Robot Fixture Centering for CNC Workpiece Loading
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Solution Overview
Problem
Existing methods for aligning a robotic arm with a CNC machine's holding fixture are tedious, prone to error, and lack flexibility, requiring manual jogging and reteaching when fixture locations change.
Innovation Solution
A system using a force sensor on the robot to automatically detect contact points with the holding fixture surfaces, computing a three-dimensional center point for precise alignment without manual jogging, and enabling free-drive mode for operator-assisted initial positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If manual jogging method is used to teach robot location, then robot can be positioned at holding fixture, but the process is tedious and requires repetition for every workpiece and fixture combination
Solution Approach 1:
The patent replaces the manual mechanical jogging process with an automated vision-based system. A camera mounted on the robot captures images of the holding fixture, and image processing algorithms automatically compute the transformation between robot coordinate system and fixture coordinate system, eliminating the need for manual teaching operations.
Solution Approach 2:
The robot system performs self-positioning by using its own mounted camera to capture and process images of the holding fixture. The system automatically computes its own transformation parameters without requiring external manual intervention or teaching operations.
2Length of moving object
If robot is extended significantly to load workpieces, then robot can reach holding fixture, but compliance or elasticity is not perfectly reflected by joint encoders causing positioning error
Solution Approach 1:
The patent replaces reliance on mechanical joint encoder measurements with an optical vision-based measurement system. The camera captures the actual position of the holding fixture, and image processing computes the precise transformation, bypassing the inaccuracies introduced by mechanical compliance in extended robot arms.
3Ease of operation
If free-drive mode is used to manually move gripper, then operator can position workpiece, but residual force applied by robot causes error in recording loading position
Solution Approach 1:
The patent replaces the manual free-drive positioning method with an automated vision-based positioning system. The camera mounted on the robot automatically captures the holding fixture location and computes the transformation, eliminating residual forces and manual positioning errors while maintaining operational flexibility.
4Adaptability or versatility
If holding fixture location changes, then new loading positions are required, but manual teaching process must be repeated
Solution Approach 1:
The robot system performs self-reconfiguration by using its mounted camera to automatically capture and process images of the new holding fixture location. The vision system computes the new transformation parameters automatically, enabling the robot to adapt to fixture location changes without requiring manual reteaching operations.
Solution Approach 2:
The patent implements a dynamic adaptation mechanism where the robot system can automatically reconfigure itself when the holding fixture location changes. The vision-based system captures real-time images and computes new transformation parameters, allowing the system to dynamically adapt to changing conditions without manual intervention.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate, automated, and flexible alignment of workpieces with holding fixtures, reducing manual intervention and positioning errors, and allowing for efficient loading and unloading of parts.
Implementation Method 1
A system using a force sensor on the robot to automatically detect contact points with the holding fixture surfaces
Data Source
AI summary
A system is provided for determining a loading location of a workpiece relative to a holding fixture, comprising: a robot including a sensor; and a controller coupled to the robot and configured to activate the robot to grip the workpiece; enable a free-drive mode to permit an operator to move the gripped workpiece to a starting location; execute a center location routine including causing the robot to: move in a first direction until the sensor senses contact with a first surface of the holding fixture; move in a second direction until the sensor senses contact with a second surface; move in a third direction until the sensor senses contact with a third surface; and compute a three-dimensional center point of the holding fixture representing the loading location of the workpiece using the first, second and third sensed positions of contact.