CN115800866A - Automatic tuning method of servo amplifier and motor control device - Google Patents

Abstract

When performing auto-tuning of a servo amplifier for servo control of a motor, the auto-tuning can be performed regardless of the size of a load connected to the motor, and the control parameter of a position command filter can be optimized. Before tuning the gain of the servo amplifier, the following steps are performed: a step (103) of estimating an inertia ratio relating to the motor based on a response of the motor when the motor is driven at a speed slower than that used in gain tuning; and an initial value determination step (104) for determining an initial value of a control parameter of the position command filter when performing auto-tuning, based on the inertia ratio.

Description

Automatic tuning method of servo amplifier and motor control device

Technical Field

The present invention relates to servo control for controlling a rotational position of a motor based on a position command, and more particularly to an automatic tuning method for a servo amplifier used for servo control and a motor control device for executing the automatic tuning method.

Background

If the servo motor is driven by a rapidly changing position command, the position of the motor may vibrate back and forth at the target position, the motor may lose stability in operation, and the time to reach the target position may be increased. In order to ensure the operational stability of the motor and to be able to smoothly follow the position command and improve the stability, it is necessary to perform filtering processing such as smoothing on the input position command and perform servo control based on the filtered position command in a servo amplifier used for driving the motor. The filter for smoothing 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 a time constant, a cutoff frequency, and the number of moving averages in the position command filter need to be appropriately determined in accordance with a load connected to the motor. In the servo amplifier, a position gain, a feed-forward gain, a velocity gain, and the like, which are generally called gains or gain parameters, are also set as control parameters. The value of the gain also needs to 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 plurality of representative combinations of values of these control parameters are prepared in advance and stored in a table, combinations of values of the control parameters are read out from the table in accordance with a stiffness value of a load, and the respective control parameters in the servo amplifier are set in accordance with the read values. According to the technique described in patent document 1, the gain of 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 that control parameters used in a position command filter unit, a position control unit, a speed control unit, a current control unit, and the like are automatically calculated from a responsiveness setting signal indicating a response speed to be achieved and a load machine type determination signal indicating what the load is.

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 in accordance with the load has been proposed in order to cope with various loads. The auto-tuning technique is a technique of determining each control parameter based on a response when the motor is driven in a state where a load is 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 automatic tuning unit that measures the magnitude of load inertia of the mechanical system and automatically determines a control gain; a gain storage unit for storing the determined gain; and a gain reading unit which reads the stored gain and sets the gain in the servo amplifier, based on the input command value and the response of the control target. Patent document 3 does not disclose automatic setting of control parameters of a position command filter for performing filtering processing on a position command. As for the position command filter, it is known that when the position command filter is a moving average filter, the vibration period of the positional deviation when the motor is driven is measured, and the number of moving averages (a value using several consecutive data in calculation of the moving average) in the position command filter is adjusted based on the vibration period.

[ Prior art documents ]

[ patent document ]

Patent document 1, japanese patent laid-open No. 2007-336792

Patent document 2 Japanese patent laid-open publication No. 2011-97758

Patent document 3 Japanese patent laid-open publication No. 9-9662

Disclosure of Invention

In the case of performing auto-tuning based on a response when the motor is driven in a state in which a load is connected to the motor, the control parameter of the position command filter is held at an initial value and is not set to an optimum value when the vibration period of the positional deviation cannot be measured until the end condition of the auto-tuning is satisfied or when no vibration occurs in the positional deviation. For example, in the case where the mass or inertia (inertia moment) of the load is sufficiently large as compared with the rotor of the motor, if the value of the control parameter of the position command filter is a value that does not substantially smooth the position command, the torque command value caused by the position deviation becomes excessively large during execution of the auto-tuning, and sometimes the auto-tuning has to be suspended in view of safety. In this case, the control parameter of the position instruction filter is kept unchanged from the initial value and is not optimized. In this case, the value of each gain is also kept as an initial value, and is not optimized. On the other hand, if the auto-tuning is executed when the control parameter is set to a value that smoothes the position command excessively, the vibration is less likely to occur in the positional deviation, and the vibration period cannot be measured, and in this case, the control parameter of the position command filter cannot be optimized.

An object of the present invention is to provide an auto-tuning method capable of performing auto-tuning regardless of the size of a load connected to a motor and also optimizing a control parameter of a position command filter, and a motor control apparatus implementing such an auto-tuning method.

The automatic tuning method comprises a step of estimating an inertia ratio of a motor based on a 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.

In the automatic tuning method of the present invention, in order to execute a series of automatic tuning operations, the motor is driven, an inertia ratio relating to the motor is obtained, and an initial value of a control parameter of a position command filter for automatic tuning is set based on the inertia ratio. Thus, when the inertia ratio is large, the initial value of the control parameter of the position command filter becomes a value that, for example, smoothes the position command to a greater extent, and as a result, the possibility of executing the automatic tuning to the end is increased by preventing the torque command value from becoming excessively large during the automatic tuning. Even if the automatic tuning is stopped 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 the initial value can be used safely and directly 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 a value at which the position command is not substantially smoothed, for example, and therefore, the vibration period in the positional deviation is easily detected in the auto-tuning, and the control parameter of the position command filter can be reliably optimized.

In the automatic tuning method of the present invention, the position instruction filter is, for example, a moving average filter, and the control parameter of the position instruction filter is the number of moving averages in the moving average filter. In this case, in the initial value setting step, the moving average frequency increases as the inertia ratio increases. If a moving average filter is used as the position command filter, the number of moving averages that are control parameters of the position command filter can be set to a value obtained by multiplying the estimated inertia ratio by an appropriate coefficient, and therefore the arithmetic processing for setting the control parameters of the position command filter can be simplified.

In the automatic tuning method according to the present invention, it is preferable that the gain tuning step of automatically tuning a plurality of gains to be automatically tuned in the servo amplifier is performed after the initial value setting step. 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 supplying a position command via a position command filter in which a control parameter is set to an initial value. By performing the gain tuning process using the initial value of the control parameter of the position command filter determined based on the inertia ratio, the possibility of stopping the gain tuning halfway is reduced, and it is easy to set each gain to an optimum value, and also to set the control parameter of the position command filter to an optimum value.

In the auto-tuning method according to the present invention, it is preferable that the motor is driven at a second speed faster than the first speed in the gain tuning step. In this way, the possibility that the gain tuning is stopped in the middle of the tuning process or is not completed completely can be reduced, and the gain tuning process can be completed in a short time under conditions close to those in actual use.

In the automatic tuning method according to the present invention, it is preferable that, after a plurality of gain sets are prepared by using a combination of values of each of the plurality of gains as a gain set, the gain tuning step includes a response detection step of selecting one gain set from the plurality of gain sets and obtaining a response of the motor when each of the plurality of gains in the gain set is applied to the servo amplifier; and a step of determining an optimum gain set from the plurality of gain sets by repeatedly executing the response detection step for different gain sets of the plurality of gain sets, and setting respective values of the plurality of gains in the optimum gain set as set values. By preparing a plurality of gain sets in advance and selecting an optimum gain set from the gain sets according to the response of the motor, the time and the number of steps required for performing the gain tuning process can be significantly reduced. In this case, the gain set selected first in the response detection process is preferably set according to the inertia ratio. When the optimal gain set is selected by trial and error in a state where the inertia ratio is large, if a gain set sensitive to the response of the servo amplifier is used first, the torque command value becomes excessively large at that time, and an error may occur, and the gain tuning process may be stopped. By determining the initially selected gain set from the inertia ratio, the gain tuning can be terminated normally with greater reliability.

In the automatic tuning method according to the present invention, it is preferable that, when vibration occurs due to positional deviation of the motor during the implementation of the gain tuning step, the control parameter of the position command filter is updated in accordance with a period of the vibration. By updating the control parameter of the position command filter in accordance with the period of the vibration, the control parameter of the position command filter can be made to be an optimum value.

In the automatic tuning method of the present invention, before the step of estimating the inertia ratio, the step of driving the motor at a speed slower than the first speed and checking the movable range of the motor may be performed. By checking the movable range of the motor while driving the motor at a low speed, it is possible to avoid a situation such as collision with another object in a subsequent step.

The motor control device comprises a servo amplifier having a position command filter for smoothing a position command, feeding back the position of a motor, and controlling the position of the motor according to the position command; and a parameter setting unit connected to the servo amplifier, capable of outputting a position command to the servo amplifier to automatically tune a control parameter used in the servo amplifier and setting the control parameter in the servo amplifier, wherein the parameter setting unit outputs a position command for driving the motor at a first speed to the servo amplifier, estimates an inertia ratio with respect to the motor from a response of the motor, and sets an initial value of the control parameter of the position command filter from the inertia ratio.

In the motor control device of the present invention, a parameter setting unit is provided that performs auto-tuning of the servo amplifier, and the parameter setting unit first drives the motor, obtains an inertia ratio of the motor, and sets an initial value of a control parameter of a position command filter for the auto-tuning based on the inertia ratio. Thus, when the inertia ratio is large, the initial value of the control parameter of the position command filter becomes, for example, a value that smoothes the position command to a greater extent, and the possibility of executing the auto-tuning to the end can be increased. Even if the automatic tuning is stopped in the middle, the initial value of the control parameter of the position command filter is a value close to the optimum value as the control parameter of the position command filter, and is a value that can be used safely and directly in the actual use of the servo amplifier. Further, when the inertia ratio is small, the initial value of the control parameter of the position command filter is set to a value that does not substantially smooth the position command, for example, so that the vibration period in the positional deviation is easily detected in the auto-tuning, and the control parameter of the position command filter is easily optimized.

In the motor control device of the present invention, the position command filter is, for example, a moving average filter, and the control parameter of the position command filter is the number of moving averages in the moving average filter. In this case, the parameter setting unit increases the number of moving averages set as the initial values as the inertia ratio increases. With such a configuration, the arithmetic processing 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 sets the initial values of the control parameters of the position command filter, and then executes gain tuning for determining the set values of each of the plurality of gains to be automatically tuned in the servo amplifier 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. By implementing gain tuning using the initial value of the control parameter of the position command filter determined based on the inertia ratio, the possibility of stopping the gain tuning halfway is reduced, it is easy to set each gain to an optimum value, and it is also easy to set the control parameter of the position command filter to an optimum value.

In the motor control device of the present invention, the second speed is preferably higher than the first speed. In this way, the possibility that the gain tuning is stopped or not completed completely in the middle of the gain tuning can be reduced, and the gain tuning process can be completed in a short time under a condition close to that in actual use.

In the motor control device according to the present invention, it is preferable that the motor control device further includes a gain set storage unit that stores a plurality of gain sets as a combination of respective values of the plurality of gains, and the parameter setting unit determines an optimal gain set by repeating, for different gain sets in the plurality of gain sets, selection of one gain set from the plurality of gain sets stored in the gain set storage unit and determination of a response of the motor when the plurality of gains in the gain set are applied to the servo amplifier, respectively, and sets the respective values of the plurality of gains in the optimal gain set as the set values. A plurality of gain sets are prepared and stored in a gain set storage unit in advance, and an optimum gain set is determined from the gain sets according to the response of the motor, thereby greatly reducing the time and the number of processes required for gain tuning. In this case, it is preferable that the gain set selected by the parameter setting unit first from the plurality of gain sets stored in the gain set storage unit is set according to the inertia ratio. With this configuration, when gain tuning is performed to select an optimal gain set, the possibility of the gain tuning being suspended due to an error is reduced.

In the motor control device of the present invention, it is preferable that the parameter setting unit updates the control parameter of the position command filter in accordance with a period of vibration when vibration occurs in positional deviation of the motor during the gain tuning. By updating the control parameter of the position command filter in accordance with the period of the vibration, the control parameter of the position command filter can be made to be an optimum value.

In the motor control device of the present invention, the parameter setting unit outputs a position command for driving the motor at a speed slower than the first speed to the servo amplifier before estimating the inertia ratio, and the movable range of the motor can be checked. By checking the movable range of the motor while driving the motor at a low speed, it is possible to avoid a situation such as collision with another object during estimation of the inertia ratio or automatic tuning.

According to the present invention, it is possible to perform automatic tuning regardless of the size of the load connected to the motor, and also to optimize the control parameter of the position command filter.

Brief description of the drawings

Fig. 1 is a block diagram illustrating a servo amplifier.

Fig. 2 is a flowchart illustrating an auto-tuning process.

Fig. 3 is a flowchart illustrating a gain tuning process.

Fig. 4 is a block diagram illustrating another servo amplifier.

Detailed Description

Next, a mode for carrying out the present invention will be described with reference to the drawings. Fig. 1 shows a structure of a servo amplifier 10 to which an 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 sends 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 showing the instantaneous value of the rotational position of the motor 40.

The servo amplifier 10 executes servo control of the motor 40 so that the position of the motor 40 becomes a command position based on a command position (i.e., a target position of the motor 40) input from the outside. The servo amplifier 10 includes a position command filter 11 for smoothing an input position command and outputting an internal position command; a feedforward control unit 12 that performs calculation of feedforward control based on the internal position command and outputs a feedforward command (FF command); a subtracting unit 13 that subtracts the current position of the motor 40 fed back by the feedback signal from the internal position command to calculate a position deviation; a feedback control unit 14 that performs feedback control calculation based on the feedback signal and the torque command and outputs a feedback command (FB command); a subtracting unit 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 a torque command and outputs an adjustment command; and a current control unit 17 that generates a current according to the adjustment command and actually drives the motor 40. When an excessive torque command is input, the torque adjusting unit 16 limits the value of the torque command to ensure safety or the like.

The position command filter 11 may be any filter as long as it is a filter for smoothing the position command, but is preferably a moving average filter. The moving average filter is characterized by the number of moving averages showing the number of times of moving averages calculated using several successive data (here, position instructions), so the number of times of moving averages is a control parameter of the position instruction filter 11 as the moving average filter. When calculating the moving average, for example, when weighting data in the center of the moving average section, the moving average function indicating the degree of weighting is also referred to as a control parameter. When the position instruction filter is a low-pass filter, the time constant or the cutoff frequency of the low-pass filter can be used as the control parameter of the position instruction filter. Hereinafter, it is assumed that the position instruction filter 11 is a moving average filter, and the number of moving averages is used as a control parameter of the position instruction filter 11.

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

Next, the automatic tuning of the servo amplifier 10 shown in fig. 1 will be described. The automatic tuning here is intended to automatically calculate an optimum value of the values of the respective control parameters 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 set the optimum value as an actual control parameter in the servo amplifier 10. A parameter setting unit 50 for performing auto-tuning is connected to the servo amplifier 10. The parameter setting unit 50 has a function of setting an initial value of a control parameter in the servo amplifier 10, generating a position command for executing auto-tuning, outputting the position command to the servo amplifier 10, determining an optimum value of each control parameter based on a response of a control target at that time (actually, a response of the motor 40 grasped by a feedback signal), and setting the determined optimum value as the control parameter in the servo amplifier 10. The parameter setting unit 50 is connected to a gain set storage unit 51 in which a gain set described later is stored in advance. In the following description, among the control parameters set for the servo amplifier 10, the control parameters other than the control parameter of the position command filter 11 are collectively referred to as gains. Therefore, here, the damping ratio used in the feedback control unit 14 is included in the category of gain in addition to the integral gain and the control gain. In addition, tuning of the gain in the automatic tuning of the control parameter is referred to as gain tuning. The inertia ratio is a 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.

When performing auto-tuning, if the initial value of the control parameter (for example, the number of moving averages) of the position command filter 11 at the start of auto-tuning is not appropriate, the auto-tuning cannot be completed, and even the auto-tuning of the control parameter of the position command filter 11 cannot be performed. Therefore, in the present embodiment, the control parameters of the position command filter 11 used for the auto-tuning are determined prior to the auto-tuning. Fig. 2 is a flowchart showing the steps of auto-tuning in the present embodiment.

First, in step 101, the parameter setting unit 50 sets an initial value for each gain in the servo amplifier 10 as an initial setting, and sets an initial value of a control parameter (here, the number of moving averages) of the position command filter 11. The initial values set here are not used for auto-tuning, but used in the previous stage (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 for rotating the motor 40 at a low speed (for example, 100 revolutions per minute) to the servo amplifier 10, and checks the movable range of the motor 40. The position indicated by the position command supplied from the parameter setting unit 50 (or from the outside) to the servo amplifier 40 is a position within a range in which the motor 40 can rotate, in which the load of the motor 40 does not collide with another object. In this way, since it is dangerous to perform automatic tuning under the condition that the load collides with the object, the movable range confirmation is performed in advance. If a collision occurs, the rotation of the motor 40 is prevented and the motor 40 is overloaded, so that the parameter setting unit 50 detects the overload and ends the auto-tuning process as a tuning failure. Further, since the motor 40 is operated at a low speed, noise is not normally generated in association with the operation of the motor 40, but when noise is generated, the parameter setting unit 50 resets the values of the gains in the servo amplifier 10 to values at which noise is less likely to be generated, performs movable range confirmation again, and when noise is generated even in this case, ends the processing of automatic tuning as a tuning failure.

After the movable range check is performed, the parameter setting unit 50 outputs a position command for rotating the motor 40 at a speed (for example, 500 rpm) faster than that at the time of the movable range check to the servo amplifier 10, and estimates the inertia ratio in step 103. As is well known, the sum of the inertia of the load and the inertia of the rotor of the motor 40 can be estimated from the torque command or the adjustment command for the motor 40 and the position of the motor 40 obtained via the feedback signal. 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 the overload of the motor 40 is detected in the estimation of the inertia ratio, the parameter setting unit 50 ends the auto-tuning process as a tuning failure. When noise is generated in association with the operation of the motor 40 at this stage, the parameter setting unit 50 resets the values of the gains in the servo amplifier 10 to values at which noise is less likely to be generated, estimates the inertia ratio again, and ends the auto-tuning process as a tuning failure if noise is generated even in this case.

When the estimation of the inertia ratio is completed, next, in step 104, the parameter setting unit 50 obtains an initial value of the control parameter of the position command filter 11 used when the auto-tuning is actually performed. In the example described here, the control parameter is the moving average frequency, and the initial value of the moving average frequency is set so that the moving average frequency increases as the inertia ratio increases. For example, the minimum value of the number of moving averages (for example, 10 times) may be determined in advance, and a value obtained by rounding up a value obtained by multiplying the inertia ratio by a constant may be compared with the minimum value of the number of moving averages, and a larger value may 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 thus calculated in the position average filter 11 as an initial value of the control parameter of the position average filter 11. As a result, the position average filter 11 is set to smooth the position command to a greater extent as the inertia ratio is larger. When the position averaging filter 11 is, for example, a low-pass filter, the control parameters of the position averaging filter 11 may be set so that the cutoff frequency becomes lower (i.e., the time constant becomes longer) as the inertia ratio becomes larger.

When the setting of the initial value of the control parameter of the position command filter 11 is completed, the parameter setting unit 50 outputs a position command for rotating the motor 40 at a speed (for example, 1000 revolutions per minute) faster than the inertia ratio estimation timing to the servo amplifier 10 to perform gain tuning in step 105. The gain tuning is a process of, for example, driving the motor 40 while changing the value of each gain set in the servo amplifier 10, and finding out a gain that is optimal for the response of the system constituted by the motor 40 and the load, for example, a gain that does not cause excessive torque command, positional deviation, or vibration, and that has the shortest settling time. In the case where the positional deviation causes vibration during implementation of gain tuning, the control parameter of the position instruction filter 11 is updated based on the period of vibration.

In gain tuning, the optimum gain value is obtained by trial and error while changing the value of each gain, but if the number of gains to be tuned is large, if gain tuning is performed while independently changing the value of each gain, the number of trials becomes enormous, and a large amount of time is required for gain tuning. Therefore, in the present embodiment, a combination of the respective values of the plurality of gains to be tuned is referred to as a gain set, and a plurality of (for example, several tens of) such gain sets are prepared in advance and stored in the gain set storage unit 51. When the values defined by the gain sets are set as the respective gains of the servo amplifier 10, the loads of the motors 40 are assumed to be the same, and these gain sets include a gain set in which the response of the system is fast, the rigidity is high, the settling time is short, and vibration or noise is likely to occur, and a gain set in which the response of the system is slow, the rigidity is low, the settling time is long, and vibration or noise is unlikely to occur. Then, the parameter setting unit 50 reads out the gain sets one by one from the gain set storage unit 51, sets the values in the read gain sets as the respective gains of the servo amplifiers 10, repeatedly examines the response of the motor 40 at that time, and finds out the gain set that becomes the optimum response. This found set of gains is referred to as the optimal set of gains. Then, the parameter setting unit 50 determines the value of each gain in the optimal gain set as the value actually set as the gain of the servo amplifier 10, and ends the gain tuning.

However, if a gain set having a fast response or a short settling time is applied to the servo amplifier 10 when the inertia ratio is large, the torque command value is excessively large and an error occurs, and therefore the process of gain tuning may be terminated. When the optimum gain set is determined by trial and error, if the gain set is selected from the gain set storage unit 51 the second time or later, the gain set is selected in accordance with the response to the gain set of the previous time, and therefore, it is difficult to cause a problem. Therefore, in the present embodiment, when a gain set is first selected from among a plurality of gain sets in the gain set storage unit 51, that is, when a gain set of an initial value is selected, a gain set according to the inertia ratio is selected. As an example, assuming that the load connected to the motor 40 is the same, the gain sets stored in the gain set storage unit 51 are sequentially numbered from 1 to 25 in order of slow to fast response or long to short settling time. In this case, if the inertia ratio is less than 250, the 25 th gain set may be used as the initial value, if the inertia ratio is 250 or more and less than 800, the gain sets up to the 15 th may be used as the initial value, and likewise, if the inertia ratio is 5000 or more, the 5 th gain set may be used as the initial value.

Fig. 3 is a flowchart summarizing the processing of the gain tuning process described above. 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 at step 111, applies the selected gain set to the servo amplifier 10, drives the motor 40 by a position command, and observes a response from the motor 40 at step 112. Then, the parameter setting unit 50 determines whether or not vibration has occurred in the positional deviation of the motor 40 at step 113, and if vibration has occurred, resets the control parameter of the position command filter 11 in accordance with the vibration cycle at step 114, and proceeds to step 115. In the case where no vibration is detected in step 113, the process directly shifts to step 115. In step 115, the parameter setting unit 50 determines whether or not the currently selected gain set is the optimum gain set based on the response of the motor 40, and in the case of the optimum gain set, the parameter setting unit 50 sets the values in the optimum gain set as values to be actually used as 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 that the gain set is 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 processing from step 112.

After the gain tuning in step 105 described above is completed, the parameter setting unit 50 outputs a position command to the servo amplifier 10 to return the position of the motor 40 to the initial position. This is because the motor 40 is 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 is already separated from the initial position before the start of the series of processes of auto tuning.

In the automatic tuning method according to the present embodiment described above, the inertia ratio is estimated before the gain tuning, and the initial value of the control parameter of the position instruction 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 excessively large and an error occurs when the inertia ratio is large, and the auto-tuning is suspended halfway. Compared with the conventional example in which the initial value of the control parameter of the position command filter 11 is not set according to the inertia ratio, when the load is the same condition, the number of times of suspending the auto-tuning in the middle is reduced, and the operation characteristics of the servo amplifier 10 set by the auto-tuning are also improved. Further, even when the automatic tuning is completed in an incomplete state, a more appropriate value can be set as the control parameter of the position instruction filter 11 than in the conventional example. Further, 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 errors is reduced in the initial stage of the gain tuning.

The structure of the servo amplifier to which the automatic tuning method according to the present invention can be applied is not limited to the structure shown in fig. 1, and any servo amplifier can apply the automatic tuning method according to the present invention as long as it is a servo amplifier that feeds back the position of the motor in some way. Fig. 4 shows another servo amplifier to which the auto-tuning method according to the 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 includes a position command filter 11, a torque adjustment unit 16, and a current control unit 17, and is connected to a parameter setting unit 50, as in the servo amplifier shown in fig. 1. A position control unit 22 is provided to which an internal position command is input from the position command filter 11. The position control unit 22 is configured to input a feedback signal indicating the position of the motor 40 from an encoder connected to the motor 40, calculate a position deviation, which is a deviation between the internal position command and the position of the motor 40, apply a position gain Kp to the position deviation, and output a speed command. The output from the position control unit 22 is input to the speed control unit 23. A differentiating unit 24 that calculates the speed of the motor 40 from the feedback signal is also provided in the servo amplifier 10. The speed control unit 23 is configured to calculate a deviation between the speed command and the speed of the motor 40, apply a speed gain Kv thereto, and output a torque command. The torque command is input to the torque adjusting unit 16 in the same manner as shown in fig. 1. In the servo amplifier 10, a selector 21 is provided in a stage preceding 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 from the parameter setting unit 50, and supplies the position command to the position command filter 11.

The control parameters in the servo amplifier 10 shown in fig. 4 are the control parameter of the position instruction filter 11, the position gain Kp, and the velocity gain Kv. The parameter setting unit 16 receives a feedback signal from the encoder 41 and an adjustment command for estimating the inertia ratio output from the torque adjustment unit 16. The parameter setting unit 50 estimates the inertia ratio in the same manner as described above, sets the initial value of the control parameter of the position command filter 11, and performs gain tuning with respect to the position gain Kp and the velocity gain Kv.

Description of the symbols

10 servo amplifier

11-position instruction filter

12 feedforward control part

13. 15 subtraction unit

14 feedback control part

16 torque adjusting part

17 current control part

21 selector

22 position control part

23 speed control part

24 differentiation unit

40 motor

41 encoder

50 parameter setting unit

51 a gain set storage section.

Claims (14)

1. An automatic tuning method in a servo amplifier having a position command filter for smoothing a position command inputted from the outside, feeding back a position of a motor, and controlling the position of the motor based on the position command,

the auto-tuning method is characterized by comprising:

estimating an inertia ratio associated with the motor based on a response of the motor when the motor is driven at a first speed; and

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.

2. The automatic tuning method of claim 1,

the position command filter is a moving average filter, the control parameter of the position command filter is a moving average frequency in the moving average filter, and the initial value setting step increases the moving average frequency as the inertia ratio increases.

3. The automatic tuning method of claim 1 or 2,

a gain tuning step of automatically tuning a plurality of gains to be automatically tuned in the servo amplifier after the initial value setting step,

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 supplying a position command via the position command filter in which the control parameter is set to the initial value.

4. The automatic tuning method of claim 3,

in the gain tuning step, the motor is driven at a second speed that is faster than the first speed.

5. The automatic tuning method of claim 3 or 4,

a combination of respective values of the plurality of gains is made into a gain set and a plurality of gain sets are prepared,

the gain tuning process includes:

a response detection step of selecting one gain set from the plurality of gain sets and obtaining a response of the motor when the plurality of gains in the gain set are applied to the servo amplifier, respectively; and

determining an optimal gain set from the plurality of gain sets by repeating the response detection step for different gain sets among the plurality of gain sets, and setting the value of each of the plurality of gains in the optimal gain set as the set value,

a gain set selected when the response detection process is initially performed is set according to the inertia ratio.

6. The automatic tuning method of any one of claims 3 to 5,

and updating the control parameter of the position command filter according to a period of the vibration when the position deviation of the motor generates the vibration during the implementation of the gain tuning process.

7. The automatic tuning method of any one of claims 1 to 6,

the method further includes a step of driving the motor at a speed slower than the first speed and checking a 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 outside, comprising:

a servo amplifier including a position command filter for smoothing the position command, the servo amplifier feeding back a position of the motor and controlling the position of the motor based on the position command; and

a parameter setting unit connected to the servo amplifier and capable of outputting a position command to the servo amplifier to automatically tune a control parameter used in the servo amplifier and setting the control parameter in the servo amplifier,

the parameter setting unit outputs a position command for driving the motor at a first speed to the servo amplifier, estimates an inertia ratio relating to 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.

9. The motor control device according to claim 8,

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 to the initial value as the inertia ratio increases.

10. The motor control device according to claim 8 or 9,

the parameter setting unit sets an initial value of a control parameter of the position command filter, and then executes gain tuning for determining a set value of each of a plurality of gains to be automatically tuned in the servo amplifier, based on a response of the motor when outputting a position command to the servo amplifier and driving the motor at a second speed.

11. The motor control apparatus of claim 10,

the second speed is a speed faster than the first speed.

12. The motor control device according to claim 10 or 11,

includes a gain set storage unit that stores a plurality of gain sets with a combination of respective values of the plurality of gains as a gain set,

the parameter setting unit determines an optimum gain set by repeating selection of one gain set from among the plurality of gain sets stored in the gain set storage unit and determination of a response of the motor when the plurality of gains in the gain set are applied to the servo amplifier, respectively, for different gain sets in the gain tuning, and sets values of the plurality of gains in the optimum gain set as the setting values,

setting a gain set initially selected by the parameter setting section from the plurality of gain sets stored in the gain set storage section, in accordance with the inertia ratio.

13. The motor control device according to any one of claims 8 to 12,

the parameter setting unit updates the control parameter of the position command filter in accordance with a period of the vibration when the vibration occurs in the positional deviation of the motor during the implementation of the gain tuning.

14. The motor control device according to any one of claims 8 to 13,

before estimating the inertia ratio, the parameter setting unit outputs a position command to the servo amplifier to drive the motor at a speed slower than the first speed, and confirms a movable range of the motor.

Images