A parallel link scanner for inspection of bores and tubes

This paper shows a novel scanner to inspect hollow components such as tubes, hollow bolts or rotors with a central bore using ultrasound technology (UT). It uses a flexible lance which can be bent to get around obstacles such as tube elbows or turbine housings. A parallel link drive consisting of 2 motor-driven disks with inclined rollers drives the lance. As the coordinate system of the 2 motors is not Cartesian, a coordinate transformation is to be applied between the motor/encoder positions and the position information to be send to the measurement device. For this reason a microcontroller is built into the scanner. As an additional benefit, a cumbersome and heavy external motor controller, most often used today, is no longer needed. The system is operated via an easy-to-understand graphical user interface from a standard laptop PC or similar.