Servo Amplifier Auto-Tuning Method and Motor Control Device

Abstract

To perform auto-tuning regardless of the size of the load connected to a motor when performing auto-tuning of a servo amplifier used for servo control of the motor, and achieve optimization of a control parameter of a position command filter.SOLUTION: Before performing tuning of gain of a servo amplifier, a step (103) of estimating an inertia ratio concerning a motor based on a response of the motor when driving the motor at a slower speed than a speed used at a time of gain tuning, and an initial value determination step (104) of determining an initial value of a control parameter of a position command filter when performing auto-tuning based on the inertia ratio are performed.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to servo control for controlling the rotational position of a motor based on a position command, and more particularly, to an auto-tuning method for a servo amplifier used in servo control and a motor control device that executes the auto-tuning method.

Background Art

[0002] When driving a servo motor with a rapidly changing position command, the operating stability of the motor may be lost, such as the position of the motor oscillating before and after the target position, and the time required to reach the target position may even become longer. In order to ensure the operating stability of the motor and improve the stability so that it can smoothly follow the position command, in the servo amplifier used to drive the motor, it is necessary to perform, for example, a filter process such as smoothing on the input position command, and perform servo control based on the position command after the filter process. A filter that performs the smoothing process of the position command is called a position command filter, and is composed of, for example, a low-pass filter or a moving average filter. Control parameters such as the time constant or cut-off frequency, and the number of moving averages in the position command filter need to be appropriately determined according to the load connected to the motor. Further, in the servo amplifier, control parameters such as a position gain, a feedforward gain, and a speed gain, generally referred to as a gain or gain parameter, are also set. 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, regarding various control parameters used in a servo amplifier, preparing in advance a plurality of representative combinations of the values of these control parameters, storing them in a table, reading out a combination of the values of the control parameters from the table according to the rigidity value of the load, and setting each control parameter in the servo amplifier with the read-out values. According to the technique described in Patent Document 1, the gain in the servo amplifier is set according to the rigidity value of the load, and the cut-off frequency of the position command filter is set. Patent Document 2 discloses automatically calculating control parameters used in a position command filter section, a position control section, a speed control section, a current control section, etc. based on a responsiveness setting signal indicating the speed of response to be achieved and a load machine type discrimination signal indicating what kind of load it is.

[0004] Since the control parameters set in the servo amplifier depend on the load connected to the motor, an auto-tuning technique for automatically setting these control parameters in the servo amplifier according to the load has been proposed in order to be able to handle various loads. The auto-tuning 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 auto-tuning technique, Patent Document 3 discloses a motor control device including a servo amplifier, an auto-tuning section that measures the magnitude of the inertia of the mechanical load and automatically determines the control gain, a gain storage section that stores the determined gain, and a gain read-out section that reads out the stored gain based on the input command value and the response of the control target and sets it in the servo amplifier. Patent Document 3 does not disclose the automatic setting of the control parameters of the position command filter that performs filter processing on the position command. Regarding the position command filter, when the position command filter is a moving average filter, it is known that the vibration period in the position deviation when the motor is driven is measured, and the number of moving averages (the value of how many consecutive data are used in calculating the moving average value) in the position command filter may be adjusted according to the vibration period.

Prior Art Documents

Patent Document

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the case of auto-tuning based on the response when driving the motor with a load connected to the motor, if the measurement of the oscillation period of the position deviation cannot be performed before the end condition of the auto-tuning is satisfied, or if no oscillation occurs in the position deviation, the control parameters of the position command filter remain at the initial values and are not set to the optimal values. For example, when the mass or inertia (moment of inertia) of the load is sufficiently larger than that of the rotor of the motor, if the value of the control parameter of the position command filter is such that it does not smooth the position command enough, the torque command value due to the position deviation becomes excessively large during the execution of the auto-tuning, and it may be necessary to abort the auto-tuning in consideration of safety. In that case, the control parameters of the position command filter remain at the initial values and are not optimized. Furthermore, in this case, the values of each gain also remain at the initial values and are not optimized. On the other hand, when performing auto-tuning when a value that excessively smooths the position command is set in the control parameter, the oscillation in the position deviation becomes less likely to occur, and the oscillation period cannot be measured. Also in this case, the optimization of the control parameters of the position command filter cannot be performed.

[0007] An object of the present invention is to provide an auto-tuning method capable of performing auto-tuning regardless of the magnitude of a load connected to a motor and also capable of optimizing control parameters of a position command filter, and a motor control device for implementing such an auto-tuning method.

Means for Solving the Problems

[0008] The auto-tuning method of the present invention is an auto-tuning method in a servo amplifier that includes a position command filter for smoothing a position command input from the outside, the position of the motor is feedback, and the position of the motor is controlled based on the position command, and includes a step of estimating an inertia ratio regarding the motor based on the response of the motor when the motor is driven at a first speed, and an initial value setting step of setting an initial value of a control parameter of the position command filter based on the inertia ratio.

[0009] In the auto-tuning method of the present invention, in order to execute a series of auto-tuning operations, the motor is driven to obtain an inertia ratio regarding the motor, and based on the inertia ratio, an initial value of a control parameter of a position command filter for auto-tuning is set. 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 more, and as a result, it is possible to prevent the torque command value from becoming excessive during auto-tuning, and the possibility of executing the auto-tuning to the end is increased. Even if the auto-tuning is interrupted 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 optimum value as the control parameter of the position command filter, and it can be safely used as it is in the actual use of the servo amplifier without optimizing the control parameter of the position command filter. 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 so much, so that it becomes easier to detect the vibration period in the position deviation during auto-tuning and it becomes possible to surely optimize the control parameter of the position command filter.

[0010] In the auto-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 number of moving averages in the moving average filter. In this case, in the initial value setting step, the number of moving averages is increased as the inertia ratio is larger. If a moving average filter is used as the position command filter, it becomes possible to set, as the number of moving averages which is the control parameter of the position command filter, a value obtained by multiplying an appropriate coefficient by the estimated inertia ratio. Therefore, the arithmetic processing for setting the control parameter of the position command filter can be made simple.

[0011] In the auto-tuning method of the present invention, preferably, following the initial value setting step, a gain tuning step is executed in which auto-tuning is performed for a plurality of gains to be auto-tuned in the servo amplifier. The gain tuning step is a step of determining setting values for each of the plurality of gains based on the response of the motor when the motor is driven by giving a position command through a position command filter whose control parameter is set to the initial value. By performing the gain tuning step using the initial value of the control parameter of the position command filter determined based on the inertia ratio, as described above, the possibility that the gain tuning is interrupted halfway is reduced, and each gain is likely to be set to the optimum value, and the control parameter of the position command filter is also likely to be set to the optimum value.

[0012] In the auto-tuning method of the present invention, in the gain tuning step, it is preferable to drive the motor at a second speed higher than the first speed. By doing so, it is possible to complete the gain tuning step in a short time under conditions close to actual use while reducing the possibility that the gain tuning is interrupted halfway or completed incompletely.

[0013] In the auto-tuning method of the present invention, a plurality of gain sets are prepared with combinations of values of a plurality of gains as gain sets. In the gain tuning process, one gain set is selected from the plurality of gain sets, and a response detection process for obtaining the response of the motor when each of the plurality of gains in the gain set is applied to the servo amplifier is performed. By repeating the response detection process for different gain sets within the plurality of gain sets, an optimal gain set is determined from the plurality of gain sets, and a process of setting the values of each of the plurality of gains in the optimal gain set as set values is preferably executed. By preparing a plurality of gain sets in advance and selecting an optimal gain set from them according to the response of the motor, the time and man-hours required for the implementation of the gain tuning process can be significantly reduced. At this time, it is preferable that the gain set first selected in the response detection process 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 gives a sensitive response to the servo amplifier is used first, the torque command value becomes excessive at that time and an error occurs, and the gain tuning process may be aborted. By determining the gain set first selected according to the inertia ratio, the gain tuning can be more reliably and normally completed.

[0014] In the auto-tuning method of the present invention, when vibration occurs in the position deviation of the motor during the implementation of 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.

[0015] In the auto-tuning method of the present invention, before the step of estimating the inertia ratio, a step of driving the motor at a speed slower than the first speed to check the movable range of the motor can be executed. By checking the movable range of the motor while driving the motor at a low speed, it is possible to avoid situations such as collisions with other objects in subsequent steps.

[0016] 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 position command filter that smoothes the position command, the position of the motor is fed back, and a servo amplifier that controls the position of the motor based on the position command. A parameter setting unit that can output the position command to the servo amplifier for auto-tuning of control parameters used in the servo amplifier and set the control parameters in the servo amplifier. The parameter setting unit outputs a position command for driving the motor at the first speed to the servo amplifier, estimates the inertia ratio related to the motor based on the response of the motor, and sets an initial value of the control parameter of the position command filter based on the inertia ratio.

[0017] In the motor control device of the present invention, a parameter setting unit that executes auto-tuning of a servo amplifier is provided. First, the parameter setting unit drives the motor to obtain the inertia ratio of the motor, and based on the inertia ratio, sets an initial value of the control parameter of the position command filter for auto-tuning. 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, smoother the position command more, increasing the likelihood of being able to execute the auto-tuning to the end. Even if the auto-tuning is interrupted halfway, 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 it can be safely used as it is in the actual use of the servo amplifier. 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 so much, making it easier to detect the vibration period in the position deviation during auto-tuning and making it easier to optimize the control parameter of the position command filter.

[0018] 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. At this time, the parameter setting unit increases the number of moving averages set as the initial value as the inertia ratio increases. When configured in this way, the arithmetic processing for setting the control parameter of the position command filter in the parameter setting unit can be made simple.

[0019] In the motor control device of the present invention, after the parameter setting unit sets the initial value of the control parameter of the position command filter, based on the response of the motor when the position command is output to the servo amplifier and the motor is driven at the second speed, it is preferable to execute gain tuning for determining the setting value for each of a plurality of gains to be auto-tuned in the servo amplifier. By performing gain tuning using the initial value of the control parameter of the position command filter determined based on the inertia ratio, the possibility of the gain tuning being interrupted midway is reduced, making it easier to set each gain to the optimum value, and also making it easier to set the control parameter of the position command filter to the optimum value.

[0020] In the motor control device of the present invention, it is preferable that the second speed is higher than the first speed. In this way, while reducing the possibility that the gain tuning is interrupted midway or completed incompletely, the gain tuning process can be completed in a short time under conditions close to actual use.

[0021] In the motor control device of the present invention, a gain set storage unit that stores a plurality of gain sets with combinations of values of a plurality of gains as gain sets is provided, and when the parameter setting unit performs gain tuning, it selects one gain set from among the plurality of gain sets stored in the gain set storage unit and determines the response of the motor when each of the plurality of gains in that gain set is applied to the servo amplifier. It is preferable to repeat this for different gain sets within the plurality of gain sets to determine the optimal gain set, and set the value of each of the plurality of gains in the optimal gain set as the set value. By preparing a plurality of gain sets in advance, storing them in the gain set storage unit, and then determining the optimal gain set from among them according to the response of the motor, the time and man-hours required for gain tuning can be significantly reduced. At this time, it is preferable that the gain set first 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. With this configuration, when performing gain tuning to select the optimal gain set, the possibility that the gain tuning is interrupted due to an error is reduced.

[0022] 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 according to the period of vibration when vibration occurs in the position deviation of the motor during the implementation of gain tuning. 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 set to optimal values.

[0023] In the motor control device of the present invention, before estimating the inertia ratio, the parameter setting unit can output a position command for driving the motor at a speed slower than the first speed to the servo amplifier to check the movable range of the motor. By checking the movable range of the motor while driving the motor at a low speed, it is possible to avoid situations such as collisions with other objects during the estimation of the inertia ratio and auto-tuning.

Advantages of the Invention

[0024] According to the present invention, auto-tuning can be performed regardless of the magnitude of the load connected to the motor, and optimization of the control parameters of the position command filter is also possible.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0026] Next, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of a servo amplifier 10 to which the auto-tuning 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 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 transmits a feedback signal for feeding back the rotational position of the motor 40 to the servo amplifier 10. The feedback signal may be an encoder pulse or digital data representing the instantaneous value of the rotational position of the motor 40.

[0027] Servo amplifier 10 executes servo control of motor 40 so that the position of motor 40 becomes the commanded position based on the commanded position input from the outside (i.e., the target position of motor 40). 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 an operation of feedforward control 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 motor 40 fed back by a feedback signal from the internal position command, a feedback control unit 14 that performs an operation of feedback control 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 sum of the position deviation and the feedforward command, 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 and actually drives motor 40. Torque adjustment unit 16 limits the value of the torque command for ensuring safety when an excessive torque command is input.

[0028] Position command filter 11 may be of any form as long as it smoothes the position command, but is preferably a moving average filter. Since the moving average filter is characterized by the number of moving averages (here, the position command) used to calculate the moving average, the number of moving averages is a control parameter of position command filter 11 which is a moving average filter. When weighting is performed, for example, to emphasize the data at the center of the moving average interval when calculating the moving average, 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. Hereinafter, it is assumed that position command filter 11 is a moving average filter and the number of moving averages is used as a control parameter of position command filter 11.

[0029] The feedforward control unit 12 performs feedforward compensation by calculation, and for this calculation, for example, two control gains are used. 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, a damping ratio, an integral gain, and two control gains are used. Eventually, in the servo amplifier shown in FIG. 1, for its operation, as control parameters, it is necessary to set the number of moving average times of the position command filter 11, the damping ratio and each gain used in the feedforward control unit 12 and the feedback control unit 14.

[0030] Next, the auto-tuning for the servo amplifier 10 shown in FIG. 1 will be described. The purpose of the auto-tuning here is to automatically calculate the optimum values of the respective control parameter values to be set in the servo amplifier 10 when a load is connected to the motor 40 or when there is a change in the load connected to the motor 40, and to actually set the optimum values as control parameters in the servo amplifier 10. A parameter setting unit 50 for executing auto-tuning is connected to the servo amplifier 10. The parameter setting unit 50 sets the initial values of the control parameters in the servo amplifier 10, generates a position command for executing auto-tuning, outputs it to the servo amplifier 10, determines the optimum values of the respective control parameters based on the response of the control target at that time (actually, the response of the motor 40 grasped via the feedback signal), and has a function of setting the determined optimum values as control parameters in the servo amplifier 10. A gain set storage unit 51 in which a gain set to be 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 parameters of the position command filter 11 are collectively referred to as gains. Therefore, here, in addition to the integral gain and the control gain, the damping ratio used in the feedback control unit 14 is also included in the category of gains. Also, tuning the gain in the auto-tuning of the control parameters is called gain tuning. The inertia ratio is defined as the value obtained by dividing the sum of the inertia of the load and the inertia of the rotor of the motor 40 by the inertia of the rotor of the motor 40.

[0031] When performing auto-tuning, if the initial value of the control parameter (for example, the number of moving average times) of the position command filter 11 at the start of auto-tuning is inappropriate, the auto-tuning may not be completed, or the auto-tuning of the control parameter of the position command filter 11 may not be performed. Therefore, in the present embodiment, prior to auto-tuning, the control parameter of the position command filter 11 used in the auto-tuning is determined. FIG. 2 is a flowchart showing the procedure of auto-tuning in the present embodiment.

[0032] First, in step 101, the parameter setting unit 50 sets initial values for each gain in the servo amplifier 10 and sets an initial value for the control parameter (here, the number of moving average times) of the position command filter 11 as initial settings. Each initial value set here is not used in auto-tuning, but is used in the previous stage (confirmation of the movable range in step 102 and estimation of the inertia ratio in step 103).

[0033] 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) to confirm 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 the outside) is within the range where the motor 40 can rotate without the load of the motor 40 colliding with other objects, but for some reason, an object may enter the moving path of the load and prevent the movement of the load. Since it is dangerous to perform auto-tuning under conditions where the load and the object collide in this way, the movable range is confirmed in advance. If a collision occurs, the rotation of the motor 40 is hindered and the motor 40 becomes overloaded. Therefore, when the parameter setting unit 50 detects an overload, it ends the auto-tuning process as a tuning failure. Also, since the motor 40 is being moved at a low speed, normally no noise should occur due to the operation of the motor 40. However, if noise occurs, the parameter setting unit 50 re-sets the value of each gain in the servo amplifier 10 to a value where noise is less likely to occur, and performs the movable range confirmation again. If noise still occurs, the auto-tuning process is ended as a tuning failure.

[0034] After the execution of the movable range confirmation, in step 103, the parameter setting unit 50 outputs a position command for rotating the motor 40 at a speed faster than that during the movable range confirmation (for example, 500 revolutions per minute) to the servo amplifier 10 to estimate the inertia ratio. As is well known, based on the torque command or adjustment command for the motor 40 and the position of the motor 40 obtained via the feedback signal, the sum of the inertia of the load and the inertia of the rotor of the motor 40 can be estimated. Since the inertia of the rotor of the motor 40 is known, the inertia ratio can be calculated by dividing the sum of the inertia of the load and the inertia of the rotor by the inertia of the rotor. When an overload of the motor 40 is detected during the estimation of the inertia ratio, the parameter setting unit 50 also ends the auto-tuning process as a tuning failure. Also, when noise occurs due to the operation of the motor 40 at this stage, the parameter setting unit 50 re-sets the value of each gain in the servo amplifier 10 to a value less likely to cause noise, estimates the inertia ratio again, and if noise still occurs, ends the auto-tuning process as a tuning failure.

[0035] Once the estimation of the inertia ratio is completed, next, in step 104, the parameter setting unit 50 obtains the initial value of the control parameter of the position command filter 11 used when actually performing auto-tuning. 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 so that the larger the inertia ratio, the larger the number of moving averages. As an example, a minimum value of the number of moving averages (for example, 10 times) is determined in advance, and the value obtained by multiplying the inertia ratio by a constant is rounded up to an integer and compared with the minimum value of the number of moving averages, and the larger value can be determined as the initial value of the number of moving averages. If the constant is 0.1 and the inertia ratio is 255, 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 parameter of the position averaging filter 11 in the position averaging filter 11. As a result, the position averaging filter 11 is set to smooth the position command more as the inertia ratio increases. When the position averaging filter 11 is, for example, a low-pass filter, the control parameter of the position averaging filter 11 may be set so that the cut-off frequency becomes lower (that is, the time constant becomes longer) as the inertia ratio increases.

[0036] Once the setting of the initial value of the control parameter of the position command filter 11 is completed, next, the parameter setting unit 50 outputs a position command for rotating the motor 40 at a speed faster (for example, 1000 revolutions per minute) than when estimating the inertia ratio to the servo amplifier 10 in step 105 and executes gain tuning. Gain tuning is, for example, a process of driving the motor 40 while changing the value of each gain set in the servo amplifier 10 to find a gain at which the response of the system composed of the motor 40 and the load is most preferable, for example, a gain at which the torque command does not become excessively large and the settling time is the shortest without vibration occurring in the position deviation. When vibration occurs in the position deviation during the execution of gain tuning, the control parameter of the position command filter 11 is updated based on the period of the vibration.

[0037] In gain tuning, the optimal gain value is obtained by trial and error while changing the value of each gain. However, if gain tuning is performed while independently changing the value of each gain when the number of gains to be tuned is large, the number of trials will become enormous, and a great deal of time will be required for gain tuning. Therefore, in the present embodiment, a combination of values of a plurality of gains to be tuned is referred to as a gain set, and a plurality of such gain sets (for example, several tens) are prepared in advance and stored in the gain set storage unit 51. These gain sets include those in which, when the values defined by the gain set are set for the respective gains of the servo amplifier 10, assuming that the load on the motor 40 is the same, the response of the system becomes fast, the rigidity is large, the settling time is short, and vibration and noise are likely to occur, and conversely, the response of the system becomes slow, the rigidity is small, the settling time is long, and vibration and noise are unlikely to occur. Then, the parameter setting unit 50 repeatedly reads out the gain sets one by one from within the gain set storage unit 51, sets the values in the read gain set for the respective gains of the servo amplifier 10, and examines the response of the motor 40 at that time, to find a gain set that gives an optimal response. This found gain set is called the optimal gain set. Then, the parameter setting unit 50 determines the values of the respective gains in the optimal gain set as the values to be actually set for the gains of the servo amplifier 10, and ends the gain tuning.

[0038] By the way, when applying a gain set with a fast response or a short settling time to the servo amplifier 10 when the inertia ratio is large, the torque command value may become excessive and an error may occur, in which case the gain tuning process may end. When determining the optimal gain set by trial and error, when selecting a gain set from the gain set storage unit 51 for the second and subsequent times, the gain set is selected based on the response to the previous gain set, so problems are less likely to occur. However, if an inappropriate gain set is selected when selecting the gain set for the first time, the gain tuning will be aborted there. Therefore, in the present embodiment, when selecting a gain set from a plurality of gain sets in the gain set storage unit 51 for the first time, that is, when selecting the initial value gain set, a gain set set according to the inertia ratio is selected. As an example, assuming that the load connected to the motor 40 is the same, it is assumed that the gain sets stored in the gain set storage unit 51 are sequentially assigned serial numbers from 1 to 25 in descending order of response delay or long settling time. In this case, if the inertia ratio is less than 250, the 25th gain set is used as the initial value. If the inertia ratio is 250 or more and less than 800, the gain sets up to the 15th are used as the initial value. Similarly, if the inertia ratio is 5000 or more, the 5th gain set can be used as the initial value.

[0039] Figure 3 is a flowchart summarizing the processing of the gain tuning step described above. In step 111, the parameter setting unit 50 selects a gain set determined according to the inertia ratio from among a plurality of gain sets in the gain set storage unit 51. In step 112, the selected gain set is applied to the servo amplifier 10 to drive the motor 40 according to the position command, and 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. When vibration has occurred, in step 114, the control parameters of the position command filter 11 are reset based on the vibration period, and the process proceeds to step 115. If vibration is not detected in step 113, the process directly proceeds 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. When it is the optimal gain set, the parameter setting unit 50 sets the values at that optimal gain set as the actual values to the respective gains of the servo amplifier 10 in step 116, and ends the gain tuning process. On the other hand, when it is not determined to be the optimal gain set 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.

[0040] When the gain tuning of 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 has been driven in the confirmation of the movable range in step 102, the estimation of the inertia ratio in step 103, and the gain tuning in step 105, and the position of the motor 40 has moved from the initial position before starting a series of auto-tuning processes.

[0041] In the auto - tuning method of the present embodiment described above, prior to gain tuning, the inertia ratio is estimated, and based on the estimated inertia ratio, the initial value of the control parameter of the position command filter 11 is set. As a result, when the inertia ratio is large, it is possible to avoid a situation where the torque command value becomes excessive, an error occurs, and the auto - tuning is aborted midway. Compared with the conventional example where the initial value of the control parameter of the position command filter 11 is not set based on the inertia ratio, when the load is under the same conditions, the occurrence of the auto - tuning being aborted midway is reduced, and the operating characteristics of the servo amplifier 10 set by the auto - tuning are also improved. Further, even when the auto - tuning ends in an incomplete state, a more appropriate value is set as the control parameter of the position command filter 11 compared with the conventional example. Furthermore, in the present embodiment, when performing gain tuning using a gain set, since the initial value of the gain set is determined based on the inertia ratio, the occurrence of an error at the initial stage of gain tuning is reduced.

[0042] The configuration of the servo amplifier to which the auto - tuning method based on the present invention is applicable is not limited to that shown in FIG. 1. The auto - tuning method based on the present invention can be applied to any servo amplifier as long as the position of the motor is feedback - controlled in some form. FIG. 4 shows another servo amplifier to which the auto - tuning method based on the present invention is applicable.

[0043] The servo amplifier 10 shown in Fig. 4 drives the motor 40 based on a position command input from the outside, and includes a position command filter 11, a torque adjustment unit 16, and a current control unit 17, similar to those shown in Fig. 1, and is connected to a parameter setting unit 50. A position control unit 22 is provided to which the internal position command from the position command filter 11 is input. The position control unit 22 is configured such that a feedback signal indicating the position of the motor 40 is input from an encoder connected to the motor 40, a deviation between the internal position command and the position of the motor 40, that is, a position deviation, is calculated, and a position gain Kp is applied thereto to output a speed command. The output from the position control unit 22 is input to the 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 a deviation between the speed command and the speed of the motor 40 and apply a speed gain Kv thereto to output a torque command. The torque command is input to the torque adjustment unit 16, similar to that shown in Fig. 1. Further, 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 to switch between the position command supplied from the outside and the position command output by the parameter setting unit 50 and supply it to the position command filter 11.

[0044] 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 value of the control parameters of the position command filter 11, and performs gain tuning for the position gain Kp and the speed gain Kv.

Explanation of Signs

[0045] 10 Servo amplifier 11 Position command filter 12 Feedforward control unit 13, 15 Subtraction element 14 Feedback control unit 16 Torque adjustment unit 17 Current control unit 21 Selector 22 Position control unit 23 Speed control unit 24 Differentiation element 40 Motor 41 Encoder 50 Parameter setting unit 51 Gain set storage unit

Claims

1. An auto - tuning method in a servo amplifier that includes a position command filter for smoothing a position command input from the outside, where the position of a motor is fed back and the position of the motor is controlled based on the position command, comprising: estimating an inertia ratio related to the motor based on the response of the motor when the motor is driven at a first speed; an initial value setting step of setting an initial value of a control parameter of the position command filter based on the inertia ratio; An auto - tuning method having the above.

2. 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 in the initial value setting step, the number of moving averages is made larger as the inertia ratio is larger. The auto - tuning method according to Claim 1.

3. After the initial value setting step, there is a gain tuning step of performing auto - tuning for a plurality of gains to be subjected to auto - tuning in the servo amplifier, The gain tuning step is a step of determining a set value for each of the plurality of gains based on the response of the motor when the motor is driven by applying a position command through the position command filter whose control parameter is set to the initial value. The auto - tuning method according to Claim 1 or 2.

4. In the gain tuning step, the motor is driven at a second speed higher than the first speed. The auto - tuning method according to Claim 3.

5. A plurality of gain sets are prepared with combinations of values of each of the plurality of gains, The gain tuning step includes: a response detection step of selecting one gain set from the plurality of gain sets and obtaining the response of the motor when each of the plurality of gains in the gain set is applied to the servo amplifier; a step of determining an optimal gain set from the plurality of gain sets by repeating the response detection step for different gain sets within the plurality of gain sets, and setting the values of each of the plurality of gains in the optimal gain set as the set values; having; The gain set selected when the response detection step is first executed is set according to the inertia ratio. The auto - tuning method according to Claim 3 or 4.

6. The auto - tuning method according to any one of claims 3 to 5, wherein when vibration occurs in the position deviation of the motor during the execution of the gain tuning process, the control parameter of the position command filter is updated according to the period of the vibration.

7. The auto - tuning 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 confirm the movable range of the motor before the step of estimating the inertia ratio.

8. A motor control device for controlling a motor based on a position command input from the outside, comprising a position command filter for smoothing the position command, wherein the position of the motor is fed back, and a servo amplifier for controlling the position of the motor based on the position command; a parameter setting unit connected to the servo amplifier, capable of outputting a position command to the servo amplifier for auto - tuning of control parameters used in the servo amplifier, and setting the control parameters in the servo amplifier; having The parameter setting unit outputs a position command for driving the motor at a first speed to the servo amplifier, estimates an inertia ratio related to the motor based on the response of the motor, and sets an initial value of the control parameter of the position command filter based on the inertia ratio.

9. 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 parameter setting unit increases the number of moving averages set as the initial value as the inertia ratio becomes larger. The motor control device according to claim 8.

10. After setting the initial value of the control parameter of the position command filter, the parameter setting unit outputs a position command to the servo amplifier and executes gain tuning to determine setting values for each of a plurality of gains to be auto - tuned in the servo amplifier based on the response of the motor when the motor is driven at a second speed. The motor control device according to claim 8 or 9.

11. The motor control device according to claim 10, wherein the second speed is higher than the first speed.

12. comprising a gain set storage unit for storing a plurality of gain sets with combinations of values of each of the plurality of gains as gain sets. When performing the gain tuning, the parameter setting unit repeats, for different gain sets within the plurality of gain sets, determining an optimal gain set by obtaining the response of the motor when one gain set is selected from the plurality of gain sets stored in the gain set storage unit and each of the plurality of gains in the gain set is applied to the servo amplifier, and setting the value of each of the plurality of gains in the optimal gain set as the set value. The motor control device according to claim 10 or 11, wherein the gain set first 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.

13. The motor control device according to any one of claims 10 to 12, wherein the parameter setting unit updates the control parameter of the position command filter according to the period of the vibration when vibration occurs in the position deviation of the motor during the execution of the gain tuning.

14. The motor control device according to any one of claims 8 to 13, wherein the parameter setting unit outputs a position command for driving the motor at a speed slower than the first speed to the servo amplifier to check the movable range of the motor before estimating the inertia ratio.

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