Millimeter wave backscatter measurements in support of collision avoidance applications

Millimeter-wave short range radar systems have unique advantages in surface navigation applications, such as military vehicle mobility, aircraft landing assistance, and automotive collision avoidance. In collision avoidance applications, characterization of clutter due to terrain and roadside objects is necessary in order to maximize the signal-to-clutter ratio (SCR) and to minimize false alarms. The results of two types of radar cross section (RCS) measurements at 95 GHz are reported in this paper. The first set of measurements presents data on the normalized RCS (NRCS) as well as clutter distributions of various terrain types at low grazing angles of 5° and 7.5°. The second set of measurements presents RCS data and statistics on various types of roadside objects, such as metallic and wooden sign posts. These results are expected to be useful for designers of short-range millimeter-wave collision avoidance radar systems.     

Wheel slippage and sinkage detection for planetary rovers

Mobile robots are increasingly being used in high-risk rough terrain situations, such as planetary exploration and military applications. Current control and localization algorithms are not well suited to rough terrain, since they generally do not consider the physical characteristics of the vehicle and its environment. Little attention has been devoted to the study of the dynamic effects occurring at the wheel-terrain interface, such as slip and sinkage. These effects compromise odometry accuracy, traction performance, and may even result in entrapment and consequent mission failure. This paper describes methods for wheel slippage and sinkage detection aiming at improving vehicle mobility on soft sandy terrain. Novel measures for wheel slip detection are presented based on observing different onboard sensor modalities and defining deterministic conditions that indicate vehicle slippage. An innovative vision-based algorithm for wheel sinkage estimation is discussed based on edge detection strategy. Experimental results, obtained with a Mars rover-type robot operating in high-slippage sandy environments and with a wheel sinkage testbed, are presented to validate our approach. It is shown that these techniques are effective in detecting wheel slip and sinkage.     

Studies of base-station antenna height effects on mobile radio

As is well known, a base-station antenna height gain factor of 6 dB/octave has been predicted theoretically for signal path loss over flat ground and has been verified by measured data. However, the 6-dB/octave rule for antenna height effect cannot be used to predict signal strength for terrain contours if the terrain is not flat. A model has been developed for waves propagating over a nonflat ground which allows the antenna height effect to be predicted in different types of actual terrain contours. In the model, the actual terrain profile is classified as one of two different kinds of general terrain types. The relative received power due to the actual terrain path contour is predicted by considering the reflection points of the waves along the path. Experimental data have been used to verify the theoretically estimated results and they show good agreement.     

穿透叶簇UWB雷达人造目标简化电磁模型

穿透叶簇的VHF／UHF超宽带(UWB)SAR具有相对带宽很宽,积累角大的特点,可同时获得距离、方位的高分辨能力,能用于探测叶簇隐蔽的军用车辆等人造目标而有着重要的军事应用价值。在VHF／UHF低频段,一般的人造目标可简单模化为目标主侧面与地表面之间形成的直二面角。本文详细推导了二面角人造目标光学区的散射场,建立了低频UWB雷达人造目标的光学区简化电磁模型,进而分析预测了二面角目标的散射特性。预测结果与外场试验分析得到的目标特性之间的一致性表明本文所建立的电磁模型是正确合理的。     

Network-Centric Systems for Military Operations in Urban Terrain: The Role of UAVs

Military systems are the motivational driver for much of the technology development conducted at applied research laboratories around the world. As the needs of the world's militaries change, so does the focus of this research and development. In this paper, we discuss how the fundamental characteristics of military operations in urban terrain (MOUT) impose requirements and constraints on sensing and reconnaissance. We highlight the importance of a new class of small unmanned aerial vehicles (UAVs) for network-centric military urban operations. We review some of the UAVs that have been developed in recent years, and that are under development, with particular attention to their endurance, portability, performance, payload, and communication capabilities. Selected university testbeds are also briefly noted. Over the last few years there has been considerable research focused on how these small UAVs, both individually and collectively, can operate autonomously in urban environments and help capture and communicate needed information. We discuss some of this research; specific topics covered include guidance and control for autonomous operation, multi-UAV coordination and route optimization, and ad-hoc networking with UAV nodes. A new concept of operations is described that relies on coordination and control of a heterogeneous suite of small UAVs for surveillance and reconnaissance operations in urban terrain     

一个地形可视化系统的建立与阴影分析计算

地形可视化对土地的规划利用和综合决策都具有重要的应用价值。它能够给人们提供一个直观的地理形象，便于实施操作和想定作战方案，从而取代传统的沙盘模型且易于进行地形定量计算。本文根据某工程的实际需要建立了一个地形可视化系统，并对太阳时角地形造影(阴影)进行了分析计算。实用结果证明：该系统效果良好。     

灾区军用车辆优化调度方法研究与仿真

在军用车辆调度过程中,由于军用物资运送的目的地有时会比较偏僻,而且运输路径中会存在堵塞情况,造成传统的军用车辆调度方法无法选取最优路径,使军用物资不能及时运输到目的地,从而无法满足军队战备需要.因此,提出了一种基于改进蚁群算法的车辆优化调度方法.建立军用车辆调度数学模型,描述运输车辆之间的联系.利用改进蚁群算法,对军用车辆调度模型进行优化处理.实验结果表明,这种算法能够有效提高军用车辆运输效率,取得了令人满意的结果.     

基于建模仿真的战车分类算法研究

战车类型的识别分类是现代情报获取的重要研究内容。为了获得数据并研究战车分类算法,常进行外场真实实验,但其时间长、耗资巨大。本文在虚拟战场仿真平台上建立坦克、装甲车、运兵车三种战车模型。利用仿真环境中的战车噪声、磁场、振动特征信号作为样本数据,进行战车的分类算法研究。同时基于一对一多分类支持向量机,设计了一种战车分类算法,并给出了分类器交叉验证参数调整策略。实验表明,相比于AdaBoost算法,文章提出的战车分类算法的分类准确率较高。     

Seismic source model for moving vehicles

We develop a method for the loading of ground by moving vehicles in large finite-difference time-domain simulations of seismic wave propagation. The objective is to realistically produce two distinct types of ground loading for either wheeled or tracked vehicles in our propagation models: lower frequency loading associated with suspension dynamics and higher frequency impulsive loading associated with tire treads or wheels rolling over individual track blocks. These loading characteristics are important because field measurements show that vehicle ground forcing in both frequency bands produces seismic surface waves that networked sensors can remotely process for security applications. The method utilizes a vehicle-dynamics model to calculate a response to vehicle acceleration and ground features such as bumps; calculates forces transmitted to the ground; distributes these forces to staggered points of a finite-difference model; and simulates seismic wave propagation away from the vehicle. We demonstrate the method using bounce-and-pitch models of wheeled and tracked vehicles. We show that by carefully preprocessing force inputs, we can accurately simulate wave propagation and seismic signatures in finite-difference analyses of vehicles moving continuously over terrain.     

Modeling and Simulation of Various Hybrid-Electric Configurations of the High-Mobility Multipurpose Wheeled Vehicle (HMMWV)

Although hybrid-electric vehicles have been studied mainly with the aim of increasing fuel economy, little has been done in order to improve both fuel economy and performance. However, vehicular-dynamic-performance characteristics such as acceleration and climbing ability are of prime importance in military vehicles such as the high-mobility multipurpose wheeled vehicle (HMMWV). This paper concentrates on the models that describe hybridized HMMWV vehicles and the simulation results of those models. Parallel and series configurations have been modeled using the advanced-vehicle-simulator software developed by the National Renewable Energy Laboratory. Both a retrofit approach and a constant-power approach have been tested, and the results are compared to the conventional model results. In addition, the effects of using smaller engines than the existing ones in hybrid HMMWV drive trains have been studied, and the results are compared to the data collected from an actual implementation of such a vehicle. Moreover, the integrated-starter/alternator (ISA) configuration has been considered, and the results were encouraging     

Architectural principles for safety-critical real-time applications

This paper addresses the general area of computer architectures for safety-critical real time applications. The maximum acceptable probability of failure for these applications ranges from about 10^-4 to 10^-10 per hour depending on whether it is a military or civil application. Typical examples include commercial and military aircraft fly-by-wire, full authority engine control, satellite and launch vehicle control, ground transport vehicles, etc. Realtime response requirements for these applications are also very demanding, with correct control inputs required every 10 to 100 ms, depending on the application. These dual goals of ultrahigh reliability and real-time response necessitate computer systems that are quite different from other dependable systems in their architecture, design and development methodology, validation and verification, and operational philosophy. This paper highlights these differences by describing each of these aspects of safety-critical systems. Architectural principles and techniques to address these unique requirements are described     

装甲车辆与地面背景的热交互作用及红外仿真

为了全面揭示装甲车辆与地面背景之间热交互作用对地面背景温度以及红外辐射特性的影响,建立了装甲车辆和地面背景的温度和红外辐射特性的模型,重点考虑了装甲车辆与地面之间的传热。通过对地面和履带相关力学关系的引入,建立运动车辆和地面之间热学以及力学的模型,采用了动网格方法对车辆目标在运动后对地面所产生的沉陷现象及在地面上留下的热痕迹进行模拟仿真。基于红外辐射理论,综合考虑自身辐射、反射辐射以及大气传输特性,计算了车辆在3种不同状态下与地面背景之间的热交互作用及红外辐射特征分布,并比较了模拟温度与实验测量温度的误差,验证了模型的精度。仿真结果表明:该方法对地面目标的隐身设计和隐身技术评估具有十分重要的意义。     

The Military and Air Traffic Control

The Department of Defense currently operates about 30 000 aircraft, the largest most varied single fleet of aircraft of those using the National Aviation System (NAS). For this and other important reasons discussed herein, military participation in evolving an efficient and effective NAS forces consideration of a number of important issues by the developers and operators of any future Air Traffic Control (ATC) system. These issues range from those critical aspects of national security and the sovereignty of our air space, through major economic factors in equipping military aircraft and facilities for operation in the NAS, to the necessity for optimizing safety and using efficiently the air space of the world. This paper discusses the roles of the military, both as a user and operator of ATC systems and as a developer of ATC related systems and equipments. The different areas of the NAS in which interfaces exist between the civil and military are defined. These areas include operations, organizational interfaces, and equipment and facility interfaces and in many cases are covered by formal agreements. By way of illustration, two typical military flights are used to show the combined interaction of a military aircraft with both civil and military ground facilities. Communications, navigation, and surveillance requirements are discussed with respect to the various phases of the example flights. An indication of the future ground systems (military and civil) with which military aircraft might interact emphasizes the heavy burden placed on the airborne electronics systems. The paper finally suggests possible approaches that can be considered to ensure that the airborne equipment will not only be compatible with the various military, FAA, and ICAO ground environments in which the aircraft will function, but will also provide some basis for standardization and for efficient spectrum utilization.     

VHF propagation over hilly, forested terrain

Propagation measurements at low altitudes over hilly, forested terrain made with the objective of developing a computer-based propagation model capable of predicting path loss over similar terrain given the terrain profile between transmitter and receiver are reported. The measurements were made at a frequency of 110.6 MHz with the very high frequency omnidirectional range (VOR) station at Gardner, MA, as a transmitter. The received signals were measured at distances between 7 and 15 km by making vertical descents with a helicopter from altitudes of roughly 600 m down to 10 m above ground. Negligible specular ground reflection was observed from this terrain, and no reflection is included in the model. We found good agreement between the measurements and a multiple-diffraction model based on an extension of the Deygout approximation. Use of two knife edges was sufficient to characterize the terrain diffraction. Predictions of the Longley-Rice computer model are included for comparison.     

基于Knowledge-Analysis的军事知识联通研究

军事专业知识在军事决策系统、军事智能教学系统、军事知识查询系统等高技术产品中具有重要的作用。知识库是机器智能的重要来源,所以有必要建立一个完善、协调、具有良好联通性的大型军事知识库,而大量实践证明计算机真正具有智能不仅需要大型知识库,而且更需要知识间广泛的联通。本文主要讨论军事概念联通。所谓概念联通是指通过关系链或属性或属性值将两个概念联系起来的过程。概念联通的目的之一就是通过概念联通帮助发现不同知识源的知识之间的不一致性,尽可能保证所获取知识的完备性和精确性,建立一个大型的军事专业知识库。     

针对复杂地形的热红外成像仿真研究

红外热成像系统由于具有全天时观测能力而得到广泛应用。为了测试和评估高分辨率红外热成像系统的性能,需要大量多种成像条件下的热红外影像作为输入数据源。为获取真实可信的地面热红外仿真图像,提出了一种针对复杂地形的热红外成像模拟方法。该方法综合起伏地表的地形、光照、遮蔽和邻近地域辐射等因素,系统研究了三维地表热辐射的产生和传递机理。利用光学遥感影像和数字高程数据,生成了一天中不同时刻的地面热红外图像。结果表明:该方法生成的24 h序列图像,符合实际地表热辐射场的日变化规律,从而为可见光图像制备红外基准图提供了一种有效途径。     

冲击脉冲雷达探雷

基于毫微秒电磁脉冲理论发展起来的探地雷达技术是一种浅层地下目标探测雷达。根据某型工程侦察车中配置的冲击脉冲探地雷达研制经验,对探地雷达探测地雷时所遇到的若干关键技术进行了研究,给出了工程设计方法。结合具体探测试验数据,对地雷目标识别问题进行了分析,对今后从事冲击脉冲雷达探雷研究工作具有一定参考价值。     

基于LiDAR点云的地理电磁环境建模及仿真研究

在复杂地理环境中,不规则的地形和多样化的地表覆盖物会给电波的传播造成较大的影响.针对数字高程模型（Digital Elevation Model,DEM）电磁建模缺少地表覆盖物信息的不足,研究了基于LiDAR点云的地理电磁环境的建模.采用数学形态学方法对格网化后的LiDAR点云数据进行处理,从点云数据中先后提取了地物、地形的信息,在此基础上,对各种地物赋予其相匹配的电磁参数,得到了更为准确的地理电磁环境的模型,并采用抛物方程模型对有真实地表覆盖物环境下的电波传播特性进行了仿真分析.相较于传统的基于DEM的电磁建模,该电磁建模方法能够获取到地形、地物的信息,更全面地考虑到地物对电波传播特性的影响,预测结果也将更加准确有效.     

Large scale space diversity in a widely spaced network of meteorscatter communication systems and its application to mobilecommunications

A model is developed for predicting the inherent spatial multiplexing or diversity in a widely dispersed network of meteor scatter receivers. The primary measure, network diversity, is defined as the ratio of the arrival rate of useful trails observed by the entire network to the arrival rate at an average node and is less than the number of receivers in the network. Network diversity is calculated from the ground illumination footprint of individual meteor trails and weighted by the spatial arrival pattern of trails. Predictions using the model are compared to an experiment conducted in the western US. Ramifications on the design of meteor scatter communication systems for very large network applications such as automatic vehicle location and tracking are discussed     

An Optimal Traction Control Scheme for Off-Road Operation of Robotic Vehicles

Active degrees of freedom provide a robotic vehicle the ability to enhance its performance in all terrain conditions. While active suspension systems are now commonplace in on-road vehicles, their application to off-road terrains has been little investigated. A fundamental component of such an application is a need to translate desired body motion commands into actuator values through the use of proprioceptive algorithms. The diverse nature of the terrains that might be encountered places variable demands upon the operation of the vehicle. This entails the potential use of a diverse set of algorithms designed to optimize mobility and performance. This paper presents a cohesive control scheme designed for the operation of an autonomous vehicle under all conditions. The ideas presented have been tested in simulation, and some have been used extensively in the field