This thesis poses a feedback control method for obtaining humanlike bipedal walking on a human-inspired hybrid biped model. The end goal was to understand better the fundamental mechanisms that underlie bipedal walking in the hopes that this newfound understanding will facilitate better mechanical and control design for bipedal robots. Bipedal walking is hybrid in nature, characterized by periodic contact between a robot and the environment, i.e., the ground. Dynamic models derived from Lagrangians modeling mechanical systems govern the continuous dynamics while discrete dynamics were handed by an impact model using impulse-like forces and balancing angular momentum. This combination of continuous and discrete dynamics motivated the use of hybrid systems for modeling purposes. The framework of hybrid systems was used to model three-dimensional bipedal walking in a general setup for a robotic model with a hip, knees, and feet with the goal of obtaining stable walking. To achieve three-dimensional walking, functional Routhian reduction was used to decouple the sagittal and coronal dynamics. By doing so, it was possible to achieve walking in the two-dimensional sagittal plane on the three-dimensional model, restricted to operate in the sagittal plane. Imposing this restriction resulted in a reduced-order model, referred to as the sagittally-restricted model. Sagittal control in the form of controlled symmetries and additional control strategies was used to achieve stable walking on the sagittally-restricted model. Functional Routhian reduction was then applied to the full-order system. The sagittal control developed on the reduced-order model was used with reduction to achieve walking in three dimensions in simulation. The control schemes described resulted in walking which was remarkably anthropomorphic in nature. This observation is surprising given the simplistic nature of the controllers used. Moreover, the two-dimensional and three-dimensional dynamics were completely decoupled inasmuch as the dynamic models governing the sagittal motion were equivalent. Additionally, the reduction resulted in swaying in the lateral plane. This motion, which is generally present in human walking, was unplanned and was a side-effect of the decoupling process. Despite the approximate nature of the reduction, the motion was still almost completely decoupled with respect to the sagittal and coronal planes.

This thesis provides a real-time algorithmic optimal control framework for autonomous switched systems. Traditional optimal control approaches for autonomous switched systems are open-loop in nature. Therefore, the switching times of the system can not be adjusted or adapted when the system parameters or the operational environments change. This thesis aims to close this loop, and apply adaptations to the optimal switching strategy based on new information that can only be captured on-line. One important contribution of this work is to provide the means to allow feedback (in a general sense) to the control laws (i.e. the switching times) of the switched system so that the control laws can be updated to maintain optimality of the switching-time control inputs. Furthermore, convergence analyses for the proposed algorithms are presented. The effectiveness of the real-time algorithms is demonstrated by an application in optimal formation and coverage control of a networked system. This application is implemented on a realistic simulation framework consisting of a number of Unmanned Aerial Vehicles (UAVs) that interact in a virtual 3D world.

Many emerging controls applications have seen increased operational complexity due to the deployment of embedded, networked systems that must interact with the physical environment. In order to manage this complexity, we design different control modes for each system and use motion description languages (MDL) to specify a sequence of these controllers to execute at run-time. Unfortunately, current MDL frameworks lose some of the important details (i.e. power, spatial, or communication capabilities) that affect the execution of the control modes. This work presents several computational tools that work towards closing MDL's specification-to-execution gap, which can result in undesirable behavior of complex systems at run-time. First, we develop the notion of an MDL compiler for control specifications with spatial, energy, and temporal constraints. We define a new MDL for networked systems and develop an algorithm that automatically generates a supervisor to prevent incorrect execution of the multi-agent MDL program. Additionally, we derive conditions for checking if an MDL program satisfies actuator constraints and develop an algorithm to insert new control modes that maintain actuator bounds during the execution of the MDL program. Finally, we design and implement a software architecture that facilitates the development of control applications for systems with power, actuator, sensing, and communication constraints.

La thèse porte sur la synthèse d'observateurs pour les systèmes dynamiques hybrides.<br />Nous considérons particulièrement considéré les systèmes décrits par un ensemble fini de sous-systèmes linéaires à temps discret et<br />une loi de commutation. Le sous-système actif et les commutations d'un sous-système à un autre peuvent être définis par une commande externe contrôlable (systèmes à commutation), ou par des transitions autonomes (systèmes affines par morceaux). Sous<br />l'hypothèse du mode actif à chaque instant, nous montrons que l'association de l'observateur commuté avec une contrainte de<br />placement de pôles permet de proposer un schéma d'observation à entrée inconnue pour résoudre le problème de la synchronisation<br />des systèmes à commutation chaotiques avec un message incorporé. Dans le cas de des systèmes affines par morceaux, nous proposons une méthode pour détecter le mode actif. L'association de cette méthode avec l'observateur commuté permet l'estimation conjointe de l'état continu et état discret. Enfin, nous considérons le cas de commutations régies par un RdP. Nous proposons un schéma d'observation utilisant un observateur de RdP et un observateur commuté.

Στη συγκεκριμένη Διατριβή μελετήσαμε την ανάλυση ευστάθειας υβριδικών δυναμικών συστημάτων τα οποία έχουν μοντελοποιηθεί με Διαφορικά Δίκτυα Petri. Τα αποτελέσματα που προτείναμε για την ανάλυση ευστάθειας χρησιμοποιούν Γραμμικές Ανισότητες Πινάκων γεγονός που τις καθιστά υπολογιστικά επιλύσιμες. Προτείναμε επίσης μια μεθοδολογία σχεδίασης ευσταθών υβριδικών συστημάτων. Χρησιμοποιήσαμε το μοντέλο Διαφορικά Δίκτυα Petri για την μοντελοποίηση δικτυακών υβριδικών συστημάτων. Προτείναμε επίσης συνθήκες ευστάθειας για διακοπτικά χρονικά καθυστερούμενα συστήματα. / In this thesis we study stability for hybrid dynamical systems modelled by Differential Petri Nets.Our stability results are formulated as Linear Matrix Inequalities in order to be computational solvable. A methodology for stabilization of hybrid dynamical systems is also introduced. The notion of Networked Hybrid System is also introduced and the model of Differential Petri Net is proposed for modelling. Stability results for switched time-dealy systems are also proposed.

A hybrid system is a system that presents both continuous time evolution and discrete events. To define and analyse such systems prior to building actual products, a hybrid process algebra can be employed. Simulation is often used as a convenient way for a better understanding of the systems’ evolution and its potential weaknesses. This study aims at creating a general architecture of the simulation tool for hybrid process algebras, together with a practical implementation of Behavioural Hybrid Process Calculus simulator. For achieving this objective, a list of tasks has been composed, including the analysis of several hybrid process algebra operators, development of an easily extendible architecture of the tool, the definition of the input language, capable of describing BHPC processes, and a programming solution of the simulator. Together with a simulator tool, a programming solution for the visualisation of hybrid systems’ evolution is created and presented. The application uses Message Sequence Plots diagrams to represent such evolution, which allows a convenient overview and analysis for most of hybrid system simulations. The currently developed simulation and visualisation tools may be regarded as a working ground for both the usage and further development. The improvement points of the tools should be constantly collected from the user experience and implemented. The long term goal of the work is to achieve an expanding community with the joint effort to create a... [to full text] / Hibridinė sistema yra sistema, sudaryta iš laike tolydžios evoliucijos ir diskrečių įvykių. Hibridinių procesų algebros pagalba tokias sistemas galima apibrėžti ir analizuoti dar prieš sukuriant galutinį produktą. Tuo tarpu simuliacija yra dažnai naudojama kaip patogus būdas geresniam sistemos evoliucijos suvokimui ir jos potencialių silpnybių identifikavimui. Šiuo darbu siekiama sukurti bendrą architektūrą hibridinių procesų algebrų simuliavimo įrankiui bei sukurti praktinę priemonę – simuliatorių, skirtą Elgsenos Hibridinių Procesų Algebrai (angl. Behavioural Hybrid Process Calculus – BHPC). Siekiant įgyvendinti šį tikslą, buvo sudarytas užduočių sąrašas, įtraukiant į jį kelių hibridinių procesų algebrų operatorių analizę, nesudėtingai plečiamos programos architektūros sukūrimą, įvedimo kalbos, gebančios aprašyti BHPC procesus, apibrėžimą bei programinio simuliatoriaus sprendimo įgyvendinimą. Hibridinių sistemų evoliucijos vaizdavimui buvo sukurtas programinis sprendimas, naudojantis Pranešimų Sekos Grafiko (angl. Message Sequence Plots) vaizdavimo tipą grafiniam hibridinės evoliucijos atvaizdavimui, kuris suteikia galimybę patogiai apžvelgti ir analizuoti daugumą hibridinių sistemų evoliucijų. Šiuo metu sukurti simuliavimo ir vaizdavimo įrankiai gali būti naudojami praktikoje, tuo pačiu renkant vartotojų patirtį tolesniam jų tobulinimui. Įrankių tobulinimo aspektai turėtų būti nuolatos kaupiami ir įgyvendinami siekiant ilgalaikio šio darbo tikslo – suburti augančią... [toliau žr. visą tekstą]

Ethyl lactate is a promising, and environmentally benign chemical, which requires efficient separation techniques to overcome the equilibrium limitations in its production. Pervaporation based hybrid systems are successful in these type of equilibrium limited reactions, where product and/or by-product are removed from reaction medium by pervaporation unit(s) so as to drive reaction to completion. For the production of ethyl lactate four possible semi-batch hybrid systems were previously proposed. However, in order to select the suitable hybrid system within the proposed layouts phase equilibrium and reaction kinetics of the system must be well defined in addition to the performance data of the pervaporation membranes. Therefore, vapor pressure curve of ethyl lactate, VLE curves of ethanol-ethyl lactate and ethyl lactate-water were determined and performances of commercial hydrophobic membranes were investigated experimentally for the separation of ethanol-ethyl lactate mixtures. As a result of vapor pressure and VLE experiments, azeotrope was observed at 71wt% of water for ethyl lactate-water binary mixture at 80mmHg pressure. Furthermore, dependence of vapor composition on pressure was found to be slight for ethanol-ethyl lactate mixtures. Two commercial hydrophobic membranes, and an organoselective one were used in the separation of ethyl lactate-ethanol mixtures. It is found that hydrophobic membranes have sufficient fluxes and reasonable selectivities. Moreover, it is observed that as temperature increase flux increases and selectivity decreases. Finally, it is concluded that it would be possible to produce ethyl lactate by using the previously proposed integrated PV-esterification reactor systems.

Inference of regulatory networks has received attention of researchers from many fields. The challenge offered by this problem is its being a typical modeling problem under insufficient information about the process. Hence, we need to derive the apriori unavailable information from the empirical observations. Modeling by inference consists of selecting or defining the most appropriate model structure and inferring the parameters. An appropriate model structure should have the following properties. The model parameters should be inferable. Given the observation and the model class, all parameters used in the model should have a unique solution restriction of the solution space). The forward model should be accurately computable (restriction of the solution space). The model should be capable of exhibiting the essential qualitative features of the system (limit of the restriction). The model should be relevant with the process (limit of the restriction). A piecewise linear formulation, described by a switching state transition matrix and a switching state transition vector with a Boolean function indicating the switching conditions is proposed for the inference of gene regulatory networks. This thesis mainly concerns using a formulation of switching networks obeying all the above mentioned requirements and developing an inference algorithm for estimating the parameters of the formulation. The methodologies used or developed during this study are applicable to various fields of science and engineering.

Thesis (M.S.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Στην παρούσα εργασία μελετάται η λειτουργία και η προστασία υβριδικών συστημάτων αποτελούμενων από φωτοβολταϊκά στοιχεία και κυψέλες υδρογόνου. Τέτοιου είδους υβριδικά συστήματα περιλαμβάνουν δύο πηγές ενέργειας με σκοπό να επιτυγχάνεται σταθερή παραγωγή ισχύος και κατά τη διάρκεια της νύχτας, όταν η ηλιακή ενέργεια δεν είναι διαθέσιμη. Η ισορροπία αυτή διατηρείται μέσω της χρήσης κυψελών καυσίμου. Στο πρώτο κεφάλαιο δίνονται γενικές πληροφορίες για τα φ/β συστήματα. Ξεκινώντας από την ηλιακή ακτινοβολία και την ελάχιστη μονάδα κάθε φ/β συστήματος, το φ/β στοιχείο ή κύτταρο επεξηγούνται τα χαρακτηριστικά κι οι κατηγορίες των φ/β συστημάτων. Εν συνεχεία, περιγράφεται ο μηχανισμός δημιουργίας του φ/β φαινομένου και τα ηλεκτρικά χαρακτηριστικά των φ/β συστημάτων. Ακολουθεί μια συνοπτική παρουσίαση των διάφορων τεχνολογιών φ/β πλαισίων, καθώς και της απόδοσης αυτών και των παραγόντων που την επηρεάζουν. Το κεφάλαιο ολοκληρώνεται με αναφορά στα υπόλοιπα μέρη ενός φ/β συστήματος, όπως ο αντιστροφέας, οι μπαταρίες και λοιπά βοηθητικά συστήματα. Το δεύτερο κεφάλαιο αναφέρεται στο υδρογόνο και την μετατροπή αυτού σε ηλεκτρισμό ή θερμότητα μέσω κυψελών καυσίμου. Στην αρχή, δίνονται γενικά στοιχεία για το υδρογόνο, τις ιδιότητές του, τις μεθόδους παρασκευής και αποθήκευσης αυτού κι ακόμη στοιχεία για το υδρογόνο ως καύσιμο. Κατόπιν, παρουσιάζονται οι βασικές αρχές λειτουργίας και οι κύριοι τύποι κελιών καυσίμου, ενώ γίνεται προσπάθεια θεωρητικής και πρακτικής προσέγγισης της απόδοσης και της μέγιστης τάσης αυτών. Τέλος, το κεφάλαιο συμπληρώνουν σκέψεις για το υδρογόνο ως μελλοντικό φορέα ενέργειας και την οικονομία του υδρογόνου. Στο τρίτο κεφάλαιο εξηγείται η έννοια του υβριδικού συστήματος, καθώς και πλεονεκτήματα των υβριδικών συστημάτων φ/β με κυψέλες υδρογόνου. Ακολούθως, αναλύεται ο καταμερισμός φορτίου σε υβριδικό σύστημα φ/β με κυψέλες υδρογόνου, όπως κι η περιγραφή κι η λειτουργία ενός τέτοιου συστήματος. Στην τελευταία ενότητα αναζητείται η βέλτιστη διασύνδεση φ/β συστοιχιών και PEM ηλεκτρολυτών σε υβριδικά συστήματα κατάλληλα για την τροφοδότηση απομακρυσμένων περιοχών για την επίτευξη μέγιστης μεταφοράς ισχύος, αλλά και χαμηλότερου ανά μονάδα κόστους. Στο τέταρτο και τελευταίο κεφάλαιο, ακολουθoύνται οι κανόνες της διεθνούς εμπειρίας και οι ισχύοντες κανονισμοί για την προστασία υβριδικού συστήματος φ/β στοιχείων με κυψέλες υδρογόνου. Μελετάται η περίπτωση βραχυκυκλώματος και προτείνονται μέτρα που πρέπει να ληφθούν μέσω της καλωδίωσης, διακοπτών προστασίας αγωγών, διόδων κι ασφαλειών. Γίνεται σύγκριση των I – V χαρακτηριστικών καμπυλών σε κανονικές συνθήκες και σε συνθήκες σκίασης και σφάλματος. Έπεται η αντικεραυνική προστασία διαμέσου εξωτερικού ΣΑΠ, ισοδυναμικών συνδέσεων κι απαγωγών κρουστικών υπερτάσεων. Η εργασία ολοκληρώνεται με αναφορά στην επικινδυνότητα εγκαταστάσεων υδρογόνου, τους κινδύνους και τα σενάρια ατυχημάτων. Το κεφάλαιο καταλήγει με τρόπους περιορισμού αυτών των επικίνδυνων καταστάσεων και τους κανόνες ασφαλείας που έχουν θεσπιστεί για το υδρογόνο. / This essay examines hybrid systems’ operation and protection consisted of photovoltaic and fuel cells. Such hybrid systems include two energy sources in order to maintain a consistent level in power production even during the night, when solar radiation is not available. The use of fuel cells ensures this equilibrium. In the first chapter a piece of general information about pv systems is given. Firstly, explaining meanings like solar radiation and pv cell, pv systems are classified. Subsequently, the mechanism of pv phenomenon and the pv systems’ electrical characteristics are described. A concise presentation of pv modules’ technology and efficiency follows. The chapter concludes with regard to rest parts of pv systems, such as inverter, batteries and auxiliary systems. The second chapter refers to hydrogen and its conversion into electricity or heat via fuel cells. Firstly, a piece of general data about hydrogen and its properties, conoction and storage methods is given. Furthermore, the fuel cell’s fundamental principles and basic types are presented, whilst a theoretical and a practical approach of fuel cell’s efficiency and maximum voltage follows. Some thoughts about the future hydrogen economy end this chapter. In the third chapter the meaning of hybrid system, as well the advantages of pv-hydrogen systems are explained. Subsequently, load sharing in a hybrid pv-fc system as well as the description and the operation of such a system are analysed. In the last unit the optimal coupling of pv arrays to PEM electrolysers in solar-hydrogen systems for remote area power supply is searching out. In the last chapter, according to international codes, protection of solar-hydrogen system is analysed. The case of a short-circuit is examined and measures must be taken via wiring, circuit breakers, diodes and fuses. Then,I –V characteristics at normal conditions are compared with characteristics recorded under partial shadowing or failure. In addition, lightning protection via LSP and SPDs is described. The essay concludes with regard to hydrogen installations’ dangers and possible accidents. Some implemented measures and safety rules end this unit.