bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flight data reduction methodology for performance evaluation and comparison of model-following adaptive control laws
Authors: Perhinschi M. G. , Napolitano M. R. 
Published: February 2016

AbstractEven small differences in atmospheric and/or flight conditions can potentially impact significantly the evaluation of the performance of the control laws and prevent a correct comparison, especially in the case of reduced size aircraft (autonomous or remotely piloted). Consistent deterministic control inputs can only be guaranteed through some form of computer-based on-board excitation system. In this paper, a methodology is proposed for flight data reduction with the purpose of accounting for non-homogeneous atmospheric conditions and inconsistent pilot inputs. The method is developed for the specific purpose of comparing model-following adaptive control laws. Performance evaluation parameters based on angular rate tracking errors are defined and used for the comparison. As a result of this approach, an additive correction is applied to the angular rate measurements to compensate for non-homogeneous turbulence effects. A multiplicative correction factor is applied to the angular rate tracking error to take into account non-identical pilot inputs. The procedure is validated with simulation and flight data obtained in the process of designing a set of fault tolerant control laws based on non-linear dynamic inversion with neural network augmentation for the reduced size WVU YF-22 aircraft model.
Dynamic inflow modelling for autorotating
rotors
Authors: Murakami Y. , Houston S.S. 
Published: February 2016

AbstractThe dynamic inflow model is a powerful tool for
predicting the induced velocity distribution over a
rotor disc. On account of its closed form and
simplicity, the model is especially practical for
studying flight mechanics or for designing control
systems for helicopters. Scant attention has,
however, been paid so far in utilising the dynamic
inflow model to analyse an autorotating rotor, which
is different from a powered rotor in the geometric
relation between the direction of the inflow and the
rotor disc. Autorotation is an abnormal condition
for helicopters, but for gyroplanes it is the normal
mode of operation. Therefore the theoretical
discussion on an autorotating rotor is of importance
not only to improve the understanding of present
gyroplanes, but also in the development of new
gyroplanes and to analyse the windmill-brake state
of helicopters. Dynamic inflow modelling is reviewed
from first principles, and this identifies a
modification to the mass flow parameter. A
qualitative assessment of this change indicates that
it is likely to have a negligible impact on the trim
state of rotorcraft in autorotation, but a
significant effect on the dynamic inflow modes in
certain flight conditions. This is confirmed by
numerical simulation, although considerable
differences only become apparent for steep descents
with low forward speed. It is concluded that while
modification of the mass flow parameter is perhaps
mathematically accurate, for practical purposes it
is required only in a limited area of the flight
envelope of autorotating rotorcraft.
Analysis of a reversible flight control system response to atmospheric turbulence
Authors: Raissi K. , Mani M. , Ghaffari H. , Nobari A. 
Published: February 2016

AbstractA mathematical model was developed for the reversible longitudinal control system of a regional commuter aircraft using the available geometry, mass property and kinematics. The model was incorporated into a general multi-body dynamics code and validated using existing manufacturer’s data as well as recorded data from several flights. Analysis of the flight data revealed light atmosphere turbulence level. To investigate the effect of higher turbulence intensity on the reversible flight control system, a sever turbulence level was generated using Von Karman model for the same flight level and velocity. The result was used as a random input to the dynamic model for computation of the frequency response of control column. It was shown that turbulence could act as a random input through the hinge moment during the flight and introduced a new mode in the lower end of power spectral density curve. The energy induced by this low frequency input resulted in large displacement of control column in simulation which surpassed the existing limits. Therefore it should be taken into account when dealing with handling quality as well as autopilot design.
A low-Reynolds-number one-equation model of turbulence
Authors: Elkhoury M. 
Published: February 2016

AbstractThis work proposes an improved form of Menter’s single-equation eddy viscosity transport model. The new transport equation follows from the transformation of the k-ε closure that includes the Yap-correction term, which is known to improve the (k-ε) model’s prediction in adverse pressure gradient flows. The damping functions of the (low-Reynolds-number) LRN model are constructed using the ingenious approach of Baldwin and Barth. Hence, the model provides the correct wall-limiting behaviour of turbulence. Furthermore, the destruction term is modified to better account for non-equilibrium anisotropy effects. An assessment of the present proposed model against experiments, as well as Menter and Spalart-Allmaras (SA) turbulence models is provided via several boundary layer computations. Good agreement with experimental data is indicated, which merits the model to be considered for further refinement.
Some features of steady separated flow from low speed to hypersonic
Authors: Gai S. L. 
Published: February 2016

Steady non-vortex shedding base flow behind a bluff body is considered. Such a flow is characterised by the flow separation at the trailing edge of the body with an emerging shear layer which reattaches on the axis with strong recompression and recirculating flow bounded by the base, the shear layer, and the axis.Steady wake flows behind a bluff body at low speeds have been studied for more than a century (for example, Kirchhoff; Riabouchinsky). Recently, research on steady bluff body wake flow at low speeds has been reviewed and reinterpreted by Roshko. Roshko has also commented on some basic aspects of steady supersonic base flow following on from Chapman and Korst analyses.In the present paper, we examine the steady base flow features both at low speeds and supersonic speeds in the light of Roshko’s model and expand on some further aspects of base flows at supersonic and hypersonic speeds, not covered by Roshko.
Converging towards synthetic environment interoperability
Authors: Lalonde B. 
Published: February 2016

AbstractThe evolution of simulators from proprietary hardware platforms to affordable commercial-off-the-shelf (COTS) platforms has gone on for the past 15 years and is now nearly complete. Nevertheless, past efforts to standardise simulator synthetic environments (SE) have only been partially successful and have engendered considerable aggravation for users in need of creating content that can be deployed to distributed full-mission simulators. This paper provides a detailed description of the SE generation pipeline and the reasoning that has modeled its evolution over the past few decades. The arrival of digital multi-spectral high-resolution satellite imagery and highly capable visual systems now requires orders of magnitude more storage and processing than equivalent databases just a few years ago. These factors are threatening the equilibrium of the SE pipeline and are becoming important elements affecting SE interoperability, portability and re-usability. Past design trade-offs and compromises, appropriate at the time, must now be re-examined along with all SE-related processes, starting from ingestion of raw source data right through to the processing by the simulator devices. Clearly, greater standardisation is needed within the simulation community and a comprehensive, open SE representation would palliate to the many challenges we now face. To this end, this paper provides a checklist of the characteristics for a future ‘ideal’ SE representation and evaluates four emerging synthetic environment initiatives against this extensive checklist.
Development of mechanical guidance actuators for a supersonic projectile
Authors: Massey K. C. , McMichael J. , Warnock T. , Hay F. 
Published: February 2016

AbstractIn this paper, the results of a series of experiments funded by DARPA to determine the feasibility of using small actuators to provide directional control for a supersonic projectile are presented. Controlling the flight of the projectile was accomplished by taking advantage of complex shock-boundary-layer interactions produced by mechanical devices. Experimental tests were conducted at GTRI to screen several control concepts and actuator locations. Further experiments were conducted on a scale projectile in a supersonic stream to investigate the rise time of the forces. Several different mechanical actuators were tested which served to provide guidance for future actuator designs. CFD results were also used to predict the results in flight as well as gain insights into the fluid mechanics involved. Flight tests of a Mach 4 round proved the viability of the guidance actuator.
Numerical simulation of rime ice accretions on an aerofoil using an Eulerian method
Authors: Cao Y. , Zhang Q. , Sheridan J. 
Published: February 2016

AbstractBased on two-phase flow theory, an Eulerian method to simulate rime ice accretions on an aerofoil has been developed. The SIMPLE (semi-implicit method for pressure linked equations) algorithm on a collocated grid is employed to solve the governing equations for the airflow. In order to simulate droplets impinging on an aerofoil, a permeable wall is proposed to solve the governing equations for supercooled droplets. The collection efficiency and impingement limits are obtained from the droplets’ flowfield. The process of ice accretion is simulated using the assumption that ice accumulates layer-by-layer and the ice shape is predicted with the assumption that ice grows in the direction normal to the aerofoil surface. The rime ice accretions on a NACA0012 aerofoil at 0° and 4° angles-of-attack have been investigated and there is agreement between the simulated results and previously published experimental data. The change of the pressure coefficient along the iced aerofoil is also analysed.
Indirect aircraft structural monitoring using artificial neural networks
Authors: Reed S. C. 
Published: February 2016

AbstractFrom necessity, military aircraft often operate in a highly fatigue damaging environment and history has shown in lost lives and aircraft the consequences of failure to appreciate fully the usage environment. The need for robust and cost effective structural usage monitoring of military aircraft to ensure operations are conducted within acceptable levels of risk is paramount. Furthermore, increased economic pressures require ever-inventive methods to be employed to maximise the lives of military fleets; structural usage monitoring will be a key asset in this drive. A highly cost effective indirect structural health and usage neural network (SHAUNN) monitoring system is proposed. A SHAUNN uses regression relationships determined by artificial neural networks to predict stresses, strains, loads, or fatigue damage from flight parameters. Within this paper the development of a SHAUNN monitoring system is described. Flight parametric data, captured during Operational Loads Measurement of the Royal Air Force Dominie TMk1 aircraft have been used to predict stresses at the key structural location in the wing, using mapping relationships determined by artificial neural networks. A framework for the development of the SHAUNN monitoring system is discussed and the basic architecture of the multilayer perceptron artificial neural network is described. It is concluded that this technology could provide the basis for an accurate, cost-effective structural usage monitoring system and further work to investigate the prediction of ground – based stresses in the wing is recommended.
Generic stability and control for aerospace flight vehicle conceptual design
Authors: Chudoba B. , Coleman G. , Smith H. , Cook M. V. 
Published: February 2016

AbstractThe recent period has been filled with exceptionally interesting developments and advances, resulting in high-performance conventional and non-conventional manned and unmanned aircraft. Although those vehicles seem to comply well with specific mission performance requirements, one is still confronted with an apparent weakness to reliably stabilise and control throughout the flight envelope. Since the provision of satisfactory stability and control characteristics invariably compromises flight performance, it becomes essential to identify and integrate performance-optimal stability and control design solutions early during the flight vehicle definition phase. In particular, the conceptual design of integrated control effectors for advanced aircraft is far from being trivial. Never before have we been presented with such tremendous wealth of specialised data and information suitable for detail design of controls. In contrast, never before has it been necessary to approach any one of the primary design disciplines still as entirely ad hoc and inconsistent as in the case of designing controls during the conceptual design phase. This need initiated the development of a configuration independent (generic) stability and control methodology capable of sizing primary control effectors of fixed wing subsonic to hypersonic designs of conventional and unconventional, symmetric and asymmetric configuration layouts. This paper summarises the methodology concept and demonstrates its versatility and validity by analyzing selected stability and control characteristics of the Northrop YB-49 flying wing.
The role of drag prediction in combat aircraft design and development
Authors: Newton J. B. 
Published: February 2016

AbstractThis paper gives an overview of combat aircraft drag prediction in the context of the overall design and development process.Following a brief summary of the author’s experience in this field, the importance of drag prediction during initial configuration design is discussed, emphasising the need for the drag aerodynamicist to develop a good understanding of the other aerodynamic disciplines involved, as well as an appreciation of the of the total design process encompassing structural design, propulsion integration and systems installation.A brief description is given of typical simplified prediction methods used in initial design, followed by an example of drag synthesis procedures based on wind-tunnel test and analysis, illustrating the need for good understanding of test techniques and the requirements of other aerodynamic disciplines.Some future challenges are identified, requiring continual involvement in research and methods development programmes.
Aircraft gust load estimation due to atmospheric turbulence under different flight conditions
Authors: Abdulwahab E. N. , Hongquan C. 
Published: February 2016

AbstractBased on power spectral technique and Lyapunov approach, methodology to determine the vertical gust load on aircraft encountering atmospheric turbulence under different flight conditions is presented in this paper. Modified longitudinal short period aircraft equations of motion to reflect gust inputs are solved. Family of five linear dynamics models of increasing gust excitation complexity are developed to describe the normal load factor throughout an aircraft due to vertical gust. These models (except Model 2) give a rapid estimation of normal load factor in case complete data are not readily available. Numerical model constructed for a Boeing 747 jet transport is solved to illustrate the results. These results show that Model 5 exhibits higher frequency contents when compared with other models under different flight conditions. The normal load factor of aircraft is estimated at different probabilities of not exceeding the corresponding load factor value based on statistical technique. The Models 1, 3, 4 and 5 predict the load factor with maximum 5% error when compared with Model 2 which considered all gust penetration effects. Finally, the results show a good agreement with the published work in load factor determination, at different probabilities of not exceeding this value when encountering a turbulent vertical gust.
Balloons, airships and kites – lighter than air: past, present and future
Authors: Folkes J. 
Published: February 2016

AbstractOne hundred years on from the advent of aeronautics at Queen Mary, University of London, developments in lighter than air technology have progressed at a somewhat slower pace than the technology for heavier than air. Innovations afforded by the ‘discovery’ of helium, the development of the modern day hot air balloon and the application of new materials have all contributed to today’s technical innovations. A review is given of the past history of lighter than air, a note is made of the current state of the art and a brief overview of future applications is discussed. The author’s personal experience in long distance gas balloon flights is mentioned.
Dimensionless analysis of the unstart boundary for 2D mixed hypersonic inlets
Authors: Chang J. , Yu D. , Bao W. , Qu L. 
Published: February 2016

AbstractInlet unstart boundary is one of the most important issues of the hypersonic inlet and is also the foundation of the protection control of a scramjet. To solve this problem, the 2D internal steady flow of a 2D mixed internal/external compression hypersonic inlet was numerically simulated at different freestream conditions and backpressures with a RANS (Reynolds-Averaged Navier-Stokes) solver using a RNG (Renormalisation Group) k-ε turbulence model, and two different inlet unstart phenomena were analysed. The dimensional analysis method was introduced to find the essence variables describing the inlet unstart boundary based on “numerical experimental” data in this paper. The dimensionless pressure ratios of the forebody and isolator were analysed respectively. The results show that the unstart boundary of the 2D mixed hypersonic inlet is determined by M0, α and Re0. Pressure ratio π increases with M0 increasing, and it increases firstly and decreases then with α increasing. Pressure ratio π increases with Re0 increasing. Re0 (Re0 < 2 × 107) has a major effect on π and Re0 (Re0 > 2×107) has little effect on π.
A timed method for the estimation of aeroplane take-off and landing distances
Authors: Gratton G. B. 
Published: February 2016

AbstractThis paper describes a method by which, without the use of external personnel or equipment, take-off and landing distances of an aeroplane may be estimated. An error analysis for the method, allowing determination of outcome accuracy, is also shown. The method is validated through use of flight test results from two certification programmes: one on a light aeroplane, and one on a microlight aeroplane.
Toward an intelligent, deterioration accommodating controller for aging turbofan engines
Authors: Turso J. A. , Litt J. S. 
Published: February 2016

AbstractA method for accommodating engine deterioration via a scheduled linear parameter varying quadratic Lyapunov function (LPVQLF)-based controller is presented. The LPVQLF design methodology provides a means for developing unconditionally stable, robust control of linear parameter varying (LPV) systems. The controller is scheduled on the engine deterioration index, a function of estimated parameters that relate to engine health, and is computed using a multilayer feedforward neural network. Acceptable thrust response and tight control of exhaust gas temperature (EGT) is accomplished by adjusting the performance weighting on these parameters for different levels of engine degradation. Nonlinear simulations demonstrate that the controller achieves specified performance objectives while being robust to engine deterioration as well as engine-to-engine variations.
Helicopter load alleviation using active control
Authors: Voskuijl M. , Walker D. J. , Manimala B. J. 
Published: February 2016

AbstractThis paper discusses how structural load objectives can be included in a rotorcraft flight control system design in an efficient and straightforward way using multivariable control techniques. Several research studies have indicated that pitch link loads for various rotorcraft types can reach high or even unacceptable values, both in steady state and maneuvering flight. This is especially the case for high-speed aggressive maneouvers. Pitch link loads at high-speed flight are therefore taken as a case study. A novel longitudinal control system is presented, designed to reduce helicopter pitch-link loads during high-speed longitudinal manoeuvres whilst providing a pitch attitude command attitude hold response type. The design is based on a high-order model of a helicopter representative of the UH-60 Black Hawk. New metrics are presented for the analysis of structural loads that can be used in combination with ADS-33 handling qualities requirements.
Performance simulation of a high-bypass turbofan with a 2D representation of the intake and fan components
Authors: Mund F. C. , Pilidis P. 
Published: February 2016

AbstractIn conventional gas turbine performance simulation, engine components are represented by characteristics where the 3D properties of the flow fields are averaged providing key flow properties at the component interfaces. Even though a very efficient method, the simplification of 3D flows to an averaged value is not always desirable. In particular for high-bypass turbofan aero-engines, the fan generates significant pressure variations from hub to tip. These profiles are affected by the flow profile resulting from the intake where boundary layers introduce radial distortion patterns.This study investigates a performance simulation method where the intake and fan component of a two-shaft high-bypass turbofan are represented in an axi-symmetric 2D fashion. The intake was modelled using a commercial computational fluid dynamics tool. The remaining engine components were modelled using an in-house conventional gas turbine simulation tool with a radial representation of the fan. The coordinated application of both tools required an iterative data exchange, which is described in detail.The inclusion of the radial representation of fan and intake showed twice the effect on thrust per inlet loss at cruise conditions. It was therefore worth considering despite the significant numerical effort.
Dither-based compensating strategy for radome boresight error and gimbal friction
Authors: Lin Y.-C. , Lin C.-L. , Shi W.-C. , Huang S.-W. 
Published: February 2016

AbstractThis paper proposes an effective missile radome error compensator by incorporating a nondestructive dither on the missile guidance loop to improve tracking accuracy. The compensation strategy predicts the radome slope error by introducing the dithering techniques along with band-pass filtering mechanism. A new condition is derived to ensure the guidance and control system stability while there is in the presence of the compensation error. As an application, the design methodology is extended to deal with the gimbal friction compensation problem. Simulation study confirms efficacy of our proposed approach.
Solid propellants burning enhancement using foil embedding method
Authors: Darabkhanid H. G. , Mehdizadeh N. S. 
Published: February 2016

AbstractThe method of metal embedding is widely employed in solid propellant motors with end-burning configuration, thereby significantly improving the burning rate of the propellants. In this study, the cylindrical foil embedding method is applied to double-base solid propellant, as a new method, and the effects of the type and thickness of the foil on the burning surface, as well as the burning rate, are experimentally investigated. It is shown that by using the foil embedding method, the burning characteristics of solid propellants can be improved. Results have been compared to some available data. To the best of the author’s knowledge there are no published data available on this method.