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1 
Symptom Onset to FirstMedicalContact in STSegment Elevation Myocardial Infarction PatientsBalbaa, Amira January 2016 (has links)
STsegment elevation myocardial infarctions (STEMI) make up approximately 25% to 40% of total myocardial infarction (MI) presentations. The total occlusion of the coronary artery that results in a STEMI makes timeliness to reperfusion crucial. Previously, the focus has been on decreasing doortoballoon time (D2B). Although D2B time plays an important role in achieving timely treatment, it is only one component of the route from symptom onset to reperfusion. It has been shown that total ischemic time is a better predictor of clinical outcomes, including mortality and infarct time. Delays between symptom onset to firstmedicalcontact (FMC) consume the majority of total ischemic time, and remains one of the main reasons that patients do not receive timely care. Factors affecting symptom onset to FMC for STEMI patients receiving primary PCI as a method of reperfusion at the Aswan Heart Center (AHC) in Egypt and the Hamilton General Hospital (HGH) in Canada were examined using the prospectively collected data held in the STEMI registries at these sites and a modified version of the Response to Systems Questionnaire applied in Egypt. Exploring factors linked to early and late presentation in STEMI patients showed that delays were associated with gender, smoking, cardiac history, cardiogenic shock and mortality rate. Furthermore, the type and number of symptoms, presence and actions of bystanders, emotional response and the actions of the patients, as well as transportation time was shown to be different among delay groups. / Thesis / Master of Science (MSc)

2 
Robust Power Control of Optical Networks with TimedelaysStefanovic, Nemanja 23 February 2011 (has links)
We study the stability of power control algorithms applied to optical networks in the presence of both timedelays and uncertainties. The objective of power control algorithms acting on optical networks is to ensure each signal channel attains an optimal optical signaltonoise ratio (OSNR) value such that transmission errors are minimized. The inputs to the optical network are the transmitter powers and the outputs of the optical network are the OSNR values. The primal control algorithms adjust the channel powers at the transmitters using the channel OSNR values as feedbacks to attain OSNR optimality. We also present the dual control algorithm located at the links which transmits a channel price as an additional feedback to the primal control algorithms. Together, these are called primaldual control algorithms.
We present robust OSNR models for optical networks with multiple timedelays. Specifically, we consider additive system uncertainties, input multiplicative uncertainties on the signal powers, and transmitter noise uncertainties, all within a normbounded uncertainty framework. We analyze and modify both central cost based algorithms and gametheoretic based algorithms, with an emphasis on the latter, to ensure the stability of the closedloop system. We apply timedelay stability analyses to exploit the structures of the closedloop systems for each type of control algorithm. These techniques include frequency analyses, LyapunovRazumikhin techniques, and LyapunovKrasovskii techniques. Due to nonlinearities in the closedloop system models, and their timescale separated dynamics, we apply singular perturbation theory modified to handle either LyapunovRazumikhin theory or LyapunovKrasovskii theory. Singular perturbation theory, modified for timedelays, allows us to decouple complicated closedloop systems into two simpler subsystems, one on a "slow" timescale, and the other on a "fast" timescale. We develop stability conditions for primal algorithms applied to arbitrary networks with delays. We also develop stability conditions for primaldual algorithms applied to singlelinks, singlesink networks, two channel networks, and multilink networks with both timedelays and uncertainties. The main results are presented as either LMI conditions and algebraic criteria. Simulations verify the stability of the closedloop systems in the presence of timedelays. In addition, the simulations show the stabilization of perturbed systems at the expense of transient convergence time.

3 
Robust Power Control of Optical Networks with TimedelaysStefanovic, Nemanja 23 February 2011 (has links)
We study the stability of power control algorithms applied to optical networks in the presence of both timedelays and uncertainties. The objective of power control algorithms acting on optical networks is to ensure each signal channel attains an optimal optical signaltonoise ratio (OSNR) value such that transmission errors are minimized. The inputs to the optical network are the transmitter powers and the outputs of the optical network are the OSNR values. The primal control algorithms adjust the channel powers at the transmitters using the channel OSNR values as feedbacks to attain OSNR optimality. We also present the dual control algorithm located at the links which transmits a channel price as an additional feedback to the primal control algorithms. Together, these are called primaldual control algorithms.
We present robust OSNR models for optical networks with multiple timedelays. Specifically, we consider additive system uncertainties, input multiplicative uncertainties on the signal powers, and transmitter noise uncertainties, all within a normbounded uncertainty framework. We analyze and modify both central cost based algorithms and gametheoretic based algorithms, with an emphasis on the latter, to ensure the stability of the closedloop system. We apply timedelay stability analyses to exploit the structures of the closedloop systems for each type of control algorithm. These techniques include frequency analyses, LyapunovRazumikhin techniques, and LyapunovKrasovskii techniques. Due to nonlinearities in the closedloop system models, and their timescale separated dynamics, we apply singular perturbation theory modified to handle either LyapunovRazumikhin theory or LyapunovKrasovskii theory. Singular perturbation theory, modified for timedelays, allows us to decouple complicated closedloop systems into two simpler subsystems, one on a "slow" timescale, and the other on a "fast" timescale. We develop stability conditions for primal algorithms applied to arbitrary networks with delays. We also develop stability conditions for primaldual algorithms applied to singlelinks, singlesink networks, two channel networks, and multilink networks with both timedelays and uncertainties. The main results are presented as either LMI conditions and algebraic criteria. Simulations verify the stability of the closedloop systems in the presence of timedelays. In addition, the simulations show the stabilization of perturbed systems at the expense of transient convergence time.

4 
Stabiity for Systems with Unknown Time DelaysGaudette, Darrell January 2013 (has links)
Time delays are of longstanding interest in the study of control systems since they appear in many practical control problems and tend to degrade overall system performance. In this thesis, we consider two distinct problems involving uncertain time delays.
The first problem that we consider is the achievable delay margin problem, which is determining the longest delay for which stability can be maintained when using a linear time invariant (LTI) controller. This problem has been considered in continuoustime, where bounds (often tight) have been found for plants with nonzero right half plane poles. In this work, we consider the discretetime case, where we prove that an LTI controller exists which stabilizes the plant and the plant with a one step delay if and only if the plant has no negative, real unstable poles.
The second problem that we consider is stabilizing any continuoustime singleinput singleoutput LTI plant with an arbitrarily large time delay and gain. To solve this problem, we propose a simple generalized hold whose resulting discretized system is amenable to adaptive control. Furthermore, by exploiting the structure of the resulting discretized system, we propose purpose built estimators for the unknown gain and delay, which allows us to not only provide boundedinput boundedoutput (BIBO) closedloop stability, but also guarantees the exponential decay of any plant initial conditions, robustness to unmodelled dynamics, and tolerance to occasional, possibly persistent, jumps in the gain and delay. Furthermore, for the case of a first order plant, a similar, but suitably modified controller is shown to tolerate continuous variation of the unknown delay while still providing BIBO closedloop stability.

5 
Stabiity for Systems with Unknown Time DelaysGaudette, Darrell January 2013 (has links)
Time delays are of longstanding interest in the study of control systems since they appear in many practical control problems and tend to degrade overall system performance. In this thesis, we consider two distinct problems involving uncertain time delays.
The first problem that we consider is the achievable delay margin problem, which is determining the longest delay for which stability can be maintained when using a linear time invariant (LTI) controller. This problem has been considered in continuoustime, where bounds (often tight) have been found for plants with nonzero right half plane poles. In this work, we consider the discretetime case, where we prove that an LTI controller exists which stabilizes the plant and the plant with a one step delay if and only if the plant has no negative, real unstable poles.
The second problem that we consider is stabilizing any continuoustime singleinput singleoutput LTI plant with an arbitrarily large time delay and gain. To solve this problem, we propose a simple generalized hold whose resulting discretized system is amenable to adaptive control. Furthermore, by exploiting the structure of the resulting discretized system, we propose purpose built estimators for the unknown gain and delay, which allows us to not only provide boundedinput boundedoutput (BIBO) closedloop stability, but also guarantees the exponential decay of any plant initial conditions, robustness to unmodelled dynamics, and tolerance to occasional, possibly persistent, jumps in the gain and delay. Furthermore, for the case of a first order plant, a similar, but suitably modified controller is shown to tolerate continuous variation of the unknown delay while still providing BIBO closedloop stability.

6 
Stable bilateral teleoperation with timevarying delaysYang, Yuan 12 July 2017 (has links)
A teleoperation system is a masterslave robotic system in which the master and slave robots are at different geographical locations and synchronize their motions through the communication channel, with the goal of enabling the human operator to interact with a remote environment. The two primary objectives of bilateral teleoperation systems, position tracking and force feedback, are necessary for providing the user with high fidelity telepresence. However, time delays in communication channels impede the realization of the two objectives and even destabilize the system. To guarantee stability and improve performance, several damping injectionbased controllers have been developed in this thesis for two channel and four channel teleoperation systems. For two channel teleoperation, an adaptive bounded state feedback controller has firstly been proposed to address teleoperation with timevarying delays, model uncertainties and bounded actuations. Next, a simplified and augmented globally exponentially convergent velocity observer has been designed and incorporated in the conventional P+d control to obtain stable bilateral teleoperation without using velocity measurements. Then, the more challenging bounded output feedback control problem has been solved by combining the bounded state feedback control and output feedback control two techniques with more conservative control gains. In four channel teleoperation, a hybrid damping and stiffness adjustment strategy has been introduced to tightly constrain the master and slave robots and achieve robust stability. Further, the nonsingular version is developed to conquer the singularity problem in the hybrid strategy, which has been proved to avoid unexpected torque spikes due to the singularity problem at zero velocities. Besides, this thesis has also provided a reducedorder controller to guarantee position coordination for arbitrarily large position errors and maintain the tight coupling between the master and slave sites. After concluding all the research results, future study directions are pointed out at the end of this thesis. / Graduate

7 
Some Aspects on Robust Stability of Uncertain Linear Singularly Perturbed Systems with Multiple Time DelaysChen, ChingFa 21 June 2002 (has links)
In this dissertation, the robust stability of uncertain continuous and discrete singularly perturbed systems with multiple time delays is investigated. Firstly, the asymptotic stability for a class of linear continuous singularly perturbed systems with multiple time delays is investigated. A simple estimate of an upper bound of singular perturbation parameter is proposed such that the original system is asymptotically stable for any . Moreover, a delaydependent criterion, but independent, is proposed to guarantee the asymptotic stability of the original system. Secondly, we consider the robust stability problem of uncertain continuous singularly perturbed systems with multiple time delays. Two delaydependent criteria are proposed to guarantee the robust stability of a class of uncertain continuous multiple timedelay singularly perturbed systems subject to unstructured perturbations. Thirdly, the robust Dstability of nominally stable discrete uncertain systems with multiple time delays is considered. Finally, the robust stability of nominally stable uncertain discrete singularly perturbed systems with multiple time delays subject to unstructured and structured perturbations is investigated. Some criteria, delaydependent or delayindependent, will be proposed to guarantee the robust stability of the uncertain discrete multiple timedelay singularly perturbed systems. The improvements of our results over those in recent literature are also illustrated if the comparisons are possible. Some numerical examples will also be provided to illustrate our main results.

8 
Output Feedback Bilateral Teleoperation with Force Estimation in the Presence of Time DelaysDaly, John Michael January 2010 (has links)
This thesis presents a novel bilateral teleoperation algorithm for n degree of freedom nonlinear manipulators connected through time delays. Teleoperation has many practical uses, as there are many benefits that come from being able to operate machines from a distance. For instance, the ability to send a remote controlled robotic vehicle into a hazardous environment can be a great asset in many industrial applications. As well, the field of remote medicine can benefit from these technologies. A highly skilled surgeon could
perform surgery on a patient who is located in another city, or even country. Earth to space operations and deep sea exploration are other areas where teleoperation is quite useful.
Central to the approach presented in this work is the use of second order sliding mode unknown input observers for estimating the external forces acting on the manipulators. The use of these observers removes the need for both velocity and force sensors, leading to a lower cost hardware setup that provides all of the advantages of a positionforce
teleoperation algorithm. Stability results for this new algorithm are presented for several cases. Stability of each of the master and slave sides of the teleoperation system is demonstrated, showing that the
master and slave are both stabilized by their respective controllers when the unknown input observers are used for state and force estimation. Additionally, closed loop stability results for the teleoperation system connected to a variety of slave side environments are presented. Delayindependent stability results for a linear
springdamper environment as well as a general finitegain stable nonlinear environment are given. Delaydependent stability results for the case where the slave environment is a liner springdamper and the delays are commensurate are also presented. As well, stability results
for the closed loop under the assumption that the human operator is modeled as a finitegain stable nonlinear environment are given. Following the theoretical presentation, numerical simulations illustrating the algorithm are presented, and
experimental results verifying the practical application of the approach are given.

9 
Title Optimal Fractional Order Proportional And Integral Controller For Processes With Random Time DelaysBhambhani, Varsha 01 May 2009 (has links)
This work made publicly available electronically on July 7, 2011.This thesis developed a new practical tuning method for fractional order proportional and integral controllers (FOPI / PI®) for varying timedelay systems like networked con trol systems (NCS), sensor networks, etc. Based on previously proposed FOPI controller tuning rules using fractional Ms constrained integral gain optimization (FMIGO), simulta neous maximization of the jitter margin and integrated time weighted absolute error (ITAE) performance for a set of hundred gain delay timeconstant (KLT) systems having di®erent timeconstants and timedelay values are achieved. A multiobjective optimization algo rithm is used to simultaneously maximize the ITAE factor and jitter margin of the plants at initial FMIGO gain parameters. The new values of controller gain parameters are gen eralized to give a new set of optimal fractional order proportional integral (OFOPI) tuning rules such that the jitter margin and system performance of closedloop KLT systems are maximized and yet the closedloop feedback system is stable. This is further tested and veri¯ed by simulation techniques. Comparisons are made with other existing proportional integral derivative (PID) and fractional order proportional integral (PI) tuning rules to prove the e±ciency of the new technique. It is further shown that OFOPI tuning rules per form better than traditional tuning methods for lagdominated FOPDT systems, because it can take the varying timedelay better into account. The tuning method is modi¯ed to work with discretetime controllers in the context of NCSs. Furthermore, experimental results in a NCS platform, Standalone Smart Wheel (omnidirectional networked control robot wheel), are reported using the tuning rules developed in this thesis. The optimization tuning method performed almost equally well in practice as in simulations. The thesis also shows that the tuning rule development procedure for OFOPI is not only valid for FOPDT systems but is also applicable for other general classes of plants which could be reduced to ¯rst order plant systems. Temperature control in heat °ow apparatus and waterlevel control in a coupled tank system using FOPI tuning rules are other major contributions of this thesis work.

10 
Output Feedback Bilateral Teleoperation with Force Estimation in the Presence of Time DelaysDaly, John Michael January 2010 (has links)
This thesis presents a novel bilateral teleoperation algorithm for n degree of freedom nonlinear manipulators connected through time delays. Teleoperation has many practical uses, as there are many benefits that come from being able to operate machines from a distance. For instance, the ability to send a remote controlled robotic vehicle into a hazardous environment can be a great asset in many industrial applications. As well, the field of remote medicine can benefit from these technologies. A highly skilled surgeon could
perform surgery on a patient who is located in another city, or even country. Earth to space operations and deep sea exploration are other areas where teleoperation is quite useful.
Central to the approach presented in this work is the use of second order sliding mode unknown input observers for estimating the external forces acting on the manipulators. The use of these observers removes the need for both velocity and force sensors, leading to a lower cost hardware setup that provides all of the advantages of a positionforce
teleoperation algorithm. Stability results for this new algorithm are presented for several cases. Stability of each of the master and slave sides of the teleoperation system is demonstrated, showing that the
master and slave are both stabilized by their respective controllers when the unknown input observers are used for state and force estimation. Additionally, closed loop stability results for the teleoperation system connected to a variety of slave side environments are presented. Delayindependent stability results for a linear
springdamper environment as well as a general finitegain stable nonlinear environment are given. Delaydependent stability results for the case where the slave environment is a liner springdamper and the delays are commensurate are also presented. As well, stability results
for the closed loop under the assumption that the human operator is modeled as a finitegain stable nonlinear environment are given. Following the theoretical presentation, numerical simulations illustrating the algorithm are presented, and
experimental results verifying the practical application of the approach are given.

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