Robot Tool Guidance With Multi-Frame Clamp Offset Compensation
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Solution Overview
Problem
High precision robotic drilling and machining operations face inaccuracies due to kinematic, compliance, and backlash errors, as well as clamping forces that can displace the tool or workpiece, leading to reduced positional and orientation accuracy.
Innovation Solution
A method and system that utilize multiple frames of reference (first, second, and third) to track the position of a robotic tool relative to a workpiece, incorporating a metrology system to measure and update offsets based on clamping forces, ensuring accurate machining by accounting for clamping-induced movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a clamp is used to hold the machining head in position against the workpiece, then positioning stability is improved, but clamping forces cause displacement of the tool leading to reduced machining precision
Solution Approach 1:
The system uses a metrology system to continuously monitor the position of the clamp and machining head, providing feedback data about clamping-induced displacements. This feedback is used to calculate offset values that compensate for the positioning errors, thereby maintaining machining precision while using clamping forces for stability.
Solution Approach 2:
The system changes the parameter of position by introducing offset values that adjust the target position based on measured clamping displacements. By dynamically adjusting the position parameter through offset compensation, the system maintains precision despite the stabilizing clamping forces causing displacement.
2Stability of the object's composition
If high clamping pressure is applied to ensure tool positioning, then tool stability is improved, but the workpiece may be damaged or displaced leading to reduced accuracy
Solution Approach 1:
The metrology system provides feedback on the position of both the clamp and machining head, enabling detection of workpiece displacement caused by clamping pressure. This feedback allows for real-time compensation through offset calculations, maintaining tool stability while preventing workpiece damage from excessive clamping forces.
3Manufacturing precision
If multiple frames of reference and offset calculations are implemented to compensate for clamping movements, then machining accuracy is improved, but system complexity increases
Solution Approach 1:
The system segments the positioning problem by creating multiple frames of reference (workpiece holder frame, clamp frame, machining head frame) and calculating offsets between them. This segmentation allows independent measurement and compensation of displacements at each level, improving accuracy while managing complexity through modular measurement approaches.
Data Source
AI summary
A method and system for tracking a position of a robotic tool relative to a workpiece mounted on a workpiece holder. The method includes: i) identifying a first frame of reference defining the position of the workpiece; ii) identifying a second frame of reference defining a position of a machining head of the tool attached to a robotic arm, the tool further including a clamp moveable relative to the machining head; iii) identifying a third frame of reference defining a position of the clamp; iv) actuating the robotic arm to move the tool to a first target position relative to the workpiece; v) operating the clamp to apply a clamping force on the workpiece; vi) measuring a position of the third frame of reference; and vii) updating an offset to the first target position based on movement of the third frame of reference after operating the clamp.