A new avionics based GNSS integrity augmentation system: Part 1 - fundamentals

The aviation community has very stringent navigation integrity requirements that apply to a variety of manned and Unmanned Aerial Vehicle (UAV) operational tasks. This paper presents the results of the research activities carried out by the Italian Air Force Flight Test Centre (CSV-RSV) in collaboration with the Nottingham Geospatial Institute (NGI) and Cranfield University (CU) in the area of Avionics-Based Integrity Augmentation (ABIA) for mission- and safety-critical Global Navigation Satellite System (GNSS) applications. Based on these activities, suitable models were developed to describe the main causes of GNSS signal outage and degradation in flight, namely: antenna obscuration, multipath, fading due to adverse geometry and Doppler shift. Adopting these models in association with suitable integrity thresholds and guidance algorithms, the ABIA system delivers integrity caution (predictive) and warning (reactive) flags, as well as steering information to the pilot and electronic commands to the aircraft/UAV flight control system. These features allow real-time avoidance of safety-critical flight conditions and fast recovery of the required navigation performance in case of GNSS data losses. This paper presents the key ABIA concepts, architecture and mathematical models. A successive paper will address the ABIA integrity thresholds criteria and detailed results of a TORNADO simulation case-study

Management, processing and dissemination of sensory data for the Earth Resource Technology Satellite

Data center for management, processing, and dissemination of photographic products generated by ERT

Carrier-phase GNSS attitude determination and control system for unmanned aerial vehicle applications

This paper presents the results of a research activity performed by Cranfield University to assess the potential of carrierphase Global Navigation Satellite Systems (GNSS) for attitude determination and control of small to medium size Unmanned Aerial Vehicles (UAV). Both deterministic and recursive (optimal estimation) algorithms are developed for combining multiple attitude measurements obtained from different observation points (i.e., antenna locations), and their efficiencies are tested in various dynamic conditions. The proposed algorithms converge rapidly and produce the required output even during high dynamics manoeuvres. Results of theoretical performance analysis and simulation activities are presented in this paper, with emphasis on the advantages of the GNSS interferometric approach in UAV applications (i.e., low cost, high data-rate, low volume/weight, low signal processing requirements, etc.). Modelling and simulation activities focussed on the AEROSONDE UAV platform and considered the possible augmentation provided by interferometric GNSS techniques to a low-cost and low-weight/volume integrated navigation system recently developed at Cranfield University, which employs a Vision-based Navigation (VBN) system, a Micro-Electro-mechanical Sensor (MEMS) based Inertial Measurement Unit (IMU) and code-range GNSS (i.e., GPS and GALILEO) for position and velocity computations. The integrated VBN-IMU-GNSS (VIG) system is augmented by using the inteferometric GNSS Attitude Determination (GAD) and a comparison of the performance achievable with the VIG and VIG/GAD integrated Navigation and Guidance Systems (NGS) is presented. Finally, the data provided by these NGS are used to optimise the design of an hybrid controller employing Fuzzy Logic and Proportional-Integral-Derivative (PID) techniques for the AEROSONDE UAV

Temperature Chaos in Two-Dimensional Ising Spin Glasses with Binary Couplings: a Further Case for Universality

We study temperature chaos in a two-dimensional Ising spin glass with random quenched bimodal couplings, by an exact computation of the partition functions on large systems. We study two temperature correlators from the total free energy and from the domain wall free energy: in the second case we detect a chaotic behavior. We determine and discuss the chaos exponent and the fractal dimension of the domain walls.Comment: 5 pages, 6 postscript figures; added reference

Low-cost vision sensors and integrated systems for unmanned aerial vehicle navigation

A novel low cost navigation system based on Vision Based Navigation (VBN) and other avionics sensors is presented, which is designed for small size Unmanned Aerial Vehicle (UAV) applications. The main objective of our research is to design a compact, light and relatively inexpensive system capable of providing the required navigation performance in all phases of flight of a small UAV, with a special focus on precision approach and landing, where Vision Based Navigation (VBN) techniques can be fully exploited in a multisensory integrated architecture. Various existing techniques for VBN are compared and the Appearance-based Navigation (ABN) approach is selected for implementation. Feature extraction and optical flow techniques are employed to estimate flight parameters such as roll angle, pitch angle, deviation from the runway and body rates. Additionally, we address the possible synergies between VBN, Global Navigation Satellite System (GNSS) and MEMS-IMU (Micro-Electromechanical System Inertial Measurement Unit) sensors and also the use of Aircraft Dynamics Models (ADMs) to provide additional information suitable to compensate for the shortcomings of VBN and MEMS-IMU sensors in high-dynamics attitude determination tasks. An Extended Kalman Filter (EKF) is developed to fuse the information provided by the different sensors and to provide estimates of position, velocity and attitude of the UAV platform in real-time. Two different integrated navigation system architectures are implemented. The first uses VBN at 20 Hz and GPS at 1 Hz to augment the MEMS-IMU running at 100 Hz. The second mode also includes the ADM (computations performed at 100 Hz) to provide augmentation of the attitude channel. Simulation of these two modes is performed in a significant portion of the AEROSONDE UAV operational flight envelope and performing a variety of representative manoeuvres (i.e., straight climb, level turning, turning descent and climb, straight descent, etc.). Simulation of the first integrated navigation system architecture (VBN/IMU/GPS) shows that the integrated system can reach position, velocity and attitude accuracies compatible with CAT-II precision approach requirements. Simulation of the second system architecture (VBN/IMU/GPS/ADM) also shows promising results since the achieved attitude accuracy is higher using the ADM/VBS/IMU than using VBS/IMU only. However, due to rapid divergence of the ADM virtual sensor, there is a need for frequent re-initialisation of the ADM data module, which is strongly dependent on the UAV flight dynamics and the specific manoeuvring transitions performed

Nutrient-sensing mechanisms and pathways

The ability to sense and respond to fluctuations in environmental nutrient levels is a requisite for life. Nutrient scarcity is a selective pressure that has shaped the evolution of most cellular processes. Different pathways that detect intracellular and extracellular levels of sugars, amino acids, lipids and surrogate metabolites are integrated and coordinated at the organismal level through hormonal signals. During food abundance, nutrient-sensing pathways engage anabolism and storage, whereas scarcity triggers homeostatic mechanisms, such as the mobilization of internal stores through autophagy. Nutrient-sensing pathways are commonly deregulated in human metabolic diseases.National Institutes of Health (U.S.) (Grant R01 CA129105)National Institutes of Health (U.S.) (Grant R01 CA103866)National Institutes of Health (U.S.) (Grant R01 AI047389)National Institutes of Health (U.S.) (Grant R21 AG042876)American Federation for Aging ResearchStarr FoundationDavid H. Koch Institute for Integrative Cancer Research at MIT (Frontier Research Program)Ellison Medical FoundationCharles A. King TrustAmerican Cancer Society (Ellison Medical Foundation Postdoctoral Fellowship PF-13-356-01-TBE