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The goal of this project was to integrate NASA’s Aircraft Noise Prediction Program (ANOPP2) into the RCAS2WOPWOP code suite. The implementation was made to be generalized for an arbitrary number of rotors, requiring changes to the previous ANOPP2 procedure to allow for multiple ANOPP2 runs in succession. Individual rotor noise predictions are combined into a total noise prediction. Another second goal was to use the updated RCAS2WOPWOP code suite to predict noise for a propeller-wing case, focusing specifically on the influence of interactional aerodynamics on the predicted noise. A case with an isolated propeller was run, then a propeller-wing case, and the results were compared to highlight where interactional aerodynamics had altered the noise produced. [ABSTRACT FROM AUTHOR]

The objective of this work is to assess the ability to predict noise generated by incident turbulence on aerodynamic forces. New batery technology has made multi rotor vehicle designs feasible that have disparate sound signatures compared to conventional rotorcrati (i.e., helicopters). A greater interest in rotorcrati broadband noise followed but is not complete. Leading edge noise created by incident turbulence is still required for a comprehensive understanding of rotorcraft noise. This research uses high-fidelity computational fluid dynamics (CFD) simulation to evaluate the turbulence near the leading edge of rotor blades. High fidelity grids are required to resolve the blade tip vortices and the surrounding turbulence in the blade wakes. From the CFD solutions, the turbulence kinetic energy is extracted and the turbulence intensity and turbulence integral length scale are calculated. The broadband noise is then calculated from the turbulence quantities using Amiet’s leading edge noise formula. [ABSTRACT FROM AUTHOR]

The rotorcraft is a complex dynamical system that demands specialist modelling skills, and a high level of understanding of the aeromechanics arising from the main rotor wake and aerodynamic couplings. One such example is the difficulty predicting off-axis responses, particularly in hover and low-speed flight, associated with induced velocity variation through the rotor disk resulting from the rotor wake distortions. Various approaches have been developed to deal with this phenomenon but usually demand prerequisites of high levels of expertise and profound aerodynamic knowledge. This paper presents a new and practical approach to capturing this wake distortion through an augmented rotor inflow model. The proposed model is coupled with a nonlinear simulation using the FLIGHTLAB environment, and comparisons are made between the simulation results and flight test data from the National Research Council of Canada's Advanced System Research Aircraft in hover and low speed. Results show good predictability of the proposed nonlinear model structure, demonstrated by its capability to closely match the time responses to multi-step control inputs from flight test. The results reported are part of ongoing research at Liverpool and Cranfield University into rotorcraft simulation fidelity. [ABSTRACT FROM AUTHOR]

The cost of Reynolds-Averaged Navier-Stokes simulations can be restrictive to implement in aeromechanics design and analysis of vertical lift configurations given the cost to resolve the flow on a mesh sufficient to provide accurate aerodynamic and structural loads. Dual-solver hybrid methods have been developed that resolve the configuration and the near field with the Reynolds-Averaged Navier-Stokes solvers, while the wake is resolved with vorticity-preserving methods that are more cost-effective. These dual-solver approaches can be integrated into an organisation's workflow to bridge the gap between lower-fidelity methods and the expensive Reynolds-Averaged Navier-Stokes when there are complex physics present. This paper provides an overview of different dual-solver hybrid methods, coupling approaches, and future efforts to expand their capabilities in the areas of novel configurations and operations in constrained and turbulent environments. [ABSTRACT FROM AUTHOR]

NASA is conducting investigations in Advanced Air Mobility (AAM) aircraft and operations. AAM missions are characterised by ranges below 300 nm, including rural and urban operations, passenger carrying as well as cargo delivery. Urban Air Mobility (UAM) is a subset of AAM and is the segment that is projected to have the most economic benefit and be the most difficult to develop. The NASA Revolutionary Vertical Lift Technology project is developing UAM VTOL aircraft designs that can be used to focus and guide research activities in support of aircraft development for emerging aviation markets. These NASA concept vehicles encompass relevant UAM features and technologies, including propulsion architectures, highly efficient yet quiet rotors, and aircraft aerodynamic performance and interactions. The configurations adopted are generic, intentionally different in appearance and design detail from prominent industry arrangements. Already these UAM concept aircraft have been used in numerous engineering investigations, including work on meeting safety requirements, achieving good handling qualities, and reducing noise below helicopter certification levels. Focusing on the concept vehicles, observations are made regarding the engineering of Advanced Air Mobility aircraft. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper develops a neural-network-based model reference adaptive control (MRAC) scheme for a rotorcraft in the presence of input saturation. Such a control scheme provides acceptable tracking performance for the rotorcraft in a wide range of flight conditions. Combined with hyperbolic tangent functions, the MRAC scheme is capable of tracking the reference signals without violating input constraints. A modified projection operator is utilized to prevent system from parameter drift due to the strong nonlinearity and uncertainty of the rotorcraft mathematical model. Stability of the proposed MRAC scheme is proved based on Lyapunov stability theory. The performance of the resulting controller is tested by conducting numerical simulations for an autonomous rotorcraft in various flight missions. • A robust modification of adaptive control is proposed to prevent nonlinear system from parameter drift. • A neural network based MRAC scheme is conducted in the presence of input saturation using hyperbolic tangent function. • The proposed MRAC scheme is applied to a nonlinear rotorcraft model. [ABSTRACT FROM AUTHOR]

Rotor Track and Balance (RTB) is an important part of regular helicopter maintenance. The ability to perform this service assessment during normal operations, rather than with a series of explicit RTB flights, would greatly reduce the time the vehicle is non-operational and the maintenance costs associated with these flights and adjustments. This paper presents a novel methodology for identifying the RTB-related flight regimes, using a minimal number of vibration signals and comparing these to repeatable and stable characteristic vibration profiles. The technique is stable, with an 81% success in correct identification of the flight regime, when applied to a whole flight with a number of unknown regime events. The method can be run in real time, making it an effective way of identifying periods of flight that are suitable for RTB measurements. A new technique for visually representing any real-time flight signal, such as vibration, is also presented. [ABSTRACT FROM AUTHOR]

Maintenance research activities in the area of HUMS began at UofSC in 1998 and the Center for Predictive Maintenance (CPM) at the UofSC College of Engineering and Computing was established in August 2007. Since its inception, the Center has strived to undertake new tasks and responsibilities to satisfy the needs of defense aviation. CPM at UofSC continues to lead the way in advancing this technology through rotorcraft drive train component testing, exploration of alternate sensor and signal processing technologies, as well as investigation of historical fleet data for rapid verification and integration of experimental results. The Center's core capabilities include testing, cost-benefit analysis, creating predictive analytics tools, digital transformation, and fundamental research. Years of experience and lessons learned have allowed CPM to create an effective methodology for predictive maintenance. [ABSTRACT FROM AUTHOR]

To address the problem of control surface redundancy for compound high-speed rotorcraft in multi-mode conversion process, a hybrid multi-objective control allocation strategy based on adaptive particle swarm optimization (PSO) algorithm is proposed. First, the control allocation problem is converted to a hybrid multi-objective optimization problem to solve the control redundancy, and a hybrid multi-objective optimization performance function is designed to satisfy the multiple requirements of flight mission. Second, a preference matrix is designed to determine the weight coefficients of the optimization performance function. The preference matrix can simplify the complexity of hybrid multi-objective optimization problem. Finally, an adaptive PSO algorithm is designed to solve the hybrid multi-objective control allocation dynamically. The simulation verifies the feasibility and effectiveness of the control allocation strategy, which eliminates the need of extra controllers in the mode conversion, reduces the difficulty of flight control system design and improves the system security. • A control allocation strategy is designed to solve control redundancy problem. • An adaptive PSO is designed to improve optimization. responding speed and accuracy. • A construction method of AMS is proposed to evaluate control allocation efficiency. • A multi-objective optimization function evaluates the multi-flight requirements. [ABSTRACT FROM AUTHOR]

Advanced design offices have traditionally applied conceptual design techniques based on semi-empirical methods in an attempt to develop an accurate prediction of aircraft designs at the end of the development process. Continuing advances in computer capability and rotorcraft analysis software present an opportunity to re-think conceptual design to include the greater use of physics-based analyses. A roadmap for developing this capability is outlined, taking into account techniques and ideas from Model-Based Systems Engineering, Design Thinking and Multidisciplinary Optimisation. Recent activities that demonstrate some of these desired capabilities are briefly described along with lessons learned. [ABSTRACT FROM AUTHOR]

The rotorcraft industry needs Virtual Engineering first to ensure decisions made early in the life-cycle, at the requirements capture and preliminary design phases for example, are reliably informed. Later, in design, development and qualification, Virtual Prototypes can become the centre of attention for critical reviews and, ultimately, certification itself. A significant challenge is to ensure that model fidelity is good enough, not only for supporting design decisions but also in establishing requirements based on sufficiently mature technologies. This international conference, Rotorcraft virtual engineering; supporting life-cycle engineering through design and development, test and certification and operations and co-sponsored by the RAeS/AHS/A3F/DGLR/AIDAA addressed these themes and this paper reviews and assesses the value of the various contributions. [ABSTRACT FROM AUTHOR]

Abstract A novel kinematic formation controller based on null-space theory is proposed to transport a cable-suspended payload with two rotorcraft UAVs considering collision avoidance, wind perturbations, and properly distribution of the load weight. An accurate 6-DoF nonlinear dynamic model of a helicopter and models for flexible cables and payload are included to test the proposal in a realistic scenario. System stability is demonstrated using Lyapunov theory and several simulation results show the good performance of the approach. Highlights • It is proposed a multi-objective control for cooperative payload transport with rotorcraft UAVs based on null-space theory. • The proposal allows to set on-line the load weight that each vehicle must transport. • Strategies to avoid conflicts of interest between objectives are proposed. • Accurate dynamic models for helicopters, flexible cables and payload are used to test the proposal in a realistic scenario. • System stability is proven using Lyapunov theory and several simulation results show the good performance of the approach. [ABSTRACT FROM AUTHOR]

The basic mechanism of the vertical bounce in tiltrotors in hovering flight is discussed. This rotorcraft-pilot coupling phenomenon arises when the pilot's biomechanics interact with the airframe elastic modes, in particular with the first symmetric wing bending mode. For this reason, it can be referred to as wing-pilot vertical bounce. This work proposes a simple mathematical model to predict the phenomenon. The XV-15 tiltrotor is used as benchmark. The closed-loop pilot-vehicle system shows that the direct effect of a change in collective input, through a vertical power lever, results in a nearly immediate change in thrust, which accelerates the aircraft, exciting the symmetric wing bending mode and, in turn, the pilot biomechanics, leading to a feedback path that could easily become unstable. Robust stability analyses are performed to take into account the large variability of some influential parameters. The tiltrotor shows a significant proneness to this rotorcraft-pilot coupling problem, which must be considered from the earliest phases of the design, especially when fly-by-wire architectures are considered. Means of prevention, considering both active and passive devices, are investigated and compared. [ABSTRACT FROM AUTHOR]

Over the past decade, NASA, under a succession of rotary-wing programs, has been moving towards coupling multiple discipline analyses to evaluate rotorcraft conceptual designs. Handling qualities is one of the component analyses to be included in such a future Multidisciplinary Analysis and Optimization framework for conceptual design of Vertical Take-Off and Landing (VTOL) aircraft. Similarly, the future vision for the capability of the Concept Design and Assessment Technology Area of the U.S Army Aviation Development Directorate also includes a handling qualities component. SIMPLI-FLYD is a tool jointly developed by NASA and the U.S. Army to perform modelling and analysis for the assessment of the handling qualities of rotorcraft conceptual designs. Illustrative scenarios of a tiltrotor in forward flight and a single-main rotor helicopter at hover are analysed using a combined process of SIMPLI-FLYD integrated with the conceptual design sizing tool NDARC. The effects of variations of input parameters such as horizontal tail and tail rotor geometry were evaluated in the form of margins to fixed- and rotary-wing handling qualities metrics and the computed vehicle empty weight. The handling qualities Design Margins are shown to vary across the flight envelope due to both changing flight dynamics and control characteristics and changing handling qualities specification requirements. The current SIMPLI-FLYD capability, lessons learned from its use and future developments are discussed. [ABSTRACT FROM AUTHOR]

As simulation has become an integral part of the overall life-cycle support of aircraft, the need for effective Virtual Engineering (VE) tools to support these activities has increased. FLIGHTLAB is a state-of-the-art, aircraft modelling and simulation software tool, that has been designed to address this need and is widely used in rotorcraft design, analysis, test and evaluation, and full-flight simulation applications. This VE tool supports the development and analysis of both fixed and rotary wing aircraft with an extensive library of modelling components which have been successfully used and validated in numerous, real-world applications. These components provide comprehensive modelling of aerodynamic, structural, control and propulsion disciplines. Analyses include performance, dynamic response, stability and control, airloads, and structural loads. Graphical User Interfaces and an interactive scripting language provide user-friendly operation. This paper describes the capabilities and validation activities that have been undertaken to support the development of the commercial VE toolset FLIGHTLAB over the last 20 years and discusses future rotorcraft challenges that could be addressed by enhancements to current generation VE tools. [ABSTRACT FROM PUBLISHER]

The purpose of this paper is to outline the structure of the DLR integrated rotorcraft design process. The complexity of rotorcraft design requires the development of the tools directly by the specialists of the respective institutes, where the tools are continuously refined and published to authorised users. The integration of the tools into a suitable software framework by means of distributed computation and the harmonisation of the tools among each other are presented. This framework delivers a high level of modularity making the layout and testing of the process very flexible. This design environment covers the conceptual and preliminary design phases. Not only conventional main/tail rotor configurations can be designed, but also some other configurations with more than one main rotor. The fundamental concept behind the layout of the tools is demonstrated, especially the use of scaling and optimisation loops in connection with the different levels of fidelity and the different phases of design. [ABSTRACT FROM PUBLISHER]

Virtual engineering tools are not currently employed extensively during the certification and commissioning of flight simulator motion systems. Subjective opinion is regarded as sufficient for most applications, as it provides verification that the motion platform does not cause false cueing. However, the results of this practice are systems that may be far from optimal for their specific purpose. This paper presents a new method for tuning motion systems objectively using a novel tuning process and tools which can be applied throughout the simulators life-cycle. The use of the tuning method is shown for a number of simulated test cases. [ABSTRACT FROM PUBLISHER]

Virtual Engineering (VE), also known as Model-Based Systems Engineering (MBSE), is necessary in both current operational engineering qualifications and to help reduce the costs of future vertical lift design and analysis. As computational power continues to provide increasing capability to the rotorcraft engineering community to perform simulations in both real time and off line, it is imperative that the community develop verification and validation protocols and processes to certify these methods so that they can be reliably used to help reduce engineering cost and schedule. Computational Fluid Dynamics (CFD) has become a major Computational Science and Engineering (CSE) tool in the fixed wing and vertical lift communities, but it has not been developed to the point where it is accepted as a replacement for testing in certification of new or existing systems or vehicles. Since the rise of modern CFD in the 1980s, the promise of CFD’s capabilities has been met or exceeded, but its role in certification arguably remains less prominent than projected. The ability to implement transformative technologies further drives the need for CFD in design. To meet CFD’s role in certification, several goals must be met to provide a true “numerical experiment” from which accuracies (error estimates), sensitivities, and consistent application results can be extracted. This paper discusses the progress and direction towards developing CFD strategies for certification. [ABSTRACT FROM PUBLISHER]

This work presents the capabilities of a novel L-shaped trailing-edge Gurney flap as a device for vibration reduction. The primary effect of this L-tab is represented by a modification of the reference aerofoil mean line shape through by two counter-rotating vortical structures created at the trailing edge. The comparison of the aerodynamic loads generated by the novel L-tab Gurney flap and a classical trailing-edge flap allows to estimate the ranges of reduced frequency where the L-tab is expected to perform better than a trailing edge flap and vice versa. Linear aerostructural models for a typical section representative of a helicopter blade equipped with a partial-span L-tab or a trailing-edge flap are built, and a higher harmonic control algorithm is applied. Performance are compared between the two devices to reduce separately the N/rev harmonics of the blade root rotating frame vertical force, flapping and feathering moments. The attainment of similar results with classical trailing-edge device is a further confirmation of the potential feasibility of this novel L-tab as an effective alternative means for vibration reduction on rotor blades. [ABSTRACT FROM PUBLISHER]

This design study applied parameterisation to rotor blade for improved performance. In the design, parametric equations were used to represent blade planform changes over the existing rotor blade model. Design variables included blade twist, sweep, dihedral and the radial control point. Updates to the blade structural properties with changes in the design variables allowed accurate evaluation of performance objectives and realistic structural constraints – blade stability, steady moments (flap bending, chord bending and torsion) and the high-g manoeuvre pitch link loads. Performance improvement was demonstrated with multiple parametric designs. Using a parametric design with advanced aerofoils, the predicted power reduction was 1.0% in hover, 10.0% at μ = 0.30 and 17.0% at μ = 0.40, relative to the baseline UH-60A rotor, but these were obtained with a 35% increase in the steady chord bending moment at μ = 0.30 and a 20% increase in the half peak-to-peak pitch link load during the UH-60A UTTAS manoeuvre. Low vibration was maintained for this design. More rigorous design efforts, such as chord tapering and/or structural redesign of the blade cross section, would enlarge the feasible design space and likely provide significant performance improvement. [ABSTRACT FROM PUBLISHER]

Helicopter downwash impact on ship airwake is addressed from a three-pronged approach: (1) Analysis of one-point statistics of autospectrum and two-point statistics of cross-spectrum and coherence from a Computational Fluid Dynamics database of flow velocities effected by helicopter downwash and shipboard airwake; (2) Development of a mathematical framework for extracting interpretive turbulence models in closed form from these autospectral statistics; and (3) Simulation through white-noise-driven filters for the extracted models. The framework begins with an earlier-exercised perturbation-type series expansion of the autocorrelation for all three velocity components, where the first term of the series has a form of the von Karman longitudinal or lateral correlation function. After transformation into equivalent series of autospectrum, the coefficients in the series are evaluated by satisfying theoretical constraints and fitting a curve on a set of selected autospectral data points generated from the database. The framework represents a sensible combination of series expansion, exploitation of a database, and theoretical constraints to provide a foothold on airwake-downwash phenomenon for engineering analysis. It ensures that the extracted model and the autospectral data points have the same time scale, mean square value, and asymptotic decay according to the Kolmogorov –5/3 Law. The framework's strengths and weaknesses, and its major advancement over the earlier series-expansion schemes are also addressed. Finally it is shown that downwash increases airwake energy (mean square value) by one order of magnitude, and almost all of this airwake-downwash energy is concentrated within the bandwidth (0.16 < f(Hz) < 1.6) that affects flight mechanics. [ABSTRACT FROM PUBLISHER]

This paper considers the problem of controlling the position and the orientation of a Coaxial-Rotor Unmanned Aerial Vehicle -CRUAV- despite unknown aerodynamic efforts. A hierarchical flight controller is designed, allowing the trajectory tracking and the stabilization of the vehicle. The designed controller is build through a hierarchical approach yielding two control loops, an inner one to control the attitude and an outer one to control the translational trajectory of the rotorcraft. An Extended State Observer -ESO- is used to estimate the state and the unknown aerodynamic disturbances. The analysis further extends to the design of a control law that takes the disturbance estimation procedure into account. Numerical simulations are carried out to demonstrate the efficiency of the proposed control strategy. [ABSTRACT FROM AUTHOR]

A control-theoretic model of the human pilot as an adaptive element in a flight control system is presented. An earlier version of the model has been discussed in the literature for use with single-axis linear, vehicle system descriptions, including an application to a two-axis task with a linear vehicle model. The current study expands the model's applicability to multiaxis, nonlinear systems. Three illustrative examples are presented: 1) a single-axis control problem with a transfer function description of the controlled-element dynamics; 2) a two-axis flight control problem involving a linear, highly coupled rotorcraft model including fundamental rotor degrees of freedom; and 3) a two-axis flight control problem involving a nonlinear, coupled aircraft model with dynamics patterned after the subscale NASA Langley Research Center's Generic Transport Model. The ability of the refined adaptive pilot model to accommodate significant and sudden variations in elements of the flight control system, as well as departed flight, is demonstrated through computer simulation. Particular attention is paid to ensuring that the adapted pilot model obeys the dictates of the crossover model of the human pilot, before and after adaptation. A brief human-in-the-loop tracking study via a desktop simulation of the single-axis task is included in the study. Potential applications of the adaptive pilot model include the evaluation of adaptive flight control structures and evaluation of aircraft loss-of-control events. [ABSTRACT FROM AUTHOR]

I was honoured to have been selected to deliver the 35th Nikolsky Honorary Lecture. My graduate education at Princeton University owed much to the influence of Alexander A. Nikolsky, the second faculty member appointed to the Princeton Aeronautical Engineering Department in 1943(1). I arrived in 1963, only months after he passed away, but the memory of his presence was still vivid in the minds of his students and colleagues, as well as the professors who introduced me to rotorcraft(2,3). Bob Lynn, Senior Vice President at Bell Helicopter Textron, one of Nikolsky's most illustrious students, recalled the impact of his teaching in the 12th Nikolsky Lecture in 1992(4).This paper briefly reviews the history and development of compounds, tiltrotors and hingeless rotors. Largely through a quirk of history, the compound has been neglected for over three decades. The mission performance potential of the compound is re-examined based on basic aerodynamic principles and by surveying recent NASA and Army mission design studies. A rational case can be made that the compound is the preferred rotorcraft for intermediate-speed missions and that it can be a worthy complement to the helicopter and tiltrotor. Past US Army Aeroflightdynamics Directorate (AFDD) aeromechanics research in aeroelastic stability and prediction methodology is reviewed in support of advancing both conventional and compound rotorcraft. This paper describes ten research and development (R&D) initiatives to revitalise advanced rotorcraft research for both conventional and future compound rotorcraft. [ABSTRACT FROM PUBLISHER]

The involuntary interaction of a pilot with an aircraft can be described as pilot-assisted oscillations. Such phenomena are usually only addressed late in the design process when they manifest themselves during ground/flight testing. Methods to be able to predict such phenomena as early as possible are therefore useful. This work describes a technique to predict the adverse aeroservoelastic rotorcraft-pilot couplings, specifically between a rotorcraft's roll motion and the resultant involuntary pilot lateral cyclic motion. By coupling linear vehicle aeroservoelastic models and experimentally identified pilot biodynamic models, pilot-assisted oscillations and no-pilot-assisted oscillation conditions have been numerically predicted for a soft-in-plane hingeless helicopter with a lightly damped regressive lead-lag mode that strongly interacts with the roll mode at a frequency within the biodynamic band of the pilots. These predictions have then been verified using real-time flight-simulation experiments. The absence of any similar adverse couplings experienced while using only rigid-body models in the flight simulator verified that the observed phenomena were indeed aeroelastic in nature. The excellent agreement between the numerical predictions and the observed experimental results indicates that the techniques developed in this paper can be used to highlight the proneness of new or existing designs to pilot-assisted oscillations. [ABSTRACT FROM AUTHOR]

This paper puts forward use of a Kalman filter algorithm to improve the accuracy and the stability of a four rotor aircraft control. The algorithm principle used covariance to estimate the system's optimal output. The flight and control theory of a four rotor aircraft was first analyzed; furthermore, it was found that the attitude angle had the biggest influence on its control. Then the Kalman filter model was established for processing attitude angle information from gyro and accelerometer sensors. Finally, the algorithm was compared with a complementary filter. The flight conditions were simulated in different flight environments; it is shown that the Kalman filter algorithm can improve the precision and real time in attitude angle acquisition. [ABSTRACT FROM AUTHOR]

Smart materials that are directly embedded in the rotor blade structure are an attractive concept for active blade control. A promising approach is the use of anisotropic piezoelectric strain actuators embedded in the rotor blade skin. Especially in Europe and the US this concept has been intensively investigated over the past years. A major drawback of all configurations studied so far is the high operation voltage of up to 2,000V of state of the art piezoelectric actuators. Within the Green Rotorcraft Project of the European Joint Technology Initiative Clean Sky, a new approach with a low voltage piezoelectric actuation system is investigated to demonstrate the feasibility of this technology. A first major step in this direction was completed by conducting a centrifugal test with a model rotor blade. The objective of the centrifugal test was to demonstrate the performance of the actuation system and the structural concept under centrifugal loads by showing that the expected twist deformation can be achieved at the nominal rotation speed and different actuation frequencies. It was demonstrated that the new actuation system is capable of operating under representative centrifugal loads. In comparison to state-of-the-art actuators (operation voltage 500V to +1500V) the new actuation system (operation voltage -20V to 120V) exhibits higher active twist performance per active area. [ABSTRACT FROM AUTHOR]

This paper describes research to develop handling qualities guidelines and criteria for a new category of aircraft: the personal aerial vehicle, which it is envisaged will demand no more skill to fly than that associated with driving a car today. Testing of concept personal aerial vehicle response types has been conducted with inexperienced "pilots" ranging from private pilot's license holders through to those with no prior flight experience. The objective was to identify, for varying levels of flying skill, the personal aerial vehicle response type requirements that will ensure safe and precise flight. Conventional rotorcraft response types such as "rate command", "attitude command/attitude hold" are unsuitable for likely personal aerial vehicle pilots. However, response types such as "translational rate command" and "acceleration command, speed hold" permit "flight-naive" pilots to perform demanding tasks repeatably and with the required precision. [ABSTRACT FROM AUTHOR]

This paper describes the development of a methodology to assess the handling qualities requirements for vertical takeoff and landing-capable personal aerial vehicles. It is anticipated that such a personal aerial vehicle would be flown by a "flight-naïve" pilot who has received much less training than is typically received even by today's general aviation private pilots. The methodology used to determine handling requirements for a personal aerial vehicle cannot therefore be based entirely on existing best practice; the use of highly experienced test pilots in a conventional handling assessment limits the degree to which results apply to the flight-naïve pilot. Using rotary-wing handling qualities methods as a start point, this paper describes both existing and newly developed alternative methods to subjectively and objectively analyze the performance and workload of flight-naïve pilots in typical personal aerial vehicle tasks. A highly reconfigurable generic flight dynamics simulation model that has been used to validate the methodology is also described. Results that highlight the efficacy of the various methods used are presented, and their suitability for use with flight-naïve pilots demonstrated. [ABSTRACT FROM AUTHOR]

The terminology 'rotorcraft-pilot coupling' denotes phenomena arising from interaction between pilot and rotorcraft. Among these, the present work deals with 'pilot-assisted oscillations' that derive from unintentional pilot actions on controls due to seat vibrations, and are strictly related to rotor-aeroelasticity/airframe-structural-dynamics coupling, with involvement of blade control actuator dynamics. Focusing the attention on helicopters, a comprehensive rotorcraft model is developed and applied, with main rotor unsteady aerodynamics described in state-space form. This makes it particularly suited for stability and frequency-response analysis, as well as control applications. Numerical investigations address two critical rotorcraft-pilot coupling aeroelastic issues: stability of vertical bouncing and gust response in hovering. Results from main rotor unsteady aerodynamics modelling are compared with widely-used quasi-steady aerodynamics predictions. These suggest that, for accurate RPC/PAO phenomena predictions, mathematical modelling should include the three-dimensional, unsteady-flow effects, and that the pilot-in-the-loop passive behaviour produces a beneficial effect on the load factor generated by gust encountering. [ABSTRACT FROM AUTHOR]

This paper demonstrates the application of an integrated rotorcraft multidisciplinary design and optimisation framework, deployed for the purpose of preliminary design and assessment of optimum regenerative powerplant configurations for rotorcraft applications. The proposed approach comprises a wide-range of individual modelling theories applicable to rotorcraft flight dynamics, gas turbine engine performance and weight estimation as well as a physics-based stirred reactor model, for the rapid estimation of various gas turbine gaseous emissions. A single-objective Particle Swarm Optimiser is coupled with the aforementioned rotorcraft design framework. The overall methodology is deployed for the design and optimisation of a reference multipurpose Twin-Engine- Light civil rotorcraft, modelled after the Bo 105 helicopter, which employs two Rolls-Royce Allison 250-C20B turboshaft engines. Through the implementation of a single-objective optimisation strategy, notionally based optimum engine design configurations are acquired in terms of engine weight, mission fuel burn and mission gaseous emissions inventory at constant technology level. The acquired optimum regenerative engine configurations are subsequently deployed for the design of conceptual rotorcraft regenerative engine configurations, targeting improved mission fuel economy, enhanced payload-range capability as well as overall environmental impact, while maintaining the respective rotorcraft airworthiness requirements. The proposed methodology essentially constitutes as an enabler for designing rotorcraft powerplants within realistic, threedimensional operations and towards realising their associated design trade-offs at mission level. [ABSTRACT FROM AUTHOR]

This paper presents a new robust control based on finite-time Lyapunov stability controller and proved with backstepping method for the position and the attitude of a small rotorcraft unmanned aerial vehicle subjected to bounded uncertainties and disturbances. The dynamical motion equations are obtained by the Newton–Euler formalism. The proposed controller combines the advantage of the backstepping approach with finite-time convergence techniques to generate a control laws to guarantee the faster convergence of the state variables to their desired values in short time and compensate for the bounded disturbances. A formal proof of the closed-loop stability and finite-time convergence of tracking errors is derived using the Lyapunov function technique. Simulation results are presented to corroborate the effectiveness and the robustness of the proposed control method. [ABSTRACT FROM AUTHOR]

The flapping rotary wing as a novel layout of micro air vehicle (MAV) remains being tested. Boring-hole design was applied to decrease the negative lift generated in wing's upstroke motion. The lift of traditional and boring-hole wingwere measured, contrasted and analyzed by experiments. Another series of experiments was conducted to explore the effect of the hinge material. It is indicated that a critical angle of attack ( α t ) exist to confirm the lift increment of the perforated wing, and the maximum increment can be up to 35% of the maximummean lift. [ABSTRACT FROM AUTHOR]

A parameter-based study of a novel self-cleaning barrier filter concept for rotorcraft engines is presented. Existing engine inlet barrier filters for rotorcraft achieve a high separation efficiency (up to 99% for a dust resembling a coarse test dust) at the expense of a pressure drop that increases over time. Other engine protection devices with invariant pressure loss signals cannot offer the same level of efficiency. Furthermore, inlet barrier filters are absent on rotorcraft with larger mass flow demands, due to larger filtration area required. This work proposes a solution that addresses each of these limitations, and establishes the parametric framework upon which such a design could be realised. The drum-shaped self-cleaning barrier filter is affixed to the engine inlet and spins about its longitudinal axis, such that each of its fibrous filter pleats can be cleaned once per cycle. An initial increase of pressure loss gives way to a period of sustained invariance. The key parameters are the internal particle capacity of the chosen filter medium and the speed of rotation. Other design parameters can be optimised to yield minimum pressure drop for given set of flow conditions. [ABSTRACT FROM AUTHOR]