Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: This thesis presents the development of a stall prevention flight control subsystem,
which can easily be integrated into existing flight control architectures of fixed-wing
unmanned aerial vehicles (UAV’s). This research forms an important part of faulttolerant
flight control systems and will ensure that the aircraft continues to operate
safely within its linear aerodynamic region.
The focus of this thesis was the stall detection and prevention problem. After a thorough
literature study on the topic of stall, a model based stall prevention control algorithm
with feedback from an angle of attack sensor was developed. This algorithm
takes into account the slew rate and saturation limits of the aircraft’s servos and is
able to predict when the current flight condition will result in stall. The primary concern
was stall during wings-level flight and involved the prevention of stall by utilising
only the elevator control surface. A model predictive slew rate control algorithm was
developed to override and dynamically limit the elevator command to ensure that the
angle of attack does not exceed a predefined limit. The stall prevention control system
was designed to operate as a switching control scheme, to minimise any restrictions
imposed on the existing flight control system.
Finally, software in the loop simulations were conducted using a nonlinear aircraft
model and realistic sensor noise, to verify the theoretical results obtained during
the development of this stall prevention control strategy. A worst-case performance
analysis was also conducted to investigate the robustness of the control algorithms
against model uncertainties. / AFRIKAANSE OPSOMMING: Hierdie tesis handel oor die ontwikkeling van ’n staak voorkomings-vlugbeheer substelsel
wat maklik geïntegreer kan word in bestaande vlugbeheer argitektuur van
onbemande vaste-vlerk lugvaartuie. Hierdie tesis vorm ’n belangrike deel van fouttolerante
vlugbeheertegnieke en sal verseker dat die vliegtuig slegs binne sy lineêre
aerodinamiese werksgebied bly.
Die fokus van hierdie tesis is die staak opsporing en voorkomings probleem. Na afloop
van ’n deeglike literatuurstudie oor die onderwerp van staak, is ’n model gebaseerde
staak voorkomings-beheertegniek ontwikkel, wat terugvoer van ’n invalshoek sensor
ontvang. Hierdie algoritme neem die sleur tempo en defleksie limiete van die vliegtuig
se servos in ag en is in staat om staak te voorspel. Die primêre oorweging was
staak tydens simmetriese vlugte en behels slegs die voorkoming van staak deur gebruik
te maak van die hei beheer oppervlak. ’n Model voorspellings sleur tempo
beheeralgoritme is ontwikkel om die hei-roer dinamies te beperk sodat die invalshoek
nie ’n sekere vooraf bepaalde limiet oorskry nie. Die staak voorkomings beheerstelsel
is ontwerp om te funksioneer as ’n skakel beheer skema om die beperkings op die
bestaande vlugbeheerstelsel te minimaliseer.
Laastens was sagteware-in-die-lus simulasies gebruik om die teoretiese resultate, wat
verkry is tydens die ontwikkeling van hierdie staak voorkomings beheer-strategie, te
kontroleer. Om die robuusthied van hierdie beheeralgoritmes teen model onsekerhede
te ondersoek, is ’n ergste-geval prestasie analise ook uitgevoer.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/4310 |
| Date | 03 1900 |
| Creators | Basson, Matthys Michaelse |
| Contributors | Peddle, I. K., University of Stellenbosch. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 145 p. : ill. |
| Rights | University of Stellenbosch |
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