Evaluation system for residual vibration from HDD mounting mechanism

An evaluation system for calculating the residual vibration caused by a HDD (Hard Disk Drive) mounting system is presented. It contains both the elements for measurement and analysis. The PES (Position Error Signal) of an ideally balanced rigid rotary actuator depends on the rotational vibration of the HDD, specifically at lower frequencies. First, this evaluation technique obtains a measurement of the transfer function of the HDD rotational acceleration over actuator current. Next, using the measured power spectrum of the actuator in combination with the HDD's tracking error transfer function, the response of the entire HDD and mount system is calculated in the frequency domain. Finally the time domain system response is calculated by computation of the Inverse Fast Fourier Transform (IFFT) of the frequency response solution, assuming a random phase of the input force. Good correlation is obtained between measured and calculated system responses. Experimental result show that the dominant residual vibration is caused by the mounting mechanism response and that both the HDD and HDD mount system need to be evaluated and understood as a system, in order to achieve higher TPI (Track per inch) in the future.