International Journal of Aerospace Engineering http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. A Miniature Integrated Navigation System for Rotary-Wing Unmanned Aerial Vehicles Thu, 28 Aug 2014 11:33:15 +0000 http://www.hindawi.com/journals/ijae/2014/748940/ This paper presents the development of a low cost miniature navigation system for autonomous flying rotary-wing unmanned aerial vehicles (UAVs). The system incorporates measurements from a low cost single point GPS and a triaxial solid state inertial/magnetic sensor unit. The navigation algorithm is composed of three modules running on a microcontroller: the sensor calibration module, the attitude estimator, and the velocity and position estimator. The sensor calibration module relies on a recursive least square based ellipsoid hypothesis calibration algorithm to estimate biases and scale factors of accelerometers and magnetometers without any additional calibration equipment. The attitude estimator is a low computational linear attitude fusion algorithm that effectively incorporates high frequency components of gyros and low frequency components of accelerometers and magnetometers to guarantee both accuracy and bandwidth of attitude estimation. The velocity and position estimator uses two cascaded complementary filters which fuse translational acceleration, GPS velocity, and position to improve the bandwidth of velocity and position. The designed navigation system is feasible for miniature UAVs due to its low cost, simplicity, miniaturization, and guaranteed estimation errors. Both ground tests and autonomous flight tests of miniature unmanned helicopter and quadrotor have shown the effectiveness of the proposed system, demonstrating its promise in UAV systems. Yu Xu, Wenda Sun, and Ping Li Copyright © 2014 Yu Xu et al. All rights reserved. On the Effects of Modeling As-Manufactured Geometry: Toward Digital Twin Wed, 27 Aug 2014 08:11:17 +0000 http://www.hindawi.com/journals/ijae/2014/439278/ A simple, nonstandardized material test specimen, which fails along one of two different likely crack paths, is considered herein. The result of deviations in geometry on the order of tenths of a millimeter, this ambiguity in crack path motivates the consideration of as-manufactured component geometry in the design, assessment, and certification of structural systems. Herein, finite element models of as-manufactured specimens are generated and subsequently analyzed to resolve the crack-path ambiguity. The consequence and benefit of such a “personalized” methodology is the prediction of a crack path for each specimen based on its as-manufactured geometry, rather than a distribution of possible specimen geometries or nominal geometry. The consideration of as-manufactured characteristics is central to the Digital Twin concept. Therefore, this work is also intended to motivate its development. Albert Cerrone, Jacob Hochhalter, Gerd Heber, and Anthony Ingraffea Copyright © 2014 Albert Cerrone et al. All rights reserved. Thermochemical Analysis of Hypergolic Propellants Based on Triethylaluminum/Nitrous Oxide Wed, 27 Aug 2014 00:00:00 +0000 http://www.hindawi.com/journals/ijae/2014/269836/ The vacuum specific impulse, density vacuum specific impulse, and solid exhaust products were examined for several propellant formulations based on the pyrophoric material triethylaluminum (TEA) using CEA thermodynamics code. Evaluation of TEA neat and mixed with hydrocarbon fuels with LOX, N2O, N2O4, liquefied air, and HNO3 were performed at stoichiometry. The vacuum specific impulse of neat TEA with N2O is comparable to that of nitric acid with the same, but the N2O formulation will produce slightly less solid products during combustion. Additionally, N2O-TEA propellants have vacuum specific impulses and density vacuum specific impulses within 92.9% and 86.7% of traditional hydrazine propellant formulations under stoichiometric conditions. Stephen M. Davis and Nadir Yilmaz Copyright © 2014 Stephen M. Davis and Nadir Yilmaz. All rights reserved. External Aerodynamics Simulations in a Rotating Frame of Reference Mon, 14 Jul 2014 11:32:02 +0000 http://www.hindawi.com/journals/ijae/2014/654037/ This paper presents the development of a tool integrated in the UNS3D code, proprietary of Alenia Aermacchi, for the simulation of external aerodynamic flow in a rotating reference frame, with the main objective of predicting propeller-aircraft integration effects. The equations in a rotating frame of reference have been formulated in terms of the absolute velocity components; in this way, the artificial dissipation needed for convergence is lessened, as the Coriolis source term is only introduced in the momentum equation. An Explicit Algebraic Reynolds Stress turbulence model is used. The first assessment of effectiveness of this method is made computing stability derivatives of a NACA 0012 airfoil. Finally, steady Navier-Stokes and Euler simulations of a four-blade single-rotating propeller are presented, demonstrating the efficiency of the chosen approach in terms of computational cost. Filomena Cariglino, Nicola Ceresola, and Renzo Arina Copyright © 2014 Filomena Cariglino et al. All rights reserved. Active Vibration Control of Plate Partly Treated with ACLD Using Hybrid Control Mon, 14 Jul 2014 10:05:23 +0000 http://www.hindawi.com/journals/ijae/2014/432970/ A finite element model of plate partly treated with ACLD treatments is developed based on the constitutive equations of elastic, piezoelectric, viscoelastic materials and Hamilton’s principle. The Golla-Hughes-Mctavish (GHM) method is employed to describe the frequency-dependent characteristics of viscoelastic material (VEM). A model reduction is completed by using iterative dynamic condensation and balance model reduction method to design an effective control system. The emphasis is concerned on hybrid (combined feedback/feedforward) control system to attenuate the vibration of plates with ACLD treatments. The optimal linear quadratic Gaussian (LQG) controller is considered as a feedback channel and the adaptive filtered-reference LMS (FxLMS) controller is used as a feedforward channel. They can be utilized individually or in a hybrid way to suppress the vibration of plate/ACLD system. The results show that the hybrid controller which combines feedback/feedforward together can reduce the displacement amplitude of plate/ACLD system subjected to a complicated disturbance substantially without requiring more control effort. Furthermore, the hybrid controller has more rapid and stable convergence rate than the adaptive feedforward FxLMS controller. Meanwhile, perfect robustness to phase error of the cancellation path in feedforward controller and the weight matrices in feedback LQG controller is demonstrated in proposed hybrid controller. Therefore, its application in structural engineering can be highly appreciated. Dongdong Zhang and Ling Zheng Copyright © 2014 Dongdong Zhang and Ling Zheng. All rights reserved. A Numerical Study on a Vertical-Axis Wind Turbine with Inclined Arms Mon, 30 Jun 2014 10:31:02 +0000 http://www.hindawi.com/journals/ijae/2014/180498/ This work focuses on a particular type of vertical-axis wind turbine, in which a number of inclined arms with airfoil-shaped cross-sections are mounted to connect the principal blades to their hub. While the majority of the known studies on vertical-axis turbines is devoted to the role of principal blades, in most of the cases without taking into account other parts of the wind turbine, the objective of this work is to investigate the effect of uncommon arm geometries, such as the inclined arms. The inclined arms are known to have a potentially beneficial role in the power extraction from the wind current but, due to the complexity of the phenomena, the investigation on aerodynamics of this type of turbine is often impossible through analytical models, such as blade-element momentum theory. It turns out that adequate studies can only be carried out by wind tunnel experiments or CFD simulations. This work presents a methodical CFD study on how inclined arms can be used on a selected wind turbine configuration to harvest additional power from the wind. The turbine configuration, geometry, and some fundamental definitions are introduced first. Then an in-depth CFD analysis is presented and discussed. Agostino De Marco, Domenico P. Coiro, Domenico Cucco, and Fabrizio Nicolosi Copyright © 2014 Agostino De Marco et al. All rights reserved. Use of Active Learning to Design Wind Tunnel Runs for Unsteady Cavity Pressure Measurements Thu, 19 Jun 2014 09:11:12 +0000 http://www.hindawi.com/journals/ijae/2014/218710/ Wind tunnel tests to measure unsteady cavity flow pressure measurements can be expensive, lengthy, and tedious. In this work, the feasibility of an active machine learning technique to design wind tunnel runs using proxy data is tested. The proposed active learning scheme used scattered data approximation in conjunction with uncertainty sampling (US). We applied the proposed intelligent sampling strategy in characterizing cavity flow classes at subsonic and transonic speeds and demonstrated that the scheme has better classification accuracies, using fewer training points, than a passive Latin Hypercube Sampling (LHS) strategy. Ankur Srivastava and Andrew J. Meade Copyright © 2014 Ankur Srivastava and Andrew J. Meade. All rights reserved. Effects of Surface Coating Preparation and Sliding Modes on Titanium Oxide Coated Titanium Alloy for Aerospace Applications Tue, 06 May 2014 06:24:45 +0000 http://www.hindawi.com/journals/ijae/2014/640364/ This paper investigates the mechanical response of a coated Ti-6Al-4V alloy surface under different sliding contact stress conditions. The surface was coated with an oxide ceramic material created through the use of a recently developed technique known as plasma electrolytic oxidation (PEO). During the PEO procedure, a composition of silicate and phosphate was used as the electrolyte. In order to evaluate the coating, pin-on-disk (POD) tribology tests and cyclic inclined sliding tests were used under dry room conditions. Furthermore, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were utilized to examine the morphology and composition of the coating surfaces. The results of the POD tests revealed that the PEO coating could have a low coefficient of friction and suggested that high silicon concentrations in the PEO coatings take away oxygen from stoichiometric Ti oxides to create lubricating oxides. In addition, cyclic inclined sliding tests showed that smaller pores on the surface of the coating could permit a higher coating cohesive strength and allow the coated Ti alloy surface to perform better under high inclined sliding forces. Bo Yuan Peng, Xueyuan Nie, and Ying Chen Copyright © 2014 Bo Yuan Peng et al. All rights reserved. Airloads Correlation of the UH-60A Rotor inside the 40- by 80-Foot Wind Tunnel Sun, 23 Mar 2014 09:17:01 +0000 http://www.hindawi.com/journals/ijae/2014/473989/ The presented research validates the capability of a loosely coupled computational fluid dynamics (CFD) and comprehensive rotorcraft analysis (CRA) code to calculate the flowfield around a rotor and test stand mounted inside a wind tunnel. The CFD/CRA predictions for the Full-Scale UH-60A Airloads Rotor inside the National Full-Scale Aerodynamics Complex (NFAC) 40- by 80-Foot Wind Tunnel at NASA Ames Research Center are compared with the latest measured airloads and performance data. The studied conditions include a speed sweep at constant lift up to an advance ratio of 0.4 and a thrust sweep at constant speed up to and including stall. For the speed sweep, wind tunnel modeling becomes important at advance ratios greater than 0.37 and test stand modeling becomes increasingly important as the advance ratio increases. For the thrust sweep, both the wind tunnel and test stand modeling become important as the rotor approaches stall. Despite the beneficial effects of modeling the wind tunnel and test stand, the new models do not completely resolve the current airload discrepancies between prediction and experiment. I-Chung Chang, Thomas R. Norman, and Ethan A. Romander Copyright © 2014 I-Chung Chang et al. All rights reserved. An Efficient Nonlinear Filter for Spacecraft Attitude Estimation Wed, 12 Mar 2014 08:07:31 +0000 http://www.hindawi.com/journals/ijae/2014/540235/ Increasing the computational efficiency of attitude estimation is a critical problem related to modern spacecraft, especially for those with limited computing resources. In this paper, a computationally efficient nonlinear attitude estimation strategy based on the vector observations is proposed. The Rodrigues parameter is chosen as the local error attitude parameter, to maintain the normalization constraint for the quaternion in the global estimator. The proposed attitude estimator is performed in four stages. First, the local attitude estimation error system is described by a polytopic linear model. Then the local error attitude estimator is designed with constant coefficients based on the robust filtering algorithm. Subsequently, the attitude predictions and the local error attitude estimations are calculated by a gyro based model and the local error attitude estimator. Finally, the attitude estimations are updated by the predicted attitude with the local error attitude estimations. Since the local error attitude estimator is with constant coefficients, it does not need to calculate the matrix inversion for the filter gain matrix or update the Jacobian matrixes online to obtain the local error attitude estimations. As a result, the computational complexity of the proposed attitude estimator reduces significantly. Simulation results demonstrate the efficiency of the proposed attitude estimation strategy. Bing Liu, Zhen Chen, Xiangdong Liu, and Fan Yang Copyright © 2014 Bing Liu et al. All rights reserved. Numerical Calculation of Effect of Elastic Deformation on Aerodynamic Characteristics of a Rocket Mon, 17 Feb 2014 09:17:09 +0000 http://www.hindawi.com/journals/ijae/2014/478534/ The application and workflow of Computational Fluid Dynamics (CFD)/Computational Structure Dynamics (CSD) on solving the static aeroelastic problem of a slender rocket are introduced. To predict static aeroelastic behavior accurately, two-way coupling and inertia relief methods are used to calculate the static deformations and aerodynamic characteristics of the deformed rocket. The aerodynamic coefficients of rigid rocket are computed firstly and compared with the experimental data, which verified the accuracy of CFD output. The results of the analysis for elastic rocket in the nonspinning and spinning states are compared with the rigid ones. The results highlight that the rocket deformation aspects are decided by the normal force distribution along the rocket length. Rocket deformation becomes larger with increasing the flight angle of attack. Drag and lift force coefficients decrease and pitching moment coefficients increase due to rocket deformations, center of pressure location forwards, and stability of the rockets decreases. Accordingly, the flight trajectory may be affected by the change of these aerodynamic coefficients and stability. Laith K. Abbas, Dongyang Chen, and Xiaoting Rui Copyright © 2014 Laith K. Abbas et al. All rights reserved. Actuator Fault Diagnosis in a Boeing 747 Model via Adaptive Modified Two-Stage Kalman Filter Mon, 10 Feb 2014 09:44:54 +0000 http://www.hindawi.com/journals/ijae/2014/472395/ An adaptive modified two-stage linear Kalman filtering algorithm is utilized to identify the loss of control effectiveness and the magnitude of low degree of stuck faults in a closed-loop nonlinear B747 aircraft. Control effectiveness factors and stuck magnitudes are used to quantify faults entering control systems through actuators. Pseudorandom excitation inputs are used to help distinguish partial loss and stuck faults. The partial loss and stuck faults in the stabilizer are isolated and identified successfully. Fikret Caliskan, Youmin Zhang, N. Eva Wu, and Jong-Yeob Shin Copyright © 2014 Fikret Caliskan et al. All rights reserved. Boost Full Bridge Bidirectional DC/DC Converter for Supervised Aeronautical Applications Wed, 22 Jan 2014 09:23:45 +0000 http://www.hindawi.com/journals/ijae/2014/808374/ The More Electrical Aircraft concept requires electronic devices able to efficiently and safely convert electrical power between different voltage levels. The entire realization of a bidirectional DC/DC converter, from design to validation phase, is here discussed in detail. First, a boost full bridge electrical structure is selected, adopting a Parallel Input Parallel Output (PIPO) interleaving technique and an optimal turns ratio selection for the transformers in order to reduce both weight and size of the equipment. Next, modulation schemes in both step-down and step-up modes are discussed. Successively ad hoc PI regulators for both operative modes are presented. A key idea of the paper is that the converter behavior must be related not only to the control strategy but also to a global supervision logic able to safely conduct the converter operations and to react from external stimuli. Thus, a finite state machine (FSM) approach is employed. An innovative strategy called buffer mode is presented, defined as an intelligent combination of buck and boost modes. Extensive simulations and experimental results are shown, in order to confirm the effectiveness of the proposed approach. Alberto Cavallo, Beniamino Guida, and Luigi Rubino Copyright © 2014 Alberto Cavallo et al. All rights reserved. A Low-Cost Photodiode Sun Sensor for CubeSat and Planetary Microrover Tue, 17 Dec 2013 12:01:29 +0000 http://www.hindawi.com/journals/ijae/2013/549080/ This paper presents the development of low-cost methodologies to determine the attitude of a small, CubeSat-class satellite and a microrover relative to the sun's direction. The use of commercial hardware and simple embedded designs has become an effective path for university programs to put experimental payloads in space for minimal cost, and the development of sensors for attitude and heading determination is often a critical part. The development of two compact and efficient but simple coarse sun sensor methodologies is presented in this research. A direct measurement of the solar angle uses a photodiode array sensor and slit mask. Another estimation of the solar angle uses current measurements from orthogonal arrays of solar cells. The two methodologies are tested and compared on ground hardware. Testing results show that coarse sun sensing is efficient even with minimal processing and complexity of design for satellite attitude determination systems and rover navigation systems. Mark A. Post, Junquan Li, and Regina Lee Copyright © 2013 Mark A. Post et al. All rights reserved. A New Method for Initial Parameters Optimization of Guided Projectiles Wed, 11 Dec 2013 09:01:36 +0000 http://www.hindawi.com/journals/ijae/2013/486020/ A new algorithm was developed for the initial parameters optimization of guided projectiles with multiple constraints. Due to the relationship between the analytic guidance logic and state variables of guided projectiles, the Radau pseudospectral method was used to discretize the differential equations including control variables and state variables with multiple constraints into series algebraic equations that were expressed only by state variables. The initial parameter optimization problem was transformed to a nonlinear programming problem, and the sequential quadratic programming algorithm was used to obtain the optimal combinations of initial height and range to target for the final velocity of guided projectiles maximum with constraints. Comparing with the appropriate initial conditions solved by Monte Carlo method and the flight characteristics solved by integrating the original differential equations in the optimal initial parameters computed by the new algorithm, the feasibility of new algorithm was validated. Feng Bi-Ming and Nie Wan-Sheng Copyright © 2013 Feng Bi-Ming and Nie Wan-Sheng. All rights reserved. RF Field Build-Up inside a Manned Space Vehicle Using Novel Ray-Tracing Algorithm Thu, 05 Dec 2013 08:28:19 +0000 http://www.hindawi.com/journals/ijae/2013/438239/ The radio-frequency (RF) field mapping and its analysis inside a space vehicle cabin, although of immense importance, represent a complex problem due to their inherent concavity. Further hybrid surface modeling required for such concave enclosures leads to ray proliferation, thereby making the problem computationally intractable. In this paper, space vehicle is modeled as a double-curvatured general paraboloid of revolution (GPOR) frustum, whose aft section is matched to an end-capped right circular cylinder. A 3D ray-tracing package is developed which involves a uniform ray-launching scheme, an intelligent scheme for ray bunching, and an adaptive reception algorithm for obtaining ray-path details inside the concave space vehicle. Due to nonavailability of image method for concave curvatured surfaces, the proposed ray-tracing method is validated with respect to the RF field build-up inside a closed lossy cuboid using image method. The RF field build-up within the space vehicle is determined using the details of ray paths and the material parameters. The results for RF field build-up inside a metal-backed dielectric space vehicle are compared with those of highly metallic one for parallel and perpendicular polarizations. The convergence of RF field within the vehicle is analyzed with respect to the propagation time and the number of bounces a ray undergoes before reaching the receiving point. Balamati Choudhury, Hema Singh, and R. M. Jha Copyright © 2013 Balamati Choudhury et al. All rights reserved. Platform and State Estimation Design of a Small-Scale UAV Helicopter System Wed, 04 Dec 2013 17:39:42 +0000 http://www.hindawi.com/journals/ijae/2013/524856/ This paper presents the development of a small-scale unmanned aerial vehicle (UAV) helicopter system based on a Raptor 90 hobby helicopter. Firstly, onboard avionics system and ground station are designed carefully. The onboard avionics system mainly consists of sensors, flight control board, RF modem, and power supply system. The ground station comprises a computer and a RF modem. The main function of ground station is to monitor the status of onboard avionics. To avoid the effect of noises, some efficient sensor data processing and integrated navigation algorithms are designed and implemented on the onboard avionics. As a result, the constructed system exhibits low weight, small size, antivibration, and low power consumption; the essential information for system identification and automatic control can be easily acquired. Several ground and flight tests have been performed to verify the feasibility and reliability of the total system. The results show that it is sufficient for system identification and automatic control. Shuai Tang, Xingju Lu, and Zhiqiang Zheng Copyright © 2013 Shuai Tang et al. All rights reserved. Development of a Landing Mechanism for Asteroids with Soft Surface Thu, 21 Nov 2013 10:29:59 +0000 http://www.hindawi.com/journals/ijae/2013/873135/ A landing mechanism to an asteroid with soft surface is developed. It consists of three landing feet, landing legs, cardan element, damping element, equipment base, anchoring system, and so on. Static structural analysis and modal analysis are carried out to check the strength and natural frequency of the landing mechanism with FEA. Testing platform for the anchoring system is introduced, and then the penetrating and anchoring tests of the anchoring system are carried out in different media. It shows that cohesion of the media has large influence on the penetrating and anchoring performance of the anchoring system. Landing tests of the landing mechanism with different velocities under simulated microgravity environment are carried out on the air-floating platform, and the impact accelerations are measured by the sensors on the landing mechanism. At the same time, these impact accelerations are processed by spectrum analysis to find the natural frequency of the landing mechanism. Zhijun Zhao, Jingdong Zhao, and Hong Liu Copyright © 2013 Zhijun Zhao et al. All rights reserved. Wind Tunnel Testing on Start/Unstart Characteristics of Finite Supersonic Biplane Wing Wed, 13 Nov 2013 09:44:53 +0000 http://www.hindawi.com/journals/ijae/2013/231434/ This study describes the start/unstart characteristics of a finite and rectangular supersonic biplane wing. Two wing models were tested in wind tunnels with aspect ratios of 0.75 (model A) and 2.5 (model B). The models were composed of a Busemann biplane section. The tests were carried out using supersonic and transonic wind tunnels over a Mach number range of with angles of attack of 0°, 2°, and 4°. The Schlieren system was used to observe the flow characteristics around the models. The experimental results showed that these models had start/unstart characteristics that differed from those of the Busemann biplane (two dimensional) owing to three-dimensional effects. Models A and B started at lower Mach numbers than the Busemann biplane. The characteristics also varied with aspect ratio: model A () started at a lower Mach number than model B () owing to the lower aspect ratio. Model B was located in the double solution domain for the start/unstart characteristics at , and model B was in either the start or unstart state at . Once the state was determined, either state was stable. Hiroshi Yamashita, Naoshi Kuratani, Masahito Yonezawa, Toshihiro Ogawa, Hiroki Nagai, Keisuke Asai, and Shigeru Obayashi Copyright © 2013 Hiroshi Yamashita et al. All rights reserved. Numerical Simulation of Airfoil Aerodynamic Penalties and Mechanisms in Heavy Rain Thu, 07 Nov 2013 19:13:55 +0000 http://www.hindawi.com/journals/ijae/2013/590924/ Numerical simulations that are conducted on a transport-type airfoil, NACA 64-210, at a Reynolds number of and LWC of 25 g/m3 explore the aerodynamic penalties and mechanisms that affect airfoil performance in heavy rain conditions. Our simulation results agree well with the experimental data and show significant aerodynamic penalties for the airfoil in heavy rain. The maximum percentage decrease in is reached by 13.2% and the maximum percentage increase in by 47.6%. Performance degradation in heavy rain at low angles of attack is emulated by an originally creative boundary-layer-tripped technique near the leading edge. Numerical flow visualization technique is used to show premature boundary-layer separation at high angles of attack and the particulate trajectories at various angles of attack. A mathematic model is established to qualitatively study the water film effect on the airfoil geometric changes. All above efforts indicate that two primary mechanisms are accountable for the airfoil aerodynamic penalties. One is to cause premature boundary-layer transition at low AOA and separation at high AOA. The other occurs at times scales consistent with the water film layer, which is thought to alter the airfoil geometry and increase the mass effectively. Zhenlong Wu, Yihua Cao, and M. Ismail Copyright © 2013 Zhenlong Wu et al. All rights reserved. Global Modeling of N2O Discharges: Rate Coefficients and Comparison with ICP and Glow Discharges Results Thu, 10 Oct 2013 15:00:42 +0000 http://www.hindawi.com/journals/ijae/2013/737463/ We developed a Global Model for N2O plasmas valid for applications in various power, gas flow rate, and pressure regimes. Besides energy losses from electron collisions with N2O, it takes into consideration those due to molecular N2 and O2 and to atomic N and O species. Positive atomic N+ and O+ and molecular N2O+, , and have been treated as separate species and also negative O− ions. The latter confer an electronegative character to the discharge, calling for modified plasma sheath and plasma potential formulas. Electron density and temperature and all species densities have been evaluated, hence the ionization and dissociation percentages of N2O, N2, and O2 molecules and the plasma electronegativity. The model is extended to deal with N2/O2 mixtures feedings, notably with air. Rate coefficients and model results are discussed and compared with those from available theoretical and experimental work on ICP and glow discharge devices. Konstantinos Katsonis and Chloe Berenguer Copyright © 2013 Konstantinos Katsonis and Chloe Berenguer. All rights reserved. Global Modeling of N2O Discharges: Helicon Plasma Thruster Application Mon, 07 Oct 2013 09:22:35 +0000 http://www.hindawi.com/journals/ijae/2013/467503/ A global (volume averaged) model pertaining to N2O discharges is used to design and to study electric propulsion applications, especially helicon plasma thrusters fed with pure N2O and also with N2/O2 mixtures including air. Results obtained for N2O feeding are discussed and compared to those pertaining to an air-like N2/O2 mixture feeding. An interesting similarity is observed. Comparison of the N2O model results versus those of Ar shows lower ionization percentage with higher electron temperature for N2O propellant. Konstantinos Katsonis and Chloe Berenguer Copyright © 2013 Konstantinos Katsonis and Chloe Berenguer. All rights reserved. Real-Time Hardware-in-the-Loop Tests of Star Tracker Algorithms Wed, 11 Sep 2013 14:25:20 +0000 http://www.hindawi.com/journals/ijae/2013/505720/ This paper deals with star tracker algorithms validation based on star field scene simulation and hardware-in-the-loop test configuration. A laboratory facility for indoor tests, based on the simulation of star field scenes, is presented. Attainable performance is analyzed theoretically for both static and dynamic simulations. Also, a test campaign is presented, in which a star sensor prototype with real-time, fully autonomous capability is exploited. Results that assess star field scene simulation performance and show the achievable validation for the sensor algorithms and performance in different operating modes (autonomous attitude acquisition, attitude tracking, and angular rate-only) and different aspects (coverage, reliability, and measurement performance) are discussed. Giancarlo Rufino, Domenico Accardo, Michele Grassi, Giancarmine Fasano, Alfredo Renga, and Urbano Tancredi Copyright © 2013 Giancarlo Rufino et al. All rights reserved. Interpolation of Transonic Flows Using a Proper Orthogonal Decomposition Method Thu, 05 Sep 2013 11:58:44 +0000 http://www.hindawi.com/journals/ijae/2013/928904/ A proper orthogonal decomposition (POD) method is used to interpolate the flow around an airfoil for various Mach numbers and angles of attack in the transonic regime. POD uses a few numerical simulations, called snapshots, to create eigenfunctions. These eigenfunctions are combined using weighting coefficients to create a new solution for different values of the input parameters. Since POD methods are linear, their interpolation capabilities are quite limited when dealing with flow presenting nonlinearities, such as shocks. In order to improve their performance for cases involving shocks, a new method is proposed using variable fidelity. The main idea is to use POD to interpolate the difference between the CFD solution obtained on two different grids, a coarse one and a fine one. Then, for any new input parameter value, a coarse grid solution is computed using CFD and the POD interpolated difference is added to predict the fine grid solution. This allows some nonlinearities associated with the flow to be introduced. Results for various Mach numbers and angles of attack are compared to full CFD results. The variable fidelity-based POD method shows good improvement over the classical approach. Benoit Malouin, Jean-Yves Trépanier, and Martin Gariépy Copyright © 2013 Benoit Malouin et al. All rights reserved. Autonomous Planning of Multigravity-Assist Trajectories with Deep Space Maneuvers Using a Differential Evolution Approach Mon, 26 Aug 2013 15:26:38 +0000 http://www.hindawi.com/journals/ijae/2013/145369/ The biologically inspired concept of hidden genes has been recently introduced in genetic algorithms to solve optimization problems where the number of design variables is variable. In multigravity-assist trajectories, the hidden genes genetic algorithms demonstrated success in searching for the optimal number of swing-bys and the optimal number of deep space maneuvers. Previous investigations in the literature for multigravity-assist trajectory planning problems show that the standard differential evolution is more effective than the standard genetic algorithms. This paper extends the concept of hidden genes to differential evolution. The hidden genes differential evolution is implemented in optimizing multigravity-assist space trajectories. Case studies are conducted, and comparisons to the hidden genes genetic algorithms are presented in this paper. Ossama Abdelkhalik Copyright © 2013 Ossama Abdelkhalik. All rights reserved. Film Cooling Optimization Using Numerical Computation of the Compressible Viscous Flow Equations and Simplex Algorithm Sat, 24 Aug 2013 09:46:25 +0000 http://www.hindawi.com/journals/ijae/2013/859465/ Film cooling is vital to gas turbine blades to protect them from high temperatures and hence high thermal stresses. In the current work, optimization of film cooling parameters on a flat plate is investigated numerically. The effect of film cooling parameters such as inlet velocity direction, lateral and forward diffusion angles, blowing ratio, and streamwise angle on the cooling effectiveness is studied, and optimum cooling parameters are selected. The numerical simulation of the coolant flow through flat plate hole system is carried out using the “CFDRC package” coupled with the optimization algorithm “simplex” to maximize overall film cooling effectiveness. Unstructured finite volume technique is used to solve the steady, three-dimensional and compressible Navier-Stokes equations. The results are compared with the published numerical and experimental data of a cylindrically round-simple hole, and the results show good agreement. In addition, the results indicate that the average overall film cooling effectiveness is enhanced by decreasing the streamwise angle for high blowing ratio and by increasing the lateral and forward diffusion angles. Optimum geometry of the cooling hole on a flat plate is determined. In addition, numerical simulations of film cooling on actual turbine blade are performed using the flat plate optimal hole geometry. Ahmed M. Elsayed, Farouk M. Owis, and M. Madbouli Abdel Rahman Copyright © 2013 Ahmed M. Elsayed et al. All rights reserved. Solid Carbon Produced in an Inductively Coupled Plasma Torch with a Titan Like Atmosphere Sun, 16 Jun 2013 11:52:30 +0000 http://www.hindawi.com/journals/ijae/2013/546385/ Solid carbon is deposited on the surfaces of an inductively coupled plasma torch operating with a Titan like atmosphere plasma gas. The frame of the initial research is the study of the radiative properties of plasma encountered around a spacecraft during its hypersonic entry in upper layers of planetary atmosphere. Deposition of carbon is observed not only on the quartz tube outside the inductor but also on the ceramic protection of the torch injector. Carbon exhibits two types of morphology more or less dense and it is analyzed by various analytic devices as MEB, SEM, TEM, EDS and Raman spectroscopy. The gathered carbon powder shows the presence of nanostructured particles. D. Vacher, S. Menecier, M. Dudeck, M. Dubois, B. Devouard, and E. Petit Copyright © 2013 D. Vacher et al. All rights reserved. Real-Time Hardware-in-the-Loop Laboratory Testing for Multisensor Sense and Avoid Systems Thu, 13 Jun 2013 08:36:14 +0000 http://www.hindawi.com/journals/ijae/2013/748751/ This paper focuses on a hardware-in-the-loop facility aimed at real-time testing of architectures and algorithms of multisensor sense and avoid systems. It was developed within a research project aimed at flight demonstration of autonomous non-cooperative collision avoidance for Unmanned Aircraft Systems. In this framework, an optionally piloted Very Light Aircraft was used as experimental platform. The flight system is based on multiple-sensor data integration and it includes a Ka-band radar, four electro-optical sensors, and two dedicated processing units. The laboratory test system was developed with the primary aim of prototype validation before multi-sensor tracking and collision avoidance flight tests. System concept, hardware/software components, and operating modes are described in the paper. The facility has been built with a modular approach including both flight hardware and simulated systems and can work on the basis of experimentally tested or synthetically generated scenarios. Indeed, hybrid operating modes are also foreseen which enable performance assessment also in the case of alternative sensing architectures and flight scenarios that are hardly reproducible during flight tests. Real-time multisensor tracking results based on flight data are reported, which demonstrate reliability of the laboratory simulation while also showing the effectiveness of radar/electro-optical fusion in a non-cooperative collision avoidance architecture. Giancarmine Fasano, Domenico Accardo, Lidia Forlenza, Alfredo Renga, Giancarlo Rufino, Urbano Tancredi, and Antonio Moccia Copyright © 2013 Giancarmine Fasano et al. All rights reserved. Development and Validation of a New Boundary Condition for Intake Analysis with Distortion Mon, 03 Jun 2013 15:37:32 +0000 http://www.hindawi.com/journals/ijae/2013/284206/ The design of an intake for a gas turbine engine involves CFD-based investigation and experimental assessment in an intake test rig. In both cases, the engine is represented by a mass flux sink, usually positioned a few fan radii aft of the real fan face. In general, this approach is sufficient to analyze intake geometry for low distortion at the fan face, because in this case the interaction of the fan with the inlet flow can be neglected. Where there are higher levels of distortion at the fan face, the interaction could become more significant and a different approach would be preferable. One alternative that takes into account the interaction in such cases includes the fan in the analysis of the intake, using either a steady or unsteady flow model approach. However, this solution is expensive and too computationally intensive to be useful in design mode. The solution proposed in this paper is to implement a new boundary condition at the fan face which better represents the interaction of the fan with the flow in the air intake in the presence of distortion. This boundary condition includes a simplified fan model and a coupling strategy applied between the fan and the inlet. The results obtained with this new boundary condition are compared to full 3D unsteady CFD simulations that include the fan. Foad Mehdi Zadeh, Jean-Yves Trépanier, and Eddy Petro Copyright © 2013 Foad Mehdi Zadeh et al. All rights reserved. Adaptive and Resilient Flight Control System for a Small Unmanned Aerial System Thu, 16 May 2013 15:58:00 +0000 http://www.hindawi.com/journals/ijae/2013/289357/ The main purpose of this paper is to develop an onboard adaptive and robust flight control system that improves control, stability, and survivability of a small unmanned aerial system in off-nominal or out-of-envelope conditions. The aerodynamics of aircraft associated with hazardous and adverse onboard conditions is inherently nonlinear and unsteady. The presented flight control system improves functionalities required to adapt the flight control in the presence of aircraft model uncertainties. The fault tolerant inner loop is enhanced by an adaptive real-time artificial neural network parameter identification to monitor important changes in the aircraft’s dynamics due to nonlinear and unsteady aerodynamics. The real-time artificial neural network parameter identification is done using the sliding mode learning concept and a modified version of the self-adaptive Levenberg algorithm. Numerically estimated stability and control derivatives are obtained by delta-based methods. New nonlinear guidance logic, stable in Lyapunov sense, is developed to guide the aircraft. The designed flight control system has better performance compared to a commercial off-the-shelf autopilot system in guiding and controlling an unmanned air system during a trajectory following. Gonzalo Garcia and Shahriar Keshmiri Copyright © 2013 Gonzalo Garcia and Shahriar Keshmiri. All rights reserved.