Ulm, Univ., Diss., 2007.

Marburg, Univ., Diss., 2009

Major advances have been observed during the last two decades in the field of seismic engineering with further refinements of performance-based seismic design philosophies and the subsequent definition of corresponding compliance criteria. Following the globally recognized expectation and ideal aim to provide a modern society with high (seismic) performance structures able to sustain a design level earthquake with limited or negligible damage, alternative solutions have been developed for high-performance, seismic resisting systems. In the last two decades, an alternative approach in seismic design has been introduced for precast concrete buildings in seismic regions with the introduction of “dry” jointed ductile systems also called “hybrid” systems based on unbonded post-tensioned rocking connections. As a result structural systems with high seismic performance capabilities can be implemented, with the unique capability to undergo inelastic displacement similar to their traditional monolithic counterparts, while limiting the damage to the structural system and assuring full re-centring capabilities (negligible residual or permanent deformations). The continuous and rapid development of jointed ductile connections for seismic resisting systems has resulted in the validation of a wide range of alternative arrangements, encompassed under the general umbrella of “hybrid” systems. This research provides a comprehensive experimental and analytical investigations of 2- and 3-Dimensional, 2/3 scaled, exterior beam-column joints subjected both uni and bi-directional (four clove) quasic-static loading protocols into the behaviour, modelling, design and feasibility of new arrangements for “dry” jointed ductile systems for use in regions of high seismicity. In order to further emphasize the enhanced performance of these systems, a comparison with the experimental response and observed damage of 2-D and 3-D monolithic beam-column benchmark specimens is presented. However, after a lot of attention given to the behaviour of the skeleton structure, more recently the focus of research in Earthquake Engineering has concentrated on the behaviour of the floor system within the overall 3D behaviour of the building and the effects of beam elongation. The effects of beam elongation in precast frame systems have been demonstrated to be a potential source of un-expected damage, unless adequate detailing is provided in order to account for displacement incompatibilities between the lateral resisting systems and the floor. Two contributions to beam elongation are typically recognized: a) the material contribution due to the cumulative residual strain within the steel, and b) the geometrical contribution due to the presence of a neutral axis and actual depth of the beam. Regarding jointed ductile connections with re-centering characteristics, the extent of beam elongation is significantly reduced, being limited to solely the geometrical contribution. Furthermore, such effects could be minimized when a reduced depth of the beam is adopted due to the use of internal prestressing or external post-tensioning. However, damage to precast floor systems, resulting from a geometric elongation of the beam, has yet to be addressed in detail. In order to emphasize the enhanced performance in controlling and minimizing the damage of the structural elements via the use of the proposed advanced hybrid solutions, this research presents via experimental and analytical validation of two alternative and innovative solutions to reduce the damage to the floor using 2 and 3-Dimensional, 2/3 scaled, exterior beam-column joints. The first approach consists of using standard precast rocking/dissipative frame connections (herein referred to as “gapping”) in combination with an articulated or “jointed” floor. This system uses mechanical devices to connect the floor and the lateral beams which can accommodate the displacement incompatibilities in the connection. The second approach to reduce the floor damage investigates the implementation of a “non-gapping” connection, also called non-tearing-floor connection, using a top hinge at the beam-column interface, while still relying on more traditional floor-to-frame connections (i.e. topping and continuous starter bars). Additionally, further refinements and constructability issues for the non gapping connection are investigated under the experimental and analytical validation of a major 2-Dimensional, 2/3 scaled, two-story one-bay frame using non-tearing floor connections. Based on the non-tearing floor connections, a series of parametric analysis for beam-column joints and frames are carried out. Furthermore, the analysis and design of two prototype frames using different solutions is presented. The frames are subjected to cyclic adaptive pushover and inelastic time history analysis in order to investigate analytically the response characteristics of hybrid frames using non-tearing connections, as well as how the beam growth affects the frame response under earthquake loading. Computational models for hybrid PRESSS frames and a conventional reinforced concrete frames are developed and compared with the ones using non-tearing connections.

Doctor of Philosophy / Department of Electrical and Computer Engineering / Balasubramaniam Natarajan / Stochastic hybrid system (SHS) is a class of dynamical systems that experience interaction of both discrete mode and continuous dynamics with uncertainty. State estimation for SHS has attracted research interests for decades with Kalman filter based solutions dominating the area. Mode-based Kalman filter is an extended version of the traditional Kalman filter for SHS. In general, as Kalman filter is unbiased for non-hybrid system estimation, prior research efforts primarily focus on the behavior of error covariance. In SHS state estimate, mode mismatch errors could result in a bias in the mode-based Kalman filter and have impacts on the continuous state estimation quality. The relationship between mode mismatch errors and estimation stability is an open problem that this dissertation attempts to address. Specifically, the probabilistic model of mode mismatch errors can be independent and identically distributed (i.i.d.), correlated across different modes and correlated across time. The proposed approach builds on the idea of modeling the bias evolution as a transformed system. The statistical convergence of the bias dynamics is then mapped to the stability of the transformed system. For each specific model of the mode mismatch error, the system matrix of the transformed system varies which results in challenges for the stability analysis. For the first time, the dissertation derives convergence conditions that provide tolerance regions for the mode mismatch error for three mode mismatch situations. The convergence conditions are derived based on generalized spectral radius theorem, Lyapunov theorem, Schur stability of a matrix polytope and interval matrix method. This research is fundamental in nature and its application is widespread. For example, the spatially and timely correlated mode mismatch errors can effectively capture cyber-attacks and communication link impairments in a cyber-physical system. Therefore, the theory and techniques developed in this dissertation can be used to analyze topology errors in any networked system such as smart grid, smart home, transportation, flight management system etc. The main results provide new insights on the fidelity in discrete state knowledge needed to maintain the performance of a mode-based Kalman filter and provide guidance on design of estimation strategies for SHS.

Technology replaces newer technology with improved efficiency. Solar technology is going to draw out a new life to make a green change in the terms of energy. As a result energy from the sunlight is being changed into electric energy by using solar cell. But still its efficiency could not be able to make a sense as a depending energy technology. In order to look up the solution, solar technology is changing rapidly to get maximum output. To take up this new challenge solar technology is trying to change its building component that are used to make solar cell, for example solar cell material, bypass diode system, blocking diode system etc.   Now-a-days, solar energy system is designed as a hybrid system that can make electricity and hot water at the same time. In the hybrid solar system, photovoltaic and solar thermal systems are integrated at the same system and as a result heat and electricity are produced simultaneously at the same area. Solar cells are attached with both top and the bottom side of the module and the collectors are set up inside the module. By using collector inside the module, rejected heat from the solar cell is absorbed by the water that flows through the collectors. But a problem arises at the midday or after midday because the reflector of this system cannot reflect sunlight properly on the bottom side of the module. That’s why shading is occurred on the bottom side which reduce the total electrical output of this system.   To work out this shading problem, a bypass diode is connected in parallel with the group of solar cells. Schottky diodes are being used as bypass diodes inside in the most of the solar cells. Schottky diode forward voltage drop is almost 0.45 Volt which is an important cause of reducing the output power as well as the efficiency of this hybrid system. To solve this problem, new lossless diode is attached inside the hybrid solar system instead of schottky diode which can work with a very low forward voltage drop roughly 50mV at 10amp.   To make a comparison between the performance of PVT system with the schottky diode and the new lossless diode, many data has been collected from the outdoor test. After getting the output result, it is clear that the output power and efficiency is going to be changed for using the new lossless diode. For using the lossless diode, the efficiency of the bottom side of the module was increased by 0.31 %.

After enjoying one week in the Swedish Lapland, the idea of providing energy to one of those isolated cabins in the far landscape caught our attention. Nowadays, there still exist many dwellings, usually located in rural isolated sites, which have no easy access or even no possibility to get connected to the distribution and transport electricity grids. This situation may cause some inconvenience to the owners, therefore, the interest in finding new alternatives for supplying electricity. Such a problem requires specific solutions, including the development of electrification programs in those countryside isolated spots. Thus, the present project intends to perform a study which would provide the proper electric system to a summerhouse in the North of Sweden. Regarding the current European environmental politics and considering the rural location of the dwelling of study, the project will focus on various renewable alternatives to reach the above mentioned goal. In fact, Sweden has the greatest share of renewable energies in all European Union countries with a fixed goal of reaching 50% of its total energy production by renewable sources by the year 2020. For the present moment, Sweden already accounts for 9.4 GWh on solar energy production and 3.5 TWh on wind power production by the end of 2010. Therefore, the study will build on these alternatives as they represent two of the most extensively developed renewable possibilities in the country. Thereby, the first objective of the project was to determine a concrete location considering both our initial idea and the possibility of obtaining the wind speed and solar radiation data. A plot located 20 km to the north of Lulea was finally chosen. Then, once having the necessary baseline data comes the sizing of the different alternative: stand alone wind turbine system, stand alone PV system and a hybrid system combining wind power with the support of an electric generator. No option including grid connection is taken into consideration due to the lack of accessibility. Finally, it is performed an economic study of each alternative that would lead to a clear conclusion of which is the most appropriate choice in the study case. Economic criteria will therefore be the most significant factor when choosing the optimum alternative. However, environmental issues would also be taken into account. As no traditional electrification is studied, the economic analysis will not refer to the obtained monetary savings regarding to the grid connected option but will be performed by comparing initial investments. After all, it is concluded that the studied dwelling will be electrified by a hybrid system combining wind power with an electric generator. The system includes a 20 kW wind turbine and a diesel fueled generator with 8 kW power service. The generator will provide the required energy to the house during those days when the wind resource is not capable to cover the demand. Therefore, the lack of electricity supply will be avoided. Regarding investment costs of the chosen alternative, the hybrid system accounts for 20,729€ investment, which corresponds to about 40% the total price of both solar and wind stand alone systems. . Considering environmental criteria, the hybrid system only requires 23 diesel liters to be burned during the six summer months. Therefore, emissions due to combustion are relatively low and not considered as damaging. So, the chosen alternative meets both economical and environmental requirements.

Universiẗat, Diss., 2005--Freiburg (Breisgau). / Erscheinungsjahr an der Haupttitelstelle: 2004.

Dans cette thèse nous avons proposé une méthode d’étude des variations paramétriques pour les systèmes mécatroniques continus et hybrides puis une approche du tolérancement mécatronique. Nous avons d’abord étudié les différentes approches existantes pour la prise en compte de la variation de paramètres. Pour les systèmes continus à paramètres variables nous avons choisi la méthode des inclusions différentielles. Nous avons repris l’algorithme de Raczynski et nous avons développé un algorithme d’optimisation qui se base sur la méthode du steepest descent, avec une extension permettant d’obtenir l’optimum global. Pour les systèmes hybrides, contenant des évolutions continues et des sauts discrets, et qui présentent des variations paramétriques, nous avons choisi le formalisme de l’inclusion différentielle impulsionnelle comme outil de modélisation. Nous avons repris ce formalisme et identifié ses éléments sur un système mécatronique. Nous avons développé des algorithmes de résolution des inclusions différentielles impulsionnelles pour un puis pour plusieurs paramètres variables. Pour visualiser les résultats, les algorithmes développés ont été implémentés sous Mathématica. Nous avons fini cette partie par une comparaison entre notre approche et d’autres comme celles autour des automates hybrides à invariant polyèdre, les inclusions différentielles polygonales et l’algorithme pratique de résolution des inclusions différentielles. Nous avons montré alors certains avantages de notre approche. En dernière partie, nous avons repris les différents outils utilisés et résultats obtenus pour définir et affiner notre approche du tolérancement. Nous avons défini la zone du fonctionnement désiré, les différents cas de figures qu’elle peut présenter et son intersection avec le domaine atteignable. Nous avons présenté un outil métrique basé sur la distance topologique de Hausdorff pour le calcul des distances entre ces différents ensembles. Munis de ces éléments, nous avons proposé une démarche itérative pour le tolérancement dans l’espace d’état. / In this thesis we proposed a method for the study of parametric variation for continuous and hybrid systems and an approach for mechatronics tolerancing. We first studied the different existing approaches to take into account the variation of parameters. For continuous systems with variable parameters we chose the method of differential inclusions. We took the Raczynski algorithm and we have developed an optimization algorithm which is based on the steepest descent method with an extension to obtain global optimum. For hybrid systems, containing continuous evolutions and discrete jumps, and have parametric variations, we have chosen the formalism of impulse differential inclusion as a modeling tool. We took this formalism and identified its components on a mechatronic system. We have developed algorithms for solving impulse differential inclusions for several variable parameters. To view the results, the developed algorithms were implemented in Mathematica. We ended this part by a comparison between our approach and others like those around hybrid automata invariant polyhedron, polygonal differential inclusions and practical algorithm for solving differential inclusion. We showed then some advantages of our approach. In the last part, we organized the different tools used and results obtained to define and refine our approach to tolerancing. We defined the area of the desired operation, the various scenarios that may present, and its intersection with reachable area. We presented a metric tool based on topological Hausdorff distance for the calculation of distances between the different sets. With these elements, we proposed an iterative approach to tolerancing in the state space.

The vibration control problem for flexible structures is examined within the context of overall controller performance and power reduction. First, the issue of optimal sensor and actuator placement is considered along with its associated control robustness aspects. Then the option of alternately activating subsets of the available devices is investigated. Such option is considered in order to better address the effects of spatiotemporally varying disturbances acting on a flexible structure while reducing the overall energy consumption. Towards the solution to the problem of optimal device placement, three different approaches are proposed. First, a computationally efficient scheme for the simultaneous placement of multiple devices is presented. The second approach proposes a strategy for the optimal placement of sensors and collocated sensor/actuator pairs, taking into account the influence of the spatial distribution of disturbances. The third approach provides a solution to the actuator location problem by incorporating considerations with respect to preferred spatial regions within the flexible structure. Then the second problem named above is considered. Activating a subset of the available and optimally placed actuators and sensors in a flexible structure provides enhanced performance with reduced energy consumption. Such approach of switching on and off different actuating devices, depending on their local-in-time authority, results in a hybrid system. Therefore the proposed work draws on existing results on hybrid systems and includes an additional degree of freedom, whereby both the actuating devices and the control signals allocated to them are switched in and out. To enable this switching an activation strategy, which insures also that stability-under-switching is guaranteed, is required. Three different strategies are considered for such actuators allocation: first a cost-to-go index is considered, then a cost function based on the mechanical energy of the flexible structure and finally a performance index based on the maximum deviation of the transverse displacement. A flexible aluminum plate was chosen to validate and test the proposed approaches. The set up utilized four pairs of collocated piezoceramic patches that serve to provide sensing and actuating capabilities. Extensive numerical simulations were performed for both the placement strategies and the switching policies proposed, in order to predict the behavior of the flexible plate and provide the optimal actuator and sensor locations that were to be affixed on the flexible structure. Finally, to complete the validation process a sequence of experimental tests were performed. The objective of these tests was to compare the performance of the proposed hybrid control system to traditional non switched control schemes. In order to provide a repeatable perturbation, four of the piezoceramic patches were allocated to simulate a spatiotemporally varying disturbance, while the remaining four patches were used as sensors and controlling actuators. The experimental results showed a significant performance improvement for the switched controller over the traditional controller. Moreover the switched controller exhibited improved robustness towards spatiotemporally varying disturbances while the traditional controller showed a significant loss of controller performance. The improvement achieved in vibration control problems could be extended to a wider range of applications. In particular, although this study was concentrated on a rectangular thin plate, the proposed strategies can be applied to emph{any} structure and more generally to any plant whose dynamics can be represented by a second order linear system. For example, by removing the restriction of spatially fixed actuators and sensors, the proposed theory can be applied to the problem of unmanned vehicles control.

An isolated hybrid system comprised of a dispatchable and a non-dispatchable power generation sources, is proposed to supply the load of a remote village in the west coast region of The Gambia. The thesis presents an artificial neural network (ANN) based approach to tune the parameters of the frequency regulator in hybrid wind/diesel power system for isolated area power supply. The multi-layer feed-forward ANN with the error back-propagation training is employed to tune the frequency regulator in the simulation of hybrid system under different load and wind conditions. Using MATLAB/Simulink, dynamic simulations are performed to investigate the interaction between these two power sources for the load management, and the voltage and frequency behaviors during wind speed and load variations. Simulation results show that the wind turbine and the diesel generator can be operated suitably in parallel. During simulation, the frequency and voltage regulators used in the proposed hybrid system performed fairly well under wind speed variations and load changing conditions. A good frequency regulator interface, which is around 50Hz is observed for nearly the entire period of operation.