Method of controlling a redundant robot

Patent metadata

Field	Value
Publication number	US-9327401-B2
Application number	US-201314021051-A
Country	US
Kind code	B2
Filing date	Sep 9, 2013
Priority date	Sep 10, 2012
Publication date	May 3, 2016
Grant date	May 3, 2016

Abstract

A method for controlling a redundant robot arm includes the steps of selecting an application for performing a robotic process on a workpiece with the arm and defining at least one constraint on motion of the arm. Then an instruction set is generated based upon the selected application representing a path for a robot tool attached to the arm by operating the arm in one of a teaching mode and a programmed mode to perform the robotic process on the workpiece and movement of the arm is controlled during the robotic process. A constraint algorithm is generated to maintain a predetermined point on the arm to at least one of be on, be near and avoid a specified constraint in a robot envelope during movement of the arm, and a singularity algorithm is generated to avoid a singularity encountered during the movement of the arm.

First claim

What is claimed is:

1. A method for controlling a redundant robot arm comprising the steps of:
selecting an application for performing a robotic process on a workpiece;
generating an instruction set based upon the selected application representing a path for a robot tool attached to the redundant robot arm that is calculated with an inverse kinematics method directly using a Cartesian position of a tool center point of the tool and a scalar factor to produce joint angles for the redundant robot arm; and
operating the redundant robot arm in a programmed mode to perform the robotic process on the workpiece according to the generated instruction set.

2. The method according to claim 1 including modifying the path of an elbow point of the redundant robot arm to avoid a singularity position of the redundant robot arm.

3. The method according to claim 1 including controlling the redundant robot arm during the robotic process to maintain a predetermined point on the redundant robot arm to at least one of be on, be near and avoid a specified constraint in a robot envelope.

4. The method according to claim 3 including where the specified constraint is an elbow plane including an elbow point of the redundant robot arm and using the elbow plane to define the scalar factor.

5. The method according to claim 3 including controlling the tool center point of the tool to track the workpiece moving on a conveyor where the specified constraint is one of stationary relative to the conveyor and attached to the workpiece.

6. The method according to claim 3 where the specified constraint is at least one of a region, a space, a barrier or an obstacle in the robot envelope or a minimization of a power consumption of the redundant robot arm or a joint axis limit of the redundant robot arm.

7. The method according to claim 6 wherein the redundant robot arm is controlled to prevent a collision between the redundant robot arm and the specified constraint.

8. The method according to claim 3 including displaying a visual representation of the redundant robot arm, the workpiece, the specified constraint and a 3-D curve of a trajectory of self-motion of the predetermined point.

9. The method according to claim 1 wherein the redundant robot arm includes an offset wrist.

10. The method according to claim 1 wherein the redundant robot arm has seven axes of rotation.

11. A method for controlling a redundant robot arm comprising the steps of:
selecting an application for performing a robotic process on a workpiece;
generating an instruction set based upon the selected application representing a path for a robot tool attached to the redundant robot arm that is calculated with an inverse kinematics method directly using a Cartesian position of a tool center point of the tool and a scalar factor to produce joint angles for the robot including:
selecting a vector between a robot base of the redundant robot arm and a wrist center point of the redundant robot arm and treating the redundant robot arm as an infinite series of six axis robots rotating around the selected vector;
using the scalar factor and the selected vector to convert a given Cartesian position of the redundant robot arm to a Cartesian position of a six axis robot;
using the Cartesian position of the six axis robot to solve inverse kinematics for six intermediate joint angles;
using the six intermediate joint angles to compute locations of an elbow point and a wrist center point of the six axis robot;
using the scalar factor and the selected vector to convert the six axis robot elbow point and the six axis robot wrist center point to an elbow point and the wrist center point respectively of the redundant robot arm;
using the elbow point and the wrist center point of the redundant robot arm and a location of the given Cartesian position to solve for a first four axes joint angles of the redundant robot arm;
using an orientation part of the given Cartesian position and the first four axes joint angles to solve for remaining wrist joint angles five, six and seven of the redundant robot arm; and

operating the redundant robot arm in a programmed mode to perform the robotic process on the workpiece according to the generated instruction set.

12. The method according to claim 11 including modifying the path of the elbow point of the redundant robot arm to avoid a singularity position of the redundant robot arm.

13. The method according to claim 11 including controlling the redundant robot arm during the robotic process to maintain a predetermined point on the redundant robot arm to at least one of be on, be near and avoid a specified constraint in a robot envelope.

14. The method according to claim 13 including where the specified constraint is an elbow plane including the elbow point of the redundant robot arm and using the elbow plane to define the scalar factor.

15. The method according to claim 13 including controlling the tool center point of the tool to track the workpiece moving on a conveyor where the specified constraint is one of stationary relative to the conveyor and attached to the workpiece.

16. The method according to claim 13 where the specified constraint is at least one of a region, a space, a barrier or an obstacle in the robot envelope or a minimization of a power consumption of the redundant robot arm or a joint axis limit of the redundant robot arm.

17. The method according to claim 16 wherein the redundant robot arm is controlled to prevent a collision between the redundant robot arm and the specified constraint.

18. The method according to claim 13 including displaying a visual representation of the redundant robot arm, the workpiece, the specified constraint and a 3-D curve of a trajectory of self-motion of the elbow point.

19. The method according to claim 11 wherein the redundant robot arm includes an offset wrist.

20. The method according to claim 11 wherein the redundant robot arm has seven axes of rotation.

Assignees

• Fanuc America Corp

Inventors

• Xiao Di
• Cheng Sai-Kai
• Graca Randy A
• Sikowski Matthew R
• Tsai Jason

Classifications

• B25J9/163 Primary

  learning, adaptive, model based, rule based expert control · CPC title

• G05B2219/40367

  Redundant manipulator · CPC title

• Y10S901/03

  Teaching system · CPC title

• G05B2219/40333

  Singularity, at least one movement not possible, kinematic redundancy · CPC title

• Y10S901/28

  Joint · CPC title