Measuring device for measuring the frequency response of a servo system

Abstract

A measuring device for measuring the frequency response of a servo system applies a prescribed vibration whose application time is associated with an excitation frequency to the servo system, and based on the result of the vibration application, determines a pair of a first vibration application signal corresponding to a first range that includes the resonance frequency of the servo system and does not include the anti-resonance frequency of the servo system, and a first response signal corresponding in time to the first vibration application signal. Further, a pair of a second vibration application signal corresponding to a second range that is lower than the first range and includes the anti-resonance frequency, and a second response signal corresponding in time to the second vibration application signal is determined. Then, based on the first vibration application signal and the first response signal, a first frequency response that is the frequency response corresponding to the first range is calculated, and based on the second vibration application signal and the second response signal, a second frequency response that is the frequency response corresponding to the second range is calculated, and the first frequency response and the second frequency response are synthesized.

Description

Technical Field

[0001] The present invention relates to a measuring device for measuring the frequency response of a servo system that servo-controls a load. Background Art

[0002] In order to construct a servo system that servo-controls a load, it is sometimes necessary to measure the frequency response of the servo system. Generally, considering the measured frequency response, gain adjustment of control loops such as the speed loop and position loop of the servo system is performed. For example, in the technique disclosed in Patent Document 1, a response signal obtained by adding an oscillation signal having an oscillation period based on the reference periods of a plurality of different pseudo-random signals to the servo system is used to calculate the frequency response for each oscillation period and synthesize them, thereby obtaining the final frequency response of the servo system. As a result, a frequency response in which the influence of disturbances such as friction is suppressed can be obtained.

[0003] In addition, in order to accurately determine the frequency response, a method of dividing the frequency band and determining the response characteristics for each divided frequency band is known. For example, in the partial fraction iteration method, a method of limiting the number of modes included in each of the divided frequency bands and determining the transfer function within each frequency band is known, and in the mode circle matching method, a method of dividing the frequency band so that only one mode exists within the frequency band and determining the quadratic transfer function for each divided frequency band is known.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2016-10287

[0007] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2006-195543 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] When measuring the frequency response of a servo system connected to a load, generally, vibration including frequency components in the range to be measured is applied to the servo system, and the frequency response is measured based on the response signal and the oscillation signal of the servo system at this time. Here, when vibration at the resonance frequency is applied to the servo system, a peak appears in its response signal, but even when vibration at a frequency other than the resonance frequency is applied, there is a case where the resonance frequency is excited in its response signal. As a result, in the frequency response of the servo system, the gain of the resonance frequency appears larger than the value that should originally be presented, which may prevent the proper use of the frequency response.

[0010] The reasons for the excitation of unwanted resonant frequencies during vibration application in such a servo system are considered to be various. Among them, the influence of the anti-resonant frequency in the servo system connected to the load is considered to be significant. That is, when a vibration application signal containing the resonant frequency is applied to the servo system, in the calculation of the frequency response, there is a case where the response to the input at the anti-resonant frequency is actually measured as the response to the input at the resonant frequency. As a result, it is difficult to accurately measure the frequency response.

[0011] The present invention has been completed in view of such problems, and its object is to provide a technique for accurately measuring the frequency response of a servo system connected to a load.

[0012] Means for Solving the Problem

[0013] In the present invention, in order to solve the above problems, the following structure is adopted: when measuring the frequency response of a servo system, on the basis of dividing the measured frequency range into a range including the resonant frequency of the servo system and a range including the anti-resonant frequency, the frequency responses of each are calculated and the calculation results are synthesized, thereby obtaining the frequency response of the servo system. Thereby, the influence of the excitation of unwanted resonant frequencies caused by vibration application at the anti-resonant frequency can be excluded.

[0014] Specifically, the present invention is a measuring device for measuring the frequency response of a servo system, comprising: a vibration application execution unit that applies a specified vibration whose vibration application time is associated with the excitation frequency to the servo system; a determination unit that, based on the vibration application result of the vibration application execution unit, determines a pair of a first vibration application signal corresponding to a first range that includes the resonant frequency of the servo system and does not include the anti-resonant frequency of the servo system and a first response signal corresponding to the first vibration application signal in time, and further determines a pair of a second vibration application signal corresponding to a second range that is lower than the first range and includes the anti-resonant frequency and a second response signal corresponding to the second vibration application signal in time; a calculation unit that calculates a first frequency response corresponding to the first range, which is the frequency response corresponding to the first range, based on the first vibration application signal and the first response signal, and calculates a second frequency response corresponding to the second range, which is the frequency response corresponding to the second range, based on the second vibration application signal and the second response signal; and a synthesis unit that synthesizes the frequency responses within the frequency range corresponding to the first range and the second range based on the first frequency response and the second frequency response.

[0015] The vibration application time of the specified vibration applied by the vibration application execution unit of the above measuring device is associated with the excitation frequency. This means that the vibration application of the vibration application execution unit is performed in such a way that the vibration application time of applying a vibration at a certain excitation frequency can be determined. As an example of the specified vibration, a so-called Sweptsine signal can be cited.

[0016] Then, based on the results obtained from the vibration application to the servo system by the vibration application execution unit, the determination unit determines pairs of vibration application / response signals corresponding to the first range and pairs of vibration application / response signals corresponding to the second range. The vibration application signal is a signal related to the vibration applied to the servo system, and the response signal is a signal output from the servo system through this vibration application. Here, the first range is a frequency range that includes the resonance frequency of the servo system but does not include its anti-resonance frequency, and the second range is a frequency range that includes its anti-resonance frequency. That is, the frequency ranges of the first range and the second range are set in such a way that the resonance frequency and the anti-resonance frequency are not included simultaneously. As described above, in the specified signal, the vibration application time is associated with the excitation frequency, so the determination unit can determine pairs of vibration application / response signals.

[0017] And when the determination unit determines pairs of vibration application / response signals corresponding to the first range and pairs of vibration application / response signals corresponding to the second range, the calculation unit calculates the frequency response corresponding to the first range and the frequency response corresponding to the second range using each pair. Here, the anti-resonance frequency and the resonance frequency belong to different ranges, and each vibration application / response signal corresponds in time. Therefore, even if the resonance frequency is excited due to the vibration at the anti-resonance frequency in the actual servo system, the influence of this excitation is excluded, and the frequency response within the frequency ranges corresponding to the first range and the second range is calculated. On this basis, the synthesis unit synthesizes the frequency responses corresponding to each frequency range calculated by the calculation unit, thereby generating a frequency response corresponding to the two frequency ranges.

[0018] In this way, in the measurement device disclosed in the present application, it is possible to exclude the influence of the excitation of the unnecessary resonance frequency caused by the vibration application at the anti-resonance frequency during the vibration application to the servo system, and accurately measure the frequency response of the servo system connected to the load.

[0019] Here, in the above-mentioned measurement device, it may also be that the determination unit further determines a pair of a third vibration application signal corresponding to a third range, which is the remaining frequency range other than the first range and the second range in the specified vibration, and a third response signal corresponding in time to the third vibration application signal based on the result of the vibration application by the vibration application execution unit. And it may also be that the calculation unit further calculates a third frequency response, which is the frequency response corresponding to the third range, based on the third vibration application signal and the third response signal, and the synthesis unit synthesizes the frequency responses within all the frequency ranges included in the specified vibration based on the first frequency response, the second frequency response, and the third frequency response. According to this structure, it is possible to accurately measure the frequency response of the servo system within all the frequency ranges included in the specified vibration including the third range.

[0020] Here, two methods related to the application of the specified vibration by the above-described vibration application execution unit are exemplified. In the first method, it is also possible that the vibration application execution unit applies the vibration in the frequency range including the first range and the second range as one of the specified vibrations to the servo system. In this case, it is also possible that the determination unit determines the vibration signal corresponding to the first range in the specified vibration as the first vibration application signal, and determines the response signal in the response signal of the servo system corresponding to the vibration application time of the first vibration application signal as the first response signal, and further, the determination unit determines the vibration signal corresponding to the second range in the specified vibration as the second vibration application signal, and determines the response signal in the response signal of the servo system corresponding to the vibration application time of the second vibration application signal as the second response signal.

[0021] That is, in the first method, the vibration application execution unit applies the specified vibration as one vibration concentratedly to the servo system. Therefore, in the response signal of the servo system that is a direct result of the vibration application as the specified vibration, the excitation of the resonance frequency caused by the vibration application at the anti-resonance frequency (the excitation of the above-mentioned unnecessary resonance frequency) is included. However, the determination unit determines the pair of the first vibration application signal and the first response signal, and the pair of the second vibration application signal and the second response signal by considering the temporal correspondence of the frequency range, the vibration application signal, and the response signal as described above, so that when the frequency response is calculated by the calculation unit, the influence of the excitation of the unnecessary resonance frequency caused by the vibration application at the anti-resonance frequency can be excluded.

[0022] Next, in the second method, it is also possible that the vibration application execution unit applies the vibration in the first range as the first vibration, which is one of the specified vibrations, to the servo system, and applies the vibration in the second range as the second vibration, which is the other vibration of the specified vibration, to the servo system. In this case, it is also possible that the determination unit determines the vibration signal of the first vibration as the first vibration application signal, and determines the response signal of the servo system when the first vibration is applied as the first response signal, and further, the determination unit determines the vibration signal of the second vibration as the second vibration application signal, and determines the response signal of the servo system when the second vibration is applied as the second response signal.

[0023] That is, in the second method, the vibration application unit applies the specified vibration, which is divided into the first vibration and the second vibration, to the servo system. Therefore, the pair of vibration application / response signals associated with the first vibration and the pair of vibration application / response signals associated with the second vibration are temporally separated. Thus, the determination unit determines the pair of the first vibration application signal and the first response signal, and the pair of the second vibration application signal and the second response signal as described above, so that in the subsequent process of the calculation unit calculating the frequency responses corresponding to the first range and the second range respectively, the influence of the excitation of the unnecessary resonance frequency caused by the vibration application at the anti-resonance frequency can be excluded.

[0024] In addition, in the above measurement device, it may be that the servo system is configured to perform servo control on a motor connected to a specified load. In this case, as an example, the first range and the second range may be set based on the ratio of the inertia torque of the specified load to the inertia torque of the motor. That is, the anti-resonance frequency can be physically estimated based on the ratio of the inertia torque of the specified load to the inertia torque of the motor, so the first range and the second range can be set based on the estimation result.

[0025] Here, in the above measurement device, when the resonance frequency of the servo system is known, sometimes filtering processing based on a notch filter is performed for oscillation suppression based on the high gain of the servo system and the like. The notch filter can be defined by the center frequency (i.e., the frequency near the resonance frequency) that is the center of this filtering process and the Q value that represents the expansion of the frequency range that brings the effect of the filtering process. In such a case, the following methods can be exemplified for setting the first range and the second range. First, the first range and the second range may be set based on the center frequency and the Q value of the notch filter. As another method, the first range and the second range may be set based on the center frequency of the notch filter and the gain in the frequency response. As yet another method, it may be that the first range and the second range are set based on the center frequency of the notch filter, and the widths of the first range and the second range are each set to be narrower than a specified upper width. These methods can be appropriately selected considering the mechanical characteristics and control characteristics of the servo system, and in addition, the first range and the second range can be set in other ways than these.

[0026] In addition, regarding the setting of the first range and the second range, regardless of whether a notch filter is used, the widths of the first range and the second range may be set to the same width. As another method, the width of the second range may be set to be wider than the width of the first range.

[0027] In addition, in the above-described measurement device, it is also possible that the synthesizing unit performs a prescribed averaging process on the synthesized frequency response. That is, the synthesizing unit performs a prescribed averaging process as post-processing after synthesis. As described above, the first frequency response and the second frequency response are calculated on the basis of dividing the frequency range into a first range and a second range. Therefore, at the time of synthesis, discontinuity of the frequency response sometimes occurs at the boundary of the ranges. Therefore, by performing a prescribed averaging process, such discontinuity can be eliminated. As the prescribed averaging process, a moving average process can be exemplified.

[0028] Advantages of the Invention

[0029] A technique for accurately measuring the frequency response of a servo system connected to a load can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a diagram showing a schematic configuration of a system including a servo system whose frequency response is measured by a measurement device.

[0031] Figure 2 is a diagram for explaining a servo system.

[0032] Figure 3 is a first diagram showing excitation of a resonance frequency caused by vibration application at an anti-resonance frequency that occurs when measuring a frequency response.

[0033] Figure 4 is a second diagram showing excitation of a resonance frequency caused by vibration application at an anti-resonance frequency that occurs when measuring a frequency response.

[0034] Figure 5 is a diagram showing functional units related to the measurement device.

[0035] Figure 6 is a diagram for explaining setting of a frequency range in the frequency response measurement process.

[0036] Figure 7 is a diagram for explaining calculation and synthesis of a frequency response in the frequency response measurement process.

[0037] Figure 8 is a first flowchart showing a process flow of frequency response measurement performed by the measurement device.

[0038] Figure 9 is a diagram showing a measurement result of a frequency response in the measurement device.

[0039] Figure 10 is a second flowchart showing a process flow of frequency response measurement performed by the measurement device.

[0040] ​​​​​​​​​​Figure 11 is a diagram for explaining the setting of the frequency range in the measurement process of the frequency response.

[0041] Figure 12 is a diagram for explaining the averaging process in the measurement process of the frequency response. DETAILED DESCRIPTION OF THE INVENTION

[0042] <APPLICATION EXAMPLE>

[0043] Hereinafter, an application example of the measurement device of the present application will be described based on the drawings. Figure 1 is a diagram showing a schematic configuration of a control system of a servo system that measures the frequency response by the measurement device 10. The control system includes a network 1, a motor 2, a load device 3, a servo drive 4, and a programmable logic controller (PLC) 5. This control system is a system for driving and controlling the load device 3 together with the motor 2. Moreover, the motor 2 and the load device 3 become a control object 6 controlled by this control system. Here, as the load device 3, various mechanical devices (for example, an arm of an industrial robot, a transfer device) can be exemplified, and the motor 2 is assembled in the load device 3 as an actuator for driving the load device 3. For example, the motor 2 is an AC servo motor. In addition, an encoder (not shown) is attached to the motor 2, and a parameter signal related to the operation of the motor 2 is feedback-transmitted to the servo drive 4 through this encoder. The feedback-transmitted parameter signal (hereinafter, referred to as a feedback signal) includes, for example, position information about the rotational position (angle) of the rotation axis of the motor 2, information about the rotational speed of the rotation axis, and the like.

[0044] The servo drive 4 receives an operation instruction signal related to the operation of the motor 2 from the PLC 5 via the network 1, and also receives a feedback signal output from the encoder connected to the motor 2. The servo drive 4 calculates servo control related to the drive of the motor 2, that is, an instruction value related to the operation of the motor 2, based on the operation instruction signal from the PLC 5 and the feedback signal from the encoder, and supplies a drive current to the motor 2 so that the operation of the motor 2 follows the instruction value. In addition, the supplied current uses AC power delivered from an AC power supply 7 to the servo drive 4. In the present embodiment, the servo drive 4 is of a type that accepts three-phase alternating current, but it may also be of a type that accepts single-phase alternating current. In addition, in the servo drive 4, a servo system for performing feedback control using a position controller 41, a speed controller 42, and a current controller 43 (see Figure 2 ) is formed.

[0045] Here, as Figure 2 ​​As shown, the servo drive 4 includes a position controller 41, a speed controller 42, and a current controller 43. Therefore, based on Figure 2 , the servo system in the servo drive 4 will be described. The position controller 41 performs, for example, proportional control (P control). Specifically, a speed command is calculated by multiplying the position deviation, which is the deviation between the position command notified from the PLC 5 and the detected position, by the position proportional gain Kpp. In addition, the position controller 41 has the position proportional gain Kpp as a control parameter in advance.

[0046] Next, the speed controller 42 performs, for example, proportional-integral control (PI control). Specifically, the integral of the speed deviation, which is the deviation between the speed command calculated by the position controller 41 and the detected speed, is multiplied by the speed integral gain Kvi, and the sum of the calculation result and the speed deviation is multiplied by the speed proportional gain Kvp, thereby calculating a torque command. In addition, the speed controller 42 has the speed integral gain Kvi and the speed proportional gain Kvp as control parameters in advance. In addition, the speed controller 42 may perform P control instead of PI control. In this case, the speed controller 42 has the speed proportional gain Kvp as a control parameter in advance. Next, the current controller 43 outputs a current command based on the torque command calculated by the speed controller 42, thereby performing drive control on the motor 2. The current controller 43 includes a filter (first-order low-pass filter) related to the torque command and one or more notch filters, and has a cut-off frequency, a center frequency, etc. related to the performance of these filters as control parameters.

[0047] Moreover, the control structure of the servo drive 4 includes a speed feedback system with the speed controller 42, the current controller 43, and the controlled object 6 as forward elements, and further includes a position feedback system with the speed feedback system and the position controller 41 as forward elements. With the control structure configured in this way, the servo drive 4 can perform servo control on the motor 2 to make it follow the position command supplied from the PLC 5.

[0048] Here, returning Figure 1 , a measuring device 10 is electrically connected to the servo drive 4 when it is powered on. This electrical connection can be a wired connection or a wireless connection. The measuring device 10 is equipped with software (program) for measuring the frequency response of the servo system in order to set and adjust the control parameters of the servo drive 4. Specifically, the measuring device 10 is a computer having an arithmetic device, a memory, etc., and the measuring software that can be executed is installed here. Moreover, the measuring device 10 uses this measuring software to measure the frequency response of the servo system.

[0049] Here, based on Figure 3 and Figure 4 the problems in measuring the frequency response of the servo system will be described. Figure 3Shows the change in the detected speed when a speed vibration is applied to the servo system. Figure 3 In Figure 3 , S1 represents the speed vibration, and S2 represents the detected speed. The speed vibration becomes a vibration signal of a so-called sine sweep, and the vibration application time is associated with the excitation frequency. In addition, the resonance frequency of the servo system is 617 Hz, and its vibration application time is 0.39 s. Furthermore, the anti-resonance frequency of this servo system is 200 Hz, and its vibration application time is 0.31 s. In addition, for this servo system, a notch filter is set in the current controller 43, and its center frequency is set to the resonance frequency.

[0050] Observation Figure 3 It can be seen that at the timing when the vibration of the anti-resonance frequency is applied, a vibration of the resonance frequency is excited in the detected speed. On the other hand, at the timing when the vibration of the resonance frequency is applied, due to the effect of the notch filter, no large vibration is found in the detected speed. And, taking S1 as the vibration application signal and S2 as the response signal, the frequency response calculated by FFT (Fast Fourier Transform) processing is Figure 4 shown as a Bode plot in Figure 4 . Figure 4 The upper part of Figure 4 represents the gain plot, and the lower part represents the phase plot. Observing the gain plot, it can be seen that a peak with a large gain is found near the resonance frequency (the area surrounded by the dotted line). This reflects the excitation of the resonance frequency due to the vibration at the anti-resonance frequency, rather than the resonance corresponding to the vibration at the resonance frequency. However, if one observes Figure 4 the Bode plot of Figure 4 , it is only misperceived that resonance occurs, and doubts are raised about the effect of the set notch filter.

[0051] If the frequency response is calculated by the conventional FFT processing in this way, it is affected by the excitation of the unwanted resonance frequency caused by the vibration at the anti-resonance frequency of the servo system, and it is difficult to accurately measure the frequency response of this servo system. Therefore, it may hinder the setting of appropriate control parameters for the servo system.

[0052] Therefore, in view of the above problems, the measuring device 10 disclosed in the present application is configured as Figure 5 shown. Figure 5 is a functional block diagram showing the visualization of various functions executed by the software executed in the measuring device 10. The measuring device 10 has a vibration application execution unit 11, a determination unit 12, a calculation unit 13, and a synthesis unit 14. Based on Figure 6 and Figure 7 the operations of each functional unit will be described. Figure 6 represents the time response signal S2 of the servo system when a sine sweep vibration application signal S1 in the entire frequency range to be measured is applied to the servo system. In addition, Figure 7 is a diagram for explaining the operations of the calculation unit 13 and the synthesis unit 14.

[0053] The vibration application execution unit 11 is configured to apply a prescribed vibration to the servo system, where the vibration application time is associated with the excitation frequency. In Figure 6 the example shown in FIG. Figure 6 , the vibration application execution unit 11 applies a vibration application signal S1, which is a sine sweep over the entire frequency range, to the servo system. Further, as a result of the vibration application by the vibration application execution unit 11, a time response signal S2 of the servo system is obtained. The determination unit 12 is configured to determine pairs of vibration application signals and their response signals corresponding to a plurality of frequency ranges based on this result. Here, the setting of the plurality of frequency ranges will be described. First, a frequency range (corresponding to the first range of the present application) including the resonance frequency (617 Hz) of the servo system is set as interval 2. The lower boundary value ω1 of this interval 2 is 435 Hz, the upper boundary value ω2 is 876 Hz, and the anti-resonance frequency (200 Hz) of the servo system is not included in interval 2. Also, a frequency range lower than interval 2 (corresponding to the second range of the present application) is set as interval 1. The anti-resonance frequency (200 Hz) of the servo system is included in this interval 1. Further, a frequency range higher than interval 2 (corresponding to the third range of the present application) is set as interval 3. In this interval 3, the anti-resonance frequency (200 Hz) and the resonance frequency (617 Hz) of the servo system are not included. Additionally, details of the setting of each frequency range will be described later. Figure 6 Next, the determination unit 12 determines pairs of vibration application signals and their corresponding response signals in time for each interval. For example, regarding interval 1, since its frequency range is less than 435 Hz, the pair of the vibration application signal from the start of vibration application until the timing when the vibration application frequency rises to 435 Hz in the sine sweep vibration and the time response signal from the start of this vibration application until this timing is determined as the vibration application / response signal pair corresponding to interval 1 (corresponding to the second vibration application signal and the second response signal pair of the present application). Similarly, regarding interval 2, the pair of the vibration application signal from 435 Hz to 876 Hz in the sine sweep vibration and the time response signal corresponding to this vibration application signal in time is determined as the vibration application / response signal pair corresponding to interval 2 (corresponding to the first vibration application signal and the first response signal pair of the present application). Furthermore, regarding interval 3, the pair of the vibration application signal from when the vibration application frequency is 876 Hz until the end of vibration application in the sine sweep vibration and the time response signal corresponding to this vibration application signal in time is determined as the vibration application / response signal pair corresponding to interval 3 (corresponding to the third vibration application signal and the third response signal pair of the present application).

[0054]

[0055] ​Next, the calculation unit 13 will be described. The calculation unit 13 is configured to calculate the frequency response corresponding to each interval using FFT processing based on the vibration application signal and the response signal in the pair corresponding to each interval. Here, during the FFT processing, on the basis of covering the data of the response signal in the intervals other than the interval to be calculated with "0", the vibration application signal S1 is used as the input, and the covered response signal is used as the output to perform the FFT processing. On this basis, the data corresponding to the frequency range of the interval to be calculated is extracted from the FFT processing result, and it is calculated as the frequency response of the interval to be calculated. For example, when calculating the frequency response corresponding to interval 1, the data of the response signal S2 corresponding to interval 2 and interval 3 is covered with "0", the vibration application signal S1 is used as the input, and the covered response signal S2 is used as the output to perform the FFT processing. Furthermore, according to this FFT processing result, the frequency response corresponding to the frequency range of interval 1, that is, the frequency range less than 435 Hz, is calculated as the frequency response corresponding to interval 1. The calculation of the frequency response corresponding to interval 2 and interval 3 is the same.

[0056] Next, the synthesis unit 14 will be described. The synthesis unit 14 is configured to generate the frequency response of the servo system by synthesizing and summarizing the frequency responses corresponding to each interval calculated by the calculation unit 13. Based on Figure 7 The specific method of synthesizing the frequency response will be described. In Figure 7 (a) shows the vibration application signal and the response signal corresponding to interval 1 (upper section), and the frequency response corresponding to interval 1 calculated therefrom. And, in Figure 7 (b) shows the vibration application signal and the response signal corresponding to interval 2 (upper section), the frequency response corresponding to interval 2 calculated therefrom, and Figure 7 the state after synthesizing the frequency response corresponding to interval 1 shown in the lower section of (a). In the calculation process of the calculation unit 13, the frequency responses corresponding to each interval are calculated as described above. Therefore, the synthesis unit 14 connects the frequency responses corresponding to each interval in a continuous manner in terms of the frequency range. And, in Figure 7 (c) shows the vibration application signal and the response signal corresponding to interval 3 (upper section), the frequency response corresponding to interval 3 calculated therefrom, and Figure 7 the state after synthesizing the frequency responses corresponding to interval 1 and interval 2 shown in the lower section of (b). In addition, the synthesis unit 14 can either perform synthesis each time the frequency responses corresponding to each interval are calculated by the calculation unit 13, or perform summary synthesis after calculating the frequency responses corresponding to all intervals.

[0057] Based on Figure 8The process of measuring the frequency response of the servo system for the measurement device 10 configured as such will be described. First, in S101, the vibration application unit 11 applies a specified vibration to the servo system, and as a result, a response signal of the servo system is obtained. Next, in S102, the frequency range is set. Regarding the setting of the frequency range, as described above, at least the frequency range that includes the resonance frequency of the servo system and does not include its anti-resonance frequency (the frequency range of interval 2 shown in Figure 6 ) and the frequency range that includes the anti-resonance frequency of the servo system (the frequency range of interval 1 shown in Figure 6 ) are set. Further, other frequency ranges can also be set as in the frequency range of interval 3 shown in Figure 6 .

[0058] Next, in S103, the determination unit 12 determines the vibration application signal and the response signal corresponding to each interval of the frequency range set in S102 based on the vibration application result of the servo system obtained in S101. After that, in S104, the calculation unit 13 calculates the frequency response corresponding to the intervals of each frequency range, and in S105, their synthesis process is performed (refer to Figure 7 above).

[0059] The measurement result (gain plot) of the measurement process shown in Figure 8 is compared with the measurement result (gain plot) of the prior art and shown in Figure 9 . The measurement result of the prior art (left figure) is the same as the gain plot shown in Figure 4 . In both results, the vicinity of the resonance frequency of the servo system is shown surrounded by a dotted line. As shown in Figure 9 , it can be seen that in the measurement result of the embodiment of the present application, the peak value of the gain near the resonance frequency is suppressed. This means that the influence of the excitation of the unnecessary resonance frequency caused by the vibration at the anti-resonance frequency can be excluded, and the frequency response of the servo system can be accurately measured. Based on this measurement result, the user can accurately judge the effect of the notch filter set in the servo system and can achieve appropriate parameter adjustment.

[0060] <Measurement process variation example>

[0061] Based on Figure 10 the process of the measurement process of the variation example will be described. In this variation example, since the application of the specified vibration by the vibration application unit 11 is performed separately for each frequency range, in S201, the frequency range is set first. In addition, the frequency range is the same as that in Figure 6In the same manner as shown. Then, in S202, vibration application corresponding to the interval of the set frequency range is performed by the vibration application execution unit 11. Specifically, vibration applications corresponding to interval 1 (vibration application that changes the vibration frequency to 435 Hz, vibration application of vibration equivalent to the second vibration of the present application), interval 2 (vibration application that changes the vibration frequency from 435 Hz to 876 Hz, vibration application of vibration equivalent to the first vibration of the present application), and interval 3 (vibration application that changes the vibration frequency from 876 Hz to the upper limit frequency) are respectively performed. Then, as a result of these vibration applications, response signals of the servo system corresponding to each interval are obtained (processing of S203).

[0062] Then, when the processing of S203 ends, in S103, the determination unit 12 determines the pairs of vibration application signals and response signals corresponding to each interval. In the case of this modification example, the determination unit 12 pairs the vibration application signals of the vibration applications performed corresponding to each interval in S202 and the response signals corresponding to each interval obtained in S203 as a result thereof. After that, in S104, the calculation unit 13 calculates the frequency response corresponding to the interval of each frequency range. In this calculation, the calculation is limited to the frequency response of the frequency range of the interval as the object. Therefore, for example, when calculating the frequency response corresponding to interval 1 shown, the calculation is limited to the frequency response in the range of 0 to 435 Hz. Thus, even if the response signal corresponding to interval 1 includes the excitation of the resonance frequency caused by the vibration at the anti-resonance frequency, the response frequency excluding the influence of this excitation is calculated. Then, in S105, a synthesis process of the frequency responses corresponding to the intervals of each frequency range calculated in S104 is performed. Figure 6 Through the measurement process of such a modification example, it is also possible to accurately measure the frequency response of the servo system by excluding the influence of the excitation of the unnecessary resonance frequency caused by the vibration at the anti-resonance frequency. Therefore, the user can accurately judge the effect of the notch filter set in the servo system and can achieve appropriate parameter adjustment.

[0063]

[0064] <Setting of Frequency Range (Interval)>

[0065] Here, regarding the measurement process disclosed in the present application, in order to exclude the influence of the excitation of the unnecessary resonance frequency caused by the vibration at the anti-resonance frequency, in the setting of the frequency range, it is necessary to distinguish the frequency range including the resonance frequency of the servo system (corresponding to the first range of the present application) and the frequency range including the anti-resonance frequency of the servo system (corresponding to the second range of the present application) to set the frequency range (interval) for the measurement process. Therefore, the setting method of the frequency range for the measurement process is exemplified below.

[0066] (1) First Method

[0067] When the resonance frequency ωr of the servo system is known, the anti-resonance frequency ωa of the servo system can be estimated according to the following Equation 1 based on the ratio of the inertia moment of the load device 3 to the inertia moment of the motor 2 (hereinafter, simply referred to as "inertia ratio").

[0068]

[0069] Here, JL is the inertia moment of the load device 3, JM is the inertia moment of the motor 2, and R is the inertia ratio.

[0070] Based on the thus estimated anti-resonance frequency ωa and resonance frequency ωr, a frequency range including the anti-resonance frequency ωa and a frequency range including the resonance frequency ωr can be set.

[0071] (2) Second method

[0072] In the servo system, when the notch filter is set for the current controller 43 as described above, in order to appropriately judge the effect of the notch filter, it is desirable to accurately measure the frequency response. Therefore, from this viewpoint, the frequency range for the measurement process can also be set based on the parameters forming the function of the notch filter, namely, the center frequency and the Q value. Generally, the center frequency of the notch filter is set to the resonance frequency of the servo system, and the Q value is represented by the following Equation 2.

[0073]

[0074] Here, ωH is the frequency at which the vibration energy becomes half value on the high-frequency side of the resonance peak, and ωL is the frequency at which the vibration energy becomes half value on the low-frequency side of the resonance peak.

[0075] Moreover, the frequency (boundary frequency) fL that forms the boundary of the frequency range including the resonance frequency and the anti-resonance frequency can be represented by the following Equation 3.

[0076]

[0077] As an example of the Q value, Q = 5 can be adopted, but other values can also be adopted.

[0078] Based on the thus calculated boundary frequency fL, a frequency range including the anti-resonance frequency ωa and a frequency range including the resonance frequency ωr can be set.

[0079] (3) Third method

[0080] In the third method, when a notch filter is set in the servo system, based on the center frequency of the notch filter and the gain in the frequency response, the boundary frequency that forms the boundary of the adjacent frequency ranges is set. Based onFigure 11 Describe the setting method. Figure 11 The shown gain line graph is the same as Figure 4 the shown gain line graph. In this gain line graph, with the center frequency of the notch filter (i.e., the resonance frequency ωr of the servo system) as the center, the frequency on the low-frequency side where the gain is lower than the specified gain threshold (e.g., -10 dB) is set as the low-frequency side boundary frequency ω3. On this basis, the high-frequency side boundary frequency ω4 can be calculated according to the following formula 4.

[0081]

[0082] According to the boundary frequencies ω3 and ω4 calculated in this way, the frequency range for the measurement process can be set. Specifically, based on the low-frequency side boundary frequency ω3, the low-frequency side frequency range including the anti-resonance frequency ωa and the frequency range including the resonance frequency ωr can be divided. Furthermore, based on the high-frequency side boundary frequency ω4, the high-frequency side frequency range adjacent to the frequency range including the resonance frequency ωr on the high-frequency side can be set. The anti-resonance frequency ωa and the resonance frequency ωr are not included in this high-frequency side frequency.

[0083] (4) The fourth method

[0084] In the fourth method, when a notch filter is set in the servo system, based on the center frequency of the notch filter and the upper limit value of the width of the preset frequency band (e.g., 512 Hz), the boundary frequency that becomes the boundary of the adjacent frequency ranges is set. This upper limit value considers the situation that if the width of the frequency band becomes larger, the noise level in the frequency response becomes larger. For example, when the center frequency is 617 Hz, setting the frequency band based on the boundary frequencies shown in case 2 can suppress the noise level in the frequency response compared to case 1 below.

[0085] (Case 1)

[0086] Boundary frequency: 435 Hz, 876 Hz

[0087] (Case 2)

[0088] Boundary frequency: 435 Hz, 876 Hz, 1388 Hz, 1900 Hz, 2412 Hz, 2924 Hz, 3436 Hz

[0089] (5) The fifth method

[0090] When the resonance frequency ωr of the servo system is not known, the widths of all the frequency ranges can also be set to be the same. In this case, it is preferable to appropriately set the widths of the respective frequency ranges according to the mechanical structure of the load device 3 connected to the motor 2 in the servo system and the like, such that the resonance frequency and the anti-resonance frequency of the servo system are included in different frequency ranges.

[0091] (6) Sixth mode

[0092] When the resonance frequency ωr of the servo system is not known, regarding the calculation of the frequency response performed by the calculation unit 13, the width of the frequency range on the low-frequency side is set wider than the width of the frequency range on the high-frequency side so that the number of data in the frequency range on the low-frequency side is more than the number of data in the frequency range on the high-frequency side. By setting the frequency range in this way, the noise level in the frequency response corresponding to the frequency range on the low-frequency band side can be suppressed to a lower level.

[0093] <Averaging process>

[0094] In the measurement process disclosed in the present application, the calculation unit 13 calculates the frequency response corresponding to a part of the frequency ranges in all the frequency ranges. Therefore, due to the boundary values of this part of the frequency ranges, the frequency response corresponding to a part of the frequency ranges calculated and the frequency response corresponding to other adjacent frequency ranges become discontinuous, which may prevent the accurate measurement of the frequency response of the servo system. Therefore, in order to eliminate such discontinuity in the frequency response, the synthesis unit 14 is configured to perform a moving average process on the synthesis result after synthesizing the frequency responses corresponding to each frequency range.

[0095] Here, the number of moving average points in the moving average process can also be set to increase as it advances to the high-frequency side. Since the noise level on the high-frequency side is higher than the noise level on the low-frequency side, by performing such a moving average process, the continuity of the frequency response on the high-frequency side can be maintained. Here, Figure 12 shows side by side the frequency response (the result measured by the measurement process disclosed in the present application) in the case where the above-mentioned moving average process is not implemented and the frequency response in the case where the result measured by the measurement process disclosed in the present application is further subjected to the above-mentioned moving average process. In this case, the number of moving average points on the high-frequency side is about 3 times that on the low-frequency side. Observing Figure 12 it can be seen that by implementing the moving average process, the continuity of the measured frequency response of the servo system is good.

[0096] <Supplementary Note 1>

[0097] A measuring device (10) that measures the frequency response of a servo system, the measuring device (10) includes:

[0098] A vibration application execution unit (11) that applies a specified vibration whose vibration application time is associated with an excitation frequency to the servo system;

[0099] A determination unit (12) that determines, based on the vibration application result of the vibration application execution unit (11), a pair of a first vibration application signal corresponding to a first range that is a frequency range including the resonance frequency of the servo system and excluding the anti-resonance frequency of the servo system, and a first response signal corresponding to the first vibration application signal in terms of time, and further determines a pair of a second vibration application signal corresponding to a second range that is a frequency range lower than the first range and including the anti-resonance frequency, and a second response signal corresponding to the second vibration application signal in terms of time;

[0100] A calculation unit (13) that calculates, based on the first vibration application signal and the first response signal, a frequency response corresponding to the first range, i.e., a first frequency response, and calculates, based on the second vibration application signal and the second response signal, a frequency response corresponding to the second range, i.e., a second frequency response; and

[0101] A synthesis unit (14) that synthesizes, based on the first frequency response and the second frequency response, a frequency response within a frequency range corresponding to the first range and the second range.

[0102] Reference Numeral Explanation

[0103] 1: Network; 2: Motor; 3: Load device; 4: Servo driver; 5: PLC; 11: Vibration application execution unit; 12: Determination unit; 13: Calculation unit; 14: Synthesis unit.

Claims

1. A measuring device for measuring the frequency response of a servo system, the measuring device comprising: A vibration application execution unit that applies a specified vibration to the servo system, where the vibration application time is associated with an excitation frequency; A determination unit that, based on the vibration application result of the vibration application execution unit, determines a pair of a first vibration signal corresponding to a first range, which is a frequency range that includes the resonance frequency of the servo system and does not include the anti-resonance frequency of the servo system, and a first response signal corresponding to the first vibration signal in time. Further, the determination unit determines a pair of a second vibration signal corresponding to a second range, which is a frequency range lower than the first range and includes the anti-resonance frequency, and a second response signal corresponding to the second vibration signal in time; A calculation unit that calculates a first frequency response corresponding to the first range based on the first vibration signal and the first response signal, and calculates a second frequency response corresponding to the second range based on the second vibration signal and the second response signal; and A synthesis unit that synthesizes the frequency response within the frequency range corresponding to the first range and the second range based on the first frequency response and the second frequency response.

2. The measuring device according to claim 1, wherein The determination unit further determines a pair of a third vibration signal corresponding to a third range, which is the remaining frequency range other than the first range and the second range in the specified vibration, and a third response signal corresponding to the third vibration signal in time based on the vibration application result of the vibration application execution unit, The calculation unit further calculates a third frequency response corresponding to the third range based on the third vibration signal and the third response signal, The synthesis unit synthesizes the frequency response within all frequency ranges included in the specified vibration based on the first frequency response, the second frequency response, and the third frequency response.

3. The measuring device according to claim 1, wherein The vibration application execution unit applies a vibration within a frequency range including the first range and the second range as one specified vibration to the servo system, The determination unit determines the vibration signal corresponding to the first range in the specified vibration as the first vibration signal, and determines the response signal corresponding to the vibration application time of the first vibration signal in the response signal of the servo system as the first response signal, And the determination unit determines the vibration signal corresponding to the second range in the specified vibration as the second vibration signal, and determines the response signal corresponding to the vibration application time of the second vibration signal in the response signal of the servo system as the second response signal.

4. The measuring device according to claim 1, wherein The vibration application execution unit applies the vibration of the first range as a first vibration, which is one of the specified vibrations, to the servo system, and applies the vibration of the second range as a second vibration, which is the other vibration of the specified vibration, to the servo system. The determination unit determines the vibration signal of the first vibration as the first excitation signal, and determines the response signal of the servo system when the first vibration is applied as the first response signal. Further, the determination unit determines the vibration signal of the second vibration as the second excitation signal, and determines the response signal of the servo system when the second vibration is applied as the second response signal.

5. The measurement device according to claim 1, wherein the servo system is configured to perform servo control on a motor connected to a predetermined load, the first range and the second range are set based on the ratio of the inertia torque of the predetermined load to the inertia torque of the motor.

6. The measurement device according to claim 1, wherein the widths of the first range and the second range are set to be the same width.

7. The measurement device according to claim 1, wherein the width of the second range is set to be wider than the width of the first range.

8. The measurement device according to any one of claims 1 to 7, wherein the synthesis unit performs a predetermined averaging process on the synthesized frequency response.

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