Thesis (MScEng)-- Stellenbosch University, 2012. / ENGLISH ABSTRACT: This thesis presents the analysis, design, simulation and practical implementation of a
control system to achieve an accurate autonomous landing of a fixed-wing unmanned
aerial vehicle in the presence of wind gust atmospheric disturbances.
Controllers which incorporate the concept of direct-lift control were designed based on
a study of the longitudinal dynamics of the UAV constructed as a testbed. Direct-lift
control offers the prospect of an improvement in the precision with which aircraft height
and vertical velocity can be controlled by utilising actuators which generate lift directly,
instead of the conventional method whereby the moment produced by an actuator
results in lift being indirectly generated. Two normal specific acceleration controllers
were designed. The first being a conventional moment-based controller, and the second
a direct-lift-augmented controller. The moment-based controller makes use of the aircraft’s
elevator while the direct-lift augmented controller in addition makes use of the
flaps of the aircraft which serve as the direct-lift actuator.
Controllers were also designed to regulate the airspeed, altitude, climb rate, and roll
angle of the aircraft as well as damp the Dutch roll mode. A guidance controller was implemented
to allow for the following of waypoints. A landing procedure and methodology
was developed which includes the circuit and landing approach paths and the concept of
a glide path offset to calibrate the touchdown point of a landing.
All controllers and the landing procedure were tested in a hardware-in-the-loop simulation
environment as well as practically in a series of flight tests. Five fully autonomous
landings were performed, three of these using the conventional NSA controller, and the
final two the direct-lift-augmented NSA controller.
The results obtained during the landing flight tests show that the project goal of a landing
within five meters along the runway and three meters across the runway was achieved
in both normal wind conditions as well as in conditions where wind gusts prevailed. The
flight tests also showed that the direct-lift-augmented NSA controller appears to achieve
a more accurate landing than the conventional NSA controller, especially in the presence
of greater wind disturbances. The direct-lift augmented NSA controller also exhibited
less pitch angle rotation during landing. / AFRIKAANSE OPSOMMING: Hierdie tesis verteenwoordig die analise, ontwerp, simulasie en praktiese implementering
van ’n beheerstelsel wat ten doel het om ’n akkurate en outonome landing van ’n
onbemande vastevlerk vliegtuig in rukwind atmosferiese toestande te bewerkstellig.
Gegrond op ’n studie van die longitudinale dinamika van die vliegtuig wat as proeftuig
gebruik is, is beheerders ontwerp wat die beginsel van direkte-lig insluit. Direkte-lig
beheer hou die potensiaal in om die vliegtuig se hoogte en vertikale snelheid akkuraat
te beheer deur gebruik te maak van aktueerders wat lig direk genereer in teenstelling
met die konvensionele metode waar die moment van die aktueerder indirek lig genereer.
Twee normaal-versnellings beheerders is ontwerp. Die eerste is ’n konvensionele
moment-gebaseerde beheerder wat gebruik maak van die hys-aktueerder van die vliegtuig,
en die tweede is ’n direkte-lig-bygestaande beheerder wat addisioneel gebruik maak
van die flappe van die vliegtuig wat as die direkte-lig aktueerder dien.
Vedere beheerders is ontwerp wat die lugspoed, hoogte, klimkoers, en rolhoek van die
vliegtuig reguleer asook die “Dutch roll” gedrag afklam. ’n Leiding-beheerder wat die
volg van vliegbakens hanteer, is ingestel. Die landingsprosedure en -metodologie is ontwikkel
wat die landingspad sowel as die sweef-pad bepaal en wat terselfdertyd ’n metode
daarstel om die posisie van die landingspunt te kalibreer.
Die beheerders en landingsprosedure is in ’n hardeware-in-die-lus omgewing gesimuleer
en deur middel van ’n reeks proefvlugte getoets. Vyf ten volle outonome landings is
uitgevoer waarvan drie van die konvensionele normaal-versnellings beheerder gebruik
gemaak het, en die laaste twee die direkte-lig-bygestaande normaal-versnellings beheerder.
Die vlugtoetsuitslae bevestig dat die navorsingsdoel om ’n landing binne vyf meter in
lyn met en drie meter dwarsoor die landingstrook te bewerkstellig, behaal is. Hierdie
akkuraatheid is verkry in beide goeie atmosferiese toestande sowel as toestande
met rukwinde. Volgens die vlugtoetse blyk dit dat die direkte-lig-bygestaande normaalversnellings
beheerder ’n meer akkurate landing kan bewerkstellig as die konvensionele
normaal-versnellings beheerder, veral dan in toestande met rukwinde. Die direkte-ligbygestaande
normaal-versnellings beheerder het ook ’n laer hei-hoek rotasie tydens die
landing vertoon.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/71672 |
| Date | 12 1900 |
| Creators | Alberts, Frederik Nicolaas |
| Contributors | Jones, T., Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 171 p. : ill. |
| Rights | Stellenbosch University |
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