Control method and control system

Abstract

Provided is a control method for controlling an articulated robot which has a plurality of joints each provided with a motor and a speed reducer that is connected to the motor and that reduces the speed of rotation of the motor, said method comprising a step a) and a step b). In step a), for each of the plurality of speed reducers, the degree of deterioration of the speed reducer is calculated on the basis of: the input rotational speed of the speed reducer or the input torque of the speed reducer; and the output torque of the speed reducer. In step b), on the basis of the results obtained in step a), the respective degrees of deterioration of the plurality of speed reducers are compared, and a load applied to the speed reducer determined to have the highest degree of deterioration is decreased. Thus, it is possible to improve the durability of the speed reducer determined to have the highest degree of deterioration. This makes it possible to extend the life of the articulated robot as a whole.

Description

Control Method and Control System

[0001] The present invention relates to a control method and a control system. This application claims priority based on Japanese Patent Application No. 2024-197116 filed in Japan on November 12, 2024, and incorporates its content herein by reference.

[0002] Conventionally, an articulated robot in which a plurality of arms are connected via a plurality of joints is known. For each joint of the articulated robot, for example, a motor that outputs a rotational motion for rotating the arm and a speed reducer that decelerates the rotational motion output from the motor are mounted. Regarding conventional speed reducers, for example, they are described in Patent Document 1. International Publication No. 2014 / 098008

[0003] The rotational drive device of Patent Document 1 includes a motor, a speed reducer, a first encoder, a second encoder, a difference detection unit, a tooth skipping detection unit, and a life prediction unit. The speed reducer decelerates the rotation of the rotation shaft on the motor side and transmits the decelerated rotation to the rotation shaft on the load side. The first encoder detects the rotation angle of the rotation shaft on the motor side of the speed reducer. The second encoder detects the rotation angle of the rotation shaft on the load side of the speed reducer. The difference detection unit obtains a difference value between a first detection value obtained by dividing the output of the first encoder by the reduction ratio of the speed reducer and a second detection value obtained from the output of the second encoder. The tooth skipping detection unit detects the occurrence of tooth skipping of the speed reducer based on the difference value calculated by the difference detection unit. The life prediction unit predicts the life of the speed reducer based on the detection result of the tooth skipping detection unit.

[0004] In an articulated robot, in order to perform an operation prioritizing productivity, the load applied to the speed reducer of a specific joint may increase. In such a case, there is a risk that the speed reducer of the said joint will reach its life early. Then, even if the speed reducers of other joints have not reached their life, there is a risk that the maintenance cycle of the entire articulated robot will be shortened. In other words, it can be said that the life of the said articulated robot has been shortened.

[0005] An object of the present invention is to provide a technology capable of extending the life of an entire articulated robot having a plurality of joints equipped with speed reducers.

[0006] The first invention is a control method for controlling a multi-joint robot having a plurality of joints, each joint comprising a motor and a reduction gear connected to the motor and used to reduce the rotation of the motor, comprising: a) a step of calculating the degree of deterioration of each of the plurality of reduction gears based on the input rotational speed of the reduction gear or the input torque of the reduction gear and the output torque of the reduction gear; and b) a step of comparing the degrees of deterioration of the plurality of reduction gears based on the results obtained in step a), and reducing the load on the reduction gear that is determined to have the highest degree of deterioration.

[0007] The second invention relates to a multi-joint robot having a plurality of joints, each joint comprising a motor and a reduction gear connected to the motor for reducing the rotation of the motor, and a control unit for controlling the drive of the multi-joint robot, wherein the control unit performs the steps of: a) calculating the degree of deterioration of each of the plurality of reduction gears based on the input rotational speed of the reduction gear or the input torque of the reduction gear and the output torque of the reduction gear; and b) comparing the degrees of deterioration of the plurality of reduction gears based on the results obtained in step a), and reducing the load on the reduction gear that is determined to have the highest degree of deterioration.

[0008] According to the first and second inventions, the load on the reduction gear, which is judged to be the most deteriorated, can be reduced, thereby improving the lifespan of the reduction gear. This can extend the lifespan of the entire articulated robot.

[0009] Figure 1 is a schematic diagram of the control system. Figure 2 is a longitudinal cross-sectional view of the speed reducer. Figure 3 is a transverse cross-sectional view of the speed reducer. Figure 4 is a partial longitudinal cross-sectional view of the flexible external gear. Figure 5 is a plan view of the sensor substrate. Figure 6 is a partial plan view of the sensor substrate. Figure 7 is a partial plan view of the sensor substrate. Figure 8 is a circuit diagram of the first bridge circuit. Figure 9 is a circuit diagram of the third bridge circuit. Figure 10 is a circuit diagram of the fourth bridge circuit. Figure 11 is a graph showing the time change of the measured value of the third voltmeter of the third bridge circuit and the measured value of the fourth voltmeter of the fourth bridge circuit. Figure 12 is a block diagram conceptually showing some of the functions of the control unit. Figure 13 is a block diagram conceptually showing some of the functions of the control unit according to the second modified example.

[0010] Hereinafter, exemplary embodiments of the present application will be described with reference to the drawings.

[0011] <1. Configuration of the Control System> Figure 1 is a schematic diagram of a control system 300 according to one embodiment. As shown in Figure 1, the control system 300 consists of an articulated robot 100 and a control unit 200 that controls the driving of the articulated robot 100. That is, the control system 300 has an articulated robot 100 and a control unit 200. The articulated robot 100 in this embodiment is a so-called industrial robot that performs tasks such as transporting, processing, and assembling parts in, for example, an industrial product manufacturing line. However, the articulated robot 100 may be a household robot or a humanoid robot.

[0012] The articulated robot 100 includes a base frame 101, a plurality of arms 102, a plurality of joints 103, and an end-effector working arm 105. In this embodiment, the articulated robot 100 has two arms 102 and three joints 103. Each of the three joints 103 is equipped with a motor 104 and a reduction gear 1. That is, the articulated robot 100 has a plurality of joints 103, each equipped with a motor 104 and a reduction gear 1 connected to the motor 104 to reduce the rotation of the motor 104. However, the number of arms 102, joints 103, motors 104, and reduction gears 1 in the articulated robot 100 is not limited to this. In this embodiment, the three motors 104 in the articulated robot 100 have substantially the same structure. Also, the three reduction gears 1 in the articulated robot 100 have substantially the same structure.

[0013] In the following, when it is necessary to distinguish between the two arms 102, they will be denoted with sub-numbers p and q, as shown in Figure 1, and will be described as "arm 102p" and "arm 102q" in order from the one closest to the base frame 101. Similarly, when it is necessary to distinguish between the three joints 103, they will be denoted with sub-numbers p to r, as shown in Figure 1, and will be described as "joint 103p," "joint 103q," and "joint 103r" in order from the one closest to the base frame 101.

[0014] Furthermore, if it is necessary to distinguish between the motors 104 mounted on the three joints 103p, 103q, and 103r, the motor 104 mounted on joint 103p shall be described as "motor 104p", the motor 104 mounted on joint 103q as "motor 104q", and the motor 104 mounted on joint 103r as "motor 104r". Furthermore, if it is necessary to distinguish between the reduction gears 1 mounted on the three joints 103p, 103q, and 103r, the reduction gear 1 mounted on joint 103p shall be described as "reduction gear 1p", the reduction gear 1 mounted on joint 103q as "reduction gear 1q", and the reduction gear 1 mounted on joint 103r as "reduction gear 1r".

[0015] Motor 104 is a drive source that generates rotational motion in accordance with the power value input to it. Motor 104 has a stationary part having a stator, a rotating part having magnets, and an encoder (not shown). In other words, motor 104 in this embodiment is a so-called "motor with encoder". The stator included in the stationary part of motor 104 has a configuration in which coils are wound around a stator core made of laminated electromagnetic steel sheets. When a drive current is supplied to the coils, magnetic flux is generated in multiple teeth of the stator core around which the coils are wound. Then, due to the action of the magnetic flux between each tooth and the magnets included in the rotating part facing each tooth, a circumferential torque is generated between the stationary part and the rotating part. As a result, the rotating part rotates around the stationary part on a rotation axis parallel to the central axis 9 of the reduction gear 1 (see Figure 2, described later). As a result, rotational motion around the rotation axis is output from motor 104.

[0016] In this embodiment, the stationary part of motor 104p is directly or indirectly fixed to the base frame 101. The rotational motion output from motor 104p is reduced by the reduction gear 1p and transmitted to arm 102p. As a result, arm 102p rotates relative to the base frame 101 around the central axis 9 of the reduction gear 1p at the reduced speed. The stationary part of motor 104q is directly or indirectly fixed to arm 102p. The rotational motion output from motor 104q is reduced by the reduction gear 1q and transmitted to arm 102q. As a result, arm 102q rotates relative to arm 102p around the central axis 9 of the reduction gear 1q at the reduced speed. The stationary part of motor 104r is directly or indirectly fixed to arm 102q. The rotational motion output from motor 104r is reduced by the reduction gear 1r and transmitted to the end-effector working arm 105. As a result, the tip working arm 105 rotates around the central axis 9 of the reduction gear 1r relative to the arm 102q at the reduced speed.

[0017] As a result, in this embodiment, the tip working arm 105 can be moved to a desired position by controlling the drive of each of the three motors 104p, 104q, and 104r. Here, in order to control the drive of each motor 104, it is necessary to adjust the power value input to each motor 104. More specifically, it is necessary to adjust the current value or voltage value input to each motor 104.

[0018] The output of each motor 104 can be expressed, for example, by the following formula (1): Pm = 0.10471 × Tm × Cm (1) In formula (1), Pm is the output of motor 104, and its unit is W (watts). Tm is the force applied by the rotating part of motor 104 as it rotates, i.e., the output torque of motor 104, and its unit is N・m. The output torque of motor 104 is the input torque of the reduction gear 1 connected to motor 104. Cm is the number of rotations per minute of motor 104, i.e., the output rotational speed of motor 104, and its unit is r / min. The output rotational speed of motor 104 is the input rotational speed of the reduction gear 1 connected to motor 104. As shown in formula (1), the output of motor 104 is proportional to the product of the output torque and the output rotational speed of motor 104. The output of motor 104 becomes the load on the reduction gear 1 connected to motor 104.

[0019] The control unit 200 is configured, for example, by a computer. As shown in Figure 1, the control unit 200 is configured by a computer having a processor 201 such as a CPU, memory 202 such as RAM, and a storage device 203 such as a NAND flash memory such as an SSD. The storage device 203 stores a computer program D for controlling the drive of each motor 104 of the articulated robot 100. The detailed functions of the control unit 200 will be described later.

[0020] <2. Configuration of the Speed ​​Reducer> Next, the detailed configuration of each speed reducer 1 of the articulated robot 100 will be explained. In the following, the direction parallel to the central axis 9 will be referred to as the "axial direction," the direction perpendicular to the central axis 9 will be referred to as the "radial direction," and the direction along the arc centered on the central axis 9 will be referred to as the "circumferential direction." In the following, in Figures 2 and 4 described later, the direction of the central axis 9 of the speed reducer 1 will be defined as the left-right direction, with the left side being referred to as the "axial side" and the right side as the "other axial side," and the shape and positional relationship of each part will be explained accordingly. In Figures 2 and 4 described later, the "axial side" will be indicated as "a1," and the "other axial side" as "a2." In Figures 2, 3, 5, 6, and 7 described later, the "radial direction" will be indicated as "r0," and in Figures 3, 5, 6, and 7, the "circumferential direction" will be indicated as "c0."

[0021] However, this definition of left-right direction is not intended to limit the orientation of the reducer 1 during manufacturing and use according to the present invention. Furthermore, in this application, "parallel directions" are not limited to cases where they are strictly parallel geometrically. In other words, it is sufficient if a direction that is substantially parallel to a certain direction is substantially parallel to a degree that produces the effects of the invention. Furthermore, in this application, "orthogonal directions" are not limited to cases where they are strictly orthogonal geometrically. In other words, it is sufficient if a direction that is substantially orthogonal to a certain direction is substantially orthogonal to a degree that produces the effects of the invention.

[0022] Figure 2 is a longitudinal cross-sectional view of the speed reducer 1. Figure 3 is a transverse cross-sectional view of the speed reducer 1 as seen from position A-A in Figure 2. To avoid cluttering the diagram, hatching indicating the cross-section has been omitted in Figure 3.

[0023] The speed reducer 1 is a device that reduces the rotational motion of the input rotational speed output from the motor 104 to an output rotational speed smaller than the input rotational speed. As shown in Figures 2 and 3, the speed reducer 1 comprises an input shaft 10, an internal gear 20, a flexible external gear 30, a wave generator 40, a circuit board 45, and a sensor 50. As will be described later, the sensor 50 in this embodiment has a torque sensor 60 and an angle sensor 70. The speed reducer 1 in this embodiment is a wave gear speed reducer having a flexible external gear 30, an internal gear 20, a wave generator 40, and a torque sensor 60.

[0024] The input shaft 10 is a member that extends axially along the central axis 9 around the central axis 9. In this embodiment, the input shaft 10 is cylindrical with the central axis 9 as its center. The input shaft 10 is connected to the rotating part of the motor 104. As a result, the input shaft 10 can rotate at the input rotational speed before reduction in conjunction with the rotation of the rotating part of the motor 104. The input shaft 10 passes through the reduction gear 1 in the axial direction. Note that the input shaft 10 may be the same member as the rotating part of the motor 104.

[0025] The internal gear 20 is an annular gear centered on the central axis 9. In this embodiment, the internal gear 20 of the reduction gear 1p is fixed to the arm 102p. The internal gear 20 of the reduction gear 1q is fixed to the arm 102q. The internal gear 20 of the reduction gear 1r is fixed to the tip working arm 105. The internal gear 20 is positioned radially outward of the external teeth 32 of the flexible external gear 30, which will be described later. The rigidity of the internal gear 20 is sufficiently higher than the rigidity of the body 31 of the flexible external gear 30, which will be described later.

[0026] The internal gear 20 has a plurality of internal teeth 21. Each of the plurality of internal teeth 21 protrudes 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. Some of the plurality of internal teeth 21 mesh with some of the plurality of external teeth 32 of the flexible external gear 30, which will be described later. The internal gear 20 corresponds to the "output member 400" in this embodiment. In this embodiment, the internal gear 20 of the reduction gear 1p rotates at the output rotation speed after the input rotation speed input from the motor 104p has been reduced. Similarly, the internal gear 20 of the reduction gear 1q rotates at the output rotation speed after the input rotation speed input from the motor 104q has been reduced. Similarly, the internal gear 20 of the reduction gear 1r rotates at the output rotation speed after the input rotation speed input from the motor 104r has been reduced. The internal gear 20 is provided with a through hole 600. The through-hole 600 penetrates the internal gear 20 in the axial direction.

[0027] The flexible external gear 30 is an annular gear that can bend and deform due to the rotation of the cam 41, which will be described later. In this embodiment, the flexible external gear 30 of the reduction gear 1p is fixed to the base frame 101. The flexible external gear 30 of the reduction gear 1q is fixed to the arm 102p. The flexible external gear 30 of the reduction gear 1r is fixed to the arm 102q. As shown in Figures 2 and 3, the flexible external gear 30 has a cylindrical body 31, a plurality of external teeth 32, a diaphragm portion 33, and a thickened portion 34.

[0028] The body portion 31 is a cylindrical part 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 positioned radially outward of the wave generator 40 and radially inward of the internal gear 20. Because the body portion 31 is flexible, it can bend and deform in the radial direction.

[0029] Multiple external teeth 32 are arranged on the radially outer surface of the other axial end of the body portion 31. Each of the multiple external teeth 32 protrudes 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 mesh with some of the multiple internal teeth 21. The number of internal teeth 21 in the internal gear 20 and the number of external teeth 32 in the flexible external gear 30 are slightly different.

[0030] 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. In other words, the diaphragm portion 33 expands radially on one axial side of the position where the flexible external gear 30 and the internal gear 20 mesh. The diaphragm portion 33 is annular in shape, surrounding the central axis 9. Because the diaphragm portion 33 is thin-walled, it is slightly flexible and deformable.

[0031] The thickened portion 34 is an annular portion located radially outward from the diaphragm portion 33, centered on the central axis 9. The thickened portion 34 extends radially outward from the radially outer end of the diaphragm portion 33. The axial thickness of the thickened portion 34 is greater than the axial thickness of the diaphragm portion 33. In this embodiment, the thickened portion 34 of the reducer 1p is fixed to the base frame 101, for example, with bolts. The thickened portion 34 of the reducer 1q is fixed to the arm 102p, for example, with bolts. The thickened portion 34 of the reducer 1r is fixed to the arm 102q, for example, with bolts.

[0032] Furthermore, the flexible external gear 30, including the thickened portion 34, rotatably supports the internal gear 20 by a cross roller bearing 150. The cross roller bearing 150 has an outer ring 152, an inner ring 151, and rollers 161. In this embodiment, the outer ring 152 is fixed to the other axial side of the thickened portion 34. The outer ring 152 rotatably supports the inner ring 151 via the rollers 161.

[0033] Furthermore, the inner ring 151 is provided with a screw hole 153. The screw hole 153 is formed extending from the other axial end face of the inner ring 151 toward the one axial side. In this embodiment, a screw 155 that passes through the through hole 600 of the internal gear 20 and the through hole 500 that penetrates the output side housing 90, which is provided on the other axial side of the internal gear 20, is fastened to the screw hole 153. This allows the inner ring 151 to be fixed to the internal gear 20 and the output side housing 90. As a result, the inner ring 151, the internal gear 20, and the output side housing 90 are rotatably supported by the outer ring 152 via the rollers 161.

[0034] The wave generator 40 is a mechanism that generates periodic deflection deformation in the flexible external gear 30. The wave generator 40 is positioned radially inward of the external teeth 32. The wave generator 40 includes a cam 41 and a flexible bearing 42.

[0035] The cam 41 is a component that imparts displacement to the flexible external gear 30 with a period of 180°. The cam 41 has a non-circular outer surface. In this embodiment, the cam 41 has an elliptical outer surface centered on the central axis 9. In this embodiment, the input shaft 10 and the cam 41 are formed from a single component. However, the cam 41 may be a separate component from the input shaft 10. In that case, it is sufficient that the cam 41 is fixed to the input shaft 10. As a result, the input shaft 10 and cam 41 of the reduction gear 1p can rotate at the input rotational speed before reduction in conjunction with the rotation of the rotating part of the motor 104p. Similarly, the input shaft 10 and cam 41 of the reduction gear 1q can rotate at the input rotational speed before reduction in conjunction with the rotation of the rotating part of the motor 104q. Similarly, the input shaft 10 and cam 41 of the reduction gear 1r can rotate at the input rotational speed before reduction in conjunction with the rotation of the rotating part of the motor 104r.

[0036] The flexible bearing 42 is a bearing that can be deformed by bending. The flexible bearing 42 is positioned 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. As a result, the body 31 deforms into an elliptical shape along the radially outer surface of the cam 41. Consequently, at two locations corresponding to the ends of the major axis of the ellipse, the external teeth 32 of the flexible external gear 30 and the internal teeth 21 of the internal gear 20 mesh. At other positions in the circumferential direction, the external teeth 32 and the internal teeth 21 do not mesh.

[0037] When the motor 104 is driven, the cam 41 rotates along with the input shaft 10 around the central axis 9 at the input rotational speed. As a result, the major axis of the ellipse of the flexible external gear 30 also rotates in the circumferential direction at the input rotational speed. Consequently, the meshing position between the external teeth 32 and the internal teeth 21 also changes in the circumferential direction at the input rotational speed. Furthermore, as described above, the number of internal teeth 21 of the internal gear 20 and the number of 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 with each rotation of the cam 41.

[0038] As described above, in the reduction gear 1p, the flexible external gear 30 having external teeth 32 is fixed to the base frame 101 at the thickened portion 34 and does not rotate. On the other hand, the internal gear 20 having internal teeth 21 is supported together with the arm 102p so as to be rotatable around the central axis 9. As a result, in the reduction gear 1p, the internal gear 20 and the arm 102p rotate around the central axis 9 at an output rotational speed smaller (slower) than the input rotational speed output from the motor 104p, relative to the flexible external gear 30 and the base frame 101.

[0039] Furthermore, in the reduction gear 1q, the flexible external gear 30 having external teeth 32 is fixed to the arm 102p at the thickened portion 34. On the other hand, the internal gear 20 having internal teeth 21 is supported together with the arm 102q so as to be rotatable around the central axis 9. As a result, in the reduction gear 1q, the internal gear 20 and the arm 102q rotate around the central axis 9 at an output rotational speed smaller (slower) than the input rotational speed output from the motor 104p, relative to the flexible external gear 30 and the arm 102p.

[0040] Furthermore, in the reduction gear 1r, the flexible external gear 30 having external teeth 32 is fixed to the arm 102q at the thickened portion 34. On the other hand, the internal gear 20 having internal teeth 21 is supported together with the end working arm 105 so as to be rotatable around the central axis 9. As a result, in the reduction gear 1r, the internal gear 20 and the end working arm 105 rotate around the central axis 9 at an output rotational speed smaller (slower) than the input rotational speed output from the motor 104r, relative to the flexible external gear 30 and the arm 102q.

[0041] However, as a modification, in the reduction gear 1p, the internal gear 20 and inner ring 151 may be fixed to the base frame 101, while the flexible external gear 30 and outer ring 152 may be fixed to the arm 102p. Then, in the reduction gear 1p, the flexible external gear 30 and arm 102p may rotate around the central axis 9 at the output rotational speed relative to the internal gear 20 and base frame 101. Alternatively, in the reduction gear 1q, the internal gear 20 and inner ring 151 may be fixed to the arm 102p, while the flexible external gear 30 and outer ring 152 may be fixed to the arm 102q. Then, in the reduction gear 1q, the flexible external gear 30 and arm 102q may rotate around the central axis 9 at the output rotational speed relative to the internal gear 20 and arm 102p. Alternatively, in the reduction gear 1r, the internal gear 20 and inner ring 151 may be fixed to the arm 102q, while the flexible external gear 30 and outer ring 152 may be fixed to the end working arm 105. Furthermore, in the reduction gear 1r, the flexible external gear 30 and end working arm 105 may rotate around the central axis 9 at the output rotational speed relative to the internal gear 20 and arm 102q. In other words, the flexible external gear 30 and the internal gear 20 should be configured to mesh with each other, and at least one of them should rotate around the central axis 9 at the output rotational speed of the reduction gear 1.

[0042] The circuit board 45 is a plate-shaped member that extends radially outward from the input shaft 10, with the central axis 9 as the central axis. The circuit board 45 is fixed to the input side housing 80 by screws or the like.

[0043] <3. About the sensor> <3-1. Structure of the sensor> Next, the structure of the sensor 50 will be described. As shown in FIG. 2, the sensor 50 includes a sensor substrate 51 and a signal processing circuit 52. FIG. 4 is a partial longitudinal sectional view of the flexible external gear 30. FIG. 5 is a plan view of the sensor substrate 51. As shown in FIGS. 4 and 5, the diaphragm portion 33 of the flexible external gear 30 has a surface 331 that intersects the central axis 9 and extends in an annular shape around the central axis 9. The surface 331 is a surface on one axial side of the diaphragm portion 33. The sensor substrate 51 is adhesively fixed to the surface 331 of the diaphragm portion 33. The sensor substrate 51 has an insulating layer 511 and a conductor layer 512.

[0044] The insulating layer 511 is flexible and deformable. The insulating layer 511 extends in a direction intersecting the central axis 9. The insulating layer 511 is annular around the central axis 9. The insulating layer 511 is made of a resin or an inorganic insulating material that is an insulator such as polyimide. The insulating layer 511 is disposed on the surface 331 of the diaphragm portion 33.

[0045] The conductor layer 512 is formed on the surface of the insulating layer 511 facing one axial side. A metal, which is a conductor foil, is used as the material of the conductor layer 512. Specifically, for example, a copper alloy, a chromium alloy, or copper is used as the material of the conductor layer 512.

[0046] 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 composed of a plurality of strain gauges. The signal processing circuit 52 includes a torque calculation unit 521 and an angle calculation unit 522. The torque calculation unit 521 is electrically connected to the torque sensor 60. The angle calculation unit 522 is electrically connected to the angle sensor 70. However, the angle sensor 70 and the angle calculation unit 522 do not necessarily have to be provided.

[0047] <3-2. Detailed Configuration of Torque Sensor>Next, the detailed configuration of the torque sensor 60 will be described. As described above, the torque sensor 60 includes a plurality of strain gauges. Further, the plurality of strain gauges are adhesively fixed to the surface 331 of the diaphragm portion 33. That is, the torque sensor 60 is configured by attaching a plurality of strain gauges to the diaphragm portion 33. In other words, the torque sensor 60 is disposed on the flexible external gear 30. By disposing the plurality of strain gauges on the diaphragm portion 33 in this manner, the torque sensor 60 can be provided in a compact manner in each speed reducer 1.

[0048] The torque sensor 60 can detect the torque applied to the output member 400, which is the internal gear 20 that meshes with the flexible external gear 30, by detecting the torque applied to the diaphragm portion 33 using the plurality of strain gauges. The torque applied to the output member 400 is, in other words, the output torque of the speed reducer 1. Specifically, the output signals from the plurality of strain gauges change according to the distortion of the diaphragm portion 33 distorted by the torque around the central axis 9 applied to the diaphragm portion 33. Thereby, based on the output signal from the torque sensor 60, the torque around the central axis 9 acting on the output member 400, which is the internal gear 20 that partially meshes with the flexible external gear 30 having the diaphragm portion 33, can be detected. This will be further described in detail below.

[0049] As shown in FIG. 5, in the present embodiment, the torque sensor 60 has four strain gauges. Hereinafter, the four strain gauges included in the torque sensor 60 will be referred to as 'first strain gauge Ra', 'first strain gauge Rb', 'first strain gauge Rc', and 'first strain gauge Rd'. Among the four first strain gauges Ra, Rb, Rc, and Rd, two first strain gauges Ra and Rb are arranged at intervals in the circumferential direction. In the present embodiment, the two first strain gauges Ra and Rb are provided in a semi-arc shape in a range of approximately 180° centered on the central axis 9, respectively. The radial distance from the central axis 9 to the first strain gauge Ra and the radial distance from the central axis 9 to the first strain gauge Rb are substantially the same.

[0050] Of the four first strain gauges Ra, Rb, Rc, and Rd, the other two first strain gauges Rc and Rd are positioned radially outward from the two first strain gauges Ra and Rb. The two first strain gauges Rc and Rd are positioned with a circumferential gap between them. In this embodiment, the two first strain gauges Rc and Rd are each provided in a semi-circular arc shape within a range of approximately 180° around the central axis 9. The radial distance from the central axis 9 to the first strain gauge Rc and the radial distance from the central axis 9 to the first strain gauge Rd are approximately the same.

[0051] As described above, the two first strain gauges Rc and Rd are positioned radially outward from the two first strain gauges Ra and Rb. The two first strain gauges Ra and Rb are arranged circumferentially. Furthermore, the two first strain gauges Rc and Rd are arranged circumferentially, radially outward from the two first strain gauges Ra and Rb.

[0052] Furthermore, two inner gap regions Gi are positioned between two circumferentially adjacent first strain gauges Ra and Rb. When viewed from the axial direction, the two inner gap regions Gi are positioned at an angle of 180° around the central axis 9. Furthermore, two outer gap regions Go are positioned between two circumferentially adjacent first strain gauges Rc and Rd. When viewed from the axial direction, the two outer gap regions Go are positioned at an angle of 180° around the central axis 9. In addition, the inner gap regions Gi and the outer gap regions Go are adjacent in the radial direction. Furthermore, the two first strain gauges Ra and Rc and the two first strain gauges Rb and Rd are positioned concentrically and symmetrically.

[0053] The first strain gauges Ra, Rb, Rc, and Rd each have a pattern that extends circumferentially while bending in a zigzag pattern. Figures 6 and 7 are partial plan views of the sensor substrate 51, respectively. As shown in Figures 6 and 7, each of the first strain gauges Ra, Rb, Rc, and Rd has a plurality of substantially parallel resistance wires r1 arranged circumferentially. Each resistance wire r1 extends in a direction having both radial and circumferential components.

[0054] The resistance wires r1 of the first strain gauges Ra and Rd are inclined to one side in the circumferential direction with respect to the radial direction. The resistance wires r1 of the first strain gauges Rb and Rc are inclined to the other side in the circumferential direction with respect to the radial direction. The angle of inclination of the resistance wires r1 with respect to the radial direction is, for example, 45°. The ends of adjacent resistance wires r1 in the circumferential direction are alternately connected radially inward or radially outward. As a result, multiple resistance wires r1 are connected in series as a whole.

[0055] Figure 8 is a circuit diagram of the first bridge circuit C1, which includes four first strain gauges Ra, Rb, Rc, and Rd. As shown in Figure 8, the four first strain gauges Ra, Rb, Rc, and Rd are connected to each other to form the first bridge circuit C1.

[0056] The first strain gauges Ra and Rb are connected in series in this order. The first strain gauges Rc and Rd are connected in series in this order. Then, between the positive and negative terminals of the power supply voltage that applies voltage to the four first strain gauges Ra, Rb, Rc, and Rd, two rows of first strain gauges Ra, Rb and two rows of first strain gauges Rc, Rd are connected in parallel. In addition, the first voltmeter V1 is connected between the midpoint M11 of the two first strain gauges Ra, Rb and the midpoint M12 of the two first strain gauges Rc, Rd.

[0057] The resistance value of each resistance wire r1 changes according to the torque applied to the region where the resistance wire r1 is located. For example, when a torque is applied to the diaphragm portion 33 in one direction circumferentially around the central axis 9, the resistance values ​​of the resistance wires r1 of the two first strain gauges Ra and Rd increase, while the resistance values ​​of the resistance wires r1 of the other two first strain gauges Rb and Rc decrease. On the other hand, when a torque is applied to the diaphragm portion 33 in the other direction circumferentially around the central axis 9, the resistance values ​​of the resistance wires r1 of the two first strain gauges Ra and Rd decrease, while the resistance values ​​of the resistance wires r1 of the other two first strain gauges Rb and Rc increase. Thus, the resistance values ​​of the two first strain gauges Ra and Rd and the other two first strain gauges Rb and Rc show changes in opposite directions with respect to torque.

[0058] When the resistance values ​​of the four first strain gauges Ra, Rb, Rc, and Rd change, the potential difference between the midpoint M11 of the two first strain gauges Ra and Rb and the midpoint M12 of the two first strain gauges Rc and Rd changes, and therefore the measured value of the first voltmeter V1 also changes.

[0059] As described above, the torque sensor 60 is electrically connected to the torque calculation unit 521 of the signal processing circuit 52. The torque calculation unit 521 is composed of an electrical circuit equipped with a microprocessor. The torque calculation unit 521 is formed on the circuit board 45. The torque calculation unit 521 is electrically connected to the first bridge circuit C1 of the torque sensor 60 via wiring. The torque calculation unit 521 is also provided with an amplifier circuit (not shown) that amplifies the electrical signal output from the first bridge circuit C1.

[0060] The torque calculation unit 521 detects the torque (direction and magnitude) applied to the diaphragm section 33 based on the measurement value of the first voltmeter V1. Here, the torque applied to the diaphragm section 33 and the torque applied to the output member 400 are in opposite directions and have the same magnitude due to the action-reaction relationship. Therefore, the torque calculation unit 521 calculates the torque (direction and magnitude) applied to the output member 400 based on the detection result of the torque applied to the diaphragm section 33. As described above, the torque applied to the output member 400 is, in other words, the output torque of the reduction gear 1. That is, in this embodiment, the output torque of the reduction gear 1 is calculated from the measurement value of the torque sensor 60. The torque calculation unit 521 also outputs the calculated value of the output torque of the reduction gear 1 to the life calculation unit 81 of the control unit 200, which will be described later. In this way, in this embodiment, the output torque of each reduction gear 1 can be calculated based on the measurement value of the torque sensor 60 provided inside each reduction gear 1. This makes it possible to miniaturize the articulated robot 100, including each reduction gear 1, and the control system 300.

[0061] However, the location where the torque sensor 60 is positioned is not limited to the diaphragm portion 33 of the flexible external gear 30. For example, an elastically deformable annular strain generating body may be provided separately inside the reduction gear 1, fixed to the output member 400 or to a member that meshes with the output member 400. A torque sensor may then be formed by arranging a plurality of strain gauges on this strain generating body.

[0062] Furthermore, in order to calculate the output torque of the reducer 1, encoders for detecting the rotation angle may be placed on the input and / or output sides of the reducer 1. As will be described later, the angle sensor 70 in this embodiment detects the rotation angle on the input side of the reducer 1. The difference between the detected rotation angle on the input side of the reducer 1 divided by the reduction ratio of the reducer 1 and the detected rotation angle on the output side of the reducer 1, which is the "torsional angle of the reducer 1," may be multiplied by the "torsional stiffness (spring characteristics)," which is the stiffness value of the reducer 1. This allows the output torque of the reducer 1 to be calculated.

[0063] <3-3. Detailed Configuration of the Angle Sensor> Next, the detailed configuration of the angle sensor 70 will be explained. As described above, the angle sensor 70 has multiple strain gauges. The multiple strain gauges are bonded and fixed to the surface 331 of the diaphragm portion 33. By arranging the multiple strain gauges on the diaphragm portion 33 in this way, the angle sensor 70 can be compactly installed in each reduction gear 1.

[0064] As shown in Figure 5, in this embodiment, the angle sensor 70 has eight strain gauges as resistance wires for detecting the rotation angle of the internal gear 20 that partially meshes with the flexible external gear 30. Hereinafter, the eight strain gauges of the angle sensor 70 will be referred to as "second strain gauge Ri", "second strain gauge Rj", "second strain gauge Rk", "second strain gauge Rl", "second strain gauge Rm", "second strain gauge Rn", "second strain gauge Ro", and "second strain gauge Rp".

[0065] The eight second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp are positioned in the diaphragm portion 33 of the flexible external gear 30 at different locations from the four first strain gauges Ra, Rb, Rc, and Rd. This allows for a wider arrangement space for the multiple second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp. Also, as shown in Figure 5, the eight second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp are spaced apart in the circumferential direction. Each of the eight second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp is formed by a single wire. Furthermore, each of the eight second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp spreads out in an arc shape along the circumferential direction.

[0066] In this embodiment, the eight second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp are positioned radially outward from the four first strain gauges Ra, Rb, Rc, and Rd. However, the eight second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp may be positioned radially inward from the four first strain gauges Ra, Rb, Rc, and Rd.

[0067] As shown in Figures 6 and 7, each of the eight second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp includes a portion r3. The portion r3 extends in the circumferential direction. However, the circumferentially extending portion r3 may be repeatedly arranged in the radial direction. Furthermore, the portion r3 may extend in the radial direction. Furthermore, the radially extending portion r3 may be repeatedly arranged in the circumferential direction.

[0068] Of the eight second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp, four second 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. Figure 9 is a circuit diagram of the third bridge circuit C3. As shown in Figure 9, the second strain gauge Ri and the second strain gauge Rk are connected in series in this order. The second strain gauge Ro and the second strain gauge Rm are connected in series in this order. Then, between the positive and negative terminals of the power supply voltage that applies voltage to the four second strain gauges Ri, Rk, Rm, and Ro, two rows of second strain gauges Ri, Rk and two rows of second strain gauges Ro, Rm are connected in parallel. In addition, the midpoint M31 of two second strain gauges Ri, Rk and the midpoint M32 of two second strain gauges Ro, Rm are connected to the third voltmeter V3.

[0069] Of the eight second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp, the remaining four second strain gauges Rj, Rl, Rn, and Rp are connected to each other to form a fourth bridge circuit C4. Figure 10 is a circuit diagram of the fourth bridge circuit C4. As shown in Figure 10, the second strain gauge Rp and the second strain gauge Rn are connected in series in this order. The second strain gauge Rj and the second strain gauge Rl are connected in series in this order. Then, between the positive and negative terminals of the power supply voltage that applies voltage to the four second strain gauges Rj, Rl, Rn, and Rp, two rows of second strain gauges Rp, Rn and two rows of second strain gauges Rj, Rl are connected in parallel. In addition, the midpoint M41 of two second strain gauges Rp, Rn and the midpoint M42 of two second strain gauges Rj, Rl are connected to the fourth voltmeter V4.

[0070] When each reduction gear 1 is driven, the diaphragm portion 33 of the flexible external gear 30, which partially meshes with the internal gear 20, which is the output member 400 that rotates at the output rotational speed, generates portions that expand in the circumferential direction and portions that contract in the circumferential direction. Specifically, two expanded portions and two contracted portions alternately occur in the circumferential direction. That is, the expanded portions and contracted portions alternately occur at 90° intervals in the circumferential direction with respect to the central axis 9. These locations where the expanded and contracted portions occur rotate at the input rotational speed of the reduction gear 1.

[0071] The resistance values ​​of the eight second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp change according to the circumferential expansion and contraction of the diaphragm portion 33. For example, when the expanded portion overlaps with a certain second strain gauge, the resistance value of that second strain gauge increases. Conversely, when the contracted portion overlaps with a certain second strain gauge, the resistance value of that second strain gauge decreases.

[0072] In this embodiment, when the contracted portion overlaps with the second strain gauges Ri and Rm, the extended portion overlaps with the second strain gauges Rk and Ro. Conversely, when the extended portion overlaps with the second strain gauges Ri and Rm, the contracted portion overlaps with the second strain gauges Rk and Ro. Therefore, in the third bridge circuit C3, the second strain gauges Ri and Rm and the second strain gauges Rk and Ro exhibit resistance changes in opposite directions.

[0073] Furthermore, in this embodiment, when the contracted portion overlaps with the second strain gauges Rp and Rl, the extended portion overlaps with the second strain gauges Rn and Rj. Conversely, when the extended portion overlaps with the second strain gauges Rp and Rl, the contracted portion overlaps with the second strain gauges Rn and Rj. Therefore, in the fourth bridge circuit C4, the second strain gauges Rp and Rl and the second strain gauges Rn and Rj exhibit resistance changes in opposite directions.

[0074] Figure 11 is a graph showing the time variation of the measured value v3 from the third voltmeter V3 of the third bridge circuit C3 and the measured value v4 from the fourth voltmeter V4 of the fourth bridge circuit C4. The horizontal axis of the graph in Figure 11 represents time. The vertical axis of the graph in Figure 11 represents voltage value. When the reduction gear 1 is driven, as shown in Figure 11, periodically changing sinusoidal measured values ​​v3 and v4 are output from the third voltmeter V3 and the fourth voltmeter V4, respectively. The period T of these measured values ​​v3 and v4 corresponds to half the period of the input rotational speed. Furthermore, the direction of rotational motion can be determined by whether the phase of the measured value v4 from the fourth voltmeter V4 is ahead of the phase of the measured value v3 from the third voltmeter V3 by 1 / 8 of the input rotational speed (1 / 4 of the measured values ​​v3 and v4) or behind by 1 / 8 of the input rotational speed (1 / 4 of the measured values ​​v3 and v4).

[0075] As described above, the angle sensor 70 is electrically connected to the angle calculation unit 522 of the signal processing circuit 52. The angle calculation unit 522 is composed of an electrical circuit equipped with a microprocessor. The angle calculation unit 522 is formed on the circuit board 45. The angle calculation unit 522 is electrically connected to the third bridge circuit C3 and the fourth bridge circuit C4 of the angle sensor 70 via wiring.

[0076] The angle calculation unit 522 detects the rotation angle around the central axis 9 of the input shaft 10, i.e., the rotation angle on the input side of the reduction gear 1, based on the measured value v3 of the third voltmeter V3 and the measured value v4 of the fourth voltmeter V4. Specifically, for example, the angle calculation unit 522 has a storage unit that stores a function table that associates the combination of the measured value v3 of the third voltmeter V3 and the measured value v4 of the fourth voltmeter V4 with the rotation angle. The angle calculation unit 522 calculates the rotation angle by inputting the measured values ​​v3 and v4 into the function table. The angle calculation unit 522 also converts the calculated value of the rotation angle around the central axis 9 of the input shaft 10 into a value per unit time. As a result, the angle calculation unit 522 calculates the rotation speed around the central axis 9 of the input shaft 10, i.e., the input rotation speed of the reduction gear 1. Furthermore, the angle calculation unit 522 outputs the calculated input rotation speed of the reduction gear 1 to the life calculation unit 81 of the control unit 200, which will be described later.

[0077] <4. Detailed Functions of the Control Unit> Next, the detailed functions of the control unit 200 will be explained. Figure 12 is a block diagram conceptually showing some of the functions of the control unit 200. The control unit 200 in this embodiment calculates the "lifespan" of each reduction gear 1, which is an indicator of the "degree of deterioration" of each reduction gear 1. As described above, the control unit 200 has a processor 201, a memory 202, and a storage device 203. The storage device 203 stores a computer program D for controlling the driving of the three motors 104p, 104q, and 104r of the articulated robot 100, based on the results of calculating the degree of deterioration of each of the three reduction gears 1p, 1q, and 1r of the articulated robot 100.

[0078] As shown in Figure 12, the control unit 200 of this embodiment includes a lifespan calculation unit 81 and a motor control unit 82. These functions are realized by temporarily reading the computer program D stored in the storage device 203 into the memory 202, and having the processor 201 perform calculation processing based on the computer program D.

[0079] Thus, in this embodiment, the functions of the life calculation unit 81 and the motor control unit 82 are provided in the control unit 200 that controls the articulated robot 100. However, the functions of the life calculation unit 81 and the motor control unit 82 may also be provided in each reduction gear 1. For example, the functions of the life calculation unit 81 and the motor control unit 82 may be mounted in the signal processing circuit 52 of each reduction gear 1. This allows each reduction gear 1 itself to be equipped with a function to predict the life of each reduction gear 1, thereby enabling miniaturization of the entire control system 300.

[0080] Next, we will explain in detail how to calculate the lifespan of each reduction gear 1. Lifespan refers to the service life. In other words, the lifespan of the reduction gear 1 is the time during which the reduction gear 1 can operate without failure. Among the components that make up the reduction gear 1, the flexible bearing 42 is mainly the component with the shortest service life. Therefore, the lifespan of the flexible bearing 42 can be considered equivalent to the lifespan of the reduction gear 1. Accordingly, the control unit 200 calculates the lifespan of each reduction gear 1 by predicting the lifespan of the flexible bearing 42 in each reduction gear 1.

[0081] The life calculation unit 81 is electrically connected to the torque sensors 60 of the three gear reducers 1p, 1q, and 1r. More specifically, the life calculation unit 81 is electrically connected to the torque sensors 60 of the three gear reducers 1p, 1q, and 1r via the torque calculation units 521 of the three gear reducers 1p, 1q, and 1r. As described above, the life calculation unit 81 receives the output torque of each gear reducer 1 from the torque calculation unit 521 of each gear reducer 1. Hereafter, the "output torque" of gear reducer 1p that is input from the torque calculation unit 521 of gear reducer 1p will be referred to as "output torque Top". The "output torque" of gear reducer 1q that is input from the torque calculation unit 521 of gear reducer 1q will be referred to as "output torque Toq". The "output torque" of gear reducer 1r that is input from the torque calculation unit 521 of gear reducer 1r will be referred to as "output torque Tor".

[0082] Furthermore, the life calculation unit 81 is electrically connected to the angle sensors 70 of the three speed reducers 1p, 1q, and 1r. More specifically, the life calculation unit 81 is electrically connected to the angle sensors 70 of the three speed reducers 1p, 1q, and 1r via the angle calculation units 522 of the three speed reducers 1p, 1q, and 1r. As described above, the life calculation unit 81 receives the calculated values ​​of the input rotational speed of each speed reducer 1 from the angle calculation unit 522 of each speed reducer 1. Hereafter, the "input rotational speed" of speed reducer 1p input from the angle calculation unit 522 of speed reducer 1p will be referred to as "input rotational speed Nop". The "input rotational speed" of speed reducer 1q input from the angle calculation unit 522 of speed reducer 1q will be referred to as "input rotational speed Noq". The "input rotational speed" of speed reducer 1r input from the angle calculation unit 522 of speed reducer 1r will be referred to as "input rotational speed Nor".

[0083] However, instead of being connected to the angle sensor 70 and the angle calculation unit 522, the life calculation unit 81 may be connected to an encoder for detecting the rotation angle, which is separately provided on the input side of each reduction gear 1. An example of an encoder for detecting the rotation angle on the input side of each reduction gear 1 is the encoder of each motor 104. In that case, the encoder measures the rotation speed input from each motor 104 to each reduction gear 1, that is, the input rotation speed of each reduction gear 1, and outputs the measurement result to the life calculation unit 81.

[0084] Next, the life calculation unit 81 calculates the life of the flexible bearing 42 in the reducer 1p, i.e., the life of the reducer 1p, Hp, based on the output torque Top and input rotational speed Nop. The life calculation unit 81 also calculates the life of the flexible bearing 42 in the reducer 1q, i.e., the life of the reducer 1q, Hq, based on the output torque Toq and input rotational speed Noq. The life calculation unit 81 also calculates the life of the flexible bearing 42 in the reducer 1r, i.e., the life of the reducer 1r, Hr, based on the output torque Tor and input rotational speed Nor.

[0085] In other words, the lifespan calculation unit 81 can calculate the lifespan of each of the three speed reducers 1, which serves as an indicator of the degree of deterioration, based on the input rotational speed of each speed reducer 1 and the output torque of each speed reducer 1.

[0086] The lifespan of the flexible bearing 42, i.e., the lifespan of the speed reducer 1, can be expressed, for example, by the following formula (2): Lhe = kr × (Tar / Tao)^3 × (nar / nai) (2) In formula (2), Lhe is the lifespan of the flexible bearing 42, i.e., the lifespan of the speed reducer 1, and its unit is time. kr is a unique value determined by the specifications of the speed reducer 1, and is a value that changes depending on the basic dynamic load rating. In the case of a harmonic drive gear reducer 1, 10000 is used as a typical value for kr. Tar is the rated torque of the speed reducer 1, and its unit is N・m. Tao is the average torque, and its unit is N・m. The average torque is, for example, the average value of the output torque of the speed reducer 1 per unit time. nar is the rated input rotational speed of the speed reducer 1, and its unit is r / min. nai is the average input rotational speed, and its unit is r / min. In this embodiment, the average input rotational speed is the average value of the input rotational speed of the reduction gear 1 per unit time.

[0087] Of the above, the rated torque Tar and the rated input rotational speed nar are fixed values. The rated torque Tar and the rated input rotational speed nar are stored in advance in the memory 202 of the control unit 200. The life calculation unit 81 calculates the average torque Tao for the reduction gear 1p based on the measured value of the output torque Top obtained from the torque sensor 60 of the reduction gear 1p. The life calculation unit 81 also calculates the average torque Tao for the reduction gear 1q based on the measured value of the output torque Toq obtained from the torque sensor 60 of the reduction gear 1q. The life calculation unit 81 also calculates the average torque Tao for the reduction gear 1r based on the measured value of the output torque Tor obtained from the torque sensor 60 of the reduction gear 1r.

[0088] Furthermore, the life calculation unit 81 calculates the average input rotation speed nai for the reduction gear 1p based on the measured value of the input rotation speed Nop obtained from the angle sensor 70 in the reduction gear 1p. Furthermore, the life calculation unit 81 calculates the average input rotation speed nai for the reduction gear 1q based on the measured value of the input rotation speed Noq obtained from the angle sensor 70 in the reduction gear 1q. Furthermore, the life calculation unit 81 calculates the average input rotation speed nai for the reduction gear 1r based on the measured value of the input rotation speed Nor obtained from the angle sensor 70 in the reduction gear 1r.

[0089] Furthermore, the life calculation unit 81 substitutes the rated torque Tar and rated input rotational speed nar read from memory, along with the calculated average torque Tao and average input rotational speed nai, for each of the three speed reducers 1p, 1q, and 1r, into the above formula (2). This allows the life calculation unit 81 to calculate the lifespan of the flexible bearings 42 of the three speed reducers 1p, 1q, and 1r, i.e., the lifespans Hp, Hq, and Hr of the three speed reducers 1p, 1q, and 1r, respectively. The life calculation unit 81 then inputs the calculated lifespans Hp, Hq, and Hr of the speed reducers 1p, 1q, and 1r to the motor control unit 82.

[0090] Next, the motor control unit 82 compares the lifespans Hp of the reduction gear 1p, Hq of the reduction gear 1q, and Hr of the reduction gear 1r, which are input from the lifespan calculation unit 81. Based on the comparison results, the motor control unit 82 calculates a correction value Pp for correcting the power input to the motor 104p connected to the reduction gear 1p, a correction value Pq for correcting the power input to the motor 104q connected to the reduction gear 1q, and a correction value Pr for correcting the power input to the motor 104r connected to the reduction gear 1r. Then, based on the calculated correction values ​​Pp, Pq, and Pr, the motor control unit 82 controls the drive circuits (not shown) of the motors 104p, 104q, and 104r.

[0091] Specifically, the motor control unit 82 determines that a short calculated lifespan for the reduction gear 1, as input from the lifespan calculation unit 81, indicates that the reduction gear 1 is at its most deteriorated state. The motor control unit 82 then calculates a correction value to reduce the power input to the motor 104 connected to the reduction gear 1, which is determined to be at its most deteriorated state. The correction value is, for example, a command value to reduce the power input to the motor 104, and is a negative value. The motor control unit 82 then controls the motor 104 based on the calculated correction value.

[0092] Furthermore, methods for reducing the power input to the motor 104 include reducing the current input to the motor 104 and reducing the voltage input to the motor 104. By reducing the current input to the motor 104, the output torque of the motor 104 can be reduced. The output torque of the motor 104 is the input torque input from the motor 104 to the reduction gear 1. Also, by reducing the voltage input to the motor 104, the output rotational speed of the motor 104 can be reduced. The output rotational speed of the motor 104 is the rotational speed around the central axis 9 of the input shaft 10 of the reduction gear 1 connected to the motor 104, that is, the input rotational speed of the reduction gear 1. As described above, the output of the motor 104 is proportional to the product of the output torque of the motor 104 and the output rotational speed of the motor 104. The output of the motor 104 becomes the load on the reduction gear 1 connected to the motor 104. Therefore, by reducing the current input or voltage input to the motor 104, the load on the reduction gear 1 can be reduced.

[0093] In other words, in this embodiment, the motor control unit 82 reduces the load on the reduction gear 1 connected to the motor 104 by adjusting the power value input to the motor 104 to lower the input rotational speed of the reduction gear 1 and / or reduce the input torque of the reduction gear 1. This reduces the load on the reduction gear 1 that is judged to be the most deteriorated, thereby improving the lifespan of the reduction gear 1. This extends the lifespan of the articulated robot 100 as a whole. Furthermore, the reduction of the load on the reduction gear 1 can be achieved by controlling the motor 104.

[0094] For example, suppose the motor control unit 82 compares the lifespans Hp, Hq, and HR of the reducers 1p, 1q, and 1r input from the lifespan calculation unit 81 and determines that the lifespan Hq of reducer 1q is the shortest, i.e., that reducer 1q is the most deteriorated. In this case, the motor control unit 82 calculates a correction value Pq to correct the power value input to the motor 104q connected to reducer 1q and inputs it to motor 104q. The correction value Pq is, for example, a command value to reduce the current value input to motor 104q, and is a negative value. This makes it possible to reduce the output torque of motor 104q, i.e., the input torque input to reducer 1q. As a result, the load on reducer 1q can be reduced, and the durability of the reducer 1q can be improved. This makes it possible to extend the lifespan of the articulated robot 100 as a whole.

[0095] Next, the motor control unit 82 calculates the correction values ​​Pp, Pq, and Pr to increase the power input to the motor 104 connected to the reduction gear 1 other than the reduction gear 1 in the articulated robot 100 that has the shortest calculated lifespan, i.e., is judged to have the highest degree of deterioration. In this case, the correction values ​​Pp, Pq, and Pr are, for example, command values ​​to increase the power input to the motor 104, and are positive values. Then, the motor control unit 82 controls the motor 104 based on the calculated correction values ​​Pp, Pq, and Pr.

[0096] Furthermore, methods for increasing the power input to the motor 104 include increasing the current input to the motor 104 and increasing the voltage input to the motor 104. By increasing the current input to the motor 104, the output torque of the motor 104, that is, the input torque of the reduction gear 1, can be increased. Also, by increasing the voltage input to the motor 104, the output rotational speed of the motor 104, that is, the input rotational speed of the reduction gear 1, can be increased. The output of the motor 104 is proportional to the product of the output torque of the motor 104 and the output rotational speed of the motor 104. The output of the motor 104 becomes the load on the reduction gear 1 connected to the motor 104. Therefore, by increasing the current input or voltage input to the motor 104, the load on the reduction gear 1 can be increased.

[0097] In other words, in this embodiment, the motor control unit 82 compares the lifespan Hp of reduction gear 1p, the lifespan Hq of reduction gear 1q, and the lifespan Hr of reduction gear 1r, which are input from the lifespan calculation unit 81, and increases the load on at least one reduction gear 1 other than the reduction gear 1 that is determined to have the highest degree of deterioration. The motor control unit 82 also increases the load on the reduction gear 1 by adjusting the power value input to the motor 104 to increase the input rotational speed of the reduction gear 1 and / or increase the input torque of the reduction gear 1.

[0098] For example, the motor control unit 82 compares the lifespans Hp, Hq, and Hr of the speed reducers 1p, 1q, and 1r input from the lifespan calculation unit 81 and assumes that it has determined that the lifespan of speed reducer 1r is relatively long, that is, that the degree of degradation of speed reducer 1r is relatively low. In this case, the motor control unit 82 calculates a correction value Pr to correct the power value input to the motor 104r connected to speed reducer 1r and inputs it to the motor 104r. The correction value Pr is, for example, a command value to increase the current value input to the motor 104r, and is a positive value. This makes it possible to increase the output torque of the motor 104r, that is, the input torque input to speed reducer 1r. In this way, in this embodiment, an increase in the load on the speed reducer 1 can be achieved by controlling the motor 104.

[0099] Simply reducing the load on the reduction gear 1, which is judged to have the highest degree of deterioration, may reduce the overall workload of the articulated robot 100. Therefore, increasing the load on the other reduction gears 1 can restore the overall workload of the articulated robot 100. For example, simply reducing the current input to the motor 104q connected to the reduction gear 1q, which is judged to have a short lifespan Hq, i.e., a high degree of deterioration, and thereby reducing the input torque input from the motor 104q to the reduction gear 1q, may not be able to move the end-effector working arm 105 of the articulated robot 100 to the desired position. Therefore, by increasing the current input to the motor 104r connected to the other reduction gear 1r, and thereby increasing the input torque input from the motor 104r to the reduction gear 1r, the overall movement of the articulated robot 100 can be compensated for. As a result, the end-effector working arm 105 of the articulated robot 100 can be moved to the desired position.

[0100] <5. Modifications> Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above.

[0101] <5-1. First Modification> In the above embodiment, the motor control unit 82 calculated a correction value to reduce the power input to the motor 104 connected to the reduction gear 1 which was determined to have the highest degree of deterioration, and controlled the drive of the motor 104 based on the correction value. However, in addition to this, the motor control unit 82 may also calculate a correction value to reduce the power input to the motor 104 connected to the reduction gear 1 which was determined to have the second highest degree of deterioration, and control the drive of the motor 104 based on the correction value. That is, the motor control unit 82 may calculate correction values ​​to reduce the power input to each of the multiple motors 104 connected to the multiple reduction gears 1, including the reduction gear 1 which was determined to have the highest degree of deterioration, in order to reduce the load on the multiple reduction gears 1. Then, the motor control unit 82 may control the drive of these motors 104 based on the multiple correction values ​​that have been calculated.

[0102] Furthermore, the motor control unit 82 may calculate correction values ​​to increase the power input to each of the motors 104 connected to multiple reduction gears 1 that are determined to have a relatively long lifespan, i.e., a relatively low degree of degradation, among the multiple reduction gears 1 included in the articulated robot 100. The motor control unit 82 may then control the driving of these motors 104 based on the calculated correction values.

[0103] <5-2. Second Modification> Figure 13 is a block diagram conceptually showing some of the functions of the control unit 200B according to the second modification. The control unit 200B of this modification calculates the "efficiency" of each reduction gear 1, which is an indicator of the "degree of deterioration" of each reduction gear 1. As shown in Figure 13, the control unit 200B of this modification has an efficiency calculation unit 81B and a motor control unit 82B. However, the functions of the efficiency calculation unit 81B and the motor control unit 82B may be provided in each reduction gear 1.

[0104] First, let's explain how to calculate the efficiency of each gearbox 1. The efficiency of a gearbox 1 is the ratio of the output torque (direction and magnitude) of the gearbox 1 to the input torque (direction and magnitude) of the gearbox 1. As the gearbox 1 deteriorates over time, the ratio of the output torque of the gearbox 1 to the input torque of the gearbox 1 may decrease. In such cases, excessive load may be applied to the meshing points between the flexible external gear 30 and the internal gear 20 of the gearbox 1 over a long period of time. In this case, it may be necessary to replace the gearbox 1, which may shorten the maintenance cycle for the entire articulated robot 100. Therefore, in this embodiment, the control unit 200B improves the durability of the gearbox 1 by reducing the load on the gearbox 1 whose efficiency has decreased when the efficiency of the gearbox 1 has decreased.

[0105] As shown in Figure 13, the efficiency calculation unit 81B is electrically connected to the torque sensors 60 of the three reduction gears 1p, 1q, and 1r. More specifically, the efficiency calculation unit 81B is electrically connected to the torque sensors 60 of the three reduction gears 1p, 1q, and 1r via the torque calculation units 521 of the three reduction gears 1p, 1q, and 1r. The output torque of each reduction gear 1 is input to the efficiency calculation unit 81B from the torque calculation unit 521 of each reduction gear 1. Hereinafter, the "output torque" of reduction gear 1p input from the torque calculation unit 521 of reduction gear 1p will be referred to as "output torque Top". The "output torque" of reduction gear 1q input from the torque calculation unit 521 of reduction gear 1q will be referred to as "output torque Toq". The "output torque" of reduction gear 1r input from the torque calculation unit 521 of reduction gear 1r will be referred to as "output torque Tor".

[0106] Furthermore, the efficiency calculation unit 81B is electrically connected to the drive circuits of the three motors 104p, 104q, and 104r. The efficiency calculation unit 81B receives the output torques of motors 104p, 104q, and 104r, that is, the input torques of the reduction gears 1p, 1q, and 1r, from motors 104p, 104q, and 104r. Hereafter, the "input torque" of reduction gear 1p input from motor 104p will be referred to as "input torque Tip". The "input torque" of reduction gear 1q input from motor 104q will be referred to as "input torque Tiq". The "input torque" of reduction gear 1r input from motor 104r will be referred to as "input torque Tir".

[0107] However, torque sensors may be provided separately for each of the three reduction gears 1p, 1q, and 1r to detect the input torque of reduction gears 1p, 1q, and 1r. The measurement results from these torque sensors may then be input to the efficiency calculation unit 81B.

[0108] Next, the efficiency calculation unit 81B calculates the efficiency of each of the multiple reduction gears 1, which serves as an indicator of degradation, based on the input torque and output torque of the reduction gear 1. Specifically, for reduction gear 1p, the efficiency calculation unit 81B calculates the efficiency Ep of reduction gear 1p based on the input torque Tip and output torque Top, and inputs it to the motor control unit 82B. Also, for reduction gear 1q, the efficiency calculation unit 81B calculates the efficiency Eq of reduction gear 1q based on the input torque Tiq and output torque Toq, and inputs it to the motor control unit 82B. Also, for reduction gear 1r, the efficiency calculation unit 81B calculates the efficiency Er of reduction gear 1r based on the input torque Tir and output torque Tor, and inputs it to the motor control unit 82B.

[0109] Next, the motor control unit 82B compares the efficiency Ep of the reduction gear 1p, the efficiency Eq of the reduction gear 1q, and the efficiency Er of the reduction gear 1r, which are input from the efficiency calculation unit 81B. Based on the comparison results, the motor control unit 82B calculates a correction value Pp to correct the power input to the motor 104p connected to the reduction gear 1p, a correction value Pq to correct the power input to the motor 104q connected to the reduction gear 1q, and a correction value Pr to correct the power input to the motor 104r connected to the reduction gear 1r. Then, based on the calculated correction values ​​Pp, Pq, and Pr, the motor control unit 82B controls the drive circuits (not shown) of the motors 104p, 104q, and 104r.

[0110] Specifically, the motor control unit 82B determines that a low efficiency value for the reduction gear 1, input from the efficiency calculation unit 81B, indicates that the reduction gear 1 is at its most degraded state. The motor control unit 82 then calculates a correction value to reduce the power input to the motor 104 connected to the reduction gear 1, which is determined to be at its most degraded state. The correction value is, for example, a command value to reduce the power input to the motor 104, and is a negative value. The motor control unit 82 then controls the motor 104 based on the calculated correction value.

[0111] Furthermore, the motor control unit 82B calculates correction values ​​Pp, Pq, and Pr to increase the power input to the motor 104 connected to the reduction gear 1 other than the reduction gear 1 that has the lowest calculated efficiency, i.e., the reduction gear 1 that is judged to have the highest degree of degradation, among the three reduction gears 1 included in the articulated robot 100. In this case, the correction values ​​Pp, Pq, and Pr are, for example, command values ​​to increase the power input to the motor 104, and are positive values. The motor control unit 82 then controls the motor 104 based on the calculated correction values ​​Pp, Pq, and Pr.

[0112] In other words, the control unit 200 of the present invention performs the following steps: a) calculate the degree of deterioration of each of the multiple reduction gears 1 based on the input rotational speed or input torque of the reduction gear 1 and the output torque of the reduction gear 1; and b) compare the degrees of deterioration of the multiple reduction gears 1 based on the results obtained in step a), and reduce the load on the reduction gear 1 that is determined to have the highest degree of deterioration. By doing so, the lifespan of the reduction gear 1 can be improved by reducing the load on the reduction gear 1 that is determined to have the highest degree of deterioration. This can extend the lifespan of the articulated robot 100 as a whole.

[0113] The detailed configuration of the control system 300 may be modified as appropriate without departing from the spirit of the present invention. Furthermore, elements appearing in the above embodiments and modifications may be combined as appropriate without causing inconsistencies. For example, in the second modification described above, the efficiency of the reduction gear 1 may fluctuate due to the influence of the temperature of the reduction gear 1 and the motor 104 connected thereto. Therefore, the accuracy of the calculated efficiency value of the reduction gear 1 may be improved by suppressing the influence caused by these temperatures. Specifically, for example, a temperature sensor may be provided on at least one of the reduction gear 1 and the motor 104, and a temperature correction value may be calculated based on the temperature detected by the temperature sensor. In this case, the temperature correction value may be calculated by referring to a function table that has been set in advance to correspond to the combination of the calculated efficiency value of the reduction gear 1 and the detected temperature value. The motor control unit 82B may then reflect the calculated temperature correction value in the calculated efficiency value of the reduction gear 1.

[0114] <6. Summary> This technology can be configured as follows:

[0115] (1) A control method for controlling a multi-joint robot having a plurality of joints, each joint comprising a motor and a reduction gear connected to the motor for reducing the rotation of the motor, the control method comprising: a) a step of calculating the degree of deterioration of each of the plurality of reduction gears based on the input rotational speed of the reduction gear or the input torque of the reduction gear and the output torque of the reduction gear; and b) a step of comparing the degrees of deterioration of the plurality of reduction gears based on the results obtained in step a), and reducing the load on the reduction gear that is determined to have the highest degree of deterioration.

[0116] (2) A control method according to (1), further comprising the step of c) increasing the load on at least one of the reduction gears other than the reduction gear that is determined to have the highest degree of deterioration, based on the results obtained in step a).

[0117] (3) A control method according to (2), wherein in step b), the load on the reduction gear is reduced by adjusting the power value input to the motor to lower the input rotational speed of the reduction gear and / or the input torque of the reduction gear, and in step c), the load on the reduction gear is increased by adjusting the power value input to the motor to raise the input rotational speed of the reduction gear and / or the input torque of the reduction gear.

[0118] (4): A control method according to any one of (1) to (3), wherein in step a), for each of the plurality of reduction gears, the life of the reduction gear, which is an indicator of the degree of deterioration, is calculated based on the input rotational speed of the reduction gear and the output torque of the reduction gear.

[0119] (5): A control method according to (4), wherein when the life of the reduction gear is Lhe, the value that changes depending on the basic dynamic load rating of the reduction gear is kr, the rated torque of the reduction gear is Tar, the output torque of the reduction gear is Tao, the rated input rotational speed of the reduction gear is nar, and the average input rotational speed of the reduction gear is nai, the control method satisfies Lhe = kr × (Tar / Tao)^3 × (nar / nai).

[0120] (6): A control method according to any one of (1) to (3), wherein in step a), for each of the plurality of speed reducers, the efficiency of the speed reducer, which is an indicator of the degree of deterioration, is calculated based on the input torque of the speed reducer and the output torque of the speed reducer.

[0121] (7): A control method according to any one of (1) to (6), wherein the speed reducer is a wave gear speed reducer having a flexible external gear, an internal gear, a wave generator, and a torque sensor including a plurality of strain gauges, the flexible external gear and the internal gear mesh with each other and at least one of them rotates around a central axis at the output rotational speed of the speed reducer, and in step a), the output torque of the speed reducer is calculated from the measured value of the torque sensor.

[0122] (8): A control method according to (7), wherein the torque sensor is located on the flexible external gear.

[0123] (9): A control method according to (8), wherein the flexible external gear has a diaphragm portion that extends radially on one axial side of the position where the flexible external gear and the internal gear mesh, and the torque sensor is configured by attaching a plurality of strain gauges to the diaphragm portion.

[0124] (10): A multi-joint robot having a plurality of joints, each joint comprising a motor and a reduction gear connected to the motor for reducing the rotation of the motor, and a control unit for controlling the drive of the multi-joint robot, wherein the control unit performs the steps of: a) calculating the degree of deterioration of each of the plurality of reduction gears based on the input rotational speed of the reduction gear or the input torque of the reduction gear and the output torque of the reduction gear; and b) comparing the degree of deterioration of the plurality of reduction gears based on the result obtained in step a), and reducing the load on the reduction gear that is determined to have the highest degree of deterioration.

[0125] The present invention can be used in control methods and control systems.

[0126] 1, 1p, 1q, 1r Reducer 9 Central shaft 10 Input shaft 20 Internal gear 30 Flexible external gear 33 Diaphragm section 40 Wave generator 41 Cam 42 Flexible bearing 50 Sensor 51 Sensor board 52 Signal processing circuit 60 Torque sensor 70 Angle sensor 81 Life calculation unit 81B Efficiency calculation unit 82, 82B Motor control unit 100 Articulated robot 101 Base frame 102, 102p, 102q Arm 103, 103p, 103q, 103r Joint 104, 104p, 104q, 104r Motor 105 End-effect working arm 200, 200B Control unit 300 Control system 400 Output member 521 Torque calculation unit 522 Angle calculation unit Ep, Eq, Er Efficiency Hp, Hq, HR (Gear reducer) Life Nop, Noq, Nor (Gear reducer) Output rotational speed Pp, Pq, Pr (Motor) Correction value Ra, Rb, Rc, Rd First strain gauge Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp Second strain gauge Tip, Tiq, Tir (Gear reducer) Input torque Top, Toq, Tor (Gear reducer) Output torque

Claims

1. A control method for controlling a multi-joint robot having multiple joints, each joint comprising a motor and a reduction gear connected to the motor for reducing the rotation of the motor, the control method comprising: a) a step of calculating the degree of deterioration of each of the multiple reduction gears based on the input rotational speed of the reduction gear or the input torque of the reduction gear and the output torque of the reduction gear; b) a step of comparing the degrees of deterioration of the multiple reduction gears based on the results obtained in step a), and reducing the load on the reduction gear that is determined to have the highest degree of deterioration.

2. A control method according to claim 1, further comprising the step of c) increasing the load on at least one of the reduction gears other than the reduction gear that is determined to have the highest degree of deterioration, based on the results obtained in step a).

3. A control method according to claim 2, wherein in step b), the load on the reduction gear is reduced by adjusting the power value input to the motor to lower the input rotational speed of the reduction gear and / or the input torque of the reduction gear, and in step c), the load on the reduction gear is increased by adjusting the power value input to the motor to raise the input rotational speed of the reduction gear and / or the input torque of the reduction gear.

4. A control method according to claim 1 or claim 2, wherein in step a), for each of the plurality of reduction gears, the life of the reduction gear, which serves as an indicator of the degree of deterioration, is calculated based on the input rotational speed of the reduction gear and the output torque of the reduction gear.

5. A control method according to claim 4, wherein when the life of the reduction gear is Lhe, the value that changes depending on the basic dynamic load rating of the reduction gear is kr, the rated torque of the reduction gear is Tar, the output torque of the reduction gear is Tao, the rated input rotational speed of the reduction gear is nar, and the average input rotational speed of the reduction gear is nai, the control method satisfies Lhe = kr × (Tar / Tao)^3 × (nar / nai).

6. A control method according to claim 1 or claim 2, wherein in step a), for each of the plurality of reduction gears, the efficiency of the reduction gear, which serves as an indicator of the degree of deterioration, is calculated based on the input torque of the reduction gear and the output torque of the reduction gear.

7. A control method according to claim 1 or claim 2, wherein the speed reducer is a wave gear speed reducer having a flexible external gear, an internal gear, a wave generator, and a torque sensor including a plurality of strain gauges, wherein the flexible external gear and the internal gear mesh with each other and at least one of them rotates around a central axis at the output rotational speed of the speed reducer, and in step a), the output torque of the speed reducer is calculated from the measured value of the torque sensor.

8. A control method according to claim 7, wherein the torque sensor is located on the flexible external gear.

9. A control method according to claim 8, wherein the flexible external gear has a diaphragm portion that extends radially on one axial side of the position where the flexible external gear and the internal gear mesh, and the torque sensor is configured by attaching a plurality of strain gauges to the diaphragm portion.

10. A multi-joint robot having a plurality of joints, each joint comprising a motor and a reduction gear connected to the motor for reducing the rotation of the motor, and a control unit for controlling the drive of the multi-joint robot, wherein the control unit performs the steps of: a) calculating the degree of deterioration of each of the plurality of reduction gears based on the input rotational speed of the reduction gear or the input torque of the reduction gear and the output torque of the reduction gear; and b) comparing the degrees of deterioration of the plurality of reduction gears based on the results obtained in step a), and reducing the load on the reduction gear that is determined to have the highest degree of deterioration.

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