船桥碰撞简化动力分析方法:简化模型的精度

为分析船桥碰撞动力分析简化模型的精度,以具体桥梁工程实例为背景,分别采用数值模拟分析方法和简化动力分析方法进行船桥碰撞动力反应计算,并定义3种数学指标评价简化模型动力分析结果的精度.实例计算结果表明,动力分析简化模型具有良好的工程计算精度.     

带防撞设施的船桥碰撞数值模拟

采用LS-DYNA对一座带防护设施的斜拉桥进行船桥碰撞模拟. 防护设施为钢套箱. 通过对单元和材料本构关系的合理选取、接触和摩擦的处理,实现采用合理的全桥模型进行船桥碰撞模拟,并研究船撞桥的碰撞细节和桥梁动力反应.     

混合动力汽车模型预测控制策略研究

针对传统混合动力汽车控制方法无法实现实时最优控制的问题,提出了基于简化混合动力汽车系统模型的预测控制智能优化策略.通过将3自由度的系统模型简化为1自由度的系统模型,并采用连续广义最小残量方法求解模型预测控制问题.运用MATLAB/Simulink与GT-POWER联合仿真平台进行仿真,实验结果验证了系统模型简化的有效性,以及所设计的模型预测控制算法大幅度提高混合动力汽车的燃油经济性的能力和实时控制性能.     

船桥碰撞桥梁防护装置横纵舱壁材料改进的研究

文章对桥梁防护装置横纵舱壁材料进行改进,利用MSC.Dytran有限元软件对桥梁在船舶冲击载荷作用下的防护问题进行了数值仿真研究,建立了船桥碰撞有限元模型,分析了碰撞过程中碰撞力变化、能量转换及结构损伤变形情况,并与原先的结构进行了比较。     

船桥碰撞桥梁防护装置上下甲板材料改进的研究

文章对桥梁防护装置上下甲板材料进行改进,利用MSC.Dytran有限元软件对桥梁在船舶冲击载荷作用下的防护问题进行了数值仿真研究,建立了船桥碰撞有限元模型,分析了碰撞过程中碰撞力变化、能量转换及结构损伤变形情况,并与改进前的结构进行了比较。     

基于虚拟样机技术的动力换档离合器动力学仿真

该文针对目前自动变速（AT）车辆普遍采用的动力换档离合器,应用大型CAD软件Pro/E和机械系统动力学仿真分析软件ADAMS建立了其虚拟样机模型.并且对离合器在工作过程中的受力状况进行了较详细地描述,得出了其动力学方程.通过对其接合与分离等工况进行动力学分析,最后得到了与实际情况相吻合的仿真结果,并总结出了一套动力换档离合器在ADAMS中设计的简化方法.此外,这个离合器模型还可以作为一个子系统,在今后用于整体动力传动虚拟样机系统的分析与设计.     

粘弹性沥青路面车辆动力响应仿真分析研究

不同载重车体对粘弹性沥青路面的应力反映波动性极为复杂,路面的响应规律,车辆的车速、负载等瞬态信息很难与应力反应建立稳定的规范模型.传统方法将移动的车辆荷载假定为作用在固定位置的静载荷;采用线弹性材料模型来仿真实际沥青路面材料;与实际的路面受力状况有所差别,造成结果失真.为解决上述问题,提出一种粘弹沥青性路面的三维瞬态有限元分析模型;计算行车荷载作用下路面动力响应规律,比较车速变化,载荷变化,不同载荷作用位置以及不同深度对动力响应的影响.实验结果表明:模型可以很好得到应力响应,在应力响应有明显的波动性的情况下;准确计算载荷横向作用位置对动力响应的影响,与真实结果比较吻合.     

飞机起降过程中机场道面的动力响应

利用改进的Kantorovich法分析了飞机起降过程中机场道面板的动力响应问题.在分析中把机场道面板简化成Winkler地基上四边自由的矩形弹性薄板,通过引入两端自由的梁函数,采用改进的Kantorovich法将机场道面板的动力微分方程化简成为常微分方程,然后利用Duhamel积分求得问题的精确解.文中还通过具体算例,分析了移动载荷的速度、加速度、道面板厚度和地基基床系数对板的动力响应的影响.计算结果表明：移动载荷的速度和地基的基床系数对道面板的动力响应有较大影响;而飞机起降时的加速度、减速度及道面板厚度对机场道面动力响应的影响不大.     

动力学效应的动力定位船舶模型在线辨识算法

由于船舶模型的高度非线性以及外界干扰力、推进器推力的无法测量性,导致它们的在线辨识和估计显得十分困难.本文提出一种以动力学效应为基础,应用无味卡尔曼滤波器（unscented Kalman filters,UKF）进行动力定位船舶动力学模型、外界载荷以及推进器推力在线辨识的算法.此算法能够在动力定位过程中不断求解船舶模型和其受到的载荷力,使得拥有这些参数的船舶模型和载荷所反映出的动力学效应不断逼近传感器检测到的运动反馈.基于此原理,用这些参数作为名义上的船舶模型、外界力、推进器推力就能够完成高效、自适应的定位控制.通过控制仿真,证明了此算法的有效性和正确性.     

动态加载方式下防爆墙动力响应分析

为分析防爆墙在不同爆炸载荷下的动力响应和破坏机理,研究波纹板式防爆墙与平板式防爆墙的差异,分别采用三角波加载和基于流固耦合方法的爆炸仿真2种动态加载方式模拟爆炸载荷。分析结果表明：三角波载荷可以较好地模拟爆炸载荷且具有明显的计算速度优势。分析得到2种类型防爆墙的P I曲线,通过对比发现波纹板式防爆墙的抗爆性能优于平板式防爆墙。     

电磁振动式微扑翼飞行器动态特性研究

电磁驱动具有驱动电压低、作用力大等优点, 是微机械领域一种重要驱动方式。本文设计了一种电磁振动式微扑翼飞行器，在此基础上，建立了电磁振动式微扑翼飞行器非线性动力学模型，研究了不同电磁力激励下系统动态特性，获得了系统固有频率，并得出方波和正弦半波电磁力驱动能够产生较大扑动幅度的结论。最后，研究了电磁振动式微扑翼飞行器机-磁耦合非线性系统动态特性，研究结果表明电磁振动式微扑翼飞行器适合采用正弦半波电压激励，而且通过结构改进措施，提高了扑动的对称性和稳定性。     

Improving performance of rigid body dynamics simulation by removing inaccessible regions from geometric models

Rigid body simulations require collision detection for determining contact points between simulated bodies. Collision detection performance can become dramatically slow, if geometric models of rigid bodies have intricate inaccessible regions close to their boundaries, particularly when bodies are in close proximity. As a result, frame rates of rigid body simulations reduce significantly in the states in which bodies come into close proximity. Thus, removing inaccessible regions from models can significantly improve rigid body simulation performance without influencing the simulation accuracy because inaccessible regions do not come in contact during collisions. This paper presents an automated pair-wise contact preserving model simplification approach based upon detection and removing of inaccessible regions of a given model with respect to another colliding model. We introduce a pose independent data-structure called part section signature to perform accessibility queries on 3D models based on a conservative approximation scheme. The developed approximation scheme is conservative and does not oversimplify but may undersimplify models, which ensures that the contact points determined using simplified and unsimplified models are exactly identical. Also, we present a greedy algorithm to reduce the number of simplified models that are needed to be stored for satisfying memory constraints in case of a simulation scene with more than two models. This paper presents test results of the developed simplification algorithm on a variety of part models. We also report results of collision detection performance tests in rigid body simulations using simplified models, which are generated using developed algorithms, and their comparison with the identical performance tests on respective unsimplified models.     

共线三球链问题的碰撞动力学研究

共线三球链的碰撞动力学问题能够展示多刚体系统碰撞问题的困难之一：非唯一解的问题.本文建立了三球链碰撞的Hertz接触模型,研究对其求解的数值算法,并用有限元模型（FEM）对其进行验证,研究表明：同线性模型比较,采用Hertz接触力模拟小球之间的接触力更接近有限元计算结果;在Hertz接触模型基础上,分析碰撞过程中接触力的变化过程;研究刚度比和质量比对于碰撞结束后各个小球运动状态的影响,并研究了两种刚体模型下碰撞次序假设成立的条件.     

Pseudo-interference stiffness estimation, a highly efficient numerical method for force evaluation in contact problems

This paper presents a novel method, Pseudo-Interference Stiffness Estimation (PISE), for evaluating the contact compliance and the contact load in the contacting elastic solids. The PISE method is based on the evaluation of the geometric overlap of two assumedly rigid bodies and estimation of the contact force based on this artificial overlap area (or volume). In this paper, an example of the dynamic simulation of two disk collision problem is solved both by PISE method and finite element contact model. The contact force and velocity changes during impact from both methods are shown to be in good agreement. However, PISE method is, computationally, orders of magnitude (about 3000 times in our numerical simulations) faster than finite element contact analysis. The proposed method will be of practical use in contact force approximation of contacting bodies, such as meshing of spur gear teeth, cam analysis and synthesis, robotic grabbing, and numerous other applications.     

Motion control of a snake robot moving between two non-parallel planes

A control method that makes the head of a snake robot follow an arbitrary trajectory on two non-parallel planes, including coexisting sloped and flat planes, is presented. We clarify an appropriate condition of contact between the robot and planes and design a controller for the part of the robot connecting the two planes that satisfies the contact condition. Assuming that the contact condition is satisfied, we derive a simplified model of the robot and design a controller for trajectory tracking of the robot’s head. The controller uses kinematic redundancy to avoid violating the limit of the joint angle and a collision between the robot and the edge of a plane. The effectiveness of the proposed method is demonstrated in experiments using an actual robot.     

船舶高能搁浅外部动力学的数值仿真研究

基于Simonsen的假设，提出了船舶高能搁浅外部动力学的简化计算公式，并对船舶高能搁浅外部动力学过程进行了数值仿真研究。研究表明，在船舶高能搁浅动力学过程中，有相当部分的初动能转化为旋转形式的动能，包括纵摇、横摇和艏摇；不同于某些船舶碰撞问题，摩擦的影响不能忽略不计；对于船艏高能搁浅的情况，损伤路径会向船体外侧偏离，船舶与礁石之间的接触由剧烈的冲击逐渐过度到侧向挤压和滑动摩擦；相比于简化解析法，数值仿真法可以得到详细的动力学时历结果以及船体结构损伤变形图。     

The flexural rigidity of reinforced concrete slabs

To allow reliability analyses and design optimisation, two probabilistic models for the flexural rigidity of effectively uncracked reinforced concrete slabs are developed theoretically from a probabilistic model of concrete compliance. A simulation model uses finite difference equations to model concrete and steel stresses and strains, as concrete creeps and shrinks in a slab section. This model accounts for 17 parameters to yield an unbiased estimate of rigidity with a coefficient of variation of 0.23. A simulation study for a normal class of slabs shows that flexural rigidity is effectively independent of steel reinforcement, so rigidity is well represented by the product of a gross moment of inertia and a time-dependent effective gross modulus of elasticity. This modulus is primarily a function of concrete strength, humidity and duration of loading, and it approaches an effective long-term limiting value at about 5000 days. A simplified (design) model approximates this long-term modulus by a simple function of concrete strength and humidity. This model gives an unbiased estimate with a coefficient of variation of 0.27.     

轴向受力梁结构线弹性碰撞问题求解

研究了质点对轴向受力的Euler-Bernoulli梁结构任意位置的横向撞击问题.把撞击体系简化为质量-弹簧体系模型,采用积分变换方法,对撞击体系的控制微分方程、边界条件和连续条件进行Laplace变换,在频域内求得其解析表达式,然后采用Crump逆变换方法进行数值反演,得到时域内的各种动力响应.数值算例给出了撞击力、弯曲应力和剪力随时间变化的曲线,通过与有限元比较验证了本方法的正确性.最后研究了撞击位置、轴向压力、撞击质量、撞击速度和柔度系数等参数对撞击力的影响,得出了一些有用的结论.     

Human–robot collision model with effective mass and manipulability for design of a spatial manipulator

As the use of service robots becomes more popular, many solutions to ensure human safety during human–robot collision have been proposed. In this paper, we address one of the most fundamental solutions to design an inherently safe robot manipulator. A collision model is developed to evaluate the collision safety of any spatial manipulator. Most collision studies have focused on collision analysis and safety evaluation, but not on the use of evaluation results to design a safer robot arm. Therefore, we propose a collision model that relates design parameters to collision safety by adopting effective mass and manipulability. The model was then simplified with several assumptions. Furthermore, experimental results from biomechanical literature were employed to describe a human–robot collision. The major advantage of this collision model is that it can be used to systemically determine the design parameters of a robot arm.