Servomotor control device

Abstract

The present invention stabilizes learning control, with respect to controls that have different operational patterns or operating frequencies.　This servomotor control device, which drives a servomotor with a plurality of periodic operational patterns about a feed axis, is configured such that, in response to the switching of the operational patterns, the cutoff frequency of a band-limiting filter of a learning control unit for correcting a positional deviation is either switched to a cutoff frequency corresponding to an operational pattern or set to a cutoff frequency found by multiplying the operating frequency of the operational pattern by a predetermined scaling factor. A learning control unit for correcting positional deviations, which is a part of the servomotor control device which drives the servomotor in the plurality of periodic operational patterns about the feed axis, is configured such that, in response to switching of the operational pattern, the number of divisions used when converting between the positional deviation at each of the sampling periods and the positional deviation at a position in a sampling period is switched to a number of divisions corresponding to the operational pattern.

Description

Servo motor control device

[0001] The present disclosure relates to a servo motor control device that drives a servo motor to operate a feed axis in a plurality of periodic operation patterns.

[0002] For example, Patent Document 1 discloses a servo motor control device used in machine tools or industrial machinery that, when performing machining or the like according to commands of a periodic operation pattern, uses learning control to converge a position deviation to near zero, thereby improving machining accuracy. Specifically, Patent Document 1 describes a servo motor drive control system that drives and controls a servo motor of a machine tool or industrial machinery that drives a driven object that performs periodic high-speed oscillation using the servo motor, in which a numerical control device includes reference angle calculation means that calculates a reference angle θ (=ωt) and swing command calculation means that calculates a periodic swing command F(t) based on the reference angle θ and machining conditions, and the servo control device includes a calculator that calculates a position deviation ε, which is the deviation between the swing command F(t) and position feedback Pf from a position detection means that detects the position of the servo motor, for each sampling period, and learning control means that performs learning control based on the reference angle θ, the swing command F(t), and the position deviation ε.

[0003] JP 2011-123616 A

[0004] In a servo motor control device that drives a servo motor with a feed axis according to a plurality of periodic operation patterns, when a plurality of operations with different bands of operation patterns are performed, the learning control may become unstable.

[0005] Therefore, when a plurality of operations with different bands of operation patterns are to be performed, a servo motor control device that can stably perform learning control is desired.

[0006] A first representative aspect of the present disclosure is a servo motor control device including a servo motor control unit that drives a servo motor with a feed axis in a plurality of periodic operation patterns, and a learning control unit that corrects a position deviation of the servo motor control unit, wherein the learning control unit includes: a learning controller that stores correction data created by attenuating high-frequency components of a position deviation in an operation pattern using a band-limiting filter in a learning memory and corrects the position deviation; a cut-off frequency memory unit that stores a plurality of cut-off frequencies of the band-limiting filter; an operation pattern switching detection unit that determines which of a plurality of operation patterns is currently being executed and detects a switch of the operation pattern; and a cut-off frequency switching unit that, when the operation pattern switching detection unit detects a switch of the operation pattern, obtains a cut-off frequency corresponding to the switched operation pattern from the cut-off frequency memory unit and switches the cut-off frequency of the band-limiting filter to the obtained cut-off frequency.

[0007] A second representative aspect of the present disclosure is a servo motor control device including a servo motor control unit that drives a servo motor with a feed axis in a plurality of periodic operation patterns, and a learning control unit that corrects a position deviation of the servo motor control unit, wherein the learning control unit is a learning controller that converts a position deviation for each sampling period in the operation pattern into a position deviation at a division position obtained by dividing a position range in the sampling period into a plurality of regions, stores correction data created based on the converted position deviation in a learning memory, and converts the correction data corresponding to the division position into correction data for each sampling period, thereby correcting the position deviation; a division number memory unit that stores a plurality of division numbers for dividing the position range in the sampling period into the plurality of regions; an operation pattern switch detection unit that determines which of a plurality of operation patterns is currently being executed and detects a switch of operation patterns; and a division number switch unit that, when the operation pattern switch detection unit detects a switch of the operation pattern, obtains a division number corresponding to the switched operation pattern from the division number memory unit, and switches the division number used for division in the learning controller to the obtained division number.

[0008] A third representative aspect of the present disclosure is a servo motor control device including a servo motor control unit that drives a servo motor with a feed axis in a plurality of periodic operation patterns, and a learning control unit that corrects a position deviation of the servo motor control unit, wherein the learning control unit includes: a learning controller that stores correction data created by attenuating high-frequency components of the position deviation in the operation pattern using a band-limiting filter in a learning memory and corrects the position deviation; an operating frequency acquisition unit that acquires the operating frequency of the operation pattern; a magnification setting unit that sets a magnification of the operating frequency; and a cut-off frequency setting unit that sets the cut-off frequency of the band-limiting filter to a cut-off frequency obtained by multiplying the operating frequency by the magnification.

[0009] FIG. 1 is a block diagram showing an example of the overall configuration of a servo motor control device according to a first embodiment of the present disclosure. FIG. 2 is a block diagram showing an example of the configuration of a learning control unit according to the first embodiment. FIG. 3 is a diagram showing waveforms of a position command and a position feedback, and a waveform of a position deviation when the position command is a repetitive command according to the first embodiment. FIG. 4 is a diagram showing how disturbances are removed by a band-limiting filter when the position deviation includes a high-frequency disturbance that is not synchronized with the position command according to the first embodiment. FIG. 5 is a waveform diagram showing a position deviation under normal control and a position deviation under learning control when the position command is a repetitive command according to the first embodiment. FIG. 6 is a diagram showing first and second operation patterns, bands required for the first and second operation patterns, and the cutoff frequency of a band-limiting filter according to the first embodiment. FIG. 7 is a diagram for explaining eccentric turning. FIG. 8 is a diagram showing a workpiece produced by eccentric turning. FIG. 9 is a waveform diagram showing X-axis movement and Y-axis movement of a tool in eccentric turning. FIG. 10 is a diagram for explaining normal turning and turning with servo learning oscillation. FIG. 11 is a flowchart showing the operation of a learning control unit of a servo motor control device according to the first embodiment. FIG. 12 is a block diagram showing an example of the configuration of a learning control unit of a servo motor control device according to a second embodiment of the present disclosure. FIG. 10 is an explanatory diagram of a process for converting a position deviation ε obtained during sampling by the time-position converter into a position deviation at a predetermined reference position θ(n) of the reference position θ in the second embodiment. FIG. 11 is a waveform diagram showing how the time-position converter converts a position deviation that is a function of time into a position deviation that is a function of the reference axis position in the second embodiment. FIG. 12 is a waveform diagram for explaining the sampling period of the position deviation that is a function of time and the number of divisions of the position deviation that is a function of the reference axis position in the second embodiment. FIG. 13 is a waveform diagram of a position deviation showing the relationship between the conversion processes of the time-position converter and the position-time converter and the filtering process of the band-limiting filter. FIG. 14 is a flowchart showing the operation of a learning control unit of a servo motor control device according to a second embodiment. FIG. 15 is a block diagram showing an example configuration of a learning control unit of a servo motor control device according to a third embodiment of the present disclosure. FIG. 16 is a block diagram showing an example configuration of a learning control unit of a servo motor control device according to a fourth embodiment of the present disclosure.FIG. 13 is a block diagram showing an example configuration of a learning control unit of a servo motor control device according to a fifth embodiment of the present disclosure.

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. (First Embodiment) Fig. 1 is a block diagram showing an example of the overall configuration of a servo motor control device according to a first embodiment of the present disclosure. Fig. 2 is a block diagram showing an example of the configuration of a learning control unit. As shown in Fig. 1, the servo motor control device 10 includes a servo motor control unit 100 and a learning control unit 110.

[0011] As shown in FIG. 1 , the servo motor control unit 100 includes a subtractor 101, an adder 102, a position control unit 103, a subtractor 104, a speed control unit 105, a current control unit 106, a servo motor 107, and an integrator 108. The servo motor 107 is a motor having a rotating shaft, a linear motor, or the like. The object driven by the servo motor 107 is, for example, a mechanical part of a machine tool or industrial machine. The servo motor 107 may be provided as a part of the machine tool, industrial machine, or the like. In the following explanation, a case will be described in which the servo motor 107 is a motor having a rotating shaft.

[0012] 2, the learning control unit 110 includes an adder 111, a band-limiting filter 112, a learning memory 113, a dynamic characteristic compensation element 114, a cut-off frequency storage unit 115, an operation pattern switching detection unit 116, and a cut-off frequency switching unit 117. The adder 111, the band-limiting filter 112, the learning memory 113, and the dynamic characteristic compensation element 114 constitute a learning controller 200. In FIG. 2, the adder 102 and the position control unit 103 of the servo motor control unit 100 are also shown. The learning control unit 110 may be provided together with the servo motor control unit 100 as part of a machine tool, industrial machinery, or the like.

[0013] First, the operation of the servo motor control unit 100 and the learning control unit 110 will be outlined.

[0014] Servo motor control unit 100 controls the operation of a machine tool or industrial machine by controlling servo motor 107 based on a position command. Servo motor control unit 100 calculates the difference between a detected position detected by a position detector consisting of servo motor 107 and integrator 108 and a position command input to servo motor control unit 100 from a numerical control device or the like, and outputs this difference as a position deviation to learning control unit 110. Servo motor control unit 100 adds the correction data output from learning control unit 110 to the position deviation using adder 102, and controls so that the position deviation converges to zero.

[0015] In the learning control unit 110, an adder 111 adds the input position error to the correction data stored in a learning memory 113, and the output from the adder 111 is band-limited by a band-limiting filter 112 and stored in the learning memory 113 as correction data. The learning control unit 110 stores correction data consisting of position error data in one pattern cycle of the same repeated command pattern in the learning memory 113, and in the next pattern cycle, outputs the correction data stored in the learning memory 113 to the adder 102 via a dynamic characteristic compensation element 114. When the repeated same command pattern becomes a different command pattern and the operation pattern changes, the learning control unit 110 changes the cutoff frequency of the band-limiting filter 112 using a cutoff frequency storage unit 115, an operation pattern switch detection unit 116, and a cutoff frequency switch unit 117. The configurations and operations of the servo motor control unit 100 and the learning control unit 110 will be described in detail below.

[0016] 1 calculates the difference between the input position command and the detected position that is fed back, and outputs the difference as a position deviation to the learning control unit 110 and the adder 102. The adder 102 adds the position deviation and the correction data output from the learning control unit 110 to the position deviation, and outputs the result to the position control unit 103.

[0017] Position control unit 103 outputs a value obtained by multiplying the position deviation by position gain Kp as a speed command value to subtractor 104. Subtractor 104 calculates the difference between the speed command value and the speed detection value that is fed back as speed, and outputs this difference to speed control unit 105 as a speed deviation.

[0018] The speed control unit 105 performs PI control (Proportional-Integral Control), adds together the value obtained by multiplying the speed deviation by an integral gain K1v and integrating the result, and the value obtained by multiplying the speed deviation by a proportional gain K2v, and outputs the result as a torque command to the current control unit 106. The speed control unit 105 is not particularly limited to PI control, and may use other control, for example, PID control (Proportional-Integral-Differential Control).

[0019] The current control unit 106 calculates the value of the current (current value) to be passed through the servo motor 107 based on the torque command, and controls the servo motor 107 based on this current value.

[0020] The rotation speed of the servo motor 107 is detected by a rotary encoder (not shown) provided on the servo motor 107, and the detected speed is input as speed feedback to the subtractor 104. The detected position is integrated by the integrator 108, and the resulting detected position is input as position feedback (hereinafter referred to as position FB) to the subtractor 101. The rotary encoder serves as a speed detector, and the rotary encoder and the integrator 108 serve as a position detector.

[0021] (Learning control unit 110) First, the configuration and operation of the learning controller 200 including the adder 111, the band-limiting filter 112, the learning memory 113, and the dynamic characteristic compensation element 114 will be described. The adder 111 shown in Fig. 2 adds the position error output from the servo motor control unit 100 and the correction data stored in the learning memory 113, and outputs the added value to the band-limiting filter 112. The band-limiting filter 112 is a filter for stabilizing the learning control system, for example, a low-pass filter for cutting signals in a high-frequency range within a certain frequency range, and stores the added value output from the adder 111 in the learning memory 113 as correction data.

[0022] As shown in Fig. 3, when the position command is a repetitive command, the position FB also has a repetitive waveform, and the position deviation, which is the difference between the position command and the position FB, also has a repetitive waveform synchronized with the position command. As shown in Fig. 4, when the position deviation includes a high-frequency disturbance that is not synchronized with the position command, the band-limiting filter 112 removes this disturbance and extracts the component synchronized with the position command, thereby stabilizing the learning control.

[0023] The learning memory 113 stores the correction data from one previous period that has been subjected to band limiting processing by the band limiting filter 112. The correction data stored in the learning memory 113 is output to the adder 111 and also to the dynamic characteristic compensation element 114.

[0024] The dynamic characteristic compensation element 114 compensates for the phase delay and gain reduction of the controlled object with respect to the correction data, and outputs the result to the adder 102. The adder 102 adds the position deviation and the correction data output from the dynamic characteristic compensation element 114 to the position deviation, and outputs the result to the position control unit 103.

[0025] As shown in Fig. 5, in the control of the servo motor control device 10 without the learning control unit 110 (referred to as normal control), when a repetitive command is input as a position command, the convergence of the position error is slow. However, in the control of the servo motor control device 10 with the learning control unit 110 including the adder 111, band-limiting filter 112, learning memory 113, and dynamic characteristic compensation element 114 (referred to as learning control), as shown in Fig. 5, the repetitive command is followed at high speed and with high accuracy, and the convergence of the position error is quick.

[0026] Next, the configurations and operations of the cutoff frequency storage unit 115, the operation pattern switching detection unit 116, and the cutoff frequency switching unit 117 will be described.

[0027] The cutoff frequency storage unit 115 stores a plurality of cutoff frequencies corresponding to a plurality of different operation patterns. The cutoff frequency is a frequency at which the gain characteristic of the Bode diagram is −3 dB or a frequency at which the phase characteristic is −180 degrees. FIG. 2 shows an example in which the cutoff frequency storage unit 115 stores two cutoff frequencies as the plurality of cutoff frequencies. As shown in FIG. 2, the cutoff frequency storage unit 115 includes a cutoff frequency storage unit 114A (shown as first cutoff frequency 114A in FIG. 2) that stores a first cutoff frequency F1 corresponding to a first operation pattern P1 in association with the first operation pattern P1, and a second cutoff frequency storage unit 114B (shown as second cutoff frequency 114B in FIG. 2) that stores a second cutoff frequency F2 corresponding to a second operation pattern P2 in association with the second operation pattern P2, for two different operation patterns. Specific examples of the two different operation patterns will be described later.

[0028] In the following description, a case will be described in which the operation pattern switching detector 116 and the cutoff frequency switching unit 117 switch between the first cutoff frequency F1 and the second cutoff frequency F2.

[0029] The motion pattern switching detection unit 116 detects switching of the motion pattern between the first motion pattern P1 and the second motion pattern P2, and outputs a signal indicating whether the switched motion pattern is the first motion pattern P1 or the second motion pattern P2 to the cutoff frequency switching unit 117. The motion pattern switching detection unit 116 detects the motion pattern based on, for example, the G code of the machining program or a signal output from the numerical control device. Note that, when the two different motion patterns are eccentric turning and servo learning oscillation, as will be described later, dedicated G codes are prepared for each of the eccentric turning and servo learning oscillation in the machining program. The motion pattern switching detection unit 116 can detect the motion pattern using the dedicated G code of the machining program.

[0030] Based on the input signal, the cutoff frequency switching unit 117 acquires a cutoff frequency corresponding to the post-switching operation pattern from the cutoff frequency storage unit 115 and switches the cutoff frequency of the band-limiting filter 112 to the acquired cutoff frequency. For example, suppose that the cutoff frequency of the band-limiting filter 112 is set to the second cutoff frequency F2 and the operation pattern switching detection unit 116 detects that the operation pattern has changed from the second operation pattern P2 to the first operation pattern P1. In this case, the operation pattern switching detection unit 116 outputs a signal indicating the first operation pattern P1 to the cutoff frequency switching unit 117. The cutoff frequency switching unit 117 acquires the first cutoff frequency F1 corresponding to the first operation pattern P1 from the cutoff frequency storage unit 115 and switches the cutoff frequency of the band-limiting filter 112 from the second cutoff frequency F2 to the first cutoff frequency F1.

[0031] The cutoff frequency of the band-limiting filter is automatically switched depending on the operation pattern by the cutoff frequency storage unit 115, operation pattern switching detection unit 116, and cutoff frequency switching unit 117 described above.

[0032] The reason for switching the cutoff frequency in accordance with the operation pattern will be explained below. Fig. 6 is a diagram showing the first and second operation patterns, the bands required for the first and second operation patterns, and the cutoff frequency of the band-limiting filter 112.

[0033] Assume that the cutoff frequency of the band-limiting filter 112 is set to cutoff frequency F2. When the servo motor control unit 100 operates in band B2 required for the second operation pattern P2, as shown in Figure 6, even if a disturbance with a frequency higher than the cutoff frequency F2 occurs, the disturbance is removed by the band-limiting filter 112. However, when the servo motor control unit 100 operates in band B1 required for the first operation pattern P1, if an asynchronous disturbance with a frequency higher than band B1 but lower than the cutoff frequency F2 occurs, the disturbance cannot be removed by the band-limiting filter 112 set to cutoff frequency F2. Therefore, the asynchronous disturbance causes the learning control of the learning controller 200 to become unstable.

[0034] 6, in the case of the first operation pattern P1, it is desirable that the cutoff frequency of the band-limiting filter 112 is set to cutoff frequency F1, and in the case of the second operation pattern P2, it is desirable that the cutoff frequency of the band-limiting filter 112 is set to cutoff frequency F2. Therefore, the servo motor control device 10 of this embodiment stabilizes learning control by switching the cutoff frequency in response to switching of the operation pattern.

[0035] Specific examples of two motion patterns are described below. Two motion patterns requiring different bandwidths are, for example, eccentric turning and servo learning oscillation in the case of machining motion patterns for machine tools. As shown in FIG. 7, eccentric turning is a machining method in which one rotation of the workpiece (direction C in the figure) is synchronized with one circumference of the tool to create a workpiece W, shown in FIG. 8, which has a shape that is offset from the center of the workpiece. When the horizontal axis represents time, the X-axis and Y-axis movements of the tool relative to the workpiece produce a repeating waveform as shown in the waveform diagram in FIG. 9.

[0036] Servo learning oscillation is a machining method in which a tool is oscillated in the feed direction during turning or drilling to shred chips. For example, as shown in Figure 10, in turning, the tool advances at a constant speed in the Z direction during normal turning, but in turning with servo learning oscillation, the tool advances by oscillating in the Z direction. The oscillation command is a command with a repeating pattern.

[0037] Next, the operation of the learning control unit 110 will be described using a flowchart. In the following description, a case will be described in which the operation pattern switching detection unit 116 and the cutoff frequency switching unit 117 switch between the first cutoff frequency F1 and the second cutoff frequency F2.

[0038] 11 is a flowchart showing the operation of the learning control unit 110. In step S11, the operation pattern switch detection unit 116 detects a switch in the operation pattern. Then, the operation pattern switch detection unit 116 outputs a signal indicating whether the switched operation pattern is the first operation pattern P1 or the second operation pattern P2 to the cutoff frequency switch unit 117.

[0039] In step S12, based on the input signal, the cutoff frequency switching unit 117 acquires the first cutoff frequency F1 or the second cutoff frequency F2 corresponding to the first operation pattern P1 or the second operation pattern P2 after switching from the cutoff frequency storage unit 115. The cutoff frequency storage unit 115 stores the first cutoff frequency F1 corresponding to the first operation pattern P1 in association with the first operation pattern P1, and stores the second cutoff frequency F2 corresponding to the second operation pattern P2 in association with the second operation pattern P2.

[0040] In step S13, the cutoff frequency switching unit 117 switches the cutoff frequency of the band-limiting filter 112 to the acquired cutoff frequency. For example, if the cutoff frequency of the band-limiting filter 112 is set to the second cutoff frequency F2 and the acquired cutoff frequency is the first cutoff frequency F1, the cutoff frequency switching unit 117 switches the cutoff frequency F2 of the band-limiting filter 112 to the first cutoff frequency F1.

[0041] In step S14, the adder 111, the band-limiting filter 112 switched to the acquired cutoff frequency, the learning memory 113, and the dynamic characteristic compensation element 114 perform learning control and output correction data to the adder 102.

[0042] In step S15, the learning control unit 110 determines whether or not to execute the process again. If the process is to be executed, the process returns to step S11, and if the process is not to be executed, the process ends.

[0043] The servo motor device of the first embodiment described above has the effect of stabilizing learning control for control with different operation patterns. Furthermore, the servo motor device of the first embodiment automatically switches the cutoff frequency of the band-limiting filter depending on the operation pattern, eliminating the need to manually switch the cutoff frequency setting and reducing the burden on the site.

[0044] Second Embodiment In the first embodiment, the learning band of the learning control was changed by switching the cutoff frequency of the band-limiting filter 112 depending on the operation pattern. In this embodiment, an example will be described in which the actual response band of the learning control is changed by a different method without changing the learning band of the learning control. FIG. 12 is a block diagram showing an example configuration of a learning control unit of a servo motor control device according to a second embodiment of the present disclosure. In the servo motor control device according to the second embodiment of the present disclosure, the learning control unit 110 shown in FIG. 2 is replaced with a learning control unit 110A shown in FIG. The configuration of the servo motor control unit of the servo motor control device according to this embodiment is the same as the servo motor control unit 100 of the first embodiment.

[0045] The learning control unit 110A is configured by deleting the cutoff frequency storage unit 115 and cutoff frequency switching unit 117 from the learning control unit 110 and adding a time-position converter 118, a position-time converter 119, a division number storage unit 120, and a division number switching unit 121 to the learning control unit 110. The adder 111, the band-limiting filter 112, the learning memory 113, the dynamic characteristic compensation element 114, the time-position converter 118, and the position-time converter 119 constitute a learning controller 200A. The operation of the time-position converter 118 and the position-time converter 119 is described in, for example, Japanese Patent No. 4043996. The following description will explain the configurations of the time-position converter 118, the position-time converter 119, the division number storage unit 120, and the division number switching unit 121 that are different from those of the servo motor control device of the first embodiment, and the operation related to such configurations. Descriptions of configurations and operations that overlap with those of the first embodiment will be omitted.

[0046] The time-position converter 118 converts the position deviation ε at the input reference position θ for each predetermined sampling period (each position and velocity loop processing period) into a position deviation relative to a predetermined position θ(n) at the input reference position θ. n represents 0 or a natural number. The reference position θ is a reference position synchronized with the driven object controlled by the servo motor 107. The reference position θ is, for example, a position command issued to the servo motor 107 or a feedback position from a position detector. The position deviation ε is calculated for each predetermined sampling period (position and velocity loop processing period) as a function of time, and is not calculated in accordance with the position of the driven object or the rotational position of the servo motor. Therefore, the time-position converter 118 converts the position deviation ε calculated at each sampling period into a position deviation at a predetermined position θ(n) at the reference position θ based on the reference position θ.

[0047] 13 is an explanatory diagram of the process of converting the position deviation ε obtained during sampling by the time-position converter 118 into a position deviation at a predetermined reference position θ(n) of the reference position θ. The horizontal axis represents time (sampling time), and the upward direction of the vertical axis represents the reference position θ. Furthermore, the downward direction of the vertical axis represents the position deviation ε. Assume that the position deviation obtained in the previous sampling period t(n-1) is ε(n-1) and the reference position is θ(n-1), and the position deviation obtained in the current sampling period t(n) is ε(n) and the reference position is θ(n). The time-position converter 118 divides between the reference position θ(n-1) and the reference position θ(n) to obtain the reference position θ(c), and interpolates the position deviation.

[0048] In learning control, a band-limiting filter 112 limits the response band (frequency) of learning control for stabilization. The cutoff frequency of the band-limiting filter 112 is called the learning band. In this embodiment, the actual response band (cutoff frequency) of learning control is calculated taking into account the number of divisions between the reference position θ(n-1) and the reference position θ(n). The actual response band is calculated using Equation 1 (Equation 1 below). The reference axis speed [Hz] in Equation 1 represents the number of rotations of the reference axis per second. The reference axis indicates the axis synchronized with the motion pattern to be learned, and in the eccentric turning shown in FIG. 7, the workpiece rotation spindle is the reference axis. When the number of divisions satisfies the relationship of Equation 2 (Equation 2 below), the actual response band becomes the learning band. When the actual response band is the learning band, the actual response band is determined by the cutoff frequency set by the cutoff frequency switching unit 117. The meaning of the actual response band will be described later. Note that the reference axis speed may vary depending on the machining conditions, and the number of divisions may not necessarily be set as in Equation 2. FIG. 14 is a waveform diagram showing how the time-position converter 118 converts the position deviation, which is a function of time, into the position deviation, which is a function of the reference axis position. As shown in FIG. 14, the time-position converter 118 divides the range of the reference axis position ω and outputs the divided position deviation to the adder 111. FIG. 15 is a waveform diagram for explaining the sampling period of the position deviation, which is a function of time, and the number of divisions of the position deviation, which is a function of the reference axis position, that the time-position converter 118 uses. The position deviation is sampled every command generation period of the position command. In other words, the sampling period of the position deviation is the same as the command generation period of the position command. When the repetition period ω of the position deviation after time-position conversion is 360°, as shown in FIG. 15, to align the sampling period of the position deviation with the scale of the number of divisions, the number of divisions is set as calculated by Equation 2.

[0049] The position-time converter 119 performs the inverse operation of the time-position converter 118. That is, the position-time converter 119 converts the position deviation (which serves as correction data) at a predetermined position θ(n) at the reference position θ into a position deviation ε calculated at a sampling period based on the input reference position θ. The number of divisions used in the conversions of the time-position converter 118 and the position-time converter 119 is set by the operation pattern switching detection unit 116, the number-of-divisions storage unit 120, and the number-of-divisions switching unit 121. The dynamic characteristics compensation element 114 compensates for the phase delay and gain reduction of the controlled object for the position deviation (correction data) obtained by the position-time conversion, and outputs the result to the adder 102. The adder 102 adds the position deviation and the correction data output from the dynamic characteristics compensation element 114 to the position deviation, and outputs the result to the position control unit 103.

[0050] The division number storage unit 120 stores a plurality of division numbers corresponding to a plurality of different movement patterns. Fig. 12 shows an example in which the division number storage unit 120 includes a first division number storage unit 120A (shown as a first division number 1204A in Fig. 12) that stores a first division number D1 corresponding to a first movement pattern P1 in association with the first movement pattern P1, and a second division number storage unit 120B (shown as a second division number 1204B in Fig. 12) that stores a second division number D2 corresponding to a second movement pattern P2 in association with the second movement pattern P2, for two different movement patterns.

[0051] The division number switching unit 121 acquires the division number corresponding to the movement pattern output from the movement pattern switching detection unit 116 from the division number storage unit 120, and switches the division numbers of the time-position converter 118 and the position-time converter 119 to the acquired division number. For example, when the division number of the time-position converter 118 and the position-time converter 119 is set to the second division number D2, the movement pattern switching detection unit 116 detects that the movement pattern has changed from the second movement pattern P2 to the first movement pattern P1. In this case, the movement pattern switching detection unit 116 outputs a signal indicating the first movement pattern P1 to the division number switching unit 121. The division number switching unit 121 acquires the first division number D1 corresponding to the first operation pattern P1 from the division number memory unit 120 based on a signal indicating the first operation pattern P1, and switches the division numbers of the time-position converter 118 and the position-time converter 119 from the second division number D2 to the first division number D1.

[0052] The operation pattern switching detector 116, division number storage unit 120, and division number switching unit 121 automatically switch the division numbers of the time-position converter 118 and the position-time converter 119 depending on the operation pattern.

[0053] The actual response frequency will be explained below with reference to Fig. 16. Fig. 16 is a waveform diagram of a position deviation showing the relationship between the conversion processing of the time-position converter 118 and the position-time converter 119 and the filtering processing of the band-limiting filter 112. As shown in Fig. 16, the position deviation before being band-limited by the band-limiting filter contains components with frequencies higher than the sampling period, and the position deviation after being band-limited by the band-limiting filter has the high-frequency components removed.

[0054] 16, the black arrows indicate the actual processing path in learning control, and the white arrows indicate the apparent processing converted into the time domain. The actual processing path in learning control is the number of divisions set by the division number switching unit 121, in which the time-position converter 118 performs time-position conversion of the position deviation (conversion from the time domain to the position domain), and the band-limiting filter 112 performs the cutoff frequency F Ａ The position-time converter 119 performs position-to-time conversion (conversion from the position domain to the time domain) of the band-limited position deviation using the division number set by the division number switching unit 121. The position deviation after the position-to-time conversion is band-limited by the band-limiting filter at a cutoff frequency F Ｔ The band is limited by the cutoff frequency F Ｔ is the actual response band.

[0055] Next, the operation of the learning control unit 110A will be described with reference to a flowchart shown in Fig. 17.

[0056] In step S21, the operation pattern switching detection unit 116 detects a switch in the operation pattern and outputs a signal indicating whether the switched operation pattern is the first operation pattern P1 or the second operation pattern P2 to the division number switching unit 121.

[0057] In step S22, based on the input signal, the division number switching unit 121 acquires the first division number D1 or the second division number D2 corresponding to the first operation pattern P1 or the second operation pattern P2 after switching from the division number storage unit 120. The division number storage unit 120 stores the first division number D1 corresponding to the first operation pattern P1 in association with the first operation pattern P1, and stores the second division number D2 corresponding to the second operation pattern P2 in association with the second operation pattern P2.

[0058] In step S23, the number-of-divisions switching unit 121 switches the number of divisions of the time-position converter 118 and the position-time converter 119 to the acquired first number of divisions D1 or second number of divisions D2. For example, if the number of divisions of the time-position converter 118 and the position-time converter 119 is set to the second number of divisions D2 and the acquired number of divisions is the first number of divisions D1, the number-of-divisions switching unit 121 switches the number of divisions D2 of the time-position converter 118 and the position-time converter 119 to the first number of divisions D1.

[0059] In step S24, the adder 111, the band-limiting filter 112, the learning memory 113, the position-time converter 119, and the dynamic characteristic compensation element 114 perform learning control and output correction data to the adder .

[0060] In step S25, the learning control unit 110A determines whether to execute the process again, and if so, returns to step S21, otherwise ends the process. The learning control of the operation described above is called position synchronization type learning control.

[0061] The servo motor device of the second embodiment described above has the effect of stabilizing learning control for control with different operation patterns. Furthermore, with the servo motor device of the second embodiment, the division numbers of the time-position converter and position-time converter are automatically switched depending on the operation pattern, eliminating the need to manually switch the division number settings of the time-position converter and position-time converter, thereby reducing the burden on the site.

[0062] Third Embodiment Fig. 18 is a block diagram showing an example configuration of a learning control unit of a servo motor control device according to a third embodiment of the present disclosure. In the servo motor control device according to the third embodiment of the present disclosure, the learning control unit 110 shown in Fig. 2 is replaced with a learning control unit 110B shown in Fig. 18. The configuration of the servo motor control unit of the servo motor control device according to this embodiment is the same as that of the servo motor control unit 100 according to the first embodiment.

[0063] The learning control unit 110B has a configuration in which the time-position converter 118 and the position-time converter 119 of the learning controller 200 of the learning control unit 110A of the second embodiment are added to the learning control unit 110 of the first embodiment. The adder 111, the band-limiting filter 112, the learning memory 113, the dynamic characteristic compensation element 114, the time-position converter 118, and the position-time converter 119 constitute the learning controller 200A (not shown in FIG. 18 ).

[0064] In the third embodiment, the number of divisions of the time-position converter 118 and the position-time converter 119 is configured to be switched in response to switching of the operation pattern by the operation pattern switching detection unit 116, the number of divisions storage unit 120, and the number of divisions switching unit 121. In this embodiment, the number of divisions is set to one in the time-position converter 118 and the position-time converter 119. The operations of the time-position converter 118 and the position-time converter 119 have been explained in the second embodiment, so explanations thereof will be omitted in this embodiment.

[0065] The servo motor device of the third embodiment has the effect of stabilizing learning control for control with different operation patterns. In addition to the effects of the servo motor device of the first embodiment, the servo motor device of the third embodiment has the effect of making it possible to apply the position-synchronized learning control of the servo motor device of the second embodiment when the division number is one.

[0066] (Fourth embodiment) In this embodiment, an example will be described in which the control of switching the cutoff frequency of the band-limiting filter according to the operation pattern in the first embodiment is combined with the control of switching the division number of the time-position converter and the position-time converter according to the operation pattern in the second embodiment.

[0067] Fig. 19 is a block diagram showing an example configuration of a learning control unit of a servo motor control device according to a fourth embodiment of the present disclosure. In the servo motor control device according to the fourth embodiment of the present disclosure, the learning control unit 110 shown in Fig. 2 is replaced with a learning control unit 110C shown in Fig. 19. The configuration of the servo motor control unit of the servo motor control device according to this embodiment is the same as that of the servo motor control unit 100 according to the first embodiment.

[0068] The learning control unit 110C has a configuration in which the time-position converter 118, position-time converter 119, division number storage unit 120, and division number switching unit 121 of the learning controller 200 of the learning control unit 110A shown in Fig. 12 are added to the learning control unit 110. The adder 111, band-limiting filter 112, learning memory 113, dynamic characteristic compensation element 114, time-position converter 118, and position-time converter 119 constitute a learning controller 200A (not shown in Fig. 19).

[0069] In this embodiment, the operation pattern switching detection unit 116 is connected to the cutoff frequency switching unit 117 and the division number switching unit 121, detects switching of the operation pattern, and outputs a signal indicating the switched operation pattern to the cutoff frequency switching unit 117 and the division number switching unit 121.

[0070] The cutoff frequency switching unit 117 acquires the cutoff frequency corresponding to the operation pattern indicated by the signal output from the operation pattern switching detection unit 116 from the cutoff frequency memory unit 115, and switches the cutoff frequency of the band-limiting filter 112 to the acquired cutoff frequency.

[0071] The division number switching unit 121 acquires the division number corresponding to the operation pattern indicated by the signal output from the operation pattern switching detection unit 116 from the division number memory unit 120, and switches the division numbers of the time-position converter 118 and the position-time converter 119 to the acquired division number.

[0072] In this embodiment, the learning band shown in Equation 1 is the cutoff frequency set by the cutoff frequency switching unit 117, and the division number shown in Equation 1 is the division number set by the division number switching unit 121.

[0073] The servo motor device of the fourth embodiment has the effect of stabilizing learning control for control with different operation patterns. In addition to the effects of the servo motor device of the first embodiment, the servo motor device of the fourth embodiment has the effect of automatically switching the division numbers of the time-position converter and position-time converter depending on the operation pattern, eliminating the need to manually switch the division numbers of the time-position converter and position-time converter, thereby reducing the burden on the site.

[0074] Fifth Embodiment In this embodiment, an example will be described in which the cutoff frequency of the band-limiting filter 112 is set based on the operating frequency of the operating pattern.

[0075] Fig. 20 is a block diagram showing an example configuration of a learning control unit of a servo motor control device according to a fifth embodiment of the present disclosure. In the servo motor control device according to the fifth embodiment of the present disclosure, the learning control unit 110B shown in Fig. 18 is replaced with a learning control unit 110D shown in Fig. 20. The configuration of the servo motor control unit of the servo motor control device according to this embodiment is the same as that of the servo motor control unit 100 according to the first embodiment.

[0076] The learning control unit 110D has a configuration in which the cutoff frequency memory unit 115, operation pattern switching detection unit 116, and cutoff frequency switching unit 117 of the learning control unit 110B are deleted, and an operation frequency acquisition unit 122, a magnification setting unit 123, and a cutoff frequency setting unit 124 are added to the learning control unit 110B.

[0077] The operating frequency acquisition unit 122 outputs the operating frequency to the acquired cutoff frequency setting unit 124 based on the G code of the machining program or a signal output from the numerical control device.

[0078] The magnification setting unit 123 sets a magnification by which the operating frequency is multiplied, and outputs the magnification to the cutoff frequency setting unit 124. The magnification is set to 1 or more. The cutoff frequency setting unit 124 multiplies the operating frequency by the magnification to obtain a cutoff frequency, and sets the cutoff frequency of the band-limiting filter 112.

[0079] The servo motor device of the fifth embodiment has the effect of stabilizing learning control for control with different operating frequencies. Furthermore, the servo motor device of the fifth embodiment has the effect of automatically switching the cutoff frequency of the band-limiting filter depending on the operating frequency, which eliminates the need to manually switch the cutoff frequency setting of the band-limiting filter, thereby reducing the burden on the site.

[0080] In order to realize the functional blocks included in the servo motor control device in each embodiment described above, the servo motor control device can be realized by hardware, software, or a combination of these. Here, being realized by software means being realized by a computer reading and executing a program.

[0081] In this embodiment, the functional blocks included in the servo motor control device are implemented by software or a combination thereof. Specifically, each servo motor control device includes a processing unit such as a CPU (Central Processing Unit) and a main storage device such as a RAM (Random Access Memory) for storing data temporarily required for the processing unit to execute a program.

[0082] Furthermore, according to the servo motor control device of the present disclosure including each embodiment, it is possible to stabilize learning control for control with different operation patterns or operation frequencies.

[0083] Although the above-described embodiments are preferred embodiments of the present invention, the scope of the present invention is not limited to only the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the fifth embodiment may be applied to the second embodiment. In this case, the cutoff frequency of the band-limiting filter 112 shown in Fig. 12 is set by the operating frequency acquisition unit 122, the magnification setting unit 123, and the cutoff frequency setting unit 124 shown in Fig. 20.

[0084] The following supplementary note is further disclosed regarding the above embodiment: (Supplementary note 1) A servo motor control device (10) including a servo motor control unit (100) that drives a servo motor (107) for a feed axis in a plurality of periodic operation patterns, and a learning control unit (110, 110B) that corrects a position deviation of the servo motor control unit, wherein the learning control unit (110, 110B) includes: a learning controller (200, 200A) that stores correction data created by attenuating high frequency components of a position deviation in an operation pattern using a band limiting filter (112) in a learning memory (113) and corrects the position deviation; a cutoff frequency storage unit (115) that stores a plurality of cutoff frequencies of the band limiting filter; and an operation pattern switching detection unit (116) that determines which of a plurality of operation patterns is being executed and detects switching of the operation pattern. a cutoff frequency switching unit (117) that, when the operation pattern switching detection unit detects a switch in the operation pattern, acquires a cutoff frequency corresponding to the switched operation pattern from the cutoff frequency storage unit and switches the cutoff frequency of the band limiting filter to the acquired cutoff frequency.

[0085] (Supplementary Note 2) The servo motor control device according to Supplementary Note 1, wherein the learning controller (200A) converts the position deviation for each sampling period in the operation pattern into position deviations at divided positions obtained by dividing the position range in the sampling period into a plurality of regions, attenuates high frequency components of the converted position deviation using the band limiting filter to create correction data, stores the created correction data in the learning memory, converts the correction data corresponding to the divided positions into correction data for each sampling period, and corrects the position deviation.

[0086] (Supplementary Note 3) A servo motor control device (10) comprising a servo motor control unit (100) that drives a servo motor (107) for a feed axis in a plurality of periodic operation patterns, and a learning control unit (110A, 110C) that corrects a position deviation of the servo motor control unit, wherein the learning control unit (110A, 110C) is a learning controller (200A) that converts a position deviation for each sampling period in the operation pattern into a position deviation at a divided position obtained by dividing a position range in the sampling period into a plurality of regions, stores correction data created based on the converted position deviation in a learning memory (113), converts correction data corresponding to the divided position into correction data for each sampling period, and corrects the position deviation; a division number storage unit (120) that stores a plurality of division numbers for dividing a position range in the sampling period into a plurality of regions; and an operation pattern switch detection unit (116) that determines which of a plurality of operation patterns is being executed and detects a switch of the operation pattern. a division number switching unit (121) that, when the operation pattern switching detection unit detects a switch in the operation pattern, acquires a division number corresponding to the switched operation pattern from the division number storage unit, and switches the division number for division performed by the learning control unit to the acquired division number.

[0087] (Supplementary Note 4) The servo motor control device according to Supplementary Note 3, wherein the learning controller (200A) comprises a band-limiting filter (112) that attenuates high-frequency components of a position deviation in an operation pattern, and the correction data stored in the learning memory (113) is correction data created by attenuating high-frequency components with the band-limiting filter, a cut-off frequency storage unit (115) that stores a plurality of cut-off frequencies of the band-limiting filter, and a cut-off frequency switching unit (117) that, when the operation pattern switching detection unit (116) detects a switch of the operation pattern, acquires a cut-off frequency corresponding to the switched operation pattern from the cut-off frequency storage unit and switches the cut-off frequency of the band-limiting filter to the acquired cut-off frequency.

[0088] (Supplementary Note 5) A servo motor control device (10) comprising: a servo motor control unit (100) that drives a servo motor (107) for a feed axis in a plurality of periodic operation patterns; and a learning control unit (110D) that corrects a position deviation of the servo motor control unit, wherein the learning control unit (110D) comprises: a learning controller (200, 200A) that stores correction data created by attenuating high frequency components of a position deviation in the operation pattern using a band limiting filter (112) in a learning memory (113) and corrects the position deviation; an operating frequency acquisition unit (122) that acquires an operating frequency of the operation pattern; a magnification setting unit (123) that sets a magnification of the operating frequency; and a cutoff frequency setting unit (124) that sets the cutoff frequency of the band limiting filter to a cutoff frequency obtained by multiplying the operating frequency by the magnification.

[0089] (Supplementary Note 6) The servo motor control device according to any one of Supplementary Notes 1 to 4, wherein the operation pattern switching detection unit (116) detects switching of the operation pattern according to a machining program.

[0090] (Supplementary Note 7) The servo motor control device according to any one of Supplementary Notes 1 to 4, wherein the operation pattern switching detection unit (116) detects switching of the operation pattern by a signal.

[0091] 10 Servo motor control device 100 Servo motor control unit 101 Subtractor 102 Adder 103 Position control unit 104 Subtractor 105 Speed ​​control unit 106 Current control unit 107 Servo motor 108 Integrator 110, 110A, 110B, 110C, 110D Learning control unit 111 Adder 112 Band limiting filter 113 Learning memory 114 Dynamic characteristic compensation element 115 Cut-off frequency storage unit 116 Operation pattern switching detection unit 117 Cut-off frequency switching unit 118 Time-position converter 119 Position-time converter 120 Division number storage unit 121 Division number switching unit 200, 200A Learning controller

Claims

1. A servo motor control device comprising a servo motor control unit which drives a servo motor for a feed axis in a plurality of periodic operation patterns, and a learning control unit which corrects a position deviation of the servo motor control unit, wherein the learning control unit comprises: a learning controller which stores in a learning memory correction data created by attenuating high frequency components of a position deviation in an operation pattern using a band limiting filter, and corrects the position deviation; a cutoff frequency storage unit which stores a plurality of cutoff frequencies of the band limiting filter; an operation pattern switching detection unit which determines which of a plurality of operation patterns is being executed and detects a switch in the operation pattern; and a cutoff frequency switching unit which, when the operation pattern switching detection unit detects a switch in the operation pattern, obtains a cutoff frequency corresponding to the switched operation pattern from the cutoff frequency storage unit, and switches the cutoff frequency of the band limiting filter to the obtained cutoff frequency.

2. A servo motor control device as described in claim 1, wherein the learning controller converts the position deviation for each sampling period in the operating pattern into position deviations at divided positions obtained by dividing the position range in the sampling period into a plurality of regions, attenuates the high frequency components of the converted position deviation using the band limiting filter to create correction data, stores the created correction data in the learning memory, converts the correction data corresponding to the divided positions into correction data for each sampling period, and corrects the position deviation.

3. A servo motor control device comprising a servo motor control unit which drives a servo motor with a feed axis in a plurality of periodic operation patterns, and a learning control unit which corrects position deviation of the servo motor control unit, wherein the learning control unit comprises: a learning controller which converts the position deviation for each sampling period in the operation pattern into position deviation at a divided position obtained by dividing the position range in the sampling period into a plurality of regions, stores correction data created based on the converted position deviation in a learning memory, and converts the correction data corresponding to the divided position into correction data for each sampling period, thereby correcting the position deviation; a division number storage unit which stores a plurality of division numbers for dividing the position range in the sampling period into the plurality of regions; an operation pattern switch detection unit which determines which of a plurality of operation patterns is being executed and detects a switch of the operation pattern; and a division number switching unit which, when the operation pattern switch detection unit detects a switch of the operation pattern, obtains a division number corresponding to the switched operation pattern from the division number storage unit, and switches the division number used for division in the learning controller to the obtained division number.

4. A servo motor control device as described in claim 3, wherein the learning controller is provided with a band-limiting filter which attenuates high-frequency components of position deviation in an operating pattern, and the correction data stored in the learning memory is correction data created by attenuating high-frequency components with the band-limiting filter, and further comprising: a cut-off frequency storage unit which stores a plurality of cut-off frequencies of the band-limiting filter; and a cut-off frequency switching unit which, when the operating pattern switching detection unit detects a switch in the operating pattern, obtains a cut-off frequency corresponding to the switched operating pattern from the cut-off frequency storage unit and switches the cut-off frequency of the band-limiting filter to the obtained cut-off frequency.

5. A servo motor control device comprising a servo motor control unit which drives a servo motor with a feed axis in a plurality of periodic operation patterns, and a learning control unit which corrects a position deviation of the servo motor control unit, wherein the learning control unit comprises: a learning controller which stores correction data created by attenuating high frequency components of the position deviation in the operation pattern using a band limiting filter in a learning memory and corrects the position deviation; an operating frequency acquisition unit which acquires the operating frequency of the operation pattern; a magnification setting unit which sets a magnification of the operating frequency; and a cutoff frequency setting unit which sets the cutoff frequency of the band limiting filter to a cutoff frequency obtained by multiplying the operating frequency by the magnification.

6. A servo motor control device according to any one of claims 1 to 4, wherein the operation pattern change detection unit detects a change in operation pattern according to a machining program.

7. A servo motor control device according to any one of claims 1 to 4, wherein the operation pattern switch detection unit detects a switch in the operation pattern by a signal.

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