Adaptive Control of a Flexible Robot Using Fuzzy Logic

Abstract

Operational problems with robot manipulators in space relate to several factors, one most importantly being structural flexibility and subsequently significant difficulties with the control systems, especially, for endpoint position control. Elastic vibrations of the links coupled with their large rotations and nonlinear dynamics is the primary cause. This paper presents a control scheme for tracking the endpoint of a two-link flexible robot. The dominant assumed modes of vibration for Euler-Bernoulli cantilever and pinned-pinned beam boundary conditions are coupled with the nonlinear dynamics for rigid links to form an Euler-Lagrange inverse flexible dynamics robot model. A Jacobian transpose control law actuating the robot joints is adapted by a fuzzy logic system (FLS) with link deformation inputs and a single variable output. Results obtained with an FLS adaptive control strategy show significantly diminished vibration amplitudes for both cantilever and pinned-pinned link dynamics and greatly improved control performance compared to the nonadaptive strategy.