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1.
研制了步进摩擦分析测试平台,可用于检测人体在静止及运动路面上的步进摩擦特性.该平台主要由六自由度摇摆台、三维测力台和数据采集系统三部分构成,六自由度摇摆台可提供六个自由度的任意组合运动,用来模拟舰船、海浪和地震等工况;三维测力台可测量出人体在行走时的三维力和力矩;数据采集系统将六自由度运动平台和三维测力台的输出数据采集并保存到计算机中,用来分析人体运动时的步进摩擦特性.采用研制平台进行了一组试验,结果表明:人在上、下坡行走时的垂直地面反作用力与在水平路面行走时的垂直地面反作用力具有不同的分布规律,并且垂直地面反作用力均随坡度角的增大而减小.  相似文献   

2.
基于放顶煤开采中顶煤渗透率对工作面安全生产的重要性, 对煤壁前方极限平衡区内顶煤渗透率的变化规律进行了研究. 应用损伤力学和数理统计方法对顶煤垂直和水平应变进行了研究分析, 并建立了数学模型. 以甲烷气体为渗流体, 应用自制三轴实验机对煤样体积应变与渗透率的关系进行了试验研究, 并利用多项式拟合方法对试验结果进行了分段拟合. 结果表明:根据所建立的顶煤应变计算模型, 可以求出综放顶煤内任意点的体积应变, 且顶煤的水平应变与其距底板的高度无关. 依据试验及拟合所得到的煤体体积应变与渗透率的函数关系, 可以求得顶煤内任意点渗透率. 最后对计算模型进行了实践检验.  相似文献   

3.
赵健  刘彦辰  朱冰  李扬  李雅欣  孔德成  姜泓屹 《力学学报》2022,54(10):2922-2935
根据越野车辆在不同路面上行驶时的动力学响应特征, 可以实现路面类型的在线识别, 为面向路面特征调整底盘控制子系统参数从而获取更好的行驶性能奠定基础. 但越野环境地面特征复杂, 车辆响应机理分析困难, 给基于车辆动力学响应进行路面准确识别带来挑战. 提出了一种SHAP-RF路面识别算法设计框架, 通过SHAP (Shapley additive explanations)模型解释方法实现高维随机森林(random forest, RF)路面识别模型的降维化: 首先采集了试验车在压实土路、沙地、良好沥青路与冰雪路4种路面上的行驶数据并计算了3个次级行驶特征; 进一步计算了行驶数据的共计105个时域特征和频域特征, 并以此为输入特征建立了高维随机森林路面识别模型; 利用SHAP解释法分析高维模型输入特征对识别结果的影响从而提炼出各个特征与路面类型的关联性, 完成特征筛选; 最后, 利用筛选后的特征设计降维随机森林路面分类器. 基于实车数据的算法验证试验表明, 设计的降维路面识别模型对4种路面的识别精确率在94%以上, 召回率在93%以上, 相比高维的随机森林路面识别模型, 各种路面上的精确率和召回率最大降幅不超过3.2%, 证明本文提出的SHAP-RF路面识别算法设计框架能够在选用较少特征的情况下依然保证车辆行驶路面类别的准确识别.   相似文献   

4.
人车路系统三维耦合振动分析及舒适度评价   总被引:2,自引:0,他引:2  
张丙强  李亮 《计算力学学报》2013,30(2):302-307,318
基于将车身视作三维弹性梁、车轮为刚性体的全车模型,人体采用坐姿并联动力模型,路面简化成Kelvin地基上的板,通过轮胎的刚性滚子接触模型将车辆与路面耦合在一起,建立起考虑人车、车路耦合作用的用于评价车辆乘坐舒适度的三维人车路耦合系统振动模型,并推导出其运动平衡方程;通过Galerkin法对路面方程进行离散,采用New-mark积分法对耦合系统方程组进行求解,对人车路系统振动响应进行了分析;采用人体加权振动加速度均方根值对车辆乘坐舒适度进行评价,并对系统各参数对车辆乘坐舒适度的影响进行探讨.数值分析表明:传统模型下车辆乘坐舒适度指标与本文模型的指标相差最高可达到约30%;在分析车辆振动响应及乘坐舒适度时,不能忽视车辆与路面、人体与车辆相互作用,系统各参数对车辆乘坐舒适度都有一定程度的影响.  相似文献   

5.
同源演变随机激励下的非平稳响应   总被引:7,自引:0,他引:7  
在复模态分析与演变谱分析的基础上任意点的三维坐提出了时不变线性系统的在一般演变随机的激励下的时变均方响应的一个简便实用解法。并以简化模型为例,用本方法考察了变速车辆的路面响应问题。  相似文献   

6.
本文推导粘弹介质中圆孔孔径时变时的应力和位移.由粘弹解与弹性解的对应关系得到粘弹时变应力解.用直接解方程法求径向位移,最终归结为求解关于待定函数的l阶非齐次微分方程.将半径时变函数泰勒展开,用幂级数解法得到一般情况下的解.在寻找定解条件时,采用了对待定函数的光滑化处理,认为在t=0的微小邻域内函数仍满足微分方程,通过积分得到与待定系数数目相同的定解条件,从而获得本问题径向位移解析解.对Maxwell粘弹模型的求解证明了该法的可靠性.文中解适用于任意粘弹模型和孔径任意时变的情况.  相似文献   

7.
为了分析着陆冲击力对起落架摆振特性的影响,考虑支柱缓冲器的负油孔面积,在ADAMS中建立了某飞机起落架的虚拟样机模型,并对该模型进行了动力学分析,得到了起落架缓冲系统负油孔面积对轮胎与地面之间接触力的影响曲线、对前轮摆角的影响曲线、在不同垂直降落速度下摆幅的对比曲线,并结合摆振基本理论进行分析。结果表明:负油液阻尼孔面积减小或飞机触地垂直降落速度增大时,对应的着陆冲击力增大,使摆幅增大;当负油孔面积小于50.5mm2或飞机着陆时的垂直降落速度大于1773mm/s时,由于着陆冲击力过大,使摆振极不稳定。  相似文献   

8.
入水结构体在从空中弹道转入水下弹道的入水阶段,其周围的流体将呈现出强非线性性质,本文针对传统基于Wagner理论的结构体入水载荷计算模型不能很好描述流体三维流动的情况,基于无黏不可压流体流动模型,考虑流体弹性,采用微元边界运动等效方法对运动边界进行分段分析,计及入水过程中系统的动能损失,根据能量守恒,对刚性球体高速垂直自由入水过程中流体的三维流动进行了理论分析,建立了基于无黏不可压弹性流体的刚性球体垂直高速入水载荷计算模型,并与基于多介质任意拉格朗日欧拉方法的有限元模型进行了对比分析,验证了该方法的可行性。基于此模型,本文进一步分析了入水载荷的影响因素。该方法提供了一种计算结构体垂直高速入水载荷的思路,具有一定的理论意义和工程应用价值。  相似文献   

9.
磁流变液阻尼器的分数阶Bingham模型结构形式简单, 而且可以更好地描述系统的滞回特性. 建立了含有分数阶Bingham模型的单自由度1/4车辆悬架系统模型, 利用磁流变液阻尼器对在路面简谐激励下的非线性车辆悬架系统进行振动控制. 研究了含有分数阶Bingham模型的悬架系统在天棚阻尼半主动控制下的主共振响应, 利用平均法得到了系统的近似解析解. 求解了系统定常解的幅频响应方程, 并根据李雅普诺夫稳定性理论得到了悬架系统的稳定性条件. 通过绘制数值解和解析解的幅频响应曲线对比图, 验证了近似解析解的正确性. 利用簧载质量垂直方向的加速度均方根值分析了半主动控制对车辆乘坐舒适性的影响, 发现天棚阻尼半主动控制策略在低频激励区域反而会降低车辆的乘坐舒适性. 因此提出了一种被动控制与半主动控制相结合的组合控制策略, 并分析了半主动控制参数对振动控制效果的影响. 分析结果表明, 该组合控制策略不但能够提高车辆的乘坐舒适性, 而且能有效抑制悬架系统的主共振振动幅值.   相似文献   

10.
基于可变安全间距敏感驾驶模型对道路收费站系统进行了模拟研究. 与采用NS模型的 收费站系统进行了比较, 发现在慢化概率较大时(p=0.5), 该模型不仅使道路的通行能力 得到完全恢复, 还使其得到一定程度的提高; 当道路扩张区域长度L_{\rm B} \ge 7时, 通行能力得到很好的恢复; 当L_{\rm B}<7时, 随着L_{\rm B}的减少, 通行能 力也随之降低.  相似文献   

11.
Road surface roughness is the excitation source for the dynamic response of a moving vehicle system. Driving comfort is indicated by either the driver absorbed power level or the vehicle vertical acceleration level. An autocorrelation function model for road roughness is proposed to specify the road surface random characteristics. Subsequently, the power spectral densities (PSDs) for both road roughness and vehicle response, the driver-absorbed power level, are formulated. A road quality index (RQI) in accordance with such energy considerations is defined to catalog the road grade. The laboratory test results show the applicability of the RQI method for road classification using the ISO criteria as a comparison check.  相似文献   

12.
李韶华  冯桂珍  丁虎 《力学学报》2021,53(9):2554-2568
轮毂电机驱动电动汽车的簧下质量大, 使得轮胎动载荷增加, 且电机激励进一步加剧车轮振动. 同时, 轮胎与路面单点接触的简化模型, 其动力学计算结果与实际存在差别. 鉴于此, 考虑电机的电磁激励、胎路多点接触和非线性地基, 建立了电动汽车?路面系统机电耦合动力学模型, 通过Galerkin法推导了非线性地基梁的垂向振动, 利用积化和公式推导了非线性地基梁中非线性项积分的精确表达式, 提出了路面截断阶数选取的简易方法, 并通过路面位移响应的收敛性进行了验证. 在此基础上, 研究了胎路多点接触、非线性地基、电机激励、车速、路面不平顺幅值等对路面及车辆响应的影响. 结果表明, 非线性地基及多点接触对车辆响应的影响中, 轮胎动载荷的影响最大, 车身加速度和悬架动挠度的影响较小, 且考虑电机激励时, 二者对车辆响应的影响显著增大. 从对路面响应的影响看, 电机激励的影响最大, 非线性地基的影响次之, 多点接触的影响较小. 所建模型及研究方法可为电动汽车的垂向动力学分析提供一种新思路.   相似文献   

13.
The rolling of a wheeled vehicle is considered in the case when the turning angles of the front wheels about the vertical axis are small. The small relative slip is taken into account in the adopted model of contact between the wheels and the road surface. It is shown that, when the stiffness of the wheels tends to infinity, the system of equations of motion may become nonclassical and its form is specified by the no-slip conditions along the longitudinal direction of motion and by the primary Dirac constraints arising because of the degeneracy of the Lagrangian.  相似文献   

14.
In spite of an increasing number of rubber-tracked crawlers, the literature provides few guidelines and calculation models suitable for minimizing their internal motion resistance. This article presents a model where the internal resistance of double-flanged road wheels for rubber-tracked vehicles is calculated as a sum of the losses resulting from the indentation of the wheels into the track surface and friction of the wheels against the track guide lugs. The model allows for vertical and lateral load of the wheels, the non-uniform distribution of the wheel pressure on the track, and the relationship between the friction coefficient and normal reaction force in the interface between the wheel and track guide lugs. The model has been verified by experiments. According to the results of model computations and experiments discussed in the article, the internal losses of a given rubber-tracked undercarriage might be reduced if: the road wheels are covered with a material that exhibits low friction coefficient and mechanical hysteresis, the vehicle suspension system features oscillating bogie wheels, the undercarriage is fitted with the largest possible number of road wheels, and the vehicle weight is evenly distributed to all of the road wheels.  相似文献   

15.
Fatigue life of agricultural machinery is strongly affected by the surfaces that these machines operate on. In the present paper a sensor-frame was developed to acquire road and field profiles in absolute geo-referenced coordinates. The sensor-frame was validated by measuring discrete trapezoidal bumps with known dimensions resulting in a root mean squared (RMS) error of 6–8 mm. Profiles were acquired from a country road and from a mowed grass field. Using the quarter-car vehicle model, the movement of an agricultural vehicle was simulated for various speeds. The resulted vertical loads were rainflow-counted and the accumulated fatigue pseudo damage was calculated using Palmgren–Miner linear rule. Based on the derived Power Spectrum Density (PSD), the profiles were classified according to ISO 8608 standard. Two methodologies were followed to model and create a number of synthetic realisations for each profile: Direct Spectrum Estimate (DSE) and ISO based modelling. Simulating the produced synthetic profiles with the quarter-car vehicle model, the corresponding pseudo damage was calculated. The accumulated damages from the DSE models were closer to the corresponding ones from the measured profiles. ISO based models could not model the profile irregularities, which proved to contribute the largest part of the accumulated fatigue damage.  相似文献   

16.
The road damage assessment methodology in this paper utilizes an artificial neural network that reconstructs road surface profiles from measured vehicle accelerations. The paper numerically demonstrates the capabilities of such a methodology in the presence of noise, changing vehicle mass, changing vehicle speeds and road defects. In order to avoid crowding out understanding of the methodology, a simple linear pitch-plane model is employed. Initially, road profiles from known roughness classes were applied to a physical model to calculate vehicle responses. The calculated responses and road profiles were used to train an artificial neural network. In this way, the network renders corresponding road profiles on the availability of fresh data on model responses. The results show that the road profiles and associated defects can be reconstructed to within a 20% error at a minimum correlation value of 94%.  相似文献   

17.
针对车辆行驶在高速公路过程中,传统地图匹配算法存在大量冗余检索时间,且消除垂直误差后仍存在水平误差等问题,设计了一种基于初始定位信息的快速地图匹配算法。该算法首先利用初始定位点到候选路段的距离与夹角确定车辆所行驶道路,然后考虑道路网拓扑结构和连通性,将后续定位点直接投影到初始确定的道路上,减少检索道路的时间;同时为提高算法的精确度,在引用初始定位信息时,通过设置距离阈值剔除定位数据漂移点,并利用一元线性方程建立HP模型以消除水平误差。经理论计算和实际测试表明,该算法利用初始获得的7个连续定位点,能准确检索出车辆正在行驶的道路,节省36%的检索时间,借助HP模型可以减少定位点与车辆实际位置之间45%的投影误差。因此,与连续匹配算法和垂直投影方式相比,该算法具有检索过程简单、检索准确率高、误差消除大的优势。  相似文献   

18.
Design and mobility evaluation of tracked lunar vehicle   总被引:2,自引:0,他引:2  
Past lunar vehicles have had difficulty traveling through soft sand areas due to the thick, soft and dry regolith. This paper describes the design and evaluation results of a tracked lunar vehicle which aims at achieving greater mobility, particularly improved climbing ability on pure sand slopes, by reducing contact pressure with a crawler link. The tracked vehicle uses mesh crawler links to reduce complexity, weight and parts count. Single-crawler tests on simulated lunar soil revealed that the crawler’s slip ratio was lower than that of a rigid wheel at any slope angle, and that its power consumption was lower than that of a wheel on slopes of 10° or more. Furthermore, the crawler’s slip ratio was stable or decreasing along the traveling distance on steep slopes, contrary to the wheel. Our tracked lunar vehicle, the “Light Crawler”, is equipped with four such mesh-crawlers, each of which is independently driven and steered. It is intended to realize high climbing ability, a small turning circle, and an obstacle-crossing capability using a unique suspension system. The vehicle’s climbing and obstacle-crossing capabilities were tested on both simulated lunar soil and a rock-scattered field, and its mobility performance was successfully confirmed.  相似文献   

19.
The development of wheels for the Lunar Roving Vehicle   总被引:2,自引:0,他引:2  
The Lunar Roving Vehicle (LRV) was developed for NASA’s Apollo program so astronauts could cover a greater range on the lunar surface, carry more science instruments, and return more soil and rock samples than by foot. Because of the unique lunar environment, the creation of flexible wheels was the most challenging and time consuming aspect of the LRV development. Wheels developed for previous lunar systems were not sufficient for use with this manned vehicle; therefore, several new designs were created and tested. Based on criteria set by NASA, the choices were narrowed down to two: the wire mesh wheel developed by General Motors, and the hoop spring wheel developed by the Bendix Corporation. Each of these underwent intensive mechanical, material, and terramechanical analyses, and in the end, the wire mesh wheel was chosen for the LRV. Though the wire mesh wheel was determined to be the best choice for its particular application, it may be insufficient towards achieving the objectives of future lunar missions that could require higher tractive capability, increased weight capacity, or extended life. Therefore lessons learned from the original LRV wheel development and suggestions for future Moon wheel projects are offered.  相似文献   

20.
为了研究考虑随机车辆冲击效应的简支梁桥疲劳安全水平,提出了基于车-桥耦合振动与随机车流的桥梁疲劳应力谱模拟方法,并应用于疲劳可靠度评估。基于某高速公路桥梁动态称重数据建立随机车流模型,采用小样本车辆数据拟合桥梁等效疲劳应力范围的插值响应函数,最后由高斯混合模型拟合大样本随机车流作用于桥梁构件的疲劳应力谱。分析了25 m标准跨径简支T梁桥底部普通钢筋的疲劳应力谱,评估了考虑路面劣化与交通量增长的桥梁疲劳可靠度。数值分析结果表明,基于随机车流模拟的疲劳应力谱具有典型的多峰分布特征,包含了超载车辆产生的疲劳应力;车辆对桥梁的冲击效应致使等效疲劳应力放大系数略大于冲击系数,当路面等级为一般时,采用规范冲击系数将低估车辆冲击效应的疲劳损伤;路面劣化与交通量增长均会导致桥梁运营期内的疲劳可靠指标显著降低,由路面劣化导致车辆对简支梁桥的冲击效应不可忽略。  相似文献   

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