Control method for robot apparatus, computer readable recording medium, and robot apparatus

Patent metadata

Field	Value
Publication number	US-2016008983-A1
Application number	US-201514792987-A
Country	US
Kind code	A1
Filing date	Jul 7, 2015
Priority date	Jul 9, 2014
Publication date	Jan 14, 2016
Grant date	—

Abstract

Semi-closed control or fully closed control is selected as a control system for a joint using a motor configured to drive a joint of a robot arm via a reduction gear, an input-side encoder, and an output-side encoder, the semi-closed control being control in which an output of the input-side encoder is used, the fully closed control being control in which an output of the output-side encoder is used. A test run is performed plural times in which the robot arm is caused to perform a specific operation while semi-closed control is being performed on the joint, and semi-closed control or fully closed control is selected using outputs of the output-side encoder obtained in the test runs or in accordance with the content of a task that the robot arm is to be caused to perform.

First claim

What is claimed is:

1 . A control method for a robot apparatus, the robot apparatus including a robot arm having an end effector located at an end of the robot arm, the robot arm including a plurality of links coupled one to another by one or more joints, and a control device configured to selectively perform semi-closed control or fully closed control on the joint, the joint including a motor configured to drive the joint via a reduction gear, an input-side encoder configured to detect an angle of an input drive shaft of the reduction gear, and an output-side encoder configured to detect an angle of an output drive shaft of the reduction gear, the semi-closed control being control in which an angle of the joint is controlled in accordance with an output of the input-side encoder, the fully closed control being control in which an angle of the joint is controlled in accordance with an output of the output-side encoder, the control method comprising:
controlling in which of either semi-closed control or fully closed control is selected and used to control the joint in accordance with an evaluation result on a bias of or a variation in a tip position of the robot arm.

2 . The control method for a robot apparatus according claim 1 , wherein the controlling includes
performing a test run a plurality of times in which the control device causes the robot arm to operate while performing semi-closed control on the joint, selecting in which cases the control device selects either the semi-closed control or the fully closed control for use to control the joint in accordance with an evaluation result, which is obtained by the control device evaluating the tip position of the robot arm at a specific point using outputs of the output-side encoder obtained in the test runs, and causing the robot arm to perform semi-closed control or fully closed control on the joint, as selected in the selecting step.

3 . The control method for a robot apparatus according to claim 2 , wherein in a case where semi-closed control is used to control the joint during operation, the control device calculates the bias of the tip position of the robot arm at specific points using the outputs of the output-side encoder obtained in the test runs and performs semi-closed control on the joint using a driving distance based on a correction value for correcting this bias.

4 . The control method for a robot apparatus according claim 2 , wherein in the selecting step, the control device selects either semi-closed control or fully closed control for use to control the joint in accordance with the variation in the tip position of the robot arm at the specific point, the variation being calculated using the outputs of the output-side encoder obtained in the test runs.

5 . The control method for a robot apparatus according to claim 2 , wherein in the selecting step, the control device converts a variation in a joint angle of the joint, the variation being calculated using the outputs of the output-side encoder of the joint obtained in the test runs, into a variation in the tip position of the robot arm at a specific point, selects the semi-closed control for use to control the joint in a case where the variation satisfies a user's desired accuracy, and selects the fully closed control for use to control the joint in a case where the variation does not satisfy the user's desired accuracy.

6 . The control method for a robot apparatus according to claim 2 , wherein in the selecting step, in a case where the variation in the tip position of the robot arm at the specific point is calculated, the control device calculates variations in different directions in a space where the robot arm is caused to operate and uses a user's desired accuracies, which are different accuracies, for the respective variations calculated in the respective directions.

7 . The control method for a robot apparatus according to claim 2 , wherein the robot arm includes a plurality of joints including the joint, and in the selecting, the control device converts, for each joint, a variation in a joint angle of the joint, the variation being calculated using outputs of an output-side encoder of the joint obtained in the test runs into the variation in the tip position of the robot arm at the specific point, and in a case where fully closed control is selected to control certain joints among the plurality of joints in accordance with a user's desired accuracy at a specific point, the control device selects either the semi-closed control or the fully closed control on a per-joint basis by selecting the fully closed control for joints, from a joint having the greatest degree of effect on the variation in the tip position, in a sequential manner.

8 . The control method for a robot apparatus according to claim 2 , wherein the specific point is a target position point to which the tip position of the robot arm is to be moved.

9 . The control method for a robot apparatus according to claim 2 , wherein the specific point is an intermediate point on a path to a target position point to which the tip position of the robot arm is to be moved.

10 . The control method for a robot apparatus according to claim 1 , wherein the controlling includes
determining the content of a task that the robot arm is to be caused to perform, selecting either the semi-closed control or the fully closed control for use to control the joint in accordance with the content of the task that is determined in the determining step and that the robot arm is to be caused to perform, and performing a certain operation using the semi-closed control or the fully closed control on the joint, which is selected in the selecting step.

11 . The control method for a robot apparatus according to claim 10 , wherein in the selecting step, the control device selects either the semi-closed control or the fully closed control for use to control the joint in accordance with an object that the end effector is to be caused to operate.

12 . The control method for a robot apparatus according to claim 11 , wherein in the selecting step, the control device selects the fully closed control in a case where the object is an object applying random external forces to the robot arm.

13 . The control method for a robot apparatus according to claim 11 , wherein in the selecting step, in a case where, as the object, a plurality of objects are present that are identically shaped but made of different materials, the control device selects the fully closed control.

14 . The control method for a robot apparatus according to claim 11 , wherein in the selecting step, in a case where the object is an object whose center of gravity changes when the object is operated by the end effector, the control device selects the fully closed control.

15 . The control method for a robot apparatus according to claim 10 , wherein in the selecting step, the control device selects either the semi-closed control or the fully closed control for use to control the joint in accordance with an operation that the robot arm is to be caused to perform.

16 . The control method for a robot apparatus according to claim 10 , wherein in the selecting step, in a case where a target value of a joint angle of the joint is in a range of looseness or hysteresis of a system constituting the joint, the control device selects the fully closed control.

17 . The control method for a robot apparatus according to claim 10 , wherein in a case where fully closed control is selected in the selecting step and where an accuracy of the tip position of the robot arm

Assignees

• Canon Kk

Inventors

• Osaka Tsutomu
• Ishikawa Takahiro
• Kawamura Shunsuke

Classifications

• G05B2219/39206

  Joint space position control · CPC title

• Y10S901/02

  Arm motion controller · CPC title

• Y10S901/09

  Closed loop, sensor feedback controls arm movement · CPC title

• G05B19/404

  characterised by control arrangements for compensation, e.g. for backlash, overshoot, tool offset, tool wear, temperature, machine construction errors, load, inertia (G05B19/19, G05B19/41 take precedence) · CPC title

• B25J9/1628 Primary

  characterised by the control loop · CPC title