Life prediction device, reduction gear, robot, and method for predicting life

Abstract

To provide a technology that can manage a life of a reduction gear irrespective of tooth skipping.SOLUTION: A life prediction device calculates a threshold relating to a life of at least one of the flexible bearing and flexible external tooth gear on the basis of at least one of the input rotation speed and output rotation speed of a reduction gear and a measurement value of a torque sensor. The life prediction device outputs an alert signal when drive time of the reduction gear reaches the threshold.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] The present invention relates to a life prediction device, a reducer, a robot, and a life prediction method. [Background technology]

[0002] 2. Description of the Related Art Conventionally, there has been known a reducer that reduces the speed of a rotational motion output from a motor. A conventional reducer is described in, for example, Patent Document 1. [Patent Document 1] International Publication No. 2004 / 098008 Summary of the Invention [Problem to be solved by the invention]

[0003] In the above document, the rotary drive device includes a tooth skipping detection unit and a life prediction unit. The tooth skipping detection unit detects the occurrence of tooth skipping when a difference between a detection value of a first encoder and a detection value of a second encoder is equal to or greater than a threshold value. The life prediction unit predicts the life of the reducer based on the number of times that tooth skipping has been detected.

[0004] However, the method of the above-mentioned document makes it impossible to predict the life of the reducer unless tooth skipping occurs.

[0005] An object of the present invention is to provide a technique capable of managing the life of a reducer, regardless of the presence or absence of tooth skipping. [Means for solving the problem]

[0006] The first invention is a life prediction device for a reducer having a flexible external gear, an internal gear, a flexible bearing, and a torque sensor arranged on at least one of the flexible external gear and the internal gear, which calculates a threshold value for the life of at least one of the flexible bearing and the flexible external gear based on at least one of the input rotational speed and output rotational speed of the reducer and the measurement value of the torque sensor, and outputs an alert signal when the driving time of the reducer reaches the threshold value.

[0007] The second invention is a life prediction device for a reducer having a flexible external gear, an internal gear, a flexible bearing, and a torque sensor arranged on at least one of the flexible external gear and the internal gear, which outputs the remaining life of at least one of the flexible bearing and the flexible external gear based on at least one of the input rotational speed and output rotational speed of the reducer and the measurement value of the torque sensor.

[0008] A third aspect of the present invention is a reducer comprising the life prediction device of the first or second aspect of the present invention.

[0009] A fourth invention is a robot comprising the life prediction device of the first or second invention, or the reducer of the third invention.

[0010] A fifth invention is a method for predicting the life of a reducer having a flexible external gear, an internal gear, a flexible bearing, and a torque sensor arranged on at least one of the flexible external gear and the internal gear, which calculates a threshold value for the life of at least one of the flexible bearing and the flexible external gear based on at least one of the input rotational speed and output rotational speed of the reducer and the measurement value of the torque sensor, and outputs an alert signal when the driving time of the reducer reaches the threshold value.

[0011] A sixth invention is a method for predicting the life of a reducer having a flexible external gear, an internal gear, a flexible bearing, and a torque sensor arranged on at least one of the flexible external gear and the internal gear, which outputs the remaining life of at least one of the flexible bearing and the flexible external gear based on at least one of the input rotational speed and output rotational speed of the reducer and the measurement value of the torque sensor. Effect of the Invention

[0012] According to the first, second, third, fourth, fifth, and sixth inventions, the life of at least one of the flexible bearing and the flexible external gear can be managed based on the measurement value of a torque sensor mounted on the reducer. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram of the robot. [Diagram 2] FIG. 2 is a vertical cross-sectional view of the reducer. [Diagram 3] FIG. 3 is a cross-sectional view of the reducer. [Figure 4] FIG. 4 is a partial vertical cross-sectional view of the flexible external gear in the vicinity of the sensor board. [Diagram 5] FIG. 5 is a plan view of the sensor substrate. [Figure 6] FIG. 6 is a circuit diagram of the first bridge circuit of the first torque sensor. [Figure 7] FIG. 7 is a circuit diagram of the second bridge circuit of the second torque sensor. [Figure 8] FIG. 8 is a circuit diagram of a third bridge circuit of the angle sensor. [Figure 9] FIG. 9 is a circuit diagram of the fourth bridge circuit of the angle sensor. [Figure 10] FIG. 10 is a graph showing changes over time in the output value of the third voltmeter of the third bridge circuit and the output value of the fourth voltmeter of the fourth bridge circuit. [Figure 11]FIG. 11 is a block diagram showing a configuration related to life prediction of a reducer. [Figure 12] FIG. 12 is a flowchart showing the flow of operations of the life prediction device according to the first embodiment. [Figure 13] FIG. 13 is a graph showing the life of a flexible bearing and a flexible external gear. [Figure 14] FIG. 14 is a flowchart showing the flow of operations of the life prediction device according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, exemplary embodiments of the present application will be described with reference to the drawings.

[0015] <1. Robot configuration> 1 is a schematic diagram of a robot 100 equipped with a reducer 1 according to an embodiment. The robot 100 is a device that performs tasks such as transporting, processing, and assembling parts in, for example, an industrial product manufacturing line. As shown in FIG. 1, the robot 100 includes a base frame 101, an arm 102, a motor 103, and the reducer 1.

[0016] The arm 102 is rotatably supported with respect to the base frame 101. The motor 103 and the reducer 1 are incorporated in a joint between the base frame 101 and the arm 102. When a driving current is supplied to the motor 103, a rotational motion is output from the motor 103. The reducer 1 reduces the speed of the rotational motion output from the motor 103 and transmits it to the arm 102. As a result, the arm 102 rotates with respect to the base frame 101 at a reduced speed.

[0017] <2. Configuration of the reducer> Next, the detailed structure of the reducer 1 will be described.

[0018] In the following, a direction parallel to the central axis 9 of the reducer 1 is referred to as the "axial direction", a direction perpendicular to the central axis 9 of the reducer 1 is referred to as the "radial direction", and a direction along an arc centered on the central axis 9 of the reducer 1 is referred to as the "circumferential direction". However, the above "parallel direction" also includes a direction that is approximately parallel. Furthermore, the above "orthogonal direction" also includes a direction that is approximately orthogonal.

[0019] Fig. 2 is a vertical cross-sectional view of the reducer 1 according to one embodiment. Fig. 3 is a horizontal cross-sectional view of the reducer 1 as seen from the position AA in Fig. 2. To avoid complicating the drawing, hatching indicating a cross section is omitted in Fig. 3.

[0020] The reducer 1 is a device that reduces the rotational motion of a first rotational speed output from a motor 103 to a second rotational speed that is slower than the first rotational speed. As shown in Figures 2 and 3, the reducer 1 includes an input shaft 10, an internal gear 20, a flexible external gear 30, and a wave generator 40.

[0021] The input shaft 10 is a member that rotates at a first rotational speed before reduction. The input shaft 10 is connected to an output shaft of the motor 103. The input shaft 10 extends in the axial direction along a central axis 9. The input shaft 10 of this embodiment is cylindrical with the central axis 9 as its center. The input shaft 10 passes through the reducer 1 in the axial direction. Note that the input shaft 10 may be the same member as the output shaft of the motor 103.

[0022] The internal gear 20 is a gear that rotates at a second rotational speed after deceleration. The internal gear 20 is fixed to the arm 102. The internal gear 20 is annular about the central axis 9. The internal gear 20 has a plurality of internal teeth 21. The plurality of internal teeth 21 protrude radially inward from the inner circumferential surface of the internal gear 20. The plurality of internal teeth 21 are arranged at a constant pitch in the circumferential direction on the inner circumferential surface of the internal gear 20. The rigidity of the internal gear 20 is sufficiently higher than the rigidity of a body portion 31 of the flexible external gear 30, which will be described later.

[0023] The flexible external gear 30 is a gear that undergoes flexible deformation due to rotation of a cam 41, which will be described later. The flexible external gear 30 is fixed to a base frame 101. As shown in Fig. 2 and Fig. 3, the flexible external gear 30 has a body portion 31, a plurality of external teeth 32, a diaphragm portion 33, and a thick portion 34.

[0024] The body portion 31 is a cylindrical portion centered on the central axis 9. One axial end of the body portion 31 is connected to the diaphragm portion 33. The other axial end of the body portion 31 is disposed radially outside the wave generator 40 and radially inside the internal gear 20. The body portion 31 is flexible and therefore capable of bending and deforming in the radial direction.

[0025] The multiple external teeth 32 are arranged on the radially outer surface of the other axial end of the body portion 31. The multiple external teeth 32 protrude radially outward from the radially outer surface of the body portion 31. The multiple external teeth 32 are arranged at a constant pitch in the circumferential direction. Some of the multiple external teeth 32 and some of the multiple internal teeth 21 described above mesh with each other. The number of internal teeth 21 that the internal gear 20 has and the number of external teeth 32 that the flexible external gear 30 has are slightly different.

[0026] The diaphragm portion 33 expands radially outward from one axial end of the body portion 31. That is, the diaphragm portion 33 expands in a direction intersecting the central axis 9. The diaphragm portion 33 is annular and surrounds the central axis 9. The diaphragm portion 33 is thin-walled and therefore capable of slight flexural deformation.

[0027] The thick portion 34 is an annular portion located radially outward of the diaphragm portion 33. The axial thickness of the thick portion 34 is greater than the axial thickness of the diaphragm portion 33. The thick portion 34 is fixed to the base frame 101 directly or via another member.

[0028] The wave generator 40 is a mechanism that generates periodic bending deformation in the flexible external gear 30. The wave generator 40 is disposed radially inside the external teeth 32. The wave generator 40 has a cam 41 and a flexible bearing 42.

[0029] The cam 41 is a component that gives a displacement to the flexible external gear 30 at a period of 180°. In this embodiment, the input shaft 10 and the cam 41 are formed as a single component. However, the cam 41 may be a component separate from the input shaft 10. In that case, it is sufficient that the cam 41 is fixed to the input shaft 10. The cam 41 has a non-circular outer surface. The cam 41 in this embodiment has an elliptical outer surface centered on the central axis 9.

[0030] The flexible bearing 42 is a bearing that can be flexibly deformed. The flexible bearing 42 is disposed between the radially outer surface of the cam 41 and the radially inner surface of the body 31 of the flexible external gear 30. The inner ring of the flexible bearing 42 contacts the radially outer surface of the cam 41. The outer ring of the flexible bearing 42 contacts the radially inner surface of the body 31. Therefore, the body 31 deforms into an elliptical shape along the radially outer surface of the cam 41. As a result, the external teeth 32 of the flexible external gear 30 and the internal teeth 21 of the internal gear 20 mesh with each other at two points corresponding to both ends of the major axis of the ellipse. At other circumferential positions, the external teeth 32 and the internal teeth 21 do not mesh with each other.

[0031] When the motor 103 is driven, the cam 41 rotates together with the input shaft 10 at a first rotation speed around the central axis 9. As a result, the major axis of the ellipse of the flexible external gear 30 also rotates at the first rotation speed. Then, the meshing position between the external teeth 32 and the internal teeth 21 also changes in the circumferential direction at the first rotation speed. Also, as described above, the number of the internal teeth 21 of the internal gear 20 and the number of the external teeth 32 of the flexible external gear 30 are slightly different. Due to this difference in the number of teeth, the meshing position between the external teeth 32 and the internal teeth 21 changes slightly in the circumferential direction for each rotation of the cam 41. As a result, the internal gear 20 rotates at a second rotation speed slower than the first rotation speed around the central axis 9 relative to the flexible external gear 30.

[0032] <3. About sensors> <3-1.Sensor structure> The reducer 1 has a sensor 50. As shown in Fig. 2, the sensor 50 has a sensor substrate 51. The sensor substrate 51 is fixed to the surface of the diaphragm portion 33.

[0033] Fig. 4 is a partial vertical cross-sectional view of the flexible external gear 30 in the vicinity of the sensor substrate 51. Fig. 5 is a plan view of the sensor substrate 51. As shown in Fig. 4, the sensor substrate 51 has an insulating layer 511 and a conductor layer 512.

[0034] The insulating layer 511 is flexibly deformable. The insulating layer 511 spreads in a direction intersecting the central axis 9. The insulating layer 511 is annular about the central axis 9. The insulating layer 511 is made of an insulating resin or an inorganic insulating material. The insulating layer 511 is disposed on the surface of the diaphragm portion 33. The conductor layer 512 is formed on the surface of the insulating layer 511. The conductor layer 512 is made of a metal that is a conductor. The conductor layer 512 is made of a material such as a copper alloy, a chromium alloy, or copper.

[0035] The conductor layer 512 includes a torque sensor 60 and an angle sensor 70. The torque sensor 60 and the angle sensor 70 are each formed of a strain gauge. As shown in FIG. 2, the sensor 50 has a signal processing circuit 52. The signal processing circuit 52 is electrically connected to the torque sensor 60 and the angle sensor 70.

[0036] <3-2. Torque sensor> The torque sensor 60 is a sensor for detecting the torque applied to the flexible external gear 30. In other words, the torque sensor 60 is a sensor whose output value changes according to the torque applied to the flexible external gear 30. As shown in Fig. 5, the torque sensor 60 of this embodiment has a first torque sensor 61 and a second torque sensor 62. The second torque sensor 62 is disposed radially outward of the first torque sensor 61.

[0037] The first torque sensor 61 has four strain gauges Ra, Rb, Rc, and Rd. Of the four strain gauges Ra, Rb, Rc, and Rd, two strain gauges Ra and Rb are arranged at intervals in the circumferential direction. The two strain gauges Ra and Rb are each provided in a semicircular arc shape within a range of approximately 180° centered on the central axis 9. The radial distance from the central axis 9 to the strain gauge Ra and the radial distance from the central axis 9 to the strain gauge Rb are approximately the same.

[0038] Of the four strain gauges Ra, Rb, Rc, and Rd, the other two strain gauges Rc and Rd are arranged radially outward of the above two strain gauges Ra and Rb. The two strain gauges Rc and Rd are arranged at an interval in the circumferential direction. The two strain gauges Rc and Rd are each provided in a semicircular arc shape within a range of approximately 180° centered on the central axis 9. The radial distance from the central axis 9 to the strain gauge Rc and the radial distance from the central axis 9 to the strain gauge Rd are approximately the same.

[0039] Moreover, the two strain gauges Ra, Rc and the two strain gauges Rb, Rd are arranged concentrically and line-symmetrically.

[0040] As shown in Fig. 5, the strain gauges Ra, Rb, Rc, and Rd each have a zigzag pattern extending in the circumferential direction. Each of the strain gauges Ra, Rb, Rc, and Rd has a plurality of resistance wires r1 arranged in the circumferential direction and substantially parallel to each other. Each of the resistance wires r1 extends obliquely relative to the radial direction. That is, each of the resistance wires r1 extends in a direction having both radial and circumferential components.

[0041] The resistance wires r1 of the strain gauges Ra and Rd are inclined toward one circumferential side with respect to the radial direction. The resistance wires r1 of the strain gauges Rb and Rc are inclined toward the other circumferential side with respect to the radial direction. The inclination angle of the resistance wires r1 with respect to the radial direction is, for example, 45°. The ends of the resistance wires r1 adjacent to each other in the circumferential direction are alternately connected on the radial inside or the radial outside. As a result, the multiple resistance wires r1 are connected in series as a whole.

[0042] The second torque sensor 62 has four strain gauges Re, Rf, Rg, and Rh. Of the four strain gauges Re, Rf, Rg, and Rh, two strain gauges Re and Rf are arranged at intervals in the circumferential direction. The two strain gauges Re and Rf are each provided in a semicircular arc shape within a range of approximately 180° centered on the central axis 9. The radial distance from the central axis 9 to the strain gauge Re is approximately the same as the radial distance from the central axis 9 to the strain gauge Rf.

[0043] Of the four strain gauges Re, Rf, Rg, and Rh, the other two strain gauges Rg and Rh are arranged radially outward of the above two strain gauges Re and Rf. The two strain gauges Rg and Rh are arranged at an interval in the circumferential direction. The two strain gauges Rg and Rh are each provided in a semicircular arc shape within a range of approximately 180° centered on the central axis 9. The radial distance from the central axis 9 to the strain gauge Rg and the radial distance from the central axis 9 to the strain gauge Rh are approximately the same.

[0044] Moreover, the two strain gauges Re, Rg and the two strain gauges Rf, Rh are arranged concentrically and line-symmetrically.

[0045] As shown in Fig. 5, the strain gauges Re, Rf, Rg, and Rh each have a zigzag pattern extending in the circumferential direction. Each of the strain gauges Re, Rf, Rg, and Rh has a plurality of resistance wires r2 arranged in the circumferential direction and substantially parallel to each other. Each of the resistance wires r2 extends obliquely with respect to the radial direction. That is, each of the resistance wires r2 extends in a direction having both radial and circumferential components.

[0046] The resistance wires r2 of the strain gauges Re and Rh are inclined toward one circumferential side with respect to the radial direction. The resistance wires r2 of the strain gauges Rf and Rg are inclined toward the other circumferential side with respect to the radial direction. The inclination angle of the resistance wires r2 with respect to the radial direction is, for example, 45°. The ends of the resistance wires r2 adjacent in the circumferential direction are alternately connected on the radial inside or the radial outside. As a result, the multiple resistance wires r2 are connected in series as a whole.

[0047] Fig. 6 is a circuit diagram of a first bridge circuit C1 including four strain gauges Ra, Rb, Rc, and Rd of the first torque sensor 61. As shown in Fig. 6, the four strain gauges Ra, Rb, Rc, and Rd are connected to each other to form the first bridge circuit C1.

[0048] The strain gauges Ra and Rb are connected in series in this order. The strain gauges Rc and Rd are connected in series in this order. Then, between the positive and negative poles of the power supply voltage, a row of two strain gauges Ra, Rb and a row of two strain gauges Rc, Rd are connected in parallel. In addition, a first voltmeter V1 is connected between a midpoint M11 of the two strain gauges Ra, Rb and a midpoint M12 of the two strain gauges Rc, Rd.

[0049] The resistance value of each resistance wire r1 changes according to the torque applied to the area in which the resistance wire r1 is disposed. For example, when a torque is applied to the diaphragm portion 33 in one circumferential direction around the central axis 9, the resistance value of each resistance wire r1 of the two strain gauges Ra, Rd decreases, and the resistance value of each resistance wire r1 of the other two strain gauges Rb, Rc increases. On the other hand, when a torque is applied to the diaphragm portion 33 in the other circumferential direction around the central axis 9, the resistance value of each resistance wire r1 of the two strain gauges Ra, Rd increases, and the resistance value of each resistance wire r1 of the other two strain gauges Rb, Rc decreases. In this way, the two strain gauges Ra, Rd and the other two strain gauges Rb, Rc show resistance value changes in opposite directions with respect to torque.

[0050] When the resistance values ​​of the four strain gauges Ra, Rb, Rc, and Rd change, the potential difference between the midpoint M11 of the two strain gauges Ra, Rb and the midpoint M12 of the two strain gauges Rc, Rd changes, and the output value of the first voltmeter V1 also changes. The signal processing circuit 52 detects the direction and magnitude of the torque applied to the diaphragm portion 33 based on the output value of the first voltmeter V1.

[0051] Fig. 7 is a circuit diagram of a second bridge circuit C2 including four strain gauges Re, Rf, Rg, and Rh of the second torque sensor 62. As shown in Fig. 7, the four strain gauges Re, Rf, Rg, and Rh are connected to each other to form the second bridge circuit C2.

[0052] The strain gauges Re and Rf are connected in series in this order. The strain gauges Rg and Rh are connected in series in this order. Then, between the positive and negative poles of the power supply voltage, a row of two strain gauges Re, Rf and a row of two strain gauges Rg, Rh are connected in parallel. In addition, a second voltmeter V2 is connected between a midpoint M21 of the two strain gauges Re, Rf and a midpoint M22 of the two strain gauges Rg, Rh.

[0053] The resistance value of each resistance wire r2 changes according to the torque applied to the area in which the resistance wire r2 is disposed. For example, when a torque is applied to the diaphragm portion 33 in one circumferential direction around the central axis 9, the resistance value of each resistance wire r2 of the two strain gauges Re, Rh decreases, and the resistance value of each resistance wire r2 of the other two strain gauges Rf, Rg increases. On the other hand, when a torque is applied to the diaphragm portion 33 in the other circumferential direction around the central axis 9, the resistance value of each resistance wire r2 of the two strain gauges Re, Rh increases, and the resistance value of each resistance wire r2 of the other two strain gauges Rf, Rg decreases. In this way, the two strain gauges Re, Rh and the other two strain gauges Rf, Rg show resistance value changes in opposite directions with respect to torque.

[0054] When the resistance values ​​of the four strain gauges Re, Rf, Rg, and Rh change, the potential difference between the midpoint M21 of the two strain gauges Re and Rf and the midpoint M22 of the two strain gauges Rg and Rh changes, and the output value of the second voltmeter V2 also changes. The signal processing circuit 52 detects the direction and magnitude of the torque applied to the diaphragm portion 33 based on the output value of the second voltmeter V2.

[0055] Moreover, the reducer 1 of this embodiment has two torque sensors 61, 62. The signal processing circuit 52 uses one of the output signals of the two torque sensors 61, 62 as the output signal of the torque sensor 60. By having the two torque sensors 61, 62, even if an abnormality occurs in one of the torque sensors, the torque can be detected by the other torque sensor. Furthermore, if an abnormality occurs in one of the torque sensors, the occurrence of the abnormality can be detected.

[0056] <3-3.Angle sensor> The angle sensor 70 is a sensor for detecting the rotation angle of the rotational motion input to the reducer 1. That is, the angle sensor 70 is a sensor whose output value changes according to the rotation angle of the cam 41. As shown in Fig. 5, the angle sensor 70 has eight strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp. The eight strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp are arranged at intervals in the circumferential direction.

[0057] Each of the eight strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp is formed by one conducting wire. Each of the strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp has a resistance wire extending in an arc shape along the circumferential direction. However, in each of the strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp, the resistance wire extending in the circumferential direction may be repeatedly arranged in the radial direction. Also, the resistance wire of each of the strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp may extend in the radial direction. Also, in each of the strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp, the resistance wire extending in the radial direction may be repeatedly arranged in the circumferential direction.

[0058] Of the eight strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp, the four strain gauges Ri, Rk, Rm, and Ro that are not adjacent to each other are connected to each other to form a third bridge circuit C3. FIG. 8 is a circuit diagram of the third bridge circuit C3. As shown in FIG. 8, the strain gauge Ri and the strain gauge Rk are connected in series in this order. The strain gauge Ro and the strain gauge Rm are connected in series in this order. Then, between the positive and negative poles of the power supply voltage, a row of two strain gauges Ri and Rk and a row of two strain gauges Ro and Rm are connected in parallel. In addition, a third voltmeter V3 is connected between a midpoint M31 of the two strain gauges Ri and Rk and a midpoint M32 of the two strain gauges Ro and Rm.

[0059] Of the eight strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp, the remaining four strain gauges Rj, Rl, Rn, and Rp are connected to each other to form a fourth bridge circuit C4. FIG. 9 is a circuit diagram of the fourth bridge circuit C4. As shown in FIG. 9, the strain gauges Rp and Rn are connected in series in this order. The strain gauges Rj and Rl are connected in series in this order. Then, between the positive and negative poles of the power supply voltage, a row of two strain gauges Rp and Rn and a row of two strain gauges Rj and Rl are connected in parallel. In addition, a fourth voltmeter V4 is connected between a midpoint M41 of the two strain gauges Rp and Rn and a midpoint M42 of the two strain gauges Rj and Rl.

[0060] When the reducer 1 is driven, a portion that expands in the circumferential direction (hereinafter referred to as an "expanded portion") and a portion that contracts in the circumferential direction (hereinafter referred to as a "contracted portion") are generated in the diaphragm portion 33 of the flexible external gear 30. Specifically, two expanded portions and two contracted portions are generated alternately in the circumferential direction. That is, the expanded portions and contracted portions are generated alternately at intervals of 90° in the circumferential direction around the central axis 9. The locations where these expanded portions and contracted portions are generated rotate at the first rotation speed described above.

[0061] The resistance value of each of the eight strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp changes according to the circumferential expansion and contraction of the diaphragm portion 33. For example, when the above-mentioned expansion portion overlaps with a certain strain gauge, the resistance value of that strain gauge increases. Also, when the above-mentioned contraction portion overlaps with a certain strain gauge, the resistance value of that strain gauge decreases.

[0062] In the example of Fig. 5, when the contraction portion overlaps with the strain gauges Ri, Rm, the expansion portion overlaps with the strain gauges Rk, Ro. Also, when the expansion portion overlaps with the strain gauges Ri, Rm, the contraction portion overlaps with the strain gauges Rk, Ro. Therefore, in the third bridge circuit C3, the strain gauges Ri, Rm and the strain gauges Rk, Ro show resistance value changes in opposite directions.

[0063] 5, when the contraction portion overlaps with the strain gauges Rp, Rl, the expansion portion overlaps with the strain gauges Rn, Rj. When the expansion portion overlaps with the strain gauges Rp, Rl, the contraction portion overlaps with the strain gauges Rn, Rj. Therefore, in the fourth bridge circuit C4, the strain gauges Rp, Rl and the strain gauges Rn, Rj show opposite resistance value changes.

[0064] Fig. 10 is a graph showing the time change of the output value v3 of the third voltmeter V3 of the third bridge circuit C3 and the output value v4 of the fourth voltmeter V4 of the fourth bridge circuit C4. The horizontal axis of the graph in Fig. 10 indicates time. The vertical axis of the graph in Fig. 10 indicates voltage value. When the reducer 1 is driven, as shown in Fig. 10, the third voltmeter V3 and the fourth voltmeter V4 respectively provide periodically changing sinusoidal output values ​​v3 and v4. The period T of the output values ​​v3 and v4 corresponds to 1 / 2 the period of the first rotation speed described above.

[0065] Furthermore, the output value v3 of the third voltmeter V3 and the output value v4 of the fourth voltmeter V4 have a phase difference of 1 / 4 period. That is, the output values ​​of the two bridge circuits C3, C4 have a phase difference of 1 / 4 period. The direction of the input rotational motion can be determined based on whether the phase of the output value v4 of the fourth voltmeter V4 leads the phase of the output value v3 of the third voltmeter V3 by 1 / 8 period of the first rotation speed (1 / 4 period of the output values ​​v3, v4) or lags behind the phase of the output value v3 of the third voltmeter V3 by 1 / 8 period of the first rotation speed (1 / 4 period of the output values ​​v3, v4).

[0066] The signal processing circuit 52 detects the rotation angle of the rotary motion input to the reducer 1 based on the output value v3 of the third voltmeter V3 and the output value v4 of the fourth voltmeter V4. Specifically, the signal processing circuit 52 stores a function table that associates combinations of the output value v3 of the third voltmeter V3 and the output value v4 of the fourth voltmeter V4 with the rotation angle. The signal processing circuit 52 inputs the output values ​​v3 and v4 into the function table to output the rotation angle.

[0067] When the reducer 1 is driven, periodic flexural deformation occurs in the flexible external gear 30. For this reason, the output signal of the first torque sensor 61 and the output signal of the second torque sensor 62 described above contain a component reflecting the torque that is originally to be measured, and an error component (ripple error) caused by the periodic flexural deformation of the flexible external gear 30. The ripple error changes in a sinusoidal shape according to the rotation angle of the rotational motion input to the reducer 1.

[0068] Therefore, the signal processing circuit 52 calculates the above-mentioned ripple error according to the rotation angle detected by the angle sensor 70. Then, the output signals of the first torque sensor 61 and the second torque sensor 62 are corrected using the calculated ripple error. Specifically, the signal processing circuit 52 increases or decreases the output signals of the first torque sensor 61 and the second torque sensor 62 in a direction that cancels the ripple error. As a result, the signal processing circuit 52 can output the torque applied to the flexible external gear 30 with higher accuracy.

[0069] Alternatively, the signal processing circuit 52 may multiply the output values ​​v3, v4 of the third voltmeter V3 and the fourth voltmeter V4 by a predetermined coefficient and combine the results with the output signals of the first torque sensor 61 and the second torque sensor 62, without calculating the rotation angle described above. In this way, the processing load for calculating the rotation angle can be reduced. Therefore, the calculation speed of the signal processing circuit 52 can be improved.

[0070] In the above embodiment, the torque sensor 60 and the angle sensor 70 are disposed on the flexible external gear 30. However, the torque sensor 60 and the angle sensor 70 may be disposed on the internal gear 20.

[0071] <4. Life expectancy prediction> <4-1. First embodiment> Next, a description will be given of the life prediction of the reducer 1. Fig. 11 is a block diagram showing a configuration related to the life prediction of the reducer 1. The life prediction device 80 is a device that predicts the life of the reducer 1 having the flexible external gear 30, the internal gear 20, the flexible bearing 42, and the torque sensor 60 arranged on at least one of the flexible external gear 30 and the internal gear 20 as described above.

[0072] The lifespan is the service life. In other words, the lifespan of the reducer 1 is the time during which the reducer 1 can operate without breaking down. Among the components constituting the reducer 1, the component with the shortest service life is the flexible bearing 42 or the flexible external gear 30. For this reason, the lifespan prediction device 80 predicts the service life of at least one of the flexible bearing 42 and the flexible external gear 30.

[0073] The life prediction device 80 is configured by an electric circuit having a processor 801 such as a CPU and a memory 802 such as a RAM. The life prediction device 80 of this embodiment is provided in the reducer 1. For example, the life prediction device 80 is mounted on the signal processing circuit 52. This allows the reducer 1 itself to be equipped with a function for predicting life. However, the life prediction device 80 may be provided in a controller that controls the robot 100. The life prediction device 80 may also be provided in a computer connected to at least one of the reducer 1 and the robot 100 via a network. By providing the robot 100 with the life prediction device 80 or the reducer 1 equipped with the life prediction device 80, the life of at least one of the flexible bearing 42 and the flexible external gear 30 can be managed based on the measurement value of the torque sensor 60 mounted on the reducer 1.

[0074] 11, the life prediction device 80 is electrically connected to the torque sensor 60. More specifically, the life prediction device 80 is electrically connected to the torque sensor 60 via the signal processing circuit 52.

[0075] 11, the life prediction device 80 is electrically connected to an encoder 81. The encoder 81 is, for example, an encoder of the motor 103. In this case, the encoder 81 measures and outputs the input rotation speed of the reducer 1. However, the encoder 81 may be provided on the output side of the reducer 1. In this case, the encoder 81 measures and outputs the output rotation speed of the reducer 1.

[0076] The encoder 81 may also use the angle sensor 70 described above. In that case, the encoder 81 is mounted on, for example, the signal processing circuit 52. The encoder 81 calculates the input rotation speed of the reducer 1 based on the measurement value of the angle sensor 70.

[0077] Next, there will be described the operation of the life prediction device 80. Fig. 12 is a flowchart showing the flow of the operation of the life prediction device 80 according to the first embodiment.

[0078] 12, the life prediction device 80 first acquires a torque measurement value from the torque sensor 60 (step S1). Specifically, the measurement value of the torque sensor 60 is output from the signal processing circuit 52. Then, the measurement value is input to the life prediction device 80.

[0079] Next, the life prediction device 80 acquires at least one of the input rotation speed and the output rotation speed of the reducer 1 (step S2). Specifically, at least one of the input rotation speed and the output rotation speed is output from the encoder 81. Then, the rotation speed is input to the life prediction device 80.

[0080] Next, the life prediction device 80 calculates a threshold value for the life of at least one of the flexible bearing 42 and the flexible external gear 30 based on at least one of the input rotational speed and the output rotational speed of the reducer 1 and the measurement value of the torque sensor 60 (step S3).

[0081] The life of the flexible bearing 42 is expressed, for example, by the following formula (1). Lhe=10000×(Tar / Tao)^3×(nar / nai) (1) In formula (1), Lhe is the life of the flexible bearing 42 in hours. Tar is the rated torque in N·m. Tao is the average torque in Nm. nar is the rated input speed in r / min. nai is the average input speed in r / min.

[0082] Among the above, the rated torque Tar and the rated input rotation speed nar are fixed values. The rated torque Tar and the rated input rotation speed nar are stored in advance in the memory 802 of the life prediction device 80. The life prediction device 80 calculates the average torque Tao based on the torque measurement value obtained from the torque sensor 60. The life prediction device 80 also calculates the average input rotation speed nai based on at least one of the input rotation speed and the output rotation speed obtained from the encoder 81.

[0083] The life prediction device 80 substitutes the rated torque Tar and the rated input rotation speed nar read from the memory and the calculated average torque Tao and average input rotation speed nai into the above formula (1). In this way, the life prediction device 80 calculates the life Lhe of the flexible bearing 42.

[0084] Fig. 13 is a graph showing the lives of the flexible bearing 42 and the flexible external gear 30. The horizontal axis of Fig. 13 represents the total rotation speed N of the input shaft 10. The vertical axis of Fig. 13 represents the average torque Tao.

[0085] As shown in Fig. 13, when the average torque Tao is Tao1, the total rotation speed N of the input shaft 10, which represents the life of the flexible bearing 42, is N1. Also, as shown in Fig. 13, when the average torque Tao is Tao1, the total rotation speed N of the input shaft 10, which represents the life of the flexible external gear 30, is N2. In this way, in the present speed reducer 1, the total rotation speed N of the input shaft 10, which represents the life of the flexible bearing 42 and the flexible external gear 30, can be predicted according to the average torque Tao.

[0086] 13 as reference data in advance in the memory 801. The life prediction device 80 calculates the average torque Tao based on the torque measurement value obtained from the torque sensor 60. Then, the life prediction device 80 specifies the total rotation speed N corresponding to the average torque Tao based on the above reference data read from the memory. In this way, the total rotation speed N of the input shaft 10 indicating the life of the flexible bearing 42 and the flexible external gear 30 is specified. The life prediction device 80 calculates the life as the useful time of the flexible bearing 42 and the flexible external gear 30 by dividing the total rotation speed N by the average input rotation speed nai.

[0087] As described above, the life prediction device 80 calculates the life of at least one of the flexible bearing 42 and the flexible external gear 30 based on the formula (1) or the reference data. After that, the life prediction device 80 calculates the threshold value Lth for the life based on the calculated life. The threshold value Lth is set to a time shorter than the life. For example, the threshold value Lth is set to a time obtained by multiplying the life by a predetermined coefficient such as 0.9. The threshold value Lth may also be set to a time obtained by subtracting a predetermined time from the life.

[0088] The life prediction device 80 determines whether or not the total driving time from the start of use of the reducer 1 reaches a threshold value Lth (step S4). If the driving time has not reached the threshold value Lth (No in step S4), the life prediction device 80 repeats the processes from step S1 to step S4.

[0089] When the drive time reaches the threshold value Lth (Yes in step S4), the life prediction device 80 outputs an alert signal Al (step S5). The alert signal Al is a signal indicating that the end of the life of the reducer 1 is approaching. For example, the life prediction device 80 displays a warning on a display based on the alert signal Al. The life prediction device 80 may also turn on a warning light or sound an alarm based on the alert signal Al. The life prediction device 80 may also stop the motor 103 based on the alert signal Al.

[0090] As described above, the life prediction device 80 calculates the threshold value Lth for the life of at least one of the flexible bearing 42 and the flexible external gear 30 based on at least one of the input rotation speed and output rotation speed of the reducer 1 and the measurement value of the torque sensor 60, and outputs an alert signal Al when the drive time of the reducer 1 reaches the threshold value Lth. This makes it possible to manage the life of at least one of the flexible bearing 42 and the flexible external gear 30 based on the measurement value of the torque sensor 60 mounted on the reducer 1.

[0091] The life prediction device 80 may predict only one of the life of the flexible bearing 42 and the life of the flexible external gear 30. The life prediction device 80 can manage the life of the flexible bearing 42 by predicting the life of at least the flexible bearing 42. Furthermore, the life prediction device 80 can manage the life of the flexible external gear 30 by predicting the life of at least the flexible external gear 30.

[0092] The life prediction device 80 may calculate both a first threshold value Lth1 related to the life of the flexible bearing 42 and a second threshold value Lth2 related to the life of the flexible external gear 30 based on at least one of the input rotation speed and the output rotation speed of the reducer 1 and the measurement value of the torque sensor 60. The life prediction device 80 may output an alert signal Al when the driving time of the reducer 1 reaches either the first threshold value Lth1 or the second threshold value Lth2. In this way, the alert signal Al can be output at the time when the driving time of the reducer 1 reaches the shorter of the first threshold value Lth1 and the second threshold value Lth2. Therefore, the life can be managed based on the shorter life of either the flexible bearing 42 or the flexible external gear 30.

[0093] <4-2. Second embodiment> Next, a description will be given of a second embodiment of the operation of the life prediction device 80. Fig. 14 is a flowchart showing the flow of the operation of the life prediction device 80 according to the second embodiment.

[0094] 14, the life prediction device 80 first acquires a torque measurement value from the torque sensor 60 (step S11). Specifically, the measurement value of the torque sensor 60 is output from the signal processing circuit 52. Then, the measurement value is input to the life prediction device 80.

[0095] Next, the life prediction device 80 acquires at least one of the input rotation speed and the output rotation speed of the reducer 1 (step S12). Specifically, at least one of the input rotation speed and the output rotation speed is output from the encoder 81. Then, the rotation speed is input to the life prediction device 80.

[0096] Next, the life prediction device 80 calculates the remaining life Lr of at least one of the flexible bearing 42 and the flexible external gear 30 based on at least one of the input rotational speed and output rotational speed of the reducer 1 and the measurement value of the torque sensor 60 (step S13).

[0097] Specifically, similarly to the first embodiment, the life prediction device 80 calculates the life of at least one of the flexible bearing 42 and the flexible external gear 30 based on at least one of the input rotation speed and the output rotation speed of the reducer 1, the measurement value of the torque sensor 60, and formula (1) or reference data. After that, the life prediction device 80 calculates the remaining life Lr by subtracting the total driving time from the calculated life.

[0098] Thereafter, the life prediction device 80 outputs the calculated remaining life time Lr (step S14). For example, the life prediction device 80 displays the remaining life time Lr on a display. The life prediction device 80 may also output the remaining life time Lr as data to an external information terminal. The life prediction device 80 repeats the operations of steps S11 to S14 to successively update and output the remaining life time Lr.

[0099] As described above, the life prediction device 80 outputs the remaining life Lr of at least one of the flexible bearing 42 and the flexible external gear 30 based on at least one of the input rotation speed and output rotation speed of the reducer 1 and the measurement value of the torque sensor 60. This makes it possible to manage the life of at least one of the flexible bearing 42 and the flexible external gear 30 based on the measurement value of the torque sensor 60 mounted on the reducer 1.

[0100] The life prediction device 80 may calculate a first remaining time Lr1, which is the remaining time Lr of the flexible bearing 42, and a second remaining time Lr2, which is the remaining time Lr of the flexible external gear 30, based on at least one of the input rotation speed and the output rotation speed of the reducer 1 and the measurement value of the torque sensor 60. In this case, it is preferable that the life prediction device 80 outputs the shorter of the first remaining time Lr1 and the second remaining time Lr2. This makes it possible to manage the remaining time Lr of the life based on the shorter life of the flexible bearing 42 or the flexible external gear 30. Note that, in order to calculate the second remaining time Lr2, it is preferable to count the number of times that a torque threshold value exceeding the stress value of the fatigue limit of the flexible external gear 30 is exceeded.

[0101] <5. Modifications> Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. Various modified examples will be described below, focusing on the differences from the above embodiment.

[0102] In the above embodiment, the reducer 1 includes the signal processing circuit 52. However, the signal processing circuit 52 may be provided outside the reducer 1. Furthermore, one signal processing circuit 52 may be connected to the sensors 50 of multiple reducers 1.

[0103] In the above embodiment, the torque sensor 60 includes the first torque sensor 61 and the second torque sensor 62. However, the torque sensor 60 may include only one of the first torque sensor 61 and the second torque sensor 62.

[0104] In the reducer 1 of the above embodiment, the flexible external gear 30 is fixed to the base frame 101, and the internal gear 20 rotates at the second rotation speed after deceleration. However, the internal gear 20 may be fixed to the base frame 101, and the flexible external gear 30 may rotate at the second rotation speed after deceleration.

[0105] The flexible external gear 30 in the above embodiment is a so-called "hat-shaped" gear in which the diaphragm portion 33 spreads radially outward from the body portion 31. However, the flexible external gear 30 may be a so-called "cup-shaped" gear in which the diaphragm portion 33 spreads radially inward from the body portion 31.

[0106] In the above embodiment, the robot 100 is an industrial robot having an arm. However, the robot 100 may be another device such as an assist suit or an automated guided vehicle.

[0107] In addition, the detailed configurations of the reducer, the robot, and the life prediction device may be appropriately modified without departing from the spirit of the present invention. Furthermore, the elements appearing in the above-described embodiment and modified examples may be appropriately combined without causing any contradiction.

[0108] <6. Summary> The present technology can have the following configurations.

[0109] (1) A life prediction device for a reducer having a flexible external gear, an internal gear, a flexible bearing, and a torque sensor arranged on at least one of the flexible external gear and the internal gear, the life prediction device calculating a threshold value for the life of at least one of the flexible bearing and the flexible external gear based on at least one of the input rotational speed and output rotational speed of the reducer and the measurement value of the torque sensor, and outputting an alert signal when the driving time of the reducer reaches the threshold value.

[0110] (2) A life prediction device for a reducer having a flexible external gear, an internal gear, a flexible bearing, and a torque sensor arranged on at least one of the flexible external gear and the internal gear, the life prediction device outputting the remaining life of at least one of the flexible bearing and the flexible external gear based on at least one of the input rotational speed and output rotational speed of the reducer and the measurement value of the torque sensor.

[0111] (3) A life prediction device according to (1) or (2), wherein the life includes at least the life of the flexible bearing.

[0112] (4) A life prediction device according to any one of (1) to (3), wherein the life includes at least the life of the flexible external gear.

[0113] (5) A life prediction device as described in (1), which calculates a first threshold value for the life of the flexible bearing and a second threshold value for the life of the flexible external gear based on at least one of the input rotational speed and the output rotational speed of the reducer and the measurement value of the torque sensor, and outputs an alert signal when the driving time of the reducer reaches either the first threshold value or the second threshold value.

[0114] (6) A life prediction device as described in (2), which calculates a first remaining time which is the remaining life of the flexible bearing and a second remaining time which is the remaining life of the flexible external gear based on at least one of the input rotational speed and the output rotational speed of the reducer and the measurement value of the torque sensor, and outputs the shorter of the first remaining time and the second remaining time.

[0115] (7) A reducer equipped with any one of the life prediction devices described in (1) to (6).

[0116] (8) A robot comprising the life prediction device according to (1) or (2), or the reducer according to (7).

[0117] (9) A method for predicting a life span of a reducer having a flexible external gear, an internal gear, a flexible bearing, and a torque sensor arranged on at least one of the flexible external gear and the internal gear, the method calculating a threshold value for the life span of at least one of the flexible bearing and the flexible external gear based on at least one of the input rotational speed and the output rotational speed of the reducer and the measurement value of the torque sensor, and outputting an alert signal when the driving time of the reducer reaches the threshold value.

[0118] (10) A method for predicting the remaining life of a reducer having a flexible external gear, an internal gear, a flexible bearing, and a torque sensor arranged on at least one of the flexible external gear and the internal gear, the method outputting the remaining life of at least one of the flexible bearing and the flexible external gear based on at least one of the input rotational speed and output rotational speed of the reducer and the measurement value of the torque sensor.

[0119] (11) A life prediction method according to (9) or (10), wherein the life includes at least the life of the flexible bearing.

[0120] (12) A life prediction method according to any one of (9) to (11), wherein the life includes at least the life of the flexible external gear.

[0121] (13) A life prediction method as described in (9), comprising: calculating a first threshold value for the life of the flexible bearing and a second threshold value for the life of the flexible external gear based on at least one of the input rotational speed and the output rotational speed of the reducer and the measurement value of the torque sensor; and outputting an alert signal when the driving time of the reducer reaches either the first threshold value or the second threshold value.

[0122] (14) A life prediction method as described in (10), comprising: calculating a first remaining time, which is the remaining life of the flexible bearing, and a second remaining time, which is the remaining life of the flexible external gear, based on at least one of the input rotational speed and the output rotational speed of the reducer and the measurement value of the torque sensor; and outputting the shorter of the first remaining time and the second remaining time. [Industrial Applicability]

[0123] INDUSTRIAL APPLICABILITY The present invention can be used in a life prediction device, a reducer, and a life prediction method. [Explanation of symbols]

[0124] 1: Reducer 9: Central axis 10: Input shaft 20: Internal gear 30: Flexible external gear 40: Wave generator 41: Cam 42: Flexible bearing 50: Sensor 51: Sensor board 52: Signal processing circuit 60: Torque sensor 70: Angle sensor 80: Life prediction device 81: Encoder 100: Robot Al: Alert signal Lr: remaining time

Claims

1. A life prediction device for a reducer having a flexible external gear, an internal gear, a flexible bearing, and a torque sensor disposed on at least one of the flexible external gear and the internal gear, calculating a threshold value for a life of at least one of the flexible bearing and the flexible external gear based on at least one of an input rotational speed and an output rotational speed of the reducer and a measurement value of the torque sensor; The life prediction device outputs an alert signal when the drive time of the reducer reaches the threshold value.

2. A life prediction device for a reducer having a flexible external gear, an internal gear, a flexible bearing, and a torque sensor disposed on at least one of the flexible external gear and the internal gear, A life prediction device that outputs the remaining life of at least one of the flexible bearing and the flexible external gear based on at least one of the input rotational speed and output rotational speed of the reducer and the measurement value of the torque sensor.

3. 3. The life prediction device according to claim 1, The life prediction device, wherein the life includes at least the life of the flexible bearing.

4. 3. The life prediction device according to claim 1, The life prediction device, wherein the life includes at least the life of the flexible external gear.

5. 2. The life prediction device according to claim 1, calculating a first threshold value related to a life of the flexible bearing and a second threshold value related to a life of the flexible external gear based on at least one of an input rotational speed and an output rotational speed of the reducer and a measurement value of the torque sensor; The life prediction device outputs an alert signal when a drive time of the reducer reaches either the first threshold value or the second threshold value.

6. 3. The life prediction device according to claim 2, calculating a first remaining time, which is a remaining time of the life of the flexible bearing, and a second remaining time, which is a remaining time of the life of the flexible external gear, based on at least one of the input rotational speed and the output rotational speed of the reducer and the measurement value of the torque sensor; The life prediction device outputs the shorter of the first remaining time and the second remaining time.

7. A reducer comprising the life prediction device according to claim 1 or 2.

8. A robot, A robot comprising the life prediction device according to claim 1 or 2, or the reducer according to claim 7.

9. A method for predicting a life span of a reducer having a flexible external gear, an internal gear, a flexible bearing, and a torque sensor disposed on at least one of the flexible external gear and the internal gear, comprising: calculating a threshold value for a life of at least one of the flexible bearing and the flexible external gear based on at least one of an input rotational speed and an output rotational speed of the reducer and a measurement value of the torque sensor; The method of predicting a life span includes outputting an alert signal when a drive time of the reducer reaches the threshold value.

10. A method for predicting a life span of a reducer having a flexible external gear, an internal gear, a flexible bearing, and a torque sensor disposed on at least one of the flexible external gear and the internal gear, comprising: A life prediction method that outputs the remaining life of at least one of the flexible bearing and the flexible external gear based on at least one of the input rotational speed and output rotational speed of the reducer and the measurement value of the torque sensor.

11. The life prediction method according to claim 9 or 10, The life prediction method, wherein the life includes at least the life of the flexible bearing.

12. The life prediction method according to claim 9 or 10, The life prediction method, wherein the life includes at least the life of the flexible external gear.

13. 10. The life prediction method according to claim 9, calculating a first threshold value related to a life of the flexible bearing and a second threshold value related to a life of the flexible external gear based on at least one of an input rotational speed and an output rotational speed of the reducer and a measurement value of the torque sensor; The method of predicting a life span includes outputting an alert signal when a drive time of the reducer reaches either the first threshold value or the second threshold value.

14. The life prediction method according to claim 10, calculating a first remaining time, which is a remaining time of the life of the flexible bearing, and a second remaining time, which is a remaining time of the life of the flexible external gear, based on at least one of the input rotational speed and the output rotational speed of the reducer and the measurement value of the torque sensor; outputting the shorter of the first remaining time and the second remaining time.

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