Measurement support device

Abstract

A measurement support device is provided that can suppress positional deviation of a load in frequency response analysis that is performed by inputting a speed command to a servo system. [Solution] This measurement support device is a measurement support device that inputs a measurement signal used for frequency response analysis of a servo system to the servo system, and includes: a generation unit that generates a first signal determined to eliminate the discrepancy between a first position of a load of the servo system at the start of excitation of the servo system by a speed command signal that changes over time to include a large number of frequency components, and a second position of the load at the end of excitation of the speed command signal; a synthesis unit that generates a synthesized signal by superimposing the first signal on the speed command signal; and an excitation execution unit that inputs the synthesized signal to the servo system.

Description

[Technical Field]

[0001] The present invention relates to a measurement support device. [Background technology]

[0002] Techniques for analyzing the frequency characteristics of servo systems have been proposed. For example, Patent Document 1 proposes a technique for inputting a time-varying position command containing multiple frequency components into a motor control device and analyzing the frequency characteristics (see Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-030557 [Patent Document 2] Japanese Patent Application Publication No. 2020-030558 Summary of the Invention [Problem to be solved by the invention]

[0004] Since position control using a position command is equivalent to speed control using a low-pass filter, analyzing frequency characteristics using a position command results in lower analysis accuracy in the high frequency range than analyzing frequency characteristics using a speed command. Furthermore, when frequency response analysis is performed using a speed command, the load position at the start of the frequency response analysis will differ from the load position at the end. If such positional deviations are accumulated, there is a risk that the load will move outside the operating range, for example.

[0005] An object of one aspect of the disclosed technique is to provide a measurement support device that can suppress positional deviation of a load in a frequency response analysis that is performed by inputting a speed command to a servo system. [Means for solving the problem]

[0006] One aspect of the disclosed technology is exemplified by the following measurement support device: The measurement support device inputs a measurement signal used for frequency response analysis of a servo system to the servo system, and includes: a generation unit that generates a first signal determined so as to eliminate a discrepancy between a first position of a load of the servo system at the start of input of a speed command signal that changes over time to include a large number of frequency components to the servo system, and a second position of the load at the end of input of the speed command signal, a synthesis unit that generates a synthesis signal by superimposing the first signal on the speed command signal, and an execution unit that inputs the synthesis signal to the servo system.

[0007] When a time-varying speed command signal containing multiple frequency components is input to a servo system, a deviation may occur between the first position and the second position. In this measurement support device, the first signal determined to eliminate such a deviation is superimposed on the speed command signal to generate a composite signal. Then, the measurement support device inputs the composite signal to the servo system. Since the composite signal is a signal on which the first signal is superimposed, the measurement support device can suppress position deviation of the load in frequency response analysis performed by inputting a speed command to the servo system. Here, the speed command signal may be sweptsine.

[0008] In addition, the first signal is expressed as follows: a is an arbitrary odd number, V Lmax is the amplitude of the speed command signal, t is time, and the time for inputting the speed command to the servo system is T inv When the difference between the first position and the second position is L, the first signal may be expressed by equation (6) that satisfies the following equation (7).

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[0009] The measurement support device may further include the following feature: an analysis unit that performs the frequency response analysis using as input the velocity signal fed back from the servo system to which the composite signal has been input, and the composite signal, to calculate the frequency response characteristics of the servo system. The frequency response analysis may be FFT analysis, or the FFT analysis may include a divided FFT analysis. According to the measurement support device, it is possible to perform the frequency response analysis of the servo system while suppressing positional deviation of the load. [Effects of the Invention]

[0010] According to the disclosed technology, it is possible to suppress positional deviation of a load in frequency response analysis using a speed command. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a system including a servo system whose frequency response is measured by a measuring device. [Figure 2] FIG. 2 is a diagram for explaining the servo system. [Figure 3] FIG. 3 is a diagram illustrating a Sweptsine vibration signal. [Figure 4] FIG. 4 is a functional block diagram that visualizes various functions executed by software executed in the measurement device. [Figure 5] FIG. 5 is a diagram illustrating an example of a low-frequency sine wave generated by the generating unit. [Figure 6] FIG. 6 is a diagram illustrating an example of a composite wave generated by the synthesis unit. [Figure 7] FIG. 7 is a diagram comparing a case where a synthesized wave generated by a synthesizer is input to a servo system with a case where a sweptsine vibration signal is input to a servo system. [Figure 8] FIG. 8 is a diagram showing an example of a response signal acquired by the analysis unit from the servo system to which the composite wave is input. [Figure 9]FIG. 9 illustrates the frequency response characteristics when FFT is performed as the frequency response analysis by the analysis unit. [Figure 10] FIG. 10 illustrates an example of a frequency response characteristic when a divided FFT is performed as a frequency response analysis by the analysis unit. [Figure 11] FIG. 11 is a diagram illustrating an example of a processing flow of the measurement device according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] <Application example> An application example of the present invention will be described. An example of the application of the present invention is a measuring device 10 shown in FIG. 1. The measuring device 10 is used for frequency response analysis of a servo system shown in FIG. 2. When a speed command is used in frequency response analysis, the position of the load device 3 may shift between the start and end of input of the speed command. If such a shift is accumulated, there is a risk that the load device 3 will move outside its operating range.

[0013] Therefore, in the measuring device 10, a first signal is generated that is determined so as to eliminate the positional deviation of the load device 3 in response to a speed command input to the servo system. Then, the measuring device 10 generates a composite signal by superimposing the first signal on the speed command, and uses the composite signal as a servo signal. By inputting such a composite signal to the servo system, it is possible to suppress positional deviation of the load device 3 in frequency response analysis using a speed command.

[0014] <Embodiment> The embodiments will be further described below with reference to the drawings. FIG. 1 is a diagram showing the schematic configuration of a system including a servo system whose frequency response is measured by a measuring device 10. The control system includes a network 1, a motor 2, a load device 3, a servo driver 4, and a programmable logic controller (PLC) 5. The control system is a system for driving and controlling the motor 2 and the load device 3. The motor 2 and the load device 3 are controlled as a control target 6 controlled by the control system. Here, the load device 3 can be exemplified by various mechanical devices (e.g., an arm of an industrial robot or a conveying device), and the motor 2 is incorporated within the load device 3 as an actuator that drives the load device 3. For example, the motor 2 is an AC servo motor. An encoder (not shown) is attached to the motor 2, and the encoder transmits a parameter signal related to the operation of the motor 2 to the servo driver 4 as feedback. The parameter signal (hereinafter referred to as a feedback signal) transmitted as feedback includes, for example, position information regarding the rotational position (angle) of the rotational shaft of the motor 2, information about the rotational speed of the rotational shaft, etc.

[0015] The servo driver 4 receives an operation command signal related to the operation (motion) of the motor 2 from the PLC 5 via the network 1, and also receives a feedback signal output from an encoder connected to the motor 2. Based on the operation command signal from the PLC 5 and the feedback signal from the encoder, the servo driver 4 performs servo control related to the drive of the motor 2, i.e., calculates a command value related to the operation of the motor 2, and supplies a drive current to the motor 2 so that the operation of the motor 2 follows the command value. This supply current is AC power sent to the servo driver 4 from an AC power supply 7. In this embodiment, the servo driver 4 is of a type that receives three-phase AC, but it may also be of a type that receives single-phase AC. In the servo driver 4, a servo system (see FIG. 2) that performs feedback control using the position controller 41, speed controller 42, and current controller 43 of the servo driver 4 is formed.

[0016] FIG. 2 is a diagram for explaining a servo system. As shown in FIG. 2, the servo driver 4 includes a position controller 41, a speed controller 42, and a current controller 43. The servo system in the servo driver 4 will now be explained based on FIG. 2. The position controller 41 performs, for example, proportional control (P control). Specifically, it calculates a speed command by multiplying a position deviation, which is the deviation between a position command notified from the PLC 5 and a detected position, by a position proportional gain Kpp. The position controller 41 has the position proportional gain Kpp in advance as a control parameter.

[0017] Next, the speed controller 42 performs, for example, proportional-plus-integral control (PI control). Specifically, the torque command is calculated by multiplying the integral of the speed deviation, which is the deviation between the speed command calculated by the position controller 41 and the detected speed, by a speed integral gain Kvi, and then multiplying the sum of the calculation result and the speed deviation by a speed proportional gain Kvp. The speed controller 42 has the speed integral gain Kvi and the speed proportional gain Kvp as control parameters in advance. The speed controller 42 may also 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 driving and controlling 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, as control parameters, a cutoff frequency, a center frequency, etc. related to the performance of these filters.

[0018] The control structure of the servo driver 4 includes a speed feedback system in which the speed controller 42, the current controller 43, and the controlled object 6 are forward elements, and further includes a position feedback system in which the speed feedback system and the position controller 41 are forward elements. With this control structure configured in this way, the servo driver 4 can servo-control the motor 2 so that it follows the position command supplied from the PLC 5.

[0019] Returning to FIG. 1, a measuring device 10 is electrically connected to the servo driver 4. This electrical connection may 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 driver 4. Specifically, the measuring device 10 is a computer having an arithmetic unit, memory, etc., and executable measurement software is installed therein. The measuring device 10 then uses this measurement software to measure the frequency response of the servo system.

[0020] Here, we will explain the issues involved in measuring the frequency response of a servo system. When measuring the frequency response, for example, a speed command in which the speed varies with time is used. As such a speed command, for example, a sweptsine vibration signal is used. FIG. 3 is a diagram illustrating an example of a sweptsine vibration signal. The vertical axis of FIG. 3 illustrates speed, and the horizontal axis illustrates time. In addition, for the sweptsine vibration signal illustrated in FIG. 3, the period from time T1 to time T2 is the period during which the vibration signal is input to the servo system. Hereinafter, in this specification, inputting a signal to a servo system is also referred to as "excitation."

[0021] A Sweptsine vibration signal is, for example, a speed command signal as shown in FIG. 3. When such a vibration signal is used to measure frequency response, a discrepancy may occur between the position of the load device 3 at the start and end of excitation. For example, automatic gain adjustment automatically applies vibration multiple times to improve the accuracy of identifying device characteristics, and this positional discrepancy is accumulated. As a result of the accumulated positional discrepancy, it is possible that the load device 3 may move outside its operating range, for example.

[0022] Therefore, in this embodiment, the following configuration is adopted to suppress such positional deviation of the load device 3 at the start and end of vibration application. Fig. 4 is a functional block diagram illustrating various functions executed by software running in the measurement device 10. The measurement device 10 has a generation unit 11, a synthesis unit 12, a vibration application unit 13, and an analysis unit 14.

[0023] The generator 11 generates a low-frequency sine wave to be superimposed on the sweptsine vibration signal. The sweptsine vibration signal is stored in advance in a storage unit of the measuring device 10, for example. The low-frequency sine wave is determined so as to suppress positional deviation of the load device 3 caused by the sweptsine vibration signal when superimposed on the vibration signal. The low-frequency sine wave is defined, for example, by the following equation (1). In equation (1), V Lmax is the amplitude, ω L is the angular frequency and t is the time.

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[0024] The positional deviation (position offset) of the load device 3 caused by the vibration signal before the low-frequency sine wave is superimposed is L, and the excitation time for exciting the vibration signal is T. inv Then, the amount of movement of the load device 3 due to the low-frequency sine wave can be expressed by the following equation (2).

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[0025] For simplicity, we will assume that the low-frequency sine wave is a waveform that moves only in one direction opposite to the position offset. Also, we will assume that the low-frequency sine wave superimposed on the vibration signal has a half cycle. The low-frequency sine wave assumed in this way has a half cycle that is equal to the excitation time T inv Therefore, the angular frequency ω L can be expressed by the following equation (3).

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[0026] Substituting equation (3) into equation (2) and rearranging it, the amplitude V is obtained by the following equation (4): Lmax is derived.

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[0027] By substituting equations (2) and (3) into equation (1), the desired low-frequency sine wave can be expressed by the following equation (5). The generator 11 generates the low-frequency sine wave determined in this manner. FIG. 5 is a diagram showing an example of a low-frequency sine wave generated by the generator 11. The vertical axis of FIG. 5 illustrates speed, and the horizontal axis illustrates time. The low-frequency sine wave expressed by equation (5) is, for example, a speed command signal as illustrated in FIG. 5. As with the sweptsine vibration signal illustrated in FIG. 3, the speed command signal illustrated in FIG. 5 is a period from time T1 to time T2 during which the servo system is vibrated.

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[0028] Returning to FIG. 4, the synthesis unit 12 generates a synthetic wave by superimposing the low-frequency sine wave generated by the generation unit 11 on the sweptsine vibration signal. FIG. 6 is a diagram showing an example of the synthetic wave generated by the synthesis unit 12. The synthetic wave illustrated in FIG. 6 is generated by superimposing the low-frequency sine wave illustrated in FIG. 5 on the sweptsine vibration signal illustrated in FIG. 3. The synthetic wave is an example of a "synthetic signal."

[0029] The excitation execution unit 13 inputs a composite wave, which is the Sweptsine vibration signal superimposed on a low-frequency sine wave by the synthesis unit 12, to the servo system. The composite wave is a superimposed low-frequency sine wave determined to suppress positional deviation of the load device 3 due to the Sweptsine vibration signal. Therefore, by inputting the composite wave to the servo system, positional deviation of the load device 3 is suppressed compared to when the Sweptsine vibration signal is input directly to the servo system.

[0030] FIG. 7 is a diagram comparing the case where a composite wave generated by the synthesis unit 12 is input to a servo system with the case where a sweptsine vibration signal is input to the servo system. Waveform P1 illustrates an example of the fluctuation in the position of the load device 3 when a composite wave is input to the servo system. Waveform P2 illustrates an example of the fluctuation in the position of the load device 3 when a sweptsine vibration signal is input to the servo system. In the example of FIG. 7, in both waveform P1 and waveform P2, vibration is applied when the starting position of the load device 3 is at position "0".

[0031] As can be seen from Figure 7, in waveform P2, the position of the load device 3 at time T2 when the vibration ends is position "Z1", which is different from position "0". On the other hand, in waveform P1, the position of the load device 3 at time T2 when the vibration ends has returned to position "0". This is because in waveform P1, a low-frequency sine wave is superimposed on the sweptsine vibration signal, thereby suppressing the positional deviation of the load device 3 due to the sweptsine vibration signal.

[0032] 4, the analysis unit 14 receives a response signal (speed signal) indicating the moving speed of the load device 3 as feedback for the composite wave input by the excitation execution unit 13. The analysis unit 14 performs frequency response analysis using as input a combination of the composite wave input by the excitation execution unit 13 and the received response signal. In the frequency response analysis by the analysis unit 14, for example, a fast Fourier transform (FFT) or a divided FFT may be performed.

[0033] FIG. 8 is a diagram showing an example of a response signal acquired by the analysis unit 14 from a servo system to which a composite wave is input. The vertical axis of FIG. 8 illustrates speed, and the horizontal axis illustrates time. In FIG. 8, waveform P3 illustrated by a solid line illustrates the composite wave, and waveform P4 illustrated by a dotted line illustrates a response signal indicating the actually measured speed of the load device 3 in the servo system to which the composite wave is input. The analysis unit 14 performs frequency response analysis based on the composite wave illustrated by waveform P3 and the response signal illustrated by waveform P4.

[0034] FIG. 9 illustrates frequency response characteristics when FFT is performed as the frequency response analysis by the analysis unit 14. The upper part of FIG. 9 illustrates the correspondence between gain and frequency. The lower part of FIG. 9 illustrates the correspondence between phase and frequency. Furthermore, FIG. 10 illustrates frequency response characteristics when divided FFT is performed as the frequency response analysis by the analysis unit 14. The upper part of FIG. 10 illustrates the correspondence between gain and frequency. The lower part of FIG. 10 illustrates the correspondence between phase and frequency. In this way, the frequency response analysis is performed by the analysis unit 14, whereby the correspondence between gain and frequency and the correspondence between phase and frequency are analyzed. The analysis unit 14 may, for example, output the results of the frequency response analysis to an output device such as a display connected to the measurement device 10.

[0035] 11 is a diagram showing an example of a processing flow of the measurement device 10 according to the embodiment. Hereinafter, an example of a processing flow of the measurement device 10 will be described with reference to FIG.

[0036] In step S1, the generator 11 generates a low-frequency sine wave that suppresses positional deviation of the load device 3 due to the sweptsine vibration signal. In step S2, the combiner 12 combines the low-frequency sine wave generated in step S1 with the sweptsine vibration signal previously stored in the memory of the measuring device 10 to generate a combined wave.

[0037] In step S3, the excitation execution unit 13 excites the servo system with the composite wave generated in step S2. In step S4, the analysis unit 14 performs frequency response analysis using as input a combination of the composite wave input to the servo system in step S3 and a response signal received as feedback from the servo system.

[0038] <Effects of the embodiment> In this embodiment, the low-frequency sine wave is determined so as to eliminate positional deviation of the load device 3 when a sweptsine vibration signal is input to the servo system. Then, in this embodiment, a composite wave in which the low-frequency sine wave determined in this manner is superimposed on the sweptsine vibration signal is input to the servo system. Therefore, according to this embodiment, positional deviation of the load device 3 is suppressed, as described with reference to FIG. 7. Therefore, according to this embodiment, positional deviation of the load device 3 is suppressed in frequency response analysis performed by inputting a speed command to the servo system.

[0039] Here, performing frequency response analysis using a position command suppresses positional deviation of the load device 3. However, since position control using a position command is equivalent to speed control using a low-pass filter, frequency response analysis using a position command reduces analysis accuracy in the high-frequency band. In this embodiment, the composite wave input to the servo system is a speed command, so this decrease in analysis accuracy is suppressed. In addition, by superimposing a low-frequency excitation signal (low-frequency sine wave) on the sweptsine vibration signal, the S / N ratio of that frequency is improved, and analysis accuracy is improved.

[0040] Furthermore, in this embodiment, the analysis unit 14 performs frequency response analysis based on the response signal received from the servo system to which the composite wave is input and the composite wave input to the servo system. For example, FFT or divided FFT is used for the frequency response analysis. For example, by using divided FFT, the analysis accuracy near the resonance frequency is improved. Therefore, according to this embodiment, the frequency response analysis of the servo system can be performed while suppressing positional deviation of the load device 3.

[0041] <Modification> In the embodiment described above, the low-frequency sine wave expressed by equation (5) is superimposed on the sweptsine vibration signal, but the low-frequency sine wave superimposed by the sweptsine vibration signal is not limited to the waveform expressed by equation (5). The low-frequency sine wave superimposed by the sweptsine vibration signal may be any wave that suppresses the positional deviation (position offset L) of the load device 3 caused by the excitation of the sweptsine vibration signal. Such a low-frequency sine wave may be expressed, for example, by equation (6), which satisfies the following equation (7) where a is any odd number.

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[0042] In the embodiment described above, the measuring device 10 inputs the composite wave to the servo system and also performs frequency response analysis of the servo system, but the measuring device 10 may input the composite wave to the servo system, and frequency response analysis based on the response signal from the servo system and the composite wave may be performed by a device other than the measuring device 10. In such a case, the measuring device 10 may input a signal equivalent to the composite wave to the other device.

[0043] The embodiments and modifications disclosed above can be combined with each other.

[0044] <Appendix 1> 1. A measurement support device that inputs a measurement signal used for frequency response analysis of a servo system to the servo system, comprising: a generator that generates a first signal determined to eliminate a difference between a first position of a load of the servo system at the start of excitation of the servo system by a speed command signal that changes over time to include a large number of frequency components, and a second position of the load at the end of excitation of the speed command signal; a synthesis unit that generates a synthesis signal by superimposing the first signal on the speed command signal; a vibration execution unit that inputs the composite signal to the servo system, Measurement support equipment. <Appendix 2> the speed reference signal is Sweptsine; 2. A measurement assistance device as described in appendix 1. <Appendix 3> Let a be any odd number, V Lmax is the amplitude of the speed command signal, t is time, and the time for inputting the speed command to the servo system is T inv When the difference between the first position and the second position is L, the first signal is expressed by Equation (6) which satisfies Equation (7) below:

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[0045] 1. Network 2. Motor 3...Load device 4. Servo driver 5. PLC 6. Control Object 7...AC power supply 10. Measuring equipment 11...Generation part 12. Synthesis section 13. Vibration execution unit 14··Analysis Department 41 Position Controller 42 Speed ​​controller 43 Current Controller

Claims

1. 1. A measurement support device that inputs a measurement signal used for frequency response analysis of a servo system to the servo system, comprising: a generator that generates a first signal determined to eliminate a difference between a first position of a load of the servo system at the start of excitation of the servo system by a speed command signal that changes over time to include a large number of frequency components, and a second position of the load at the end of excitation of the speed command signal; a synthesis unit that generates a synthesis signal by superimposing the first signal on the speed command signal; a vibration execution unit that inputs the composite signal to the servo system, Measurement support equipment.

2. the speed command signal is Sweptsine; The measurement support device according to claim 1.

3. Let a be an odd number, V Ｌｍａｘ Let be the amplitude of the speed command signal, let be time, and let be the time to input the speed command to the servo system. ｉｎｖ If L is the difference between the first position and the second position, the first signal is represented by equation (6) which satisfies the following equation (7): [Equation 9] The measurement support device according to claim 1.

4. an analysis unit that performs the frequency response analysis using as input a velocity signal fed back from the servo system to which the composite signal has been input, and the composite signal, to calculate a frequency response characteristic of the servo system; The measurement support device according to any one of claims 1 to 3.

5. The analysis unit performs an FFT analysis as the frequency response analysis. The measurement support device according to claim 4.

6. the analysis unit, wherein the FFT analysis includes a divided FFT analysis; The measurement support device according to claim 5.

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