查看更多>>摘要：Aiming at the problem that it is difficult to build model and identify the vulnerable equipment for aviation armament System-of-Systems(SoS)due to complex equipment interaction relationships and high confrontation,the interdependent network theory is introduced to solve it.Firstly,a two-layer heterogeneous interdependent network model for aviation armament SoS is proposed,which reflects the information interaction,functional dependency and inter-network dependence effectively.Secondly,using the attack cost to describe the confrontation process and taking the comprehensive impact on kill chains as the entry point,the node importance index and the attack cost measurement method are constructed.Thirdly,the identification of vulnerable nodes is transformed into the optimization problem of node combinatorial selection,and the vul-nerable node identification method based on tabu search is proposed.Based on vulnerable nodes,a robustness enhancement strategy for aviation armament SoS network is presented.Finally,the above methods are used to an aerial confrontation SoS,and the results verify the rationality and effectiveness of the proposed methods.
查看更多>>摘要：This work evaluates the viability of a cutting-edge flexible wing prototype actuated by Shape Memory Alloy(SMA)wire actuators.Such flexible wings have garnered significant interest for their potential to enhance aerodynamic efficiency by mitigating noise and delaying flow separa-tion.SMA actuators are particularly advantageous due to their superior power-to-weight ratio and adaptive response,making them increasingly favored in morphing aircraft applications.Our methodology begins with a detailed delineation of the fishbone camber morphing wing rib structure,followed by the construction of a multi-mode morphing wing segment through 3D-printed rib assembly.Comprehensive testing of the SMA wire actuators'actuation capacity and efficiency was conducted to establish their operational parameters.Subsequent experimental analyses focused on the bi-directional and reciprocating morphing performance of the fishbone wing rib,which incorporates SMA wires on the upper and lower sides.These experiments confirmed the segment's multi-mode morphing abilities.Aerodynamic assessments have demonstrated that our design sub-stantially improves the Lift-to-Drag ratio(L/D)when compared to conventional rigid wings.Finally,two phases of flight tests demonstrated the feasibility of SMA as an aircraft actuator and the validity of flexible wing structures to adjust the aircraft attitude,respectively.
Muhammad Aamir RAZATao SUOUzair Ahmed DARMuhammad ATIF...
388-403页
查看更多>>摘要：The flexural strength of glass is a critical design parameter for applications encountering impact loadings.However,the micro defects,specimen geometry,loading rate,and load transfor-mation from a quasi-dynamic to quasi-impulsive state may influence the measurement accuracy.Due to the stochastic and amorphous nature of the material,an accurate determination of the flex-ural strength remains a challenge.In this two-fold study,a coupled experimental-numerical strategy was devised to evaluate the dynamic flexural strength.In the first phase,three-point bending exper-iments were conducted on a novel"Electromagnetic Split Hopkinson Pressure Bar(ESHPB)".The incident stress signal and fracture time were recorded from experimental data,while the flexural strength was indirectly computed from a numerical algorithm.A quantitative comparison of the flexural strength with those in existing literature established the accuracy of the proposed method-ology.Results of the study indicate that the specimen response became independent of the support conditions under impulsive loading.That being said,the specimen behaved like it had an infinite span length,and the measured flexural strength remained the same whether the specimen was sup-ported or not.Besides,the specimen also maintained contact at the interfaces of the incident bar and fixture supports for the entire loading duration.In the second part of this study,the computed flexural strength was used to calibrate the existing JH-2 model.Numerical prediction of the damage propagation corroborated with that obtained from reprography images,though qualitatively.This work presents a precise and robust methodology to determine the dynamic flexural strength of brit-tle ceramics like Aluminosilicate glass over traditional experimental procedures to facilitate its adoption.
查看更多>>摘要：This paper presents a novel suspension support tailored for wind tunnel tests of spinning projectiles based on Wire-Driven Parallel Robot(WDPR),uniquely characterized by an SPM(Spinning Projectile Model)-centered mobile platform.First,an SPM-centered mobile platform,featuring two redundant and another unconstrained Degree of Freedom(DOF),and its suspension support mechanism are designed together,collectively constructing a WDPR endowed with kine-matic redundancy.Afterward,the kinematics of the mechanism,boundary equations for the redun-dant DOFs,and relevant kinematic performance indices are then proposed and formulated.The results from both prototype experiments and numerical assessments are presented.The capability of the support mechanism to replicate the complex coupled motions of the SPM is verified by the experimental results,while the proposed kinematics and boundary equations are also validated.Furthermore,it is revealed by numerical assessments that the redundant DOFs of the mobile plat-form exert a minimal impact on the kinematic performance of the suspension support.Finally,the optimal global attitude performance is obtained when these DOFs are set to zero if they are restricted to constants.However,local attitude performance can be further improved by the vari-able values.
查看更多>>摘要：Modular Unmanned Aerial Vehicles(UAVs)can adapt to rapidly changing payload requirements based on the shape and weight of the load by adding or subtracting units,reconfigur-ing,or changing the type of units.The existing research has addressed aerial docking and hover con-trol post-docking but fails to achieve coordinated flight following combination,leading to delayed response and oscillations as the number of UAV units increases.Moreover,the configuration of modular UAVs is complex and variable,making it challenging to adjust the controller parameters of each unit online.Therefore,this paper presents:(A)Adaptive attitude allocation method for dif-ferent combined UAV configurations:establishing a mapping relationship between constant con-troller parameters of the unit and the combination angular acceleration.The desired torque of the combination is allocated based on the size of the lever arm,enabling adaptive attitude control of the combination for varying configurations by controlling the attitude of the local unit;(B)A power allocation strategy based on a leader-wingman mode:employing a leader to control the entire combination,distributing the combination's force and torque to wingman units according to the mapping relationship of the attitude allocation method.This transforms the complex control of the combination into unit control in the leader-wingman mode.Compared to current average allocation methods,the step response of attitude angle improves by about 60％on average,and spatial trajectory tracking increases by an average of 11.5％.As the number of units grows,the response of the combination becomes similar to that of a single,independently flying UAV,resolv-ing the oscillation issue in combined flight.Additionally,this approach eliminates the need to change the controller parameters of all units,facilitating convenient reconfiguration and coordi-nated flight for modular UAVs post-combination.
查看更多>>摘要：Adverse weather during aircraft operation generates more complex scenarios for tactical trajectory planning,which requires superior real-time performance and conflict-free reliability of solving methods.Multi-aircraft real-time 4D trajectory planning under adverse weather is an essen-tial problem in Air Traffic Control(ATC)and it is challenging for the existing methods to be applied effectively.A framework of Double Deep Q-value Network under the Critic guidance with heuristic Pairing(DDQNC-P)is proposed to solve this problem.An Agent for two aircraft syner-getic trajectory planning is trained by the Deep Reinforcement Learning(DRL)model of DDQNC,which completes two aircraft 4D trajectory planning tasks preliminarily under dynamic weather conditions.Then a heuristic pairing algorithm is designed to convert the multi-aircraft synergetic trajectory planning into multi-time pairwise synergetic trajectory planning,making the multi-aircraft trajectory planning problem processable for the trained Agent.This framework compresses the input dimensions of the DRL model while improving its generalization ability significantly.Sub-stantial simulations with various aircraft numbers,weather conditions,and airspace structures were conducted for performance verification and comparison.The success rate of conflict-free trajectory resolution reached 96.56％with an average calculation time of 0.41 s for 350 4D trajectory points per aircraft,finally confirming its applicability to make real-time decision-making support for con-trollers in real-world ATC systems.
查看更多>>摘要：Within the context of ground-air cooperation,the distributed formation trajectory track-ing control problems for the Heterogeneous Multi-Agent Systems(HMASs)is studied.First,con-sidering external disturbances and model uncertainties,a graph theory-based formation control protocol is designed for the HMASs consisting of Unmanned Aerial Vehicles(UAVs)and Unmanned Ground Vehicles(UGVs).Subsequently,a formation trajectory tracking control strat-egy employing adaptive Fractional-Order Sliding Mode Control(FOSMC)method is developed,and a Feedback Multilayer Fuzzy Neural Network(FMFNN)is introduced to estimate the lumped uncertainties.This approach empowers HMASs to adaptively follow the expected trajectory and adopt the designated formation configuration,even in the presence of various uncertainties.Addi-tionally,an event-triggered mechanism is incorporated into the controller to reduce the update fre-quency of the controller and minimize the communication exchange among the agents,and the absence of Zeno behavior is rigorously demonstrated by an integral inequality analysis.Finally,to confirm the effectiveness of the proposed formation control protocol,some numerical simula-tions are presented.
查看更多>>摘要：The high-performance Basalt Fiber Reinforced Polymer(BFRP)composites have been prepared by guiding Micro/Nano Short Aramid Fiber(MNSAF)into the interlayer to improve the resin-rich region and the interfacial transition region,and the flexible fiber bridging claws of MNSAF were constructed to grasp the adjacent layers for stronger interlaminar bond.The low-velocity impact results show that the MNSAF could improve the impact resistance of BFRP com-posites.The compression test results demonstrate that the compressive strength and the residual compressive strength after impact of MNSAF-reinforced BFRP composites were greater than those of unreinforced one,exhibiting the greatest 56.2％and 73.3％increments respectively for BFRP composites improved by 4wt％MNSAF.X-ray micro-computed tomography scanning results indicate that the"fiber bridging claws"contributed to better mechanical interlocking to inhibit the crack generation and propagation under impact and compression load,and the original delamination-dominated failure of unreinforced BFRP composites was altered into shear-dominated failure of MNSAF-reinforced BFRP composites.Overall,the MNSAF interleaving might be an effective method in manufacturing high-performance laminated fiber in industrial pro-duction.
查看更多>>摘要：Excellent surface integrity is an eternal pursuit in high performance manufacturing,with microstructure being a crucial component of the surface integrity dataset and a key factor control-ling surface properties such as fatigue and creep.The multi-physical fields generated by thermo-mechanical loads during high-speed machining act on the processed surface layer,influencing the evolution of microstructures.To investigate the microstructural evolution mechanisms of ATI718 plus during high-speed machining,cutting experiments and techniques such as Electron back scatter diffraction(EBSD),Transmission Kikuchi diffraction(TKD),and Precession electron diffraction(PED)is conducted to quantitatively analyze the microstructures in the chip shear zone and the machined surface.Subsequently,a combined finite element(FE)and cellular automata(CA)model is developed to simulate the microstructure evolution during the cutting process.The discontinuous dynamic recrystallization(DDRX)mechanism is employed to demonstrate the nucleation and growth of grains under the influence of multiple physical fields.The simulation and experimental results show similar dynamic recrystallization(DRX)grain sizes,indicating acceptable accuracy of the CA model in terms of DRX grain size.The comparison between experimental and simulation results confirms the occurrence of both continuous dynamic recrystallization(CDRX)and DDRX during the cutting process.The synergistic competition between CDRX induced grain lamellar refinement and DDRX induced grain growth emerge as the primary mechanism driving microstruc-tural evolution.A layer of ultrafine grains,with a thickness within 20 pm,is formed on the machined surface.Results under different parameters demonstrate that the temperature has a more significant impact on the thickness of the ultrafine grain layer and the diameter of grains within the layer compared to the strain rate.
查看更多>>摘要：Owing to their remarkable flexibility and favorable cost-effectiveness,industrial robots have found extensive applications to cutting of materials across sophisticated manufacturing fields.However,the structurally low rigidity of these robots renders the tool tip prone to substantial oscil-lations during machining processes,significantly impacting product fabrication quality.The objec-tive of this study is to present a novel methodology employing magnetorheological dampers for mitigating vibrations during robotic milling operations.Specifically,a new type of ring nested Magneto-Rheological Foam Damper(MRFD)working in the squeeze mode is developed.Firstly,the MRFD's structure is designed considering the vibrational characteristics of robotic milling.Subsequently,a damping force model of the MRFD is derived.The feasibility of the MRFD's structural design is validated by the finite element analyses,which is instrumental in comprehending the influence of structural parameters on the electromagnetic characteristics of the MRFD.Next,a prototype of the MRFD is fabricated selecting appropriate parameters.Finally,a series of excita-tion and milling experiments are conducted on a KUKA KR500 robot.The outcomes demonstrate a substantial reduction(37％-69％)in radial vibration amplitude at the tool tip during robotic milling,highlighting the effectiveness of the developed MRFD.This research endeavor has intro-duced a pioneering avenue and framework for vibration control in robotic milling,offering a novel paradigm for enhancing the precision of robotic machining.
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