Decoupled Stabilization of Spring-Mass Rigid-Body Locomotion

Stable and reliable legged locomotion is critical for humans and humanoid robots. In the study of legged locomotion, simple models consisting of point-mass bodies and massless legs with telescoping actuators have been insightful. Several variants have been used, including the telescoping leg as a general force actuator [1], a simple passive linear or nonlinear spring [2], and a spring in series with a general force actuator [3]. These models serve as analogs that simplify the problem of understanding the mechanics of legged locomotion of real animals. One of defects of these simple models is the representation of the body by a point mass. Hence, trunk stabilization is not addressed. Nevertheless, this is a major problem in human and humanoid locomotion. In this study we propose a novel decoupled strategy to stabilize the trunk. First, we describe how this decoupled strategy works theoretically. Then, we present a case study based on the CT-SLIP model. Finally, we summarize the work and its expected impacts.