Electromagnetic brake failure determination device, electromagnetic brake failure determination method, electromagnetic brake failure determination program, and recording medium

Abstract

A determination as to whether an electromagnetic brake 1 has failed with respect to a motor 2 is made on the basis of the result of a response of feedback control to a virtual disturbance variation operation for changing a torque command signal S7 by changing a disturbance signal S6. Specifically, the response of the feedback control to a change in the torque command signal S7 (a change in a position control signal S5) is different between cases where a brake release fault does not occur and cases where a brake release fault occurs. Accordingly, a determination as to whether the electromagnetic brake 1 has failed is made on the basis of the result of the response of the feedback control. Thus, it is possible to determine whether a brake release fault has occurred in the non-excitation-operation-type electromagnetic brake 1.

Description

Electromagnetic brake failure determination device, electromagnetic brake failure determination method, electromagnetic brake failure determination program, and recording medium

[0001] The present invention relates to a technique for detecting a fault in an electromagnetic brake that applies a brake to a motor.

[0002] Patent Documents 1 to 3 describe devices for controlling robots. To control such robots, a non-excitation type electromagnetic brake, such as that shown in Patent Document 1, can be used. This electromagnetic brake includes an armature and an excitation coil. When the excitation coil is not energized, the armature is pressed against the motor by the biasing force of a spring, thereby braking the motor. When the excitation coil is energized, the magnetic force generated by the excitation coil pulls the armature away from the motor, thereby releasing the brake. Patent Document 2 also describes technology for dealing with brake failures. According to this technology, if a drop of a moving part is detected while the brake is applied, it is determined that there is a brake failure.

[0003] Japanese Patent Application Laid-Open No. 2017-185595 Japanese Patent Application Laid-Open No. 2017-087493 Japanese Patent Application Laid-Open No. 07-027411

[0004] However, in a non-excitation operation type electromagnetic brake, a brake release failure (failure) can occur, in which the brake does not release even when the excitation coil is energized. Such a brake release failure can occur for a variety of reasons, such as a broken circuit that energizes the excitation coil or the armature sticking to the motor. If an attempt is made to operate the motor while a brake release failure exists, a load is applied to the brake, which could cause further failure (secondary failure) in the brake. However, the above-mentioned technology cannot determine whether or not such a failure has occurred.

[0005] SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to make it possible to determine whether or not there is a brake release failure in a non-excitation operation type electromagnetic brake.

[0006] The electromagnetic brake fault determination device of the present invention comprises a position control unit that acquires a target value for the motor position and a detected value for the motor position, and outputs a position control signal for performing feedback control on the motor position in accordance with deviation of the detected value from the target value; a disturbance output unit that outputs a disturbance signal; a composite signal generation unit that generates a composite signal by combining the position control signal and the disturbance signal; a torque control unit that causes the motor to generate torque in accordance with the composite signal generated by the composite signal generation unit; and a fault determination unit that determines whether or not there is a fault in the electromagnetic brake for the motor based on the result of the response of the feedback control of the position control unit to a disturbance variation operation that changes the composite signal by changing the disturbance signal output by the disturbance output unit.

[0007] The electromagnetic brake fault determination method according to the present invention includes the steps of: acquiring a target value for the motor position and a detected value for the motor position; outputting a position control signal for executing feedback control on the motor position in response to deviation of the detected value from the target value; generating a composite signal by combining the position control signal and a disturbance signal; causing the motor to generate torque in response to the composite signal; and determining whether or not there is a fault in the electromagnetic brake for the motor based on the result of the feedback control response to a disturbance variation operation that changes the composite signal by changing the disturbance signal.

[0008] An electromagnetic brake failure determination program according to the present invention causes a computer to execute the electromagnetic brake failure determination method described above.

[0009] A recording medium according to the present invention stores the electromagnetic brake failure determination program in a computer-readable manner.

[0010] The present invention (electromagnetic brake fault detection device, electromagnetic brake fault detection method, electromagnetic brake fault detection program, and recording medium) configured as described above causes the motor to generate torque corresponding to a position control signal. This position control signal is a signal for acquiring a target value for the motor position and a detected value for the motor position, and for executing feedback control on the motor position corresponding to the deviation of the detected value from the target value. In other words, the motor position is controlled by feedback control that brings the motor position closer to the target value. Furthermore, a composite signal is generated by combining the position control signal and a disturbance signal, and the motor generates torque corresponding to this composite signal. In particular, the presence or absence of an electromagnetic brake fault for the motor is determined based on the response of the feedback control to a disturbance variation operation that changes the composite signal by changing the disturbance signal. In other words, the response of the feedback control to changes in the composite signal differs between when a brake release failure does not occur and when a brake release failure occurs. Therefore, the presence or absence of an electromagnetic brake fault is determined based on the response of the feedback control. In this way, it is possible to determine the presence or absence of a brake release failure in a non-excitation operation type electromagnetic brake.

[0011] Furthermore, the present invention can determine whether or not a brake release failure has occurred with a simple configuration in which the disturbance signal is changed and the response of the feedback control is confirmed. In other words, there is an advantage in that the function of determining whether or not a brake release failure has occurred can be provided without requiring a complex and expensive mechanism.

[0012] The electromagnetic brake fault determination device may also be configured so that the fault determination unit determines whether or not there is a fault in the electromagnetic brake for the motor based on the position control signal after the disturbance fluctuating operation. In this configuration, the presence or absence of a brake release failure can be determined simply by checking the change in the position control signal accompanying the response of the feedback control.

[0013] The electromagnetic brake fault determination device may also be configured so that the fault determination unit determines whether or not there is a fault in the electromagnetic brake based on the difference between the value of the position control signal before and after the disturbance fluctuation operation. With this configuration, it is possible to determine whether or not there is a brake release failure with a simple configuration such as checking the values ​​of the position control signal before and after the disturbance fluctuation operation.

[0014] The electromagnetic brake fault determination device may be configured so that the fault determination unit determines that there is no fault in the electromagnetic brake when the difference is equal to or greater than a threshold value, and determines that there is a fault in the electromagnetic brake when the difference is less than the threshold value. With this configuration, it is possible to determine whether or not there is a brake release failure with a simple configuration in which the difference between the values ​​of the position control signal before and after the disturbance fluctuation operation is compared with a threshold value.

[0015] The electromagnetic brake fault determination device may be configured so that the fault determination unit determines whether or not there is a fault in the electromagnetic brake for the motor based on the composite signal after the disturbance variation operation. In this configuration, the presence or absence of a brake release failure can be determined simply by checking the change in the composite signal accompanying the response of the feedback control.

[0016] The electromagnetic brake failure determination device may also be configured to determine whether or not there is a failure in the electromagnetic brake for the motor based on the composite signal after a predetermined time has elapsed since the disturbance change operation. In other words, a spike may occur in the composite signal due to the disturbance change operation. The influence of this spike may lead to an erroneous determination of whether or not there is a brake release failure. In contrast, by determining whether or not there is a failure in the electromagnetic brake after a predetermined time has elapsed since the disturbance change operation, the influence of the spike can be suppressed.

[0017] The electromagnetic brake fault determination device may also be configured so that the fault determination unit determines whether or not there is a fault in the electromagnetic brake based on the difference between the value of the combined signal before and after the disturbance fluctuation operation. With this configuration, it is possible to determine whether or not there is a brake release failure with a simple configuration such as checking the values ​​of the combined signal before and after the disturbance fluctuation operation.

[0018] The electromagnetic brake fault determination device may be configured so that the fault determination unit determines that there is no fault in the electromagnetic brake when the difference is less than a threshold value, and determines that there is a fault in the electromagnetic brake when the difference is equal to or greater than the threshold value. With this configuration, it is possible to determine whether or not there is a brake release failure with a simple configuration in which the difference in the value of the combined signal before and after the disturbance fluctuation operation is compared with a threshold value.

[0019] Various specific modes for changing the disturbance signal in the disturbance variation control are possible. For example, the electromagnetic brake fault determination device may be configured so that the fault determination unit changes the disturbance signal by decreasing the absolute value of the disturbance signal from a value greater than zero to zero, thereby performing the disturbance variation control. Alternatively, the electromagnetic brake fault determination device may be configured so that the fault determination unit changes the disturbance signal by increasing the absolute value of the disturbance signal from zero to a value greater than zero, thereby performing the disturbance variation control.

[0020] According to the present invention, it is possible to determine whether or not there is a brake release failure in a non-excitation operation type electromagnetic brake.

[0021] Fig. 2 is a partial cross-sectional view schematically showing the configuration and operation of a non-excitation operation type electromagnetic brake. Fig. 3 is a block diagram showing the configuration of a computer used to control the electromagnetic brake of Fig. 1. Fig. 4 is a block diagram showing an example of the configuration of a motor control unit. Fig. 5 is a diagram showing an example of the response of a position feedback control unit to a disturbance signal. Fig. 6 is a diagram showing an example of the response of a position feedback control unit to a disturbance signal. Fig. 7 is a flowchart showing a first example of an electromagnetic brake failure determination process. Fig. 8 is a flowchart showing a second example of an electromagnetic brake failure determination process.

[0022] Figure 1 is a partial cross-sectional view showing the structure and operation of a non-excitation type electromagnetic brake. The electromagnetic brake 1 in Figure 1 is used to brake a motor 2 used in various robots such as SCARA robots and single-axis robots. Figure 1 shows an axial direction X parallel to the output shaft (rotation axis) of the motor 2, and a rotation direction R about the rotation axis parallel to the axial direction X.

[0023] The electromagnetic brake 1 brakes the motor 2 by restricting rotation of the motor 2 in the rotational direction R. In other words, when the motor 2 generates torque, the output shaft of the motor 2 rotates in accordance with the torque to drive a driven object. The motor 2 has a rotor 21 and a hub 22 provided at the center of the rotor 21, and the rotor 21 is connected to the output shaft of the motor 2 via the hub 22. The rotor 21 rotates integrally with the output shaft of the motor 2. In contrast, the electromagnetic brake 1 brakes the motor 2 by restricting rotation of the rotor 21 in the rotational direction R. For example, if the motor 2 is used to drive a driven object against gravity, the electromagnetic brake 1 restricts rotation of the rotor 21 in the rotational direction R, thereby restricting rotation of the output shaft of the motor 2 connected to the rotor 21 by the hub 22 in the rotational direction R, thereby stopping the driven object against gravity (in other words, preventing the driven object from falling).

[0024] The electromagnetic brake 1 has a brake body 11. The brake body 11 has a base plate 111 disposed perpendicular to the axial direction X, and a support plate 112 protruding from the base plate 111 in the axial direction X. The support plate 112 protrudes from the base plate 111 toward the rotor 21 of the motor 2.

[0025] The electromagnetic brake 1 also has a backup plate 12 and an armature 13 that are provided closer to the rotor 21 than the base plate 111 in the axial direction X. The backup plate 12 and the armature 13 are disposed on both sides of the rotor 21 in the axial direction X. That is, in the axial direction X, the rotor 21 is located between the backup plate 12 and the armature 13 and faces both the backup plate 12 and the armature 13. The backup plate 12 is disposed on the opposite side of the base plate 111 with respect to the armature 13 and is attached to the support plate 112. In the axial direction X, the armature 13 is disposed between the base plate 111 and the rotor 21 and faces the base plate 111. The armature 13 fits into the hub 22 from the outside via a hole that opens in the center, and is movable in the axial direction X relative to the hub 22.

[0026] Furthermore, the electromagnetic brake 1 has a brake spring 14 that biases the armature 13 in the axial direction X relative to the base plate 111. The base plate 111 has a spring arrangement hole 113 that extends in the axial direction X, and the brake spring 14 is arranged in the spring arrangement hole 113 in the axial direction X. The spring arrangement hole 113 opens toward the armature 13, and the brake spring 14 protrudes from the spring arrangement hole 113 toward the armature 13. The brake spring 14 is arranged between the bottom of the spring arrangement hole 113 and the armature 13, and generates a biasing force that biases the armature 13 in a direction away from the base plate 111 (in other words, toward the rotor 21).

[0027] The electromagnetic brake 1 also has a plurality of excitation coils 15 built into the base plate 111. These excitation coils 15 face the armature 13 in the axial direction X.

[0028] When the excitation coil 15 is energized, the excitation coil 15 generates an attractive force that attracts the armature 13 toward the base plate 111 (i.e., the opposite side of the rotor 21). Therefore, as shown in the "When energized" column in FIG. 1 , the attractive force of the excitation coil 15 attracts the armature 13 toward the base plate 111 against the biasing force of the brake spring 14. As a result, the armature 13 moves away from the rotor 21, creating a gap between the armature 13 and the rotor 21. As a result, the rotor 21 is able to rotate in the rotational direction R without being restricted by the armature 13 (brake released state).

[0029] On the other hand, when the exciting coil 15 is not energized, the exciting coil 15 does not generate the above-mentioned attractive force. Therefore, as shown in the "de-energized" column in Fig. 1, the armature 13 is pressed against the rotor 21 by the biasing force of the brake spring 14. As a result, the rotation of the rotor 21 in the rotational direction R is restricted by the frictional force between the armature 13 and the rotor 21 (brake operating state).

[0030] Figure 2 is a block diagram showing the configuration of a computer used to control the electromagnetic brake of Figure 1. The computer 3 of Figure 2 includes a calculation unit 31, a storage unit 32, and a display 33. The calculation unit 31 is a processor such as a central processing unit (CPU). The storage unit 32 is a storage device such as an SSD (solid state drive). The display 33 functions as a user interface that displays a screen to the user in response to commands from the calculation unit 31.

[0031] A control program 321 is recorded in the storage unit 32 so as to be readable by the calculation unit 31. This control program 321 is a program that causes the calculation unit 31 to execute processing ( FIGS. 5A and 5B ) for determining whether or not there is a fault in the electromagnetic brake 1. The control program 321 is downloaded from, for example, an external server (recording medium) and stored in the storage unit 32.

[0032] The calculation unit 31 has an electromagnetic brake control unit 4 and a motor control unit 5. The electromagnetic brake control unit 4 and the motor control unit 5 are constructed within the calculation unit 31 as the calculation unit 31 executes a control program 321. The electromagnetic brake control unit 4 controls the operation of the electromagnetic brake 1, and the motor control unit 5 controls the operation of the motor 2.

[0033] When the motor control unit 5 starts operating the motor 2, the electromagnetic brake control unit 4 sends a brake release command to the electromagnetic brake 1. When the electromagnetic brake 1 receives the brake release command, it starts energizing the excitation coil 15. As a result, as shown in the "Electrified" column of FIG. 1 , the armature 13 moves away from the rotor 21, allowing the rotor 21 to rotate in the rotational direction R (brake released state). Furthermore, when the motor control unit 5 stops the rotation of the motor 2, the electromagnetic brake control unit 4 sends a brake operation command to the electromagnetic brake 1. When the electromagnetic brake 1 receives the brake operation command, it stops energizing the excitation coil 15. As a result, as shown in the "De-energized" column of FIG. 1 , the armature 13 comes into contact with the rotor 21, restricting rotation of the rotor 21 in the rotational direction R (brake activated state).

[0034] 3 is a block diagram showing an example of the configuration of the motor control unit 5. The motor control unit 5 has a position feedback control unit 51 that feedback controls the rotation angle (position) of the motor 2 (specifically, the output shaft) in the rotation direction R. The position feedback control unit 51 has a position controller 511, a speed controller 512, a differentiator 513, and subtractors 514 and 515.

[0035] The position feedback control unit 51 acquires a target angle θc, which is a target value for the rotation angle of the motor 2, and a detected angle θd, which is a detected value of the actual rotation angle of the motor 2. The detected angle θd is the rotation angle of the motor 2 output by the encoder of the motor 2, and the position feedback control unit 51 acquires the detected angle θd from the motor 2. The target angle θc and the detected angle θd are input to a subtractor 514, which generates a signal S1 (= θc - θd) that is the difference between the target angle θc and the detected angle θd and outputs the signal S1 to a position controller 511. The position controller 511 generates a signal S2 for proportional control based on the signal S1 and outputs the signal S2 to a subtractor 515. Note that the control performed by the position controller 511 is not limited to this example, and the position controller 511 may generate a signal S2 for performing appropriate control from among differential control, proportional control, and integral control.

[0036] The detected angle θd is also input to a differentiator 513, which generates a signal S3 by differentiating the detected angle θd with respect to time and outputs the signal S3 to a subtractor 515. The subtractor 515 generates a signal S4 (=S2-S3), which is the difference between the signals S2 and S3, and outputs the signal S4 to a speed controller 512. The speed controller 512 generates and outputs a signal S5 for performing proportional control and integral control based on the signal S4. Note that the control performed by the speed controller 512 is not limited to this example, and the speed controller 512 may generate a signal S5 for performing appropriate control from among differential control, proportional control, and integral control. In this way, the position feedback control unit 51 generates and outputs a signal S5 for performing feedback control (position control and speed control) to bring the detected angle θd closer to the target angle θc.

[0037] The motor control unit 5 also includes a torque controller 53, a virtual disturbance generator 54, a fault determination unit 55, an adder 56, and a subtractor 57. A signal S5 output from the position feedback control unit 51 is input to the adder 56. The virtual disturbance generator 54 generates a signal S6 (disturbance signal) indicating a virtual disturbance in response to a command from the fault determination unit 55, and outputs the signal S6 to the adder 56. The adder 56 adds the signals S5 and S6 together to generate a signal S7 (=S5+S6), and outputs the signal S7 to the subtractor 57. The signal S7 corresponds to a torque command signal that specifies the torque to be generated by the motor 2.

[0038] The subtractor 57 also receives a signal S8 from the motor 2 that indicates the current flowing through the motor 2. This signal S8 corresponds to a torque detection signal that indicates the detected value of the torque actually output by the motor 2. The subtractor 57 generates a signal S9 (=S7-S8) by subtracting the signals S7 and S8, and outputs the signal S9 to the torque controller 53. The torque controller 53 generates a signal S10 for causing the motor 2 to generate a torque corresponding to the signal S9, and outputs the signal S10 to the motor 2. The motor 2 then generates a torque corresponding to the signal S10 to rotate the rotary shaft.

[0039] 4A and 4B are diagrams showing an example of the response of the position feedback control unit to a disturbance signal. In Figures 4A and 4B, the time change of signal S6 (disturbance signal S6) at position Pa is shown in the "disturbance signal" column, signal S5 (position control signal S5) at position Pb and signal S7 (torque command signal S7) at position Pc when there is no brake release failure are shown in the "no brake release failure" column, and signal S5 (position control signal S5) at position Pb and signal S7 (torque command signal S7) at position Pc when there is a brake release failure are shown in the "brake release failure" column.

[0040] Here, a brake release failure is a failure in which the armature 13 contacts the rotor 21 and restricts rotation of the rotor 21 in the rotational direction R, despite the electromagnetic brake control unit 4 sending a brake release command to the electromagnetic brake 1. This failure occurs for various reasons, such as a break in the circuit that supplies electricity to the excitation coil 15, or the armature 13 sticking to the rotor 21. In other words, the "No brake release failure" column shows the changes over time in the signals S5 and S7 in a situation in which the armature 13 separates from the rotor 21 in response to the electromagnetic brake control unit 4 sending a brake release command to the electromagnetic brake 1. The "Brake release failure" column shows the changes over time in the signals S5 and S7 in a situation in which the armature 13 contacts the rotor 21, despite the electromagnetic brake control unit 4 sending a brake release command to the electromagnetic brake 1.

[0041] In the example of Figure 4A, a disturbance signal S6 that increases in a stepwise manner from 0 to 2 at time ts is input to adder 56. If there is no brake release failure, the position control signal S5 changes by an amount of change Δ5a before and after time ts (step application time) when the disturbance signal S6 changes in a stepwise manner, and the torque command signal S7 changes very little. However, immediately after time ts, the torque command signal S7 increases and decreases in a spike-like manner. If there is a brake release failure, the position control signal S5 changes very little before and after time ts (step application time) when the disturbance signal S6 changes in a stepwise manner, and the torque command signal S7 changes by an amount of change Δ7a.

[0042] Therefore, if the change in the position control signal S5 before and after the step application time ts is equal to or greater than a predetermined threshold T5a (greater than zero and smaller than the change amount Δ5a), it can be determined that there is no brake release failure. Also, if the change in the position control signal S5 before and after the step application time ts is less than the predetermined threshold T5a, it can be determined that there is a brake release failure.

[0043] Alternatively, if the change in the torque command signal S7 before and after the step application time ts is equal to or greater than a predetermined threshold T7a (greater than zero and smaller than the change amount Δ7a), it can be determined that there is a brake release failure. Also, if the change in the torque command signal S7 before and after the step application time ts is less than the predetermined threshold T7a, it can be determined that there is no brake release failure.

[0044] In the example of Figure 4B, the disturbance signal S6, which decreases in a stepwise manner from 2 to 0 at time ts, is input to the adder 56. If there is no brake release failure, the position control signal S5 changes by an amount of change Δ5b before and after time ts (step application time) when the disturbance signal S6 changes in a stepwise manner, and the torque command signal S7 changes very little. However, immediately after time ts, the torque command signal S7 increases and decreases in a spike-like manner. If there is a brake release failure, the position control signal S5 changes very little before and after time ts (step application time) when the disturbance signal S6 changes in a stepwise manner, and the torque command signal S7 changes by an amount of change Δ7b.

[0045] Therefore, if the change in the position control signal S5 before and after the step application time ts is equal to or greater than a predetermined threshold T5b (greater than zero and smaller than the change amount Δ5b), it can be determined that there is no brake release failure. Also, if the change in the position control signal S5 before and after the step application time ts is less than the predetermined threshold T5b, it can be determined that there is a brake release failure.

[0046] Alternatively, if the change in the torque command signal S7 before and after the step application time ts is equal to or greater than a predetermined threshold T7b (greater than zero and smaller than the change Δ7b), it can be determined that there is a brake release failure. Also, if the change in the torque command signal S7 before and after the step application time ts is less than the predetermined threshold T7b, it can be determined that there is no brake release failure.

[0047] 5A is a flowchart showing a first example of the electromagnetic brake failure determination process. In step S101, the failure determination unit 55 sends a servo lock start command to the position feedback control unit 51 and the torque controller 53. As a result, the position feedback control unit 51 and the torque controller 53 each start the above-described control.

[0048] In step S102, the failure determination unit 55 causes the electromagnetic brake control unit 4 to send a brake release command to the electromagnetic brake 1. This causes the electromagnetic brake 1 to energize the exciting coil 15. In step S103, the failure determination unit 55 executes a virtual disturbance variation operation that temporally varies the disturbance signal S6 output by the virtual disturbance generator 54. The virtual disturbance generator 54 varies the disturbance signal S6 in a stepwise manner, for example, as shown in FIG. 4A or 4B .

[0049] In step S104, the fault determination unit 55 determines whether the amount of change in the position control signal S5 before and after the virtual disturbance variation operation is equal to or greater than a predetermined threshold. If it is determined that the amount of change in the position control signal S5 is equal to or greater than the predetermined threshold ("YES" in step S104), the position control signal S5 is determined to be at the release level. Then, the fault determination unit 55 determines that the braking of the motor 2 by the electromagnetic brake 1 has been released and that there is no brake release failure (step S105). For example, the determination result of step S105 by the fault determination unit 55 is displayed on the display 33.

[0050] If it is determined that the amount of change in the position control signal S5 is less than the predetermined threshold value ("NO" in step S104), it is determined that the position control signal S5 is not at the release level. Then, the fault determination unit 55 determines that the braking of the motor 2 by the electromagnetic brake 1 has not been released and that there is a brake release failure (step S106). For example, the determination result by the fault determination unit 55 in step S106 is displayed on the display 33.

[0051] In the embodiment described above, the position feedback control unit 51 (position control unit) acquires a target rotation angle θc (target value) of the motor 2 and a detected rotation angle θd (detected value) of the motor 2, and outputs a position control signal S5 for executing feedback control on the rotation angle of the motor 2 in response to the deviation of the detected angle θd from the target angle θc. The torque controller 53 then causes the motor 2 to generate torque in response to the position control signal S5. That is, the rotation angle of the motor 2 is controlled by feedback control that brings the position of the motor 2 closer to the target angle θc. Furthermore, a torque command signal S7 (combined signal) is generated by adding the position control signal S5 and the disturbance signal S6, and the torque controller 53 causes the motor 2 to generate torque in response to this torque command signal S7. In particular, the presence or absence of a fault in the electromagnetic brake 1 for the motor 2 is determined (steps S104, S105, and S106) based on the result of the feedback control response (change in the position control signal S5) to the virtual disturbance varying operation (step S103) that changes the torque command signal S7 by changing the disturbance signal S6. In other words, the response of the feedback control to a change in the torque command signal S7 (change in the position control signal S5) differs between when a brake release failure does not occur and when a brake release failure occurs. Therefore, the presence or absence of a fault in the electromagnetic brake 1 is determined based on the result of the response of the feedback control. In this way, it is possible to determine the presence or absence of a brake release failure in the non-excitation operation type electromagnetic brake 1.

[0052] Furthermore, in this embodiment, the presence or absence of a brake release failure can be determined with a simple configuration in which the disturbance signal S6 is changed and the response of the feedback control is confirmed. In other words, there is no need to provide a circuit or the like for detecting the energization state of the exciting coil 15. This has the advantage of providing a function for determining the presence or absence of a brake release failure without requiring a complex and expensive mechanism.

[0053] Furthermore, the failure determination unit 55 determines whether or not there is a failure in the electromagnetic brake 1 for the motor 2 based on the position control signal S5 after the virtual disturbance variation operation (step S103) (steps S103, S105, S106). With this configuration, the presence or absence of a brake release failure can be determined with a simple configuration such as checking the change in the position control signal S5 accompanying the response of the feedback control.

[0054] Furthermore, the failure determination unit 55 determines whether or not there is a failure in the electromagnetic brake 1 based on the difference between the value of the position control signal S5 before the virtual disturbance variation operation (step S103) and the value of the position control signal S5 after the virtual disturbance variation operation (step S103) (steps S104, S105, S106). With this configuration, the presence or absence of a brake release failure can be determined with a simple configuration in which the values ​​of the position control signal S5 before and after the virtual disturbance variation operation (step S103) are checked.

[0055] Furthermore, if the difference in the position control signal S5 before and after the virtual disturbance variation operation (step S103) is equal to or greater than a threshold value (if "YES" in step S104), the failure determination unit 55 determines that there is no failure in the electromagnetic brake 1 (step S105), and if the difference is less than the threshold value (if "NO" in step S104), it determines that there is a failure in the electromagnetic brake 1 (step S106). With this configuration, the presence or absence of a brake release failure can be determined with a simple configuration in which the difference in the value of the position control signal S5 before and after the virtual disturbance variation operation (step S103) is compared with a threshold value.

[0056] 5B is a flowchart showing a second example of the electromagnetic brake failure determination process. The first example in FIG. 5A and the second example in FIG. 5B differ in that step S107 is executed instead of step S104, but the first and second examples are otherwise common. Therefore, the following description will focus on the differences from the first example, and the parts common to the first example will be assigned the same reference numerals and will not be described again.

[0057] In the second example of FIG. 5B , in step S107 following the virtual disturbance variation operation (step S103), the fault determination unit 55 determines whether the amount of change in the torque command signal S7 before and after the virtual disturbance variation operation is less than a predetermined threshold. If it is determined that the amount of change in the torque command signal S7 is less than the predetermined threshold ("YES" in step S107), the torque command signal S7 is determined to be at the release level. Then, the fault determination unit 55 determines that the braking of the motor 2 by the electromagnetic brake 1 has been released and that there is no brake release failure (step S105). For example, the determination result of step S105 by the fault determination unit 55 is displayed on the display 33.

[0058] If it is determined that the amount of change in the torque command signal S7 is equal to or greater than the predetermined threshold value ("NO" in step S107), it is determined that the torque command signal S7 is not at the release level. Then, the fault determination unit 55 determines that the braking of the motor 2 by the electromagnetic brake 1 has not been released and that there is a brake release failure (step S106). For example, the determination result of the fault determination unit 55 in step S106 is displayed on the display 33.

[0059] In this second example, the failure determination unit 55 determines whether or not there is a failure in the electromagnetic brake 1 for the motor 2 based on the torque command signal S7 (synthetic signal) after the virtual disturbance variation operation (step S103) (steps S107, S105, S106). With this configuration, it is possible to determine whether or not there is a brake release failure with a simple configuration such as checking the change in the torque command signal S7 accompanying the response of the feedback control.

[0060] Furthermore, the failure determination unit 55 determines whether or not there is a failure in the electromagnetic brake 1 based on the difference between the value of the torque command signal S7 before the virtual disturbance variation operation (step S103) and the value of the torque command signal S7 after the virtual disturbance variation operation (step S103) (steps S107, S105, S106). With this configuration, the presence or absence of a brake release failure can be determined with a simple configuration in which the value of the torque command signal S7 before and after the virtual disturbance variation operation (step S103) is checked.

[0061] Furthermore, if the difference in the torque command signal S7 before and after the virtual disturbance variation operation (step S103) is less than the threshold value ("YES" in step S107), the failure determination unit 55 determines that there is no failure in the electromagnetic brake 1 (step S105), and if the difference is equal to or greater than the threshold value ("NO" in step S107), it determines that there is a failure in the electromagnetic brake 1. With this configuration, the presence or absence of a brake release failure can be determined with a simple configuration in which the difference in the value of the torque command signal S7 before and after the virtual disturbance variation operation (step S103) is compared with the threshold value.

[0062] As shown in FIGS. 4A and 4B , the torque command signal S7 increases or decreases in a spike-like manner in response to the virtual disturbance variation operation (step S103). Therefore, the failure determination unit 55 determines whether or not there is a failure in the electromagnetic brake 1 for the motor 2 based on the torque command signal S7 after waiting for a predetermined time (the time until the spike-like increase or decrease in the torque command signal S7 ends) to elapse from the virtual disturbance variation operation (step S103). In other words, a spike may occur in the torque command signal S7 in response to the virtual disturbance variation operation (step S103). The influence of this spike may lead to an erroneous determination of whether or not there is a brake release failure. In response to this, the influence of the spike can be suppressed by waiting for a predetermined time to elapse from the virtual disturbance variation operation (step S103) before executing step S107 to determine whether or not there is a failure in the electromagnetic brake 1. This predetermined time can be determined, for example, based on experiments or simulations.

[0063] As described above, in the above embodiment, the motor 2 corresponds to an example of the "motor" of the present invention, the target angle θc corresponds to an example of the "target value" of the present invention, the detected angle θd corresponds to an example of the "detected value" of the present invention, the position control signal S5 corresponds to an example of the "position control signal" of the present invention, the position feedback control unit 51 corresponds to an example of the "position control unit" of the present invention, the disturbance signal S6 corresponds to an example of the "disturbance signal" of the present invention, the virtual disturbance generator 54 corresponds to an example of the "disturbance output unit" of the present invention, the torque command signal S7 corresponds to an example of the "synthetic signal" of the present invention, and the adder 56 corresponds to an example of the "synthetic signal" of the present invention. the torque controller 53 corresponds to an example of a "torque control unit" of the present invention; the virtual disturbance variation operation of step S103 corresponds to an example of a "disturbance variation operation" of the present invention; the electromagnetic brake 1 corresponds to an example of an "electromagnetic brake" of the present invention; the fault determination unit 55 corresponds to an example of a "fault determination unit" of the present invention; the computer 3 corresponds to an example of an "electromagnetic brake fault determination device" of the present invention; the control program 321 corresponds to an example of an "electromagnetic brake fault determination program" of the present invention; and the memory unit 32 or the external server corresponds to an example of a "recording medium" of the present invention.

[0064] The present invention is not limited to the above embodiment, and various modifications can be made to the above without departing from the spirit of the present invention. For example, various modes for changing the disturbance signal S6 in the virtual disturbance varying operation in step S103 are conceivable. Therefore, the disturbance signal S6 may be changed in a sinusoidal wave shape rather than in a step shape.

[0065] Furthermore, the specific configurations for realizing the position feedback control unit 51 and the torque controller 53 may be changed as appropriate. The type of the motor 2 may also be changed from the above example, and the motor 2 may be a linear motor.

[0066] REFERENCE SIGNS LIST 1... Electromagnetic brake 2... Motor 3... Computer 32... Storage unit 321... Control program 51... Position feedback control unit 53... Torque controller 54... Virtual disturbance generator 55... Fault determination unit 56... Adder S103... Step S5... Position control signal S6... Disturbance signal S7... Torque command signal θc... Target angle θd... Detected angle

Claims

1. An electromagnetic brake fault determination device comprising: a position control unit that acquires a target value for a motor position and a detected value for the motor position, and outputs a position control signal for executing feedback control on the motor position in accordance with deviation of the detected value from the target value; a disturbance output unit that outputs a disturbance signal; a composite signal generation unit that generates a composite signal by combining the position control signal and the disturbance signal; a torque control unit that causes the motor to generate torque in accordance with the composite signal generated by the composite signal generation unit; and a fault determination unit that determines whether or not there is a fault in the electromagnetic brake for the motor based on the result of the response of the feedback control of the position control unit to a disturbance variation operation that changes the composite signal by changing the disturbance signal output by the disturbance output unit.

2. An electromagnetic brake fault determination device according to claim 1, wherein the fault determination unit determines whether or not there is a fault in the electromagnetic brake for the motor based on the position control signal after the disturbance variation operation.

3. An electromagnetic brake fault determination device as described in claim 2, wherein the fault determination unit determines whether or not there is a fault in the electromagnetic brake based on the difference between the value of the position control signal before the disturbance variation operation and the value of the position control signal after the disturbance variation operation.

4. An electromagnetic brake fault determination device as described in claim 3, wherein the fault determination unit determines that there is no fault in the electromagnetic brake if the difference is equal to or greater than a threshold value, and determines that there is a fault in the electromagnetic brake if the difference is less than the threshold value.

5. An electromagnetic brake fault determination device according to claim 1, wherein the fault determination unit determines whether or not there is a fault in the electromagnetic brake for the motor based on the composite signal after the disturbance variation operation.

6. An electromagnetic brake fault determination device according to claim 5, wherein the presence or absence of a fault in the electromagnetic brake for the motor is determined based on the composite signal after a predetermined time has elapsed since the disturbance variation operation.

7. An electromagnetic brake fault determination device as described in claim 5 or 6, wherein the fault determination unit determines whether or not there is a fault in the electromagnetic brake based on the difference between the value of the composite signal before the disturbance variation operation and the value of the composite signal after the disturbance variation operation.

8. An electromagnetic brake fault determination device as described in claim 7, wherein the fault determination unit determines that there is no fault in the electromagnetic brake if the difference is less than a threshold value, and determines that there is a fault in the electromagnetic brake if the difference is equal to or greater than the threshold value.

9. An electromagnetic brake fault determination device as described in any one of claims 1 to 8, wherein the fault determination unit performs the disturbance variation operation by changing the disturbance signal by reducing the absolute value of the disturbance signal from a value greater than zero to zero.

10. An electromagnetic brake fault determination device as described in any one of claims 1 to 8, wherein the fault determination unit performs the disturbance variation operation by changing the disturbance signal by increasing the absolute value of the disturbance signal from zero to a value greater than zero.

11. A method for determining whether or not there is a fault in an electromagnetic brake for the motor, comprising the steps of: acquiring a target value for the position of a motor and a detected value for the position of the motor, and outputting a position control signal for executing feedback control on the position of the motor in accordance with the deviation of the detected value from the target value; generating a composite signal by combining the position control signal and a disturbance signal; causing the motor to generate torque in accordance with the composite signal; and determining whether or not there is a fault in an electromagnetic brake for the motor, based on the result of the response of the feedback control to a disturbance variation operation that changes the composite signal by changing the disturbance signal.

12. An electromagnetic brake fault detection program that causes a computer to execute the electromagnetic brake fault detection method according to claim 11.

13. A recording medium on which the electromagnetic brake fault determination program according to claim 12 is recorded so as to be readable by a computer.

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