JP7794059B2 - Servo motor inertia ratio setting method and inertia ratio adjustment device - Google Patents

Description

The present invention relates to a method for setting the inertia ratio of a servo motor and an inertia ratio adjustment device.

Servo systems that control multiple servo motors, such as gantry mechanisms and tandem mechanisms, are used. Technology has been proposed for such servo systems that estimates the inertia ratio and sets the estimated inertia ratio for all of the multiple servo motors (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2020-141437

In a servo system that controls multiple servo motors, the inertia ratio of each servo motor changes depending on the position of the load. As a result, vibrations and oscillations can occur when the load position moves from the position where the inertia ratio was estimated. Therefore, to suppress such vibrations and oscillations, adjustments to the inertia ratio and gain are repeatedly performed even after the inertia ratio has been set. This adjustment work places a burden on the workers operating the servo system.

One aspect of the disclosed technology aims to provide a method for setting the inertia ratio of a servo system and an inertia ratio adjustment device that can reduce the frequency of inertia ratio adjustment as much as possible.

One aspect of the disclosed technology is exemplified by the following method for setting the inertia ratio of a servo motor. This method for setting the inertia ratio of a servo motor is a method for setting the inertia ratio of a servo system that drives a load through the cooperation of multiple servo motors. This method of setting an inertia ratio includes an acquisition process for 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 for determining, for each of the plurality of servo motors, a provisional inertia ratio based on the fluctuation range between the acquired first estimated value and the acquired second estimated value and the first estimated value and the second estimated value; a first setting process for setting the determined provisional inertia ratio to the plurality of servo motors; an adjustment process for adjusting the gains of the plurality of servo motors after setting the provisional inertia ratio; and a second setting process for setting, for each of the plurality of servo motors, an inertia ratio calculated as the average of the acquired first estimated value and second estimated value for all of the servo motors after the adjustment process.

In the above-mentioned method for setting an inertia ratio for a servo motor, a provisional inertia ratio is set based on the estimated inertia ratio and its fluctuation range, and then gain adjustment is performed. After gain adjustment, the average inertia ratio of the above-mentioned estimated values is set for multiple servo motors, making it less likely that vibration will occur even if the inertia ratio fluctuates due to load position fluctuations. Consequently, the above-mentioned method for setting an inertia ratio for a servo motor can minimize the frequency of inertia ratio adjustments.

The method for setting an inertia ratio of a servo motor may have the following features: the first position is a position at which the load is farthest from the servo motor within a driving range of the load, and the second position is a position at which the load is closest to the servo motor within a driving range of the load, and 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.

The variation in inertia ratio due to the load position can be considered to be the inertia ratio when the load is located closest to the servo motor within the load's driving range, and the inertia ratio when the load is located farthest from the servo motor. By incorporating the above-mentioned features, the servo motor inertia ratio setting method determines a provisional inertia ratio and adjusts the gain, taking into account the maximum range of inertia ratio variation, thereby minimizing the occurrence of vibrations as much as possible even when the load is moved to various positions within the driving range.

The disclosed technology can also be understood from the perspective of an inertia ratio setting device that executes the above-mentioned servo motor inertia ratio setting method.

The disclosed technology makes it possible to reduce the frequency of inertia ratio adjustments as much as possible.

FIG. 1 is a diagram illustrating an example of a servo system according to an embodiment. FIG. 2 is a diagram illustrating an example of a schematic configuration of a load machine. 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. FIG. 4 is a block diagram showing a schematic configuration of a servo driver and an adjustment support device according to the embodiment. FIG. 5 is a first diagram illustrating an example of a processing flow of the inertia ratio setting process in the embodiment. FIG. 6 is a second diagram illustrating an example of the processing flow of the inertia ratio setting process in the embodiment. FIG. 7 is a diagram schematically showing the calculation of the coefficient α used to calculate the provisional inertia ratio. FIG. 8 is a diagram schematically showing a first method for calculating the coefficient α used to calculate the provisional inertia ratio. FIG. 9 is a diagram schematically showing a second method for calculating the coefficient α used in calculating the provisional inertia ratio. FIG. 10 is a diagram illustrating an example of a processing flow of a process for determining a provisional inertia ratio. FIG. 11 is a diagram showing an example of a Bode diagram in a servo system according to a comparative example. FIG. 12 is a diagram illustrating an example of a Bode diagram in the servo system according to the embodiment.

Embodiments will now be described with reference to the drawings. FIG. 1 shows 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 between the servo drivers 4a, 4b, and 4c. The servo system 1 is an example of a "servo system."

The load machine 2 is a multi-axis machine having multiple axes that may cause axis interference, such as a gantry mechanism or tandem mechanism. Figure 2 shows an example of the general 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 so as 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.

In the load machine 2, the first axis 21 is driven by a servo motor 3a, and the second axis 22 is driven by a 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 a 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."

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

Note that Figure 1 illustrates a configuration in which two axes, the first axis 21 and the second axis 22, are capable of causing shaft interference, and only one axis, the third axis 23, is capable of not causing shaft interference. However, a loaded machine with three or more axes capable of causing shaft interference may also be used. When a loaded machine with three or more axes capable of causing shaft interference is used, a servo motor, servo driver, and controller may be provided for each axis, and an adjustment support device 9 may be connected to each servo driver.

When adjusting the 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, the inertia ratio of each axis of the load machine 2 is estimated. For example, by employing the technology described in Patent Document 1 above, the inertia ratio can be estimated as accurately as possible.

However, even when the technology described in Patent Document 1 is adopted, 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. Figure 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 Figure 3 illustrates a state in which the estimated inertia ratio and the actual inertia ratio are equal. The line L2 in Figure 3 illustrates a state in which the actual inertia ratio is greater than the estimated inertia ratio. The line L3 in Figure 3 illustrates a state in which the actual inertia ratio is smaller than the estimated inertia ratio. Furthermore, "Kvp" in Figure 3 is the velocity proportional gain.

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.

Figure 4 is a block diagram showing the general configuration of the servo drivers 4a, 4b and the adjustment support device 9 in this embodiment. Figure 4 shows the servo drivers that control the first axis 21 and second axis 22, which may cause axis interference. Figure 4 also shows the controller 7. Below, the general configuration of the servo drivers 4a, 4b and the adjustment support device 9 will be explained with reference to Figure 4.

The servo driver 4a includes a control unit 41a that outputs a drive current to the servo motor 3a based on commands 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 are omitted. The servo driver 4a also includes an estimation unit 42a that estimates the inertia ratio. The estimation unit 42a can use the technology described in Patent Document 1, for example, as a method for estimating the inertia ratio. The servo driver 4a has a memory unit 43a that stores various information and a communication unit 44a for communicating with the outside. The servo driver 4b also includes a control unit 41b, an estimation unit 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 are omitted.

The controller 7 includes a signal relay unit 71 that relays the 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 numerical control programs, etc., memory, a communication unit, etc., but as these can be configured in a known manner as appropriate, detailed explanations will be omitted.

The adjustment support device 9 is configured, for example, by a computer having a CPU that executes a program for adjusting the inertia ratio (described below) 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.

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.

When the servo drivers 4a, 4b receive the provisional inertia ratio, the control units 41a, 41b store the received provisional inertia ratio in the memory units 43a, 43b. The provisional inertia ratio stored in the memory units 43a, 43b is used to set the inertia ratio in the control units 41a, 41b. The servo drivers 4a, 4b adjust the gain with the provisional inertia ratio set. Gain adjustments include, for example, adjusting the velocity proportional gain and position proportional gain.

When gain adjustment in the servo drivers 4a and 4b is complete, 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 and 4b via the signal relay unit 71.

When the servo drivers 4a, 4b receive the inertia ratio, the control units 41a, 41b store the received inertia ratio in the memory units 43a, 43b. The inertia ratio stored in the memory units 43a, 43b is used to set the inertia ratio in the control units 41a, 41b.

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

In S1, the variable i that identifies the axis for which inertia ratio estimation is to be 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 experience axis interference with each other, are assigned unique numbers starting from 1 to identify the axes, and the axis identified in this way will be described as the i-th axis.

In S2, the load machine 2 attempts a positioning operation involving multiple 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 specified memory area provided in the inertia ratio acquisition unit 91.

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

In S6, i is incremented. Then, the processing from S2 onwards is executed for the axis indicated by the incremented i.

In S7, the inertia ratio setting control unit 92 reads the estimated inertia ratio value 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 inertia ratio value by a predetermined coefficient α. The process of determining the provisional inertia ratio will be described in detail later.

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.

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

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

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.

<Calculation of coefficient α>
7 is a diagram schematically illustrating 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 multiple positions, and the servo drivers 4a and 4b estimate the inertia ratio at each position. The example of FIG. 7 illustrates a state in which the precision stage 24 is moved to the positions indicated by the circled numbers "1,""2,""3," and "4," and the servo drivers 4a and 4b estimate the inertia ratio.

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 Figure 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.

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 communication units 44a and 44b and recorded in a predetermined memory area provided in the inertia ratio acquisition unit 91. The process of estimating the inertia ratio for each axis described with reference to Figure 7 is executed, for example, in steps S1 to S5 and S6 in Figure 5. Here, the following two methods can be used to calculate the coefficient α using the estimated inertia ratio.

Figure 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 Figure 8 correspond to the circled numbers "1," "2," "3," and "4," respectively, in Figure 7. Figure 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 of 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.

In the first method for calculating the coefficient α, the inertia ratio setting control unit 92 calculates the average value of the estimated inertia ratios for each of the first axis 21 and the second axis 22, while the precision stage 24 is moved to the circled numbers "1," "2," "3," and "4." 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 furthest from the average value.

Figure 9 is a schematic diagram showing a second method for calculating the coefficient α used to calculate the provisional inertia ratio. In this 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 Figure 9 correspond to the circled numbers "1," "2," "3," and "4" in Figure 7, respectively. The example in Figure 9 illustrates a state in which the precision stage 24 is moved to the positions of 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 of circled numbers "2" and "4," where the inertia ratio is estimated by the servo driver 4b. The positions of circled numbers "1" and "3" correspond to when the precision stage 24 is located on the first axis 21, and the positions of circled numbers "2" and "4" correspond to when the precision stage 24 is located on the second axis 22.

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 for the first axis 21 in each of the states in which the precision stage 24 is positioned on the first axis 21 (states indicated by the circled numbers "1" and "3" in Figure 7). 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 inertia ratio estimated for the first axis 21 that is furthest from the average value.

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 (the 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 of 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):

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

Figure 10 shows an example of the processing flow for determining a tentative inertia ratio. The processing in Figure 10 is executed in S7 of Figure 5. Below, an example of the processing flow for determining a tentative inertia ratio will be described with reference to Figure 10.

In S21, the variable i, which identifies the axis for which the provisional inertia ratio is to be determined, is set to i = 1. Here, the axes for which the provisional inertia ratio is to be determined are multiple axes that may cause axis interference (e.g., first axis 21, second axis 22).

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 Figures 8 and 9.

In S24, the inertia ratio setting control unit 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.

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

In S26, i is incremented. Then, the processing from S22 onwards is executed for the axis indicated by the incremented i.

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. Figure 11 is a diagram showing an example of a Bode plot for a servo system according to the comparative example. Figure 12 is a diagram showing an example of a Bode plot for servo system 1 according to the embodiment. The vertical axis of Figures 11 and 12 represents gain (dB), and the horizontal axis represents frequency (Hz).

11 and 12, in the comparative example of Fig. 11, gain adjustment after setting a tentative inertia ratio was omitted, and as a result, although the gain decreases overall as the frequency increases, a gain exceeding 0 dB was confirmed at a frequency of around 10 ³ Hz, and it can be seen that vibration occurs 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 of 0 dB or more occurs, and it can be seen that vibration occurring in the load machine 2 is suppressed.

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

The inertia ratio varies depending on the position of the precision stage 24. In this embodiment, as illustrated in Figure 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, based on the multiple estimated inertia ratios, the coefficient α is determined, and a provisional inertia ratio is determined. By using the inertia ratio 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.

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. The coefficient α is then determined based on the estimated inertia ratio. For each axis, the farthest and closest positions from the driving motor are considered to be the positions with the largest fluctuations in the inertia ratio. The coefficient α is calculated based on the estimated inertia ratio with the precision stage 24 positioned in such a position, and a provisional inertia ratio determined using the calculated α is set and gain adjustment is performed. This suppresses vibration when the precision stage 24 is moved to various positions on the axis.

In the process of S12 in FIG. 6, the inertia ratio setting control unit 92 may set the average value of all inertia ratios recorded in S5 to the servo drivers 4a, 4b. In other words, 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 each of the servo drivers 4a, 4b. Being able to set a uniform inertia ratio simplifies the process.

<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;
a determination process (S7) for determining a provisional 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 (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 provisional inertia ratio;
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 of the acquired servo motors, for each of the plurality of servo motors,
How to set the inertia ratio of a servo motor.

<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), comprising:
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 ratios 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;
and executing a second setting process after the adjustment process to set 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 to each of the plurality of servo motors.
Inertia ratio setting device (9).

DESCRIPTION OF SYMBOLS 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. First axis 22. Second axis 23. Third axis 24. Precision stage 41a. Control unit 41b. Control unit 42a. Estimation unit 42b. Estimation unit 43a. Storage unit 43b. Storage unit 44a. Communication unit 61. Control unit 71. Signal relay unit 91. Inertia ratio acquisition unit 92. Inertia ratio setting control unit

Claims (3)

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. 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. 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 the 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.