ABSTRACT
This chapter presents an introduction to the main problems and principles of robust control based on certain transfer function approaches. According to Kharitonov’s theorem, in order to guarantee robust stability of the given interval polynomial, it is sufficient to test the stability of the different Kharitonov polynomials. Control engineers are always aware that any design of a controller based on a fixed plant model is very often unrealistic. This is because there is always a nagging doubt about the performance specifications if the model on which the design is based deviates from the assumed value over a certain range. Robust control refers to the control of uncertain plants with unknown disturbance signals, uncertain dynamics, and imprecisely known parameters making use of fixed controllers. That is, the problem of robust control is to design a fixed controller that guarantees acceptable performance norms in the presence of plant and input uncertainty.
