Actuator

Abstract

To further accurately perform motion control of an actuator.SOLUTION: An actuator 1 includes a reducer 15, a motor 12, and a control unit 31 for controlling the motor 12 based on predetermined control parameters. The actuator 1 has a sensor 19 which is installed on the reducer 15 and detects information affected by an abrasion state of the reducer 15, and a correction unit 32 for correcting the control parameters based on the detected information of the sensor 19. The correction unit 32 acquires control parameters corresponding to the abrasion state of the reducer 15 and updates the control parameters to new control parameters. The control unit 31 performs operation control of the motor 12 based on the updated control parameters.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an actuator.

Background Art

[0002] In an actuator including a motor and a speed reducer, when performing control in consideration of various characteristics of the speed reducer, various characteristics that affect the control are measured in advance, and parameter identification for reflecting them in the control model of the actuator is performed (see, for example, Patent Document 1). And when the parameters of various characteristics change or deteriorate due to the aging of the speed reducer, it is necessary to perform calibration to measure the necessary various characteristics again and perform parameter identification.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when the actuator is attached to another device and placed in an actual use environment, it is usually not possible to re-measure the characteristics according to the aging, so it is only possible to continue using the parameters at the initial setting. For this reason, in order to allow each parameter error caused by the aging of the speed reducer, it is necessary to perform control with low sensitivity such as reducing the control gain.

[0005] An object of the present invention is to maintain high control accuracy of an actuator.

Means for Solving the Problems

[0006] The present invention is An actuator comprising a speed reducer, a motor, and a control unit that controls the motor based on predetermined control parameters, a sensor installed in the speed reducer that detects information affected by the wear condition of the speed reducer; a correction unit that corrects the control parameters based on the detection information of the sensor; A storage unit that pre-holds a data group with secular changes regarding information affected by the wear condition of the speed reducer, and a measured value of the control parameter after the change accompanying the secular change regarding the control parameter. The control unit refers to the storage unit, specifies the data that most closely approximates the information affected by the wear condition of the speed reducer detected by the sensor from among the data group with secular changes of the information affected by the wear condition of the speed reducer, specifies the measured value of the control parameter in the same period as the most closely approximating data, and replaces and updates it with the current control parameter. is configured as such.

Advantages of the Invention

[0007] According to the present invention, it becomes possible to maintain high control accuracy of the actuator.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0010] FIG. 1 is a cross-sectional view showing a driving device as an actuator according to an embodiment of the present invention. FIG. 2 is a perspective view of the driving device according to this embodiment.

[0011] The driving device 1 of this embodiment is a device that outputs rotational power, and its application is not particularly limited. For example, it can be used as a joint driving device for a collaborative robot that works in cooperation with a human. Hereinafter, the direction along the central axis O1 is referred to as the axial direction, the radial direction of the central axis O1 is referred to as the radial direction, and the rotational direction centered on the central axis O1 is referred to as the circumferential direction. The central axis O1 is the central axis of the shaft portion 16c of the output member 16 and the rotor shaft 13. Further, in the axial direction of the central axis O1, the side where the output member 16 is located (the left side in FIG. 1) is referred to as the output side, and the opposite side (the right side in FIG. 1) is referred to as the reverse output side or the input side.

[0012] The driving device 1 includes a casing 11 connected to a support member 201 outside the device, a motor (electric motor) 12 that generates rotational power, a rotor shaft 13 to which torque is input by the motor 12, a brake 14 that can apply a braking force to the rotor shaft 13, a speed reducer 15 that decelerates the rotational motion of the rotor shaft 13, an output member 16 that outputs the rotational motion decelerated by the speed reducer 15 to the outside of the device (the mating member 202), a circuit portion 17 on which an electric circuit is mounted, and a detection portion 18 that detects the rotation of the rotor shaft 13 and the output member 16. The circuit portion 17 includes a motor driver board on which a drive circuit for the motor 12 is mounted and an encoder board on which a detection circuit for the detection portion 18 is mounted. The detection portion 18 includes an input-side rotation detector 18A that detects the rotation of the rotor shaft 13 and an output-side rotation detector 18B that detects the rotation of the output member 16. The speed reducer 15, the motor 12, the brake 14, the detection portion 18, and the circuit portion 17 are arranged side by side in this order from the output side to the reverse output side.

[0013] The casing 11 includes hollow cylindrical or annular members 11a to 11g that are connected to each other and is connected to and supported by a support member 201 outside the device. Hereinafter, specific structural examples of the members 11a to 11g will be described, but the casing 11 is not limited to this specific example.

[0014] The member 11a covers the periphery of one end of the shaft portion 16c on the anti-output side. The member 11a has a through hole that penetrates in the axial direction, and the through hole of the member 11a communicates with the through hole of the shaft portion 16c. The member 11a abuts against the outer ring of the bearing 21 from the axial direction. The member 11a is connected to the member 11b via a bolt (connecting member).

[0015] The member 11b covers the circuit portion 17 from the radial direction and the anti-output side in the axial direction, fits the outer ring of the bearing 21, and is connected to the member 11c via a bolt.

[0016] The member 11c is located radially outside the detection unit 18 and covers the detection unit 18 from the radial direction. The member 11c is connected to the member 11b and the member 11d via bolts. The member 11c has a wiring lead-out hole 11c1 for leading out the wirings of the motor 12 and the brake 14 at a part in the circumferential direction.

[0017] The member 11d is located radially outside the brake 14, covers the brake 14 from the radial direction, and supports the fixed-side member of the brake 14. The member 11d has an annular protrusion 11dt protruding on the anti-output side. The annular protrusion 11dt has a smaller diameter than the maximum outer diameter of the member 11d and is fitted (inro-fitted) into the member 11c. The member 11d has flange portions 11d1 at a plurality of locations in the circumferential direction on the anti-output side, and the flange portions 11d1 are connected to the member 11c via bolts. It is connected. Further, the member 11d has flange portions 11d2 at a plurality of circumferential positions on the output side, and the flange portions 11d2 are connected to the member 11e via bolts. The member 11d includes fin portions 11d3 disposed on the outer peripheral portion other than the flange portions 11d1 and 11d2. The fin portions 11d3 include a plurality of heat dissipation fins extending in the radial direction and spreading in the circumferential direction. In the fin portions 11d3, through holes 11d4 and 11d5 for passing the bolts and the tips of tools are provided at positions corresponding to the bolt holes of the flange portions 11d1 and 11d2 (positions overlapping the bolt holes when the bolt holes are extended in the axial direction).

[0018] The member 11e is located radially outside the motor 12, covers the motor 12 from the radial direction, and supports the fixed-side member of the motor 12. The member 11e has an annular protrusion 11et1 protruding from the anti-output side and an annular protrusion 11et2 protruding from the output side. The annular protrusion 11et1 on the anti-output side has a smaller diameter than the maximum outer diameter of the member 11e and is fitted (in-rolled fit) into the member 11d. The annular protrusion 11et2 on the output side has a smaller diameter than the maximum outer diameter of the member 11e and is fitted (in-rolled fit) into the member 11f. The member 11e has flange portions 11e1 at a plurality of circumferential positions, and the flange portions 11e1 are connected to the members 11d and 11f via bolts. The member 11e includes fin portions 11e2 disposed on the outer peripheral portion other than the flange portions 11e1. The fin portions 11e2 include a plurality of heat dissipation fins extending in the radial direction and spreading in the circumferential direction. The fin portions 11e2 are adjacent to the fin portions 11d3 of the above-described member 11d, and through holes 11e3 for passing the bolts and the tools are provided at positions continuous with the through holes 11d4 of the fin portions 11d3 (positions overlapping when the through holes 11d4 are extended).

[0019] The member 11f covers the output side of the motor 12, and the outer ring of the bearing 23 arranged on the opposite output side of the speed reducer 15 is fitted therein. The member 11f rotatably supports the vibrating body 15a via the bearing 23. The member 11f has a flange portion 11f1 at a position corresponding to the flange portion 11e1 of the adjacent member 11e, and the adjacent flange portions 11f1 and 11e1 are connected via bolts. In the flange portions 11f1 and 11e1, the bolt holes for connecting the members 11f and 11e and the bolt holes for connecting the members 11e and 11d on the opposite output side thereof may be arranged coaxially. The member 11f is further connected to the internal gear member (the first internal gear 15d) of the speed reducer 15 via bolts. The member 11f has an annular protrusion 11ft protruding on the output side. The annular protrusion 11ft has a smaller diameter than the maximum outer diameter of the member 11f and is fitted (inrolled fit) into the first internal gear 15d.

[0020] The member 11g covers the output member 16 from the radial direction at the output-side end, and fits the outer ring of the bearing 22 and the seal 25 therein. The member 11g rotatably supports the output member 16 via the bearing 22. The member 11g has a flange portion 11g1 that projects radially, and the flange portion 11g1 is connected to a component member (the first internal gear 15d) of the speed reducer 15 via bolts. Further, in a state where the first internal gear 15d is clamped together, it is connected to the support member 201 via bolts. In the speed reducer 15, the first internal gear 15d has a portion that projects to the output side beyond the second internal gear 15e so as to cover the radial outside of the second internal gear 15e, and this portion is connected to the member 11g. An annular protruding portion 15dt that protrudes to the output side is provided at the portion of the first internal gear 15d that projects to the output side. The annular protruding portion 15dt has a smaller diameter than the maximum outer diameter of the first internal gear 15d and is fitted (inrolled and fitted) into the member 11g. In the flange portion 11g1 of the member 11g, at a plurality of positions different in the circumferential direction, there are a bolt insertion hole 11g5 that communicates with a screw hole provided in a component member of the speed reducer 15 and a screw hole 11g4 that communicates with a bolt insertion hole provided in a component member of the speed reducer 15. By combining the direct connection of the member 11g and the first internal gear 15d via the bolt insertion hole 11g5 and the connection of the member 11g and the support member 201 with the first internal gear 15d clamped together via the screw hole 11g4, a specified connection strength between the member 11g and the first internal gear 15d is achieved.

[0021] Furthermore, the member 11g projects inward in the radial direction and has a positioning projection (ring portion) 11g2 that determines the axial position of the bearing 22 and the axial position of the seal 25. Further, the member 11g has a cylindrical extending portion 11g3 that extends in the axial direction and houses the seal 25. The cylindrical extending portion 11g3 extends to the output side beyond the flange portion 11g1 on the output side of the bearing 22.

[0022] The output member 16 includes members 16a and 16b connected to each other and a shaft portion 16c, and is rotatably supported by the casing 11 via bearings 21 and 22. The output member 16 has a hollow structure (hollow cylindrical shape). A part of the output member 16 is exposed on the output side, and the exposed part is connected to the mating member 202. More specifically, the shaft portion 16c extends to the counter-output side where the detection unit 18 and the circuit unit 17 are arranged through the speed reducer 15. A rotating portion 18Ba of the output-side rotation detector 18B is fixed to the shaft portion 16c. The shaft portion 16c is press-fitted into the member 16a on the output side. The member 16b is connected to the second internal gear 15e of the speed reducer 15 by bolts and fits inside the outer ring of the bearing 24 on the output side of the speed reducer 15. The member 16b introduces the rotational motion decelerated by the speed reducer 15 and rotatably supports the vibrator 15a via the bearing 24.

[0023] The member 16a is arranged on the output side of the member 16b, fits inside the shaft portion 16c, and fits outside the inner ring of the bearing 22. The member 16a has a bolt insertion hole 16a1 that passes through the shaft portion of the bolt and houses the head of the bolt, and a bolt insertion hole 16a2 that passes through the shaft portion of the bolt. The bolt insertion holes 16a1 and 16a2 communicate with any of a plurality of screw holes 16b1 of the adjacent member 16b. The member 16b is directly connected (temporarily fixed) to the member 16b via a bolt inserted through the bolt insertion hole 16a1. Further, the member 16a is clamped together between the mating member 202 and the member 16b via a bolt inserted through the bolt insertion hole 16a2. That is, the mating member 202 is connected to the output member 16 via a bolt screwed into the screw hole of the member 16b through the bolt insertion hole 16a2. The member 16a achieves a specified connection strength with respect to the member 16b by the direct connection to the member 16b (connection by four bolts with different circumferential positions) and the clamping together (connection by eight bolts with different circumferential positions) between the member 16b and the mating member 202.

[0024] The member 16a has a cylindrical portion 16a3 that faces the cylindrical extending portion 11g3 of the casing 11 in the radial direction. The cylindrical portion 16a3 is arranged on the output side with respect to the bolt insertion hole 16a1. A sleeve 26 with which the lip portion of the seal 25 contacts is externally fitted to the cylindrical portion 16a3, and the seal 25 is arranged between the sleeve 26 and the cylindrical extending portion 11g3 of the casing 11. Note that the structure of the output member 16 is not limited to the above specific example.

[0025] The motor 12 has a stator 12a and a hollow cylindrical rotor 12b. The rotor 12b is composed of permanent magnets, and the stator 12a is composed of electromagnets. The rotor shaft 13 has a hollow structure and is externally fitted to the shaft portion 16c of the output member 16 with a gap therebetween. The rotor shaft 13 is connected to the rotor 12b of the motor 12. The motor 12 and the rotor shaft 13 are arranged on the reverse output side of the speed reducer 15. On the reverse output side of the rotor shaft 13, the rotating portion 18Aa of the input-side rotation detector 18A is fixed via a hub member 18c.

[0026] The speed reducer 15 is a cylindrical flexible meshing gear mechanism, and includes an oscillating body 15a, an oscillating body bearing 15b, an external gear 15c that is elastically deformed by the rotation of the oscillating body 15a, a first internal gear 15d that meshes with the external gear 15c, and a second internal gear 15e. Note that the speed reducer is not limited to a cylindrical flexible meshing gear mechanism, and various speed reducers can be adopted. For example, it may be a cup-type or silk hat-type flexible meshing gear mechanism, an eccentric swing-type speed reducer, or a simple planetary speed reducer. The oscillating body 15a has a hollow structure and is disposed outside the shaft portion 16c of the output member 16 with a gap therebetween. The oscillating body 15a is connected (for example, spline-connected) to the rotor shaft 13 and rotates integrally with the rotor shaft 13. The oscillating body 15a is rotatably supported by the casing 11 and the output member 16 via bearings 23 and 24 at its shaft portion. The cross-sectional outer shape of the oscillating body 15a perpendicular to the axial direction at the shaft portion is circular with the central axis O1 as the center, and the cross-sectional outer shape perpendicular to the axial direction at the portion where the oscillating body bearing 15b contacts is, for example, elliptical. The external gear 15c has flexibility. The first internal gear 15d is connected to the casing 11 and meshes with the external gear 15c in the range on the non-output side in the axial direction of the external gear 15c. The second internal gear 15e is connected to the output member 16 and meshes with the external gear 15c in the range on the output side in the axial direction of the external gear 15c.

[0027] In the speed reducer 15, a rotational motion is input to the oscillating body 15a, and the reduced rotational motion is output to the second internal gear 15e. In the speed reducer 15, the torque input to the oscillating body 15a is amplified, the amplified torque is transmitted to the second internal gear 15e, and the reaction force of the amplified torque is transmitted to the first internal gear 15d. That is, the amplified torque is transmitted to the first internal gear 15d and the second internal gear 15e.

[0028] The detection unit 18 includes an input-side rotation detector 18A that detects the rotation of the rotor shaft 13 and an output-side rotation detector 18B that detects the rotation of the output member 16. The input-side rotation detector 18A has a rotating part 18Aa that rotates integrally with the rotor shaft 13 and a sensor 18Ab that is disposed in the vicinity of the rotating part 18Aa and detects the amount of rotation of the rotating part 18Aa. The output-side rotation detector 18B has a rotating part 18Ba that rotates integrally with the output member 16 and a sensor 18Bb that is disposed in the vicinity of the rotating part 18Ba and detects the amount of rotation of the rotating part 18Ba. The input-side rotation detector 18A and the output-side rotation detector 18B are, for example, rotary encoders that output the displacement of the rotation of the rotating part as a digital signal, but may be resolvers that output as an analog signal, or other rotation detectors. The rotary encoder may have a configuration having an optical detection unit or a configuration having a magnetic detection unit. The input-side rotation detector 18A and the output-side rotation detector 18B may be different types of detectors.

[0029] In the input-side rotation detector 18A and the output-side rotation detector 18B, the two sensors 18Ab and 18Bb are mounted on the encoder board of the circuit unit 17, and the two rotating parts 18Aa and 18Ba are arranged so as to face the circuit unit 17 from the output side. More specifically, the installation position of the rotating part 18Ba on the output member 16 and the installation position of the rotating part 18Aa on the rotor shaft 13 are substantially the same position in the axial direction. Similarly, the two sensors 18Ab and 18Bb are arranged at substantially the same position in the axial direction. That is, the rotating part 18Aa and the rotating part 18Ba are arranged at positions overlapping when viewed from the radial direction, and the rotating part 18Aa is arranged on the outer side in the radial direction. Also, the sensor 18Ab and the sensor 18Bb are arranged at positions overlapping when viewed from the radial direction, and the sensor 18Ab is arranged on the outer side in the radial direction.

[0030] The brake 14 includes a hub member 14a fixed to the rotor shaft 13 so as to restrict relative rotation, a disk-shaped rotor 14b spline-fitted to the hub member 14a, an armature 14c displaceable toward the rotor 14b, an electromagnetic coil 14d for driving the armature 14c, a spring member for returning the armature 14c to its original position, a plate 14e facing the rotor 14b on the opposite side of the armature 14c, a lining (wear-resistant material) 14f fixed to the plate 14e and the armature 14c, and a frame 14g supported by the casing 11 for holding the electromagnetic coil 14d and the plate 14e. In the brake 14, a braking force is applied to the rotor shaft 13 by sandwiching the rotor 14b via the lining 14f between the armature 14c and the plate 14e by the action of the electromagnetic coil 14d or the spring member. Also, the braking force on the rotor shaft 13 is released by releasing the force with which the armature 14c and the plate 14e sandwich the rotor 14b by the action of the spring member or the electromagnetic coil 14d.

[0031] [Operation of the driving device] When the motor 12 is driven and the rotor shaft 13 and the vibrator 15a rotate, the operation of the vibrator 15a The movement is transmitted to the external gear 15c. At this time, the external gear 15c is restricted to a shape along the outer peripheral surface of the vibration body 15a, and when viewed from the axial direction, it is bent into an elliptical shape having a major axis portion and a minor axis portion. Further, the external gear 15c meshes with the fixed first internal gear 15d at the major axis portion. For this reason, the external gear 15c does not rotate at the same rotational speed as the vibration body 15a, and the vibration body 15a rotates relatively inside the external gear 15c. Along with this relative rotation, the external gear 15c bends and deforms so that the major axis position and the minor axis position move in the circumferential direction. The period of this deformation is proportional to the rotational period of the vibration body 15a. When the external gear 15c bends and deforms, the position where the external gear 15c meshes with the first internal gear 15d changes in the rotational direction due to the movement of the major axis position thereof. Here, assume that the number of teeth of the external gear 15c is 100 and the number of teeth of the first internal gear 15d is 102. Then, every time the meshing position makes one full turn, the meshing teeth between the external gear 15c and the first internal gear 15d shift, and thereby the external gear 15c rotates (spins). With the above number of teeth, the rotational movement of the vibration body 15a is decelerated at a reduction ratio of 100:2 and transmitted to the external gear 15c. On the other hand, since the external gear 15c also meshes with the second internal gear 15e, the meshing position between the external gear 15c and the second internal gear 15e also changes in the rotational direction due to the rotation of the vibration body 15a. Here, assume that the number of teeth of the second internal gear 15e is the same as the number of teeth of the external gear 15c. Then, the external gear 15c and the second internal gear 15e do not rotate relatively, and the rotational movement of the external gear 15c is transmitted to the second internal gear 15e at a reduction ratio of 1:1. By these, the rotational movement of the vibration body 15a is decelerated at a reduction ratio of 100:2 and transmitted to the second internal gear 15e, and is output from the second internal gear 15e to the mating member 202 via the output member 16.

[0032] During the transmission of the above rotational movement, the rotational position of the rotor shaft 13 is detected by the input-side rotational detector 18A, and the rotational position of the output member 16 is detected by the output-side rotational detector 18B.

[0033] When the drive of the motor 12 stops and the brake 14 is actuated, the armature 14c is driven, and the rotor 14b is sandwiched between the plate 14e and the armature 14c via the lining 14f, and a braking force acts on the rotor shaft 13. When the motor 12 is driven, the armature 14c is separated from the rotor 14b, and the braking force is released.

[0034] [Monitoring the influence of the wear condition of the speed reducer] Incidentally, the first internal gear 15d of the speed reducer 15 of the drive device 1 is equipped with a strain gauge 19 (strain sensor) as a sensor for detecting the strain at a predetermined location of the first internal gear 15d as information affected by the wear condition of the speed reducer.

[0035] FIG. 3 is a front view of the first internal gear 15d. As shown in the figure, the first internal gear 15d includes an internal gear ring portion 151d having internal teeth formed on the inner circumference on the reverse output side, an external connection portion 152d connected to the support member 201 together with the member 11g, and a deformation - prone portion 153d provided between the internal gear ring portion 151d and the external connection portion 152d in the radial direction and configured to be more easily deformed (having a larger deformation amount) than the internal gear ring portion 151d when torque acts on the first internal gear 15d.

[0036] A plurality (exemplified as eight) of through - holes 154d penetrating in the axial direction at uniform intervals in the circumferential direction are provided between the internal gear ring portion 151d and the external connection portion 152d. And the columnar portions along the radial direction between the respective through - holes 154d are the deformation - prone portions 153d. That is, each deformation - prone portion 153d has a narrow width in the circumferential direction due to the through - holes 154d on both sides, and is more easily deformed in the circumferential direction compared to the outer and inner portions in the radial direction of the deformation - prone portion 153d. Also, as an example, eight deformation - prone portions 153d are provided at regular intervals in the circumferential direction. The circumferential intervals of the respective deformation - prone portions 153d are preferably uniform, but this is not essential. Also, the number of the deformation - prone portions 153d can be increased or decreased. Note that the easily deformable portion 153d may have a smaller axial width than the outer and inner portions in the radial direction, or the easily deformable portion 153d may not be provided.

[0037] The strain gauge 19 is exemplified in the case where it is attached to the easily deformable portion 153d in a direction for detecting the strain of expansion and contraction in the radial direction in the easily deformable portion 153d. Note that the direction of the strain detected by the strain gauge 19 is not limited to the radial direction, and may be the circumferential direction, the axial direction, or an oblique direction obtained by combining these. When torque acts on the first internal gear 15d (specifically, when the external connection portion 152d is connected to the support member 201 and the internal gear ring portion 151d receives the meshing reaction force, so when torque acts on the first internal gear 15d), the easily deformable portion 153d deforms more than the internal gear ring portion 151d. As a result, the strain of expansion and contraction in the radial direction generated in the easily deformable portion 153d also increases. Since there is a correlation between the strain of this easily deformable portion 153d and the wear state of the internal and external teeth of the speed reducer 15, by detecting the strain with the strain gauge 19, the change in the wear state can be monitored.

[0038] [Measuring device] Each strain gauge 19 is connected to the measuring device 191. Note that in FIG. 3, only one strain gauge 19 is shown as being connected, but actually all the strain gauges 19 are connected to the measuring device 191. Since the strain gauge 19 has the characteristic that its resistance value changes according to the strain, the measuring device 191 can receive a detection signal (for example, a voltage signal) indicating the resistance value of each strain gauge 19 and obtain the strain. Furthermore, the measuring device 191 can obtain the stress distribution of the first internal gear 15d shown in FIG. 4 from the strains detected by the eight strain gauges 19. Then, the measuring device 191 inputs the stress distribution of the first internal gear 15d to the control device 30 of the drive device 1 connected to the measuring device 191.

[0039] [Control device] The control device 30 of the drive device 1 includes, for example, an arithmetic processing unit having a CPU, a ROM and a RAM which are storage devices, and other peripheral circuits. In the present embodiment, the control device 30 is constituted by the circuit unit 17 in FIG. 1, but is not limited thereto, and may be provided separately from the circuit unit 17. The control device 30 has a control unit 31 that controls the operation of the drive device 1, and a correction unit 32 that corrects the control parameters of the control unit 31 described later. These are functional configurations realized by the central processing unit included in the control device 30 executing a program in the data storage device. Note that one or both of the control unit 31 and the correction unit 32 may be configured by hardware.

[0040] [Control device: Control unit] The control unit 31 has a disturbance observer using a basic control model of the drive device 1 and an inverse model of the control model, determines an output value based on a plurality of predetermined control parameters, and executes operation control for the motor 12. Here, the control parameters (1) to (5) included in the plurality of control parameters of the control unit 31 will be described.

[0041] Note that the control parameters (1) to (5) shown below are examples of the control parameters of the control unit 31, and are not limited thereto, and more control parameters can be used for operation control. Conversely, the control unit 31 does not necessarily perform operation control for the motor 12 using all of the control parameters (1) to (5) shown below as control parameters, and may be configured to perform operation control for the motor 12 using some of the control parameters (1) to (5) as control parameters.

[0042] The control parameter (1) is the starting torque of the drive device 1 shown in FIG. 5. The value of the starting torque indicates the starting characteristics of the drive device 1 and is a control parameter for friction compensation. The starting torque indicates the value of the torque required to start the drive device 1 in a no-load state. Fig. 5 shows the shaft angle (dotted line), shaft speed (dashed-dotted line), and torque value (solid line) of the output member 16 during the measurement of the starting torque. During the measurement, the torque output of the motor 12 is gradually increased from 0, and the shaft angle and shaft speed of the output member 16 are detected from the output of the output-side rotation detector 18B at that time. The torque value when these deviate from the 0 state is defined as the starting torque.

[0043] The control parameter (2) is the angle transmission error of the drive device 1 shown in Fig. 6. The angle transmission error indicates the speed stability and vibration characteristics of the drive device 1 and serves as a control parameter for speed and speed deviation compensation. The angle transmission error is obtained from the difference between the theoretical output rotation angle and the measured output rotation angle when an arbitrary rotation angle is input in a no-load state. In Fig. 6, the horizontal axis represents the shaft angle of the output member 16, and the vertical axis represents the value of the measured angle transmission error.

[0044] The control parameter (3) is the twist angle generated in the output member 16 of the speed reducer 15 of the drive device 1 shown in Fig. 7. The value of the twist angle indicates the positioning, vibration, and response characteristics of the drive device 1 and serves as a control parameter for twist compensation. Fig. 7 shows the values of the load and the displacement (twist angle) of the output member 16 measured by fixing the rotor shaft 13 and gradually increasing the load from the output member 16 side to the rated torque and then unloading. When the rated torque is T3, the specified torques T1, T2 (T1 < T2 < T3) smaller than the rated torque T3 and the twist angles θ1, θ2, θ3 at the rated torque T3 are measured, and the respective spring constants K1, K2, K3 (K = T / θ) are calculated. The values of each twist angle and each spring constant are used as the characteristic values of the control parameter.

[0045] The control parameter (4) is the hysteresis of the twist angle generated in the output member 16 of the speed reducer 15 of the drive device 1 shown in Fig. 8. The value of the hysteresis of the twist angle indicates the positioning characteristics of the drive device 1 and serves as a control parameter for error compensation. Figure 8 shows the load and the displacement (twist angle) of the output member 16 when the rotor shaft 13 is fixed and the load is slowly applied from the output member 16 side up to the rated torque for both the above-mentioned forward rotation and reverse rotation until the load is removed, and shows the relationship therebetween. From the measured values of the twist angle when the load is gradually increased up to the rated torque for both the forward rotation and the reverse rotation, a rigidity hysteresis curve as shown in Figure 8 is obtained. Here, the lost motion described in Figure 8 is defined as the twist angle at the rated torque ±3%. The values of the hysteresis loss and the lost motion in this case serve as control parameters.

[0046] The control parameter (5) is the magnitude of the backlash generated between the external gear 15c of the speed reducer 15 of the drive device 1, the first internal gear 15d, and the second internal gear 15e, as shown in Figure 9. Note that Figure 9 is an explanatory diagram showing an image of the backlash, and in order to facilitate understanding, the backlash in the meshing of the external gears is illustrated. The backlash mentioned here is the backlash in the direction perpendicular to the tooth surface. The measurement of the backlash is performed by inserting a feeler gauge into the clearance between the meshing tooth surfaces. The value of the backlash indicates the positioning characteristics of the drive device 1 and serves as a control parameter for error compensation.

[0047] [Control device: Correction unit] The various control parameters used for the operation control of the control unit 31 are measured and acquired at a stage (referred to as the initial stage) after the drive device 1 is manufactured and before the drive device 1 is mounted on the host machine and actual use is started. Then, the acquired various control parameters are recorded in the storage device of the control device 30 and used for the operation control during actual use. And although the numerical adequacy of the various control parameters acquired at the initial stage deteriorates with the aging change after the actual use of the drive device 1 starts, for example, the aging change due to the wear condition of the speed reducer 15, it is not easy and not realistic to perform the measurement of the various control parameters again for the drive device 1 incorporated in the host machine and having an aging change.

[0048] The implementation details of the correction of various control parameters performed by the correction unit 32 to solve the above problems will be described below. First, the control device 30 preliminarily holds in a storage device (not shown) a data group associated with the secular change of the stress distribution of the first internal gear 15d based on the strain detected from each strain gauge 19, which is information affected by the wear condition of the speed reducer. The correction unit 32 can refer to these data groups. Note that the "data group associated with the secular change of the stress distribution of the first internal gear 15d" indicates a data group of the stress distribution at each stage with different degrees of progress of the secular change of the speed reducer 15.

[0049] The stress distribution of the first internal gear 15d can be obtained by a well-known method from the 3D data of the first internal gear 15d, the arrangement of each strain gauge 19, the strain amount detected by each strain gauge 19, and the direction of the strain. And the data of each stress distribution constituting the data group associated with the secular change of the stress distribution of the first internal gear 15d is obtained by continuously operating the driving device 1, which is a sample machine (a dedicated test machine for data collection), for a long time, and detecting each strain gauge 19 every time a certain period has elapsed since the start of operation (for example, every 100 hours or every 1000 hours, etc., not particularly limited and set as appropriate), and measuring the stress distribution of the first internal gear 15d from each detected value. Thereby, for example, the data group associated with the secular change of the stress distribution of the first internal gear 15d is composed of the stress distribution of the first internal gear 15d at the beginning of operation, the stress distribution of the first internal gear 15d after 100 hours of operation, the stress distribution of the first internal gear 15d after 200 hours of operation, the stress distribution of the first internal gear 15d after 300 hours of operation, and so on.

[0050] Note that the operating conditions such as the operating speed and load state during data collection by the driving device 1 of the sample machine are set to predetermined conditions assuming actual use. Also, in this embodiment, the detection timing of each strain gauge 19 is set to the timing when the position of any one of the strain gauges 19 coincides with the major axis of the vibrating body 15a in the circumferential direction. These measurement conditions are also stored in the storage device of the control device 30.

[0051] Further, the control device 30 stores in advance in the above-described storage device the measured values of the respective control parameters (1) to (5) after the change due to the secular change for the respective control parameters (1) to (5), and the correction unit 32 can refer to these measured values. In the case of each of the control parameters (1) to (5) as well, in the same manner as in the case of the data group involving the secular change of the stress distribution, the drive device 1 which is a sample machine is continuously operated for a long time, and every time a certain period (the same time interval as the measurement of the stress distribution) has elapsed since the start of the operation, the control parameters (1) to (5) are measured to obtain a data group of the measured values. The measurement of the control parameters (1) to (5) may be performed on the same sample machine as the measurement of the stress distribution, or may be performed on another sample machine. Thereby, for example, the data group of the measured values obtained by the above measurement of the control parameters (1) to (5) is configured as follows: the control parameters (1) to (5) at the beginning of the operation, the control parameters (1) to (5) after 100 hours of operation, the control parameters (1) to (5) after 200 hours of operation, the control parameters (1) to (5) after 300 hours of operation, and so on.

[0052] Then, when the correction unit 32 satisfies a predetermined update execution condition, it causes the measuring device 191 to perform the detection of the strain by each strain gauge 19 and the derivation of the stress distribution of the first internal gear 15d for the drive device 1 which is the own machine. It is preferable that the measurement conditions of each strain gauge 19 at this time coincide with the measurement conditions of the data group involving the secular change of the stress distribution of the first internal gear 15d described above. Further, when performing the measurement by this measuring device 191, in order to eliminate the influence of disturbance as much as possible, it is preferable to cause the host machine (for example, a robot) to perform a predetermined correction-time operation (for example, rotating the target joint from 0 degrees to 180 degrees without load) and perform the measurement during the correction-time operation. Incidentally, the execution conditions for the above update may be any conditions as long as a certain frequency can be ensured, such as regular execution or when the main power supply of the device is turned on.

[0053] When the correction unit 32 acquires the derivation result of the stress distribution of the first internal gear 15d for the driving device 1 which is the own device, it refers to the data group with the secular change of the stress distribution of the first internal gear 15d based on the sample machine, and compares it with the stress distribution of the first internal gear 15d for each operation period therein, and specifies the stress distribution of the first internal gear 15d in the operation period with the most approximation. When the stress distribution of the first internal gear 15d in the operation period with the most approximation is other than the stress distribution of the first internal gear 15d at the beginning of operation, it refers to the data group of the measured values of the control parameters (1) to (5), specifies the measured values of the control parameters (1) to (5) in the same period as the stress distribution of the first internal gear 15d in the operation period with the most approximation, and updates by swapping with the set values of the current control parameters (1) to (5).

[0054] In this way, when the driving device 1 is used and the execution conditions for a certain update are satisfied, the correction unit 32 acquires the stress distribution of the first internal gear 15d from the detection of the strain by each strain gauge 19, specifies the stress distribution of the first internal gear 15d in any operation period approximating the stress distribution, and can specify the control parameters (1) to (5) in the same operation period therefrom. The strain detected by each strain gauge 19 and the stress distribution of the first internal gear 15d based on the detected strain are correlated with the wear conditions of the internal teeth and external teeth of the speed reducer 15. Therefore, by comparing the stress distributions of the first internal gear 15d, it is possible to specify the stress distribution with a similar wear condition (close operation period) of the driving device 1 of the sample machine, and it is possible to acquire the control parameters (1) to (5) measured from the sample machine at a time with a similar wear condition (close operation period).

[0055] Note that the data group with the secular change in the stress distribution of the first internal gear 15d is not limited to that based on a single sample machine, and a data group with the secular change in the stress distribution of the first internal gear 15d may be prepared for each of a plurality of sample machines. Alternatively, a plurality of measurements may be performed at each timing when each strain gauge 19 becomes the major axis position of the vibrator 15a within a period sufficiently shorter than the period of detection by each strain gauge 19, and a plurality of stress distributions may be obtained. In those cases, a classifier may be generated by a machine learning method using, as learning data, a plurality of stress distributions for each operation period, and it may be determined by the classifier for each operation period which operation period's stress distribution the stress distribution of the first internal gear 15d of the currently used drive device 1 is.

[0056] When each control parameter (1) to (5) is updated by the correction unit 32, the control unit 31 executes operation control for the motor 12 thereafter using the updated control parameters (1) to (5).

[0057] [Technical effects in the embodiment of the invention] In the drive device 1 described above, a strain gauge 19 that detects the strain in the easily deformable portion 153d of the first internal gear 15d as information affected by the wear condition of the speed reducer 15, and based on the detection information of the strain gauge 19, corrects the control parameters (1) to (5) to new control parameters (1) to (5). It includes a correction unit 32 and a control unit 31 that controls the motor 12 based on the control parameters (1) to (5). For this reason, for the drive device 1 in which the wear condition of the speed reducer 15 has progressed, new control parameters (1) to (5) that are correlated with the wear condition of the speed reducer 15 can be obtained without actually measuring each of the control parameters (1) to (5). The control unit 31 can maintain an appropriate gain without setting the gain low in the control of the motor 12, and it becomes possible to perform the control of the motor 12 with higher precision.

[0058] In particular, when the sensor for acquiring information affected by the wear condition is the strain gauge 19, since the strain of the first internal gear 15d in the driving state of the driving device 1 is correlated with the progress of the wear condition, it becomes possible to appropriately acquire the control parameters (1) to (5) according to the progress of the wear condition, and it becomes possible to control the motor 12 with higher precision.

[0059] Further, since a plurality of strain gauges 19 are installed in the circumferential direction of the first internal gear 15d constituting the speed reducer 15, it is easy to obtain a correlation with the wear conditions of the internal teeth and external teeth arranged in the circumferential direction as well, and it becomes possible to acquire information affected by the wear condition of the more appropriate speed reducer 15.

[0060] Further, the correction unit 32 specifies secular changes in control parameters such as the angular transmission error, backlash, torsional angle hysteresis with respect to torque, and starting torque of the speed reducer 15 based on the detection information of the strain gauge 19, and corrects the control parameters based on the specified secular changes. For this reason, more appropriate control parameters are set according to the secular changes of the speed reducer 15, and more precise operation control of the motor 12 becomes possible.

[0061] [Another example of updating control parameters] Also, in the above embodiment, in order to acquire a data group involving secular changes in the stress distribution of the first internal gear 15d referred to by the correction unit 32, in the driving device 1 of the sample machine, continuous operation of the motor 12 is performed at a constant speed for a long period of time. However, the operation of the driving device 1 of the sample machine when acquiring the above data group is not limited to the above.

[0062] For example, in a state where the driving device 1 of the sample machine is mounted on a parent machine (for example, a robot or the like), a predetermined correction-time operation (for example, rotating the target joint from 0 degrees to 180 degrees without load) determined in advance for the parent machine is repeatedly executed, and for each predetermined number of repetitions, data on the stress distribution of the first internal gear 15d based on the detection of each strain gauge 19 is acquired, whereby a data group involving secular changes in the stress distribution of the first internal gear 15d referred to by the correction unit 32 may be acquired. In that case, it is also preferable to measure and acquire a data group of measured values of the control parameters (1) to (5) after the change due to aging for each predetermined number of repetitions of the above-described correction operation.

[0063] Also in the above case, regarding the execution condition for updating the correction unit 32, any condition may be used as long as a certain frequency can be ensured. Then, when the correction unit 32 meets the execution condition for updating, the stress distribution of the first internal gear 15d acquired for the driving device 1, which is the own device, is compared with the data group with the aging change of the stress distribution of the first internal gear 15d based on the sample device, and the control parameters (1) to (5) with the same number of repetitions as the stress distribution of the number of repetitions of the correction operation that is the most approximate are specified, and the control parameters (1) to (5) are updated. Then, the control unit 31 executes operation control for the motor 12 thereafter using the updated control parameters (1) to (5).

[0064] When performing the above update, since the data group with the aging change of the stress distribution of the first internal gear 15d referred to by the correction unit 32 is composed of the operation at the time of mounting the driving device 1 on the parent machine, it is possible to obtain a data group with the aging change of the stress distribution of the first internal gear 15d that reflects the wear condition of the speed reducer 15 caused by the operation of the parent machine. Therefore, it becomes possible to update to more appropriate control parameters (1) to (5), and it becomes possible to perform more accurate control of the motor 12. As the data group with the aging change of the stress distribution of the first internal gear 15d that reflects the wear condition of the speed reducer 15 caused by the operation of the parent machine is composed of the operation at the time of mounting the driving device 1 on the parent machine, it is possible to obtain a data group with the aging change of the stress distribution of the first internal gear 15d that reflects the wear condition of the speed reducer 15 caused by the operation of the parent machine. Therefore, it becomes possible to update to more appropriate control parameters (1) to (5), and it becomes possible to perform more accurate control of the motor 12.

[0065] [Application to Other Uses of Strain Gauges] The strain gauge 19 as a sensor for detecting information affected by the wear condition of the speed reducer 15 may also be used for other uses. For example, in a state where the drive device 1 is mounted on a parent machine (e.g., a robot or the like), the control unit 31 may execute predetermined operation control based on the detection information (detected strain) of the strain gauge 19. Specifically, during the normal operation of the robot (e.g., the operation when the robot is used for a predetermined purpose), when the detected strain of the strain gauge 19 exceeds a threshold value prepared in advance, it is determined that a part of the robot has come into contact with an external object or the like, and the control unit 31 performs operation control so as to execute an avoidance operation as a predetermined operation, etc. Thereby, each strain gauge 19 mounted on the drive device 1 can be used not only for utilization only when the execution condition of the update is achieved, but also for other purposes, and it becomes possible to effectively utilize the constituent resources of the drive device 1.

[0066] [Others] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the above embodiments. For example, in the above drive device 1, the stress distribution of the first internal gear 15d based on the detected strains of the plurality of strain gauges 19 is adopted as information affected by the wear condition of the speed reducer 15. However, the values of the detected strains of the plurality of strain gauges 19 themselves or other numerical values derived from each detected value may be used as information affected by the wear condition of the speed reducer 15. When using the values of the detected strains of the plurality of strain gauges 19 themselves, one numerical value may be derived from the plurality of detected values by a statistical method.

[0067] Also, in the above embodiment, the control device 30 prepares a data group with the secular change of the stress distribution of the first internal gear 15d by actual measurement for the sample machine in advance in the storage device, and compares it with the stress distribution of the first internal gear 15d based on the detection of the actually used drive device 1. However, it is not limited to this. For example, if the secular change in the stress distribution of the first internal gear 15d can be obtained by a predetermined calculation process or the like, it is not necessary to prepare in advance a data group involving the secular change in the stress distribution of the first internal gear 15d by actual measurement on the sample machine. Since it is possible to specify the degree of progress of the secular change in the stress distribution of the first internal gear 15d based on the detection of the drive device 1 actually used from the calculation process for obtaining the secular change in the stress distribution of the first internal gear 15d, it is only necessary to specify each control parameter corresponding to the degree of progress of the secular change.

[0068] And in that case, for each degree of progress of the secular change, corresponding control parameters may be prepared in advance with data obtained by actual measurement. However, even for these control parameters, if they can be calculated based on the degree of progress of the secular change in the stress distribution of the first internal gear 15d, new control parameters may be obtained by the calculation process.

[0069] Also, the sensor for detecting information affected by the wear condition of the speed reducer 15 is not limited to a strain gauge, and may be a sensor that performs other detections affected by the wear condition. For example, it may be a sensor for detecting the amount of wear powder in the lubricant enclosed in the speed reducer 15 or a sensor for detecting vibration.

[0070] In the above embodiment, an example of a deflection meshing type gear device as the speed reducer is shown However, the speed reducer according to the present invention is not particularly limited in the type of speed reduction mechanism, and any type of speed reducer may be used. For example, the speed reducer according to the present invention may be a center crank type eccentric swing type gear device, a so-called distribution type eccentric swing type gear device in which two or more shafts having an eccentric body are arranged offset from the axis of the gear device, or a simple planetary gear device. Furthermore, it may be a parallel shaft speed reducer or a right angle speed reducer. In the above embodiment, an example of the speed reducer being a so-called cylindrical deflection meshing type gear device is shown, but the speed reducer according to the present invention may be a so-called cup type or silk hat type deflection meshing type gear device.

[0071] Further, the strain gauge 19 may be provided not only on the first internal gear 15d but also on the second internal gear 15e as an internal gear member, or on other parts.

[0072] In addition, the details shown in the embodiments can be appropriately changed without departing from the gist of the invention.

Explanation of Reference Numerals

[0073] 1 Drive device (actuator) 12 Motor 15 Reducer 15a Oscillator 15b Oscillator bearing 15c External gear 15d First internal gear (internal gear member) 15e Second internal gear (internal gear member) 16 Output member 16a Member 18 Detection unit 18A Input-side rotation detector 18B Output-side rotation detector 19 Strain gauge (strain sensor) 30 Control device 31 Control unit 32 Correction unit 151d Internal gear ring part 152d External connection part 153d Easily deformable part 154d Through hole 191 Measuring device 201 Support member 202 Counterpart member O1 Central axis

Claims

1. A speed reducer, a motor, a control unit that controls the motor based on predetermined control parameters, and an actuator comprising: a sensor installed in the speed reducer that detects information affected by the wear condition of the speed reducer; a correction unit that corrects the control parameters based on the detection information of the sensor; and a storage unit that pre-holds a data group with secular changes for information affected by the wear condition of the speed reducer and a measured value of the control parameters after the secular changes for the control parameters. The control unit refers to the storage unit, identifies the data that most closely approximates the information affected by the wear condition of the speed reducer detected by the sensor from among the data group with secular changes for the information affected by the wear condition of the speed reducer, identifies the measured value of the control parameters in the same period as the most closely approximated data, and replaces and updates the current control parameters.

2. The control parameter is a control parameter for determining the output value of the motor. The actuator according to claim 1.

3. The sensor is a strain sensor. The actuator according to claim 1 or claim 2.

4. A plurality of the sensors are installed in the circumferential direction of the internal gear member constituting the speed reducer. The actuator according to claim 3.

5. The correction unit identifies secular changes for at least one of the angular transmission error, backlash, torsional angle hysteresis with respect to torque, and starting torque of the speed reducer based on the detection information of the sensor, and corrects the control parameters based on the identified secular changes. The actuator according to any one of claims 1 to 4.

6. The correction unit corrects the control parameters based on the detection information of the sensor when the host machine on which the actuator is mounted performs a predetermined correction operation. The actuator according to any one of claims 1 to 5.

7. The control unit controls the actuator based on the information detected by the sensor while the host machine on which the actuator is mounted is operating normally. The actuator according to any one of claims 1 to 6.

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