Validation of 2DOF Tracked Vehicle Model Due to Road Disturbance

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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
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Validation of 2DOF Tracked Vehicle Model Due to Road Disturbance

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