THE DEVELOPMENT OF A NOVEL SUSPENSION ARM WITH 2-DIMENSIONAL ACTUATION, FOR USE IN ADVANCED HARD DISK DRIVES

As magnetic computer disks are developed to ever-greater data storage densities, the accuracy required for head positioning is moving beyond the accuracy provided by present technology using single-stage voice-coil motors in hard disk drives. This thesis details work to develop a novel active suspension arm with 2-dimensional actuation for use in advanced hard disk drives. The arm developed is capable of high-bandwidth data tracking as well as precision head flying height control motion. High-bandwidth data tracking is facilitated by the use of piezoelectric stack actuator, positioned closer to the head. The suspension arm is also capable of motion in the orthogonal axis. This motion represents active flying height control to maintain the correct altitude during drive operation. To characterise the suspension arm's structural dynamics, a high-resolution measurement system based on the optical beam deflection technique has been developed. This has enabled the accurate measurement of minute end-deflections of the suspension arm in 2-dimensions, to sub-nanometre resolution above noise. The design process of the suspension arm has led into the development of novel piezoelectric-actuated arms. In the work involving lead zirconate titanate (PZT) thick films as actuators, work in this thesis shows that reinforcing the films with fibre improves the overall actuation characteristics of the thick films. This discovery benefits applications such as structural health monitoring. The final suspension arm design has been adopted because it is simple in design, easier to integrate within current hard disk drive environment and easier to fabricate in mass. Closed-loop control algorithms based on proportional, integral and derivative (PID) controller techniques have been developed and implemented to demonstrate high bandwidths that have been achieved. The suspension arm developed presents an important solution in head-positioning technology in that it offers much higher bandwidths for data tracking and flying height control; both very essential in achieving even higher data storage densities on magnetic disks at much reduced head flying heights, compared to those in existing hard disk drives

A multi-chanel electrical impedance meter based on digital lock-in technology

Abstract The presented multichannel measuring system working on various frequencies is suitable either for electrical impedance spectroscopy or tomography. The authors of this paper have developed the complete measurement system and a graphical user interface platform. The accuracy of impedance amplitude and phase are 1 ppm and 0.01°, respectively. The basic instrument works with 8 channels and can be expanded to 64 channels with the application of multiplexing or multiple parallel connected instruments in the same system

A scanning tunneling microscope control system with potentiometric capability

Includes bibliographical references.This report starts by describing the background research and work that had already been done on the UCT scanning tunneling microscope (STM). This system is being developed in the Department of Electrical Engineering at UCT. It goes on to describe the continuation of the research work that was done for this dissertation on the STM at UCT. The work was originally started by Dr. Tapson for his PhD (1994). and continued by the author for his MTech degree in ) 997 and 1998. The work was temporary discontinued from May 2000 till August 2002 to enable the author to work as a contract engineer at the Institute of Physics in Basel, Switzerland to learn more about the construction of probe microscopes. The new work evolved around the need to implement scanning tunneling potentiometry (STP) capability in the new STM. This capability should give the end-user the capability of looking at the sub-surface structure of any material on a sub-micron scale. The basic STP function must be implemented in two dimensions in the plane of the specimen. The STM tip is then used as a highly localized voltmeter to sense what the potential distribution is at that point on the surface. The potential information that is obtained is then used to plot two images of the potential distribution over the surface in the X and Y directions. The topographic information is obtained in the usual way from the STM scan. This method gives three collocated imagesas the result and a better understanding of the surface structure is obtained in this way. The penetration depth of the potential scan can be varied by adjusting the frequency of the applied AC signal in the X and Y directions. This use of the skin effect should allow the end user to obtain slices of the surface at various penetration levels of the specimen. These slices will give a picture of what happens from the surface up to a certain penetration depth. The interpretation of these images could be very difficult because the skin effect does not stop at a defined penetration depth. Only the 3 dB point is defined, which means that sub surface structures below the 3 dB point will also have an influence on the obtained image. During the course of the research new hardware and scanning software was implemented to enable the error-free acquisition of new data. This entailed splitting the existing XY controller into three separate parts namely a Communications interface, and two STP measurement boards. This was suggested as one of the conclusions of the MTech thesis results. The PC software stayed the same but for a change in the array size, that holds theacquired data. This was again changed after the work experience in Basel and is explained in chapter 6

NASA Tech Briefs, June 1990

Topics: New Product Ideas; NASA TU Services; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences

NASA Tech Briefs, October 1990

Topics: New Product Ideas; NASA TU Services; Electronic Components and Circuits; Electronic Systems; Physical' Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences

Development of a self-tuned drive-train damper for utility-scale variable-speed wind turbines

This thesis describes the development of a procedure that tunes a wind turbine drivetrain damper (DTD) automatically. This procedure, when integrated into the controller of any utility-scale variable-speed wind turbine, will allow the turbine to autonomously and automatically tune its DTD on site. In practice this means that the effectiveness of the damper becomes independent on the accuracy of the model or the simulations used by the control engineers in order to tune the damper. This research is motivated by the fact that drive-train failures are still one of the biggest problems that stigmatises the wind turbine industry. The development of an automatically tuned DTD that alleviates the drive-train fatigue loads and thus increases the reliability and lifetime of the drive-train is thus considered very beneficial for the wind turbine industry. The procedure developed begins by running an experimental procedure to collect data that is then used to automatically system identify a linear model describing the drivetrain. Based on this model a single band-pass filter acting as a DTD is automatically tuned. This procedure is run for a number of times, and the resulting DTDs are compared in order to select the optimal one. The thesis demonstrates the effectiveness of the developed procedure and presents alternative procedures devised during research. Finally, insight into future work that could be performed is indicated in the last chapter of the thesis

Identification of visual evoked response parameters sensitive to pilot mental state

Systems analysis techniques were developed and demonstrated for modeling the electroencephalographic (EEG) steady state visual evoked response (ssVER), for use in EEG data compression and as an indicator of mental workload. The study focused on steady state frequency domain stimulation and response analysis, implemented with a sum-of-sines (SOS) stimulus generator and an off-line describing function response analyzer. Three major tasks were conducted: (1) VER related systems identification material was reviewed; (2) Software for experiment control and data analysis was developed and implemented; and (3) ssVER identification and modeling was demonstrated, via a mental loading experiment. It was found that a systems approach to ssVER functional modeling can serve as the basis for eventual development of a mental workload indicator. The review showed how transient visual evoked response (tVER) and ssVER research are related at the functional level, the software development showed how systems techniques can be used for ssVER characterization, and the pilot experiment showed how a simple model can be used to capture the basic dynamic response of the ssVER, under varying loads