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  • 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.
21

Design of Adaptive Sliding Mode Controllers for Perturbed MIMO Systems

Chien, Shih-Hsiang 18 January 2008 (has links)
In this dissertation three robust control strategies are proposed for a class of multi-input multi-output dynamic systems with matched or mismatched perturbations. Firstly, an adaptive variable structure observer and controller are introduced for solving the regulation problems, where some state variables are not measurable. By utilizing adaptive mechanisms in the design of sliding mode controller, one can enable the controlled systems not only to generate a reaching mode in finite time, but also to suppress the mismatched perturbations during the sliding mode. Secondly, the design of adaptive sliding mode controllers with application to robot manipulators is presented to solve the tracking problems. The dynamic equations of the controlled systems contain a perturbed leading coefficient matrix and can be either positive definite or negative definite. The asymptotical stability of the controlled systems will be attained if the proposed control scheme is employed. Thirdly, a design methodology of adaptive sliding mode controller based on T-S fuzzy model is proposed to solve tracking problems. It is shown that the trajectories of the controlled systems can be driven into a designated sliding surface in finite time, and the property of asymptotical stability is also guaranteed. All these three control schemes are designed by means of Lyapunov stability theorem. Each control scheme contains three parts. The first part is designed for eliminating measurable feedback signals. The second part is used for adjusting the convergent rate of state variables (or tracking errors) of the controlled system. The third part is the adaptive control mechanism, which is used to adapt some unknown constants of the least upper bounds of perturbations, so that the knowledge of the least upper bounds of matched or mismatched perturbations are not required. Several numerical examples and an application of controlling robot manipulator are demonstrated for showing the feasibility of the proposed control methodologies.
22

Stability Analysis of Uncertain Nonlinear Systems with High-Gain Observers

Liou, Fa-jiun 10 February 2010 (has links)
Based on the Lyapunov stability theorem, a modified stability analysis as well as a modified observer is proposed in this thesis for a class of uncertain nonlinear systems with an existent high gain observer. By assuming that the first two state variables are indirectly measurable, reanalyzing the stability of the error dynamics is presented first. The advantage of this modified analytic method is that the upper bound of the disturbance distribution functions is not required to be known in advance, and the asymptotic stability is still guaranteed. Next, based on this existent observer, a slightly modified observer is presented for systems with disturbances whose upper bound is unknown. An adaptive mechanism is embedded in the proposed observer, so that the upper bound of perturbations is not required to be known beforehand. The resultant dynamics of estimation errors can be driven into the sliding surface in a finite time, and guarantee asymptotic stability. A numerical example and a practical example are given to demonstrate the feasibility of the proposed observer.
23

Design of Fault Tolerant Control System for Electric Vehicles with Steer-By-Wire and In-Wheel Motors

Hayakawa, Yoshikazu, Ito, Akira 09 1900 (has links)
7th IFAC Symposium on Advances in Automotive Control, The International Federation of Automatic Control, September 4-7, 2013. Tokyo, Japan
24

State Estimation and Parameter Identification of Continuous-time Nonlinear Systems

DHALIWAL, SAMANDEEP SINGH 01 November 2011 (has links)
The problem of parameter and state estimation of a class of nonlinear systems is addressed. An adaptive identifier and observer are used to estimate the parameters and the state variables simultaneously. The proposed method is derived using a new formulation. Uncertainty sets are defined for the parameters and a set of auxiliary variables for the state variables. An algorithm is developed to update these sets using the available information. The algorithm proposed guarantees the convergence of parameters and the state variables to their true value. In addition to its application in difficult estimation problems, the algorithm has also been adapted to handle fault detection problems. The technique of estimation is applied to two broad classes of systems. The first involves a class of continuous time nonlinear systems subject to bounded unknown exogenous disturbance with constant parameters. Using the proposed set-based adaptive estimation, the parameters are updated only when an improvement in the precision of the parameter estimates can be guaranteed. The formulation provides robustness to parameter estimation error and bounded disturbance. The parameter uncertainty set and the uncertainty associated with an auxiliary variable is updated such that the set is guaranteed to contain the unknown true values. The second class of system considered is a class of nonlinear systems with timevarying parameters. Using a generalization of the set-based adaptive estimation technique proposed, the estimates of the parameters and state are updated to guarantee convergence to a neighborhood of their true value. The algorithm proposed can also be extended to detect the fault in the system, injected by drastic change in the time-varying parameter values. To study the practical applicability of the developed method, the estimation of state variables and time-varying parameters of salt in a stirred tank process has been performed. The results of the experimental application demonstrate the ability of the proposed techniques to estimate the state variables and time-varying parameters of an uncertain practical system. / Thesis (Master, Chemical Engineering) -- Queen's University, 2011-10-31 22:04:58.762
25

Gender Bias in Observer Ratings of Pediatric Procedural Pain

Sims, Jeff 15 February 2007 (has links)
The current study attempted to discern the extent to which a gender bias influences the adult ratings of observed childhood pain. While gender differences in pain sensation are well documented in physiologically mature individuals, there seems to be no such difference in children. The effect of manipulating gender on the procedural pain ratings of 201 university undergraduate and nursing students was examined via a deceptive pain observation task. Results demonstrated no significant difference between gender conditions; however a strong link was established between prior exposure to painful pediatric medical procedures and lower pain ratings. The results suggest that, while a gender bias failed to alter pain ratings, desensitization to viewing painful procedures could alter how much pain healthcare professionals believe a patient is experiencing.
26

Switching observer design, consensus management, and time-delayed control with applications for rigid-body attitude dynamics

Chunodkar, Apurva Arvind 29 January 2013 (has links)
This dissertation addresses three diverse research problems pertaining to rigid body attitude stabilization and control. The problems addressed result in theoretical development for the topics of cooperative control, delayed feedback, and state estimation, through the formulation of a novel class of switching observers. In the area of consensus management for cooperative control, the problem of designing torque control laws that synchronize the attitude of a team of rigid bodies under constant, unknown communication time delays is addressed. Directed communication graphs are considered, which encompass both leader-follower and leaderless architectures. A feedback linearization result involving the Modified Rodrigues parameter (MRP) representation of attitude kinematics reduces the attitude dynamics equations to double integrator agents and the remainder of the control effort achieves position consensus. New necessary and sufficient delay dependent stability conditions for the system of double integrator agents are presented. This dissertation also considers the problem of stabilizing attitude dynamics with unknown piecewise-constant delayed feedback. The problem is addressed through stability analysis of switched linear time-invariant and nonlinear timedelay systems. In the case of linear systems with switched delay feedback, a new sufficiency condition for average dwell time result is presented using a complete type Lyapunov-Krasovskii (L-K) functional approach. Further, the corresponding switched system with nonlinear perturbations is proven to be exponentially stable inside a well characterized region of attraction for an appropriately chosen average dwell time. Finally, this dissertation provides a new switching angular velocity observer formulation to the classical problem of rigid body attitude tracking in the absence of angular rate measurements. Exponential convergence of the angular velocity state estimation errors is proven independent of control design by using a novel error signal definition through this switching-type observer. The switching ensures C0 continuity for all the estimated states. Further, the maximum number of switches required by the observer is shown to be finite and that zeno-type behavior cannot occur. A “separation property” type result in the absence of actual angular rate measurements is established, wherein a linear and nonlinear controller utilizes angular velocity estimates from the proposed observer to achieve attitude tracking. / text
27

Developing a computational model of the pilot's best possible expectation of aircraft state given vestibular and visual cues

Onur, Can 12 January 2015 (has links)
Loss of Control (LOC) accidents are a major threat for aviation, and contribute the highest risk for fatalities in all aviation accidents. The major contributor to LOC accidents is pilot spatial disorientation (SD), which accounts for roughly 32% of all LOC accidents. A pilot experiences SD during flight when the pilot's expectation of the aircraft's state deviates from reality. This deviation results from a number of underlying mechanisms, such as distraction, failure to monitor flight instruments, and vestibular illusions. Previous researchers have developed computational models to understand those mechanisms. However, these models are limited in scope as they do not model the pilot's knowledge of the aircraft dynamics. This research proposes a novel model to predict the best-possible-pilot-expectation of the aircraft state given vestibular and visual cues. The proposed model uses a Model-Based Observer (MBO) as the infrastructure needed to establish an “expert pilot”. Expert pilots are known to form an internal model of the operated system through training and experience, which allows the expert to generate better internal expectations of the system states. Pilots' internal expectations are enhanced by the presence of information fed through the pilots̕ sensory systems. Thus, the proposed model integrates pilot's knowledge of the system dynamics (i.e. an aircraft model) with a continuous vestibular sensory model and a discrete visual-sampling sensory model. The computational model serves to investigate the underlying mechanisms of SD during flight and provide a quantitative analysis tool to support flight deck and countermeasure designs.
28

DIFFERENCES IN DIMENSIONS OF CHILDHOOD FUNCTIONING IN CHILDREN OF PRETERM VERSUS FULL TERM BIRTH STATUS

Turner, Tameika Shenay 01 January 2006 (has links)
As medical advances are made in the area of neonatology, more and more premature babies are surviving at younger gestational ages and lower birth weights. Growth in the survival rates of preterm infants leads to questions regarding the long term developmental trajectory of these children. The current study sought to expand on research regarding dimensions of childhood functioning and to apply it to the problem of prematurity by (a) utilizing a new instrument: the Merrill Palmer Revised edition, (b) including children of preterm and full term birth statuses from as young as 2 months of age, and (c) collecting data from parental and clinician reports. In addition to attempts to clarify the relationship between birth status and childhood dysfunction, this study also sought to augment existing literature by exploring the correlation between parental report and clinician observation of childhood dysfunction. The results of this study did not support the hypothesis that children of preterm birth will demonstrate more problems in functioning when compared to full term peers. Although there were more significant differences between preterm and full term children in the older cohort group, those differences did not consistently reflect dysfunction by the preterm children. Additionally, this study considered dimensions of dysfunction as measured by parental report and clinician observations. Notably, a lack of agreement between parent and clinician observations emerged for the young age cohort group. However, the high level of agreement for the older children suggests that parental and clinician perspectives converge with older children. Contrary to the hypothesis, birth status, gender, ethnicity, and SES did not collectively form a specific risk index for dysfunction. However, these factors did interact with each other to predict functioning on several scales. In fact, there were no significant main effects. Instead, predictors of dysfunction were interactions of variables such as birth status, age, gender, and ethnicity. This general finding illustrates the importance of taking into consideration all aspects of the childs situation when making an assessment of functioning.
29

Gender Bias in Observer Ratings of Pediatric Procedural Pain

Sims, Jeff 15 February 2007 (has links)
The current study attempted to discern the extent to which a gender bias influences the adult ratings of observed childhood pain. While gender differences in pain sensation are well documented in physiologically mature individuals, there seems to be no such difference in children. The effect of manipulating gender on the procedural pain ratings of 201 university undergraduate and nursing students was examined via a deceptive pain observation task. Results demonstrated no significant difference between gender conditions; however a strong link was established between prior exposure to painful pediatric medical procedures and lower pain ratings. The results suggest that, while a gender bias failed to alter pain ratings, desensitization to viewing painful procedures could alter how much pain healthcare professionals believe a patient is experiencing.
30

Driveline Observer for an Automated Manual Gearbox

Juhlin-Dannfelt, Peter, Stridkvist, Johan January 2006 (has links)
The Automated Manual Transmission system Opticruise is dependent on signals from sensors located in different parts of the Scania trucks. These signals are of different qualities and have different update frequencies. Some signals and quantities that are hard or impossible to measure are also of importance to this system. In this thesis a driveline observer for the purpose of signal improvement is developed and estimations of unknown quantities such as road incline and mass of the vehicle are performed. The outputs of the observer are produced at a rate of 100 Hz, and include in addition to the mass and road incline also the speed of the engine, output shaft of the gearbox, wheel and the torsion in the driveline. Further the use of an accelerometer and the advantages gained from using it in the observer are investigated. The outputs show an increased quality and much of the measurement noise is successfully removed without introducing any time delays. A simulation frequency of 100 Hz is possible, but some dependency toward the stiffness of the driveline is found. The observer manages to estimate the road slope accurately. With the use of an accelerometer the road slope estimation is further improved and a quickly converging mass estimation is obtained.

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