Validation of 2DOF Tracked Vehicle Model Due to Road Disturbance

JOURNAL OF MECHANICAL ENGINEERING ISSN 2165 - 8145 VOL. 1, NO. 3 NOVEMBER 2012 15Validation of 2DOF Tracked Vehicle ModelDue to Road DisturbanceZulkiffli Abd Kadir, Mohd Azzeri Md Naiem, Baizura Bohari, Khalid Abdul Jalil, MohdFazli Mohd YusoffDepartment of Mechanical Engineering, Faculty of Engineering,Universiti Pertahanan, Nasional Malaysia, Kem Sg. Besi, 57000 Kuala lumpurAbstract— This paper presents a validation of tracked vehicle,which consists of two DOF in vertical motion namely sprung massand unsprung mass. One source of road disturbance is consideredin this study. The two DOF tracked vehicle model is thendeveloped using Mathlab-Simulink. An instrumented test rig fortracked vehicle is developed to study the actual behaviors invertical direction. Simulation and experimental results namelysuspension working space is compared. From the validationresult, it can be seen that suspension working space obtained fromsimulation closely follow the suspension working space obtainedfrom experiment with minor error.Index Terms— tracked vehicle model, suspension working spaceTI. INTRODUCTIONhe performance of suspension system usually associatedwith the behavior of vertical motions namely sprung massand unsprung mass. The disturbance of suspension system isobtained from road surface irregularities and transferred it tounsprung mass. Suspension system is used to reduce themotion of sprung mass due to the motion of unsprung mass.The sprung mass performance usually related with thesuspension deflection or suspension working space.Tracked vehicle is designed to travel on the high frequencyand amplitude of road condition. This condition can cause theunwanted motion felt by the driver and reduce rideperformance of the tracked vehicle [1, 2, 3, 4]. Ride comfortin tracked vehicles depends on suspension working space invertical motion. Since tracked vehicle is designed to travel onhigh frequency of rough road profile [5], minimizing thesuspension deflection for the tracked vehicles is a must. Thereare several previous researches in reducing suspensiondeflection of tracked vehicle. The studies focus onimprovement of mobility system [6, 7] as well as to achievehigh comfort level during travelling [8].Zulkiffli Abd Kadir is with the Department of Mechanical Engineering,National Defence University of Malaysia. (e-mail: zulkiffli@upnm.edu.my)This paper is structured as follows: The first section consistsof introduction and the previous works on tracked vehicle,followed by equation of motion of 2-DOF tracked vehicle insecond section. The third section presents the results ofvalidation of the tracked vehicle model. The last sectioncontains some conclusions.II. TWO DOF TRACKED VEHICLE MODELUsually, a test rig is used to study the behavior of vehicledue to the variation in road profile which is commonly knownas ride analysis. The performance criteria in designing vehiclesuspension system are body acceleration, suspension workingspace and wheel acceleration. Performance of the suspensionsystem is characterized by the ability of the suspension systemin reducing those three performance criteria effectively. Thetest rig should be developed in such a way that closelyresembles the test rig of a real vehicle. The test rig should havethe ability to mount several different designs o actual trackedvehicle suspensions, able to perform a wide range of testswhich include variation in body loads and the frequency ofroad disturbance, and have the ability to perform the futuredevelopments.Figure 1(a) shows the drawing of tracked vehicle model.The model consists of sprung mass, unsprung mass,suspension system and road profile. The drawing of trackedvehicle model can be drawn as two degree-of-freedom asshown in Figure 1(b). The sprung mass is connected tounsprung mass. The unsprung mass is free to bounce verticallywith respect to the sprung mass through suspension system.The suspension system consists of spring and damperelements, as well as tyre is modeled as spring element with ahigh spring constant. The similar model was used by manyresearchers to reduce the unwanted motion in vertical directionusing controllable damper [9, 10].

JOURNAL OF MECHANICAL ENGINEERING ISSN 2165 - 8145 VOL. 1, NO. 3 NOVEMBER 2012 16Equations of motion in (1) and (2) for both sprung andunsprung masses can be rewritten due to the effect of springelement, damper element and road input:K ( Z Z ) C ( Z Z) m Z(3)susdusK ( Z Z ) K ( Z Z ) C( Z Z) m Z(4)trusussdsusuuwhere,K s = suspension spring stiffnessC d = suspension dampingZu = unsprung mass displacement(a)Zs = sprung mass displacementZr= road inputZ u= unsprung mass velocityZ s= sprung mass velocity(b)Figure 1: Tracked Vehicle ModelThe tracked vehicle model is then developed in Matlab-Simulink based on mathematical equation that has beenderived and discussed. The relationship of unsprung mass,sprung mass and road profile is illustrated in Figure 2. Input ofthe model is road profile with maximum amplitude of 0.06mand frequency of 14.3Hz as presented in Figure 3. Theparameters of the 2-DOF tracked vehicle are shown in Table 1and some of the values of parameters are assumed. Thebehavior of suspension system namely suspension workingspace is compared with the experimental result.From the Figure 1(b), the force on sprung mass is written as:Fs F m Z(1)dsswhere,F s = spring forceF d = damper forcem s = sprung massZ s = sprung mass accelerationThe force balance on unsprung mass can be written as:Ft F F m Z(2)sduuwhere,F t = tyre forcem u = unsprung massZ u= unsprung mass accelerationFigure 2: Tracked vehicle model in Matlab-Simulink

JOURNAL OF MECHANICAL ENGINEERING ISSN 2165 - 8145 VOL. 1, NO. 3 NOVEMBER 2012 17The dynamic response characteristics of a test rig that includesuspension working space and road profile can be verifiedusing actual data through road disturbance procedure. Inexperimental work, the data of suspension working space isfiltered using low pass filter while the simulation is completedfor a period of 3.5 seconds. The validation result can beobtained in Figure 5. It can be seen that the magnitude of bothresults are similar with maximum magnitude of 0.015m. Thedifference value in magnitude for both results might be due tothe effect of DC motor as road input in experimental test. Itcan be said that the model is valid in representing actual smallscaledsystem of tracked vehicle.Figure 3: Road InputIII. VALIDATION RESULTThe measurement computing is installed into trackedvehicle test rig to obtain the experimental data to evaluate thesuspension performance in terms of suspension working spaceand acceleration of road input. The measurement computingconnected with several types of sensors namely accelerometersensor to measure the road profile and LVDT to measure thesuspension deflection. DaisyLab software is used as the realtime data collecting and show the result as a graph. Theinstallation of the measurement computing and transducers tothe tracked vehicle test rig can be obtained in Figure 4.Figure 5: Validation resultTABLE ITHE NUMERICAL VALUES OF THE TRACKED VEHICLE MODELSymbol Quantity ValueKs Spring stiffness 37500Cd Damper stiffness 1000ms Sprung mass 10mu Unsprung mass 5Kt Tyre stiffness 30000There are several potential applications of the tracked vehicletest rig that has been developed such as able to investigate thetracked vehicle response due to road disturbance as well asability to study the damping behaviors of suspension system.For the future research, the test rig can be used to perform astudy on the application of a controllable damper in reducingthe vibration and unwanted motion in vertical.Figure 4: Instrumented test rigIV. CONCLUSIONSA 2-DOF tracked vehicle model which consists of sprungand unsprung masses has been developed in Mathlab-Simulink. An instrumented test rig has been developed toverify the tracked vehicle model with the two types oftransducers and measurement computing system. One road

JOURNAL OF MECHANICAL ENGINEERING ISSN 2165 - 8145 VOL. 1, NO. 3 NOVEMBER 2012 18disturbance test has been considered as the input and resultcollected from the test was set as the basic target of the modelverification. The result of model validation shows that thebehavior of suspension working space of both simulation andexperimental results are similar in terms of the maximummagnitude.REFERENCES[1] Ming-ming, D. and Liang, G., “Simulation Of NonlinearTracked Vehicle Suspension With ADAMS”, Journal ofBeijing Institute of Technology, ISSN:1001-0645.0.2005-08-003, 2005.[2] Sankar, S., Dhir, A. and Shankhla, V., “Simulation AndField Testing Of Tracked Vehicle Suspension Dynamics”,Proc. ASME Winter Annual Meeting, Atlanta, Georgia,U.S.A, pp. 423–436, 1–6 December , 1991.[3] Rakheja, S., Afonso, M. F. R. and Sankar, S., “DynamicAnalysis Of Tracked Vehicles With Trailing ArmSuspension And Assessment Of Ride Vibrations”,International Journal of Vehicle Design, Vol.13, No.1,1992.[4] Yamakawa, J. and Watanabe, K., “A Spatial MotionAnalysis Model Of Tracked Vehicles With Torsion BarType Suspension”, Journal of Terramechanics, Vol. 41,Issues 2–3, pp. 113–126, 2004.[5] Ryu, H. S., Bae, D. S., Choi, J. H. and Shabanain, A. A.,“A Compliant Track Link Model For High-Speed, High-Mobility Tracked Vehicles”, International Journal forNumerical Methods in Engineering, Vol. 48, Issue 10, pp1481–1502, 2000.[6] Ferretti, G. and Girelli, R., “Modelling And Simulation OfAn Agricultural Tracked Vehicle”, Journal ofTerramechanics, Vol. 36, Issue 3, pp. 139–158, 1999.[7] Bodin, A., “Development Of A Tracked Vehicle To StudyThe Influence Of Vehicle Parameters On TractivePerformance In Soft Terrain”, Journal of Terramechanics,Vol. 36, Issue 3, pp 167–181, 1999.[8] Dhir, A. and Sankar, S., “Analytical Track Models ForRide Dynamic Simulation Of Tracked Vehicles”, Journalof Terramechanics, Vol. 31, Issue 2, pp 107–138, 1994.[9] Prabakar, R. S., Sujatha, C. and Narayanan, S., “StationaryResponse Of A Quarter Car Vehicle Model WithMagnetorheological Damper”, Int. J. of Vehicle SystemsModelling and Testing,Vol. 3, No.4, pp. 251 – 270, 2008.[10] Ubaidillah, Hudha, K. and Jamaluddin, H., “SimulationAnd Experimental Evaluation On A Skyhook Policy-BasedFuzzy Logic Control For Semi-Active Suspension System”,Int. J. of Structural Engineering, Vol. 2, No.3, pp. 243 –272, 2011.Zulkiffli Abd Kadir received his BEng and MSc in theDepartment of Automotive Engineering, Universiti TeknikalMalaysia Melaka. He is currently attached with the NationalDefence University of Malaysia. His research interests includetyre modeling, evaluation of vehicle dynamics and control.Mohd Azzeri Md Naiem received his both BEng inMechanical Engineering and MEng in Mechanical Engineering(Marine Technology) from Malaysia University of Technology(UTM). He is currently attached with the National DefenceUniversity of Malaysia. His research interests include marinetechnology system and ship maintenance system.Baizura Bohari received her BEng (Hons) in AerospaceEngineering from Universiti Putra Malaysia and completed herMSc of Aerospace Technology at University of Sussex, UK.Her research interests include CFD modelling on aircraftengine, aerodynamics analysis of a wind turbine andevaluation of impact dynamics and kinetic energy projectiledesign.Khalid Abd Jalil was born on 1963 at Johor, Malaysia. Lt ColIr Khalid Abd Jalil received his BSc in MechanicalEngineering from Han Yang University, Seoul Korea andcompleted his Master in Airworthiness and Aircraft Safetyfrom ENCISA/ENCA, Toulouse, France. He served in the AirForce since 1989 as an engineer and was seconded to NationalDefence University, Malaysia (UPNM) as academics since2004. He has more than 15 years experience in themaintenance of military aircraft and as a lecturer; he is alsoactively involved with research work. He currently works as anAssociate Professor in Faculty of Engineering, and held theposition as Deputy Dean, Faculty of Engineering. He is aprofessional engineer registered with the Board of EngineersMalaysia and he research interests is on small arms ballisticimpact on soft body armor.Mohd Fazli Mohd Yusoff received his BEng from UIAM inMechatronic Engineering. Then he obtained his MSc inEngineering from Australia National University (ANU). He iscurrently attached with the National Defence University ofMalaysia. His research interest is in intelligent control systemand evaluation of dynamic system.