一种混合型四阶格式、基于特征的边界条件及其应用

本文描述并应用差分格式的构造原则,采用了时空转换的格式构造方法构造了一个四阶精度的差分格式,文中还进一步提出将四阶格式和二阶ＮＮＤ格式混合的方法,即在光滑区格式保持四阶精度、在激波附近降为二阶ＮＮＤ格式,来增强格式捕捉激波的能力。同时,本文基于特征传播的思想,建立了一种开边界的数值计算方法,并采用将边界条件嵌入控制方程的方法以及新的简化形式的边界处理方法,完整给出了无粘、粘性物面和开边界的的边界计     

燃气流量可控的固体火箭冲压发动机动态建模及模型降阶

燃气流量可控的固体火箭冲压发动机促进了其燃气流量控制系统的研究.模型研究是控制系统设计的基础.基于集中参数的思想建立了燃气流量可控的固体火箭冲压发动机动态模型,分析了固体火箭冲压发动机动态模型参数的物理意义及其工作过程中的变参数特性, 固体火箭冲压发动机动态响应时间由冷区容积时间常数、热区容积时间常数、激波传播时间常数和激波容积时间常数等组成, 工作条件的较大变化使得固体火箭冲压发动机在工作过程中具有较强的变参数特性.最后对固体火箭冲压发动机动态模型进行模型降阶,由频率分析的结果可知,模型降阶是合理的.     

太阳高能粒子的电荷态和粒子强度间的相关性

本文发表了在太阳高能粒子事件中,元素氦、碳、氮、氧、氖、镁、硅、硫和铁的离子电荷态的分布。研究结果表明,除氦之外上述元素的电荷态分布的不同离子价的数目是随元素的质量而增大。核子能量在2—3MeV范围内,这些元素的平均粒子强度相对于碳的平均粒子强度之间的相关性能够用离子价的数目随元素质量的增加来解释,而不能用日冕温度确定的电荷态平衡模型来解释。且得出结论,太阳高能粒子的离子电荷是在太阳耀斑区而不是在星际激波区产生。      

航空发动机周转量计算与控制

从航空发动机的使用和周转过程分析,提出了其计划周转数量预测模型、年提前换发和使用消耗的数量计算方法,以及机上发动机的控制使用原则,为装备订货机关和飞机管理单位提供科学决策手段。     

一类分数阶薛定谔方程孤立解的对称性研究

在有界环形区域上,研究了一类分数阶薛定谔方程孤立解的对称性问题。首先将分数阶薛定谔方程转化为包含Bessel位势和Riesz位势的积分方程组,然后利用移动平面法和Hardy-Littlewood-Sobolev不等式,证明了当方程边值为常数时,环形区域必为同心球,方程正解是径向对称的,且随着到对称点的距离增大而单调递减。     

Static aeroelastic analysis including geometric nonlinearities based on reduced order model

This paper describes a method proposed for modeling large deflection of aircraft in non-linear aeroelastic analysis by developing reduced order model (ROM). The method is applied for solving the static aeroelastic and static aeroelastic trim problems of flexible aircraft containing geo-metric nonlinearities; meanwhile, the non-planar effects of aerodynamics and follower force effect have been considered. ROMs are computational inexpensive mathematical representations com-pared to traditional nonlinear finite element method (FEM) especially in aeroelastic solutions. The approach for structure modeling presented here is on the basis of combined modal/finite ele-ment (MFE) method that characterizes the stiffness nonlinearities and we apply that structure mod-eling method as ROM to aeroelastic analysis. Moreover, the non-planar aerodynamic force is computed by the non-planar vortex lattice method (VLM). Structure and aerodynamics can be cou-pled with the surface spline method. The results show that both of the static aeroelastic analysis and trim analysis of aircraft based on structure ROM can achieve a good agreement compared to anal-ysis based on the FEM and experimental result.     

基于虚拟主轴的分数阶趋近律同步控制策略

针对机械臂各关节高精度同步控制问题,选取与传统趋近律不同的分数阶趋近律,采用交叉耦合控制结构,提出了一种基于方差虚拟主轴的分数阶趋近律同步控制策略,并对所提的控制策略进行了稳定性证明。以两关节机械臂为研究对象进行了仿真验证。仿真结果表明:所提的控制策略可以使机械臂系统的跟踪误差和同步误差均快速收敛,且具有更快的响应速度和较强的鲁棒性。     

Fractional order modeling and control of dissimilar redundant actuating system used in large passenger aircraft

In this paper, a methodology has been developed to address the issue of force fighting and to achieve precise position tracking of control surface driven by two dissimilar actuators. The nonlinear dynamics of both actuators are first approximated as fractional order models. Based on the identified models, three fractional order controllers are proposed for the whole system. Two Fractional Order PID (FOPID) controllers are dedicated to improving transient response and are designed in a position feedback configuration. In order to synchronize the actuator dynamics, a third fractional order PI controller is designed, which feeds the force compensation signal in position feedback loop of both actuators. Nelder-Mead (N-M) optimization technique is employed in order to optimally tune controller parameters based on the proposed performance criteria. To test the proposed controllers according to real flight condition, an external disturbance of higher amplitude that acts as airload is applied directly on the control surface. In addition, a disturbance signal function of system states is applied to check the robustness of proposed controller. Simulation results on nonlinear system model validated the performance of the proposed scheme as compared to optimal PID and high gain PID controllers.     

分数阶Hopfield型神经网络的全局渐近稳定性

研究了分数阶Hopfield型神经网络的全局渐近稳定性,通过LMI方法得到了一种实现系统全局渐近稳定性的LMI形式条件,通过实例仿真验证了结论的正确性。     

基于本征正交分解和代理模型的高超声速气动热模型降阶研究

气动热弹性分析是高超声速飞行器设计的关键技术之一。高超声速飞行器气动热的准确快速预测是气动热弹性分析的重要前提。针对当前气动加热工程计算、数值计算和实验研究均不能很好满足设计要求的问题,采用本征正交分解(POD)与代理模型(Surrogate)技术结合的模型降阶(POD-Surrogate)方法,建立了一种快速高效的高超声速气动热降阶模型框架。针对典型高超声速三维翼面气动热预测研究结果表明:当保留的POD基模态个数大于20时,PODKriging方法和POD-RBF(Radial Basis Function)方法的降阶模型得到的翼面温度分布与计算流体力学(CFD)计算温度L∞平均误差分别达到6%和14%,相对均方根误差(NRMSE)平均误差分别达到4%和12%,继续增加POD的基模态并不能提高降阶模型的预测精度;针对高超声速机翼气动热计算,POD-Kriging方法比POD-RBF方法具有更高的精度;针对典型的高超声速三维翼面气动热预测表明:基于POD-Surrogate方法的气动热降阶模型具有较高的精度和效率。