Power control actuator

Abstract

A power control actuator of the present disclosure includes: an output-side bearing provided on a side on which torque is to be output; the speed reducer comprises an output shaft; and a torque sensor that detects a torque associated with rotation of the output shaft, in which an outer circumferential surface of the torque sensor and an inner circumferential surface of the output-side bearing constitute a sleeve engagement structure, and an inner circumferential surface of the torque sensor and an outer circumferential surface of the output shaft of the decelerator constitute a sleeve engagement structure, and the output side bearing, the output shaft of the speed reducer and the torque sensor have a coaxial structure.

Description

Technical Field

[0001] The present disclosure relates to power control actuators. Background Art

[0002] In recent years, power control (torque control type) actuators are used in various devices. For example, a robot arm (manipulator) is known. In the robot arm, a power control actuator is provided in a joint portion of the robot, and a plurality of arms are connected through the joint portion. Power control is a control that directly receives a target value of a force applied to an operation target and drives an actuator based on the target value. Typically, a power control actuator includes a torque sensor for performing power control (see, for example, Patent Document 1).

[0003] Reference List

[0004] Patent Literature

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2017-151072. Summary of the invention

[0006] In order to achieve accurate power control, the power control actuator needs to increase the accuracy of detecting torque through a torque sensor. In addition, in order to reduce the size of the robot, the actuator needs to reduce its size.

[0007] It is desirable to provide a power control actuator that has a reduced size and enables increased accuracy in detecting torque.

[0008] A power control actuator according to one embodiment of the present disclosure includes: an output side bearing, which is arranged on one side of the output torque; a reducer including an output shaft; and a torque sensor, which detects the torque related to the rotation of the output shaft, wherein the outer peripheral surface of the torque sensor and the inner peripheral surface of the output side bearing have a sleeve joint structure, the inner peripheral surface of the torque sensor and the outer peripheral surface of the output shaft of the reducer have a sleeve joint structure, and the output side bearing, the output shaft of the reducer and the torque sensor have a coaxial structure.

[0009] In a power control actuator according to one embodiment of the present disclosure, the torque sensor is fixed to an output side bearing and an output shaft of a speed reducer through a sleeve engagement structure, and the output side bearing, the output shaft of the speed reducer and the torque sensor have a coaxial structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] [ Figure 1 ] Figure 1 is a block diagram schematically showing one example of a structure in which a power control actuator according to a comparative example is coupled to a robot.

[0011] [ Figure 2 ] Figure 2 is an appearance perspective view schematically showing one configuration example of a power control actuator according to one embodiment of the present disclosure.

[0012] [ Figure 3 ] Figure 3 is a cross-sectional view schematically showing a configuration example of a power control actuator according to an embodiment.

[0013] [ Figure 4 ] Figure 4 is an exploded cross-sectional view schematically showing a configuration example of a power control actuator according to an embodiment.

[0014] [ Figure 5 ] Figure 5 is a front view schematically showing one configuration example of a torque sensor in a power control actuator according to one embodiment.

[0015] [ Figure 6 ] Figure 6 is a cross-sectional view schematically showing one configuration example of a torque sensor in a power control actuator according to one embodiment.

[0016] [ Figure 7 ] Figure 7 is a circuit diagram showing an equivalent circuit of a torque sensor in a power control actuator according to one embodiment.

[0017] [ Figure 8 ] Figure 8 is a diagram for describing one example of a method of suppressing fluctuation in a sensor value of a torque sensor in a power control actuator according to one embodiment.

[0018] [ Fig. 9 ] Fig. 9 is a diagram for describing one example of a method of suppressing a change in a sensor value of a torque sensor before and after attaching a power control actuator to a robot according to one embodiment.

[0019] [ Fig.10 ] Fig.10 is a diagram for describing one example of idealized joint control using a power-controlled actuator according to one embodiment. DETAILED DESCRIPTION

[0020] Hereinafter, the embodiments according to the present disclosure will be described in detail with reference to the accompanying drawings. Note that the description will be made in the following order.

[0021] 0. Comparative Example ( Figure 1 )

[0022] 1. One Implementation Method

[0023] 1.1 An example configuration of a power control actuator ( Figures 2 to 4 )

[0024] 1.2 Specific example of torque sensor ( Figures 5 to 9 )

[0025] 1.3 Specific example of idealized joint control ( Fig.10 )

[0026] 1.4 Effect

[0027] <0. Comparative Example>

[0028] (Structure of actuator according to comparative example and its problems)

[0029] In order to solve social problems such as worker shortages, there is an increasing demand for manipulators that operate autonomously in the same environment as humans. The manipulator uses a power-controlled actuator including, for example, a torque sensor. In a collaborative robot including such a manipulator, it is necessary to accurately detect external forces and appropriately control torque to ensure safety, thereby achieving safe operation. From the viewpoint of collision safety and controllability, the manipulator is expected to have a reduced size. In order to reduce the size of the manipulator, the actuator is expected to have a reduced size. In addition, in order to accurately control the torque in a safer manner, it is expected that the torque acting on the manipulator should be accurately detected and transmitted without any gap. Therefore, in order to achieve precise power control, a power-controlled actuator is required to improve the accuracy of the torque sensor in detecting the torque. In addition, it is expected to provide such a human-collaborative manipulator at a very low cost.

[0030] Figure 1 One example of a structure in which a power control actuator according to a comparative example is coupled to the robot 100 is schematically shown.

[0031] A speed reducer, a motor, an encoder, etc. are arranged in the actuator body 101. In order to detect an external force, a torque sensor 102 is installed at the output portion of the actuator. The power of the motor of the actuator is transmitted to the robot 100 through the torque sensor 102. The torque sensor 102 includes a structure called a strain generating body that is easily deformed. The strain generating body includes an element capable of detecting deformation. When receiving a torque from the inside of the actuator and receiving a torque from the outside of the actuator, the strain generating body deforms, and at the same time, transmits the torque to the torque sensor 102. By detecting the deformation, the torque sensor 102 enables the detection of the torque acting on the actuator.

[0032] The torque sensor 102 is installed in the middle between the bearing on the actuator side and the bearing on the robot side. In addition, the torque sensor 102 is connected to the robot 100 through a coupling 103 such as an "Oldham slider". The torque sensor 102 is configured so that, by using the coupling 103 and the bearing structure, external forces other than the torque centered on the rotation axis are not transmitted to the torque sensor 102 as much as possible. How to firmly fix the portion of the torque sensor 102 adjacent to the strain generating body and make the actual torque generated at the actuator act on the strain generating body as much as possible is an important factor in achieving high precision. If an alignment error occurs when the actuator is assembled to the frame of the robot 100, the strain generating body of the torque sensor 102 always remains deformed. This has an impact on the detection accuracy of the torque. Therefore, an intermediate transmission structure that absorbs the alignment error of the center of the coupling 103 and the like is adopted. However, in the case of adopting the coupling structure, there is looseness (gap) between the coupling 103 and the robot 100. This causes the controllability of the robot 100 to deteriorate. The alignment error between the actuator and the robot 100 can be reduced by increasing the manufacturing accuracy and adjusting the assembly between the parts. This leads to an increase in cost due to the number of adjustment processes and parts manufactured with high accuracy.

[0033] Therefore, it is necessary to develop an output structure for a power control actuator which has resistance against external force without providing a coupling and enables torque to be detected with high accuracy at low cost.

[0034] <1. One Implementation Method>

[0035] [1.1 A configuration example of a power control actuator]

[0036] (Overall Configuration)

[0037] Figures 2 to 4 A configuration example of the power control actuator 1 according to an embodiment of the present disclosure is schematically shown respectively. Figure 2 1 is a perspective view of the external appearance of the power control actuator 1 . Figure 3 is a cross-sectional view of the power control actuator 1 . Figure 4 is an exploded sectional view of the power control actuator 1 .

[0038] For example, the power control actuator 1 according to one embodiment can be applied to the joint part of a manipulator of a robot or the like. The power control actuator 1 includes a speed reducer 10, a motor 20, a brake 30, an input side encoder 40, an output side encoder 50, a torque sensor 60, an output side cross roller bearing 70, a drive substrate 110, and a VA control microcomputer substrate 120. In addition, the power control actuator 1 includes a hollow tube 80, a housing 90, and an output frame 91. The drive substrate 110 and the VA control microcomputer substrate 120 are controllers for realizing a virtual actuator (VA: virtual actuator) with idealized joint control to be described later.

[0039] Here, for example, Figure 3 The right side in is called the input side of the power control actuator 1, and Figure 3 The left side in is referred to as the output side of the power control actuator 1. In addition, for example, Figure 3 The X axis in FIG. 8 is referred to as the central axis of the power control actuator 1. The central axis of the hollow tube 80 is the same axis as the central axis X of the power control actuator 1. The VA control microcomputer substrate 120, the drive substrate 110, the brake 30, the input side encoder 40, the motor 20, the speed reducer 10, the output side encoder 50, the torque sensor 60, and the output side cross roller bearing 70 are arranged in sequence from the input side toward the output side along the central axis X. Note that the arrangement order of these components is not limited to this.

[0040] (Housing 90)

[0041] The housing 90 has, for example, a tubular shape, and accommodates, for example, the brake 30 , the input-side encoder 40 , the motor 20 , and the speed reducer 10 .

[0042] (Brake 30)

[0043] The brake 30 is arranged around the hollow tube 80 and can be arranged coaxially with the hollow tube 80. The brake 30 reduces the rotation speed of the motor 20. For example, the brake 30 can be a power-off brake. The brake 30 is arranged on the opposite side of the reducer 10 relative to the motor 20. That is, the brake 30 is arranged at a position before being decelerated by the reducer 10. This makes it possible to reduce the braking torque required to stop the rotation of the motor 20 by the reduction ratio of the reducer 10. This makes it possible to reduce the size of the mechanism of the brake 30.

[0044] (Input side encoder 40)

[0045] The input side encoder 40 is disposed around the hollow tube 80, and can be disposed coaxially with the hollow tube 80. The input side encoder 40 acquires information on the rotation, such as the rotation angle of the motor 20. The input side encoder 40 is, for example, a reflective optical absolute encoder, and detects, for example, the absolute rotation angle of the motor 20. For example, the input side encoder 40 may be fixed to the brake 30.

[0046] (Motor 20)

[0047] The motor 20 is arranged around the hollow tube 80 and can be arranged coaxially with the hollow tube 80. Once powered, the motor 20 rotates to generate a rotation torque. The motor 20 can be, for example, a coreless motor. The motor 20 includes a motor shaft 21. The motor shaft 21 is a rotating shaft of the motor 20. The motor shaft 21 can be hollow in shape. The hollow tube 80 can be arranged inside the motor shaft 21.

[0048] (Reducer 10)

[0049] The reducer 10 is arranged around the hollow tube 80 and can be arranged coaxially with the hollow tube 80. For example, the reducer 10 can be configured with a harmonic drive (registered trademark) used as a strain wave gear device with a flexible wheel. In this case, the flexible wheel can be the output shaft 11 of the reducer 10. The reducer 10 reduces the rotation speed generated by the motor 20 at a predetermined reduction ratio, thereby generating a rotational driving force (torque). At the reducer 10, the output shaft 11 rotates at a reduced speed. The torque associated with the rotation of the output shaft 11 of the reducer 10 is transmitted to the torque sensor 60 through the output shaft 11. The reducer 10 includes an actuator side cross roller bearing 12. The actuator side cross roller bearing 12 includes an inner ring 13 and an outer ring 14. The output shaft 11 is rotatably supported by the actuator side cross roller bearing 12.

[0050] (Output side encoder 50)

[0051] The output side encoder 50 acquires and outputs rotation information such as the rotation angle of the output shaft 11 decelerated by the reducer 10. The output side encoder 50 is, for example, a reflective optical absolute encoder, and detects, for example, the absolute rotation angle of the output shaft 11. For example, the output side encoder 50 may be fixed to the torque sensor 60.

[0052] (Torque sensor 60)

[0053] The torque sensor 60 is fixed to the output shaft 11 of the speed reducer 10, and detects the torque corresponding to the rotation of the output shaft 11 (the torque generated by the power control actuator 1). The torque sensor 60 includes a first rotating body 61 and a second rotating body 62, which are concentrically arranged to have different diameters from each other. The second rotating body 62 is arranged on the outside of the first rotating body 61. In other words, the first rotating body 61 is arranged at a position closer to the inside than the second rotating body 62. The first rotating body 61 and the second rotating body 62 are connected to each other by a strain generating body. For example, the strain generating body may be as follows: Figure 5 The plurality of beams (first to fourth beams 171 to 174) shown will be described later. The strain generating body includes a strain gauge. The strain gauge may be, for example, Figure 5 The plurality of strain gauges G1 to G8 shown will be described later.

[0054] The torque sensor 60 detects a rotation torque corresponding to the detection result of the deformation occurring in the strain generating body. The second rotating body 62 on the outer side is coupled to the first rotating body 61 through the strain generating body, and the rotation torque input into the first rotating body 61 is transmitted to the second rotating body 62 through the strain generating body. The output side cross roller bearing 70 is connected to the second rotating body 62, whereby the output side cross roller bearing 70 rotates with the rotation of the second rotating body 62. At this time, the strain generating body transmits the rotation torque input into the first rotating body 61 to the second rotating body 62 when deformed.

[0055] (Output side cross roller bearing 70, output frame 91)

[0056] The output side cross roller bearing 70 is an output side bearing provided on the side where the torque generated by the power control actuator 1 is outputted. The output side cross roller bearing 70 includes an inner ring 71 and an outer ring 72. A gap is provided between the outer peripheral surface of the outer ring 72 along the axial direction (thrust direction) of the output side cross roller bearing 70 and the inner peripheral surface of the output frame 91. In addition, a gap is provided between the radial (radial) outer peripheral surface of the output side cross roller bearing 70 of the outer ring 72 and the inner peripheral surface of the output frame 91.

[0057] In the power control actuator 1, the outer peripheral surface of the torque sensor 60 (the outer peripheral surface of the second rotating body 62) and the inner peripheral surface of the output side cross roller bearing 70 (the inner peripheral surface of the inner ring 71) are configured as a sleeve joint structure. In addition, the inner peripheral surface of the torque sensor 60 (the inner peripheral surface of the first rotating body 61) and the outer peripheral surface of the output shaft 11 of the speed reducer 10 constitute a sleeve joint structure. Therefore, the output side cross roller bearing 70, the output shaft 11 of the speed reducer 10 and the torque sensor 60 have a coaxial structure.

[0058] The output frame 91 is attached to the output side cross roller bearing 70 so that there is a gap relative to the outer peripheral surface of the output side cross roller bearing 70. The output frame 91 includes a fastening hole 92 through which a fastening member such as a screw passes. Figure 2 As shown. The output frame 91 and the output side cross roller bearing 70 are fastened using a fastening member through the fastening hole 92 and the gap. This configuration enables the torque sensor 60 to be set at the output side cross roller bearing 70 without applying any load on the strain generating body. Note that a configuration may be adopted in which the inner peripheral surface of the output frame 91 and the outer peripheral surface of the output side cross roller bearing 70 are bonded together using an adhesive so as to fill the gap.

[0059] The size of the gap provided between the output side cross roller bearing 70 and the output frame 91 is preferably larger than the cumulative tolerance of the output frame 91 and the output side cross roller bearing 70. By using the sleeve joint structure to make the output side cross roller bearing 70, the output shaft 11 of the speed reducer 10 and the torque sensor 60 have a coaxial structure, the cumulative tolerance generated by the assembly of the respective components in the output portion of the power control actuator 1 can be mainly generated at a part of the outer ring 72 of the output side cross roller bearing 70. In one embodiment, by using the gap provided between the output side cross roller bearing 70 and the output frame 91, it is possible to fasten with a fastening member such as a screw from the outer peripheral direction, or to perform engagement and fixing while absorbing the alignment error between the center of the power control actuator 1 and the center of the output frame 91. By preventing the load from acting on the strain generating body of the torque sensor 60 while sufficiently receiving the external force at the output side cross roller bearing 70, the power control actuator 1 capable of detecting torque with high accuracy with reduced backlash can be realized.

[0060] In addition, in one embodiment, the output side cross roller bearing 70 used as a bearing and the torque sensor 60 are integrated using a sleeve joint structure. This makes it possible to reduce the size and also enhance the structural rigidity. Since the torque sensor 60 is provided at the inner diameter portion of the output side cross roller bearing 70, the thickness of the output side of the strain generating body of the torque sensor 60 can be reduced and also enhance its rigidity. This makes it possible to reduce the size of the structural body on the output side of the power control actuator 1, and also improve the sensor sensitivity of the torque sensor 60 to increase the detection accuracy of the torque.

[0061] For example, in the case of an arm of a vertical articulated structure, even if the backlash of the robot joint is small, the endpoint position error increases from the base to the distal end. By reducing the backlash, the accuracy of torque detection can be increased, and the repeatability error and absolute accuracy of the endpoint position can also be improved. In one embodiment, it is only necessary to increase the size of the gap provided between the output side cross roller bearing 70 and the output frame 91 so as to be larger than the cumulative tolerance resulting from the assembly of the individual components in the output part. This makes it possible to obtain the above-mentioned effect even in the case of large machining tolerances. Compared with the method of using a coupling structure obtained by high-precision machining, as the demand for machining tolerances is reduced, the expected cost is reduced.

[0062] [1.2 Specific example of the torque sensor 60]

[0063] Figure 5 1 is a front view schematically showing one configuration example of the torque sensor 60 in the power control actuator 1 according to one embodiment. Figure 6 : is a cross-sectional view schematically showing a configuration example of the torque sensor 60 in the power control actuator 1 according to one embodiment. Note that, Figure 5 An example of a configuration viewed from the output side is shown. Figure 6 FIG. 1 shows a configuration example of the first beam portion 171 and the second beam portion 172 including the torque sensor 60. Figure 6 In FIG. 1 , the left side is the output side (output side cross roller bearing 70 side), and the right side is the input side (speed reducer 10 side).

[0064] As described above, the torque sensor 60 includes the first rotating body 61 and the second rotating body 62 which are arranged concentrically so that the first rotating body 61 and the second rotating body 62 have different diameters from each other. In addition, as described above, the torque sensor 60 has a strain generating body which is provided to couple the first rotating body 61 and the second rotating body 62. Here, a configuration example in which the strain generating body includes the first to fourth beam portions 171 to 174 which extend radially with the central axis X as the center will be described.

[0065] The first to fourth beams 171 to 174 are arranged so that the beams adjacent to each other form an angle of 90 degrees, for example, in the circumferential direction. The first beam 171 and the second beam 172 connect the first rotating body 61 and the second rotating body 62 to each other so that these beams are opposite to each other at an angle of 180 degrees, with the first rotating body 61 interposed therebetween. For example, the first beam 171 includes a front surface provided with a plurality of strain gauges G1 and G2, and also includes a rear surface provided with a plurality of strain gauges G7 and G8. For example, the second beam 172 includes a front surface provided with a plurality of strain gauges G3 and G4, and also includes a rear surface provided with a plurality of strain gauges G5 and G6. The first sensor 161 includes a plurality of strain gauges G1, G2, G7 and G8 included in the first beam 171, and also includes a plurality of strain gauges G3, G4, G5 and G6 included in the second beam 172.

[0066] The third beam 173 and the fourth beam 174 couple the first rotating body 61 and the second rotating body 62 to each other in each different direction 90 degrees from the first beam 171 and the second beam 172 in the circumferential direction so that these beams are opposite to each other at an angle of 180 degrees with the first rotating body 61 interposed therebetween. Although not shown in the figure, the third beam 173 includes a front surface provided with a plurality of strain gauges G1 and G2, and also includes a rear surface provided with a plurality of strain gauges G7 and G8, for example, as in the first beam 171. In addition, although not shown in the figure, the fourth beam 174 includes a front surface provided with a plurality of strain gauges G3 and G4, and also includes a rear surface provided with a plurality of strain gauges G5 and G6, for example, as in the second beam 172. The second sensor 162 includes a plurality of strain gauges G1, G2, G7, and G8 included in the third beam 173, and also includes a plurality of strain gauges G3, G4, G5, and G6 included in the fourth beam 174.

[0067] The torque sensor 60 outputs the sum of the first sensor value of the first sensor 161 and the second sensor value of the second sensor 162 as the sensor value of the torque sensor 60 .

[0068] Figure 7 1 shows an equivalent circuit of the torque sensor 60 in the power control actuator 1 according to one embodiment. Note that here, the constituent components (the first beam 171 and the second beam 172) of the first sensor 161 will be described as an example. However, this is similarly applicable to the constituent components (the third beam 173 and the fourth beam 174) of the second sensor 162.

[0069] In the torque sensor 60, a bridge (Wheatstone bridge) having an eight-active four-meter method is configured using a plurality of strain gauges G1, G2, G7, and G8 provided in the first beam portion 171 and a plurality of strain gauges G3, G4, G5, and G6 provided in the second beam portion 172. Figure 7 , equivalent resistors including a plurality of strain gauges G1, G2, G7, and G8 disposed in the first beam portion 171 are represented as R1, R2, R7, and R8. In addition, equivalent resistors including a plurality of strain gauges G3, G4, G5, and G6 disposed in the second beam portion 172 are represented as R3, R4, R5, and R6. In the torque sensor 60, a circuit in which resistors R1, R2, R7, and R8 are arranged in series and a circuit in which resistors R3, R4, R5, and R6 are arranged in series are coupled in parallel, thereby configuring a bridge using an eight-active four-meter method.

[0070] When deformation occurs in the first beam portion 171 and the second beam portion 172 serving as the strain generating body, the resistance value of each resistor is calculated according to Figure 7 When a voltage VE is applied across the circuit in which a circuit including resistors R1, R2, R7, and R8 is coupled in parallel with a circuit including resistors R3, R4, R5, and R6, a potential difference between a midpoint B of the circuit including resistors R1, R2, R7, and R8 and a midpoint A of the circuit including resistors R3, R4, R5, and R6 is output as an output voltage Ve, which is used as a sensor value of the torque sensor 60.

[0071] Here, assuming that for example Figure 6 A clockwise bending moment occurs in the torque sensor 60 shown. In this case, a plurality of strain gauges G1 and G2 and G3 and G4 provided at the respective front surfaces of the first beam 171 and the second beam 172 are stretched. On the other hand, a plurality of strain gauges G7 and G8 and G5 and G6 provided at the respective rear surfaces of the first beam 171 and the second beam 172 are compressed. This causes the resistor values ​​to change so as to offset the resistors R1 and R2 and R3 and R4 corresponding to the front surface of each of the first beam 171 and the second beam 172, and the resistors R7 and R8 and R5 and R6 corresponding to the rear surfaces opposite to each other. By this configuration, the influence of deformation caused by the bending moment around an axis perpendicular to the central axis X can be suppressed, and the detection accuracy of the rotational torque with the central axis X as the rotation axis, which is the detection object of the torque sensor 60, can be improved.

[0072] Figure 8 1 is a diagram for describing an example of a method of suppressing a variation in the sensor value of the torque sensor 60 in the power control actuator 1 according to an embodiment.

[0073] Figure 8The torque sensor value (output voltage) detected by the first sensor 161 and the torque sensor value (output voltage) detected by the second sensor 162 are shown. Figure 8 The sum of the torque sensor value detected by the first sensor 161 and the torque sensor value detected by the second sensor 162 is shown.

[0074] The torque sensor value detected by the first sensor 161 and the torque sensor value detected by the second sensor 162 fluctuate periodically. Meanwhile, in one embodiment, the first sensor 161 and the second sensor 162 are arranged in directions that differ from each other by 90 degrees in the circumferential direction. With this arrangement, the torque noise detected by the first sensor 161 and the torque noise detected by the second sensor 162 appear in opposite phases to each other. Therefore, by adding the torque sensor value detected by the first sensor 161 and the torque sensor value detected by the second sensor 162, the periodic variation can be suppressed, so that the detection accuracy of the torque sensor 60 can be improved.

[0075] Fig. 9 1 is a diagram for describing one example of a method of suppressing a change in the sensor value of the torque sensor 60 between the front and rear of attachment of the power control actuator 1 to the robot 2 according to one embodiment.

[0076] For example, the power control actuator 1 is attached to an attachment target such as a robot 2 by using a female thread provided in an inner ring 71 of an output side cross roller bearing 70. In this case, the sensor value of the torque sensor 60 may vary between before and after attachment. Therefore, a correction unit 3 may be provided that corrects the sensor value of the torque sensor 60 after attachment to the attachment target. The correction unit 3 may include a processor. The correction unit 3 offsets the voltage difference before and after attachment based on the difference between the sensor value (output voltage) of the torque sensor 60 before attachment to the attachment target such as the robot 2 and the sensor value of the torque sensor 60 after attachment to the attachment target, thereby correcting the sensor value of the torque sensor 60 after attachment to the attachment target. By this configuration, the influence of, for example, attachment to the robot 2 by tightening a screw on the torque sensor 60 is offset.

[0077] [1.3 Specific example of idealized joint control]

[0078] Here, an example in which the power control actuator 1 is applied to, for example, a joint portion of a manipulator of a robot is described. The motion of the joint portion is modeled by a motion equation of a second-order delay system in the following expression (1).

[0079] Equation 1

[0080]

[0081] Here, I a represents the moment of inertia (inertia) (target inertia) at the joint part; τ a represents the torque (target torque) generated at the joint part; τ e represents the external torque acting on the joint part from the outside; ν a represents the viscous resistance coefficient (target viscous resistance) at the joint portion; and q represents the rotation angle (joint angle). It can also be said that the above expression (1) is a theoretical model representing the motion of the power control actuator 1 at the joint portion.

[0082] By using the calculation of generalized inverse dynamics, using the motion goal and constraints, the generated torque τ can be calculated a , which is used as the actual force acting on the joint part in order to achieve the movement goal. Therefore, ideally, the generated torque τ is calculated by a Applied to the above equation (1), a response in accordance with the theoretical model indicated by equation (1) is achieved. That is, the desired motion target should be achieved.

[0083] However, in reality, due to the influence of various interferences, there is a possibility that an error (modeling error) occurs between the movement of the joint part and the theoretical model represented by the above formula (1). The modeling error can be divided into an error caused by mass characteristics such as the weight, center of gravity or inertia tensor of the multi-link structure, and an error caused by friction or inertia in the joint part. Among these errors, the former modeling error caused by mass characteristics can be relatively easily reduced by improving the accuracy of CAD (computer-aided design) data or applying an identification method when establishing a theoretical model.

[0084] On the other hand, the latter modeling error caused by friction or inertia in the joint part is caused by friction of the reducer 10 in the joint part, for example, which is a phenomenon that is difficult to model, and there may still be a modeling error that cannot be ignored when establishing a theoretical model. In addition, in the above formula (1), the inertia I a or viscous drag coefficient ν a There is a possibility that there is an error between the values ​​of and the actual values ​​of the joint part. These errors that are difficult to model may cause interference in the drive control of the joint part. Therefore, in some cases, due to the influence of such interference, the movement of the joint part may not actually respond in a way that conforms to the theoretical mode shown in the above formula (1). Therefore, even if the force of the joint calculated using generalized inverse dynamics is applied, the torque τ generated a, the motion target as the control target may not be achieved in some cases. One embodiment considers correcting the response of the joint part so that an active control system is added to the joint part to perform an ideal response according to the theoretical model shown by the above formula (1). Specifically, one embodiment not only performs a torque control of the friction compensation type using the torque sensor 60 on the joint part, but also makes it possible to correct the response of the joint part in consideration of the inertia I a and the viscous drag coefficient ν a At the same time, the required torque τ is generated according to the theoretical value a and external torque τ e Implement the ideal response.

[0085] In one embodiment, controlling the drive of the joint part so that the joint part performs an ideal response according to formula (1) in this manner is called idealized joint control. Here, in the following description, the actuator whose drive is controlled by idealized joint control is also called a virtualized actuator (VA: virtual actuator) because the ideal response is performed. The power control actuator 1 performs a response according to the theoretical model shown in the above formula (1), which makes it possible to offset the mechanical impedance within the power control actuator 1, and also to achieve flexible and smooth operation and operation with large inertia. In addition, the size and weight of the power control actuator 1 can be reduced, and flexible operation can also be achieved.

[0086] Fig.10 is an illustrative view of an example of idealized joint control using a power control actuator 1 according to one embodiment. Note that Fig.10 Schematically illustrates blocks representing conceptual computational units that perform various types of computations related to idealized joint control. Fig.10 , block 636 indicates the aforementioned virtual actuator (VA).

[0087] Here, the power control actuator 1 responds according to the theoretical mode shown in the above equation (1). This means that when the right-hand side of equation (1) is given, the target value of the rotational angular velocity (target value of the rotational angle q ref In addition, as shown in equation (1), the theoretical model includes the external torque τ acting on the power control actuator 1 e In one embodiment, in order to perform idealized joint control, the external torque τ is measured by the torque sensor 60 e In addition, interference observer 620 is used to calculate the interference estimate τ d , the interference estimate τ d is an estimated value of the torque generated by the disturbance based on the rotation angle (joint angle) q of the power control actuator 1 measured by the input-side encoder 40 .

[0088] Block 631 represents a calculation unit that performs calculations according to the ideal joint model of the joint part represented by the above equation (1). a , external torque τ e and the rotational angular velocity (the first derivative of the rotational angle q), block 631 makes it possible to output a target value of the rotational angular velocity indicated on the left-hand side of the above equation (1).

[0089] In one embodiment, the generated torque τ is calculated using generalized inverse dynamics a and the external torque τ measured by the torque sensor 60 e is input to block 631. In addition, the rotation angle q measured by the input side encoder 40 is input to block 632 representing a calculation unit, which performs a differential calculation to calculate the rotation angular velocity (the first-order derivative of the rotation angle q). a and external torque τ e In addition, the rotational angular velocity calculated by block 632 is input to block 631, and a target value of the rotational angular velocity is calculated by block 631. The target value of the rotational angular velocity thus calculated is input to block 633.

[0090] Block 633 represents a calculation unit that calculates the torque generated at the power control actuator 1 based on the target value of the rotational angular velocity of the power control actuator 1. Specifically, in one embodiment, block 633 multiplies the target value of the rotational angular velocity by the nominal inertia J in the power control actuator 1. n To obtain the torque target value τ ref In the ideal response, the power control actuator 1 generates the torque target value τ ref , thereby expecting to obtain the desired moving target. However, as mentioned above, in the actual response, influences such as interference may occur. Therefore, in one embodiment, the interference estimate τ is calculated in the interference observer 620 d , to use the interference estimate τ d To correct the torque target value τ ref .

[0091] The configuration of the interference observer 620 will be described. Fig.10 As shown, the disturbance observer 620 calculates the disturbance estimation value τ based on the torque command value τ and the rotation angular velocity calculated based on the rotation angle q measured by the input side encoder 40. d Here, the torque command value τ is the value of the torque that the power control actuator 1 finally generates after the influence of the disturbance is corrected. For example, without calculating the disturbance estimation value τ d In the case of ref .

[0092] The disturbance observer 620 includes a block 634 and a low-pass filter 635. The block 634 represents a calculation unit that calculates the torque generated at the power control actuator 1 based on the rotational angular velocity of the power control actuator 1. Specifically, in one embodiment, the rotational angular velocity calculated by the block 632 based on the rotational angle q measured by the input-side encoder 40 is input to the block 634. The block 634 performs the calculation by the transfer function J n s represents the calculation, that is, applying the differential to the rotational angular velocity to obtain the rotational angular acceleration, and further multiplying the calculated rotational angular acceleration by the nominal inertia J n This enables calculation of an estimated value of the torque actually acting on the power control actuator 1 (torque estimated value).

[0093] In the disturbance observer 620, the difference between the torque estimation value and the torque command value τ is calculated to estimate the disturbance estimation value τ d , the interference estimate τ d is the value of the torque caused by the disturbance. Specifically, the disturbance estimate τ d It can be the difference between the torque command value τ of the previous control cycle and the torque estimation value of the current control cycle. The torque estimation value is calculated in block 634 based on the actual measurement value. In addition, the torque command value τ is calculated in block 633 based on the ideal theoretical model of the joint part indicated in block 631. Therefore, by obtaining the difference between these values, the influence of the disturbance not considered in the above theoretical model can be estimated.

[0094] In addition, a low-pass filter 635 is provided in the disturbance observer 620 to prevent the system from diverging. The low-pass filter 635 performs a calculation represented by the transfer function g / (s+g) and outputs only a low-frequency component relative to the input value, thereby stabilizing the system. In one embodiment, the torque estimation value calculated in block 634 is compared with the torque command value τ ref The difference between them is input into the low pass filter 635 to calculate the interference estimate τ d The low-frequency component of this value.

[0095] One embodiment implements feed-forward control, where the disturbance estimate τ calculated by the disturbance observer 620 d is added to the torque target value τ ref The torque command value τ is calculated to be the torque value finally generated at the power control actuator 1. Then, the power control actuator 1 is driven based on the torque command value τ. Specifically, the torque command value τ is converted into a corresponding current value (current command value), and the current command value is applied to the motor 20 to drive the power control actuator 1.

[0096] As mentioned above, by using the reference Fig.10The configuration described above can make the response of the power control actuator 1 follow the target value in the drive control of the joint part even in the presence of interference components such as friction. In addition, for the drive control of the joint part, the inertia I assumed by the theoretical model can be used. a and the viscous drag coefficient ν a Implement the ideal response.

[0097] [1.4 Effect]

[0098] As described above, with the power control actuator 1 according to one embodiment, the torque sensor 60 is fixed to the output side bearing (output side cross roller bearing 70) of the reducer 10 and the output shaft 11 having a sleeve joint structure. In addition, the output side bearing, the output shaft 11 of the reducer 10 and the torque sensor 60 have a coaxial structure. This makes it possible to reduce the size and also provides accuracy in torque detection.

[0099] Note that the effects described in this specification are given as examples only, and are not limited to these effects. Other effects are also possible. This applies similarly to the effects of other embodiments described below.

[0100] <2. Other Implementation Methods>

[0101] The technology of the present disclosure is not limited to the technology described in one embodiment above, and implementation of various modifications is possible.

[0102] For example, the present technology can adopt the following configurations.

[0103] In the case of the present technology having the following configuration, the torque sensor is fixed to the output side bearing and the output shaft of the reducer through a sleeve joint structure, and the output side bearing, the output shaft of the reducer and the torque sensor have a coaxial structure. This makes it possible to reduce the size and improve the accuracy of torque detection.

[0104] (1) A power control actuator comprising:

[0105] An output side bearing, wherein the output side bearing is arranged on the side where the torque is to be output;

[0106] a speed reducer, the speed reducer comprising an output shaft; and

[0107] a torque sensor that detects torque associated with the rotation of the output shaft, wherein

[0108] The outer peripheral surface of the torque sensor and the inner peripheral surface of the output side bearing form a sleeve joint structure,

[0109] The inner circumference of the torque sensor and the outer circumference of the output shaft of the reducer form a sleeve joint structure, and

[0110] The output side bearing, the output shaft of the reducer, and the torque sensor have a coaxial structure.

[0111] (2) The power control actuator according to (1) above, further comprising:

[0112] An output frame is attached to the output side bearing and has a clearance with respect to an outer peripheral surface of the output side bearing.

[0113] (3) The power control actuator according to (2) above, wherein

[0114] The size of the gap is at least larger than the accumulated tolerance of the output frame and the output side bearing.

[0115] (4) The power control actuator according to (2) or (3) above, wherein

[0116] The output frame has a fastening hole, and the fastening member passes through the fastening hole, and

[0117] The output frame and the output side bearing are fastened by a fastening member passing through the fastening hole and the gap.

[0118] (5) The power control actuator according to any one of (2) to (4) above, wherein

[0119] The output side bearing comprises a crossed roller bearing having an inner ring and an outer ring, and

[0120] In the axial direction of the output side cross roller bearing, the gap is provided between the outer peripheral surface of the outer ring and the inner peripheral surface of the output frame, and in the radial direction of the output side cross roller bearing, the gap is provided between the outer peripheral surface of the outer ring and the inner peripheral surface of the output frame. (6) The power control actuator according to any one of (1) to (5) above, wherein

[0121] The torque sensor comprises:

[0122] a first rotating body;

[0123] a second rotating body, the second rotating body being disposed on an outer side of the first rotating body;

[0124] a first beam portion including a front surface and a rear surface each including a plurality of strain gauges, the first beam portion coupling the first rotating body and the second rotating body to each other; and

[0125] a second beam portion, the second beam portion including a front surface and a rear surface, the front surface and the rear surface each including a plurality of strain gauges, the second beam portion coupling the first rotating body and the second rotating body to each other, the second beam portion being opposite to the first beam portion, and the first rotating body being interposed between the second beam portion and the first beam portion, and

[0126] The plurality of strain gauges disposed in the first beam portion and the plurality of strain gauges disposed in the second beam portion constitute a Wheatstone bridge.

[0127] (7) The power control actuator according to any one of (1) to (6) above, wherein

[0128] The torque sensor comprises:

[0129] a first rotating body;

[0130] a second rotating body, the second rotating body being disposed on an outer side of the first rotating body;

[0131] a first beam portion and a second beam portion, each of the first beam portion and the second beam portion including a plurality of strain gauges, the first beam portion and the second beam portion coupling the first rotating body and the second rotating body to each other so that the first beam portion and the second beam portion are opposite to each other and the first rotating body is interposed between the first beam portion and the second beam portion; and

[0132] a third beam and a fourth beam, each of which includes a plurality of strain gauges, and which couples the first rotating body and the second rotating body to each other so that the third beam and the fourth beam are opposite to each other and the first rotating body is interposed between the third beam and the fourth beam in a direction different from that of the first beam and the second beam,

[0133] A plurality of strain gauges disposed in the first beam portion and a plurality of strain gauges disposed in the second beam portion constitute a first sensor,

[0134] The plurality of strain gauges disposed in the third beam portion and the plurality of strain gauges disposed in the fourth beam portion constitute a second sensor,

[0135] A sum of a first sensor value of the first sensor and a second sensor value of the second sensor is output as the sensor value of the torque sensor.

[0136] (8) The power control actuator according to any one of (1) to (7) above, further comprising:

[0137] a correction unit that corrects the sensor value of the torque sensor after the attachment target is attached based on a difference between the sensor value of the torque sensor before the attachment target and the sensor value of the torque sensor after the attachment target. (9) The power control actuator according to any one of (1) to (8) above, wherein

[0138] The speed reducer includes a strain wave gear device, the strain wave gear device includes a flex spline, and

[0139] The flexible wheel constitutes the output shaft of the speed reducer.

[0140] This application claims priority based on Japanese Patent Application No. 2022-098068 filed with the Japan Patent Office on June 17, 2022, the entire contents of which are incorporated into this application by reference.

[0141] It should be understood that those skilled in the art will realize various modifications, combinations, sub-combinations and alterations depending on design requirements and other factors insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims

1. A power control actuator, comprising: An output side bearing, wherein the output side bearing is arranged on the side where the torque is to be output; a speed reducer, the speed reducer comprising an output shaft; and a torque sensor that detects torque associated with the rotation of the output shaft, wherein The outer peripheral surface of the torque sensor and the inner peripheral surface of the output side bearing form a sleeve joint structure, The inner circumference of the torque sensor and the outer circumference of the output shaft of the reducer form a sleeve joint structure, and The output side bearing, the output shaft of the reducer, and the torque sensor have a coaxial structure.

2. The power control actuator according to claim 1, further comprising: An output frame is attached to the output side bearing and has a clearance with respect to an outer peripheral surface of the output side bearing.

3. The power control actuator according to claim 2, wherein The size of the gap is at least larger than the accumulated tolerance of the output frame and the output side bearing.

4. The power control actuator according to claim 2, wherein The output frame has a fastening hole, and the fastening member passes through the fastening hole, and The output frame and the output side bearing are fastened by the fastening member passing through the fastening hole and the gap.

5. The power control actuator according to claim 2, wherein The output side bearing comprises a crossed roller bearing having an inner ring and an outer ring, and In the axial direction of the output side crossed roller bearing, the gap is set between the outer circumferential surface of the outer ring and the inner circumferential surface of the output frame, and in the radial direction of the output side crossed roller bearing, the gap is set between the outer circumferential surface of the outer ring and the inner circumferential surface of the output frame.

6. The power control actuator according to claim 1, wherein The torque sensor comprises: a first rotating body; a second rotating body, the second rotating body being disposed on an outer side of the first rotating body; a first beam portion including a front surface and a rear surface each including a plurality of strain gauges, the first beam portion coupling the first rotating body and the second rotating body to each other; and a second beam portion, the second beam portion including a front surface and a rear surface, the front surface and the rear surface each including a plurality of strain gauges, the second beam portion coupling the first rotating body and the second rotating body to each other, the second beam portion being opposite to the first beam portion, and the first rotating body being interposed between the second beam portion and the first beam portion, and The plurality of strain gauges disposed in the first beam portion and the plurality of strain gauges disposed in the second beam portion constitute a Wheatstone bridge.

7. The power control actuator according to claim 1, wherein The torque sensor comprises: a first rotating body; a second rotating body, the second rotating body being disposed on an outer side of the first rotating body; a first beam portion and a second beam portion, each of the first beam portion and the second beam portion including a plurality of strain gauges, the first beam portion and the second beam portion coupling the first rotating body and the second rotating body to each other so that the first beam portion and the second beam portion are opposite to each other and the first rotating body is interposed between the first beam portion and the second beam portion; and a third beam and a fourth beam, each of which includes a plurality of strain gauges, and which couples the first rotating body and the second rotating body to each other so that the third beam and the fourth beam are opposite to each other and the first rotating body is interposed between the third beam and the fourth beam in a direction different from that of the first beam and the second beam, The plurality of strain gauges disposed in the first beam portion and the plurality of strain gauges disposed in the second beam portion constitute a first sensor, The plurality of strain gauges disposed in the third beam portion and the plurality of strain gauges disposed in the fourth beam portion constitute a second sensor, A sum of a first sensor value of the first sensor and a second sensor value of the second sensor is output as the sensor value of the torque sensor.

8. The power control actuator according to claim 1, further comprising: A correction unit that corrects a sensor value of the torque sensor after attachment to the attachment target based on a difference between a sensor value of the torque sensor before attachment to the attachment target and a sensor value of the torque sensor after attachment to the attachment target.

9. The power control actuator according to claim 1, wherein The speed reducer includes a strain wave gear device, the strain wave gear device includes a flex spline, and The flexible wheel constitutes the output shaft of the speed reducer.

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