Disk drive pivot nonlinearity modeling. I. Frequency domain

This paper describes studies done at HP Labs on the actuator pivot bearing nonlinearity of a small disk drive. The nonlinear frictional behavior of the pivot bearing varies with actuator position, from drive to drive, and with time and temperature. This nonlinear behavior has made the traditional linear disk drive models inadequate. The paper shows how the swept-sine/describing function method was used to develop a nonlinear model of the pivot. This model departs from the classical friction models, but does a good job of matching laboratory frequency domain measurements.