农林车辆安全驾驶室碰撞的数值模拟

农林用车辆安全驾驶室碰撞系统具有几何非线性和材料非线性等多重非线性特点,应用大变形弹塑性理论,建立驾驶安全系统数学模型,对安全驾驶室强度特性进行分析,预估车辆翻车时驾驶室结构件的力—变形,预测变形侵入驾驶员容身空间的安全性,并进行变形的屈服评判,实现车辆安全驾驶室结构碰撞的数值模拟。文中以某农林车辆安全驾驶室碰撞的数值模拟为例,理论计算和试验结果吻合,方法切实可行,为车辆驾驶室安全设计提供依据。     

基于人体测量学的拖拉机驾驶员工作空间设计

针对中国拖拉机驾驶员工作空间设计在操纵性、舒适性、方便性和安全性等方面存在的不足,该文从人机工程学角度出发,基于中国成年男性人体测量尺寸,计算出设计所需的28项人体主要尺寸的平均值、标准差和百分位数值,建立了拖拉机驾驶员人体关节生物力学模型,确定了模型中连接与人体测量尺寸的数值关系。以乘坐基准点为参考,对驾驶员工作空间内的座椅、踏板、转向盘、变速杆、液压操纵杆和仪表盘等进行了设计布置。选取了5个国产拖拉机样机T1、T2、T3、T4、T5,针对样机T1,以驾驶员工作空间各相应部件位置的设计理论值为依据,对其驾驶员工作空间布置进行了评价分析,结果表明:样机T1的座椅靠背宽度与夹角分别偏离理论值130 mm和15°;离合器踏板及制动踏板在水平方向上分别偏离理论值131和145 mm;转向盘在垂直方向上偏离理论值114 mm;仪表盘在水平、垂直方向及其与水平面夹角分别偏离理论值121 mm、199 mm和23.2°,与理论值偏差较大。同理,对其他样机进行了评价分析,结果表明:样机之间同类部件参数值差异较大,样机驾驶员工作空间尺寸与通过人体测量尺寸数据计算得出的设计理论值差异明显,样机驾驶员工作空间设计布置不合理。该文为评价驾驶室工作空间布置是否合理提供了一定的参考依据,同时为拖拉机驾驶员工作空间的优化设计奠定了理论基础。     

基于行驶车速的车辆防撞时间预警算法

针对一般车辆碰撞时间(time to collision,TTC)算法预警阈值固定造成车辆低速行驶中出现预警过早及高速行驶出现预警不及时的问题,该文提出一种基于行驶车速的车辆防撞时间预警方法。行驶车辆通过车载设备实时获取自车与他车的状态信息,根据车辆状态信息建立高斯平面坐标系获取车辆位置坐标,对车辆可能发生的碰撞进行分类处理,依据车辆行驶速度设定相应的安全防撞时间,然后将车辆发生碰撞需要的时间与安全防撞时间进行比较,存在碰撞危险则通过预警显示提醒驾驶员。试验结果表明:该方法预警准确率达88.89%,而一般TTC固定阈值方法则预警过早率达81.48%,预警过晚率达70.37%,故该方法对进行车辆危险预警更有效,更符合实际车辆防撞情形,提高了车辆行驶的安全性,可为车辆的及时预警提供参考。     

基于驾驶员生物力学特性的拖拉机座椅位置参数优化

座椅为拖拉机与驾驶员的主要接触部件，其参数设计与优化对提高驾驶舒适性具有重要意义。基于此，该研究采用生物力学软件AnyBody建立驾驶员-驾驶环境生物力学耦合模型，并以小、中、大体型驾驶员为研究对象，以拖拉机座椅靠背倾角、水平距离及垂直高度为参数，以竖脊肌、多裂肌、腹直肌及腹外斜肌激活程度为评价指标，分析研究座椅位置参数对驾驶员腰部肌肉生物力学特性的影响规律，确定座椅最佳位置参数；其次以课题组研制的多自由度驾驶平台为基础，按照上述参数调节座椅位置，测试计算不同体型驾驶员腰部四个主要活动肌群的激活程度，并将测试结果与仿真分析结果进行对比，发现二者具有较好一致性，通过调整座椅参数能有效提升驾驶员腰部舒适性。对小体型驾驶员，当座椅靠背倾角为9.7°，水平距离为472.1 mm，垂直高度为465.3 mm时，4个肌群总的激活程度最低，驾驶员腰部舒适性最高；对中体型驾驶员，座椅最适靠背倾角为13.9°，水平距离为495.6 mm，垂直高度为485.3 mm；对大体型驾驶员，座椅最适靠背倾角为14.8°，水平距离为526.4 mm，垂直高度为520.7 mm。本文研究成果可为农机装备座椅位置参数优化提供一种新思路。     

工程车辆翻车事故中司机头部伤害与保护仿真

为了研究司机的头部在碰撞中的机械响应特性,该文采用有限元三维实体建模技术,建立了成人头部碰撞模型。通过虚拟试验方法使用成人头部模型对驾驶室内饰进行冲击分析,比较不同厚度和密度的聚氨酯泡沫对人体头部损伤评价指标的影响。结果表明：头部损伤值（HIC(d)）随着泡沫厚度的增加而减小,随着密度的增大,呈现先减后增的二次抛物线趋势。在驾驶室内壁覆盖18 mm厚的聚氨酯泡沫材料可以降低翻车事故中二次碰撞对司机头部的损伤。     

基于Pro/E Manikin的拖拉机驾驶室人机工程评价方法

人机工程学设计是拖拉机驾驶室设计中非常重要的部分.该文以确定的H点为参考,运用人机工程学设计原则,对拖拉机驾驶室的驾驶员座椅和各操纵装置进行了布局和设计,并建立了驾驶室的 Pro/E 三维模型,运用Pro/E Manikin模块对驾驶员的坐姿舒适性、驾驶员视野性能、驾驶员的操作空间3个方面进行仿真和评价.结果表明,原设计方案中无法同时满足对各操纵装置的舒适性.对驾驶室优化布局和设计,首先,H点位置在X方向的坐标位置为550和581 mm时,分别调用第5百分位和第95百分位的中国男性人体模型进行分析,各操纵装置在操纵舒适性的RULA分析分数为1时,方向盘、变速杆、侧控台和前控台距踵点水平距离范围分别为290~352、366~437、375~420和128~213 mm.其次,通过Pro/E Manikin中到达包络的阴影区域检查操作空间是否符合要求.最后,在进行驾驶室设计过程中,将消音器和空气滤清器的位置设计在前立柱对驾驶员形成的盲区范围内,将水平面前方2个不可避免的盲区(12.81°和14.36°)叠加,最大程度的减小了驾驶员的盲区.优化设计后的驾驶舒适性、视野性能及易操作性在一定程度上都得到了改善.该方法为拖拉机驾驶室人机工程学设计提供了一定的参考.     

基于生物力学模型的拖拉机离合踏板人机工程设计

针对拖拉机离合踏板人机工程设计不足导致驾驶员容易产生疲劳的问题,该文搭建了驾驶员-离合踏板人机交互特性测试系统,基于试验结果分析了拖拉机驾驶员-离合踏板人机交互特性。在Any Body生物力学软件中建立了拖拉机驾驶员-踏板生物力学模型,并采用表面肌电测试结果验证了仿真模型的合理性。提出下肢关节出力程度为舒适性主观感受评价指标,基于仿真结果定量研究了离合踏板阻力和踏板布局对驾驶员踏板操纵舒适性影响规律和驾驶员人体尺寸对踏板布局的影响,给出不同人体百分位尺寸前提下踏板布局极限尺寸的推荐范围。通过优化踏板连杆长度、连杆夹角以及踏板-座椅布局降低踏板阻力,驾驶员下肢受力最大值从154 N降低到120 N,降低了22%,驾驶员下肢关节出力程度降低了20.98%,本文提出的研究方法及其研究结果可为拖拉机踏板人机工程设计提供参考。     

Mckibben型气动人工肌肉缓冲座椅减振特性分析

Mckibben型气动人工肌肉作为一种新型仿生气动执行元件,其力学特性与生物肌肉相似。以Mckibben型气动人工肌肉为履带式工程车辆座椅的缓冲执行器,建立起座椅缓冲减振模型;运用Simulink软件,并采用模糊PID控制对座椅的减振特性进行仿真。结果表明,在选定的4种工况下,Mckibben型气动肌肉缓冲座椅较传统座椅的垂直加速度和位移均有效减小,其缓冲减振效果明显。研究结果可为气动人工肌肉型缓冲座椅的研发提供参考。     

割草机连续翻滚中翻滚保护装置的有限元分析

针对割草机在斜坡上工作时引起的连续翻滚工况,利用有限元非线性分析法建立了ROPS 有限元模型, 对ROPS进行强度分析,预测了车辆连续翻滚时ROPS构件的应力、变形及吸能,并预测了变形后的ROPS是否侵入驾驶员容身空间（Clearance Zone）。最后进行了翻滚试验验证有限元模型的准确性,结果表明：ROPS的有限元分析与试验结果吻合,翻滚过程中,ROPS 未进入驾驶员容身空间,有限元分析为车辆ROPS安全设计提供了可靠依据。     

政和县乐溪流域梯级电站建设项目水土流失及其防治

梯级水电站在建设过程中如不采取有效的水土流失防治措施,势必造成严重的水土流失。本文通过计算预测政和县乐溪流域梯级电站建设过程中造成的水土流失量,分析了可能造成的水土流失危害,提出了切实可行的防治措施。     

Initial rollover effectiveness evaluation of an alternative seat belt design for agricultural tractors

A test program was conducted to determine the effectiveness of a seat belt restraint in preventing occupant movement in a rollover accident. A baseline type-2 seat belt (pelvic and torso restraint), and an improved type-2 seat belt restraint, both designed to restrict occupant motion in a rollover accident, were tested in a rollover restraints tester (RRT). Each seat belt was placed on a H-III 50th percentile male dummy and testing conducted at a single roll rate and two D-ring adjustment positions. Each test simulated what was approximately a 260 degrees per second rollover parallel to the longitudinal axis of the tractor with the top of the ROPS impacting the ground after 180 degrees of roll. Forces on the dummy's head and neck were measured, and video was taken to measure the head motion in the x-, y-, and z-axis of the dummy. The average vertical, forward, and lateral head movement in the baseline seat belt was 144, 222, and 184 mm, respectively, when the adjustable D-ring anchorage supporting the shoulder belt was in its lowest position. At the lowest D-ring height, the shoulder belt became ineffective and the seat belt performance became similar to a type-1 restraint (required for tractors with ROPS) resulting in increased vertical, forward, and lateral movement. The improved restraint reduced vertical head movement by as much as 75% without increasing head and neck loads above established injury criteria. Testing seat belts for rollover effectiveness will become increasingly important as seat belt usage on tractors with ROPS increases.     

Evaluating the protective capacity of two-post ROPS for a seat-belted occupant during a farm tractor overturn

This study evaluated the effectiveness of a commercial rollover protective structure (ROPS) and size-extended ROPS in protecting a 95th percentile male operator during tractor overturns. Six rear upset tests (commercial ROPS) and ten side upset tests (commercial and size-extended ROPS) were conducted. A 95th percentile instrumented male manikin was used in all tests. Head injury criterion (HIC15), 80 g limit on resultant head acceleration, neck injury criterion (Nij), and peak axial force (extension-compression) were employed to evaluate injury potential. In all rear tests, the manikin's head impact with the ground was within the tolerance limits for head/neck injuries. Based on limited trials in the side tests, the study observed a small to moderate chance of neck injuries under the commercial and size-extended ROPS conditions; the injury risk was not statistically significant between these two test conditions. This study identified a risk of non-fatal injuries for large-size operators in side overturns, although the prevention effectiveness of commercial versus size-extended ROPS cannot be determined without further testing. These findings may have implications for future ROPS designs.     

拖拉机安全驾驶室强度非线性有限元分析

为了避免由于拖拉机翻车事故引起的人员伤亡,提高拖拉机工作时的安全性,设计安全可靠的大中马力拖拉机驾驶室,并且使之能通过OECD标准,以某型号拖拉机驾驶室为研究对象,建立了该安全驾驶室的精确三维模型,并采用非线性有限元方法,按照OECD标准规定的要求,对模型进行了加载分析。驾驶室被简化成梁和板单元,采用弹簧单元模拟驾驶室与机身前支架之间的橡胶减震垫。计算结果表明：拖拉机驾驶室在按照试验要求模拟加载完成后,驾驶室变形吸收能量达到OECD标准规定的要求时,驾驶室部分粱和底板的应力已经达到屈服应力,进入了塑性变形,但变形后的驾驶室没有侵入安全容身区。后推、后压、侧推、前压和前推试验中驾驶室的最大变形分别为111、4、168、19和 47 mm,变形最大发生在力的作用位置处。该方法为设计能通过OECD标准试验的拖拉机安全驾驶室提供了一定的参考依据。     

拖拉机驾驶室模型的声学灵敏度分析

车身的声学灵敏度是指施加于车身的单位力在车内产生的声压,是衡量车辆NVH特性的一种很有效的指标。该文以一拖拉机驾驶室模型为研究对象,建立了其声振耦合的有限元分析模型,计算了该驾驶室模型的声学模态和声振耦合模态。并根据声振耦合特性和声学灵敏度分析方法,计算分析了在悬架接触点处施加振动激励引起的驾驶员耳旁的噪声灵敏度。     

振动压路机用于不同土壤地面的平顺性评价

实际工况中振动压路机车轮会在各种土壤地面上作业和行驶,为了评价振动式压路机在不同土壤路面上的行驶平顺性,该文针对车轮―不同土壤地面的接触分析,建立了某单钢轮振动压路机非线性动力学模型;描述了振动轮在弹塑性土壤下压实对前车架产生垂直激励力.基于Adam D和Kopf F的弹塑性土壤模型,建立了振动轮在作业时的三自由度振动模型;采用软性土壤地面的Bekker假设,建立了轮胎―变形土壤地面接触模型.对建立的非线性动力学模型进行了仿真,并根据ISO2631-1:1997(E)标准分析与评价了不同路况、工况和速度对驾驶员乘坐舒适性的影响.结果表明,刚性路面不平度等级对振动压路机行驶平顺性有较大影响,路面等级越差,驾驶员的主观感觉越不舒适;路面的变形对驾驶室水平晃动有较大影响,土壤路面越软,驾驶室晃动越大;弹塑性土壤对振动压路机的影响表现在低频工况压实时,车辆平顺性比较差.该研究可为振动式压路机的平顺性设计提供参考.     

Three-dimensional computer-aided human factors engineering analysis of a grafting robot

The objective of this research was to conduct a human factors engineering analysis of a grafting robot design using computer-aided 3D simulation technology. A prototype tubing-type grafting robot for fruits and vegetables was the subject of a series of case studies. To facilitate the incorporation of human models into the operating environment of the grafting robot, I-DEAS graphic software was applied to establish individual models of the grafting robot in line with Jack ergonomic analysis. Six human models (95th percentile, 50th percentile, and 5th percentile by height for both males and females) were employed to simulate the operating conditions and working postures in a real operating environment. The lower back and upper limb stresses of the operators were analyzed using the lower back analysis (LBA) and rapid upper limb assessment (RULA) functions in Jack. The experimental results showed that if a leg space is introduced under the robot, the operator can sit closer to the robot, which reduces the operator's level of lower back and upper limbs stress. The proper environmental layout for Taiwanese operators for minimum levels of lower back and upper limb stress are to set the grafting operation at 23.2 cm away from the operator at a height of 85 cm and with 45 cm between the rootstock and scion units.     

Determinants of high pesticide exposure events in the agricultural health cohort study from enrollment (1993-1997) through phase II (1999-2003)

We conducted an analysis of the determinants of high pesticide exposure events (HPEEs), which are defined as self-reported incidents of high exposure to pesticides, fertilizers, or other chemicals in the Agricultural Health Study, a cohort of private applicators and their spouses residing in North Carolina or Iowa, and commercial applicators residing in Iowa. We examined the risk of HPEEs occurring between enrollment (phase 1: 1993-1997) and follow-up (phase II: 1999-2003) among participants who completed the phase II questionnaire (n=43,149) by calculating hazard rate ratios and 95% confidence intervals using Cox proportional-hazard regression. During the followup period, 1,582 HPEEs were reported (3.8%). HPEE risk was significantly higher among Iowa residents, younger participants, those with a hearing deficit, a risk-taking personality, and an HPEE prior to enrollment. Among private applicators (n=30,102), larger farm size, higher frequency and duration of pesticide use, spraying pesticides with open cab windows, using a tractor cab without a charcoal filter, repairing spray equipment, wearing work clothing more than two days without changing, not removing work boots before entering the home, and storing pesticides in the home were associated with significantly higher HPEE risk. Among commercial applicators (n=2326), higher frequency of pesticide use was associated with a significantly higher HPEE risk. Among spouses (n=10,721), higher frequency of pesticide use, using an application vehicle with a cab, and storing pesticides in the home were associated with a significantly higher HPEE risk. Our findings indicate that HPEEs were associated with several modifiable pesticide handling procedures that can be targeted in safety training and education.