Robot control device, control method, and program

Abstract

To improve buck drivability of a human symbiotic robot.SOLUTION: A robot control device includes: a speed calculation part which calculates a speed of an output shaft of a drive part for driving a robot; and a compensation value calculation part which calculates a viscous resistance compensation value for compensating a supply torque instruction so that viscous resistance at a second speed becomes closer to 0 than viscous resistance at a first speed when comparing the first speed detected by the speed calculation part with the second speed smaller than the first speed and generating an output torque instruction to be output to the drive part.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a robot control device, a control method, and a program. [Background technology]

[0002] Patent Document 1 discloses a technique for subtracting a disturbance estimated by a disturbance observer from a set control signal to output an actuator control signal. The disturbance observer estimates the disturbance using the actuator speed and the control signal fed back from the actuator as inputs. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-178399 A Summary of the Invention [Problem to be solved by the invention]

[0004] Highly flexible robot arms are required to aim for symbiosis with humans. It is also expected that the robot arms will operate by, for example, machine learning. In order to increase the flexibility of the robot arm, it is important to increase the backdrivability (ease of movement when moved from the outside) of the actuator. In Patent Document 1, a disturbance observer is used to compensate for external forces by feedback control, so it is difficult to obtain sufficient backdrivability.

[0005] The present disclosure has been made to solve such problems, and has as its main object to provide a robot control device, a control method, and a program that can improve backdrivability. [Means for solving the problem]

[0006] A robot control device according to one aspect of the present disclosure includes: a speed calculation unit that calculates the speed of an output shaft of a drive unit that drives the robot; a compensation value calculation unit that calculates a viscous resistance compensation value for generating an output torque command to be output to the drive unit by compensating a supply torque command so that, when a first speed calculated by the speed calculation unit is compared with a second speed lower than the first speed, the viscous resistance at the second speed becomes closer to 0 than the viscous resistance at the first speed; and Equipped with.

[0007] A control method according to an embodiment of the present disclosure includes: The computer A process of calculating the speed of an output shaft of a drive unit that drives the robot; a process of calculating a viscous resistance compensation value for generating an output torque command to be output to the drive unit by compensating a supply torque command so that, when a first speed obtained in the process of calculating a speed is compared with a second speed lower than the first speed, the viscous resistance at the second speed is closer to 0 than the viscous resistance at the first speed; Execute.

[0008] A program according to one embodiment of the present disclosure includes: A process of calculating the speed of an output shaft of a drive unit that drives the robot; a process of calculating a viscous resistance compensation value for generating an output torque command to be output to the drive unit by compensating a supply torque command so that, when a first speed obtained in the process of calculating a speed is compared with a second speed lower than the first speed, the viscous resistance at the second speed is closer to 0 than the viscous resistance at the first speed; to be executed by the computer. Effect of the Invention

[0009] According to the present disclosure, it is possible to provide a robot control device, a control method, and a program capable of improving backdrivability. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view showing a schematic configuration of an arm unit of a robot according to an embodiment. [Diagram 2] 1 is a block diagram showing a schematic configuration of a robot control device according to an embodiment. [Diagram 3] 3 is a flow diagram illustrating calculation of a compensation value in a compensation value calculation unit in FIG. 2. [Figure 4] 13 is a graph showing an example of a viscous resistance compensation value. [Diagram 5] 11A to 11C are diagrams illustrating the effects of the embodiment. [Figure 6] 11A to 11C are diagrams illustrating the effects of the embodiment. [Figure 7] 11A to 11C are diagrams illustrating the effects of the embodiment. [Figure 8] 11A to 11C are diagrams illustrating the effects of the embodiment. [Figure 9] 11A to 11C are diagrams illustrating the effects of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. In addition, the same elements are given the same reference numerals in each drawing, and duplicate explanations are omitted as necessary. In the embodiment, an example in which the technology disclosed herein is applied to the arm part of a robot will be described.

[0012] First, a robot arm to which a robot control device according to an embodiment is applied will be described. FIG. 1 is a perspective view showing a schematic configuration of an arm unit 1 of a robot according to an embodiment. The arm unit 1 extends from a main body unit 2 of the robot. In the example shown in FIG. 1, the main body unit 2 is configured as a base, but is not limited to this. For example, the main body unit 2 may be configured as the trunk of a humanoid robot.

[0013] The arm unit 1 is configured as a robot arm having one or more joint units 3 via links or the like at a position at least a predetermined distance away from the base. Each joint unit 3 may be configured to rotate around at least one axis among a yaw axis, a pitch axis, and a roll axis that are mutually perpendicular.

[0014] In the example shown in Fig. 1, the arm unit 1 has a wrist joint 31, an elbow joint 32, and a shoulder joint 33. The shoulder joint 33 is provided at the base of the arm unit 1. The elbow joint 32 and the wrist joint 31 are provided at a position that is a predetermined distance or more away from the base of the arm unit 1. Here, the wrist joint 31, the elbow joint 32, and the shoulder joint 33 are each configured to rotate around two axes, but are not limited to this. The wrist joint 31, the elbow joint 32, and the shoulder joint 33 may be configured to rotate around one axis or three or more axes, for example.

[0015] An end effector 8 capable of gripping an object is provided at the tip of the arm unit 1. A plurality of actuators 4 that generate driving forces for driving each joint unit 3 are collectively provided at the base of the arm unit 1.

[0016] The actuator 4 is a specific example of a drive unit. The actuator 4 may be configured as, for example, a servo motor with a reducer. Each actuator 4 generates a drive force that rotates the rotation axis of the corresponding joint unit 3. In the example shown in FIG. 1, eight actuators 4 that generate drive forces that rotate two axes, a wrist joint 31, an elbow joint 32, and a shoulder joint 33, are collectively provided at the base of the arm unit 1.

[0017] For example, as shown in Fig. 1, a belt 5 is hung between each rotation shaft of the elbow joint 32 and the corresponding output shaft of each actuator 4. The belt 5 is a specific example of a transmission section. The output shaft of each actuator 4 transmits a driving force to each rotation shaft of the elbow joint 32 via the belt 5.

[0018] Similarly, a belt 5 is hung between each rotation shaft of the shoulder joint 33 and the output shaft of the corresponding actuator 4. The output shaft of each actuator 4 transmits driving force to each rotation shaft of the shoulder joint 33 via the belt 5. A wire 6 is hung between each rotation shaft of the wrist joint 31 and the output shaft of the corresponding actuator 4. The output shaft of each actuator 4 transmits driving force to each rotation shaft of the wrist joint 31 via the wire 6.

[0019] In the above example, the belt 5 and the wire 6 are used as the transmission unit, but the present invention is not limited to this. The transmission unit may be, for example, a chain, a gear, a shaft, or any other transmission member capable of transmitting the driving force of the actuator 4.

[0020] The encoder 7 is a specific example of a rotation detection unit. The encoder 7 is integrally provided with the actuator 4. The encoder 7 detects the rotation position of the output shaft of the actuator 4. Note that the rotation detection unit is not limited to the encoder 7, and may be another angle sensor.

[0021] Conventionally, actuators are provided at each joint of the arm. In addition, peripheral parts such as wiring required for the actuators are provided on the arm. This leads to an increase in the weight of the arm and reduced backdrivability.

[0022] In contrast, in the embodiment, the actuators 4 are provided in a concentrated manner at the base of the arm unit 1, and power is transmitted by a belt or wire. Therefore, there is no need to provide actuators or peripheral parts at the tip or middle part of the arm unit 1. This leads to a significant weight reduction of the arm unit 1, and the backdrivability of the arm unit 1 can be improved.

[0023] In a robot, one of the main causes of deterioration in backdrivability is the effect of friction in the actuator 4, especially in the reducer. Here, the torque T required for backdrive is f is expressed by the following equation (1).

number

[0024] Here, T s is a constant determined by the internal friction of the reducer and the self-holding torque of the motor. θ indicates the rotation angle of the output shaft. I a denotes the moment of inertia, and C a is the viscous friction coefficient, and K a indicates the rigidity of the drive unit. For example, improving backdrivability is achieved by reducing T in equation (1). s , I a , C a , K a By reducing one or more of these by physical or control, the torque T f Ideally, the inertial resistance, viscous resistance, and frictional resistance of the reducer should be reduced to zero.

[0025] As described above, even if the weight of the robot arm is reduced and the backdrivability of the hardware itself is increased, each term in the above formula (1) cannot be set to 0. Therefore, in the embodiment, the backdrivability is improved by compensation through control. In the embodiment, compensation is performed for the viscous resistance, which is a term proportional to the speed among the terms of the backdrivability.

[0026] As mentioned above, the goal is to compensate until the viscous resistance becomes zero. However, if you try to compensate to the limit, for example when trying to compensate a motor with small viscous resistance, there is a risk that parameter errors will cause the motor to rotate on its own due to the compensation torque. For this reason, the compensation value is usually set small, taking into account variations, etc.

[0027] The purpose of compensating for friction in a human symbiotic robot is to increase the detection accuracy of external forces when the robot touches an object or the surrounding environment, such as when picking up an object. Therefore, the region in which friction compensation is necessary is limited to extremely low speeds. On the other hand, if friction compensation is attempted by control up to the high speed region, it is necessary to deal with nonlinear regions such as hysteresis and high-order fluctuations, which may lead to the complication of the compensator, such as high order, or the deterioration of compensation performance due to setting a safe compensation value. Therefore, in the embodiment, friction compensation is designed as follows, focusing on the low-speed operation region required for the human symbiotic robot. The above-mentioned low-speed operation region can be, for example, a region of speeds smaller than 10 to 20 [rad / s].

[0028] FIG. 2 is a block diagram showing a schematic configuration of a robot control device 10 according to an embodiment. As shown in FIG. 2, the robot control device 10 includes an adder 11, a speed calculation unit 12, and a compensation value calculation unit 13. In the following description, the actuator 4 is assumed to include, as an example, a motor and a gear reducer that reduces the speed at a high reduction ratio by utilizing mechanical meshing. In the gear reducer, when the gears rotate at a predetermined rotation speed, friction occurs due to contact between the tips of the gear teeth. The robot control device 10 performs feedforward control to cancel out the friction caused by the reducer by adding a compensation value that compensates for this friction in advance to a torque command supplied to the motor.

[0029] The adder 11 adds the compensation value T calculated by the compensation value calculation unit 13 (to be described later) to the set torque command F0. d and outputs a torque command F1 to the actuator 4. A speed calculation unit 12 calculates the speed of the output shaft from the rotation angle θ of the actuator 4. The rotation angle θ of the output shaft of the actuator 4 can be obtained by an angle sensor such as the encoder 7 described above.

[0030] Here, further referring to Fig. 3, the calculation of the compensation value in the compensation value calculation unit 13 will be described. First, the speed calculation unit 12 calculates the speed ω of the output shaft of the actuator 4, and inputs the generated speed ω to the compensation value calculation unit 13. As shown in Fig. 3, the compensation value calculation unit 13 first determines whether or not ω is greater than 0 (S1).

[0031] When the speed ω is greater than 0 (S1, YES), the viscous resistance compensation value T d is calculated. T d =-k1×ω 2 +k2×ω (2) On the other hand, when the speed ω is equal to or less than 0 (S1, NO), the viscous resistance compensation value T d is calculated. T d =k1×ω 2 +k2×ω (3) The values ​​in equations (2) and (3) are as follows: ω: Speed ​​[rad / s] k2: Measured value of viscous resistance measured in the low speed operating region k1:k2 / (2ω0) ω0: Maximum speed to be compensated

[0032] However, for ω>k2 / 2k1 and ω>-k2 / 2k1, the viscous resistance compensation value T at ω0 d An example of the viscous resistance compensation value calculated in this manner is shown in FIG. 4. In FIG. 4, the maximum speed ω0 to be compensated is assumed to be, for example, 20 [rad / s]. As shown in FIG. 4, the viscous resistance compensation value decreases as the speed of the actuator 4 decreases. In addition, the viscous resistance compensation value T d are constant values.

[0033] The robot control device 10 calculates a viscous resistance compensation value T d This viscous resistance compensation value T dBy superimposing this on the torque command, which is the control voltage of the motor, it is possible to offset the viscous resistance of the actuator 4. In this way, the robot control device 10 according to the embodiment can make the viscous resistance approach zero as the speed of the output shaft of the actuator 4 decreases in the low-speed operation region.

[0034] Here, the effect of the control according to the embodiment will be described. In FIG. 5, an example of a simple collision experiment will be described in which an external force is generated in the arm 23 by contact with a hammer (not shown). As shown in FIG. 5, an actuator 21 is provided on a base 20 that is L-shaped in a side view. An arm 23 is connected to an output shaft of the actuator 21 via a bracket 22. The results caused by the operation of the arm 23 when a hammer (not shown) is collided with the arm 23 from the side will be described with reference to FIGS. 6 to 9. In addition, in FIGS. 6 to 9, A shows the results when compensation for viscous resistance is performed, and B shows the results when compensation is not performed.

[0035] Fig. 6 shows the speed of the output shaft of actuator 21 when an external force is generated by contact with a hammer. In Fig. 6, the horizontal axis is time (seconds) and the vertical axis is speed (rad / s). As shown in Fig. 6, when compensation is performed, the time during which arm 23 moves when an external force is applied is longer when compensation is performed compared to when no compensation is performed, and it is clear that backdrivability can be improved.

[0036] FIG. 7 shows the Q-axis current generated in the motor of the actuator 21 when an external force is applied. Torque is expressed as the product of the Q-axis current and the torque constant. In FIG. 7, the horizontal axis is time (seconds) and the vertical axis is Q-axis current (A). FIGS. 8 and 9 show frequency characteristics based on the speed and torque of the output shaft of the actuator 21. In FIG. 8, the horizontal axis is frequency (rad / s) and the vertical axis is amplitude (dB). In FIG. 9, the horizontal axis is frequency (rad / s) and the vertical axis is phase (deg). As can be seen from this, the amplitude on the low frequency side is higher when compensation is performed than when compensation is not performed, and the cutoff frequency is shifted to the low frequency side.

[0037] As described above, according to the embodiment, it is possible to more effectively improve backdrivability in the low-speed operation range that is the main area of ​​motion of a human-symbiotic robot. This makes it possible to obtain high responsiveness and improve the flexibility of the robot compared to the case where feedback control is used.

[0038] Although the embodiment of the present disclosure has been described, this embodiment is presented as an example and is not intended to limit the scope of the invention. This novel embodiment can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. This embodiment and its modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

[0039] In the present disclosure, for example, the various processes described in FIGS. 2 and 3 can be realized by causing a processor to execute a computer program.

[0040] The program can be stored and provided to a computer using various types of non-transitory computer readable media. The non-transitory computer readable media includes various types of tangible storage media. Examples of the non-transitory computer readable media include magnetic recording media (e.g., flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (e.g., magneto-optical disks), CD-ROMs (Read Only Memory), CD-Rs, CD-R / Ws, and semiconductor memories (e.g., mask ROMs, PROMs (Programmable ROMs), EPROMs (Erasable PROMs), flash ROMs, and RAMs (random access memories)).

[0041] The program may be provided to the computer by various types of transitory computer readable media. Examples of the transitory computer readable medium include an electric signal, an optical signal, and an electromagnetic wave. The transitory computer readable medium can provide the program to the computer via a wired communication path such as an electric wire and an optical fiber, or via a wireless communication path.

[0042] Each unit constituting the robot control device 10 according to each of the above-mentioned embodiments can be realized not only by a program, but also in part or in whole by dedicated hardware such as an ASIC (Application Specific Integrated Circuit) or an FPGA. [Explanation of symbols]

[0043] 1 Arm section 2 Main unit 3. Joints 4 Actuators 5 Belt 6 Wire 7 Encoders 8 End Effector 10 Robot control device 11 Adder 12 Speed ​​calculation section 13 Compensation value calculation section 20 Pedestal 21 Actuator 22 Bracket 23 Arm 31 Wrist Joint 32 Elbow Joint 33 Shoulder Joint

Claims

1. a speed calculation unit that calculates the speed of an output shaft of a drive unit that drives the robot; a compensation value calculation unit that calculates a viscous resistance compensation value for generating an output torque command to be output to the drive unit by compensating a supply torque command so that a viscous resistance at the second speed is closer to 0 than a viscous resistance at the first speed when a first speed detected by the speed calculation unit is compared with a second speed lower than the first speed; Equipped with Robot control device.

2. The compensation value calculation unit When the speed of the output shaft of the driving unit is greater than 0, calculate a viscous resistance compensation value according to the following formula: T ｄ =-k １ ×ω ２ +k ２ ×ω、 When the speed of the output shaft of the driving unit is less than or equal to 0, calculate the viscous resistance compensation value according to the following formula: T ｄ =k １ ×ω ２ +k ２ ×ω The robot control device according to claim 1 . In addition, ω is the speed [rad / s], k ２ is the measured value of viscous resistance in the low speed operating range. k １ is k ２ / (2ω ０ ) ω ０ is the maximum speed to be compensated It is.

3. an adder that adds the viscous resistance compensation value to the supply torque command to generate the output torque command; The robot control device according to claim 1 .

4. The drive unit includes a motor that rotates and drives the joint unit of the robot, and a reducer. The robot control device according to claim 1 .

5. The robot comprises: an arm portion extending from the main body portion and having at least one joint portion at a position spaced a predetermined distance or more from a base of the arm portion; At least one drive unit that generates a drive force for rotationally driving the joint unit; At least one transmission unit is provided between the corresponding joint unit and the driving unit, and transmits a driving force of the driving unit to the corresponding joint unit; Equipped with The drive unit is provided in a concentrated manner at the base of the arm unit. The robot control device according to claim 1 .

6. The robot further includes at least one rotation detector that detects rotation information of the drive unit, The speed calculation unit calculates the speed based on rotation information of the drive unit detected by the rotation detection unit. The robot control device according to claim 3.

7. The computer A process of calculating the speed of an output shaft of a drive unit that drives the robot; a process of calculating a viscous resistance compensation value for generating an output torque command to be output to the drive unit by compensating a supply torque command so that, when a first speed obtained in the process of calculating a speed is compared with a second speed lower than the first speed, the viscous resistance at the second speed is closer to 0 than the viscous resistance at the first speed; Execute Control methods.

8. A process of calculating the speed of an output shaft of a drive unit that drives the robot; a process of calculating a viscous resistance compensation value for generating an output torque command to be output to the drive unit by compensating a supply torque command so that, when a first speed obtained in the process of calculating a speed is compared with a second speed lower than the first speed, the viscous resistance at the second speed is closer to 0 than the viscous resistance at the first speed; to cause a computer to execute program.

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