Nonlinear Vibration Control for a High-T_c Superconducting Levitation System

The present article discusses a modeling and control of high–T_c superconducting levitation system. The paper first clarifies analytical expressions for obtaining nonlinear levitation force given by the present author, then presents a vibration control method in which feedback currents involving frequency weights. In the method, an addition of a square of the displacement and currents in a 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 nonlinear vibration will be reduced. Numerical calculations have been carried out for some typical problems. To validate the present method, experimental tests also have been carried out.