Laser-Etched Grid Positioning for Precise Robotic Machining
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Solution Overview
Problem
In large-scale manufacturing, such as aircraft and automotive manufacturing, robots face significant errors when locating target points on large workpieces due to backlash and variance in robot arm repeatability, especially at distances far from the origin, leading to imprecise machining operations.
Innovation Solution
A system and method involving laser etching a coordinate grid directly on the workpiece, using a machine vision system to compare the etched grid to a computer model, and determining offsets to enable precise robotic machining operations, including a first ring of lasers for longitudinal gridlines and a second ring for circumferential gridlines, with a rail system and robotic drive for precise positioning and rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If robots are used to locate target points on large workpieces using a nominal coordinate system, then automated machining operations can be performed, but accumulated errors due to backlash and robot arm variance introduce significant positioning errors at distances far from the origin
Solution Approach 1:
The system performs preliminary action by laser-etching a physical coordinate grid on the workpiece surface before machining operations begin. This etched grid serves as a reference that the vision system captures and uses to establish accurate coordinate transformations, allowing the robot to locate features with high precision without relying solely on the nominal coordinate system that accumulates errors over long distances
Solution Approach 2:
The etched coordinate grid acts as an intermediary between the robot's coordinate system and the workpiece features. Instead of the robot directly locating features using the nominal coordinate system (which introduces accumulated errors), the grid provides intermediate reference points that enable accurate coordinate transformation and precise feature localization
2Device complexity
If a single nominal coordinate system is used for the entire workpiece, then the system is simple to implement, but positioning accuracy deteriorates at locations far from the origin due to accumulated errors
Solution Approach 1:
The system segments the global coordinate system into local reference frames defined by the etched grid cells. Each cell or node on the grid serves as a local origin for positioning operations in that region. This segmentation allows the robot to maintain high positioning accuracy locally at each grid point while avoiding the accumulated errors that would occur if a single nominal coordinate system were used across the entire large workpiece
3Area of stationary object
If the robot arm extends to reach distant target points, then coverage of the entire workpiece is achieved, but backlash and repeatability variance increase significantly
Solution Approach 1:
The etched grid is created in advance across the entire workpiece surface, providing pre-established reference points throughout the coverage area. When the robot needs to machine features at distant locations, it can move to any grid node and use the local grid coordinates for precise positioning, rather than relying on long extensions from a single origin that amplify backlash and repeatability errors
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
This approach significantly enhances the precision of robotic machining operations by accurately aligning the working grid with the reference grid, reducing errors and ensuring precise location of machining operations on large workpieces.
Implementation Method 1
a first ring of lasers configured to etch longitudinal gridlines on the workpiece; a second ring of lasers configured to etch circumferential gridlines on the workpiece
Implementation Method 2
each laser in the first ring of lasers and the second ring of lasers includes a distance sensing and focusing system to focus each laser on the workpiece
Data Source
AI summary
Systems, methods and computer program products for laser etching and robotic machining of large workpieces are disclosed. An example system includes a first ring of lasers configured to etch longitudinal gridlines on a workpiece, a second ring of lasers configured to etch circumferential gridlines on the workpiece, where the longitudinal gridlines and the circumferential gridlines define a working grid on the workpiece, and a machine vision system to scan the working grid and compare the working grid to a reference grid in a computer model of the workpiece and to determine offsets between the working grid and the reference grid for positioning a robotic machining tool.