Introduction and realization of four fractional-order sliding mode controllers for nonlinear open-loop unstable system: a magnetic levitation study case

Abstract

The concept of magnetic levitation attracts the attention of researchers and developers on the global platform for its serviceability in both industrial and research applications. Sliding mode controller is a nonlinear and robust control strategy to provide efficient control over variable structure systems. This paper is initiating with nonlinear modelling of magnetic levitation system dynamics. Various sliding mode controllers for controlling the current through electromagnetic coil to levitate the ferromagnetic ball are presented. This paper is mainly focusing on design robust and energy-efficient fractional sliding mode controller for a nonlinear system. Four novel controllers called fractional static sliding mode controller, fractional integral static sliding mode controller, fractional dynamic sliding mode controller and fractional integral dynamic sliding mode controller are proposed. Stability proof of Lyapunov criteria for the proposed controller has been done. Performance of the proposed controllers is analysed in comparison with the existing sliding mode controllers. Experimental validation is done on a benchmark Feedback 33–210 magnetic levitation system.