Methods for controller tuning for unstable systems

The paper deals with tuning of controllers for unstable plants. The controllers are presented for two types of plants: the unstable first order system and the unstable second order system, both with the uncertain plant gain. The control system design based on the algebraic approach using polynomials, the internal model control (IMC) structure and neuro-fuzzy inference system controller is used. The designed controllers are verified and compared by simulations on illustrative examples. The presented results show satisfactory control responses for the tracking of the step reference as well as for the step load disturbance attenuation.