Simulation Study on Dynamic Stiffness of Kick-reaction Link Actuator

Under the same aerodynamic load,the load transmitted by the kick-reaction link actuator to the aircraft structure is only 1/5 to 1/3 of that of the point-to-point actuator,which can significantly reduce the weight of the structure,and is widely used in the main flight control surface of large and medium-sized civil airliners.In order to restrain the flutter of aircraft rudder surface,it is necessary to design the servo stiffness of the kick-reaction link actuator in the development stage,so that it can meet the dynamic stiffness requirement within the frequency range.Taking the actuator of a civil airliner as the research object,the dynamic stiffness modeling of elevator actuator is carried out on MATLAB platform,and the dynamic stiffness test is carried out to verify the correctness of dynamic stiffness modeling.The simulation and test results show that the actuator can meet the dynamic stiffness design requirements.

电动汽车电控液压制动系统CarSim/Simulink联合仿真研究

针对某款国产电动汽车的电控液压制动系统,文章基于滑移率的比例-积分-微分(PID)控制提出了防抱死制动系统(ABS)模型,以改善车辆制动性能,提高在对开路面上的制动有效性和安全性。首先,使用Simulink软件建立液压电控制动系统的动力学模型;然后,基于滑移率设计PID控制器,并通过1/4车辆模型验证其有效性;最后,利用S函数将ABS控制器的Simulink模型输入CarSim平台中,开展CarSim/Simulink双平台联合控制仿真。结果表明,基于滑移率的PID控制的ABS对比无ABS的车辆,制动性能更加优越,在对开路面上制动稳定性更加明显。

Adaptive functional link network control of near-space vehicles with dynamical uncertainties

The control law design for a near-space hypersonic vehicle（NHV） is highly challenging due to its inherent nonlinearity,plant uncertainties and sensitivity to disturbances.This paper presents a novel functional link network（FLN） control method for an NHV with dynamical thrust and parameter uncertainties.The approach devises a new partially-feedback-functional-link-network（PFFLN） adaptive law and combines it with the nonlinear generalized predictive control（NGPC） algorithm.The PFFLN is employed for approximating uncertainties in flight.Its weights are online tuned based on Lyapunov stability theorem for the first time.The learning process does not need any offline training phase.Additionally,a robust controller with an adaptive gain is designed to offset the approximation error.Finally,simulation results show a satisfactory performance for the NHV attitude tracking,and also illustrate the controller＇s robustness.

Simulation of Dynamic Electromagnetic Interference Environment for Unmanned Aerial Vehicle Data Link

In order to test the anti-interference ability of an Unmanned Aerial Vehicle(UAV) data link in a complex electromagnetic environment,a method for simulating the dynamic electromagnetic interference of an indoor wireless environment is proposed.This method can estimate the relational degree between the actual face of an UAV data link in an interface environment and the simulation scenarios in an anechoic chamber by using the Grey Relational Analysis(GRA) theory.The dynamic drive of the microwave instrument produces a real-time corresponding interference signal and realises scene mapping.The experimental results show that the maximal correlation between the interference signal in the real scene and the angular domain of the radiation antenna in the anechoic chamber is 0.959 3.Further,the relational degree of the Signal-toInterference Ratio(SIR) of the UAV at its reception terminal indoors and in the anechoic chamber is 0.996 8,and the time of instrument drive is only approximately 10 μs.All of the above illustrates that this method can achieve a simulation close to a real field dynamic electromagnetic interference signal of an indoor UAV data link.

ON THE DYNAMIC MODELING AND CONTROL OF 2-DOF PLANAR PARALLEL MECHANISM WITH FLEXIBLE LINKS

The object of study is about dynamic modeling and control for a 2degree-of-freedom (DOF) planar parallel mechanism (PM) with flexible links. The kinematic anddynamic equations are established according to the characteristics of mixed rigid and flexiblestructure. By using the singular perturbation approach (SPA), the model of the mechanism can beseparated into slow and fast subsystems. Based on the feedback linearization theory and inputshaping technique, the large scale rigid motion controller and the flexible link vibrationcontroller can be designed separately to achieve fast and accurate positioning of the PM.

Dynamic Characteristics of Inter-Satellite Links in LEO Networks

To establish an efficient inter-satellite link (ISL) in an LEO network, the effect of geometric characteristics of ISL on the ISLs and the devices on the LEO satellite should be examined. Because of the continuous movement of the LEO satellite, the time-varying behaviours of the ISL's geometric charactersistics continuously change with the changes of the satellite's position on the orbit. These dynamic geometric characteristics of the ISLs are important for ISL's performance analyzing and the design of the devices on the LEO satellite. This paper describes dynamic geometric characteristics of ISL, analyzes the impact of these regulations on the tracking system of the satellite's antenna and the power adjusting system of the satellite's transmitter, with the Iridium system as an example.

DYNAMIC SUBSTRUCTURING ANALYSISOF COMPOSITE STRUCTURES WITHNONLINEAR LINKS

The paper deals with the dynamic response prediction of the composite structure,which consists of two linear components coupled by some nonlinear vibration isolators. Based on the measured impulse response functions of the linear components, three kinds of dynamic equations of interfacial integration are proposed and a procedure to transform the dynamic equations of integral type into a set of ordinary differential equations is suggested. Computer simulations and a real test are given to verify the effectiveness of the theoretical results.

Dynamic analysis of multi-link spatial flexible manipulator arms with dynamic stiffening effects

The dynamics for multi-link spatial flexible manipulator arms is investigated. The system considered here is an N-flexible-link manipulator driven by N DC-motors through N revolute flexiblejoints. The flexibility of each flexible joint is modeled as a linearly elastic torsional spring, and the mass of the joint is also considered. For the flexibility of the link, all of the stretching deformation, bending deformation and the torsional deformation are included. The complete governing equations of motion of the system are derived via the Lagrange equations. The nonlinear description of the deformation field of the flexible link is adopted in the dynamic modeling, and thus the dynamic stiffening effects are captured. Based on this model, a general-purpose software package for dynamic simulation of multi-link spatial flexible manipulator arms is developed. Several illustrative examples are given to validate the algorithm presented in this paper and to indicate that not only dynamic stiffening effects but also the flexibility of the structure has significant influence on the dynamic performance of the manipulator.

An Approach for Implementing Dynamically Linkable Component

IntelligentPad approach provides a standard for dynamically linkable components. Based on the standard, this paper introduces an approach of developing dynamically linkable components by using object oriented techniques.

Learning-Based Dynamic Connectivity Maintenance for UAV-Assisted D2D Multicast Communication

Unmanned aerial vehicles(UAVs) enable flexible networking functions in emergency scenarios.However,due to the movement characteristic of ground users(GUs),it is challenging to capture the interactions among GUs.Thus,we propose a learningbased dynamic connectivity maintenance architecture to reduce the delay for the UAV-assisted device-todevice(D2D) multicast communication.In this paper,each UAV transmits information to a selected GU,and then other GUs receive the information in a multi-hop manner.To minimize the total delay while ensuring that all GUs receive the information,we decouple it into three subproblems according to the time division on the topology:For the cluster-head selection,we adopt the Whale Optimization Algorithm(WOA) to imitate the hunting behavior of whales by abstracting the UAVs and cluster-heads into whales and preys,respectively;For the D2D multi-hop link establishment,we make the best of social relationships between GUs,and propose a node mapping algorithm based on the balanced spanning tree(BST) with reconfiguration to minimize the number of hops;For the dynamic connectivity maintenance,Restricted Q-learning(RQL) is utilized to learn the optimal multicast timeslot.Finally,the simulation results show that our proposed algorithms perfor better than other benchmark algorithms in the dynamic scenario.

Dynamic Mechanical and Thermal Properties of Cross-linked Polystyrene/Glass Fiber Composites

Cross-linked polystyrene/glass fiber composites were fabricated using cross-linked polystyrene （CLPS） as matrix and E-glass fiber as the reinforcement. Surfaces of E-glass fibers were modified by vinyl triethoxysilane （VTES）, vinyl trimethoxysilane （VTMS） and γ-methacryloylpropyl trimethoxysilane （MPS）. The treated glass fibers were analyzed by fourier transform infrared spectroscopy （FTIR）. Dynamic mechanical thermal analysis （DMTA） and thermo-gravimetric analysis （TGA） were employed to investigate the effect of glass fibers surface modification on viscoelastic behavior and thermal properties. The morphology of fracture surfaces of various composites was observed by scanning electron microscopy （SEM）. The results revealed that these coupling agents were connected to the surfaces of the fibers by chemical bonding. Dynamic mechanical properties as well as thermal stability of the composites were improved considerablely, but to varying degrees depending on the fiber modification. The diversities of improvement of properties were attributed to the different interfacial adhesion between CLPS matrix and the glass fibers.

Research on Weighted Directed Dynamic Multiplexing Network of World Grain Trade Based on Improved MLP Framework

As the main food source for humans, the global movement of the three major grains significantly impacts human survival and development. To investigate the evolution of the world cereal trade network and its development trend, a weighted directed dynamic multiplexed network was established using historical data on cereal trade, cereal import dependency ratio, and arable land per capita. Inspired by the MLP framework, we redefined the weight determination method for computing layer weights and edge weights of the target layer, modified the CN, RA, AA, and PA indicators, and proposed the node similarity indicator for weighted directed networks. The AUC metric, which measures the accuracy of the algorithm, has also been improved in order to finally obtain the link prediction results for the grain trading network. The prediction results were processed, such as web-based presentation and community partition. It was found that the number of generalized trade agreements does not have a decisive impact on inter-country cereal trade. The former large grain exporters continue to play an important role in this trade network. In the future, the world trade in cereals will develop in the direction of more frequent intercontinental trade and gradually weaken the intracontinental cereal trade.

Interactive Heuristic D* Path Planning Solution Based on PSO for Two-Link Robotic Arm in Dynamic Environment

This paper is devoted to find an intelligent and safe path for two-link robotic arm in dynamic environment. This paper focuses on computational part of motion planning in completely changing dynamic environment at every motion sample domains,?since the local minima and sharp edges are the most common problems in all path planning algorithms. In addition, finding a path solution in a dynamic environment represents a challenge for the robotics researchers,?so in this paper, a proposed mixing approach was suggested to overcome all these obstructions. The proposed approach methodology?for obtaining robot interactive path planning solution in known dynamic environment utilizes?the use of modified heuristic D-star (D*) algorithm based on the full free Cartesian space analysis at each motion sample with the Particle Swarm Optimization (PSO) technique.?Also, a modification on the?D* algorithm has been done to match the dynamic environment requirements by adding stop and return backward cases which is not included in the original D* algorithm theory. The resultant interactive path solution was computed by taking into consideration the time and position changes of the moving obstacles. Furthermore, to insure the enhancement of the?final path length optimality, the PSO technique was used.?The simulation results are given to show the effectiveness of the proposed method.

基于系统动力学的图书馆网络健康信息有效传播形成机理研究

文章依据拉斯韦尔的5W模式和马莱兹克模式,探讨图书馆网络健康信息有效传播的基本要素和过程要素,使用系统动力学构建包含动力因、环境因、需求因、任务因、资源因和媒介因的图书馆网络健康信息有效传播形成机理模型,以期为图书馆网络健康信息有效传播提供参考。

大涵道比涡扇发动机安装节动力学设计及性能评估分析进展

综述了大涵道比涡扇发动机安装节动力学设计及评估问题。首先从减振设计需求出发,论述了发动机安装节开展动力学设计的重大意义,并对安装节的主要结构形式及特点进行了详细的阐述;进一步从军民用标准规范和工程实践经验出发,归纳了安装系统动力学设计技术要求;而后从动力学设计、性能评估、系统验证等方面回顾了涡扇发动机安装节的国内外研究现状,指出国内外差距主要体现在设计要求、设计理念和应用实践经验等方面。在此基础上,展望了大涵道比涡扇发动机安装节动力学设计及性能评估技术的发展趋势和热点。

多馆模式下高校纸质文献学科化典藏体系的构建与思考——以北京大学为例

面向支持高校“双一流”建设,图书馆应正确认识或重新认识文献典藏工作。文章在文献调研的基础上,以北京大学为例,首先梳理总分馆文献典藏工作现状和问题,进而分析构建总分馆纸质文献典藏体系应考虑的因素,重点探讨构建纸质文献学科化典藏体系的框架,明确了优化三线动态典藏制,在全校实现按学科组织纸质文献的典藏体系。最后对新的典藏体系进行深入分析和思考,为构建良性循环的总分馆学术资源生态系统夯实基础。

基于时序图卷积的动态网络链路预测

动态网络链路预测广泛的应用前景,使得其逐渐成为网络科学研究的热点.动态网络链路演化过程中具有复杂的空间相关性和时间依赖性,导致其链路预测任务极具挑战.提出一个基于时序图卷积的动态网络链路预测模型(dynamic network link prediction based on sequential graph convolution, DNLP-SGC).针对网络快照序列不能有效反映动态网络连续性的问题,采用边缘触发机制对原始网络权重矩阵进行修正,弥补了离散快照表示动态网络存在时序信息丢失的不足.从网络演化过程出发,综合考虑节点间的特征相似性以及历史交互信息,采用时序图卷积提取动态网络中节点的特征,该方法融合了节点时空依赖关系.进一步,采用因果卷积网络捕获网络演化过程中潜在的全局时序特征,实现动态网络链路预测.在2个真实的网络数据集上的实验结果表明,DNLP-SGC在precision, recall, AUC指标上均优于对比的基线模型.

可自修复海藻酸基离子凝胶的制备及性能

为了解决传统人工合成高分子基离子凝胶难降解、成本高、环境污染等问题,本文以天然高分子—海藻酸为聚合物基体,通过在离子液体中对其进行化学接枝改性和交联反应,设计并制备了一种具有自修复性能的化学交联型生物基离子凝胶。流变测试结果表明,该离子凝胶的模量随着海藻酸和交联剂含量的增加而升高,且在150℃的高温下离子凝胶依然可以保持凝胶结构。所制备的离子凝胶具有优异的压缩性能,压缩强度随着海藻酸含量的增加而增加,压缩强度可达1.02 MPa。电化学测试结果表明,离子凝胶具有良好的导电性能,其室温离子电导率都高于0.3 mS/cm。重要的是,离子凝胶在室温下无需任何辅助手段可在6 h完全自修复,表现出良好的自修复性。该研究为开发具有自修复性的高性能生物基离子凝胶提供了有效途径。

基元库构建思想的机器人动作与策略演示学习方法

为解决机器人演示学习过程中演示数据优化、动作与任务策略的存储调用问题,提出一种利用基元库思想的演示学习方法。动作学习采用专家拖动机械臂执行动作获取演示数据,利用高斯混合模型与高斯混合回归提升数据质量,由动态运动基元算法转换为基函数的权重值。策略学习将任务步骤创建为动作基元,向基元内添加得到的权重值并构建包含任务执行策略的基元名片,由基元组成基元库完成存储。执行任务时从基元库中有序调用基元,利用YOLOv5目标检测网络和AlexNet图像分类网络检测目标信息,匹配动作并泛化出具有原动作特征的新动作。该方法实现了从演示中学习动作与策略存储,根据实际目标组合合适动作完成任务。钢筋绑扎实验创建5个动作基元,通过专家演示学习10个动作,机器人利用动作基元库成功完成水平面与竖直面钢筋交叉点绑扎任务说明其有效性。

“探索”视角下的书目关联数据化与图书馆服务创新研究

《IFLA图书馆参考模型》(IFLA-LRM)概念模型取代FRBR,以此为统领,RDA、BIBFRAME和MARC21的一系列元数据标准的革新,体现了关联数据时代图书馆资源数据突破平台限制、提升在互联网的可见度、实现复用与共享的意图。新增的“探索”用户任务是理解多个元数据标准文件不断更新迭代的关键线索,把握书目关联数据化这一趋势,并且不受限于以文献为中心的思维定式,将“探索”思维贯穿在图书馆工作的各个方面,将为转型时期的图书馆事业创新带来启发,更好地服务于智慧图书馆时代的用户群体。