Comparative Metrics of Advanced Serial/Parallel Biped Design and Characterization of the Main Contemporary Architectures

The best achievements in bipedal locomotion have resulted from associating an intelligent and efficient design with clever and robust control. While several control frameworks exist, the design of the legs of our biped robots still lacks a systematic approach and remains a crucial challenge for robot mobility. This paper introduces several criteria to characterize the design of bipedal legs. They aim to guide the design choices and could be implemented in a codesign approach. They reflect the leg overall performances (ability to produce dynamic and accurate foot movements, absorb impacts, lower the motor torques needed to stand up) and characterize the design compactness. We give the algorithmic formulations to evaluate them beyond classical serial designs, to account for any parallel mechanisms. To validate these criteria, we developed a library of open-source CAD models describing the main existing biped architectures, which can be used as a database for future design studies. We discuss the comparative performances of these architectures. We hope this quantified discussion can serve as a baseline to better design future biped robots.