一种用于导弹姿态控制系统的直接力非线性控制法

为改善传统导弹姿控系统线性控制法的不足,用相平面法分析了直接力作用下导弹的姿态运动规律和气动力作用对直接力控制的影响,提出了一种综合控制精度、姿控发动机产品特性和推进剂消耗量等指标的直接力非线性控制方法,给出了控制模型。仿真结果表明,该法能在气动力作用或干扰无法忽略的条件下实现导弹姿控发动机的开关工作正常,保证精度及推进剂消耗最省,其控制精度与线性比例微分(PD)控制律相当。     

地球-火星的燃料最省小推力转移轨道的设计与优化

小推力转移轨道的设计与优化一直是深空探测轨道设计方面的难点。针对这些问题，提出了一种基于等高线图的初始发射机会搜索方法，该方法通过绘制探测器一火星距离的等高线图寻找满足任务约束的小推力转移轨道发射机会；同时，本文还给出了一种小推力轨道的直接优化算法，该算法通过将连续的控制变量参数化，把轨道优化问题转化为参数优化问题，然后基于所提搜索方法，采用逐次二次规划方法进行求解。数值计算验证了该发射机会初值猜测方法和优化算法的有效性。     

A direct position determination method with combined TDOA and FDOA based on particle filter

The localization of a stationary transmitter using moving receivers is considered. The original Direct Position Determination (DPD) methods, with combined Time Difference of Arrival (TDOA) and Frequency Difference of Arrival (FDOA), do not perform well under low Signal-to-Noise Ratio (SNR), and worse still, the computation cost is difficult to accept when the computational capabilities are limited. To get better positioning performance, we present a new DPD algorithm that proves to be more computationally efficient and more precise for weak signals than the conventional approach. The algorithm partitions the signal received with the same receiver into multiple non-overlapping short-time signal segments, and then uses the TDOA, the FDOA and the coherency among the short-time signals to locate the target. The fast maximum likelihood estimation, one iterative method based on particle filter, is designed to solve the problem of high computation load. A secondary but important result is a derivation of closed-form expressions of the Cramer-Rao Lower Bound (CRLB). The simulation results show that the algorithm proposed in this paper outperforms the traditional DPD algorithms with more accurate results and higher computational efficiency, and especially at low SNR, it is more close to the CRLB.     

Real-time trajectory planning for UCAV air-to-surface attack using inverse dynamics optimization method and receding horizon control

This paper presents a computationally efficient real-time trajectory planning framework for typical unmanned combat aerial vehicle (UCAV) performing autonomous air-to-surface (A/S) attack. It combines the benefits of inverse dynamics optimization method and receding horizon optimal control technique. Firstly, the ground attack trajectory planning problem is mathematically formulated as a receding horizon optimal control problem (RHC-OCP). In particular, an approximate elliptic launch acceptable region (LAR) model is proposed to model the critical weapon delivery constraints. Secondly, a planning algorithm based on inverse dynamics optimization, which has high computational efficiency and good convergence properties, is developed to solve the RHCOCP in real-time. Thirdly, in order to improve robustness and adaptivity in a dynamic and uncer- tain environment, a two-degree-of-freedom (2-DOF) receding horizon control architecture is introduced and a regular real-time update strategy is proposed as well, and the real-time feedback can be achieved and the not-converged situations can be handled. Finally, numerical simulations demon- strate the efficiency of this framework, and the results also show that the presented technique is well suited for real-time implementation in dynamic and uncertain environment.     

Neural network-based model predictive control with fuzzy-SQP optimization for direct thrust control of turbofan engine

A nonlinear model predictive control method based on fuzzy-Sequential Quadratic Programming(SQP) for direct thrust control is proposed in this paper for the sake of improving the accuracy of thrust control. The designed control system includes four parts, namely a predictive model, rolling optimization, online correction, and feedback correction. Considering the strong nonlinearity of engine, a predictive model is established by Back Propagation(BP) neural network for the entire flight envelope,...     

DDS激励PLL频率合成器的研究

频率合成器是现代通信设备的重要组成部分。首先介绍频率合成技术，然后分析了倍频式ＤＤＳ激励ＰＬＬ频率合成器的噪声性能，最后讨论设计中应注意的问题     

民用飞机阵风载荷及减缓技术的研究

由于民用飞机机翼具有大展弦比的特点,因此阵风载荷经常成为民用飞机飞行载荷的严重情况,是各国适航标准重点考察的飞行情况。而且,阵风干扰还会因飞机机体的自身弹性引起结构弹性振动,使飞机结构刚度降低,造成机体疲劳损伤,甚至引起颤振。因此,在民用飞机载荷设计过程中对阵风载荷及其减缓技术进行研究具有非常重要的意义。介绍了民用飞机阵风载荷的原理及相关技术,以及阵风载荷减缓技术中用直接升力控制方法来实现机翼的阵风载荷减缓。     

一种宽带高速跳频载波频综结构的设计

将DDS（直接数字合成）与PLL（锁相环）频率合成技术相结合,采用多环并列流水线结构,设计出混合扩/跳频系统的载波频率综合单元。利用DDS技术可实现频率分辨率高、转换时间快等要求,利用PLL技术可实现杂散抑制性能高、扩展宽带等要求,并采用多环并列硬件结构保证了系统的跳变速度和宽频带指标。经闭环测试平台的测试,系统达到350～1800MHz带宽可变,频率跳变速度10 000跳/s可变,杂散抑制优于-80dBc。文章首先给出详细的硬件设计方案及其实现,同时理论分析了个各项指标的优化,最后给出闭环测试平台的搭建以及最终测试结果。     

一种DS/FH混合扩频信号的并行捕获方法

为了解决低信噪比条件下高跳速DS/FH（直接扩频/跳频扩频）混合扩频信号的快速捕获问题,提出了一种FFT-IFFT（快速傅里叶变换-快速傅里叶逆变换）与非相干累加相结合的并行捕获算法。通过多支路同时运算的方式构建非相干累加矩阵,使非相干累加运算可以并行实施。分析表明,采用并行非相干累加后,既提高了捕获判决的准确性,又保证了捕获搜索的快速性。     

直接模拟蒙特卡罗羽流模拟的两相作用模型

为了数值模拟包含气体分子和凝相颗粒的两相羽流场,使用自主开发的羽流计算软件(PWS)对两相作用模型进行研究。计算均匀气流对颗粒的加速过程,结果与理论解一致,证明气体分子对颗粒的单向作用模型合理。计算气体分子在颗粒表面的反射时,将全局坐标系转换到颗粒坐标系确定其法线,再转换到法线坐标系进行镜面反射或漫反射。将这种间接法与使用反射向量的分布函数的直接法进行了对比。对同一个气体分子在颗粒表面的反射进行1×106次数值试验,两种方法所得镜面反射的速度向量均符合空间均匀分布,漫反射的速度向量分布相互一致。使用两种方法模拟150N液体火箭发动机的两相羽流场,所得气相羽流场几乎相同,间接法计算效率较高。液滴颗粒对气流场的影响主要集中在轴线附近,与无液滴的气流场相比,有液滴时会使气流温度升高、压强增大、马赫数减小。