Brake diagnostic method, brake diagnostic device, brake diagnostic program, and control device for robot

Abstract

In order to measure gravitational torque with high precision and diagnose a brake with high precision, a brake diagnosis method of a robot includes: detecting a gravitational torque in a state where the brake of a motor driving a second member with respect to a first member is released; acquiring a torque during movement generated by the motor during movement of the second member relative to the first member based on operation of the motor; calculating a brake diagnostic torque on the basis of the acquired torque at the time of movement; and determining the presence or absence of an abnormality in the brake using the calculated brake diagnostic torque.

Description

Technical Field

[0001] The present invention relates to a brake diagnosis method, a brake diagnosis device, a brake diagnosis program, and a control device for a robot. Background Art

[0002] Conventionally, a method has been known in which, in order to diagnose a decrease in the holding torque of a brake provided in a motor of a robot, a motor torque is applied in a state where the brake is applied, and whether the motor slips is detected (for example, refer to Patent Document 1). When the brake to be diagnosed is provided in a motor that drives a component on which gravity acts, as the motor torque applied during diagnosis, in addition to the brake holding torque, the gravity torque needs to be considered. The gravity torque applied to the motor is obtained from the measured value of the motor torque required to stop the component on which gravity acts in a state where the brake is released.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2005-254410 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] However, when measuring the gravity torque in a state where the robot is stationary, the static friction of the mechanism part of the robot has a large influence, and the measured value deviates. Therefore, it is desired to measure the gravity torque with high accuracy and diagnose the brake with high accuracy.

[0008] Solutions to the Problems

[0009] One aspect of the present invention is a brake diagnosis method for a robot, the brake diagnosis method for the robot including: in a state where a brake of a motor that drives a second component with respect to a first component is released, obtaining a moving torque generated by the motor during a process in which the second component moves with respect to the first component based on the operation of the motor; calculating a brake diagnosis torque based on the obtained moving torque; and determining whether the brake is abnormal using the calculated brake diagnosis torque. Brief Description of the Drawings

[0010] Figure 1 It is a perspective view showing an example of a robot and a control device to which the brake diagnosis method according to the first embodiment of the present invention is applied.

[0011] Figure 2 It shows the execution Figure 1 The block diagram of the brake diagnosis device of the brake diagnosis method.

[0012] Figure 3 is a flowchart of a brake diagnosis method indicating Figure 1 .

[0013] Figure 4 is a flowchart for explaining Figure 3 the gravity torque measurement step of

[0014] Figure 5 is a diagram for explaining Figure 3 the speed command for the target motor and the time variation of the torque in the gravity torque measurement step of

[0015] Figure 6 is a flowchart for explaining Figure 3 the abnormality determination step of

[0016] Figure 7 is a flowchart for explaining the abnormality determination step of the brake diagnosis method according to the second embodiment of the present invention. Detailed Embodiment

[0017] Hereinafter, with reference to the drawings, a brake diagnosis method and a brake diagnosis device 10 of a robot 1 according to a first embodiment of the present invention will be described.

[0018] The brake diagnosis method of the robot 1 according to the present embodiment is a method for diagnosing, for example, brakes 9 provided in six motors 8 of a vertical six-axis multi-joint robot.

[0019] As Figure 1 shown, the robot 1 includes: a base 2 fixed to a mounting surface such as the ground; and a rotating body 3 supported so as to be rotatable relative to the base 2 about a vertical first axis J1. In addition, the robot 1 includes a first arm 4 supported so as to be rotatable relative to the rotating body 3 about a horizontal second axis J2.

[0020] Furthermore, the robot 1 includes: a second arm 5 supported so as to be rotatable relative to the first arm 4 about a third axis J3 parallel to the second axis J2; and a three-axis wrist unit 6 attached to the front end of the second arm 5. A tool S such as a hand or a workpiece is fixed to the front end of the wrist unit 6. In the figure, reference numeral 7 is a control device.

[0021] Here, for example, a case where the brake 9 of a motor (hereinafter, referred to as a target motor) 8 that rotationally drives the first arm (second component) 4 about the second axis J2 with respect to the rotating body (first component) 3 will be described as an example.

[0022] As Figure 2As shown, the brake diagnosis device 10 of the present embodiment includes at least one processor 11 and a memory 12. The processor 11 acquires angle information from an encoder 13 provided in the target motor 8. In addition, the processor 11 outputs a brake operation command for operating the brake 9 or releasing the brake 9 with respect to the brake 9 provided in the target motor 8. In addition, the processor 11 outputs a torque command for rotationally driving the target motor 8 to the target motor 8.

[0023] The brake diagnosis method of the present embodiment is implemented in any posture of the robot 1. For example, the diagnosis of the brake 9 of the target motor 8 that rotationally drives the first arm 4 is implemented in a state where the first arm 4 is disposed at an arbitrary first position with respect to the rotating body 3.

[0024] As Figure 3 shown, the brake diagnosis method of the present embodiment includes a gravity torque measurement step S1, a diagnostic torque calculation step S2, and an abnormality determination step S3.

[0025] As Figure 4 shown, the gravity torque measurement step S1 includes a brake release step S11, a torque measurement step S12, a torque calculation step S13, and a reset step S14.

[0026] In the brake release step S11, the processor 11 only sends a brake operation command to the target motor 8 and releases the brake 9 of the target motor 8.

[0027] In the torque measurement step S12, while moving the target motor 8 from the first position to the second position in one direction, the processor 11 measures the torque (torque during movement). The first position, the second position, and each position during the movement are calculated by the processor 11 based on the angle information from the encoder 13 provided in the target motor 8.

[0028] In Figure 5 shows the speed command of the target motor 8 in the torque measurement step S12 and the time change of the torque command (current value) output to the target motor 8 based on the speed command. When the torque measurement step S12 starts, the target motor 8 accelerates, then operates at a fixed speed, and then decelerates and reaches the second position.

[0029] In the torque calculation step S13, the processor 11 calculates the torque during movement by performing time averaging on the torque command of the target motor 8 measured during the constant speed period of operating at this fixed speed. The torque during movement includes: the gravity counteracting torque required for the target motor 8 to counteract gravity; and the dynamic friction counteracting torque required to counteract dynamic friction.

[0030] As Figure 5As shown, since the torque command varies at a high frequency, it is also possible to perform time averaging on the torque command smoothed by passing it through a low-pass filter, for example.

[0031] The displacement amount of the target motor 8 from the first position to the second position can be suppressed to be very small by sufficiently suppressing the speed during the constant speed period.

[0032] In the reset step S14, the processor 11 supplies a torque command to the target motor 8, causing the target motor 8 to operate in the direction opposite to the operation in the torque measurement step S12 and return to the first position. In the reset step S14, the processor 11 accelerates the target motor 8 from the second position in the direction opposite to the torque measurement step S12, then operates at a fixed speed, and then decelerates to reach the first position.

[0033] In the diagnostic torque calculation step S2, the processor 11 calculates the brake diagnostic torque by adding, for example, the calculated moving torque and a preset brake holding torque. The brake holding torque is the torque that can be held by the brake 9 in a normal state and is stored in the memory 12.

[0034] As Figure 6 shown, the abnormality determination step S3 includes a brake operation step S31, a diagnostic torque addition step S32, and a change amount detection step S33. In addition, the abnormality determination step S3 includes a comparison step S34 and a notification step S35.

[0035] In the brake operation step S31, the processor 11 outputs a brake operation command to cause only the brake 9 of the target motor 8 to operate.

[0036] In the diagnostic torque addition step S32, the processor 11 causes the target motor 8 to generate the brake diagnostic torque calculated in the diagnostic torque calculation step S2 in the direction opposite to the gravitational torque.

[0037] In the change amount detection step S33, based on the angle information from the encoder 13, the angle change amount (operation amount) of the target motor 8 from the moment when the brake diagnostic torque is generated in the target motor 8 based on the torque command from the processor 11 is detected. In the comparison step S34, the processor 11 determines whether the angle change amount detected in the change amount detection step S33 is greater than a threshold value pre-stored in the memory 12.

[0038] In the notification step S35, the processor 11 outputs a brake abnormality alarm for notifying the meaning that there is an abnormality in the brake 9 when the result of the determination in the comparison step S34 shows that the amount of angular change is greater than the threshold value. When the amount of angular change is equal to or less than the threshold value, the brake 9 is normal and the process ends. Regarding the brake abnormality alarm, for example, in addition to displaying its meaning on a monitor (not shown), it can be any alarm that can be recognized by the five senses of the operator, such as sound, buzzer, lighting of a warning lamp, vibration, etc.

[0039] Hereinafter, the operation of the brake diagnosis method and the brake diagnosis device 10 of this embodiment configured as described above will be described.

[0040] According to this embodiment, since the moving torque is measured in a state where the brake 9 is released and the motor 8 performs a constant-speed operation, there are the following advantages: the influence of static friction can be excluded, and the gravitational torque including dynamic friction can be measured with high precision.

[0041] Moreover, since the moving torque measured with high precision is used, there are the following advantages: the diagnosis of whether there is an abnormality in the brake 9 can be performed with high precision.

[0042] In addition, according to this embodiment, since the moving torque is measured before the diagnosis of the brake 9, there are the following advantages: the diagnosis of the brake 9 can be performed regardless of the posture of the robot 1. In addition, since the moving torque is measured before the diagnosis of the brake 9, there are the following advantages: even if the weight and the center of gravity of the tool S or the workpiece mounted at the front end of the wrist unit 6 of the robot 1 are changed, the diagnosis of the brake 9 can be performed with high precision.

[0043] That is, a method of pre-storing the diagnostic posture of the robot 1 for diagnosing the brake 9 and the gravitational torque in this diagnostic posture is also considered. However, in this case, each time the brake 9 is diagnosed, the robot 1 needs to be in the diagnostic posture. In addition, in this case, each time the weight or the center of gravity position of the tool S or the workpiece mounted at the front end of the wrist unit 6 is changed, the gravitational torque needs to be measured, which is troublesome. According to this embodiment, these disadvantages do not exist, and the diagnosis of the brake 9 can be performed simply.

[0044] In addition, in this embodiment, the case where the motor 8 and the brake 9 are operated by the brake diagnosis device 10 is illustrated. However, in this case, the control device 7 that operates the robot 1 may also include the brake diagnosis device 10. When the brake diagnosis device 10 is provided separately from the control device 7, in the gravitational torque measurement step S1 and the abnormality determination step S3, the brake diagnosis device 10 only needs to obtain the torque command for the target motor 8 from the control device 7.

[0045] In addition, in the present embodiment, the brake diagnostic device 10 diagnoses whether there is an abnormality in the brake 9 by using the brake diagnostic torque. Instead, it is also possible to diagnose whether there is an abnormality in the brake 9 by executing a brake diagnostic program. In this case, the above-described brake diagnostic method may be executed in the brake diagnostic device 10 or the control device 7.

[0046] In addition, in the present embodiment, the torque generated by the target motor 8 is detected and the moving torque is calculated during the constant-speed operation of the target motor 8. However, it is not limited to the constant-speed operation, and the moving torque may also be detected during the acceleration operation. If the acceleration is known, the influence of static friction can be excluded and the moving torque can be calculated with high precision in the same manner as in the constant-speed operation.

[0047] In addition, the moving torque was calculated based on the torque measured during the constant-speed period while the target motor 8 was moved from the first position to the second position. Instead, the moving torque may also be calculated based on the torque measured during the constant-speed period while returning from the second position to the first position. Alternatively, the moving torque may also be calculated based on the torque measured during both reciprocating motions between the first position and the second position.

[0048] In addition, in the abnormality determination step S3, the target motor 8 generates a brake diagnostic torque that is the sum of the moving torque and the brake holding torque in a direction opposite to the gravity torque. Instead, the target motor 8 may also be caused to generate a brake diagnostic torque in a direction the same as the gravity torque, which is calculated by subtracting the gravity torque from the brake holding torque.

[0049] In addition, in the present embodiment, an example is described in which the motor that rotationally drives the first arm 4 with respect to the rotating body 3 is used as the target motor 8 to diagnose the brake 9. Instead, the motor that rotationally drives the second arm 5 with respect to the first arm 4 or the motors of the respective wrist elements that rotationally drive the wrist unit 6 may be used as the target motor 8.

[0050] Moreover, in the present embodiment, the motor in the case where the gravity torque acts is described as the target motor 8. Instead, the brake diagnostic method of the present embodiment may also be applied to the case where a motor in which gravity does not act, such as a motor that rotationally drives the rotating body 3 with respect to the base 2, is used as the target motor 8 to diagnose the brake 9.

[0051] In addition, in the present embodiment, the case of diagnosing the brake 9 of the vertically articulated six-axis multi-joint robot has been illustrated. Instead, it can also be applied to other arbitrary-shaped robots such as horizontally articulated multi-joint robots. Further, instead of the brake 9 of the motor 8 that drives the rotary joint, the brake diagnosis method of the present embodiment can be applied to the diagnosis of the brake 9 of the motor 8 that drives the linear joint.

[0052] Next, the brake diagnosis method and the brake diagnosis device 10 according to the second embodiment of the present invention will be described with reference to the accompanying drawings.

[0053] This embodiment is different from the first embodiment in the abnormality determination step S3.

[0054] In this embodiment, as Figure 7 shown, the abnormality determination step S3 includes a brake release step S36, a diagnostic torque addition step S37, a determination step S38, and a notification step S35. In the brake release step S36, the processor 11 outputs a brake release command, so that only the brake 9 of the target motor 8 is released. The target motor 8 with the brake 9 released generates a torque against the gravitational torque, thereby maintaining the target motor 8 in a stationary state.

[0055] In the diagnostic torque addition step S37, the processor 11 causes the brake 9 to operate while or after causing the target motor 8 to generate the brake diagnostic torque calculated in the diagnostic torque calculation step S2 in a direction opposite to the gravitational torque. By generating the brake diagnostic torque, the target motor 8 starts rotational driving in a direction opposite to the gravitational torque, but is decelerated by the operation of the brake 9.

[0056] In the determination step S38, the processor 11 determines whether the operation of the target motor 8 stops, that is, whether the rotational speed becomes zero, based on the result of deceleration due to the operation of the brake 9. If the rotational speed becomes zero and the target motor 8 stops, the brake 9 is normal and the process ends. If the rotational speed does not become zero and the target motor 8 does not stop, the process proceeds to the notification step S35, and a message indicating that there is an abnormality in the brake 9 is notified.

[0057] According to the present embodiment, compared with the case of adding the brake diagnostic torque in a state where the brake 9 is operating, there is an advantage that the influence of static friction during abnormality determination can be excluded. That is, it is possible to prevent the target motor 8 from maintaining a stationary state due to static friction even when the holding torque of the brake decreases, and to prevent misjudging that the brake 9 is normal.

[0058] In addition, in the present embodiment, in the determination step S38, the processor 11 determines whether the rotational speed becomes zero as a result of deceleration based on the operation of the brake 9. Instead, similarly to the first embodiment, in the determination step S38, the processor 11 may also determine whether the displacement amount is less than a predetermined threshold value.

[0059] As described above, the embodiments of the present invention have been described in detail, but the present invention is not limited to the above-described respective embodiments. In these embodiments, various additions, conversions, changes, and partial deletions can be made without departing from the gist of the invention, or without departing from the idea and purpose of the present invention derived from the content described in the claims and their equivalents. For example, in the above-described embodiments, the order of each action and the order of each process are shown as an example and are not limited to these orders.

[0060] Appendix 1

[0061] A method for diagnosing a brake of a robot includes:

[0062] In a state where the brake of a motor that drives a second component relative to a first component is released, acquiring a moving torque generated by the motor during a process in which the second component moves relative to the first component based on the operation of the motor;

[0063] Based on the acquired moving torque, calculating a torque for brake diagnosis; and

[0064] Using the calculated torque for brake diagnosis to determine whether there is an abnormality in the brake.

[0065] Appendix 2

[0066] In the method for diagnosing a brake of a robot according to Appendix 1,

[0067] In a state where the brake is applied, based on the amount of movement of the motor after generating the torque for brake diagnosis by the motor, determining whether there is an abnormality in the brake.

[0068] Appendix 3

[0069] In the method for diagnosing a brake of a robot according to Appendix 1,

[0070] Based on the amount of movement or rotational speed of the motor after generating the torque for brake diagnosis by the motor during a process in which the second component moves relative to the first component, determining whether there is an abnormality in the brake.

[0071] Appendix 4

[0072] In the method for diagnosing a brake of a robot according to Appendix 2 or 3,

[0073] When the amount of movement of the motor is greater than a predetermined threshold value, it is determined that there is an abnormality in the brake.

[0074] Appendix 5

[0075] In the brake diagnosis method for a robot described in Appendix 3,

[0076] When the rotational speed of the motor does not become zero, it is determined that there is an abnormality in the brake.

[0077] Appendix 6

[0078] In the brake diagnosis method for a robot described in any one of Appendices 1 to 3,

[0079] The torque during movement is the time average of the torque generated by the motor during the constant-speed operation of the motor.

[0080] Appendix 7

[0081] In the brake diagnosis method for a robot described in any one of Appendices 1 to 4,

[0082] The torque for brake diagnosis is the sum of the torque during movement and the brake holding torque, or the difference between the brake holding torque and the torque during movement.

[0083] Appendix 8

[0084] In the brake diagnosis method for a robot described in any one of Appendices 1 to 5,

[0085] When it is determined that there is an abnormality in the brake, the meaning of the existence of the abnormality is notified.

[0086] Appendix 9

[0087] In a brake diagnosis device for a robot,

[0088] It includes at least one processor,

[0089] The processor is configured to execute the brake diagnosis method described in any one of Appendices 1 to 8.

[0090] Appendix 10

[0091] In a brake diagnosis program for a robot,

[0092] The computer is made to execute the brake diagnosis method described in any one of Appendices 1 to 8.

[0093] Appendix 11

[0094] In a control device for a robot,

[0095] Comprising at least one processor,

[0096] The processor is configured to perform the following processes:

[0097] Release the brake of the motor that drives the second component relative to the first component;

[0098] In a state where the brake is released, move the second component relative to the first component by the operation of the motor;

[0099] Obtain the moving torque generated by the motor during the movement of the second component relative to the first component;

[0100] Based on the obtained moving torque, calculate the torque for brake diagnosis; and

[0101] Use the calculated torque for brake diagnosis to determine whether there is an abnormality in the brake.

[0102] Explanation of reference numerals:

[0103] 1: Robot

[0104] 3: Rotating body (first component)

[0105] 4: First arm (second component)

[0106] 7: Control device

[0107] 8: Motor

[0108] 9: Brake

[0109] 10: Brake diagnosis device

[0110] 11: Processor

Claims

1. A method for diagnosing a brake of a robot, characterized in that, it includes: In a state where the brake of the motor that drives the second component relative to the first component is released, obtain the torque during movement generated by the motor during the process of moving the second component relative to the first component based on the operation of the motor; Based on the obtained torque during movement, calculate the torque for brake diagnosis; and Use the calculated torque for brake diagnosis to determine whether there is an abnormality in the brake.

2. The method for diagnosing a brake of a robot according to claim 1, characterized in that, In a state where the brake is applied, based on the amount of movement of the motor after generating the torque for brake diagnosis by the motor, determine whether there is an abnormality in the brake.

3. The method for diagnosing a brake of a robot according to claim 1, characterized in that, Based on the amount of movement or rotational speed of the motor after generating the torque for brake diagnosis by the motor during the process of moving the second component relative to the first component, determine whether there is an abnormality in the brake.

4. The method for diagnosing a brake of a robot according to claim 2 or 3, characterized in that, If the amount of movement of the motor is greater than a predetermined threshold, it is determined that there is an abnormality in the brake.

5. The method for diagnosing a brake of a robot according to claim 3, characterized in that, If the rotational speed of the motor does not become zero, it is determined that there is an abnormality in the brake.

6. The method for diagnosing a brake of a robot according to any one of claims 1 to 3, characterized in that, The torque during movement is the time average of the torque generated by the motor during the period when the motor performs a constant-speed operation.

7. The method for diagnosing a brake of a robot according to any one of claims 1 to 4, characterized in that, The torque for brake diagnosis is the sum of the torque during movement and the brake holding torque, or the difference between the brake holding torque and the torque during movement.

8. The method for diagnosing a brake of a robot according to any one of claims 1 to 5, characterized in that, If it is determined that there is an abnormality in the brake, notify the meaning of this abnormality.

9. A brake diagnosis device for a robot, characterized in that, It includes at least one processor, The processor is configured to execute the method for diagnosing a brake of a robot according to any one of claims 1 to 8.

10. A brake diagnosis program for a robot, characterized in that, It causes a computer to execute the method for diagnosing a brake of a robot according to any one of claims 1 to 8.

11. A control device for a robot, characterized in that, It includes at least one processor, The processor is configured to execute the following processing: Release the brake of the motor that drives the second component relative to the first component; In a state where the brake is released, move the second component relative to the first component through the operation of the motor; Obtain the torque during movement generated by the motor during the process of moving the second component relative to the first component; Based on the obtained torque during movement, calculate the torque for brake diagnosis; and Determine whether there is an abnormality in the brake by using the calculated torque for brake diagnosis.

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