Contact modeling and directional adhesion for climbing robots

Climbing robots have the potential to perform a variety of useful tasks including maintenance, exploration, and search and rescue. Unfortunately, current climbing robots have not achieved robust performance in unstructured real-world environments, except when tasked with very limited and specific goals. Examples from Nature, such as the gecko lizard, can provide insight for achieving a new level of robot performance, potentially able to climb a wide range of surfaces and materials.; Developing such robots requires a detailed understanding of the interaction between the feet and the climbing substrate. Climbing is a relatively new challenge for legged robots and there has been little previous work on adhesion models specifically for climbing. The adhesive characteristics of the contact govern the magnitudes of forces that can be applied at the feet without them popping off or slipping along the surface. Classical contact and adhesion models between elastic materials, as well as most synthetic adhesives, are not able to describe the adhesion systems observed in animals such as the gecko lizard.; The gecko lizard is able to climb vertical and even overhanging surfaces composed of materials ranging from glass to painted wallboard. Its adhesion system contains an important property necessary for robust climbing - directionality. A new adhesion model, termed Frictional Adhesion, captures the directionality of the gecko's adhesive system. This model differs from many previous adhesive models and provides distinct advantages for climbing vertical surfaces.; A new synthetic adhesive is presented that duplicates the directionality of the gecko adhesion system. Directional adhesives present new challenges when testing and characterizing their adhesive qualities compared to non-directional adhesives. A custom experimental setup and procedures used for testing this adhesive are described. Results characterizing the adhesive are given and its ability to duplicate the directionality of the gecko adhesion system is discussed.; The nature of directional adhesion also presents new considerations for the design and control of climbing robots. Simplified two- and three-dimensional analyses highlight the differences between non-directional and directional adhesion models. In many cases the optimal force control and foot orientation strategies are quite different when using directional adhesion as opposed to conventional, isotropic adhesion. These simple models also explain some of the climbing behaviors seen in gecko lizards.; Directional adhesion enables control of the adhesion forces, which in turn facilitates smooth attachment and detachment of feet and robust climbing. However, appropriate use of directional adhesion necessitates added consideration of the force distribution to and orientation of the feet. With proper application, directional adhesion can greatly improve overall performance in climbing robots.