Stabilizing control strategies: A comparison between the fractional order controller and the IMC

Magnetic levitation systems are widely used in practice and especially as a research topic due to their nonlinear and unstable characteristics. In this paper, two rarely used control algorithms for unstable systems are proposed: a special type of a fractional order controller and an IMC (Internal Model Control) based controller. The two control algorithms are compared and tested on an experimental laboratory scale magnetic levitation system. The results show that both control strategies may be used as a viable option for controlling such types of systems, with the fractional order controller ensuring a better closed loop performance in comparison with the IMC algorithm. Robustness issues are also addressed, with the fractional order controller turning out to be an adequate alternative to compensate for modeling uncertainties and variable process parameters.