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Defence Technology（防务技术） 2024年第2期32卷 1-22页

作者： Zengliang Han Mou Chen Haojie Zhu Qingxian Wu school of Automation engineering Nanjing University of Aeronautics and AstronauticsNanjing 211106China

Unmanned autonomous helicopter(UAH)path planning problem is an important component of the UAH mission planning system.Aiming to reduce the influence of non-complete ground threat information on UAH path planning,a ground threat prediction-based path planning method is proposed based on artificial bee colony(ABC)algorithm by collaborative thinking strategy.Firstly,a dynamic threat distribution probability model is developed based on the characteristics of typical ground threats.The dynamic no-fly zone of the UAH is simulated and established by calculating the distribution probability of ground threats in real time.Then,a dynamic path planning method for UAH is designed in complex environment based on the real-time prediction of ground threats.By adding the collision warning mechanism to the path planning model,the flight path could be dynamically adjusted according to changing no-fly zones.Furthermore,a hybrid enhanced ABC algorithm is proposed based on collaborative thinking strategy.The proposed algorithm applies the leader-member thinking mechanism to guide the direction of population evolution,and reduces the negative impact of local optimal solutions caused by collaborative learning update strategy,which makes the optimization performance of ABC algorithm more controllable and efficient.Finally,simulation results verify the feasibility and effectiveness of the proposed ground threat prediction path planning method.

关键词： UAH Path planning Ground threat prediction Hybrid enhanced Collaborative thinking

An Aerial–Wall Robotic Insect That Can Land, Climb, and Take Off from Vertical Surfaces

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Research 2024年第1期2023卷 149-163页

作者： Qian Li Haoze Li Huan Shen Yangguang Yu Haoran He Xincheng Feng Yi Sun Zhiyuan Mao Guangming Chen Zongjun Tian Lida Shen Xiangming Zheng Aihong Ji College of Mechanical and Electrical engineering Nanjing University of Aeronautics and AstronauticsNanjingChina College of Aerospace engineering Nanjing University of Aeronautics and AstronauticsNanjingChina State Key Laboratory of Mechanics and Control for Aerospace Structures Nanjing University of Aeronautics and AstronauticsNanjingChina

Insects that can perform flapping-wing flight,climb on a wall,and switch smoothly between the 2 locomotion regimes provide us with excellent biomimetic models.However,very few biomimetic robots can perform complex locomotion tasks that combine the 2 abilities of climbing and flying.Here,we describe an aerial–wall amphibious robot that is self-contained for flying and climbing,and that can seamlessly move between the air and wall.It adopts a flapping/rotor hybrid power layout,which realizes not only efficient and controllable flight in the air but also attachment to,and climbing on,the vertical wall through a synergistic combination of the aerodynamic negative pressure adsorption of the rotor power and a climbing mechanism with bionic adhesion performance.On the basis of the attachment mechanism of insect foot pads,the prepared biomimetic adhesive materials of the robot can be applied to various types of wall surfaces to achieve stable climbing.The longitudinal axis layout design of the rotor dynamics and control strategy realize a unique cross-domain movement during the flying–climbing transition,which has important implications in understanding the takeoff and landing of insects.Moreover,it enables the robot to cross the air–wall boundary in 0.4 s(landing),and cross the wall–air boundary in 0.7 s(taking off).The aerial–wall amphibious robot expands the working space of traditional flying and climbing robots,which can pave the way for future robots that can perform autonomous visual monitoring,human search and rescue,and tracking tasks in complex air–wall environments.

关键词： robot smoothly Vertical

Image-Based Flow Prediction of Vocal Folds Using 3D Convolutional Neural Networks

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Journal of Bionic engineering 2024年第2期21卷 991-1002页

作者： Yang Zhang Tianmei Pu Jiasen Xu Chunhua Zhou College of astronautics Nanjing University of Aeronautics and AstronauticsNanjing210016China College of Electrical Energy and Power EngineeringYangzhou UniversityYangzhou225127China College of aeronautics Nanjing University of Aeronautics and AstronauticsNanjing210016China

In this work,a three dimensional(3D)convolutional neural network(CNN)model based on image slices of various normal and pathological vocal folds is proposed for accurate and efficient prediction of glottal flows.The 3D CNN model is composed of the feature extraction block and regression block.The feature extraction block is capable of learning low dimensional features from the high dimensional image data of the glottal shape,and the regression block is employed to flatten the output from the feature extraction block and obtain the desired glottal flow data.The input image data is the condensed set of 2D image slices captured in the axial plane of the 3D vocal folds,where these glottal shapes are synthesized based on the equations of normal vibration modes.The output flow data is the corresponding flow rate,averaged glottal pressure and nodal pressure distributions over the glottal surface.The 3D CNN model is built to establish the mapping between the input image data and output flow data.The ground-truth flow variables of each glottal shape in the training and test datasets are obtained by a high-fidelity sharp-interface immersed-boundary solver.The proposed model is trained to predict the concerned flow variables for glottal shapes in the test set.The present 3D CNN model is more efficient than traditional Computational Fluid Dynamics(CFD)models while the accuracy can still be retained,and more powerful than previous data-driven prediction models because more details of the glottal flow can be provided.The prediction performance of the trained 3D CNN model in accuracy and efficiency indicates that this model could be promising for future clinical applications.

关键词： Vocal folds Computational fluid dynamics Machine learning 3D convolutional neural network

Deflagration and detonation induced by shock wave focusing at different Mach numbers

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Chinese Journal of aeronautics 2024年第2期37卷 249-258页

作者： Zezhong YANG Jun CHENG Bo ZHANG school of aeronautics and astronautics Shanghai Jiao Tong UniversityShanghai 200240China

Shock wave focusing is an effective way to create a hot spot or a high-pressure and hightemperature region at a certain place,showing its unique usage in detonation initiation,which is beneficial for the development of detonation-based engines.The flame propagation behavior after the autoignition induced by shock wave focusing is crucial to the formation and self-sustaining of the detonation wave.In this study,wedge reflectors with two different angles(60°and 90°)and a planar reflector are employed,and the Mach number of incident shock waves ranging from 2.0 to 2.8 is utilized to trigger different flame propagation modes.Dynamic pressure transducers and the high-speed schlieren imaging system are both employed to investigate the shock-shock collision and ignition procedure.The results reveal a total of four flame propagation modes:deflagration,DDT(Deflagration-to-Detonation Transition),unsteady detonation,and direct detonation.The detonation wave formed in the DDT and unsteady detonation mode is only approximately 75%-85%of the Chapman-Jouguet(C-J)speed;meanwhile,the directly induced detonation wave speed is close to the C-J speed.Transverse waves,which are strong evidence for the existence of detonation waves,are discovered in experiments.The usage of wedge reflectors significantly reduces the initial pressure difference ratio needed for direct detonation ignition.We also provide a practical method for differentiating between detonation and deflagration modes,which involves contrasting the speed of the reflected shock wave with the speed of the theoretically nonreactive reflected shock wave.These findings should serve as a reference for the detonation initiation technique in advanced detonation propulsion engines.

关键词： Deflagration Detonation Hydrogen Ignition Shock wave focusing

Flat jet electrochemical milling of TC4 alloy with tailoring backward parallel flow

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Chinese Journal of aeronautics 2024年第4期37卷 574-592页

作者： Huanghai KONG Ningsong QU College of Mechanical and Electrical engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

In flat jet electrochemical milling, the electrolyte forms a backward parallel flow after impacting the workpiece, resulting in a weak current density distribution on the workpiece. Poor surface quality usually occurs on the machined titanium alloy surface because it inevitably suffers from the weak current density. In this study, a method of flat jet electrochemical milling with tailoring the backward parallel flow was proposed to eliminate the negative effects caused by the weak current density. Multiphysics simulations are carried out to comprehend the mechanism of flat jetEC milling with tailoring backward parallel flow and better construct the novel tool electrode.Experiments on flat jet electrochemical milling of TC4 alloy with and without tailoring backward parallel flow are conducted. The results reveal that, compared with flat jet electrochemical milling without tailoring backward parallel flow, the recommended tool reduces the surface roughness by86% to 93%, and improves the material removal rate by 93% to 163% with different feed rates.Additionally, the recommended tool is more conducive to maintaining the inherent hardness of the material. Finally, a surface with low Sa of 0.37 μm is obtained.

关键词： Flat jet electrochemical milling TC4 alloy Surface roughness Micro-hardness Material removal rate

Design method and experimental study of a cathode tool with an extremely high leveling ratio for electrochemical machining of blisk

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Chinese Journal of aeronautics 2024年第4期37卷 593-608页

作者： Moqi SHEN Jia LIU Jingtao WANG Di ZHU College of Mechanical and Electrical engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

To obtain final parts with the desired dimensional accuracy and repeatability via electrochemical machining(ECM), the machining process must enter an ECM balanced state. However,for the ECM processing of blisk, a key component of aerospace engines, the surface of the blade blank often has an uneven allowance distribution due to the narrow passage of the cascade. It is difficult to remedy this issue in subsequent processing steps, which is necessary to ensure the dimensional accuracy and repeatability of the final blade profile. To solve this problem, electrolytic machining must be preceded by electrolytic shaping, which requires cathode tools with large leveling ratios to quickly homogenize the blank surface of the blade. In this study, to obtain a cathode tool with an extremely high leveling ratio, a design method based on the variation in the electrode gap in the non-equilibrium electrolytic state is proposed, and a dissolution model based on the nonequilibrium state is established. In this design method, the allowance on the blank to be machined is first divided into many discrete allowances with the normal direction. The initial machining clearance, feed rate, and total machining time are then calculated using classical ECM equilibrium state theory based on the maximum allowance. Meanwhile, the point coordinates of the cathode tool at maximum allowance can be determined. The non-equilibrium model can then be used to calculate the relative coordinate positions corresponding to the remaining discrete allowances. Finally, the entire cathode tool profile is designed. Simulations, fundamental experiments, and blisk unit workpiece experiments were carried out to validate the design approach. In the simulated processing of the plane workpiece, the leveling ratio of the cathode tool designed by the proposed method(0.77)was 83% higher than that of the cathode tool designed using the traditional method. The simulation results were confirmed by processing experiments. In the machining of blisk unit workpieces with compl

关键词： Electrochemical machining(ECM) Non-equilibrium machining Large leveling ratios Cathode design Finite element simulation Blisk

Comparison of electrochemical behaviors of Ti-5Al-2Sn-4Zr-4Mo-2Cr-1Fe and Ti-6Al-4V titanium alloys in NaNO_(3) solution

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International Journal of Minerals,Metallurgy and Materials 2024年第4期31卷 750-763页

作者： Jia Liu Shuanglu Duan Xiaokang Yue Ningsong Qu College of Mechanical and Electrical engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

The Ti-5Al-2Sn-4Zr-4Mo-2Cr-1Fe(β-CEZ)alloy is considered as a potential structural material in the aviation industry due to its outstanding strength and corrosion resistance.Electrochemical machining(ECM)is an efficient and low-cost technology for manufacturing theβ-CEZ alloy.In ECM,the machining parameter selection and tool design are based on the electrochemical dissolution behavior of the materials.In this study,the electrochemical dissolution behaviors of theβ-CEZ and Ti-6Al-4V(TC4)alloys in NaNO3solution are discussed.The open circuit potential(OCP),Tafel polarization,potentiodynamic polarization,electrochemical impedance spectroscopy(EIS),and current efficiency curves of theβ-CEZ and TC4 alloys are analyzed.The results show that,compared to the TC4 alloy,the passivation film structure is denser and the charge transfer resistance in the dissolution process is greater for theβ-CEZ alloy.Moreover,the dissolved surface morphology of the two titanium-based alloys under different current densities are analyzed.Under low current densities,theβ-CEZ alloy surface comprises dissolution pits and dissolved products,while the TC4 alloy surface comprises a porous honeycomb structure.Under high current densities,the surface waviness of both the alloys improves and the TC4 alloy surface is flatter and smoother than theβ-CEZ alloy surface.Finally,the electrochemical dissolution models ofβ-CEZ and TC4 alloys are proposed.

关键词： electrochemical machining dissolution behavior β-CEZ titanium alloy polarization curve current efficiency

Triad-displaced ULAs configuration for non-circular sources with larger continuous virtual aperture and enhanced degrees of freedom

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Journal of Systems engineering and Electronics 2024年第1期35卷 81-93页

作者： SHAIKH Abdul Hayee DANG Xiaoyu HUANG Daqing College of Electronic and Information engineering Nanjing University of Aeronautics and AstronauticsNanjing 211106China

Non-uniform linear array(NULA)configurations are well renowned due to their structural ability for providing increased degrees of freedom(DOF)and wider array aperture than uniform linear arrays(ULAs).These characteristics play a significant role in improving the direction-of-arrival(DOA)estimation accuracy.However,most of the existing NULA geometries are primarily applicable to circular sources(CSs),while they limitedly improve the DOF and continuous virtual aperture for noncircular sources(NCSs).Toward this purpose,we present a triaddisplaced ULAs(Tdis-ULAs)configuration for NCS.The TdisULAs structure generally consists of three ULAs,which are appropriately placed.The proposed antenna array approach fully exploits the non-circular characteristics of the sources.Given the same number of elements,the Tdis-ULAs design achieves more DOF and larger hole-free co-array aperture than its sparse array competitors.Advantageously,the number of uniform DOF,optimal distribution of elements among the ULAs,and precise element positions are uniquely determined by the closed-form expressions.Moreover,the proposed array also produces a filled resulting co-array.Numerical simulations are conducted to show the performance advantages of the proposed Tdis-ULAs configuration over its counterpart designs.

关键词： direction-of-arrival(DOA)estimation sparse array non-circular source(NCS) sum co-array difference co-array degrees of freedom(DOF)

A probabilistic model based on the peak-over-threshold approach for risk assessment of airport controllers’performance

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Journal of Safety Science and Resilience 2024年第1期5卷 110-118页

作者： Lili Zu Yijie Lu Min Dong College of Economics and Management Nanjing University of Aeronautics and AstronauticsNanjing 211106China school of engineering and Applied Science George Washington UniversityWashington DC 20052USA College of Civil Aviation Nanjing University of Aeronautics and AstronauticsNanjing 211106China

Airport tower control plays an instrumental role in ensuring airport safety.However,obtaining objective,quantitative safety evaluations is challenging due to the unavailability of pertinent human operation data.This study introduces a probabilistic model that combines aircraft dynamics and the peak-over-threshold(POT)approach to assess the safety performance of airport controllers.We applied the POT approach to model reaction times extracted from a radiotelephony dataset via a voice event detection algorithm.The model couples the risks of tower control and aircraft operation to analyze the influence of human factors.Using data from radiotele-phony communications and the Base of Aircraft Data(BADA)database,we compared risk levels across scenarios.Our findings revealed heightened airport control risks under low demand(0.374)compared to typical conditions(0.197).Furthermore,the risks associated with coupling under low demand exceeded those under typical de-mand,with the final approach stage presenting the highest risk(4.929×107).Our model underscores the significance of human factors and the implications of mental disconnects between pilots and controllers for safety risks.Collectively,these consistent findings affirm the reliability of our probabilistic model as an evaluative tool for evaluating the safety performance of airport tower controllers.The results also illuminate the path toward quantitative real-time safety evaluations for airport controllers within the industry.We recommend that airport regulators focus on the performance of airport controllers,particularly during the final approach stage.

关键词： Safety evaluation Performance Probabilistic model Task demand Airport controller

On the global smooth solutions of 3D incompressible Hall-MHD equations

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Applied Mathematics(A Journal of Chinese Universities) 2024年第2期39卷 319-327页

作者： YUE Gao-cheng SUN Wen-da school of Mathematics Nanjing University of Aeronautics and AstronauticsNanjing 211106China

The present paper is devoted to the well-posedness issue for the 3D incompressible Hall-MHD system obtained from kinetic models. Our analysis strongly relies on the use of the Fourier analysis. We establish the global existence of smooth solutions for a class of large initial data, this result implies the initial velocity and magnetic field can be arbitrarily large.

关键词： 3D Hall-MHD well-posedness Fourier analysis