To expedite design cycles and to evaluate performance of designed hard disk drives, mathematical models to predict position error signal (PES) are needed. Existing mathematical model can successfully predict PES during track following. However, there is no computational efficiency approach to predict PES after a long seek presently. In this paper, we presents a feasible mathematical model to achieve this purpose. Detail mathematical derivations and numerical simulations are also included in this paper. Our mathematical models are capable to obtain reasonable qualitative predications after a long seek.
The objective of this research was to investigate the effects of manufactur ing variables (injection pressure, pre-heated temperature and vacuum assistance) on resin transfer molding (RTM). Specimens were made of 40 plies of TGFC-7628 cloth fiberglass mats or 12 plies of TGFW-600 woven roving fiberglass mats under different process condi tions. The fiber volume contents of the specimens were 50.3 % or 45% in the experiments. The flexural strengths of all the finished products tested by the method of three point bend ing were compared to each other to understand the influences of each process variable on the RTM products. Both the pre-heated temperatures and the injection pressure were found to affect the quality of the RTM product.
This paper is to study how stray magnetic forces encountered in a long seeking process affect position errors of a hard disk drive after it finishes the seek and settles. The study consists of three parts: analysis of stray magnetic forces, numerical modeling, and analysis of numerical results. In the analysis of stray magnetic forces, we lump the stray magnetic forces into three components D1, D2 and D4. Specifically, D1 is a pair of stray magnetic forces in the plane of the voice coil. The two forces act on the two equal legs of the voice coil. In addition, the two forces point to and away from the pivot center, respectively. D2 is a pair of stray magnetic forces out of the plane of the voice coil. The two forces are equal in magnitudes but opposite in directions. The two force components also act on the two equal legs of the voice coil. D4 is identical to D2, except that the two force components in D4 act in the same direction. In the numerical study, we adopt a numerical model that includes a spinning spindle motor, a spinning disk pack with multiple disks, a stationary base plate with a top cover, and a slewing head-stack assembly. Moreover, multiple bearings are present in the model to connect the multiple components. In particular, fluiddynamic bearings connect the rotating spindle and disk pack with the base plate, pivot bearings connect the base plate with the head-stack assembly, and air bearings connect the spinning disk pack with head sliders located at the tip of the slewing head-stack assembly. Also, the numerical model assumes that the head-stack assembly seeks according to a user-specified seeking profile. Numerical simulations show two major conclusions. First, stray magnetic force component D1 does not lead to significant position errors when the head-stack assembly settles. Stray magnetic force components D2 and D4, however, can affect the position errors by significantly exciting torsion and bending modes of the head-stack assembly. Second, a flex cable can significantly increase position errors below 1 kHz during settling.
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