基于激光与视觉的车辆防撞技术的研究

提出了一种基于视觉与激光测距相结合的车辆防撞技术.首先采用改进的Hough变换对车道标志线进行检测与提取,根据车辆底部的阴影特征搜寻车辆可能出现的位置;利用边缘检测排除非车辆区域;然后结合车辆在图像中的宽度,利用激光测距传感器对前方车辆动态扫描,计算出两车的车距和相对速度;最后用卡尔曼滤波算法连续跟踪检测到的车辆;实验表明:该方法能够实时有效地检测前方车辆,在高精度汽车防撞系统中具有一定的意义.     

Minimum-time approach to obstacle avoidance constrained by envelope protection for autonomous UAVs

An integrated approach is needed for combining path planning for obstacle avoidance with envelop protection to ensure that a UAV is operated within its safe operational limits while maneuvering in obstacle fields. This paper presents a minimum-time approach to this problem by treating obstacle avoidance and envelope protection as inequality constraints in a state space formulation. The approach is used to study the guidance of a rotary wing UAV for aggressive maneuvering in avoiding an obstacle while staying within its operational envelope. The Nonlinear Trajectory Generator (NTG) is used as a real-time optimization solver, and load factor and rotor flapping angle are considered as limit parameters. A nonlinear simulation model of a rotary wing test bed within the Georgia Tech Unmanned Aerial Vehicle Simulation Tool (GUST) is used to evaluate the proposed approach.     

TDD和FDD移动通信系统邻频应用研究

TDD和FDD移动通信系统邻频应用已经成为一种趋势，但同时也带来了一定的干扰问题。本文就TDD和FDD邻频应用时的关键因素展开研究和分析，对高效利用频率提出了相关建议。     

A COLLISION-AVOIDANCE CONTROL ALGORITHM FOR SPACECRAFT PROXIMITY OPERATIONS BASED ON IMPROVED ARTIFICIAL POTENTIAL FUNCTION 1)

针对航天器近距离操作的安全问题,提出了一种基于人工势函数改进的碰撞规避控制算法.根据航天器与目标、障碍物之间的实时状态, 利用人工势函数算法,计算航天器的实时加速度, 规划航天器的轨迹. 为改进人工势函数方法的适用性,提出三个方面的改进措施: 首先, 在人工势函数算法中, 为提高碰撞预警的准确性,减少额外机动, 碰撞预警采用碰撞概率代替相对距离. 其次, 为了提高对接安全,降低接近目标航天器的相对速度, 利用相对速度的安全接近走廊来计算目标排斥力.最后, 针对大多航天器不能提供任意连续变化推力的情况, 设置两种实用的推力形式,如bang-bang控制的推力形式和恒定变化率的推力形式, 代替连续变推力形式.通过对不同算例的比较,成功地揭示了主要任务参数(如碰撞预警方法、速度安全边界和实际加速度形式)对近距离操作安全的影响.结果表明, 该方法可以提高航天器近距离操作的安全性、效率性, 并且结构简单,实时性强.     

微型扑翼飞行器控制系统设计

微型扑翼飞行器的控制是一个难点问题,不仅对体积和重量有一定限制,还需要使飞行器能够有一定的鲁棒性和自主飞行能力。本文设计的控制系统通过遥控和自主飞行相结合的方式,很好的实现了对微型扑翼飞行器的控制。并进一步通过飞行实验验证了控制系统的可行性,飞行效果良好。     

Collision Avoidance by a Ship with a Moving Obstacle: Computation of Feasible Command Strategies

Typographical errors on page 57 of Ref. 1 are corrected.     

A Hybrid Collision Avoidance Scheme for Ad Hoc Networks

A novel hybrid collision avoidance scheme that combines both sender-initiated and receiver-initiated collision-avoidance handshake is proposed for multi-hop ad hoc networks. The new scheme is compatible with the popular IEEE 802.11 MAC protocol and involves only some additional queue management and book-keeping work. Simulations of both UDP- and TCP-based applications are conducted with the IEEE 802.11 MAC protocol, a measurement-based fair scheme and the new scheme. It is shown that the new scheme can alleviate the fairness problem with almost no degradation in throughput. More importantly, it is shown that without explicit information exchange among nodes, the fairness problem cannot be solved conclusively if reasonable throughput is to be maintained. Hence it calls for further work to integrate the new collision avoidance scheme with other schemes that approximate fair queueing and use more contention information in channel access to achieve some QoS assurances in ad hoc networks.     

一种高可靠、高安全性系统--三取二计算机系统

根据容错理论 ,着重阐述了三取二计算机系统的基本组成和工作原理 ,分析了影响三取二计算机系统安全、可靠性的一些关键因素 ,说明了在开发三取二计算机系统过程中所采用的改善和提高安全、可靠性的措施     

Splitting and cone avoidance in the D.C.E. degrees

It is shown that the Cooper splitting theorem for the n-c.e. degrees is not compatible with cone avoidance: For any n > 1, there exist n-c.e. degree a, c.e. degree b such that 0 < b < a and such that for any n-c.e. degrees x,y, if x ∨ y = a, then either b ≤ x or b ≤ y. This provides a new type of elementary difference between the classes of c.e. and d.c.e. degrees, implementable at lower levels of the high/low hierarchy.