Thesis (MScEng)--Stellenbosch University, 2012 / ENGLISH ABSTRACT: This thesis presents the design and implementation of an autonomous navigational system
and the automation of a practical demonstrator vehicle. It validates the proposed
navigation architecture using simple functional navigational modules on the said vehicle.
The proposed navigation architecture is a hierarchical structure, with a mission planner
at the top, followed by the route planner, the path planner and a vehicle controller with
the vehicle hardware at the base. A vehicle state estimator and mapping module runs in
parallel to provide feedback data.
The controls of an all terrain vehicle are electrically actuated and equipped with feedback
sensors to form a complete drive-by-wire solution. A steering controller and velocity
control state machine are designed and implemented on an existing on-board controller
that includes a six degrees-of-freedom kinematic state estimator.
A lidar scanner detects obstacles. The lidar data is mapped in real time to a local
three-dimensional occupancy grid using a Bayesian update process. Each lidar beam is
projected within the occupancy grid and the occupancy state of a ected cells is updated.
A lidar simulation environment is created to test the mapping module before practical implementation.
For planning purposes, the three-dimensional occupancy grid is converted
to a two-dimensional drivability map.
The path planner is an adapted rapidly exploring random tree (RRT) planner, that assumes
Dubins car kinematics for the vehicle. The path planner optimises a cost function
based on path length and a risk factor that is derived from the drivability map.
A simple mission planner that accepts user-de ned waypoints as objectives is implemented.
Practical tests veri ed the potential of the navigational structure implemented
in this thesis. / AFRIKAANSE OPSOMMING: In hierdie tesis word die ontwerp en implementering van 'n outonome navigasiestelsel
weergegee, asook die outomatisering van 'n praktiese demonstrasievoertuig. Dit regverdig
die voorgestelde navigasie-argitektuur op die bogenoemde voertuig deur gebruik te maak
van eenvoudige, funksionele navigasie-modules.
Die voorgestelde navigasie-argitektuur is 'n hi erargiese struktuur, met die missie-beplanner
aan die bo-punt, gevolg deur die roetebeplanner, die padbeplanner en voertuigbeheerder,
met die voertuighardeware as basisvlak. 'n Voertuigtoestandsafskatter en karteringsmodule
loop in parallel om terugvoer te voorsien.
Die kontroles van 'n vierwiel-motor ets is elektries geaktueer en met terugvoersensors
toegerus om volledig rekenaarbeheerd te wees. 'n Stuur-beheerder en 'n snelheid-toestandmasjien
is ontwerp en ge mplementeer op 'n bestaande aanboordverwerker wat 'n
kinematiese toestandsafskatter in ses grade van vryheid insluit.
'n Lidar-skandeerder registreer hindernisse. Die lidar-data word in re ele tyd na 'n lokale
drie-dimensionele besettingsrooster geprojekteer deur middel van 'n Bayesiese opdateringsproses.
Elke lidar-straal word in die besettingsrooster geprojekteer en die besettingstoestand
van betrokke selle word opdateer. 'n Lidar-simulasie-omgewing is geskep
om die karteringsmodule te toets voor dit ge mplementeer word. Die drie-dimensionele
besettingsrooster word na 'n twee-dimensionele rybaarheidskaart verwerk vir beplanningsdoeleindes.
Die padbeplanner is 'n aangepaste spoedig-ontdekkende-lukrake-boom en neem Dubinskar
kinematika vir die voertuig aan. Die padbeplanner optimeer 'n koste-funksie, gebaseer
op padlengte en 'n risiko-faktor, wat vanaf die rybaarheidskaart verkry word.
'n Eenvoudige missie-beplanner, wat via-punte as doelstellings neem, is ge mplementeer.
Praktiese toetsritte veri eer die potensiaal van die navigasiestruktuur, soos hier beskryf.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/20263 |
| Date | 03 1900 |
| Creators | Visser, Wynand |
| 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 | 129 p. : ill. |
| Rights | Stellenbosch University |
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