反坦克导弹带落角约束滑模导引律研究

为增大反坦克导弹终端落角,提高战斗部的毁伤效能,基于终端滑模控制理论,及弹目相对运动模型,选取弹目相对速度偏角作为滑模面,同时引入落角约束项,结合快速幂次趋近律,推导出了一种带落角约束的滑模导引律。采用有限时间控制理论对导引律的稳定性和有限时间收敛特性进行了证明。最后基于弹道仿真,将该导引律与带落角约束的偏置比例导引律进行了对比仿真分析,结果表明该导引律能够满足制导精度和末端落角约束的要求,脱靶量更小,落角控制精度更高,鲁棒性更强。     

带落角约束三维导引律在反坦克导弹上的应用

针对现代作战环境不仅希望反坦克导弹脱靶量最小,还希望导弹命中目标时姿态最佳的问题,对传统比例导引律和带落角约束的比例导引律进行了研究,并提出了带有碰撞角约束的三维比例导引律,即在俯仰通道采用带落角约束的比例导引,在偏航通道采用传统比例导引。最后以某型自寻的反坦克导弹制导控制系统的设计为背景,通过结合导弹总体参数,建立弹体运动数学模型、制导控制系统模型、舵机模型等,并利用Simulink对其进行了仿真。仿真表明,2种导引律结合运算的方法不仅易于实现,而且具有精度高、落角变化范围大,过载小的优点。     

自寻的多用途反坦克导弹基准弹道设计与仿真

为了使反坦克导弹满足现代战场多用途化的需要,可实现平飞攻击和攻顶攻击,对某型反坦克导弹平射弹道和攻顶弹道进行了初步设计,提出了一种可以实现平射和攻顶的弹道方案,在外弹道学和导弹总体参数的基础上建立了它的运动方程,最后基于Simulink对其进行了编程和仿真。仿真结果表明,采用设计的弹道方案平射时导弹落角可达-15°的要求,攻顶时导弹落角可达到-30°的要求,即可以实现平射和攻顶弹道,所以设计的弹道可为未来多用途反坦克导弹弹道提供借鉴。     

基于预测碰撞点带落角约束的导引律设计

为提高导弹导引精度,增强对落角的控制,针对带倾角运动的目标,推导了攻击运动目标带落角约束的偏置比例导引律。通过在偏置项中加入导弹-目标的相对运动状态,实现对带倾角运动目标指定角度攻击;考虑到导弹带落角约束攻击运动目标时传统剩余飞行时间估计精度不高的问题,通过对弹目碰撞点的预测,在推导的导引律基础上设计了基于预测碰撞点的剩余飞行时间估计方法。仿真结果表明:在不同的落角约束下,设计的基于预测碰撞点的剩余飞行时间估计方法估计精准;推导的攻击运动目标带落角约束的偏置比例导引律攻击精度高,对落角控制强,过载分布合理。     

一种基于过重力补偿的双角度约束制导律研究

为保证被动寻的导弹在较低的平飞弹道情况下实现对坦克目标的最佳毁伤效果,设计了一种提升末端落角的修正比例导引制导律。在传统比例导引的基础上加入过重力补偿的修正项,同时考虑导引头框架角的约束,实现对导引头框架角约束下的大角度攻击。仿真表明,该导引律能在满足导引头框架角约束的条件下以大落角命中坦克目标。     

俯冲击顶弹道落角研究

采用俯冲击顶弹道时,为保证对目标的毁伤效果,要求导弹命中目标时具有较大的落角。为增大落角,分别研究了射程和弹道高度、转比点、比例导引系数以及可用法向过载等因素对落角的影响,并进一步提出了提高落角的措施。仿真和引证表明,通过采取调高发射角、加入推力矢量控制以及改进末制导律等措施可有效提高导弹落角。     

利用反步控制法的带角度约束制导律研究北大核心

针对制导炸弹对地垂直攻击的要求,研究了导弹攻击地面运动目标的弹目三维运动规律,构造了带有落角约束的导弹运动方程,并利用反步控制方法,研究了带落角约束的三维近垂直击顶新型末制导律。仿真结果表明,该新型制导律能够在目标机动的情况下满足近垂直击顶的要求,脱靶量也在允许的范围之内。     

利用反步控制法的带角度约束制导律研究

针对制导炸弹对地垂直攻击的要求,研究了导弹攻击地面运动目标的弹目三维运动规律,构造了带有落角约束的导弹运动方程,并利用反步控制方法,研究了带落角约束的三维近垂直击顶新型末制导律。仿真结果表明,该新型制导律能够在目标机动的情况下满足近垂直击顶的要求,脱靶量也在允许的范围之内。     

考虑弹体动态特性的机动效率约束导引律

针对考虑交会角和过载约束导引律在大机动时能量损失大的问题,提出一种考虑导弹机动效率的多约束制导律。应用最优二次型原理推导出考虑一阶弹体延迟的时变导引系数闭环次优制导形式,将导弹机动时刻阻力系数引入时变权系数,并通过迭代确定机动效率约束边界。将时变约束表示成剩余时间与弹体延迟时间的函数,代入制导指令,进行弹道仿真。结果表明,对于常值与机动目标,文中制导律与过载约束导引律同只考虑交会角约束的导引律相比,对目标均能实现末端弹道成型要求,而考虑机动效率的制导指令分配更为合理,在避免指令加速度饱和的同时有效降低了拦截末端速度损耗,提高制导精度与毁伤效果。且该制导律中时变权系数无须配平求解,在保证精度的同时极大地提高了迭代速度。     

带落角约束的自适应滑模变结构导引律

针对某些制导武器在精确命中目标的同时还要满足落角约束的要求,基于滑模变结构理论,提出一种带落角约束的自适应滑模变结构导引律。考虑末端弹目视线角速率变化剧烈和变结构抖振现象的问题,选取相对速度偏角作为滑模面,引入落角约束项;将目标机动视为有界干扰,利用Lyapunov理论进行了稳定性分析;采用变开关系数法和饱和函数法相结合的方法,大大削弱了变结构的抖振现象。最后,将该导引律应用于导弹实际模型中进行对比仿真,结果表明所提导引律针对固定目标和机动目标,相比传统方法,都能以更小的脱靶量和落角误差命中目标。     

An Unlikely Alliance: Portuguese and South African Airpower in Angola, 1968–1974

The war that Portugal was obliged to fight in Africa began in 1961 and immediately stretched the resources of its armed forces. Nowhere was this thinness more apparent than in policing the vast territory of Angola. The east and southeast of Angola were particularly vulnerable, as the area was a vast, sparsely populated region characterised by enormous featureless plains or chanas covered in tall grass and broken by an extensive river system and mountainous forests. The only military solution to policing these immense spaces was aviation and specifically the helicopter that could carry troops into battle, protect them with a gunship and bring them home when the operation was concluded. The immediate problem for the Portuguese Air Force (Força Aérea Portuguesa or FAP) in Angola and elsewhere was a scarcity of helicopters. The solution was an alliance with South Africa, which had a strong inventory of Alouette IIIs, to help in policing the east. This move was likewise in the interest of South Africa, as its threat came from Zambia through south-eastern Angola. This article examines the strategic and tactical development of this unusual, cross-cultural alliance and the symbiotic relationship that resulted in destruction of the enemies of both in Angola.     

国内外结构钢焊条研究的现状与发展

本文主要介绍了国外焊条的现状和发展趋势,包括焊条的高韧性、高效率、低尘低毒和耐吸潮性能,为国内的焊条研究提供了参考依据。     

A Sign of Victory?: ‘Scottish Swords’ and Other Weapons in the Possession of the ‘Auld Innemie’

Many late medieval documents, notably inventories of arms and armour, of Englishmen contain references to ‘Scottish swords’ and other weapons. What did the compilers of these documents mean when they described a weapon as ‘Scottish’? How did such weapons come to be in the possession of these men? This article will attempt to explain this phenomenon drawing on primary documentary sources and surviving material culture from Glasgow Museums’ collections and others, as well as artworks from the period.     

Helping hands: civil–military cooperation and Italy's military operation abroad

In the Post-Bipolar Era the growing complexity of the military operations requires a new approach for the resolution of international crises. Since the end of the Cold War, peace support operations (PSO) have become the mainstay and principal occupation of most Western armies. At the same time, Italy has been one of the most important actors in such an area. The article focuses on the cooperation between military and civil components (a process called CIMIC) as a key variable in the Italian PSOs. We will analyse in detail the main lessons learned from past military interventions as well as the general context in which new tendencies are taking place. The maintaining of a minimum security frame becomes essential to fulfil activities ‘collateral’ to the mission: reconstructing services and infrastructure, food distribution, water and medication, law and order, de-mining, training of local forces, and supporting local institutions. These are the main tasks to obtain thrust and support from the population.     

Terrorism,insurgency, kidnapping,and security in Africa's energy sector

Energy continues to serve as the bedrock of modern economies and the main driver of modern society. For Africa, the production and supply of energy resources such as crude oil, natural gas, uranium, coal, biomass, biofuels and other renewables are an important source of employment, rents, taxes, royalties and profits. This sector brings in several tens of billions of dollars of revenue annually. The production and delivery of such resources, however, depend on critical infrastructures such as pipelines, refineries, processing plants, terminals, rigs, electrical energy pylons, substations, pump stations, vessels, and tankers. These infrastructures have been attacked by terrorists, insurgents, vandals and saboteurs, all of whom see them as targets against which to register their grievances and extract concessions from the state. This paper is a chronological account of some of the documented incidents of terrorism, insurgency, kidnapping, destruction, sabotage, and human casualties suffered in the oil and gas sectors in Africa between 1999 and 2012. It is based on data extracted from the databases of the RAND Database of World Terrorism Incidents and the University of Maryland's Global Terrorism Database (GTD).     

Cyberpower in Strategic Affairs: Neither Unthinkable nor Blessed

Abstract

This article explores the effect of connectivity on strategic affairs. It argues that the effect on war's character is potentially, although not yet shown in practice, considerably large. Its effect upon the distribution of power among states in the international system is small, contrary to the claims of ‘cyberwar’ alarmists. All told, however, its effect upon strategic affairs is complex. On the one hand, it represents a significant advance in the ‘complexification’ of state strategies, understood in the sense of the production of intended effects. On the other hand, strategists today – still predominantly concerned with the conflicts and confrontations of states and organised military power – are generally missing the power which non-traditional strategic actors, better adapted to the network flows of the information age, are beginning to deploy. These new forms of organization and coercion will challenge the status quo.     

Tacit support for terrorism: The rapprochement between the USSR and Palestinian guerrilla organizations following the 1967 war

This article demonstrates the inconsistent and wavering Soviet attitude towards national liberation movements in general and the Palestinian organizations in particular. Until the late 1960s, the Soviets viewed these organizations with suspicion, hesitating to engage in political dialogue with them. However, in the 1970s, political and military events in the region, as well as modifications in the Kremlin's Cold War strategies, led to a general shift towards the Middle East in Soviet foreign policy. Soviet leaders showed increased willingness to provide certain Palestinian organizations with arms with which to conduct terrorist activities against Israeli, pro-Israeli, Jewish and Western targets. The article explores the complex relations between Palestinian organizations and the USSR in the field of international terror. The study also exposes and analyzes the nature and content of Soviet–Palestinian arms dialogues and transactions. It provides clear evidence that Soviet policymakers and other luminaries were fully informed of, and sometimes directly involved in, these transactions and dialogues at the highest levels.     

A1 Qaeda and the radical Islamic challenge to western strategy

The September 11 global crisis prompted by the attacks on the World Trade Center and the Pentagon raises major questions concerning the nature and trajectory of terrorism in the post-Cold War global order. Hitherto, terrorism has been largely debated by analysts at the level of nation states. Terrorist and insurgent movements have also been largely anchored in nationalist and ethnic power bases even when they have sought to mobilise a transnational ideological appeal on religious or class grounds. There have been a few exceptions to this pattern such as the alliance between the German Baader-Meinhof group and the Japanese Red Army Faction, but even such international alliances as this did not, until at least the 1980s, presage anything like a global terrorist network necessitating a global strategic response. This study examines terrorism and global strategic responses.