An Adaptive Computed Torque Controller for Manipulators with Limited Torque

Abstract

Abstract Computed torque strategies (CTS) have been proposed (see e.g. [1] and references therein) to “linearize” and decouple the robot equations of motion by exact cancellation of nonlinear and crosscoupling terms from the rigid body model of robot dynamics. Computing time limitation and uncertainties, both numerical and of the link dynamical parameters, hamper its practical appliestion. On the other hand, it is now widely recognized [2] that from a control design point of view, the current (torque) limiter is the most significant nonlinearity, which is rarely conside red in the robot control literature. A simple adaptive CTS that takes into account the torque saturation is reported here. Global L ∞ -stability is shown to be guaranteed in the absence of any robot stationarity assumption or prior information regarding dynamical parameters. Simulation results of a 3 degree of freedom manipulator examine the performance of the proposed strategy.