• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 187
  • 68
  • 51
  • 19
  • 9
  • 7
  • 6
  • 4
  • 4
  • 4
  • 3
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 416
  • 144
  • 73
  • 67
  • 63
  • 54
  • 54
  • 51
  • 46
  • 44
  • 42
  • 38
  • 37
  • 37
  • 36
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Structure-Inspired Disturbance Observer Design and Disturbance Observer-Based Control/estimation

Chen, Ying-Chun 15 August 2023 (has links)
This dissertation consists of two topics: (1) structure-inspired disturbance observer design and (2) disturbance observer-based control/estimation. The disturbance is defined as the discrepancy between a model and the system the model represents. A disturbance observer is an algorithm that generates an estimate of the disturbance. The first topic illustrates a disturbance observer that provides a big class of nonlinear systems with a large basin of attraction, even ensuring global convergence. Such robustness is achieved by leveraging particular system nonlinearities in the observer design. The second topic discusses the usage of disturbance estimates to counteract or capture the effects of disturbances to recover the nominal controller/estimator performance. The main research results are theorems concerning stability analysis of the disturbance observer and the disturbance observer-based systems, whose practical aspects are supported by three application examples---a fixed-wing aircraft, an underwater vehicle, and a Furuta pendulum. / Doctor of Philosophy / This dissertation consists of two topics: (1) structure-inspired disturbance observer design and (2) disturbance observer-based control/estimation. Disturbances are the unknown signals entering the system; an external force, for example, such as the additional lift force due to turbulence surrounding an aircraft is a disturbance. A disturbance observer is an algorithm that estimates the mathematical value of disturbances. The first topic illustrates a disturbance observer whose convergence is guaranteed regardless of the initial condition. Such robustness is achieved by leveraging the system's special properties in the observer design. The second topic discusses the usage of disturbance observers to recover the nominal controller/estimator performance. Control is a study of how make systems behave ideally by properly designing the inputs, while estimation is about how to infer quantities that cannot be directly measured using the measurements that really are available; the solutions are correspondingly called controller and estimator. Disturbance estimates can be exploited by existing controllers and estimators as extra information to counteract or capture the effects of disturbances. The main research results are theorems about the conditions under which these algorithms perform as desired. Practical aspects are supported by three application examples---a fixed-wing aircraft, an underwater vehicle, and a Furuta pendulum.

Path-following Control of Container Ships

Zhao, Yang 25 July 2019 (has links)
No description available.

Observation and Estimation of Nonlinear Systems

Wei, Jianfeng 04 April 2006 (has links)
No description available.

Toward a theory of observation

Carney, Daniel Joseph, Jr. 06 November 2014 (has links)
Quantum mechanics is usually formulated in terms of a single Hilbert space and observables are defined as operators on this space. Attempts to describe entire spacetimes and their resident matter in this way often encounter paradoxes. For example, it has been argued that an observer falling into a black hole may be able to witness deviations from unitary, violations of semi-classical quantum field theory, and the like. This thesis argues that the essential problem is the insistence on the use of a single, global Hilbert space, because in general it may be that a physical observer cannot causally probe all of the information described by this space due to the presence of horizons. Instead, one could try to define unitary quantum physics directly in terms of the information causally accessible to particular observers. This thesis makes steps toward a systematization of this idea. Given an observer on a timelike worldline, I construct coordinates which (in good cases) cover precisely the set of events to which she can send and then receive a signal. These coordinates have spatial sections parametrized by her proper time, and the metric manifestly encodes the equivalence principle in the sense that it is flat along her worldline. To describe the quantum theory of fields according to these observers, I define Hilbert spaces in terms of field configurations on these spatial sections and show how to implement unitary time-evolution along proper time. I explain how to compare the observations of a pair of observers, and how to obtain the description according to some particular observer given some a priori global description. In this sense, the program outlined here constructs a manifestly unitary description of the events which the observer can causally probe. I give a number of explicit examples of the coordinates, and show how the quantum theory works for a uniformly accelerated observer in flat spacetime and for an inertial (co-moving) observer in an inflating universe. / text

State estimation for improved control in batch reaction and distillation processes

Martinez, Claudio de Lima Miguel January 1997 (has links)
No description available.

Coordinated control of the turbo electrically assisted variable geometry turbocharged diesel engine with exhaust gas recirculation

Glenn, Bradley Charles 07 October 2005 (has links)
No description available.

Design and control of a pneumatically driven MRI-compatible tele-operated haptic interface

Turkseven, Melih 27 May 2016 (has links)
This study presents methods for understanding, modeling and control of tele-operated pneumatic actuators for rehabilitation in Magnetic Resonance Imaging (MRI). Pneumatic actuators have excellent MRI-compatibility as opposed to conventional electro-mechanical systems; however, the actuator and the system drivers cannot be co-located due to the MRI-compatibility requirements. The actuators are driven via long transmission lines, which affect the system dynamics significantly. Methods provided in this work produced accurate pressure estimation and control by accounting for the pressure dynamics in the lines, which has been neglected by previous work in this area. The effectiveness of the presented modeling and control methods were demonstrated on tele-operation test setups. This research also includes the design of necessary system components for the developed algorithms. An MRI-compatible optical sensor was developed for force feedback and its design was analyzed for high precision. Directions and opportunities for future research are discussed.

Speed sensorless control of induction motors

Sevinc, Ata January 2001 (has links)
No description available.

Design and Assessment of Cardiac SPECT Systems

Lee, Chih-Jie January 2012 (has links)
Single-photon emission computed tomography (SPECT) is a modality widely used to detect myocardial ischemia and myocardial infarction. Objectively assessing and comparing different SPECT systems is important so that the best detectability of cardiac defects can be achieved. Whitaker, Clarkson, and Barrett's study on the scanning linear observer (SLO) shows that the SLO can be used to estimate the location and size of signals. One major advantage of the SLO is that it can be used with projection data rather than reconstruction data. Thus, this observer model assesses overall hardware performance independent by any reconstruction algorithm. In addition, we will show that the run time of image-quality studies is significantly reduced. Several systems derived from the GE CZT-based dedicated cardiac SPECT camera Discovery 530c design, which is officially named the Alcyone Technology: Discovery NM 530c, were assessed using the performance of the SLO for the task of detecting cardiac defects and estimating the properties of the defects. Clinically, hearts can be virtually segmented into three coronary artery territories: left anterior descending artery (LAD), left circumflex artery (LCX), and right coronary artery (RCA). One of the most important functions of a cardiac SPECT system is to produce images from which a radiologist can correctly predict in which territory the defect exists. A good estimation of the defect extent from the images is also very helpful for determining the seriousness of the myocardial ischemia. In this dissertation, both locations and extent of defects were estimated by the SLO, and system performance was assessed using localization receiver operating characteristic (LROC) / estimation receiver operating characteristic (EROC) curves. Area under LROC curve (AULC) / area under EROC curve (AUEC) and true positive fraction (TPF) at specific false positive fraction (FPF) can be treated as the figures of merit (FOMs). As the results will show, a combination of the SLO and LROC / EROC curves can determine the configuration that has the most estimation/detection information and thus is a useful method for assessing cardiac SPECT systems.

Development of a model of work-personality

Owens, Courtney Elizabeth January 2019 (has links)
Personality is important to job performance; meta-analyses published over the years repeatedly showed that self-rated personality traits can significantly predict overall job performance (Barrick & Mount, 1991; Barrick, Mount, & Judge, 2001). Despite their significance, these same meta-analyses, generally showed personality only had a small effect on overall job performance. The exception was conscientiousness, which had a less than medium effect. However, there is also a growing body of evidence suggesting that other-ratings of personality can show higher concurrent validities than self-ratings. Meta-analytic results showed that personality can have a large effect on overall job performance, if the personality traits are rated by others (Connelly & Ones, 2010). Moreover, concurrent validities increased when utilising narrow measures of both personality (Judge, Rodell, Klinger, Simon, & Crawford, 2013) and job performance (Bartram, 2005). In this study, the author examined the suggestion from meta-analyses that observer-ratings, rather than self-ratings, provide greater explanatory power when predicting job performance. Further, the concurrent validities of using narrow personality traits (facets) as predictors of narrow measures of job performance were investigated. This study comprised 1,041 participants, of which 92% were employed in a UK police organisation. Employees provided self-ratings and identified two co-workers and a manager who could provide other-ratings of personality and job performance. Online questionnaires measured 71 personality facets of the 11+ Factor Model (Irwing & Booth, 2013) and Bartram's (2005) Great Eight factors of job performance. Arguably the most comprehensive measure of personality, the 11+ Factor Model is comprised of 11 factors and 74 facets. Items from the International Personality Item Pool (IPIP; Goldberg, 1999) were utilised to create scales for each of the 74 personality facets. A planned missing data design was implemented to improve response rates (Graham, Taylor, Olchowski, & Cumsille, 2006). Measurement models were estimated first, followed by testing of the structural models (J. C. Anderson & Gerbing, 1988) to estimate the combined effects of personality facets on each of the job performance outcomes. Since cross-validation is a powerful approach for evaluating models (Millsap & Meredith, 2007), all models were cross-validated on two datasets. Fifty-two personality facets were identified and cross-validated. Some of these facets provided superior prediction over factors, when predicting narrow measures of job performance. The facets of integrity, leadership, harm avoidance and empathy explained much of the variance in the Great Eight job competencies. In some cases, self-ratings of personality provided superior prediction over other-ratings.

Page generated in 0.0366 seconds