Contact warning by monitoring nonlinearity of interaction in head disk interface

A contact warning method by monitoring nonlinearity of interaction in head disk interface is proposed, simulated and demonstrated. The analysis shows the nonlinearity of interaction increases with decrease of flying height, the simulation results show that the high order harmonic vibrations of AC frequency can be observed before contact happens when the slider is excited by an AC voltage applied in head disk interface. The experiment results shows the high order harmonic frequencies are observed before the resonating frequency of air bearing is excited by contact. The high order harmonic frequencies are also detectable in the readback signal.