Σχεδιασμός, έλεγχος και αυτόνομη πλοήγηση μη επανδρωμένων εναέριων οχημάτων με ρότορες μεταβαλλόμενης κλίσης

This Dissertation addresses the design and development of small-scale UnmannedAerial Vehicles of the TiltRotor class, alongside their autonomous navigation requirements,including the fully-onboard state estimation, high-efficiency flight control,and advanced environment perception.Starting with an educated Computer Assisted Design-based methodology, a mechanicallyrobust, customizable, and repeatable vehicle build is achieved, relyingon high-quality Commercially Available Off-The Shelf equipment –sensors, actuators,structural components–, optionally aided by Rapid Prototyping technology.A high-fidelity modeling process is conducted, incorporating the rigid-body dynamics,aerodynamics, and the actuation subsystem dynamics, exploiting fistprincipleapproaches, Frequency Domain System Identification, as well as computationaltools. Considering the most significant phenomena captured in thisprocess, a more simplified PieceWise Affine system model representation is developedfor control purposes –which however incorporates complexities such as flight(state) envelope-associated aerodynamics, the differentiated effects of the directthrust-vectoring (rotor-tilting) and the underactuated (body-pitching) actuationauthorities, as well as their interferences through rigid-body coupling–.Despite the switching system dynamics, and –as thoroughly elaborated– theirreliance on constrained manipulated variables, to maintain a meaningful controlorientedrepresentation, the real-time optimal flight control of the TiltRotor vehicleis achieved relying on a Receding Horizon methodology, and more specifically anexplicit Model Predictive Control framework. This synthesis guarantees globalstability of the switching dynamics, observance of state and control input constraints,response optimality, as well as efficient execution on low computationa power modules due to its explicit representation. Accompanied by a proper Lowand-Mid-LevelControl synthesis, this scheme provides exceptional flight handlingqualities to the aerial vehicle, particularly in the areas of aggressive maneuveringand high-accuracy trajectory tracking.Moreover, the utility of TiltRotor vehicles in the field of aerial robotic forcefulphysical interaction is researched. Exploiting the previously noted properties ofthe PieceWise Affine systems Model Predictive Control strategy, the guaranteedstabilityFree-Flight to Physical-Interaction switching of the system is achieved,effectively bringing the aerial vehicle into safe, controlled physical contact withthe surface of structures in the environment.More importantly, employing rotor-tilting actuation –collectively and differentially–significant forces and moments can be applied onto the environment, while via thestandard underactuated authority the vehicle maintains a stable hovering-attitudepose, where the system’s disturbance rejection properties are maximized. Overall,the complete control framework enables coming into physical contact with environmentstructures, and manipulating the enacted forces and moments. Exploitingsuch capabilities the TiltRotor is used to achieve the execution of physicallydemandingwork-tasks (surface-grinding) and the manipulation of realisticallysizedobjects (of twice its own mass) via pushing.Additionally, the fully-onboard state estimation problem is tackled by implementingdata fusion of measurements derived from inertial sensors and customdevelopedcomputer vision algorithms which employ Homography and OpticalFlow calculation. With a proper sensorial setup, high-rate and robust ego-motionestimation is achieved, enabling the controlled aggressive maneuverability withoutreliance on external equipment, such as motion capture systems or GlobalPositioning System coverage.Finally, a hardware/software framework is developed which adds advanced autonomousperception and navigation capabilities to small-scale unmanned vehicles,employing stereo vision and integrating state-of-the art solutions for incrementalenvironment building, dense reconstruction and mapping, and point-to-pointcollision-free navigation. Within this framework, algorithms which enable the detection,segmentation, (re-)localization, and mobile tracking –and avoidance– of adynamic subject within the aerial vehicle’s operating space are developed, substantiallyincreasing the operational potential of autonomous aircraft within dynamicenvironments and/or dynamically evolving missions

Navigation Technologies over low bandwidth links for Thin Clients. An introduction to the CC/PP protocol

Over the last few years, the rapid growth of the world wide web itself and the increment of the amount of data it facilitates is amazing. Concurrently, along with the world wide web, rapid development is held in the area of the devices that are accessing the web. The technology used by such devices is improved and their variety is getting larger. Despite of their high technology they have limited capabilities when compared to the classic desktop personal computers. Their main weaknesses are the low bandwidth network that they usually use to connect to the Internet and the small screen size that is incapable of presenting many of the current available data. In order for such a device connected to the Web to be served in a reasonable amount of time, with content that can be appropriately handled by that device, many techniques and methods have been proposed. One of these techniques used is caching technology in proxies. Caching in conjunction with Prefetching reduces the latency of the data transfers. Another technique, that has been proposed lately, is the minimization of the information transferred through the Web, by removing all the unnecessary information. This method in collaboration with our approach of the URL substitution in an HTML file, can have satisfactory performance. There is also the method of data transcoding in a variety of formats depending on the capabilities of the device that requested the data. In order for the data transcoding and other methods to be applied efficiently for each device used, Web content providers need extra information. This information will supply to the servers a brief description of the characteristics of each device, and the kind of the network used. This kind of information can be transferred in the Web throughΤα τελευταία χρόνια ο ρυθμός εξάπλωσης του παγκόσμιου ιστού και η αύξηση των δεδομένων που διαθέτει είναι πραγματικά ένα εντυπωσιακό φαινόμενο. Μαζί όμως με τον παγκόσμιο ιστό έχουν γνωρίσει ραγδαία ανάπτυξη και οι συσκευές που προσπαθούν να τον προσπελάσουν. Πέρα από την τεχνολογική ανάπτυξη έχει αυξηθεί πάρα πολύ και το πλήθος τους. Οι συσκευές αυτές αν και προηγμένες έχουν περιορισμένες δυνατότητες σε σχέση με τους κλασσικούς υπολογιστές γραφείου. Κυριότερες αδυναμίες τους είναι το αργό (ασύρματο συνήθως) δίκτυο με το οποίο συνήθως συνδέονται και η έλλειψη ικανοποιητικού μεγέθους οθόνης για την απεικόνιση των δεδομένων. Για την καλύτερη εξυπηρέτηση όλων των συσκευών, τόσο από πλευράς ταχύτητας όσο και από πλευράς κατάλληλων δεδομένων, έχουν εφαρμοστεί κατά καιρούς διάφορες τεχνικές και μέθοδοι. Κάποιες από αυτές είναι η προσωρινή αποθήκευση των δεδομένων σε ενδιάμεσους κόμβους (proxies), που σε συνεργασία με την πρόβλεψη των δεδομένων που πρόκειται να ζητηθούν στο μέλλον μειώνουν αρκετά τον χρόνο στον οποίο εξυπηρετούνται οι χρήστες του Διαδικτύου. Μια σχετικά νεότερη τεχνική είναι η ελαχιστοποίηση των πληροφοριών που μεταφέρονται και πετυχαίνεται με την αφαίρεση των περιττών πληροφοριών και την συμπίεση των δεδομένων. Παρόμοια τεχνική είναι η μετατροπή των δεδομένων σε κατάλληλη μορφή σύμφωνα με τις δυνατότητες της κάθε συσκευής. Για να πραγματοποιηθούν αυτές οι μέθοδοι την κατάλληλη στιγμή, για την κατάλληλη συσκευή, απαιτείται επιπλέον πληροφορία που θα ενημερώνει τους εξυπηρετητές του παγκόσμιου ιστού για το είδος και τις δυνατότητες της συσκευής αλλά και του δικτύου που χρησιμοποιεί. Αυτή η πληροφορία μπορεί να μεταφερθεί με το νέο CC/PP πρωτόκολλο που προσπαθεί να γίνει πρότυπο σε αυτό τον τομέα

Modeling, control, state estimation and path planning methods for autonomous multirotor aerial robots

This monograph will be a valuable starting point for researchers and developers working in the exciting area of aerial robots of the rotorcraft class, or drones