CCRobot-S: A Robotic Cable-Climbing Squad Collaborating for Fast Inspection and Heavy-Duty Maintenance

This study introduces a novel climbing strategy, reconfigurable parallel-type cable-driven climbing designed for long-span, large-scale bridge stay cable robotic applications, which has the potential to revolutionize the stay cable inspection and maintenance practice. The proposed methodology features the development of a Collaborative Climbing Robot Squad (CCRobot-S), which builds upon the design principles of the previous CCRobot series. In this study, CCRobot-S implements a parallel-type cable-driven manipulation design, allowing for reconfigurable kinematic morphology by its movable anchor bases and realizing the capacity of crossing over the stay cables for its flying platform. The collaborative robot squad design liberates the dimensions and scales of the robot's reachable workspace and moves the part of the robotic system that indeed needs to be moved, enhancing the working efficiency and climbing agility. This strategy also utilizes controllable adhesion instead of friction to interact with the bridge cable surface for the flying platform, realizing force multiplication for forceful manipulation. Toward bringing high efficiency and heavy-duty capacity, we propose the applicable climbing frameworks (zero-downtime climbing gait for cable inspection and spider-like climbing gait for cable maintenance) and the optimization frameworks (optimal anchor configuration for the movable anchor bases and optimal grasp arrangement for the flying gripper). This article includes the exploration of the design and climbing gaits of CCRobotS, the formulation of the CCRobot-S model, a comprehensive analysis of its workspace, and its climbing strategy and optimization. Extensive experiments have assessed the proposed climbing strategy's effectiveness and showcased CCRobot-S' capabilities.