Design of an Orbit-holding Traveling Mechanism of Girth Weld Ultrasonic Scanner

An orbit-holding traveling mechanism which is used in Automatic Ultrasonic Testing (AUT) equipment is designed in this paper. It is composed of an elastic orbit and an orbit traveler. The AUT equipment is used to inspect the defects of girth weld. The orbit is attached to a pipe near the girth weld. The traveler travels along the orbit with an angle adjusting mechanism used to make the scanner adapt to pipes of different diameters and a self-locking holding mechanism used for the constraint between the orbit and the traveler. The traveler is driven by a DC servo motor. The location of the traveler is measured using an encoder. The traveler is controlled by a PID speed feedback loop to make it travel along the orbit smoothly.