Visual control of an unmanned aerial vehicle for power line inspection

Using a robotic vehicle to inspect overhead power lines has many attractions. The concept of a small, rotorcraft which draws its power from the lines is introduced here. Some of its advantages compared with a free-flying aircraft are discussed. Achieving the required degree of autonomy and reliable power pick-up needs good control of the position and attitude of the vehicle relative to the overhead line. The paper considers an artificial-vision system, based on the Hough transform, for this purpose. A laboratory test rig is described which incorporates a dynamic model for a small, ducted-fan rotorcraft so that the response of the vehicle to wind gusts can be emulated. Measurements show that the closed-loop vision system is capable of counteracting the effect of such disturbances and maintaining the vehicle's position relative to the line