Mitigating shock of operating HDDs using smart suspensions
Djati Wibowo Djamari
Date of Issue2010
School of Mechanical and Aerospace Engineering
Seagate Technology International
Small form factor (1” HDD) and 2.5” hard disk drives are widely used in mobile consumer electronics. Due to their mobile applications, mobile HDDs are susceptible to an environmental shock/ vibration. The shock/ vibration can be very severe that can damage the HDDs and the data stored in it. In this thesis, we propose several different shock/ vibration isolation techniques to reduce the risk of head slap which can happen if the HDD is subjected to a very severe shock. These techniques are compared and documented in this thesis. The core of this thesis is divided into two parts. The first part discusses the techniques to mitigate the shock in 1” HDD, in which we use Seagate ST1 as our case study. The first technique is to use a cantilever beam as an external shock isolator. The technique covers the study of the cantilever beam natural frequency, the cantilever beam damping ratio, and the mechanical properties of the HDD’s mountings; which can reduce the shock input significantly. A Simulink model is first created to help develop the shock isolator. The model is created using mode superposition and reduced mode method. The final design which is created in Simulink – MATLAB® is then compared with a finite element model in ANSYS. Simulation results show that the cantilever beam shock isolator is able to protect the micro HDD from operational shock up to 1000 G’s 0.5 ms and has increased the ST1 shock tolerance by 77%. As a comparison, we have designed another type of external shock isolator for the ST1 using elastomeric materials. The elastomer layers are added beneath the base plate of the ST1 and outside of the ST1 case. The analysis of the elastomeric shock isolator system is done in ANSYS. The results show that the cantilever beam performs better than the elastomeric system to reduce the shock to the HDD.