主被动传感器UT-DC目标定位算法

主被动传感器融合定位具有高度非线性,针对采用传统的线性化方法计算变量统计特性,理论定位结果与实际定位结果相差较大的情况,文章提出了基于不敏变换(UT)的数据压缩(DC)融合定位算法。首先,通过不敏变换精确计算了二维变量的统计特性,减小了非线性误差的影响;其次,针对数据压缩过程中量测信息重复利用的问题进行去相关性处理,获得较高的定位精度;最后,通过理论分析和仿真结果验证,相较于传统的线性化处理方式相差较大的情况,基于不敏变换的数据压缩融合定位方法理论结果与实际结果相吻合。     

直升机旋翼黏弹阻尼器时域动力学建模与分析

建立一种适用于旋翼气动弹性分析的黏弹阻尼器模型,该模型考虑了黏弹材料本身的刚度非线性及激振力频率和幅值对黏弹阻尼器应力-应变关系的影响。通过引入新型几何非线性弹簧模块,根据需要调整模型的刚度变化规律,避免了现有黏弹阻尼器模型模拟不同类型材料时因刚度变化规律差异而需重新建模的缺陷,模型适应性强。模型采用多个内变量场,既能体现阻尼器幅变特性,也能准确反映多频激励下的黏弹性特性。以两种不同类型黏弹材料制造的黏弹阻尼器为研究对象,在旋翼黏弹阻尼器的典型工作幅值和频率范围内,进行了简谐实验。利用建立的旋翼黏弹阻尼器非线性时域动力学模型,计算不同类型黏弹材料制造的阻尼器在多种应变幅值、频率下的动态特性并与实验相比较,分析了黏弹阻尼器损耗模量、储能模量频变特性和双频激励对阻尼器的影响。结果表明,建立的非线性黏弹阻尼器动力学模型能够更好地反映不同类型黏弹材料构成的黏弹阻尼器的动刚度和阻尼,适合于直升机旋翼载荷计算和气动弹性分析。     

基于声波传播时间估计的气流速度测量方法

 为实现对亚声速和超声速气流速度的统一测量,提出了一种基于声传感器的新型测量方法。首先,根据声波在亚声速和超声速气流中的传播特性,利用特定的测量装置建立了声波传播时间与气流速度之间的数学模型,从而将气流速度的测量问题转化为声波传播时间的测量问题。然后,在此基础上,利用计时法和最大似然估计(MLE)方法来估计声波传播时间;其中,计时法在实时性上优势明显,而MLE方法则在可靠性上优于前者。最后,分别从阵元位置扰动性、计时误差和克拉美-罗界(CRB)3个方面对所提算法的性能进行了分析与仿真验证。结果表明,该算法能够实现对亚声速和超声速气流速度的精确测量。     

Intelligent modeling and identification of aircraft nonlinear flight

In this paper, a new approach has been proposed to identify and model the dynamics of a highly maneuverable fighter aircraft through artificial neural networks（ANNs）. In general, aircraft flight dynamics is considered as a nonlinear and coupled system whose modeling through ANNs, unlike classical approaches, does not require any aerodynamic or propulsion information and a few flight test data seem sufficient. In this study, for identification and modeling of the aircraft dynamics, two known structures of internal and external recurrent neural networks（RNNs） and a proposed structure called hybrid combined recurrent neural network have been used and compared.In order to improve the training process, an appropriate evolutionary method has been applied to simultaneously train and optimize the parameters of ANNs. In this research, it has been shown that six ANNs each with three inputs and one output, trained by flight test data, can model the dynamic behavior of the highly maneuverable aircraft with acceptable accuracy and without any priori knowledge about the system.     

Recent advance in nonlinear aeroelastic analysis and control of the aircraft

A review on the recent advance in nonlinear aeroelasticity of the aircraft is presented in this paper. The nonlinear aeroelastic problems are divided into three types based on different research objects, namely the two dimensional airfoil, the wing, and the full aircraft. Different non- linearities encountered in aeroelastic systems are discussed firstly, where the emphases is placed on new nonlinear model to describe tested nonlinear relationship. Research techniques, especially new theoretical methods and aeroelastic flutter control methods are investigated in detail. The route to chaos and the cause of chaotic motion of two-dimensional aeroelastic system are summarized. Var- ious structural modeling methods for the high-aspect-ratio wing with geometric nonlinearity are dis- cussed. Accordingly, aerodynamic modeling approaches have been developed for the aeroelastic modeling of nonlinear high-aspect-ratio wings. Nonlinear aeroelasticity about high-altitude long- endurance （HALE） and fight aircrafts are studied separately. Finally, conclusions and the chal- lenges of the development in nonlinear aeroelasticity are concluded. Nonlinear aeroelastic problems of morphing wing, energy harvesting, and flapping aircrafts are proposed as new directions in the future.     

基于热声网络法的燃烧不稳定性分析研究

为研究预混燃烧的燃烧不稳定性,采用低阶热声网络分析方法确定燃烧不稳定性的模态特征及非线性特性。在热声网络程序中利用声网络来描述燃烧室结构的声学特性,利用速度脉动的函数描述火焰的热释放脉动。在火焰模型中,在线性模型中增加非线性以求解不稳定模态的极限环幅值。分析了钝体模型燃烧室中火焰模型参数对燃烧不稳定性的影响,模拟结果与实验结果符合得很好。结果表明声网络方法结合非线性火焰模型能描述燃烧系统的燃烧不稳定性和直接预测极限环幅值。     

基于改进的混合粒子群算法的变循环发动机模型求解

为了降低变循环发动机模型求解时对初始值的依赖性,提升算法的全局收敛性,同时提高模型求解的效率,提出了一种基于改进的混合粒子群算法的变循环发动机模型求解思路。首先建立了变循环发动机的部件级模型,并建立了发动机的共同工作方程组;然后采用Broyden法对牛顿-拉夫森算法中的雅可比矩阵进行更新计算,在经典粒子群算法的基础上引入粒子中心,作为干扰项,并引入限制因子和自适应时变惯性系数;最后,综合了两种改进的算法,提出改进的混合粒子群算法。实验结果表明:该算法不仅继承了牛顿-拉夫森算法的高计算效率,还吸收了改进的粒子群算法的全局收敛优点,可实现模型大范围收敛。     

粒子群混合算法在变导向器面积计算中的应用

求解非线性方程组经典方法具有严格的局部收敛性;粒子群等进化算法解决了全局收敛的问题,但计算效率偏低,存在最优解不稳定的问题。结合经典Newton-Raphson法的超线性收敛速度和粒子群算法全局收敛能力的粒子群混合算法具备2类算法的优点。在迭代初期采用粒子群算法获得的近似全局解作为Newton-Raphson算法的初始值,以确定高精度的解。利用粒子群混合算法在发动机变导向器面积的大偏离计算中获得了较好的收敛效果,解决了常规Newton-Raphson法不收敛的问题。     

图像处理的非线性扩散方法

介绍了非线性扩散方法的原理和数学性质;对图像处理领域的非线性扩散方法进行了分类和总结,并探讨了各类方法的优缺点;同时从平滑去噪与保留图像特征点之间的矛盾、结构的封闭性、不连续点的保留以及参数简化等方面指出了非线性扩散方法的发展趋势和亟待解决的问题。     

微缝共振器的非线性吸声机理

为模拟高声压级时微缝处涡声相互作用现象并计算微缝声阻抗,发展了一种离散涡模型.联合微缝离散涡模型和一维声传播模型,计算了微缝共振器的声阻抗和吸声系数.数值结果表明,微缝声学性质主要取决于涡脱落和脱落涡层的演化;共振器的吸声系数随着入射声压级的增加而增大;入射声波频率对共振器吸声系数有显著影响.研究结果和先前直接数值模拟...