Design of fractional order controllers satisfying frequency domain specifications for magnetic levitation system with time delay

Abstract

The paper delineates the concept of applying Fractional Order (FO) controller design approach with the given Gain Margin (GM) and Phase Margin (PM) for different second order nonlinear plants. Afterward, the proposed strategies are successfully tested and verified on Magnetic Levitation (Maglev) system transfer function with certain time delay. Here, the two controller design approaches namely Modified Synthesis Method (MSM) and Improved Synthesis Method (ISM) which are mathematical extension of Synthesis Method (SM) are proposed. These Synthesis Methods perform a mathematical simplification of the entire system transfer function based on an open loop bode ideal transfer function. By using frequency domain analysis based on Bode plot and transient analysis based on step response the behavior of highly nonlinear systems is tested by introducing different time delays in the plant transfer function. The comparative study based on time as well as frequency domain analysis of nonlinear Maglev system reveals that amongst the three different controller design techniques, the Improved Synthesis Method (ISM) outperforms the other two techniques.