MODE SPACE SMOOTHING ALGORITHM TO ESTIMATE DOA OF COHERENT SIGNALS IMPINGING ON UNIFORM CIRCULAR ARRAY

A novel method to estimate DOA of coherent signals impinging on a uniform circular array( UCA) is presented in this paper. A virtual uniform linear array (VULA) is first derived by using spatial DFT technique, transforming the UCA from element space to phase mode space to obtain the properties of ordinary ULA, and then the well known spatial smoothing technique is applied to the VULA so that the lost rank of covariance matrix due to signal coherence can be retrieved. This method makes it feasible to use the simple MUSIC algorithm to estimate DOA of coherent signals impinging on a UCA without heavy computation burden. Simulation results strongly verify the effectiveness of the algorithm.

Separation of closely spaced modes by combining complex envelope displacement analysis with method of generating intrinsic mode functions through filtering algorithm based on wavelet packet decomposition

One of the important issues in the system identification and the spectrum analysis is the frequency resolution, i.e., the capability of distinguishing between two or more closely spaced frequency components. In the modal identification by the empirical mode decomposition （EMD） method, because of the separating capability of the method, it is still a challenge to consistently and reliably identify the parameters of structures of which modes are not well separated. A new method is introduced to generate the intrin- sic mode functions （IMFs） through the filtering algorithm based on the wavelet packet decomposition （GIFWPD）. In this paper, it is demonstrated that the CIFWPD method alone has a good capability of separating close modes, even under the severe condition beyond the critical frequency ratio limit which makes it impossible to separate two closely spaced harmonics by the EMD method. However, the GIFWPD-only based method is impelled to use a very fine sampling frequency with consequent prohibitive computational costs. Therefore, in order to decrease the computational load by reducing the amount of samples and improve the effectiveness of separation by increasing the frequency ratio, the present paper uses a combination of the complex envelope displacement analysis （CEDA） and the GIFWPD method. For the validation, two examples from the previous works are taken to show the results obtained by the GIFWPD-only based method and by combining the CEDA with the GIFWPD method.

EXPLORATION OF SUBSTITUTION OF REPEATED MODE SUBSPACES FOR CLOSELY SPACED MODE SUBSPACES

A new quantitative concept is introduced in this paper, which may be used to facilitate the measurement of the controllability of a subspace similar to subspace controllability degree. Then the concrete form of the subspace controllability degree of a flexible structure is derived, and the errors of subspace controllability degree and dynamical response caused by the substitution of a repeated mode subspace for a closely spaced mode subspace are discussed. All the results show that this substitution is rational under some conditions.

Adaptive sliding mode backstepping control for near space vehicles considering engine faults

A fault tolerant control methodology based adaptive sliding mode(ASM) backstepping is proposed for near space vehicle(NSV) attitude control system under engine faults. The proposed scheme combined adaptive backstepping with the sliding mode control strategy could guarantee the system’s stability and track desired signals under external disturbances and engine faults. Firstly, attitude mode description and the engine faulty model are given. Secondly, a nominal control law is designed.Thirdly, a sliding mode observer is given later in order to estimate both the information of engine faults and external disturbances. An adaptive sliding mode technology based on the previous nominal control law is developed via updating faulty parameters. Finally,analyze the system’s fault-tolerant performance and reliability through experiment simulation, which verifies the proposed design of fault-tolerant control can tolerate engine faults, as well as the strong robustness for external disturbance.

Feedback Attitude Sliding Mode Regulation Control of Spacecraft Using Arm Motion

The problem of spacecraft attitude regulation based on the reaction of arm motion has attracted extensive attentions from both engineering and academic fields.Most of the solutions of the manipulator’s motion tracking problem just achieve asymptotical stabilization performance,so that these controllers cannot realize precise attitude regulation because of the existence of non-holonomic constraints.Thus,sliding mode control algorithms are adopted to stabilize the tracking error with zero transient process.Due to the switching effects of the variable structure controller,once the tracking error reaches the designed hyper-plane,it will be restricted to this plane permanently even with the existence of external disturbances.Thus,precise attitude regulation can be achieved.Furthermore,taking the non-zero initial tracking errors and chattering phenomenon into consideration,saturation functions are used to replace sign functions to smooth the control torques.The relations between the upper bounds of tracking errors and the controller parameters are derived to reveal physical characteristic of the controller.Mathematical models of free-floating space manipulator are established and simulations are conducted in the end.The results show that the spacecraft’s attitude can be regulated to the position as desired by using the proposed algorithm,the steady state error is 0.000 2 rad.In addition,the joint tracking trajectory is smooth,the joint tracking errors converges to zero quickly with a satisfactory continuous joint control input.The proposed research provides a feasible solution for spacecraft attitude regulation by using arm motion,and improves the precision of the spacecraft attitude regulation.

Robust chattering-free sliding mode control of space robot in task space

This paper studies the tracking control problem of a free-floating space robot in a task space. Considering the model uncertainties and external disturbance, a robust sliding mode controller is proposed using the Lyapunov direct method and dissipative theory. To eliminate the chattering phenomenon, an radial basis function （RBF） neural network is applied to replace the discontinuous part of the control signal. A novel on-line learning method of the weights and parameters of the RBF neural network established using Lyapunov function assures the stability of the system. It is proved that the proposed controller can guarantee that the L2 gain from disturbance to tracking error is lower than the given index y. Simulation results show that the control method is valid.

数据空间建设的实践进展与运营模式分析——基于Data Spaces Radar的案例

数据空间建设为数据要素的价值实现提供了可资借鉴的实践经验,全面解析其实践进展与运营模式,有助于破解数据流通的现实堵点、拓展数据利用的发展思路。文章首先将结构主义分析方法中的案例研究法作为主要研究方法,综合运用文献调研、比较分析等方法,以Data Spaces Radar为案例来源,从实践进展、运营模式、核心要素等维度提炼数据空间建设特征。其次,在制度与技术的双轮驱动下,数据空间建设秉持制度规范统一性、技术设计整体性和治理模式协同性的架构原则,并按照产业思维、底线思维、信任思维、链式思维、集约思维的底层逻辑,形成较为完整的运营体系。未来应着力探索和解决数据空间视域下的数据资源价值化开发路径,针对数据流通堵点、利用痛点及信任难点问题,从体制机制、政策框架与技术应用等角度为推进我国的数据要素流通利用提供有益参考。

Fiber transmission demonstrations in vector mode space division multiplexing

Much attention has been focused on the use of scalar modes for space division multiplexing （SDM）. Alternative vector mode bases offer another solution set for SDM, expanding the available trade-offs in system performance and complexity. We present two types of ring core fiber conceived and designed to explore SDM with fibers exhibiting low interactions between supported modes. We review demonstrations of fiber data transmis- sion tbr two separate vector mode bases： one for orbital angular momentum （OAM） modes and one for linearly polarized vector （LPV） modes. The OAM mode demon- strations include short transmissions using commercially available transceivers, as well as kilometer length transmission at extended data rates. The LPV demonstra- tions span kilometer length transmissions at high data rate with coherent detection, as well as a radio over fiber experiment with direct detection of narrowband signals.

基于dSPACE的新型双滑模PMSM控制方法

设计一种基于滑模理论的永磁同步电机控制系统,利用滑模控制器代替传统的PID控制器,用滑模观测器代替传统的位置传感器。滑模控制器中针对传统滑模控制的抖振问题,引入准滑模和趋近律的概念,设计一种新的滑模控制器。滑模观测器使用连续饱和函数代替传统的开关函数,有效地减少高频噪声信号,经李亚普诺夫稳定方程证明系统的稳定性。本设计方法充分发挥滑模控制的优势。通过d SPACE实验平台的验证和Control Desk环境的实时观测,证明所设计的新的滑模控制器在消除抖振和抗干扰方面明显优于传统的滑模控制器和PID控制器,滑模观测器能准确地观测位置信号,而且针对具有噪声干扰的场合,加入卡尔曼滤波器,有效地减少了干扰信号。

新工科背景下交通管理工程本科人才培养“SPACE”模式的构建与探索——以湖南警察学院为例

“SPACE”模式,即坚持以学生(Student)为中心,以思政素养(Political and ideological qualities)为初心,以培养复杂工程问题解决能力(Ability of solving complex engineering problem)为重心,以培养创新精神(Creative spirit)为核心,践行“初心要红,重心要实,核心要强”的培养理念。面对新工科建设对人才培养提出的新要求,湖南警察学院结合自身拥有国家首批一流本科专业建设点和省综合改革试点专业的实际,创新构建了交通管理工程专业人才培养的“SPACE”模式,初步实现卓越(Excellent)交通管理工程警务人才培养的目标,产生了较好的社会反响。

基于Dual-Mode MMA+MDD双模式T/2分数间隔盲均衡算法的研究

均衡技术是用来解决通信系统中码间干扰的常用方法.针对传统恒模算法的收敛速度和稳态剩余码间干扰大的缺点,将双模式多模算法和改进型判决引导算法结合起来,并且应用于分数间隔盲均衡器中.该算法初期用双模式算法收敛均衡器,然后切换到改进型判决引导算法中进一步收敛,由于分数间隔均衡器解决了波特间隔均衡器因抽样率不高带来的频谱混叠问题,从而进一步地提高了均衡效果.蒙特卡罗仿真表明,该算法不仅收敛速度快,而且得到较低的剩余码间干扰.

Concept Design,Modeling and Station-keeping Attitude Control of an Earth Observation Platform

The stratosphere airship provides a unique and promising platform for earth observation. Researches on the project design and control scheme for earth observation platforms are still rarely documented. Nonlinear dynamics, model uncertainties, and external disturbances contribute to the difficulty in maneuvering the stratosphere airship. A key technical challenge for the earth observation platform is station keeping, or the ability to remain fixed over a geo-location. This paper investigates the conceptual design, modeling and station-keeping attitude control of the near-space earth observation platform. A conceptual design of the earth observation platform is presented. The dynamics model of the platform is derived from the Newton-Euler formulation, and the station-keeping control system of the platform is formulated. The station-keeping attitude control approach for the platform is proposed. The multi-input multi-output nonlinear control system is decoupled into three single-input single-output linear subsystems via feedback linearization, the attitude controller design is carried out on the new linear systems using terminal sliding mode control, and the global stability of the closed-loop system is proven by using the Lyapunov theorem. The performance of the designed control system is simulated by using the variable step Runge-Kutta integrator. Simulation results show that the control system tracks the commanded attitude with an error of zero, which verify the effectiveness and robustness of the designed control system in the presence of parametric uncertainties. The near-space earth observation platform has several advantages over satellites, such as high resolution, fast to deploy, and convenient to retrieve, and the proposed control scheme provides an effective approach for station-keeping attitude control of the earth observation platform.

基于场所精神的建筑室内空间设计研究

人与场所交互对话方式是近年来设计者研究的主要方向。建筑室内空间作为人们物质和精神生活的场所,传递着一种生活方式的态度。建筑室内空间的场所精神,映射出社会环境与生产方式多维度空间行为体验逻辑价值认同的特定意义。文章结合场所精神的行为体验研究,通过对“人”的需求尊重来诠释建筑室内空间场所设计的“内在精神气质”,强化人与环境互动的双向作用生成,实现场所空间营造内在价值的有效途径。

A UNIVERSAL MATRIX PERTURBATION TECHNIQUE FOR COMPLEX MODES

A universal matrix perturbation technique for complex modes is presented. This technique is applicable to all the three cases of complex eigenvalues: distinct, repeated and closely spaced eigenvalues. The lower order perturbation formulas are obtained hy performing two complex eigensubspace condensations, and the higher order perturbation formulas are derived hy a successive approximation process. Three illustrative examples are given to verify the proposed method and satisfactory results are observed.

Design and Implementation of Space Dust Database

Space debris is very dangerous to the security of on-the-orbit spacecrafts, and it is increasing in number at high speed with the expansion of human space exploration. Space debris has become a serious space pollutant noticed by many astronomers. The increase of space dust sources and the development of research on space dust urgently need space dust data sharing and exchanging. It is necessary for us to establish the Space Dust Database to realize the sharing and canonical management of the data. The Space Dust Database (SDD) management system, based on the 3-layer B/S computer mode, was designed and implemented in this paper. The system’s features include significantly improved runtime efficiency, good scalability and maintainability. The Space Dust Database can provide some scientific bases for the study of the chemical constituents, mineral composition, origin and sources of space dust, but also provide excellent data services and decision-making support for the protection of space and model construction of space dust.

基于复合阵列的矩阵循环重构DOA估计算法

相干源角度估计一直是困扰雷达角度测量的一个重要难题,基于均匀阵列假设提出了模式空间解相干算法,一定程度上解决了相干干扰条件下的目标角度估计问题,但是上述算法对复合阵列的适应性较差。针对复合阵列下相干多源测角问题,本文提出一种基于模式空间循环重构的解相关算法,利用圆阵外其他任意天线赋形空域滤波特性,在信号源数多于阵元数时较好地解决相干源角度估计问题。仿真试验结果表明,该算法能较好地解决复合阵列天线下的相干源测角问题,并且其角分辨性能优于传统算法。

A Modal Identification Algorithm Combining Blind Source Separation and State Space Realization

A modal identification algorithm is developed, combining techniques from Second Order Blind Source Separation (SOBSS) and State Space Realization (SSR) theory. In this hybrid algorithm, a set of correlation matrices is generated using time-shifted, analytic data and assembled into several Hankel matrices. Dissimilar left and right matrices are found, which diagonalize the set of nonhermetian Hankel matrices. The complex-valued modal matrix is obtained from this decomposition. The modal responses, modal auto-correlation functions and discrete-time plant matrix (in state space modal form) are subsequently identified. System eigenvalues are computed from the plant matrix to obtain the natural frequencies and modal fractions of critical damping. Joint Approximate Diagonalization (JAD) of the Hankel matrices enables the under determined (more modes than sensors) problem to be effectively treated without restrictions on the number of sensors required. Because the analytic signal is used, the redundant complex conjugate pairs are eliminated, reducing the system order (number of modes) to be identified half. This enables smaller Hankel matrix sizes and reduced computational effort. The modal auto-correlation functions provide an expedient means of screening out spurious computational modes or modes corresponding to noise sources, eliminating the need for a consistency diagram. In addition, the reduction in the number of modes enables the modal responses to be identified when there are at least as many sensors as independent (not including conjugate pairs) modes. A further benefit of the algorithm is that identification of dissimilar left and right diagonalizers preclude the need for windowing of the analytic data. The effectiveness of the new modal identification method is demonstrated using vibration data from a 6 DOF simulation, 4-story building simulation and the Heritage court tower building.

ChatGPT赋能高校图书馆元宇宙空间服务

ChatGPT赋能高校图书馆元宇宙空间服务,推动图书馆智慧空间转型,为高校图书馆元宇宙空间服务的发展提供可参考的思路与方向。文章对高校图书馆元宇宙空间进行整体概括,结合ChatGPT的特征与图书馆以人为本的服务理念,探究ChatGPT赋能高校图书馆元宇宙空间服务的作用机理,并对高校图书馆元宇宙空间服务场景重新架构,从基础构建、数据转换、应用分析以及场景协作四个层面,解析ChatGPT赋能高校图书馆元宇宙空间服务运行模式。建议高校图书馆从技术、资源、理念等方面对元宇宙空间服务进行创新与提升,改善服务效能,促进空间协同。

中国发展方式绿色转型的统计测度及时空演进分析

加快发展方式绿色转型,是贯彻落实新发展理念的战略要求,是践行绿色发展理念的时代命题。评估中国发展方式绿色转型进程,对于实现“双碳”目标、推动经济社会高质量发展具有重要现实意义。本文采用熵权法,选取2011~2022年我国30个省(区、市)的面板数据,对各省(区、市)发展方式绿色转型水平进行测度并分析其时空演变特征和地区差异。研究发现:(1)中国发展方式绿色转型进程取得了阶段性成果,东部地区发展方式绿色转型程度最高;(2)东部地区与其他三大地理区域的发展方式绿色转型水平差异显著,其中东部地区与东北地区的差异最大;(3)发展方式绿色转型是一个渐进式过程,存在稳定的β收敛特征。研究结论对于缩小地区间发展方式绿色转型差异、加快发展方式绿色转型进程具有参考意义。