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DYNAMIC CHARACTERJZATION AND ANALYSIS OF AERJAL LIFTS
A Thesis Presented to
The Academic Faculty by
Eileen C. Hernandez
In Partial Ful丑llment
of the Rβquirements for the Degree Master of Science in the
George W. Woodruff School of Mechanical Engineering
Georgia Institute of Technology December 2012
SUMMARY
Aerial lifts 町e used to elevate people and material to high heights. There 町e 皿皿y different types of aerial lifts which have vastly different dyn缸nics characteristics. Thus, a new categorization for aerial lifts w出created and organizes them by their kinematics. Many accidents occur while using aerial lifts. Haz町ds of aerial lifts and current solutions to those hazards were reviewed to understand the causes of the accidents. Some major accidents are due to the compl缸 dynamics and flexibility of a啟Z劃 lifts, such as oscillations and tip-overs. Oscillations of full-size a町ial lifts were experimenta』ly tested to determine 仕equencies in different configurations. Machine-motion induced oscillations of an articulati衛(wèi)g aerial lift were simulated and analyzed for both non-overcenter and overcenter configurations. fuput shaping was used to achieve reduction in machine-皿otion induced oscillations. Tip-over stability margin was used to simulate and analyze the stability of both non-overcenter and overcenter configurations. The effect of increased platform m回s on tip-over stability m町gin W出also analyzed. The results in this thesis are a categorization of aerial lifts including their hazards and methods of reducing those hazards, an experimental verification of the dyna皿ic response of full-size aeria』 lifts, a fully dynamic tip-over prediction model of double-boom articulating aerial lift by applying flexibility in the joints and realistic velocity profiles, and a detailed study of the dynamics of a double-boom articulating aerial lift.
Xl
CHAPTER I
INTRODUCTION
There are many ways people reach high heights to work on buildings, trees, airplanes, and other tall structures. In many cases, aerial lifts 缸e used to provide the desired height and work environment. Aerial work lifts, like the one shown in Figure 1, provide many necess町y benefits to users that need an elevated work platform. However, with those benefits come significant hazards.
“According to the U.S. Bureau of Labor Statistics about 26 construction workers die each ye町 from using aerial lifts. Approximately 70% involve boom- supported lifts, such as bucket trucks and cherry pickers; 25% of the other
deaths involve scissor lifts” ［ 1].
／／
Figure 1: An Altec truck-mounted articulated aerial lift working on electrical lines.
1
From 也ese statistica.1. facts two ma.in challeng四can be infeITed. The 位就 challenge is deter回國ng how to reduce fatalities that occur when using aerial lifts. Tb創(chuàng)甘：ore, there is a n四d to identi島r 也e most co皿mon hazards of 樹總al lifts and how they occur. The second
challenge is widersta.nding the 祖erent aerial work lifts (i息 bucket trucks, cbeny pick，棚，
SC兇sor lifts, etc.), their respective b相ards, and m創(chuàng)hods to reduce those h拙ards. Before detennilling how to redu,創(chuàng) 制iden餡，it is 國1portant to understand 也e different 槌rial 且她 well enough to develop po協(xié)ntial solutions that could be applied to the 嗣ria.l work lifts under consideration.
1.1 Desc時俐 ” and Categoriza銳on of Ae付 t L梆s
Aerie.I work lifts have e. wide range of a.ppearan臼s; however, all of them, a.re 四ed to position people high 兇the air [1]. Different m礎.anisms m四創(chuàng) 始 陽form this 兇ing motion.
The kinematic structur程 ie what 部，para也·ee difl趾·ent typ劇 f aerie.I work lifts. The 缸'St
distinguishing factor 礎 ng 棉對al lifts is 必rectionality of 白白motion: i) only vertical or, 總） Vi ical and horizontal，掘礎 wn in Figure 2. A S部ond catego歸ation is 也.e method used to elev在te the work platform. 四ere are thr錦 different m礎 ds of elevation within each
位ectional ca.te靜思 Ve民ic創(chuàng)兇s use：斗 部i筋 z，總.） ve約iβal mast，礎d i均 pulley Sy侃錮s.
’
Lifts performing v的ical and horizontal motion use: i) tel制叩ic, ii) a.rticul就問，and 詛） te1錦oopic articulating. The final major way to dilferentia:悔 aerial 1出s is by their a.b山在y or 國功迫ity to drive on the ground while elevated.
3
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，，
，
，
，
，，
，
····－
4
一
，
‘ ’川 ，
，
1也·u·····a
（礙 nly vertical motion
（均 Vertical and ho歸ontal motion
Figure 2: Two Categori郁 f Aerial Li成 Motion.
Mobility while elevat.ed depends on the b副e ofthe aeriAl lift. L也a 份1at are able 協(xié) 缸ive while i總 部eration have a cab base to hold the power supply 仰d削略 Figure 3(a） 兇礎 example of a cab-base lift. Ifa lift b錦a skeletal struct山珍 for the base or is 也ruck-mounted, then the aeria.I lift is unable to drive while elevat創(chuàng).A1l 姐ample of 8ll immobile aerial lift with a skeletal b毗兇shown in R腳跟 3{b).
(a) Genie Z-80 mobile cab base (b) Genie TZ-34／到回mobile telescopic tele閡 ，pie 惱ticulating lift articulating lift with an skeletal base
Figure 3: Examples of mobile 1and immobile 輔rill』 lifts a.
Overall, moat aeri劍 work 兇S 錦n be 以aced 恒 ne of 出.e following 膽 d翩翩：
1. Sci”。r L出a
2. Verti惱J Mast L出8
3. Pulley Lifts
a τelesc。p沁 Lifts
、
5. Articula.ting Lifts
6. τ lesco以c Articulating Lifts
Scissor 崎S, V礎ica.I m崎t 溢缸，and pulley li島sperform only v礎ica.I motion. τ副閣copic lifu:I 館也ic叫.a.t墜g lifu:I, and teleacopic articulating lifts perform verti兇J and horizontal mo- tion. Each cate伊叩h礎varia悅 ns that c礎 r c礎not drive while elevated. By including 輔ria.I lifts’ mobility or i.mm抽出ty while el劇時時，th.e complete categorizat沁n of a衍兇險加 is giv， in Table 1.
1http://www.gemelilt.com/en/prod.uct吶何:.equipmeutfb即脅／iDdex.h陽
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τ'he power supply used by aerial lifts do四not depend on the directionality of itsmotion. It depends on the intended work environment. Two different work environments for aerial l出s are: i) indoor 皿d ii) outdoor environments. Indoor environments re的rict the power supplies to those that do not emit 但:ha.ust such as electric, manual, battery, and sometim四 a hybrid that uses E翩 r diesel outdoors and electricity or b也.ttery indoors. Outdoor en- vironments 町e not 田restrictive as indoors; thus, all power suppli田can be used. Other options that apply to all aerial lifts 町e insulation for electrical work and/or reinforced heavy duty for industrial work.
Some companies that 町e well lmown for aerial work lifts include：τer眩 Ni缸yli丘 Alt鈕，
JLG, Haulotte, R刷.chm嗣ter, Skyjack, Snorkel, E血的，Versalift, MLE Man Li晶 Manuf脅 tur國g Co., and Hi-Rea.ch. MLE Man Li丘 Manufacturing Co. sp臼ializ由國皿a.king custom aerial lifts such 回clean room lifts and pedestal mount man-lifts. Bridge Across Specialties,
Wes也 Co屆t Under Bridge Platforms, and Pal.finger specialize in truck-mounted aerial work l監(jiān)s capable of accessing beneath bridges for rep膛，皿aintena.nce, and 且spection，劇由傭n in Figure 4.
Figure 4: Palfinger’s vehicle-mounted bridge 皿spection l出performing 皿aintenance under a bridge. 14
14htt回：／／市附w.陰腦血.ger.oom/en-US/usa/products/
9
1.1.1 Verti恤l Lifts
V目世cal 兇s are 11Plit into thr喃wbl蜘ti()Illj: IICis盹r lift8, vertical 國劇t lifts 阻d pulley 蹄，Sci閡 r lift.a a.re 陸ntilied by th席四que structure that r酬mbles mul句，le scis陽m retra.c出sto redu曲M梆礎d 8X陰.nd問to m翩翩e heigl攏 幽幽翩 in Figure 5.
Figure 5: Genie GS”1530 刷刷 r lift with 鈾b b割e.15
W此icsl. m翩 翩e ha晦 田1且］ti 陽ti 但a a篇 either fit in.side 惆e 礎 由er or equal 鵬也io惚也at slide up agAilJBt one a:na也er to 總翩翩lheight. A且但.11111ple of a verti錦l m礎 lift Iss』own InFi .ire 6. Both 能lssor lifts and var舶d mast lifts have 也e option of mob心lty while ell!V就ed. If the lift h劇 a cab bl!i酶，lib the 咽ne i且 F地歸嗡 5，他刷出e lift c皿 dri喃
W祖ile d回事協(xié)d.
Pulley lifts 1幽也e comm仙”ill！’＼ ”腳，m t.oelev&te 他e locatlon 。.fthe響出且g plat陽m.
Cun回街 th晴 啞ly known pulley H島倒亂ilable has & sb,let侃 而ucture 如‘b劇院 A pulley 溢ft 創(chuàng)地not be mobile W洶l(fā)e ele喃，ted b帽刷晶e it b嗣a d岱坊ta! struct植re for a b制峙 楠ab.own in Fi .Ire 7.
All var悅陽I lifts 曲n be us創(chuàng)帆1tdoore. Due to t』.e small bodi帽 and fo的prints of vertical
溢疵，they c陸al陽all be uaed indoors 棉long 礎 they a.re not 伊a or di回el p陽惚ed.
抽油囂，fl曹帽嘟由她 ；叫.事 曲礎':t.11/'IJ8W·啪”回國國叫陸／m幅幅
Figure 6: Haulotte immobile vertical mast lift.6
Figure 7: JLG’s Liftpod that uses a pulley system.7
1.1.2 Vertical and Horizontal Lifts
Vertical and horizontal lifts are comprised of: articulating lifts, telescopic lifts, and telescopic articulating lifts. All vertical and horizontal motion aerial lifts achieve lifting by pivoting their boom(s), represented 回 a dashed red line in Figure 2(b). The booms of a vertical and horizontal aβrial lift are commonly referred to as the arm of the aerial lift. In addition, vertical and horizontal motion aerial lifts rotate at the base to provide access in all directions.
Figure 8(a) shows a rotation at the base around the vertical axis of an aerial lift commonly referred to as a slew movement. Figure 8(b) shows a rotation around a horizontal 缸is of an aerial lift commonly referred to as a luffing moveme時，which is the result from pivoting their booms.
Base
＋
1
TW
」
TL
(a) Slewing motion (overhead view) (b) Luffing motion (side view) Figure 8: Movements of vertical and horizontal motion aerial lifts.
An articulating aerial lift has two or more hinged boom sections that pivot at the hinges to elevate the working platform [1]. Figure 9 shows a truck-mounted articulating aerial lift with multiple boom sections.
Figure 9: Altec articulating aerial lift.
Aerial lifts with only one hinged boom section may be telescopic lifts or just a one boom aerial lift. Telescopic lifts can slew, luff, and their boom length can increase due to the
Figure 10: Genie S-60’sτ'ra.x cab base t.elesc呻ic aerial lift. 16
multiple s出tions wi也in e. boom. The c配，b-mount.ed telescopic li丘 in Figure 10 b幅a.sm刻ler
”ction extendi.Dg out of the top pa.rt of 出怠 boom to i.Dcrease the boom length.
白lesc ，pie 缸銳cul.at兇惡 aer圳 ］出s are 館ti，.ua創(chuàng)ng lifts and t.el，鄰copie 坦fts comb麗時－ Teleacopic 彼ticulating lifts have multiple hinged boom 錦ctior邸 傭a slew, luff 礎d 也heir
booms c陽were回e in length. F泡出e 11sho· 植 樹rial 時b with multiple booms and its
upper boom can 部pa.nd iD Ieng協(xié) due to the tel倒copic sectio出．
Fig11. 1re 11: Ge皿e Z-60β4 c也b b嗣e telescopic a.r秘culat兇g lift. 10
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