41 
Stability of Hybrid Singularly Perturbed Systems with Time DelayAlwan, Mohamad January 2006 (has links)
Hybrid singularly perturbed systems (SPSs) with time delay are considered and exponential stability of these systems is investigated. This work mainly covers switched and impulsive switched delay SPSs . Multiple Lyapunov functions technique as a tool is applied to these systems. Dwell and average dwell time approaches are used to organize the switching between subsystems (modes) so that the hybrid system is stable. Systems with all stable modes are first discussed and, after developing lemmas to ensure existence of growth rates of unstable modes, these systems are then extended to include, in addition, unstable modes. Sufficient conditions showing that impulses contribute to yield stability properties of impulsive switched systems that consist of all unstable subsystems are also established. A number of illustrative examples are presented to help motivate the study of these systems.

42 
HInfinity Performance Limitations for Problems with Sensor Time DelaysGaudette, Darrell 21 January 2008 (has links)
Motivated by ongoing research into automating radiotherapy, this thesis is concerned with linear feedback control and estimation problems where only a delayed output signal is measurable. Various discretetime performance limitations are derived using tools from modelmatching theory as well as the early $H_\infty$ literature. It is shown that there exist performance limitations for both onedegreeoffreedom control and estimation problems, but the nature of the limitations differs depending on whether the plant is stable or unstable. Some continuoustime performance limitations are also found, with more complete results in the case where the plant is unstable. Extensions of the various performance limitation to twodegreeoffreedom control are also studied.

43 
Stability of Hybrid Singularly Perturbed Systems with Time DelayAlwan, Mohamad January 2006 (has links)
Hybrid singularly perturbed systems (SPSs) with time delay are considered and exponential stability of these systems is investigated. This work mainly covers switched and impulsive switched delay SPSs . Multiple Lyapunov functions technique as a tool is applied to these systems. Dwell and average dwell time approaches are used to organize the switching between subsystems (modes) so that the hybrid system is stable. Systems with all stable modes are first discussed and, after developing lemmas to ensure existence of growth rates of unstable modes, these systems are then extended to include, in addition, unstable modes. Sufficient conditions showing that impulses contribute to yield stability properties of impulsive switched systems that consist of all unstable subsystems are also established. A number of illustrative examples are presented to help motivate the study of these systems.

44 
HInfinity Performance Limitations for Problems with Sensor Time DelaysGaudette, Darrell 21 January 2008 (has links)
Motivated by ongoing research into automating radiotherapy, this thesis is concerned with linear feedback control and estimation problems where only a delayed output signal is measurable. Various discretetime performance limitations are derived using tools from modelmatching theory as well as the early $H_\infty$ literature. It is shown that there exist performance limitations for both onedegreeoffreedom control and estimation problems, but the nature of the limitations differs depending on whether the plant is stable or unstable. Some continuoustime performance limitations are also found, with more complete results in the case where the plant is unstable. Extensions of the various performance limitation to twodegreeoffreedom control are also studied.

45 
Generalized MaximumLikelihood Algorithm for Time Delay Estimation in UWB RadioTsai, WenChieh 24 July 2004 (has links)
The main purpose of this thesis is to estimate the direct path in dense multipath Ultra WideBand (UWB) environment. The timeofarrival (ToA) estimation algorithm used is based on Generalized MaximumLikelihood (GML) algorithm. Nevertheless, GML algorithm is so timeconsuming that the results usually take a very long period of time, and sometimes fail to converge. Hence, the schemes that would improve the algorithm are investigated. In the schemes, the search was executed in sequential form. Two threshold parameters are to be determined¡Xone is about the arrival time of the estimation path while the other is the fading amplitude of the estimation path. The thresholds are determined in order to terminate the sequential algorithm. The determination of thresholds is based on error analysis, including the probability of error and rootmeansquare error. The analysis of the probability of error is subject to the probability of false alarm and the probability of miss. However, a tradeoff problem on the probability of false alarm and the probability of miss exists in the process of determining thresholds. The thresholds are determined according to the requirement of the probability of error. We propose an improvement scheme for determining the two thresholds. In the proposed scheme, candidate pairs are evaluated within an appropriate range. The rootmeansquare error value for each pair of thresholds is calculated. The smallest error, corresponding to the desired thresholds, is chosen for use in ToA estimation. From the simulation results, it is seen that, when SNR falls between 4dB and 16dB, the improvement proposed scheme results has the smaller estimation error.

46 
MUSIC Algorithms in FrequencySpace Domain for Time Delay Estimation in UWB Multipath ChannelsChen, KuanHsun 27 July 2006 (has links)
In this thesis, an algorithm based on frequencyspace domain MUSIC method is presented for estimating the propagation delay of a wireless multipath channel.For indoor geolocation systems, the timeofarrival (TOA) is the most popular technique for accurate positioning system. The basic idea in TOAbased techniques is to accurately estimate the propagation delay of the radio signal arriving from the direct lineofsight (DLOS) path. However, dense multipath environments may cause unresolved paths, and yield an error in the estimation of the DLOS path. UWB (Ultrawideband) technology provides an excellent means for wireless positioning due to its high resolution capability in the time domain. Its ability to resolving multipath components makes it possible to obtain accurate location estimates. In this thesis, we investigate the use of UWB signals in positioning and combine frequencydomain MUSIC algorithm. At the same time, the structure of timespacetime method is studied.
In addition, we propose a frequencyspace domain MUSIC algorithm, called FSFMUSIC algorithm, and use the spatial smoothing technique to improve the performance of the algorithm. For a twomultipath case, analysis and simulation results of multipath resolvability and the variance of estimation errors of signal arrival time are discussed.

47 
Design of Model Reference Adaptive Variable Structure Controllers for Uncertain Dynamic SystemsChou, ChienHsin 08 July 2002 (has links)
Abstract
In this dissertation, four variable structure controllers are proposed for four different class of systems subjected to uncertainties and time varying delays respectively. In most cases, the variable structure control is incorporated with an adaptive law to drive the tracking error between the desired model and the controlled plant to zero. By using the Lyapunov stability theorem, the adaptive law is utilized for adapting the unknown upper bounds of the lumped perturbations so that the objective of asymptotical stability is achieved, and the variable structure control scheme is used for enhancing the robustness of stability of the controlled systems. Once the system enters the sliding region, the dynamics of controlled systems are insensitive to matching perturbations. It also shows that the proposed methodologies ensure the property of the globally uniformly ultimate boundness for the overall controlled system. Finally, four numerical examples are given for demonstrating the feasibility of the proposed control schemes.

48 
Comparative Study: TimeDelay Method and Sliding Mode Technique for Perturbation EstimationHuang, JennMing 15 July 2002 (has links)
Two different perturbation estimation methodologies are compared in
this thesis. One is time delay method (TDM), the other is sliding mode
techniqueli (SMT). When analyzing the TDM, Pade approximation is used
to approximate a function with timedelay argument. The comparisons
of perturbation estimation accuracy resulted from TDM and SMT both
in time domain and frequency domain are addressed, and two numerical
examples are also given for demonstration.

49 
Realtime control over networksJi, Kun 17 September 2007 (has links)
A control system in which sensors, actuators, and controllers are interconnected over a
communication network is called a networked control system (NCS). Enhanced computational
capabilities and bandwidths in the networking technology enabled researchers to develop NCSs
to implement distributed control schemes. This dissertation presents a framework for the
modeling, design, stability analysis, control, and bandwidth allocation of realtime control over
networks. This framework covers key research issues regarding control over networks and can
be the guidelines of NCS design. A single actuator ball magneticlevitation (maglev) system is
implemented as a test bed for the realtime control over networks to illustrate and verify the
theoretical results of this dissertation. Experimentally verifying the feasibility of Internetbased
realtime control is another main objective of this dissertation.
First, this dissertation proposes a novel NCS model in which the effects of the networkinduced
time delay, datapacket loss, and outoforder data transmission are all considered.
Second, two simple algorithms based on modelestimator and predictor and timeoutscheme are
proposed to compensate for the networkinduced time delay and packet loss simultaneously.
These algorithms are verified experimentally by the ball maglev test bed. System stability analyses of original and compensated systems are presented. Then, a novel codesign
consideration related to realtime control and network communication is also proposed. The
working range of the sampling frequency is determined by the analysis of the system stability
and network parameters such as time delay, data rate, and datapacket size. The NCS design
chart developed in this dissertation can be a useful guideline for choosing the network and
control parameters in the design of an NCS. Using a realtime operating system for realtime
control over networks is also proposed as one of the main contributions of this dissertation.
After a realtime NCS is successfully implemented, advanced control theories such as
robust control, optimal control, and adaptive control are applied and formulated to improve the
quality of control (QoC) of NCSs. Finally, an optimal dynamic bandwidth management method
is proposed to solve the optimal network scheduling and bandwidth allocation problem when
NCSs are connected to the same network and are sharing the network resource.

50 
Some stability results for timedelay control problemsYim, Lihing. January 2000 (has links)
Thesis (M. Ed.)University of Hong Kong, 2001. / Includes bibliographical references (leaves 2731).

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