Learning control for a class of nonlinear systems and its application to a direct drive manipulator

The authors propose an iterative learning control method using the relative degree of a system for precise tracking control of a class of nonlinear systems over a finite time interval. The class of nonlinear systems, in which the iterative learning control is applied, can be extended by using the proposed method. A sufficient condition is derived for guaranteeing a uniform convergence to the desired output. The results obtained for a class of nonlinear systems are shown to be a generalization of the existing results for linear time-invariant systems. To show the effectiveness of the proposed method, tracking control of a single-link manipulator driven directly by a brushless DC motor is studied