<title>Robust control of a shape-changing flexible robot arm</title>

Abstract

We investigate the robust vibration control of an elastic robot arm. This robot arm, called the Elasticarm, is a new design that exploits the flexibility of a beam to generate motion that usually requires an elbow. Shape control is accomplished using a system of cables and motors. The resulting structure exhibits lightly damped, large-scale vibrations. The vibration control problem for the Elasticarm is challenging because the natural frequencies depend on the static shape of the beam. In this paper we compare two simple controllers that are designed to be insensitive to plant uncertainty and to offer satisfactory performance. The first controller is an H<SUB>(infinity</SUB> ) design using an imaginary axis shift. The second controller uses direct strain feedback to increase vibration damping. Experimental results show that both controllers maintain adequate performance across a wide range of configurations.