Design and Optimization for the Occupant Restraint System of Vehicle Based on a Single Freedom Model

Throughout the vehicle crash event, the interactions between vehicle, occupant, restraint system (VOR) are complicated and highly non-linear. CAE and physical tests are the most widely used in vehicle passive safety development, but they can only be done with the detailed 3D model or physical samples. Often some design errors and imperfections are difficult to correct at that time, and a large amount of time will be needed. A restraint system concept design approach which based on single-degree-of-freedom occupant-vehicle model (SDOF) is proposed in this paper. The interactions between the restraint system parameters and the occupant responses in a crash are studied from the view of mechanics and energy. The discrete input and the iterative algorithm method are applied to the SDOF model to get the occupant responses quickly for arbitrary excitations (impact pulse) by MATLAB. By studying the relationships between the ridedown efficiency, the restraint stiffness, and the occupant response, the design principle of the restraint stiffness aiming to reduce occupant injury level during conceptual design is represented. Higher ridedown efficiency means more occupant energy absorbed by the vehicle, but the research result shows that higher ridedown efficiency does not mean lower occupant injury level. A proper restraint system design principle depends on two aspects. On one hand,the restraint system should lead to as high ridedown efficiency as possible, and at the same time, the restraint system should maximize use of the survival space to reduce the occupant deceleration level. As an example, an optimization of a passenger vehicle restraint system is designed by the concept design method above, and the final results are validated by MADYMO, which is the most widely used software in restraint system design, and the sled test. Consequently, a guideline and method for the occupant restraint system concept design is established in this paper.

Nonlinear dynamic response analysis of supercavitating vehicles

A finite element model for the supercavitating underwater vehicle was developed by employing 16-node shell elements of relative degrees of freedom.The nonlinear structural dynamic response was performed by introducing the updated Lagrangian formulation.The numerical results indicate that there exists a critical thickness for the supercavitating plain shell for the considered velocity of the vehicle.The structure fails more easily because of instability with the thickness less than the critical value,while the structure maintains dynamic stability with the thickness greater than the critical value.As the velocity of the vehicle increases,the critical thickness for the plain shell increases accordingly.For the considered structural configuration,the critical thicknesses of plain shells are 5 and 7 mm for the velocities of 300 and 400 m/s,respectively.The structural stability is enhanced by using the stiffened configuration.With the shell configuration of nine ring stiffeners,the maximal displacement and von Mises stress of the supercavitating structure decrease by 25% and 17% for the velocity of 300 m/s,respectively.Compared with ring stiffeners,longitudinal stiffeners are more significant to improve structural dynamic performance and decrease the critical value of thickness of the shell for the supercavitating vehicle.

Practical Model for Real Structure and Performance of Heavy Vehicles

In this paper, a new practical model for real heavy vehicle structure is developed to investigate dynamic responses under steering/acceleration or braking maneuvers. The generalized six DoFs （degrees-of-freedom） nonlinear vehicle model M1 including longitudinal, lateral, yaw, vertical, roll and pitch dynamics is validated using the measured data reported in different studies. This model takes the CG （center of gravity） of sprung mass, unsprung mass and total vehicle mass into account. Based on this model, the effects of the inertia parameters on the vehicle dynamic responses are investigated for more comprehensive assessments of the model structure. Another nonlinear vehicle model 342 derived from M1 which assumes that the vehicle has a single CG as reported in literature is also developed. The dynamic responses of the vehicle model Mj are compared with those of the model M2 to demonstrate the performance potential of the proposed nonlinear model. The results of dynamic responses with the nonlinear vehicle model MI suggest that the model could offer considerable potential in realizing enhanced ride and handling performance, as well as improved roll and pitch properties in a flexible manner.

Model Simplification and Parameter Modification for Offshore Platforms Using Experiment Data

In this paper, a computation method has been developed so as to compare the finite element method (FEM) with the test results directly. The structure is divided into the 'master' and 'slave' degrees of freedom. The simplified model can be obtained with modal reduction. Then the design sensitivity analysis of the eigenvalues and eigenvectors has been carried out using the modal frequency and modal shape of the test. A two-story frame structure and a jacket model structure have been calculated. Meanwhile, the modified coefficient, the FEM computational and experimental values have been given. It has been shown that the FEM model modified using the test modal value is efficient.

Study on Dynamic Characteristics of Hydraulic Pumping Unit on Offshore Platform

A new technology of offshore oil rod pumping production is developed for offshore heavy oil recovery. A new type of miniature hydraulic pumping unit with long-stroke, low pumping speed and compact structure is designed based on the spatial characteristics of offshore platforms. By combining the strengths of sinusoidal velocity curve and trapezoidal velocity curve, a kinematical model of the acceleration, the velocity and displacement of the pumping unit＇s hanging point is established. The results show that the pumping unit has good kinematic characteristics of smooth motion and small dynamic load. The multi-degree-of-freedom dynamic model of the single-well pumping unit is established. The first and second order natural frequencies of the sucker rod string subsystem and the pumping unit subsystem are studied. The results show that the first and the second order natural frequencies among the pumping rod string, pumping unit-platform subsystem and the dynamic excitation have differences over 5 times from each other, indicating that resonance phenomenon will not appear during the operation and the dynamic requirements for field use are met in the system.

Modeling and Stability Analysis for Dual-Spinning Projectiles with Canards

To develop the guided spin-stabilized projectiles with high hit precision,a class of dual-spinning stabilized projectile equipped with canards in atmospheric is studied.The 7 degrees of freedom(DOF) nonlinear equations are written in a non-rolling body frame.The work reported here focuses on the ballistic property analysis including the spin rates,incidence angle,ballistic drift and lateral velocity.The dual-spinning projectiles are fundamentally less stable than conventional spin-stabilized projectiles.Hence,the gyroscopic stability is also studied in this paper.Theoretical models are given in this work,and the results of numerical analysis are discussed.

Four-Degree-of-Freedom Course Stability of an Air Cushion Vehicle

A four-degree-of-freedom mathematical model was established to investigate the course stability of an air cushion vehicle (ACV). The forces of aerodynamic,propeller and rudder were obtained by wind tunnel experiments. A series of constrained model experiments with horizontal-planar-motion-mechanism (HPMM) were conducted to determine the hydrodynamics. The ACV's course stability was analyzed by using Hurwitz deter-mination method with differential equation of perturbation,and the four-degree-of-freedom course stability was then checked by simulated calculation. The analysis and simulation results show that the course stability of fourdegree-of-freedom is applicable to ACV and is stricter than that of two-degree-of-freedom.

六自由度机械臂若干基本问题的研究

六自由度机械臂作为一种重要的工业自动化设备,其应用越来越广泛,基于此,分析了近几年我国六自由度机械臂的研究文献,探讨了当下该领域研究的主流方向和相应的研究方法,总结了部分研究的创新之处.通过分析研究方法中的异同,结合市场调研结果指出了当下六自由度机械臂研究中存在的一些问题,总结为动力学问题、控制问题、感知问题、精度问题及软硬件集成问题,并根据当下研究成果针对每个问题提出了改进措施,最后对未来六自由度机械臂发展方进行了展望.

多自由度机械臂关节角度自动控制方法设计研究

为解决目前机械臂运动轨迹控制与精度补偿中的问题,提出了一种多自由度机械臂关节角度自动控制方案.在对多自由度机械臂的连杆和关节部位的运动过程进行动力学分析的基础上,结合梯度下降法和人工神经系统,提出了能够实现对机械手臂连接部分和控制部分自动控制的策略,建立了针对多自由度的机械臂关节的角度控制模型.实验证明,所提出的控制策略能够很好地控制机械臂关节角度,并且能够很好地跟踪机械臂运动轨迹,有效提高了机械臂抓取精度,抓取精度达到了96%.

新型双体波浪能转换装置多自由度耦合水动力特性研究

提出一种新型双体波浪能转换装置,其主体由浮标和可调节质心的摆体构成。利用AQWA进行频域仿真,获取装置的水动力参数,建立含黏性项的多自由度耦合的时域模型,并将水动力参数代入模型,分别开展规则波、不规则波的仿真,研究质心位置、PTO(power take-off)阻尼对装置性能的影响,最终根据真实海况划分若干不规则波并分别开展仿真,研究装置在真实海况下的发电性能。结果表明,装置可通过调节配重位置在不同周期的波浪中高效发电,且装置在小波高情况下也可以有效利用波浪能量,具有持续的发电能力。

风场下翼伞系统运动特性研究

为探究风场对翼伞系统运动特性的影响,建立了翼伞系统六自由度动力学模型,采用龙格库塔法对风场下翼伞系统运动特性进行了仿真计算。在此基础上,开展了翼伞系统在不同风向与不同飞行高度下运动特性变化的对比研究。结果表明:风场会改变翼伞空速,引起气动角变化,导致翼伞气动性能改变,使系统力、力矩不平衡,系统速度、姿态出现波动,而后重新恢复稳定,稳定后速度略大于无风时飞行速度与风速的矢量和;系统在顺风条件下前俯,逆风条件下后仰,侧风情况下会出现明显的滚转、偏航运动;飞行高度通过影响风速与大气密度改变系统平衡速度,高度越高平衡速度越大,但滑翔比与姿态角变化较小。文章所得风场下翼伞系统运动特性变化规律对翼伞轨迹规划及飞行控制有一定应用价值。

柔性齿轮运动特性及其振动抑制性能的实验研究

在三缸发动机平衡轴齿轮传动系统的传动过程中,存在着较大的振动和噪声问题,为此,提出了一种附加阻尼环的齿轮传动系统刚柔耦合模型,对柔性齿轮结构的运动特性及其振动抑制性能进行了实验研究。首先,采用集中质量法,建立了考虑齿轮间隙和时变啮合刚度的附加阻尼环6自由度齿轮传动系统的弯曲-扭转模型,利用石川公式计算出了柔性齿轮的时变啮合刚度,对比了有无阻尼环的齿轮系统的振动响应;然后,搭建了专门的齿轮传动系统测试设备,测试了不同转速下钢齿轮和柔性齿轮的加速度和噪声峰值;最后,设计了激光位移试验台,对比分析了不同转速下齿轮的微抖动,对柔性齿轮的减振效果进行了测试,并验证了理论模型的正确性。研究结果表明:当转速为1000 r/min时,钢齿轮和柔性齿轮的最大加速度信号分别为35.58 m/s^(2)和20.37 m/s^(2);当齿轮转速为4000 r/min时,柔性齿轮的阻尼效果最佳,加速度峰值降低了45.23%,噪声峰值降低了39.06%;钢齿轮的微抖动幅值明显高于柔性齿轮,两者的变化趋势相似。柔性齿轮能有效抑制轮齿微抖动振幅曲线的不平滑、毛刺现象,从而增强了三缸发动机平衡轴系的稳定性。

面向变形飞行器的时变气动参数在线辨识方法

针对变形飞行器快时变气动参数的在线高精度获取问题,本文提出一种基于BP神经网络模型的气动参数在线辨识方法。基于变形飞行器气动模型的非线性输入/输出映射关系,建立能够在一定精度范围内逼近变形飞行器气动模型的BP神经网络模型。根据在线实测动力学参数观测数据,采用扩展卡尔曼滤波方法在线训练神经网络,实时校正并获取神经网络模型参数,基于神经网络模型快速计算并预测气动参数,从而跟踪快时变、非线性气动模型的变化。通过对变形飞行器连续变形/构型突变的气动参数辨识进行数学仿真验证。结果表明:提出的方法收敛速度快、在线辨识精度较高,可以实现对变形飞行器气动参数的有效辨识。

汽车半主动座椅悬架主要参数优化研究

半主动座椅悬架能有效改善驾驶平顺性,减少人体垂向振动,提升车内驾乘人员的乘坐体验.其中,半主动悬架的初始性能参数对悬架性能起到决定性作用.为此,本文针对半主动座椅悬架的初始性能参数(弹簧刚度和阻尼系数)的优化问题展开研究,在使用了随机路面模型、六自由度半车模型的基础上,以优化前后座椅垂向加速度之比作为适应度函数,利用遗传算法对半主动座椅悬架的刚度及阻尼系数进行优化.最后,利用MATLAB软件对优化结果进行仿真分析.结果表明,经算法优化后,座椅垂向加速度的均方根减少了16.4%,最大值下降了11.3%;座椅相对位移的均方根减少了36%,最大值下降了39.2%.

电动汽车物理建模技术分析

该研究旨在分析电动汽车物理建模技术及其在典型领域的应用,通过对模型的技术分析,优化电动汽车的设计。文章基于电动汽车的工作原理和相关理论,提出可行的建模方法,运用基于牛顿力学的方法,建立了能够反映电动汽车实际运行状态的“二自由度动力学”公式模型。采用文献分析、数学建模手段建立了物理模型技术框架,可对电动汽车性能和安全性进行深入分析和优化,为后续的运动分析、控制策略设计以及性能优化提供了依据,该分析对于推动电动汽车的发展具有重要意义。

Global modeling and simulation of vehicle to analyze the inertial parameters effects

This paper mainly studies the comparison of the global vehicle models and the effects of the inertial parameters due to the center of gravity(CG)positions when we consider that the vehicle has only one CG.This paper proposes a new nonlinear model vehicle model which considers both unsprung mass and sprung mass CG.The CG positions and inertial parameters effects are analyzed in terms of the published vehicle dynamics models.To this end,two 14 degree-of-freedom(DOF)vehicle models are developed and compared to investigate the vehicle dynamics responses due to the different CG height and inertial parameters concepts.The proposed models describe simultaneously the vehicle motion in longitudinal,lateral and vertical directions as well as roll,pitch and yaw of the vehicle about corresponding axis.The passive and active moments and the forces acting on the vehicle are also described and they are considered as a direct consequence of acceleration,braking and steering maneuvers.The proposed model M1 takes both the CG of sprung mass,unsprung mass and total vehicle mass into account.The second model M2 assumes that the vehicle is one solid body which has a single CG as reported in majority of literature.The two vehicle models are compared and analyzed to evaluate vehicle ride and handling dynamic responses under braking/acceleration and cornering maneuvers.Simulation results show that the proposed model M1 could offer analytically some abilities and driving performances,as well as improved roll and pitch in a very flexible manner compared to the second model M2.

基于开关阻尼控制的铁道客车系统的动力学性能研究

建立具有23个自由度的铁道客车系统非线性数学模型。在客车二系悬挂系统中采用具有开关阻尼控制的横向半主动减振器,并考虑半主动悬挂系统的时滞。分析被动悬挂和具有开关阻尼控制的半主动悬挂客车在直线轨道上的蛇行运动稳定性和随机振动响应。研究半主动减振器的阻尼参数和半主动悬挂系统的时滞对客车系统临界速度和随机响应的影响。计算表明,尽管半主动悬挂使客车系统的临界速度低于被动悬挂,构架的横向加速度和轮轨横向力也要大于被动悬挂,但它能够大大减小车体的横向振动加速度,改善旅客的乘坐舒适性。

基于四轮独立驱动电动汽车的动力学仿真模型

四轮独立驱动技术是电动汽车驱动系统研究的热点。建立了包括转向角在内的18自由度四轮独立驱动电动汽车的动力学模型并详细给出了各运动方程。通过整车试验数据与相同工况下的仿真结果对比,表明所述模型可以以很好的精度反映汽车在各种工况下的动力学性能。为开展四轮独立驱动电动汽车动力学控制研究奠定了基础。

基于MATLAB汽车动力学仿真研究

对影响汽车行驶安全的各方面因素进行了较为深入的分析和研究,建立车体6个自由度加上前轮转向系统1个自由度的汽车数学模型;该汽车数学模型不需引入很多的人为假设;可以实现给定汽车前轮转角,也可以不给定前轮转角;不依赖需要复杂测定的侧向力函数及相关模型参数;考虑了轮胎的滚动特性。利用MATLAB语言开发了一个模块化的仿真软件,该软件能够满足所建模型的校验和在特殊工况下的仿真研究;也可以进一步完善该软件使之服务于汽车运行的其他方面的仿真研究。

基于AMESim的液压并联机构建模及耦合特性仿真

针对液压六自由度并联机构,采用AMESim和Simulink分别对单缸液压系统及平台机构部分建模,建立了液压并联机构的通用仿真模型.在AMESim模型中单缸系统的等效负载为Simulink模型反馈的负载力而非等效质量.联合仿真模型详细考虑了液压系统,保证了系统的精度,为研究液压并联机构提供了便捷的理论分析手段.通过联合仿真模型研究了并联机构由于液压缸不一致带来的耦合特性.数值仿真结果表明,当液压缸性能不一致时会出现耦合现象,耦合度随着液压缸性能不一致程度的增大而增强.在并联机构设计时,必须保证液压缸性能的一致性.