Control device

Abstract

In this control device of an electric motor, a technique capable of selecting energy-saving or accuracy-focused control according to the accuracy required in a processing operation or the like is provided. A control device 10 comprises: a feedback control unit 11 that causes an electric motor 1 to follow a drive command by feedback control; a feedback acquisition unit 12 that acquires feedback from the electric motor 1; a filter unit 13 that filters the feedback acquired by the feedback acquisition unit 12; a filter change unit 14 that changes the filter strength of the filter unit 13; and a filter change determination unit 15 that determines, on the basis of the drive command, whether the control is focused on accuracy, extends the transmission band by lowering the filter strength when the control is focused on accuracy, and controls the filter change unit 14 so as to cut a noise component by increasing the filter strength when the control is not focused on accuracy.

Description

control device

[0001] The present disclosure relates to a control device for controlling an electric motor.

[0002] A conventional technique for controlling an electric motor is known in which feedback obtained from the electric motor is filtered to perform feedback control so that the feedback follows a drive command. This type of technique is described in, for example, Patent Document 1 and Patent Document 2.

[0003] Patent Document 1 describes a variable speed drive device for a motor in which a speed control loop for controlling the motor speed is provided outside a current control loop that controls the motor current via a power converter, and a state observer is provided that estimates the motor load torque from the motor speed and the motor output torque component, and the load torque estimate is added to the output of the speed control loop to compensate for the motor output torque.In this variable speed drive device for a motor, a low-pass filter that automatically adjusts the cutoff frequency in accordance with changes in the load torque estimate value and a proportional amplifier that optimizes response during load fluctuations are provided on the output side of the state observer.

[0004] Patent Document 2 describes a servo control device configured to control the rotation of a servo motor in response to a position deviation signal from the arm tip of a robot driven by the servo motor, and to decelerate or stop the servo motor in response to an excessive position deviation signal from the position deviation detection means, the servo control device comprising: a low-pass filter whose time constant changes in response to the load on the motor; and time constant changing means which, when the position deviation signal value is excessive, changes the time constant of the low-pass filter to a value greater than the value at the maximum load of the servo motor.

[0005] Special Publication No. 5-024756 Publication No. 7-019176

[0006] In motor control using feedback control, if there is noise in the feedback, the noise is treated as an error and a motor control command is generated to pass current through the motor. This causes excess current to flow, increasing loss (power consumption) and promoting heat generation in the motor. In this way, feedback noise can also cause heat generation, resulting in extra energy consumption for cooling.

[0007] One way to reduce power consumption and energy consumption is to use a filter to cut noise from the feedback. However, filtering the feedback in order to cut noise from the feedback reduces the stability of the control. From the perspective of achieving both energy savings and control accuracy, there is room for improvement in conventional technology.

[0008] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a technology in an electric motor control device that allows selection of energy-saving or precision-oriented control depending on the accuracy required in machining operations, etc.

[0009] The present disclosure provides a control device that includes a feedback control unit that causes an electric motor to follow a drive command through feedback control, a feedback acquisition unit that acquires feedback from the electric motor, a filter unit that filters the feedback acquired by the feedback acquisition unit, a filter change unit that changes the filter strength of the filter unit, and a filter change determination unit that determines whether priority is given to control accuracy from the drive command, and controls the filter change unit to lower the filter strength and extend the pass band if priority is given to control accuracy, or to increase the filter strength and cut out noise components if control accuracy is not important.

[0010] According to the present disclosure, it is possible to provide a technique for controlling an electric motor that allows selection of energy-saving control or precision-oriented control depending on the precision required for machining operations or the like.

[0011] FIG. 1 is a schematic diagram showing the configuration of a control device according to a first embodiment. FIG. 2 is a flowchart showing a process of changing a filter strength by a filter changing unit based on a determination result of a filter change determination unit according to the first embodiment. FIG. 3 is a diagram showing an example of a machining program applied to the control device according to the present embodiment. FIG. 4 is a diagram explaining an example in which a filter strength is changed in response to a command speed or a speed command. FIG. 5 is a diagram explaining an acceleration / deceleration determination threshold for determining whether a command acceleration or a derivative of a speed command is equal to or greater than a certain level. FIG. 6 is a graph showing the behavior of speed and current when the filter strength is high and when it is low. FIG. 7 is a schematic diagram showing the configuration of a control device according to a second embodiment. FIG. 8 is a schematic diagram showing the configuration of a control device according to a third embodiment. FIG. 9 is a schematic diagram showing the configuration of a control device according to a fourth embodiment. FIG. 10 is a schematic diagram showing the configuration of a control device according to a fifth embodiment. FIG. 11 is a flowchart showing a process of changing a filter strength and a feedback gain based on a determination result of a filter change determination unit according to the fifth embodiment.

[0012] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the description of each embodiment, common or similar components will be denoted by the same reference numerals, and detailed description thereof may be omitted.

[0013] 1 is a schematic diagram showing the configuration of a control device 10 according to a first embodiment. The control device 10 is, for example, a numerical control device that controls an electric motor 1 based on drive commands such as a machining program. The electric motor 1 is a driving means for operating a processing machine or robot that performs cutting processing.

[0014] The control device 10 is configured using, for example, a computer including memories such as a ROM (read only memory) and a RAM (random access memory), a CPU (central processing unit), and a communication control unit, all connected to one another via a bus. The functions and operations of each functional unit of the control device 10 described below are achieved by the cooperation of the CPU and memory installed in the computer and the control program stored in the memory. The control device 10 may also be configured to control the electric motor 1 based on information input from an external computer.

[0015] The control device 10 of this embodiment includes a feedback control unit 11, a feedback acquisition unit 12, a filter unit 13, a filter change unit 14, and a filter change determination unit 15 as functional units.

[0016] The feedback control unit 11 makes the electric motor 1 follow the drive commands, such as speed commands and current commands, by feedback control based on feedback from the electric motor 1 .

[0017] The feedback acquisition unit 12 acquires the current flowing through the electric motor 1, the rotation angle of the electric motor 1, or the rotation speed of the electric motor 1. The information acquired by the feedback acquisition unit 12 becomes feedback.

[0018] The filter unit 13 is configured by a moving average filter that takes a predetermined number of samples and averages them, or a low-pass filter that cuts off high frequency components. The feedback acquired by the feedback acquisition unit 12 is filtered by the filter unit 13 and then input to the feedback control unit 11.

[0019] The filter change unit 14 changes the filter strength of the filter unit 13. The filter strength is a parameter that determines the degree (strength) of filtering by the filter unit 13. Based on the determination result of the filter change determination unit 15 (described later), the filter change unit 14 performs a change process in which, when emphasis is placed on control accuracy, the filter strength is lowered to extend the transmission band, and when emphasis is not placed on control accuracy, the filter strength is increased to cut out noise components.

[0020] In the case of the filter unit 13 configured as a moving average filter, the filter changing unit 14 sets a larger number of averages for the filter unit 13 when increasing the filter strength, and sets a smaller number of averages (sampling points) when decreasing the filter strength. In the case of the filter unit 13 configured as a low-pass filter, the filter changing unit 14 sets a lower cutoff frequency when increasing the filter strength, and sets a higher cutoff frequency when decreasing the filter strength.

[0021] The filter change determination unit 15 determines whether or not to prioritize control accuracy based on the drive command. The filter change determination unit 15 outputs the determination result to the filter change unit 14, and the filter change unit 14 changes the filter strength of the filter unit 13 in accordance with the determination result.

[0022] The filter strength change process will be described with reference to Fig. 2. Fig. 2 is a flowchart showing the filter strength change process performed by the filter change unit 14 based on the determination result of the filter change determination unit 15 in the first embodiment.

[0023] In step S1, the filter change determination unit 15 determines whether the machining operation is in a state where control accuracy is not important or a state where control accuracy is important based on the drive command. The drive command that serves as the determination criterion for the filter change determination unit 15 is, for example, a machining program or a movement command. A specific example of the determination method of the filter change determination unit 15 will be described later.

[0024] If the filter change determination unit 15 determines that the state is one in which control accuracy is not important, the process proceeds to step S2 (step S1; No).If the filter change determination unit 15 determines that the state is one in which control accuracy is important, the process proceeds to step S3 (step S1; Yes).

[0025] In step S2, the filter change determination unit 15 outputs a signal indicating a determination result that does not prioritize control accuracy to the filter changing unit 14. The filter changing unit 14 outputs a command to the filter unit 13 to relatively increase the filter strength based on the signal indicating a determination result that does not prioritize control accuracy from the filter change determination unit 15. This sets the filter strength of the filter unit 13 to "high." After processing in step S2, the process returns to step S1.

[0026] In step S3, the filter change determination unit 15 outputs a signal indicating a determination result that prioritizes control accuracy to the filter changing unit 14. The filter changing unit 14 outputs a command to the filter unit 13 to relatively lower the filter strength based on the signal indicating a determination result that prioritizes control accuracy from the filter change determination unit 15. This sets the filter strength of the filter unit 13 to "low." After the processing of step S3, the processing returns to step S1.

[0027] Next, an example of a specific determination method for determining whether or not to prioritize control accuracy based on a machining program will be described with reference to Fig. 3. Fig. 3 is a diagram showing an example of a machining program applied to the control device of this embodiment.

[0028] In the machining program in Figure 3, N is a sequence number. Blocks N2 to N5 contain codes that specify operations. Of these codes, GOO is a fast-forward code that specifies positioning, and the X that follows GOO specifies the coordinates. GO1 is a code that specifies linear movement of the cutting feed tool, and the X that follows GO1 specifies the coordinates, and F specifies the feed rate. G04 is a code that specifies dwell (wait), and the previous filter state is inherited.

[0029] In this example, the filter change determination unit 15 determines that control accuracy is not important because low control accuracy is acceptable for blocks with sequence numbers specifying GOO, which is a positioning movement command in the machining program, whereas it determines that control accuracy is important because high control accuracy is desired for blocks with sequence numbers specifying G01, which is a cutting command.

[0030] When the filter change determination unit 15 determines that control accuracy is important, it outputs a signal to the filter change unit 14 to instruct it to set the filter strength relatively low. In the machining program of Fig. 3, in blocks N3 and N5 which include the code G01, feedback control is performed with the filter strength set relatively low.

[0031] When the filter change determination unit 15 determines that control accuracy is not important, it outputs a signal to the filter change unit 14 to instruct it to set the filter strength relatively high. In the machining program of Fig. 3, in blocks N2 and N4 which include the code G00, feedback control is performed with the filter strength set relatively high.

[0032] The above describes an example of a method for determining whether or not to prioritize control accuracy based on the type of program. However, the criteria for the determination are not limited to the above embodiment. For example, a block containing a code specifying a return to origin may have a higher filter strength than a block having a sequence number containing a code specifying fast forward. Furthermore, when an operation requiring a high gain, such as gear machining or synchronous operation, is specified, the filter strength may be set relatively low. Furthermore, while the filter strength is set to two levels, "low" and "high," in the above embodiment, the criteria for the determination may be set to three or more levels. For example, the filter strength may be configured to be changeable to three or more levels, such as "low," "medium," and "high," depending on the type of program.

[0033] Next, an example of determining whether or not to prioritize control accuracy based on a movement command will be described with reference to FIGS.

[0034] FIG. 4 is a diagram illustrating an example in which the filter strength is changed in response to a command speed or a speed command. FIG. 4 shows the setting of the filter strength, which changes in response to the command speed (= the differential value of the position command) or the speed command. The differential value of the position command is the differential value of the command value of the machining program. The speed command is a command value in which the feedback deviation is reflected in the position command. The dotted line in FIG. 4 indicates a threshold value for the speed (command speed or speed command) set in the filter change determination unit 15 as a criterion for determining whether or not emphasis is placed on control accuracy. In this example, a predetermined range of speed determined by an upper limit value and a lower limit value is set as the threshold value.

[0035] When the filter change determination unit 15 determines that the speed is outside the threshold range and that control accuracy is not important, it outputs a signal to the filter change unit 14 to instruct it to set the filter strength relatively high. In principle, when the filter change determination unit 15 determines that the speed is within the threshold range and that control accuracy is important, it outputs a signal to instruct it to set the filter strength relatively low.

[0036] However, even if the speed temporarily falls within the threshold range, there are cases where it is not necessary to emphasize control accuracy. For example, in a fast-forward operation for the purpose of positioning, since no machining is being performed, it is preferable to determine that control accuracy is not emphasized even if the speed temporarily falls within the threshold range. In this embodiment, the filter change determination unit 15 exceptionally determines that control accuracy is not emphasized when the acceleration / deceleration value is outside a preset acceleration / deceleration determination threshold, even if it is within the threshold range.

[0037] 5 is a diagram illustrating an acceleration / deceleration determination threshold for determining whether the command acceleration or the derivative of the speed command is equal to or greater than a certain value. In FIG. 5, the command acceleration (= the derivative of the command speed) or the speed command is shown with a dashed line, along with the acceleration / deceleration determination threshold set for the acceleration (the derivative of the command acceleration or the command speed). In this example, a predetermined range defined by an upper limit and a lower limit is set as the acceleration / deceleration determination threshold.

[0038] 4 and 5 show regions in which, because the acceleration is above a certain level (outside the range of the acceleration / deceleration determination threshold), it is determined that control accuracy is not important even when the speed falls within the threshold range, and the filter strength is maintained at high. During positioning, even if the speed increases from below the lower limit of the threshold to above the upper limit of the threshold, as shown in FIG. 4, if the acceleration shown in FIG. 5 is outside the range of the acceleration / deceleration determination threshold, it is determined that control accuracy is not important, and the filter strength is maintained at high. Similarly, even if the speed decreases from above the upper limit of the threshold to below the lower limit of the threshold, it is determined that control accuracy is not important, and the filter strength is maintained at high, as long as the deceleration is outside the range of the acceleration / deceleration determination threshold.

[0039] The threshold and acceleration / deceleration determination threshold may be determined using the absolute value of the speed or acceleration of the monitored object, or may be determined based on a threshold set including a positive or negative sign. Also, in this example, the filter strength is set to two levels, "low" and "high," but the determination criteria may be set to three or more levels. For example, a configuration may be adopted in which multiple thresholds are set and the filter strength can be changed to three or more levels, such as "low," "medium," and "high."

[0040] 6 is a graph showing the behavior of velocity and current when the filter strength is high and low. The upper part of the graph in FIG. 6 shows the time change of velocity after filtering, and the lower part shows the time change of current. For both velocity and current, the dark lines show the behavior when the filter strength is set high, and the light lines show the behavior when the filter strength is set low.

[0041] As can be seen by comparing the thick and thin lines in the velocity behavior in Figure 6, when the filter strength is low, there is more noise than when the filter strength is high. Conversely, by increasing the filter strength, it is possible to cut out noise and reduce loss. Furthermore, as can be seen by comparing the thick and thin lines in the current behavior, by increasing the filter strength, the blur width becomes smaller compared to when the filter strength is low. A smaller blur width means smaller loss and reduced energy consumption.

[0042] In this way, increasing the filter strength can reduce losses. However, increasing the filter strength reduces control stability due to a phase delay, resulting in a decrease in control accuracy. There are cases where control accuracy should be prioritized over loss reduction. In this regard, in this embodiment, the filter strength is selected based on the determination by the filter change determination unit 15 as to whether or not to prioritize control accuracy.

[0043] As described above, the control device 10 of this embodiment includes a feedback control unit 11 that causes the electric motor 1 to follow a drive command through feedback control, a feedback acquisition unit 12 that acquires feedback from the electric motor 1, a filter unit 13 that filters the feedback acquired by the feedback acquisition unit 12, a filter change unit 14 that changes the filter strength of the filter unit 13, and a filter change determination unit 15 that determines from the drive command whether priority is given to control accuracy, and controls the filter change unit 14 to lower the filter strength and extend the pass band if priority is given to control accuracy, or to increase the filter strength and cut out noise components if control accuracy is not important.

[0044] As a result, when control accuracy is not important, the filter strength can be increased to suppress torque command changes in response to feedback noise, thereby reducing losses and achieving energy savings. On the other hand, when control accuracy is important, the filter strength can be decreased to stabilize the operation of the electric motor 1. In this way, the filter strength is automatically changed depending on whether control accuracy is important or not, making it possible to focus on energy savings or control accuracy according to the type of machining and the situation.

[0045] In addition, in this embodiment, the drive command is a machining program, and the filter change determination unit 15 determines whether or not to prioritize control accuracy depending on the type of operation specified in the machining program, and changes the filter strength.

[0046] This allows the filter strength to be set according to the machining operation by specifying the machining program. For example, in a block that only performs positioning or stopping, the filter strength can be set high to prioritize energy saving, while in a block that specifies cutting feed, the filter strength can be set low to prioritize control accuracy and stable operation of the electric motor 1.

[0047] In this embodiment, the drive command is a position command or a speed command, and the filter change determining unit 15 determines that emphasis is placed on control accuracy when the absolute value of the feed speed is within the threshold range.

[0048] By setting the speed range where control accuracy is expected to be important as the threshold range, the filter strength is set low within the threshold range, ensuring operational stability. Also, outside the threshold range where control accuracy is expected to be less important, the filter strength is set high, achieving energy savings.

[0049] In this embodiment, the filter unit 13 is a moving average filter or a low-pass filter.

[0050] This allows the filter strength to be adjusted by changing the averaging number of the moving average filter or the cutoff frequency of the low-pass filter, thereby realizing energy saving or emphasis on control accuracy according to the situation.

[0051] In this embodiment, the feedback acquisition unit 12 acquires the current flowing through the electric motor 1, the rotation angle of the electric motor 1, or the rotation speed of the electric motor 1 as feedback.

[0052] This makes it possible to use the current, rotation angle, or rotation speed reflected in the operation of the electric motor 1 as feedback, thereby realizing energy saving or emphasizing control accuracy according to the situation.

[0053] Second Embodiment Next, a control device 10a according to a second embodiment, which is different from the above-described embodiment, will be described with reference to Fig. 7. Fig. 7 is a schematic diagram showing the configuration of a control device 10a according to the second embodiment.

[0054] The feedback control unit 11a of the control device 10a of the second embodiment includes a proportional control unit 21 and an integral control unit 22 as components for performing PI control. The proportional control unit 21 performs proportional processing to make the manipulated variable proportional to the magnitude of the deviation between the command and the feedback. The integral control unit 22 performs integral processing to add an amount proportional to the accumulated value of the error between the command and the feedback to the manipulated variable. When the command is a speed command, the feedback is the speed of the electric motor 1, and when the command is a current, the feedback is the current flowing through the electric motor 1.

[0055] In addition, the control device 10a of the second embodiment includes a filter unit 13a that filters the feedback input to the proportional control unit 21, and a filter unit 13b that filters the feedback input to the integral control unit 22.

[0056] In the second embodiment, the filter strength change process of the filter change unit 14 based on the determination result of the filter change determination unit 15 is performed on the filter unit 13a corresponding to the proportional control unit 21 related to high frequency components. Therefore, the filter strength change process based on the determination result of the filter change determination unit 15 is not performed on the filter unit 13b corresponding to the integral control unit 22.

[0057] Third Embodiment Next, a control device 10b according to a second embodiment, which is different from the above-described embodiments, will be described with reference to Fig. 8. Fig. 8 is a schematic diagram showing the configuration of a control device 10b according to a third embodiment.

[0058] A feedback control unit 11b of a control device 10b of the third embodiment includes, as components for performing PID control, a proportional control unit 21, an integral control unit 22, and a differential control unit 23. The proportional control unit 21 and the integral control unit 22 have the same configurations as those of the second embodiment. The differential control unit 23 performs differential processing based on the rate of change of the error between the command and the feedback.

[0059] In addition, the control device 10b of the third embodiment is equipped with a filter unit 13c that filters the feedback input to the proportional control unit 21 and the differential control unit 23, and a filter unit 13b that filters the feedback input to the integral control unit 22.

[0060] In the third embodiment, the filter strength change process of the filter change unit 14 based on the determination result of the filter change determination unit 15 is performed on the filter unit 13c corresponding to the proportional control unit 21 and the differential control unit 23, which are related to high frequency components. Therefore, also in the third embodiment, the filter strength change process based on the determination result of the filter change determination unit 15 is not performed on the filter unit 13b corresponding to the integral control unit 22.

[0061] Fourth Embodiment Next, a control device 10c according to a second embodiment, which is different from the above-described embodiments, will be described with reference to Fig. 9. Fig. 9 is a schematic diagram showing the configuration of a control device 10c according to a fourth embodiment.

[0062] The feedback control unit 11b of the control device 10c of the fourth embodiment has the same configuration as that of the third embodiment, and includes a proportional control unit 21, an integral control unit 22, and a differential control unit 23, and performs PID control.

[0063] The control device 10c of the fourth embodiment includes a filter unit 13a that filters the feedback input to the proportional control unit 21, a filter unit 13b that filters the feedback input to the integral control unit 22, and a filter unit 13d that filters the feedback input to the differential control unit 23. That is, filter units 13a, 13b, and 13d are provided corresponding to the proportional control unit 21, the integral control unit 22, and the differential control unit 23, respectively.

[0064] In the fourth embodiment, the filter strength change processing of the filter change unit 14 based on the determination result of the filter change determination unit 15 is performed on the filter unit 13a corresponding to the proportional control unit 21 related to high frequency components, and the filter unit 13d corresponding to the differential control unit 23. Therefore, also in the fourth embodiment, the filter strength change processing based on the determination result of the filter change determination unit 15 is not performed on the filter unit 13b corresponding to the integral control unit 22.

[0065] The filter strength can be changed by setting different values ​​for the filter unit 13a corresponding to the proportional control unit 21 and the filter unit 13d corresponding to the differential control unit 23. For example, the filter unit 13d corresponding to the differential control unit 23 can be configured to have a higher filter strength than the filter unit 13a corresponding to the proportional control unit 21.

[0066] As described above, in the second to fourth embodiments, the feedback control units 11a and 11b perform PI control or PID control, and the filter change unit 14 changes the filter strength for feedback other than that performing integral processing.

[0067] This allows the filter strength change process to be applied effectively to proportional processes and differential processes other than the delayed integral process.

[0068] Fifth Embodiment Next, a control device 10d according to a fifth embodiment, which is different from the above-described embodiments, will be described with reference to Fig. 10 and Fig. 11. Fig. 10 is a schematic diagram showing the configuration of a control device 10d according to the fifth embodiment.

[0069] 10, a control device 10d of the fifth embodiment includes a gain change unit 20 in addition to the configuration of the first embodiment. The gain change unit 20 changes the feedback gain of the feedback control unit 11 in response to the process of changing the filter strength.

[0070] The gain change unit 20 receives a signal indicating the result of the filter strength change process from, for example, the filter unit 13, the filter change unit 14, or the filter change determination unit 15, and outputs a signal to change the feedback gain based on the result of the change process. In this example, the determination result of the filter change determination unit 15 also serves as information for determining the level of filter strength, so the gain change unit 20 changes the gain based on the signal from the filter change determination unit 15.

[0071] FIG. 11 is a flowchart showing a process of changing the filter strength and feedback gain based on the determination result of the filter change determination unit 15 of the fifth embodiment.

[0072] In step S11, the filter change determination unit 15 determines whether the machining operation is in a state where control accuracy is not important or a state where control accuracy is important, based on the drive command. Note that the determination method of the filter change determination unit 15 can use the examples described with reference to Figures 3 to 5 in the first embodiment.

[0073] If the filter change determination unit 15 determines that the state is one in which control accuracy is not important, the process proceeds to step S12 (step S11; No).If the filter change determination unit 15 determines that the state is one in which control accuracy is important, the process proceeds to step S14 (step S11; Yes).

[0074] In step S12, the filter change determination unit 15 outputs a signal indicating a determination result that does not prioritize control accuracy to the filter changing unit 14. The filter changing unit 14 outputs a command to the filter unit 13 to relatively increase the filter strength based on the signal indicating a determination result that does not prioritize control accuracy from the filter change determination unit 15. This sets the filter strength of the filter unit 13 to "high." After processing in step S12, the process proceeds to step S13.

[0075] In step S13, the gain change unit 20 sets the feedback gain to be lower based on the change process of increasing the filter strength performed by the filter change unit 14. After the process of step S13, the process returns to step S11.

[0076] In step S14, the filter change determination unit 15 outputs a signal indicating a determination result that prioritizes control accuracy to the filter changing unit 14. The filter changing unit 14 outputs a command to the filter unit 13 to relatively lower the filter strength based on the signal indicating a determination result that prioritizes control accuracy from the filter change determination unit 15. This sets the filter strength of the filter unit 13 to "low." After processing in step S14, the process proceeds to step S15.

[0077] In step S15, the gain change unit 20 sets the feedback gain to be high based on the change process of lowering the filter strength performed by the filter change unit 14. After the process of step S15, the process returns to step S11.

[0078] As described above, the control device 10 of the fifth embodiment further includes a gain change unit 20 that changes the feedback gain of the feedback control unit 11. When the filter strength is changed by the filter change unit 14, the gain change unit 20 applies a high gain if the filter strength is lowered, and applies a low gain if the filter strength is higher.

[0079] This allows the feedback gain to be automatically adjusted to an appropriate range depending on the filter strength.

[0080] The above-described series of processes can be executed by hardware or software. In other words, the above-described functional configuration is merely exemplary and is not particularly limited. That is, it is sufficient for a computer to have the functionality to execute the above-described series of processes as a whole, and the functional blocks used to realize these functions are not particularly limited to the above-described example. Furthermore, the locations of the functional blocks are also not particularly limited and may be arbitrary. For example, one functional block may be configured as a single piece of hardware, a single piece of software, or a combination thereof. When the series of processes are executed by software, the program that constitutes the software is installed into a computer or the like from a network or a recording medium. The computer may be a computer built into dedicated hardware. Furthermore, the computer may be a computer capable of executing various functions by installing various programs, such as a server, a general-purpose smartphone, or a personal computer.

[0081] A recording medium containing such a program may be constituted not only by a removable medium (not shown) that is distributed separately from the device main body in order to provide the program to users, but also by a recording medium that is provided to users in a state where it is pre-installed in the device main body. Since the program can be distributed via a network, the recording medium may be installed in or accessible from a computer that is connected to or connectable to the network. Furthermore, the steps that describe the program recorded on the recording medium include not only processes that are performed chronologically in accordance with the order in which they are written, but also processes that are not necessarily processed chronologically but are executed in parallel or individually.

[0082] Although the present disclosure has been described in detail, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible in these embodiments without departing from the gist of the present disclosure or the spirit of the present disclosure derived from the content of the claims and their equivalents. These embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical expressions are used in the description of the above-described embodiments.

[0083] The following supplementary note is further disclosed regarding the above embodiment and modified examples. (Supplementary note 1) A control device (10) comprising: a feedback control unit (11) that causes an electric motor (1) to follow a drive command through feedback control; a feedback acquisition unit (12) that acquires feedback from the electric motor (1); a filter unit (13) that filters the feedback acquired by the feedback acquisition unit (12); a filter change unit (14) that changes the filter strength of the filter unit (13); and a filter change determination unit (15) that determines whether priority is given to control accuracy from the drive command, and controls the filter change unit (14) to lower the filter strength to extend the passband if priority is given to control accuracy, and to increase the filter strength to cut out noise components if priority is not given to control accuracy.

[0084] (Supplementary Note 2) In the above control device (10), the drive command is a machining program, and the filter change determination unit (15) determines whether or not to prioritize the control accuracy depending on the type of operation specified in the machining program, and changes the filter strength.

[0085] (Supplementary Note 3) In the above control device (10), the drive command is a position command or a speed command, and the filter change determination unit (15) determines that the control accuracy is important when the feed speed is within a threshold range.

[0086] (Note 4) In the control device (10), the feedback control unit (11) performs PI control or PID control, and the filter change unit (14) changes the filter strength for feedback other than that performing integral processing.

[0087] (Supplementary Note 5) The control device (10) further comprises a gain change unit (20) that changes a feedback gain of the feedback control unit (11), and when the filter strength is changed by the filter change unit (14), the gain change unit (20) applies a high gain when the filter strength is lowered, and applies a low gain when the filter strength is higher.

[0088] (Supplementary Note 6) In the above control device (10), the filter unit (13) is a moving average filter or a low-pass filter.

[0089] (Supplementary Note 7) In the control device (10), the feedback acquisition unit (12) acquires, as the feedback, a current flowing through the electric motor (1), a rotation angle of the electric motor, or a rotation speed of the electric motor.

[0090] REFERENCE SIGNS LIST 1 Electric motor 10, 10a to 10d Control device 11, 11a, 11b Feedback control unit 12 Feedback acquisition unit 13, 13a to 13d Filter unit 14 Filter change unit 15 Filter change determination unit 20 Gain change unit 21 Proportional control unit 22 Integral control unit 23 Differential control unit

Claims

1. A control device comprising: a feedback control unit that causes an electric motor to follow a drive command through feedback control; a feedback acquisition unit that acquires feedback from the electric motor; a filter unit that filters the feedback acquired by the feedback acquisition unit; a filter change unit that changes the filter strength of the filter unit; and a filter change determination unit that determines whether control accuracy is important from the drive command, and controls the filter change unit to lower the filter strength and extend the pass band if control accuracy is important, or to increase the filter strength and cut out noise components if control accuracy is not important.

2. The control device according to claim 1, wherein the drive command is a machining program, and the filter change determination unit determines whether or not to prioritize control accuracy depending on the type of operation specified in the machining program, and changes the filter strength.

3. The control device according to claim 1 or 2, wherein the drive command is a position command or a speed command, and the filter change determination unit determines that the control accuracy is important when the feed speed is within a threshold range.

4. The control device according to any one of claims 1 to 3, wherein the feedback control section performs PI control or PID control, and the filter change section changes the filter strength for feedback other than that performing integral processing.

5. A control device as described in any one of claims 1 to 4, further comprising a gain change unit that changes the feedback gain of the feedback control unit, wherein when the filter strength is changed by the filter change unit, the gain change unit applies a higher gain if the filter strength is lowered, and applies a lower gain if the filter strength is higher.

6. The control device according to any one of claims 1 to 5, wherein the filter section is a moving average filter or a low-pass filter.

7. The control device according to any one of claims 1 to 6, wherein the feedback acquisition unit acquires the current flowing through the electric motor, the rotation angle of the electric motor, or the rotation speed of the electric motor as the feedback.

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