Head-Disk Proximity Sensing Using Contact Sensors in Hard Disk Drives

In this paper, a new approach for predicting the touch-down power (TDP) of a thermal flying-height control slider is presented. The method utilizes the contact sensor to sense head-disk proximity before actual head-disk contact. This is accomplished by measuring the contact sensor voltage in response to a step in heater power while decreasing the flying height of the slider. From the step response data, the transfer function from heater power to contact sensor voltage is estimated as a function of flying height using the step realization algorithm. The effect of step height is investigated and it is shown that the coefficients of the transfer function can be used to predict the TDP without having to perform a complete touch-down measurement.