Journal of Engineering Science and Technology Review 10 (3) (2017) Research Article

Transcription

1 Jesr Journal of Engineering Science and Technology Review () (7) 97- Research Aricle Analysis on Wheel Ground Conac Load Characerisics of Unmanned Off-road Vehicles Feng Ren,,, Longhai Li, hengying Jiang *, Tao Song, Xun Gong, Yaowu Shi and Boliang Liu 4 School of Engineering, Changchun Normal Universiy, Changchun,China School of Mechanical Science and Engineering, Jilin Universiy,Changchun,China Jiangsu LiuGong Machinery Co., Ld, Jiangsu 5457, China 4 School of Engineering, Universiy of Torono, Ooario M5SA,Canada JOURNAL OF Engineering Science and Technology Review Received April 7; Acceped July 7 Absrac The wheel ground conac load characerisics of unmanned ground vehicles are an imporan foundaion for vehicle design, srucural parameer opimiaion, off-road performance evaluaion, and conrol sraegy formulaion. The load characerisics of unmanned ground vehicles are mainly invesigaed based on radiional vehicle erramechanics heory, which canno reflec wheel ground conac. This sudy proposed a model inegraed wih qualiaive heoreical analysis and quasi-quaniaive simulaion o evaluae wheel ground conac load characerisics during he off-road movemen of unmanned vehicles. Predicion and es models of sysem wheel conac load characerisics were buil by muli-physical field coupling analysis. Flow and power characerisics during unilaeral seering were discussed sysemaically hrough erramechanics heory. The accuracy of he models was verified by experimens. Resuls show ha changes in he ire load affec he average sress on he ground conac surface of ire, which leads o he forward graviy cener of he enire machine. The opimal combinaion of srucural parameers under dynamic working condiions of he unmanned vehicles is deermined based on muli-physics coupling analysis model o opimie he srucural design. The load pressure of he sysem reaches 9.5 MPa in he acceleraed sar-up phase, and he error of simulaion and es resuls is wihin %. This sudy provides ools for heoreical and simulaion analysis for developmen of he opimied srucure design and conrol sraegy formulaion of unmanned ground vehicles. Keywords: Unmanned vehicles, Dynamic characerisics, Muli-physics coupling analysis. Inroducion Operaing in a dangerous environmen is he bounded duy of unmanned vehicles, raher han human beings. Unmanned vehicles are necessary in dangerous and complicaed errain condiions, such as nuclear power plans wih high radiaion levels, dangerous disaser assisance sies, haardous geological mining, ransporaion of maerials and ammuniion for army forces in mounainous areas, and environmenal invesigaion of balefield. Wih increasing applicaion of unmanned plaforms, research on relaed echnology has considerably progressed; in paricular, research on he lunar rover and Mars explorer has achieved saisfacory resuls. In foreign counries, Carnegie Mellon Universiy, Sanford Universiy, and Massachuses Insiue of Technology conduced exensive research in his field [-]. Miliary ground unmanned plaforms in China have been increasingly invesigaed due o serious echnical barriers and blockade. The key echnology research on miliary ground unmanned plaforms was performed o mee he requiremens of modern warfare. Relaed echnologies have been developed in Harbin * address: rfcus@6.com ISSN: Easern Macedonia and Thrace Insiue of Technology. All righs reserved. doi:.5/jesr..4 Universiy, Jilin Universiy, hejiang Universiy, Beijing Universiy of Technology, and Weapon for unmanned plaforms. However, exising research was performed under ideal condiions wihou simulaing he real balefield environmen, resuling in significanly obsolee resuls in relaion o he demands. Mos sudies on unmanned mobile vehicles in he srucural environmen are sill in he wodimensional obsacle avoidance sage, and hese vehicles show insufficien saisfacory adapive capaciy in D nonsrucural errains. Therefore, many scholars have invesigaed he basic heories of unmanned ground vehicles for miliary use. Wong sudied he basic heory of ground mechanics and esablished a basic mechanical model of slipseering rack-laying vehicles [4]. Yi e al. invesigaed he navigaion algorihm of slip-seering robo wih four wheels [5]. Helmick e al. sudied he pah planning problem of unmanned vehicles by using he slip-compensaed model [6]. These sudies focused on he load characerisics of wheelground conac. Hence, he load characerisics of unmanned vehicles during off-road walking mus be invesigaed.. Sae of he ar American scholars firs sudied he basic vehicle ground ineracion heories. Professor Bekker esablished he basic heory of ground mechanics, heoreically invesigaed he

2 Journal of Engineering Science and Technology Review () (7) 97- sinkage and driving resisance of vehicles, and sysemaically evaluaed he ire ground ineracion by esing. This heory provides he foundaion for analying he load characerisics of vehicles and ground by applying mechanical mehods. However, his heory only focuses on he ire ground poin conac, which significanly differs from he real load characerisics [7]. Professor J.Y.Wong, a Canadian Chinese researcher, deduced he rack-laying vehicle ground ineracion based on fricion heory and analyed he seering characerisics of vehicles under differen urning radii [8]. This sudy only focused on he hard surface and assumed he lack of surface deformaion during he ire ground conac. Bruce Maclaurin e al. examined he slip behavior of rack-laying vehicles by using a magic formula and proved he feasibiliy of he magic formula for rubber ires o slip seering vehicles [9-]. However, hey did no analye he load characerisics of wheeled vehicles. The load characerisics of racked vehicles are compleely differen from hose of wheeled vehicles. Jesus morales e al. discussed he load characerisics of racked vehicles during slip seering [-] and analyed he sysem load characerisics hrough pressure feaures. However, hey quaniaively analyed a single parameer and did no examine he load characerisics of muliple parameers. Lei e al. from he Beijing Insiue of Technology performed a simulaion analysis on he seering characerisics of armored racked vehicles [] bu did no analye he influence of ground parameers on he performance of he enire machine. Karafiah analyed he seering and slip performances of ires on sof surface bu did no analye he coupling relaionship beween he ground and srucural parameers of he enire machine. The ire soil mechanical model proposed by Darius e al. revealed he complicaed ineracion beween he ire and soil. Hence, he ire soil mechanics for ground and unmanned off-road engineering vehicles ha frequenly operae in differen environmens mus be analyed [4-5]. Saviski, D e al. analyed he ire ground conac feaures of wheeled offroad vehicles and invesigaed he slip characerisics of vehicle ires on nonsrucural road surface [6-]. This sudy provided a basis for invesigaion of he ire ground conac feaures of unmanned vehicles. This research focuses on he Mars rover and lunar rover, which are generally small and ground unmanned plaform weigh beween.5-. The weigh of unmanned ground vehicles generally ranges beween.5-. The compression behavior and shear properies of he plaform ground conac significanly differ from hose of robos, such as moon rovers. Few sudies are repored regarding he load characerisics during he wheel ground ineracion of unmanned ground vehicles. Unmanned vehicles operae in dangerous environmens, where slippage and sinkage frequenly occur, and canno be sudied using he radiional heory of ground mechanics, which is he Bekker formula of pressure resisance. Thus, a mehod for heoreical sudy and online predicion of wheel ground conac characerisics mus be developed. A heoreical model for calculaing wheel ground conac load characerisics was consruced based on he ground mechanics and muli-body dynamics, and he corresponding influencing facors were analyed. The influences of ground parameers on he performance of he enire plaform, especially on he srucural parameers of he machine, were analyed. A muli-physics coupling analysis model was esablished for he enire plaform. This model could be an effecive ool for research and developmen. The res of his paper is organied as follows. Secion describes he prerequisies for kinemaic model analysis of unmanned ground vehicles and esablishes a heoreical analysis model. Secion 4 summaries he pressure, flow, and a power characerisic during unilaeral seering based on he muli-physics coupling analysis model and verifies hem hrough experimen. Secion 5 provides he conclusions.. Mehodology. Theoreical model Several hypoheses are drawn when he kinemaic model of unmanned vehicles was esablished: () Slippage and slide are ignored for unmanned vehicles operaing on firm ground. () A cerain relaionship exised beween he shear sress and shear displacemen. The iniial posiion is seleced a he ire ground conac poin. () The shear sress a any ire ground conac poin is opposie wih he slippage velociy of he poin. The kinemaics analysis of he vehicle during urning is shown in Fig.. Poin O is he insan roaion cener of he vehicle. In his sudy, he righ fron wheel of he vehicle was analyed as an example. The relaive coordinae sysem of he righ fron wheel is xy, and he cener of he righ fron wheel is origin O. On he Y direcion, he longiudinal offse of CG and OO is s. Fig.. Roaional kinemaics of he vehicle When he unmanned vehicles roae around O a he angular velociy Ω, he velociy a he axial cener of he righ fron wheel O is: ''' '' B L VO = R Ω = ( R + ) + ( so + cy) Ω () ''' L VOx = R Ω sin ( ) α = So+ c () y 98

3 Journal of Engineering Science and Technology Review () (7) 97- The roaional angular velociy of he righ wheel is ω. The slip velociies of he projecion poin ( y ) of O on he wheel ground conac surface along y and x are: '' Vx = ( R + B ) Ω rωo () Vx = ( L S ) O+ cy Ω (4) Any poin (, ) x y on he lef fron wheel ground conac surface was analyed. The longiudinal and ransverse x, y in relaive o O can be velociy componens of ( ) expressed by xω and yω, respecively, because he wheel roaed around O a he angular velociy Ω. x, y In summary, he shear displacemens of poins ( ) and ( x, y ) on he lef and righ fron wheels are: v l ( )( y ) v j d o rw jo v l v ( ( y) j d o ) rw jo = = v l j v d ( )( y ) jo o rw j o v 4 j d o v l 4 ( )( y4) rw When he vehicle is skid-seering around O a he angular velociy Ω, he roaional velociies of ceners for four wheels around O are: V ''' O R '' B L V '''' ( R ) + ( so + cy) O R ''''' V = Ω = O R '' B L '''''' ( R + ) + ( + so + cy) V R O 4 '' B L ( R + ) + ( so + cy) B L ( R - ) + ( + s + c ) '' o y " where R (m) is he radius of roaion of poin O " around he insananeous seering cener, R (m) is he radius of roaion of poin O around he insananeous '''' seering cener, R (m) is he radius of roaion of poin O '''' around he insananeous seering cener, R (m) is he radius of roaion of poin O4 around he insananeous seering cener, Ω ( rad / s ) is he roaional angular velociy of he skid-seering vehicle around he '' insananeous seering cener, R (m) is he radius of roaion of poin O around he insananeous seering v (5) (6) cener, c y (m) is he longiudinal offses of he geomeric cener and he cener of graviy of he vehicle, B (m) is he read of he skid-seering vehicle, L (m) is he wheel base of he skid-seering vehicle, and S O is he longiudinal offse disance beween he cener of graviy CG and he connecion line of he insananeous seering and exernal ire roaional ceners. Based from he above heoreical model, he key parameers of he enire machine are conneced wih he ground characerisic parameers, and he dynamic characerisics of he enire machine can be analyed hrough differen ground parameers, which provide he heoreical basis for he nex simulaion analysis.. Esablishmen of he simulaion model A simulaion model of he enire hydraulic sysem was consruced hrough AMESim sofware (Fig. ) o accuraely analye he dynamic performance of unmanned vehicles during off-road driving. The muli-body kinemaics model of he enire machine was esablished hrough LMS Moion sofware (Fig. ). The join simulaion was realied by he communicaion inerfaces of he wo sofware, and he muli-physics coupling analysis of he enire machine was implemened. The simulaion parameers, including cornering coefficien (.68), raed speed of he engine (4r/min), dead load of he vehicle (6Kg), variable pump, plaform read ( mm), and CG heigh (784mm), are mainly lised in Table. The mechanical characerisics of he enire machine are ransmied hrough ires and ground. The major parameers of ire and ground for muli-body kinemaics modeling are shown in Table. Table.. Main parameers of he muli-physics coupling analysis model Parameers (uni) Values Dead load of he machine (kg) 6 Moor displacemen (ml/r) 5/56 Tread (mm) Wheelbase(mm) 5 Secion widh of ire (mm) 7 Diameer of ire (mm) 8 Heigh of CG (mm) 784 Heigh of he machine (mm) 5 Mass of swing arm (kg) Table.. model Parameers Main parameers of he muli-body kinemaics Values Radius of ire /mm 45.5 Verical damping coefficien /kg/s 85 Rolling resisance coefficien. Fricion coefficien.65 Cornering siffness /m*kg/s/rad 54 Verical siffness /N/m

4 Feng Ren, Longhai Li, hengying Jiang, Tao Song, Xun Gong, Yaowu Shi and Boliang Liu/ Journal of Engineering Science and Technology Review () (7) 97- Fig.. Simulaion model of he raveling hydraulic sysem Fig.. Muli-body kinemaics model of he vehicle Fig. 4. Simulaion curves for he fron pump of he raveling hydraulic sysem 4 Resul Analysis and Discussion In he es, he working condiions of he unilaeral seering are: he prooype is empy, he engine speed is 4 r/min, he hard ground is hard, he righ wheel is cu off a he conrol por of he pison pump, and he inpu signal of he pison pump corresponding o he righ wheel is no inpued. All he condiions in he simulaion and es resuls are compleed o ensure he effeciveness of he simulaion resuls. Pressure, flow, and power characerisic curves for he walking fron and rear pumps of he unmanned vehicle under unilaeral seering condiions are shown in Figs. 4 and 5. Fig. 5. Simulaion curves for he rear pump of he raveling hydraulic sysem

5 Journal of Engineering Science and Technology Review () (7) 97- A quasi-quaniaive analysis on dynamic power flow characerisics of he unmanned vehicle can be realied by he simulaion model. A prooype is used in he es o verify he validiy of he muli-physics coupling analysis model. The simulaion and res resuls will be analyed in deail. 4. Tes To es he raveling hydraulic sysem, pressure sensors were insalled on he variable pump, oil inle and oule of he walking engine, oil pump oule and he wo sides of he variable oil cylinder o measure he pressure a differen poins of he raveling hydraulic sysem. The sensor channels are lised in Table, and he disribuion of sensors is shown in Fig. 6. Fig. 7. Tes curves for he fron pump of he raveling hydraulic sysem Table.. Sensor channels No. of channels Tes poin No. of es poin Sensor range Channel Channel Channel 4 Channel 5 Channel 6 Channel 7 Channel 8 Channel 9 Channel Channel Channel Channel fron pump por B rear pump por A rear pump por B Pressure of he fron pump X Pressure of he fron pump X Pressure of he rear pump X Pressure of he rear pump X por Y muliandem valve enrance Oupu flow of he fron pump Oupu flow of he rear pump Oupu flow of he working pump Fig. 6. Disribuion of sensors P P P4 P5 P6 P7 P8 P9 P Q Q Q -5 MPa -5 MPa -5 MPa -5 L/min -5 L/min -5 L/min Fig.8. Tes curves of he rear pump of he raveling hydraulic sysem The pressure, flow, and power characerisics of he unmanned vehicle during he iniial acceleraion, sable walking, and braking sages are shown in Figs. 4, 5, 7 and 8. The comparison resuls are shown in Table 4. Table 4. Comparison beween he simulaion and es resuls under unilaeral seering condiions Operaing Tes Simulaion Comparison iems condiions resuls resuls Maximum pressure of he high-pressure loop Iniialiaion acceleraion sage Sable walking sage Braking sage /MPa Time of he maximum pressure of he highpressure loop /s Flow rise ime /s..7 Maximum power /Kw Pressure mean of he high-pressure loop in he fron pump /MPa Pressure mean of he high-pressure loop in he rear pump /MPa Average flow /L/min Average power / Kw 8.9. Maximum pressure of he high-pressure loop /MPa Braking ime consumpion /s..4 The es resuls are shown in Figs. 7 and 8. The major differences beween he simulaion and es curves under unilaeral seering condiions are: () he es curve showed small flow in he rear pump, and he simulaion curve presened no flow. In he es, he rear pump will be locked under unilaeral seering condiions and

6 Journal of Engineering Science and Technology Review () (7) 97- causes pump moor. The variable pump is driven by he inernal wheel and serves as he moor, hereby producing high-pressure oil and small flow in he hydraulic loop a he rear pump por B. The corresponding power is called he parasiic power and is compensaed by he driving power of he exernal wheel o he dependen variable pump. However, he simulaion model canno simulae he pump moor of plunger pump. () In he simulaion curve, he pressure a he high-pressure por of he fron por is higher han he es resul, which is caused by he poor accuracy of wheel ground mechanical parameers. No naional sandard on ire of unmanned vehicles exiss and no delivery es is needed. Therefore, his sudy has insufficien effecive daa on parameers, such as laeral siffness. This sudy mainly focused on he ranges of ire parameers in he auomobile indusry and relaed empirical values. 5. Conclusions Flow, pressure, and power characerisics of he sysem were analyed based on he wheel ground conac mechanical model by combining he heoreical analysis, muli-physics coupling analysis and esing o evaluae he dynamic performances of unmanned ground vehicles and idenify he load characerisics during wheel ground ineracion. The following conclusions are drawn: () Based on he heoreical analysis of unmanned vehicles, he sliding speed of he enire machine is closely relaed o read and wheel base. During he design process, he load characerisics during he skid-seering sage of he plaform can be qualiaively analyed by he esablished model. () The simulaion analysis of unmanned vehicles showed ha he rear pump caused pump moor under unilaeral seering condiions. Key aenions mus be provided for he sysem maching during he design process. () According o he enire machine es, he simulaion resuls of muli-physics coupling analysis model are very close o he es resuls in erms of numerical values and change rend. The simulaion resuls are applicable for sudy of unmanned vehicles and reduce huge labor requiremen and maerial consumpion. The wheel-ground conac load characerisics of unmanned ground vehicles are invesigaed by using heoreical, simulaion, and es mehods. The corresponding muli-physics coupling analysis model is esablished, which is an effecive ool for he design of wheeled unmanned ground vehicles. However, verifying he simulaion resuls of oher ypical road surfaces and soil environmens is necessary because he wheel ground conac load characerisics of unmanned ground vehicles are sensiive o road surface and soil environmen. Acknowledgemens This work was suppored by he Naional Science Foundaion of China (Gran No ) and he Naural Science Foundaion of Changchun Normal Universiy. This is an Open Access aricle disribued under he erms of he Creaive Commons Aribuion Licence References.Nilanjan Chakrabory and Ashiava Ghosal., Kinemaics of wheeled mobile robos on uneven errain. Mechanism and Machine Theory, 9(),4,pp N. Seegmiller, F. Rogers-Marcovi, G. Miller, and A. Kelly., Vehicle model idenificaion using inegraed predicion error minimiaion. Inernaional Journal of Roboics Research, (8),,pp.9-9..Mahmoud Tarokh, Huy Dang Ho, and Anonios Bouloubasis., Sysemaic kinemaics analysis and balance conrol of high mobiliy rovers over rough errain. Roboics and Auonomous Sysems, 6(),,pp J.Y.Wong., Theory of Ground vehicles, rd ediion. Hoboken: Wiley Press, America,,pp.-. 5.Jingang Yi, Hongpeng Wang, Junjie hang, Dehen Song, Suhada Jayasuriya, Jingai Liu., Kinemaic modeling and analysis of skidseered mobile robos wih applicaions o low-cos inerial measuremen uni based moion esimaion, IEEE Transacions on Roboics, 5(5),9,pp D. M. Helmick, S. I. Roumeliois, Y. Cheng, D. S. Clouse, M. Bajracharya, and L. H. Mahies, Slip-compensaed pah following for planeary exploraion rovers, Adv. Robo., (),6,pp Bekker MG., Off-road locomoion: research and developmen in erramechanics. Michigan: The Universiy of Michigan Press, 96, pp J.Y.Wong, CHIANG C F., A general heory for skid seering of racked vehicles on firm ground. Proceedings of Insiuion of Mechanical Engineers, Par D: Journal of Auomobile Engineering, 5(),,pp Bruce maclaurin., A skid seering model using he magic formula. Journal of erramechanics, 48(4),,pp Ding Shihong and Sun Jinlin., Direc yaw-momen conrol for 4WID elecric vehicle via finie-ime conrol echnique.nonlinear dynamics,88(),7,pp clarke, M. and Blanchard, T., Developmen of a Conrol Sysem for a Skid-Seer Amphibious Vehicle. In: Proceedings of TAROS, Plymouh, Unied Kingdom: Inelligen Roboics Group,,pp Jesus Morales, Jorge L. Marine, Alfonso J.Garcia-Cereo, Salvador Pedraa., Power consumpion modeling of skid-seer racked mobile robos on rigid errain. IEEE Transacions on Roboics. 5(5),9,pp YANG Lei, MA Biao,LIHe-yan, CHEN Bao-rui., Simulaion of seering characerisic for hydrosaic drive racked vehicle. Binggong Xuebao,(6),,pp E.Mohammadpour, M.Naraghi., Posure sabiliaion of skid seer wheeled mobile robos. In: IEEE conference on roboics, Auomaion and Mecharonics, Singapore, Singapore: IEEE,,pp Darius Ei Pebrian, Ami Yahya., A new muli-purpose 4WD prime mover for oil palm planaion mechanisaion. Inernaional Journal of heavy vehicle sysems, 9(),,pp Saviski,D, Ivanov, V., Augsburg, K., Barber, Knauder, B., ehener, J., The new paradigm of an ani-lock braking sysem for a full elecric vehicle: experimenal invesigaion and benchmarking. Proceedings of he Insiuion of Mechanical Engineers Pard-Journal of Auomobile Engineering, (),6,pp Osinenko, P.V., Geissler, M., Herliius, T., A mehod of opimal racion conrol for farm racors wih feedback of drive orque. Biosys. Eng, 9(),5,pp..

7 Journal of Engineering Science and Technology Review () (7) 97-8.Ning Sun,Yongchun,Fang He Chen, Tracking conrol for magneic-suspension sysems wih online unknown mass idenificaion. Conrol Engineering Pracice, 58(),7,pp Daher N, Ivanysynova M., Yaw Sabiliy Conrol of Ariculaed Frame Off-highway Vehicles via Displacemen Conrolled Seerby-wire. Conrol Engineering Pracice, 45(),5,pp Sallmann M J, Els P S., Parameeriaion and modelling of large off-road yres for ride analyses: Par -Parameeriaion and validaion of yre models. Journal of Terramechanics, 55(7), 4,pp Ji-wung Choi, Member, IEEE, and Kalevi Huhala., Consrained Global Pah Opimiaion for Ariculaed Seering Vehicles. IEEE Transacionson Vehicular Technology. 65(4), 6, pp