Motor control device and robot
The motor control device addresses encoder fault detection challenges by continuously adding a test signal to the encoder feedback or control command, facilitating prompt and precise fault diagnosis in both operating and stopped states.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- SHIBAURA MASCH CO LTD
- Filing Date
- 2025-01-10
- Publication Date
- 2026-07-23
AI Technical Summary
Existing motor control systems face challenges in accurately detecting encoder failures, particularly when the motor is in a stopped state, as it is difficult to distinguish between normal motor stoppage and encoder malfunction.
A motor control device that continuously adds a test signal (noise) to the encoder feedback value or control command, allowing for continuous fault diagnosis of the encoder regardless of the motor's operational state, using a diagnostic unit to determine encoder functionality based on encoder value changes.
Enables timely and accurate detection of encoder faults, reducing detection delays and simplifying the fault diagnosis process by differentiating between normal motor stoppage and encoder malfunctions.
Smart Images
Figure 2026121073000001_ABST
Abstract
Description
Technical Field
[0001] Embodiments according to the present invention relate to a motor control device and a robot.
Background Art
[0002] In a servo motor, the motor may be controlled based on the detection value of a sensor (encoder) that detects the position (rotation position) of the motor. When a failure occurs in the encoder, it is desirable to appropriately detect the failure of the encoder.
[0003] When the motor is controlled to be in a stopped state, it may be difficult to determine whether the detection value of the encoder does not change because the motor has stopped normally or because the encoder has failed.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Patent Document 2
Patent Document 3
Patent Document 4
Patent Document 5
Summary of the Invention
Problems to be Solved by the Invention
[0005] An object of the present invention is to provide a motor control device and a robot that can more appropriately detect a failure of a sensor.
Means for Solving the Problems
[0006] The motor control device according to this embodiment includes a first receiving unit that receives a detection value from a position sensor that detects the position of the motor, and an amplifier unit that controls the operation of the motor based on a control command value and the detected value from the position sensor that is fed back. Regardless of whether the motor is operating or controlled to a stopped state, a test signal is continuously added to the control command value or the detected value from the position sensor that is fed back, and it is diagnosed whether or not the position sensor is malfunctioning based on the detected value from the position sensor when the test signal is not being added. [Brief explanation of the drawing]
[0007] [Figure 1] This block diagram shows an example of the configuration of a host device and a motor control device according to the first embodiment. [Figure 2] This figure shows an example of noise according to the first embodiment. [Figure 3] This block diagram shows an example of the configuration of a host device and a motor control device according to a modification of the first embodiment. [Figure 4] This block diagram shows an example of the configuration of a host device and motor control device according to the second embodiment. [Figure 5] This block diagram shows an example of the configuration of a host device and a motor control device according to a modification of the second embodiment. [Modes for carrying out the invention]
[0008] Embodiments of the present invention will be described below with reference to the drawings. These embodiments are not limiting to the present invention. The drawings are schematic or conceptual, and the proportions of each part may not necessarily be the same as those of actual objects. In the specification and drawings, elements similar to those described above with respect to previously shown drawings are denoted by the same reference numerals, and detailed explanations are omitted as appropriate.
[0009] (First Embodiment) Figure 1 is a block diagram showing an example of the configuration of the host device 100 and motor control device 200 according to the first embodiment.
[0010] The upper device 100 transmits a control command value to the motor control device 200. In the example shown in FIG. 1, the control command value is a position command value. Note that the control command value is not limited to the position command value, and may be a speed command value or the like.
[0011] The motor control device 200 includes a motor 10, an encoder 20, a servo amplifier 30, a noise transmission unit 40, and a diagnostic unit 50.
[0012] The motor control device 200 controls the motor 10 based on the control command value transmitted from the upper device 100. At least a part of the motor control device 200 including the servo amplifier 30 is used, for example, in a robot, but may also be used in industrial machinery or the like.
[0013] The motor 10 is connected to a drive mechanism (not shown) and operates the drive mechanism. The drive mechanism is, for example, a drive mechanism of a robot.
[0014] The encoder (position sensor) 20 detects the position of the motor 10. The encoder 20 transmits an encoder value (detection value of the position sensor) to the servo amplifier 30 and the diagnostic unit 50.
[0015] The servo amplifier 30 has an encoder value receiving unit (first receiving unit) 31, an amplifier unit 32, and a noise receiving unit (second receiving unit) 33.
[0016] The encoder value receiving unit 31 receives the encoder value. The encoder value receiving unit 31 transmits the received encoder value to the amplifier unit 32.
[0017] The amplifier unit 32 receives the control command value and the encoder value. The amplifier unit 32 uses the encoder value for feedback control. The amplifier unit 32 controls the operation of the motor 10 based on the control command value and the feedback encoder value.
[0018] The noise receiving unit 33 receives noise (test signal) that is added to the encoder value being fed back. When minute noise is added, the motor 10 makes minute movements. Details of the noise will be described later with reference to FIG. 2.
[0019] The noise receiving unit 33 continues to receive noise regardless of whether the motor 10 is operating or is controlled to be in a stopped state (whether it is stopped). As a result, noise continues to be added to the encoder value fed back to the amplifier unit 32 regardless of whether the motor 10 is operating or is controlled to be in a stopped state. Therefore, minute movement due to noise is superimposed on the operation of the motor 10 regardless of whether the motor 10 is operating or is controlled to be in a stopped state.
[0020] The noise transmitting unit 40 transmits noise to the noise receiving unit 33. The noise transmitting unit 40 may generate noise or may receive noise generated outside the noise transmitting unit 40.
[0021] The diagnostic unit 50 receives an encoder value from the encoder 20. In the example shown in FIG. 1, the diagnostic unit 50 is arranged outside the servo amplifier 30.
[0022] Also, the diagnostic unit 50 diagnoses whether the encoder 20 is faulty based on the encoder value in a state where no noise is added. Therefore, based on the encoder value in a state where no noise is added, it is diagnosed whether the encoder 20 is faulty. When minute movement based on noise appears in the encoder value, the diagnostic unit 50 diagnoses that the encoder 20 is not faulty. When minute movement based on noise does not appear in the encoder value, the diagnostic unit 50 diagnoses that the encoder 20 is faulty.
[0023] More specifically, the diagnostic unit 50 diagnoses that the encoder 20 is not faulty if the change in the encoder value over a predetermined period is greater than or equal to a predetermined value. On the other hand, the diagnostic unit 50 diagnoses that the encoder 20 is faulty if the change in the encoder value over a predetermined period is less than or equal to a predetermined value. The predetermined value is set to a value less than or equal to the change in the encoder value due to minute movements caused by noise. Therefore, if the encoder value does not change over a predetermined period, the encoder 20 is diagnosed as faulty.
[0024] Furthermore, the noise level is, for example, significantly smaller than the magnitude of the control command value. Therefore, the change in encoder value during motor 10 operation is significantly larger than the change in encoder value due to minute movements. While motor 10 is operating, if encoder 20 is functioning correctly, it is difficult to detect the minute signals themselves, but encoder 20 is diagnosed as not malfunctioning.
[0025] The predetermined period is set, for example, according to the period during which the motor 10 is controlled to a stopped state. The predetermined period may be longer than the maximum period during which the motor 10 is controlled to a stopped state.
[0026] Furthermore, if the diagnostic unit 50 diagnoses that the encoder 20 is faulty, it outputs a signal indicating the diagnostic result of the encoder 20 (encoder malfunction).
[0027] Next, I will explain the details of the noise.
[0028] Figure 2 shows an example of noise according to the first embodiment.
[0029] In the example shown in Figure 2, the noise is a square wave. However, the noise may also be a triangular wave or the like. The period of the noise is, for example, 100 ms. The period of the noise is shorter than the diagnostic time (predetermined period) of the diagnostic unit 50. The maximum value of the noise is, for example, +10. In Figure 2, +10 means a value of +10 times the minimum resolution of the encoder 20. The minimum value of the noise is, for example, -10. In Figure 2, -10 means a value of -10 times the minimum resolution of the encoder 20.
[0030] The noise waveform, period, amplitude, and duty cycle are set appropriately for each motor 10 or drive mechanism. If the noise effect is too small, minute vibrations will not appear in the encoder value. On the other hand, if the noise effect is too large, it will affect the operation of the motor 10 or drive mechanism.
[0031] The noise is a signal capable of changing the encoder value of a normal, non-malfunctioning encoder 20. Furthermore, the noise is a signal capable of changing the encoder value when the noise is not present. The magnitude (amplitude) of the noise is, for example, greater than the minimum resolution of the encoder 20.
[0032] The noise is within a range that does not affect the operation of the motor 10 or drive mechanism based on the control command value. In other words, the noise is within a range that allows the motor 10 or drive mechanism to operate normally based on the control command value. The magnitude (amplitude) of the noise is, for example, 10 times or less the minimum resolution of the encoder 20.
[0033] As described above, according to the first embodiment, noise is continuously added to the encoder value fed back to the amplifier unit 32, regardless of whether the motor 10 is operating or controlled to a stopped state. Based on the encoder value when the noise is not added, it is diagnosed whether or not the encoder 20 is faulty. This makes it possible to detect faults in the encoder 20 more appropriately. Furthermore, fault diagnosis of the encoder 20 is performed continuously, regardless of whether the motor 10 is operating or controlled to a stopped state.
[0034] While the motor 10 is operating, diagnosing a fault in the encoder 20 is relatively easy. If the encoder value changes while the motor 10 is operating, the encoder 20 is functioning correctly. On the other hand, if the encoder value does not change while the motor 10 is operating, the encoder 20 is faulty. However, when the motor 10 is controlled to a stopped state, it can be difficult to determine whether the lack of change in the encoder value is due to the motor 10 being properly stopped or due to a fault in the encoder 20. By adding noise as a test signal to the feedback encoder value, a fault in the encoder 20 can be detected more appropriately, even when the motor 10 is controlled to a stopped state.
[0035] Note that the noise does not necessarily have to be added during the operation of the motor 10. However, by adding the noise during the operation of the motor 10, fault diagnosis of the encoder 20 can be performed even while the motor 10 is operating, and the noise addition process can be simplified.
[0036] As a comparative example, if the encoder value does not change for a certain period of time, the control command value to the motor may be changed. If the encoder value does not change after the control command value is changed, an encoder failure is detected. However, in the encoder failure diagnosis using the comparative example, the control command value is changed only after it has been confirmed that the encoder value has not changed. Therefore, a delay occurs before the encoder failure is detected.
[0037] In contrast, in the first embodiment, noise is continuously added regardless of whether the motor 10 is operating or controlled to a stopped state. That is, noise is continuously added almost constantly, allowing the encoder 20 to be diagnosed almost constantly. This eliminates the need to determine whether or not the encoder value is changing. As a result, the delay until a fault in the encoder 20 is detected can be suppressed.
[0038] (Modification of the first embodiment) Figure 3 is a block diagram showing an example of the configuration of the host device 100 and motor control device 200 according to a modification of the first embodiment. In this modification of the first embodiment, the arrangement of the diagnostic unit 50 is different compared to the first embodiment.
[0039] The diagnostic unit 50 is located inside the servo amplifier 30. The diagnostic unit 50 receives encoder values from the encoder value receiving unit 31.
[0040] Other configurations of the motor control device 200 according to the modification of the first embodiment are the same as the corresponding configurations of the motor control device 200 according to the first embodiment, so a detailed description thereof will be omitted.
[0041] As in the modified version of the first embodiment, the arrangement of the diagnostic unit 50 may be changed. The motor control device 200 according to the modified version of the first embodiment can obtain the same effects as the first embodiment.
[0042] (Second Embodiment) Figure 4 is a block diagram showing an example of the configuration of the host device 100 and motor control device 200 according to the second embodiment. The second embodiment differs from the first embodiment in that noise is added to the position command value (control command value) instead of the encoder value.
[0043] The noise receiving unit 33 receives noise that is added to the control command value. As a result, noise is continuously added to the control command value regardless of whether the motor 10 is operating or controlled to a stopped state. In the example shown in Figure 4, the noise is added to the control command value inside the servo amplifier 30.
[0044] The other configurations of the motor control device 200 according to the second embodiment are the same as the corresponding configurations of the motor control device 200 according to the first embodiment, so a detailed description thereof will be omitted.
[0045] As in the second embodiment, noise may be added to the position command value (control command value). The motor control device 200 according to the second embodiment can obtain the same effects as the first embodiment. Furthermore, the second embodiment may be combined with a modified version of the first embodiment. In this case, the diagnostic unit 50 is located inside the servo amplifier 30.
[0046] (Modified version of the second embodiment) Figure 5 is a block diagram showing an example of the configuration of the host device 100 and motor control device 200 according to a modification of the second embodiment. The modification of the second embodiment differs from the second embodiment in that the noise is added outside the servo amplifier 30.
[0047] In the modified version of the second embodiment, the noise receiving unit 33 is not provided.
[0048] The motor control device 200 further includes a noise receiving unit 60. The noise receiving unit 60 is located outside the servo amplifier 30. Similar to the noise receiving unit 33, the noise receiving unit 60 receives noise that is added to the control command value. In the example shown in Figure 5, the noise is added to the control command value outside the servo amplifier 30.
[0049] Other configurations of the motor control device 200 according to the modification of the second embodiment are the same as the corresponding configurations of the motor control device 200 according to the second embodiment, so a detailed description thereof will be omitted.
[0050] As in the modified version of the second embodiment, noise may be added outside the servo amplifier 30. The motor control device 200 according to the modified version of the second embodiment can obtain the same effects as the second embodiment. Furthermore, the modified version of the second embodiment may be combined with the modified version of the first embodiment. In this case, the diagnostic unit 50 is located inside the servo amplifier 30.
[0051] At least a portion of the data processing method in the motor control device according to this embodiment may be implemented in hardware or in software. If implemented in software, a program that implements at least a portion of the functions of the data processing method may be stored on a recording medium such as a flexible disk or CD-ROM, loaded into a computer, and executed. The recording medium is not limited to removable ones such as magnetic disks or optical disks, but may also be a fixed recording medium such as a hard disk drive or memory. Furthermore, the program that implements at least a portion of the functions of the data processing method may be distributed via a communication line such as the Internet (including wireless communication). In addition, the program may be encrypted, modulated, or compressed, and then distributed via a wired or wireless line such as the Internet, or stored on a recording medium.
[0052] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of symbols]
[0053] 200 Motor control device, 10 Motor, 20 Encoder, 30 Servo amplifier, 31 Encoder value receiving unit, 32 Amplifier unit, 33 Noise receiving unit, 50 Diagnostic unit
Claims
1. A first receiving unit that receives the detected value from a position sensor that detects the position of the motor, An amplifier unit controls the operation of the motor based on the control command value and the detected value of the position sensor that is fed back, Equipped with, The control command value or the detected value of the position sensor that is fed back will continue to have a test signal added to it, regardless of whether the motor is operating or controlled to a stopped state. A motor control device that diagnoses whether or not the position sensor is malfunctioning based on the detected value of the position sensor when the test signal is not being added.
2. The motor control device according to claim 1, wherein if the detected value of the position sensor does not change for a predetermined period of time, the position sensor is diagnosed as being faulty.
3. The motor control device according to claim 1, wherein the test signal is capable of changing the detected value of the position sensor when the test signal is not added, and is a signal that does not affect the operation of the motor based on the control command value.
4. The motor control device according to claim 1, wherein the test signal is capable of changing the state in which the test signal is not added, and is a signal that enables the motor to operate normally based on the control command value.
5. The motor control device according to claim 1, wherein the magnitude of the test signal is greater than the minimum resolution of the position sensor and less than or equal to 10 times the minimum resolution of the position sensor.
6. The motor control device according to claim 1, further comprising a diagnostic unit that diagnoses whether or not the position sensor is malfunctioning based on the detected value of the position sensor when the test signal is not being added.
7. The motor control device according to claim 6, wherein the diagnostic unit diagnoses that the position sensor is malfunctioning if the change in the detected value of the position sensor over a predetermined period is less than a predetermined value.
8. The motor control device according to claim 6, wherein the diagnostic unit is disposed inside a servo amplifier having the first receiving unit and the amplifier unit.
9. The motor control device according to claim 6, wherein the diagnostic unit is located outside the servo amplifier having the first receiving unit and the amplifier unit.
10. The motor and, The position sensor and, The motor control device according to claim 1, further comprising:
11. The motor control device according to claim 1, further comprising a second receiving unit for receiving the test signal.
12. A robot comprising the motor control device described in claim 1.