Active sound control (ASC) based on surface potentials is one of two methods of noise control using potential-based method. The method does not require detailed knowledge of the noise source parameters, boundary conditions, characteristics of the acoustic medium or the transmission path. It allows significant volumetric noise cancellation inside the shielded region using only the knowledge of the total acoustic field which includes the wanted sound at the boundary of the shielded region(s) to obtain additional secondary sound sources known as controls which are distributed at the boundary of the shielded region. It allows the presence of a wanted sound inside the shielded region, which it preserves while canceling the noise. In contrast, other methods require various detailed knowledge. In many cases, they do not allow the wanted sound to be generated inside the protected region. The aim of this thesis is to implement numerically the ASC method in 3D bounded regions and confirm its theoretical predictions. The theoretical framework for the method has already been established in previous related literature. Experimental work in this area is mostly limited to laboratory experiments in one dimensional settings. The algorithm was tested in 3D numerical test cases in the frequency domain involving single and composite regions. The Helmholtz equation was used to model the wave propagation. In both single and composite regions, volumetric noise cancellation of over 20 dB was achieved at most areas of the shielded regions. Outside the shielded region, the field remained practically unchanged during noise cancellation. On the other hand, in test cases involving wanted sound, the noise inside the shielded region was canceled while the wanted sound was preserved. However, outside the shielded region, the field was amplified. Moreover in composite regions, the selective cancellation/propagation of the wanted sound was demonstrated successfully in regions having two and three sub-regions by allowing the wanted sound to propagate to one region but not to the other. To enforce selective propagation of the wanted sound, additional steps are required to obtain the separate field of the wanted sound in addition to the total field. A study on the effect of the number of controls on noise cancellation showed that in both single and composite regions, as the number of controls fell there was a corresponding decrease in the level of noise cancellation. A doubling of the number of controls yields about ~3 dB of noise cancellation, and vice versa. The independence of the operation of the algorithm on characteristics or number of noise sources, shape, size or position of shielded region is also demonstrated via further test cases. In all test cases considered, the results confirmed the theoretical predictions. However, at resonance modes the method did not provide noise cancellation, though at near-resonance modes a lower level of noise cancellation was obtained. Although this work considered only monochromatic waves, the method is applicable to broadband noise. In real-time application of the method, the assumption in the thesis that only the field of the noise source(s) is known does not hold and therefore its implementation is more complicated.

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Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The successful design, implementation and testing of a feedback control system for tab-deflection control of a shape memory alloy (SMA) based control surface actuator is presented. The research is performed as part of the Control Surfaces in Confined Spaces (CoSICS) research project conducted at Stellenbosch University. The research group investigates ways to provide control surface actuation in size-restricted spaces in commercial aircraft such as the Airbus A320 and A330. This is achieved by investigating the concept of trailing edge tabs to reduce the required torque load, resulting in reduced actuator requirements enabling the use of smaller actuators. This thesis contributes to the project by investigating the possibility of using SMA-based actuators in reduced hinge moment requirement applications. An SMA-based tab actuator demonstrator design is presented. Mathematical models are derived for the SMA material, thermodynamics and actuator geometry. The models are combined to formulate an SMA-based control surface actuator model. The model is utilised in four tracking feedback controller designs; two based on linear and two based on non-linear control techniques. The manufactured prototype is presented along with the incorporated hardware for controller implementation. System identification follows and validates the three mathematical models. Practical verification of the model and two of the controllers is conducted. The unimplemented controllers are implemented through a validated model simulation. Controller evaluation, based on the dynamic controller performance, is conducted. The results validate the concept of using an SMA actuator for tab-deflection control and indicate important limitations for the intended application. / AFRIKAANSE OPSOMMING: Die tesis behels die ontwerp, implementering en toetsing van ’n terugvoer beheerstelsel vir hulpvlak defleksie beheer van ’n vorm-geheue allooi (SMA) gebaseerde aktueerder. Die navorsing vorm deel van die Beheervlakke in Begrensde Ruimtes (CoSICS) navorsingsprojek by Stellenbosch Universiteit. Die CoSICS navorsing behels ’n ondersoek na beheervlak aktueering in beknopte spasies in kommersiële vliegtuie soos die Airbus A320 en A330. Die probleem word aangespreek deur ’n ondersoek na aerodinamiese hulpvlakke wat ’n vermindering in skarnier moment tot gevolg het en sodoende die aktueerder vereistes verminder. Hierdie tesis dra by tot die projek deur die moontlikheid van die gebruik van SMAgebaseerde aktueerders in verminderde skarnier moment vereiste toepassings te ondersoek. ‘n SMA gebaseerde hulpvlak demonstrasie aktueerder ontwerp word voorgelê. Wiskundige modelle vir die SMA materiaal, termodinamika en prototipe geometrie is geformuleer en gekombineer om ‘n SMA gebaseerde beheervlak aktueerder model te ontwikkel. Die model word in vier beheerder ontwerpe toegepas. Twee ontwerpe is op liniëre en twee op nie-liniëre beheer tegnieke gebaseer. Die prototipe en nodige hardeware vir beheerder implementasie is voorgedra. Stelsel identifikasie is toegepas en verifieer die drie wiskundige modelle. Praktiese verifikasie van die model en twee beheerders is gedoen. Die ongeïmplementeerde beheerders is deur die geverifieerde aktueerder model gesimuleer. ‘n Beheerder evaluasie gebaseer op die dinamiese beheerder gedrag word toegepas. Die evaluasie beklemtoon kritiese aspekte en beperkinge in verband met SMA aktueering. Die resultate regverdig die gebruik van ‘n SMA aktueerder vir hulpvlak defleksie beheer en beklemtoon belangrike beperkinge ten opsigte van die voorgestelde toepassing.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2004. 220 leaves single printed pages ,preliminary pages i-xiv and numberd pages 1-188.Includes bibliography.list of figures and used a Hp Scanjet 8250 Scanner to pdf format (OCR), / ENGLISH ABSTRACT: This thesis describes the process followed to determine the short-term control and stability derivatives of an ASK-13 glider (ZS-GHB). The short-term control and stability derivatives are obtained by parameter estimation done using data recorded in flight. The algorithm used is the MMLE3 implementation of a maximum likelihood estimator. To collect the flight data sensors were installed in the ZS-GHB. Sensors measuring the control surface deflections, translation acceleration, angular rates and the dynamic and static pressure are needed to provide enough data for the estimation. To estimate accurate derivatives specific manoeuvres were flown by the pilot, to ensure that all the modes of the glider were stimulated. The results reveal that the control and stability derivatives estimated from the flight data are not very accurate but are still suitable to be used in simulating the glider's motion. / AFRIKAANSE OPSOMMING: Hierdie tesis beskryf die proses wat gebruik is om die kort periode beheer en stabiliteit afgeleides van 'n ASK-13 sweeftuig vas te stel. Die kort periode beheer en stabiliteit afgeleides is verkry deur parameter afskatting op data wat gedurend vlugte van die sweeftuig opgeneem is. Die algoritme wat gebruik is om die parameters af te skat is die MMLE3 voorstelling van 'n maksimale moontlikheid afskatter. Om vlug data te versamel sensore moes in die sweeftuig geinstalleer word. Die sensore meet beheer oppervlak hoeke, versnellings, hoeksnellhede en die dinamies en statiese lugdruk om te verseker dat daar genoeg data is vir die afskatting. Om die afgeskatte parameters akkuraad te kry moet die loods spesefieke manoeuvres vlieg om seker te maak dat al die moduse van die sweeftuig is gestimuleer. Die resultate wat gelewer is 'n stel kort periode beheer en stabiliteit afgeleides wat nie akkuraad is nie, maar wat weI goed genoeg is or ie bewegings van die sweeftuig te simuleer.

The main area of emphasis in this study is to investigate the methods and technology for aerodynamic configuration sizing of missiles and to develop a software platform in MATLAB&reg / environment as a design tool which has an ability of optimizing the external configuration of missiles for a set of flight requirements specified by the user through a graphical user interface. A genetic algorithm based optimization tool is prepared by MATLAB is expected to help the designer to find out the best external geometry candidates in the conceptual design stage. Missile DATCOM software package is employed to predict the aerodynamic coefficients needed in finding the performance merits of a missile for each external geometry candidate by integrating its dynamic equations of motion. Numerous external geometry candidates are rapidly eliminated according to objectives and constraints specified by designers, which provide necessary information in preliminary design. In this elimination, the external geometry candidates are graded according to their flight performances in order to discover an optimum solution. In the conceptual design, the most important performance objectives related to the external geometry of a missile are range, speed, maneuverability, and control effectiveness. These objectives are directly related to the equations of motion of the missile, concluding that the speed and flight range are related to the total mass and the drag-to-lift ratio acting on missile. Also, maneuverability depends on the normal force acting on missile body and mass whereas the control effectiveness is affected by pitching moment and mass moment of inertia of missile. All of the flight performance data are obtained by running a two degree-of-freedom simulation. In order to solve the resulting multi-objective optimization problem with a set of constraint of linear and nonlinear nature and in equality and inequality forms, genetic-algorithm-based methods are applied. Hybrid encoding methods in which the integer configuration variables (i.e., nose shape and control type) and real-valued geometrical dimension (i.e., diameter, length) parameters are encoded in the same individual chromosome. An external configuration design tool (EXCON) is developed as a synthesis and external sizing tool for the subsonic cruise missiles. A graphical user interface (GUI), a flight simulator and optimization modules are embedded into the tool. A numerical example, the re-configuration problem of an anti-ship cruise missile Harpoon, is presented to demonstrate the accuracy and feasibility of the conceptual design tool. The optimum external geometries found for different penalty weights of penalty terms in the cost function are compared according to their constraint violations and launch mass values. By means of using EXCON, the launch mass original baseline Harpoon is reduced by approximately 30% without deteriorating the other flight performance characteristics of the original Harpoon.

The primary research objective was to develop a methodology to support conceptual design of the Hybrid Wing Body (HWB) configuration. The absence of a horizontal tail imposes new stability and control requirements on the planform, and therefore requiring greater emphasis on control authority assessment than is typical for conceptual design. This required investigations into three primary areas of research. The first was to develop a method for designing an appropriate amount of redundancy. This was motivated widely varying numbers of trailing edge elevons in the HWB literature, and inadequate explanations for these early design decisions. The method identifies stakeholders, metrics of interest, and synthesizes these metrics using the Breguet range equation for system level comparison of control surface layouts. The second area of research was the development trim analysis methods that could accommodate redundant control surfaces, for which conventional methods performed poorly. A new measure of control authority was developed for vehicles with redundant controls. This is accomplished using concepts from the control allocation literature such as the attainable moment subset and the direct allocation method. The result is a continuous measure of remaining control authority suitable for use during HWB sizing and optimization. The final research area integrated performance and control authority to create a HWB sizing environment, and investigations into how to use it for design space exploration and vehicle optimization complete the methodology. The Monte Carlo Simulation method is used to map the design space, identify good designs for optimization, and to develop design heuristics. Finally, HWB optimization experiments were performed to discover best practices for conceptual design.

Cette thèse CIFRE est réalisée dans le cadre d’un partenariat entre le laboratoire IMS de l’Université Bordeaux I et Airbus Operations S.A.S à Toulouse. Le thème abordé concerne la détection robuste et précoce de deux types particuliers de pannes dans le système de commandes de vol, à savoir l’embarquement et le grippage des gouvernes de profondeur. Afin de contribuer à l’optimisation du design structural des futurs avions, l’objectif est de proposer des méthodes capables d’améliorer les performances en détection des techniques actuellement en place, tout en garantissant un haut niveau de robustesse. Trois stratégies de surveillance à base de modèle sont présentées. La première solution est basée sur un filtre de Kalman dédié, associé à une procédure d’optimisation de ses paramètres. La seconde technique est basée sur un test de décision appliqué dans l’espace paramétrique, à une direction sensible identifiée. Finalement, une troisième approche consiste à utiliser un différentiateur à modes glissants pour estimer les dérivées du signal d’entrée et de sortie de la boucle d’asservissement. Les méthodes développées ont été implémentées dans le calculateur de commandes de vol et validées sur les bancs de tests Airbus et même en vol. Les résultats expérimentaux ont clairement mis en évidence l’apport des techniques présentées dans cette thèse par rapport à l’état de l’art industriel. / The research work done in this PhD has been carried out under an industrial convention (CIFRE) between the IMS laboratory (Bordeaux University, France) and Airbus Operations S.A.S. (Toulouse, France). The thesis deals with two important Electrical Flight Control System failure cases: runaway (a.k.a. hard over) and jamming (or lock-in-place failure) of aircraft control surfaces. Early and robust detection of such failures is an important issue for achieving sustainability goals and for early system reconfiguration. The thesis focuses on the elevator runaway and jamming. Three model-based monitoring strategies are presented. The first approach is based on a dedicated Kalman filtering with optimised tuning parameters. The second method is based on a decision test applied to an identified sensitive direction in the parametric space. Finally, the third solution is based on a sliding mode differentiator. The techniques have been implemented in the flight control computer and validated on Airbus test facilities and during real flight tests. The experimental results confirmed that good level of performance and robustness can be obtained.