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数控卧式镗铣床刀库机械手升降机构设计,机械毕业设计全套
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railwayconsiststheeldto inherentlyandotherscomputer vision guidance 5,6. These trucks have better visibility for drivers but they are not fundamental solutions to overcomeMechanism and Machine Theory 45 (2010) 18921896Contents lists available at ScienceDirectMechanism and Machine Theorythe shortages of the general mast structures, and the problem of high self weight has not been cracked completely either.In order to improvethe driving comfort andsafety for the drivers andto reduceenergy consumption, this paper focuses ontheinnovativedesignof the lifting mechanismfor forklift trucks. A spatial multi-link lift-guidance mechanism is proposed, and then anew kind of lifting mechanism based on it is presented. This mechanism not only expands the vision eld of the driver but alsoreduces the whole weight of the vehicle.2. Proposition of a lift-guidance mechanismExpanding the drivers vision hasalwayschangingtheformsofthemast2,3,whileAsiswellknown,aplanarRRR-open-chaSuppose that two such planar RRR-linkagesRRR-open-chain linkages are connected with Corresponding author. Fax: +86 10 62788308.E-mail address: jingshanzhao0094-114X/$ see front matter 2010 Elsevier Ltd.doi:10.1016/j.mechmachtheory.2010.08.002been an importantresearchproject. Somekinds of trucks haveimproved visibility viautilizethevisualguidancemethodsofmobilecamera-spacemanipulation4orcomponentswillbadlyaffectthedriversbetween pedestrians and trucks are duean important role in supporting the loadsenough and its self-weight has to be increasedthe unnecessary waste of energy.stations, warehouses, ports and factories for loading, unloading and conveying. Aof a chassis and a work device which can be tilted and lifted vertically.following major disadvantages. First, the mast system composed of several largeofvisionbecauseitlocatesinfrontofthedriver.Manyaccidentsinvolvingcollisionsbad visibilities of the forklift trucks 1,2. In addition, the mast system playsguiding the fork frame to lift vertically. So its strength and stiffness must be high. The weight of the rear equilibrator is increased as a result, which surely improves1. IntroductionForklift trucks are usually used atgeneral weight-balanced forklift truckHowever, the general forklifts haveShort communicationInnovative design of the lifting mechanisms for forklift trucksJian-Yi Wang, Jing-Shan Zhao, Fu-Lei Chu, Zhi-Jing FengDepartment of Precision Instruments and Mechanology, Tsinghua University, Beijing 100084, PR Chinaarticle info abstractArticle history:Received 17 June 2010Received in revised form 3 August 2010Accepted 4 August 2010Available online 1 September 2010Forklift truck is one of the most important tools in logistics. However, the general mast systemof a forklift truck not only restrains the drivers vision, but also increases the whole weight of atruck anddecreases thefueleconomy.Therefore,this paper focuseson theinnovativedesign ofa new lifting mechanism for forklift truck. Firstly, a spatial multi-link lift-guidance mechanismis proposed. And then, under the constraints of this mechanism, the mobility of the fork andfork frame is investigated in theory. Lastly, a new lifting mechanism based on it is presentedandcomputersimulationisusedtodemonstratethefeasibilityofmotion.Thismulti-linkliftingmechanism takes advantage of exible cable drive and rigid body guidance, which not onlyprovides the operator with a wider eld of vision but also reduces the equilibrate weight of avehicle and therefore improves the fuel economy. 2010 Elsevier Ltd. All rights reserved.Keywords:Forklift truckSpatial multi-link mechanismRigid body guidanceFlexible driving methodjournal homepage: /locate/mechmtinlinkagethatconsistsofthreerevolutepairsandtwolinksgeneratesplanarmotions.are placed in two planes with a certain nonzero subtended angle. The ends of the twoa same rigid body through revolute pairs shown in Fig. 1. Link 1 is the base and rigid(J.-S. Zhao).All rights reserved.nts1893J.-Y. Wang et al. / Mechanism and Machine Theory 45 (2010) 18921896body 4 is connected with the base through two parallel RRR-kinematic chains, ABC and DEF. It is easy to nd that, these twokinematicchainsarebothplanarRRR-kinematiclinkages.Thereforethetrackofrigidbody4mustbeparalleltobothofplaneandplane. Thatis, rigid body4 canonlymakea free translation parallelto the intersection line, mn, ofthe twoplanes. As a result,thetrack of rigid body 4 is a straight line.Slider-crank mechanism is a common mechanism that applies RRR-open-chain structure. It is widely used and examples of itsFig. 1. Spatial multi-link structure.applications are easily found in gasoline and diesel engines 7. However, in the applications of slider-crank mechanism, deadpoints possibly lead to actuating failure. In order to improve the stability and avoid the dead points, this paper replaces the RRR-kinematic chains with RPR-kinematic chains, which are composed of two revolute pairs and one prismatic pair and can also onlygenerate planar motions without dead points.Suppose the two vertical planes that the support blocks and their RPR-kinematic chains located are symmetrical withrespect to the longitudinal symmetrical plane of the vehicle. As is shown in Fig. 2, the subtended angle between the twoplanes is denoted by (0bb180). Two RPR-kinematic chains are placed in the two planes, respectively. Every RPR-kinematic chain includes two revolute pairs and one prismatic pair, a connecting rod and a slideway. The connecting rod andthe slideway are connected through a prismatic pair. The fork frame has two extruded revolute pairs connected with theends of the two RPR-kinematic chains. As is discussed above, in such a spatial multi-link structure, the track of the forkframe is in a straight line.In addition, one can improve the strength and stiffness by adding another similar kinematic chain in each vertical plane, inwhich the support blocks located, to connect the fork frame and the truck chassis. Meanwhile, the upper and lower kinematicchains are connected by constraint rods. As the track of the upper and lower kinematic chains are parallel, the constraint rodsprovide redundant restraints and improve the stiffness and stability of the lift-guidance mechanism and the load-carryingcapacity 8.Now the kinematic principles of the spatial multi-link lift-guidance mechanism can be analyzed in theory. In order toinvestigate the degreeof freedom(DoF) of the fork frame, onecan establisha Cartesian coordinatesystem, where xoy-plane is theplane determined by the axes of revolute pairs A and D, the originof coordinate systemis the intersection point of axesof A and D,x-axis is the axis of revolute pair A. The coordinate system is shown in Fig. 3.Assume that the subtended angle of the axes of revolute pair D and revolute pair A is denoted by (0obb180o), the distancefrom revolute pairs A and D to the origin of coordinate system are equal and denoted by a. The coordinates of A and D area 00and acos asin 0, respectively. In addition, the coordinates of C and F can be expressed as ayCzCandxFyFzF, individually.It is not difcult to nd that, the axes of revolute pairs A and C are parallel, and so are the axes of revolute pairs D and F.s1=100Tdenotes the direction vector of the axes of revolute pairs A and C, s2= cos sin 0Tdenotes the unitdirection vector of the axes of revolute pairs D and F, s3=0yCzCTdenotes the direction vector of prismatic pair B ands4= xFbcos yFbsin zFTdenotes the direction vector of prismatic pair E.ntsAccording to the screw theory 9, the terminal constraint screw matrix of a kinematic chain can be obtained by solving thereciprocal screw equation$TE$=0 1whereThethe terminalFig. 2. A new lift-guidance mechanism. 1fork; 2fork frame; 3extruded revolute pair; 4connecting rod; 5constraint rod; 6slideway; 7support block.1894 J.-Y. Wang et al. / Mechanism and Machine Theory 45 (2010) 18921896000001in accordance with Eq. (1), one can obtain the terminal constraint screw matrix composed of a set of base screws ofconstraint screw system.$ABC=1000000000102435T31000zCyCTherefore,$ is a kinematic screw matrix and $ is the terminal constraint screw.kinematic screw matrix of a kinematic chain, ABC, can be expressed as$ABC= $A$B$CC138=10000 00000yCzC2435T2Fig. 3. Cartesian coordinate system.ntsIt proves1895J.-Y. Wang et al. / Mechanism and Machine Theory 45 (2010) 18921896Under the constraints of the lift-guidance mechanism, the fork frame can be lifted up and down perpendicular to the ground.3. ImplementThissimulateAswhileisshownof theworks,InraisedmechanisperpendicuThisCable-driveweightrequiremMeanwhilthiskindthembecomes$CF=000001T6that the fork frame has only one DoF along z-direction, i.e., the track of the fork frame is restricted to a straight line.According to Eq. (1), so long as 0bb180, the kinematic screw matrix of the frame CF can be solely obtained$CF= $ABC$DEFC2C35Consequently, the terminal constraint screw matrix on CF can be expressed as$DEF=cos sin 00 0 00 0 0 sin cos 000000 14 54Similarly, the terminal constraint screw matrix of kinematic chain DEF is obtained:2 3TFig.4.Implementation of thenewliftingmechanism andcomputer simulations. 1forkframe;2front pulley; 3front supporting rods;4back supportingrods;5cables; 6back pulley.ation of a new lifting mechanismsection will present a new lifting mechanism for forklift truck based on the lift-guidance mechanism proposed above andits motion in a computer.is discussed above, the lift-guidance mechanism restrains the track of the fork frame in a straight line. In order to lift goodsnotaffectingthedriverseldofvision,onecanusewindlassandsoftsteelcablestolifttheforkandforkframe.ThestructureinFig.4(a).Onecanset awindlassattherearoftheforklifttruckandplacessomepulleysandsupportingrodsonthetopcab. One end of each cable is connected with the fork frame and the other end is xed to the windlass. When the windlassthe cables will lift or drop the fork frame.order to verify whether this kind of forklift truck can achieve the desired movements, especially insure the fork frame to bevertically, Pro/engineer software is utilized to simulate its motion. Fig. 4(a), (b) and (c) show different positions when themliftstheforkandforkframeup.Fromthesimulationonendsthatthetrackoftheforkandforkframeisa straightlinelar to the ground. In addition, without the mast system, the driver has a better vision forwards and backwards.kind of lifting mechanism consists of the exible cable drive and rigid body guidance with better structural performances.n manipulators have been widely investigated in applications for their unique advantages such as low inertia, lightand so on 10. It is not difcult to nd that the weight of goods is supported mostly by the cables. Therefore, theent for strength and stiffness of the lift-guidance mechanism is lower, and the weight of it can be decreased as a result.e, compared with components of the general forklift trucks, such as cylinder, chains, chain wheels and the mast system,ofliftingmechanismutilizeswindlass,cablesandseveralconnectingrods.Theirweightis lowerandthegravitycenterofmoves backwards. Consequently, the weight of rear equilibrator is greatly decreased and the whole weight of the truckmuch lower. So the proposed forklift truck reduces energy consumption and improves the fuel economy of the vehicle.nts4. ConclusionsThis paper proposes a new kind of lifting mechanism, which is based on a spatial multi-link lift-guidance mechanism, forforklift trucks. Theoretical analysis and computer simulations are used to verify the single DoF of the fork frame under theconstraintsofthemechanism. Theliftingmechanismconsistsofexiblecabledriveandrigidbodyguidance,andthereforeshouldseparatetheliftingfromtheguidancewhichdecreasestheselfweightofamastsystem.Comparedwiththegeneralforklifttrucks,the driver has a wider eld of vision without the mast system and hence both the reliability of a truck and the driving comfort areenhanced obviously. In addition, because of lower requirement of strength and stiffness for every link of the new liftingmechanism, the whole weight of a truck is greatly decreased. Consequently, it improves the fuel economy of the vehicle.AcknowledgementsThis research was supported by the National Natural Science Foundation of China under Grant 50805083 and a Foundation forthe Author of National Excellent Doctoral Dissertation of China under Grant 200741. The authors gratefully acknowledge thesesupport agencies.References1 T. Horberry, T.J. Larsson, I. Johnston, J. Lambert, Forklift safety, trafc engineering and intelligent transport systems: a case study, Applied Ergonomics 35(2004) 575581.2 G. Rechnitzer, T.J. Larsson, Forklift Trucks and Severe Injuries: Priorities for Prevention, , 1992 Available from: b/muarc/reports/muarc030c.pdfN, cited March 22, 2010.3 R.L. Dunnhow, How to buy a forklift truck, Plant Engineering 56 (2002) 4044.4 M. Seelinger, J.D. Yoder, Automatic visual guidance of a forklift engaging a pallet, Robotics and Autonomous Systems 54 (2006) 10261038.5 G. Garibotoo, S. Masciangelo, P. Bassino, C. Coelho, A. Pavan, M. Marson, E. Bailey, Industrial exploitation of computer vision in logistic automation:autonomous control of an intelligent forklift truck. In: Proceedings of the 1998 IEEE International Conference on Robotics & Automation, Leuven,Belgium. pp. 14591464.6 C. Pradalier, Vision-based handling tasks for an autonomous outdoor forklift, Field and Service Robotics, Springer, Berlin/Heidelberg, 2008, pp. 6170,doi:10.1007/978-3-540-75404-6_6.7 R.F. Fung, K.W. Chen, J.Y. Yen, Fuzzy sliding mode controlled slider-crank mechanism using a PM synchronous servo motor drive, International Journal ofMechanical Sciences 41 (1999) 337355.1896 J.-Y. Wang et al. / Mechanism and Machine Theory 45 (2010) 189218968 L.Ojeda,J.Borenstein, Reductionofodometryerrorsinover-constrainedmobilerobots,ProceedingsoftheUGVTechnology Conferenceatthe2003SPIEAeroSense Symposium, Orlando. Vol. 5083, 2003, pp. 431439.9 J.-S. Zhao, Z.-J. Feng, F.-L. Chu, Analytical Theory of Degrees of Freedom for Robot Mechanisms, Science Press, Beijing, 2009.10 S. Behzadipour, Kinematics and dynamics of a self-stressed Cartesian cable-driven mechanism, Journal of Mechanical Design 131 (2009) 061005,doi:10.1115/1.3125206.nts 毕业设计（论文）中期报告 题目： 数控卧式镗铣床刀库机械手升降机构设计与分析 系 别 机电信息系 专 业 机械设计制造及其自动化 班 级 姓 名 学 号 导 师 2013 年 3 月 20 日 nts 1 1.设计（论文 ）进展状况 : 本毕业设计的主要内容是 了解刀库机械手升降机构的性能要求 ， 了解刀库机械手升降机构的工作原理，进行结构设计和计算分析 ，从一开始拿到任务书正式开始毕业设计以来，按照任务书的要求，我的工作进展还较为顺利。至今为止，通过大量查阅相关资料，我了解了课题的背景和发展状况，完成了对课题的分析， 对升降机构的装配图有了认识，并提出了自己的方案，完成了开题报告和对外文文献的翻译，对升降机构 有了一定的认识 。 图 1 升降机构 自动换刀机械手由升降丝杠 1、滑座 2、横梁 3、液动机 4、装刀手 5、手架 6
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