Abstract: Regarding the working task requirement of inspection robot and the rugged surroundings of high voltage transmission line， a novel inspection robot with multiunit mechanisms in series was designed. Each unit mechanism was composed of two parallelogram mechanisms in series. Based on the obstaclecrossing mechanism of the robot and the types of obstacles over the transmission line， prime structure parameters and four representative obstaclecrossing modes of the robot were provided. The workspace of the robot was analyzed for the typical crossing mode. The analysis results show that the robot has ability to cross typical obstacles over the 500kV transmission line， the robot mechanisms with multiunit in series can meet the requirements of crossing obstacles and turning on the transmission line which has certain inclination.

Key words: inspection robot, parallelogram mechanism, multiunit serial mechanism, obstaclecrossing, workspace