1,720,968 research outputs found
Boomerang flight mechanics: Unsteady effects on the motion characteristics
Full text linkThis work describes a simulation program suitable for predicting the behavior of the boomerang in function of its geometrical characteristics, of the throw parameters and of the environmental conditions, taking into account any non-stationary states corresponding to some motion steps (throw, transition from helicopter mode to autogyro mode, landing). These phases certainly have a significant effect on the characteristics of the trajectory. Boomerang has been treated as a lifting rotor and the nonlinear Pitt-Peters dynamic inflow model has been used, even at very high values of the advancing ratio. The mathematical model is strongly nonlinear and thus greatly dipendent on the initial condition. The influence of different environmental conditions as well as different geometric and throw parameters have been shown through the graphical comparison of the geographical trajectories. Each qualitative trend has been experimentally verified and this is a preliminary confirmation of the reliability of the numerical code. Finally a whole flight has been described and analysed in each aspect and the necessity to use an unsteady model has been shown through a time-topographical analysis of the advancing blade angles of attack
Articulated and flexible multibody satellite dynamics modeling
No full textThis paper is concerned with the derivation of the equations of motion for a maneuvering flexible satellite orbiting around the Earth. The structure is assumed to undergo large rigid-body maneuvers and small elastic deformations. The mathematical model is worked out in two levels: in the first one attention is focused on the effects of the rigid dynamics on the flexible motion, while in the second one the reciprocal influence is evaluated. The satellite is provided with flexible solar arrays linked up with the main body with torsional and bending articulations: the mathematical model also considers hinges compliance, when the appendages are blocked in the desired position. Different rotational maneuvers are simulated and numerical results highlight the limitation of the first level modelization, which can be used with confidence for structural analysis, but results inadequate for flight dynamics and control applications. © 2002 by the author(s). Published by the American Institute of Aeronautics and Astronautics, Inc
Multi-objective and multi-phase 4d trajectory optimization for climate mitigation-oriented flight planning
Full text linkAviation contribution to global warming and anthropogenic climate change is increasing every year. To reverse this trend, it is crucial to identify greener alternatives to current aviation technologies and paradigms. Research in aircraft operations can provide a swift response to new environmental requirements, being easier to exploit on current fleets. This paper presents the development of a multi-objective and multi-phase 4D trajectory optimization tool to be integrated within a Flight Management System of a commercial aircraft capable of performing 4D trajectory tracking in a Free Route Airspace context. The optimization algorithm is based on a Chebyshev pseudospectral method, adapted to perform a multi-objective optimization with the two objectives being the Direct Operating Cost and the climate cost of a climb-cruise-descent trajectory. The climate cost function applies the Global Warming Potential metric to derive a comprehensive cost index that includes the climate forcing produced by CO2 and non-CO2 emissions, and by the formation of aircraft-induced clouds. The output of the optimization tool is a set of Pareto-optimal 4D trajectories among which the aircraft operator can choose the best solution that satisfies both its economic and environmental goals
An unconventional adaptive flutter suppression actuation system: From modeling to experimentation
No full textThis paper contributes to the definition of an unconventional actuation system, intended specifically for slender/highly flexible wings' flutter suppression, and coupled with an adaptive control algorithm to handle post-flutter flight dynamics and uncertainties deriving from unpredictable degradation of the structural properties. The design and validation process of the novel actuation architecture is presented. It is based on a row of multiple small spoiler, located at fifteen percent of the mean aerodynamic chord and coordinated by a modified Model Reference Adaptive Control (MRAC) algorithm. The spoilers' concept design is optimized by Computational Fluid Dynamics (CFD) numerical simulation, afterwards realized and wind tunnel tested to derive the aerodynamic database by means of a six-axes force balance. The mathematical model has served to implement and validate the adaptive control algorithm for a wide range of condition. The modeled system is tested from on-design flutter speed and nominal structural stiffness to post-flutter speed and reduced structural stiffness through the analysis of the wing proper frequencies and phases, which has demonstrated to be very effective in testing the adaptivity of the control architecture. This approach proves the robustness of the proposed architecture before experimentation, which is performed through a custom-made wind tunnel apparatus. The two degree of freedom oscillations during flutter are successfully controlled in all conditions. This paper aims at defining a robust procedure for aeroelastic phenomena control system design, which employs a synergy of modeling, simulation and experimental approaches. Discussions and pertinent conclusions are outlined in the final section of the paper
Maneuver-Based Cross-Validation Approach for Angle-of-Attack Estimation
Full text linkThe estimation of the Angle of Attack (AOA) and Angle of Sideslip (AOS) is crucial for
flight monitoring and control. However, a gap has been identified on the data selection technique for the
class of estimators based on data-driven methods, such as the synthetic sensor based on Neural Network
(NN). This paper proposes a Cross Validation (CV) technique applied on a manoeuver-based partitioning
method to provide evidence that a given selection of data can lead to better estimation performance, with
the final aim of providing a list of manoeuvers suitable for the training phase of the estimator. Results
are shown using simulated data related to the CleanSky 2 project MIDAS
Flight control system rapid prototyping for the remotely-controlled elettra-twin-flyer airship
Full text linkNautilus S.p. A. is a small company investing in the design and development of a low-cost multipurpose multi-mission platform, known as Elettra-Twin-Flyer, which is a very innovative radio-controled airship, equipped with high precision sensors and telecommunication devices. In the prototype phase, Nautilus policy is oriented towards a massive employment of external collaborators to reduce the development costs. The crucial problem of this kind of management is the harmonious integration of all the teams involved on the project. This paper describes the integration process of the PC-104 on-board computer with the avionic devices, which are electronic systems characterized by complex communication protocols. Attention is focused on the testing, verification, validation and final translation of the embedded control software into the on-board computer, through techniques derived from the automatic code generation, such as Rapid Prototyping and Hardware-In-the-Loop. Copyright © 2006 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved
Erratum to: Joseph covariance formula adaptation to Square-Root Sigma-Point Kalman filters (Nonlinear Dyn, 10.1007/s11071-017-3356-x)
No full textExperimental investigations on high-lift wing stall control strategies with synthetic jet actuators
No full textAutonomous taxi operations: Algorithma for the solution of the routing problem
No full textIn past decades, airport ground operations have attracted researchers, with the aim of increasing airport
efficiency and reducing the environmental impact of airport operations. Airplane taxi operations have received
particular attention for their significant impact on the airport efficiency and pollutant emissions and on the
fuel cost for airlines. Alternative solutions have been proposed to the engine-on taxi procedures, including the
employment of autonomous vehicles to tow the aircraft between gates and runways. In order to be performed,
autonomous taxi procedures require precise planning and scheduling by means of sophisticated management
systems. At the base of these management systems, lie algorithms for the solution of the routing problem, which
provide feasible paths on the airport surface. Two different approaches can be used: compute the paths on the
fly, or pre-compute all the possible paths between all the pairs of starting/ending points on the airport grid and
store them in a database that is called when needed. In this paper, four different algorithms are implemented
and compared for the computation of paths on the fly: two Hopfield-type neural networks and two algorithms
based on graph theory. Furthermore, two algorithms for the generation of the path database are presented:
a modified version of the Breadth-first search and an implementation of the k-shortest paths algorithm. Each
taxi mission, performed by the tractors, consists of three different events, called phases: one central towing
phase, where the tractor tows the aircraft between gate and runway and two repositioning phases in which the
tractors move from its actual position to the airplane or from the airplane back to the depot
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