Further experimental results on nonlinear control of flexible joint manipulators

Abstract

We focus on the experimental comparison of feedback controllers for flexible joint manipulators. It completes a previous set of experimental results presented by Brogliato et al. (1998), on a 2 degree-of-freedom (DOF) manipulator with a stiff second joint (50 Nm/rad). The process considered is quite different since it consists of a 1-DOF flexible joint manipulator (i.e. a 4th order linear system) with a high flexibility (3.4 Nm/rad). The main goal of the present work is to apply a systematic way of tuning the gains of backstepping- and energy shaping-like controllers, using a method developed for LQ controllers by De Larminat. It is shown that although other linear controllers could be applied to the process tested in this paper, we restrict ourselves to those control laws that extend to the nonlinear general case of flexible joint manipulators, and yield global stability results.