International Journal of Aerospace Engineering The latest articles from Hindawi Publishing Corporation © 2016 , Hindawi Publishing Corporation . All rights reserved. On the Topology Optimization of Elastic Supporting Structures under Thermomechanical Loads Mon, 27 Jun 2016 16:31:49 +0000 This paper is to present a thermomechanical topology optimization formulation. By designing structures that support specific nondesignable domain, optimization is to suppress the stress level in the nondesignable domain and maintain global stiffness simultaneously. A global stress measure based on -norm function is then utilized to reduce the number of stress constraints in topology optimization. Sensitivity analysis employs adjoint method to derive the global stress measure with respect to the topological pseudodensity variables. Some particular behaviors in thermomechanical topology optimization of elastic supports, such as the influence of different thermomechanical loads and the existence of intermediate material, are also analyzed numerically. Finally, examples of elastic supports on a cantilever beam and a nozzle flap under different thermomechanical loads are tested with reasonable optimized design obtained. Jie Hou, Ji-Hong Zhu, and Qing Li Copyright © 2016 Jie Hou et al. All rights reserved. Nominal Performance of Future Dual Frequency Dual Constellation GBAS Sun, 26 Jun 2016 13:31:42 +0000 In this work an overview of numerous possible processing modes in future dual frequency, dual constellation GBAS is given and compared to the current GAST D standard. We discuss the individual error contributions to GBAS protection levels and give an overview of the general processing. Based on this the consequences when adding a second constellation as well as frequency are investigated. Geometrical implications and changes to the residual differential error bounds are studied separately first. In terms of geometry a comparison between the single and dual constellation case is presented using dilution of precision as metric. The influence on the different sigma contributions when using new satellites (Galileo) and signals (E1, L5, and E5a) is individually discussed based on recent measurements. Final simulations for different varying parameters are carried out to compare relevant processing modes in terms of achieved nominal protection levels. A concluding discussion compares the outcomes and analyzes the implications of choosing one or the other mode. Daniel Gerbeth, Mihaela-Simona Circiu, Maria Caamano, and Michael Felux Copyright © 2016 Daniel Gerbeth et al. All rights reserved. Midcourse Guidance Law Based on High Target Acquisition Probability Considering Angular Constraint and Line-of-Sight Angle Rate Control Wed, 22 Jun 2016 13:13:12 +0000 Random disturbance factors would lead to the variation of target acquisition point during the long distance flight. To acquire a high target acquisition probability and improve the impact precision, missiles should be guided to an appropriate target acquisition position with certain attitude angles and line-of-sight (LOS) angle rate. This paper has presented a new midcourse guidance law considering the influences of random disturbances, detection distance restraint, and target acquisition probability with Monte Carlo simulation. Detailed analyses of the impact points on the ground and the random distribution of the target acquisition position in the 3D space are given to get the appropriate attitude angles and the end position for the midcourse guidance. Then, a new formulation biased proportional navigation (BPN) guidance law with angular constraint and LOS angle rate control has been derived to ensure the tracking ability when attacking the maneuvering target. Numerical simulations demonstrates that, compared with the proportional navigation guidance (PNG) law and the near-optimal spatial midcourse guidance (NSMG) law, BPN guidance law demonstrates satisfactory performances and can meet both the midcourse terminal angular constraint and the LOS angle rate requirement. Xiao Liu, Shengjing Tang, Jie Guo, Yuhang Yun, and Zhe Chen Copyright © 2016 Xiao Liu et al. All rights reserved. Aeroelastic Analysis of Wings in the Transonic Regime: Planform’s Influence on the Dynamic Instability Wed, 22 Jun 2016 08:18:30 +0000 This paper presents a study of transonic wings whose planform shape is curved. Using fluid structure interaction analyses, the dynamic instability conditions were investigated by including the effects of the transonic flow field around oscillating wings. To compare the dynamic aeroelastic characteristics of the curved wing configuration, numerical analyses were carried out on a conventional swept wing and on a curved planform wing. The results confirm that, for a curved planform wing, the dynamic instability condition occurs at higher flight speed if compared to a traditional swept wing with similar profiles, aspect ratio, angle of sweep at root, similar structural layout, and similar mass. A curved wing lifting system could thus improve the performances of future aircrafts. Mario Rosario Chiarelli and Salvatore Bonomo Copyright © 2016 Mario Rosario Chiarelli and Salvatore Bonomo. All rights reserved. Subsonic Flutter of Cantilever Rectangular PC Plate Structure Sun, 19 Jun 2016 06:24:04 +0000 Flutter characteristics of cantilever rectangular flexible plate structure under incompressible flow regime are investigated by comparing the results of commercial flutter analysis program ZAERO© with wind tunnel tests conducted in Ankara Wind Tunnel (ART). A rectangular polycarbonate (PC) plate, 5 × 125 × 1000 mm in dimension, is used for both numerical and experimental investigations. Analysis and test results are very compatible with each other. A comparison between two different solution methods (-method and -method) of ZAERO© is also done. It is seen that the -method gives a closer result than the other one. However, -method results are on a conservative side and it is better to use conservative results, namely, -method results. Even if the modal analysis results are used for the flutter analysis for this simple structure, a modal test should be conducted in order to validate the modal analysis results to have accurate flutter analysis results for more complicated structures. Kemal Yaman Copyright © 2016 Kemal Yaman. All rights reserved. On-Orbit Thermal Design and Validation of 1 U Standardized CubeSat of STEP Cube Lab Wed, 15 Jun 2016 09:49:25 +0000 The Cube Laboratory for Space Technology Experimental Projects (STEP Cube Lab) is a cube satellite (CubeSat) classified as a pico-class satellite of 1 U (unit) size. Its main mission objective is to exploit core space technologies researched by domestic universities and verify the effectiveness of these technologies through on-orbit tests using the CubeSat. To guarantee a successful mission under extreme space thermal environments, proper thermal design is important. This paper describes the development process undertaken in the thermal design of the STEP Cube Lab, based on a passive approach, and its validation test. The system functionality and thermal design were verified through thermal vacuum and thermal balance tests under space simulated thermal vacuum environment condition. Finally, the orbital temperature of each component was predicted using a highly reliable correlated thermal mathematical model of the CubeSat obtained from the thermal balance test. Soo-Jin Kang and Hyun-Ung Oh Copyright © 2016 Soo-Jin Kang and Hyun-Ung Oh. All rights reserved. Sandwich Structured Composites for Aeronautics: Methods of Manufacturing Affecting Some Mechanical Properties Mon, 06 Jun 2016 09:34:04 +0000 Sandwich panels are composites which consist of two thin laminate outer skins and lightweight (e.g., honeycomb) thick core structure. Owing to the core structure, such composites are distinguished by stiffness. Despite the thickness of the core, sandwich composites are light and have a relatively high flexural strength. These composites have a spatial structure, which affects good thermal insulator properties. Sandwich panels are used in aeronautics, road vehicles, ships, and civil engineering. The mechanical properties of these composites are directly dependent on the properties of sandwich components and method of manufacturing. The paper presents some aspects of technology and its influence on mechanical properties of sandwich structure polymer composites. The sandwiches described in the paper were made by three different methods: hand lay-up, press method, and autoclave use. The samples of sandwiches were tested for failure caused by impact load. Sandwiches prepared in the same way were used for structural analysis of adhesive layer between panels and core. The results of research showed that the method of manufacturing, more precisely the pressure while forming sandwich panels, influences some mechanical properties of sandwich structured polymer composites such as flexural strength, impact strength, and compressive strength. Aneta Krzyżak, Michał Mazur, Mateusz Gajewski, Kazimierz Drozd, Andrzej Komorek, and Paweł Przybyłek Copyright © 2016 Aneta Krzyżak et al. All rights reserved. An Online Multisensor Data Fusion Framework for Radar Emitter Classification Mon, 30 May 2016 12:02:42 +0000 Radar emitter classification is a special application of data clustering for classifying unknown radar emitters in airborne electronic support system. In this paper, a novel online multisensor data fusion framework is proposed for radar emitter classification under the background of network centric warfare. The framework is composed of local processing and multisensor fusion processing, from which the rough and precise classification results are obtained, respectively. What is more, the proposed algorithm does not need prior knowledge and training process; it can dynamically update the number of the clusters and the cluster centers when new pulses arrive. At last, the experimental results show that the proposed framework is an efficacious way to solve radar emitter classification problem in networked warfare. Dongqing Zhou, Xing Wang, Siyi Cheng, and Xi Zhang Copyright © 2016 Dongqing Zhou et al. All rights reserved. Transport Aircraft Conceptual Design Optimization Using Real Coded Genetic Algorithm Wed, 25 May 2016 09:52:09 +0000 Due to soaring oil prices, increased air traffic and competition among air transport companies, and environmental concerns, aircraft maximum takeoff weight (MTOW) is becoming a critical aspect, of air transport industry. It is very important to estimate the MTOW of the aircraft in order to determine its performance. However, estimating the weight of an aircraft is not a simple task. The purpose of this paper is to present a simplified method to optimize the aircraft MTOW using a genetic algorithm approach. For the optimization of MTOW of transport aircraft, a MATLAB program consisting of genetic algorithm techniques with appropriate genetic algorithm parameters setting was developed. The objective function for the optimization was a minimization of MTOW. The use of genetic real coded algorithm (GA) as an optimization tool for an aircraft can help to reduce the number of qualitative decisions. Also, using GA approach, the time and the cost of conceptual design can considerably be reduced. The model is applicable to the air transport industry. The proposed model has been validated against the known configuration of an aircraft. Vedant Singh, Somesh K. Sharma, and S. Vaibhav Copyright © 2016 Vedant Singh et al. All rights reserved. Preliminary Design of a Small Unmanned Battery Powered Tailsitter Mon, 23 May 2016 08:54:48 +0000 This paper presents a preliminary design methodology for small unmanned battery powered tailsitters. Subsystem models, including takeoff weight, power and energy consumption models, and battery discharge model, were investigated, respectively. Feasible design space was given by simulation with mission and weight constraints, while the influences of wing loading and battery ratio were analyzed. Case study was carried out according to the design process, and the results were validated by previous designs. The design methodology can be used to determine key parameters and make necessary preparations for detailed design and vehicle realization of small battery powered tailsitters. Bo Wang, Zhongxi Hou, Zhaowei Liu, Qingyang Chen, and Xiongfeng Zhu Copyright © 2016 Bo Wang et al. All rights reserved. Fluid-Structure Interaction Analysis of Parachute Finite Mass Inflation Thu, 19 May 2016 06:31:43 +0000 Parachute inflation is coupled with sophisticated fluid-structure interaction (FSI) and flight mechanic behaviors in a finite mass situation. During opening, the canopy often experiences the largest deformation and loading. To predict the opening phase of a parachute, a computational FSI model for the inflation of a parachute, with slots on its canopy fabric, is developed using the arbitrary Lagrangian-Euler coupling penalty method. In a finite mass situation, the fluid around the parachute typically has an unsteady flow; therefore, a more complex opening phase and FSI dynamics of a parachute are investigated. Navier-Stokes (N-S) equations for uncompressible flow are solved using an explicit central difference method. The three-dimensional visualization of canopy deformation as well as the evolution of dropping velocity and overload is obtained and compared with the experimental results. This technique could be further applied in the airdrop test of a parachute for true prediction of the inflation characteristics. Xinglong Gao, Qingbin Zhang, and Qiangang Tang Copyright © 2016 Xinglong Gao et al. All rights reserved. Flow Characteristics Study of Wind Turbine Blade with Vortex Generators Thu, 12 May 2016 13:29:05 +0000 The blade root flow control is of particular importance to the aerodynamic characteristic of large wind turbines. The paper studies the feasibility of improving blade pneumatic power by applying vortex generators (VGs) to large variable propeller shaft horizontal axis wind turbines, with 2 MW variable propeller shaft horizontal axis wind turbine blades as research object. In the paper, three cases of VGs installation are designed; they are scattered in different chordwise position at the blade root, and then they are calculated, respectively, with CFD method. The results show that VGs installed in the separation line upstream, with the separation line of the blade root as a benchmark, show a better effect. Pneumatic power of blades increases by 0.6% by installing VGs. Although the effect on large wind turbines is not obvious, there is a space for optimization. Hao Hu, Xin-kai Li, and Bo Gu Copyright © 2016 Hao Hu et al. All rights reserved. Inverse Optimal Attitude Stabilization of Flexible Spacecraft with Actuator Saturation Tue, 26 Apr 2016 11:51:16 +0000 This paper presents a new robust inverse optimal control strategy for flexible spacecraft attitude maneuvers in the presence of external disturbances and actuator constraint. A new constrained attitude controller for flexible spacecraft is designed based on the Sontag-type formula and a control Lyapunov function. This control law optimizes a meaningful cost functional and the stability of the resulting closed-loop system is ensured by the Lyapunov framework. A sliding mode disturbance observer is used to compensate unknown bounded external disturbances. The ultimate boundedness of estimation error dynamics is guaranteed via a rigorous Lyapunov analysis. Simulation results are provided to demonstrate the performance of the proposed control law. Chutiphon Pukdeboon Copyright © 2016 Chutiphon Pukdeboon. All rights reserved. Receptivity of Boundary Layer over a Blunt Wedge due to Freestream Pulse Disturbances at Mach 6 Thu, 14 Apr 2016 07:48:23 +0000 Direct numerical simulation (DNS) of a hypersonic compressible flow over a blunt wedge with fast acoustic disturbances in freestream is performed. The receptivity characteristics of boundary layer to freestream pulse acoustic disturbances are numerically investigated at Mach 6, and the frequency effects of freestream pulse wave on boundary layer receptivity are discussed. Results show that there are several main disturbance mode clusters in boundary layer under acoustic pulse wave, and the number of main disturbance clusters decreases along the streamwise. As disturbance wave propagates from upstream to downstream direction, the component of the modes below fundamental frequency decreases, and the component of the modes above second harmonic components increases quickly in general. There are competition and disturbance energy transfer between different boundary layer modes. The nose boundary layer is dominated by the nearby mode of fundamental frequency. The number of the main disturbance mode clusters decreases as the freestream disturbance frequency increases. The frequency range with larger growth narrows along the streamwise. In general, the amplitudes of both fundamental mode and harmonics become larger with the decreasing of freestream disturbance frequency. High frequency freestream disturbance accelerates the decay of disturbance wave in downstream boundary layer. Jianqiang Shi, Xiaojun Tang, Zhenqing Wang, Mingfang Shi, and Wei Zhao Copyright © 2016 Jianqiang Shi et al. All rights reserved. Monte Carlo Uncertainty Quantification Using Quasi-1D SRM Ballistic Model Mon, 11 Apr 2016 16:03:13 +0000 Compactness, reliability, readiness, and construction simplicity of solid rocket motors make them very appealing for commercial launcher missions and embarked systems. Solid propulsion grants high thrust-to-weight ratio, high volumetric specific impulse, and a Technology Readiness Level of 9. However, solid rocket systems are missing any throttling capability at run-time, since pressure-time evolution is defined at the design phase. This lack of mission flexibility makes their missions sensitive to deviations of performance from nominal behavior. For this reason, the reliability of predictions and reproducibility of performances represent a primary goal in this field. This paper presents an analysis of SRM performance uncertainties throughout the implementation of a quasi-1D numerical model of motor internal ballistics based on Shapiro’s equations. The code is coupled with a Monte Carlo algorithm to evaluate statistics and propagation of some peculiar uncertainties from design data to rocker performance parameters. The model has been set for the reproduction of a small-scale rocket motor, discussing a set of parametric investigations on uncertainty propagation across the ballistic model. Davide Viganò, Adriano Annovazzi, and Filippo Maggi Copyright © 2016 Davide Viganò et al. All rights reserved. Study on Impedance Characteristics of Aircraft Cables Tue, 05 Apr 2016 14:05:49 +0000 Voltage decrease and power loss in distribution lines of aircraft electric power system are harmful to the normal operation of electrical equipment and may even threaten the safety of aircraft. This study investigates how the gap distance (the distance between aircraft cables and aircraft skin) and voltage frequency (variable frequency power supply will be adopted for next generation aircraft) will affect the impedance of aircraft cables. To be more precise, the forming mechanism of cable resistance and inductance is illustrated in detail and their changing trends with frequency and gap distance are analyzed with the help of electromagnetic theoretical analysis. An aircraft cable simulation model is built with Maxwell 2D and the simulation results are consistent with the conclusions drawn from the theoretical analysis. The changing trends of the four core parameters of interest are analyzed: resistance, inductance, reactance, and impedance. The research results can be used as reference for the applications in Variable Speed Variable Frequency (VSVF) aircraft electric power system. Weilin Li, Wenjie Liu, Xiaobin Zhang, Zhaohui Gao, Meng Xie, and Hongxia Wang Copyright © 2016 Weilin Li et al. All rights reserved. Adaptive Flutter Suppression for a Fighter Wing via Recurrent Neural Networks over a Wide Transonic Range Tue, 05 Apr 2016 11:44:36 +0000 The paper presents a digital adaptive controller of recurrent neural networks for the active flutter suppression of a wing structure over a wide transonic range. The basic idea behind the controller is as follows. At first, the parameters of recurrent neural networks, such as the number of neurons and the learning rate, are initially determined so as to suppress the flutter under a specific flight condition in the transonic regime. Then, the controller automatically adjusts itself for a new flight condition by updating the synaptic weights of networks online via the real-time recurrent learning algorithm. Hence, the controller is able to suppress the aeroelastic instability of the wing structure over a range of flight conditions in the transonic regime. To demonstrate the effectiveness and robustness of the controller, the aeroservoelastic model of a typical fighter wing with a tip missile was established and a single-input/single-output controller was synthesized. Numerical simulations of the open/closed-loop aeroservoelastic simulations were made to demonstrate the efficacy of the adaptive controller with respect to the change of flight parameters in the transonic regime. Haojie Liu, Yonghui Zhao, and Haiyan Hu Copyright © 2016 Haojie Liu et al. All rights reserved. Integrated Power and Attitude Control Design of Satellites Based on a Fuzzy Adaptive Disturbance Observer Using Variable-Speed Control Moment Gyros Wed, 23 Mar 2016 08:29:13 +0000 To satisfy the requirements for small satellites that seek agile slewing with peak power, this paper investigates integrated power and attitude control using variable-speed control moment gyros (VSCMGs) that consider the mass and inertia of gimbals and wheels. The paper also details the process for developing the controller by considering various environments in which the controller may be implemented. A fuzzy adaptive disturbance observer (FADO) is proposed to estimate and compensate for the effects of equivalent disturbances. The algorithms can simultaneously track attitude and power. The simulation results illustrate the effectiveness of the control approach, which exhibits an improvement of 80 percent compared with alternate approaches that do not employ a FADO. Zhongyi Chu and Jing Cui Copyright © 2016 Zhongyi Chu and Jing Cui. All rights reserved. A Simplified Mobile Ad Hoc Network Structure for Helicopter Communication Tue, 08 Mar 2016 09:42:48 +0000 There are a number of volunteer and statutory organizations who are capable of conducting an emergency response using helicopters. Rescue operations require a rapidly deployable high bandwidth network to coordinate necessary relief efforts between rescue teams on the ground and helicopters. Due to massive destruction and loss of services, ordinary communication infrastructures may collapse in these situations. Consequently, information exchange becomes one of the major challenges in these circumstances. Helicopters can be also employed for providing many services in rugged environments, military applications, and aerial photography. Ad hoc network can be used to provide alternative communication link between a set of helicopters, particularly in case of significant amount of data required to be shared. This paper addresses the ability of using ad hoc networks to support the communication between a set of helicopters. A simplified network structure model is presented and extensively discussed. Furthermore, a streamlined routing algorithm is proposed. Comprehensive simulations are conducted to evaluate the proposed routing algorithm. Abdeldime Mohamed Salih Abdelgader, Lenan Wu, and Mohammed Mohsen Mohammed Nasr Copyright © 2016 Abdeldime Mohamed Salih Abdelgader et al. All rights reserved. Time-Varying Biased Proportional Guidance with Seeker’s Field-of-View Limit Tue, 01 Mar 2016 09:28:07 +0000 Traditional guidance laws with range-to-go information or time-to-go estimation may not be implemented in passive homing missiles since passive seekers cannot measure relative range directly. A time-varying biased proportional guidance law, which only uses line-of-sight (LOS) rate and look angle information, is proposed to satisfy both impact angle constraint and seeker’s field-of-view (FOV) limit. In the proposed guidance law, two time-varying bias terms are applied to divide the trajectory into initial phase and terminal phase. The initial bias is designed as a function of LOS rate and look angle to maintain the seeker’s lock-on while the final bias eliminates the deviation between the integral value of angle control bias and the expected bias amount. A switching logic is adopted to change the biases continuously so that there is no abrupt acceleration change during the engagement. Extensive simulations considering both kinematic and realistic missile models are performed to illustrate the efficiency of the proposed method. Zhe Yang, Hui Wang, and Defu Lin Copyright © 2016 Zhe Yang et al. All rights reserved. Online Adaptive Error Compensation SVM-Based Sliding Mode Control of an Unmanned Aerial Vehicle Thu, 25 Feb 2016 16:50:40 +0000 Unmanned Aerial Vehicle (UAV) is a nonlinear dynamic system with uncertainties and noises. Therefore, an appropriate control system has an obligation to ensure the stabilization and navigation of UAV. This paper mainly discusses the control problem of quad-rotor UAV system, which is influenced by unknown parameters and noises. Besides, a sliding mode control based on online adaptive error compensation support vector machine (SVM) is proposed for stabilizing quad-rotor UAV system. Sliding mode controller is established through analyzing quad-rotor dynamics model in which the unknown parameters are computed by offline SVM. During this process, the online adaptive error compensation SVM method is applied in this paper. As modeling errors and noises both exist in the process of flight, the offline SVM one-time mode cannot predict the uncertainties and noises accurately. The control law is adjusted in real-time by introducing new training sample data to online adaptive SVM in the control process, so that the stability and robustness of flight are ensured. It can be demonstrated through the simulation experiments that the UAV that joined online adaptive SVM can track the changing path faster according to its dynamic model. Consequently, the proposed method that is proved has the better control effect in the UAV system. Kaijia Xue, Congqing Wang, Zhiyu Li, and Hanxin Chen Copyright © 2016 Kaijia Xue et al. All rights reserved. A Fault-Tolerant Multiple Sensor Fusion Approach Applied to UAV Attitude Estimation Wed, 24 Feb 2016 13:32:40 +0000 A novel sensor fusion design framework is presented with the objective of improving the overall multisensor measurement system performance and achieving graceful degradation following individual sensor failures. The Unscented Information Filter (UIF) is used to provide a useful tool for combining information from multiple sources. A two-step off-line and on-line calibration procedure refines sensor error models and improves the measurement performance. A Fault Detection and Identification (FDI) scheme crosschecks sensor measurements and simultaneously monitors sensor biases. Low-quality or faulty sensor readings are then rejected from the final sensor fusion process. The attitude estimation problem is used as a case study for the multiple sensor fusion algorithm design, with information provided by a set of low-cost rate gyroscopes, accelerometers, magnetometers, and a single-frequency GPS receiver’s position and velocity solution. Flight data collected with an Unmanned Aerial Vehicle (UAV) research test bed verifies the sensor fusion, adaptation, and fault-tolerance capabilities of the designed sensor fusion algorithm. Yu Gu, Jason N. Gross, Matthew B. Rhudy, and Kyle Lassak Copyright © 2016 Yu Gu et al. All rights reserved. Unmanned Aerial Vehicles for Photogrammetry: Analysis of Orthophoto Images over the Territory of Lithuania Mon, 22 Feb 2016 10:08:41 +0000 It has been recently observed that aircrafts tend to be replaced by light, simple structure unmanned aerial vehicles (UAV) or mini unmanned aerial vehicles (MUAV) with the purpose of updating the field of aerial photogrammetry. The built-in digital photo camera takes images of the Earth’s surface. To satisfy the photogrammetric requirements of the photographic images, it is necessary to carry out the terrestrial project planning of the flight path before the flight, to select the appropriate flying height, the time for acquiring images, the speed of the UAV, and other parameters. The paper presents the results of project calculations concerning the UAV flights and the analysis of the terrestrial images acquired during the field-testing flights. The experience carried out so far in the Lithuanian landscape is shown. The taken images have been processed by PhotoMod photogrammetric system. The paper presents the results of calculation of the project values of the UAV flights taking the images by digital camera Canon S100 and the analysis of the possibilities of the UAV orthophoto images’ mode. J. Suziedelyte Visockiene, R. Puziene, A. Stanionis, and E. Tumeliene Copyright © 2016 J. Suziedelyte Visockiene et al. All rights reserved. Modeling of Particle Trajectory and Erosion of Large Rotor Blades Sun, 21 Feb 2016 12:19:39 +0000 When operating in hostile environments, engines components are facing a serious problem of erosion, leading to a drastic drop in aerodynamic performance and life-cycle. This paper outlines the modeling and simulation of particle trajectory and erosion induced by sand particles. The governing equations of particle dynamics through the moving of large rotor blades are introduced and solved separately from the flow field by using our in-house particle tracking code based on the finite element method. As the locations of impacts are predicted, the erosion is assessed by semiempirical correlations in terms of impact conditions and particle and target surface characteristics. The results of these computations carried out for different concentrations of suspended dust (sand) cloud generated at takeoff conditions reveal the main areas of impacts with high rates of erosion seen over a large strip from the blade suction side, around the leading edge and the pressure side of blade. The assessment of the blade geometry deterioration reveals that the upper corner of blade suffers from an intense erosion wear. Adel Ghenaiet Copyright © 2016 Adel Ghenaiet. All rights reserved. Trajectory Optimization for Velocity Jumps Reduction considering the Unexpectedness Characteristics of Space Manipulator Joint-Locked Failure Sun, 21 Feb 2016 10:07:21 +0000 Aiming at reducing joint velocity jumps caused by an unexpected joint-locked failure during space manipulator on-orbit operations without shutting down manipulator, trajectory optimization strategy considering the unexpectedness characteristics of joint-locked failure is proposed in the paper, which can achieve velocity jumps reduction in both operation space and joint space simultaneously. In the strategy, velocity in operation space concerning task completion directly is treated as equality constraints, and velocity in joint space concerning motion performance is treated as objective function. Global compensation vector which consists of coefficient, gradient of manipulability, and orthogonal matrix of null space is constructed to minimize the objective function. For each particular failure time, unique optimal coefficient can be obtained when the objective function is minimal. As a basis, a method for optimal coefficient function fitting is proposed based on a priori failure information (possible failure time and the corresponding optimal coefficient) to guarantee the unexpectedness characteristics of joint-locked failure. Simulations are implemented to validate the efficiency of trajectory optimization strategy in reducing velocity jumps in both joint space and operation space. And the feasibility of coefficient function is also verified in reducing velocity jump no matter when joint-locked failure occurs. Qingxuan Jia, Tong Li, Gang Chen, Hanxu Sun, and Jian Zhang Copyright © 2016 Qingxuan Jia et al. All rights reserved. Evaluation of the Mechanical Properties of Microcapsule-Based Self-Healing Composites Tue, 16 Feb 2016 12:55:46 +0000 Self-healing materials are beginning to be considered for applications in the field of structural materials. For this reason, in addition to self-healing efficiency, also mechanical properties such as tensile and compressive properties are beginning to become more and more important for this kind of materials. In this paper, three different systems based on epoxy-resins/ethylidene-norbornene (ENB)/Hoveyda-Grubbs 1st-generation (HG1) catalyst are investigated in terms of mechanical properties and healing efficiency. The experimental results show that the mechanical properties of the self-healing systems are mainly determined by the chemical nature of the epoxy matrix. In particular, the replacement of a conventional flexibilizer (Heloxy 71) with a reactive diluent (1,4-butanediol diglycidyl ether) allows obtaining self-healing materials with better mechanical properties and higher thermal stability. An increase in the curing temperature causes an increase in the elastic modulus and a slight reduction of the healing efficiency. These results can constitute the basis to design systems with high regenerative ability and appropriate mechanical performance. Liberata Guadagno, Marialuigia Raimondo, Umberto Vietri, Carlo Naddeo, Anja Stojanovic, Andrea Sorrentino, and Wolfgang H. Binder Copyright © 2016 Liberata Guadagno et al. All rights reserved. Precise Orbit Determination of BDS MEO Satellites Based on Satellite TT&C Stations Mon, 15 Feb 2016 09:59:25 +0000 A novel method, which is based on the triple-frequency combination and Space-Based Telemetry, Tracking, and Command (STT&C) stations, is proposed in this paper. Considering BeiDou Navigation Satellite System (BDS) Geostationary Orbit (GEO) and Inclined Geostationary Orbit (IGSO) satellites as the STT&C facilities, firstly, we presented the BDS Medium Earth Orbit (MEO) satellites’ precise orbit determination scheme based on triple-frequency combination. Then, we gave the sufficient and necessary conditions about the visibility and the coverage rate calculation model of STT&C to BDS MEO satellite. And then we deduced the model of BDS MEO satellites precise orbit determination based on triple-frequency combination observations. At last, we designed the simulation calculation. The simulation results show that orbit determination of BDS MEO satellite based on STT&C station can be realized at all times. And most of the simulation period time, under the condition of the dm level orbit determination for GEO/IGSO satellites, the position accuracy of the relative orbit determination is better than 4 m, the horizontal accuracy of the relative orbit determination is within 2.5 m, and the vertical accuracy of the relative orbit determination is less than 3.5 m. Kezhao Li, Zhiwei Li, Lin Chai, An-min Ding, Jin-ben Wei, and Long Li Copyright © 2016 Kezhao Li et al. All rights reserved. Effects of Duct Cross Section Camber and Thickness on the Performance of Ducted Propulsion Systems for Aeronautical Applications Tue, 09 Feb 2016 14:20:19 +0000 The axisymmetric flow field around a ducted rotor is thoroughly analysed by means of a nonlinear and semi-analytical model which is able to deal with some crucial aspects of shrouded systems like the interaction between the rotor and the duct, and the slipstream contraction and rotation. Not disregarding the more advanced CFD based methods, the proposed procedure is characterised by a very low computational cost that makes it very appealing as analysis tool in the preliminary steps of a design procedure of hierarchical type. The work focuses on the analysis of the effects of the camber and thickness of the duct cross section onto the performance of the device. It has been found that an augmentation of both camber and thickness of the duct leads to an increase of the propulsive ideal efficiency. Rodolfo Bontempo and Marcello Manna Copyright © 2016 Rodolfo Bontempo and Marcello Manna. All rights reserved. Aero Engine Fault Diagnosis Using an Optimized Extreme Learning Machine Tue, 26 Jan 2016 13:20:06 +0000 A new extreme learning machine optimized by quantum-behaved particle swarm optimization (QPSO) is developed in this paper. It uses QPSO to select optimal network parameters including the number of hidden layer neurons according to both the root mean square error on validation data set and the norm of output weights. The proposed Q-ELM was applied to real-world classification applications and a gas turbine fan engine diagnostic problem and was compared with two other optimized ELM methods and original ELM, SVM, and BP method. Results show that the proposed Q-ELM is a more reliable and suitable method than conventional neural network and other ELM methods for the defect diagnosis of the gas turbine engine. Xinyi Yang, Shan Pang, Wei Shen, Xuesen Lin, Keyi Jiang, and Yonghua Wang Copyright © 2016 Xinyi Yang et al. All rights reserved. Triangle Interception Scenario: A Finite-Time Guidance Approach Sun, 24 Jan 2016 14:16:19 +0000 Considering an aircraft threatened by an interceptor, one of the effective penetration strategies is to release a Defender from the aircraft to confront the interceptor. In this case, the aircraft, the Defender, and the interceptor constitute the three-body guidance relationship, and the cooperation of the aircraft and its Defender to achieve the best tactical effects turns into a concerned problem. This paper studies the triangle interception guidance problem via the finite-time theory. The paper presents linear system Input-Output Finite-Time Stabilization (IO-FTS) method. The sufficient conditions of the linear system, being IO-FTS, under Finite-Time Boundedness (FTB) constraint are proposed, by which the state feedback controllers design method is obtained, via Linear Matrix Inequalities (LMIs). The triangle interception guidance problems are studied in three different cases, where the proposed methods are applied to the guidance design. The simulation results illustrate the effectiveness of the proposed methods. Yang Guo, Xiaoxiang Hu, Fenghua He, Hongjie Cheng, and Qinhe Gao Copyright © 2016 Yang Guo et al. All rights reserved.