A Bio-Inspired Musculoskeletal Model of the Lower Limb for Energy Economical Bipedal Walking

Abstract

This paper aims to transfer the properties of passive dynamics to fully actuated humanoid robots in order to reduce their energy cost while preserving their versatility. To achieve this purpose, muscle-actuated walking simulation which can offer insights into the actions of muscles during walking is performed in the open-source software OpenSim. The contributions of major muscles of the lower limb to body propulsion and support during walking are analyzed. The analysis indicates that for normal walking, hip flexor, hip extensor, knee extensor, and ankle plantar flexor are the most important contributors in providing propulsion and support, whereas knee flexor and ankle dorsiflexor play a very small role. On this basis, a new twodimensional musculoskeletal model of the lower limb is proposed by replacing the muscles that contribute little to walking with passive elastic elements. In the model, the hip joint is actuated by a pair of Hill-type muscles, while the knee and ankle joints are antagonistically actuated by muscle and spring. The effectiveness of the proposed model in realizing economical bipedal walking is demonstrated by simulation.