Design of a Self-Adaptive Robotic Leg Using a Triggered Compliant Element

Abstract

The ability of legged robots to traverse obstacles is typically achieved using either independently actuated multiple degree-of-freedom (DOF) designs that require numerous sensors and complex control schemes, or through compliance in single-DOF legs. In this letter, a third option is explored, combining these approaches by adding a second, passively triggered mobility to a single-DOF leg mechanism. Contact of the leg with an obstacle during the swing phase activates a variation in the mechanical transmission of this leg which, through proper design, can be used to overcome this obstacle. Using the Hoeckens-Pantograph leg architecture as an example, the conditions required for overcoming colliding objects are first presented. As will be shown, they relate to the velocity of the leg endpoint along its trajectory. To obtain this velocity, the kinematics of the mechanism are determined using planar screw theory. Finally, experiments are presented showing the effectiveness of the proposed approach, keeping control simplicity while allowing for a greater robustness in the traversable terrains.