Nonlinear Adaptive Control of an N-Link Robot with Unknown Load

Abstract

An N-link planar robot holding an unknown load and driving its end-effector along a prespecified trajectory is studied. The effect of the unknown load is discussed, and the nonlinear dynamic equation with the unknown load is derived. A non linear model-reference adaptive control algorithm is devel oped for tracking of a trajectory that is a piecewise continuous function of time. The tracking error dynamics represent a linear stable system with persistent disturbances, and the Germaidze-Krasovskii theorem in the Lyapunov second method is applied to show the error stability. Digital com puter simulations show the effectiveness of the adaptive con trol algorithm for the unknown load with mass 2 kg, 5 kg, and 10 kg. The effect of the computation time delay on the system dynamics is also addressed.