Vibration analysis and control design comparison of HDDs using fluid bearing and ball bearing spindles

This paper identifies the system model and major disturbances in a hard disk drive (HDD) with fluid bearing spindle motor and applies linear matrix inequality (LMI) approach to design an H₂ controller for the HDD. Experimental measurement of the head´s position signal in ontrack mode is used to determine the spectrum of the position. The modeling of disturbances is based primarily upon the spectral decomposition of the position signal and is appropriate when the measurement point of position error signal (PES) is not available on HDD. Upon determining the disturbances, an H₂ controller is designed via LMI approach to achieve a minimal track mis-registration (TMR) for the HDD. The simulation results show the effectiveness of the H₂ controller to minimize TMR. Also, the performance comparison of H₂ control in the fluid bearing drive and a ball bearing drive is made.