Explosive Motions with Compliant Actuation Arrangements in Articulated Robots

This paper presents the optimisation of explosive jumping motions on a 3-DoF leg prototype. The leg is based on the recently introduced asymmetric compliant actuator scheme, in which a series-elastic main drive is augmented with a parallel adjustable compliant branch with significantly different stiffness and energy storage capacity properties. The leg prototype implements two such actuation configurations, one of which includes a biarticulated branch, and they are compared to conventional series-elastic based actuation. An optimisation problem is formulated to optimise the joint trajectories and elastic element pretension to maximise jumping height. A simulation study demonstrates that the biarticulated configuration yields maximum jumping height, and that it achieves the highest peak joint power. Compared to series-elastic based actuation, the augmented leg jumps 4% higher with a monoarticulated parallel compliance configuration while using less energy, and over 10% higher in biarticulated configuration.