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Lightweight multifunctional metamaterial with low-frequency vibroacoustic reduction and load-bearing performances

Applied Mathematics and Mechanics(English Edition) 2025年第3期46卷 403-422页

作者： Qi JIA Dianlong YU Donghai HAN Jihong WEN National Key Laboratory of Equipment State Sensing and Smart Support College of Intelligence Science and TechnologyNational University of Defense TechnologyChangsha 410073China

Metamaterials can control and manipulate acoustic/elastic waves on a subwavelength scale using cavities or additional ***,the large cavity and weak stiffness components of traditional metamaterials may cause a conflict between vibroacoustic reduction and load-bearing capacity,and thus limit their ***,we propose a lightweight multifunctional metamaterial that can simultaneously achieve low-frequency sound insulation,broadband vibration reduction,and excellent load-bearing performance,named as vibroacoustic isolation and bearing metamaterial(VIBM).The advent of additive manufacturing technology provides a convenient and reliable method for the fabrication of VIBM *** results show that the compressive strength of the VIBM is as high as 9.71 MPa,which is nearly 87.81%higher than that of the conventional grid structure(CGS)under the same volume ***,the vibration and sound transmission are significantly reduced over a low and wide frequency range,which agrees well with the experimental data,and the reduction degree is obviously larger than that obtained by the *** design strategy can effectively realize the key components of metamaterials and improve their application scenarios.

关键词： multifunctional metamaterial low-frequency sound insulation broadband vibration reduction load bearing

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A guidance and control design with reduced information for a dual-spin stabilized projectile

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Defence technology（防务技术） 2024年第3期33卷 494-505页

作者： Yu Wang Jiyan Yu Xiaoming Wang Jia Fangxiu Intelligent Ammunition Technology National Defense Key Discipline Laboratory Nanjing University of Science and TechnologyNanjingJiangsu210094China

In this paper,an integrated guidance and control method based on an adaptive path-following controller is proposed to control a spin-stabilized projectile with only translational motion information under the constraint of an actuator,uncertainties in aerodynamic parameters and measurements,and control system *** to the fairly high rotation speed,the dynamic model of this missile is strongly nonlinear,uncertain and coupled in pitch,yaw and roll channels.A theoretical equivalent resultant force and uncertainty compensation method are comprehensively used to realize decoupling of pitch and *** response to the strong nonlinear and time-varying characteristics of the dynamic system,the quasi-linear model whose parameters are obtained by interpolation of points selected as the segmentation points in the trajectory envelope,is used for calculation in each *** cope with the system uncertainty caused by model approximation,parameter uncertainty and ballistic interference,an extended state estimator is used to compensate the output feedback according to the test ballistic *** order to improve the tracking efficiency and ensure the tracking error convergence with only translational motion information,the virtual guide point,whose derivative is deduced according to the Lyapunov principle,is calculated in real time according to the projection relationship between the real-time position and the reference trajectory,and a virtual line-of-sight angle and the backstepping method are used for the design of the guidance and control *** order to avoid the influence of control input saturation on the guidance and control performance due to the actuator limitation and improve the robustness of the system,an anti-saturation compensator is designed according to the two-step *** feasibility and effectiveness of the path-following controller is verified through closed-loop flight simulations with measurement,control,and condition *** result

关键词： Spin-stabilized projectile Reduced information Path-following control Extended state observer Coupled nonlinear system Input saturation

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Deep reinforcement learning using least-squares truncated temporal-difference

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CAAI Transactions on Intelligence technology 2024年第2期9卷 425-439页

作者： Junkai Ren Yixing Lan Xin Xu Yichuan Zhang Qiang Fang Yujun Zeng College of Intelligence Science and Technology National University of Defense TechnologyChangshaChina State Key Laboratory of Astronautic Dynamics Xi'an Satellite Control CenterXi'anChina

Policy evaluation(PE)is a critical sub-problem in reinforcement learning,which estimates the value function for a given policy and can be used for policy ***,there still exist some limitations in current PE methods,such as low sample efficiency and local convergence,especially on complex *** this study,a novel PE algorithm called Least-Squares Truncated Temporal-Difference learning(LST2D)is *** LST2D,an adaptive truncation mechanism is designed,which effectively takes advantage of the fast convergence property of Least-Squares Temporal Difference learning and the asymptotic convergence property of Temporal Difference learning(TD).Then,two feature pre-training methods are utilised to improve the approximation ability of ***,an Actor-Critic algorithm based on LST2D and pre-trained feature representations(ACLPF)is proposed,where LST2D is integrated into the critic network to improve learning-prediction *** simulation studies were conducted on four robotic tasks,and the corresponding results illustrate the effectiveness of *** proposed ACLPF algorithm outperformed DQN,ACER and PPO in terms of sample efficiency and stability,which demonstrated that LST2D can be applied to online learning control problems by incorporating it into the actor-critic architecture.

关键词： Deep reinforcement learning policy evaluation temporal difference value function approximation

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A Study for Inter-Satellite Cooperative Computation Offloading in LEO Satellite Networks

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China Communications 2025年第2期22卷 12-25页

作者： Gang Yuanshuo Zhang Yuexia Wu Peng Zheng Hui Fan Guangteng Key Laboratory of Modern Measurement and Control Technology Ministry of EducationBeijing Information Science and Technology UniversityBeijing 102206China 2 National Innovation Institute of Defense Technology Academy of Military ScienceBeijing 100071China

Low Earth orbit(LEO)satellite networks have the advantages of low transmission delay and low deployment cost,playing an important role in providing reliable services to ground *** paper studies an efficient inter-satellite cooperative computation offloading(ICCO)algorithm for LEO satellite ***,an ICCO system model is constructed,which considers using neighboring satellites in the LEO satellite networks to collaboratively process tasks generated by ground user terminals,effectively improving resource utilization ***,the optimization objective of minimizing the system task computation offloading delay and energy consumption is established,which is decoupled into two *** terms of computational resource allocation,the convexity of the problem is proved through theoretical derivation,and the Lagrange multiplier method is used to obtain the optimal solution of computational *** deal with the task offloading decision,a dynamic sticky binary particle swarm optimization algorithm is designed to obtain the offloading decision by *** results show that the ICCO algorithm can effectively reduce the delay and energy consumption.

关键词： computation offloading inter-satellite co-operation LEO satellite networks

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Improving aircraft nose wheel steering stability based on control continuation method

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science China(Technological sciences) 2025年第3期68卷 258-277页

作者： Qiaozhi YIN Dexu KONG Jiawei WANG Hong NIE Xiaohui WEI National Key Laboratory of Helicopter Aeromechanics Nanjing210016China State Key Laboratory of Mechanics and Control for Aerospace Structures Nanjing210016China Key Laboratory of Fundamental Science for National Defense-Advanced Design Technology of Flight Vehicle Nanjing210016China AVIC Nanjing Engineering Institute of Aircraft Systems Nanjing211106China

Aircraft steering instability during the taxiing process sometimes occurs resulting from the unstable bifurcation phenomena of the nonlinear steering dynamic system,which may lead to severe *** this study,the control parameter design of an aircraft nose wheel steering control system based on the control continuation method is proposed to reduce the number of unstable bifurcation points and enlarge the system stable region area in a certain parameter ***,the aircraft turning performance can be improved ***,a nonlinear aircraft rollout dynamic model is constructed,and the aircraft ground steering bifurcation characteristics are obtained under the open-loop steering control ***,the bifurcation performances under three closed-loop nose wheel steering controllers based on the feedback control method are compared,and the control parameter of the quadratic nonlinear controller with a better bifurcation control effect is selected as a second bifurcation parameter to analyze the directional system stability via two-parameter bifurcation ***,the influence of a crosswind on the aircraft ground steering bifurcation performance is studied for various control parameter ***,the control effects of a traditional proportional-integral-derivative(PID)nose wheel steering control law and the designed feedback controller are compared and ***,a semi-physical experiment of the aircraft nose wheel steering system is carried out,and different control parameter values are selected for test verification,which can further verify the control effect of the designed nonlinear feedback *** results indicate that the feedback control method is unable to vary the system bifurcation types,but appropriate control parameter design can effectively shrink the system instability region and even eliminate the unstable Hopf bifurcation points under some specific working conditions,improving the aircraft ground turning stability re

关键词： aircraft taxiing dynamics and stability nose wheel steering control system control continuation steering bifurcation characteristics quadratic feedback control

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Spatial Coded Modulation:Coding over Antennas

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China Communications 2024年第11期21卷 104-122页

作者： Luo Junshan Wang Fanggang Wang Shilian School of Electronic Science National University of Defense TechnologyChangsha 410073China State Key Laboratory of Rail Traffic Control and Safety Beijing Jiaotong UniversityBeijing 100044China

In spatial modulation systems,the reliability of the active antenna detection is of vital importance since the modulated symbols tend to be correctly demodulated when the active antennas are accurately *** this paper,we propose a spatial coded modulation(SCM)scheme,which improves the accuracy of the active antenna detection by coding over the transmit ***,the antenna activation pattern in the SCM corresponds to a codeword in a properly designed codebook with a larger minimum Hamming distance than the conventional spatial *** the minimum Hamming distance increases,the reliability of the active antenna detection is directly enhanced,which yields a better system *** addition to the reliability,the proposed SCM scheme also achieves a higher capacity with the identical antenna configuration compared to the conventional *** optimal maximum likelihood detector is first ***,a low-complexity suboptimal detector is proposed to reduce the computational *** derivations of the channel capacity and the bit error rate are presented in various channel *** derivation on performance bounding is also provided to reveal the insight of the benefit of increasing the minimum Hamming *** results validate the analysis and demonstrate that the proposed SCM outperforms the conventional spatial modulation techniques in both channel capacity and system reliability.

关键词： antenna correlation channel capacity Hamming distance reliability spatial modulation

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Autonomous relative optical navigation based on unified modeling of external systematic errors

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Chinese Journal of Aeronautics 2024年第3期37卷 282-289页

作者： Dayi WANG Bowen SUN Maodeng LI Jiaxing LI Haiyin ZHOU Beijing Institute of Spacecraft System Engineering Beijing 100191China College of Sciences National University of Defense TechnologyChangsha 410073China National Key Laboratory of Space Intelligent Control Beijing Institute of Control EngineeringBeijing 100191China

To solve the problem that external systematic errors of the optical camera cannot be fully estimated due to limited computing resources,a unified dimensionality reduction representation method for the external systematic errors of the optical camera is proposed,and autonomous relative optical navigation is *** camera translational and misalignment errors are converted into a three-dimensional rotation error,whose differential model can be established through specific attitude control and appropriate ***,the rotation error and the relative motion state are jointly estimated in an augmented Kalman filter *** with the traditional method that estimates the camera translational and misalignment errors,the proposed method reduces the computational complexity in that the estimated state dimension is ***,as demonstrated by numerical simulation,the estimation accuracy is improved significantly.

关键词： Unified model Systematic errors Optical navigation Observability analysis Calibration

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Design and Optimization of a High Thrust Density Voice Coil Motor with Auxiliary Enhanced Magnetic Circuits

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IEEE Transactions on Energy Conversion 2024年第2期40卷 1215-1224页

作者： Zhu, Zhijun Xiao, Yong Li, Yongqiang Zhou, Minrui Yu, Dianlong National University of Defense Technology College of Intelligence Science and Technology Changsha410073 China National Key Laboratory of Equipment State Sensing and Smart Support Changsha410073 China

Precision instruments of aerospace equipment are often affected by low frequency and broadband vibration. Active vibration isolation system (AVIS) is usually employed to suppress vibration. Voice coil motor (VCM) is widely used in AVIS because of its compact structure, fast response speed, good linearity and high control accuracy. To ensure the normal operation of precision instruments, VCM is required to have a large stroke, a large thrust density and a low fluctuation. However, traditional VCM designs require a careful trade-off between large thrust density and low thrust fluctuations. This paper proposes a design of VCM with novel auxiliary enhanced magnetic circuits. The proposed VCM uses bipolar basic magnetic circuit to improve the utilization of permanent magnets and yokes, and further concentrate and even the magnetic flux in the airgap by adding auxiliary magnetic circuits, leading to a high thrust density and a low thrust fluctuation. Equivalent magnetic circuit method and finite element method are combined to optimize the structural parameters of the proposed VCM to obtain better comprehensive performance. Experimental results demonstrate that the average thrust of the proposed VCM is increased by 74.5% and the thrust fluctuation is reduced by 23.9% compared with the conventional VCM. © 1986-2012 IEEE.

关键词： Permanent magnets

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Making waste profitable: Efficient recovery of metallic iron from jarosite residues

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Chinese Journal of Chemical Engineering 2024年第7期71卷 66-76页

作者： Songshan Zhou Yunhui Han Rong Huang Yin Huang Qingyuan Dong Haiyin Gang Jinchuan Qin Xi Yu Xiangfei Zeng Wenxing Cao Jiqin Wang Shaoqin Chen Rong Wang Mengjun Chen Key Laboratory of Solid Waste Treatment and Resource Recycle(SWUST) Ministry of EducationSouthwest University of Science and TechnologyMianyang 621010China School of Environment Key Laboratory of Yellow River and Huai River Water Environment and Pollution ControlMinistry of EducationHenan Normal UniversityXinxiang 453007China School of National Defense Science and Technology College SWUST Ministry of EducationSouthwest University of Science and TechnologyMianyang 621010China

To address the hazardous by-product of zinc smelting and resource utilization of jarosite residue,this study applies an electric field-assisted hot acid treatment to completely recycle iron(Fe).This innovative approach aims to enhance the leaching efficiency of Fe from jarosite *** introduction of an electric field changes the charge distribution on the surface of the particles to enhance ions and electrons exchange and promotes the collision between particles to strengthen reaction *** on the above,the leaching efficiency of Fe in jarosite under sulfuric acid attack has improved *** result shows that Fe leaching efficiency reaches 98.83%,which is increased by 28%under the optimal experimental conditions:current density of 30 mA·cm^(-2),H_(2)SO_(4) concentration of 1.5 mol·L^(-1),solid-liquid ratio of 70 g·L^(-1),temperature of 80℃ and time of 12 *** kinetics calculations show that the apparent activation energy is 16.97 kJ·mol^(-1) and the leaching of jarosite residue is controlled by a mixture of chemical reaction and diffusion,as well as the temperature and concentration of the leaching solution have an influence on *** work provides a feasible idea for the efficient leaching of Fe from jarosite residue.

关键词： Jarosite residue Electric filed Leaching kinetics

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Effect of Water Soaking on the Microstructure and Spontaneous Combustion Characteristics of Bituminous Coal During Low−Temperature Oxidation

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Combustion science and technology 2024年第11期196卷 1743-1767页

作者： Yi, Xin Zhang, Shaohang Bai, Zujin Deng, Jun Shu, Chimin Qu, Gaoyang Ge, Long School of Safety Science and Engineering Xi’an University of Science and Technology Shaanxi Xi’an China Shaanxi Key Laboratory of Prevention and Control of Coal Fire Xi’an University of Science and Technology Shaanxi Xi’an China Center for Process Safety and Disaster Prevention National Yunlin University of Science and Technology Yunlin Taiwan

The effects of water soaking on the microstructure and spontaneous combustion characteristics of coal samples were investigated by scanning electronic microscopy (SEM), Fourier transform infrared (FTIR) spectrometer, and temperature programmed testing system (TPTS). The SEM results showed that the pore structures on the surface of water−soaked coal were more developed than raw coal, the pores increased and enlarged, and the phenomenon of water absorption swelling occurred. At the same time, water soaking had a certain influence on the functional groups in coal. The results of FTIR clearly illustrated that the surface functional groups of water−soaked coal were more active, and the contents of functional groups such as hydroxyl, methylene, aliphatic ether and aromatic ether all increased to varying degrees. During the low−temperature oxidation process, the analysis results of TPTS indicated that the oxygen consumption rate and the production of CO, C2H4, and other gases of water−soaked coal were higher. Based on the analysis method of CO, CO/CO2 and C2H4 gas growth rate, the three peaks of the curve obtained correspond to the characteristic temperatures of each oxidation stage of the coal samples. The critical temperature, dry cracking temperature and fission temperature of water−soaked coal were 60 ± 10 ℃, 90 ± 10 ℃ and 120 ± 10 ℃, respectively, which was 10 ℃ lower than raw coal. The apparent activation energy (Ea) of coal was calculated by the CO model and fitted in sections. It can be seen that the Ea of water−soaked coal at different stages of low−temperature oxidation was lower, and the maximum difference was 2.1 kJ/mol. Therefore, from the above results, it inferred that the activity of bituminous coal became stronger after soaking in water, which may be due to the effect of soaking on the surface structure and active groups of coal, thus showing a higher risk of spontaneous combustion. © 2022 Taylor & Francis Group, LLC.

关键词： Temperature

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