“…The assumption that the bounce motion is prescribed is valid because, theoretically, one can adjust by varying the electro-magnetic field between the rotor and Equation (41) is a quasiperiodically driven Mathieu equation with cubic nonlinearity and external forcing. This equation has been extensively studied [7]- [10] for the case of no substrate motion, that is, when . In [7], it is shown that in the nonlinear Mathieu equation, one obtains finite-amplitude motion, which may be quasiperiodic or chaotic, due to the nonlinear resonance in contrast to the linear Mathieu equation where instability implies unboundedness.…”