according to claim 1, wherein the torque adjustment unit sets the notch frequency to a frequency that is a certain percentage lower than the corresponding peak frequency when the servo amplifier determines that vibration is present. 2. The motor control device according to claim 1, wherein the torque adjusting unit causes the notch frequency to correspond to one of the two vibration modes having a higher peak frequency . The servo amplifier that adjusts the motor gain analyzes the feedback signal and determines whether or not there is vibration above a certain reference level.
When a torque adjustment unit having a notch filter recognizes that the feedback signal has two vibration modes having different peak frequencies, and the difference in peak frequencies between the two vibration modes is within a certain range, the notch frequency of the notch filter is made to correspond to only one of the peak frequencies of the two vibration modes, and vibrations in the two vibration modes are attenuated only by adjusting the strength of the notch filter having a notch frequency set to correspond only to the peak frequency.
A motor control method comprising: 5. The motor control method according to claim 4, wherein the torque adjustment unit sets the notch frequency to a frequency that is a certain percentage lower than the corresponding peak frequency when the servo amplifier determines that vibration is present.

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