Servo motor inertia ratio setting method and inertia ratio adjustment device

Abstract

To reduce the frequency to adjust an inertia ratio as much as possible.SOLUTION: The present inertia ratio setting method for a servo motor includes: acquisition processing of acquiring, for each of a plurality of servo motors, a first estimated value of an inertia ratio when a load is moved to a first position, and a second estimated value of the inertia ratio when the load is moved to a second position; determination processing of determining, for each of the plurality of servo motors, a temporary inertia ratio based on the fluctuation range between the acquired first estimated value and second estimated value, the first estimated value, and the second estimated value; first setting processing of setting the temporary inertia ratio to the plurality of servo motors; adjustment processing of executing adjustment of gain in the plurality of servo motors after the setting of the temporary inertia ratio; and second setting processing of, after the adjustment processing, setting an inertia ratio calculated as the average of the acquired first estimated value and second estimated value for all the servo motors, to each of the plurality of servo motors.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a method for setting an inertia ratio of a servo motor and an inertia ratio adjusting device. [Background technology]

[0002] Servo systems that control multiple servo motors, such as gantry mechanisms and tandem mechanisms, are used. In such servo systems, a technique has been proposed in which an inertia ratio is estimated and the estimated inertia ratio is set for all of the multiple servo motors (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-141437 Summary of the Invention [Problem to be solved by the invention]

[0004] In a servo system that controls multiple servo motors, the inertia ratio of each servo motor changes depending on the position of the load. Therefore, if the position of the load moves from the position where the inertia ratio was estimated, vibration or oscillation may occur. Therefore, in order to suppress such vibration or oscillation, adjustment of the inertia ratio and gain is repeatedly performed even after the inertia ratio is set. This adjustment work places a burden on the worker who operates the servo system.

[0005] An object of one aspect of the disclosed technique is to provide a method for setting an inertia ratio of a servo system and an inertia ratio adjusting device that can reduce the frequency of adjusting the inertia ratio as much as possible. [Means for solving the problem]

[0006] One aspect of the disclosed technology is exemplified by the following method for setting an inertia ratio of a servo motor. The method for setting an inertia ratio of a servo motor is a method for setting an inertia ratio of a servo system in which a load is driven by cooperation of multiple servo motors. This method of setting an inertia ratio includes an acquisition process of acquiring, for each of the plurality of servo motors, a first estimated value of the inertia ratio when the load is moved to a first position and a second estimated value of the inertia ratio when the load is moved to a second position; a determination process of determining, for each of the plurality of servo motors, a provisional inertia ratio based on a fluctuation range between the acquired first estimated value and the acquired second estimated value, the first estimated value, and the second estimated value; a first setting process of setting the determined provisional inertia ratio to the plurality of servo motors; an adjustment process of adjusting gains in the plurality of servo motors after setting the provisional inertia ratio; and a second setting process of setting, for each of the plurality of servo motors, an inertia ratio calculated as an average of the acquired first estimated value and the second estimated value for each of all of the servo motors after the adjustment process.

[0007] In the servo motor inertia ratio setting method, a provisional inertia ratio is set based on an estimated inertia ratio and its fluctuation range, and then gain adjustment is performed. After gain adjustment, an average inertia ratio of the estimated values ​​is set for the plurality of servo motors, making it less likely that vibration will occur even if the inertia ratio fluctuates due to load position fluctuations. Consequently, the servo motor inertia ratio setting method can reduce the frequency of inertia ratio adjustment as much as possible.

[0008] The method for setting an inertia ratio of a servo motor may have the following features: The first position is a position where the load is farthest from the servo motor within the driving range of the load, and the second position is a position where the load is closest to the servo motor within the driving range of the load. In the determination process, a predetermined coefficient is calculated for each of the plurality of servo motors based on an average value of the acquired first estimated value and second estimated value, and the tentative inertia ratio is determined for each of the plurality of servo motors based on the calculated predetermined coefficient and the average value.

[0009] The variation in the inertia ratio depending on the position of the load can be considered to be the inertia ratio when the load is located closest to the servo motor within the drive range of the load, and the inertia ratio when the load is located farthest from the servo motor. By having the above-mentioned features, the method for setting the inertia ratio of a servo motor determines a provisional inertia ratio taking into account the maximum range of variation in the inertia ratio and performs gain adjustment, thereby making it possible to suppress the occurrence of vibration as much as possible even when the load is moved to various positions within the drive range.

[0010] The disclosed technology can also be understood from the aspect of an inertia ratio setting device that executes the above-described method for setting an inertia ratio of a servo motor. [Effects of the Invention]

[0011] According to the disclosed technology, it is possible to reduce the frequency of adjusting the inertia ratio as much as possible. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating an example of a servo system according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of a schematic configuration of a load machine. [Figure 3] FIG. 3 is a diagram illustrating the influence on the velocity open loop characteristics of the inertia ratio fluctuation caused by the movement of the third axis or the precision stage. [Figure 4]FIG. 4 is a block diagram showing a schematic configuration of a servo driver and an adjustment support device according to the embodiment. [Figure 5] FIG. 5 is a first diagram illustrating an example of a processing flow of the inertia ratio setting process in the embodiment. [Figure 6] FIG. 6 is a second diagram illustrating an example of the processing flow of the inertia ratio setting process in the embodiment. [Figure 7] FIG. 7 is a diagram schematically showing the calculation of the coefficient α used to calculate the provisional inertia ratio. [Figure 8] FIG. 8 is a diagram schematically showing a first method for calculating the coefficient α used in calculating the provisional inertia ratio. [Figure 9] FIG. 9 is a diagram schematically showing a second method for calculating the coefficient α used to calculate the provisional inertia ratio. [Figure 10] FIG. 10 is a diagram illustrating an example of a processing flow of a process for determining a provisional inertia ratio. [Figure 11] FIG. 11 is a diagram showing an example of a Bode diagram in a servo system according to a comparative example. [Figure 12] FIG. 12 is a diagram illustrating an example of a Bode diagram in the servo system according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment will be described with reference to the drawings. Fig. 1 is a diagram showing an example of a servo system 1 according to an embodiment. The servo system 1 includes a load machine 2, servo motors 3a, 3b, and 3c, servo drivers 4a, 4b, and 4c, a controller 7, and an adjustment support device 9. The servo system 1 is a system that drives the load machine 2 through cooperation of the servo drivers 4a, 4b, and 4c. The servo system 1 is an example of a "servo system."

[0014] The load machine 2 is a multi-axis machine having multiple axes that may cause axis interference, such as a gantry mechanism or a tandem mechanism. FIG. 2 is a diagram showing an example of the schematic configuration of the load machine 2. The load machine 2 includes a first axis 21 driven by a servo motor 3a, a second axis 22 driven by a servo motor 3b, and a third axis 23 driven by a servo motor 3c. The first axis 21 and the second axis 22 are arranged in parallel. The third axis 23 is mechanically connected to be perpendicular to the first axis 21 and the second axis 22, which are arranged in parallel. A precision stage 24 is arranged on the third axis 23.

[0015] In the load machine 2, the first axis 21 is driven by the servo motor 3a, and the second axis 22 is driven by the servo motor 3b, causing the third axis 23 to move along the axial direction of the first axis 21 and the second axis 22. Furthermore, the third axis 23 is driven by the servo motor 3c, causing the precision stage 24 to move along the axial direction of the third axis 23. The precision stage 24 is an example of a "load."

[0016] Servo drivers 4a, 4b, and 4c are connected to the servo motors 3a, 3b, and 3c, respectively, and output drive signals for the servo motors 3a, 3b, and 3c in accordance with command signals. A controller 7 is connected to the servo drivers 4a, 4b, and 4c, and outputs command signals in accordance with input from a user or an external device. The controller 7 is also provided with an adjustment support device 9 that supports the adjustment of the inertia ratio by the servo drivers 4a and 4b. The adjustment support device 9 can be realized, for example, by a personal computer or PLC that executes a predetermined program. The adjustment support device 9 is an example of an "inertia ratio setting device."

[0017] 1 illustrates a configuration in which the first axis 21 and the second axis 22 are two axes that may cause shaft interference, and the third axis 23 is one axis that does not cause shaft interference, but a loaded machine with three or more axes that may cause shaft interference may also be employed. When a loaded machine with three or more axes that may cause shaft interference is employed, a servo motor, a servo driver, and a controller may be provided for each axis, and an adjustment support device 9 may be connected to each servo driver.

[0018] When adjusting control parameters used to control the servo motors 3a and 3b in a servo system 1 having a load machine 2 with a multi-axis configuration, an inertia ratio is estimated for each axis of the load machine 2. For example, by employing the technology described in Patent Document 1 for estimating the inertia ratio, it is possible to realize an estimation of the inertia ratio as accurately as possible.

[0019] However, even when the technology described in Patent Document 1 is employed, the inertia ratios of the first axis 21 and the second axis 22 change when the third axis 23 or the precision stage 24 moves from the position where the inertia ratio was estimated. FIG. 3 is a diagram illustrating the effect of fluctuations on the first axis 21 and the second axis 22 when the inertia ratio fluctuates due to movement of the third axis 23 or the precision stage 24. The line L1 in FIG. 3 illustrates a state in which the estimated inertia ratio and the actual inertia ratio are equal. The line L2 in FIG. 3 illustrates a state in which the actual inertia ratio is greater than the estimated inertia ratio. The line L3 in FIG. 3 illustrates a state in which the actual inertia ratio is smaller than the estimated inertia ratio. Furthermore, "Kvp" in FIG. 3 is a velocity proportional gain.

[0020] As can be seen from Figure 3, fluctuations in the actual inertia ratio cause fluctuations in the speed control band. Fluctuations in the speed control band result in vibrations and oscillations. Therefore, in this embodiment, the following configuration is adopted to suppress vibrations and oscillations even when the third axis 23 or precision stage 24 moves from the point where the inertia ratio was estimated, and to minimize the need for readjustment of the inertia ratio.

[0021] Fig. 4 is a block diagram showing a schematic configuration of the servo drivers 4a, 4b and the adjustment support device 9 in this embodiment. Fig. 4 shows the servo drivers that control the first axis 21 and the second axis 22, in which axis interference may occur. Fig. 4 also shows the controller 7. Below, the schematic configuration of the servo drivers 4a, 4b and the adjustment support device 9 will be described with reference to Fig. 4.

[0022] The servo driver 4a includes a control unit 41a that outputs a drive current to the servo motor 3a based on a command input from the controller 7. The control unit 41a includes a position controller, a speed controller, a torque controller, etc., but these can be configured using known components as appropriate, so detailed descriptions will be omitted. The servo driver 4a also includes an estimator 42a that estimates an inertia ratio. For example, the technique described in Patent Document 1 can be used as a method for estimating the inertia ratio using the estimator 42a. The servo driver 4a has a memory unit 43a that stores various information and a communication unit 44a that communicates with the outside. The servo driver 4b also includes a control unit 41b, an estimator 42b, a memory unit 43b, and a communication unit 44b, but the configuration of each unit is the same as that of the servo driver 4a, so descriptions will be omitted.

[0023] The controller 7 includes a signal relay unit 71 that relays transmission and reception of signals between the servo drivers 4a, 4b and the adjustment support device 9. The controller 7 has a processor consisting of a CPU that executes a numerical control program, etc., a memory, a communication unit, etc., but these can be appropriately configured using known configurations, so detailed explanations will be omitted.

[0024] The adjustment support device 9 is configured by, for example, a computer having a CPU that executes a program for adjusting the inertia ratio (described later) and a storage device that stores the program and data. The adjustment support device 9 has an inertia ratio acquisition unit 91 and an inertia ratio setting control unit 92. The inertia ratio acquisition unit 91 acquires the inertia ratios estimated by the estimators 42a and 42b from the servo drivers 4a and 4b via the communication units 44a and 44b and the signal relay unit 71.

[0025] The inertia ratio setting control unit 92 transmits the provisional inertia ratio determined based on the inertia ratio acquired by the inertia ratio acquisition unit 91 to each of the servo drivers 4a and 4b via the signal relay unit 71.

[0026] In the servo drivers 4a and 4b that have received the provisional inertia ratios, the control units 41a and 41b store the received provisional inertia ratios in the memories 43a and 43b. The provisional inertia ratios stored in the memories 43a and 43b are used to set the inertia ratios in the control units 41a and 41b. In the servo drivers 4a and 4b, gain adjustment is performed with the provisional inertia ratios set. In the gain adjustment, for example, a speed proportional gain or a position proportional gain is adjusted.

[0027] When the gain adjustment in the servo drivers 4a, 4b is completed, the inertia ratio setting control unit 92 of the adjustment support device 9 transmits the inertia ratio acquired by the inertia ratio acquisition unit 91 to each of the servo drivers 4a, 4b via the signal relay unit 71.

[0028] In the servo drivers 4a and 4b that have received the inertia ratios, the control units 41a and 41b store the received inertia ratios in the memories 43a and 43b. The inertia ratios stored in the memories 43a and 43b are used to set the inertia ratios in the control units 41a and 41b.

[0029] <Processing flow> 5 and 6 are diagrams showing an example of a processing flow of the inertia ratio setting processing in the embodiment. Hereinafter, the processing of the inertia ratio setting processing in the embodiment will be described with reference to FIGS. 5 and 6. An example of the flow will be described.

[0030] In S1, a variable i that identifies an axis for which inertia ratio estimation is performed is set to i = 1. Here, the axes for which inertia ratio estimation is to be performed, i.e., the multiple axes that may cause axis interference with each other, are assigned unique numbers in order starting from 1 to identify the axes, and the axis identified in this way will be described as the ith axis.

[0031] In S2, the load machine 2 attempts a positioning operation including a plurality of axes that may cause axis interference. In S3, the inertia ratio of the axis indicated by the variable i (for example, the first axis 21 when "i=1") is estimated. In S4, the estimated inertia ratio of the axis indicated by the variable i is transmitted to the adjustment support device 9 via the communication units 44a and 44b and recorded in a predetermined storage area provided in the inertia ratio acquisition unit 91.

[0032] In S5, the inertia ratio setting control unit 92 determines whether or not inertia ratios are stored for related axes, i.e., for all of the multiple axes that may cause axis interference with one another (in the example of FIG. 2, these correspond to the first axis 21, the second axis 22, and the third axis 23). If they are stored (YES in S5), the process proceeds to S7. If inertia ratios for at least some of the axes are not stored (NO in S5), the process proceeds to S6.

[0033] In S6, i is incremented. After that, the processes from S2 onwards are executed for the axis indicated by the incremented i.

[0034] In S7, the inertia ratio setting control unit 92 reads out the estimated value of the inertia ratio for each axis from the inertia ratio acquisition unit 91 and determines a provisional inertia ratio. The provisional inertia ratio is determined, for example, by multiplying the estimated value of the inertia ratio by a predetermined coefficient α. The process of determining the provisional inertia ratio will be described in detail later.

[0035] In S8, the inertia ratio setting control unit 92 transmits the provisional inertia ratio determined in S7 to the servo drivers 4a and 4b corresponding to each axis.

[0036] In S9, a temporary inertia ratio is set for each axis, and the axis is initialized to i = 1. In S10, the gain is adjusted for the axis indicated by the variable i (for example, the second axis 22 when "i = 2").

[0037] In S11, the inertia ratio setting control unit 92 determines whether or not gain adjustment has been completed for all related axes, i.e., all of the multiple axes that may cause axis interference with each other (in the example of FIG. 2, the first axis 21 and the second axis 22). If it has been completed (YES in S11), the process proceeds to S12. If gain adjustment has not been completed for at least some of the axes (NO in S11), the process proceeds to S13.

[0038] In S12, the inertia ratio setting control unit 92 transmits the estimated inertia ratio recorded in S5 to the servo drivers 4a and 4b corresponding to each axis.

[0039] <Calculation of coefficient α> 7 is a diagram showing a schematic diagram of the calculation of the coefficient α used to calculate the provisional inertia ratio. When calculating the coefficient α, the precision stage 24 of the load machine 2 is moved to a plurality of positions, and the inertia ratio is estimated by the servo drivers 4a and 4b at each position. The example in FIG. 7 illustrates a state in which the precision stage 24 is moved to the positions of the circled numbers "1," "2," "3," and "4," and the inertia ratio is estimated by the servo drivers 4a and 4b.

[0040] The coefficient α is determined, for example, based on an estimated inertia ratio. Here, preferred inertia ratios for estimating the coefficient α include inertia ratios estimated at multiple positions where the load from the precision stage 24 is biased toward one of the first axis 21 and the second axis 22. In the example of FIG. 7 , the circled number "1" is a position far from all of the servo motors 3a, 3b, and 3c; the circled number "2" is a position far from the servo motors 3a and 3b but closest to the servo motor 3c; the circled number "3" is a position far from the servo motors 3b and 3c but closest to the servo motor 3a; and the circled number "4" is a position far from the servo motors 3a and 3c but closest to the servo motor 3b. All of the circled numbers "1," "2," "3," and "4" are positions where the load is biased toward either the first axis 21 or the second axis 22.

[0041] The estimating units 42a and 42b of the servo drivers 4a and 4b estimate the inertia ratio when the precision stage 24 is moved to each of the circled numbers "1," "2," "3," and "4." The estimated inertia ratios are transmitted to the adjustment support device 9 via the communicating units 44a and 44b and recorded in a predetermined storage area provided in the inertia ratio acquiring unit 91. The process of estimating the inertia ratio for each axis described with reference to FIG. 7 is executed, for example, in steps S1 to S5 and S6 in FIG. 5. Here, the coefficient α can be calculated using the estimated inertia ratio by, for example, the following two methods.

[0042] 8 is a diagram schematically illustrating a first method for calculating the coefficient α used to calculate the provisional inertia ratio. The circled numbers "1," "2," "3," and "4" listed under "Position" in FIG. 8 correspond to the circled numbers "1," "2," "3," and "4," respectively, in FIG. 7. FIG. 8 illustrates the inertia ratios estimated for each of the first axis 21 and the second axis 22 when the precision stage 24 is moved to the positions indicated by the circled numbers "1," "2," "3," and "4," as well as the average values ​​of the inertia ratios estimated for each of the first axis 21 and the second axis 22.

[0043] In the first method for calculating the coefficient α, the inertia ratio setting control unit 92 calculates the average value of the inertia ratios estimated while the precision stage 24 is moved to the positions of the circled numbers "1," "2," "3," and "4" for each of the first axis 21 and the second axis 22. The inertia ratio setting control unit 92 calculates the coefficient α for each of the first axis 21 and the second axis 22 based on the amount of change between the average value of the estimated inertia ratios and the value of the estimated inertia ratios that is farthest from the average value.

[0044] FIG. 9 is a diagram illustrating a second method for calculating the coefficient α used to calculate the provisional inertia ratio. In the second method, the inertia ratio estimated when the precision stage 24 is on its own axis is used to determine the coefficient α. The circled numbers "1," "2," "3," and "4" listed under "Position" in FIG. 9 correspond to the circled numbers "1," "2," "3," and "4" in FIG. 7, respectively. The example in FIG. 9 illustrates a state in which the precision stage 24 is moved to the positions indicated by the circled numbers "1" and "3," where the inertia ratio is estimated by the servo driver 4a, and the precision stage 24 is moved to the positions indicated by the circled numbers "2" and "4," where the inertia ratio is estimated by the servo driver 4b. The positions indicated by the circled numbers "1" and "3" correspond to the position when the precision stage 24 is located on the first axis 21, and the positions indicated by the circled numbers "2" and "4" correspond to the position when the precision stage 24 is located on the second axis 22.

[0045] In the first method for calculating the coefficient α, the inertia ratio setting control unit 92 calculates, for the first axis 21, the average value of the inertia ratios estimated in each of the states (states indicated by the circled numbers "1" and "3" in FIG. 7) in which the precision stage 24 is positioned on the first axis 21. The inertia ratio setting control unit 92 calculates the coefficient α to be applied to the first axis 21 based on the amount of change between the average value calculated for the first axis 21 and the value of the inertia ratios estimated for the first axis 21 that is the furthest from the average value.

[0046] Furthermore, for the second axis 22, the inertia ratio setting control unit 92 calculates the average value of the inertia ratios estimated in each of the states in which the precision stage 24 is positioned on the second axis 22 (states indicated by the circled numbers "2" and "4" in FIG. 7). The inertia ratio setting control unit 92 calculates a coefficient α to be applied to the second axis 22 based on the amount of change between the average value calculated for the second axis 22 and the largest value among the inertia ratios estimated for the second axis 22 that differs from the average value. Using the coefficient α calculated in this manner, a provisional inertia ratio is determined, for example, in S7 of FIG. 5. The provisional inertia ratio can be calculated using, for example, the following equation (1):

number

[0047] In equation (1), T is a tentative inertia ratio, Y1 is an average value of the inertia ratios estimated on the first axis 21, and Y2 is an average value of the inertia ratios estimated on the second axis 22.

[0048] Fig. 10 is a diagram showing an example of a processing flow of a process for determining a provisional inertia ratio. The processing in Fig. 10 is the processing executed in S7 in Fig. 5. Hereinafter, an example of a processing flow of a process for determining a provisional inertia ratio will be described with reference to Fig. 10.

[0049] In S21, a variable i that specifies an axis for which a provisional inertia ratio is to be determined is set to 1. Here, the axes for which a provisional inertia ratio is to be determined are a plurality of axes (for example, the first axis 21 and the second axis 22) that may cause axis interference.

[0050] In S22, the inertia ratio setting control unit 92 calculates the average value of the estimated inertia ratios for the i-th axis. In S23, the inertia ratio setting control unit 92 calculates the coefficient α using the average value calculated in S22 and the estimated inertia ratio. Methods for calculating the average value of the inertia ratios in S22 and the coefficient α in S23 include, for example, the first method and the second method described with reference to FIGS. 8 and 9.

[0051] In S24, the inertia ratio setting control section 92 determines a provisional inertia ratio using the coefficient α determined for the third axis 23 and the average value of the estimated inertia ratios.

[0052] In S25, the inertia ratio setting control unit 92 determines whether or not temporary inertia ratios have been determined for all of the related axes, i.e., the multiple axes that may cause axis interference with each other (corresponding to the first axis 21 and the second axis 22 in the example of FIG. 2). If they have been determined (YES in S25), the process ends. If temporary inertia ratios have not been determined for at least some of the axes (NO in S25), the process proceeds to S26.

[0053] In S26, i is incremented. After that, the processes from S22 onwards are executed for the axis indicated by the incremented i.

[0054] In order to verify the effects of this embodiment, a comparative example will be described. In the comparative example, gain adjustment is not performed after setting a tentative inertia ratio, but rather the estimated inertia ratio is set as is and gain adjustment is performed. FIG. 11 is a diagram showing an example of a Bode plot in a servo system according to the comparative example. FIG. 12 is a diagram showing an example of a Bode plot in the servo system 1 according to the embodiment. The vertical axis of FIGS. 11 and 12 is gain (dB), and the horizontal axis is frequency (Hz).

[0055] As can be seen by comparing Fig. 11 and Fig. 12, in the comparative example of Fig. 11, the virtual inertia As a result of omitting the gain adjustment after setting the ratio, the gain decreases as the frequency increases overall, but at a frequency of 10 3 A gain exceeding 0 dB was confirmed in the vicinity of 50 Hz, and it can be seen that vibrations were occurring in the load machine 2. On the other hand, in the embodiment illustrated in Fig. 12, the gain decreases overall as the frequency increases, and once it falls below 0 dB, no gain exceeding 0 dB is generated, and it can be seen that vibrations occurring in the load machine 2 are suppressed.

[0056] That is, the servo system 1 according to this embodiment performs gain adjustment after setting a provisional inertia ratio that is set higher than the estimated inertia ratio by a coefficient α for servo drivers (e.g., servo drivers 4a and 4b) corresponding to multiple axes that may cause axis interference. Then, after gain adjustment, the average value of the inertia ratios estimated for the servo motors 3a and 3b is set for the servo drivers 4a and 4b, thereby suppressing the occurrence of vibration even when the precision stage 24 of the load machine 2 is moved. Therefore, according to this embodiment, the frequency of inertia ratio adjustment can be reduced as much as possible.

[0057] The inertia ratio varies depending on the position of the precision stage 24. In this embodiment, as illustrated in FIG. 7 , the precision stage 24 is moved to multiple locations, and the inertia ratio is estimated while the precision stage 24 is moved to each location. Then, the coefficient α is determined based on the multiple estimated inertia ratios, and a provisional inertia ratio is determined. By using the inertia ratios estimated while the precision stage 24 is moved to multiple locations in this way, the effect on the coefficient α of fluctuations in the inertia ratio due to movement of the precision stage 24 is suppressed, and ultimately, the occurrence of vibrations when the precision stage 24 is moved to various positions on the axis is suppressed.

[0058] In this embodiment, for each of the multiple axes (first axis 21 and second axis 22) that may cause axial interference, the inertia ratio is estimated with the precision stage 24 positioned at the farthest position (e.g., the positions indicated by the circled numbers "1" and "2" in FIG. 7) and the closest position (e.g., the circled numbers "3" and "4" in FIG. 7) within the driving range of the precision stage 24 driven by the servo motors (servo drivers 4a and 4b) that drive these axes. Then, a coefficient α is determined based on the estimated inertia ratio. For each axis, the farthest and closest positions from the driving motor are considered to be positions where the fluctuation in the inertia ratio is greatest. The coefficient α is calculated based on the inertia ratio estimated with the precision stage 24 positioned at such a position, and a tentative inertia ratio determined using the calculated α is set and gain adjustment is performed. This suppresses the occurrence of vibration when the precision stage 24 is moved to various positions on the axis.

[0059] 6, the inertia ratio setting control unit 92 may set the average value of all the inertia ratios recorded in S5 to the servo drivers 4a, 4b. That is, the inertia ratio setting control unit 92 may set a uniform inertia ratio to the servo drivers 4a, 4b instead of the inertia ratios estimated by the respective servo drivers 4a, 4b. Being able to set a uniform inertia ratio can simplify the processing.

[0060] <Appendix 1> A method for setting an inertia ratio of a servo system that drives a load by cooperation of a plurality of servo motors (3a, 3b), comprising: an acquisition process (S4) for acquiring, for each of the plurality of servo motors (3 a, 3 b), a first estimated value of an inertia ratio when the load (24) is moved to a first position and a second estimated value of an inertia ratio when the load is moved to a second position; For each of the plurality of servo motors, a tentative inertia ratio is determined based on a fluctuation range between the acquired first estimated value and the acquired second estimated value, and the acquired first estimated value and the acquired second estimated value. A determination process (S7) a first setting process (S8) for setting the determined provisional inertia ratios in the plurality of servo motors (3 a, 3 b); an adjustment process (S10) for adjusting gains of the plurality of servo motors (3 a, 3 b) after setting the temporary inertia ratio; and a second setting process (S12) of setting, after the adjustment process, an inertia ratio calculated as an average of the first estimated value and the second estimated value for each of all the acquired servo motors, for each of the plurality of servo motors. How to set the inertia ratio of a servo motor.

[0061] <Appendix 2> An inertia ratio setting device (9) for setting an inertia ratio of a servo system (1) that drives a load by cooperation of a plurality of servo motors (3 a, 3 b), an acquisition unit (91) that acquires, for each of the plurality of servo motors (3 a, 3 b), a first estimated value of an inertia ratio when the load (24) is moved to a first position and a second estimated value of an inertia ratio when the load is moved to a second position; a setting control unit (92) for setting an inertia ratio when controlling the servo motor, The setting control unit (92) a determination process for determining a provisional inertia ratio for each of the plurality of servo motors (3 a, 3 b) based on a fluctuation range between the acquired first estimated value and the acquired second estimated value, the acquired first estimated value, and the acquired second estimated value; a first setting process for setting the determined provisional inertia ratio in the plurality of servo motors (3 a, 3 b); an adjustment process for adjusting gains of the plurality of servo motors (3 a, 3 b) after setting the temporary inertia ratio; After the adjustment process, a second setting process is executed in which the inertia ratio calculated as the average of the first estimated value and the second estimated value for each of all the acquired servo motors is set for each of the plurality of servo motors. Inertia ratio setting device (9). [Explanation of symbols]

[0062] 1. Servo system 2...Load machine 3a··Servo motor 3b Servo motor 3c··Servo motor 4a Servo driver 4b Servo driver 4c··Servo motor 7. Controller 9...Adjustment support device 21...1st axis 22...2nd axis 23...3rd axis 24 Precision Stage 41a Control section 41b Control section 42a·Estimation part 42b... Estimation part 43a...Storage section 43b...Storage section 44a··Communications Department 61 Control unit 71 Signal relay section 91 Inertia ratio acquisition section 92 Inertia ratio setting control section

Claims

1. 1. A method for setting an inertia ratio of a servo system in which a load is driven by cooperation of a plurality of servo motors, comprising: an acquisition process for acquiring, for each of the plurality of servo motors, a first estimated value of an inertia ratio when the load is moved to a first position and a second estimated value of an inertia ratio when the load is moved to a second position; a determination process for determining a tentative inertia ratio for each of the plurality of servo motors based on a fluctuation range between the acquired first estimated value and the acquired second estimated value, the acquired first estimated value, and the acquired second estimated value; a first setting process for setting the determined provisional inertia ratios to the plurality of servo motors; an adjustment process for adjusting gains of the plurality of servo motors after setting the provisional inertia ratio; a second setting process for setting, after the adjustment process, an inertia ratio calculated as an average of the first estimated value and the second estimated value for each of all of the acquired servo motors, for each of the plurality of servo motors, How to set the inertia ratio of a servo motor.

2. the first position is a position where the load is farthest from the servo motor within a driving range of the load, the second position is a position where the load is closest to the servo motor within a driving range of the load; In the determination process, a predetermined coefficient is calculated based on an average value of the acquired first estimated value and the acquired second estimated value for each of the plurality of servo motors; The provisional inertia ratio is determined for each of the plurality of servo motors based on the calculated predetermined coefficient and the average value.

2. The method for setting an inertia ratio of a servo motor according to claim 1.

3. An inertia ratio setting device for setting an inertia ratio of a servo system that drives a load by cooperation of a plurality of servo motors, an acquisition unit that acquires, for each of the plurality of servo motors, a first estimated value of an inertia ratio when the load is moved to a first position and a second estimated value of an inertia ratio when the load is moved to a second position; a setting control unit that sets an inertia ratio when controlling the servo motor, The setting control unit a determination process for determining a tentative inertia ratio for each of the plurality of servo motors based on a fluctuation range between the acquired first estimated value and the acquired second estimated value, the acquired first estimated value, and the acquired second estimated value; a first setting process for setting the determined provisional inertia ratios to the plurality of servo motors; an adjustment process for adjusting gains of the plurality of servo motors after setting the provisional inertia ratio; and executing a second setting process after the adjustment process to set the inertia ratio calculated as an average of the first estimated value and the second estimated value for each of all the acquired servo motors to each of the plurality of servo motors. Inertia ratio setting device.

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