1,720,966 research outputs found
Design and testing methodologies for UAVs under extreme environmental conditions
Get PDFL'abstract è presente nell'allegato / the abstract is in the attachmen
An Experimental Analysis on Propeller Performance in a Climate-controlled Facility
No full textDespite many commercial applications make extensive use of Unmanned Aircraft Systems (UAS), there is still lack of published data about their performance under unconventional weather conditions. In the last years, multirotors and fixed wing vehicles, commonly referred to as drones, have been studied in wind environments so that stability and controllability have been improved. However, other important weather variables have impact on UAS performance and they should be properly investigated for a deeper understanding of such vehicles. The primary objective of our study is the preliminary characterization of a propeller in a climate-controlled chamber. Mechanical and electrical data have been measured while testing the propeller at low pressure and cold temperatures. Test results point out that thrust and electric power are strongly affected by air density. A comparison between the experimental data and the results of the Blade Element Theory is carried out to assess the theory capability to estimate thrust in unconventional environments. The overlap between experimental data and theory computation is appropriate despite geometrical uncertainties and corroborate the need of a reliable aerodynamic database. Propeller performance data under unconventional atmospheres will be leveraged to improve UAS design, propulsion system modelling as well as provide guidelines to certify operations in extreme environments
Numerical modelling of sinusoidal brushless motor for aerospace actuator systems
Get PDFThe interest in electromechanical actuators (EMA) has been growing because of the development of next generation aircraft, based on the More Electric design. Electromechanical actuators have been gaining increased acceptance as they are becoming more and more safety-critical actuation devices: for prognostics and health management purposes of EMA, reliable and representative simulation models are needed in order to identify failures. This paper presents a multi domain model of EMA and it focuses on the numerical modelling of the Permanent Magnet Synchronous Motor (PMSM), also kwon as Sinusoidal Brushless Motor. The choice of the multi domain simulation is necessary to improve the simplifying hypotheses that are typically considered in numerical models and that are mostly used for prognostic analyses of electromechanical actuators
A new facility for UAV testing in climate-controlled environments
No full textEnvironmental conditions have a great influence on aircraft performance. Thrust reduction with altitude and temperature increase is a well known problem in the aviation industry. For commercial multirotor (UAVs) a systematic approach on performance varying environmental conditions is still an open research field. Many of the existing applications designed for UAVs (e.g. precision agriculture, delivery of instruments or medical supplies) have not been fully exploited by the market so far. This is due to the lack of existing knowledge about flight under variable weather conditions. A bias in the existing tests has been the non-reproducibility of the same climatic conditions. In this paper a dedicated test facility for a systematic study on UAV performance in a climate-controlled laboratory is presented: use cases as well as technical challenges related to the particular environment are discussed. Preliminary tests on thrust performance at different temperatures are reported to provide insight and highlight measurement complexities involved in harsh environmental conditions. Ultimately, this work will facilitate the development of UAV design and safety accounting for weather influence to improve flight stability and controllability
A methodology for multirotor aircraft power budget analysis
Get PDFThe primary purpose of this study is to analyse the performance of multirotor unmanned aircraft system platforms for passenger transport and compare them with an ordinary helicopter solution. This study aims to define a standard procedure for power budget analysis of unconventional vehicles recently proposed in the aerospace industry, providing guidelines on rotor sizing in terms of required power and the total number of rotors. The ultimate purpose of the proposed work is to describe a methodology for power estimation with regard to emerging electric vertical takeoff and landing (EVTOL) vehicles.
In the context of urban mobility, short-range passenger transport between critical hubs in cities is taken into account and innovative aircraft and traditional helicopters are compared according to a common mission profile. The power budget equations used in the helicopter literature are revisited to consider different multirotor configurations (up to 20 rotors) and evaluate the feasibility of innovative aerospace vehicle design.
The paper includes insights into the maximum number of rotors that ensure a significative, relative power reduction compared to helicopter platforms (the power-to-cruise over power-to-hover ratio appears to be improved). Based on this preliminary analysis, the results suggest the benefit of reducing the installed rotors to avoid excessive power loss in forward flight.
The proposed study provides guidelines for further design considerations and the future development of EVTOL multirotor aircraft.
This paper fulfils the identified need for a systematic approach on performance analysis for innovative vehicles involved in commercial applications
Experimental and numerical analysis of multicopter rotor aerodynamics
No full textUnmanned Aircraft Systems (UAS) are state of the art in aerospace industry and are
involved in many operations. While initially developed for military purposes, nowadays com-
mercial applications with small scale UAS, such as multicopters, are quite common. Accurate
engineering tools are required to asses the performance of these vehicles and optimize power
consumption. Thrust and power curves of rotors used by small scale UAS are essential to
design efficient vehicles. The lack of experimental data as well as accurate prediction models to
evaluate rotor coefficients over the UAS flight envelope are two major limitations in UAS science.
In addition, Reynolds numbers based on the chord for small scale rotors at normal rotation
rates are usually smaller than 100, 000 resulting in degraded performance. In the following
paper, experimental data on small scale multicopter propulsion systems are presented and
combined with a Computational Fluid Dynamics (CFD) model to describe the aerodynamics
of these vehicles in low Reynolds conditions. The commercial CFD software STAR-CCM+
will be used to perform CFD simulations which will include both a dynamic grid with a time
accurate analysis and a static grid steady state approach solving Navier-Stokes equations in an
adequate reference frame. Numerical simulation results for a conventional UAS propeller are
corroborated by the experimental data and suggest the proposed approach is able to properly
describe thrust and torque coefficients within the Reynolds numbers range characterizing the
UAS flight envelop
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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