Robotic acoustic seam tracking: system development and application

The description of an ultrasonic-based seam-tracking robotic system that guides a nonwelding torch along different welding grooves is presented. A 100 kHz airborne transducer is used to inspect the workpiece ahead of a welding torch and measures the joint orientation and lateral deviation caused by curvature or discontinuities in the joint part. Data pertaining to the joint orientation and lateral deviation (echo pulse amplitude and time of flight) are obtained periodically by sampling equi-spaced points along the joint as the torch advances. A trajectory-generating algorithm uses this data to calculate the x, y, θ coordinates of the torch-tip trajectory needed to meet the tracking requirements. The experimental results from a feasibility study conducted to determine if this system could be used for tracking during live welding are also presented