Design of characteristics of air-pressure-controlled hydraulic shock absorbers in an intercity bus

The air-pressure-controlled shock absorber is capable of changing its damping force depending on the air pressure in the air springs. Due to the possibility of improving dynamic properties of all vehicles that use the axles’ air suspensions, BRANO Inc. (the Czech producer of shock absorbers) started to develop semi-active air-pressure-controlled hydraulic telescopic shock absorbers. The SOR C 12 intercity bus is the reference vehicle for which the research and development of controlled shock absorbers is done and on which the shock absorbers are verified. Force–velocity characteristics of the controlled shock absorbers of the axles’ air suspension were designed on the basis of results of computer simulations with the bus multibody models created in the alaska simulation tool. Multibody models of an empty vehicle, a fully loaded vehicle and three variants of a partly loaded vehicle were created. For each weight of the bus two multibody models of various levels of complexity were created. Since the bus multibody models should be used especially for designing force–velocity characteristics of air-pressure-controlled shock absorbers, great attention (in the framework of the possibilities of multibody dynamics) was paid to the correct interpretation of the real behaviour of hydraulic shock absorbers and air springs of the axles’ suspension. As a criterion for the design of the optimum force–velocity characteristics of the controlled shock absorbers, the maximum similarity of the dynamic responses of multibody models of the bus of all the considered weights to dynamic response of the reference multibody model of the bus with the same load as during the experimental measurements on the real vehicle (approx. 71.5% of the maximum loaded vehicle weight) was chosen. In the course of the measurements the non-controlled shock absorbers’ characteristics were optimally tuned for that vehicle weight. Time histories of relative deflections of the axles’ air springs determined during the simulations of the vehicle running over the vertical artificial obstacle were compared. The approach based on the evaluation of the correlation coefficient of two time series was used for the evaluation of the dynamic responses accordance.     

压电叠堆电静液作动器Simscape模型与实验研究

将海德福斯螺纹插装换向阀集成到压电叠堆电静液作动器中,形成一体化集成式双向运动的压电叠堆电静液作动器。基于压电叠堆电静液作动器的物理系统,采用Simscape搭建压电叠堆电静液作动器系统模型。对比了在不同蓄能器偏压、不同电压峰值条件作用下,压电叠堆电静液作动器的实验输出流量与仿真输出流量;以及换向阀换向周期为4s时,压电叠堆电静液作动器的实验输出位移与仿真输出位移,验证了搭建的Simscape模型的准确性。在系统模型得到验证的基础上,分析发现阀片的回流现象是造成压电叠堆电静液作动器在高频驱动时输出流量衰减的原因。     

多体系统动力学Lie 群微分⁃代数方程约束稳定方法

针对多体系统动力学微分-代数方程求解问题,研究基于Lie群表达的约束稳定方法.首先引入新的Lagrange乘子,结合位移约束、速度级约束和加速度级约束方程,构造了新的Lie群微分-代数方程.然后使用向后差商隐式方法和CG(Crouch-Grossman)方法,对微分–代数方程进行离散求解,得到精确度较高的动力学仿真结果.该方法在精确保持各级约束方程的同时,保持旋转矩阵的正交性,并且使系统总能量误差较小.     

Linearization and parametric vibration analysis of some applied problems in multibody systems

The paper deals with the application of the Runge–Kutta method for calculating steady-state periodic vibrations of the parametric vibration systems governed by linearized differential equations. The numerical calculation is also demonstrated by two models of multibody systems and measurements on real objects. Good agreement is obtained between the numerical and experimental results. Consequently, the obtained results can also be applicable to investigate other complicated models of multibody systems which perform the steady-state motions.     

A Model-Selection Framework for Multibody Structure-and-Motion of Image Sequences

Given an image sequence of a scene consisting of multiple rigidly moving objects, multi-body structure-and-motion (MSaM) is the task to segment the image feature tracks into the different rigid objects and compute the multiple-view geometry of each object. We present a framework for multibody structure-and-motion based on model selection. In a recover-and-select procedure, a redundant set of hypothetical scene motions is generated. Each subset of this pool of motion candidates is regarded as a possible explanation of the image feature tracks, and the most likely explanation is selected with model selection. The framework is generic and can be used with any parametric camera model, or with a combination of different models. It can deal with sets of correspondences, which change over time, and it is robust to realistic amounts of outliers. The framework is demonstrated for different camera and scene models. Most of the presented research was carried out while all three authors were at Monash University.     

Multiframe Motion Segmentation with Missing Data Using PowerFactorization and GPCA

We consider the problem of segmenting multiple rigid-body motions from point correspondences in multiple affine views. We cast this problem as a subspace clustering problem in which point trajectories associated with each motion live in a linear subspace of dimension two, three or four. Our algorithm involves projecting all point trajectories onto a 5-dimensional subspace using the SVD, the PowerFactorization method, or RANSAC, and fitting multiple linear subspaces representing different rigid-body motions to the points in ℝ⁵ using GPCA. Unlike previous work, our approach does not restrict the motion subspaces to be four-dimensional and independent. Instead, it deals gracefully with all the spectrum of possible affine motions: from two-dimensional and partially dependent to four-dimensional and fully independent. Our algorithm can handle the case of missing data, meaning that point tracks do not have to be visible in all images, by using the PowerFactorization method to project the data. In addition, our method can handle outlying trajectories by using RANSAC to perform the projection. We compare our approach to other methods on a database of 167 motion sequences with full motions, independent motions, degenerate motions, partially dependent motions, missing data, outliers, etc. On motion sequences with complete data our method achieves a misclassification error of less that 5% for two motions and 29% for three motions.     

COMPUTER AIDED ANALYSIS OF FLEXI－BLE MEMBER IN CONSIDERATION OF THE EFFECTS OF DYNAMIC STI－FFEN－ING

ＣＯＭＰＵＴＥＲＡＩＤＥＤＡＮＡＬＹＳＩＳＯＦＦＬＥＸＩ－ＢＬＥＭＥＭＢＥＲＩＮＣＯＮＳＩＤＥＲＡＴＩＯＮＯＦＴＨＥＥＦＦＥＣＴＳＯＦＤＹＮＡＭＩＣＳＴＩ－ＦＦＥＮ－ＩＮＧＣＯＭＰＵＴＥＲＡＩＤＥＤＡＮＡＬＹＳＩＳＯＦＦＬＥＸＩ－ＢＬＥＭＥＭＢＥＲＩ...     

凸轮机构动力学前沿的若干问题

为了适应高速度高精度的要求，动态特性分析成为凸轮机构学的主要研究课题。运用可变形多体系统动力学、接触力学及概率分析方法的新成果，使凸轮机构动力学的研究进入了一个新阶段。本文介绍这方面研究工作的动向，评述近期发表的文献，提出问题，对有关资料进行了整理。     

过盈接触式伸缩杆的动态特性

某无控空间飞行器的轴向展开机构是一类过盈接触式伸缩杆,伸缩杆的动态特性对飞行器的正常工作起重要作用。为研究伸缩杆在工作过程中的动力学特性,基于柔性多体系统动力学理论,结合含摩擦的连续碰撞模型,建立混合坐标下的过盈接触式伸缩杆的动力学研究方法,对伸缩杆拉开过程的运动行为和动力学特性进行数值研究,得到杆的位移和受力情况,同时对0.31 s时刻的各伸缩杆进行有限元分析,有限元分析结果与运动分析相吻合。研究结果表明:伸缩杆在恒定拉力作用下依次打开,能够完成动态过盈配合;拉力直接作用的伸缩杆先发生扰动,并且扰动幅度最大,四根伸缩杆的扰动趋势一致;伸缩杆受力产生变形,变形造成杆间的接触碰撞,接触碰撞进一步加剧杆的变形和扰动。     

空间机器人的可变增益滑模控制方法

针对空间机器人抓捕目标的轨迹跟踪过程,提出了一种基于可变增益的滑模控制算法,并利用MATLAB/Simscape对空间机器人的理论动力学模型和控制算法进行了仿真校验。首先,基于拉格朗日法构建了空间机器人的动力学模型,并给出了系统参数不确定时的动力学方程。设计了一种滑模控制器,在控制器中引入了可变增益,该增益可根据系统的不确定性和系统的运动状态进行调整,从而使控制器具有很强的鲁棒性。基于Simscape Multibody软件模块,对空间机器人的理论动力学模型进行了验证。在此基础上,针对多关节运动和系统模型不确定两种情形,利用可变增益滑模控制算法进行了空间机器人的轨迹跟踪仿真实验。实验结果表明,与传统的计算力矩法相比,本文提出的控制算法呈现出更高的运动控制精度和误差收敛速度。