Energy based control of compass gait soft limbed bipeds

Abstract

Soft limb locomotion is a relatively new and challenging research field. However, soft limbs can not yet transition to practical application due to difficulties associated with control methods. Motivated by this research problem, in this paper, we investigate the performance of energy based control of underactuated soft limbed systems. We augment the previously reported energy shaping function for rigid bipeds with a new set of functions for the novel class of underactuated compass gait soft bipeds. We evaluate the controller performance and identify desired features and characteristics for better speed performance of such a biped. The proposed energy shaping functions are compared through controlled Lagrangian (CL) method for Euler-Lagrangian (EL) models and interconnection and damping assignment passivity-based control (IDA-PBC) methods for port-controlled Hamiltonian (PCH) models. Results for system stability, speed performance, and input torque profiles are compared. The IDA-PBC controllers are observed to produce better input torque and performance over the CL methods.The findings assist in extending and developing novel controllers to implement on soft limbed robots for practical control applications of soft multi-continuum limbed robots.