考虑动力刚化的挠性飞行器动力学建模与仿真

文中以挠性飞行器的刚柔耦合物理模型为研究对象,引入非惯性系中的力学问题理论,建立了考虑动力刚化的模型,明确地阐明了动力刚化是一种非惯性系中的力学现象。首先分别应用材料力学和角动量定理建立了两个子系统的连续动力学模型,而后基于正则约束模态的正交化结论,建立了离散动力学模型。数值仿真结果表明,文中建立的一次动力学模型考虑了动力刚化,能够准确预测大角度机动下挠性飞行器的动力学响应,可直接用于控制器设计。

Dynamic modeling and simulation for the flexible spacecraft with dynamic stiffening

A rigid flexible coupling physical model which can represent a flexible spacecraft is investigated in this paper. By applying the mechanics theory in a non-inertial coordinate system,the rigid flexible coupling dynamic model with dynamic stiffening is established via the subsystemmodeling framework. It is clearly elucidated for the first time that,dynamic stiffening is produced by the coupling effect of the centrifugal inertial load distributed on the beamand the transverse vibration deformation of the beam. The modeling approach in this paper successfully avoids problems which are caused by other popular modeling methods nowadays： the derivation process is too complex by using only one dynamic principle; a clearly theoretical explanation for dynamic stiffening can＇t be provided. First,the continuous dynamic models of the flexible beamand the central rigid body are established via structural dynamics and angular momentumtheory respectively. Then,based on the conclusions of orthogonalization about the normal constrained modes,the finite dimensional dynamic model suitable for controller design is obtained. The numerical simulation validations showthat： dynamic stiffening is successfully incorporated into the dynamic characteristics of the first-order model established in this paper,which can indicate the dynamic responses of the rigid flexible coupling system with large overall motion accurately,and has a clear modeling mechanism,concise expressions and a good convergence.

Dynamic modeling and simulation for the rigid flexible coupling system with a non-tip mass

The rigid flexible coupling system with a mass at non-tip position of the flexible beam is studied in this paper. Using the theory about mechanics problems in a non-inertial coordinate sys- tem, the dynamic equations of the rigid flexible coupling system with dynamic stiffening are estab- lished. It is clearly elucidated for the first time that, dynamic stiffening is produced by the coupling effect of the centrifugal inertial load distributed on the beam and the transverse vibration deformation of the beam. The modeling approach in this paper successfully solves problems of popular modeling methods nowadays： the derivation process is too complex by using only one dynamic principle; a clearly theoretical mechanism for dynamic stiffening can＇ t be offered. First, the mass at non-tip po- sition is incorporated into the continuous dynamic equations of the system by use of the Dirac lunch tion and the Heaviside function. Then, based on the conclusions of orthogonalization about the nor- mal constrained modes, the finite dimensional state space equations suitable for controller design are obtained. The numerical simulation results show that： dynamic stiffening is included in the first-or- der model established in this paper, which indicates the dynamic responses of the rigid flexible cou- pling system with large overall motion accurately. The results also show that the mass has a soften- ing effect on the dynamic behavior of the flexible beam, and the effect would be more obvious when the mass has a larger mass, or lies closer to the tip of the beam.

一种基于RBF神经网络实现波束形成的方法

以最小均方差(LMS)算法的解为基础,提出一种基于径向基函数(RBF)神经网络的波束形成方法。首先方法将一定量、等步长的DOA值通过LMS算法计算出的阵列权值向量作为训练集,而后基于训练集RBF神经网络进行训练,最终在DOA估计后可快速计算出阵列天线中各阵元的权值。上述方法利用RBF神经网络快速逼近非线性函数的特点,替代原有LMS自适应波束形成算法的迭代过程,以期减小计算量。Matlab仿真结果表明,上述方法能够有效减少阵列权值向量计算过程的运算量,提高波束形成的实时性。

不稳定分层海洋湍流对厄米-高斯光通信系统的影响

推导了不稳定分层海洋湍流下厄米-高斯光束闪烁指数的理论公式,以及考虑海洋湍流和瞄准误差综合影响下UWOC系统信道系数的概率分布函数,进一步推导了系统主要性能参数即误码率、信道容量和中断概率的理论计算公式,并采用高斯-厄米正交积分近似方法求得3个性能参数的闭合表达式,仿真分析了不稳定分层和稳定分层湍流情况下,光束模数、传输距离、海洋湍流参数和瞄准误差对系统的平均误码率、平均信道容量和中断概率的影响。结果表明:相比于稳定分层,不稳定分层的系统计算误差更小;当盐度波动占主导时,系统性能更好;随着均方温度耗散率增大、湍流动能耗散率减小、瞄准误差增大,系统信道容量减小,中断概率增大。本研究结果可为厄米-高斯光在水下光通信领域的应用提供参考。