Design and experiments on cable inspection robot

Cables are the most important parts of cable-stayed bridges. Safety of the cables on a bridge is among the most important public concerns. This paper proposes an ameliorated wheel-based cable inspection robotic system of the authors, which is able to climb up and down the cables to detect cable defections of a bridge. The robotic system is consisted of three modules equally spaced circularly, which are joined together by six connecting boards to form a closed hexagonal body for clasping a cable. Each module consists of two wheels for climbing, one CCD camera for visual inspection, 2 pairs of actuating permanent magnets and 5 Holl sensors for the detection magnetic flux leakage. The kinematics and the statics of the robot are detailedly analyzed. The amelioration is the newly designed electric circuit which is employed to limit the descending speed of the robot during its sliding down after finishing detection. The principle of detection the cable defection through magnetic flux leakage is also discussed.