A robust controller for uncertain systems

The design problem for a precise control system with uncertainty such as parameter variations, nonlinearity and disturbances is investigated in this paper. Treating uncertainties as equivalent disturbances and using the zeroing element concept for the zeroing of equivalent disturbances, a method of designing a robust controller is presented. The new method is composed of two steps. First, a modern or classical method is used to design a controller which satisfies design specifications for the nominal plant; second, based on the system designed by step 1, a design of the robust controller is produced for uncertainties. Combining two controllers to form an optimal robust controller for an uncertain system is investigated. As an example, a turntable control system is designed by using the method presented. Experimental and simulation results for such a system show that the optimal robust controller is successful