Tunable antennas have emerged as a promising technology to address the challenges of achieving optimal performance across a wide range of frequencies. This abstract presents a study focused on designing and implementing an ideal antenna system design within a closed-loop system. Background. Tunable antennas offer a solution for achieving efficient signal transmission and reception over a broad spectrum. Traditionally fixed-frequency antennas have limitations in terms of bandwidth and efficiency, making them unfit for applications requiring adaptability to varying frequencies. The integration of tunable components in antenna systems results in greater flexibility and improved performance. Objectives. The main objective of this research is to evaluate and determine the ideal antenna design for closed-loop antenna systems which achieves maximum frequency coverage and efficiency. This involves the design of an architecture that seamlessly integrates components. Methods. The experimental methodology involves designing an antenna system design. The selected components are interconnected in a closed loop, allowing continuous monitoring and adjustment of the antenna’s characteristics. The Micro Controlling Unit (MCU) is programmed using the Arduino Integrated Development Environment (IDE), serves as the controller for managing the antenna tuner’s settings based on real-time feedback from the directional coupler and power detector. The bi-directional logic level converter ensures proper voltage compatibility between the MCU and the antenna tuner. Results. The results of the study showed that the proposed antenna system architecture was able to achieve the desired goals. The implemented closed-loop system demonstrates significant enhancements in frequency coverage and efficiency of the selected antenna. The antenna system was also able to maintain its efficiency even when the environment changed. Conclusions. The experimental results show that in closed-loop systems the performance of an antenna is optimised. The integration of the components enables dynamic frequency tuning, by enhancing the antenna’s maximum frequency coverage and efficiency. The results underscore the potential of tunable antennas in revolutionizing wireless communication systems, showing the way for more adaptable and high-performance devices in various applications.

Stochastic system identification is of great interest in the areas of control and communication. In stochastic system identification, a model of a dynamic system is determined based on given inputs and received outputs from the system, where stochastic uncertainties are also involved. The scope of the report is to consider continuous-time models used within control and communication and to estimate the model parameters from sampled data with high accuracy in a computational efficient way. Continuous-time models of systems controlled in a networked environment, stochastic closed-loop systems, and wireless channels are considered. The parameters of a transfer function based model for the process in a networked control system are first estimated by a covariance function based approach, relying upon the second order statistical properties of the output signal. Some other approaches for estimating the parameters of continuous-time models for processes in networked environments are also considered. Further, the parameters of continuous-time autoregressive exogenous models are estimated from closed-loop filtered data, where the controllers in the closed-loop are of proportional and proportional integral type, and where the closed-loop also contains a time-delay. Moreover, a stochastic differential equation is derived for Jakes's wireless channel model, describing the dynamics of a scattered electric field with the moving receiver incorporating a Doppler shift. / <p>Article I was still in manuscript form at the time of the defense.</p>

In this paper, we identify sufficient conditions for Lyapunov Mean Square Stability (LMSS) of a contention-based network of first-order systems, with state-based schedulers. The stability analysis helps us to choose policies for adapting the scheduler threshold to the delay from the network and scheduler. We show that three scheduling laws can result in LMSS: constant-probability laws and additively increasing or decreasing probability laws. Our results counter the notions that increasing probability scheduling laws alone can guarantee stability of the closed-loop system, or that decreasing probability scheduling laws are required to mitigate congestion in the network. / <p>QC 20130116</p>

This thesis presents the development of high resolution, wide dynamic range sigma-delta type readout circuits for capacitive MEMS accelerometers. Designed readout circuit employs fully differential closed loop structure with digital output, achieving high oversampling ratio and high resolution. The simulations of the readout circuit together with the accelerometer sensor are performed using the models constructed in Cadence and Matlab Simulink environments. The simulations verified the stability and proper operation of the accelerometer system. The sigma-delta readout circuit is implemented using XFab 0.6 &micro / m CMOS process. Readout circuit is combined with Silicon-On-Glass (SOG) and Dissolved Wafer Process (DWP) accelerometers. Both open loop and closed loop tests of the accelerometer system are performed. Open loop test results showed high sensitivity up to 8.1 V/g and low noise level of 4.8 &micro / g/&amp / #61654 / Hz. Closed loop circuit is implemented on a PCB together with the external filtering and decimation electronics, providing 16-bit digital output at 800 Hz sampling rate. High acceleration tests showed &plusmn / 18.5 g of linear acceleration range with high linearity, using DWP accelerometers. The noise tests in closed loop mode are performed using Allan variance technique, by acquiring the digital data. Allan variance tests provided 86 &micro / g/&amp / #61654 / Hz of noise level and 74 &micro / g of bias drift. Temperature sensitivity tests of the readout circuit in closed loop mode is also performed, which resulted in 44 mg/&ordm / C of temperature dependency. Two different types of new adaptive sigma-delta readout circuits are designed in order to improve the resolution of the systems by higher frequency operation. The two circuits both change the acceleration range of operation of the system, according to the level of acceleration. One of the adaptive circuits uses variation of feedback time, while the other circuit uses multi-bit feedback method. The simulation results showed micro-g level noise in closed loop mode without the addition of the mechanical noise of the sensor.

Rigid multibody systems have been studied extensivley due to its direct application in design and analysis of various mechanical systems such as robots and spacecraft structures. The dynamics of multibody system is governed by its equations of motion and various terms associated with it, such as the mass matrix, the generalized force vector, are well known..Forward dynamics algorithms play an important role in the simulation of multibody systems and the recursive forward dynamics algorithm for branched multibody systems is very popular. The recursive forward dynamic algorithm is highly efficient algorithm with O(n) computational complexity and scores over other algorithms when number of rigid bodies n in the system is very large. The algorithm involves finding an important mass matrix, which has been popularly termed as articulated body inertia (AB inertia). To find ijth term of any general mass matrix, we separately give virtual change to ith and jth generalized coordinates. At each point of the multibody system, the dot product of the resulting virtual displacements are taken with each other and eventually integrated over the entire multibody system, weighted by the mass. This quantity divided by the virtual changes in ith and jth coordinates gives the ijth element of the mass matrix. This is one of the fundamental ways of looking at the mass matrix. However, in literature, the AB inertia is obtained as a result of mathematical manipulation and its physical or geometrical significance from the above view point is not clear. In this thesis we present a more geometric and physical explanation for the AB inertia. The main step is to obtain a new set of generalized coordinates which relate directly to the AB inertia. We have also shown the equivalence of our method with existing methods. A comprehensive treatement on change of generalized coordinates and its effect on equations of motion has also been presented as preliminaries. The second part of the thesis deals with closed loop multibody systems.A few years ago an iterative algorithm called the sequential regularization method (SRM) was proposed for simulation of closed loop multibody systems with attractive claims on its efficiency. In literature we find that this algorithm has been implemented and studied only for planar multibody systems. As a part of the thesis work, we have developed a C-programming language code which can simulate 3-dimensional spatial multibody systems using the SRM algorithm. The programme can also perform simulation using a relatively efficient Conventional algorithm having O(n+m3) complexity, where m denotes number of closed loop constraints. Simulation studies have been carried out on a few multibody systems using the two algorithms. Some of the results have been also been validated using the commercial simulation package -ADAMS. As a result of our simulation studies, we have detected certain points, after which the solution from SRM loses it convergence. More study is required to understand this lack of convergence.

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The goal of this work is to describe a robotics platform called the Building Wide Intelligence Segbot (segbot). The segbot is a two wheeled robot that can robustly navigate our building, perform obstacle avoidance, and reason about the world. This work has two main goals. First we introduce the segbot platform to anyone that may use it in the future. We begin by examining off-the-shelf components we used and how to build a robot that is able to navigate in a complex multi-floor building environment with moving obstacles. Then we explain the software from a top down viewpoint, with a three layer abstraction model for segmenting code on any robotics platform. The second part of this document describes current work on the segbot platform, which is able to non-robustly take requests for coffee and navigate to a coffee shop while having to move across multiple floors in a building. My contribution to this work is building an infrastructure for multi-floor navigation. The multi-floor infrastructure built is non-robust but has helped identify several issues that will need to be tackled in future iterations of the segbot. / text

This Thesis is concerned with the approximation of high order controllers or the controller reduction problem. We firstly consider approximating high-order controllers by low order controllers based on the closed-loop system approximation. By approximating the closed-loop system transfer function, we derive a new parametrized double-sided frequency weighted model reduction problem. The formulas for the input and output weights are derived using three closed-loop system configurations: (i) by placing a controller in cascade with the plant, (ii) by placing a controller in the feedback path, and (iii) by using the linear fractional transformation (LFT) representation. One of the weights will be a function of a free parameter which can be varied in the resultant frequency weighted model reduction problem. We show that by using standard frequency weighted model reduction techniques, the approximation error can be easily reduced by varying the free parameter to give more accurate low order controllers. A method for choosing the free parameter to get optimal results is being suggested. A number of practical examples are used to show the effectiveness of the proposed controller reduction method. We have then considered the relationships between the closed-loop system con gurations which can be expressed using a classical control block diagram or a modern control block diagram (LFT). Formulas are derived to convert a closed-loop system represented by a classical control block diagram to a closed-loop system represented by a modern control block diagram and vice versa.

Dans le secteur de la santé et particulièrement en unité des soins intensifs, diverses situations cliniques sont rencontrées et l'interprétation d'une grande quantité de données, y compris celles fournies par les équipements tels que moniteurs et ventilateurs, est exigée pour une prise de décision appropriée. La disparité entre cette quantité importante d'information et la capacité humaine limitée crée une variabilité inutile à la décision clinique. Pour faire face au problème, les experts médicaux ont défini des stratégies en vue de promouvoir une pratique fondée sur les données probantes. Cette méthode est devenue un standard pour la pratique clinique et a montré beaucoup d'avantages en menant à la définition de directives spécifiques ou des protocoles précis à appliquer dans certaines situations. Cependant, l'utilisation de directives/protocoles, particulièrement dans les soins intensifs, exige une participation continue des professionnels au chevet du malade et est ainsi difficile à appliquer en pratique clinique. La définition d'assistants informatisés est une solution technologique intéressante à explorer pour faciliter l'introduction des protocoles dans la routine clinique. En ventilation mécanique, on assiste à une prise de conscience croissante sur le potentiel de l'informatisation et son applicabilité au-delà de la recherche et plus concrètement dans le soutien du clinicien dans sa prise de décision quotidienne. Ceci à travers la prise en charge des tâches répétitives et la proposition de suggestions. Ce domaine constitue un environnement idéal pour de telles applications surtout que les ventilateurs de réanimation son aujourd'hui des équipements électroniques sophistiqués qui peuvent embarquer des protocoles informatisés. L'objectif de cette thèse était d'explorer les aspects de développement, déploiement et d'efficacité des « contrôleurs intelligents » en ventilation mécanique afin d'accélérer leur création et leur adoption. Pour examiner les phases de développement et de déploiement, nous nous sommes concentrés sur l'utilisation et l'extension du SmartCare®, une plateforme logicielle qui facilite l'automatisation des procédures thérapeutiques en ventilation mécanique à partir de la modélisation des connaissances expertes jusqu'à leur exécution en temps réel dans un équipement médical. A travers une approche ascendante, en se basant particulièrement sur notre expérience pratique dans le design de contrôleurs intelligents et après l'examen de divers contrôleurs existants, l'objectif était de définir un catalogue de pièces maitresses pour la représentation des protocoles en ventilation mécanique. L'utilisation d'une ontologie du domaine assure une formalisation saine de ces pièces.Sur base de cette approche, nous avons développé un contrôleur pour l'oxygénation testé au chevet du malade. Nous rapportons ses performances comparées à la pratique standard / In healthcare, especially in critical care, various clinical situations are encountered and a huge amount of data, including those provided by equipment such as monitors and ventilators, are required for an appropriate decision-making. The mismatch between this vast amount of information and the human capability creates unnecessary variability in clinical decision. To cope with this problem, medical experts have defined specific strategy called evidence based medicine. This method has become the standard of practice and showed many benefits by leading to the definition of specific guidelines or precise protocols to follow in specific situations. However, the use of guidelines/protocols, especially in critical care, requires the continuous involvement of professionals at the patient's bedside strongly limiting their application in practice. The introduction of computerized assistants for implementing such guidelines/protocols may be an interesting technological solution. In mechanical ventilation where various protocols are available there is a growing acceptance that such computerization might be useful beyond research, in assisting clinicians in their daily decision making by taking over some routine tasks or providing suggestions. Moreover, this domain constitutes an ideal environment because mechanical ventilators are presently powerful electronic equipments in which computerized protocols can be efficiently embedded. The objective of this thesis was to explore several aspects of the development, deployment, and effectiveness of computerized protocols or smart controllers in mechanical ventilation in order to accelerate their creation and adoption. For this purpose, we focused on the use and the extension of SmartCare®, a computer framework for the automation of respiratory therapy starting from clinical knowledge modelling to execution in real time of specific routines embedded into medical products [1]. Through a reengineering approach, from practical experience in smart controller design and investigation of existing controllers, the objective was to define a catalogue of building blocks to facilitate the creation of new controllers. The modeling of such blocks using dedicated domain ontology ensures a sound formalization. To prove the effectiveness of such a generic approach, we built a smart controller for oxygenation tested on the patient's bedside. We reported its performance compared to standard therapy