Browsing by Author "Lone, Mudassir M."
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Item Open Access Effects of nonlinear flight control system elements on aircraft(Cranfield University, 2011-09) Lone, Mudassir M.; Cooke, Alastair K.This report presents the experimental method and results from a series of desktop simulation tests designed to investigate manual control characteristics of young and relatively inexperienced civil pilots (24 years average age and 66 hours flight experience). Subjects were asked to perform tasks during which they had to establish longitudinal control through pitch attitude shown on a primary flight display. A linear aircraft model coupled with nonlinear flight control system was used to produce realistic vehicle dynamics. Increased encroachment into nonlinear command gearing was found to make aggressive subjects resort to high levels of crossover regression. The combined effects of rate-limiting and nonlinear command gearing was observed only for demanding tasks during which over-control was a typical feature. The classical precision and bimodal models were used for an in-depth study of pilot dynamics observed during compensatory tasks. Model parameters were found through the definition of a constrained nonlinear optimisation problem. A single feedforward equalisation element was used for tracking tasks. It was found that subjects developed similar low frequency feedforward equalisations, whilst large inter-subject variations exist for high frequency equalisations. The resulting models also provided some insight into the Neal-Smith and Bandwidth handling qualities criteria. Actuator rate-limiting could not be directly correlated to any of the pilot model parameters.Item Open Access Evaluating the Rationale for Folding Wing Tips Comparing the Exergy and Breguet Approaches(American Institute of Aeronautics and Astronautics, 2017-01) Hayes, D.; Lone, Mudassir M.; Whidborne, James F.The design and development processes for future aircraft aims to address the environmental and efficiency challenges needed to facilitate the engineering of concepts that are far more integrated and require a multidisciplinary approach. This study investigates the benefit of incorporating span extension wing tips onto future aircraft configurations as a method of providing improved aerodynamic efficiency, whilst allowing the extension to fold on the ground to meet airport gate size constraints. Although the actuated wing tips are not studied in detail, the focus of this study is to compare two different methods of analysis that can be used to identify the benefit and limitations of adding such devices. The two methods considered are a quasi-steady implicit energy analysis based on the Breguet Range Equation and an explicit energy analysis based on the first and second laws of thermodynamics known as Exergy Analysis. It has been found that both methods provide agreeable results and have individual merits. The Breguet Range Equation can provide quick results in early design, whilst the Exergy Analysis has been found to be far more extensive and allows the complete dynamic behaviour of the aircraft to be assessed through a single metric. Hence, allowing comparison of losses from multiple subsystems.Item Open Access Exergy methods for commercial aircraft integrating the laws of thermodynamics into all disciplines of aircraft design.(2018-07) Hayes, David; Lone, Mudassir M.; Whidborne, James F.; Coetzee, EtienneAs a consequence of practicalities, work share and difficulties in designing complex aerospace systems, there has been historical segregation of sub-systems in aircraft design. This methodology has proved successful for conventional swept wing aircraft configurations, as the sub-systems are only loosely integrated with one another. This results in discipline-specific performance, loss and optimization metrics being developed at sub-system level, which are not clearly linked to the overall system performance or objective. To meet social, economic and environmental needs, the next generation of aircraft require revolutionary concepts, which tend to be far more integrated, similar to military vehicles. Thus, performance, loss and optimization metrics need to be considered at system level, in order to account for the interactions between competing engineering disciplines. This thesis advocates an alternative systems engineering approach to developing future commercial aircraft, where the universal thermodynamic metrics energy and entropy are coupled to provide a holistic performance, loss and optimization metric for all aircraft disciplines. The method known as exergy analysis has been applied in the development of propulsion systems, but is sparsely applied in other aerospace disciplines. Applying the laws of thermodynamics to all aircraft sub-systems can seem obscure, especially in mature disciplines such as aerodynamics where energy may only be considered implicitly. Along with conventional configurations, this thesis studies a conceptual highly integrated High Aspect Ratio Wing (HARW) aircraft with morphing wing-tips, where the extended wingspan improves aerodynamic performance but as a consequence the wings have greater flexibility. Morphing is not a widely proliferated technology primarily due to the conservative approach to civil aircraft design, but original equipment manufacturers also struggle to demonstrate how the morphing effectiveness on a scale model can be scaled up to a full size aircraft. This thesis shows a clear contribution to knowledge in extending the current exergy methodology by investigating flight dynamic exergy analysis, and its application to morphing technologies for large commercial aircraft, evaluating the aerodynamic and aeroelastic contribution to an aircraft’s overall exergy use. To achieve this, each node of the Collar’s triangle [27] is evaluated using the exergy metric. In the absence of an open-source code, a non-linear structural code designated the Beam Reduction (BeaR ) model, has been written to study the structural dynamics of an airframe written in MSC Nastran format within a MATLAB® / Simulink® environment. To facilitate the study of flight dynamics, a bespoke Prandtl-Glauert aerodynamics model with an exergy post-processing script has been developed. Static and dynamic aeroelastic effects were studied through a coupling of the aforementioned structure and aerodynamic exergy based models. One of the main barriers to applying exergy analysis to commercial aircraft is gaining acceptance of a novel methodology in disciplines with entrenched practices. An example being in aerodynamic design, where the force balance approach is the established analysis method, yet exergy analysis requires the engineer to consider an alternative view of the aerodynamics as a system that uses and converts energy. To counter this, the thesis shows the capability and benefits of exergy analysis over conventional analysis techniques. This is emphasised in the comparison of using exergy based methods or the Breguet Range Equation for assessing the performance benefit of morphing wing extensions, where both methods provide the same top level conclusion, but exergy provides additional insight into the system the Breguet analysis can not.Item Open Access Fibre optic sensing for measuring rotor blade structural dynamics.(Cranfield University, 2019-04) Weber, Simone; Lone, Mudassir M.; Cooke, Alastair K.Researchers and practitioners spend much e ort in developing theoretical methods to design and predict the performance of helicopter rotor blades. These blades have evolved to become complex structures designed to operate in extreme conditions and over the exceptionally broad flight envelopes of helicopters. As a result, these vehicles are subject to strict maintenance regimes that increase the overall operational costs. The need to reduce such costs and improve aircraft performance together with the emergence of novel fibre optic-based sensor technologies form the context of the research presented in this thesis. Opportunities for blade health and usage monitoring created by sensor technologies such as fibre Bragg gratings (FBG) for measuring strain and direct fibre optic shape sensing (DFOSS) present today's industry with a critical question: Does the designer follow contemporary technological trends and adopt a preventative approach where he/she invests in such instrumentation systems or is a reactive approach more appropriate where he/she awaits to have sufficient evidence of operational need? A survey was carried out as part of this research to understand this dichotomy faced by rotorcraft engineers and systems architects. Adhering to the safety orientated culture within the aerospace community, the aim of this research work is the numerical and experimental exploration of challenges associated with the deployment of fibre optic instrumentation systems for future health and usage monitoring. This was achieved through three objectives: (1) development of a computational framework allowing the simulation of rotor blade dynamics at an appropriate fidelity, (2) exploration of blade health monitoring capabilities using fibre optic instrumentation systems and, (3) laboratory-based structural testing. Health and usage monitoring capabilities were explored theoretically through a parametric damage study using the computational framework. The experimental testing highlighted the need for a sensor placement methodology for distributing FBG-based strain sensors over the blade (both in terms of spanwise and chordwise locations) for accurately recovering mode shapes. This was followed by investigating the accuracy of the novel DFOSS system by deploying it on a bearingless main rotor blade along with other commercially available instrumentation systems. Test results were used to (1) perform multi-step indirect finite element modelling to increase the accuracy of the developed structural model and, (2) to explore the suitability of FBG and DFOSS measurements for damage detection. The main finding of this work is that future rotor health and usage monitoring systems based on fibre optic sensing technologies require the development of a hybrid FBG and DFOSS instrumentation system. Although numerous areas of further work have been identified, it is hoped that the adoption of such an instrumentation system will not only help reduce operational costs but also provide much needed operational data on helicopter blade dynamics to validate methods and improve designs.Item Open Access Handling qualities of high aspect ratio wing aircraft.(2018-07) Portapas, Vilius; Lone, Mudassir M.; Cooke, Alastair K.To reduce the environmental impact of the aviation industry aircraft designers invest much effort to develop new and improve existing technologies to create new aircraft configurations. New high aspect ratio wings allow to improve aerodynamic efficiency while reducing aircraft weight through the use of new lightweight materials. However, their slenderness tends to introduce significant interaction between flight dynamics and aeroelastics. These interactions need to be identified in order to allow future pilots to anticipate behaviour of those aircraft. The literature review revealed a gap in the knowledge of flying and handling qualities (HQs) of large transport highly flexible wing aircraft. Hence, this thesis presents a comparison between rigid and flexible aircraft configurations carried out by the means of the pilot-in-the-loop simulations of flight test manoeuvres. Firstly, the analysis of the extended equations of motion, which consider the structural flexibility, revealed significant flexibility impact on the lateral/directional dynamics of the aircraft. Then, the equations were integrated into the Simulation Framework for Flexible Aircraft (SFFA) that was developed by integrating the aeroservoelastic model CA² LM with the engineering flight simulator EFS500. The simulation campaign was performed using the SFFA for the HARTEN aircraft model, which exhibited an unusually aft neutra point position. The results of the simulation campaign revealed minor differences in the longitudinal dynamics between the rigid and flexible aircraft. However, the lateral/directional dynamics showed significant differences, especially in the change of the Dutch roll shape from horizontal to vertical and the spiral mode from unstable to neutrally stable. It also highlighted the ‘wing rocking’ phenomenon and the ‘wing ratcheting’ significantly decreased roll performance. Finally, a new slalom task proved its applicability to efficiently assess HQs and revealed a degradation of HQs for the flexible aircraft configuration. The SFFA was also assessed and limiting hardware issues were indicated to support the comparison of aircraft HQs. For the future it is recommended to identify a set of dynamic parameters that would allow to highlight deficiencies of flexible aircraft and to improve the SFFA allowing pilots to fully concentrate on the task.Item Open Access High aspect ratio wings on commercial aircraft: a numerical and experimental approach(Cranfield University, 2019-12-20) Pontillo, Alessandro; Lone, Mudassir M.; Whidborne, James F.The aim of this work is to assess the aeroelastic response to gust of a flexible high aspect ratio wing (HARW) single-aisle commercial aircraft and to design a viable open-loop Gust Load Alleviation (GLA) system. Aeroservoelastic assessment was carried out by adopting the low-fidelity Cranfield Accelerated Aircraft Load Model (CA2LM ) aeroelastic framework. Wind tunnel testing of two flexible wing models was carried out to assess the limitations of low-fidelity numerical frameworks in modelling highly flexible structures. The numerical work firstly focused on upgrading the CA2LM framework by including the non-linear aerodynamic effects of spoiler deflection into the low-fidelity model. The novel method was able to locally change the wing lift distribution evaluated with strip theory by combining ESDU 14004 experimental data with the numerical estimation. Finally, the aeroelastic response of the High Aspect Ratio Technology ENabler (HARTEN) concept aircraft to gust input was carried out for a single flight condition (h=26000 ft and v=200 m/s) and for two different structural configurations: rigid wing and flexible wing structure. Tuned discrete gust analysis, as specified in CS-25, was adopted in this analysis. Results showed that tuned gust is able to excite flexible wing dynamics along with the rigid-body dynamics, having a detrimental impact on aircraft performance. Finally, an open-loop GLA system was designed to alleviate Wing Root Bending Moment (WRBM) increment due to gust load. The GLA deflected spoilers and ailerons for a fixed amount of time (hold time) once a specific vertical load factor was crossed. An optimization algorithm was used to optimize parameters such as control surfaces deflection, hold time and load factor threshold. Several configurations of the GLA were evaluated. The optimal GLA configuration was able to alleviate WRBM from a minimum of 2.4% to a maximum of 8.1% with respect to the non-alleviated scenario. Two wind tunnel models were built with the common spar and skin configuration, while a novel approach for the skin manufacturing was introduced: the skin was 3D printed with PolyJet technology which allowed to provide a continuous aerodynamic shape removing the typical gaps necessary for flexible models to allow wing bending, limiting the impact of the skin to less than 12.5% of the overall model stiffness. The first model was tested in the Cranfield Weybridge wind tunnel at 27 m/s (Re = 3.5e5) and α = 6 ◦ . The model span was 0.840 m and Aspect Ratio AR = 12. The model was successfully tested to prove the ability of the skin to retain the aerodynamic shape and sustain the load under large deformation, reaching a max wingtip displacement of 32% of the model span. The second model was tested in the Cranfield 8x6 ft wind tunnel in the speed range of 20 m/s to 40 m/s (3.1e5 < Re < 6.2e5) at −2 ◦ < α < 8 ◦ . The model span was 1.5 m and AR = 18.8. The main result showed that in the most severe aerodynamic load scenario (v = 40 m/s and α = 8 ◦ ), the spanwise force coefficient accounted for 10% of the wing overall CL and was 2.5 times higher than CD . The overall damping was also estimated for different velocities at α = 6 ◦ , reaching a maximum of 26.9% at 35 m/s and a minimum of 17.8% at 20 m/s, with aerodynamic damping accounting for a minimum of 61% to a maximum of 74% of the overall damping. Maximum displacement of the wing tip was 13.7% of the model span (0.21 m). In both tests a low-cost acquisition system built with off-the-shelf components was used. The system was based on Raspberry Pi board able to acquire accelerations and rotations from four MPU6050 IMU boards, with the main benefit being the small size of the sensors, which were able to fit within tiny volumes typical of HARW wind tunnel models.Item Open Access In-flight folding wingtip system: inspiration from the XB-70 Valkyrie(AIAA, 2019-01-06) Dussart, Gaétan X.; Lone, Mudassir M.; O’Rourke, Ciaran; Wilson, ThomasWingtip folding can be used to extend aircraft wingspan, allowing designers to take advantage of reduced induced drag whilst respecting ground operational limitations. Such devices can also be used in-flight for a variety of other benefits including load alleviation and flight control. The majority of in-flight folding research takes inspiration in past developments made on the XB-70 Valkyrie, which used the folding devices for stability and lift performance benefits. In this paper, the authors investigate the capabilities of the folding wingtip system and potential scaling to large civil aircraft. Manufacturing details are used to size the actuators whilst the aerodynamic loading acting on the wingtip hinges is found from flight test results. Dimensions and aerodynamic loading at cruise of a set of conventional civil aircraft wing are used to evaluate the scaling potential of the system for controlled in-flight folding. An estimate of the weight penalty due to the folding device is also given and compared to structural weight savings on the XB-70. The results presented herein help in the evaluation of conventional actuator limits for in-flight folding using arguably the most inspiring military example of wingtip folding so far.Item Open Access Modelling framework for flight dynamics of flexible aircraft(Vilnius Gediminas Technical University Press, 2016-12-20) Portapas, Vilius; Cooke, Alastair K.; Lone, Mudassir M.The flight dynamics and handling qualities of any flexible aircraft can be analysed within the Cranfield Aircraft Accelerated Loads Model (CA2LM) framework. The modelling techniques and methods used to develop the framework are presented. The aerodynamic surfaces were modelled using the Modified Strip Theory (MST) and a state-space representation to model unsteady aerodynamics. With a modal approach, the structural flexibility and each mode’s influence on the structure deflections are analysed. To supplement the general overview of the framework equations of motion, models of atmosphere, gravity, fuselage and engines are introduced. The AX-1 general transport aircraft model is analysed as an example of the CA2LM framework capabilities. The results showed that, according to the Gibson Dropback criterion, the aircraft with no control system lacks the stability and its longitudinal handling qualities are unsatisfactory. Finally, the steps for future developments of the CA2LM framework are listed within conclusions.Item Open Access Multi-objective optimal longitudinal flight control system design for a large flexible transport aircraft.(2018-05) Song, Sipeng; Lone, Mudassir M.; Whidborne, James F.This thesis presents a multi-objective evolutionary algorithm design of a longitudinal optimal controller for a large exible transport aircraft. The algorithm uses a mixed optimization approach based on a combination of Linear Quadratic Regulator(LQR) control and a Multi-Objective Genetic Algorithm (MOGA) to search over a set of possible weighting function structures and parameter values in order to satisfy a number of conflicting design criteria. The proposed approach offers a number of potential optimal solutions lying on or near the Pareto optimal front of competing objectives. The approach is explained in this thesis and some results are presented.Item Open Access Neural network based dynamic model and gust identification system for the Jetstream G-NFLA(Sage, 2016-05-18) Antonakis, Aristeidis; Lone, Mudassir M.; Cooke, Alastair K.Artificial neural networks are an established technique for constructing non-linear models of multi-input-multi-output systems based on sets of observations. In terms of aerospace vehicle modelling, however, these are currently restricted to either unmanned applications or simulations, despite the fact that large amounts of flight data are typically recorded and kept for reasons of safety and maintenance. In this paper, a methodology for constructing practical models of aerospace vehicles based on available flight data recordings from the vehicles’ operational use is proposed and applied on the Jetstream G-NFLA aircraft. This includes a data analysis procedure to assess the suitability of the available flight databases and a neural network based approach for modelling. In this context, a database of recorded landings of the Jetstream G-NFLA, normally kept as part of a routine maintenance procedure, is used to form training datasets for two separate applications. A neural network based longitudinal dynamic model and gust identification system are constructed and tested against real flight data. Results indicate that in both cases, the resulting models’ predictions achieve a level of accuracy that allows them to be used as a basis for practical real-world applications.Item Open Access Non-elliptic lift distribution wings to decrease vertical tailplane size in commercial aircraft(AIAA, 2019-01-07) Carrizales Rodriguez, Martin Alejandro; Bragado Aldana, Estela; Lone, Mudassir M.Aircraft performance can be assessed and improved by considering the key variables linked toweight and aerodynamics in the Breguet range equation. In this paper, the authors present a methodfor wing design that allows a reduction in induced drag and minimization of the weight associated withthe aircraft’s vertical tailplane, whilst ensuring desirable lateral-directional flight dynamics. The usecase is a general aviation aircraft for which the wing has been modified using Prandtl’s 1933 approachwhere the span constraint is removed to yield a non-elliptic lift distribution. It is shown that such a liftdistribution also contributes to the aircraft’s lateral-directional stability and as a result, the size andweight of the vertical tail can be reduced. This study was carried out using an analytical frameworkthat combines early design tools such as XFOIL and AVL deemed to be adequate for subsonic flight.Both cruise and approach configurations are considered. Wing twist distribution and span extensionhave been calculated using lifting line theory. The study demonstrates the design trade-off neededbetween flight dynamic modes, such as the Dutch roll mode, and vertical tailplane size when theaircraft is equipped with a wing designed to generate a non-elliptic lift distribution. It is shown thatthis approach allows a 14% improvement in the lift to drag ratio with 44.34% reduction in V-tailweight. These yield a total of 17% improvement in aircraft range. As for the approach phase it shareall the characteristics observed in cruise with the difference that Dutch roll mode is stable for almostall the smaller size of V-tail. Further work requires to focus on the placement of ailerons to removeadverse yaw tendencies.Item Open Access On scaling and system identification of flexible aircraft dynamics.(Cranfield University, 2019-10) Yusuf, Sezsy Yuniorrita; Lone, Mudassir M.; Cooke, Alastair K.The use of subscale models has been common practice in the industry and has helped engineers gain more confidence in their design processes. However, each subscale model is developed for a specifc test, and consequently, different types of models are needed for observing aerodynamic, structural and aeroelastic characteristics of a full-scale aircraft. Yet, traditional aircraft design methods face serious challenges when a novel aircraft de- sign emerges and a proof-of-concept is needed for investigating this multi-disciplinary problem. An example of such a problem is the development of aircraft configurations with high aspect ratio wings for which the disciplines of aeroelastic and flight mechanics are strongly interconnected. Moreover, if the prediction of dynamic behaviour is of interest, a method that utilises system identification for analysing experimental data is of importance. Therefore, this thesis aims to develop a methodology to investigate the complex flight dynamic behaviour of flexible aircraft by combining techniques for developing subscale models and methods with the field of system identification. This aim is achieved through three objectives: 1) assessment of system identification methods for subscale flexible aircraft, 2) theoretical development of subscale modelling in terms of scaling laws and aeroelastic simulation framework and, 3) wind tunnel testing of the subscale model. Aspects of System Identification have been explored through use-cases where experimental data for a rigid aircraft both in full-scale and subscale configuration is used. The results highlight the fact that in testing a subscale model, dynamics are more prone to exhibit non-linear behaviour when compared to the full-scale model. It followed by the application of system identification for a flexible aircraft based on a simulation framework. This study emphasised the need for non-linear identification methods, such as an output error method, to characterise a flexible aircraft system. The work continues with the exploration of scaling laws applied to a simple aerofoil that is free to pitch and plunge. These results build the foundation for the development of a subscale high aspect ratio wing for wind tunnel experiments. The work highlights the trade-o s and compromises faced during the development of a dynamically subscaled model and the practice of system identification. The main contribution lies in the development of a low-cost methodology in building a subscale model that allows the use of dynamically scaled models at the early design stages. This practice provides the designer with a means to de-risk novel aircraft concepts as early as possible and in doing so, reduce overall development costs.Item Open Access Pilot modelling for airframe loads analysis(Cranfield University, 2013-01) Lone, Mudassir M.; Cooke, Alastair K.The development of large lightweight airframes has resulted in what used to be high frequency structural dynamics entering the low frequency range associated with an aircraft’s rigid body dynamics. This has led to the potential of adverse interactions between the aeroelastic effects and flight control, especially unwanted when incidents involving failures or extreme atmospheric disturbances occur. Moreover, the pilot’s response in such circumstances may not be reproducible in simulators and unique to the incident. The research described in this thesis describes the development of a pilot model suitable for the investigation of the effects of aeroelasticity on manual control and the study of the resulting airframe loads. After a review of the state-ofthe- art in pilot modelling an experimental approach involving desktop based pilot-in-the-loop simulation was adopted together with an optimal control based control-theoretic pilot model. The experiments allowed the investigation of manual control with a nonlinear flight control system and the derivation of parameter bounds for single-input-single-output pilot models. It was found that pilots could introduce variations of around 15 dB at the resonant frequency of the open loop pilot-vehicle-system. Sensory models suitable for the simulation of spatial disorientation effects were developed together with biomechanical models necessary to capture biodynamic feedthrough effects. A detailed derivation and method for the application of the modified optimal control pilot model, used to generate pilot control action, has also been shown in the contexts of pilot-model-in-the-loop simulations of scenarios involving an aileron failure and a gust encounter. It was found that manual control action particularly exacerbated horizontal tailplane internal loads relative to the limit loads envelope. Although comparisons with digital flight data recordings of an actual gust encounter showed a satisfactory reproduction and highlighted the adverse affects of fuselage flexibility on manual control, it also pointed towards the need for more incident data to validate such simulations.Item Open Access Pilot-induced oscillation detection and mitigation(Cranfield University, 2012-12) Liu, Qingling; Cooke, Alastair K.; Lone, Mudassir M.The aim of this thesis is to develop a real time PIO detection and mitigation system that consists of a detector based on short time Fourier transform(STFT) and autoregressive model(ARX) with exogenous inputs, together with an adaptive controller based mitigation system. The system not only detects the traditional PIO characteristics but also focuses on the trend of pilot behaviour by calculating the rate of change in the open loop crossover frequency. In the detection system, a sliding windowed STFT method was applied to identify the frequency and phase characteristics of the system via processing the signal of pilot input and aircraft state. An ARX model was also applied to get the rate of change of the crossover frequency. After detection, a PIO cue was shown on the primary flight display. A scheduled gain controller was coupled to provide PIO mitigation by varying stick input gain. Compensatory and tracking tests for the evaluation of this system were performed using a quasi-linear Boeing-747 aircraft model including nonlinear command gearing and actuator rate-limiting. Bandwidth and Gibson criteria were used to design PIO prone control laws for system evaluation experiments. Results from PIO tests conducted on desktop PCs were presented. These were analyzed and compared with those obtained from implementing the Real-time Oscillation Verifier module available in literature.Item Open Access Technical note: recent experiences of helicopter main rotor blade damage(Vertical Flight Society, 2019-08-01) Weber, Simone; Lone, Mudassir M.; Cooke, AlastairResults of a survey investigating commonly occurring minor rotor blade damage incidents are presented in this paper. Over 100 participants worldwide ranging from test pilots to commercial pilots and licensed engineers answered the survey. The focus of this work was to provide a user-oriented context that can inform the decision-making process for integrating state-of-the-art instrumentation systems for rotor blade health monitoring onboard operational helicopters. This paper highlights the dichotomy faced by designers who have a choice to follow either a reactive strategy based on operational experience or a preventative approach based on technological trends.