Mechanical and Empirical Parameter Design on a Multi-wound Differential Pulley Winch for a Wall-Climbing Robot

This paper proposes a novel multi-wound differential pulley winch (MWDPW) component for assisting the ascending/descending operations of a wall climbing robot. The robotic platform enabling rope access in dangerous environments (ROPE RIDE) climbs vertical walls using a rope and embedded winch. The original winch installed on the ROPE RIDE was a single wound winch, which had problems such as rope slip, velocity ripple during descending motion, resulting the bad cleaning performance and unstable motion on the wall. These problems are mainly due to the concentration of traction force on the rope because a small portion of the winch pulley holds the entire weight of the robot. Therefore, we have developed a new winch, MWDPW, by using multi-wound differential traction pulley and pressure rollers to solve the traction force concentration problem by distributing the traction force along the entire wrapping angle. Compared to other multi-wound winches, the MWDPW has the special feature of a differential gear and pressure roller to distribute the traction force and minimize the rope slip. The tension of the MWDPW is analyzed using the basic capstan equation, and empirical results to minimize the rope slip are presented by varying design parameters such as the winding method and presence of the pressure rollers. We expect the proposed mechanism to improve the safety of a wall-climbing robot for wall-cleaning operations.