1,720,964 research outputs found
Sigma Point Kalman Filters for GPS Navigation with Integrity in Aviation
No full textThis paper presents an investigation into the benefits of Sigma Point Kalman Filters (SPKF) applied to GPSOnly estimation problem for highintegrity navigation in aviation applications. Navigation systems used for aircraft approach and landing must meet strict requirements for accuracy, integrity, availability and continuity. Modern GPS is capable of meeting the accuracy and availability requirements, however the integrity and continuity required for approach navigation mandate the use of additional sensors to meet the standards. Modern signal processing techniques can allow greater capability of existing systems, lowering the costs for all users of the system, particularly in the General Aviation sector. This work begins by comparing the raw estimation performance of the sigmapoint filter against established approaches of the Extended Kalman Filter (EKF) and snapshot Leastsquares (LSQ). The fault detection algorithms are then developed for the SPKF filters based on an approach used for highgrade navigation systems. It is hypothesised that since the SPKF can provide a more accurate estimate of the state covariance, then the fault detection scheme, including the integrity protection level, will be more reliable. Comparisons of the faultdetection performance against current techniques are presented. Finally, conclusions are drawn as to the overall benefits of the SPKF approach to navigation integrity. It is demonstrated that whilst the accuracy of the SPKF is not significantly different than the EKF or Least Squares approaches, the\ud
covariance estimation and resultant integrity protection level is reliable
UAV Avionics "Hardware in the Loop" Simulator
No full textThe avionics systems, especially the flight management and control systems, are some of the most critical elements of any aircraft, more so for an autonomous aircraft. Testing these systems in a realistic synthetic environment is an important process. It is logical therefore, to develop a suitable simulation environment in which the avionics systems can be tested. It is desirable for this system to be easy to implement, cost effective and representative of the aircraft being simulated.\ud
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This paper discusses the development of such a simulation system, known as the Aircraft\ud
Simulation And Testing Environment (ASATE). ASATE is the continuation of work initiated in 2001 for the testing of avionics developed as part of the QUT UAV project. ASATE\ud
incorporates commercially available software packages including X-Plane for the flight visualisation and Matlab Simulink for the implementation of the dynamic flight model, sensor models and control algorithms. The mission management computer and other systems including the flight control system, are connected to the Simulink/X-Plane systems via ASATE. ASATE provides the means for designers to construct mission and control algorithms and to test the avionics hardware and software systems in real time, by simulating full missions, with realistic visual feedback of the aircraft’s response.\ud
ASATE has been successfully employed to verify the flight management system and the flight control system of the QUT UAV. A set of control system tutorials, based on ASATE, have also been developed to assist in the teaching of flight control systems at QUT. This paper describes the development of ASATE and its usage for simulating aircraft missions (excluding takeoff and landing) and as an educational tool for students
An investigation into the next generation avionics architecture for the QUT UAV project
No full textThis paper investigates the next generation Unmanned Airborne Vehicle (UAV) Avionics Architecture for QUT’s unmanned research aircraft. Firstly, the generalised UAV avionics requirements for small to medium civilian UAVs are developed, taking into account areas including flight control, guidance, navigation, interoperability, sensing, data buses, communications data links, airspace integration, airworthiness and system safety. Significant consideration is also given to the extensive experience with past avionics architectures. An exploration is undertaken as to the current and predicted advances in technology, such as the use of embedded computational clusters and alternate computing architectures that would provide benefits to the next-generation avionics architecture if they were to be incorporated. This is put in context with a comparison against the existing avionics architecture as well as the avionics currently being developed for the QUT UAV project.\ud
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The results of this paper discuss the various options for avionics architectures with respect to the design requirements, and the experiences with their physical implementations. Conclusions are drawn which make recommendations on the optimal standardised architecture for UAV research at QUT
GARDSim - A GPS Receiver Simulation Environment for\ud Integrated Navigation System Development and Analysis
No full textAirservices Australia has recently proposed the use of a Ground-based Regional Augmentation System (GRAS) to improve the safety of using the NAVSTAR Global\ud
Positioning System (GPS) in aviation. The GRAS Airborne Receiver Development project\ud
(GARD) is being conducted by QUT in conjunction with Airservices Australia and GPSat\ud
Systems. The aim of the project is to further enhance the safety and reliability of GPS and GRAS by incorporating smart sensor technology including advanced GPS signal processing and Micro-Electro-Mechanical-Sensor (MEMS) based inertial components.\ud
GARDSim is a GPS and GRAS receiver simulation environment which has been developed for\ud
algorithm development and analysis in the GARD project. GARDSim is capable of simulating\ud
any flight path using a given aeroplane flight model, simulating various GPS, GRAS and inertial system measurements and performing high integrity navigation solutions for the flight. This paper discusses the architecture and capabilities of GARDSim. Simulation results will be presented to demonstrate the usefulness of GARDSim as a simulation environment for algorithm development and evaluation
Integrity Coasting Concept for General Aviation Users of the Ground Based Regional Augmentation System
No full textIt is now widely established that high performance navigation can be achieved by integrating GPS and low-cost inertial Micro-Electro-Mechanical Sensors (MEMS) measurements. However, the high noise and drift rates of these low-cost sensors, and their subsequent inability to coast for sufficient periods during GPS outages has hampered their widespread uptake in general aviation aircraft. The Ground Based Regional Augmentation System (GRAS) will bring high-integrity GPS navigation to General Aviation aircraft, however the potential exists that the GRAS signal could be lost for seconds or minutes at a critical time due to terrain masking or aircraft manoeuvres. A system is therefore needed which can coast through short-period GRAS outages, whilst taking advantage of the superior integrity provided by the GRAS Signal in Space (SiS) when it is available. This paper presents simulation results for a high performance navigation system utilising low-cost MEMS inertial sensors and the GRAS. The system utilises the high accuracy and integrity of GPS navigation when the GRAS SiS is available to calibrate the inertial system parameters, and is then able to coast the navigation solution with high-integrity for short periods if the GRAS signal is not available
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
GPS Integrity Monitoring with an Aerodynamic Model and Low Quality INS
No full textFor civilian general aviation, the Ground-based Regional\ud
Augmentation System (GRAS) is a cost-effective system\ud
(compared to Space-Based Augmentation Systems) which is able\ud
to provide a high degree of GPS accuracy and integrity to meet\ud
aviation requirements for all modes of flight down to Approach\ud
with Vertical Guidance (APV). However, since GRAS corrections\ud
are transmitted to aircraft from ground-based VHF broadcast\ud
stations, the GRAS signal-in-space may not always be received.\ud
The signal may be masked by surrounding terrain when an aircraft\ud
is on approach, or there may be gaps in the network coverage.\ud
During a GRAS outage an alternative integrity monitoring system\ud
is required to allow continuous navigation. Another requirement is\ud
that a backup integrity monitoring system must be as low cost as\ud
possible. Building upon work presented in Greer et al. (2006), a new method is investigated which involves using a combination of\ud
GPS, low performance (low-cost) Micro-Electro-Mechanical\ud
Systems (MEMS) Inertial Navigation Sensors (INS), and an\ud
aerodynamic model of the aircraft. This information is combined\ud
in an Extended Kalman Filter (EKF). The novel aspect of this\ud
architecture is the inclusion of an aerodynamic model for the GPS\ud
integrity monitoring. During a GRAS outage, the aerodynamic\ud
model brings a greater level of robustness to the integrity\ud
monitoring procedure than the low quality inertial sensors can\ud
provide alone. This method is also highly autonomous because all\ud
measurements are local to the aircraft, without requiring external\ud
aids. By computer simulation it is shown that the aerodynamic\ud
model may replace the MEMS INS as a source of dynamic\ud
information in the EKF. This allows the benefits of using an EKF\ud
and filtered fault detection algorithm to be obtained. It is shown\ud
that a more stable and lower HPL is achieved under changing\ud
satellite conditions than a GPS-only RAIM algorithm
Airborne systems laboratory for automation research
No full textThis paper presents an Airborne Systems Laboratory for Automation Research. The Airborne Systems Laboratory (ASL) is a Cessna 172 aircraft that has been specially modified and equipped by ARCAA specifically for research in future aircraft automation technologies, including Unmanned Airborne Systems (UAS). This capability has been developed over a long period of time, initially through the hire of aircraft, and finally through the purchase and modification of a dedicated flight-testing capability. The ASL has been equipped with a payload system that includes the provision of secure mounting, power, aircraft state data, flight management system and real-time subsystem. Finally, this system has been deployed in a cost effective platform allowing real-world flight-testing on a range of projects
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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