Theoretical and numerical methods uses as design tool for an aircraft : application on three real-world configurations

The mathematical models needed to represent the various dynamics phenomena have been conceived in many disciplines related to aerospace engineering. Major aerospace companies have developed their own codes to estimate aerodynamic characteristics and aircraft stability in the conceptual phase, in parallel with universities that have developed various codes for educational and research purposes. This paper presents a design tool that includes Derivatives code, the new weight functions method and the continuity algorithm. FDerivatives code, developed at the LARCASE laboratory, is dedicated to the analytical and numerical calculations of the aerodynamic coefficients and their corresponding stability derivatives in the subsonic regime. It was developed as part of two research projects. The first project was initiated by CAE Inc. and the Consortium for Research and Innovation in Aerospace in Quebec (CRIAQ), and the second project was funded by NATO in the framework of the NATO RTO AVT–161 « Assessment of Stability and Control Prediction Methods for NATO Air and Sea Vehicles” program. Presagis gave the « Best Simulation Award" to the LARCASE laboratory for FDerivatives and data FLSIM applications. The new method, called the weight functions method, was used as an extension of the former project. Stability analysis of three different aircraft configurations was performed with the weight functions method and validated for longitudinal and lateral motions with the root locus method. The model, tested with the continuity algorithm, is the High Incidence Research Aircraft Model (HIRM) developed by the Swedish Defense Research Agency and implemented in the Aero-Data Model In Research Environment (ADMIRE)

A differential-based parallel force/velocity actuation concept : theory and experiments

textRobots are now moving from their conventional confined habitats such as factory floors to human environments where they assist and physically interact with people. The requirement for inherent mechanical safety is overarching in such human-robot interaction systems. We propose a dual actuator called Parallel Force/Velocity Actuator (PFVA) that combines a Force Actuator (FA) (low velocity input) and a Velocity Actuator (VA) (high velocity input) using a differential gear train. In this arrangement mechanical safety can be achieved by limiting the torque on the FA and thus making it a backdriveable input. In addition, the kinematic redundancy in the drive can be used to control output velocity while satisfying secondary operational objectives. Our research focus was on three areas: (i) scalable parametric design of the PFVA, (ii) analytical modeling of the PFVA and experimental testing on a single-joint prototype, and (iii) generalized model formulation for PFVA-driven serial robot manipulators. In our analysis, the ratio of velocity ratios between the FA and the VA, called the relative scale factor, emerged as a purely geometric and dominant design parameter. Based on a dimensionless parametric design of PFVAs using power-flow and load distributions between the inputs, a prototype was designed and built using commercial-off-the-shelf components. Using controlled experiments, two performance-limiting phenomena in our prototype, friction and dynamic coupling between the two inputs, were identified. Two other experiments were conducted to characterize the operational performance of the actuator in velocity-mode and in what we call ‘torque-limited’ mode (i.e. when the FA input can be backdriven). Our theoretical and experimental results showed that the PFVA can be mechanical safe to both slow collisions and impacts due to the backdriveability of the FA. Also, we show that its kinematic redundancy can be effectively utilized to mitigate low-velocity friction and backlash in geared mechanisms. The implication at the system level of our actuator level analytical and experimental work was studied using a generalized dynamic modeling framework based on kinematic influence coefficients. Based on this dynamic model, three design case studies for a PFVA-driven serial planar 3R manipulator were presented. The major contributions of this research include (i) mathematical models and physical understanding for over six fundamental design and operational parameters of the PFVA, based on which approximately ten design and five operational guidelines were laid out, (ii) analytical and experimental proof-of-concept for the mechanical safety feature of the PFVA and the effective utilization of its kinematic redundancy, (iii) an experimental methodology to characterize the dynamic coupling between the inputs in a differential-summing mechanism, and (iv) a generalized dynamic model formulation for PFVA-driven serial robot manipulators with emphasis on distribution of output loads between the FA and VA input-sets.Mechanical Engineerin

Observer-based robust fault estimation for fault-tolerant control

A control system is fault-tolerant if it possesses the capability of optimizing the system stability and admissible performance subject to bounded faults, complexity and modeling uncertainty. Based on this definition this thesis is concerned with the theoretical developments of the combination of robust fault estimation (FE) and robust active fault tolerant control (AFTC) for systems with both faults and uncertainties.This thesis develops robust strategies for AFTC involving a joint problem of on-line robust FE and robust adaptive control. The disturbances and modeling uncertainty affect the FE and FTC performance. Hence, the proposed robust observer-based fault estimator schemes are combined with several control methods to achieve the desired system performance and robust active fault tolerance. The controller approaches involve concepts of output feedback control, adaptive control, robust observer-based state feedback control. A new robust FE method has been developed initially to take into account the joint effect of both fault and disturbance signals, thereby rejecting the disturbances and enhancing the accuracy of the fault estimation. This is then extended to encompass the robustness with respect to modeling uncertainty.As an extension to the robust FE and FTC scheme a further development is made for direct application to smooth non-linear systems via the use of linear parameter-varying systems (LPV) modeling.The main contributions of the research are thus:- The development of a robust observer-based FE method and integration design for the FE and AFTC systems with the bounded time derivative fault magnitudes, providing the solution based on linear matrix inequality (LMI) methodology. A stability proof for the integrated design of the robust FE within the FTC system.- An improvement is given to the proposed robust observer-based FE method and integrated design for FE and AFTC systems under the existence of different disturbance structures.- New guidance for the choice of learning rate of the robust FE algorithm.- Some improvement compared with the recent literature by considering the FTC problem in a more general way, for example by using LPV modeling

Toward Cold Atom Guidance in a Hollow-Core Photonic Crystal Fibre Using a Blue Detuned Hollow Laser Beam

Cette thèse décrit les progrès et techniques réalisées pour obtenir un couplage efficace d'atomes froids 85Rb dans une fibre optique en cristaux photonique à coeur vide et utilisant un guidage atomique à l'aide d'un faisceau laser creux de premier ordre décalé en fréquence vers le bleu. Dans le système proposé, la faible diffraction de ce faisceau de premier ordre lui permet d'agir comme un entonnoir optique à potentiel répulsif servant à guider les atomes froids,avec l'aide de la gravité, dans le coeur de la fibre optique. L'utilisation d'une fibre optique à faible perte, plutôt qu'un capillaire permet de développer le potentiel de guider les atomes sur une trajectoire arbitraire et des distances à l'échelle du laboratoire. Ceci permettrait ainsi plusieurs nouvelles applications en nanofabrication et en métrologie optique. Pour réaliser cet objectif, un piège Magnéto-Optique de 85Rb a été bâtit de zéro et en utilisant les techniques les plus avancées de refroidissement laser par gradient de polarisation a permis d'atteindre régulièrement des températures de 9K dans une mélasse optique contenant 10 7 atomes. Ces atomes froids furent guidés au-delà de 23 cm dans un faisceau creux collimé et décalé vers le bleu et au travers de ce faisceau focalisé de manière à reproduire les conditions d'entrée dans une fibre optique tout en permettant une observation précise des dynamiques de couplage. Trois classes d'atomes furent observées : perdus, piégés et guidés. Les dynamiques de ce système ainsi que les conditions optimales de couplage ont été identifiés grâce au modèle physique numérique ayant été développée. Une nouvelle approche au problème de la modélisation de la dynamique des atomes froids dans l'entonnoir optique a été développée au cours de cette thèse. Ce nouveau modèle a permis de reproduire la dynamique des atomes observés dans l'expérience mais a aussi pu être appliqué dans la simulation d'atomes froids dans le piège Magnéto-Optique et à la prédiction des températures atteintes dans diverses conditions expérimentales. Ceci a été réalisé grâce à la modélisation 3D des composantes conservatives and non-conservatives des forces optiques agissant sur les atomes. L'implémentation des mécanismes d'échauffement connu des atomes :la diffusion de lumière et de leur quantité de mouvement, fût aussi cruciale à cette fin. Ce modèle nous a aidé à identifier les meilleures conditions de couplage dans ce système,corroboré par l'expérience, et qu'il existait un potentiel optique optimal, pour une distance de couplage déterminé, qu'il ne fallait pas dépasser. Un faisceau LG01, monomode et de haute pureté fût généré avec une efficacité supérieure à 50% en utilisant un hologramme à valeurs complexes généré par ordinateur et rendu grâce à un modulateur de phase spatiale à base de cristaux liquides.----------Abstract This thesis describes advances and techniques toward the efficient coupling of cold 85Rb atoms into a low loss hollow core photonic crystal fibre using a blue-detuned first order hollow beam. In the proposed system, the low diffraction of the blue-detuned first order hollow beam acts as a repulsive potential optical funnel that allows the coupling of cold atoms under the influence of gravity into the fibre's hollow core. Using a low loss fibre with a blue detuned hollow beam shows potential for guiding atoms over an arbitrary path and longer distances on the laboratory scale, which would enable several new applications in nanofabrication and optical metrology. To realize this objective, a Magneto-Optical Trap of 85Rb was built from scratch and by using advanced polarization gradient cooling techniques was turned into a 9 K cold optical molasses containing 107 atoms. These cold atoms were guided over 23 cm in a collimated blue detuned hollow beam tunnel and through a focused hollow beam mimicking as closely as possible the coupling conditions for a hollow core optical fibre. Three classes of atoms were observed: lost, trapped and guided atoms. The dynamics of the system as well as the optimal coupling conditions were identifed through the use of a numerical model. A novel approach to modelling cold atom dynamics in an optical funnel was developed during the course of this thesis. This new model was not only able to reproduce the dynamics of atoms in the experiment but also simulate dense cold atoms cooled into the MOT and predict final temperatures attained. This was achieved by 3D modelling of the conservative and non-conservative components of optical forces acting on atoms but also through the implementation of known heat mechanisms: light scattering and momentum diffusion. The model identifed the best coupling conditions of this system, confirmed by experiment, and an optimal light potential for a given distance of coupling that must not be exceeded. A single mode, high purity, LG01 beam was generated with over 50% conversion efficiency from a Gaussian mode using a complex-valued computer generated hologram (CGH) rendered on a phase-only liquid-crystal spatial light modulator (SLM). A system-wide 35% conversion efficiency was achieved from the laser output to the vacuum chamber input. Several micro-structured polymer optical fibres and silica hollow-core band-gap photonic crystal fibres with Kagome claddings were evaluated. A single defect, large hollow core (50m diameter) Kagome cladding fibre was identified as a suitable solution for guiding cold 85Rb atoms

Cumulative index to NASA Tech Briefs, 1970-1975

Tech briefs of technology derived from the research and development activities of the National Aeronautics and Space Administration are presented. Abstracts and indexes of subject, personal author, originating center, and tech brief number for the 1970-1975 tech briefs are presented

Introduction to Engineering: Embry-Riddle Aeronautical University EGR101 9th Edition

“Introduction to Engineering” is about making our students at Embry-Riddle Aeronautical University successful in academia and responsible engineering professionals. The collective knowledge of several authors representing all departments within the College of Engineering went into its making. Topics were chosen especially for students in the engineering programs at ERAU to specifically address their needs and tailored to assure their success.https://commons.erau.edu/oer-textbook/1003/thumbnail.jp