Anthropomimetic robot with passive compliance - Contact dynamics and control

This paper develops a dynamic model and designs a controller for a fully anthropomorphic, compliantly driven robot. To imitate muscles, the robot\´s joints are actuated by DC motors antagonistically coupled through tendons. To facilitate safe interaction with humans, the robot exploits passive mechanical compliance, in the form of elastic springs in the tendons. To enable simulation, the paper first derives a mathematical model of the robot\´s dynamics, starting from the "Flier" approach. The control of the antagonistic drives uses a biologically inspired puller-and-follower concept where at any instant the puller is responsible for the joint motion while the follower keeps the inactive tendon from slackening. In designing the controller, it was first necessary to use the advanced theory of nonlinear control for dealing with individual joints, and then to apply robust control theory in order to extend control to the multi-joint robot body.