基于webots的机器人避障及物体识别仿真

本文运用webots对机器人在家庭环境下物体识别可能遇到的问题进行了模拟仿真,验证其可行性.主要完成了对家庭环境和机器人模型的搭建及控制程序的编写并以此实现机器人避障和物体识别.仿真结果表明,此方法可行.为今后的算法改进奠定了基础.     

一种改进RRT的多机器人编队路径规划算法

多机器人路径规划是机器人领域的一个热点问题,相比于单机器人路径规划,其算法难度和复杂度都有所增加,在规划时需要兼顾多机避障、相互协作等难点问题.本文提出一种改进快速扩展随机树的多机器人编队路径规划算法,用于解决多机器人在复杂环境下的编队路径规划问题.针对多机器人在编队规划中的位置约束问题,定义机器人之间的领航-跟随结构,并对机器人队形建模.针对规划过程中编队朝向变化问题,建立搜索树扩展方向与队形方向之间的联系,通过调整队形方向改变规划时的编队朝向.针对具有质点模型和非完整约束动力学模型两种不同模型的多机器人系统,分别进行了仿真实验.仿真结果表明该算法在处理多机器人编队路径规划问题时可以取得良好的效果.     

End-to-End Rate Adaptation to Support Heterogeneous Services for Infrastructure-Based Vehicular Networks

Vehicle to Infrastructure(V2I) communications aim to provide mobile users on the road low-cost Internet and driver safety services.However, to meet Quality of Service(QoS) requirements of various applications and efficiently utilize limited wireless channel resourc-es, the transport layer protocol has to perform effective rate control in low channel quality and frequent changing topology communica-tion environment. In this paper, we propose a novel rate-control scheme in infrastructure based vehicular networks that avoids conges-tion and starvation and promotes fairness in end-to-end V2I communications. In vehicular networks, a bottleneck roadside unit(RSU)keeps track of its buffer size, aggregate incoming rate, and link throughput, and appropriately allocates bandwidth to traversing flows.With feedback information from the RSU, source nodes dynamically adjust their sending rates to avoid buffer overflow or starvation atthe bottleneck RSU. Simulation results show that the proposed scheme can reduce not only packet losses owing to buffer overflow butalso buffer starvation time, which improves the utilization efficiency of wireless channel resource.     

Distributed Power Control for Energy Conservation in Hybrid Cellular Network with Device-to-Device Communication

Device-to-Device （D2D） com- munication has been proposed as a promising implementation of green communication to benefit the existed cellular network. In order to limit cross-tier interference while explore the gain of short-range communication, we devise a series of distributed power control （DPC） schemes for energy conservation （EC） and enhancement of radio resource utilization in the hybrid system. Firstly, a constrained opportunistic power control model is built up to take advantage of the interference avoidance methodology in the presence of service requirement and power constraint. Then, biasing scheme and admission control are added to evade ineffective power consumption and maintain the feasibility of the system. Upon feasibility, a non-cooperative game is further formulated to exploit the profit in EC with minor influence on spectral efficiency （SE）. The convergence of the DPC schemes is validated and their performance is confirmed via simulation results.     

深亚微米IC物理设计流程中的串扰控制

信号完整性的设计收敛已经成为当前深亚微米集成电路物理设计流程中的关键问题。对信号完整性收敛产生不利影响的有三个因素：串扰、直流电压降和电迁移。其中影响最大的是串扰,串扰噪声会产生大量的时序违规、逻辑错误。主要关注基于串扰控制的物理设计方法,包括新的流程、各个设计阶段对串扰的分析及修正的方法,以达到快速的时序收敛。并且根据真实的设计实例,提出了几点有效的控制串扰的方法和对于信号完整性管理比较有价值的观点。     

Repair the faulty TSVs with the improved FNS-CAC codec

Through-silicon via (TSV) is a key enabling technology for the emerging 3-dimension (3D) integrated circuits (ICs). However, the crosstalk between the neighboring TSVs is one of the important sources of the soft faults. To suppress the crosstalk, the Fibonacci-numeral-system-based crosstalk avoidance code ( FNS-CAC) is an effective scheme. Meanwhile, the self-repair schemes are often used to deal with the hard faults, but the repaired results may change the mapping between signals to TSVs, thus may reduce the crosstalk suppression ability of FNS-CAC. A TSV self-repair technique with an improved FNS-CAC codec is proposed in this work. The codec is designed based on the improved Fibonacci numeral system (FNS) adders, which are adaptive to the health states of TSVs. The proposed self-repair technique is able to suppress the crosstalk and repair the faulty TSVs simultaneously. The simulation and analysis results show that the proposed scheme keeps the crosstalk suppression ability of the original FNS-CAC, and it has higher reparability than the local self-repair schemes, such as the signal-switching-based and the signal-shifting-based counterparts.     

OBS网络中基于拥塞避免的提前偏射路由研究

突发竞争是OBS(光突发交换)网络需要解决的关键问题,偏射路由作为一种有效的竞争解决方案而被广泛研究。文章提出了一种基于拥塞避免的提前偏射路由算法,利用周期性反馈的网络拥塞信息按一定概率提前偏射部分突发包。与传统的最短偏射路由算法相比,本算法达到了避免拥塞以及均衡网络负载的目的。仿真结果表明:文章所提算法在突发丢失率、吞吐量以及平均链路利用率方面性能都有所提高。     

基于多维频谱地图的干扰规避

针对复杂电磁环境下卫星移动通信系统可靠通信需求,利用频谱地图多维数据呈现优势,提出了基于多维频谱地图的干扰规避方法。通过建立卫星移动通信系统波束、时隙、子频带、干扰强度等多维信息关联的频谱地图,利用数据挖掘方法对频谱可用情况进行预测,基于预测结果及用户QoS(Quality of Service)需求生成干扰规避策略,通过星地联合频谱资源调配实现系统干扰规避。该方法为卫星移动通信系统干扰规避提供了一种全新的思路,可提升卫星移动通信系统干扰防护能力。     

基于多信道预约可冲突避免的多址接入协议

本文为多跳分布多无线网络提出了一套灵活而有效的自适应获取冲突避免（AACA）的多址接入协议。在该协议中，各节点竞争公共信道，利用RTS/CTS对话形式来预约各业务信道，成功预约后的分组传输不会受到其他节点的干扰。它使用任意确定数目信道，以异步方式工作，并且使得各节点利用半双工无线电台就可以灵活、简便地实现资源预约。分析和比较结果说明，所提出的多信道预约协议可以有效地解决隐藏终端、暴露终端以及侵入终端的问题。     

Interferometric monitoring of satellite longitudes

This paper proposes a technique for monitoring the longitudinal motion of geosynchronous satellites. A two‐antenna interferometer is used, with the baseline orientation adjusted to a particular horizontal azimuth. The interferometer then becomes insensitive to the north–south motion of the satellite, and this enables direct measurement of the satellite's longitudinal motion. Longitudes are monitored continuously, with no delay when orbital manoeuvres occur. The proposed technique is particularly useful when two or more satellites are operating in close proximity and their longitudes must be precisely monitored for safety control. Copyright © 2005 John Wiley & Sons, Ltd.