Controlling an Anthropomimetic Robot: A Preliminary Investigation

Abstract

The human body has a complex skeleton, giving a very high number of degrees of freedom, and is actuated by a large number of elastic elements – muscles and tendons. As a consequence, it has extremely challenging dynamics. Conventional humanoid robots use reduced degrees of freedom and traditional stiff actuators, and so fail to capture or exploit the important dynamic aspects of the human body. It has proved possible to build robots that mimic the human body – anthropomimetic or ‘musculo-skeletal’ robots – but the control of such robots will require very different methods from those used in existing humanoid robots. This paper reports the results of a preliminary investigation of the control problems using SIMNOS, a physics-based model of the anthropomimetic robot CRONOS. The transient and steady state effects of load changes on two simple feedforward methods for maintaining arm posture are assessed. The addition of a feedback controller reduces the steady state effects considerably, but still shows oscillatory transient effects. However, by combining this feedback controller with a velocity-limiting feedforward element, it proves possible to make smooth and reasonably accurate changes of posture under conditions of constant load.