1,721,137 research outputs found
Performance Analysis of Star Sensor with APS Photodetectors
No full textThis paper presents a performance analysis for star trackers that adopt Active Pixel Sensor photodetector technology. They have many advantages on Charge Coupled Devices such as low power consumption, single voltage supply needed (3.3V or 5V), increased radiation hardness, simplified qualification procedures, capability of local reset and readout, onchip integrated timing, control, and analog-to-digital conversion. Unfortunately, their noise level is higher than in Charge Coupled Devices. Anyway, this effect can be compensated by taking advantage of their capability to manage different local exposure times. This allows for tracking bright stars at a faster tracking frequency than the one that is selected for Charge Coupled Devices, whereas a slower frequency is set for dim stars. The resulting temporal average of the number of observed stars is closer than the one of single shutter systems to the number of stars observed by Charge Coupled Devices. As a consequence, also the accuracy in attitude determination increases because it is a function of the number of detected stars. An analytical investigation of the attainable accuracy is discussed. All sensor noise sources are considered and their effects are evaluated as a function of the exposure time. The resulting accuracy turns out to be in the range 1-3 arcsec that is the one requested for low cost star sensors
Realizzazione funzioni algoritmiche basate su modello TEM per CSC Trajectory Prediction
No full textIl progetto prevede lo sviluppo di un tool in linguaggio JAVA per la predizione in tempo reale delle traiettorie altimetriche dei velivoli sulle base delle informazioni dei radar di sorveglianza e degli strumenti di bordo
Airborne Tracking
No full textMain issues of Airborne Tracking were presented. In particular, the Kalman Filter for Airborn Tracking was discussed
Sensor Fusion Architectures for Autonomous UAV Navigation
No full textThis paper presents an innovative method to estimate the performances of different candidate sensor fusion architecture for the navigation of autonomous Unmanned Aerial Veichles. Indeed, the identical navigation system of manned aircrafts can not be adopted onboard unmanned ones because they require increased levels of autonomy that compensate the absence of the human pilot. At present, no single sensor exist that can perform standalone navigation for UAVs. For this reason, proposed solutions involves the adoption of multiple sensor configuration controlled by a data fusion logic. In typical configurations, inertial sensors are used as main source of navigation reference and other sensor such as GPS, magnetometers, air data sensors, and radar or laser altimeters are used as aiding sensors. Some configurations include all the reported systems, even if they are not always synchronously used but only in critical mission phases such as landing or terrain following. At project level, one important task is to estimate the accuracy of the navigation system architecture composed by the sensors and the integration logic. Kalman filters are often used as sensor fusion algorithms. No analytical method is known to evaluate their performances. Indeed, two main numerical methods are used such as Covariance Propagation and Montecarlo Simulation. Anyway both methods have limitations. Covariance Propagation often outputs “best case” performance instead of typical ones. Montecarlo Analysis requires an heavy processing activity to perform several simulation runs. The proposed method determines the Covariance Matrix of the error state in the Kalman filter in steady-state conditions. This method requires a finite number of computations and guarantees implicit convergence to steady-state solution. Equations governing the method are fully discussed and the results are compared to the ones of the other available techniques
Autonomous Approach and Landing Algorithms for Unmanned Aerial Vehicles
No full textIn recent years, several research activities have been developed in order to increase the autonomy features in Unmanned Aerial Vehicles (UAVs), to substitute human pilots in dangerous missions
or simply in order to execute specific tasks more efficiently and cheaply. In particular, a significant research effort has been devoted to achieve high automation in the landing phase, so
as to allow the landing of an aircraft without human intervention, also in presence of severe environmental disturbances. The worldwide research community agrees with the opportunity of
the dual use of UAVs (for both military and civil purposes), and because of this it is very important to make the UAVs and their autolanding systems compliant with the present and
future rules and with the procedures regarding autonomous flight in ATM (Air Traffic Management) airspace in addition to the typical military aims of minimizing fuel, space or other
important parameters during each autonomous task.
Developing autolanding systems with the desired level of reliability, accuracy and safety involves an evolution of all the subsystems related to the guide, navigation and control
disciplines. The main drawbacks of the autolanding systems are lack of “adaptivity” to the trajectory generating and tracking process to unpredictable external events, such as varied
environmental conditions and unexpected threats to avoid, or the missed compliance between the guidelines imposed by certification authorities and the technologies used to get the desired above
mentioned adaptivity.
During his PhD period the author contributed to the development of an autonomous approach and landing system considering all the indispensable functionalities AS mission automation
logic, runway data managing, sensor fusion for optimal estimation of vehicle state, trajectory generation and tracking considering optimality criteria and health management algorithms.
In particular the system addressed in this thesis is capable of performing a fully adaptive autonomous landing starting from any point of three dimensional space. The main novel feature
of this algorithm is that it generates on line, with a desired updating rate or at a specified event, the nominal trajectory for the aircraft, based on the actual state of the vehicle and on the desired state at touch down point. Main features of the autolanding system based on the implementation of the proposed algorithm are: on line trajectory re-planning in the landing phase, fully autonomyfrom remote pilot inputs, weakly instrumented landing runway (without ILS availability), ability to land starting from any point in space and autonomous management of failures and/or adverse atmospheric conditions, decision-making logic evaluation for key-decisions regarding possible execution of altitude recovery manoeuvre based on the Differential GPS integrity signal and
compatible with the functionalities made available by the future GNSS system.
All the algorithms developed allow reduction of computational tractability of trajectory generation and tracking problems so as to be suitable for real time implementation but still
obtaining a feasible, robust and adaptive trajectory for the UAV.
All the activities related to the current study have been conducted at CIRA (Italian Aerospace Research Center) in the framework of the aeronautical TECVOL project whose aim is to develop
innovative technologies for the autonomous flight. The autolanding system was developed by the TECVOL team and the author’s contribution to it will be outlined in the thesis. Effectiveness of
proposed algorithms has been then evaluated in real flight experiments, using the aeronautical flying demonstrator available at CIRA
Aided Inertial Navigation
No full textMain issues of integrated inertial navigation were presented including inertial navigation equations and inertial navigation error equations. Kalman Filter application for aided inertial navigation
Progetto CIRA LASA (Lightweight Affordable Sense and Avoid)
No full textThe project aimed at developing a lightweight Obstacle Detection and Tracking System for small aircrafts and UAVs
Consulenza specialistica per lo sviluppo ed il trasferimento di tecnologie innovative finalizzate, in particolare, alla progettazione e test di sensori per il controllo di assetto di satelliti
No full textIl progetto ha come scopo lo sviluppo di un prototipo non qualificato di un sensore di assetto stellare per piattaforme spaziali di tipo avanzato. Tale prototipo è di tipo funzionale e non è realizzato per la qualifica spaziale. Inoltre, sarà sviluppata una facilty per la verifica in laboratorio degli algoritmi relativi alle logiche del sensore
- …
