Robot for inspecting the power transmission lines must crawl along the line and plan its behaviors to negotiate obstacles in various shapes.The robot

deliberately designed as both hanging-arms on the same side

was developed for inspecting the 220 kV transmission lines.The problems of obstacle localization

arm positioning

and attitude adjustment were studied.The position and direction of the robot could be calculated and the horizon of its body be kept by some specific algorithms according to sensors' outputs.The experimental results showed that the robot could travel along the wires

and navigate obstacles autonomously

and proved that the system design was valid.