Experimental modeling of controlled suspension vehicles from onboard sensors

In this article, identification of vertical dynamics of vehicles with controlled suspensions is considered. Identification is performed from experimental data measured on a four-poster bench test of a segment C car, equipped with a CDC-Skyhook dampers control system. The measurements are obtained from the onboard accelerometers needed by the control system. A nonlinear model in regression form is identified, having the road profile and damper control currents as inputs and chassis accelerations as outputs. The model is identified by means of a set membership structured identification method, which takes advantage of physical information on the structure of the system, decomposing the system into three subsystems: one represents the chassis and engine and the other two represent the overall behavior of front and rear suspensions, wheels and tires. This decomposition allows us to avoid the complexity accuracy problems derived from the high dimension of required regression space. Indeed, the overall high-dimensional identification problem is reduced to the identification of lower dimensional subsystems and to the estimation of their interactions. An iterative scheme is used for solving the decomposed identification problem. As the chassis pitch is small for the usual road profiles, the chassis-engine block is considered linear and standard linear methods are used for its identification. The other two subsystems are the main sources of nonlinearities in the system, mainly due to the significant nonlinearities of controlled dampers and of tires. Owing to the complexity/accuracy problems of a physical modeling of these subsystems, an input–output approach is taken. In particular, a nonlinear set membership method that does not require the search of the functional form of involved nonlinearities is used for the identification of these subsystems. The iterative algorithm converged in two iterations to a model providing a quite satisfactory simulation accuracy for all the considered road profiles and CDC-Skyhook settings.     

一种基于Geode Gx1整合型芯片的嵌入式应用平台的设计与实现

阐述了嵌入式系统的基本定义及技术特点，设计并实现了一种基于GeDde Gx1整合型芯片的嵌入式应用平台，最后展望了嵌入式系统的应用前景。     

基于TM1300实时视频采集卡的设计

在视频数据采集、压缩及传输过程中，巨大的视频数据量对系统提出了相当高的要求。本文的设计目标是提供一种住相对较低廉的系统配置条件下提供高质量的实时视频图像的解决方案。主要从硬件方面，对视频采集卡的设计、启动以及采集过程进行了论述。     

The effect of the inflation pressure of tyres on motorcycle weave stability: experiments and simulation

Increasing the stability of a motorcycle requires an understanding of the optimal conditions of the tyre. The inflation pressure is one of the main parameters that directly affects the tyre properties, which in turn influences motorcycle stability and safety. This paper focuses on the effect of the inflation pressure of the tested tyres on motorcycle weave stability. Experimental data are collected from tests carried out in straight running at constant speed. The data analysis is based on stochastic subspace identification methods. Simulations are performed using an advanced motorcycle multi-body code with parameters measured from the tested vehicle. Finally, the comparison between simulations and experimental tests is discussed. The research results show an agreement between experimental tests and simulations where weave stability increases with inflation pressure for the specified range of tyre pressure.     

Vehicle handling dynamics modelling by a data-driven identification method

Modelling of vehicle handling dynamics has received a renewed attention in recent years. Different from traditional vehicle modelling, a novel data-driven identification method for vehicle handling dynamics is proposed, which can avoid the problems of the under-modelling and parameter uncertainties in the first-principle modelling process. By first-order Taylor expansion, the nonlinear vehicle system can be linearised as a slowly linear time-varying system with fourth-order. In order to identify the derived identifiable model structure, a recursive subspace method is presented. Derived by optimal version of predictor-based subspace identification (PBSID_opt) and projection approximation subspace tracking (PAST), the identification method is numerical stability and gives an unbiased estimation for the closed-loop system. Based on standard road tests, the proposed modelling method is proven effective and the obtained model has good predictive ability. Additionally, it is noted that the model obtained from the initial phase of straight driving is just a mathematical model to describe the relationship between input and output. And when the vehicle is steering, the model can converge to a stable phase quickly and represent vehicle dynamic performance.     

Pro-active optimal control for semi-active vehicle suspension based on sensitivity updates

This article suggests a strategy to control semi-active suspensions of vehicles in a pro-active way to adapt to future road profiles. The control strategy aims to maximise comfort while maintaining good handling properties. It employs suitably defined optimal control problems in combination with a parametric sensitivity analysis. The optimal control techniques are used to optimise the time-dependent damper coefficients in an electro-rheological damper for given nominal road profiles. The parametric sensitivity analysis is used to adapt the computed nominal optimal controls to perturbed road profiles in real time. The method is particularly useful for events with a low excitation frequency such as ramps, bumps, or potholes. For high-frequency excitations standard controllers are preferable; so we propose a switched open–closed-loop controller design. Various examples demonstrate the performance of the approach.     

黄骅港潮汐监测与发布系统

介绍了中国黄骅港潮汐监测与发布系统的研究背景和意义,详述了系统的总体结构、技术方案及功能,介绍了系统使用的计算数学模型,最后展望了该系统的应用前景。     

改进Bayes判别法在机械状态识别中的应用

Bayes判别法是统计模式识别中的一个基本方法,既考虑了各类参考总体出现的概率大小,又考虑了因误判造成的损失大小,比较适合在样本的数量不充分大,大子样统计理论不适宜的情况下进行状态判别,对它作了总体服从正态分布的合理假设后,将改进Bayes判别法成功运用到机械状态识别中,并利用这种方法对某减速箱轴承进行了状态判别,判别准确率较高,获得了满意的实验效果,从而证明了改进Bayes判别法是一种很好的机器状态识别方法。     

预应力混凝土连续刚构桥施工监测与仿真分析

预应力混凝土连续刚构桥有其自身的结构特点和施工技术,结合河南水磨湾大桥工程实例,探讨了预应力混凝土连续刚构桥的施工监测与仿真分析方法。通过建立有限元仿真分析模型,分析了预应力损失以及混凝土收缩徐变对箱梁应力状态的影响,计算了桥梁各个施工阶段应力和变形状态,与施工现场的实测数据进行了对比分析。经分析比较,可知对箱梁各节点不同施工阶段应力路径影响比较大的荷载有:施工荷载包括重力、挂篮、混凝土湿重等;预应力钢束一次张拉荷载;收缩一次作用以及徐变一次作用。施工荷载和预应力钢束张拉对顶、底板节点的影响是相反的,而其他荷载对它们的影响是同向的。得出了桥梁关键部位在荷载作用下随施工阶段的应力变化路径和挠度,使悬臂施工的梁桥达到了设计要求的合理成桥状态,总结了施工监控的规律。     

乌鞘岭隧道志留系板岩夹千枚岩地段结构验证试验研究

对乌鞘岭隧道志留系板岩夹千枚岩地段支护结构的受力特性,采用数值分析方法进行计算,开展现场结构试验并进行对比分析。试验揭示了隧道开挖后围岩应力释放引起的结构变形与支护压力变化规律,支护结构的稳定性和安全性在不同测试地段受各种影响因素的作用而不同。数值计算与现场试验结果表明,隧道衬砌的结构安全系数均满足规范要求,但应以按实测衬砌应力进行结构内力计算,并对结构安全性进行评价为宜。