Review on ducted fans for compound rotorcraft

This paper presents a survey of published works on ducted fans for aeronautical applications. Early and recent experiments on full- or model-scale ducted fans are reviewed. Theoretical studies, lower-order simulations and high-fidelity CFD simulations are also summarised. Test matrices of several experimental and numerical studies are compiled and discussed. The paper closes with a summary of challenges for future ducted fan research

Force-Canceling Mixer Algorithm for Vehicles with Fully-Articulated Radially Symmetric Thruster Arrays

A new type of fully-holonomic aerial vehicle is identified and developed that can optionally utilize automatic cancellation of excessive thruster forces to maintain precise control despite little or no throttle authority. After defining the physical attributes of the new vehicle, a flight control mixer algorithm is defined and presented. This mixer is an input/output abstraction that grants a flight control system (or pilot) full authority of the vehicle\u27s position and orientation by means of an input translation vector and input torque vector. The mixer is shown to be general with respect to the number of thrusters in the system provided that they are distributed in a radially symmetric array. As the mixer is designed to operate independently of the chosen flight control system, it is completely agnostic to the type of control methodology implemented. Validation of both the vehicle\u27s holonomic capabilities and efficacy of the flight control mixing algorithm are provided by a custom MATLAB-based rigid body simulation environment

Exploring the aerodynamic characteristics of a blown-annular wing for V/STOL aircraft

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University on 17/12/2010.This research programme explores, theoretically and experimentally, a new liftsystem for Vertical/Short Take-off and Landing (V/STOL) Aircraft. It is based upon an annular wing wrapped around a centrifugal flow generator, potentially creating a vehicle with no external moving parts, reduced vehicle aerodynamic losses compared to previous V/STOL technologies and substantially eliminating induced drag. It is shown that such a wing works best with a thick aerofoil section, and appears to offer greatest potential at a micro-aerial vehicle scale with regard to fundamental performance parameter “lift to weight ratio”. Certain efficiency losses are encountered mainly occurring from annular flow expansion and problems with achieving acceptable blower slot heights. Experimental methods are described along with results, and a comparison shows that the experimental values remain below theoretical values, partly due to flow asymmetry but possibly also other factors. Symmetrical blowing, as initially hypothesised, was found to be impracticable; this suggested use of pure upper surface blowing with Coanda effect. The modified approach was further explored and proved viable. The ultimate goal of this work was to develop an understanding and the facility to integrate the annular-wing into a vehicle to achieve controlled powered flight. To serve the purpose, issues encountered on current and past V/STOL aircraft are being investigated to set a path for further research/development and to validate/justify the design of future V/STOL aircraft. Also, presented is a feasibility study where different physical scales and propulsion systems are considered, and a turbofan has shown to achieve the best performance in terms of Range and Endurance. This privilege allows one to accurately study the V/STOL technologies around.Project was funded by the EPSRC CASE programme

Rotorcraft Blade Pitch Control Through Torque Modulation

Micro air vehicle (MAV) technology has broken with simple mimicry of manned aircraft in order to fulfill emerging roles which demand low-cost reliability in the hands of novice users, safe operation in confined spaces, contact and manipulation of the environment, or merging vertical flight and forward flight capabilities. These specialized needs have motivated a surge of new specialized aircraft, but the majority of these design variations remain constrained by the same fundamental technologies underpinning their thrust and control. This dissertation solves the problem of simultaneously governing MAV thrust, roll, and pitch using only a single rotor and single motor. Such an actuator enables new cheap, robust, and light weight aircraft by eliminating the need for the complex ancillary controls of a conventional helicopter swashplate or the distributed propeller array of a quadrotor. An analytic model explains how cyclic blade pitch variations in a special passively articulated rotor may be obtained by modulating the main drive motor torque in phase with the rotor rotation. Experiments with rotors from 10 cm to 100 cm in diameter confirm the predicted blade lag, pitch, and flap motions. We show the operating principle scales similarly as traditional helicopter rotor technologies, but is subject to additional new dynamics and technology considerations. Using this new rotor, experimental aircraft from 29 g to 870 g demonstrate conventional flight capabilities without requiring more than two motors for actuation. In addition, we emulate the unusual capabilities of a fully actuated MAV over six degrees of freedom using only the thrust vectoring qualities of two teetering rotors. Such independent control over forces and moments has been previously obtained by holonomic or omnidirection multirotors with at least six motors, but we now demonstrate similar abilities using only two. Expressive control from a single actuator enables new categories of MAV, illustrated by experiments with a single actuator aircraft with spatial control and a vertical takeoff and landing airplane whose flight authority is derived entirely from two rotors

Scientific Assessment for Urban Air Mobility (UAM)

Better connecting the international research community and the International Civil Aviation Organization (ICAO) enables effective assessments of novel aviation innovations. The International Forum for Aviation Research (IFAR) created a group on Urban Air Mobility (UAM) to explore the broad array of aspects relevant to the ICAO mandate. The assessment began with a study of the current industry landscape, including an overview of existing market studies, proposed aircraft designs and concepts, and potential paths of industry evolution. The Industry Assessment is summarized into key takeaways highlighting the need for international assessments on economic and societal factors associated with UAM, common understanding of the extent to which the nascent industry can leverage current infrastructure and regulatory structures, and harmonization of industrywide terminology. The subsequent Scientific Assessment, developed through cooperative efforts between international domain experts, captures 17 focus areas relevant to UAM. All focus areas present opportunities for further research. Key takeaways include: the need for further study of the impact of autonomous systems (AS) on the industry; infrastructure requirements (including vertiports and weather sensing) to support the industry; and data requirements (including domains such as cybersecurity, emissions, and safety) to ensure safe, scalable operations. Finally, a brief overview of the current standards landscape as relevant to the Scientific Assessment is presented, which displays the benefits of applying digital systems engineering techniques to map current research efforts to ongoing standards activities

Exploring the aerodynamic characteristics of a blown-annular wing for V/STOL aircraft

This research programme explores, theoretically and experimentally, a new liftsystem for Vertical/Short Take-off and Landing (V/STOL) Aircraft. It is based upon an annular wing wrapped around a centrifugal flow generator, potentially creating a vehicle with no external moving parts, reduced vehicle aerodynamic losses compared to previous V/STOL technologies and substantially eliminating induced drag. It is shown that such a wing works best with a thick aerofoil section, and appears to offer greatest potential at a micro-aerial vehicle scale with regard to fundamental performance parameter “lift to weight ratio”. Certain efficiency losses are encountered mainly occurring from annular flow expansion and problems with achieving acceptable blower slot heights. Experimental methods are described along with results, and a comparison shows that the experimental values remain below theoretical values, partly due to flow asymmetry but possibly also other factors. Symmetrical blowing, as initially hypothesised, was found to be impracticable; this suggested use of pure upper surface blowing with Coanda effect. The modified approach was further explored and proved viable. The ultimate goal of this work was to develop an understanding and the facility to integrate the annular-wing into a vehicle to achieve controlled powered flight. To serve the purpose, issues encountered on current and past V/STOL aircraft are being investigated to set a path for further research/development and to validate/justify the design of future V/STOL aircraft. Also, presented is a feasibility study where different physical scales and propulsion systems are considered, and a turbofan has shown to achieve the best performance in terms of Range and Endurance. This privilege allows one to accurately study the V/STOL technologies around.EThOS - Electronic Theses Online ServiceEPSRC CASE ProgrammeGBUnited Kingdo

A Summary of NASA Rotary Wing Research: Circa 20082018

The general public may not know that the first A in NASA stands for Aeronautics. If they do know, they will very likely be surprised that in addition to airplanes, the A includes research in helicopters, tiltrotors, and other vehicles adorned with rotors. There is, arguably, no subsonic air vehicle more difficult to accurately analyze than a vehicle with lift-producing rotors. No wonder that NASA has conducted rotary wing research since the days of the NACA and has partnered, since 1965, with the U.S. Army in order to overcome some of the most challenging obstacles to understanding the behavior of these vehicles. Since 2006, NASA rotary wing research has been performed under several different project names [Gorton et al., 2015]: Subsonic Rotary Wing (SRW) (20062012), Rotary Wing (RW) (20122014), and Revolutionary Vertical Lift Technology (RVLT) (2014present). In 2009, the SRW Project published a report that assessed the status of NASA rotorcraft research; in particular, the predictive capability of NASA rotorcraft tools was addressed for a number of technical disciplines. A brief history of NASA rotorcraft research through 2009 was also provided [Yamauchi and Young, 2009]. Gorton et al. [2015] describes the system studies during 20092011 that informed the SRW/RW/RVLT project investment prioritization and organization. The authors also provided the status of research in the RW Project in engines, drive systems, aeromechanics, and impact dynamics as related to structural dynamics of vertical lift vehicles. Since 2009, the focus of research has shifted from large civil VTOL transports, to environmentally clean aircraft, to electrified VTOL aircraft for the urban air mobility (UAM) market. The changing focus of rotorcraft research has been a reflection of the evolving strategic direction of the NASA Aeronautics Research Mission Directorate (ARMD). By 2014, the project had been renamed the Revolutionary Vertical Lift Technology Project. In response to the 2014 NASA Strategic Plan, ARMD developed six Strategic Thrusts. Strategic Thrust 3B was defined as the Ultra-Efficient Commercial VehiclesVertical Lift Aircraft. Hochstetler et al. [2017] uses Thrust 3B as an example for developing metrics usable by ARMD to measure the effectiveness of each of the Strategic Thrusts. The authors provide near-, mid-, and long-term outcomes for Thrust 3B with corresponding benefits and capabilities. The importance of VTOL research, especially with the rapidly expanding UAM market, eventually resulted in a new Strategic Thrust (to begin in 2020): Thrust 4Safe, Quiet, and Affordable Vertical Lift Air Vehicles. The underlying rotary wing analysis tools used by NASA are still applicable to traditional rotorcraft and have been expanded in capability to accommodate the growing number of VTOL configurations designed for UAM. The top-level goal of the RVLT Project remains unchanged since 2006: Develop and validate tools, technologies and concepts to overcome key barriers for vertical lift vehicles. In 2019, NASA rotary wing/VTOL research has never been more important for supporting new aircraft and advancements in technology. 2 A decade is a reasonable interval to pause and take stock of progress and accomplishments. In 10 years, digital technology has propelled progress in computational efficiency by orders of magnitude and expanded capabilities in measurement techniques. The purpose of this report is to provide a compilation of the NASA rotary wing research from ~2008 to ~2018. Brief summaries of publications from NASA, NASA-funded, and NASA-supported research are provided in 12 chapters: Acoustics, Aeromechanics, Computational Fluid Dynamics (External Flow), Experimental Methods, Flight Dynamics and Control, Drive Systems, Engines, Crashworthiness, Icing, Structures and Materials, Conceptual Design and System Analysis, and Mars Helicopter. We hope this report serves as a useful reference for future NASA vertical lift researchers

Survey on Aerial Multirotor Design: a Taxonomy Based on Input Allocation

This paper reviews the impact of multirotor aerial vehicles designs on their abilities in terms of tasks and system properties. We propose a general taxonomy to characterize and describe multirotor aerial vehicles and their design, which we apply exhaustively on the vast literature available. Thanks to the systematic characterization of the designs we exhibit groups of designs having the same abilities in terms of achievable tasks and system properties. In particular, we organize the literature review based on the number of atomic actuation units and we discuss global properties arising from their choice and spatial distribution in the designs. Finally, we provide a discussion on the common traits of the designs found in the literature and the main future open problems

Aerial Vehicles

This book contains 35 chapters written by experts in developing techniques for making aerial vehicles more intelligent, more reliable, more flexible in use, and safer in operation.It will also serve as an inspiration for further improvement of the design and application of aeral vehicles. The advanced techniques and research described here may also be applicable to other high-tech areas such as robotics, avionics, vetronics, and space