JP7699504B2 - Servo amplifier autotuning method and motor control device - Google Patents

Description

The present invention relates to servo control that controls the rotational position of a motor based on a position command, and in particular to an auto-tuning method for a servo amplifier used in servo control, and a motor control device that executes the auto-tuning method.

When a servo motor is driven by a position command that changes abruptly, the motor's position may oscillate before and after the target position, causing the motor to lose operational stability, and the time it takes to reach the target position may become longer. In order to ensure the motor's operational stability and improve stabilization by enabling it to smoothly follow the position command, the servo amplifier used to drive the motor must perform filtering, for example, to smooth the input position command, and perform servo control based on the position command after filtering. The filter that smoothes the position command is called a position command filter, and is composed of, for example, a low-pass filter or a moving average filter. The control parameters of the position command filter, such as the time constant or cutoff frequency and the number of moving averages, must be appropriately determined according to the load connected to the motor. In addition, in the servo amplifier, the position gain, feedforward gain, and speed gain, which are generally called gain or gain parameters, are also set as control parameters. The gain value must also be appropriately determined according to the load.

As a technique for setting control parameters, Patent Document 1 discloses that, for various control parameters used in a servo amplifier, a number of representative combinations of the values of the control parameters are prepared in advance and stored in a table, a combination of the control parameter values is read from the table according to the stiffness value of the load, and each control parameter in the servo amplifier is set according to the read value. According to the technique described in Patent Document 1, the gain in the servo amplifier is set according to the stiffness value of the load, and the cutoff frequency of the position command filter is set. Patent Document 2 discloses automatic calculation of control parameters used in the position command filter section, position control section, speed control section, current control section, etc., based on a responsiveness setting signal indicating the desired response speed and a load machine type discrimination signal indicating the type of load.

Since the control parameters set in the servo amplifier depend on the load connected to the motor, an autotuning technique has been proposed that automatically sets these control parameters in the servo amplifier according to the load in order to accommodate various loads. The autotuning technique is a technique for determining each control parameter from the response when the motor is driven with the load connected to the motor. As an example of the autotuning technique, Patent Document 3 discloses a motor control device that includes a servo amplifier, an autotuning 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 reading unit that reads 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 automatic setting of the control parameters of a position command filter that performs filtering on a position command. Regarding the position command filter, when the position command filter is a moving average filter, it is known that it is sufficient to measure the vibration period in the position deviation when the motor is driven and adjust the moving average number in the position command filter (the value of how many consecutive data are used in calculating the moving average) according to the vibration period.

JP 2007-336792 A JP 2011-97758 A Japanese Patent Application Publication No. 9-9662

In the case of autotuning based on the response when the motor is driven with a load connected to it, if the vibration period of the position deviation cannot be measured before the autotuning termination condition is met, or if no vibration occurs in the position deviation, the control parameters of the position command filter remain at their initial values and are not set to their optimal values. For example, if the mass or inertia (moment of inertia) of the load is sufficiently large compared to the motor rotor, and the value of the control parameters of the position command filter is such that the position command is not smoothed much, the torque command value caused by the position deviation may become excessively large during autotuning, and autotuning may have to be terminated for safety reasons. In that case, the control parameters of the position command filter remain 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 when the control parameters are set to values that smooth the position command excessively, vibration in the position deviation becomes difficult to occur, and the vibration period cannot be measured, and in this case too, the control parameters of the position command filter cannot be optimized.

The object of the present invention is to provide an autotuning method that can perform autotuning regardless of the magnitude of the load connected to the motor and that can also optimize the control parameters of the position command filter, and a motor control device that implements such an autotuning method.

The autotuning method of the present invention is an autotuning method for a servo amplifier that has a position command filter that smoothes a position command input from the outside, feeds back the motor position, and controls the motor position based on the position command, and includes a step of estimating an inertia ratio for the motor based on the motor response when the motor is driven at a first speed, and an initial value setting step of setting an initial value for the control parameter of the position command filter based on the inertia ratio.

In the autotuning method of the present invention, in order to perform a series of autotuning operations, the motor is driven to obtain an inertia ratio for the motor, and the initial value of the control parameter of the position command filter for autotuning is set based on the inertia ratio. As a result, when the inertia ratio is large, the initial value of the control parameter of the position command filter is set to a value that, for example, smooths the position command to a greater extent, and as a result, the torque command value is prevented from becoming excessive during autotuning, and the possibility of performing autotuning to the end is increased. Even if autotuning is terminated in an insufficient state, the initial value of the control parameter of the position command filter determined based on the inertia ratio is a value close to the optimal value for the control parameter of the position command filter, and is a value that can be safely used in actual use of the servo amplifier as it is, even if the control parameter of the position command filter is not optimized. When the inertia ratio is small, the initial value of the control parameter of the position command filter is set to a value that, for example, does not smooth the position command too much, so that it is easier to detect the vibration period in the position deviation during autotuning, and it is possible to reliably optimize the control parameter of the position command filter.

In the autotuning 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, in the initial value setting process, the moving average number is increased as the inertia ratio increases. If a moving average filter is used as the position command filter, it becomes possible to set the value obtained by multiplying the estimated inertia ratio by an appropriate coefficient as the moving average number, which is the control parameter of the position command filter, and therefore the calculation process for setting the control parameter of the position command filter can be simplified.

In the autotuning method of the present invention, it is preferable to execute a gain tuning step following the initial value setting step, which performs autotuning for multiple gains to be subject to autotuning in the servo amplifier. The gain tuning step is a step of determining a set value for each of multiple gains based on the motor response when the motor is driven by giving a position command via a position command filter whose control parameters are set to initial values. By executing the gain tuning step using the initial values of the control parameters of the position command filter determined based on the inertia ratio, as described above, the possibility of gain tuning being terminated midway is reduced, making it easier to set each gain to an optimal value, and also easier to set the control parameters of the position command filter to an optimal value.

In the autotuning method of the present invention, it is preferable to drive the motor at a second speed faster than the first speed during the gain tuning process. In this way, the possibility of the gain tuning being interrupted midway or completed incompletely can be reduced, and the gain tuning process can be completed in a short time under conditions close to those during actual use.

In the autotuning method of the present invention, it is preferable to carry out a response detection step of selecting one gain set from the multiple gain sets and determining the motor response when each of the multiple gains in the selected gain set is applied to the servo amplifier in the gain tuning step, and a step of determining an optimal gain set from the multiple gain sets by repeating the response detection step for different gain sets in the multiple gain sets and setting each of the multiple gains in the optimal gain set as a set value. By preparing multiple gain sets in advance and selecting an optimal gain set from them according to the motor response, the time and labor required to carry out the gain tuning step can be significantly reduced. At this time, it is preferable that the gain set selected first in the response detection step is set according to the inertia ratio. When selecting an optimal gain set by trial and error in a state where the inertia ratio is large, if a gain set that brings a sharp response to the servo amplifier is used first, the torque command value at that time may become excessive, causing an error, and the gain tuning step may be terminated. By determining the gain set selected first according to the inertia ratio, it is possible to more reliably finish the gain tuning normally.

In the autotuning method of the present invention, when vibration occurs in the position deviation of the motor during the gain tuning process, it is preferable to update the control parameters of the position command filter according to the period of the vibration. By updating the control parameters of the position command filter according to the period of the vibration, the control parameters of the position command filter can be set to optimal values.

In the autotuning method of the present invention, a step of checking the movable range of the motor by driving the motor at a speed slower than the first speed can be executed before the step of estimating the inertia ratio. By checking the movable range of the motor while driving the motor at a low speed, it is possible to avoid situations such as collision with other objects in the subsequent steps.

The motor control device of the present invention is a motor control device that controls a motor based on a position command input from the outside, and includes a servo amplifier that has a position command filter that smoothes the position command and feeds back the motor position, and controls the motor position based on the position command, and a parameter setting unit that is connected to the servo amplifier and can output a position command to the servo amplifier for auto-tuning of control parameters used in the servo amplifier and sets the control parameters to the servo amplifier, and the parameter setting unit outputs a position command to drive the motor at a first speed to the servo amplifier, estimates an inertia ratio for the motor based on the motor response, and sets an initial value of the control parameter of the position command filter based on the inertia ratio.

In the motor control device of the present invention, a parameter setting unit is provided for performing autotuning of the servo amplifier. The parameter setting unit first drives the motor to obtain the inertia ratio of the motor, and sets the initial value of the control parameter of the position command filter for autotuning based on the inertia ratio. As a result, when the inertia ratio is large, the initial value of the control parameter of the position command filter is set to a value that, for example, smooths the position command to a greater extent, and the possibility that autotuning can be performed to the end is increased. Even if autotuning is terminated midway, the initial value of the control parameter of the position command filter is a value close to the optimal value as the control parameter of the position command filter, and is a value that can be safely used as it is in actual use of the servo amplifier. Also, when the inertia ratio is small, the initial value of the control parameter of the position command filter is set to a value that, for example, does not smooth the position command too much, making it easier to detect the vibration period in the position deviation during autotuning and easier to optimize the control parameter of the position command filter.

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 moving average number in the moving average filter. In this case, the parameter setting unit increases the moving average number set as the initial value as the inertia ratio increases. When configured in this way, the calculation process for setting the control parameter of the position command filter in the parameter setting unit can be simplified.

In the motor control device of the present invention, it is preferable that the parameter setting unit performs gain tuning to determine the setting values for each of the multiple gains that are the subject of auto-tuning in the servo amplifier, based on the motor response when the position command is output to the servo amplifier and the motor is driven at the second speed, after setting the initial values of the control parameters of the position command filter. By performing gain tuning using the initial values of the control parameters of the position command filter determined based on the inertia ratio, the possibility of gain tuning being terminated midway is reduced, making it easier to set each gain to an optimal value, and also easier to set the control parameters of the position command filter to an optimal value.

In the motor control device of the present invention, it is preferable that the second speed is faster than the first speed. In this way, the possibility that the gain tuning will be interrupted midway or completed incompletely is reduced, and the gain tuning process can be completed in a short time under conditions close to those during actual use.

The motor control device of the present invention preferably includes a gain set storage unit that stores multiple gain sets as gain sets, each of which is a combination of the values of multiple gains, and the parameter setting unit, when performing gain tuning, selects one gain set from the multiple gain sets stored in the gain set storage unit, and determines the motor response when each of the multiple gains in that gain set is applied to the servo amplifier, by repeating this process for different gain sets in the multiple gain sets to determine an optimal gain set, and sets each value of the multiple gains in the optimal gain set as a set value. By preparing multiple gain sets in advance and storing them in the gain set storage unit, and then determining an optimal gain set from among them according to the motor response, the time and labor required for gain tuning can be significantly reduced. At this time, it is preferable that the gain set initially selected by the parameter setting unit from the multiple gain sets stored in the gain set storage unit is set according to the inertia ratio. With this configuration, the possibility of gain tuning being terminated due to an error is reduced when performing gain tuning to select an optimal gain set.

In the motor control device of the present invention, it is preferable that the parameter setting unit updates the control parameters of the position command filter in accordance with the period of vibration when vibration occurs in the position deviation of the motor while gain tuning is being performed. By updating the control parameters of the position command filter in accordance with the period of vibration, the control parameters of the position command filter can be set to optimal values.

In the motor control device of the present invention, the parameter setting unit can check the movable range of the motor by outputting a position command to the servo amplifier to drive the motor at a speed slower than the first speed before estimating the inertia ratio. By checking the movable range of the motor while driving the motor at a low speed, it is possible to avoid situations where collisions with other objects occur during inertia ratio estimation or auto-tuning.

According to the present invention, auto-tuning can be performed regardless of the load connected to the motor, and the control parameters of the position command filter can also be optimized.

FIG. 2 is a block diagram illustrating a servo amplifier. 4 is a flowchart illustrating an auto-tuning process. 11 is a flowchart illustrating a gain tuning process. FIG. 11 is a block diagram illustrating another servo amplifier.

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of a servo amplifier 10 to which an autotuning method according to an embodiment of the present invention is applied. A motor 40 is connected to the servo amplifier 10, and an encoder 41 is attached to the motor 40 to detect the rotational position of the motor 40. Although not shown, a load can be mechanically connected to the motor 40. The encoder 41 transmits a feedback signal that feeds back the rotational position of the motor 40 to the servo amplifier 10. The feedback signal may be an encoder pulse, or may be digital data that represents the instantaneous value of the rotational position of the motor 40.

The servo amplifier 10 performs servo control of the motor 40 based on a command position (i.e., the target position of the motor 40) input from the outside so that the position of the motor 40 becomes the command position. The servo amplifier 10 includes a position command filter 11 that smoothes the input position command and outputs an internal position command, a feedforward control unit 12 that performs a feedforward control calculation based on the internal position command and outputs a feedforward command (FF command), a subtraction element 13 that calculates a position deviation by subtracting the current position of the motor 40 fed back by a feedback signal from the internal position command, a feedback control unit 14 that performs a feedback control calculation based on the feedback signal and a torque command and outputs a feedback command (FB command), a subtraction element 15 that calculates a 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 a current based on the adjustment command to actually drive the motor 40. When an excessive torque command is input, the torque adjustment unit 16 limits the value of the torque command to ensure safety, etc.

The position command filter 11 may be of any type as long as it smoothes the position command, but is preferably a moving average filter. A moving average filter is characterized by the moving average number, which indicates how many consecutive pieces of data (here, position commands) are used to calculate the moving average, so the moving average number is a control parameter of the position command filter 11, which is a moving average filter. When calculating the moving average, for example, if weighting is performed so as to emphasize data in the center of the moving average section, the moving average function indicating the degree of weighting is also 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. In the following, it is assumed that the position command filter 11 is a moving average filter, and the moving average number is used as the control parameter of the position command filter 11.

The feedforward control unit 12 performs feedforward compensation by calculation, and for this calculation, for example, uses two control gains. The feedback control unit 14 is configured as an observer that estimates the state of the controlled object and performs feedback control, and for this calculation, for example, uses two control gains, a damper ratio and an integral gain. Ultimately, in the servo amplifier shown in FIG. 1, it is necessary to set the moving average number of times of the position command filter 11 and the damper ratio and each gain used in the feedforward control unit 12 and the feedback control unit 14 as control parameters for its operation.

Next, auto-tuning for the servo amplifier 10 shown in FIG. 1 will be described. The purpose of auto-tuning here is to automatically calculate the optimal value of each control parameter to 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 is changed, and to actually set the optimal value in the servo amplifier 10 as a control parameter. A parameter setting unit 50 for performing auto-tuning is connected to the servo amplifier 10. The parameter setting unit 50 has the function of setting the initial value of the control parameter in the servo amplifier 10, generating a position command for performing auto-tuning and outputting it to the servo amplifier 10, determining the optimal value of each control parameter based on the response of the control object at that time (actually the response of the motor 40 grasped via a feedback signal), and setting the determined optimal value in the servo amplifier 10 as a control parameter. A gain set storage unit 51 in which a gain set described later is stored in advance is connected to the parameter setting unit 50. In the following description, among the control parameters set in the servo amplifier 10, the control parameters other than the control parameter of the position command filter 11 are collectively called gain. Therefore, in addition to integral gain and control gain, the damper ratio used in the feedback control unit 14 is also included in the category of gain. Furthermore, tuning the gain in the autotuning of control parameters is called gain tuning. The inertia ratio is the value obtained by dividing the sum of the load inertia and the rotor inertia of the motor 40 by the rotor inertia of the motor 40.

When performing auto-tuning, if the initial values of the control parameters (e.g., the number of moving averages) of the position command filter 11 at the start of auto-tuning are inappropriate, auto-tuning may not be completed or auto-tuning of the control parameters of the position command filter 11 may not be performed. Therefore, in this embodiment, prior to auto-tuning, the control parameters of the position command filter 11 to be used in auto-tuning are determined. Figure 2 is a flowchart showing the procedure for auto-tuning in this embodiment.

First, in step 101, the parameter setting unit 50 sets initial values for each gain in the servo amplifier 10 as an initial setting, and sets initial values for the control parameters (here, the number of moving averages) of the position command filter 11. The initial values set here are not used in auto-tuning, but are used in the previous stages (confirmation of the movable range in step 102 and estimation of the inertia ratio in step 103).

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 (for example, 100 revolutions per minute) and checks the movable range of the motor 40. The position indicated by the position command given to the servo amplifier 40 from the parameter setting unit 50 (or from outside) is within the range in which the motor 40 can rotate without colliding with the load of the motor 40 and other objects, but for some reason an object may enter the movement path of the load and hinder the movement of the load. Since it is dangerous to perform auto-tuning under such conditions that the load and object collide, the movable range is checked in advance. If a collision occurs, the rotation of the motor 40 is hindered and the motor 40 becomes overloaded, so if the parameter setting unit 50 detects an overload, it ends the auto-tuning process as a tuning failure. Also, because the motor 40 is operated at a low speed, there should normally be no noise associated with the operation of the motor 40. However, if noise occurs, the parameter setting unit 50 resets the values of the gains in the servo amplifier 10 to values that are less likely to cause noise, checks the movable range again, and if noise still occurs, the auto-tuning process ends as a tuning failure.

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 speed faster than that during the movable range confirmation (for example, 500 revolutions per minute), and estimates the inertia ratio. As is well known, 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 for the motor 40 and the position of the motor 40 obtained via the feedback signal. 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. When an overload of the motor 40 is detected in the estimation of the inertia ratio, the parameter setting unit 50 also terminates the auto-tuning process as a tuning failure. Furthermore, if noise occurs during operation of the motor 40 at this stage, the parameter setting unit 50 resets the gain values in the servo amplifier 10 to values that are less likely to cause noise and re-estimates the inertia ratio; if noise still occurs, the auto-tuning process is terminated as a tuning failure.

After the estimation of the inertia ratio is completed, the parameter setting unit 50 next determines the initial value of the control parameter of the position command filter 11 to be used when actually performing autotuning in step 104. In the example described here, the control parameter is the moving average number, and the initial value of the moving average number is set so that the larger the inertia ratio, the larger the value obtained by multiplying the inertia ratio by a constant and rounding up the result to an integer, and the larger value is compared with the minimum value of the moving average number, and the larger value is set as the initial value of the moving average number. If the constant is 0.1 and the inertia ratio is 255, the initial value of the moving average number is 26. The parameter setting unit 50 sets the moving average number calculated in this way to the position average filter 11 as the initial value of the control parameter of the position average filter 11. As a result, the position average filter 11 is set so that the larger the inertia ratio, the smoother 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 so that the larger the inertia ratio, the lower the cutoff frequency (i.e., the longer the time constant).

After 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 to rotate the motor 40 at a speed (e.g., 1000 revolutions per minute) faster than when the inertia ratio was estimated, and performs gain tuning. Gain tuning is a process in which the motor 40 is driven while changing the values of the gains set in the servo amplifier 10, for example, to find a gain that provides the most favorable response for the system consisting of the motor 40 and the load, for example, a gain that provides the shortest settling time without causing the torque command to become excessively large and without causing vibration in the position deviation. If vibration occurs in the position deviation during gain tuning, the control parameters of the position command filter 11 are updated based on the period of the vibration.

In gain tuning, the optimum gain value is found by trial and error while changing the value of each gain. However, if there are many gains to be tuned, and the gain tuning is performed while changing the value of each gain independently, the number of trials will be enormous, and the gain tuning will take a long time. Therefore, in this embodiment, a combination of the values of the multiple gains to be tuned is called a gain set, and multiple such gain sets (for example, several tens of them) are prepared in advance and stored in the gain set storage unit 51. These gain sets include those in which, when the value specified in the gain set is set to each gain of the servo amplifier 10, the load on the motor 40 is the same, the system response is fast, the stiffness is large, the settling time is short, and vibration and noise are likely to occur, and conversely, the system response is slow, the stiffness is small, the settling time is long, and vibration and noise are unlikely to occur. The parameter setting unit 50 then reads out the gain sets one by one from the gain set storage unit 51, sets the value in the read gain set to each gain of the servo amplifier 10, and repeatedly checks the response of the motor 40 at that time, to find the gain set that will give the optimum response. This found gain set is called the optimum gain set. The parameter setting unit 50 then determines the values of each gain in the optimal gain set as the values that will actually be set for the gain of the servo amplifier 10, and ends the gain tuning.

However, when the inertia ratio is large, if a gain set with a fast response or a short settling time is applied to the servo amplifier 10, the torque command value may become excessive, causing an error and terminating the gain tuning process. When determining the optimal gain set by trial and error, problems are unlikely to occur when selecting a gain set from the gain set storage unit 51 for the second or subsequent times, because the gain set is selected based on the response to the previous gain set. However, if an inappropriate gain set is selected when selecting a gain set for the first time, the gain tuning will be terminated. Therefore, in this embodiment, when a gain set is selected for the first time from the multiple gain sets in the gain set storage unit 51, that is, when selecting the initial gain set, a gain set set according to the inertia ratio is selected. As an example, it is assumed that the load connected to the motor 40 is the same, and the gain sets stored in the gain set storage unit 51 are assigned serial numbers from 1 to 25 in order of slow response or long settling time. In this case, if the inertia ratio is less than 250, gain set 25 is used as the initial value, if the inertia ratio is between 250 and 800, gain sets up to 15 are used as the initial value, and similarly, if the inertia ratio is 5000 or more, gain set 5 can be used as the initial value.

3 is a flowchart summarizing the processing of the gain tuning process described above. In step 111, the parameter setting unit 50 selects a gain set determined according to the inertia ratio from among the multiple gain sets in the gain set storage unit 51, and in step 112, applies the selected gain set to the servo amplifier 10 to drive the motor 40 by a position command and observes the response from the motor 40. Then, in step 113, the parameter setting unit 50 determines whether vibration has occurred in the position deviation of the motor 40, and if vibration has occurred, in step 114, the control parameters of the position command filter 11 are reset based on the vibration period, and proceeds to step 115. If vibration is not detected in step 113, the processing proceeds directly 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, and if it is the optimal gain set, in step 116, the parameter setting unit 50 sets the value of the optimal gain set to each gain of the servo amplifier 10 as the value to be actually used, and ends the gain tuning processing. On the other hand, if the gain set is not determined to be optimal in step 115, the parameter setting unit 50 selects another gain set from the gain set storage unit 51 in step 117 and executes the process from step 112.

When the gain tuning in step 105 described above is completed, the parameter setting unit 50 outputs a position command to the servo amplifier 10 to return the position of the motor 40 to the initial position. This is because the motor 40 is driven during confirmation of the movable range in step 102, estimation of the inertia ratio in step 103, and gain tuning in step 105, and the position of the motor 40 has moved from the initial position before the start of a series of auto-tuning processes.

In the autotuning method of the present embodiment described above, the inertia ratio is estimated prior to gain tuning, and the initial value of the control parameter of the position command filter 11 is set based on the estimated inertia ratio. This makes it possible to avoid a situation in which the torque command value becomes excessive when the inertia ratio is large, causing an error and aborting autotuning midway. Compared to the conventional example in which the initial value of the control parameter of the position command filter 11 is not set based on the inertia ratio, the autotuning is less likely to be aborted midway when the load is the same, and the operating characteristics of the servo amplifier 10 set by autotuning are also improved. Furthermore, even when autotuning ends in an incomplete state, a more appropriate value is set as the control parameter of the position command filter 11 compared to the conventional example. Furthermore, in this embodiment, when gain tuning is performed using a gain set, the initial value of the gain set is determined based on the inertia ratio, so that the occurrence of errors at the beginning of gain tuning is reduced.

The configuration of the servo amplifier to which the autotuning method based on the present invention can be applied is not limited to that shown in FIG. 1, and the autotuning method based on the present invention can be applied to any servo amplifier as long as the motor position is fed back in some form. Figure 4 shows another servo amplifier to which the autotuning method based on the present invention can be applied.

The servo amplifier 10 shown in FIG. 4 drives the motor 40 based on a position command input from the outside, and is equipped with a position command filter 11, a torque adjustment unit 16, and a current control unit 17 in the same manner as that shown in FIG. 1, and is connected to a parameter setting unit 50. A position control unit 22 is provided to which an internal position command from the position command filter 11 is input. 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, and apply a position gain Kp to this to output a speed command. The output from the position control unit 22 is input to a speed control unit 23. The servo amplifier 10 is also provided with a differential element 24 that calculates the speed of the motor 40 from 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 this, and output a torque command. The torque command is input to the torque adjustment unit 16 in the same manner as that shown in FIG. 1. Furthermore, in the servo amplifier 10, a selector 21 is provided in front of the position control filter 11. The selector 21 is controlled by a signal from the parameter setting unit 50, and switches between a position command supplied from the outside and a position command output by the parameter setting unit 50, and supplies the selected command to the position command filter 11.

The control parameters in the servo amplifier 10 shown in FIG. 4 are the control parameters of the position command filter 11, the position gain Kp, and the speed gain Kv. The parameter setting unit 16 receives a feedback signal from the encoder 41 and an adjustment command output by the torque adjustment unit 16 for estimating the inertia ratio. The parameter setting unit 50 estimates the inertia ratio 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 for the position gain Kp and the speed gain Kv.

REFERENCE SIGNS LIST 10 servo amplifier 11 position command filter 12 feedforward control section 13, 15 subtraction element 14 feedback control section 16 torque adjustment section 17 current control section 21 selector 22 position control section 23 speed control section 24 differential element 40 motor 41 encoder 50 parameter setting section 51 gain set storage section

Claims (14)

1. An auto-tuning method for a servo amplifier including a position command filter that smoothes an externally input position command, and a motor position is fed back based on the position command, the method comprising:
estimating an inertia ratio for the motor based on a response of the motor when driven at a first speed;
an initial value setting step of setting initial values of control parameters of the position command filter based on the inertia ratio;
The autotuning method includes: The autotuning method according to claim 1, wherein the position command filter is a moving average filter, the control parameter of the position command filter is the number of moving averages in the moving average filter, and the number of moving averages is increased as the inertia ratio increases in the initial value setting process. a gain tuning step of performing auto-tuning for a plurality of gains to be subject to auto-tuning in the servo amplifier after the initial value setting step;
3. The auto-tuning method according to claim 1, wherein the gain tuning step is a step of determining a set value for each of the plurality of gains based on a response of the motor when the motor is driven by giving a position command via the position command filter in which the control parameter is set to the initial value. The autotuning method according to claim 3, wherein in the gain tuning process, the motor is driven at a second speed that is faster than the first speed. A plurality of gain sets are prepared, each of which is a combination of each of the plurality of gain values;
The gain tuning step includes:
a response detection step of selecting one gain set from the plurality of gain sets and determining a response of the motor when each of the plurality of gains in the selected gain set is applied to the servo amplifier;
a step of determining an optimal gain set from among the plurality of gain sets by repeating the response detection step for different gain sets among the plurality of gain sets, and setting each value of the plurality of gains in the optimal gain set as the setting value;
having
5. The autotuning method according to claim 3, wherein a gain set selected when said response detection step is executed for the first time is set according to said inertia ratio. The autotuning method according to any one of claims 3 to 5, wherein when vibration occurs in the position deviation of the motor during the gain tuning process, the control parameters of the position command filter are updated according to the period of the vibration. The autotuning method according to any one of claims 1 to 6, further comprising a step of driving the motor at a speed slower than the first speed to check the movable range of the motor before the step of estimating the inertia ratio. A motor control device that controls a motor based on a position command input from an external device,
a servo amplifier including a position command filter that smoothes the position command, and to which the position of the motor is fed back, and which controls the position of the motor based on the position command;
a parameter setting unit connected to the servo amplifier and capable of outputting a position command to the servo amplifier for auto-tuning of a control parameter used in the servo amplifier, the parameter setting unit setting the control parameter in the servo amplifier;
having
The parameter setting unit outputs a position command to the servo amplifier to drive the motor at a first speed, estimates an inertia ratio for the motor based on a response of the motor, and sets an initial value of a control parameter of the position command filter based on the inertia ratio. The motor control device according to claim 8, wherein the position command filter is a moving average filter, the control parameter of the position command filter is a moving average number in the moving average filter, and the parameter setting unit increases the moving average number set as the initial value as the inertia ratio increases. The motor control device according to claim 8 or 9, wherein the parameter setting unit performs gain tuning to determine the set values for each of a plurality of gains that are the subject of autotuning in the servo amplifier based on the response of the motor when the motor is driven at a second speed by outputting a position command to the servo amplifier after setting the initial values of the control parameters of the position command filter. The motor control device of claim 10, wherein the second speed is faster than the first speed. a gain set storage unit for storing a plurality of gain sets, each of which is a combination of each of the plurality of gain values as a gain set;
the parameter setting unit, when performing the gain tuning, selects one gain set from the plurality of gain sets stored in the gain set storage unit, and obtains a response of the motor when each of the plurality of gains in the selected gain set is applied to the servo amplifier, by repeating this process for different gain sets among the plurality of gain sets to determine an optimal gain set, and sets each value of the plurality of gains in the optimal gain set as the setting value;
12. The motor control device according to claim 10, wherein a gain set that is initially selected by the parameter setting unit from among the plurality of gain sets stored in the gain set storage unit is set according to the inertia ratio. 13. The motor control device according to claim 10 , wherein when vibration occurs in the position deviation of the motor while the gain tuning is being performed, the parameter setting unit updates the control parameter of the position command filter in accordance with a period of the vibration. The motor control device according to any one of claims 8 to 13, wherein the parameter setting unit checks the movable range of the motor by outputting a position command to the servo amplifier to drive the motor at a speed slower than the first speed before estimating the inertia ratio.

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