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  orange box Real time contour following for seam welding

The Challenge

Different Contour Following Strategies implemented
Tracking a moving target requires vision-robot coordination. Vision data is typically too slow for real time robot guidance. The challenge was to develop a "visual servo loop" that would supply path alteration data at least 30 times/sec. This would enable robots to follow a curve in real time.

ACG solution


Our Vision tracking software generates path alteration data every 32 ms. The path alteration data is akin to a force being applied to the robot to keep it in a groove. Robot motion is altered every 32 mill seconds to comply with the "force" and the robot stays in the "groove". In one application the "groove" was a black grease pencil line on an aircraft panel. A laser would cut along the pencil line. 

Our task was to customize the real time operating system to support two robots and control the composite robot system motion by generating a smooth continuous path that links all control points - supplied by the vision system- together in a smooth curve. B-Spline curves were generated automatically from a few control points and the curve patches were computed to be able to connect seamlessly.
A spring mass damper model is applied to external inputs to provide smooth and stable robot response. The spring mass and damper constants are adaptively modified based relative displacement vector sent by the vision system.  


Sensor guided control can significantly reduce the costs of fixtures and hard tooling. Vision based software has an added advantage: in process inspection is achieved at low incremental cost.