1,721,011 research outputs found
A Simulation Model for Trajectory Prediction, Performance Analysis and Aerospace Mission Planning with High Altitude Zero Pressure Balloons
No full textThe thesis deal with the design and implementation of a tool for ascent trajectory predicion and control of a stratospheric balloon. The tool is validate in the USV mission performed by the Italian Center for Aerospace Research (CIRA
Methods and systems for estimation of shapechanges applicable to navigation and control of flexible aerospace vehicles
No full textIdentification from flight data of the Italian Unmanned Space vehicle
No full textIdentification methodologies for processing flight data are frequently used to validate and improve a pre-flight aerodynamic data-base and, specifically, to reduce the associated uncertainties. This paper describes the process applied for the identification of the aerodynamic model of the Italian Unmanned Space Vehicle. The identification problem is solved through a multi-step approach, where the aerodynamic coefficients are identified first and, in a following phase, a set of model parameters are updated. The methodology was applied to actual flight data, gathered during the second flight test performed by the Italian Aerospace Research Centre
Unconventional integrated navigation systems based on redundancy of traditional navigation sensors
No full textIn this work several unconventional navigation systems are presented that include redundancy of traditional navigation sensors. Main focus is on sensor architectures, while sensor fusion algorithms will be treated as a secondary aspect. Specifically, an analysis of systems with multiple IMUs, Gyro-free INS and GPS derived attitude has been performed. Several reasons justify the application of architectures with redundant navigation sensors; the most relevant obviously concerns the capability to detect and identify some faults. Anyway, sensor redundancy also allows increasing the accuracy of some measurements (as for example in multiple IMU’s systems) or avoiding the use of some sensors, which may have disadvantages in terms of costs or accuracy, without renounce to their measurements (as for example in Gyro-free INS). In fact these systems are based on the application of pseudo-measurements
An extension of integrated navigation algorithms to estimate elastic motions of very flexible aircrafts
No full textThis paper presents an algorithm for estimating the rigid and elastic motions of aircrafts showing significant elastic displacements, based on an EKF (Extended Kalman Filter) technique. The proposed algorithm can be applied to HALE (High Attitude Long Endurance Vehicle) unmanned vehicles, which typically show a configuration with high aspect ratios wings, fuselages with high length to diameter ratios and, above all, lightweight structures. The knowledge of their actual structure shape is fundamental essentially for three reasons: health monitoring of the structure, control purposes (Active Control Technologies) and finally for the determination of onboard sensors exact position and attitude, relative to a specified reference frame, to improve the accuracy of their measurements. Filter equations have been developed considering the coupling between rigid and elastic motions. The elastic motions are modeled in the assumptions of modal decomposition. Sensors budget of the presented algorithm, consists in two GPS Antennas/Receivers for speed/position measurements, an Inertial Measurement Unit with tri-axial accelerometers, gyros and magnetometers, and at least one auxiliary tri-axial accelerometer. The matrix formulation of the algorithm allows using the desired number of auxiliary accelerometers without changes to its implementation or its mathematical structure. Filter implementation also allows defining a numerical criterion to determine the better allocation of auxiliary accelerometers. The observability of the filter error state vector is also exhaustively analyzed, considering different scenarios concerning the elastic features of the structure. Finally simulation test results are reported, which demonstrate effectiveness of the proposed algorithm
A linear time-varying approach for robustness analyses of a re-entry flight technology demonstrator
No full textA novel robustness analysis technique is proposed for atmospheric re-entry applications. The problem is stated as a finite time stability (FTS) analysis of linear time-varying (LTV) systems on a compact time domain, subject to bounded variations in initial state and unknown parameters. The FTS property is formulated as the inclusion of all the possible system trajectories into a pre-specified time-varying subset of the state space. Based on assuming the involved sets are polytopes, the proposed approach allows deducing the system FTS from the property verification on a limited number of numerically computed system trajectories. An additional result is presented which allows determination of a conservative estimate of the maximum norm-bound of time-varying perturbations under which the LTV system remains finite time stable. Results of the application of the proposed technique to a re-entry technology demonstrator are presented which demonstrate its effectiveness in complementing conventional linear time invariant-based analyses. Results also show that it is computationally viable and allows linking the system robustness to a quantitative analysis of the system trajectory dispersion around the nominal one due to concurrent initial state dispersion and uncertain parameters effects, which aids in evaluating mission objectives fulfilment
Tracking Architectures and Algorithms based on Cooperative and Non-Cooperative Sensors for Multiple UAV Applications
No full textThe increasing usage of Unmanned Aircraft Systems (UAS), together with the development of new sensors and miniaturized technologies, allows the employment of multiple UAS to perform some tasks impracticable for manned aircraft or for a single Unmanned Aerial Vehicle (UAV). In these multi-UAV architectures, proper tracking algorithms, based on the fusion of information coming from non-cooperative (i.e., cameras and radar), and cooperative sensors (i.e., Automatic Dependent Surveillance – Broadcast, ADS-B), are needed for providing the required situational awareness. This paper discusses research activities that are being carried out within this framework. In particular, after a general discussion about advantages and drawbacks of non cooperative and cooperative sensors, a detailed description of a multi ADS-B track management algorithm, and first preliminary numerical results, are provided
An optimal 3D analytical solution for collision avoidance between aircraft
No full textAbstract—This paper focuses on an optimal three-dimensional analytical solution for aircraft non-cooperative collision avoidance. Based on a geometric approach, an analytical solution to a proper kinematic optimization problem is here derived, which implies the simultaneous change of all control variables (speed module, track and slope angles), thus this approach resulting very suitable for real-time applications. In a pair-wise non-cooperative collision avoidance, the speed vector of the aircraft implementing the proposed control strategy is continuously changed with the aim of skimming the safety bubble surrounding the other aircraft (considered as an intruder).
Under certain hypotheses, the proposed solution can be proved to be optimal with respect to the minimization of aircraft deviation from its nominal trajectory. Proper performance indexes have been defined and challenging conflict scenarios, where the other aircraft be haves even a pursuer, have been analyzed
Hybrid Approach for Rotorcraft Identification from Flight Data
No full textThe availability of suitable methods for rotorcraft model identification from flight data is a key factor to enhance the competitiveness of the rotorcraft industry in the development process of new vehicles. Indeed, reliable simulation models provided by the identification techniques can be used for the design and validation of the vehicle flight control system. It allows minimizing the number of in flight experimental tests and consequently reducing costs and risks related to flight testing. In this paper the complex problem of rotorcraft model identification is decomposed in simpler sub-problems and solved by means of multi-step hybrid time-frequency approach. The hybrid time-frequency approach allows exploiting the advantage of both time and frequency domains methods, maximizing the information content extracted from the flight data and obtaining an identified model applicable in the whole frequency range of interest. The proposed methodology was applied to simulated data of the UH60 Black Hawk generated using the FLIGHTLAB simulation environment both in hover and forward flight conditions. Preliminary results show the effectiveness of the proposed identification strategy in terms of convergence and capability of extracting from flight data relevant information on the vehicle dynamic behavior
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