Examining the Effect of Rear Leg Specialization on Dynamic Climbing with SCARAB: A Dynamic Quadrupedal Robot for Locomotion on Vertical and Horizontal Surfaces

Recent investigations into biological locomotion have resulted in the development of reduced order templates that emphasize the role of lateral dynamics in achieving rapid and robust fore-aft movement, such as the Full-Goldman model for dynamic climbing and the Lateral Leg Spring model for horizontal plane running. The observation of individual animals demonstrating locomotion via both of these models motivates the development of a single platform that can do so as well. However, a drawback in developing a robot directly from these models stems from both having a bipedal configuration. While a bipedal robot could be designed, the restriction of control approaches, reduction in stability, and preclusion of leg differentiation motivates the development of a platform with additional limbs. In this study, we describe the development of the first quadrupedal platform capable of instantiating the Full-Goldman model, as well as the Lateral Leg Spring model. In particular, the climbing behavior is characterized and the effect of rear leg posture is examined for locomotion on a vertical surface.We demonstrate that climbing behavior can be impacted by the configuration of the rear legs and that minimizing the magnitude of rear leg sprawl may improve efficiency, while rear sprawl postures with a larger magnitude may improve robustness.