Solar sail formation flying on an inclined Earth orbit

The versatility of solar sail propulsion can be utilized in the exploration of Earth’s magnetotail. An inclined periodic orbit with respect to ecliptic is possible for a solar sail with its orbital plane in synchronous rotation with the sun. Solar sail evolving on such an inclined orbit is free of Earth shadow. Formation flying of a cluster of sails around such an inclined periodic orbit is investigated in this paper. The solution of the first-order approximation to the linear relative motion is used to qualitatively analyze the configurations of relative orbits. Since the relative motion is unstable, active control is necessary to keep a periodic relative motion. A typical LQR method is employed to stabilize the relative motion. The design method is validated by numerical examples.     

低压涡轮初始不平衡量超限计算分析与排除

针对某型航空发动机低压涡轮转子初始不平衡量超限问题,根据机件形位误差与不平衡量之间的影响关系进行计算分析,得出当支承锥盘与盘片组件间形位误差和低压涡轮盘片组件定位基准误差处于极限值且为不利组合时,引起的转子不平衡量值远大于或接近7500 g·mm限制值。根据计算结果,并按照效率最高原则及科研装配经验,制定了排除低压涡轮初始不平衡量超限流程,实践检验方法有效。研究结果表明:控制转子定位基准误差,减小组合件装配形位误差,根据转子不平衡量数值调整机件间安装相位,是降低和优化转子初始不平衡量的有效手段。     

着舰导引系统H∞控制器设计

舰载机着舰导引误差的最大来源是舰导气流扰动。为抑制气流扰动，提高舰载机自动着舰导引的精度，本文将Ｈ∞控制方法应用于着舰导引系统设计，将导引系统性能要求转化为对Ｈ∞控制分析的结构及权阵的选取。     

Al/Mg阻抗梯度材料超高速撞击机理数值仿真研究

文章采用数值仿真方法研究了Al/Mg阻抗梯度材料在超高速撞击下的响应过程,分析了冲击波在阻抗梯度材料中的传播规律,计算了撞击过程中的能量耗散情况,并与弹丸撞击铝合金靶的结果进行了比较。研究结果表明,相对于铝合金材料,Al/Mg阻抗梯度材料：1）延长了冲击波的传播时间,使峰值压力脉冲的比冲量提升了30%～50%;2）提高了塑性功和内能转化量,使不可逆功增加了10%。由此证明阻抗梯度材料的防护性能优于铝合金。     

基于双目视觉的无人机编队相对定位算法

针对无人机编队飞行时双目视觉定位精确性差、计算量大、实时性不高的技术现状,对基于特征点的FAST定位和BRIEF旋转(Oriented fast and rotated brief,ORB)算法进行了改进,提出了一种适用于无人机双目视觉定位的算法。在改进ORB算法中,采用提取目标区域、最近邻约束和随机抽样一致(Random sampling consensus,RANSAC)方法,提高了特征点提取与匹配效率,也提高了特征点匹配质量;对于双目视觉定位,提出了适用条件更加宽泛的双目视觉定位模型,并保证了模型的定位精度;最后使用卡尔曼滤波算法对无人机的定位信息进行估计,进一步提高了无人机的定位精度。实验表明,算法具有较高的精确性和实时性,满足无人机间的相对定位要求。     

再入轨迹多约束模型预测静态凸规划方法

针对大升阻比可重复使用飞行器再入滑翔轨迹规划问题,提出了一种基于自适应分段Chebychev伪谱离散的多约束模型预测静态凸规划算法(P CMPCP),实现了全量终端状态约束及多过程约束作用下再入轨迹的高精度迭代解算。考虑倾侧角翻转导致控制量不连续,传统规划方法难以同时严格满足终端位置、角度约束,且过程约束易超限,采用自适应分段伪谱离散策略,构建全程飞行状态及过程性能指标约束对各配点处控制调整量的敏感度关系,从而将非线性最优控制问题转化为静态凸规划问题,并利用内点法对各分段控制量进行了协调优化。本文所提方法无需对动力学模型进行简化或近似处理,即能以少量积分运算使轨迹满足再入全量模型约束,且控制量平滑,数值精度优于传统规划方法。     

某火力电厂机组控制系统的设计与实现

以某火力发电厂的建设为整体背景,结合电厂设计过程中实际出现的问题,以及以往的设计经验,利用MaxDNA控制系统,展开对于整体火力机组控制系统中的软硬件的设计。通过某火力发电厂实地进行联调联试,确保相应的设备能够正常的工作,以保证机组的正常运行。系统运行情况良好,基本实现工艺设备的控制要求,获得了用户的认可,降低了相关工作的工作强度,取得很好的经济效益。     

分布式测控环境下的实时通信研究

面向服务于航空试验的测控系统，提出了通过构架分布式测控环境的方法实现航空测控系统集成的构想，分析了航空试验测控系统中实时通信的特殊性，设计了基于以太网络的实时通信协议，并在此协议之上实现了分布式测控环境下的实时通信服务。     

重复率电光调Q Nd3+:YAG激光器输出能量及激光器效率的测定

本文提出了一种在不同的泵浦电压下测量重复率电光调Q掺钕钇铝石榴石激光器输出能量的方法 ,实际测量了脉冲激光器静态输出和动态输出能量 ,并利用电光晶体激光调Q技术得到脉宽为亚毫微秒的激光脉冲 ,使得激光器动态输出功率达兆瓦量级     

Comparison of ionospheric F2 peak parameters foF2 and hmF2 with IRI2001 at Hainan

Monthly median values of foF2, hmF2 and M(3000)F2 parameters, with quarter-hourly time interval resolution for the diurnal variation, obtained with DPS4 digisonde at Hainan (19.5°N, 109.1°E; Geomagnetic coordinates: 178.95°E, 8.1°N) are used to investigate the low-latitude ionospheric variations and comparisons with the International Reference Ionosphere (IRI) model predictions. The data used for the present study covers the period from February 2002 to April 2007, which is characterized by a wide range of solar activity, ranging from high solar activity (2002) to low solar activity (2007). The results show that (1) Generally, IRI predictions follow well the diurnal and seasonal variation patterns of the experimental values of foF2, especially in the summer of 2002. However, there are systematic deviation between experimental values and IRI predictions with either CCIR or URSI coefficients. Generally IRI model greatly underestimate the values of foF2 from about noon to sunrise of next day, especially in the afternoon, and slightly overestimate them from sunrise to about noon. It seems that there are bigger deviations between IRI Model predictions and the experimental observations for the moderate solar activity. (2) Generally the IRI-predicted hmF2 values using CCIR M(3000)F2 option shows a poor agreement with the experimental results, but there is a relatively good agreement in summer at low solar activity. The deviation between the IRI-predicted hmF2 using CCIR M(3000)F2 and observed hmF2 is bigger from noon to sunset and around sunrise especially at high solar activity. The occurrence time of hmF2 peak (about 1200 LT) of the IRI model predictions is earlier than that of observations (around 1500 LT). The agreement between the IRI hmF2 obtained with the measured M(3000)F2 and the observed hmF2 is very good except that IRI overestimates slightly hmF2 in the daytime in summer at high solar activity and underestimates it in the nighttime with lower values near sunrise at low solar activity.