Abstract: The main cable is the primary load-bearing component of a suspension bridge, continuously exposed to harsh environmental conditions, such as wind and rain, throughout the year. These adverse conditions contribute to varying degreesof degradation and damage to the main cable, necessitating regular inspections to prevent catastrophic failures. Traditional manual inspection methods not only suffer from low efficiency but also pose significant safety risks to personnel.To address these challenges and ensure the safe and effective inspection of suspension bridge main cables, this studyintroduces a novel cooperative climbing robot, designated as Main Cable Robot Version II (CCRobot-M-II), inspired bythe locomotion of the inchworm. The robot employs an alternating opening and closing mechanism of four gripper sets,mimicking the inchworm’s movement to achieve efficient crawling along the suspension bridge handrails. This paperprovides a comprehensive analysis of the structural design, key components, and motion mechanisms of CCRobot-M-II.A detailed force analysis of the robot’s crawling process is also presented, followed by the design of the control systemand the development of an efficient motion control algorithm. Laboratory experiments demonstrate that the robot achievesa positional error of 0–0.64% during crawling, with a maximum average crawling speed of 7.6 m/min. Furthermore, thebiomimetic design enables the robot to overcome obstacles up to 30 mm in height and possess the capability to handlesuspension bridge cables with spans ranging from 740 to 1100 mm. Finally, CCRobot-M-II successfully conducted aninspection of the main cable on a suspension bridge, marking the world’s first successful deployment of a climbing robotfor main cable inspection on a suspension bridge.

Key words: Bionic design, Suspension bridge, Main cable inspection, Climbing robot, Motion control')">Bionic design, Suspension bridge, Main cable inspection, Climbing robot, Motion control