A passivity based stability analysis for a fuzzy PD+ control for robot manipulators

In this paper we present a passivity analysis for a motion control scheme, based on a fuzzy system for tuning the PD gains of the well known PD+ tracking controller for robot manipulators. We demonstrate, by exploiting the full nonlinear and multivariate nature of the robot´s dynamics and its passivity property, that the overall closed loop system is asymptotically stable. In this control scheme, the fuzzy logic system plays the role of a tuner of the robot controller gains. We show that the closed loop system can be seen like two interconnected subsystems, where the nonlinear feedforward block is passive and the nonlinear feedback block is input strictly passive