A Springy Leg and a Double Backflip

This letter presents a simulation study of a planar monopod robot's motion search and control problems. The robot's passively spring-loaded prismatic joint in the lower body (between the foot and the shin) assists it in performing athletic motions. Systems of this kind can balance on a single point, hop, and produce complex movements with a suitable control strategy. We aim to investigate the application of direct orthogonal collocation (DOC) methods to nonlinear motion search problems for obtaining the continuity accuracy of using an ODE solver but exploiting the faster computation and convergence of collocation methods. Moreover, the presented controller allows the robot to get up from the ground, move to the ready position, and replicate the optimized motion (a double backflip) in a dynamic simulation.