Robust controls for flexible joint robots: a single link case study with unknown joint stiffness parameter

Abstract

We study the problem of a single flexible joint robot with an unknown parameter: the joint stiffness which is difficult to determine in experimentation. The controller must take into account the resonance phenomenon that induces oscillations at the load side. We present three control laws that have robustness properties. The first two control laws, H/sub /spl infin// and H/sub 2/ are obtained by minimization of a transfer function norm from an extended plant. The third one is based on the pole placement by using only four parameters : a control horizon and a filter horizon, and two damping factors. The three control laws are robust since they guarantee tracking performance and accuracy in the presence of high uncertainties including unknown joint elasticity, and external output perturbation rejection.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>