Robot Arc Motion Control With Fixed Reference Direction
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Solution Overview
Problem
Existing robot controllers face challenges in maintaining stable orientation of the operation tool during arc motions, leading to potential swaying and reduced welding quality, especially in applications like arc welding, due to the reliance on calculating the orientation based on the normal direction of a reference plane passing through movement points, which makes it difficult for operators to correct positions and orientations visually.
Innovation Solution
A robot controller that sets a reference direction independent of the movement points' positions, using a user or leader coordinate system to calculate the orientation of the robot at interpolation points, ensuring stability and ease of correction by fixing the reference direction regardless of position changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the orientation of the robot is calculated based on the normal direction of the reference plane passing through the three movement points, then the controller can calculate the orientation at interpolation points, but the position of the robot is corrected so as to change the inclination of the reference plane, causing the orientation of the operation tool to become unstable and sway
Solution Approach 1:
The patent separates the reference direction definition from the movement points. Instead of calculating the reference plane from three movement points (which changes when positions are corrected), the reference direction is defined independently using a user coordinate system or leader coordinate system. This segmentation allows the reference direction to remain stable while movement points can be adjusted for position correction.
Solution Approach 2:
The patent introduces a user coordinate system or leader coordinate system as an intermediary between the movement points and the orientation calculation. This intermediary coordinate system provides a stable reference frame that is not affected by position corrections of the movement points, thereby preventing orientation instability while still enabling interpolation calculations.
2Stability of the object's composition
If teaching points are narrowly spaced to prevent the operation tool from swaying, then the operation tool orientation remains stable, but the number of teaching points increases, leading to low working efficiency
Solution Approach 1:
By introducing the user coordinate system or leader coordinate system as an intermediary reference frame, the patent enables stable orientation calculation with fewer teaching points. The intermediary coordinate system provides a consistent reference that prevents tool swaying without requiring densely spaced teaching points, thereby improving working efficiency.
Solution Approach 2:
The patent changes the reference frame parameter from a dynamically calculated reference plane (based on three movement points) to a fixed user coordinate system or leader coordinate system. This parameter change stabilizes the orientation calculation and reduces the number of teaching points needed, improving productivity.
3Ease of operation
If the reference plane passing through the three movement points is calculated by the controller, then the orientation can be determined, but the operator cannot visually check the reference plane, making it difficult to correct the orientation of the robot when the position of the robot is changed
Solution Approach 1:
The patent uses the user coordinate system or leader coordinate system as an intermediary that provides a visually checkable and easily definable reference frame. Unlike an abstract reference plane calculated from three points, the user coordinate system can be defined using visible geometric features (such as the XY plane of a user coordinate system or the plane perpendicular to the optical axis of a leader), making it easy for operators to visually verify and correct orientations.
Solution Approach 2:
While not directly related to visual appearance, this principle analogously applies to making the reference frame visible and identifiable. The patent makes the reference frame visible through coordinate system definitions that can be displayed and checked, similar to how color changes make invisible phenomena visible.
Data Source
AI summary
A robot controller controls an arc motion of a robot. The robot controller includes an interpolation point setting unit that sets an interpolation point between movement points in an operation program. The robot controller includes a movement-point angle calculation unit that calculates an angle relating to a reference direction for determining the orientation of the robot, and an interpolation-point angle calculation unit that calculates an angle relating to the reference direction at an interpolation point by interpolating angles relating to the reference direction at the movement points. The reference direction is a direction independent from the positions of the movement points and is set in an operation program in a predetermined coordinate system.