Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: In recent years, the use of airships has become popular for observation purposes since they provide a cost effective alternative to other aircraft. For this project a lateral and longitudinal flight control system are required for waypoint navigation flight of an 8m long, non-rigid airship. The airship’s actuators include a rudder, elevator and a propulsion system which can be vectored longitudinally. Two airship models are evaluated for this project. A chosen model is linearised and a modal analysis is done. The modal analysis is compared to a previous modal study done on the YEZ-2A airship and is found to compare well. Each airship mode is discussed and the linear behaviour is compared to the behaviour of the non-linear model. A fuzzy logic controller design approach was undertaken for the design of speed, heading and height controllers. These non-linear controllers were designed for the non-linear model, due to the following reasons: Fuzzy logic controllers show tolerance to model inaccuracies. Complexity of design is simple. Controllers can be adjusted intuitively. Fuzzy logic controllers can be combined with conventional control techniques. Simulation results showed adequate lateral and longitudinal performance, even when subjected to light wind conditions and disturbances. The inertial measuring unit implemented in a previous project is used and additional hardware is designed and implemented for the control of the airship’s actuators. Several improvements are made to the groundstation software to allow for activation of different controllers as well as for setting up the desired flight plan. The controller performance is tested through flight tests and shows adequate performance as well as controller potential. Although further work is still required for improving the controllers’ performance, this thesis acts as a platform for future research. / AFRIKAANSE OPSOMMING: In die afgelope paar jaar het die gebruik van die lugskepe gewild geword vir waarnemings doeleindes aangesien dit ’n koste effektiewe alternatief vir ander lugvaartuie bied. In hierdie projek word ’n laterale en longitudinale beheerstelsel benodig vir merker navigasie vlugte met ’n 8m lang, nierigiede lugskip. Die lugskip se aktueerders sluit in ’n rigtingroer, hoogteroer asook ’n aandrywing stelsel wat oorlangs gestuur kan word. Vir hierdie projek is twee lugskip modelle geïmplementeer. Die gekose model is gelineariseer en ’n modale analise is gedoen. Die modale analise is met ’n vorige modale studie vir die YEZ-2A lugskip vergelyk en wys soortegelyke linieêre gedrag. Die lugskip modusse is bespreek en die linieêre gedrag word met die gedrag van die nie-linieêre model vergelyk. Daar is op ’n fuzzy logiese beheerder ontwerp besluit vir die ontwerp van spoed, rigting en hoogte beheerders. Hierdie nie-linieêre beheerders is ontwerp vir die nie-linieêre model a.g.v. die volgende redes: Fuzzy logiese beheerders toon toleransie vir modellering of meetfoute. Kompleksiteit van die ontwerp is eenvoudig. Beheerders kan intuïtief aangepas word. Fuzzy logiese beheerders kan met konvensionele beheertegnieke gekombineer word. Simulasie resultate toon voldoende werkverrigtinge, selfs in die teenwoordigheid van ligte wind sowel as ander versteurings. Die inersiële metings eenheid, wat geïmplementeer is in ’n vorige projek, is gebruik en addisionele hardeware vir die beheer van die lugskip is aktueerders is ontwerp en geïmplementeer. Talle verbeterings is aangebring aan die grondstasie sagteware vir die aktiveer van die beheerders sowel as die uitleg van die gekose vlugplan. Die beheerders se werksverrigtinge is getoets gedurende vlugtoetse en toon voldoende beheer vermoë sowel as beheerder potensiaal. Alhoewel verdere werk steeds nodig is vir die verbetering van die beheerders, dien hierdie tesis as ’n platform vir toekomstige navorsing.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Aerostats and Stratolites could play a major role in expanding current satellite and other technologies in the near future. A study was made on the development of aerostat platforms and the current state of Stratolite development. The aim was to develop an airship system that is capable of maintaining a specific position regardless of the presence of wind. The various applications of such a geostationary platform are discussed. A dynamic model of an airship was developed and a simulation was implemented in software. This was done to study the possibility of developing aerostats like these. A tethered airship system was developed and built to demonstrate that it is possible to control the position of an airship. The airship system uses current technology in an unique combination to fulfil the requirement of remaining stationary despite the influence of wind. Various control system design techniques were used to implement the controllers. Linear models of the airship system were identified practically and used to design the controllers. The controllers were tested in simulation as well as practically and the results of these tests are given. It was concluded that there exists potential for the development of Stratolite systems, although there exists a fair amount of challenges and obstacles that would need to be overcome before this technology could be implemented. / AFRIKAANSE OPSOMMING: Aerostats en Stratolites kan ’n besondere rol speel in die uitbreiding van huidige sateliet- en ander aardwaarnemingstoepassings. ’n Studie is gemaak oor die ontwikkeling van Aerostat platforms en die huidige stand van Stratolite ontwikkeling. Die mikpunt was om ’n lugskipstelsel te ontwikkel wat in staat is om ’n spesifieke posisie te handhaaf ten spyte van die invloed van wind. Die verskeidenheid van toepassings, waarvoor so ’n geostasionêre platform gebruik kan word, word genoem. ’n Dinamiese model van ’n lugskip is ontwikkel en die stelsel is in sagteware gesimuleer. Dit is gedoen om die moontlikheid te ondersoek om sulke Aerostats in die toekoms te ontwikkel. ’n Lugskipstelsel, wat aan die grond geanker word met ’n kabel, is ontwerp en gebou. Die stelsel is gedemonstreer en daar is bewys dat dit moontlik is om die posisie van die lugskip te beheer. Die lugskip gebruik huidige tegnologie wat in ’n unieke kombinasie saamgevoeg is om te illustreer dat dit moontlik is vir die lugskip om stasionêr te bly ten spyte van wind. Verskeie beheerstelsels ontwerptegnieke is gebruik om die beheerders mee te implementeer. Lineêre modelle van die lugskip is prakties geïdentifiseer en is gebruik om die beheerders te ontwerp. Die lugskip se beheerders is in simulasie sowel as prakties getoets en die resultate van hierdie toetse word gegee. Die projek bevestig dat daar ’n potensiaal bestaan vir die praktiese ontwikkeling van Stratolite stelsels. Daar is egter ’n hele paar uitdagings en probleme wat eers uit die weg geruim sal moet word, voordat hierdie tegnologie ’n alledaagse werklikheid sal word.