Fault detection system

Abstract

The invention provides a fault detection system. A failure detection system (50) is provided with a first sensor and a second sensor that are different from each other in terms of measurement, and a failure detection unit (51). The failure detection unit (51) detects a failure in either the first sensor or the second sensor. The failure detection unit (51) acquires, from the first sensor, a first output value that varies in accordance with the temperature. In addition, the failure detection unit (51) acquires, from the second sensor, a second output value that varies in accordance with the temperature. Furthermore, the failure detection unit (51) detects a failure in either the first sensor or the second sensor on the basis of whether or not the relationship between the first output value and the second output value is within a predetermined normal range. As a result, it is possible to detect a sensor failure without providing two sensors to the same measurement object.

Description

[0001] This application is a divisional application of Chinese application number 2021102187987, entitled "Power Transmission Device and Fault Detection System". Technical Field

[0002] This invention relates to a fault detection system. Background Technology

[0003] In recent years, the demand for speed reducers mounted on robot joints and other components has increased rapidly. A previous type of speed reducer is described, for example, in Japanese Patent Application Publication No. 2004-198400. In this publication, a strain gauge is attached to a flexible external gear rotating at a reduced speed. This allows for the measurement of the torque applied to the flexible external gear.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2004-198400 Summary of the Invention

[0005] The problem that the invention aims to solve

[0006] However, the resistance wires of strain gauges used for torque measurement have a complex shape, often folded back into a sawtooth pattern. Therefore, when driving a speed reducer, due to the repeated bending deformation of the gear being measured, such as a flexible external gear, faults such as localized wire breaks sometimes occur in the resistance wires of the strain gauge. When such faults occur, the strain gauge readings change. However, simply detecting the change in the strain gauge readings cannot distinguish whether the change is caused by a wire break, a change in the torque applied to the gear, or the actual strain of the gear. Previously, techniques for properly detecting such strain gauge faults were unknown.

[0007] Therefore, in the past, in order to detect strain gauge failures, it was necessary to install two strain gauges at the same location on the flexible external gear and compare the measured values ​​of these strain gauges.

[0008] The purpose of this invention is to provide a fault detection system that can detect sensor faults without setting two sensors on the same measurement object, and a technology that can detect sensor faults in a drive device for a sensor that obtains measurement values ​​based on gear strain.

[0009] Methods for solving problems

[0010] The first aspect of this invention is a fault detection system comprising: a first sensor and a second sensor with different measurement objects; and a fault detection unit for detecting faults in either the first sensor or the second sensor, wherein the fault detection unit obtains a first output value that varies with temperature from the first sensor and a second output value that varies with temperature from the second sensor, and detects faults in either the first sensor or the second sensor based on whether the relationship between the first output value and the second output value is within a predetermined normal range.

[0011] The second aspect of this invention is a fault detection system comprising: a motor; a power transmission device that decelerates and outputs the rotational motion of an input shaft input from the motor; a rotation angle acquisition unit mounted on the motor that acquires a first measurement value of the rotation angle of the input shaft; a rotation angle detection sensor mounted on the power transmission device that acquires a second measurement value of the rotation angle of the input shaft based on the strain of the gears in the power transmission device; and a fault detection unit that detects faults in the rotation angle acquisition unit or the rotation angle detection sensor, wherein the fault detection unit acquires the first measurement value from the rotation angle acquisition unit and the second measurement value from the rotation angle detection sensor, and detects faults in the rotation angle acquisition unit or the rotation angle detection sensor based on whether the relationship between the first measurement value and the second measurement value is within a predetermined range.

[0012] Invention Effects

[0013] According to the invention of this application, the output values ​​of multiple sensors for different measurement objects are obtained, and the fault of any one of the multiple sensors is detected based on whether the relationship between these output values ​​is within the normal range. Therefore, sensor faults can be detected without setting multiple sensors for the same measurement object. Attached Figure Description

[0014] Figure 1 This is a longitudinal sectional view of the power transmission device.

[0015] Figure 2 This is a cross-sectional view of the power transmission device.

[0016] Figure 3 This is a diagram showing the back side of the sensor substrate.

[0017] Figure 4 This is a diagram showing the surface of the sensor substrate.

[0018] Figure 5 This is a partial cross-sectional view of the diaphragm and the sensor substrate.

[0019] Figure 6This is the circuit diagram of the first bridging circuit.

[0020] Figure 7 This is the circuit diagram of the second bridging circuit.

[0021] Figure 8 It is a graph representing the measured values ​​of the first voltmeter and the second voltmeter.

[0022] Figure 9 This is the circuit diagram of the third bridging circuit.

[0023] Figure 10 It is a diagram that conceptually represents the correction process.

[0024] Figure 11 This is a circuit diagram of the temperature sensor's detection circuit.

[0025] Figure 12 This is a method for temperature correction based on measurements from an ammeter connected in series with a bridging circuit, and it is a flowchart illustrating the temperature correction process.

[0026] Figure 13 This is a modified circuit diagram of the third bridging circuit.

[0027] Figure 14 It is a diagram that conceptually represents the input and output of the fault detection unit.

[0028] Figure 15 It is a flowchart representing the fault detection and handling process.

[0029] Figure 16 It is a graph that represents the change in measured values.

[0030] Figure 17 This is a circuit diagram of the detection circuit of the temperature sensor in a modified example.

[0031] Figure 18 This is a diagram showing the structure of the driving device according to Embodiment 2 of the present invention.

[0032] Figure 19 This is a circuit diagram of the first bridging circuit in Embodiment 2 of the present invention.

[0033] Figure 20 This is a circuit diagram of the second bridging circuit in Embodiment 2 of the present invention.

[0034] Figure 21 This is a circuit diagram of the third bridging circuit in Embodiment 2 of the present invention.

[0035] Figure 22 This is a diagram that conceptually illustrates the correction process for the third measurement value in Embodiment 2 of the present invention.

[0036] Figure 23This is a diagram that conceptually illustrates the function of the fault detection unit in Embodiment 2 of the present invention. Detailed Implementation

[0037] Explanation of reference numerals in the attached figures

[0038] 1. Power transmission device; 2. Motor; 9. Central shaft; 10. Internal gear; 11. Internal gear; 20. Flexible gear;

[0039] 21 Cylindrical section; 22 Flat plate section; 23 External gear; 30 Wave generator; 31 Cam; 32 Flexible bearing; 40 Sensor substrate; 41 Main body; 42 Wing; 43 Insulating layer; 44 Conductor layer; 45 Double-sided tape; 46 Signal processing circuit; 47 Constant current source; 50 Fault detection system; 60 Motor housing; 52 Input shaft; 53 Encoder; 51 Fault detection unit; 100 Drive unit (fault detection system); 221 Diaphragm section; 461 Calibration processing unit; A1 First galvanometer; A2 Second galvanometer; A3 First galvanometer; Three ammeters; A4 fourth ammeter; C1 first bridging circuit; C2 second bridging circuit; C3 third bridging circuit; C4 detection circuit; R1, Ra~Rd first resistance wire pattern; R2, Re~Rh second resistance wire pattern; R3 third resistance wire pattern; R4 fourth resistance wire pattern; R5 fifth resistance wire pattern; Rs fixed resistor; S1 rotation angle detection sensor; S2 torque detection sensor; S3 temperature sensor; V1 first voltmeter; V2 second voltmeter; V3 third voltmeter; V4 fourth voltmeter.

[0040] Hereinafter, exemplary embodiments of the present application will be described with reference to the accompanying drawings.

[0041] Example 1

[0042] Furthermore, in this application, the direction parallel to the central axis of the power transmission device 1 is referred to as the "axial direction," the direction orthogonal to the central axis of the power transmission device is referred to as the "radial direction," and the direction along an arc centered on the central axis of the power transmission device is referred to as the "circumferential direction." However, the aforementioned "parallel direction" also includes substantially parallel directions. Additionally, the aforementioned "orthogonal direction" also includes substantially orthogonal directions.

[0043] <1. Structure of the power transmission device>

[0044] Figure 1 This is a longitudinal sectional view of the power transmission device 1 according to the first embodiment. Figure 2 From Figure 1The image shows a cross-sectional view of the power transmission device 1 as observed from position AA. This power transmission device 1 is a device that reduces rotational motion from a first speed obtained from a motor to a second speed lower than the first speed and transmits it to the next stage. The power transmission device 1 is used, for example, assembled with a motor into the joint of a robot. However, the power transmission device of the present invention can also be used in other devices such as assistant suits and unmanned transport vehicles.

[0045] like Figure 1 and Figure 2 As shown, the power transmission device 1 of this embodiment includes an internal gear 10, a flexible gear 20, a wave generator 30, and a sensor substrate 40.

[0046] The internal gear 10 is an annular gear with a plurality of internal teeth 11 on its inner circumferential surface. The internal gear 10 is fixed to the frame of the device housing the power transmission device 1, for example, by a locking screw. The internal gear 10 is coaxially arranged with the central shaft 9. Furthermore, the internal gear 10 is located radially outside the cylindrical portion 21 of the flexible gear 20 (described later). The rigidity of the internal gear 10 is much higher than the rigidity of the cylindrical portion 21 of the flexible gear 20. Therefore, the internal gear 10 can be substantially considered a rigid body. The internal gear 10 has a cylindrical inner circumferential surface. A plurality of internal teeth 11 are arranged circumferentially at a certain interval on this inner circumferential surface. Each internal tooth 11 protrudes radially inward.

[0047] The flexible gear 20 is a flexible, ring-shaped gear. The flexible gear 20 is supported so as to be able to rotate about a central shaft 9. The flexible gear 20 is an example of a "gear" in this invention.

[0048] The flexible gear 20 of this embodiment has a cylindrical portion 21 and a flat portion 22. The cylindrical portion 21 extends axially in a cylindrical shape around the central shaft 9. The axial front end of the cylindrical portion 21 is located outside the wave generator 30 in the radial direction and inside the internal gear 10 in the radial direction. The cylindrical portion 21 is flexible and can therefore deform in the radial direction. In particular, the front end of the cylindrical portion 21 located inside the internal gear 10 in the radial direction is a free end, and therefore can be displaced more in the radial direction than other portions.

[0049] The flexible gear 20 has a plurality of external teeth 23. The plurality of external teeth 23 are arranged at a constant circumferential spacing on the outer peripheral surface near the axial front end of the cylindrical portion 21. Each external tooth 23 protrudes outward in the radial direction. The number of internal teeth 11 in the aforementioned internal gear 10 is slightly different from the number of external teeth 23 in the flexible gear 20.

[0050] The flat plate portion 22 has a diaphragm portion 221 and a thick-walled portion 222. The diaphragm portion 221 extends outward in a flat plate shape from the axial base end of the cylindrical portion 21 toward the radial direction, and extends in an annular shape around the central axis 9. The diaphragm portion 221 is capable of slight axial bending deformation. The thick-walled portion 222 is an annular portion located radially outward of the diaphragm portion 221. The axial thickness of the thick-walled portion 222 is greater than the axial thickness of the diaphragm portion 221. The thick-walled portion 222 is fixed, for example, to the component of the device on which the drive device 100 is mounted by a locking screw.

[0051] The wave generator 30 is a mechanism that causes periodic flexural deformation of the cylindrical portion 21 of the flexible gear 20. The wave generator 30 has a cam 31 and a flexible bearing 32. The cam 31 is supported so as to be able to rotate about a central axis 9. The cam 31 has an elliptical outer peripheral surface when viewed axially. The flexible bearing 32 is located between the outer peripheral surface of the cam 31 and the inner peripheral surface of the cylindrical portion 21 of the flexible gear 20. Therefore, the cam 31 and the cylindrical portion 21 can rotate at different speeds.

[0052] The inner ring of the flexible bearing 32 contacts the outer peripheral surface of the cam 31. The outer ring of the flexible bearing 32 contacts the inner peripheral surface of the flexible gear 20. Therefore, the cylindrical portion 21 of the flexible gear 20 is deformed into an elliptical shape along the outer peripheral surface of the cam 31. As a result, at two locations corresponding to the ends of the major axis of this ellipse, the outer teeth 23 of the flexible gear 20 mesh with the inner teeth 11 of the inner gear 10. At other circumferential locations, the outer teeth 23 and the inner teeth 11 do not mesh.

[0053] Cam 31 is connected to the motor directly or via another power transmission mechanism. When driving the motor, cam 31 rotates at a first rotational speed around the central axis 9. Consequently, the major axis of the aforementioned ellipse of the flexible gear 20 also rotates at the first rotational speed. Therefore, the meshing position of the external teeth 23 and the internal teeth 11 also changes circumferentially at the first rotational speed. Furthermore, as mentioned above, the number of internal teeth 11 of the internal gear 10 is slightly different from the number of external teeth 23 of the flexible gear 20. Due to this difference in the number of teeth, the meshing position of the external teeth 23 and the internal teeth 11 changes slightly circumferentially with each rotation of cam 31. As a result, the flexible gear 20 rotates relative to the internal gear 10 at a second rotational speed around the central axis 9, which is lower than the first rotational speed. Therefore, a reduced rotational speed at the second rotational speed can be obtained from the flexible gear 20.

[0054] <2. About the sensor substrate>

[0055] <2-1. Structure of the sensor substrate>

[0056] The sensor substrate 40 is a substrate on which a sensor for detecting the torque applied to the flexible gear 20 is mounted. For example... Figure 1As shown, in this embodiment, a sensor substrate 40 is fixed on the circular surface of the circular diaphragm portion 221.

[0057] Figure 3 This is a diagram showing the back side of the sensor substrate 40 opposite to the diaphragm portion 221. Figure 4 This is a diagram showing the surface of the back side of the sensor substrate 40 that is not opposite to the diaphragm portion 221. Figure 5 This is a partial cross-sectional view of the diaphragm section 221 and the sensor substrate 40.

[0058] The sensor substrate 40 in this embodiment is a flexible printed circuit board (FPC) capable of being flexibly deformed. For example... Figure 3 and Figure 4 As shown, the sensor substrate 40 has an annular main body 41 centered on the central axis 9 and wing portions protruding from the main body 41 toward the radially outward side. 42. Additionally, such as... Figure 5 As shown, the sensor substrate 40 has an insulating layer 43 and a conductor layer 44. The insulating layer 43 is made of resin, which acts as an insulator. The conductor layer 44 is made of metal, which acts as a conductor. The material of the conductor layer 44 is, for example, copper or an alloy containing copper. In this embodiment, the sensor substrate 40 has a conductor layer 44 on both the surface and the back side of the insulating layer 43.

[0059] In addition, such as Figure 5 As shown, the sensor substrate 40 is fixed to the diaphragm portion 221 of the flexible gear 20 using double-sided adhesive tape 45. Specifically, the surface of the diaphragm portion 221 and the back surface of the sensor substrate 40 are fixed together by the double-sided adhesive tape 45. The double-sided adhesive tape 45 is a tape made of a material with adhesive properties, shaped into a strip and cured to a degree that allows it to maintain its shape. Using such a double-sided adhesive tape 45 makes the fixing of the sensor substrate 40 relative to the diaphragm portion 221 easier compared to using a free-flowing adhesive. Furthermore, it reduces operator-induced deviations during the fixing process.

[0060] The sensor substrate 40 is equipped with a rotation angle detection sensor S1, a torque detection sensor S2, a temperature sensor S3, and a signal processing circuit 46. The rotation angle detection sensor S1 and the torque detection sensor S2 are both strain sensors that detect the strain of the diaphragm portion 221, and are examples of the "first sensor" in this invention. The temperature sensor S3 is a sensor that detects the temperature of the power transmission device 1, and is an example of the "second sensor" in this invention.

[0061] The rotation angle detection sensor S1 has a resistance line pattern formed on the back side of the main body 41 opposite to the diaphragm portion 221. That is, the conductor layer 44 on the back side includes the resistance line pattern of the rotation angle detection sensor S1. The torque detection sensor S2 and the temperature sensor S3 have resistance line patterns formed on the back side of the main body 41 on a surface that does not oppose the diaphragm portion 221. That is, the conductor layer 44 on the surface side includes the resistance line pattern of the torque detection sensor S2 and the resistance line pattern of the temperature sensor S3.

[0062] The signal processing circuit 46 is disposed on the wing 42.

[0063] <2-2. About Rotation Angle Detection Sensor>

[0064] The rotation angle detection sensor S1 is a sensor that detects the rotation angle of the rotational motion input to the flexible gear 20 based on the strain of the diaphragm 221. For example... Figure 3 As shown, the rotation angle detection sensor S1 includes four first resistance wire patterns R1 and four second resistance wire patterns R2.

[0065] Four first resistance wire patterns R1 are arranged at equal intervals circumferentially around the central axis 9. Each first resistance wire pattern R1 is a single conductor bent into a zigzag shape and extending circumferentially as an overall arc shape. In this embodiment, each first resistance wire pattern R1 extends within an angle range of approximately 45° around the central axis 9. Furthermore, each first resistance wire pattern R1 comprises a plurality of first resistance wires r1. The plurality of first resistance wires r1 are arranged at small intervals circumferentially. Each first resistance wire r1 extends in a straight line along the radial direction of the flexible gear 20. The ends of adjacent first resistance wires r1 in the circumferential direction are alternately connected to each other on the inner or outer side in the radial direction. Thus, the plurality of first resistance wires r1 are connected in series as a whole.

[0066] Four second resistance wire patterns R2 are arranged at equal intervals circumferentially around the central axis 9. Each second resistance wire pattern R2 is a single conductor bent into a zigzag shape and extending circumferentially as an overall arc shape. In this embodiment, each second resistance wire pattern R2 extends within an angle range of approximately 45° around the central axis 9. Furthermore, each second resistance wire pattern R2 comprises a plurality of second resistance wires r2. The plurality of second resistance wires r2 are arranged at small intervals circumferentially. Each second resistance wire r2 extends in a straight line along the radial direction of the flexible gear 20. The ends of adjacent second resistance wires r2 in the circumferential direction are alternately connected to each other on the inner or outer side in the radial direction. Thus, the plurality of second resistance wires r2 are connected in series as a whole.

[0067] Four second resistance wire patterns R2 are arranged in a region concentric with four first resistance wire patterns R1, but in which no first resistance wire patterns R1 are arranged circumferentially. In this embodiment, the first resistance wire patterns R1 and the second resistance wire patterns R2 are arranged alternately in the circumferential direction. Furthermore, the four first resistance wire patterns R1 and the four second resistance wire patterns R2 are extended as a whole into a ring centered on the central axis 9.

[0068] Figure 6 This is a circuit diagram of the first bridge circuit C1, which includes four first resistor line patterns R1. Figure 6 In the example, the four first resistance line patterns R1 are distinguished as Ra, Rb, Rc, and Rd. The first resistance line patterns Ra, Rb, Rc, and Rd are... Figure 3 The numbers are arranged counterclockwise, with Ra as the first.

[0069] like Figure 6 As shown, four first resistor wire patterns Ra, Rb, Rc, and Rd are assembled into the first bridge circuit C1. The first resistor wire patterns Ra and Rb are connected in series. The first resistor wire patterns Rd and Rc are also connected in series. Furthermore, between the positive and negative terminals of the power supply voltage, a column of two first resistor wire patterns Ra and Rb is connected in parallel with a column of two first resistor wire patterns Rd and Rc. Additionally, the midpoint M11 of the first resistor wire patterns Ra and Rb, and the midpoint M12 of the first resistor wire patterns Rd and Rc, are connected to the first voltmeter V1.

[0070] Figure 7 This is a circuit diagram of the second bridge circuit C2, which includes four second resistor line patterns R2. Figure 7 In the example, the four second resistance line patterns R2 are distinguished as Re, Rf, Rg, and Rh. Figure 3 In the diagram, the second resistance line pattern Re is located between the first resistance line pattern Ra and the first resistance line pattern Rd. Furthermore, the second resistance line patterns Re, Rf, Rg, and Rh are... Figure 3 The numbers are arranged clockwise from Re.

[0071] like Figure 7As shown, four second resistor wire patterns Re, Rf, Rg, and Rh are assembled into the second bridge circuit C2. Second resistor wire patterns Re and Rf are connected in series. Second resistor wire patterns Rh and Rg are also connected in series. Furthermore, between the positive and negative terminals of the power supply voltage, a column of two second resistor wire patterns Re and Rf is connected in parallel with a column of two second resistor wire patterns Rh and Rg. Additionally, the midpoint M21 of second resistor wire patterns Re and Rf, and the midpoint M22 of second resistor wire patterns Rh and Rg are connected to the second voltmeter V2.

[0072] When driving the power transmission device 1, the diaphragm section 221 produces a portion that extends in the radial direction (hereinafter referred to as "extension portion") and a portion that contracts in the radial direction (hereinafter referred to as "contraction portion"). Specifically, two extension portions and two contraction portions are produced alternately in the circumferential direction. That is, the extension portions and contraction portions are produced alternately at 90° intervals in the circumferential direction. Furthermore, the portions where these extension portions and contraction portions are produced rotate at the aforementioned first rotational speed.

[0073] The resistance values ​​of the first resistance line patterns Ra, Rb, Rc, Rd and the second resistance line patterns Re, Rf, Rg, Rh disposed on the back side of the sensor substrate 40 vary according to the radial strain of the diaphragm portion 221. For example, when the aforementioned elongated portion overlaps with a certain resistance line pattern, the resistance value of that resistance line pattern increases. Conversely, when the aforementioned contracted portion overlaps with a certain resistance line pattern, the resistance value of that resistance line pattern decreases.

[0074] exist Figure 3 In the example, when the contracted portion overlaps with the first resistance line patterns Ra and Rc, the extended portion overlaps with the first resistance line patterns Rb and Rd. Furthermore, when the extended portion overlaps with the first resistance line patterns Ra and Rc, the contracted portion overlaps with the first resistance line patterns Rb and Rd. Therefore, in the first bridging circuit C1, the first resistance line patterns Ra and Rc and the first resistance line patterns Rb and Rd exhibit opposite resistance value changes.

[0075] In addition, Figure 3 In the example, when the contracted portion overlaps with the second resistance line patterns Re and Rg, the extended portion overlaps with the second resistance line patterns Rf and Rh. Furthermore, when the extended portion overlaps with the second resistance line patterns Re and Rg, the contracted portion overlaps with the second resistance line patterns Rf and Rh. Therefore, in the second bridging circuit C2, the second resistance line patterns Re and Rg and the second resistance line patterns Rf and Rh exhibit opposite resistance value changes.

[0076] Figure 8This is a graph representing the measured value v1 of the first voltmeter V1 in the first bridging circuit C1 and the measured value v2 of the second voltmeter V2 in the second bridging circuit C2. For example... Figure 8 As shown, the first voltmeter V1 and the second voltmeter V2 output periodically changing sinusoidal measurement values ​​v1 and v2, respectively. The period T of these measurement values ​​is equivalent to 1 / 2 times the period of the first rotational speed mentioned above. Furthermore, the direction of the input rotational motion can be determined by whether the phase of the measurement value of the second voltmeter V2 is advanced by 1 / 8 of the first rotational speed period (1 / 4 of the measurement value v1 and v2) or delayed by 1 / 8 of the first rotational speed period (1 / 4 of the measurement value v1 and v2).

[0077] Therefore, the rotation angle of the rotational motion input to the flexible gear 20 can be detected based on the measured values ​​v1 and v2 of the two voltmeters V1 and V2. Specifically, for example, a function table is prepared in advance to correspond the combination of the measured values ​​v1 and v2 of the first voltmeter V1 and the second voltmeter V2 with the rotation angle, and the rotation angle can be output by inputting the measured values ​​v1 and v2 into the function table.

[0078] Additionally, the rotation angle detection sensor S1 includes a first galvanometer A1. For example... Figure 6 As shown, the first ammeter A1 is connected in series with the first bridging circuit C1. Therefore, the first ammeter A1 measures the current value corresponding to the combined resistance of the first resistance line patterns Ra, Rb, Rc, and Rd in the first bridging circuit C1. Specifically, if the power supply voltage is set to Vo, and the combined resistance of the first resistance line patterns Ra, Rb, Rc, and Rd is set to Rc1, then the measured value I1 of the first ammeter A1 becomes I1 = Vo / Rc1.

[0079] The resistance values ​​of the first resistance wire patterns Ra, Rb, Rc, and Rd vary according to the elongation / contraction of the diaphragm portion 221. However, the combined resistance Rc1 of these first resistance wire patterns is less affected by the elongation / contraction of the diaphragm portion 221, and temperature-induced variations dominate. Therefore, the measured value I1 of the first ammeter A1 varies according to the temperature of the power transmission device 1. This measured value I1 of the first ammeter A1 is an example of the "first output value" in this invention.

[0080] Additionally, the rotation angle detection sensor S1 has a second galvanometer A2. For example... Figure 7As shown, the second ammeter A2 is connected in series with the second bridge circuit C2. Therefore, the second ammeter A2 measures the current value corresponding to the combined resistance of the second resistance line patterns Re, Rf, Rg, and Rh in the second bridge circuit C2. Specifically, if the power supply voltage is set to Vo, and the combined resistance of the second resistance line patterns Re, Rf, Rg, and Rh is set to Rc2, then the measured value I2 of the second ammeter A2 becomes I2 = Vo / Rc2.

[0081] The resistance values ​​of the second resistance wire patterns Re, Rf, Rg, and Rh vary according to the elongation / contraction of the diaphragm portion 221. However, the combined resistance Rc2 of these second resistance wire patterns is less affected by the elongation / contraction of the diaphragm portion 221, and temperature-induced changes are dominant. Therefore, the measured value I2 of the second ammeter A2 varies according to the temperature of the power transmission device 1. This measured value I2 of the second ammeter A2 is an example of the "first output value" in this invention.

[0082] <2-3. About Torque Detection Sensors>

[0083] The torque detection sensor S2 is a sensor that detects the torque applied to the flexible gear 20 based on the strain of the diaphragm portion 221. For example... Figure 4 As shown, the torque detection sensor S2 includes a third resistance wire pattern R3 and a fourth resistance wire pattern R4.

[0084] The third resistance wire pattern R3 is a single conductor bent into a sawtooth shape and extending circumferentially, forming an overall arc or ring shape. In this embodiment, the third resistance wire pattern R3 is provided within an area of ​​approximately 360° around the central axis 9. Furthermore, the third resistance wire pattern R3 comprises a plurality of third resistance wires r3. The plurality of third resistance wires r3 are arranged circumferentially in a generally parallel manner. Each third resistance wire r3 is inclined to one side circumferentially relative to the radial direction of the flexible gear 20. The inclination angle of the third resistance wire r3 relative to the radial direction is, for example, 45°. The ends of adjacent third resistance wires r3 in the circumferential direction are alternately connected to each other on the inner or outer side in the radial direction. Thus, the plurality of third resistance wires r3 are connected in series as a whole.

[0085] The fourth resistance wire pattern R4 is a single conductor bent into a zigzag shape and extending circumferentially, forming an overall arc or ring shape. The fourth resistance wire pattern R4 is located radially inward compared to the third resistance wire pattern R3. In this embodiment, the fourth resistance wire pattern R4 is provided within approximately 360° of the central axis 9. Furthermore, the fourth resistance wire pattern R4 comprises a plurality of fourth resistance wires r4. The plurality of fourth resistance wires r4 are arranged circumferentially in a generally parallel manner. Each fourth resistance wire r4 is inclined to the opposite side of the circumferential direction relative to the flexible gear 20. The inclination angle of the fourth resistance wire r4 relative to the radial direction is, for example, 45°. The ends of adjacent fourth resistance wires r4 in the circumferential direction are alternately connected to each other, either inside or outside the radial direction. Thus, the plurality of fourth resistance wires r4 are connected in series as a whole.

[0086] Figure 9 This is a circuit diagram of the third bridge circuit C3, which includes the third resistor line pattern R3 and the fourth resistor line pattern R4. (Example) Figure 9 As shown, the third bridging circuit C3 in this embodiment includes a third resistor line pattern R3, a fourth resistor line pattern R4, and two fixed resistors Rs. The third resistor line pattern R3 and the fourth resistor line pattern R4 are connected in series. The two fixed resistors Rs are also connected in series. Furthermore, between the positive and negative terminals of the power supply voltage, the column of the two resistor line patterns R3 and R4 is connected in parallel with the column of the two fixed resistors Rs. In addition, the midpoint M1 of the third resistor line pattern R3 and the fourth resistor line pattern R4 and the midpoint M2 of the two fixed resistors Rs are connected to the third voltmeter V3.

[0087] The resistance values ​​of the third resistance wire pattern R3 and the fourth resistance wire pattern R4 vary depending on the torque applied to the flexible gear 20. For example, when a torque is applied to the flexible gear 20 in the circumferential direction centered on the central shaft 9, the resistance value of the third resistance wire pattern R3 decreases, and the resistance value of the fourth resistance wire pattern R4 increases. On the other hand, when a torque is applied to the flexible gear 20 in the circumferential direction centered on the central shaft 9, the resistance value of the third resistance wire pattern R3 increases, and the resistance value of the fourth resistance wire pattern R4 decreases. Thus, the third resistance wire pattern R3 and the fourth resistance wire pattern R4 exhibit opposite resistance value changes relative to the torque.

[0088] Furthermore, when the resistance values ​​of the third resistance wire pattern R3 and the fourth resistance wire pattern R4 change, the potential difference between the midpoint M1 of the third resistance wire pattern R3 and the fourth resistance wire pattern R4 and the midpoint M2 of the two fixed resistors Rs changes, thus changing the measured value v3 of the third voltmeter V3. Therefore, based on the measured value v3 of the third voltmeter V3, the direction and magnitude of the torque applied to the flexible gear 20 can be detected.

[0089] Additionally, the torque detection sensor S2 has a third ammeter A3. For example... Figure 9 As shown, the third ammeter A3 is connected in series with the third bridge circuit C3. Therefore, the third ammeter A3 measures the current value corresponding to the combined resistance of the third resistance line pattern R3, the fourth resistance line pattern R4, and the two fixed resistors Rs in the third bridge circuit C3. Specifically, if the power supply voltage is set to Vo, and the combined resistance of the third resistance line pattern R3, the fourth resistance line pattern R4, and the two fixed resistors Rs is set to Rc3, then the measured value I3 of the third ammeter A3 becomes I3 = Vo / Rc3.

[0090] The resistance values ​​of the third resistance wire pattern R3 and the fourth resistance wire pattern R4 vary according to the torque applied to the flexible gear 20. However, the combined resistance Rc3 of the third resistance wire pattern R3, the fourth resistance wire pattern R4, and the two fixed resistors Rs is less affected by the torque applied to the flexible gear 20; temperature-induced variations are dominant. Therefore, the measured value I3 of the third ammeter A3 varies according to the temperature of the power transmission device 1. This measured value I3 of the third ammeter A3 is an example of the "first output value" in this invention.

[0091] <2-4. On Fluctuation Correction>

[0092] When driving the power transmission device 1, the flexible gear 20 undergoes periodic flexural deformation. Therefore, the measured value v3 of the third voltmeter V3 mentioned above includes a component reflecting the torque that was originally intended to be measured and an error component (fluctuation) caused by the periodic flexural deformation of the flexible gear 20. This error component varies according to the rotation angle of the rotational motion input to the flexible gear 20.

[0093] Therefore, the signal processing circuit 46 performs correction processing to eliminate the aforementioned error components based on the measurement value of the third voltmeter V3. Figure 10 This is a diagram conceptually representing the correction process of the signal processing circuit 46. For example... Figure 10 As shown, the signal processing circuit 46 receives the measured values ​​v1, v2, and v3 from the first voltmeter V1, the second voltmeter V2, and the third voltmeter V3. The signal processing circuit 46 first detects the rotation angle of the rotational motion input to the flexible gear 20 based on the measured values ​​v1 and v2 from the first voltmeter V1 and the second voltmeter V2. Then, based on the detected rotation angle, it estimates the aforementioned error component. Finally, it uses the estimated error component to correct the measured value v3 of the third voltmeter V3. As a result, the torque applied to the flexible gear 20 can be output with higher accuracy.

[0094] Furthermore, the signal processing circuit 46 may also skip calculating the aforementioned rotation angle and instead multiply the measured values ​​v1 and v2 of the first voltmeter V1 and the second voltmeter V2 by a predetermined coefficient, and then synthesize them with the measured value v3 of the third voltmeter V3. In this way, by reducing the processing burden involved in calculating the rotation angle, the processing speed of the signal processing circuit 46 can be improved.

[0095] <2-5. About Temperature Correction>

[0096] As described above, if the material of the conductor layer 44 is copper or a copper-containing alloy, the material cost of the sensor substrate 40 can be reduced. However, compared to other expensive materials, the resistance of copper is prone to change with ambient temperature. Therefore, the sensor substrate 40 of this embodiment includes a temperature sensor S3 to correct for the effects of temperature. Figure 4 As shown, the temperature sensor S3 has a fifth resistance line pattern R5 extending in an arc or ring shape along the circumference of the flexible gear 20.

[0097] Figure 11 This is the circuit diagram of the detection circuit C4, which includes the fifth resistor line pattern R5. (Example) Figure 11 As shown, one end of the fifth resistance wire pattern R5 is connected to the positive terminal of the power supply voltage. The other end of the fifth resistance wire pattern R5 is connected to the negative terminal of the power supply voltage. Additionally, the temperature sensor S3 has a fourth ammeter A4. Figure 11 As shown, the fourth ammeter A4 is connected in series with the fifth resistance line pattern R5. Therefore, the fourth ammeter A4 measures the current value corresponding to the resistance value of the fifth resistance line pattern R5. Specifically, if the power supply voltage is set to Vo, the measured value I4 of the fourth ammeter A4 becomes I4 = Vo / R5.

[0098] Because the fifth resistance wire pattern R5 is arc-shaped or annular, its resistance value is less affected by the torque applied to the flexible gear 20, and temperature-induced variations dominate. Therefore, the measured value I4 of the fourth galvanometer A4 varies according to the temperature of the power transmission device 1. This measured value I4 of the fourth galvanometer A4 is an example of the "second output value" in this invention.

[0099] The signal processing circuit 46 considers not only the aforementioned rotation angle but also the measured value I4 of the fourth ammeter A4 to correct the measured value v3 of the third voltmeter V3. Specifically, it increases or decreases the measured value v3 of the third voltmeter V3 in a direction that eliminates temperature-induced changes. In this way, inexpensive copper or copper alloys can be used, and the effects of temperature changes can be suppressed, thereby detecting the torque applied to the flexible gear 20 with higher accuracy.

[0100] The fifth resistance wire pattern R5 of the temperature sensor S3 is an arc or ring centered on the central axis 9. Therefore, when driving the power transmission device 1, stress is difficult to be applied to the fifth resistance wire pattern R5. Therefore, compared with other resistance wire patterns R1 to R4, the fifth resistance wire pattern R5 is less prone to failures such as wire breakage.

[0101] about Figure 13 Such a full-bridge circuit should be considered for temperature correction of the voltmeter readings. (This will be related to...) Figure 13 The measured value of the fifth ammeter A5, which is connected in series with the full-bridge circuit, is set as the measured value I5. To perform temperature correction on the measured value v3 of the third voltmeter V3 as described above, temperature correction can be performed based on the measured value I5 of the fifth ammeter A5, instead of the measured value I4 of the fourth ammeter A4. When temperature correction is performed based on the measured value I4, the position of the fifth resistance line pattern R5 included in the detection circuit C4 of the temperature sensor S3 is different from the position of the resistance line patterns included in the rotation angle detection sensor S1 and the torque detection sensor S2. Compared to the temperature sensor S3, the resistance lines of the rotation angle detection sensor S1 and the torque detection sensor S2 are longer, resulting in higher self-heating. Therefore, a temperature difference arises between the resistance line associated with the measured value I4 and the resistance line associated with the measured value v3, which is the object of correction. In contrast, when temperature correction is performed based on the measured value I5, the temperature can be detected based on the measured value I5 of the current in the bridge circuit C3 connected to the third voltmeter V3. Therefore, the temperature difference between the resistance line associated with the measured value I5 and the resistance line associated with the measured value v3, which is the object of calibration, disappears. Thus, the accuracy of temperature calibration can be further improved.

[0102] As a method for temperature correction, for example, it can be set as (voltage value after temperature correction) = (voltage value before temperature correction) + f (current value), and the value can be increased or decreased in the direction of eliminating the change in voltage value caused by temperature. In this embodiment, for example, the voltage value can be set as the measured value v3, and the current value can be set as the measured value I5. f (current value) is a formula that includes the current value, which is a variable that changes according to temperature, and the temperature correction coefficient. In order to obtain the temperature correction coefficient, for example, with the sensor substrate 40 fixed to the diaphragm portion 221 of the flexible gear 20, the torque detection sensor S2 is placed in a constant temperature bath, the power supply voltage is kept constant, and the temperature of the torque detection sensor S2 is changed without the load generated by the drive of the power transmission device 1, and the measured values ​​I5 and v3 are measured at this time. Then, based on the set of measured values ​​I5 and v3 measured for each temperature, an approximate formula for the measured values ​​I5 and v3 is calculated, and the coefficient of the approximate formula is used. The approximate formula can be derived by performing regression analysis on the measured data and deriving the equation for the measured values ​​I5 and v3. Regression analysis, for example, can be performed using the least squares method to find the coefficients. For instance, let the measured value v3 be y, the measured value I5 be x, and a, b, and c be constants. An approximate formula can be derived in the form y = a(x^2) + bx + c, and the values ​​of a and b can be set as temperature correction coefficients. Furthermore, when driving the power transmission device 1, y can be set as the temperature-corrected measured value v3, x as the measured value I5, and c as the uncorrected measured value v3.

[0103] Figure 12 This is a flowchart illustrating a method for temperature correction based on measurements from an ammeter connected in series with a bridging circuit. The signal processing circuit 46 obtains a temperature correction coefficient. This coefficient can be calculated, for example, using the method described above. Then, the power transmission device 1 is driven. Next, during the driving of the power transmission device 1, measured values ​​I5 and v3 are measured. Then, based on measured value I5 and the temperature correction coefficient, temperature correction is performed on measured value v3. Finally, based on the temperature-corrected measured value v3, the direction and magnitude of the torque applied to the flexible gear 20 are detected and output.

[0104] As described above, the method of temperature correction based on the measurement value of an ammeter connected in series with the bridging circuit is suitable for cases where resistance wire patterns are made of materials with low resistivity such as copper, aluminum, gold, and silver. Alternatively, temperature correction can be performed on the measurement value v1 of the first voltmeter V1 based on the measurement value I1 of the first ammeter A1. Similarly, temperature correction can be performed on the measurement value v2 of the second voltmeter V2 based on the measurement value I2 of the second ammeter A2. Furthermore, as... Figure 9As shown, even if the bridging circuit C3 is not a full-bridge circuit but a half-bridge circuit, the ammeter can be connected in series with the bridging circuit to perform the temperature correction described above.

[0105] <2-6. About Fault Detection>

[0106] Next, the function of detecting faults such as broken resistance wire patterns in the aforementioned rotation angle detection sensor S1 and torque detection sensor S2 will be explained. Figure 1 , Figure 3 as well as Figure 4 As shown, the signal processing circuit 46 of the sensor substrate 40 is electrically connected to the fault detection unit 51. The fault detection unit 51 is composed of a computer or circuit board equipped with a processor such as a CPU and various memories. In this embodiment, the sensor substrate 40 and the fault detection unit 51 constitute a fault detection system 50 with fault detection function.

[0107] Figure 14 This is a diagram conceptually representing the inputs and outputs of the fault detection unit 51. (Example) Figure 14 As shown, the signal processing circuit 46 of the sensor substrate 40 inputs the measured values ​​I1 of the first ammeter A1, I2 of the second ammeter A2, I3 of the third ammeter A3, and I4 of the fourth ammeter A4 to the fault detection unit 51. Based on these measured values ​​I1, I2, I3, and I4, the fault detection unit 51 outputs the detection results indicating whether the rotation angle detection sensor S1 and the torque detection sensor S2 have malfunctioned.

[0108] Figure 15 This is a flowchart illustrating the fault detection process in the fault detection unit 51. The fault detection unit 51 first compares the measured value I1 of the first ammeter A1, which is the "first output value", with the measured value I4 of the fourth ammeter A4, which is the "second output value" (step ST1).

[0109] Figure 16 This is a graph showing the changes in measured values ​​I1 and I4. Under normal circumstances, such as... Figure 16 As shown in time T1, the measured values ​​I1 and I4 change similarly with respect to the temperature change of the power transmission device 1. Therefore, when no fault occurs, the measured values ​​I1 and I4 show correlated changes. However, as mentioned above, the fifth resistance wire pattern R5 of the temperature sensor S3 is an arc or ring shape without corners, so it is not prone to faults such as wire breakage. In contrast, the four first resistance wire patterns R1 (Ra, Rb, Rc, Rd) of the rotation angle detection sensor S1 have complex shapes, so the possibility of faults such as wire breakage is relatively high. When such a fault occurs, such as Figure 16As in time T2, the measured value I1 varies considerably.

[0110] In step ST1, if the relationship between the measured values ​​I1 and I4 is within a predetermined normal range (Step ST1: Yes), the fault detection unit 51 determines that no fault such as a broken wire has occurred in any of the four first resistance wire patterns R1 (Ra, Rb, Rc, Rd) of the rotation angle detection sensor S1 (Step ST2). On the other hand, if the relationship between the measured values ​​I1 and I4 deviates from the predetermined normal range (Step ST1: No), it determines that a fault such as a broken wire has occurred in any of the four first resistance wire patterns R1 (Ra, Rb, Rc, Rd) of the rotation angle detection sensor S1 (Step ST3). The relationship between the measured values ​​I1 and I4 can be set as, for example, the difference between the measured values ​​I1 and I4 or the ratio between the measured values ​​I1 and I4.

[0111] Next, the fault detection unit 51 compares the measured value I2 of the second ammeter A2 (as the "first output value") with the measured value I4 of the fourth ammeter A4 (as the "second output value") (step ST4). Then, if the relationship between the measured values ​​I2 and I4 is within a predetermined normal range (step ST4: Yes), it is determined that no fault such as a broken wire has occurred in any of the four second resistance wire patterns R2 (Re, Rf, Rg, Rh) of the rotation angle detection sensor S1 (step ST5). On the other hand, if the relationship between the measured values ​​I2 and I4 deviates from the predetermined normal range (step ST4: No), it is determined that a fault such as a broken wire has occurred in any of the four second resistance wire patterns R2 (Re, Rf, Rg, Rh) of the rotation angle detection sensor S1 (step ST6). The relationship between the measured values ​​I2 and I4 can be set as, for example, the difference between the measured values ​​I2 and I4 or the ratio between the measured values ​​I2 and I4.

[0112] Next, the fault detection unit 51 compares the measured value I3 of the third ammeter A3 (as the "first output value") with the measured value I4 of the fourth ammeter A4 (as the "second output value") (step ST7). Then, if the relationship between the measured values ​​I3 and I4 is within a predetermined normal range (step ST7: Yes), it is determined that the third resistance wire pattern R3 and the fourth resistance wire pattern R4 of the torque detection sensor S2 have not experienced a fault such as a broken wire (step ST8). On the other hand, if the relationship between the measured values ​​I3 and I4 deviates from the predetermined normal range (step ST7: No), it is determined that the third resistance wire pattern R3 or the fourth resistance wire pattern R4 of the torque detection sensor S2 has experienced a fault such as a broken wire (step ST9). The relationship between the measured values ​​I3 and I4 can be set as, for example, the difference between the measured values ​​I3 and I4 or the ratio of the measured values ​​I3 and I4.

[0113] Afterwards, the fault detection unit 51 outputs a detection result related to the presence or absence of a fault (step ST10). Specifically, the fault detection unit 51 outputs a signal indicating the detection result to an external controller. The detection result may also be displayed on a display unit of the fault detection unit 51 or the controller.

[0114] As described above, in this fault detection system 50, the fault detection unit 51 obtains measured values ​​I1, I2, and I3, which vary according to temperature and serve as "first output values," from the rotation angle detection sensor S1 and the torque detection sensor S2, which serve as "first sensors." Additionally, the fault detection unit 51 obtains a "second output value," or measured value I4, which varies according to temperature, from a "second sensor," or temperature sensor S3, which is different from the "first sensor." Then, based on whether the relationship between the measured values ​​I1, I2, and I3 ("first output values") and the measured value I4 ("second output value") is within a predetermined normal range, faults in the rotation angle detection sensor S1 and the torque detection sensor S2 are detected.

[0115] In this way, when the measured values ​​I1, I2, and I3 show changes different from the usual changes corresponding to temperature, a fault in the sensor corresponding to that measured value can be detected. Therefore, faults in each sensor can be detected without setting two sensors for the same measurement object. That is, a fault in the rotation angle detection sensor S1 can be detected without setting two rotation angle detection sensors S1 at the same location on the flexible gear 20. In addition, a fault in the torque detection sensor S2 can be detected without setting two torque detection sensors S2 at the same location on the flexible gear 20.

[0116] <3. Variations>

[0117] The above describes one embodiment of the present invention, but the present invention is not limited to the above embodiment.

[0118] In the above embodiment, after performing the fault detection processing of the rotation angle detection sensor S1 (steps ST1 to ST6), the fault detection processing of the torque detection sensor S2 is performed (steps ST7 to ST9). However, the order of these fault detection processes can also be reversed. Alternatively, the fault detection processing of the rotation angle detection sensor S1 (steps ST1 to ST6) and the fault detection processing of the torque detection sensor S2 (steps ST7 to ST9) can be performed simultaneously and in parallel.

[0119] Furthermore, the sensor substrate 40 of the above embodiment includes a rotation angle detection sensor S1 and a torque detection sensor S2. However, the sensor substrate 40 may also include only either the rotation angle detection sensor S1 or the torque detection sensor S2. In this case, the "first sensor" may also be only either the rotation angle detection sensor S1 or the torque detection sensor S2. Alternatively, the "first sensor" may also be any other sensor capable of outputting a first output value that varies according to temperature.

[0120] Furthermore, in the above embodiment, the temperature sensor S3 mounted on the sensor substrate 40 is designated as the "second sensor". However, the "second sensor" can also be any other sensor capable of outputting a second output value that varies according to temperature. For example, a temperature sensor such as a thermocouple disposed at a different position from the sensor substrate 40 can also be designated as the "second sensor".

[0121] Alternatively, the rotation angle detection sensor S1 can be designated as the "first sensor," and the torque detection sensor S2 as the "second sensor." In this case, a malfunction in either the rotation angle detection sensor S1 or the torque detection sensor S2 can be detected based on whether the relationship between the first output value from the rotation angle detection sensor S1 and the second output value from the torque detection sensor S2 is within a predetermined normal range.

[0122] Furthermore, in the above embodiment, the ammeter measurement values ​​are used as the "first output value" and "second output value." That is, in the fault detection processing of the above embodiment, the power supply voltage Vo is set to constant, and current values ​​reflecting the resistance changes caused by temperature are compared with each other. However, the current value can also be set to constant, and voltage values ​​reflecting the resistance changes caused by temperature are compared with each other. For example, as... Figure 17 As shown, the detection circuit C4 of the temperature sensor S3 can also be a circuit in which a constant current source 47 is connected in series with the fifth resistance line pattern R5, and the fifth resistance line pattern is connected in parallel with the voltmeter V4. Furthermore, the measured value of the voltmeter V4 can be set as the "second output value". Additionally, the fault detection unit 51 can multiply the current value or voltage value by a predetermined coefficient to calculate a temperature estimate, and then compare the calculated temperature estimates with each other.

[0123] Furthermore, in the above embodiment, the signal processing circuit 46 is mounted on the sensor substrate 40. However, the signal processing circuit 46 may also be disposed outside the sensor substrate 40. For example, the signal processing circuit 46 may also be assembled in a computer or circuit board constituting the fault detection unit 51.

[0124] Furthermore, in the above embodiments, the material for each resistance line pattern is copper or a copper-containing alloy. However, other metals such as SUS and aluminum can also be used as the material for the resistance line patterns. Additionally, non-metallic materials such as ceramics and resins can also be used as the material for the resistance line patterns. Furthermore, conductive ink can also be used as the material for the resistance line patterns. When using conductive ink, it is sufficient to simply print each resistance line pattern on the surface of the sensor substrate 40 using conductive ink.

[0125] Furthermore, in the flexible gear 20 of the above embodiment, the diaphragm portion 221 extends outward in the radial direction from the base end of the cylindrical portion 21. However, the diaphragm portion 221 may also extend inward in the radial direction from the base end of the cylindrical portion 21.

[0126] In addition, in the above embodiment, the sensor substrate 40 is fixed to the flexible gear 20 of the power transmission device 1. However, the sensor substrate 40 may also be fixed to a component other than the flexible gear 20.

[0127] Example 2

[0128] This concludes the explanation of sensor fault detection in the power transmission device, focusing on the power transmission device itself. Hereinafter, with reference to the accompanying drawings, the detection of sensor faults in the drive device will be explained. Furthermore, in this application, the central axis of the drive device is the same as the central axis of the power transmission device, which is central axis 9. The following explanation will focus on the differences from Embodiment 1.

[0129] <1. Structure of the drive unit>

[0130] Figure 18 This diagram illustrates the structure of the drive unit 100. The drive unit 100 is, for example, assembled into the joints of a robot arm to enable the robot arm to move. However, the drive unit 100 can also be used in other devices such as assistive suits, unmanned transport vehicles, etc. Figure 18 As shown, the drive unit 100 includes a motor 2 and a power transmission device 1. Figure 18 In the diagram, only the power transmission device 1 is shown in cross-section, in the context of motor 2 and power transmission device 1.

[0131] Motor 2 is a drive source that generates rotational motion based on the drive current. For example... Figure 18As shown, the motor 2 includes a motor housing 60, an input shaft 52, and an encoder 53. Inside the motor housing 60 are a stator including coils and a rotor including magnets. The input shaft 52 is fixed to the rotor. When a drive current is supplied to the coils, the rotor and the input shaft 52 rotate about the central axis 9 due to the magnetic attraction and reaction force between the coils and the magnets. Hereinafter, the rotational speed of this rotor and the input shaft 52 will be referred to as the "first speed". The power transmission device 1 is a device that reduces the rotational motion of the motor 2 at the first speed to a second speed lower than the first speed and outputs it.

[0132] The encoder 53 is a measuring device for measuring the rotation angle of the input shaft 52. The encoder 53 consists of a circular plate with multiple slits arranged circumferentially and a light sensor. When the input shaft 52 rotates, the light sensor intermittently detects light passing through the slits. Thus, a measured value (first measured value) of the rotation angle of the input shaft 52 is obtained. The encoder 53 outputs the obtained first measured value to the fault detection unit 51, which will be described later. The encoder 53 is an example of the "rotation angle acquisition unit" in this invention.

[0133] like Figure 18 and Figure 2 As shown, the power transmission device 1 of this embodiment includes an internal gear 10, a flexible gear 20, a wave generator 30, and a sensor substrate 40.

[0134] The internal gear 10 is an annular gear with a plurality of internal teeth 11 on its inner circumferential surface. The internal gear 10 is fixed to the frame of the device on which the drive unit 100 is mounted, for example, by a locking screw.

[0135] The thick-walled portion 222 is a component that is fixed to the device on which the drive device 100 is mounted, for example, by a stop screw.

[0136] Cam 31 is fixed to the input shaft 52 of motor 2. When motor 2 is driven, cam 31 and input shaft 52 rotate together around the central axis 9 at a first rotational speed. Consequently, the major axis of the aforementioned ellipse of flexible gear 20 also rotates at the first rotational speed. Therefore, the meshing position of the external teeth 23 and internal teeth 11 also changes circumferentially at the first rotational speed. Furthermore, as mentioned above, the number of internal teeth 11 of internal gear 10 is slightly different from the number of external teeth 23 of flexible gear 20. Due to this difference in the number of teeth, the meshing position of external teeth 23 and internal teeth 11 changes slightly circumferentially with each revolution of cam 31. As a result, flexible gear 20 rotates relative to internal gear 10 around the central axis 9 at a second rotational speed lower than the first rotational speed. Therefore, a reduced rotational speed at the second rotational speed can be obtained from flexible gear 20.

[0137] <2. About the sensor substrate>

[0138] <2-1. About Rotation Angle Detection Sensor>

[0139] The rotation angle detection sensor S1 is a sensor that detects the rotation angle of the input shaft 52 based on the strain of the diaphragm 221. For example... Figure 3 As shown, the rotation angle detection sensor S1 includes four first resistance wire patterns R1 and four second resistance wire patterns R2.

[0140] Four first resistance wire patterns R1 are arranged at equal intervals circumferentially around the central axis 9. Each first resistance wire pattern R1 is a single conductor bent into a zigzag shape and extending circumferentially as an overall arc shape. In this embodiment, each first resistance wire pattern R1 extends within an angle range of approximately 45° around the central axis 9. Furthermore, each first resistance wire pattern R1 comprises a plurality of first resistance wires r1. The plurality of first resistance wires r1 are arranged at small intervals circumferentially. Each first resistance wire r1 extends in a straight line along the radial direction of the flexible gear 20. The ends of adjacent first resistance wires r1 in the circumferential direction are alternately connected to each other on the inner or outer side in the radial direction. Thus, the plurality of first resistance wires r1 are connected in series as a whole.

[0141] Four second resistance wire patterns R2 are arranged at equal intervals circumferentially around the central axis 9. Each second resistance wire pattern R2 is a single conductor bent into a zigzag shape and extending circumferentially as an overall arc shape. In this embodiment, each second resistance wire pattern R2 extends within an angle range of approximately 45° around the central axis 9. Furthermore, each second resistance wire pattern R2 comprises a plurality of second resistance wires r2. The plurality of second resistance wires r2 are arranged at small intervals circumferentially. Each second resistance wire r2 extends in a straight line along the radial direction of the flexible gear 20. The ends of adjacent second resistance wires r2 in the circumferential direction are alternately connected to each other on the inner or outer side in the radial direction. Thus, the plurality of second resistance wires r2 are connected in series as a whole.

[0142] Four second resistance wire patterns R2 are arranged in a region concentric with four first resistance wire patterns R1, but in which no first resistance wire patterns R1 are arranged circumferentially. In this embodiment, the first resistance wire patterns R1 and the second resistance wire patterns R2 are arranged alternately in the circumferential direction. Furthermore, the four first resistance wire patterns R1 and the four second resistance wire patterns R2 are extended as a whole into a ring centered on the central axis 9.

[0143] Figure 19 This is a circuit diagram of the first bridge circuit C1, which includes four first resistor line patterns R1. Figure 19 In the example, the four first resistance line patterns R1 are distinguished as Ra, Rb, Rc, and Rd. The first resistance line patterns Ra, Rb, Rc, and Rd are... Figure 3 The numbers are arranged counterclockwise from Ra as the first.

[0144] like Figure 19 As shown, four first resistor wire patterns Ra, Rb, Rc, and Rd are assembled into the first bridge circuit C1. The first resistor wire patterns Ra and Rb are connected in series. The first resistor wire patterns Rd and Rc are also connected in series. Furthermore, between the positive and negative terminals of the power supply voltage, a column of two first resistor wire patterns Ra and Rb is connected in parallel with a column of two first resistor wire patterns Rd and Rc. Additionally, the midpoint M11 of the first resistor wire patterns Ra and Rb, and the midpoint M12 of the first resistor wire patterns Rd and Rc, are connected to the first voltmeter V1.

[0145] Figure 20 This is a circuit diagram of the second bridge circuit C2, which includes four second resistor line patterns R2. Figure 20 In the example, the four second resistance line patterns R2 are distinguished as Re, Rf, Rg, and Rh. Figure 3 In the diagram, the second resistance line pattern Re is located between the first resistance line pattern Ra and the first resistance line pattern Rd. Furthermore, the second resistance line patterns Re, Rf, Rg, and Rh are... Figure 3 The numbers are arranged clockwise from Re.

[0146] like Figure 20 As shown, four second resistor wire patterns Re, Rf, Rg, and Rh are assembled into the second bridge circuit C2. Second resistor wire patterns Re and Rf are connected in series. Second resistor wire patterns Rh and Rg are also connected in series. Furthermore, between the positive and negative terminals of the power supply voltage, a column of two second resistor wire patterns Re and Rf is connected in parallel with a column of two second resistor wire patterns Rh and Rg. Additionally, the midpoint M21 of second resistor wire patterns Re and Rf, and the midpoint M22 of second resistor wire patterns Rh and Rg are connected to the second voltmeter V2.

[0147] When the drive device 100 is driven, a portion extending in the radial direction (hereinafter referred to as "elongation portion") and a portion contracting in the radial direction (hereinafter referred to as "contraction portion") are generated in the diaphragm portion 221. Specifically, two elongation portions and two contraction portions are generated alternately in the circumferential direction. That is, the elongation portions and contraction portions are generated alternately at 90° intervals in the circumferential direction. Furthermore, the portions where these elongation portions and contraction portions are generated rotate at the first rotational speed described above.

[0148] The resistance values ​​of the first resistance line patterns Ra, Rb, Rc, Rd and the second resistance line patterns Re, Rf, Rg, Rh disposed on the back side of the sensor substrate 40 vary according to the radial strain of the diaphragm portion 221. For example, when the aforementioned elongated portion overlaps with a certain resistance line pattern, the resistance value of that resistance line pattern increases. Conversely, when the aforementioned contracted portion overlaps with a certain resistance line pattern, the resistance value of that resistance line pattern decreases.

[0149] exist Figure 3 In the example, when the contracted portion overlaps with the first resistance line patterns Ra and Rc, the extended portion overlaps with the first resistance line patterns Rb and Rd. Furthermore, when the extended portion overlaps with the first resistance line patterns Ra and Rc, the contracted portion overlaps with the first resistance line patterns Rb and Rd. Therefore, in the first bridging circuit C1, the first resistance line patterns Ra and Rc and the first resistance line patterns Rb and Rd exhibit opposite resistance value changes.

[0150] In addition, Figure 3 In the example, when the contracted portion overlaps with the second resistance line patterns Re and Rg, the extended portion overlaps with the second resistance line patterns Rf and Rh. Furthermore, when the extended portion overlaps with the second resistance line patterns Re and Rg, the contracted portion overlaps with the second resistance line patterns Rf and Rh. Therefore, in the second bridging circuit C2, the second resistance line patterns Re and Rg and the second resistance line patterns Rf and Rh exhibit opposite resistance value changes.

[0151] Figure 8 This is a graph representing the measured value v1 of the first voltmeter V1 in the first bridging circuit C1 and the measured value v2 of the second voltmeter V2 in the second bridging circuit C2. For example... Figure 8 As shown, the first voltmeter V1 and the second voltmeter V2 output periodically changing sinusoidal measurement values ​​v1 and v2, respectively. The period T of these measurement values ​​is equivalent to 1 / 2 times the period of the first rotational speed mentioned above. Furthermore, the direction of the input rotational motion can be determined by whether the phase of the measurement value of the second voltmeter V2 is advanced by 1 / 8 of the first rotational speed period (1 / 4 of the measurement value v1 and v2) or delayed by 1 / 8 of the first rotational speed period (1 / 4 of the measurement value v1 and v2).

[0152] Therefore, the rotation angle of the rotational motion input to the flexible gear 20 can be detected based on the measured values ​​v1 and v2 of the two voltmeters V1 and V2. That is, based on these measured values ​​v1 and v2, the measured value of the rotation angle of the input shaft 52 (the second measured value) can be obtained. Specifically, for example, a function table corresponding to the combination of the measured values ​​v1 and v2 of the first voltmeter V1 and the second voltmeter V2 and the second measured value can be prepared in advance. By inputting the measured values ​​v1 and v2 into the function table, the second measured value can be output.

[0153] <2-3. About Torque Detection Sensors>

[0154] The torque detection sensor S2 is a sensor that detects the torque applied to the flexible gear 20 based on the strain of the diaphragm portion 221. For example... Figure 4 As shown, the torque detection sensor S2 includes a third resistance wire pattern R3 and a fourth resistance wire pattern R4.

[0155] The third resistance wire pattern R3 is a single conductor bent into a sawtooth shape and extending circumferentially, forming an overall arc or ring shape. In this embodiment, the third resistance wire pattern R3 is provided within an area of ​​approximately 360° around the central axis 9. Furthermore, the third resistance wire pattern R3 comprises a plurality of third resistance wires r3. The plurality of third resistance wires r3 are arranged circumferentially in a generally parallel manner. Each third resistance wire r3 is inclined to one side circumferentially relative to the radial direction of the flexible gear 20. The inclination angle of the third resistance wire r3 relative to the radial direction is, for example, 45°. The ends of adjacent third resistance wires r3 in the circumferential direction are alternately connected to each other on the inner or outer side in the radial direction. Thus, the plurality of third resistance wires r3 are connected in series as a whole.

[0156] The fourth resistance wire pattern R4 is a single conductor bent into a zigzag shape and extending circumferentially, forming an overall arc or ring shape. The fourth resistance wire pattern R4 is located radially inward compared to the third resistance wire pattern R3. In this embodiment, the fourth resistance wire pattern R4 is provided within approximately 360° of the central axis 9. Furthermore, the fourth resistance wire pattern R4 comprises a plurality of fourth resistance wires r4. The plurality of fourth resistance wires r4 are arranged circumferentially in a generally parallel manner. Each fourth resistance wire r4 is inclined to the opposite side of the circumferential direction relative to the flexible gear 20. The inclination angle of the fourth resistance wire r4 relative to the radial direction is, for example, 45°. The ends of adjacent fourth resistance wires r4 in the circumferential direction are alternately connected to each other, either inside or outside the radial direction. Thus, the plurality of fourth resistance wires r4 are connected in series as a whole.

[0157] Figure 21 This is a circuit diagram of the third bridge circuit C3, which includes the third resistor line pattern R3 and the fourth resistor line pattern R4. (Example) Figure 21As shown, the third bridging circuit C3 in this embodiment includes a third resistor line pattern R3, a fourth resistor line pattern R4, and two fixed resistors Rs. The third resistor line pattern R3 and the fourth resistor line pattern R4 are connected in series. The two fixed resistors Rs are also connected in series. Furthermore, between the positive and negative terminals of the power supply voltage, the column of the two resistor line patterns R3 and R4 is connected in parallel with the column of the two fixed resistors Rs. In addition, the midpoint M1 of the third resistor line pattern R3 and the fourth resistor line pattern R4 and the midpoint M2 of the two fixed resistors Rs are connected to the third voltmeter V3.

[0158] The resistance values ​​of the third resistance wire pattern R3 and the fourth resistance wire pattern R4 vary depending on the torque applied to the flexible gear 20. For example, when a torque is applied to the flexible gear 20 in the circumferential direction centered on the central shaft 9, the resistance value of the third resistance wire pattern R3 decreases, and the resistance value of the fourth resistance wire pattern R4 increases. On the other hand, when a torque is applied to the flexible gear 20 in the circumferential direction centered on the central shaft 9, the resistance value of the third resistance wire pattern R3 increases, and the resistance value of the fourth resistance wire pattern R4 decreases. Thus, the third resistance wire pattern R3 and the fourth resistance wire pattern R4 exhibit opposite resistance value changes relative to the torque.

[0159] Furthermore, when the resistance values ​​of the third resistance wire pattern R3 and the fourth resistance wire pattern R4 change, the potential difference between the midpoint M1 of the third resistance wire pattern R3 and the fourth resistance wire pattern R4 and the midpoint M2 of the two fixed resistors Rs changes, thus changing the measured value v3 of the third voltmeter V3. Therefore, based on the measured value v3 of the third voltmeter V3, the direction and magnitude of the torque applied to the flexible gear 20 can be detected. That is, the measured value of the torque applied to the flexible gear 20 (the third measured value) can be obtained.

[0160] <2-4. On Fluctuation Correction>

[0161] When the drive unit 100 is driven, the flexible gear 20 undergoes periodic flexural deformation. Therefore, the measured value of the torque detection sensor S2 includes a component reflecting the torque that was originally intended to be measured and an error component (fluctuation) caused by the periodic flexural deformation of the flexible gear 20. This error component varies depending on the rotation angle of the rotational motion input to the flexible gear 20.

[0162] Therefore, the signal processing circuit 46 performs correction processing to eliminate the aforementioned error components based on the measured value of the torque detection sensor S2. Figure 22 This is a diagram conceptually representing the correction process of the signal processing circuit 46. For example... Figure 22 As shown, the signal processing circuit 46 of this embodiment has a correction processing unit 461.

[0163] The correction processing unit 461 obtains a measurement value (second measurement value) of the rotation angle of the input shaft 52 from the rotation angle detection sensor S1, and a measurement value (third measurement value) of the torque applied to the flexible gear 20 from the torque detection sensor S2. Based on the obtained second measurement value, the correction processing unit 461 infers the aforementioned error component. Then, it uses the inferred error component to correct the third measurement value. Specifically, it increases or decreases the third measurement value in a direction that eliminates the error component. As a result, a third measurement value that more accurately reflects the torque applied to the flexible gear 20 can be output.

[0164] Furthermore, the correction processing unit 461 may also skip calculating the aforementioned rotation angle, multiply the second measurement value by a predetermined coefficient, and combine it with the third measurement value. In this way, by reducing the processing burden involved in calculating the rotation angle, the processing speed of the correction processing unit 461 can be increased.

[0165] <2-5. About Temperature Correction>

[0166] Figure 17 This is the circuit diagram of the detection circuit C4, which includes the fifth resistor line pattern R5. (Example) Figure 17 As shown, one end of the fifth resistance line pattern R5 is connected to the positive terminal of the constant current source 47. The other end of the fifth resistance line pattern R5 is connected to the negative terminal of the constant current source 47. Additionally, the temperature sensor S3 has a fourth voltmeter V4. Figure 17 As shown, the fourth voltmeter V4 is connected in parallel with the fifth resistance line pattern R5. Therefore, the fourth voltmeter V4 measures the voltage value corresponding to the resistance value of the fifth resistance line pattern R5. Specifically, if the current value supplied from the constant current source 47 is set as Io, then the measured value v4 of the fourth voltmeter V4 becomes v4 = Io × R5.

[0167] Because the fifth resistance wire pattern R5 is arc-shaped or annular, its resistance value is less affected by the torque applied to the flexible gear 20, and temperature-induced changes are dominant. Therefore, the measured value v4 of the fourth voltmeter V4 varies according to the temperature of the power transmission device 1. That is, a measured value (fourth measured value) representing the temperature of the power transmission device 1 can be obtained based on the measured value v4 of the fourth voltmeter V4.

[0168] like Figure 22As shown, the correction processing unit 461 of the signal processing circuit 46 considers not only the measured value (second measured value) of the rotation angle detection sensor S1, but also the measured value (fourth measured value) of the temperature sensor S3 to correct the measured value of the torque obtained from the torque detection sensor S2 (third measured value). Specifically, the third measured value is increased or decreased in the direction of eliminating temperature-induced changes. In this way, inexpensive copper or copper alloys can be used, and the influence of temperature changes can be suppressed, allowing for higher accuracy detection of the torque applied to the flexible gear 20.

[0169] <3. About the Fault Detection Department>

[0170] Next, the function of the fault detection system in the aforementioned rotation angle detection sensor S1, which detects faults such as broken resistance wire patterns, will be explained. For example... Figure 1 , Figure 3 , Figure 4 as well as Figure 18 As shown, the drive device 100 of this embodiment includes a fault detection unit 51. The signal processing circuit 46 of the sensor board 40 is electrically connected to the fault detection unit 51. The fault detection unit 51 is composed of a computer or circuit board equipped with a processor such as a CPU and various memories.

[0171] Figure 23 This is a diagram that conceptually represents the function of the fault detection unit 51. (For example...) Figure 23 As shown, the fault detection unit 51 obtains a measurement value (first measurement value) of the rotation angle of the input shaft 52 from the encoder 53 of the motor 2. Additionally, the fault detection unit 51 obtains a measurement value (second measurement value) of the rotation angle of the input shaft 52 from the rotation angle detection sensor S1 of the sensor board 40 via the signal processing circuit 46. Furthermore, the fault detection unit 51 compares these first and second measurement values.

[0172] When the rotation angle detection sensor S1 is functioning correctly, the first and second measured values ​​change similarly according to the rotation angle of the input shaft 52. However, the encoder 53 of the motor 2 is less prone to failure because it utilizes an optical sensor. In contrast, the first resistance wire pattern R1 (Ra, Rb, Rc, Rd) and the second resistance wire pattern R2 (Re, Rf, Rg, Rh) of the rotation angle detection sensor S1 have complex shapes, making them more susceptible to faults such as wire breakage. Furthermore, a fault in the encoder 53 can be detected independently by the drive circuit of the motor 2. The following describes the case where a fault in the encoder 53 is not detected by the drive circuit of the motor 2. When the rotation angle detection sensor S1 malfunctions, the relationship between the first and second measured values ​​deviates from the normal range.

[0173] When the relationship between the first measured value and the second measured value is within a predetermined normal range (the fault detection unit 51) Figure 23 If the condition is "yes", it is determined that the first resistance wire pattern R1 (Ra, Rb, Rc, Rd) and the second resistance wire pattern R2 (Re, Rf, Rg, Rh) of the rotation angle detection sensor S1 have not experienced any faults such as broken wires. On the other hand, if the relationship between the first and second measured values ​​deviates from the predetermined normal range ( Figure 23 If the condition is "No", it is determined that a fault such as a broken wire has occurred in any of the first resistance wire patterns R1 (Ra, Rb, Rc, Rd) and the second resistance wire patterns R2 (Re, Rf, Rg, Rh) of the rotation angle detection sensor S1.

[0174] Furthermore, the "relationship between the first measured value and the second measured value" used in the above-described determination process can be set as, for example, the difference between the first measured value and the second measured value, or the ratio between the first measured value and the second measured value. That is, if the difference or ratio between them deviates from the predetermined normal range, the fault detection unit 51 determines that the rotation angle detection sensor S1 has malfunctioned.

[0175] Subsequently, the fault detection unit 51 outputs detection results related to the presence or absence of a fault. Specifically, the fault detection unit 51 outputs a signal indicating the detection results to an external controller. The detection results can also be displayed on a display unit of the fault detection unit 51 or the controller.

[0176] As described above, in this drive unit 100, the fault detection unit 51 obtains a first measurement value representing the rotation angle of the input shaft 52 from the encoder 53 of the motor 2, and obtains a second measurement value representing the rotation angle of the input shaft 52 from the rotation angle detection sensor S1. Then, based on whether the relationship between the first measurement value and the second measurement value is within a predetermined normal range, a fault in the rotation angle detection sensor S1 is detected.

[0177] In this way, when the second measurement value of the rotation angle detection sensor S1 changes, it is possible to distinguish whether the change is caused by the actual rotation of the input shaft 52 or by a malfunction of the rotation angle detection sensor S1. Furthermore, it eliminates the need to install more than two rotation angle detection sensors on the same flexible gear 20 for the purpose of detecting malfunctions of the rotation angle detection sensor S1.

[0178] Furthermore, if the rotation angle detection sensor S1 malfunctions, the third measurement value corrected based on the second measurement value obtained from the rotation angle detection sensor S1 will also become inaccurate. However, the drive device 100 of this embodiment can continuously monitor whether the rotation angle detection sensor S1 has malfunctioned through the fault detection unit 51. Therefore, it is possible to determine whether the corrected third measurement value is a reliable output value.

[0179] <4. Variations>

[0180] In the above embodiment, the encoder 53 of the motor 2 is used as the "rotation angle detection unit" to obtain the first measurement value. However, the "rotation angle detection unit" may also be a measuring device other than the encoder 53. For example, the "rotation angle detection unit" may also be a measuring device that measures the rotation angle of the rotor fixed to the input shaft 52 by means of changes in induced voltage or magnetic force.

[0181] Furthermore, the fault detection unit 51 in the above embodiment detects a fault in the rotation angle detection sensor S1 by comparing a first measurement value and a second measurement value representing the rotation angle of the input shaft 52. However, the fault detection unit 51 can also detect a fault in the rotation angle detection sensor S1 by performing time differentiation on the first and second measurement values ​​respectively and comparing the values ​​representing the rotation speed of the input shaft 52 with each other.

[0182] In addition, in the above embodiment, the signal processing circuit 46 is mounted on the sensor substrate 40. However, the signal processing circuit 46 may also be disposed outside the sensor substrate 40. For example, the signal processing circuit 46 may be assembled in a computer or circuit board constituting the fault detection unit 51. Alternatively, the signal processing circuit 46 and the fault detection unit 51 may be mounted in the drive circuit of the motor 2.

[0183] Furthermore, in the above-described embodiments, such as Figure 22 As shown, the third measurement value of the torque detection sensor S2 is corrected based on the second measurement value of the rotation angle detection sensor S1. However, the third measurement value can also be corrected based on the first measurement value of the encoder 53. For example, in the event of a malfunction of the rotation angle detection sensor S1, the first measurement value can be used instead of the second measurement value to correct the third measurement value.

[0184] Furthermore, in the above-described embodiment, the strain of the gear (flexible external gear) is detected based on the change in resistance value of the resistance wire pattern. However, strain can also be detected by making the gear magnetic and using a magnetic sensor or the like to detect changes in the magnetic strain characteristics corresponding to the elastic deformation of the gear. In this case, although the strain detection sensitivity is lower compared to the above-described embodiment, strain can be detected non-contactly with the part where strain exists, thus improving the durability of the sensor compared to the above-described embodiment.

[0185] Furthermore, in the above embodiment, the fault detection unit 51 detects the fault of the rotation angle detection sensor S1, assuming that the fault of the encoder 53 is not detected by the motor drive circuit. However, even if the encoder 53 is not functioning properly, the fault detection unit 51 can also be used as a component to detect faults in the encoder 53 (rotation angle acquisition unit) or the rotation angle detection sensor S1.

[0186] Furthermore, in the above embodiment, the drive unit 100 includes a fault detection unit 51. That is, the drive unit 100 itself functions as a fault detection system. However, the fault detection unit 51 may also be provided separately from the drive unit 100. Moreover, the drive unit 100 and the fault detection unit 51 may constitute a fault detection system.

[0187] The present invention has been described above based on two embodiments in order to understand it, but these embodiments are not limiting. The structure of the fault detection system, the power transmission device, and the details of the fault detection system can be appropriately modified without departing from the spirit of the invention. Furthermore, elements appearing in the above-described embodiments and modifications can be appropriately combined without causing contradictions.

[0188] Industrial availability

[0189] This application can be used in power transmission devices and fault detection systems.

Claims

1. A fault detection system, characterized in that, have: motor; A power transmission device that reduces and outputs the rotational motion of the input shaft from the motor; A rotation angle acquisition unit, which is mounted on the motor, acquires a measured value of the rotation angle of the input shaft, i.e., a first measured value; A rotation angle detection sensor is mounted on the power transmission device to obtain a measured value of the rotation angle of the input shaft, i.e., a second measured value, based on the strain of the gears of the power transmission device. as well as The fault detection unit detects faults in the rotation angle acquisition unit or the rotation angle detection sensor. The fault detection unit obtains the first measurement value from the rotation angle acquisition unit and the second measurement value from the rotation angle detection sensor, and detects a fault in the rotation angle acquisition unit or the rotation angle detection sensor based on whether the relationship between the first measurement value and the second measurement value is within a predetermined range.

2. The fault detection system according to claim 1, characterized in that, The rotation angle acquisition unit is an encoder mounted on the motor.

3. The fault detection system according to claim 1 or 2, characterized in that, The fault detection system also has the following features: A torque detection sensor, mounted on the power transmission device, obtains a measured value of the torque applied to the gear, i.e., a third measured value, based on the strain of the gear in the power transmission device. as well as The calibration processing unit calibrates the third measurement value based on the first measurement value or the second measurement value.

4. The fault detection system according to claim 3, characterized in that, The fault detection system also includes a base plate fixed to the gears contained in the power transmission device. At least one of the rotation angle detection sensor and the torque detection sensor is mounted on the substrate.

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