Passive Dynamic Walking with a Torso Coupled via Torsional Springs

Abstract

The passive dynamic walker is well known for its success in human mimicry; however, the torso, an important part of humans and human-like biped robot, is usually ignored in the model. In this paper, a fully passive torso is coupled to the passive dynamic walker via two hip torsional springs. The performances of the walker are studied by means of numerical simulation, and the benefits brought by the torso are revealed. Comparisons with the walker without a torso are performed. On a regular slope, the gait's existence and specifications are studied with respect to the slope angle and the spring coefficient. An interesting dynamical phenomenon of having two stable walking cycles is observed, and the differences between them are presented via a parametric study. The ranges of stable walking slopes and gait performances are significantly improved. On an irregular slope, the disturbance rejection ability (DRA) is measured for three types of disturbances. The slope range of stable gait with strong DRA is significantly extended. The walker with a torso is more flexible by adjusting the slope angle, the spring coefficient and its initial state. The unique properties of our model can be utilized to design humanoid robots and walking enhancing equipment.