Switched Local Positive Velocity Feedback Controllers: Local Generation of Retraction Forces and inter-joint Coordination during Walking

摘要

In walking the step cycle of any leg can be divided into a swing and a stance phase. During the swing phase the leg can be regarded as an open kinematic chain. Yet in the stance phase this kinematic chain is closed. Because of this, the control effort during the stance phase is much higher than in the swing phase since all legs on the ground have to perform coordinated trajectories both in cartesian coordinates and in the force space. As opposed to classical approaches which solve this control task with central controllers and full knowledge of the body geometry, we introduce a decentral control approach called Switched Local Positive Velocity Feedback (SLPVF). The ingredients for this novel control strategy are elastic joints and positive velocity feedback in each single joint, both of which can be found in insects. This new positive velocity feedback controller switches between two modes of operation depending on the mechanical power generated within the joint. In this paper we develop a technical elastic joint and the corresponding SLPVF controller and finally show their application in a dynamics simulation of a 3-DOF test leg. The coordination of the participating joints is achieved mechanically.