Design of a Flexible Passive Adaptive Suction Module for Wall-Climbing Robots

As the demand for three-dimensional operations grows, wall-climbing robots must traverse complex curved surfaces featuring discontinuous curvatures and abrupt transitions between planes, cylinders, and spheres. Traditional rigid structures often fail to maintain stable, conformal adhesion under such conditions. This paper introduces a flexible, passively adaptive suction module that achieves surface conformity through multi-DOF compliant joints and spherical hinges, eliminating the need for active control. The module is implemented in a bipedal wall-climbing robot for experimental validation. Tests on flat, cylindrical (radius: 1.07 m), and spherical (radius: 0.35 m) surfaces demonstrate a 95% adhesion success rate on flat and cylindrical surfaces and 75% on spherical surfaces, with less than 6% adhesion force loss and a 36% increase in response time, providing a practical solution for robots operating on curved surfaces.