故障容错光交叉通道数据链路的可靠性

光交叉通道数据链路(OCCDL)是光传飞行控制系统余度计算机之间进行数据交换的重要途径.为了提高OCCDL系统的可靠性,提出一种新的具有多链路故障容错能力的OCCDL系统.给出了该OCCDL系统的结构配置,分析了系统正常工作和故障工作情况下的工作流程,设计了系统光开关故障、光链路等关键部分的故障容错逻辑,建立了基于马尔...     

大型回转平台调平技术研究

利用空间几何分解,通过建立空间模型,推算出一种水平度分解算法,把大型回转平台回转后当前水平传感器两正交敏感轴方向的水平度分解到可调节控制方位上,实现无需重新调整水平传感器敏感方位下使回转平台回转的自动调平。     

套语和模仿在外语学习中的作用

通过使用应用心理语言学理论,结合观察,分析描写了模仿和套语在外语学习的初级阶段所起的作用——有助于外语学习者超越自己的语言能力,具有积极的心理作用,为语言学习的创造性高级阶段打下一定的基础。     

Multi-aspect radar target recognition method based on scattering centers and HMMs classifiers

A hidden Markov model (HMM)-based method for recognizing aerial targets according to the sequential high-range-resolution (HRR) radar signature is presented. Its recognition features are the location information of scattering centers extracted from the HRR radar echoes by the relax algorithm. The HMM is used to characterize the spatio-temporal information of a target. Several HMMs are cascaded in a chain to model the variation in the target orientation and used as classifiers. Computer simulations with the inverse synthetic aperture radar (ISAR) data are given to demonstrate that for an open-set recognition, average class-recognition rates of 84.50% and 89.88% are achieved, respectively, under two given conditions.     

网格密度对流场解的影响

采用不同密度的网格,利用隐式时间有限差分方法对M6机翼进行了Euler方程解算,用Richardson外插评估数值误差,就网格密度对人工耗散和解的影响进行了分析.     

非线性系统分数阶滑模控制分析与设计

文章对非线性整数阶或分数阶系统,提出了统一的分数阶滑模控制方法。首先,对整数阶控制系统,设计分数阶滑模面,提出分数阶趋近律,通过对倒立摆系统的仿真,验证了该方法的有效性;然后,引入最优控制指标,研究了滑模控制阶次 α对控制效果的影响,对于该整数阶系统,控制指标最优时 α ..;最后,将本文方法推广到分数阶系统的控制,通过对分数阶 Chen系统的仿真,验证了该方法的有效性,并发现对于该系统控制指标最优时,控制阶次与系统阶次不同元。     

An improved approach to model ionospheric delays for single-frequency Precise Point Positioning

PPP with low-cost, single-frequency receivers has been receiving increasing interest in recent years because of its large amount of possible users. One crucial issue in single-frequency PPP is the mitigation of ionospheric delays which cannot be removed by combining observations on different frequencies. For this purpose, several approaches have been developed, such as, the approach using ionospheric model corrections with proper weight, the GRAPHIC (Group and Phase Ionosphere Calibration) approach, and the method to model ionospheric delays over a station with a low polynomial or stochastic process. From our investigation on the stochastic characteristics of the ionospheric delay over a station, it cannot be precisely represented by either a deterministic model in the form of a low-order polynomial or a stochastic process for each satellite, because of its strong irregular spatial and temporal variations. Therefore, a novel approach is developed accordingly in which the deterministic representation is further refined by a stochastic process for each satellite with an empirical model for its power density. Furthermore, ionospheric delay corrections from a constructed model using GNSS data are also included as pseudo-observations for a better solution. A large data set collected from about 200 IGS stations over one month in 2010 is processed with the new approach and several commonly adopted approaches for validation. The results show its significant improvements in terms of positioning accuracy and convergence time with a negligible extra processing time, which is also demonstrated by data collected with a low-cost, handheld, single-frequency receiver.     

一拍跟踪的直升机显模型跟踪解耦控制系统设计

针对直升机动力学表现出的高阶,强耦合的特点,本文基于一拍跟踪的原理,设计了显模型跟踪解耦控制系统,开发了控制阵,为提高系统动态和稳态性能,对系统参数进行了优化,数字仿真表明,模型跟踪解耦性能良好,同时可以迅速改变显模型,以达到改变操纵特性的目的,文章最后对如何选取采样周期及显模型带宽进行了讨论。     

大气数据测试系统的设计

大气数据系统是重要的机载电子设备，本文应用微诊断法和功能测试法，对大气数据测试系统进行了设计，实现了对大气数据系统各组件的测试，故障覆盖率高，该测试方法对其它机载计算机系统的测试具有推广价值。