Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: This thesis presents the design and implementation of all the subsystems required to
perform precision autonomous helicopter landings within a low-cost framework.
To obtain high-accuracy state estimates during the landing phase a vision-based approach,
with a downwards facing camera on the helicopter and a known landing target, was used.
An e cient monocular-view pose estimation algorithm was developed to determine the
helicopter's relative position and attitude during the landing phase. This algorithm was
analysed and compared to existing algorithms in terms of sensitivity, robustness and
runtime.
An augmented kinematic state estimator was developed to combine measurements from
low-cost GPS and inertial measurement units with the high accuracy measurements from
the camera system. High-level guidance algorithms, capable of performing waypoint navigation
and autonomous landings, were developed.
A visual position and attitude measurement (VPAM) node was designed and built to perform
the pose estimation and execute the associated algorithms. To increase the node's
throughput, a compression scheme is used between the image sensor and the processor
to reduce the amount of data that needs to be processed. This reduces processing requirements
and allows the entire system to remain on-board with no reliance on radio
links. The functionality of the VPAM node was con rmed through a number of practical
tests. The node is able to provide measurements of su cient accuracy for the subsequent
systems in the autonomous landing system.
The functionality of the full system was con rmed in a software environment, as well as
through testing using a visually augmented hardware-in-the-loop environment. / AFRIKAANSE OPSOMMING: Hierdie tesis beskryf die ontwikkeling van die substelsels wat vir akkurate outonome helikopter
landings benodig word. 'n Onderliggende doel was om al die ontwikkeling binne
'n lae-koste raamwerk te voltooi.
Hoe-akkuraatheid toestande word benodig om akkurate landings te verseker. Hierdie
metings is verkry deur middel van 'n optiese stelsel, bestaande uit 'n kamera gemonteer
op die helikopter en 'n bekende landingsteiken, te ontwikkel. 'n Doeltreffende mono-visie
posisie-en-orientasie algoritme is ontwikkel om die helikopter se posisie en orientasie, relatief
tot die landingsteiken, te bepaal. Hierdie algoritme is deeglik ondersoek en vergelyk
met bestaande algoritmes in terme van sensitiwiteit, robuustheid en uitvoertyd.
'n Optimale kinematiese toestandswaarnemer, wat metings van GPS en inersiele sensore
kombineer met die metings van die optiese stelsel, is ontwikkel en deur simulasie bevestig.
Hoe-vlak leidingsalgoritmes is ontwikkel wat die helikopter in staat stel om punt-tot-punt
navigasie en die landingsprosedure uit te voer.
'n Visuele posisie-en-orientasie meetnodus is ontwikkel om die mono-visie posisie-en orientasie algoritmes uit te voer. Om die deurset te verhoog is 'n saampersingsalgoritme
gebruik wat die hoeveelheid data wat verwerk moet word, te verminder. Dit het die
benodigde verwerkingskrag verminder, wat verseker het dat alle verwerking op aanboord
stelsels kan geskied. Die meetnodus en mono-visie algoritmes is deur middel van praktiese
toetse bevestig en is in staat om metings van voldoende akkuraatheid aan die outonome
landingstelsel te verskaf.
Die werking van die volledige stelsel is, deur simulasies in 'n sagteware en hardeware-indie-
lus omgewing, bevestig.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/6523 |
| Date | 03 1900 |
| Creators | De Jager, Andries Matthys |
| 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 | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 151 p. : ill. |
| Rights | University of Stellenbosch |
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