Linearization and PID parameters design for nonlinear systems

Proportional plus integral plus derivative (PID) controller design techniques for nonlinear systems are presented. Lyapunov´s linearization theorem is applied to a nonlinear system at an operation point. After the linearized model is obtained, a PID controller can be designed for the linearized model and the controller can then be applied to the original nonlinear counterpart at the operation point. For systems with hard nonlinearities, a multiloop control configuration is utilized to solve the problem associated with the uncontrollability due to the existence of hard nonlinearities. Theoretical background and computer simulation results are shown