Modeling and Control of a Compliantly Engineered Anthropomimetic Robot in Contact Tasks

This paper attempts to develop a dynamic model and design 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 ensure safe interaction with humans in a human-centered environment, 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 is based on 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 the theory of robustness in order to extend control to the multi-jointed robot body. INTRODUCTION Anthropomimetics refers to a new kind of robotics which copies the human body as faithfully as possible with the aim of achieving a level of performances (diversity of motions, maneuverability, etc.) comparable with that of a human. This amounts to a return to the origins of robotic science – creating an artificial man [1]. This paper attempts to develop an appropriate dynamic model and then to design a controller for an existing anthropomimetic humanoid – ECCEROBOT 1 . ECCEROBOT has joints driven by antagonistically coupled DC motors. The two joint motors, the agonist and antagonist, working through tendons, mimic muscles. Since the robot is expected to work in a human centered environment and in the presence of humans, emphasis is given to safe interaction with the surroundings. To achieve this safety, the robot features passive mechanical compliance, which is implemented by placing elastic springs in the tendons. 1 EU FP7 project: „Embodied Cognition in a Compliantly Engineered Robot“ (www.eccerobot.org)