ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California / Traditional angle of arrival algorithms operate with uniform receiver arrays. Non-uniform arrays typically introduce significant elevation of computation complexity. This paper utilizes the double-integration method for the accurate estimation of the angle of arrival with non-uniform receiver arrays, while maintaining high computation efficiency. Because of the simplicity, the double-integration method is not significantly affected by the increase of the number of receivers or the non-uniform configuration. This approach allows us to perform high-speed high-accuracy estimation of the two-dimensional bearing angle without the constraints of structured receiver arrays, which is important to the realization of real-time tracking of mobile acoustic sources.

International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / The Equipment Time-Delay (ETD) measurement technology for Continuous Wave (CW) transponder is discussed with emphasis on the principle of measuring the ETD of the intermediate frequency (IF) modulation transponder through measuring subcarrier modulation sideband tone phase. A general method for measuring ETD of different types of transponder (including IF-modulation transponder) is introduced. Finally the measurement method error is analyzed.

published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Mechanical Engineering / Doctoral / Doctor of Philosophy

Doctor of Philosophy / Department of Physics / Chii-Dong Lin / Isolated attosecond pulse (IAP) is a tool of probing electronic dynamics occurring in atoms, molecules, clusters and solids, since the time scale of electronic motion is on the order of attoseconds. The generation, characterization and applications of IAPs has become one of the fast frontiers of laser experiments. This dissertation focuses on several aspects of attosecond physics. First, we study the driving wavelength scaling of the yield of high-order harmonic generation (HHG) by applying the quantum orbit theory. The unfavorable scaling law especially for the short quantum orbit is of great importance to attoseond pulse generation toward hundreds of eVs or keV photon energy region by mid-infrared (mid-IR) lasers. Second, we investigate the accuracy of the current frequency-resolved optical gating for complete reconstruction of attosecond bursts (FROG-CRAB) and phase retrieval by omega oscillation filtering (PROOF) methods for IAP characterization by simulating the experimental data by theoretical calculation. This calibration is critical but has not been carefully carried out before. We also present an improved method, namely the swPROOF which is more universal and robust than the original PROOF method. Third, we investigate the controversial topic of photoionization time delay. We find the limitation of the FROG-CRAB method which has been used to extract the photoionization time delay between the 2s and 2p channels in neon. The time delay retrieval is sensitive to the attochirp of the XUV pulse, which may lead to discrepancies between experiment and theory. A new fitting method is proposed in order to overcome the limitations of FROG-CRAB. Finally, IAPs are used to probe the dynamic of electron correlation in helium atom by means of attosecond transient absorption spectroscopy. The agreement between the measurement and our analytical model verifies the observation of time-dependent build up of the 2s2p Fano resonance.

Lo Wang Tai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 58-63). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.iii / Tables of Content --- p.iv / List of Figures --- p.vii / List of Tables --- p.viii / Chapter Chapter1 --- Introduction --- p.1 / Chapter 1.1 --- Internet-based Tele-cooperation --- p.1 / Chapter 1.1.1 --- Cooperative Control of Multiple Robot --- p.1 / Chapter 1.1.2 --- Internet-based Teleoperation --- p.3 / Chapter 1.1.3 --- Time Delay of Internet Communication --- p.4 / Chapter 1.2 --- Related Work --- p.5 / Chapter 1.3 --- Motivation and Contribution --- p.6 / Chapter 1.3.1 --- Motivation --- p.6 / Chapter 1.3.2 --- Contribution --- p.7 / Chapter 1.4 --- Outline of the thesis --- p.8 / Chapter Chapter2 --- The Internet Robotic System --- p.9 / Chapter 2.1 --- System Architecture --- p.9 / Chapter 2.2 --- The Hardware --- p.12 / Chapter 2.2.1 --- Operator System --- p.12 / Chapter 2.2.2 --- Mobile Robot System --- p.13 / Chapter 2.2.3 --- Multi-fingered Robot Hand System --- p.17 / Chapter 2.2.4 --- Visual Tracking System --- p.19 / Chapter 2.3 --- Software Design --- p.21 / Chapter 2.3.1 --- Robot Client and Arm Client --- p.22 / Chapter 2.3.2 --- Robot Server --- p.23 / Chapter 2.3.3 --- Image Server --- p.25 / Chapter 2.3.4 --- Arm Server --- p.75 / Chapter 2.3.5 --- Arm Controller --- p.27 / Chapter 2.3.6 --- Finger Server --- p.27 / Chapter 2.3.7 --- Finger Controller --- p.27 / Chapter 2.3.8 --- Robot Tracker --- p.28 / Chapter 2.3.9 --- Interaction Forwarder --- p.28 / Chapter Chapter3 --- Event-based Control for Force Reflecting Teleoperation --- p.29 / Chapter 3.1 --- Modeling and Control --- p.29 / Chapter 3.1.1 --- Model of Operator System --- p.31 / Chapter 3.1.2 --- Model of Mobile Robot System --- p.33 / Chapter 3.1.3 --- Model of Multi-fingered Hand System --- p.34 / Chapter 3.2 --- Force Feedback Generation --- p.35 / Chapter 3.2.1 --- Obstacle Avoidance --- p.35 / Chapter 3.2.2 --- Singularity Avoidance --- p.38 / Chapter 3.2.3 --- Interaction Rendering --- p.40 / Chapter Chapter4 --- Experiments --- p.42 / Chapter 4.1 --- Experiment1 --- p.42 / Chapter 4.2 --- Experiment2 --- p.47 / Chapter 4.3 --- Experiment3 --- p.52 / Chapter Chapter5 --- Future Wok --- p.54 / Chapter Chapter6 --- Conclusions --- p.56 / Bibliography --- p.58

The purpose of this thesis is to investigate the correlation between the penetration force of cutting fluids and machining stability. General studies are made to understand the classification of cutting fluids based on their chemical compositions. It is summarized why the proper selection of cutting fluid for different machining processes is important. The role of cutting fluids in machining process is documented as well as other related issues such as delivery methods, storage, recycling, disposal and failure modes. The uniqueness of this thesis is that it constructs a new mathematical model that would help to explain and quantify the influence of the penetration force of cutting fluid on machining stability. The basic principles of milling process, especially for thin wall machining are reviewed for building the mathematical model. The governing equations of the mathematical model are derived and solved analytically. The derived solutions are used to construct the stability charts. The results show that there is a direct correlation between the machining stability and the changes of the penetration force of the cutting fluid. It is shown that the machining stability region is narrowed as the penetration force of the cutting fluid increases while other machining variables are assumed to be constant. This narrowness of the stability region is more obvious at spindle speed over 6000 rpm.

This thesis is concerned with robust control of an offshore steel jacket platform subject to nonlinear wave-induced forces. Since time delay and uncertainty are inevitably encountered for an offshore structure and their existence may induce instability, oscillation and poor performance, it is very significant to study on how the delay and uncertainty affect the offshore structure. In this thesis, a memory robust control strategy is, for the first time, proposed to reduce the internal oscillations of the offshore structure under wave-induced forces, so as to ensure the safety and comfort of the offshore structure. Firstly, when the system's states are adopted as feedback, memory state feedback controllers are introduced for the offshore structure. By using Lyapunov-Krasovskii stability theory, some delay-dependent stability criteria have been established, based on which, and by combining with some linearization techniques, memory state feedback controllers are designed to control the offshore structure. The simulation results show that such controllers can effectively reduce the internal oscillations of the offshore structure subject to nonlinear wave-induced forces and uncertainties. On the other hand, a new Lyapunov-Krasovskii functional is introduced to derive a less conservative delay-dependent stability criterion. When this criterion is applied to the offshore structure, an improved memory state feedback controller with a small gain is obtained to control the system more effectively, which is sufficiently shown by the simulation. Secondly, when the system's outputs are adopted as feedback, memory dynamic output feedback controllers are considered for the offshore structure. By employing a projection theorem and a cone complementary linearization approach, memory dynamic output feedback controllers are derived by solving some nonlinear minimization problem subject to some linear matrix inequalities. The simulation results show that the internal oscillations of the offshore structure subject to nonlinear wave-induced forces are well attenuated. Finally, robust H control is fully investigated for the offshore structure. By employing Lyapunov-Krasovskii stability theory, some delay-dependent bounded real lemmas have been obtained, under which, via a memory state feedback controller or a dynamic output feedback controller, the resulting closed-loop system is not only asymptotically stable but also with a prescribed disturbance attenuation level. The simulation results illustrate the validity of the proposed method.

<p>The demand for reliable high rate and efficient communication is ever increasing. In this thesis we look at two different problems in such systems, and their possible solutions.</p><p>In recent years orthogonal frequency division multiplexing (OFDM) has gone from a promising data transmission technique to become a mainstream technique used in several current and future standards. The main attractive property of OFDM is that it is inherently resilient to multipath reflections because of its long symbol time. However, this comes at the cost of a relatively high sensitivity to carrier frequency offsets (CFOs).</p><p>In this thesis we present a technique for CFO estimation in OFDM systems that is based on locating the spectral minimas within so-called null or virtual subcarriers embedded in the spectrum.~The spectral minimas are found iteratively over a number of symbols and is therefore mainly useful for frequency offset tracking or in systems where an estimate is not immediately required, such as in TV or radio broadcasting systems. However, complexity wise the estimator is relatively easy to implement and it does not need any extra redundancy beside a nonmodulated subcarrier. The estimator performance is studied both in a channel with additive white Gaussian noise and in a frequency selective channel environment.</p><p>A goal for many years has been to be able to implement as much as possible of a radio system in the digital domain, the ultimate goal being so called software defined radio (SDR). One important part of an SDR receiver is the high speed analog-to-digital converter(ADC) and one path to reach this goal is to use a number of parallel, time-interleaved, ADCs. Such ADCs are, however, sensitive to sampling instant offsets, DC offset and gain offset.</p><p>This thesis also discusses iterative time-delay estimators (TDEs) utilizing adjustable fractional-delay filters. The TDEs could for example be used to estimate and calibrate the relative delay between the ADCs comprising the time interleaved ADC. TDEs using a direct correlator and an average squared difference function are compared. Furthermore, an analysis of the effects of the batch length dependence is presented.</p> / Report code: LiU-Tek-Lic-2006:33.

The objective of this research is to demonstrate experimentally the feasibility of using the Internet for a Distributed Control System (DCS). An algorithm has been designed and implemented to ensure stability of the system in the presence of upper bounded time-varying delays. A single actuator magnetic ball levitation system has been used as a test bed to validate the proposed algorithm. Experiments were performed to obtain the round-trip time delay between the host PC and the client PC under varying network loads and at different times. A digital real-time lead-lag controller was implemented for the magnetic levitation system. Upper bounds for the artificial and experimental round-trip time delay that can be accommodated in the control loop for the maglev system were estimated. The artificial time delay was based on various probabilistic distributions and was generated through MATLAB. To accommodate sporadic surges in time delays that are more than these upper bounds, a timeout algorithm with sensor data prediction was developed. Experiments were performed to validate the satisfactory performance of this algorithm in the presence of the bonded sporadic excessive time delays.