Robot Arm Control Using a Virtual Travel Axis for Fast Positioning
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Solution Overview
Problem
Horizontal articulated robots with redundant degrees of freedom face challenges in efficiently moving to target positions due to complex posture determination and potential interference with surrounding objects, requiring significant calculation and potentially lengthy movement times.
Innovation Solution
A control method that defines a virtual travel axis passing through the origin in the horizontal plane, with the second joint point constrained on this axis, allowing for the determination of a unique posture and optimal virtual travel axis angle, enabling efficient movement to target positions with reduced calculation and minimized movement time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the robot uses redundant degrees of freedom to reach target positions, then the robot can access more positions and orientations, but the calculation complexity increases and movement time extends
Solution Approach 1:
The patent changes the control parameter from redundant joint angles to a non-redundant representation using virtual travel axis angle and distance. By parameterizing the robot's movement in terms of a unique virtual axis rather than multiple redundant joint variables, the system maintains full accessibility while eliminating the combinatorial explosion of possible configurations, thus reducing both calculation complexity and movement time.
Solution Approach 2:
Instead of determining robot posture by solving the forward kinematics problem with redundant degrees of freedom (which has multiple solutions), the patent inverts the approach by defining a unique virtual travel axis and constraining the second joint point to lie on this axis. This inversion transforms the under-constrained problem into a well-constrained one with a unique solution, thereby reducing calculation complexity while preserving accessibility.
2Reliability
If the robot determines posture by calculating all possible configurations, then the robot can find optimal paths, but the calculation amount becomes excessive
Solution Approach 1:
The patent extracts the essential movement characteristic by introducing a virtual travel axis that captures the dominant direction of motion. By taking out only the necessary degree of freedom (the angle and distance along the virtual axis) and discarding the redundant ones, the system maintains accurate posture determination while dramatically reducing calculation complexity from exponential to polynomial complexity.
3Productivity
If the robot moves quickly to target positions, then productivity increases, but the risk of interference with surrounding objects increases
Solution Approach 1:
The patent introduces a virtual travel axis as an intermediary conceptual construct that mediates between the robot's complex multi-joint configuration and the simple goal of reaching a target position. This virtual axis serves as a guide that inherently avoids interference with surrounding objects by defining a clear, direct path, allowing the robot to move quickly while maintaining safety through the geometric constraint that the second joint point lies on this axis.
Data Source
AI summary
When first arm is connected to a base at a joint point J0, a second arm is connected to the first arm at a joint point J1, a third arm is connected to the second arm at a joint point J2, a hand is connected to the third arm at a joint point J3, a target position of the joint point J3 is designated, and a robot is moved, the joint point J2 is set on a virtual travel axis passing through the joint point J0, an angle formed by a reference direction (X-axis) and the virtual travel axis is defined as a virtual travel axis angle, and respective motors of axes are driven using the virtual travel axis angle and the target position.