Vibration control for a high-Tc superconducting non-linear levitation system

In the present paper the modelling and control of a high-Tc superconducting levitation system are discussed. First, the analytical expressions for obtaining the non-linear levitation force, given by the present author, are clarified; and then a vibration control method is presented in which feedback currents involving frequency weights are used. In the method, the square of the displacement in the frequency domain is taken as a cost function. Optimal coefficients of the transfer function of the controller are obtained by minimizing the cost function. Hence, the spillover instability due to the non-linear vibrations will be reduced. Numerical calculations have been carried out for some typical problems. To validate the present method, experimental tests have also been carried out.