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Multi-fidelity aerodynamic and acoustic design and analysis of a heavy-lift eVTOL
Get PDFThis work presents the processes used to support the preliminary design of a large eVTOL vehicle at the University of Glasgow in collaboration with GKN Aerospace. To support the GKN heavy-lift eVTOL design, known as Skybus, a range of tools of various fidelity levels were adopted and integrated. The paper first proposes and demonstrates a multi-fidelity approach for the vehicle propeller design. The propeller pitch-RPM maps were also proposed and were demonstrated to be an efficient tool for the intuitive performance visualisation, fast and accurate performance prediction, and graphic interpolation of operating conditions. High-fidelity CFD simulations of the complete Skybus vehicle in forward flight with two and four operating propellers were later carried out. The propeller operating conditions were determined through the performance maps. Near-field acoustics of the vehicle was extracted directly from the flow solutions. Detailed discussions of the flow details and the acoustic sources due to aerodynamic interference were presented. Far-field noise features were also computed using the FW-H equations and the CFD solutions. The noise levels of the heavy-lift vehicle were about 70-75 dB perceived on the ground. Considerable differences in the noise directivities of two- and four-rotor configurations were observed and discussed
Rotorcraft pitot-static systems calibration process to reduce error in all flight regimes and all rotorcraft configurations
No full textCalibration of pitot-static systems is a priority activity to be conducted at the earliest stage of the rotorcraft certification process in order to provide accurate airspeed and altitude flight test data and to develop production pitot-static air data systems with acceptable errors. Legacy air data system did not allow any correction for position error causing great effort for the system design. State of the art Air Data Units allow correction of the airspeed and altitude errors but only for one flight regime and one configuration. Those corrections might present residual errors that are not acceptable for all the other flight regimes and rotorcraft configurations requiring re-design and re-testing. The paper explains the pitot-static systems calibration method used to discern static and total pressure errors in level flight by field test with the use of a Weather Station. Then it describes the results obtained using the GPS quasi-static Head and Tail wind method. This allowed to obtain calibration data for all flight conditions and for all helicopter configurations using a limited number of flights and without changing the helicopter configuration. The paper explains the equivalence of the level flight results between the NTPS GPS method and the GPS quasi-static Head and Tail wind method and suggests a correction for the Orbis GPS quasi-static technique. A mathematical method is shown to infer calibration curves for pitot systems which guarantee an optimal performance in all the flight conditions and configurations, leading to the creation of lookup tables for the state of art Air Data Units. Finally, the paper shows a new methodology developed based on a multi-input regressor using a fully connected Neural Network which is capable of providing a correct value of airspeed and pressure altitude in real-time for every aircraft configuration and every flight regime. In this way, the aircraft manufacturer will be able to optimize development and production costs, while having a fully calibrated airspeed in flight. The study provides detail on how to collect flight test data points, pre-processing techniques and analysis. Moreover, the paper describes the findings in optimizing the algorithm structure and in implementing such algorithm in an embedded system
Application of advanced real-time RRT and incremental backstepping control for rotary-wing unmanned aircraft systems
No full textRRT is a well-known algorithm used for path and motion planning and exhibits good performance in generating a path quickly and efficiently. Many attempts were made to use these advantages for generating paths in real time; however, critical problems were observed when the algorithm was applied to aircraft. Unlike other mobile vehicles, aircraft require careful consideration of their limits, such as velocity, turn radius, and load factors. Only a few studies consider this; hence, in this study, we propose a method to consider important dynamic characteristics when planning paths in real time. The Advanced Real-Time RRT* algorithm suggested in this paper considers the limits by adopting the concept of “trajectory” as a new approach. A trajectory contains information on the location, velocity, and acceleration of an aircraft at each waypoint. If a trajectory is determined to be infeasible for flight, a different path is created and the path is converted to a new trajectory. In addition, the proposed algorithm was combined with a nonlinear controller called the incremental backstepping control, which is a robust controller having an excellent trajectory tracking performance. For validating the system, a series of simulations were conducted using a high-fidelity rotorcraft mathematical model as a system plant. Simulation results show that the proposed algorithm is sufficient for generating paths in a dynamic environment
Numerical investigation of wing-propeller aerodynamic interaction through a vortex particle-based aerodynamic solver
No full textThe present paper describes the results of a numerical investigation of a wing with an integrated propeller using the midfidelity aerodynamic solver DUST. The wing/propeller model considered in this work was widely investigated in literature both by experiments and high-fidelity CFD simulations and represents a classical benchmark case for the aerodynamic study of tiltrotors and electrical distributed propulsion aircraft configurations. The present numerical activity showed the capabilities of a mid-fidelity aerodynamic solver based on the vortex particle method, such as DUST, to capture the aerodynamic interactional effects of the installed propeller on the wing by a direct comparison of wing pressure coefficient distributions and propeller airloads with both experimental data and high-fidelity CFD simulations. Moreover, the instantaneous representation of the flow field between the propeller and the wing, as well as the pressure fluctuations on the wing surface, highlighted the capabilities to build a robust aerodynamic model of the wing/propeller in DUST aimed at studying the aeroacoustic aspects of such a complex configuration typical of Advanced Air Mobility aircraft configurations
Prototype carbon fibre propeller dedicated for hybrid power unmanned aerial vehicles with MTOW up to 300kg
No full textThe article presents concepts of a technology demonstrator of a hybrid – electric propulsion system (HEPS) for new generation of VTOL Unmanned Aerial Vehicles with a take-off weight of up to 300 kg. The motivation to undertake such works is the increasing use of heavy drones in relation to the currently produced electric drones with low payload. The main assumption of the demonstrator project was to use commercially available components. In preliminary phase of the project, a market analysis were conducted in terms of available: propellers/rotors, drive units, generators, electric motors, and energy management systems. First version of the system was designed as four-rotor system demonstrator. This article presents the design approach and test results in general. In the following chapters, authors introduce a six - rotor development version of the demonstrator. However the main focus is put on the propeller designed for the development version of the technology demonstrator. Assumptions of the new composite propeller design are shown. The paper briefly discusses aerodynamic calculations and obtained results, which were the basis for the propeller design and its manufacturing. Furthermore, the testing method of prototype propeller, test system for dynamic models and research results are presented. In conclusion authors presented encountered problems during the design and tests and obtained tests results. Moreover, further development directions are discussed
Unified monitoring and diagnostic system of a helicopter: the concept and the operating demonstrator
Get PDFThe presented paper analyzes the situation with condition and health monitoring of a helicopter, including engines, transmission and structures. Authors discusses the concept and the operating demonstrator of unified condition monitoring system of a helicopter that is weight and cost effective. The concept considers unification of methodical and technical solutions, including application of specific sensors for costs and weight reduction. To validate the solutions chosen and to demonstrate its workability the demonstrator of unified MD system was built using the operating helicopter Ka-26
Automatic flight control system for the small-scale compound helicopter
No full textThe paper presents results obtained in the project named “Automatic Control of a Compound Helicopter” led by Warsaw University of Technology and sponsored by the BOEING Company. In the paper, the system for automatic control of the ARCHER01 unmanned compound helicopter is described. For the purpose of controlling the helicopter with additional pusher rotor a Linear Quadratic Regulator (LQR) is integrated with a proportional controller. The model of the helicopter is developed and evaluated in FLIGHTLAB software. Developed control system is presented. Simulation results for four configurations of the system are shown and discussed
Preliminary guidelines for a requirements-based approach to certification by simulation for rotorcraft
No full textThe paper presents an introduction to the preliminary guidelines for rotorcraft certification by simulation developed by the partners of the Clean Sky 2 project Rotorcraft Certification by Simulation – RoCS . The guidelines are primarily aimed at the application of (rotorcraft) flight modelling and simulation in support of certification for compliance with standards CS-27 and CS-29, PART B (Flight) and other Flight-related aspects (e.g. CS-29, Appendix B, Airworthiness Criteria for Helicopter Instrument Flight). However, the guidelines are also applicable, in principle, to the certification of other types of rotorcraft, including tilt-rotors and e-VTOL configurations. A requirements-based approach is advocated and outlined, acknowledging the profound importance of assembling preliminary requirements, as complete as possible, before embarking on simulation development processes. The proposed approach presents examples of metrics for quantifying the fidelity that is ‘sufficient’ for application to relevant Applicable Certification Requirements (ACRs). The concept of ‘adaptive fidelity’ is introduced in this Guidance to emphasise that what might be sufficient is task-specific, and therefore ACR-specific. The paper introduces the structure of the proposed Rotorcraft Certification by Simulation process, together with the main concepts that guide applicants to the development of simulations that can be effectively employed to reduce the cost, timescales, complexity and risks that may be associated with certification performed solely though flight tests
Evaluation of acoustic snapshot arrays for rotorcraft source noise characterization
Get PDFHistorical development of acoustic hemispheres has required steady flight of a rotorcraft vehicle across a large linear array of microphones. The US Army, NASA, and Navy recently conducted a rotorcraft acoustics flight test in which multiple “snapshot” microphone arrays were used alongside a traditional linear microphone array. The snapshot arrays allow for a near instantaneous capture of rotorcraft acoustic emissions, without the need for steady flight. Development of the snapshot array is contained herein, and an evaluation of effectiveness of the array during adverse weather conditions. The snapshot arrays captured significant variation in acoustic emissions throughout a single run and between multiple runs of similar conditions. Hemispheres were created and modelled in land-use planning software and an investigation of A-weighted Sound Exposure Level (SEL [dBA]) was conducted. Sideline predictions of SEL compared well (within 0.1 dBA) between traditional and snapshot arrays, while centre line locations were less favourable with a difference of 1.6 dBA. Future refinement is required for the snapshot array technique, including advanced design of microphone placement and employing a semiempirical method to interpolate between measurement points, instead of the linear frequency weighting conventionally employed