Actuator is a part of control system that converts the control signal to proper energy for process control. Actuator saturtion is one of unwanted phenomenon in industrial processes. Saturation in process means at least one part of the system has its maximum or minimum efficiency and it may cause problems such as unwanted transient response or even unstablity in industrial processes. Due to these problems saturation compensation is essential in control systems. Saturation occurs in both amplitude and rate of actuators. So far many methods have been developed to deal with input saturation for linear and nonlinear systems. In this thesis the case we have been use to simulate sturation compenstion methods is superheater system. Superheater is a heater that increase saturated steam temperature and turn it to superheated steam. The equations of superheater have been explained. One of the common methods to control nonlinear systems is to design the linear controller for the linearized model of nonlinear system. Nonlinear model linearization have been completed at equilibrium point. Some parameters of the superheater model are not known due to intense changes of temperature and pressure in superheater. To design the controller with this uncertainties an adaptive controller is proposed. The model reffrence adaptive controller for linearized model have been designed. To compensate input saturation, two methods have been used. First an adaptive model recovery Anti windup controller designed by adding an extra term to control law. Stability and error convergence to zero is proven. Another method to compensate the saturation effect is designed to change the adaptive law and useing states of a filter of nominal input and saturated input. To design controller for nonlinear model of superheater, feedback linearization method is employed. Due to uncertainties the control law is adaptive. Also backsteping controller is another method used to design controller for nonlinear model. An auxillary system is proposed to compensate the saturation effect .stability and error convergence to zero is proved. Key Words : Actuator saturation, Superheater, Adaptive control, Feedback linearization, Saturation Compensation, Back stepping
