Closed loop identification of uncertain systems

Feedback is an important element in practical systems. However, it brings challenging situations in its route. In this chapter, we deal with the closed-loop identification of a two-tank process used in industry. The identified model is then utilized to develop H∞ and sliding mode controllers to develop robustness of the system. It is shown that these controllers guarantee a satisfactory performance in the face of both model/parametric uncertainties and external disturbances. The designed controllers have been successfully tested through extensive simulation. In addition, this chapter shows that the designed linear and nonlinear robust controllers far outperform traditional controllers such as P, PI, and PID in the face of parametric model uncertainties and the effects of external disturbances. The successful use of the designed robust controllers, which are H∞, sliding-mode and high-order sliding mode controllers encourage their extension to other physical systems as well.