Two degrees of freedom fractional controller design: Application to the ball and beam system.

• A 2DOF fractional order control of a nonlinear and unstable system is investigated in this paper. • Analytical model based method is developed to design the parameters of the fractional order PD controller. • The fractional order controllers of the inner and outer loops are tuned to have a constant phase margin of the open-loop. • Based on experiment on a real ball and beam system, performance of the proposed controller is highlighted. Control engineers and researchers face challenges to design an efficient controller for Ball and beam system due to its nonlinear and unstable properties. This paper investigates two Degrees of Freedom fractional order control of the ball and beam system. It involves the model based method to design controllers' parameters for the corresponding linear model. The fractional order controllers are specially tuned to have a constant phase margin of the open-loop. This characteristic ensures the robustness of the controllers to the variations of system gain. This paper presents a proper evaluation and comparison between integer and fractional order controllers. Performance of each controller is evaluated in terms of set-point tracking, disturbance rejection, and robustness. The comparison between two controllers is validated through both simulation and experimental results. Strengths and weaknesses in the real-time control are also indicated. [ABSTRACT FROM AUTHOR]