- Aerospace Professoredit
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This paper is focused on the dynamic modelling of an unconventional remotely-piloted Lighter-Than-Air vehicle, whose mathematical model is based on a 6 degree-of-freedom, 12 states nonlinear system, described by the basic equations of the... more
This paper is focused on the dynamic modelling of an unconventional remotely-piloted Lighter-Than-Air vehicle, whose mathematical model is based on a 6 degree-of-freedom, 12 states nonlinear system, described by the basic equations of the Newtonian mechanics. Emphasis is placed on those innovative and peculiar aspects of the dynamic modelling, which allow the development of a complete low-cost-high-fidelity Flight Simulator used both for technical and commercial purposes. In particular, the availability of this tool, featuring real time simulations, is essential for the design, test and implementation of the most suitable flight control system, as well as for the pilot training of this innovative airship
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In studying reg~stering balloon climbs it is particularly important to evaluate the lnltial topping-up and the diameter of the deflated balloon if the mission)^ is to succeed. Essentially its aim is to reach a certain height (determined... more
In studying reg~stering balloon climbs it is particularly important to evaluate the lnltial topping-up and the diameter of the deflated balloon if the mission)^ is to succeed. Essentially its aim is to reach a certain height (determined by the registering zone concerned), to which the payload must be transported. Apart from the balloon itself, that payload consists of instruments for the measurement. recording and possibly transmission of the data to the ground. With this in mind, we started from simple remarks of static balance in the balloon considered as a sectioned sphere under pressure and discovered the fundamental equations that link quantities concerned: dimension, internal overpressure and external pressure. In this way we were able to define the link between the desired burst height (that is obviously the maximum recording height) and the over-pressure necessary for take-off. Simple aerostatic considerations enabled us to ascertain the law of variation of the thrust as a function of height and balloon diameter. This also produced the criterion to ensure one essential requisite of the misslon: sufficient thrust at burst height to balance the welght. All the above was done for both homotherric (i.e. gas temperature Inside the balloon always equal to external temperature) and non-homothermlc climbs. In the second case we were presented with numerical examples for two situations that may be considered extreme: one adiabatic climb and one polytropic with an exponent less than 1 (a situation deriving, that is, from notable solar heating). The whole study was conducted under the assunption of climbs into the lnternational Standard Atmosphere. We conclude however with remarks on the modifications required if atmospheric conditions during the climb differ from the standard conditions assumed. We then suggest slmple ways of ensuring the success of the mission in cases where the atmospheric conditions are not known In advance.
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ABSTRACT This paper introduces an adaptive controller, based on neural networks use, for a nonlinear six-degrees-of-freedom combat aircraft model. This controller is based on the determination of the inverse dynamics of aircraft through a... more
ABSTRACT This paper introduces an adaptive controller, based on neural networks use, for a nonlinear six-degrees-of-freedom combat aircraft model. This controller is based on the determination of the inverse dynamics of aircraft through a state feedback, taking advantage of the neural network online learning ability in dealing with any changes of the aircraft dynamics during the flight. By comparing the online and offline training, how effective the neural controller is in adaptation is investigated and highlighted in situations involving highly demanding maneuvers as well as sudden environmental disturbances. The neural controller is designed according to the reference model adaptive direct inverse scheme. The behavior of this controller is compared with that of a conventional linear stability and control augmentation system (normal acceleration limiter), implemented under military handling qualities and high maneuverability requirements. The online training of the nonlinear neural controller is based on a recursive prediction error algorithm, whose performance results from a proportional derivative performance index formulation. The stability analysis demonstrates how the extra degree of freedom, provided by the derivative term, makes the algorithm more robust than the standard recursive least-squares method. Performance is verified through numerical simulations.
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This paper is concerned with a simulation tool developed for the innovative lighter-than-air airship patented by Nautilus Srl This unmanned airship does not use aerodynamic control surfaces: the primary command system consists in a set of... more
This paper is concerned with a simulation tool developed for the innovative lighter-than-air airship patented by Nautilus Srl This unmanned airship does not use aerodynamic control surfaces: the primary command system consists in a set of propellers properly placed in order to ...
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Unmanned Aerial Vehicles (UAV) design may involve issues on redundancy of the systems due to restricted available space and allowable weight. Virtual sensors offer great advantages from this point of view and several research projects... more
Unmanned Aerial Vehicles (UAV) design may involve issues on redundancy of the systems due to restricted available space and allowable weight. Virtual sensors offer great advantages from this point of view and several research projects carry out more or less complicated solutions in order to estimate a signal without applying a physical sensor. This approach brings to a reduction of the overall cost and to improve the Reliability, Availability, Maintainability and Safety (RAMS) performance. The patented technology named Smart-ADAHRS (Smart — Attitude and Heading Reference System) is a powerful technique presented during previous research for estimation of the aerodynamic angles. This algorithm is based on Artificial Neural Network (ANN) and receive inputs from on-board sensors only. Whereas previous studies considered also the signals coming from the Flight Control System (FCS), this work presents the important simplification of not considering them in the input vector. This paper resumes the previous results obtained in simulated environment with former neural network-based estimators. Then, a comparison of the results obtained by the new estimator, applying the reduced input vector in different environments, is carried out. Moreover, it re-discusses accuracy by means of a new test case that consider simulated realistic faults and noise. Eventually, a first analysis around performance in operative environment is conducted using data obtained from flight test campaigns. Results show how accuracy is preserved both in realistic situation and critical circumstances.
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Abstract The increasing utilization of green resources is driving research toward the design and development of new and more efficient energy harvesting systems. As far as the wind energy sector is concerned, aerodynamic design and the... more
Abstract The increasing utilization of green resources is driving research toward the design and development of new and more efficient energy harvesting systems. As far as the wind energy sector is concerned, aerodynamic design and the definition of new airfoils, specifically devoted to the application of wind rotors, has given a huge impulse in this direction. However, the rigid blade concept is still an important constraint in energy extraction during off-design conditions or start-up phases. In order to cope with this problem, a new system has been developed and manufactured within the specifically funded VENTURAS® (VENTo: Una Risorsa Altamente Sfruttabile or ‘wind: a highly exploitable resource’) Project. The new system applies morphing to modify blade twisting along the blade span (modifying the pitch angle of some sections) while maintaining the same chord distribution as the design configuration. This innovation offers the possibility of partially adapting the blade configuration to the operating point, thus improving rotor efficiency. Design details mechanisms and deformable skin are discussed. Application to small/–micro wind turbines seems the most promising field for such equipment, but its extension to different fields (such as UAV morphing wings) could be of a certain interest as far as energy saving is concerned. Graphical abstract
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A simplex (not redundant) Air Data System (ADS) is adopted on air vehicles to measure a set of quantities from the external environment. Generally speaking, a simplex ADS is made up of external (i.e. installed externally on the A/C... more
A simplex (not redundant) Air Data System (ADS) is adopted on air vehicles to measure a set of quantities from the external environment. Generally speaking, a simplex ADS is made up of external (i.e. installed externally on the A/C fuselage) probes and vanes (LRUs) able to measure a full set of air data:
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Nota Scientifica e Tecnica n.° 18 del Dip. di Ing. Aeronautica e Spaziale, Politecnico di Torino
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Several architectures exist to measure aerodynamic angles based on physical sensors. As far as Unmanned Aerial Vehicle (UAV) is concerned, traditional systems hardly comply with reliability and redundancy requirements due to size and... more
Several architectures exist to measure aerodynamic angles based on physical sensors. As far as Unmanned Aerial Vehicle (UAV) is concerned, traditional systems hardly comply with reliability and redundancy requirements due to size and weight limitations. A patented virtual sensor, based on Neural Network (NN) techniques, named Smart-ADAHRS (Smart-Air Data, Attitude and Heading Reference System) has been investigated as a good estimator for aerodynamic angles in simulated environment. This paper focuses on flight testing procedures in operative environment and data processing for the Smart-ADAHRS validation with real data. As many factors interfere during the generation of the NN training set, an accurate choice and integration of the FTI (Flight Test Instrumentation) system components becomes crucial. A comprehensive description has been included about the FTI equipment and its influence on the neural network performance. Differences between numerical simulation and operative environment data are detailed as final aim of this work. Finally, feasible solutions are suggested to solve the typical gap between virtual and real scenario, both in terms of data analysis and neural network architecture.
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Using a nonlinear 15-state helicopter model in 6 DOF a MIMO neural full-authority controller, which acts as a rate-damping SCAS, has been designed. The control activity is handled by two adaptive multi-MISO neural entities, which identify... more
Using a nonlinear 15-state helicopter model in 6 DOF a MIMO neural full-authority controller, which acts as a rate-damping SCAS, has been designed. The control activity is handled by two adaptive multi-MISO neural entities, which identify the forward and the inverse nonlinear helicopter model and are connected according to the predictor-corrector scheme. Either the inverse and the forward model are trained on-line: this procedure makes the controller adaptive as well as robust as regards the uncertainties, the modelling errors and sudden modifications of the dynamics (due to demages of the command system). Robustness and reconfigurability are valued through the analysis of the time histories which represent the closed loop response. Different scenari are proposed, in which the controller is requested to operate far from nominal conditions, maintaining unchanged its performance. Results reveal poor stability features for the off-line controller even in nominal conditions, while show that the neural rate-damping is robust and fault tolerant, when is fully trained on-line.
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This paper propose a sensor calibration method based on fuzzy logic and neural learning rules. Data used for the calibration neuro-fuzzy system are obtained thro- ugh a series of simulations performed by integrating the equations of... more
This paper propose a sensor calibration method based on fuzzy logic and neural learning rules. Data used for the calibration neuro-fuzzy system are obtained thro- ugh a series of simulations performed by integrating the equations of motion of a fighter aircraft mathematical model in 6 degrees of freedom. In particular, attention is focused on the sideslip angle fi virtual sensor, and ma- neuvers are accomplished trying to stimulate as much as possible the flight variables involved. Performance of different fuzzy inference system have been evaluated, from models characterized by opera- tors which are typically fuzzy, to intermediate structures and hybrid adaptive neuro-fuzzy inference systems, with parametrized membership functions. It is shown how sensor calibration method based on the neuro-fuzzy technique, can benefit both from the ad- vantages claimed for neural networks and from the lin- guistic interpretability of fuzzy systems. Comparison among different system configurations highlights that results are promising and further im- provements could be obtained by augmenting the flight simulator with a Multi-Input, Multi-Output autipilot, to lengthen simulation time and stimulate flight variables to assume a wider range of combination within each ma- neuver.
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Nautilus S.p.A. and the Polytechnic of Turin, in cooperation with Galileo Avionica and Selex Communication, have developed a very versatile product, the ELETTRA Twin Flyers, which consists in a very innovative remotely-piloted airship... more
Nautilus S.p.A. and the Polytechnic of Turin, in cooperation with Galileo Avionica and Selex Communication, have developed a very versatile product, the ELETTRA Twin Flyers, which consists in a very innovative remotely-piloted airship equipped with high precision sensors and communication devices. This multipurpose platform is particularly suitable for border and maritime surveillance missions and for telecommunication, both in military and civil area. One of the most critical issue of the project is the structure design, which features a very innovative architecture. This paper presents a first arrangement of the primary structure, specifically defined as the best compromise between the constructive and functional constraints and the easy-to-manufacture/low-cost requirement.
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The development of an avionic system passes through several steps, which aim is to obtain a reliable equipment able to confirm the initial theoretical design. All these steps can be influenced by a lot of factors coming both from the... more
The development of an avionic system passes through several steps, which aim is to obtain a reliable equipment able to confirm the initial theoretical design. All these steps can be influenced by a lot of factors coming both from the sensors applied and from practical considerations. Thus, the identification of a valid Flight Test Instrumentation (FTI) has a key role in the design of innovative equipment. After being validated in simulated environment, an ANN (Artificial Neural Network)-based equipment started the operative environment test phase. This innovative patented virtual sensor named Smart-ADAHRS (Air Data, Attitude and Heading Reference System) is able to provide a complete suite of inertial and air data measurements using on-board sensors only plus a single external source of dynamic pressure. In contrast to the state-of-the-art ADS (Air Data System), Smart-ADAHRS is capable of estimate the aerodynamic angles by means of a non-linear regression that has been proven to meet, at least in simulated environment, the requirements given by typical aircraft control systems and safety operations. A successful training procedure has been conducted thanks to a partnership between academic and industrial entities. A prototype of Smart-ADAHRS has been placed on a ULM (Ultra-Light Machine) fully equipped by an ULMdedicated low cost, low intrusive and reliable FTI capable of synchronous acquisition of more than 40 parameters. After a comprehensive description of Mnemosine Mk-V and Smart-ADAHRS, an analysis of some results obtained by flight test is presented. Typical issues around the flight test phase, as well as future improvements are discussed in the final part of this work.
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This paper is focused on the failure detection and identification system that has been implemented on the on-board computer of the demonstrator of the Elettra-Twin-Flyers, an innovative remotely-controlled airship for monitoring,... more
This paper is focused on the failure detection and identification system that has been implemented on the on-board computer of the demonstrator of the Elettra-Twin-Flyers, an innovative remotely-controlled airship for monitoring, telecommunications, advertising and reconnaissance missions in maritime, border and inland environments. Emergency procedures are implemented to detect and identify the failure sources, warn the pilot of the failure occurrence and propose the appropriate action to take in order to reduce the associated risks.
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The purpose of this work is to set up a method for calculating the rolling moment coefficient generated on a generic wing under side-wind condition (sideslip angle /3 / 0). The wing can have any taper ratio, aspect ratio, swept angle A,... more
The purpose of this work is to set up a method for calculating the rolling moment coefficient generated on a generic wing under side-wind condition (sideslip angle /3 / 0). The wing can have any taper ratio, aspect ratio, swept angle A, dihedral angle 7, twist law and tip shape. During the first phase, we have used the Anderson method, suitably modified. This method offers an ap- proximate solution of the Prandtl integral-differential equation. Thus, we obtained the equations for the calcu- lation of the induced angle of attack trend on along the wing span and of the other parameters characteristic of the wing. In this way it is possible to determine the ac- tual lift distribution on the wing and therefore, from the different contribution given by the two semi-wings to the rolling moment, the derivative C\p = dCi/d/3 (Dihedral Effect). In order to compare the results, we have set up an- other calculation method based on determining on by using an iterative process, starting from a known arbi- trary distribution along the wing span, introduced at the beginning of the calculation loop. In this case, too, the method may be applied to wings of any shape; therefore, the geometric variables taken into account are the same. The results are presented in the shape of curves show- ing the rolling moment coefficient Ci as a function of /3 for different a, and in summary curves that show Ci^ as a function of the lift coefficient CLAnother type of representation included in the paper is that which com- bines, for a wing with certain characteristics (Aspect ra- tio, Wing taper ratio, Twist angle, etc.), all Ci^ for a predetermined range of A and 7.
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Recent developments have increased the need to investigate flight conditions at high angles of attack. Because these conditions have to be studied in wind tunnels, it is obvious that the blockage corrections must be assessed as accurately... more
Recent developments have increased the need to investigate flight conditions at high angles of attack. Because these conditions have to be studied in wind tunnels, it is obvious that the blockage corrections must be assessed as accurately as possible. With this in mind, we thought of comparing the results obtained from the same model in two different wind tunnels: the Aeritalia wind tunnel and the Emmen F + W 32.4 m2. The size of the Emmen makes the wall and blockage corrections negligible. Therefore, in practice, with any differences in the results coming from tests conducted in the two wind tunnels, it is only necessary to make corrections to those coming from the Aeritalia wind tunnel. Since the Emmen wind tunnel provided us with the exact results, our work consisted of establishing a method of correction whose validity could be verified. Initially we tried to use Maskell's formula introducing constant coefficients according to test conditions but the results were not satisfactory. We then developed Maskell's formula and decided to use the flat-plate pressure coefficient as a base pressure coefficient—which is needed in Maskell's formula—when no such coefficient can be deduced from the model. In all these cases, the induced drag coefficient was expressed as a function of the lift coefficient. Final corrections for lift and moment coefficients were very satisfactory, though the drag coefficient was slightly overcorrected.