Best practices for model-based and simulation-aided engineering of power transmission and motion control systems

This paper deals with the modelling and simulation of aircraft systems, in particular for power transmission and control. It is intended to review, propose and disseminate best practices for making model-based/simulation-aided engineering more efficient at any phase of the system life cycle. The proposals are aimed at creating value, not only by increasing the performance of the product under study but also by shortening the time to market, capitalizing knowledge, mitigating risks and facilitating concurrent engineering. The needs associated with the engineering activities are firstly identified to define a set of requirements for the models. Then, these requirements are used to drive the considerations leading to model development, focusing in particular on the process, modelled physical effects, modelling level, model architecting and concurrent engineering. The third part deals with the model implementation, giving special consideration to the different types of models, causalities, parameterization, implementation and verification. Each part is illustrated by examples related to safety critical actuators.     

Non-intrusive reduced-order model for predicting transonic flow with varying geometries

A Non-Intrusive Reduced-Order Model (NIROM) based on Proper Orthogonal Decomposition (POD) has been proposed for predicting the flow fields of transonic airfoils with geometry parameters. To provide a better reduced-order subspace to approximate the real flow field, a domain decomposition method has been used to separate the hard-to-predict regions from the full field and POD has been adopted in the regions individually. An Artificial Neural Network (ANN) has replaced the Radial Basis Function (RBF) to interpolate the coefficients of the POD modes, aiming at improving the approximation accuracy of the NIROM for non-samples. When predicting the flow fields of transonic airfoils, the proposed NIROM has demonstrated a high performance.     

Reliability estimation of mechanical seals based on bivariate dependence analysis and considering model uncertainty

The reliability estimation of mechanical seals is of crucial importance due to their wide applications in pumps in various mechanical systems. Failure of mechanical seals might cause leakage, and might lead to system failure and other relevant consequences. In this study, the reliability estimation for mechanical seals based on bivariate dependence analysis and considering model uncertainty is proposed. The friction torque and leakage rate are two degradation performance indicators of mechanical seals that can be described by the Wiener process, Gamma process, and inverse Gaussian process. The dependence between the two indicators can be described by different copula functions. Then the model uncertainty is considered in the reliability estimation using the Bayesian Model Average (BMA) method, while the unknown parameters in the model are estimated by Bayesian Markov Chain Monte Carlo (MCMC) method. A numerical simulation study and fatigue crack study are conducted to demonstrate the effectiveness of the BMA method to capture model uncertainty. A degradation test of mechanical seals is conducted to verify the proposed model. The optimal stochastic process models for two performance indicators and copula function are determined based on the degradation data. The results show the necessity of using the BMA method in degradation modeling.     

卫星结构基础加速度激励及界面力识别试验研究

针对某卫星结构模型,开展基于实测卫星结构加速度的卫星基础激励和星-箭连接界面动载荷反演试验研究.首先,根据卫星结构和试验条件,设计了用于测量星-箭界面传递载荷的工装;其次,基于卫星结构模态试验和有限元模型修正技术,获取了卫星结构的高保真有限元模型;进一步,开展基础激励下的卫星结构模型振动试验,利用动载荷识别技术获取振动...     

基于低碳经济的环京津贫困带发展模式研究

在受到资源环境约束的当代,经济发展必须采取低碳发展模式,环京津贫困带的发展更是如此。改革开放以来,环京津贫困带与京津郊县的发展差距越来越大。其中的原因是多方面的,既有京津方面的因素,也有河北方面的责任。在保证区域生态安全的前提下,促进"环京津贫困带"的发展,必须发展低碳经济,创新发展模式。     

阴影环境下陆地移动卫星信道模型及仿真研究

在对陆地移动卫星信道传播特性分析的基础上,建立阴影环境下移动卫星信道的混合模型,并采用随机数产生器实现了该信道模型的统计特性仿真。通过与实测数据的统计特性进行比较,验证了该信道模型和仿真实现方法的正确性。由于移动卫星信道是一个复杂的时变随机信道,所以,通过随机数产生器产生的统计特性具有很好的普适性。     

空间飞行器自动对接系统的多变量模型参考反馈设计方法

本文从两空间飞行器交会对接过程最后接近阶段的飞行特性出发,利用多变量频域理论,给出了空间飞行器自动对接系统的多变量模型参考反馈设计方法.     

Advanced high-order nonlinear chirp scaling algorithm for high-resolution wide-swath spaceborne SAR

Spaceborne Synthetic Aperture Radar (SAR) is a well-established and powerful imaging technology that can provide high-resolution images of the Earth’s surface on a global scale. For future SAR systems, one of the key capabilities is to acquire images with both high-resolution and wide-swath. In parallel to the evolution of SAR sensors, more precise range models, and effective imaging algorithms are required. Due to the significant azimuth-variance of the echo signal in High-Resolution Wide-Swath (HRWS) SAR, two challenges have been faced in conventional imaging algorithms. The first challenge is constructing a precise range model of the whole scene and the second one is to develop an effective imaging algorithm since existing ones fail to process high-resolution and wide azimuth swath SAR data effectively. In this paper, an Advanced High-order Nonlinear Chirp Scaling (A-HNLCS) algorithm for HRWS SAR is proposed. First, a novel Second-Order Equivalent Squint Range Model (SOESRM) is developed to describe the range history of the whole scene, by introducing a quadratic curve to fit the deviation of the azimuth FM rate. Second, a corresponding algorithm is derived, where the azimuth-variance of the echo signal is solved by azimuth equalizing processing and accurate focusing is achieved through a high-order nonlinear chirp scaling algorithm. As a result, the whole scene can be accurately focused through one single imaging processing. Simulations are provided to validate the proposed range model and imaging algorithm.     

基于结构特征比对的指纹识别方法

针对通常的指纹识别算法都不支持指纹的旋转和偏移的问题 ,文中首先提出一个在二维平面上点与点之间的距离与平面的旋转和平移无关的数学模型。然后在分析指纹特征点的基础上提出一个基于指纹结构特征的比对算法 ,该算法主要是利用特征点之间的距离、类型和跨越纹线等结构信息来进行比对。最后用实验证明这一算法的可行性