Quasi-min-max MPC for visual servoing stabilization of omnidirectional wheeled mobile robots

This paper proposes a new visual servoing quasi-min-max MPC algorithm for stabilization control of an omnidirectional wheeled mobile robot subject to physical and visual constraints. The visual servoing dynamics of the robot are modeled as the state-dependent linear error system with nonlinear control inputs of rotation and deflection velocities of wheels. The state-dependent linear error system is covered as linear parameters-varying models which is used to design the visual servoing quasi-min-max MPC controller. The actual control inputs of the robot are then computed by the solution of an inverse algebraic equation of the MPC actions. The recursive feasibility and stability of the new visual servoing MPC are ensured by some LMIs conditions. The performance and practicability of the visual servoing MPC are verified by some simulation and experiment results.     

移动式表面流场测量技术及应用研究北大核心CSCD

本文开展明渠水槽桥墩绕流和推移质输沙试验,沿水槽方向使用高速相机进行移动拍摄,通过智能识别边壁控制点坐标对图像进行裁剪。通过形态学方法提取表面示踪粒子后,使用粒子追踪测速(PTV)技术和图像特征点识别测速(FMV)计算瞬时表面流场,根据流场位置对所测表面流场区域网格化后进行插值计算,以获得较大范围的表面流场。结果表明:本文使用的移动式表面流场测量方法可提高表面流场的精度和测量范围,此方法拓宽了表面流场测量的应用工况;FMV方法在圆柱绕流试验中可更准确识别圆柱侧方及后方旋转强度较大的区域,所求断面平均流速分布曲线更符合水流特性;推移质运动过程发现紊流表面时均流速仍存在高低速流带结构现象,同时高流速条带对应沙垄而低流速条带对应沙脊处,这表明水流地形相互固定形成了稳定时均结构,也验证了大尺度流向涡模型的合理性。     

机动雷达地网接地电阻的预估算法

系统接地问题是制约机动雷达机动性能的关键因素之一。通过对垂直地网、水平地网、复合地网三种机动地网技术的理论研究与测试验证,提出了不同地网技术接地电阻的近似计算方法,并在理论推导的基础上,提出了机动地网接地电阻的预估算法。经实际测试证明本文所提算法简单可行,并且已经在某型号机动雷达上开展了实际应用,能够为后续机动雷达应急接地提供重要的技术保障。     

移动源排放遥测主要影响因素分析及预测

由于移动源污染遥感监测受到复杂外部环境影响, 难以通过传统统计方法建立车辆行驶工况与污染排放之间 的相关性模型, 为此开展了基于移动源遥感监测的影响因素分析及排放预测的研究。首先利用 Spearman 相关性分析 排除与移动源污染物主要排放气体 CO、 HC、 NO 气体浓度无相关性的因素; 其次使用 Lasso 算法确定各成分的关键 影响因子, 并采用神经网络构建污染物排放预测模型; 最后在测试集上验证该模型用于移动源污染排放主要成分预测 的有效性。模型预测的结果表明, 基于特征筛选的移动源污染排放数据预测神经网络模型具有较高的预测精度, 可以 降低城市移动源污染排放检测成本并为相关部门制定相关政策提供数据支持。     

终端近场通信天线研究北大核心CSCD

近场通信(NFC)已成为无线终端的标配功能,工作范围小、抗干扰性和安全性较高的特性使其被广泛应用于终端的移动支付和虚拟卡片等领域。由于近场天线产生的感应磁场会在临近的金属上耦合出反向涡流,并且金属屏蔽物覆盖会降低收发天线间的磁场耦合,紧凑终端中的电池、主板、外壳等金属元件将大幅影响NFC天线性能。本文从近场通信的历史、标准、系统结构出发,以终端NFC天线工作环境中的金属覆盖情况作为分类依据,对终端近场通信天线的研究进展进行了简要介绍。     

A path planning model based on nested regular hexagons using weighted centroid localization

In many wireless sensor network (WSN) applications, the location of a sensor node is crucial for determining where the event or situation of interest occurred. Therefore, localization is one of the critical challenges in WSNs. Mobile anchor node assisted localization (MANAL) is one of the promising solutions for the localization of statically deployed sensors. The main problem in MANAL localization is that the path planning of the mobile anchor (MA) node should be done so that the localization error in the network will be minimal and that all unknown nodes in the network are covered. This paper proposes a new path planning approach called nested hexagons curves (NHexCurves) for MANAL. NHexCurves guarantees that it will receive messages from at least three non-collinear anchors to locate all unknown nodes in the network. The proposed model has compared six different path planning schemes in the literature using weighted centroid localization (WCL). In these comparisons, first of all, localization errors of the models are compared using some statistical concepts. Second, the variation of the localization error according to parameters such as resolution (R) and the standard deviation of noise (σ) is observed. Then, with similar approaches, the standard deviation of errors, localization ratio, scalability performances, and finally, path lengths of the models are examined. The simulation results show that the NHexCurves static path planning model proposed in this study stands out compared to other models with high localization error and localization ratio performance, especially at low resolutions, due to its path design. At the same time, the lowest error values according to σ are obtained with the proposed model among all models considered.     

ACO–EEOLSR: enhanced energy model based link stability routing protocol in mobile ad hoc networks

A mobile ad hoc network (MANET) has abundant mobile nodes that are free to communicate independently in many locations. Many existing energy models address the inadequacy of resources based on Ad hoc On-demand Multipath Distance Vector and Optimized Link State Protocol (OLSP) routing protocols for MANET along with various parameters. The architecture of energy-efficient routing mechanisms is a challenging problem in a MANET. In this work, a novel energy-aware routing model is introduced for MANET comprising an ant colony optimization (ACO) enhanced approach to energy-efficient-optimized link state routing (named ACO–EEOLSR). Initially, the route discovery is progressed by means of neighbor estimation and also with the authentication of link stability. Parameters such as energy, distance, and hop count are employed as willingness nodes, where both the energy and distance are entrenched through the OLSP. Consequently, the hop count is applied via the ACO system that is beneficial for link stability. After the acceptance of an acknowledgement, the hop count is authorized for further performance analysis. This approach increases the Quality of Service and also uses less energy compared to other energy models. The accomplished simulation upshot depicts that the ACO–EEOLSR outperforms the EEOLSR scheme with respect to the performance metrics of energy consumption, packet delivery ratio, total remaining time, average network lifetime, and a variance of energy.     

氧化镧/聚丙烯防X射线复合纤维的制备及性能表征

先采用熔融纺丝方法制备了不同氧化镧含量的氧化镧/聚丙烯复合纤维,然后采用对二甲苯在相同处理时间(1 h)不同温度(105~109℃)下溶解复合纤维中的部分聚丙烯基体以提高纤维中氧化镧含量,并对处理过后的纤维进行扫描电镜、X射线屏蔽性能等测试。此外,采用硅烷偶联剂改性氧化镧,通过熔融纺丝法制备了表面活性氧化镧/聚丙烯复合纤维,并对其作了差示扫描量热分析、扫描电镜、力学测试等性能表征。实验结果表明,随未改性氧化镧添加量增加,纤维力学性能下降,玻璃化转变温度向低温方向移动,纤维热稳定提高;有机改性可改善氧化镧在聚丙烯中的分散,提高纤维的力学性能,纤维玻璃化转变温度较纯聚丙烯纤维升高;用对二甲苯在107℃处理1h所获取的复合纤维中氧化镧含量最高,X射线屏蔽性能最优。     

基于老年人偏好的手机图标尺寸可用性设计研究

目的提高老年人对手机界面的用户体验。方法以老年人手机界面中的启动图标为研究对象,根据Android系统中手机界面图标的设计规范,围绕48×48 px,72×72 px,96×96 px 3种常见图标尺寸,采用单因素实验方法对手机图标的可用性进行研究。结论手机图标的设计应满足用户的使用习惯,并应兼顾界面的整体美感,只有这样才能具备良好的可用性。     

不同表面活性剂处理的Sb_2O_3对PVC复合材料阻燃性能的影响

利用高能球磨法制备Sb_2O_3粉末,采用聚乙二醇-6000、十二烷基硫酸钠和OP-10对Sb_2O_3粉末进行表面改性,研究不同表面活性剂改性的Sb_2O_3颗粒对PVC复合材料体系阻燃性能的影响。运用X射线衍射仪(XRD)、透射电子显微镜(TEM)对Sb_2O_3的物相组成、颗粒形貌、平均粒径进行表征,利用X射线能量色散谱仪(EDS)、极限氧指数仪以及垂直燃烧实验分别对Sb_2O_3/PVC复合材料的粒子分布、阻燃性能进行研究。结果表明:当聚乙二醇-6000作为表面活性剂时,由于纳米Sb_2O_3粒子表面有机膜空间位阻效应较大,使得纳米Sb_2O_3在PVC基体中表现出良好的分散性。当纳米Sb_2O_3添加量为1.26%(质量分数,下同)时,PVC复合材料的氧指数为27.1%,材料处于难燃级别;当采用十二烷基硫酸钠和OP-10作为表面活性剂时,Sb_2O_3颗粒表面包覆效果差,Sb_2O_3颗粒粒径分别为100nm和150nm,Sb_2O_3在PVC基体中分散性变差,并出现团聚现象。当Sb_2O_3添加量为1.26%时,PVC复合材料的氧指数分别为24.7%和25.3%,材料未达到难燃级别。