Encoder wiring fault detection device

Abstract

To provide an encoder wiring failure detection device capable of detecting occurrence of encoder wiring failure and easily identifying a location of the failure in a system comprising a controlled device with an encoder, and a controller for controlling the controlled device.SOLUTION: An encoder wiring failure detection device is provided, comprising a first detection circuit 42 for detecting failure of encoder wiring for sending a first signal, and a second detection circuit 45 for detecting failure of encoder wiring for sending a second signal, where the first signal represents a signal that is sent from an encoder 60 to a controller 10 and the second signal represents a signal that is sent from the controller 10 to the encoder 60.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a failure detection device that detects a failure in encoder wiring in a system including a controlled device equipped with an encoder and a controller that controls the controlled device based on a signal from the encoder.

Background Art

[0002] There is a system comprising a controlled device equipped with an encoder and a controller that controls the controlled device based on a signal from the encoder. For example, in a robot system composed of a manipulator having a motor for each axis and a controller that servo-controls the motors in the manipulator, an encoder for detecting the rotational position of each motor is attached to the motor of each axis, and the motor position detected by the encoder is fed back to the controller side for servo control. In recent years, digitized encoders have become widespread, and commands are transmitted from the controller side to the digital encoder. Therefore, encoder wiring is provided between the controller and the encoder in the manipulator for signal transmission. As forms of encoder wiring, in addition to those simply configured to transmit encoder pulses or binary logical values of "0" and "1", differential signal wiring configured to transmit a pair of differential output signals composed of a logical signal and its inverted signal is known.

[0003] If a fault such as a break or short circuit occurs in the encoder wiring, the system will not function properly. Therefore, various methods for detecting faults in encoder wiring have been proposed. Patent documents 1 and 2 disclose a circuit for detecting a break in the encoder wiring when the encoder wiring is composed of differential signal wiring. This circuit inputs signals from a pair of signal lines constituting the differential signal wiring to an exclusive OR (ExOR) gate, and determines that there is a break in the encoder wiring when the output of the exclusive OR gate becomes "0". Patent document 3 discloses a method for detecting a break in the encoder wiring from an open-collector output type encoder using an encoder power supply, a break detection power supply with a higher voltage than the encoder power supply, and an overvoltage protection diode on the encoder side.

[0004] Patent Document 4 discloses an encoder communication circuit that facilitates the identification of the faulty part when an abnormality occurs in communication with an encoder, and includes a communication unit having the same interface as the encoder's interface and an encoder data creation unit that creates predetermined encoder data. When an abnormality occurs in communication with an encoder, by connecting the encoder communication circuit in place of the encoder, it is possible to determine whether the cause of the abnormality lies in the wiring, the encoder itself, or the communication circuit on the controller side. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 62-91267 [Patent Document 2] Japanese Patent Application Publication No. 4-355322 [Patent Document 3] Patent No. 4058431 [Patent Document 4] Japanese Patent Publication No. 2008-92620 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] If a fault occurs in encoder wiring, it is necessary to visually inspect all encoder wiring or replace the wiring to identify the fault location, which takes time. For example, in a system including a transport robot, the wiring length from the controller to the manipulator may exceed 10m, and the wiring length to each encoder inside the manipulator may also exceed 10m, so the total length of encoder wiring can reach several tens of meters. When a fault occurs in the encoder wiring of a robot system, the downtime required to identify the fault location becomes lengthy. Even if a break in the encoder wiring can be detected using the detection circuits shown in Patent Documents 1 to 3, it is still necessary to visually inspect the entire encoder wiring to identify the location of the break. Even if the encoder communication circuit shown in Patent Document 4 is used, it is not possible to detect where in the encoder wiring the fault occurred. Similar problems arise even if the controlled equipment controlled by the controller is not a manipulator, as long as that equipment is equipped with an encoder and the controller controls it according to the output from the encoder.

[0007] The object of the present invention is to provide a fault detection device that can detect the occurrence of a fault in encoder wiring and easily identify the location of the fault. [Means for solving the problem]

[0008] A fault detection device according to one aspect of the present invention is a system comprising a controlled device equipped with an encoder and a controller that controls the controlled device, wherein the encoder and the controller are connected via encoder wiring, and the device detects a fault occurring in the encoder wiring. logic The signal is treated as the first signal and sent from the controller to the encoder. logicThe fault detection device includes a first detection circuit that detects faults in the encoder wiring that sends the first signal, and a second detection circuit that detects faults in the encoder wiring that sends the second signal.

[0009] Previously, detection circuits for detecting faults in encoder wiring were only installed in the controller at the point where it received signals from the encoder. This alone was insufficient for detecting faults in encoder wiring, and it was difficult to pinpoint the location of the fault. Book In the fault detection device of this type, the following is sent from the encoder to the controller. logic The encoder wiring for the signal (i.e., the first signal), and the signal sent from the controller to the encoder logic By providing detection circuits on both the encoder wiring and the signal (i.e., the second signal), faults in the encoder wiring can be detected more reliably, and the location of the fault can be easily identified. In this case, by providing the second detection circuit on the controlled device, faults in the encoder wiring of the second signal in the section from the controller to the controlled device can be detected even more reliably. do .

[0010] Book In this embodiment, an interface section is provided in the controlled device, for example, as a circuit board, and the encoder wiring is divided into interface wiring between the controller and the interface section and internal wiring between the interface section and the encoder. The interface section includes a first receiver that receives a first signal via the internal wiring, a first driver that transmits a first signal via the interface wiring based on the reception result at the first receiver, a second receiver that receives a second signal via the interface wiring, and a second driver that transmits a second signal via the internal wiring based on the reception result at the second receiver. A first detection circuit is provided on the input side of the first receiver in the interface section, and a second detection circuit is provided on the input side of the second receiver in the interface section. ru.When a receiver is provided to receive signals from encoder wiring, and the driver sends a signal to another encoder wiring based on the reception result at the receiver, even if there is a fault in the encoder wiring connected to the receiver, the receiver will output a logic signal of "0" or "1", and the driver will send a signal to the encoder wiring based on this logic signal. In other words, a normal signal will be observed in the encoder wiring from which the driver is sending a signal. This means that by inserting a combination of a receiver and a driver into the encoder wiring so that the receiver's output is connected to the driver's input, it is possible to isolate faults in the encoder wiring at the insertion point. Therefore, by placing the receiver and driver in the interface section, it becomes easier to identify the location of faults in the encoder wiring.

[0011] When the first detection circuit and the second detection circuit are provided in the interface section of the controlled device, it is preferable to provide a processor such as a microprocessor connected to the controller, so that the detection results from the first and second detection circuits are input to the processor. With this configuration, the controller can know the detection results from the first and second detection circuits, and can easily identify the location of the fault in the encoder wiring. Furthermore, when the controlled device has multiple encoders, encoder wiring, the first detection circuit, and the second detection circuit are provided for each encoder, but it is preferable to provide a common processor for these multiple encoders. In this configuration, even if there are multiple encoders, only one processor is provided in the interface section, so the configuration of the interface section can be simplified and the number of wires between the interface section and the controller can be reduced.

[0012] When the first detection circuit is provided in the interface section, a third detection circuit for detecting faults in the interface wiring that sends the first signal may be provided inside the controller. By providing the third detection circuit, it becomes even easier to identify the location of the fault in the encoder wiring.

[0014] The transmission forms of the first signal and the second signal are arbitrary, but the first signal and the second signal are transmitted, for example, in the form of differential output signals. In this case, by constructing the first detection circuit and the second detection circuit using an exclusive OR gate, failures in various failure modes can be detected with a simple circuit configuration.

[0015] The controlled device targeted by the failure detection device according to the present invention is, for example, a manipulator in a robot system. In the case of a manipulator, the number of encoders provided therein tends to increase, and the encoder wiring also tends to be long. However, by applying the failure detection device according to the present invention, the time required to identify the failure location when a failure occurs in the encoder wiring can be significantly reduced.

Advantages of the Invention

[0016] According to the present invention, when a failure occurs in the encoder wiring, the occurrence of the failure can be detected and the location of the failure can be easily identified.

Brief Description of the Drawings

[0017] [Figure 1] It is a diagram showing encoder wiring in a general robot system. [Figure 2] It is a block diagram showing a robot system according to an embodiment of the present invention. [Figure 3] It is a diagram showing the configuration of the robot system shown in FIG. 2 when communication with the encoder is performed using differential output signals. [Figure 4] It is a block diagram showing a robot system according to another embodiment.

Embodiments for Carrying Out the Invention

[0018] Next, embodiments for implementing the present invention will be described with reference to the drawings. The fault detection device according to the present invention is a system that includes a controlled device provided with an encoder and a controller that controls the controlled device, and the encoder and the controller are connected via an encoder wiring, and detects a fault that has occurred in the encoder wiring. Hereinafter, it will be described on the assumption that the system is a robot system including a controller and a manipulator, and the controlled device is a manipulator. In this case, the controller performs servo control of the motors based on the outputs from the encoders provided in the motors of each axis of the manipulator. Of course, the system to which the present invention is applied is not limited to a robot controller, and the controlled device is not limited to a manipulator either.

[0019] First, the encoder wiring in a general robot system will be described with reference to FIG. 1. The robot system shown in FIG. 1 includes a controller 10 and a manipulator 40. The manipulator 40 has a plurality of axes, and a plurality of encoders 60 are also provided. In the figure, two encoders 60 are depicted. In the figure, the thick lines indicate the encoder wiring. For each encoder 60, an encoder wiring p for sending a signal from the encoder 60 to the controller 10 and an encoder wiring q for sending a signal from the controller 10 to the encoder 60 are provided. Between the controller 10 and the manipulator 40, they are connected by an interface cable 30 that bundles the encoder wirings p and q corresponding to each of the plurality of encoders 60. And the manipulator 40 is provided with a distribution unit 49 which is the connection point of the interface cable 30. In the distribution unit 49, the encoder wirings p and q bundled in the interface cable 30 are divided into encoder wirings p and q for each individual encoder 60. Between the distribution unit 49 and each individual encoder 60, the encoder wirings p and q are accommodated in the in-device cable 50 for each encoder 60.

[0020] The controller 10 includes a higher-level control circuit 11 that performs calculations for servo control based on the motor position notified by a signal from the encoder 60 and generates commands for the encoder 60, which are then sent out as signals. It also includes a connection section 12 that is connected to the higher-level control circuit 11 and to which encoder wirings p and q are connected. The connection section 12 includes, for each encoder 60, a detection circuit 13 that detects faults such as disconnections in the encoder wiring p from which signals are sent from the encoder 60, a receiver 14 that receives the signal sent through the encoder wiring p and outputs it to the higher-level control circuit 11, and a driver 15 that is connected to the higher-level control circuit 11, receives the signal, and transmits this signal to the encoder 60 via the encoder wiring q. The detection circuit 13 uses, for example, the disconnection detection circuits shown in Patent Documents 1 to 3, and the detection result from the detection circuit 13 is input to the higher-level control circuit 11. The encoder 60 is also provided with a driver 61 that sends a signal to the encoder wiring p and a receiver 62 that receives the signal via the encoder wiring q.

[0021] In the robot system shown in Figure 1, when a fault such as a break in the encoder wiring p that sends signals from the encoder 60 to the controller 10 occurs, the fault can be detected by the detection circuit 13. However, it is not possible to determine whether the fault is in the interface cable 30 or the internal cable 50. Furthermore, it is not possible to directly detect a fault in the encoder wiring q that sends signals from the controller 10 to the encoder 60. When a fault occurs in the encoder wiring q, commands will not reach the encoder 60, so it is possible to indirectly estimate the occurrence of a fault in the encoder wiring q by detecting that the encoder 60 does not send a signal corresponding to the command despite a command being sent. However, in this case, it is not possible to distinguish whether the fault is in the encoder wiring q or a failure of the encoder 60 itself, nor is it possible to determine whether the fault in the encoder wiring q is in the interface cable 30 or the internal cable 50.

[0022] The fault detection device according to the present invention aims to solve the problem that general robot systems, such as the one shown in Figure 1, are insufficient in detecting the occurrence of faults in encoder wiring and identifying the location of the fault. Figure 2 shows a robot system that embodies one embodiment of the present invention. This robot system is configured to include the fault detection device according to the present invention.

[0023] The robot system shown in Figure 2 is a modified version of the robot system shown in Figure 1, with an interface unit 41 instead of a distribution unit 49 in the manipulator 40, and a microprocessor 18 connected to the connection unit 12 of the controller 10. The detection results from the detection circuit 13 located within the controller 10 are not directly input to the higher-level control circuit 11, but are instead input to the microprocessor 18. The encoder wiring p that sends signals from the encoder 60 to the controller 10 is divided into internal wiring a, which is the encoder wiring from the encoder 60 to the interface unit 41, and interface wiring b, which is the encoder wiring from the interface unit 41 to the controller 10. Similarly, the encoder wiring q that sends signals from the controller 10 to the encoder 60 is divided into interface wiring c, which is the interface wiring from the controller 10 to the interface unit 41, and internal wiring d, which is the internal wiring from the interface unit 41 to the encoder 60. Interface cable 30 bundles interface wiring bc corresponding to multiple encoders 60. For each encoder 60, an internal cable 50 provided in the manipulator 40 bundles internal wiring a and d to the corresponding encoder.

[0024] The interface unit 41 is provided with, for each encoder 60, a detection circuit 42 for detecting faults such as open circuits or short circuits in the internal wiring a from which signals are sent from the encoder 60, a receiver 43 for receiving signals sent through the internal wiring a, and a driver 44 for transmitting signals to the controller 10 via interface wiring b based on the reception result at the receiver 43. The interface unit 41 is also provided with, for each encoder 60, a detection circuit 45 for detecting faults in the interface wiring c from which signals are sent from the controller 10, a receiver 46 for receiving signals sent through interface wiring c, and a driver 47 for transmitting signals to the corresponding encoder 60 via internal wiring d based on the reception result at the receiver 46. In this configuration, the detection circuit 42 is provided on the input side of the receiver 43, and the detection circuit 45 is provided on the input side of the receiver 46. The detection circuits 42 and 45 can be configured similarly to the detection circuit 13 provided in the controller 10.

[0025] The interface unit 41 is further equipped with a microprocessor 48. Even when the manipulator 40 is equipped with multiple encoders 60, and the number of detection circuits 42, 45, receivers 43, 46, and drivers 44, 47 in the interface unit 41 corresponds to the number of encoders 60, the number of microprocessors 48 in the interface unit 41 is, in principle, one, and this microprocessor 48 is provided in common for multiple encoders 60. The microprocessor 48 is connected to the microprocessor 18 provided in the controller 10 via a serial communication line 31 set in the interface cable 30. Detection results from the detection circuits 42, 47 provided in the interface unit 41 are input to the microprocessor 48. The microprocessor 48 sends the received detection results to the higher-level control circuit 11 via the microprocessor 18 in the controller 10. As the microprocessor 48, an existing microprocessor used to transmit measurement results from a temperature sensor (not shown) or an acceleration sensor (not shown) provided in the manipulator 40 to the controller 10 can also be used.

[0026] Consider the case where a failure occurs in the encoder wiring in the robot system shown in Figure 2. When a failure occurs in the internal wiring a of the encoder wiring that sends a signal from the encoder 60 to the controller 10, the failure is detected by the detection circuit 42 in the interface unit 41, and the failure is communicated to the controller 10 via the microprocessor 48. Even if a failure occurs in the internal wiring a, the receiver 43 that receives the signal from internal wiring a outputs a binary logic signal, for example, "0" or "1", to the driver 44, and the driver 44 outputs a signal to the interface wiring b based on the signal from the receiver 43. At this time, the signal output to interface wiring b has the same characteristics as the signal under normal circumstances and is considered a normal signal. And if interface wiring b is normal at this time, the detection circuit 13 in the controller 10 does not detect a failure. In other words, in the robot system shown in Figure 1, what would have been detected by the detection circuit 13 as a failure somewhere in the encoder wiring p is detected in the system shown in Figure 2 as a failure in the internal wiring a, which is the encoder wiring within the manipulator 40, thus the location of the failure is identified in detail. Similarly, when a fault occurs in interface wiring b, it is detected by the detection circuit 13 in the controller 10. However, in this case, the detection circuits 42 and 47 provided in the interface unit 41 do not detect the fault, and in this case as well, the location of the fault can be identified in detail. Faults in interface wiring c are detected by the detection circuit 45 provided in the interface unit 41.

[0027] In the robot system shown in Figure 2, the detection results from detection circuits 42 and 47 are transmitted to the higher-level control circuit 11 via microprocessors 48 and 18, and the detection results from detection circuit 13 are transmitted to the higher-level control circuit 11 via microprocessor 18. Based on these detection results, the higher-level control circuit 11 recognizes the occurrence of a fault in the encoder wiring and identifies the location of the fault. Once the location of the fault is identified, the higher-level control circuit can, for example, display on a display device (not shown) which part of the encoder circuit has a fault.

[0028] Figure 3 shows the configuration details when differential output signals are used for signal transmission in the encoder wiring of the robot system shown in Figure 2. In Figure 3, only one encoder 60 connected to the manipulator 40 is depicted for clarity. Since differential output signals are transmitted, drivers 15, 44, 47, and 62 are configured as line drivers that simultaneously output non-inverting logic signals and inverting logic signals, and receivers 4, 43, 46, and 61 are configured as line receivers that simultaneously receive non-inverting logic signals and inverting logic signals. Internal wiring a consists of a pair of signal lines: signal line A for the non-inverting logic signal and signal line / A for the inverting logic signal. Similarly, interface wiring b consists of signal lines B and / B, interface wiring c consists of signal lines C and / C, and internal wiring d consists of signal lines D and / D.

[0029] Detection circuits 13, 42, and 45 have the same configuration. For example, detection circuit 42 consists of an exclusive OR (ExOR) gate 21 to which signal line A is connected to one input terminal and signal line / A is connected to the other input terminal, a resistor 22 inserted between signal line A and signal line / A, and resistors 23 and 24 that pull up signal line A and signal line / A to the power supply voltage, respectively. In this detection circuit 42 using the ExOR gate 21, if the internal wiring a of the device is normal, signal line A and signal line / A are inverted from each other, so the output of the ExOR gate 21 is "1". On the other hand, if one of the signal line A and signal line / A is disconnected in the internal cable 50 of the device, the two input terminals of the ExOR gate 21 become the same level due to the presence of resistor 22, so the output of the ExOR gate 21 becomes "0", and the occurrence of a fault can be detected. Even when both signal line A and signal line / A are disconnected, the pull-up resistors 23 and 24 ensure that the levels of the two input terminals are the same, allowing for fault detection. If signal line A is outputting "1" and a ground fault occurs, the two input terminals of the ExOR gate 21 will become "0", similarly allowing for fault detection. Similarly, if signal line A is outputting "1" and signal line / A is experiencing a high-angle fault, the two input terminals of the ExOR gate 21 will become "1", similarly allowing for fault detection. When signal line A and signal line / A are short-circuited, the two input terminals of the ExOR gate 21 will be at the same level, allowing for fault detection. Detection circuits 13 and 45 can also detect faults in a similar manner. Thus, detection circuits 13, 42, and 45 allow for the detection of various fault modes in encoder wiring using a simple circuit configuration.

[0030] In the embodiment described above, an interface unit 41 is provided on the manipulator 40 to divide the encoder wiring into interface wiring b and c on the controller 10 side and internal wiring a and d on the encoder 60 side. The interface unit 41 connects the interface wiring b and c and the internal wiring a and d via a combination of receivers 43 and 46 and drivers 44 and 47. Furthermore, detection circuits 42 and 45 are provided on the input side of receivers 43 and 46, thereby enabling the detection of a fault while identifying the location of the fault.

[0031] Figure 4 shows a robot system of another embodiment. The robot systems using Figures 2 and 3 attempt to provide detection circuits 42 and 45 on the manipulator 40 side as well as the robot system shown in Figure 1. However, it is sometimes difficult to provide a detection circuit on the manipulator 40 side. In such cases, as shown in Figure 4, in addition to the detection circuit 13 that detects faults in the encoder wiring p that sends signals from the encoder 60 to the controller 10, a detection circuit 16 can be provided in the controller 10 to detect faults in the encoder wiring q that sends signals from the controller 10 to the encoder 60. In the robot system shown in Figure 1, it was not possible to directly detect the occurrence of faults in the encoder wiring q, but in the robot system shown in Figure 4, it is possible to directly detect the occurrence of faults in the encoder wiring q. Assuming that the signal is transmitted in the form of a differential output signal in the encoder wiring, and that the detection circuit 16 has the same circuit configuration as the detection circuit 13 explained using Figure 3, the robot system shown in Figure 4 can detect faults such as short circuits between the signal lines of non-inverting logic signals and the signal lines of inverting logic signals, as well as faults such as ceiling faults and ground faults in these signal lines, with respect to the encoder wiring q.

[0032] Furthermore, this technology can be configured as follows:

[0033] (1) A fault detection device for detecting a fault occurring in the encoder wiring in a system comprising a controlled device equipped with an encoder and a controller for controlling the controlled device, wherein the encoder and the controller are connected via encoder wiring, The signal sent from the encoder to the controller is designated as the first signal, and the signal sent from the controller to the encoder is designated as the second signal. A first detection circuit for detecting a fault in the encoder wiring that sends the first signal, A second detection circuit for detecting a fault in the encoder wiring that transmits the second signal, A fault detection device having the following features.

[0034] (2) The fault detection device according to (1), wherein at least a second detection circuit is provided in the controlled device.

[0035] (3) Having an interface section provided in the controlled device, The encoder wiring is divided into interface wiring between the controller and the interface unit, and internal wiring between the interface unit and the encoder. The interface unit includes a first receiver that receives the first signal via the internal wiring of the device, a first driver that transmits the first signal via the interface wiring based on the reception result at the first receiver, a second receiver that receives the second signal via the interface wiring, and a second driver that transmits the second signal via the internal wiring of the device based on the reception result at the second receiver. The fault detection device according to (2), wherein the first detection circuit is provided on the input side of the first receiver in the interface unit, and the second detection circuit is provided on the input side of the second receiver in the interface unit.

[0036] (4) The interface unit further comprises a processor that is provided in the interface unit and connected to the controller, The fault detection device according to (3), wherein the detection results from the first detection circuit and the second detection circuit are input to the processor.

[0037] (5) The fault detection device according to (4), wherein the controlled device comprises a plurality of encoders, each encoder is provided with encoder wiring, a first detection circuit, and a second detection circuit, and the processor is provided in common for the plurality of encoders.

[0038] (6) The fault detection device according to any one of (3) to (5), further comprising a third detection circuit provided inside the controller for detecting faults in the interface wiring that transmits the first signal.

[0039] (7) The fault detection device according to (1), wherein the first detection circuit and the second detection circuit are provided inside the controller.

[0040] (8) The fault detection device according to any one of (1) to (7), wherein the first signal and the second signal are transmitted in the form of differential output signals, and both the first detection circuit and the second detection circuit are equipped with exclusive OR gates.

[0041] (9) The fault detection device according to any one of (1) to (8), wherein the controlled device is a manipulator. [Explanation of symbols]

[0042] 10...Controller; 11...Higher-level control circuit; 12...Connection section; 13, 16, 42, 45...Detection circuit; 14, 43, 46, 62...Receiver; 15, 44, 47, 61...Driver; 18, 48...Microprocessor; 21...Exclusive OR (ExOR) gate; 22-24...Resistor; 30...Interface cable; 31...Serial communication line; 40...Manipulator; 41...Interface section; 49...Distribution section; 50...Internal equipment cable; 60...Encoder.

Claims

1. A fault detection device for detecting a fault occurring in the encoder wiring in a system comprising a controlled device equipped with an encoder and a controller that controls the controlled device, wherein the encoder and the controller are connected via encoder wiring, The logic signal sent from the encoder to the controller is designated as the first signal, and the logic signal sent from the controller to the encoder is designated as the second signal. A first detection circuit for detecting a fault in the encoder wiring that sends the first signal, A second detection circuit for detecting a fault in the encoder wiring that sends the second signal, It has, The controlled device is provided with an interface unit, and the encoder wiring is divided into interface wiring between the controller and the interface unit, and internal wiring between the interface unit and the encoder. The interface unit includes a first receiver that receives the first signal via the internal wiring of the device, a first driver that transmits the first signal via the interface wiring based on the reception result at the first receiver, a second receiver that receives the second signal via the interface wiring, and a second driver that transmits the second signal via the internal wiring of the device based on the reception result at the second receiver. A fault detection device wherein the first detection circuit is provided on the input side of the first receiver in the interface unit, and the second detection circuit is provided on the input side of the second receiver in the interface unit.

2. The interface unit further includes a processor that is connected to the controller, The fault detection device according to claim 1, wherein the detection results from the first detection circuit and the second detection circuit are input to the processor.

3. The fault detection device according to claim 2, wherein the controlled device comprises a plurality of encoders, each encoder is provided with encoder wiring, a first detection circuit, and a second detection circuit, and the processor is provided in common for the plurality of encoders.

4. The fault detection device according to any one of claims 1 to 3, further comprising a third detection circuit provided inside the controller for detecting faults in the interface wiring that transmits the first signal.

5. The fault detection device according to any one of claims 1 to 3, wherein the first signal and the second signal are transmitted in the form of differential output signals, and both the first detection circuit and the second detection circuit include an exclusive OR gate.

6. The fault detection device according to any one of claims 1 to 3, wherein the controlled device is a manipulator.

Images