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本科生毕业设计（论文）开题报告 学生姓名：李鑫 学 号：14020926 班 级：140209 专 业：机械工程及自动化 指导教师：李 风 毕业设计（论文）开题报告一、课题介绍1.课题名称：ZL05微型轮式装载机总体设计2.课题背景：设计课题的意义 ZL系列轮式装载机是一种高效率的工程机械，具有结构先进，性能可靠，机动性强，操纵方便等优点。广泛应用于矿山，建筑工地，道路修建，水利工程，港口，货场，电站以及其他工业部门，进行装载、推土、铲挖、起重、牵引等多种作业。对加快工程建设速度减轻劳动强度提高工程质量降低工程成本都发挥着重要作用，因此近几年来无论在国内还是国外装载机品种和产量都得到迅速发展，成为工程机械的主导产品之一。为适应工程施工，市政建设及农用水利工地的砂石、灰土等各种散装物料的装运需要，提出设计小型轮式装载机的任务。 设计课题的目的轮式装载机总体设计是机械制造，机械设计和机械电子（机电一体化）等专业的一个重要的教学环节，是学完技术基础课及有关专业课以后的一次专业课程内容的综合设计。通过设计提高学生的机构分析与综合的能力，机械构造设计的能力，机电一体化系统设计能力，掌握实践生产过程自动化的设计方法。通过设计把有关课程（机械原理，机械设计，理论力学，材料力学，液压与气动技术，工程材料，材料成型，自动控制理论，测试技术，数控技术，微型计算机原理及应用，自动机械设计等）中所获得的理论知识在实际中综合的加以运用，使这些知识得到巩固和发展，并使理论知识和生产密切的结合起来。轮式装载机总体设计是机械设计及机械制造专业和机械电子专业的学生一次比较完整的整机设计。通过设计，培养学生独立的机械整机设计的能力，树立正确的设计思想，掌握机械产品设计的基本方法和步骤。通过设计使学生能熟练的应用有关参考资料，计算图表，手册，图册和规范；熟悉有关国家标准，以完成一个工程技术人员在机械整体设计方面所必须具备的基础技能训练。 轮式装载机的发展现状1）国外轮式装载机的发展现状1 新产品不断推出近年来，轮式装载机以围绕提高效率、降低成本为核心，继续向大型化、微型化发展，不断推出新产品，加速更新换代。卡特彼勒公司90年代初推出Cat966F轮式装载机，时隔1年又推出Cat980F轮式装载机，它增加了斗容和功率。改善了性能、提高了可靠性。不久又推出更大的Cat994轮式装载机，根据物料体积质量不同而选配l8 30m3的铲斗，机重170t；装有涡轮增压后冷的Cat3516型柴油发动机牵引力大、加速性能好；加长的工作动臂增加了卸载高度，能对载重量218t的大型自卸汽车装载。马拉松勒图尔勒(Marathon Letourneau)公司1990年和1994年在LI100的基础上分别推出LI400和LI800型轮式装载机。l998年9月在美国塔克癣(Tucson)召开的Longding 2000年会上，该公司宣布正在开发的斗容204m3的L1350型轮式装载机将于21世纪初投放市场，供载重量150200t自卸汽车装载。德雷塞(Dresser)公司90年代初推出4000型轮式装载机，斗容1030m3、机重1518t，采用模块结构的传动系统，大功率、敏感按钮控制的液压系统z型单摇臂工作装置。优化的整体结构和湿式盘式制动器，具有自动调节和自动密封性能。目前，全世界约有400台(功率大于750kw)大型轮式装载机应用在露天矿山和建筑工程，与大型自卸汽车配套使用。在发展大型轮式装载机的同时，微型轮式装载机以机动灵活、效率高、多功能和价格低廉赢得市场，发展甚快。如：日本古河公司生产的FL30-1型轮式装载机斗容034m3、机重23t；小松公司的WA30-1型斗容034rn3、柴油机功率20kW；丰田织机公司的斗容017m3、机重1t等这些微型装载机适用于建筑工地和地下矿山挖沟、平地、堆料等。2 新结构不断涌现21 工作机构卡特技勒公司推出组合式八杆机构。从地面到整个举升高度范围内具有平行移动的特点。它将快速连接器和塔架式机构设计成整体式工作装置，通过快速更换不同的辅助机构完成装卸、堆垛、扫雪、平地、清扫路面、推土、吊装、搬运和地表钻孔等作业，实现一机多能，减少用户设备投资。德雷塞公司开发Z型单臂工作机构并与高压液压系统相结台，为铲斗提供更大的掘起力；缩短装载工作循环，增加铲斗装满系数，大幅度提高劳动生产率。由于铰点少、杆件少，便于维修保养，降低维修费用。22 传动机构以卡特彼勒公司为代表的轮式装载机采用液力机械传动系统，其自动动力换档变速箱自动选择档位传动比，使换档在变速箱最佳效率点进行。该公司最近推出的STIC(转向变速集成)系统，将转向和换档功能集成于一操纵手柄上，使操纵更加省力、轻便，换档更加平稳，可大幅度提高生产率。以日本小松公司WA系列中小功率(小于125kW)为代表的轮式装载机采用新型集中式结构的驱动桥。它将主传动制动器和行星轮式终传动都集中在桥的中部，桥壳断面变化连续、平缓，内应力分布台理，从根本上防止因传统结构桥壳在轮边支承轴段应力集中断裂。轮端采用浮动密封结构，安装简便，有自动补偿功能，密封性能良好。该结构设计合理、基本零件少、工艺性好、性能好、可靠性高。马拉松勒图尔勒公司的轮式装载机采用柴油机一发电机一电动轮传动，比液力机械传动系统简单。在整个作业中柴油发动机以恒定转速运转，减少燃油消耗，延长发动机寿命；无变速箱、传动轴等许多部件，提高了传动效率，操作维修方便，费用低；独立电动牵引马达为固态控制，反应迅速，减少车轮打滑和轮胎过渡磨损；设置了电动缓行器，不用工作制动停机，装料对位准确；整机重心低，行驶稳定性好，可靠性高。23 液压系统德雷塞公司轮式装载机液压系统用传感器接受柴油机转速信号，当转速下降时柱塞式变量泵便自动增加转向系统流量，以保持恒定的转向速度，在最大挖掘工况时可减少流量，减慢液压元件动作，以保持液压系统的动力平衡，减少液压系统热损耗，节省功率。卡特彼勒轮式装载机转向液压系统用负荷传感式溢流阀，使液压泵在负载决定压力下溢流，降低系统压力，提高了液压元件寿命。工作装置液压系统采用举升限位装置和下放自动定位装置，避免了机械限位时液压缸行程终了产生高压和冲击；装设的蓄能器能吸收冲击载荷，并对整机的纵向摇摆起阻尼作用；液压缸导向套处有三重密封，防止泄漏和肪尘。24 司机室新型轮式装载机司机室的设计充分考虑了人的生理需求，对仪表位置排列、操作手柄和踏板、司机座椅、能见度、防噪和隔振、温度调节等均符台人机工程学，使司机在舒适、轻松、安全环境下操作，提高工作效率。如卡特彼勒轮式装载机的司机室设有微机监控装置和可调悬挂式座椅，先导液压阀操纵铲斗控制手柄及流量放大转向系统等，使操作轻便、灵活，采用防滚翻保护结构(ROPS)和落体撞击保护结构(FOPS)符台ISO标准要求。3自动化水平不断提高微电子技术的突破性进展为轮式装载机自动控制、状态监测及视线范围内遥控技术的发展创造了条件。柴油发动机自动控制喷油系统、变速箱自动控制换档、性能参数和状态监测均取得重大进展，在视线内遥控作业已进入实用阶段，从而改善了性能，提高了可靠性，缩短了停机时间，增加了生产能力，降低了燃油消耗，取得了更大的经济效益。31 柴油发动机自动控制喷油系统卡特彼勒Cat994D型装载机采用了Cat3516B型柴油发动机，装有HEUI型电控喷油系统，根据外载荷有效控制功率和转速，发动机喷油泵随调速器动作，精确地对燃油进行调节、加压和供油，降低初始喷油速率，减少NO 和HC，噪声小，燃油效率高。32 变速箱自动控制换档日本川崎重工公司的KLD97Z型轮式装载机采用自动控制换档的变速箱，可按装载机运转工况自动选择最佳档位，用微机控制离台器，从而简化操作、提高作业效率、减少冲击，实现平稳换档；电子控制装置、传感器等使用可靠，一旦控制系统发生故障，可用手动换档，不影响工作。33 设备状态监测卡特彼勒开发的电子监控(EMS)系统对轮式装载机主要系统出现故障或潜在问题提出警告和显示，有三种不同的警告级别和信号，每种信号表明系统的状态和司机应采取的适当措施。34 机载电子称重系统目前，许多大型轮式装载机都装设机载电子称重系统，能清楚地显示出需再装的物料量，从而使心中有数，以防止过载或欠载，减少无效跑车次数，节省作业时间，提高生产效率。并可对质量累计计算显示仪表以彩色数码显示，清楚明了，校准简便，误差为3以内。2）国内轮式装载机的发展现状在今后相当长的时间内，轮式装载机仍将是工程建设机械中最重要的机种之一，国内年需求量持续稳定地保持在一较高水平，但国内装载机生产厂家也在急剧膨胀，竞争更趋激烈，各生产厂家纷纷开发新产品，来迎接市场的挑战。3t以下装载机3t以下产品主要以ZL10、ZL15、ZL16为代表，还有一些利用拖拉机底盘改装的小型装载机，主要与日益增多的农用运输车辆配套使用。主要零部件均采用一般性能及质量的发动机、驱动桥、变速箱、液压件。技术较先进的静液压传动产品，液压件国内不易配套，产品成本居高不下，制约了该类产品在国内的发展。ZL30装载机ZL30装载机主要生产厂家有成工、常林、徐工、宜工、山工等。该产品零部件配置较零乱，生产厂家具有自制的桥箱，风格各具特色，质量及性能上相对稳定，技术先进性一般。徐工最近开发的ZL30F装载机，采用电换挡变速箱，使3t级装载机技术上有了新的突破。ZL40ZL50装载机ZL40ZL50装载机，主要装载机生产厂家均拥有该产品。第一代产品几十年来沿续至今，全国几乎使用同一套图纸，有些技术力量薄弱的厂家，仍把其当作主导产品推向市场。第二、三代产品主要是对工作装置进行优化，改变外观造型。如柳工ZL40BZL50C、徐工ZL40EZL50E。第四代产品是在第三代的基础上，进一步优化整机的性能及配置，电控箱、湿式制动器等新技术得到应用，并形成了各企业的专有技术及专利技术，使产品以崭新的面貌推向市场。ZL60及6t以上装载机6t以及6t以上的装载机，这是国内潜在市场最大的产品，1998年以前大多数生产厂家均开发了ZL60装载机，但由于受传动件的制约，ZL60装载机没能成功地推向市场。在1999年北京国际工程机械博览会上，各厂家推出了新一代ZL60装载机，多数厂家选择柳州ZF合资生产的箱或桥，液压元件也有新配置，发动机可选用斯太尔或上柴6121(Cat3306)，整机可靠性得到很大提高，给国内大吨位装载机带来发展机遇。 产品在生产中的作用及使用范围ZL05装载机是一种单桥驱动、整体车架、机械传动的小型装载机。该机适用于市政工程、城市环卫、公路养护、车站码头、中小煤矿等单位装载松散物料。可与翻斗车、轻型汽车、中小型拖拉机和农用汽车配套使用，可明显提高工作效率，降低工人劳动强度，而且使用、维修简单、方便，价格低廉。3.工作内容和要求：题目的内容总体参数的确定，总体布置。工作装置及液压系统设计。典型零部件设计、选取。整机合理性分析。工作量译文6000字。开题报告。说明书20000字。4张A0图。读参考文献15篇以上。程序设计及典型零件工艺分析。4.课题的重点和难点：ZL05轮式装载机的结构组成传动系统。工作液压系统。工作装置。该机工作装置由铲斗、动臂、摇臂和拉杆构成，安装在车架的支架上。其他。（1）该机采用了增加前桥桥荷和整机配重的措施，明显地增加了前轮的附着力。（2）与全液压装载机相比，该机结构简单，操作容易，维修方便、价格低廉。ZL05轮式装载机的主要技术参数：额定装载质量(kg)： 500额定斗容量(m3)： 0.25最大卸载高度(mm)： 大于1900相应卸载距离(mm)： 大于800轴距(mm)： 1540轮距(mm)： 1150最小离地间隙(mm)： 245车速(kmh)： 前进： V1=1.9, V2=4.4 V3=5.97, V4=7.1 V5=13.9, V6=22.2 后退： VR1=4.58掘起力（KN）： 1100最大牵引力（N）： 9000发动机额定功率(kW)： 15机重（kg）： 18005.可能用到的主要知识和技能：机械原理，机械设计，理论力学，材料力学，液压与气动技术，工程材料，材料成型，自动控制理论，测试技术，数控技术，微型计算机原理及应用，自动机械设计等本科期间学到的课程。6.需要自学的知识和技能：SolidWorks,AUTOCAD,CATIA等绘图仿真软件。二、工作计划2006.022006.03 调研，译文，开题报告2006.04.012006.04.15 总体布置及草图2006.04.152006.05.01 总体设计，总装图2006.05.012006.05.15 零部件设计，说明书2006.05.152006.06.01 绘图，论文2006.06.012006.06.20 修改，完善图纸、论文，准备答辩三、参考文献1 刘慧斌，装载机工作装置优化设计方法的研究，硕士，浙江大学，2000.2 吉林工业大学工程机械教研室.轮式装载机设计.北京：中国建筑工业出版社，1982.3 李建成.矿山装载机设计.北京：机械工业出版社，1989.4 高梦熊.地下装载机结构设计与使用.北京：北京冶金工业出版社，1987.5 王国彪，杨力夫.装载机工作装置优化设计.北京：机械工业出版社，1996.6 机械设计手册联合编写组.机械设计手册.北京：化学工业出版社，1982.7 房斌，张文中，胡其颖.ZL05装载机.徐州：徐州工程机械集团公司，1997.8 赵昱东.国外轮式装载机的新进展. 马鞍山：马鞍山矿研究院，2000. 8Applied Ergonomics 34 (2003) 265271Aspects to improve cabin comfort of wheel loaders and excavatorsaccording to operatorsL.F.M. Kuijt-Eversa,*, F. Krausea, P. Vinka,baTNO Work and Employment, P.O. Box 718, Hoofddorp 2130 AS, The NetherlandsbIndustrial Design, TU Delft, The NetherlandsReceived 19 April 2002; received in revised form 25 November 2002; accepted 29 December 2002AbstractComfort plays an increasingly important role in interior design of earth moving equipment. Although research has beenconducted on vehicle interiors of wheel loaders and excavators, hardly any information is known about the operators opinion. Inthis study a questionnaire was completed by machine operators to get their opinion about aspects which need to be improved inorder to design a more comfortable vehicle interior. The results show that almost half of the operators rate the comfort of their cabinaverage or poor. According to the operators, cab comfort of wheel loaders can be increased by improving seat comfort. Besidesimproving seat comfort, cabin comfort of excavators can be improved by changing the cab design (including dimensions, ingress/egress), view, reliability, and climate control.r 2003 Elsevier Science Ltd. All rights reserved.Keywords: Cabin comfort; Operators opinion; Earth moving equipment1. IntroductionComfort plays an increasingly important role invehicle design. As machine operators of earth movingequipment often spend long hours in their vehiclesometimes even more than 8h a daycomfort is amajor issue in interior design of these machines.Operating earth-moving machinery is not a physicallyheavy job and can be sustained for long periods.Nevertheless, operating such a machine appears to bea risk factor for musculoskeletal disorders, especiallywhen the task is not interrupted by other workingactivities or breaks. Zimmerman et al. (1997) showedthat the main problems of earth-moving machineryoperators concern physical complaints in the neck/shoulder and low back region, general fatigue andfeelings of discomfort. This might be attributed to acombination of static load during prolonged sittingfrequently in awkward posturesexposure to wholebody vibrations, and handling and steering the machine(Zimmerman et al., 1997; Tola et al., 1988; de Loozeet al., 2000).A comfortable well-designed vehicle interior mayreduce awkward postures and provide an environmentthat stimulates optimal operator performance. Based ona literature review about musculoskeletal disorders andtheir risk factors, Zimmerman et al. (1997) made fourrecommendations for reducing work-related musculos-keletaldisordersamongoperators:minimizingofmagnitude and frequency of vibration reaching theoperator; locating controls optimally to minimize reachdistances, trunk flexion and trunk rotation; providingmaximum operator visibility from an upright supportedseated posture; and taking regular breaks to minimizethe effects of sustained postures. Improvements of cabcomfort are very often based on reducing the riskfactorsforwork-relatedmusculoskeletaldisorders(Zimmerman et al., 1997; Attebrant et al., 1997). Onlya few studies have mentioned aspects which operatorswish to see improved. Nakada (1997) describes thedesirability ranking for dump trucks and wheel loadersgiven by product creators, designers, design engineers,operators and young people. Nakada, (1997) shows thatmuch design attention has been paid to instrumentpanel/monitors and meters and the operator seat.*Corresponding author. Tel.: +31-23-55-49-938; fax:+31-23-55-49-305.E-mail address: l.kuijtarbeid.tno.nl (L.F.M. Kuijt-Evers).0003-6870/03/$-see front matter r 2003 Elsevier Science Ltd. All rights reserved.doi:10.1016/S0003-6870(03)00032-2Unfortunately,theoperatorsopinionscannotbedistinguished in Nakadas study (1997).However, in order to design a comfortable vehicleinterior, the opinion of the operators is important asthey are the end-users of the machines. Their userexperience may be of great help designing a morecomfortable vehicle interior. The aim of the currentstudy is to find aspects mentioned by wheel loader andexcavator operators, which can be used to improve thecomfort of vehicle interiors in the future. In this articlewe describe the results of a questionnaire given to 273machine operators. They were asked their opinion abouttheir current machine, their future demands and aspectsthey considered important to work well with themachine. This allowed us to identify aspects that needimprovement in machine design.2. Method2.1. SubjectsA convenience sample was obtained through ap-proaching operators visiting Bauma (the worlds largestexhibition for construction equipment). Most of theparticipants were wheel loader operators (n 61) andexcavator operators (n 212). The others (n 65) wereoperators of several construction machines (e.g., mobilecranes, dozers, tower cranes, off-road trucks). Only theresults for wheel loader and excavator operators arepresented in this article, as they account for 18% and62.7% of the total number of respondents respectively.Figs. 1 and 2 show a typical wheel loader and excavator.2.2. QuestionnaireData were collected by means of a questionnairewhich was completed during an interview. The ques-tionnaire was divided into three parts: (1) characteristicsof the population, (2) evaluation of the current machinebeing operated, and (3) future demands on earth movingmachinery. In the first part we asked the operators age,years of experience as operator, the kind of machinerybeing operated and its age. In the second part of thequestionnaire, operators evaluated their machine byrating overall comfort and their opinion of specific partsof the machine on a four-point scale (very good, good,average, poor). Finally, two open questions asked aboutthe operators future demands: what improvementswould make the machine more comfortable and whataspects are the most important to work well with themachine.Fig. 1. Excavator.L.F.M. Kuijt-Evers et al. / Applied Ergonomics 34 (2003) 2652712662.3. Data analysisData were sorted by machine type, after which theresponses of wheel loader operators and excavatoroperatorswereseparatelyanalyzed.Withinthesegroups, operators of older machinery (X4 years old)were separated from operators of newer machinery (o4years old). In addition, the categories very good andgood were combined (very good/good) and thecategoriesaverageandpoorwerecombined(average/poor).Frequencytablesweremadeoftheoperatorsopinions about overall machine comfort and abouttheir opinions about specific parts of their machines.Chi-square was calculated between age of machine andoverall comfort and between age of machine and theoperators opinion of specific parts of the machine. Weassumed that if fewer than 80% of the operators rated apart of the machine good/very good, improvement ofthis part could contribute to a more comfortable vehicleinterior. In part three of the questionnaire, the operatorsindicated aspects to improve machine comfort andaspects they found necessary to work well with themachine. We classified these aspects into categories andcalculated the percentage responses.3. Results3.1. Characteristics of the populationBoth the wheel loader operators (mean age: 36.579.4years) and the excavator operators (mean age: 36.379.3years) who participated in this study, were experiencedwith a mean of 12.3 (78.1) and 13.4 (79.2) years ofservice, respectively. Half of the operators operatemachines less than 4 years old (53% of the wheel loaderand 50% of the excavator operators; see Fig. 3).3.2. Evaluation of current machine57.4% of wheel loader operators and 55.9% of theexcavator operators rated the overall cabin comfortgood/very good. Fig. 4 shows that operators of newermachinery (o4 years old) rated the overall cab comfortas good/very good more often than operators of olderFig. 2. Wheel loader.Age of machinesPercentage of machines per category0102030405060ExcavatorsWheel loadersMachines (%)less than 4 years old4 years or moreFig. 3. The participants machines are divided into two categories:machines o4 years old and machines =4 years old.L.F.M. Kuijt-Evers et al. / Applied Ergonomics 34 (2003) 265271267machines (X4 years old). This was found both amongwheel loaders (w21 8:5; po0:04) and among excava-tors (w21 23:0; po0:001). Seventy-eight percent of theoperators driving wheel loaders less than 4 years old,rated the comfort of their machine as good/very good.With excavator operators this figure was 81%. Theseresults show that during recent years the experienced cabcomfort of excavators and wheel loaders has improved.Fig. 5 illustrates the opinion of the operators aboutspecific parts of the machines less than 4 years old. Asseen in Table 1, fewer aspects of wheel loaders are ratedaverage/poor by more than 20% of the operators,than excavators. Common aspects which can contributeto increase of cab comfort are dashboard and displays,adjustabilityofseatsandcontrols,vibrationanddamping, noise reduction, and seat comfort. Excavatoroperators would also like to see improvement of climateGeneral opinion about comfort of the cabPercentage of operators rating good/very good020406080100ExcavatorsWheel loadersOperators (%)less than 4 years old4 years or moreFig. 4. Percentage of operators rating their machines good andvery good on cab comfort.Excavators less than 4 years old Percentage operators rating good and very good 020406080100020406080100Seat comfortAdjustablility of seat and controlsWay controls workPedalsDashboard and displaysViewClimate controlCab dimension/interior spaceMachines appearanceNoise reductionVibration and dampingOperators (%)GoodVery goodGoodVery goodWheel loaders less than 4 years old Percentage operators rating good and very goodSeat comfortAdjustablility of seat and controlsWay controls workPedalsDashboard and displaysViewClimate controlCab dimension/interior spaceMachines appearanceNoise reductionVibration and dampingOperators (%)Fig. 5. Opinion of excavator and wheel loader operators about specific parts of the machines.L.F.M. Kuijt-Evers et al. / Applied Ergonomics 34 (2003) 265271268control, improved machine appearance, and better cabdimensions (including interior space, ingress/egress),view, and reliability.3.3. Future demandsThe participants generated 467 items desired toimprove the machines comfort. We classified theseaspects into 15 categories (see Table 2). Fig. 6 showswhich features should be improved according to theoperators. Seat comfort, climate control and accessoriesare often mentioned for both wheel loaders (20%, 12%,15%, resp.) and excavators (21%, 19%, 12%, resp.).Excavator operators also mention cab design (includingdimensions, ingress/egress; 19%).The aspects considered most important to work wellwith the machine are summarized in Table 3. Machineperformance is by far the most important issue if welook at the averages. Other aspects like view andreliability play less important roles.Table 2Classification of aspects mentioned by operatorsCategoriesExamplesTCO (total cost of ownership)Costs of machine (procurement,service costs, rest value)Machine performancePerformance, hydraulics, gearServiceabilityCleaning of the machine,manufacturer serviceReliabilityReliabilitySeat comfortSeat pan, lumbar support, armrests, curvature of back supportAdjustability of seat and controlsAdjustability of seat height,adjustability of controlsOperabilityJoystick, steering wheel,interaction joystick and beamViewView of work, dead angles,position of mirrorsDashboard and displaysUsability of dashboard/controls,readability, absent information,position of displaysClimate controlTemperature, dust filters,ventilation, blower positionDesign/dimensions/ingress andegressDesign and dimensions of cabinand machine, position of steps,grab railsNoise and vibrationNoise, vibration, dampingAccessoriesRadio, fridge, storage space, cupholderSafety and stabilityFeelings of safety, stability ofmachineEnvironmentNoise outside the machine,exhaust fumesTable 1Aspects rated average or poor by more than 20% of the operators for both wheel loaders and excavators less than 4 years oldWheel loadersExcavatorsAspectOperators (%)AspectOperators (%)Dashboard and displays32.0Seat comfort*29.5Adjustability of seat and controls31.2Vibration and damping*27.0Vibration and damping*28.1Dashboard and displays26.0Noise reduction28.1Climate control*24.1Seat comfort24.9Machines appearance24.0Cab dimensions, interior space, ingress and egress*22.3Noise reduction*21.9View21.9Adjustability of seat and controls*21.0Reliability20.9Aspects marked by* are rated by significantly more operators of newer machinery (less than 4 years old) as good or very good compared tomachines older machinery (4 years or more).Fig. 6. Aspects which need improvement according to excavator andwheel loader operators.L.F.M. Kuijt-Evers et al. / Applied Ergonomics 34 (2003) 2652712694. DiscussionThe aim of the current study was to find aspectsmentioned by wheel loader and excavator operatorswhich can be used to improve the comfort of vehicleinteriors in future. In order to find these aspects, weasked questions about three issues.*about comfort of specific aspects of the cab (rating ona four-point scale);*about aspects necessary to improve the cab comfort(open question);*about aspects important to work well with themachine (open question).Excavator and wheel loader operators mentionedimproved seat comfort, climate control and accessoriesas ways to increase cab comfort. Excavator operatorsalsomentionedcabdesign(includingdimensions,ingress/egress).Theseaspectswerealsoratedasaverage/poor by more than 20% of the operators(except accessories because this was not an item in thesecond part of the questionnaire). Other aspects whichcan be taken into account with cab design are thosewhich operators mention as most important aspects towork well with the machine. Especially when theseaspects are also rated as average/poor by more than20% of the operators, they need special attention.Improving these aspects have priority in designing amore comfortable cab.In our study, we collected our data among visitors tothe Bauma exhibition in 2001. The advantage of thiscollection method is that it is possible to reach a largegroup of operators within a short period of time, at thesame time getting a large response, which wouldnormally be very difficult. A disadvantage might bethat the vast majority of respondents were Germanwhich could mean that the results have a limited validityamong operators in other countries. The Germanoperators may have other ideas about cab comfort thanoperators, who work in other countries. The demands ofthe operators on their machine depend on the workingenvironment (e.g., climate, landscape, dust) and theirtasks (e.g., driving off road, driving on the main road),which can be different between countries. Besides, theoperators based their opinion on their current machine.It is possible that in Germany certain brands areoverrepresented compared to other countries and thatthe operators opinion might vary according to thebrand. The most common brands would thereforeinfluence the results of our study as many operatorsuse one of these machines (Excavators: brand A 22.6%,brand B 22.2%; Wheel loaders: brand A 21.3%, brand B18%, brand C 11.5%).Since we used a short questionnaire to collect thedata, no detailed information could be asked. The goalof our study was to get a global view on the operatorsopinion. The open questions gave the operators theopportunity to think open-minded which may rendervaluable information. Open questions are less suitablefor data analysis, because we needed to categorizeanswers. Inevitably information is lost in this process,but the goal of obtaining a global view was neverthelessachieved.Our results show that seat comfort, climate control,accessories (for wheel loaders and excavators) and cabdesign (including dimensions, ingress/egress), view, andreliability (for excavators only) are the aspects whichcan improve cab comfort. All these aspects are ratedaverage/poor by more than 20% of the operators andthey are also mentioned as aspects which need improve-ment in order to increase cab comfort. In our opiniondesigners should give priority to these items whenredesigning cabs. It is interesting that operators didnot mention vibration as an aspect which can improvecomfort, as it was ranked high on the list of machineparts rated average/poor. Besides, whole body vibra-tion is a serious health hazard (Houtman et al., 2001). Itis possible that the operators did not mention vibrationbecause they may see vibration as an engine property oran inevitable consequence of working on earth movingequipment. Operators might have the idea that vibrationcannot be reduced by redesigning only the cab. It is,however,unclearwhyoperators did notmentionvibration.When comparing excavators and wheel loaders,improving seat comfort is an issue for both wheelloaders and excavators. Although seat comfort inexcavators has been improved during recent years (seeTable 1), improvements are still necessary. However,this is not easy as sitting comfort depends on many otherfactors more or less related to seat design: e.g.,adjustability of seat and controls, vibration and damp-ing, and view. For example, a bad view from the cabincan result in awkward body postures, which reducescomfort in spite of a comfortable seat.Beyond the common aspect seat comfort, manydifferences exist between wheel loaders and excavators.One difference we found between the excavator and theTable 3Aspects considered most important to work well with the machineaccording to wheel loader and excavator operatorsWheel loadersExcavatorsAspectResponses(%)AspectResponses(%)Machinesperformance40.3Machinesperformance37.0View12.5Reliability14.6Reliability11.8View11.5Operability11.1The aspects noted in more than 10% of the answers are presented.L.F.M. Kuijt-Evers et al. / Applied Ergonomics 34 (2003) 265271270wheel loader was that excavator cab design (includingdimensions and ingress/egress) needs improvement. Thisdifference may be explained by access and space. First,there is a difference in machine access with gripsgenerally quite wide apart and steps to the cabin farfrom optimal, being either too high or too narrow.Operators could experience this as a problem. Secondly,there is a fundamental difference between wheel loadersand excavators in the space available for the cab. Withthe present design, excavators have a limited widthavailable for the cab as it must be positioned betweenthe boom and the left machine side, leaving approxi-mately 1m for the cab.Anotherdifferenceisthatimprovingviewcanincrease the cab comfort of the excavator. View is avery important aspect to work well with the excavator.The boom of the excavator has a wide range of motionand the operator needs to see the bucket for the fullrange. A comfortable cab provides a clear view of theworkplaceandthebucket,withoutnecessitatingawkward postures.In the introduction, we stated that comfort plays animportant role in cab design. It is therefore interesting tofind that the operators did not mention comfort as oneof the most important aspects to work well with themachine. They mentioned aspects such as the machinesperformance, reliability, view and operability. It seemsthat operators think first about the basic requirementsneeded to perform their task and apparently do not seecomfort as one of them.If we compare our results with the results of Nakada,(1997), in both studies the operator seat is ranked asimportant. Instrument panel, monitors and meters arealso ranked as important in Nakadas study. In ourstudy vibration, dashboard and displays are high on thelist of parts rated as average/poor by more than 20%of the operators, but they are not seen as aspects thatcan improve cab comfort. Nakadas study did notmention vibration at all. A reason for this may be that inour study, experienced operators played a larger rolethan in Nakadas and because that study was focused oninterior design.An increase in cab comfort has been achieved duringrecent years. From Table 1 it seems that wheel lo