Design of Nonlinear Adaptive Tracking Controllers for Industrial Robots

This paper proposes a controller for a class of industrial robots which fully handles system nonlinearity and adaptively estimates plant parameters. Using a nonlinear input transformation, we obtain a system which is linear in the transformed inputs. The resulting system is then controlled with a continious-time PD tracking controller. The critical part of this scheme is estimating the parameters of the nonlinear input transformation. We estimate them using a least-squares with a forgeting factor based on aperiodic samples of inputs and outputs. Simulation results are presented for a nonlinear three-degree-of-freedom manipulator.