Adhesion recovery and passive peeling in a wall climbing robot using adhesives

This paper presents analysis and results for a small and agile wall climbing robot's ability to regain lost adhesion due to degradation of dry fibrillar adhesives. To regain the lost adhesion, two feet are set to the surface and the robot performs a rocking motion on the side where the adhesion has dropped below a safety threshold. The rocking motion applies normal forces to preload the front and rear feet without letting the other foot detach from the surface by alternating the direction of the motor and only allowing small rotation of the leg. Experimental results show that the rocking motion is successful in regaining lost adhesion while using dry fibrillar adhesives on a smooth, vertical acrylic surface. The performance of the fibers over time limits the adhesion that can possibly be mechanically regained and as a result the fibers are over-designed, which gives rise to the need for a power efficient peeling mechanism. The peeling mechanism uses a conditionally locked ankle, implemented with magnets, and a slot to allow the axle to change a pulling force normal to the surface to be a pulling force perpendicular to the surface, which peels the fibers using the uneven loading. Experimental results illustrate that a passive peeling mechanism is successful in reducing the required power to peel. The presented advancements can be applied to other climbing robots using adhesives to allow for safer, more efficient climbing.