Compliance Optimization Control for Rigid-Soft Hybrid System and its Application in Humanoid Robot Motion Control

Flexibility and softness play a significant role in dynamic human motions. This includes the flexibility owing to ligaments in the human body and the softness of external structures such as a leaf-spring-type prosthesis. Thus, robotic systems need to utilize such flexibility to achieve dynamic and energy-efficient motion. In this study, we proposed a compliance optimization-based control framework for a rigid-soft hybrid robot system where the continuous deformation of a flexible structure is represented using the piece-wise constant strain (PCS) model. We divided the hybrid system into two states: single support and double support. We validated the proposed method in these states using forward dynamics simulations, assuming a hybrid link system that consists of a humanoid robot with a flexible prosthesis.