Design of FOPID controller for fractional-order plants with experimental verification

In this paper, a design method is proposed for a robust stabilizing fractional order proportional integral derivative (FOPID) controller for One Non-Integer Order Plus Time Delay plant (NIOPTD-I). The NIOPTD-I model is obtained after reducing the higher order continuous time process model. The FOPID controller is designed by using stability boundary locus method, which satisfies user defined frequency domain specifications phase margin and the gain crossover frequency. A robust control system is designed against gain variations by achieving flat phase condition which is due to zero slope at the gain crossover frequency of the phase plot. Thus robust stabilizing FOPID controller for NIOPTD-I fractional order plant is designed. The applicability of the proposed method is illustrated with simulation example and experimental validation with the liquid level control system. © 2017, Springer-Verlag Berlin Heidelberg.