Position control of the Thomson’s ring system using fractional operators

The position control of a magnetic levitation system, known as Thomson’s ring, is studied in this paper. The design and implementation of three control strategies are presented; the first corresponds to a pole placement control (PPC), the second is a fractional order proportional integral derivative (FOPID) control and the third consists of a sliding mode control (SMC). In all three cases, a fractional order observer is used to estimate the ring speed. A particle swarm optimization (PSO) technique was used in the case of the FOPID control, in order to select the optimal parameters of the controller. Stabilization and tracking experiments are carried out in order to observe the behavior of the controlled system. Also, the effect of external disturbances on the output of the system is addressed.