复杂电磁环境下无线接收机电磁兼容快速测试技术应用CSCD

复杂射频电磁环境下,无线接收机作为主要的敏感设备,其电磁兼容性直接影响着整个武器装备的电磁兼容特性. 本文针对GJB 151B中对于接收机非线性测试方法的局限性,引入了一种利用自动双频测试系统对接收机干扰响应的快速测试方法;并搭建了实验室半实物仿真测试平台,检测了某接收机在（ 4-6 ） GHz组合频率干扰下的所有非线性的干扰响应通道. 测试结果对于评估接收机及其所在系统的外部电磁环境适应性具有重要参考价值.     

Aircraft nonlinear stability analysis and multidimensional stability region estimation under icing conditions

Icing is one of the crucial factors that could pose great threat to flight safety,and thus research on stability and stability region of aircraft safety under icing conditions is significant for control and flight.Nonlinear dynamical equations and models of aerodynamic coefficients of an air craft are set up in this paper to study the stability and stability region of the aircraft under an icing condition.Firstly,the equilibrium points of the iced aircraft system are calculated and analyzed based on the theory of differential equation stability.Secondly,according to the correlation theory about equilibrium points and the stability region,this paper estimates the multidimensional stability region of the aircraft,based on which the stability regions before and after icing are compared.Finally,the results are confirmed by the time history analysis.The results can give a reference for stability analysis and envelope protection of the nonlinear system of an iced aircraft.     

基于非线性变换的加速度计误差标定与补偿CSCD

为提高三轴加速度计测量精度,分析其误差来源和产生机理,建立了误差模型;根据误差模型和重力场幅值不变特性,推导出非线性观测方程。引入两个未知的参数向量,通过数学变换把非线性观测方程变形为关于新未知参数的线性方程;然后采用批量最小二乘法求出新的未知参数,并根据误差模型参数和新未知参数之间的关系,利用逆解析运算求出对应的零点偏差、灵敏度误差和三轴不正交误差。实验结果表明,加速度计正负误差峰值间距可以减小100倍左右,精度可达10-3m/s2,并具有很好的可重复性。该方法算法效率较高,补偿效果显著。     

矩形悬臂板的非线性弯曲

矩形悬臂板的非线性弯曲是板理论中的一个相当困难的课题，至今还没有研究过。给出由三角函数和多项式组成的近似挠度函数ｗ（ｘ，ｙ）和应力函数Ｆ（ｘ，ｙ），它们满足矩形悬臂板的部分边界条件。然后用广义伽辽金方法得到矩形悬臂板非线性弯曲问题的解。最后给出了算例。     

Periodic relative orbits of two spacecraft subject to differential gravity and electrostatic forcing

Coulomb forces between charged close-flying satellites can be used for formation control, and constant electric potentials enable static equilibria solutions. In this work, open-loop time-varying potential functions, which produce periodic, two-craft, Coulomb formation motions are demonstrated for the first time. This is done in the rotating Hill-Frame, with linearized gravity, and craft position components assumed in the form of simple harmonic oscillators. Substitution of the oscillatory functions into the dynamics, further constrains these functions, and yields necessary potential histories, to produce the periodic flow. The assumed position functions, however, are not arbitrary, since the dynamical model restricts what oscillatory trajectories are allowed. Specifically, a Hill-Frame integral of motion is derived, and this is used to show certain candidate periodic functions to be inadmissible. The system dynamics are then linearized to expose stability properties of the solutions, and it is established that asymptotic stability is impossible for all orbit families. Finally, the degree of instability in the assumed motions, over free parameter ranges, is determined numerically via the Floquet multipliers of the associated full-cycle state-transition matrices.     

复杂结构的非线性检测

由于非线性系统的复杂性，现有的各种非线性检测方法都有局限性。从频域、幅域和时域三方面综合考察复杂结构的非线性表现，采用六种方法进行非线性检测，给出一个综合描述系统非线性程度的指标－非线性因子。鉴于非线性系统表现出的非线性强弱与系统所受的激励有直接的关系，将非线性因子定义为与激励的幅值特性和频率特性相关的系数指标。对几种典型非线性系统的仿真模型进行了检测，以验证非线性因子的有效性。     

Protostellar Disk Formation and Early Evolution

This contribution describes the formation of circumstellar disks and their earliest evolutionary phases when self-gravity in the disk plays a crucial role in eliciting the transport of mass and angular momentum. We first discuss the formation of protostellar disks within the context of analytic infall-collapse solutions. We then discuss our efforts to understand the behavior of the newly formed disks. Our specific approach consists of performing a detailed analysis of a simplified model disk which is susceptible to the growth of a spiral instability. Using a combination of numerical simulation and semi-analytic analysis, we show how the dramatic early phase of mass and angular momentum transport in the disk can be explained by a second-order nonlinear process involving self-interaction of a dominant two-armed spiral mode. This revised version was published online in June 2006 with corrections to the Cover Date.     

驾驶员诱发振荡的抑制方法

对电传操纵系统驾驶员诱发振荡（ＰＩＯ）的现象进行了分析，指出了舵回路速率饱和是造成ＰＩＯ的主要原因，并有针对对给出了一种非常规的用于解决饱和非线性问题的程序控制方法。这种方法主要是通过舵回路反馈的状态信息来改变驾驶杆输入信号的放大系数，从而达到有效抑制ＰＩＯ的目的，同时用Ｈｕｒｗｉｔｚ稳定判据进行了机理分析，最后给出了仿真验证结果，证明该方法是简单而有效的。     

Adaptive Gaussian sum squared-root cubature Kalman filter with split-merge scheme for state estimation

The paper deals with state estimation problem of nonlinear non-Gaussian discrete dynamic systems for improvement of accuracy and consistency. An efficient new algorithm called the adaptive Gaussian-sum square-root cubature Kalman filter（AGSSCKF） with a split-merge scheme is proposed. It is developed based on the squared-root extension of newly introduced cubature Kalman filter（SCKF） and is built within a Gaussian-sum framework. Based on the condition that the probability density functions of process noises and initial state are denoted by a Gaussian sum using optimization method, a bank of SCKF are used as the sub-filters to estimate state of system with the corresponding weights respectively, which is adaptively updated. The new algorithm consists of an adaptive splitting and merging procedure according to a proposed split-decision model based on the nonlinearity degree of measurement. The results of two simulation scenarios（one-dimensional state estimation and bearings-only tracking） show that the proposed filter demonstrates comparable performance to the particle filter with significantly reduced computational cost.     

A practical nonlinear robust control approach of electro-hydraulic load simulator

This paper studies a nonlinear robust control algorithm of the electro-hydraulic load simulator （EHLS）. The tracking performance of the EHLS is mainly limited by the actuator＇s motion disturbance, flow nonlinearity, and friction, etc. The developed controller is developed based on the nonlinear motion loading model. The problems of the actuator＇s disturbance and flow nonlinearity are considered. To address the friction problem, the friction model of the loading motor is identified experimentally. The friction disturbance is compensated using the obtained friction model. Therefore, this paper considers the main three factors comprehensively. The developed algorithm is easy to apply since the controller can be obtained just with one step back-stepping design. The stability of the developed algorithm is proven via Lyapunov analysis. Both co-simulation and experiments are performed to verify the effectiveness of this method.