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YC1040载货汽车底盘总体及制动器设计,YC1040,载货,汽车底盘,总体,制动器,设计
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（2007届）本科生毕业设计（论文）资料学 院、系： 机械工程学院 专 业： 机械设计制造及其自动化 学 生 姓 名： 刘 梦 华 班 级： 机本0302 学号 26030213 指导教师姓名： 黄开有 职称 副教授 最终评定成绩： 湖南工业大学教务处 二六年九月制目 录第一部分 过程管理资料一、毕业设计（论文）课题任务书3二、本科毕业设计（论文）开题报告5三、本科毕业设计（论文）进展情况记录9四、本科毕业设计（论文）中期报告11五、毕业设计（论文）指导教师评阅表12六、毕业设计（论文）评阅教师评阅表13七、毕业设计（论文）答辩及最终成绩评定表14第二部分 设计说明书八、设计说明书15- 17 -2007届本科生毕业设计（论文）资料第一部分 过程管理资料 2007届毕业设计（论文）课题任务书院(系)：机械工程学院 专业：机械设计制造及其自动化 指导教师黄开有学生姓名刘梦华课题名称YC1040载货汽车底盘总体及制动器设计内容及任务一设计内容：YC1040载货汽车主要是面向农村市场开发的，依据农民的经济能力和农村的交通的状况，提供一个合理的底盘及制动器的设计方案。1、分析与计算；2、总体结构设计；3、零部件的结构设计与计算。二设计任务：1、YC1040载货汽车的型式、主要尺寸和参数、发动机选择；2、车架、制动器的结构型式和主要尺寸的确定；3、总体设计的分析与各部件的布置、制动器的设计分析；4、用AUTOCAD编制二维工程图。拟达到的要求或技术指标一总体设计要求：1、工作可靠，结构简单，装卸方便，便于维修、调整；2、尽量使用通用件，以便降低制造成本；3、在保证功能和强度的要求下，尽量减少整备质量。二说明书及图纸要求：1、设计说明书1份，达1.5万字以上，且要符合规范要求：资料数据充分，标明数据出处；计算过程详细、完全；公式的字母含义应标明，有时还应标注公式的出处；内容条理清楚，按步骤书写；2、设计图样全部用AutoCAD绘制，总的绘图量达3张A0以上，其中：至少装配图1张。进度安排起止日期工作内容07年13周中铁五新钢模有限责任公司实习第4周搜集设计相关资料，整体规划设计全过程，方案论证第56周汽车总体设计：汽车形式、尺寸参数和质量参数的确定第78周制动器设计：结构方案分析，制动器主要参数确定第911周绘制CAD二维工程图第1213周编写设计说明书第14周通过指导老师验收主要参考资料1 成大先机械设计手册（1-4册）M.北京：化学工业出版社，19932 刘惟信.汽车设计M.北京：清华大学出版社，2001.3 张君媛汽车总布置参数化设计J.汽车技术，1997，(10):19-22.4 彭昆等基于UG平台的汽车总体设计专家系统的开发J.上海汽车，1999， (11)：3-5.5 张健等.基于UG的客车底盘三维参数化总布置设计系统J.汽车技术，2001，(6)：22-266 周天佑汽车列车选型与设计M交通部公路科学研究所情报资料室，19917 GB 1589-2004，道路车辆外廓尺寸、轴荷及质量限值S教研室意见签名：年 月 日院(系)主管领导意见签名：年 月 日湖 南 工 业 大 学本科毕业设计（论文）开题报告 （2007届）学 院、系： 机械工程学院 专 业： 机械设计制造及其自动化 学 生 姓 名： 刘 梦 华 班 级：机本0302 学号 26030213 指导教师姓名： 黄开有 职称 副教授 2007年4月5日题目：低速载货汽车底盘总体及制动器设计1.结合课题任务情况，查阅文献资料，撰写15002000字左右的文献综述。YC1040载货汽车主要是面向农村市场开发的，可以在近期或未来作为农村的主要货运工具附带作为载人工具。本课题来源于生产实践和对农村实际状况的考察。依据农民的经济能力和农村交通的状况，提供一个合理的设计方案。汽车的总体设计是汽车设计工作中最重要的一环，他对汽车的设计质量、使用性能和在市场上的竞争力有着决定性的影响. 按照目前的汽车行业状况，参考过现今市场上成熟的一些货车，我们设计载重量为1.5t的低速货车，并且力争达到以下的设计效果：1. 工作可靠，结构简单，装卸方便，便于维修、调整2. 尽量使用通用件，以便降低制造成本3. 在保证功能和强度的要求下，尽量减小整备质量。底盘的总体设计是在参考其他相似车型和相关规定的基础上，确定YC1040载货汽车的型式,包含汽车轴数的选择，驱动形式分析，布置形式的分析；主要尺寸和参数的选择,有外廓尺寸、轴距、轮距、前悬、后悬、货车的车头长度、车厢长度等；汽车质量参数的确定,包括整车整备质量、装载质量、质量系数、汽车总质量、轴荷分配等；发动机选择依照需要的功率和相关国家排放标准选用了YD480。汽车制动系是用以强制行驶中的汽车减速或停车、使下坡行驶的汽车的车速保持稳定以及使已停驶的汽车在原地（包括在斜坡上）驻留不动的机构。随着汽车速度的提高及车流密度的日益增大，为了保证行车安全，汽车制动工作的可靠性显得日益重要。根据这次设计的需要和制动器在货车上的应用状况，选择摩擦式制动器中的领从蹄式作为制动装置。制动器设计的主要工作有:制动器的结构方案分析，对比各种形式结构的优缺点后，选用了领从蹄式的方案；制动器主要参数的确定,先参考相关专业标准确定制动鼓内径，然后根据制动鼓内径就可以定下摩擦衬片宽度和包角、摩擦衬片起始角、制动器中心到张开力F作用线的距离、制动蹄支承点位置坐标。最后还需要关于制动器的设计计算。近年来在国家宏观经济形势持续良好的情况下,我国机械行业迅速发展汽车工业开始进入了快速发展时期,其增长速度大大高于GDP的增长幅度,汽车产业成为拉动工业增长的重要动力之一。随着政府对农民收入在政策上的支持，农民的收入得到很大改善。同时国家也加强了农村道路的建设力度，在未来的几年内农村的交通状况将会的到比较大的改观。相信这种有针对性的低速货车会受到农民朋友的青睐。2.选题依据、主要研究内容、研究思路及方案。通过对农村道路发展情况和市场的分析，结合农村生产实际，YC1040载货汽车在农村具有相当的需求，而目前市场上的具有针对性的产品并不多，因此，设计YC1040载货汽车具有广阔的市场前景。课题的重点是底盘的总体设计，根据其载重情况，确定了总体结构布置，确定总体的设计参数以及确定制动器的主要尺寸，可以根据载重状况选用轮胎，依据轮辋的直径来决定制动鼓内径，然后其他尺寸就可以相应的通过对应关系和计算得出并进行受力计算。课题的难点是压力沿长度方向的分布规律以及蹄片上的制动力矩的计算。除了摩擦衬片因有弹性容易变形外，制动鼓、蹄片和支承也有变形，所以在计算法向压力在摩擦衬片上的分布规律比较困难。通常只考虑衬片径向变形的影响，其他零件的变形较小而忽略不计。首先对YC1040货车的总体进行设计，在对汽车的形式选择以后，确定主要尺寸参数和质量参数。接下来做制动器的设计，结构方案分析后，确定制动器的主要参数，然后进行制动器的设计计算。3.工作进度及具体安排。3月5日3月25日毕业实习阶段。毕业实习，中铁五新钢模有限责任公司实践，撰写实习报告。3月26日4月5日 设计(论文)开题阶段。提出总体设计方案及草图，填写开题报告。4月6日5月16日 设计(论文)初稿阶段。完成总体设计图、部件图、零件图。5月16日5月26日 中期检查阶段中期检查，编写毕业设计说明书。5月26日6月2日 毕业设计定稿阶段。 图纸修改、设计说明书修改、定稿，材料复查。6月2日6月6日毕业答辩。4.指导教师意见。指导教师： 年 月 日说明：开题报告作为毕业设计（论文）答辩委员会对学生答辩资格审查的依据材料之一，此报告应在导师指导下，由学生填写，将作为毕业设计（论文）成绩考查的重要依据，经导师审查后签署意见生效。 本科毕业设计（论文）进展情况记录毕业设计（论文）题目： YC1040载货汽车底盘总体及制动器的设计班级： 机本0302 学号： 26030213 学生： 刘梦华 指导教师： 黄开有 时 间任务完成情况指导教师意见第 3 周至第 4 周搜集设计相关资料，整体规划设计全过程，方案论证指导教师签名： 年 月 日第 5 周至第 6 周汽车总体设计：汽车结构型式、尺寸参数和质量参数的确定指导教师签名： 年 月 日第 7 周至第 8 周制动器设计：结构方案分析，制动器主要参数确定指导教师签名： 年 月 日 注：教师监督学生如实记录毕业设计（论文）过程中根据课题任务书拟定的进度与进展情况以及毕业设计（论文）撰写过程中遇到的问题和困难，并签署意见。第 9 周至第 11 周绘制CAD二维工程图指导教师签名： 年 月 日第 12 周至第 13 周编写设计说明书指导教师签名： 年 月 日第 13 周至第 14 周图纸修改、设计说明书修改、定稿，材料复查。指导教师签名： 年 月 日注：教师监督学生如实记录毕业设计（论文）过程中根据课题任务书拟定的进度与进展情况以及毕业设计（论文）撰写过程中遇到的问题和困难，并签署意见。本科毕业设计（论文）中期报告 填表日期：2007年5月 16日院（系）机械工程学院班级机本0302学生姓名刘梦华课题名称：YC1040载货汽车底盘总体及制动器设计课题主要任务：YC1040载货汽车的型式、主要尺寸和参数、发动机选择；车架、制动器的结构型式和主要尺寸的确定；总体设计的分析与各部件的布置、制动器的设计分析；用AUTOCAD编制二维工程图。1、 简述开题以来所做的具体工作和取得的进展或成果开题以来做了大量相关的工作，首先对农村道路发展情况和市场进行了认真的分析思考，结合农村生产实际，YC1040载货汽车在农村具有相当的需求，设计YC1040载货汽车具有广阔的市场前景。然后参观见习了多家汽车制造工厂，包括北汽福田长沙汽车制造厂，对汽车制造的工艺流程有了一定的了解!然后我查阅了大量的相关的资料及汽车设计手册，开始对汽车的总体进行设计，形式的选择，主要尺寸参数和质量参数的确定。接下来做制动器的设计，结构方案分析，确定制动器的主要参数，然后进行制动器的设计计算。完成设计(论文)初稿。完成总体设计图、部件图、零件图。2、 下一步的主要研究任务，具体设想与安排对前期工作进行认真细致的总结，积极与黄教授展开研讨，再次对总体方案进行论证和验算，使其得到完善，优化！认真规范的编写设计说明书，对初图进行修改，规范标准！总之，力争达到如下的设计效果：工作可靠，结构简单，装卸方便，便于维修、调整；尽量使用通用件，以便降低制造成本；在保证功能和强度的要求下，尽量减少整备质量。3、 存在的具体问题主要问题是设计主要源自于理论，有关底盘和制动器的结构了解不是很清楚，所以对设计带来了不少的麻烦！另外课题的难点是压力沿长度方向的分布规律以及蹄片上的制动力矩的计算。除了摩擦衬片因有弹性容易变形外，制动鼓、蹄片和支承也有变形，所以在计算法向压力在摩擦衬片上的分布规律比较困难。所以通常只考虑衬片径向变形的影响，其他零件的变形较小而忽略不计。4、指导教师对该生前期研究工作的评价指导教师签名：日 期： 毕业设计（论文）指导教师评阅表院（系）：机械工程学院 学生姓名刘梦华学 号26030213班 级机本0302专 业机械设计制造及其自动化指导教师姓 名黄开有课题名称YC1040载货汽车底盘总体及制动器设计评语：（包括以下方面，学习态度、工作量完成情况；检索和利用文献能力、计算机应用能力；学术水平或设计水平、综合运用知识能力和创新能力；）是否同意参加答辩：是 否指导教师评定成绩分值：指导教师签字： 年 月 日毕业设计（论文）评阅教师评阅表院、系：机械工程学院 学生姓名刘梦华学 号26030213班 级机本0302专 业机械设计制造及其自动化课题名称YC1040载货汽车底盘总体及制动器设计评语：（对论文学术评语，包括选题意义；文献利用能力；所用资料可靠性；创新成果及写作规范化和逻辑性）针对课题内容给设计者（作者）提出3个问题，作为答辩时参考。1.2.3.评 分：是否同意参加答辩是 否评阅人签名： 年 月 日 毕业设计（论文）答辩及最终成绩评定表院、系（公章）： 学生姓名刘梦华学号26030213班级机本0302答辩日期课题名称YC1040载货汽车底盘总体及制动器设计指导教师黄开有成 绩 评 定分值评 定教师1教师2教师3教师4教师5小计课题介绍思路清晰，语言表达准确，概念清楚，论点正确，实验方法科学，分析归纳合理，结论严谨，设计（论文）有应用价值。30答辩表现思维敏捷,回答问题有理论根据，基本概念清楚，主要问题回答准确大、深入,知识面宽。70合 计100答 辩 评 分分值：答辩小组长签名：答辩成绩a： 指导教师评分分值：指导教师评定成绩b： 评阅教师评分分值：评阅教师评定成绩c： 最终评定成绩： 分数： 等级：答辩委员会主任签名： 年 月 日说明：最终评定成绩a+b+c，三个成绩的百分比由各院、系自己确定。2007届本科生毕业设计（论文）资料第二部分 设计说明书 实习报告一、实习的主要内容我于大四第二学期在湖南中铁五新钢模有限公司进行了半个月天的生产实践活动，在活动期间我对中铁五新有了一些了解, 中铁五新钢模有限公司位于湖南省长沙市星沙大道，毗邻三一重工集团，始建于1986年，是国内大型钢模板联合企业和线材、金属制品重要生产企业之一。占地面积约100平方公顷，地理位置优越。在册职工1000人。经过20多年的建设，特别是改革开放以来加快发展，中铁五新已形成年产钢500万吨的综合生产能力。是中部地区高速公路、铁路、桥梁建设公司重要合作伙伴企业之一。中铁五新拥有生产各种钢模板、平面钢模、异型钢模、高速铁路内外箱梁模板、轧材等一整套工艺装备。其中，进口高速线材轧机达到国际先进水平。近五年来，中铁五新围绕产品结构调整进行淘汰平炉、一火成材、全连铸等一系列技术改造，极大地优化了工艺结构，一批主要技术装备达到国内先进水平。隆隆的机器声中，我漫步在一幢幢巨大的车间厂房之间，穿梭在一根根管道之下，领略真正的创造的伟大。那边铁水顺着下面的出钢口流下，飞溅出灿烂的火花，红红的铁水经过了一段传运变黑变硬一根根钢材便由此而成了。一想到我们身边的生活中处处都是钢铁的身影，就马上感到了这创造的伟大了。农业保证了我们的吃饭温饱问题，科教文卫事业为我们提供了后方的支援，还有各种服务行业使生活更加舒适，而真正能带来国家的繁荣和发展的，能使我国早日成为世界强国的，就是我们的工业。看到中铁五新秩序井然，繁荣炼钢的情景我就为我们祖国的未来充满了希望。我所学的专业是机械设计制造及自动化，这里就是我将来奉献青春的火热田野，我现在提前置身于这钢筋水泥的围墙之中，心情是无比的激动。我能有机会熟悉这里的环境，了解生产的工艺流程，实在是难得的很。我能亲眼看到机械自动化为我们省下的力气，为我们创造的价值。在近几十年里，我国的工业的飞跃发展起来，我国的国际地位由此一步步提升上去了。现在我感到我的所学是多么的重要，大学的课程一定要学好，打好坚实的基础，才能符合21世纪工业自动化大生产下的工作的要求。这次实践活动令我对本专业有了更高的热情，使我的将来有了比较明确的方向。在有限的实习期间，我了解了整个企业的大体情况，正式接触了新时期的各种各样的工人，不同却高效的办事方法，也受到企业氛围的熏陶。我感到受益匪浅。二、实习取得的经验及收获在实习期间，我学到了许多书本和课堂上不曾学到的东西，收获很多，具体来说有以下两个方面：首先，我熟悉了中铁五新的工艺流程。工人们把石灰石和铁矿石运到烧结厂进行初步的加工，连同在炼焦厂加工的煤一起送进巨大的高炉里进行煅烧，形成了铁水灌进鱼雷铁水罐车送往转炉，在氧气顶吹之下，进行更高温度的煅烧，使得铁中的含碳量进一步降低，并调节铁水里的其他金属元素的含量达到钢的要求。钢水出炉之后，有两条途径可走。（1）经过冷却使之变硬，在连铸车间把它们铸成板坯，方坯和矩形坯。这些钢坯还不能称为钢材，它们还需要进行轧制以符合各种再生产部门的需求。经过轧制生产出的棒材，线材，角钢等便是最后的产品了。（2）钢水还须经过一座LF炉进行深加工，此时的钢铁的质量更加优异。这些钢材经过薄板坯连铸连轧后还要经过一个大的酸洗池进行酸洗处理，以便使之镀锌。这样就生产出热轧钢板，冷轧钢板，镀锌钢板，酸洗钢板，预涂层钢板等产品。这些生产过程都是在精密的仪器的控制和监测下进行的。温度的高低，煅烧的程度都需要自动或者半自动的仪器的控制。在现代化的生产条件下既保证了质又保证了量，生产出符合建设使用的大批量优等的钢材和钢模板。在产品的生产、销售、安装、调试的一系列跟踪服务中，中铁五新钢模有限责任公司进行周密、合理的安排，为产品的上市和被客户接受提供了良好的安排，为合理安排生产，公司在广西玉林、湖南长沙、怀化，以及贵州清镇等地建立了配套的分公司，实现了加快产品的上市和提高生产效率，降低运输成本。同时，也各个子公司的分工合作达到了一定的水平，加强了彼此间的技术交流和团结进步，使技术在得到逐渐的提升，公司的业务在不断的扩展。产品的合格率也在逐步得到提高，深受路桥公司和中铁各局的欢迎，产品的销路一天天在壮大；随着公司的扩大，其技术的引进显得尤为重要，2005年，中铁五新钢模有限责任公司与华中建设机械公司和新加坡亚华公司合作开发了先进的移梁车模板和隧道台车自动化技术，为国内先进技术之一。其次，我对中铁五新钢模的人员状况有了概括的了解。中铁五新钢模有限责任公司始终坚持全心全意依靠职工办企业的方针和“以人为本”的员工管理思想，并将其贯穿于生产经营和模拟市场核算机制的全过程，培养和造就一支高素质的员工队伍是公司员工管理的最终目标。近些年来，中铁五新十分重视技术创新和管理创新以及人才的引进、培养和使用，并注重人力资源的开发和合理配置。在公司内部建立了人才市场和劳动力市场，内部人员流动均通过市场的形式实现，为各类人才提供了学习提高的机会和施展才华的广阔舞台。三、存在的不足及建议通过这半个月的实习，我发现自己在很多方面存在缺点和不足之处，主要表现为：知识面有限，所学理论知识还不能很好的应用到实践中去；对所学的知识不能灵活运用到生产实践中来；对机械行业的先进制造技术还了解得不够。诸如自己的上述感受，我认为我们应该在扎实学好专业知识的同时，多锻炼自己的动手能力，多抓住机会参与生产实习，做到理论联系实践。为以后的工作和生活奠定良好的基础，使自己逐步具备一个工程技术的素质。 刘 梦 华 2007年3月20日 Handling Studies of Driver-Vehicle Systems M. Lin, A. A. Popov and S. McWilliam School of Mechanical, Materials, Manufacturing Engineering and Management, University of Nottingham, University Park, Nottingham NG7 2RD, U.K. Email: eaxmlnottingham.ac.uk The driver-vehicle system approach provides a firm basis for analysing vehicle and driver dynamics in vehicle handling design. The paper aims to provide an analysis of drivers steering and speed control during driver-vehicle interaction. Generic mathematical models of vehicle and driver are implemented, and the handling characteristics in typical manoeuvres are studied through numerical simulations. As information technology and electronic systems are widely introduced for vehicle chassis control nowadays, new human factor problems have been posed in the simulation for vehicle handling studies. The proposed models here provide tools for exploring the effects of active chassis intervention systems on the driver-vehicle. Keywords / driver-vehicle systems, vehicle dynamics, driver behaviour, chassis enhancement systems 1. INTRODUCTION Recently, as virtual prototyping has been increasingly applied in vehicle development, vehicle handling design in a virtual environment has also been widely used in both academic research and the manufacturing area. For vehicle handling simulations, vehicle dynamics simulation models (VDSMs) are necessities for the developers. Since 1960s 35611, VDSMs have been developed for a variety of applications, including dynamic analysis, interactive driving simulation, and vehicle testing. The model complexity and solution procedures are defined according to a given application. It can be seen that the vehicle and driver form a closely coupled man-machine system. The interaction between the dynamics of the vehicle and the driver behaviour plays a paramount role throughout the whole process of the simulation. At the same time, due to the desire for personal mobility, automotive chassis enhancement systems are introduced into vehicles. They are targeting on providing safety, stability and comfort, and minimising the environmental impacts. However, it is argued that in some cases these chassis enhancement systems can cause more harm than good. In 9, Sharp pointed out that the assessment of driver-vehicle dynamics qualities in the context of electronic enhanced vehicles contains many separate quality issues and many design conflicts. This involves driver-vehicle speed control and its relationship with directional/steering control, which has only recently received attention. A detailed review on automotive chassis enhancement systems in heavy vehicles, provided by Palkovics and Fries 8, includes systems such as anti-lock braking system (ABS), traction control system (TCS), rear axle steering system and dynamic stability control system. It is suggested that the driver is kept in the control loop as drivers intention is necessary to activate the systems. By making a vehicle easier to control, drivers may be encouraged to drive closer to the vehicle limits, therefore affecting the intended safety benefits. In the following sections, a basic 4-DOF (longitudinal, lateral, yaw, roll) vehicle model and a driver control model are presented. The driver model is directionally structured to control vehicle heading/yaw angle and lateral position, and longitudinally perceiving the longitudinal acceleration error. In Section 4, driver-vehicle interaction is reviewed. The simulation is then employed in Section 5 to analyse manoeuvres involving double lane change and braking in turn. 2. VEHICLE MODEL The vehicle is represented by a four degrees of freedom model 4, for the longitudinal, lateral, yaw and roll motion. As shown in Fig. 1, although the suspensions are not included in the modelling, the model uses a simplified description of body roll assuming a fixed roll axis defined by the heights of the roll centres of the front and rear axles of the vehicle. Vehicle model parameters are reported in the Appendix. The equations of motion using axes fixed to the vehicle body are given by, sincos)(yfFxfFxrFrvum+=+? sincos)(xfFyfFyrFruvm+=+? )sincos(sin)sincos(yfFxfFxrFhyrFbxfFyfFapxzIrzI+=?)sincos(cos)(sin)()(xfyfyrzrzfrfrfxzxFFFhFFhpcckkrIpI+=+? (1) mgzyC.G.hrfruVvLC.G.C.G.abFzrFyrFxfFxrFzfFxrFxfFyf,rhgxzyxFzf,rFyfroll axis Fig.1 Vehicle Model where Fxf, Fxr, Fyf, Fyr, and Fzf, Fzr are vehicle axle longitudinal, lateral and vertical forces, respectively. r is the yaw rate and p and are the roll rate and roll angle. The sideslip angles and static camber angles of the front and rear wheels f, rand f, r can be defined in terms of vehicle motion variables, rrffrhuhprbvarhuhprava?+=?+=sincostansincostan (2) rrff= (3) When the vehicle is running at constant speed, the longitudinal motion can be uncoupled from the equations of motion. The dynamics of the non-linear vehicle model includes the influence of the non-linear tyre characteristics, which are modelled by the magic formula 7. The effects of lateral and longitudinal load transfers have been evaluated through a steady state approximation 10. Assuming a fixed roll axis position, the expression of the lateral load transfer for the front and the rear axles are, )()(_hdLhhatmruFhdLhhbtmruFrgrlatrzfgflatfz+=+= (4) The longitudinal load transfer, occurring while the varied vehicle forward velocity is taken into account, is calculated as follows, LhFFFgFrfxlongz/)(_+= (5) 3. DRIVER BEHAVIOUR THROUGH PATH PREVIEW Obviously, only the vehicle itself cannot maintain a desired path. This demands a combination with driver model. The driver has visual and motion feedbacks for developing steering control actions. Driver behaviour through path preview involves actions based on perception of commands. For directional/steering control, drivers can use preview behaviour to follow curved paths. A vehicle will follow a curved path for a given steering angle, so the driver can match horizontal road curvature with appropriate steer angle, and the remaining lane displacement can be handled with compensatory control actions. For speed control, the driver tries to match road grade with a throttle angle, although the correct perception of road grade is much more difficult and imprecise than the perception for horizontal curvature. 3.1 Directional/Steering Control For drivers visual feedback, a two-level (preview and compensatory) driver steering model based on the control strategy proposed by Donges 3 is presented here. The driver exerts steering control to maintain lane position through preview control, and to manoeuvre the vehicle during curve negotiation, lane change or obstacle avoidance. Unpredictable road disturbances can randomly move the vehicle within the lane, and the driver must counteract these disturbances with compensatory control. For preview control, Weir and McRuer 12 suggested that, systems structured to control vehicle heading/yaw angle and lateral position or path angle and lateral position offer good closed-loop characteristics. Therefore, it is assumed here that the driver develops steering corrections based on perceived heading/yaw and lane position errors. By setting a preview point P on the vehicle-fixed x axis, a sort of predictive behaviour is incorporated into the system. Fig. 2 illustrates drivers behaviour through path preview. A composite heading error of the preview point relative to the desired path at the preview point is given by, )(/PPecLy+= (6) where ye is the lane position error, LP is the preview distance, is the heading angle and P is the heading angle between x axis and AP line. Instead of separately perceiving both heading and lane position errors, the driver needs only to perceive the angular error c to the preview point down the road. The preview distance LP here is the product of vehicle forward speed and preview time constant TP. This is consistent with our everyday experience that driver sees nearer distance at lower speeds and further distance at higher speeds. Following McRuers crossover model 6, drivers compensatory feedback control can be defined by the transfer function of the steering angle to the composite heading error, sILcesTsTGss+=)11()()( (7) It includes three components: a gain G which sets the magnitude of road steering angle corrections for given heading error c; a lead term ) 1(+sTLthat the driver adopts to counteract vehicle tyre delay; a lag term ) 1(+sTIcorresponding to the neuromuscular delay; and , a time delay se approximating drivers reaction time delay. For drivers motion feedback, it provides information on motion performed by human organs and on orientation with respect to the gravitational direction. In 1, Allen noted that the yaw rate information can be used as a motion feedback element. The motion feedback gain Km provides a lead that the driver can use to compensate for the vehicle yaw rate lag. 3.2 Speed Control Speed control is important in a variety of scenarios, including maintaining safe lateral acceleration levels while following curved paths, responding to speed limits, and slowing down during emergency avoidance. During straight running the driver continues at specified speed. When the driver detects curvature, speed is then reduced accordingly in order to maintain desired lateral acceleration. The driver speed control law can then be described as Fig.3 (a). The driver commands deceleration consistent with a desired speed change, and perceives deceleration errors. Especially, when electronic chassis controls, such as ABS, TCS, etc., are involved, speed control will be essential. As we can see from the operating principles of these control systems, most of them are activated under emergency situations. Speed changing is therefore inevitable. For example, by adding an effective ABS, the relationship between the brake pedal force and vehicle deceleration is illustrated in Fig.3 (b). With the application of this relationship and the speed control law described above, the assessment of effects of these electronic controls is feasible. AcPreview point P PLP y x XYye / LP Desired pathP Fig.2 Driver Model through Path Preview Fig.3 (b) Driver Speed Control Law (a) ABS System Characteristic 4. DRIVER-VEHICLE INTERACTION 4.1 Driver-Vehicle Dynamics without Speed Control Given the above dynamic characteristics for the vehicle and driver, a block diagram of the overall driver-vehicle system model without speed control can be structured as shown in Fig.4. It is assumed that the vehicle is travelling at constant forward speed. Vehicle lateral velocity v, yaw rate r and roll rate p are generated by steering inputs to the vehicle equations of motion. Vehicle lateral velocity v and yaw rate r are then under direct control of the driver. Although the roll motion is not controlled by the driver directly, it also influences driver behaviour, especially when the variation of vehicle forward velocity is taken into account. Kinematical equations then provide vehicle heading angle and lateral lane position from lateral velocity and yaw rate. Finally, steering corrections will be made by the driver based on the composite heading error. For the closed-loop analysis, there are two system inputs, one is the path command yc, and the other is the initial heading angle command P. The vehicle will be steered to follow path commands, and P will help implement the correction of visual error. However, with the application of the crossover model merely, a lateral deviation can be found in the simulation (Fig.5 (a). It is assumed that the driver continues to steer until the vehicles attitude intersects the preview point down the road. This strategy finally eliminates vehicle attitude errors but does not correct lane position errors. Therefore, an additional feedback is needed that accumulates error whenever vehicle is not correctly positioned laterally in the lane. By adding a parallel integrator in the system, this offset error can be eliminated (Fig.5 (b). The function of this integrator is to compensate for the composite heading error, which accumulates both the vehicle heading error and the lane position error (Fig.4). It develops much quicker compensation than having the integrator compensate for lane position error only. The transfer function of the steering angle to the composite heading error can then be defined as, )1 ()11()()(sKesTsTGsssILc+= (7) Fig. 4 Driver-Vehicle System Directional Control Model Brake Pedal Force+_decelerationerrorWithout ABSWith ABSVehicle decelerationSpeedControlVehicleLongitudinalDynamicsbrakePedalforceactualdecelerationdecelerationcommand(b)(a) (a) without integrator (b) with integrator Fig. 5 Effect of the Parallel Integrator 4.2 Driver-Vehicle Dynamics with Speed Control When speed control is concerned, driver-vehicle interaction is the result of drivers longitudinal and lateral controls, which reflects the driver control behaviour in a more tactical level. Fig.6 represents the structure of the interaction. The upper part of Fig.6 describes the driver directional control behaviour, and the lower part describes the speed control behaviour. By looking at the path information and feedback of vehicle responses, the relationship between them can be processed. Fig.6 Driver-Vehicle Interaction with Speed Control 5. PERFORMANCE ANALYSIS 5.1 Double Lane Change at a Constant Speed Driver-vehicle model without speed control is applied here for a double lane change manoeuvre. Refer to the Appendix for vehicle parameters. Fig.7 shows the system responses. It can be seen that path information inputs make possible the analysis of the vehicles performances. The driver steers along a standard ISO double lane change manoeuvre with the constant forward speed 80km/h, and tracks the desired path using the two-level control. Therefore, drivers steering input is determined by the motion of the desired path to be followed by the preview point through the coupling of the preview distance LP, and also by drivers behaviour of the inverse dynamics of the vehicle. As shown in Fig.7 (a), the manoeuvre requires the vehicle to travel for 15m in the original lane, to change lane with a lateral displacement of 3.5m in 30m, to stay in this lane for 25m and to return to the original lane in 25m. The driver successfully performed the required manoeuvre without touching the cones delimiting the lanes. The action of the driver is with a short delay, and with a small gain, not to induce instability. The other results show the characteristic W shape of the double lane change responses. The system responds with a peak road steering wheel angle 1.6 (Fig.7 (b), which results in peak lateral accelerations of about 0.4g (Fig.7 (c). This value is above average drivers preference 2. It stems from the tyre saturation near the peak value. The oscillations are characterised by the natural frequency and damping of the model. (a)cones (b) (c) Fig.7 Transient Response in Double Lane Change Constant Speed V = 80km/h (Driver parameters: G = 0.35, = 0.1s, TL = 0.1s, TI = 0.2s, K = 0.05, Km = 0.01, TP = 1s) 5.2 Braking in Turn Scenario Now consider the combined steering and speed control driver-vehicle model for the braking in turn manoeuvre. Fig.8 illustrates the characteristic responses of the model. The driver enters a 300m-radius turn with a speed of 100km/h. Since the turn is sharper than expected, the manoeuvre results in excessive lateral acceleration ay, about 0.3g in Fig.8. Statistically 2, a cautious driver applies low to moderate deceleration while driving, with the result of reducing ay below 0.26g. The driver model is therefore set up to reduce ay to some percentage below 0.26g, corresponding with a reduced speed at around 88km/h. The speed control law is previously described in section 3.2, and the command braking deceleration is set at 0.2gs. One should note that when the lateral acceleration exceeds 0.3gs (Fig.8 (b), the driver model begins braking, which is subsequently brought up to the longitudinal command level of 0.2gs (Fig.8 (a). The vehicle goes into oversteer as evidenced by the actual trajectory crossing the desired during the braking process (Fig.8 (c). This is a result of a reduction in the rear axle + _ Steering Wheel Angle + _ path command Speed Control Vehicle Longitudinal Dynamics brake Pedal forceactual decelerationdeceleration command Directional/Steering Control Vehicle Lateral Dynamics path information actual path cornering stiffness. The driver is then able to reduce speed and bring the vehicle back under stable control in understeer condition after the vehicle reaches the desired speed, as evidenced in the steady state of lateral acceleration. (a) (b) (c) Fig.8 Driver-Vehicle Response in Braking in Turn 6. CONCLUSIONS AND FURTHER RESEARCH Rational driver directional/steering and speed control models have been specified based on vehicle attitude, lateral position and longitudinal deceleration controls. Driver-vehicle system performances in double lane change and braking in turn scenarios are studied. The analysis has demonstrated stable control of the system simulation. Steering control stability has been achieved with preview-compensatory model over a speed range. The proposed models in the paper are aimed at the assessment of effects of electronic chassis enhancement systems. They provide tools for the exploration of the effects of active chass
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