Implementation and stability evaluation of a mobile cable-driven vertical surface spraying robot

Automated robotic spraying systems are increasingly applied in construction, automotive repair and shipbuilding for large-area painting and coating tasks. Fixed-base manipulators and manual methods are limited in reach, flexibility and safety on complex vertical surfaces. Achieving stable spraying on vertical planes remains challenging, especially for cable-driven mobile robots to prevent tipping or slipping. We propose a mobile cable-driven spraying robot (MCDSR) capable of performing spraying tasks on vertical surfaces. We introduce a Mobile Stability Index (MSI) to quantify stability margins across various configurations and develop an MSI-integrated Wrench-Feasible Workspace (WFW) analysis to accurately characterize the robot’s workspace under stable conditions. Numerical simulations demonstrate the MSI–WFW framework accurately characterizes the stable operational workspace while maintaining required force and torque under varied loads. Experimental validation of trajectory and spraying with an MCDSR prototype shows excellent motion performance and continuous curved spraying trajectories on vertical surfaces. Results show MCDSR’s WFW volume varies from 0.0337 to 0.7052 m³, and its MSI minimum of 0.9189 validates its monitoring capability. Therefore, the designed MCDSR offers a feasible solution for large-scale automated vertical surface spraying.