Robot Wrist Control Near Singular Points on Straight-Line Paths
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Solution Overview
Problem
Conventional robot controllers face issues when the robot's posture approaches a singular point, leading to sudden joint movements and errors, necessitating reteaching and restarting the robot.
Innovation Solution
A robot controller that controls articulated robots by recording position information and determining if the wrist unit's posture is a singular point, adjusting joint movements to avoid singular points through coordinated or independent motions of basic and wrist joints, ensuring smooth movement along a straight-line trajectory.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If coordinated joint control is used to move the control point along a straight line, then the movement precision and trajectory accuracy are improved, but the robot may approach singular points causing sudden joint movements and errors
Solution Approach 1:
The control unit determines in advance whether the second position corresponds to a singular point posture before executing the movement. By performing this determination beforehand, the system can prepare appropriate control strategies (coordinated control vs. independent joint control) to avoid singular points, thereby maintaining both trajectory accuracy and system stability
Solution Approach 2:
The control method dynamically switches between coordinated joint control and independent joint control based on the singular point determination. When a singular point is detected, the system transitions from coordinated control to independent joint control for the wrist joints, allowing the robot to pass through or avoid singular configurations while maintaining reliable operation
2Reliability
If the robot encounters a singular point during movement, then the control system detects an error and stops movement, but this requires additional work for reteaching and restarting
Solution Approach 1:
The control unit determines whether the target position corresponds to a singular point before executing the movement. By performing this determination in advance, the system can prevent errors from occurring during execution, eliminating the need for stopping, reteaching, and restarting, thereby maintaining both reliable error detection and high operational efficiency
Solution Approach 2:
When a singular point is detected in the trajectory, the control unit modifies the movement path to skip or bypass the singular point configuration. This allows the robot to reach the target position without encountering the error-prone singular state, maintaining productivity by avoiding stops and reteaching operations
Data Source
AI summary
A robot controller including a control unit configured to cause a control point to move from a first position to a second position by basic joints and wrist joints, and a recording unit configured to record position information including the second position and rotation angles to which the wrist joints are rotated when the control point is positioned at the second position. In a case where posture of the wrist unit at the second position is not a singular point, the control unit causes the basic joints and the wrist joints to perform straight-line motion so as to move the control point along a straight line, and in a case where the posture of the wrist unit at the second position is a singular point, the control unit causes the wrist joints to perform each-joint controlling motion.