2D Closed-Form Solution for the Measurement of the Angle of Attack and Sideslip Angle

At the beginning of 2021, the measurement of the Angle of Attack and of the Angle of Sideslip is still mainly conducted with physical protruding probes. Although several alternative methods have been proposed in literature, the attention is generally focused on data-driven methods and little discussion is conducted on the mathematical problem. If the formulation that allows to associate the aerodynamic angles to other flight parameters has a closed-form solution is still an open question in the field. This paper provides a closed-form solution for a restricted problem where one of the two angle is known. Moreover, a linearized solution is provided. The result section gives evidence of the approach in simulated environment, showing the advantages of the nonlinear solution with respect to the linear one

Mobile Ground Station for the Unmanned Elettra-Twin-Flyer Airship

In recent years the development of unmanned platforms has exasperated the concept of design and planning in aeronautics: for unmanned flight, in fact, the aerial segment is no longer the central issue and concepts like mission planning, mission and on board sensor management are becoming more and more critical. The majority of these functionalities have been separated from the aerial segment and transferred to the Ground Station (GS) which is one of the key elements of the Unmanned Aerial System (UAS) together with the Communication Link and the Launch and Recovery Element. Safety requirements are thus transferred to some of the GS components, especially to those which perform critical functions. This has contributed to increase the CS complexity. Regardless of the UAV architecture and overall dimension, in fact, the pilot must be able to operate under the same condition of situation awareness of a correspondent manned aircraft. In this context, advanced vision systems and innovative human-machine interfaces must be designed, to enable the pilot to process the flight data while accomplishing the mission task. This paper presents a technological solutions adopted for the Elettra-Twin-Flyer, a lighter-than-air unmanned platform, developed for civil applications

Range Estimation Of A Novel Concept Electric Aircraft Based On Modified Breguet Equation

The electric vertical-take off and landing aircraft are able to perform vertical flights, equipped with an electric propulsion and energy storage system. This kind of aircraft has gained more importance during the last decades, in particular for urban aerial mobility. Its design is function of several project specifications, among them the range to cover a cruise flight mission profile. The present work is intended to show a modified Breguet equation for the range estimation applied to a novel electric aircraft concept. The advantage of this equation is to avoid the knowledge of parameters which are difficult to be found a-priori in a preliminary design phase. It is worth noticing that the modified Breguet estimated range needs further corrections to obtain a correct effective cruise range. For this reason, the estimated range is compared with the effective cruise range obtained with an energy balance equation. Results show that the estimated and theoretical range values are very close and comparable, hence the modified Breguet equation for electric aircraft is correct. In order to validate the present results, a comparison with several urban air mobility aircraft is performed

Sensitivity Analysis of a Certifiable Synthetic Sensor for Aerodynamic Angle Estimation

Nowadays, some alternative methods exist for the replacement of physical vanes (or probes) for aerodynamic angles (angle of attack and sideslip) with synthetic solutions. The results are promising and there is a growing interest for the industry in this particular solution. However, a lack of methods has been observed to estimate their performance and to compare them. The MIDAS project, funded in the Clean Sky 2 frame, will provide the aerospace community with an innovative modular digital air data system (ADS) based on synthetic sensors for aerodynamic angles. To meet the system requirement specifications given by the project leader, a method of uncertainty estimation must be implemented. This paper proposes a method of estimation of the overall uncertainty based on a consolidated metrological procedure. This method holds a certain degree of generality because it can be applied to different kinds of architecture of the synthetic sensor. In this paper, it has been applied to the preliminary design of the synthetic sensor of the MIDAS air data system and the results have been reported as example

ThrustPod: a novel solution for vertical take-off and landing systems

The work introduces a patented solution, named ThrustPod, to adapt the state-of-the-art fixed-wing aircraft for vertical take-off and landing operations. The proposed system is conceived to overcome the need of tilting surfaces or rotors and to overcome the aerodynamic low performance of multicopters. The ThrustPod is applicable to very light and general aviation aircraft and next generation air vehicles that aim to operate on urban and regional routes. The proposed solution is based on retractable thrusters to provide the required vertical thrust for the take-off and landing phases. The more suitable thrusters can be adopted, e.g. ducted fans or propellers. Another characteristic is the modularity as the ThrustPod can be scaled on different vehicle categories. In fact, the proposed solution can be used on different fixed-wing aircraft to provide vertical and take-off capabilities or to design novel airframes. The work proposes an integrated preliminary design process to optimise both the aircraft and the ThrustPod configuration to define fuselage length, thruster’s arrangement, power budget, energy management and performance evaluation of a potential aircraft for urban air mobility applications. The aim of the present work is to present a preliminary design application to evaluate advantages and drawback with respect to the most promising urban air mobility vehicles

Structure Design for the Elettra Twin Flyer Prototype

This paper presents different structural solutions compared under the same manoeuvrability and operativity requirements. The structures to be analysed are chosen from an initial set, selected among many solutions which fulfil the dimensional requirements. The airship, in fact, has to be big enough to accommodate a pre-determined volume of payload, has to accommodate the motors in pre-defined locations to allow a good manoeuvrability while limiting the structural deformations, must be able to house all the systems necessary for its operation and should be able to contain enough volume of helium as to sustain at least the 95 % of the structure weight. To minimize the costs of the structural analysis two configurations has been selected as the most representative of the many configurations proposed: the non-rigid double-hull (Figure 1) and the rigid soap-shape airship (Figure 2). Among the available aeronautical technologies, the aluminium truss and the carbon sandwich structures have been considered for the exoskeleton of the soap-shape airship. On the other hand, the structure of the double-hull is too complex to be realized by standard aluminium components, so only the carbon sandwich solution has been analysed

Nonvisible Satellite Estimation Algorithm for Improved UAV Navigation in Mountainous Regions

This paper presents a very simple and computationally efficient algorithm for the calculation of the occlusion points of a scene, observed from a given point of view. This algorithm is used to calculate, in any point of a control volume, the number of visible satellites and the Dilution Of Precision (DOP). Knowledge of these information is extremely important to reject measurements of non-visible satellites and for the reconstruction of a fictitious Digital Elevation Map (DEM), that envelops all the regions characterized by a number of visible satellites lower than a given threshold. This DEM evolves in time according to the platform motion and satellite dynamics. Because of this time dependency, the Digital Morphing Map (DMM) has been defined. When the DMM is available, it can be used by the path planning algorithm to optimise the platform trajectory in order to avoid regions where the number of visible satellites is dramatically reduced, the DOP value is very high and the risk to receive corrupted measurement is large. In this paper also presents the concept of a Safety Bubble Obstacle Avoidance (SBOA) system. This technique takes advantage from the numerical properties of the covariance matrix defined in the Kalman filtering process. A space and time safety bubble is defined according to the DOP value and is used to automatically determine a minimum fly distance from the surrounding obstacles

Sensitivity Analysis of a Neural Network based Avionic System by Simulated Fault and Noise Injection

The application of virtual sensor is widely discussed in literature as a cost effective solution compared to classical physical architectures. RAMS (Reliability, Availability, Maintainability and Safety) performance of the entire avionic system seem to be greatly improved using analytical redundancy. However, commercial applications are still uncommon. A complete analysis of the behavior of these models must be conducted before implementing them as an effective alternative for aircraft sensors. In this paper, a virtual sensor based on neural network called Smart-ADAHRS (Smart Air Data, Attitude and Heading Reference System) is analyzed through simulation. The model simulates realistic input signals of typical inertial and air data MEMS (Micro Electro-Mechanical Systems) sensors. A procedure to define the background noise model is applied and two different cases are shown. The first considers only the sensor noise whereas the latter uses the same procedure with the operative flight noise. Flight tests have been conducted to measure the disturbances on the inertial and air data sensors. Comparison of the Power Spectral Density function is carried out between operative and background noise. A model for GNSS (Global Navigation Satellite System) receiver, complete with constellation simulator and atmospheric delay evaluation, is also implemented. Eventually, a simple multi-sensor data fusion technique is modeled. Results show good robustness of the Smart-ADAHRS to the sensor faults and a marginal sensitivity to the temperature-related faults. Solution for this kind of degradation is indicated at the end of the paper. Influences of noise on input signals is also discussed