旋转状态边界层速度场及温度场特性实验

针对涡轮转子叶片内冷技术,使用TR-PIV(time resolved particle image velocimetry)技术与热线技术同步原位测量了壁面加热条件下旋转通道内边界层速度场和温度场特性。结果显示:旋转数大于0.48时前缘面附近出现了回流现象,并从受力分析的角度给出了解释;回流区一般出现于流场下游、较大密度比、较高旋转数下,可以利用回流区的影响达到增强前缘面换热的目的;得到了旋转条件下无量纲温度型、温度脉动量和努塞尔数的变化规律,可以看出湍流边界层内部的温度场分布在旋转效应的影响下产生了强烈的不对称性,与静止条件下的标准规律相比会产生一定的偏差。     

卫星姿态控制推力器布局分析

针对卫星姿态控制过程中推力器数目和分布的选取问题,给出了星上常用的4种推力器安装布局,通过相平面控制,给出了各个稚力器的喷气时间,通过对不同布局下系统的控制精度、燃料消耗和可靠性等方面进行分析和比较,给出了推力器布局设计准则.该准则表明系统的可靠性和燃料消耗是推力器布局设计的主要参考依据.     

嵌入式实时操作系统在运载火箭中的应用研究

操作系统的作用随着飞行控制功能的不断增强而逐渐体现出来。本文结合我国运载火箭飞行软件的发展,梳理出可以考虑采用操作系统的前提条件,对使用操作系统的优劣进行了客观分析。针对飞行控制的典型应用,提出了适宜操作系统承担的基本功能。在此基础上,较为详细地介绍了操作系统中故障与设备状态管理功能的实现,并通过共享资源的使用对如何有效发挥操作系统多任务管理的作用进行了示例。     

减少铸造Al-Si合金Sr变质潜伏时间工艺研究

Sr变质潜伏时间延长除了给生产带来很多不便外,还会造成Sr烧损增加,变质效果衰退以及铝合金表面氧化-吸氢加剧,对合金造成污染,其中液态金属温度,液态金属的对流强度,Al-Sr合金的几何尺寸及表面状态是影响Sr变质潜伏时间的重要因素。通过建立物理模型,对Sr扩散过程进行流场模拟计算,并进行了试验验证。通过工艺改进,Sr变质潜伏时间由60分钟,缩短至20分钟,变质后合金性能优良,Al-Sr合金取得了良好的变质效果。     

一种差分跳频频率转移函数算法

 为提高差分跳频频率转移路径的随机性和均匀性,在深入研究差分跳频技术和频率转移函数的基础上,引入一种优化的混沌序列对数据信息码进行扰乱,利用纠错能力较强的RS(Reed-Solomon)码和m序列实现对跳频间隔及频率子集的选择控制,构建了一种新的差分跳频频率转移函数算法。对算法的随机性和均匀性进行了仿真验证。仿真结果表明,相比于基于混沌序列的G函数算法和基于RS码和m序列的G函数算法,本文算法产生的跳频序列的随机性和均匀性均得到了良好改善。     

一种强耦合Spalart-Allmaras湍流模型的RANS方程的高效数值计算方法

在工程实际中,一方程湍流模型或两方程湍流模型的求解通常和雷诺平均Navier-Stockes (RANS)方程的求解是解耦的,也称之为松耦合求解.在松耦合求解过程中,RANS方程和湍流模型方程通常采用不同的数值方法异步求解.这种求解方式很容易产生因两者计算精度不一致而引起的额外数值耗散.为了消除这种耗散,将RANS方程与Spalart-Allmaras模型方程耦合成一个系统方程——强耦合RANS方程,并发展了一种用于求解该系统方程的高效强耦合算法,其中对流项离散采用了Roe格式,时间项的离散采用了隐式LU-SGS(Lower-Upper Symmetric Gauss-Seidel)格式,为了提高计算效率,采用了三层V循环多重网格方法.通过翼型/机翼和振荡翼型/机翼等算例验证了本文发展的强耦合算法不仅具有较好的收敛性,而且计算精度明显优于松耦合算法,特别对于阻力的预测,强耦合算法更加准确.     

Composite control method for stabilizing spacecraft attitude in terms of Rodrigues parameters

In this paper, the attitude stabilization problem of a rigid spacecraft described by Rodrigues parameters is investigated via a composite control strategy, which combines a feedback control law designed by a finite time control technique with a feedforward compensator based on a linear disturbance observer (DOB) method. By choosing a suitable coordinate transformation, the spacecraft dynamics can be divided into three second-order subsystems. Each subsystem includes a certain part and an uncertain part. By using the finite time control technique, a continuous finite time controller is designed for the certain part. The uncertain part is considered to be a lumped disturbance, which is estimated by a DOB, and a corresponding feedforward design is then implemented to compensate the disturbance. Simulation results are employed to confirm the effectiveness of the proposed approach.     

Guidance law with impact time and impact angle constraints

A novel closed-form guidance law with impact time and impact angle constraints is pro- posed for salvo attack of anti-ship missiles, which employs missile’s normal acceleration (not jerk) as the control command directly. Firstly, the impact time control problem is formulated as tracking the designated time-to-go (the difference between the designated impact time and the current flight time) for the actual time-to-go of missile, and the impact angle control problem is formulated as tracking the designated heading angle for the actual heading angle of missile. Secondly, a biased proportional navigation guidance (BPNG) law with designated heading angle constraint is constructed, and the actual time-to-go estimation for this BPNG is derived analytically by solving the system differential equations. Thirdly, by adding a feedback control to this constructed BPNG to eliminate the time-to-go errorthe difference between the standard time-to-go and the actual time-to-go, a guidance law with adjustable coefficients to control the impact time and impact angle simultaneously is developed. Finally, simulation results demonstrate the performance and feasibility of the proposed approach.     

H1 output tracking control for flight control systems with time-varying delay

For flight control systems with time-varying delay, an H1 output tracking controller is proposed. The controller is designed for the discrete-time state-space model of general aircraft to reduce the ef...     

H∞ output tracking control for flight control systems with time-varying delay

For flight control systems with time-varying delay, an H∞ output tracking controller is proposed. The controller is designed for the discrete-time state-space model of general aircraft to reduce the effects of uncertainties of the mathematical model, external disturbances, and bounded time-varying delay. It is assumed that the feedback-control loop is closed by the communication network, and the network-based control architecture induces time-delays in the feedback information. Suppose that the time delay has both an upper bound and a lower bound. By using the Lyapu- nov-Krasovskii function and the linear matrix inequality （LMI）, the delay-dependent stability criterion is derived for the time-delay system. Based on the criterion, a state-feedback H∞ output tracking controller for systems with norm-bounded uncertainties and time-varying delay is presented. The control scheme is applied to the high incidence research model （HIRM）, which shows the effectiveness of the proposed approach.