ERF European Rotorcraft Forum
Not a member yet
4279 research outputs found
Sort by
A multi-model and multi-objective approach to the design of helicopter flight control laws
Get PDFThis study addresses the design of a full-authority Attitude Command-Attitude Hold flight control system for the Bo-105 helicopter. The usual PID-based arrangement is replaced by a single 6th-order dynamic controller. The proposed design methodology combines multi-model and multi-objective approaches within the framework of structured H¥ software tools. Owing to the multi-model approach, only two sets of gains are sufficient to cover the entire speed range between hover and maximum velocity. In addition, ?-analysis tools can be used in conjunction with this approach to improve robustness against parametric uncertainties. Simultaneously, the multi-objective approach facilitates the design process and establishes connections between the tuning parameters and handling qualities. The performance of the resulting flight control system is investigated in this study, and evaluated against the attitude quickness, bandwidth and inter-axis coupling criteria, as defined by ADS-33. The resulting design achieves Level 1 performance in most cases. Besides, the merits and limitations of the proposed methodology are discussed in this paper
Analytical framework for the electrification of light rotorcraft for urban air mobility
No full textThe present paper develops an analytical methodology to design electrical powertrains and to study the performance of multirotor configurations. The model is based on the general momentum and blade element theories and it has been modified to take into account for multiple rotors and vertical flight conditions. An iterative procedure to design battery packs and compute the discharge time is provided. The original contribution of the article is represented by the application of the above-mentioned methodology to design and compare different eVTOL vehicles against a reference lightweight helicopter with specified design features. As a result, a quadrotor configuration is identified as the best solution to fulfill all the mission requirements and improve the performance of the helicopter with additional benefits
Numerical investigations on small-scale rotor configurations with validation using acoustic wind tunnel data
Get PDFThis paper addresses the acoustic and aerodynamic characteristics of small-scale rotor configurations, including the influence of the rotor-rotor interactions. For this purpose, a Rotor/Rotor/Pylon configuration is chosen for both the test and numerical simulations. The wind tunnel experiments on various rotor configuration were performed in DLR’s Acoustic Wind Tunnel Braunschweig (AWB). The experiments involve isolated rotors, and rotors in tandem and coaxial configuration in hover and forward flight. For numerical simulations an unsteady free wake 3-D panel method (UPM) is used to account for aerodynamic non-linear effects associated with the mutual interference among the Rotor/Rotor/Pylon configurations. The effect of the pylon is simulated using potential theory in form of a panelized body. Finally, the sound propagation into the far field is calculated with DLR’s FW-H code APSIM, using UPM blade surface pressure as input. The validation effort is supported by CFD TAU steady simulations on selected hover test cases. The experiments and numerical results indicate that the harmonic noise is the dominant source of the noise for the present rotor selection. Broadband noise is also observed in the experiment, but its contribution to the overall sound pressure is small. In the numerical simulations of both the coaxial and the tandem configuration, the interferences are particularly well visible and the noise directivity becomes more complex. There is no change in time averaged inflow by applying phase angles. In the coaxial condition, in hover, the phase delay between rotors doesn’t change the maximum noise level. In forward flight, the phase delay can influence the maximum level of the noise radiation. In both coaxial and tandem configuration, the position of the downstream rotor is key for the noise radiation and therefore avoiding the interaction with upstream wake can reduce the noise radiation
A parametric study on wing design variables for tandem wing configuration eVTOL aircraft
Get PDFThe tandem wing configuration is an unconventional aircraft configuration with numerous beneficial aerodynamic and stability characteristics. It has recently gained popularity as a conceivable configuration for Electric Vertical Take-off and Landing (eVTOL) aircraft. An important factor in determining the performance of a tandem wing aircraft is the wing design that directly influences the aerodynamic efficiency and flying qualities. This paper examines this effect of multiple wing design parameters on the aerodynamics and stability for tandem wing aircraft through a parametric and optimization design study. A vortex lattice method model integrated with a Python code is used to perform the design study and facilitate the calculations of multiple specified cases in a short time. The mass properties are calculated automatically for different wing geometries and then an optimizer is used to improve the aircraft layout of the baseline tandem wing. The parametric study reveals the sensitivity of wing design parameters on the aerodynamic efficiency and flight stability. The study also highlights the interplay between wing structural weight and aerodynamic efficiency. The following optimization study provides a framework for maximizing the range of a tandem wing aircraft and generates interesting design concepts for a tandem wing eVTOL aircraft. It is demonstrated that the optimization framework provides an increase of at least 30% in the range parameter of a tandem wing aircraft with the inclusion of flight stability constraints. The study considers the interaction between aerodynamics, structural weight, and aircraft handling qualities. Overall, the results provide beneficial design insights to fixed wing and eVTOL aircraft designers
Hybrid propulsion benefit in optimal power-off landings of light multi-role helicopters
Get PDFThe present paper focuses on the simulation of helicopter Power-Off maneuvers. These complex dynamic flight conditions are here formulated as trajectory optimization problems. Our numerical procedures can be conceptually used with any blackbox flight mechanics simulators, with minimal assumptions on the functionalities of such third-party software components, and can cater to a wide range of vehicle models of varying complexity. The Maneuver Optimal Control Problem is solved through a direct approach, by means of Direct Transcription techniques or Multiple Shooting methods depending on the model complexity and problem characteristics. By considering a model similar to the Kopter AW09 single-engine helicopter, three main applications are here addressed, i.e. the Autorotation Entry, the Flare, and the full Power-Off Landing. A specific effort of this work is focusing on the effects of an extra electrical power supply following the failure of the thermal engine to enhance safety in critical conditions (”1.5 engine” concept). The delicate trade-off between the additional weight of the electrical power kit and the energy booster available in case of an emergency is addressed for typical Power-Off Landing procedures in proximity of the ground
Experimental evaluation of flow distortion at NGCTR optimized air intake full scale model
Get PDFWithin the Clean Sky 2 Fast Rotorcraft platform, a Next Generation Civil Tilt-Rotor (NGCTR) Technology Demonstrator is being developed. Within the related TRINIDAT project the key driving aerodynamic choices of the engine air intake configuration are being investigated. A wind tunnel model has been successfully designed and manufactured for full-scale intake testing of modular intake configurations. The model is comprised of a nacelle, modular intake duct, rotatable spinner hub (rotor head) and wing part including deflectable aileron. In order to assess the flow quality at the Aerodynamic Interface Plane (AIP), a novel highly instrumented rotary rake has been designed. The model also includes a large amount of static pressure taps on wing and intake duct surfaces. The results of a wind tunnel test with the basic intake configuration in the DNW-LLF have been published in an earlier paper and yield a large database containing basic intake performance and sensitivities for the full flight envelope [14]. The present paper presents the results of an optimized intake configuration which has been successfully tested in a second TRINIDAT entry at the DNW-LLF. The adopted scaling methodology is explained. The 6 x 6 m2 test section allowed to test the full-scale model at ????=0.40 which is nearly cruise Mach number. The test program included variations in angle of attack, sideslip angle, aileron deflection and suction mass-flow rate. Post-processing of the test data yielded a large database including flow distortion parameters based on the total pressure field and the velocity field in the AIP. A comparison of key flow distortion parameters and static pressure distributions between optimized and basic intake showed that the optimized intake overall features significant improvement of the flow quality. For the aircraft mode an averaged reduction in ????60?????? of 74% has been realized. The development of unsteady pressures along the optimized intake duct including AIP has been characterized as well
Scout drone: a drone-helicopter collaboration to support HEMS missions
Get PDFThe paper presents the idea to exploit the collaboration between unmanned VTOL drones and helicopters to increase the situational awareness of helicopter employed in emergency, medical or search and rescue missions. The need for this collaboration is initially presented in the introduction. Then, after performing a review of the current state of the art that indicates that no system of this type is currently under development, the principles of operation of such a system are expressed together with a first brief description of possible concepts of operation. Finally, some preliminary thought on two of the most relevant elements of this system, the drone and the control station are presented
Experimental investigation of tensile properties of flax fibre-reinforced composites
Get PDFRenewable materials for aeronautical structures have the potential to contribute to an eco-efficient sustainable aviation. High-performance flax fibres, a promising substitution for glass fibres, are available on the market and currently comprehensively studied. With bio-resins, it is possible to increase the biocontent of composite structures over 50%. However, the mechanical properties of flax fibres are highly influenced by the chosen matrix and process parameters. This paper investigates the tensile properties of composites that are produced from two epoxy, seven bio-epoxy resins and one polyfurfuryl alcohol (PFA) resin in combination with five different flax fibres. It was found that the resin type strongly influences the flax fibre, with PFA inducing a brittle fracture behaviour and lowering the tensile strength for 40.5%, however increasing the stiffness for 17% compared to epoxy matrix. The bundle type of UD sheets and BD weaves are a key factor affecting strength and stiffness with hackled flax, and rovings having the best properties for UD and BD, respectively. Furthermore, the fibre volume content is a crucial parameter influencing mechanical properties, which strongly depends on resin type and production process. Good mechanical properties can be achieved, however with the finding that there is still a great potential for further improvements on the quality and hence the mechanical properties of flax fibre-reinforced composites