Wong Chun Kit. / Thesis submitted in: October 2006. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 73-76). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Background and Motivation --- p.1 / Chapter 1.2 --- Objectives --- p.4 / Chapter 1.3 --- Contributions --- p.4 / Chapter 1.4 --- Thesis Outline --- p.5 / Chapter 2 --- Digital Signal Processing --- p.6 / Chapter 2.1 --- Introduction --- p.6 / Chapter 2.2 --- Discrete-time Signals and Systems --- p.7 / Chapter 2.2.1 --- Discrete-time Signals --- p.7 / Chapter 2.2.2 --- Discrete-time Signal Processing Systems --- p.9 / Chapter 2.2.3 --- Linear Time-Invariant (LTI) Systems --- p.10 / Chapter 2.3 --- Finite Impulse Response (FIR) Filters --- p.13 / Chapter 2.3.1 --- Introduction --- p.13 / Chapter 2.3.2 --- Windowing FIR Filter Design Method --- p.15 / Chapter 2.4 --- Infinite Impulse Response (IIR) Filters --- p.17 / Chapter 2.4.1 --- Introduction --- p.17 / Chapter 2.4.2 --- Bilinear Transform IIR Filter Design Method --- p.18 / Chapter 2.4.3 --- Spectral Transformations of IIR Filters --- p.22 / Chapter 2.5 --- Comparison on FIR and IIR Filters --- p.25 / Chapter 2.6 --- Digital Signal Resampling --- p.26 / Chapter 2.6.1 --- Introduction --- p.26 / Chapter 2.6.2 --- Resampling by Decimation --- p.26 / Chapter 2.6.3 --- Resampling by Interpolation --- p.28 / Chapter 2.6.4 --- Resampling by a Rational Factor --- p.29 / Chapter 2.7 --- Introduction to Dual Fixed-point (DFX) Representation --- p.30 / Chapter 2.8 --- Summary --- p.33 / Chapter 3 --- Lyon and Mead's Cochlea Model --- p.34 / Chapter 3.1 --- Introduction --- p.34 / Chapter 3.2 --- Digital Cochlea Model: Cascaded IIR Filters --- p.37 / Chapter 3.2.1 --- Introduction --- p.37 / Chapter 3.2.2 --- Bandwidth and Centre frequencies --- p.38 / Chapter 3.2.3 --- Zeros and Poles --- p.39 / Chapter 3.3 --- Modifications for Decimated Cochlea Model --- p.41 / Chapter 3.3.1 --- Introduction --- p.41 / Chapter 3.3.2 --- Aliasing Avoidance --- p.42 / Chapter 3.3.3 --- Coefficient Modification after Decimation --- p.43 / Chapter 3.4 --- Summary --- p.47 / Chapter 4 --- System Architecture --- p.48 / Chapter 4.1 --- Introduction --- p.48 / Chapter 4.2 --- Hardware Platform and CAD Tools --- p.48 / Chapter 4.3 --- Sequential Processing Electronic Cochlea --- p.51 / Chapter 4.3.1 --- Pipelining - An Interleaving Scheme --- p.53 / Chapter 4.3.2 --- Decimation in Sequential Processing Electronic Cochlea . --- p.54 / Chapter 4.3.3 --- Multiple Sequential Cores --- p.55 / Chapter 4.3.4 --- Architecture of the DFX Filter Computation Core --- p.55 / Chapter 4.4 --- Summary --- p.60 / Chapter 5 --- Experimental Results --- p.61 / Chapter 5.1 --- Introduction --- p.61 / Chapter 5.2 --- Testing Environment --- p.61 / Chapter 5.3 --- Performance of the Sequential Electronic Cochlea --- p.63 / Chapter 5.3.1 --- Comparisons --- p.63 / Chapter 5.4 --- Summary --- p.69 / Chapter 6 --- Conclusions --- p.70 / Chapter 6.1 --- Future Work --- p.72 / Bibliography --- p.73

In this thesis, the c-axis-oriented AlN films were deposited on piezoelectric substrates, lithium niobate (LiNbO3), ST-Quartz, and non-piezoelectric substrate, silicon (Si), by reactive rf magnetron sputtering. AlN films were deposited with the nitrogen concentration (N2/Ar+N2) of 20¡ã80%, the chamber pressure of 1¡ã15mTorr, the rf power of 200¡ã450W, the deposition time of 1~3 hours and the substrate temperature of 100¡ã400¢J. The correlation between growth parameters and piezoelectric coefficients will be investigated by XRD¡Bd33 and K2 analysis in this study. The experimental results showed that the values of d33 become larger as the intensity of X-ray is stronger. It can also be concluded that the smaller the FWHM of (002) XRD peak is, the larger the value of d33 is. With various sputtering parameters, the K2 values exhibit diversely. The multilayer structures of AlN/LiNbO3 and AlN/ST-Quartz both make lower values of K2. In general, by combining the higher K2 and d33 values of LiNbO3 and ST-Quartz with high wave velocity of AlN, the high-frequency with high performance SAW devices can be obtained.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 253-262). Available also in a digital version from Dissertation Abstracts.

Electromechanical actuators are becoming an increasingly popular alternative to traditional hydraulic actuators for ship, aircraft, vehicle suspension, robotic, and other applications. These actuators generally include an electric motor, gear train, bearings, shafts, sensors, seals, and a controller integrated into a single housing. This integration provides the advantages of a single shaft, fewer bearings, and ultimately, reduced weight and volume. Research has shown that the motor and gear train are the most critical, performance-limiting components in an actuator, and balancing the performance parameters (torque, weight, inertia, torque density, and responsiveness) among them is not trivial. The Robotics Research Group currently addresses this task by using intuitive rules of thumb and the designers’ experience, and this often requires multiple design iterations between the motor and gear train. In this regard, this research will provide preliminary guidelines for choosing the gear ratios and relative sizes of the motor and gear train when integrating a switched reluctance motor (SRM) with three different gear trains (hypocyclic gear train (HGT), star gear train coupled with a parallel eccentric gear train (Star+PEGT), and star compound gear train coupled with a parallel eccentric gear train (Star Compound+PEGT)) in the preliminary design stage. Research has also shown that there are cost benefits to developing actuator product families to meet the needs of a particular application domain. In this regard, scaling rules for the SRM, HGT, PEGT, and integrated actuators built from them (with diameters ranging from 6 to 50 inches and gear ratios from 100 to 450) will be developed. These scaling rules describe how the performance parameters vary as the size (diameter and aspect ratio) is varied and are useful for quickly sizing motor, gear train, and actuator designs. These scaling rules are useful for two purposes: 1) learning the relationships between the performance and dominant design parameters and 2) obtaining intermediate sizes not previously considered. The rules will be simple enough for designers to learn and use to make intelligent design parameter choices (purpose 1) but will also have sufficient accuracy for obtaining intermediate designs (purpose 2). The scaling rules are summarized in a series of three-dimensional design maps, with an emphasis on the development of visual decision-making tools. This research also formulates an actuator design procedure that incorporates the two central concepts of this research, balancing parameters and scaling, and this procedure is embedded within computational (MatLab) and solid modeling (SolidWorks) software programs. In addition to developing rules for scaling and balancing parameters, the procedure was also used for the following purposes. First, direct drive and geared actuators were compared in terms of their torque density and responsiveness to determine which alternative is superior for different gear ratio, diameter, and load inertia combinations. Second, alternative minimum sets of actuators were developed for an illustrative application, and the anticipated performance losses due to using common parameters among the sets were quantified. / text

Electromechanical actuators are highly complex non-linear devices that cannot be accurately modeled using only analytical formulations derived from first principles. When the application demands high model accuracy with a wide parametric range (and criteria) plus the need to take manufacturing/assembly variations associated with the asbuilt actuator into account, an empirical model based on extensive testing across the entire operating domain is the recommended approach. Since testing is an expensive, time consuming and laborious process, it is the aim of this research to determine efficient test methodologies (experimental designs) that would obtain the maximum information about actuator performance by means of a minimal number of tests. Current test standards are primarily designed to arrive at the actuator specifications by carrying out tests at either a single or a very limited set of test points. The results thus obtained are typically not valid across the entire operating domain of the actuator. Also these tests are performed for a very small set (one or two) of criteria. Furthermore most of this testing is conducted in terms of just one (occasionally two) control variables. As a result the full capability of the actuator is poorly represented. The research presented here addresses these limitations. To achieve the objective, the steps followed in this research are -- a) define a set of actuator performance criteria for testing, b) construct a test bed for actuator testing, c) develop a framework for testing actuators, d) conduct tests by applying principles from Design of Experiments, e) apply statistical techniques to identify empirical models and develop efficient experimental designs, and f) graphically present the actual capabilities of the actuator using performance maps. A commercially available permanent magnet synchronous motor-geartrain combination was chosen as the test actuator. This actuator has a nominal/peak rating of 43/86 lb-ft torque and 30/100 RPM speed. The criteria considered for characterizing the actuator’s operational capability includes noise, vibration, efficiency, current consumption, torque ripple, velocity ripple, backdriveability, and temperature. Control variables affecting the performance criteria were identified. Measurement of performance over the entire operating range of actuator requires that the actuator be operated at specific levels of these control variables and the concerned performance criteria be measured. Therefore to perform these actuator tests, a modular test bed was constructed. The test bed consists of an actuator loading mechanism (in the form of a magnetic particle brake or a geartrain-motor combination), an array of sensors, amplifiers, a signal conditioning unit, data acquisition modules, motion controller, and transformer. The measured sensor data is filtered through the signal conditioning unit (to remove noise) and digitized using the data acquisition modules. Statistical techniques were employed to process the sensor data and for each criterion, an empirical model relating the criteria to its control variables was determined. Model adequacy checks were carried out to ensure that the model did not violate important statistical assumptions and that it adequately represented the relationship between the input control variables and the output response (performance criteria). These models were used to generate performance maps for each criteria. Based on a predetermined set of run sizes, for each empirical model, alternate experimental designs were determined. Efficient experiment designs were identified by metrics such as -- Gefficiency, maximum prediction variance and average prediction variance. Besides the obvious advantage of arriving at complete and accurate performance profiles for the actuator undergoing tests (with minimal testing), the methodology could be applied to other actuators of a similar family. We might consider the methodology to be a subset of the general concept of metrology; i.e., the determination of as-built parameters vs. as designed parameters. Simplification techniques were applied to these models to remove unwanted model terms. / text

With the growing interests and high requirements in low-speed linear drives, the linear machines possessing high force density, high power density and high efficiency feature become in great demands for the linear direct-drive applications. There are many available linear machine topologies, but their performances for exhibiting the high-force density capability dissatisfy the industrial requirements. In order to solve this problem, the new machine topologies emphasizing on high force density are explored and studied. The objective of this thesis is to present the design, analysis, and application of permanent magnet (PM) linear machines which can offer a higher force density at the same magnetic loading and electric loading than the conventional machines. Although in recent years there are many emerging advanced PM rotational machines for direct-drive rotational drives, the development of advanced PM linear machines for direct-drive linear drives is sparse. In spite of the motion type of electric machines, the inherent operating principle is the same. By studying and borrowing concepts of the high torque density rotational electric machines, the linear machine morphologies of the promising candidates are designed and analyzed. The problems and side effects resulting from the linearization are discussed and suppressed. Two main approaches for machine design and analysis are developed and applied, namely the analytical calculation and the finite element method (FEM). By analytically solving the magnetic field problem, the relationships between the field quantities and the machine geometry are unveiled. With the use of analytical calculation, the machine design and dimension optimization are conveniently achieved. With the use of FEM, the machine design objective and its electromagnetic performance are verified and evaluated. Finally, the proposed low-speed PM linear machine is applied for direct-drive wave power generation. By mathematically modeling the wave power, generation system and the generator, the conditions for maximum power harvesting are determined. By using the vector control, the generator output power is maximized which is verified by the simulation results. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Thesis (M.S.)--University of Florida, 2005. / Title from title page of source document. Document formatted into pages; contains 60 pages. Includes vita. Includes bibliographical references.

Thesis (M.S.)--University of Florida, 2005. / Title from title page of source document. Document formatted into pages; contains 124 pages. Includes vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Application of fixed-arm robots in such manipulative machinery as those used in welding, cutting, packaging etc, has been limited due either to insufficient rigidity in the arm for the transmission of large forces and torques, or to the high cost of improving upon its rigidity. This work develops a cheap robotic device in the form of a linkage mechanism and tests it on a laboratory rig for positional accuracy. The closed-loop nature of the mechanism ensures sufficient rigidity, and system vibrations are greatly checked. The goal is to use this device for such jobs as the optimization of cam profiles prior to cutting them, guidance of a cutting torch, welding of flat and spherical surfaces, etc. A number of these devices can be arranged around a working space to perform a set of tasks. Put differently, this is an exercise in digital control of machine elements.