Visual Servo Control for Automatic Line-Grasping of a Power Transmission Line Inspection Robot

To guarantee that the wheel can grasp the power line reliably when the wheel-arm inspection robot crosses obstacles automatically, an image based visual servo control algorithm for line-grasping is presented. The offset distance and declination of power line, defined in image space, are used for describing the changes of image features. Then, the position and orientation decoupling control algorithm is established. For the visual Jacobian is decided by the robot status and may be singular, therefore a fuzzy method is applied to robot control. The universes of fuzzy sets are specified by experiments. Then a two-layer fuzzy controller is formulated and an automatic line-grasping program is developed. In more than 100 experiments, the offset distance and declination errors of line grasping are less than 25 pixels and 2±, reliable line-grasping is realized, and the robot can grasp the power line in 40 s when crossing obstacles. The results show that the image based visual servo control algorithm is precise, reliable and efficient, and can satisfy the requirements of the accurate, high-speed and stable line-grasping tasks.