Restricted trajectory tracking in nonlinear systems

The exact linearization of nonlinear control systems provides a useful method for designing feedback controllers based on the linear model in which the nonlinear plant is transformed. This paper deals with three drawbacks involved in this method when used for engineering applications, specially for solving the trajectory tracking problem: 1) the feedback control must be bounded, with previously set bounds, 2) the evolution of the state variables must lie within a determined region of the state space, and 3) all the system states are needed in order to design the closed - loop tracking control. Conditions for satisfying the above mentioned requirements are given. A feedback control that solves the trajectory tracking problem with the imposed constraints is designed. The state estimates are given by a nonlinear reduced - order observer. An application to a robot manipulator is shown.