Robot system, control device of robot, and robot control device

Patent metadata

Field	Value
Publication number	US-9346162-B2
Application number	US-201414149810-A
Country	US
Kind code	B2
Filing date	Jan 8, 2014
Priority date	Aug 31, 2010
Publication date	May 24, 2016
Grant date	May 24, 2016

Abstract

A robot system includes a robot arm, one or more actuators that are provided in the robot arm to drive the robot arm, a sensor unit that detects an external force applied to at least one of the robot arm and the actuators, and a controller that controls an operation of each of the actuators and limits a torque instruction value for each of the actuators on the basis of a detection result of the sensor unit.

First claim

What is claimed is:

1. A robot system comprising:
a robot arm;
one or more actuators that are provided in the robot arm to drive the robot arm;
a sensor unit that detects an external force applied to at least one of the robot arm and the actuators; and
a controller that controls an operation of each of the actuators and limits a torque instruction value for each of the actuators on the basis of a detection result of the sensor unit, wherein
the controller includes:
an external force detecting unit that detects the direction of the external force when the external force is generated on the basis of the detection result of the sensor unit; and
an avoidance axis selecting unit that selects at least one of the actuators, on which an avoidance operation is performed, from among the actuators on the basis of the direction of the external force detected by the external force detecting unit.

2. The robot system according to claim 1 , further comprising a position sensor that detects position and posture of a control point at which the position and posture is controlled by the controller in the robot arm or the actuators, wherein
the controller includes:
an operation instruction setting unit that sets a position of each of the actuators corresponding to the position and posture of the control point as a target position and sets an operation instruction of each of the actuators;
a servo unit that generates a torque instruction to each of the actuators every predetermined operation period on the basis of at least the operation instruction and a detection result of the position sensor;
a gravity compensation torque adding unit that adds a gravity compensation torque for its own weight to the torque instruction generated by the servo unit; and
a friction compensation torque adding unit that adds a friction compensation torque to operate in the direction of the external force against a frictional force of the actuator to the torque instruction generated by the servo unit for each of the actuators selected by the avoidance axis selecting unit.

3. The robot system according to claim 2 , wherein the controller further includes an operation instruction intercepting unit that intercepts the operation instruction to be given to the servo unit when the external force is detected by the external force detecting unit.

4. The robot system according to claim 3 , wherein the controller further includes an operation instruction returning unit that releases interception of the operation instruction performed by the operation instruction intercepting unit when an external force is not detected by the external force detecting unit for more than a preset time period after the operation instruction is intercepted by the operation instruction intercepting unit.

5. The robot system according to claim 2 , wherein
the controller further includes a torque instruction limiting unit that limits a value of the torque instruction for each of the actuators, and
the torque instruction limiting unit sets an upper limit and a lower limit of the torque instruction value on the basis of a sum of the gravity compensation torque and the friction compensation torque.

6. The robot system according to claim 2 , wherein the sensor unit includes a plurality of sensors that uses quartz as a piezoelectric body.

7. The robot system according to claim 6 , wherein
the sensor unit further includes a disk-shaped sensor fixing jig that is provided on a base of the most-bottom actuator in the robot arm, and
the plurality of sensors is buried in the sensor fixing jig along a same circular arc.

8. The robot system according to claim 7 , wherein the external force detecting unit extracts high frequency vibration components of signals supplied from the plurality of sensors and detects whether the external force exists on the basis of the extracted high frequency vibration components.

9. The robot system according to claim 8 , wherein the external force detecting unit calculates peak values of the extracted high frequency vibration components for the respective sensors and detects the direction of the external force on the basis of a combination of positive and negative values of the peak values of the sensors.

10. The robot system according to claim 9 , wherein the avoidance axis selecting unit executes a threshold process on each component of a vector obtained by multiplying a direction vector of the external force calculated by the external force detecting unit by a transposed matrix of a Jacobian matrix to calculate an avoidance object joint axis and a direction.

11. The robot system according to claim 10 , wherein the friction compensation torque adding unit adds a maximum static friction torque of the actuator as the friction compensation torque, when the actuator selected by the avoidance axis selecting unit is stopped, and adds a dynamic friction torque of the actuator as the friction compensation torque, when the actuator is rotated.

12. The robot system according to claim 8 , wherein the external force detecting unit detects whether the external force exists on the basis of moving averages obtained by executing a moving averaging process on the extracted high frequency vibration components for the respective sensors.

13. The robot system according to claim 12 , wherein
the controller has a data table where a combination of positive and negative values of the integration values of the respective sensors or a combination of positive and negative values of the moving averages of the respective sensors is associated with directions of the external force, and
the external force detecting unit detects the direction of the external force on the basis of combinations of positive and negative values of the integration values of the respective sensors or combinations of positive and negative values of the moving averages of the respective sensors at times after the veneration of the external force is detected.

14. The robot system according to claim 8 , wherein the external force detecting unit calculates integration values of the high frequency vibration components for the respective sensors after the generation of the external force is detected, and detects the direction of the external force on the basis of a combination of positive and negative values of the integration values.

15. A control device of a robot that includes a robot arm, one or more actuators that are provided in the robot arm to drive the robot arm, and a sensor unit that detects an external force applied to at least one of the robot arm and the actuators,
the control device, which controls an operation of each of the actuators, comprising:
a servo unit that generates a torque instruction to each of the actuators;
a torque instruction limiting unit that limits a value of the torque instruction for each of the actuators on the basis of a detection result of the sensor unit;
an external force detecting unit that detects the direction of the external force when the external force is generated on the basis of the detection result of the sensor unit; and
an avoidance axis selecting unit that selects at least one of the actuators, on which an avoidance operation is performed, from among the actuators on the basis of the direction of the external force detected by the external force detecting unit.

Assignees

• Yaskawa Denki Seisakusho Kk

Inventors

• Hashiguchi Yukio
• Ando Shingo
• Fukuda Takuya
• Oka Takenori
• Murai Shinji
• Hidaka Takeomi
• Okahisa Manabu

Classifications

• B25J13/085

  Force or torque sensors (B25J13/082, B25J13/084 take precedence) · CPC title

• B25J9/0087 Primary

  Dual arms (double SCARA arms B25J9/043) · CPC title

• B25J9/1633 Primary

  compliant, force, torque control, e.g. combined with position control · CPC title