伞翼无人机线性自抗扰高度控制

针对伞翼无人机参数不确定性和复杂环境干扰敏感的问题,提出一种伞翼无人机线性自抗扰(Linear Active Disturbance Rejection Control,LADRC)高度控制方法。建立伞翼无人机8自由度飞行动力学模型,并引入风场和降雨模型以更加准确地模拟真实飞行环境。基于LADRC确定总体控制架构,设计线性扩张状态观测器对所有扰动进行估计,并引入误差反馈率在控制中实时补偿。使用该控制方法在多种扰动工况下进行伞翼无人机高度控制仿真实验。仿真结果表明,基于LADRC的高度控制方法能够有效克服内扰和外扰的影响,实现高精度高度控制;与传统PID控制效果相比,LADRC控制器具有更好的抗扰能力和鲁棒性。     

高超声速飞行器中若干气动难题的实验研究

回顾了近几年本研究团队在高超声速飞行器若干气动难题方面的实验研究进展。在边界层转捩方面,测量了边界层转捩现象,研究了攻角效应对圆锥边界层转捩的影响,获得了边界层转捩的脉动特性以其对飞行器表面热流和摩阻的影响。在激波-边界层干扰方面,分析了突起物形状变化对流动特性的影响,研究了复杂外形的流动特性。     

数值模拟气/气喷嘴速度比对燃烧性能的影响

为研究应用于全流量补燃循环发动机的不同气/气喷嘴得到的燃烧流场,通过求解NavierStokes方程组,对不同燃料与氧化剂速度比下的流动燃烧过程进行了数值计算,计算结果与实验结果吻合。仿真结果表明:增加速度比能使燃烧火焰面提前,燃烧效率变大。如果发动机的长度受到限制,可以适当增加速度比以实现高效燃烧。     

利用时间窗权重进行航迹关联

提出一种利用传感器测量数据的时间窗权重进行航迹关联的方法,将目标运动状态的多维向量(如距离、方位角、俯仰角等)分解为多个一维状态标量;根据每个状态标量与时间的关系,提取两条航迹的共同测量时间区间,将其划分为若干个时间窗,计算对应时间窗内的权重;根据时间窗权重差计算每一个状态标量的航迹相似度;应用DS理论或Bayes理论进行航迹关联决策。     

They protect us,but are they using protection? The potential impact of HIV on the South African Police Service

The drivers of HIV/AIDS in the South African Police Service (SAPS) and impact of the disease on this workforce are neglected areas of research. Existing evidence suggests that while the occupational risk for contracting HIV is low, there are factors associated with the profession that, if left unmanaged, place police officers at risk of contracting HIV. This study's two aims are to identify the potential pathways of HIV infection within policing services and determine the probable impact of HIV/AIDS on SAPS. Through a systematic literature review on HIV/AIDS within police services, and by analysing selected SAPS human resource data, the causal pathways and impact of HIV/AIDS on police services are explored. The study finds that police officers (particularly male officers) are likely to be highly susceptible to HIV infection as a result of risky sexual behaviours born out of occupational characteristics such as high levels of stress, difficult working conditions, living away from home and interactions with sex workers. The problem is exacerbated by the ‘macho’ culture that often prevails among police officers. HIV/AIDS interventions within SAPS must focus on sustained behaviour change. Further, HIV programmes must equip officers with the knowledge and awareness to avoid engaging in high-risk sexual practices that may compromise their health and the effectiveness of the policing service.     

THE ‘EXPANDING TORRENT’: BRITISH MILITARY ASSISTANCE TO THE SOUTHERN AFRICAN REGION

In May 2012, Zambia's Inspector-General of Police announced a crackdown on sex workers. This commentary discusses the rationale behind this proposed crackdown and the problems associated with such a policy response.     

具有终端约束的制导炸弹模糊变结构制导律设计

针对INS/GPS制导炸弹对地面目标的精确打击问题,提出带落角约束的模糊变结构制导律。在变结构制导律的基础上,引入终端落角约束项,应用模糊规则对所设计制导律中的变结构开关项系数增益进行在线调节。仿真结果表明,在对地面目标进行攻击时,该制导律降低变结构控制系统的抖振,同时满足制导精度和期望落角的要求,具有有效性和鲁棒性。     

直接力/气动力复合控制系统鲁棒稳定性分析

脉冲发动机作为直接力与空气舵复合控制能有效提高导弹的快速性和末端大过载机动能力。由于脉冲发动机的喷流干扰会对复合控制系统的稳定性产生影响,本文在考虑脉冲发动机自身喷流因子效应以及对导弹气动干扰的情况下,把直接力喷流作用等效为弹体的气动力进行建模,并结合复合控制系统的性能指标以及稳定判据,对一类复合控制自动驾驶仪的鲁棒稳定性进行了分析,给出了直接力喷流作用下复合控制系统的满足性能要求的稳定边界。     

一种新的双输入多通道直流变换器

在传统的含储能单元分布式供电系统中,一般都需要多个单向直流变换器和双向直流变换器才能实现其功能。提出一种新的双输入多通道直流变换器,它的功能等效于一个单向直流变换器和一个双向直流变换器。分析了双输入多通道直流变换器的工作原理,给出了变换器的稳态关系式以及能量管理方法,并运用Saber软件进行仿真,验证了理论分析的正确性。该直流变换器除具有双输入Buck直流变换器的优点外,还能实现可再生能源向储电输入源充电。     

Review of the ordered and proportionate flow shop scheduling research

Ordered flow shop models have appeared in the literature since the mid‐1970s and proportionate flow shop models have appeared since the early 1980s. We provide a detailed review of these models along with some analysis and potential topics for future research. © 2012 Wiley Periodicals, Inc. Naval Research Logistics, 2013