Jonathan Paxman

Global tracking control of quadrotor VTOL aircraft in three dimensional space

This paper presents a new method for the design of controllers for quadrotor vertical take-off and landing (VTOL) aircraft which globally asymptotically track reference trajectories in three dimensional space. Roll and pitch angles plus the total thrust are considered immediate controls to track references in position and yaw angle of the aircraft. The control design is based on the newly introduced one-step ahead backstepping, standard backstepping and Lyapunovs direct methods. A combination of Euler angles and unit-quaternions are used to represent the aircraft attitude and angular velocities. The results are illustrated with simulations.

Automated crater detection and counting using the hough transform

A manual process for detecting and counting craters on the surface of a planetary body becomes impractical when attempting to survey a large surface area. Similarly, existing automated methods that are effective for specific areas of focus are also impractical for a large data set. We report on the work completed so far in developing a crater detection system to automatically detect craters down to sub-km sizes, across a large portion of a planetary surface. Specifically, we assess the performance of a Hough Transform (HT) for the application and in particular the influence of its preprocessing edge detection phase. Tests are performed on high resolution images of the Martian surface, anticipating a large scale crater counting application for crater chronology on the surface of Mars.

Characterising fireballs for mass determination: Steps toward automating the Australian desert fireball network

Determining the mass of a meteoroid passing through the Earths atmoshphere is essential to determining potential meteorite fall positions. This is only possible if the characteristics of these meteoroids, such as density and shape are in some way constrained. When a meteoroid falls through the atmosphere, it produces a bright fireball. Dedicated camera networks have been established to record these events with the objectives of calculating orbits and recovering meteorites. The Desert Fireball Network (DFN) is one of these programs and will eventually cover ~2 million km2. Automated observatories take high-resolution optical images throughout the night with the aim of tracking and recovering meteorites. From these optical images, the position, mass and velocity of the meteoroid at the end of its visible trajectory is required to predict the path to the ground. The method proposed here is a new aproach which aims to automate the process of mass determination for application to any trajectory dataset, be it optical or radio. Two stages are involved, beginning with a dynamic optimisation of unknown meteoroid characteristics followed by an extended Kalman filter. This second stage estimates meteoroid states (including position, velocity and mass) by applying a prediction and update approach to the raw data and making use of uncertainty models. This method has been applied to the Bunburra Rockhole dataset, and the terminal bright flight mass was determined to be 0.412 ±0.256 kg, which is close to the recovered mass of 338.9 g [1]. The optimal entry mass using this proposed method is 24.36 kg, which is consistent with other work based on the estabished photometric method and with cosmic ray analysis. The new method incorporates the scatter of the raw data as well as any potential fragmentation events and can form the basis for a fully automated method for characterising mass and velocity.

Improving Robustness of Vision Based Localization Under Dynamic Illumination

A dynamic light source poses significant challenges to vision based localization algorithms. There are a number of real world scenarios where dynamic illumination may be a factor, yet robustness to dynamic lighting is not demonstrated for most existing algorithms. Localization in dynamically illuminated environments is complicated by static objects casting dynamic shadows. Features may be extracted on both the static objects and their shadows, exacerbating localization error. This work investigates the application of a colour model which separates brightness from chromaticity to eliminate features and matches that may be caused by dynamic illumination. The colour model is applied in two novel ways. Firstly, the chromaticity distortion of a single feature is used to determine if the feature is the result of illumination alone. These features are removed before the feature matching process. Secondly, the chromaticity distortion of features matched between images is examined to determine if the monochrome based algorithm has matched them correctly. The evaluation of the techniques in a Simultaneous Localization and Mapping (SLAM) task show substantial improvements in accuracy and robustness.

The Dingle Dell meteorite: A Halloween treat from the Main Belt

We describe the fall of the Dingle Dell (L/LL 5) meteorite near Morawa in Western Australia on October 31, 2016. The fireball was observed by six observatories of the Desert Fireball Network (DFN), a continental scale facility optimised to recover meteorites and calculate their pre-entry orbits. The

The desert fireball network: A sensor network for meteorite tracking and recovery

30\,\mbox{cm}

Advanced digital fireball observatories: Enabling the expansion of the desert fireball network

meteoroid entered at 15.44

A modular hybrid SLAM for the 3D mapping of large scale environments

\mbox{km s}^{-1}

Vision based localization under dynamic illumination

, followed a moderately steep trajectory of

A novel approach to fireball modeling: The observable and the calculated

51^{\circ}