1,721,021 research outputs found
Flying robots to the rescue
No full textUAVs could one day save the lives of lost civilians and\ud
those sent to find them, and a competition in outback\ud
Australia is proving how soon that day might come.\ud
We have all seen news stories of people who ventured\ud
beyond the day-to-day reach of the community and got lost:\ud
search parties are formed, aircraft drafted in, and\ud
often large sums of money expended in the quest to find them
Single Antenna Attitude Determination for FedSat
No full textFedSat is the first satellite to be launched by Australia for 30 years. It is will be a scientific spacecraft with a number of experimental payloads. These payloads comprise of a single antenna GPS receiver, a 3-axis magnetometer, a Ka Band transponder and a re-configurable computing payload. It will be launched by Nasda on a H2A rocket as a piggyback payload with ADEOS-2.\ud
\ud
The GPS receiver is a NASA JPL designed "BlackJack" receiver, which was provided to the CRCSS by NASA. The high-level objectives, for the GPS receiver on the FedSat mission, are to provide an orbit determination capability and an attitude determination capability, whilst operating within strict power budget requirements. The current baseline is a total of 20 minutes of operation per 100 minute orbit.\ud
\ud
This paper presents the history of the attitude determination capability for FedSat, an outline of the antenna gain pattern tests performed for FedSat, a summary of results obtained to date, and recommendations for new approached to improve the performance of single antenna attitude determination systems
Single Antenna Attitude Determination for Fedsat with Improved Antenna Gain Patterns
No full textAbstract\ud
The GPS receiver on FedSat is a single antenna unit which was supplied by NASA JPL and integrated on the satellite by the Queensland University of Technology (QUT) and other participants in the Cooperative Research Centre for Satellite Systems. The high-level objectives, for the GPS receiver on the FedSat mission, are to provide an orbit determination capability and an attitude determination capability, whilst operating within strict power budget requirements. The current baseline is a total of 30 minutes of operation per 100 minute orbit.\ud
\ud
This paper presents the history of the attitude determination capability for FedSat and an outline of the antenna gain pattern tests performed for FedSat. These tests show the great impact that the spacecraft has on the measured antenna gain pattern. Extensive data collection and simulation of different antenna gain patterns was made using a GPS constellation simulator. The accuracy of the attitude determination problem results, are shown to be within 30 degrees for the signal to noise ratio (SNR) weighted approach and were improved to within 5 degrees when mapping of the SNR to elevation angle approach is taken. Recommendations for new improved approaches, in both the methodology and in the choice of antenna gain pattern are made
Robust video stabilisation algorithm using feature point selection and delta optical flow
No full textIn this study, the authors propose a novel video stabilisation algorithm for mobile platforms with moving objects in the scene. The quality of videos obtained from mobile platforms, such as unmanned airborne vehicles, suffers from jitter caused by several factors. In order to remove this undesired jitter, the accurate estimation of global motion is essential. However it is difficult to estimate global motions accurately from mobile platforms due to increased estimation errors and noises. Additionally, large moving objects in the video scenes contribute to the estimation errors. Currently, only very few motion estimation algorithms have been developed for video scenes collected from mobile platforms, and this paper shows that these algorithms fail when there are large moving objects in the scene. In this study, a theoretical proof is provided which demonstrates that the use of delta optical flow can improve the robustness of video stabilisation in the presence of large moving objects in the scene. The authors also propose to use sorted arrays of local motions and the selection of feature points to separate outliers from inliers. The proposed algorithm is tested over six video sequences, collected from one fixed platform, four mobile platforms and one synthetic video, of which three contain large moving objects. Experiments show our proposed algorithm performs well to all these video sequences
Determination and Evaluation of UAV Safety Objectives
No full textThe integration and acceptance of routine Unmanned Aerial Vehicle (UAV) operations within the civilian airspace system hinges on the ability of UAV developers, operators and regulators to prove that UAVs, at minimum, have an equivalent level of safety to that of human-piloted aircraft. Regulations, which govern the safe design, manufacture, maintenance and operation of UAV systems, are to be defined so as to ensure this safety objective is met. Therefore, it is important to provide discussion on the definition and application of such safety objectives to ensure appropriate requirements are defined. \ud
\ud
Safety objectives are defined using a historical analysis of human-piloted aviation accidents. The results of this empirical analysis are then compared against those proposed in draft regulations and in similar studies. The limitations to the approach and the metrics used are also discussed.\ud
\ud
A simple ground fatality expectation model is used to illustrate the impact that varying safety objectives have on the design and operation of UAVs. Specific applications of border security, operations over urban environments and precision farming in the sugarcane industry are investigated. \ud
\ud
The final section of this paper provides discussion on the public acceptance of risk. The paper highlights a number of key factors which influence the acceptance of risk and the impact these factors have on the definition of safety objectives
Single antenna attitude algorithm for non-uniform antenna gain patterns
No full textThe objective of this research is to investigate a new method for improving the accuracy of single antenna attitude systems based on GPS signal strength measurements. To achieve this objective, a predictive GPS signal strength model is proposed and developed. The model consists of a precisely measured three dimensional receiving antenna gain pattern (as fitted to the spacecraft), the distance dependent path loss, the effects of the ionosphere, the GPS satellite transmitting antenna gain, and the variation in GPS satellite transmission power. Furthermore, an algorithm is developed to provide an estimate of single-axis attitude solution based on this predictive GPS signal strength model. The performance of this new algorithm is evaluated and compared against two other single antenna attitude approaches using ground data and flight data. Results show that the new single antenna attitude algorithm is capable of providing attitude accuracy of 10 deg rms for static terrestrial platforms with a zenith pointing antenna. Furthermore, 15 deg rms from the FedSat satellite negative velocity pointing antenna configuration has been achieved
The Smart Skies Project
No full textSmart Skies is an international research project exploring the development and demonstration of future aviation technologies which facilitate the more efficient utilisation of airspace for both manned and unmanned aircraft. These technologies include autonomous vision-based collision avoidance systems, autonomous airspace separation management systems and a mobile ground-based radar system to support non-segregated UAS operations within the NAS. This presentation will provide an introduction to the key programs of research, detail results from recent flight trial activities and will outline future directions for the project
Solar powered UAV for fire prevention and planning
No full textThis project aims to develop a methodology for designing and conducting a systems engineering analysis to build and fly continuously, day and night, propelled uniquely by solar energy for one week with a 0.25Kg payload consuming 0.5 watt without fuel or pollution. \ud
\ud
An airplane able to fly autonomously for many days could find many applications. Including coastal or border surveillance, atmospherical and weather research and prediction, environmental, forestry, agricultural, and oceanic monitoring, imaging for the media and real-estate industries, etc. \ud
\ud
Additional advantages of solar airplanes are their low cost and the simplicity with which they can be launched. For example, in the case of potential forest fire risks during a warm and dry period, swarms of solar airplanes, easily launched with the hand, could efficiently monitor a large surface, reporting rapidly any fire starts. This would allow a fast intervention and thus reduce the cost of such disaster, in terms of human and material losses. At higher dimension, solar HALE platforms are expected to play a major role as communication relays and could replace advantageously satellites in a near future
Robust Motion Estimation for Camcorders Mounted in Mobile Platforms
Full text linkIn this paper, we propose a novel camera motion estimation algorithm for mobile platforms. Videos captured by cameras mounted in mobile platforms suffer from jitter motions caused by various factors. It is vital to obtain accurate estimates of camera motions in order to remove these undesirable jitters. But existing motion estimation methods for mobile platforms have difficulties to deal with the interference of moving objects and estimation errors. We propose to estimate camera motions from histograms of local motions as the position of the highest peak in each motion histogram is insensitive to estimation errors and robust to the interference of moving objects. We also propose to use sorted arrays to implement histograms due to its advantages. Experiments show our proposed methods can achieve promising results
- …
