Magnetic levitation system an application of the Bode's theorem

A magnetic levitation lab set is used to illustrate the perfoimance limitation of a control system design. It is pointed out that the stability of a magnetic levitation system can be treated thoroughly by using the linearization equations, therefore the performance of the system becomes the main concern of the design. But the system performance (sensitivity) is limited by the Bode's integral theorem. The influence of the horizontal floating of the ball on the system bandwidth is also discussed. The achievable minimum of the sensitivity of the maglev system is obtained by using the Bode theorem and is verified by experiments. Based on the integral constraint, the achievable performance of the system can be predicted during the design stage, and it is meaningful for practical applications.