Method for automatic tuning of a servo amplifier and motor control device

Abstract

In automatic tuning of a servo amplifier for servo control of a motor, the automatic tuning can be performed regardless of the size of a load connected to the motor, and control parameters of a position command filter can also be optimized. Before tuning of a gain of the servo amplifier is performed, the following processes are executed: a process (103) of estimating an inertia ratio related to the motor, based on a response of the motor when the motor is driven at a speed slower than a speed used at the time of the gain tuning; and an initial value decision process (104) of deciding initial values of the control parameters of the position command filter at the time of the automatic tuning, based on the inertia ratio.

Description

Technical Field

[0001] This invention relates to servo control of the rotational position of a motor based on position commands, and particularly to an automatic tuning method for a servo amplifier for servo control and a motor control device for performing the automatic tuning method. Background Technology

[0002] If a servo motor is driven by rapidly changing position commands, the motor's position will oscillate back and forth around the target position, sometimes causing instability in the motor's operation. Furthermore, the time to reach the target position may sometimes increase. To ensure stable motor operation and improve stability by smoothly following position commands, the input position command needs to be smoothed and filtered in the servo amplifier used to drive the motor. Servo control is then performed based on the filtered position command. The filter used for smoothing the position command is called a position command filter, and it can be composed of, for example, a low-pass filter or a moving average filter. Control parameters in the position command filter, such as the time constant or cutoff frequency and the number of moving averages, need to be appropriately determined according to the load connected to the motor. Additionally, in the servo amplifier, position gain, feedforward gain, and speed gain, which are generally referred to as gain or gain parameters, are also set as control parameters. The value of the gain also needs to be appropriately determined according to the load.

[0003] As a technique for setting control parameters, Patent Document 1 discloses the following: For various control parameters used in a servo amplifier, multiple representative combinations of the values ​​of these control parameters are prepared in advance and stored in a table. The combination of control parameter values ​​is read from the table based on the load stiffness value, and each control parameter in the servo amplifier is set based on the read values. According to the technique described in Patent Document 1, the gain of the servo amplifier is set based on the load stiffness value, and the cutoff frequency of the position command filter is set. Patent Document 2 discloses a method for automatically calculating control parameters used in the position command filter, position control unit, speed control unit, and current control unit based on a responsiveness setting signal indicating the desired response speed and a load machinery type discrimination signal indicating the type of load.

[0004] Since the control parameters set for the servo amplifier depend on the load connected to the motor, an automatic tuning technique has been proposed to automatically set these control parameters in the servo amplifier according to the load in order to cope with various loads. Automatic tuning technique determines each control parameter based on the response of the motor when it is driven with the load connected to it. As an example of automatic tuning technique, Patent Document 3 discloses a motor control device comprising: a servo amplifier; an automatic tuning unit that measures the magnitude of the load inertia of the mechanical system and automatically determines the control gain; a gain storage unit that stores the determined gain; and a gain readout unit that reads out the stored gain and sets it in the servo amplifier based on the input command value and the response of the controlled object. Patent Document 3 does not disclose the automatic setting of the control parameters for a position command filter that filters position commands. Regarding the position command filter, it is known that when the position command filter is a moving average filter, the vibration period of the position deviation when driving the motor is measured, and the number of moving averages in the position command filter (using the values ​​of several consecutive data points in the calculation of the moving average) is adjusted according to this vibration period.

[0005] [Existing Technical Documents]

[0006] [Patent Literature]

[0007] Patent Document 1: Japanese Patent Application Publication No. 2007-336792

[0008] Patent Document 2: Japanese Patent Application Publication No. 2011-97758

[0009] Patent Document 3: Japanese Patent Application Publication No. 9-9662 Summary of the Invention

[0010] When autotuning is performed based on the response of the motor driven under load and motor connection conditions, the vibration period of the position deviation cannot be measured until the autotuning termination condition is met, or when no vibration occurs in the position deviation, the control parameters of the position command filter remain at their initial values ​​instead of being set to optimal values. For example, if the mass or inertia (momentum of inertia) of the load is sufficiently large compared to the motor rotor, and the control parameters of the position command filter are values ​​that essentially do not smooth the position command, the torque command value caused by the position deviation becomes excessive during autotuning, sometimes necessitating termination of autotuning for safety reasons. In this case, the control parameters of the position command filter remain unchanged at their initial values ​​and are not optimized. Furthermore, in this case, the values ​​of each gain also remain at their initial values ​​and are not optimized. On the other hand, if autotuning is performed with the control parameters set to values ​​that excessively smooth the position command, vibration is unlikely to occur in the position deviation, making it impossible to measure the vibration period, and thus, optimization of the control parameters of the position command filter is also impossible.

[0011] The object of the present invention is to provide an automatic tuning method and a motor control device for implementing such an automatic tuning method, which can perform automatic tuning regardless of the magnitude of the load connected to the motor, and can also optimize the control parameters of the position command filter.

[0012] The automatic tuning method of the present invention is an automatic tuning method of a servo amplifier that smooths position command input from an external source and feeds back the position of the motor, and controls the position of the motor based on the position command. It includes: a step of estimating the inertia ratio related to the motor based on the motor's response when the motor is driven at a first speed; and an initial value setting step of setting the initial value of the control parameters of the position command filter based on the inertia ratio.

[0013] In the automatic tuning method of this invention, in order to execute a series of automatic tuning actions, a motor is driven, the inertia ratio related to the motor is determined, and an initial value for the control parameters of the position command filter used for automatic tuning is set based on the inertia ratio. Therefore, when the inertia ratio is large, the initial value of the control parameters of the position command filter becomes, for example, a value that smooths the position command to a greater extent. As a result, it prevents the torque command value from becoming too large during automatic tuning, increasing the likelihood that automatic tuning will be completed. Even if automatic tuning is stopped under insufficient conditions, the initial value of the control parameters of the position command filter determined based on the inertia ratio is a value close to the optimal value for the control parameters of the position command filter. Even without optimization of the control parameters of the position command filter, it is a value that can be directly and safely used in the actual use of the servo amplifier. When the inertia ratio is small, the initial value of the control parameters of the position command filter becomes, for example, a value that does not essentially smooth the position command. Therefore, the vibration period in the position deviation is easily detected during automatic tuning, and the optimization of the control parameters of the position command filter can be reliably performed.

[0014] In the automatic tuning method of the present invention, the position command filter is, for example, a moving average filter, and the control parameter of the position command filter is the moving average number in the moving average filter. In this case, during the initial value setting process, the larger the inertia ratio, the larger the moving average number. If a moving average filter is used as the position command filter, the value obtained by multiplying the estimated inertia ratio by an appropriate coefficient can be set as the moving average number as the control parameter of the position command filter, thus simplifying the calculation process for setting the control parameter of the position command filter.

[0015] In the automatic tuning method of the present invention, it is preferable to perform a gain tuning step after the initial value setting step, which automatically tunes multiple gains in the servo amplifier that are the targets of automatic tuning. The gain tuning step is a step of determining the set values ​​for each of the multiple gains based on the motor response when a position command is provided to the motor via a position command filter whose control parameters are set to initial values. By implementing the gain tuning step using the initial value of the control parameters of the position command filter determined based on the inertia ratio, as described above, the possibility of stopping gain tuning midway is reduced, it is easier to set each gain to its optimal value, and it is also easier to set the control parameters of the position command filter to their optimal value.

[0016] In the automatic tuning method of the present invention, it is preferable to drive the motor at a second speed, which is faster than the first speed, during the gain tuning process. This reduces the possibility of the gain tuning stopping midway or not being fully completed, and enables the gain tuning process to be completed in a short time under conditions close to actual use.

[0017] In the automatic tuning method of the present invention, it is preferable to prepare multiple gain sets by combining the values ​​of multiple gains as gain sets, and then perform the following steps in the gain tuning process: a response detection step, selecting a gain set from the multiple gain sets, and determining the motor response when each of the multiple gains in the gain set is applied to the servo amplifier; and a step of repeatedly performing the response detection step on different gain sets in the multiple gain sets, determining the optimal gain set from the multiple gain sets, and setting the values ​​of each of the multiple gains in the optimal gain set as set values. By preparing multiple gain sets in advance and selecting the optimal gain set from them based on the motor response, the time and manpower required to perform the gain tuning process can be significantly reduced. At this time, it is preferable to set the gain set initially selected in the response detection step according to the inertia ratio. When selecting the optimal gain set through trial and error when the inertia ratio is large, if a gain set that is sensitive to the response of the servo amplifier is initially used, the torque command value becomes too large at that moment, resulting in an error, and the gain tuning process may be aborted. By determining the initially selected gain set according to the inertia ratio, the gain tuning can be completed more reliably and normally.

[0018] In the automatic tuning method of the present invention, it is preferable that, during the implementation of the gain tuning step, when vibration occurs due to the position deviation of the motor, the control parameters of the position command filter are updated according to the vibration period. By updating the control parameters of the position command filter according to the vibration period, the control parameters of the position command filter can be made to optimal values.

[0019] In the automatic tuning method of the present invention, a step of driving the motor at a speed slower than the first speed and confirming the motor's range of motion can be performed before the step of estimating the inertia ratio. By confirming the motor's range of motion while driving it at a low speed, situations such as collisions with other objects in subsequent steps can be avoided.

[0020] The motor control device of the present invention is a motor control device that controls a motor according to a position command input from an external source. It includes: a servo amplifier having a position command filter that smooths the position command, feeding back the position of the motor, and controlling the position of the motor according to the position command; and a parameter setting unit connected to the servo amplifier, which can output the position command to the servo amplifier for automatic tuning of the control parameters used in the servo amplifier, and set the control parameters in the servo amplifier. The parameter setting unit outputs the position command that drives the motor at a first speed to the servo amplifier, estimates the inertia ratio related to the motor based on the motor response, and sets the initial value of the control parameters of the position command filter according to the inertia ratio.

[0021] In the motor control device of the present invention, a parameter setting unit for performing automatic tuning of a servo amplifier is provided. The parameter setting unit first drives the motor, calculates the motor's inertia ratio, and sets initial values ​​for the control parameters of the position command filter used for automatic tuning based on the inertia ratio. Therefore, when the inertia ratio is large, the initial values ​​of the control parameters of the position command filter become, for example, values ​​that smooth the position command to a greater extent, increasing the likelihood that automatic tuning will be completed to the end. Even if automatic tuning stops midway, the initial values ​​of the control parameters of the position command filter are close to the optimal values ​​for the position command filter control parameters, values ​​that can be directly and safely used in the actual use of the servo amplifier. Furthermore, when the inertia ratio is small, the initial values ​​of the control parameters of the position command filter are, for example, set to values ​​that substantially do not smooth the position command, making it easier to detect the vibration period in the position deviation during automatic tuning and facilitating the optimization of the control parameters of the position command filter.

[0022] In the motor control device of the present invention, the position command filter is, for example, a moving average filter, and the control parameter of the position command filter is the number of moving averages in the moving average filter. In this case, the larger the inertia ratio, the larger the number of moving averages set as the initial value by the parameter setting unit. With this configuration, the calculation process for setting the control parameters of the position command filter in the parameter setting unit can be simplified.

[0023] In the motor control device of the present invention, it is preferable that after the parameter setting unit sets the initial value of the control parameters of the position command filter, it performs gain tuning in the servo amplifier based on the motor's response when a position command is output to the servo amplifier and the motor is driven at a second speed. This tuning determines the set values ​​of multiple gains that are subject to automatic tuning. By using the initial value of the control parameters of the position command filter, which is determined based on the inertia ratio, to perform gain tuning, the possibility of stopping midway is reduced, and it is easy to set each gain to its optimal value, as well as to set the control parameters of the position command filter to their optimal value.

[0024] In the motor control device of the present invention, it is preferable that the second speed is faster than the first speed. This reduces the possibility of gain tuning stopping midway or not being fully completed, and enables the gain tuning process to be completed in a short time under conditions close to actual use.

[0025] In the motor control device of the present invention, a gain set storage unit is preferably provided. This gain set storage unit stores multiple gain sets as combinations of individual gain values. When performing gain tuning, the parameter setting unit repeatedly selects a gain set from the multiple gain sets stored in the gain set storage unit and calculates the motor response when each gain in that gain set is applied to a servo amplifier, thereby determining the optimal gain set and setting the individual gain values ​​of the multiple gains in the optimal gain set as set values. By preparing multiple gain sets in advance and storing them in the gain set storage unit, and determining the optimal gain set based on the motor response, the time and effort required for gain tuning can be significantly reduced. In this case, it is preferable to set the gain set initially selected by the parameter setting unit from the multiple gain sets stored in the gain set storage unit based on the inertia ratio. If configured in this way, the possibility of gain tuning being interrupted due to errors during gain tuning when selecting the optimal gain set is reduced.

[0026] In the motor control device of the present invention, it is preferable that when vibration occurs in the position deviation of the motor during gain tuning, the parameter setting unit updates the control parameters of the position command filter according to the period of vibration. By updating the control parameters of the position command filter according to the period of vibration, the control parameters of the position command filter can be made to the optimal value.

[0027] In the motor control device of the present invention, the parameter setting unit outputs a position command to the servo amplifier to drive the motor at a speed slower than the first speed before estimating the moment of inertia ratio, thereby confirming the motor's range of motion. By confirming the motor's range of motion while driving it at a low speed, situations such as collisions with other objects during moment of inertia ratio estimation or automatic tuning can be avoided.

[0028] According to the present invention, automatic tuning can be performed regardless of the magnitude of the load connected to the motor, and the control parameters of the position command filter can also be optimized. Attached Figure Description

[0029] Figure 1 This is a block diagram illustrating a servo amplifier.

[0030] Figure 2 This is a flowchart illustrating the automatic tuning process.

[0031] Figure 3 This is a flowchart illustrating the gain tuning process.

[0032] Figure 4 This is a block diagram illustrating another servo amplifier. Detailed Implementation

[0033] Next, the method for carrying out the present invention will be described with reference to the accompanying drawings. Figure 1 The diagram illustrates the structure of a servo amplifier 10 employing an automatic tuning method according to one embodiment of the present invention. A motor 40 is connected to the servo amplifier 10, and an encoder 41 for detecting the rotational position of the motor 40 is attached to the motor 40. Although not shown, a load can be mechanically connected to the motor 40. The encoder 41 sends a feedback signal indicating the rotational position of the motor 40 to the servo amplifier 10. The feedback signal can be an encoder pulse or digital data indicating an instantaneous value of the rotational position of the motor 40.

[0034] The servo amplifier 10 executes servo control of the motor 40 based on the command position input from the outside (i.e., the target position of the motor 40) to make the position of the motor 40 the command position. The servo amplifier 10 includes: a position command filter 11 that smooths the input position command and outputs an internal position command; a feedforward control unit 12 that performs feedforward control calculations based on the internal position command and outputs a feedforward command (FF command); a subtraction unit 13 that calculates the position deviation by subtracting the current position of the motor 40 fed back via a feedback signal from the internal position command; a feedback control unit 14 that performs feedback control calculations based on the feedback signal and a torque command and outputs a feedback command (FB command); a subtraction unit 15 that calculates the torque command by subtracting the feedback command from the result of adding the feedforward command to the position deviation; a torque adjustment unit 16 that adjusts the torque command and outputs an adjustment command; and a current control unit 17 that generates current based on the adjustment command and actually drives the motor 40. When an excessively large torque command is input, the torque adjustment unit 16 limits the value of the torque command to ensure safety, etc.

[0035] The position command filter 11 can be any filter that smooths the position command, but a moving average filter is preferred. The moving average filter is characterized by the number of moving averages used to calculate the moving average from several consecutive data points (here, the position command), so the number of moving averages is a control parameter of the position command filter 11. When calculating the moving average, for example, when weighting data in a way that emphasizes the central portion of the moving average interval, the moving average function showing this weighting degree is also called a control parameter. When the position command filter is a low-pass filter, the time constant or cutoff frequency of the low-pass filter can be used as a control parameter of the position command filter. Hereinafter, assuming the position command filter 11 is a moving average filter, the number of moving averages is used as a control parameter of the position command filter 11.

[0036] The feedforward control unit 12 performs feedforward compensation through calculation, and for example, two control gains are used for this calculation. The feedback control unit 14 is configured as an observer to estimate the state of the controlled object and performs feedback control; for its calculation, for example, two control gains, damping ratio and integral gain, are used. As a result, in Figure 1 In the servo amplifier shown, for it to operate, the moving average number of the position command filter 11, the damping ratio or each gain used in the feedforward control unit 12 and the feedback control unit 14 need to be set as control parameters.

[0037] Next, regarding Figure 1 The automatic tuning of the servo amplifier 10 shown will be explained. The purpose of this automatic tuning is to automatically calculate the optimal values ​​of each control parameter that should be set in the servo amplifier 10 when a load is connected to the motor 40, or when the load connected to the motor 40 changes, and set these optimal values ​​as the actual control parameters in the servo amplifier 10. A parameter setting unit 50 for performing automatic tuning is connected to the servo amplifier 10. The parameter setting unit 50 has the following functions: setting initial values ​​of control parameters in the servo amplifier 10; generating position commands for performing automatic tuning and outputting them to the servo amplifier 10; determining the optimal values ​​of each control parameter based on the response of the controlled object at this time (actually, the response of the motor 40 obtained through feedback signals); and setting the determined optimal values ​​as control parameters in the servo amplifier 10. The parameter setting unit 50 is connected to a gain set storage unit 51 that pre-stores the gain set described later. In the following description, control parameters other than the control parameters of the position command filter 11 among the control parameters set for the servo amplifier 10 will be collectively referred to as gains. Therefore, in addition to integral gain and control gain, the damping ratio used in the feedback control unit 14 is also included in the scope of gain. Furthermore, the tuning of gain in the automatic tuning of control parameters is called gain tuning. The inertia ratio is the value obtained by dividing the sum of the load's inertia and the inertia of the motor 40's rotor by the inertia of the motor 40's rotor.

[0038] During autotuning, if the initial value of the control parameters (e.g., the number of moving averages) of the position command filter 11 is inappropriate at the start of autotuning, autotuning cannot be completed, or even the control parameters of the position command filter 11 can not be automatically tuned. Therefore, in this embodiment, the control parameters of the position command filter 11 used in autotuning are determined before autotuning. Figure 2 This is a flowchart illustrating the automatic tuning steps in this embodiment.

[0039] First, in step 101, the parameter setting unit 50 sets initial values ​​for each gain in the servo amplifier 10 as initial settings, and sets initial values ​​for the control parameters (in this case, the number of moving averages) of the position command filter 11. The initial values ​​set here are not used in automatic tuning, but are used in the previous stage (the movable range confirmation in step 102 and the inertia ratio estimation in step 103).

[0040] Next, in step 102, the parameter setting unit 50 outputs a position command to the servo amplifier 10 to rotate the motor 40 at a low speed (e.g., 100 revolutions per minute) to confirm the movable range of the motor 40. The position indicated by the position command provided to the servo amplifier 40 from the parameter setting unit 50 (or from an external source) is a position within the range where the motor 40 can rotate without colliding with other objects. However, for some reason, the movement path of the load may sometimes be obstructed by objects. Therefore, since it is dangerous to perform automatic tuning under conditions where the load collides with an object, the movable range is confirmed in advance. If a collision occurs, the rotation of the motor 40 is obstructed, and the motor 40 is overloaded. Therefore, after detecting the overload, the parameter setting unit 50 terminates the automatic tuning process as a tuning failure. In addition, since the motor 40 is operated at a low speed, noise accompanying the operation of the motor 40 is usually not generated. However, if noise is generated, the parameter setting unit 50 resets the gain values ​​in the servo amplifier 10 to values ​​that are less likely to generate noise and checks the range of motion again. If noise is generated even after this, the automatic tuning process is terminated as a tuning failure.

[0041] After performing the movable range confirmation, in step 103, the parameter setting unit 50 outputs a position command to the servo amplifier 10 to rotate the motor 40 at a faster speed (e.g., 500 revolutions per minute) than when the movable range was confirmed, and performs an inertia ratio estimation. It is well known that the sum of the load inertia and the rotor inertia of the motor 40 can be estimated based on the torque command or adjustment command to the motor 40 and the position of the motor 40 obtained via feedback signals. Since the rotor inertia of the motor 40 is known, the inertia ratio can be calculated by dividing the sum of the load inertia and the rotor inertia by the rotor inertia. If an overload of the motor 40 is detected during the inertia ratio estimation, the parameter setting unit 50 also terminates the auto-tuning process as a tuning failure. Furthermore, if noise accompanying the operation of the motor 40 is generated at this stage, the parameter setting unit 50 resets the gain values ​​in the servo amplifier 10 to values ​​that are less likely to generate noise, and performs the inertia ratio estimation again. If noise is still generated even after this, the auto-tuning process is terminated as a tuning failure.

[0042] If the inertia ratio estimation is complete, then in step 104, the parameter setting unit 50 calculates the initial values ​​of the control parameters for the position command filter 11 used during actual autotuning. In the example described here, the control parameter is the number of moving averages, and the initial value of the number of moving averages is set such that the larger the inertia ratio, the more moving averages are used. As an example, a minimum value for the number of moving averages (e.g., 10 times) can be predetermined, and the value obtained by multiplying the inertia ratio by a constant and rounding it up is compared with the minimum value of the number of moving averages. The larger value is determined as the initial value of the number of moving averages. If the constant is 0.1 and the inertia ratio is 255, then the initial value of the number of moving averages is 26. The parameter setting unit 50 sets the number of moving averages calculated in this way as the initial value of the control parameters for the position averaging filter 11 in the position averaging filter 11. As a result, the position averaging filter 11 is set such that the larger the inertia ratio, the greater the smoothing of the position command. When the position averaging filter 11 is, for example, a low-pass filter, the control parameters of the position averaging filter 11 can be set in such a way that the larger the inertia ratio, the lower the cutoff frequency (i.e., the longer the time constant).

[0043] If the initial values ​​of the control parameters of the position command filter 11 are set, the parameter setting unit 50 then outputs a position command to the servo amplifier 10 in step 105, causing the motor 40 to rotate at a speed faster than the estimated moment ratio (e.g., 1000 revolutions per minute), and performs gain tuning. Gain tuning is, for example, a process that, while driving the motor 40 by changing the values ​​of each gain set in the servo amplifier 10, finds the gain that makes the response of the system consisting of the motor 40 and the load most ideal, for example, the torque command is not too large, the position deviation does not cause vibration, and the settling time is the shortest. If the position deviation causes vibration during the gain tuning process, the control parameters of the position command filter 11 are updated based on the vibration period.

[0044] In gain tuning, the optimal gain value is determined through trial and error by changing the values ​​of each gain. However, when there are many gains to be tuned, the number of trials becomes enormous if the values ​​of each gain are changed independently while performing gain tuning, requiring a significant amount of time. Therefore, in this embodiment, the combination of the individual values ​​of the multiple gains to be tuned is called a gain set, and multiple (e.g., dozens) such gain sets are prepared in advance and stored in the gain set storage unit 51. Assuming that the load on the motor 40 is the same, the gain sets include those where the system response is faster, rigidity is greater, settling time is shorter, and vibration or noise is more likely to occur, as well as those where the system response is slower, rigidity is lower, settling time is longer, and vibration and noise are less likely to occur. Then, the parameter setting unit 50 reads the gain sets one by one from the gain set storage unit 51, sets the values ​​in the read gain sets as the individual gains of the servo amplifier 10, and repeatedly examines the response of the motor 40 to find the gain set that provides the best response. This found gain set is called the optimal gain set. Then, the parameter setting unit 50 determines the value of each gain in the optimal gain set as the actual value of the gain of the servo amplifier 10, and ends the gain tuning.

[0045] However, when the inertia ratio is large, if a gain set with a fast response or short settling time is applied to the servo amplifier 10, the torque command value will be too large, resulting in an error, which may terminate the gain tuning process. When determining the optimal gain set through trial and error, the gain set selected from the gain set storage unit 51 after the second selection is based on the response to the previous gain set, thus minimizing problems. However, if an inappropriate gain set is selected initially, gain tuning will be aborted. Therefore, in this embodiment, when initially selecting a gain set from the multiple gain sets in the gain set storage unit 51, i.e., when selecting the initial value gain set, the gain set set set according to the inertia ratio is selected. As an example, assuming the load connected to the motor 40 is the same, the gain sets stored in the gain set storage unit 51 are sequentially numbered from 1 to 25 in order of slow to fast response or long to short settling time. In this case, if the inertia ratio is less than 250, the 25th gain set can be used as the initial value; if the inertia ratio is greater than 250 but less than 800, the gain sets up to the 15th can be used as the initial value; similarly, if the inertia ratio is greater than 5000, the 5th gain set can be used as the initial value.

[0046] Figure 3This is a flowchart summarizing the gain tuning process described above. In step 111, the parameter setting unit 50 selects a gain set determined based on the inertia ratio from multiple gain sets stored in the gain set storage unit 51. In step 112, the selected gain set is applied to the servo amplifier 10, and the motor 40 is driven by a position command. The response from the motor 40 is observed. Then, in step 113, the parameter setting unit 50 determines whether vibration has occurred in the position deviation of the motor 40. If vibration has occurred, in step 114, the control parameters of the position command filter 11 are reset according to its vibration period, and the process proceeds to step 115. If no vibration is detected in step 113, the process directly transfers to step 115. In step 115, the parameter setting unit 50 determines whether the currently selected gain set is the optimal gain set based on the response of the motor 40. If it is the optimal gain set, in step 116, the parameter setting unit 50 sets the values ​​in the optimal gain set as the actual values ​​used for each gain of the servo amplifier 10, and the gain tuning process ends. On the other hand, if the optimal gain set is not determined in step 115, the parameter setting unit 50 selects another gain set from the gain set storage unit 51 in step 117 and performs the processing that started from step 112.

[0047] After the gain tuning in step 105 described above is completed, the parameter setting unit 50 outputs a position command to the servo amplifier 10, causing the position of the motor 40 to return to its initial position. This is because the motor 40 was driven in step 102 (confirmation of the movable range), step 103 (estimation of the inertia ratio), and step 105 (gain tuning), and its position has moved away from the initial position before the start of a series of automatic tuning processes.

[0048] In the automatic tuning method of this embodiment described above, the inertia ratio is estimated before gain tuning, and the initial value of the control parameters of the position command filter 11 is set based on the estimated inertia ratio. This avoids the situation where the torque command value becomes excessively large due to a large inertia ratio, causing errors and interrupting automatic tuning midway. Compared to existing examples where the initial value of the control parameters of the position command filter 11 is not set based on the inertia ratio, the number of cases where automatic tuning is interrupted midway is reduced under the same load conditions, and the operating characteristics of the servo amplifier 10 set by automatic tuning are also improved. Furthermore, even when the automatic tuning ends in an incomplete state, a more appropriate value can be set as the control parameter of the position command filter 11 compared to existing examples. Furthermore, in this embodiment, when performing gain tuning using a gain set, the initial value of the gain set is determined based on the inertia ratio, thus reducing the occurrence of errors in the early stages of gain tuning.

[0049] The structure of a servo amplifier that can be applied to the automatic tuning method of the present invention is not limited to... Figure 1The structure shown allows any servo amplifier that provides feedback on the motor's position in some way to apply the automatic tuning method based on this invention. Figure 4 Another servo amplifier to which the automatic tuning method according to the present invention can be applied is shown.

[0050] Figure 4 The servo amplifier 10 shown drives the motor 40 based on position commands input from an external source, and Figure 1 The servo amplifier shown also includes a position command filter 11, a torque adjustment unit 16, and a current control unit 17, and is connected to a parameter setting unit 50. A position control unit 22 is provided that receives an internal position command from the position command filter 11. The position control unit 22 is configured to receive a feedback signal indicating the position of the motor 40 from an encoder connected to the motor 40, calculate the deviation between the internal position command and the position of the motor 40 (i.e., the position deviation), apply a position gain Kp to it, and output a speed command. The output from the position control unit 22 is input to the speed control unit 23. A differential unit 24 is also provided in the servo amplifier 10 to calculate the speed of the motor 40 based on the feedback signal. The speed control unit 23 is configured to calculate the deviation between the speed command and the speed of the motor 40, apply a speed gain Kv to it, and output a torque command. The torque command and... Figure 1 As shown, the input is sent to the torque adjustment unit 16. Furthermore, in the servo amplifier 10, a selector 21 is provided before the position control filter 11. The selector 21 is controlled according to the signal from the parameter setting unit 50, switching between the position command provided externally and the position command output from the parameter setting unit 50, and providing them to the position command filter 11.

[0051] Figure 4 The control parameters in the servo amplifier 10 shown are the control parameters of the position command filter 11, the position gain Kp, and the speed gain Kv. A feedback signal from the encoder 41 is input to the parameter setting unit 16, and an adjustment command for estimating the inertia ratio is input from the torque adjustment unit 16. The parameter setting unit 50 performs the inertia ratio estimation in the same manner as described above, sets the initial values ​​of the control parameters of the position command filter 11, and performs gain tuning related to the position gain Kp and speed gain Kv.

[0052] Symbol Explanation

[0053] 10 servo amplifiers

[0054] 11 Position Command Filter

[0055] 12 Feedforward Control Unit

[0056] Subtraction Units 13 and 15

[0057] 14 Feedback Control Department

[0058] 16 Torque Adjustment Section

[0059] 17 Current Control Section

[0060] 21 selector

[0061] 22 Position Control Unit

[0062] 23 Speed ​​Control Department

[0063] 24 differential units

[0064] 40 motors

[0065] 41 encoder

[0066] 50 parameter setting section

[0067] 51 Gain Set Storage Unit.

Claims

1. An automatic tuning method, which is an automatic tuning method in a servo amplifier, the servo amplifier having a position command filter for smoothing position commands input from an external source, feedback of the position of a motor, and control of the position of the motor according to the position commands. The automatic tuning method is characterized by comprising: The process of estimating the inertia ratio associated with the motor based on the motor's response when the motor is driven at a first speed, wherein the inertia ratio is the value obtained by dividing the sum of the inertia of the load connected to the motor and the inertia of the motor's rotor by the inertia of the motor's rotor. The initial value setting process for setting the initial value of the control parameters of the position command filter according to the inertia ratio; as well as Based on the motor's response when a position command is provided to the motor via a position command filter whose control parameters are set to the initial value, a gain tuning process is determined for the respective set values ​​of multiple gains in the servo amplifier that become targets for automatic tuning. The combination of the individual values ​​of the multiple gains is used as a gain set, and multiple gain sets are prepared. The gain tuning process includes: A response detection process is performed by selecting one gain set from the plurality of gain sets and determining the response of the motor when the plurality of gains in the gain set are respectively applied to the servo amplifier. as well as The process involves repeatedly performing the response detection step on different gain sets within the plurality of gain sets, determining the optimal gain set from the plurality of gain sets, and using the values ​​of each of the plurality of gains in the optimal gain set as the set value. The gain set selected when initially performing the response detection process is set according to the inertia ratio.

2. The automatic tuning method as described in claim 1, characterized in that, The position command filter is a moving average filter, and the control parameter of the position command filter is the number of moving averages in the moving average filter. In the initial value setting process, the larger the inertia ratio, the larger the number of moving averages.

3. The automatic tuning method as described in claim 1, characterized in that, In the gain tuning process, the motor is driven at a second speed that is faster than the first speed.

4. The automatic tuning method according to any one of claims 1 to 3, characterized in that, When the position deviation of the motor causes vibration during the gain tuning process, the control parameters of the position command filter are updated according to the period of the vibration.

5. The automatic tuning method according to any one of claims 1 to 3, characterized in that, Prior to the step of estimating the inertia ratio, there is a step of driving the motor at a speed slower than the first speed and confirming the range of motion of the motor.

6. A motor control device that controls a motor based on position commands input from an external source, characterized in that, include: A servo amplifier having a position command filter that smooths the position command, provides feedback on the position of the motor, and controls the position of the motor based on the position command; as well as The parameter setting unit, connected to the servo amplifier, is capable of outputting position commands to the servo amplifier to automatically tune the control parameters used in the servo amplifier and setting the control parameters in the servo amplifier. The parameter setting unit outputs a position command to the servo amplifier to drive the motor at a first speed. Based on the motor's response, it estimates the inertia ratio associated with the motor. Based on the inertia ratio, it sets the initial values ​​of the control parameters of the position command filter. The inertia ratio is the value obtained by dividing the sum of the inertia of the load connected to the motor and the inertia of the motor's rotor by the inertia of the motor's rotor. After setting the initial values ​​of the control parameters of the position command filter, the parameter setting unit performs gain tuning in the servo amplifier based on the motor's response when a position command is output to the servo amplifier and the motor is driven at a second speed. This tuning determines the set values ​​of multiple gain parameters that will be automatically tuned. The motor control device further includes a gain set storage unit, which stores multiple gain sets by combining the values ​​of the multiple gains themselves. When performing gain tuning, the parameter setting unit repeatedly selects a gain set from the multiple gain sets stored in the gain set storage unit and calculates the motor response when the multiple gains in that gain set are applied to the servo amplifier, thereby determining the optimal gain set. The values ​​of the multiple gains in the optimal gain set are then used as the setting values. The gain set initially selected by the parameter setting unit from the plurality of gain sets stored in the gain set storage unit is set according to the inertia ratio.

7. The motor control device as described in claim 6, characterized in that, The position command filter is a moving average filter, and the control parameter of the position command filter is the number of moving averages in the moving average filter. The larger the inertia ratio, the larger the number of moving averages set to the initial value by the parameter setting unit.

8. The motor control device as described in claim 6, characterized in that, The second speed is a speed that is faster than the first speed.

9. The motor control device as described in any one of claims 6 to 8, characterized in that, When the position deviation of the motor causes vibration during the gain tuning process, the parameter setting unit updates the control parameters of the position command filter according to the period of the vibration.

10. The motor control device as described in any one of claims 6 to 8, characterized in that, Before estimating the inertia ratio, the parameter setting unit outputs a position command to the servo amplifier to drive the motor at a speed slower than the first speed, thereby confirming the motor's range of motion.

Images