A Magnetic Rotary Encoder for Patterned Media Lithography

Bit patterned media (BPM) is expected to enable the magnetic storage density in hard disk drives (HDDs) beyond 1 Tb/in2. BPM uses isolated magnetic islands to record the data information. However, the large volume fabrication of those patterned media disks at an affordable cost is a challenge for this new technology. A master template is the first step for patterned media fabrication. Using nano-imprint technology, the master template can be replicated to tens of thousands of pattern disks. A rotary electron beam lithography machine or plasmonic nanolithography machine is recommended to assist in the fabrication of the master template. In both systems, a high resolution encoder system for positioning in the rotary lithography machine is necessary. In this paper, a magnetic rotary encoder system is introduced. The encoder system can be operated at several thousand revolution per minute (RPM). The scale pitch is 90 nm which is one to two orders smaller than current optical encoders. The resolution is about 2.8 million counts per revolution (CPR). A flying magnetic head is used to retrieve the readback signal from the magnetic encoders. A field programmable gate array (FPGA) is implemented to finish the high speed signal processing and provide a digital format encoder signal to trigger the lithography machine at a rate of several Mega Hertz.

Asymmetric Arm Design on Delta Robot System

The Delta robot system is widely used in high speed (4 cycles/s at 25-200-25 mm) pick-and-place process in production line. Some industrial applications include photo-voltaic (PV), food process, and electronic assembly, and so on. The energy saving and system cost are two critical parameters for designing the next generation of pick-and-place system. To achieve these goals, a light-weight moving structure with sufficient strength to overcome the excited vibration will be one of the solutions. In this paper, an asymmetric arm design is proposed and fabricated to gain the benefit of strength-to-weight. The asymmetric arm is designed by reinforcing a specific direction and is validated the vibration suppression capability both by simulation and experiment. A position controller that is derived from the kinematic model of Delta robot is utilized to manipulate the robot under a forward-backward motion with a polynomial trajectory with 200 mm displacement. The residual vibration, then, was measured after the forward-backward motion to compare the settling performance between symmetric- and asymmetric-arms on the Delta robot system, respectively. The results conclude as following: (1) The asymmetric arms perform slightly worse (0.03 sec more in settling time) than symmetric arm but there is 15% weight reducing comparing to symmetric arm. (2) Both energy saving and system cost reducing would be achieved by utilizing actuators with lower power consumption and fabrication on carbon fiber arms with mass customization.

The Influence of Temperature and Humidity on the ABS Contaminations

In order to increase the areal recording density of hard disk drive beyond 1 Tb/in2, the flying height has to be reduced to several nanometers. At such a low flying height, particles and lube contaminations, which could lead to a transient vibration and flying height modulation in a hard disk drive, are becoming more and more serious. In this work, it studies the influence of temperature and humidity on the air flow pattern, velocity and shear stress distribution on the air bearing surface (ABS) of slider using a self-developed simulator. It first solves the generalized steady state Reynolds equation with slip boundary conditions. Then it solves the reduced Navier-Stokes (N-S) equation with slip boundary conditions to get the air velocity distribution, i.e., identify the air flow pattern on the ABS. The stagnation lines and areas of air flow are calculated to judge the contamination area. On the other hand, it calculates the air shear stress distribution on the ABS since the air shear stress is the main driving force for the lubricant and particles migration and contaminations. After that, the impact of the temperature and humidity on the air flow pattern is analyzed by applying the Sutherland equation and mixed gas viscosity calculation equation. The simulation results indicate that the impact of temperature and humidity on the air flow pattern is un-conspicuous. However, the peak velocity of the air flow, which contains no vapor, reduces almost 10%, and the peak air flow shear stress increases less than 1.5%, with the increase of operational temperature from 298.15 K to 343.15 K. In addition, the peak velocity of the air flow increasing almost 4%, and the peak air flow shear stress keeps almost same, with the increase of the operational mole fraction of vapor from 5% to 15%.

System Dynamics and Disk Drive Head Position Error Prediction in a Data Storage Box

Disk drives are packed at ever dense arrangement in a modern data storage system, internal and external mechanical disturbances can have a great effect to disk drive’s read and write performances. The VCM torque generated during seeking affects its own as well as neighboring drives head position. In this study, we modeled a storage box with multiple HDDs installed to obtain mechanical system transfer function. The mechanical excitation is characterized by VCM torque, and HDD operational vibration behaviors on linear and rotational shakers are measured. A system level hybrid method predicting HDD head position error in a data storage box is described, and both analytical and measured results will be presented.

A New Prediction Model on the Luminance of OLEDs Subjected to Different Reverse Biases for Alleviating Degradation in AMOLED Displays

Organic light-emitting diodes (OLEDs) have drawn much attention in areas of displays and varied illumination devices due to multiple advantages, such as high brightness, high efficiency, wide viewing angle, and simple structure. However, the long-time degradation of OLED emission is a serious drawback. This degradation was investigated by past works, which pointed out that the degradation was induced by high-density currents through OLED component under the long-time operation [1][2]. Proposed by a past work [3], different reverse biases was imposed on OLED components in display frames to alleviate the long-time degradation on OLEDs. Most recently, along with the reverse bias, new pixel circuits [4][5] for AMOLED displays are designed to alleviate OLED degradation, thus successfully extending OLED life time. However, since emission luminances in different frame times during AMOLED displaying differs significantly for displaying varied images, the OLED degradation evolves in a highly unpredictable fashion. In this study, based on valid theories, the voltage across the OLED is first used as indicator for OLED degradation. Then the relation between the level of OLED degradation, in terms of OLED’s cross voltage, and the history of imposing reverse biases are precisely modeled. With the model, the degradation of the OLED under reverse bias to extend lifetime can be successfully predicted. Based on this model, engineers can then optimize the applied reverse bias on OLEDs to maximize the OLED lifetime for varied display requirement.

Investigation of Slider Vibrations and Vibration Mode Changes in Helium-Air Gas Mixtures

A numerical model for the simulation of slider vibrations in helium-air gas mixtures has been developed. The physical properties of the helium-air gas mixture, such as density, mean free path and viscosity, were determined to calculate the dynamic flying characteristics of a slider using the CMRR air bearing simulator. Frequency analysis shows that the helium percentage in the gas mixture can shift the second pitch mode of the slider to a higher frequency.

Numerical Investigation of Thermal Effects on a HAMR Head-Disk Interface

Heat-assisted magnetic recording (HAMR) is one of prospective high density recording technologies in current hard disk industry. It requires heating a spot on the recording media with the laser beam to overcome the superpara-magnetic limit. The heat produced by laser beam causes the temperature field on the hard disk surface to be highly non-uniform, which may lead to unexpectedly severe lubricant loss, or even the failure of the whole HAMR system. In the meantime, the heat loss caused by the optical delivery system may cause unwanted thermal protrusion on the slider body, which may affect slider’s flying stability in the end.

Design and Development of a Wireless Fall Detection Module for Homecare

A novel wireless circuit module is designed in this study to perform ubiquitous fall detections and then real-time fall detections of help messages. It is a common trend that as the demand for living quality increases tremendously while the technologies of electronics and medicine advances greatly, personal cares are elevated to the next level. As for the aging society, the issue of injuries due to falls among senior population arises rapidly [1,2]. Costly prices are often paid as the elderly falls without notice from companions at the site. Therefore, various modules and/or systems of automatic and wireless fall detection are developed into a past pace. Such fall-detection modules are demanded to be able to automatically detect falls of subjects and then send the help message to a remote hospital for an immediate help.

A Nonlinear Feedback Control Scheme for Transient Performance Enhancement in Hard Disk Drives

This paper aims to develop a nonlinear control algorithm to break the limitations of linear PID controls and improve the transient performance during the short-span track seeking / settling in hard disk drives (HDDs). It is designed based on a baseline PID controller which is well-designed to obtain good track following performance. The control algorithm is a combination of a nonlinear PID controller and a nonlinear turbo controller (NTC): when the position error signal (PES) is large, NTC assists the nonlinear PID controller to rapidly reduce the error; when PES is small, NTC is turned off to avoid possible chattering and ensure good steady state performance. As PES becomes even smaller, the nonlinear PID controller is reduced to the baseline PID controller to keep good steady state performance.

Efficient Air Bearing Modeling for Operational Shock Analysis in 2.5-Inch HDD

As use of mobile computing devices has spread rapidly, it is very important to accurately analyze and predict anti-shock performance of the HDD system. In this paper, we proposed an efficient air bearing modeling method to analyze op-shock performance for the in 2.5-inch HDD system with ramp-disk contact behavior. We first constructed the decoupled approach method using linear air bearing springs in finite element method and used the Lagrange multiplier method for contact modeling between disk and ramp. With the constructed finite element model, the effect of linear air bearing stiffness was investigated in the decoupled method. We found that air bearing stiffness affects the behavior of the slider dominantly in the HDDs system with ramp-disk contact. Based on the numerical results, the advanced method able to efficiently reflect air bearing characteristics was proposed and evaluated.