Getting started
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1. simulation process parameters Solver options solver Type of solution BOF ABM D Null space method NSM RKA 7 Range space method RS nn Simulation time 12 000 a step size for animation and data storage 0 01 Error tolerance 1E 0008 Delay to real time simulation Computation of accelerations and reaction forces CG iterations CG error 0 1 Use threads Number of threads 4 Fig 47 Setting simulation time 4 Set simulation time 12 s on the Solver Simulation process parameters tab and run simulation by the Integration button Universal Mechanism 6 0 29 Getting started UM Caterpillar Average tension KH Preload kN 0 10 20 30 40 50 60 Fig 48 Average track tension vs preload Let us discuss the main result of the test dependence of the average track tension on the preload in bushings Fig 48 The plot has two straight sections the first section tension 1s lower 35 KN when the load on the tension device 1s less than the tension spring preload and the second section when the tension spring compressed In our model the preload of the tension spring is 50 KN Angle of crank rotation mrad 10 20 30 40 Fig 49 Force in tension spring left and angle of the tension crank rotation right vs bushing preload These conclusions are confirmed by the plots in Fig 49 5 Now the preload in bushings can be evaluated from Fig 48 by the desired track tension Let the2. 10 Road arm orientation As it is shown in Fig 2 five road arms has a backward orientation but the front one which has a forward orientation So far all arms in our model are oriented forward The orientation is defined by the identifier rear_arm 1 The value 1 corresponds to the backward orientation To set the necessary values of this identifier in the subsystems set rear_arm 1 in the cell in Fig and press Enter Uncheck the assignment of the new value in the lower row Fig 10 As a result orientation of five road arms will be changed Fig 11 Universal Mechanism 6 0 9 Getting started UM Caterpillar Fig 11 Suspension with modified parameters Universal Mechanism 6 0 10 Getting started UM Caterpillar 1 5 Adding sprocket Rollers Sprocket Idler Frofile Estimated radius Go N sprocketteeth sprocket Track step ratio 0 0159691 Mor 0547835 0 01 70649 0 031 5054 0 01 4493 0 0315034 0 01 4493 0 01 70649 Fio 13 Tooth profile Open the Parameters Sprocket tab Fig 12 1 Assigna tooth profile by the built in curve editor e open the editor by the 4 button Fig 13 e read the preliminary created file with profile IIyrb k UM W bin Caterpillar Profiles Sprocket1 spf by the amp button 2 Set number of teeth t t ratio and geometric parameter width of the wheel the vertical and longitudinal coordinates of the wheel center Fig 12 3 Use the button to
3. Track Rollers Suspension alpha_stat 20 t stat 0 fodyn 110 rear_arm 1 ni Bight tack road_arm o hi Lefttrack Bogie1 _road_arm Letttrack Bogie _road_arm Left track Bogie3 l_road_arm Left track Bogie4d l_road_arm Left track Bogie5 l_road_arm Lefttrack Bogie6 I_road_arm i oa OK Cancel Cancel i Fig 9 Assignment of numeric values for identifiers in subsystems 3 Now some parameters of the suspension must be modified Open the Identifiers Suspension tab of the wizard Fig 8 Set the length of the torsion arm 0 36m the identifier _road_arm All the suspension subsystems contain identifiers with the same name a window appears in which the user must check the subsystems for which the identifier value will be changed by the new one Fig 9 By default the new value is assigned to all identifiers of the same name We will not change the default values of identifiers which define the position of the suspension in static state alpha_stat as well as the static and dynamic travel of wheels f_stat f_dyn Chapter 18 Sect Torsion bar suspension pai Identifiers of the same name XK Letttrack rear_arm 1 i Righttrack rear_arm 1 ww Lefttrack Bogiel rear_arm 1 w Lefttrack Bogie rear_arm 1 w Letttrack Bogies rear_arm 1 CT wi Letttrack Bogie4d rear_arm Wi Lefttrack Bogie5 rear_arm i1 Lefttrack Bogieb rear am eli _ ______j liana OK Cancai cel Fig
4. Vertical harmonic loading Fig 39 List of configurations for tests 2 2 Auxiliary tests The auxiliary tests are used for preparing the model to analysis of its dynamics In particular one of such the tests is used for getting a desired tension of track chains 2 2 1 Test equilibrium Consider an auxiliary test Equilibrium as the first dynamic test with the TV model The objective of the test is to compute positions of bodies near the equilibrium state because the positions of bodies after the automatic generation of tracks do not correspond to the TV equilibrium Solver Identifiers inital conditions Object variables gt H 1 eiker oger Latest identifier file FaBHoBecHe par Whole list Mame Expression Value Comment a xbogie 0 775 rear_arn Rear 1 offre wquide 0 04 quide_ir 1 hquide 0 1 roacwh 0 335 Radius of roa wroadwt 0 3 Width of road road 0 25 road_ 0 36 mi Length of fodyn 110 rom Dynami p_stat stat r mm Static m ahaa Ad fala Obata an Fig 40 Modification of parameters Before start of the test the user must verify numeric values of identifiers and their correspondence to the real values In particular one of the important parameters is the value static load on a road wheel which is specified by the identifier pstat Value of this parameter depends on the track tension Let the design value of this parameter be 7 KN Setting this value to the identifier ca
5. DI IT ta Ti TI 44 Type amp dof Geometry Coordinates Body 1 Body 2 Te Visual assignment Translation o o Y yo e u u y el Frasi Fig 36 Vertical shift of TV model To shift the model upwards open the joint specifying coordinates of the TV hull relative to the SCO and set the vertical coordinate in the Geometry Body1 tab Fig 36 The result is shown in Fig 37 Fig 37 Links are located on zero vertical level Now we can start dynamic tests with the developed model of TV Universal Mechanism 6 0 23 Getting started UM Caterpillar Universal Mechanism 6 0 24 Getting started UM Caterpillar 2 Simulation of TV dynamics 2 1 General remarks Computer model of TV has usually a large number of degrees of freedom and requires of high performance computers For instance the developed model of TV has 1332 degrees of freedom It is recommended to use computers with multi core physical processors and apply the multithread solver realized in UM6 0 As a rule the model of TV is fully parameterized It is important that some of the identifiers cannot be changed in the simulation module and requires regeneration of the track models in UMInput These are identifiers which influence the track chain and sprocket geometry wheel radii coordinates of wheel centers track height Object simulation inspector AYA Information Tools Tracked vehicle Soler Identif
6. E NERI VE OSE TE EVES eee ERS EMITS ai Sa Fig 3 Adding new subsystem Caterpillar 1 Run UMInput exe and create a new UM object by File New object menu command or by the L button on tool panel 2 Save the model by the File Save as command or by the button 3 Add a track as a subsystem of the Caterpillar type e select the Subsystems item in the element list e click the right mouse button on this item and select the Add element to group Subsystems Caterpillar Fig 3 As aresult the Track wizard appears in the object inspector 4 Rename the subsystem to Left track Universal Mechanism 6 0 6 Getting started UM Caterpillar 1 3 Track structure CUOIO OOLUULLLLLLLLIEELLECOOTE ka NamelLetttack a AP 5 Type amp Caterpillar Comments T ext attribute C Edit subsystem Parameters Position Identifiers Identifier Bussi Rollers sprocket Idler Structure Track Suspension sprocket position Track position Lett O Right Suspension subsystems E DA Rollers o DA Track links 108 gt Fig 4 Parameters of track structure Open the Parameters Structure tab of the wizard Fig 4 1 The modeled TV has a torsion bar suspension with six road wheels Each of the wheels 1s described by a standard subsystem Chapter 18 Sect Torsion bar suspension Thus number six must be set in the Suspension subsystems box 2 The TV has no support rollers zero value is set in the correspo
7. the second track Fig 26 Hull image 1 9 1 Adding hull 1 Read an image of the hull from the UM database Fig 26 by the Edit Read from file command select the file Path to UM bin Caterpillar Profiles Hull1 img Name Hull g AP AS Comments Text attribute C Oriented points Vectors 3D Contact Parameters Position Points Goto element Image wi Visible goHul M Compute automatically Inertia parameters amp Object 3 Object Mass 4 Curves Fix Yarlables abc Attributes P Subsystems Go Lefttrack Go Right track Images Inertia tensor none Added mass matrix d Bodies E Ground Coordinates of center of mass amp soin dl Diletta Fig 27 Adding a body 2 Add a body to the model e select the Bodies item of the element list Fig 27 e create a new body by the button in the inspector e set a name image and inertia parameters mass moments of inertia relative to central axes coordinates of center of mass gravity Universal Mechanism 6 0 18 Getting started UM Caterpillar mhull 5000 ixhull K000 ivhull 4 0000000E 4 izhull 4 0000000E 4 xC 2 605 EC 0 6 Fig 28 Example of hull inertial parameters It is recommended to parameterize the inertia parameters like in Fig 27 An example of numeric values of inertia parameter is shown in Fig 28 Namel lBase0_Hull ee e m al dot Geometry Coordinates Translationa
8. UNIVERSAL MECHANISM 6 0 Can Software NIVERSAL D MECHANIS NZ Development of Models and Dynamic Analysis of Tracked Vehicles Getting started 2010 Basic principles of development of models of tracked vehicles and their dynamic are discussed Universal Mechanism 6 0 2 Getting started UM Caterpillar Contents Getting started development and dynamic analysis of tracked vehicles in UM 3 i MC Vele prime ar Ol TV iena 4 P PIO acne ep 4 1 2 Creatine new object and track SUDSY SUCIMN corra 5 koe Ea T ea E E E E AE Ir 6 Li A SSD O e E E E 7 loi PRCT O E ceense neve neneteeoeseacpumeretunwuseracnenenscunai eoacsoesacesetonecseusnceat 10 EINE CERRI 12 Lio AGISCE i ra 13 ko Addio faber 14 L9 Development or tll TY MOL niro a 17 La Addii iia 17 k 92 COU ili affair 19 1 9 3 AGIDSINESOICIA Kina 20 Lo Corccuonorficica polonia PA Z Sunulan or Ty Gy Mat CS oa earn odio loi 24 Zi E E e Ea iii 24 2 Ml 25 2 III 25 242 Ikea Zi 229 VEU AL WarMOMi IO AGUS ille 30 Deere Itinera J Dos S MIO MOM 0 00 N RR E E E EE 32 2 3 1 Motion on sinusoidal road profile 32 Does Modo ina oT A e a E E E A EE E AT 34 References Universal Mechanism 6 0 3 Getting started UM Caterpillar Getting started development and dynamic analysis of tracked vehicles in UM Fig 1 Model of TV This document helps the user to get experience in development of models and simulation
9. alue Comment Wi 10 mhull 8000 Fig 61 TV speed 4 Set 10 m s speed of the TV on the Identifiers tab of the inspector Fig 61 5 Open a graphic window and create some variables which could be useful for dynamic analysis of the TV e g the longitudinal and vertical acceleration of the hull center of gravity 6 Run simulation 2 3 2 Modeling of jump General Irregularities Macrogeometry Type of irregularities File OA sin 2 pis4L lrreqularity files DAURE VYorabiniCaterpillanregularities Jump_e5_1 irr g Lett Right DAURE VYorabiniCaterpillanirregularities Jump_e5_1 rr g Fig 62 Setting irregularity files 10 20 30 40 s0 Fig 63 Road profile for the jump 1 Use the preliminary created road profile Path to UM bin caterpillar Irregularities jump_25_ 1 irr The file must be assigned by the S buttons to the left and right tracks on the Options Irregularities tab Fig 62 Use the amp button to visualize the road profile Fig 63 2 Assign speed 10 m s and run simulation References Crawler transporters Platonov W F Ed Moscow Mashinostroenie 1972 Rus
10. ave assigned the Cardan angle with the sequence of rotations 1 2 3 which are singular for the second rotation angle rotation about the Y axes equal to 90 degrees i e in fact by the overturning of the TV As well it 1s recommended to use the angles 3 1 2 yaw pitch and roll angles Universal Mechanism 6 0 19 Getting started UM Caterpillar 1 9 2 Coupling hull and track Fig 30 Uncoupled and coupled hull and track So far the track in the current model is not connected with the hull Fig 30 left To connect some elements of the track with the hull it 1s necessary to fix the local hull of the track with the hull body To do this we introduce a joint with zero degrees of freedom between these bodies There are several ways for adding such the joint a 6 d o f joint with disabled coordinates a generalized joint with one elementary transformation of the tc type translation on a constant vector NamellHull_Local hull Se eee aS Body Bodye Hull Lefttrack Local hul Type L Generalized v Enabled PETE E i w ET type tc translation constant Comments Text attribute C Translation vector Fig 31 Joint rigidly connecting hull of TV and local hull of left track e Add a joint e Assign connecting bodies Hull and Left track Local hull e Select the joint type Generalized e Add an elementary transformation be the lower 2 button e Set the lateral shift of the track In example in Fig 31 the gauge
11. cteristics of the element 1s similar to one of that in 1 Fig 23 Ei sascscrazanzazaonazinzaananaazIn aa nanaa nananana iaia iiiiiiiiiiaianiaiiiniiniaiiiiiaiiiiiiiiiaiiiina E Neme 2 pe ie yk pe Comments Text attribute C Comments Text attribute C Body Bode Body Body Local hull Bogieb Road arm Local hull Bogie Road arm Autodetection Autodetection Attachment points Attachment points Local hull Local hull ee arm arm Fig 24 Assignment of bodies and coordinates Rename the element assign bodies and coordinates of attachment points Fig 24 left Note that the side_key is used for the lateral coordinate to change the coordinate sign in case of the left and right tracks To add the rear shock absorber copy the front on by the bas button rename it change the second body and coordinates of attachment points as in Fig 24 right Close subsystem Close subsystem Lett track Fig 25 Model of track with shock absorbers Universal Mechanism 6 0 16 Getting started UM Caterpillar To finish the process of adding the shock absorbers close the subsystem by the Accept button Fig 25 Save the ready mode of the left track to file Remark We have developed a simplified track model Several elements are not included in the model Universal Mechanism 6 0 17 Getting started UM Caterpillar 1 9 Development of full TV model To finish the model development we must add a hull and
12. he growth of the track tension Note that these identifiers were found automatically because the standard name track_tension was used 2 Set numeric parameters of the test as in Fig 44 A uniforms increase of the preload force in bushings starts from 10KN to 45 kN with the rate 3 KN s Tension by joint preload Ty Parameters ariables Joint preload Lett track Joint preload Right track Average tension Lett track Average tension Right track Fig 45 List of standard variables of the test 3 Open a new graphic window and drag two variables from the list by the mouse into the window preload and tension Fig 45 Universal Mechanism 6 0 28 Getting started UM Caterpillar variables Joint preload Lefttracki Options Average tension Edit Tension kh Delete Del Copy to clipboard Ctl c Copy to active MS Excel book Ctrl E oo Filter Ctrl F Copy as static variables Ctrl S Save as text file COl T Save as tor file Ctl Read from text fle Read from RSF fle Lay off variable as abscissa Lay off time as abscissa Clear Ctrl Del Fig 46 Preload must be laid off as abscissa Lay off the preload as abscissa select the variable in the list of graphic window call the context menu by the right mouse button and select the menu command Fig 46 Object simulation inspector VA Information Tools IL Tracked vehicle solver Identifiers Initial conditions Object variables
13. iers Initial conditions Object variables gstv Lett track hoale list Sprocket Idler Track Rollers Suspension I Mame Expression value Comment i Itracklink 0 11167 wtracklir 0 3 i htracklin 0 03 r_pin_in 0 01 wsprokel lum on il huai 1 lt Fig 38 List of identifiers in UMSimul Other parameters can be modified without regeneration of the track models In particular these are parameters used in the description of force elements stiffness damping constants etc and inertia parameters To change values of these identifiers the user must not come back to the UMInput Usually these changes are made on the Identifiers tab of the Object simulation inspector Fig 38 Modifications in parameter values are saved in special par files and can be used in simulations The user can apply the preliminary prepared configurations for each of the tests described below The list of configurations is available by the File Read configuration Test name command Fig 39 Universal Mechanism 6 0 25 Getting started UM Caterpillar as UM Simulation d um60_work tests trackedvehicle mia Analysis Advanced analysis Tools Windows Help gt Open S RSS Bk Reopen HE mes D Game Close Shift F4 a fe S Re w a Load configuration Desktop Ctrl R BM Save configuration Computation of velocities Exit Alta equilibrium mp last Motion on sinusoidal irregularities Track tension
14. is set by the identifier gauge 2 6 m As a result we have rigidly connected the local hull of the track with the hull of TV Fig 30 right and now all the joints and force elements connecting track bodies with the local fictitious hull are coupled with the real hull of TV Universal Mechanism 6 0 20 Getting started UM Caterpillar 1 9 3 Adding the second track Type Caterpillar wf Comments ext attribute Edit subsystem Ii Farameters Position Identifiers Identifier subs 1 Rollers sprocket Idler Structure Track Suspension sprocket position Track position Left Right suspension subsystems E DA Rollers DA Track links 108 HA Fig 32 The right track Open the left track subsystem and copy it by the SF button Rename the subsystem and set the track position Right Fig 32 Body Bodye Hull Right track Local hw Type L Generalized Ty Enabled SA ee ET type te translation constant v Comments Text attribute C Translation vector ex ey gauge Ex Fig 33 Joint rigidly connecting the hull of TV with the local hull of the right track Similar to Sect Coupling hull and track create a joint fixing he local hull of the right track with the hull of TV Fig 33 Note that in this case the lateral shift is negative Universal Mechanism 6 0 21 Getting started UM Caterpillar 1 9 4 Correction of vertical TV position Fig 34 Links are under zero level Note that
15. klink_bushing joint type e Set track link length which is evaluated by the program in the Estimation of link length box e Click the Generate button Fig 19 Fig 19 Adding track chain Universal Mechanism 6 0 14 Getting started UM Caterpillar 1 8 Adding shock absorbers PITPITOVI TIVI TOO TTT VITTO TI TI TITO CITI IVO IITI TTI CITI IVI CITI TIVI CITI CITI CITI TFT CITTATI E Name Lefttrack ak BP 5 Type Caterpillar v Comments Text attribute C Edit subsystem Parameters Position Identifiers a ZII E E iili pF EI EI i iD eW U0fb EI isa Subst Fig 20 Button for editing the subsystem Description of process 1 Use the Edit subsystem button to open a window with description of the track Fig 20 Pu UM Object data input Left track File fsal Object Add Tools Help T Read from fie Fig 21 Menu command for adding an element from file 2 Add a shock absorber model from the UM database by the Edit Read from file command Fig 21 Select the file Path to UM bin Caterpillar Dampers Damperl pa Curve editor _ DX Fig 22 Image and nonlinear characteristics of shock absorber Universal Mechanism 6 0 15 Getting started UM Caterpillar cene i Fig 23 Shock absorbers characteristics form 1 The file contains the description of a nonlinear shock absorber as well as its image Fig 22 The force vs velocity chara
16. l degrees of freedom a x 0 000000000000 amp Object ZA 3 Object v 000000000000 vA Curves z o 200000000000 DA Fi variables abc Attributes Rotational aif Subsystems degrees of freedom 2 Left track Orientation angles Go Right track Images cardan 1 2 3 2 Bodies 1 Q 000000000000 Ground Hul 2 o oo0000000000 j 2 Tie 3 P o00000000000 KA A Mielen Fig 29 Adding a joint for hull 3 Add a joint to the model The joint introduces six degrees of freedom of the hull relative to Base0 SCO e select the Joints item in the list of elements Fig 29 e create anew joint by the o7 button e set the joint type 6 d o f Remark 1 Note that it is important which body in the joint description is the first one Bodyl1 and which is the second one Body2 According to the UM rules the joint introduces coordinates of the second body relative to the first one 1 e coordinates of the hull relative to the inertial frame SCO Remark 2 As it is known any three orientation angles have a singular position For instance the Euler angles are singular for zero values of coordinates and these angles practically do not used in technical applications We do not recommend the user to use the angles which are singular at zeroes 1 e angles corresponding to sequences of rotations in which the first and the third rotations axis are of the same name are 3 1 3 1 2 1 and so on In the example in Fig 29 we h
17. n be done on the Identifier tab of the inspector Note that the pstat identifier is defined in suspension subsystems Open the list of identifiers for one of the suspension subsystem by the drop down list Fig 38 Universal Mechanism 6 0 26 Getting started UM Caterpillar Object simulation inspector Solver Identifiers Initial conditions Object variables Information Tracked vehicle Options Resistance Tools Identification Tests Parameters Variables Fig 41 Equilibrium test 1 Load the model of TV in UMSimul Open the Object simulation inspector by the Analysis Simulation menu command Open the Tracked vehicle Tests tab Select the Equilibrium test from the drop down list Fig 41 2 Open a graphic window by the amp button on the tool panel Drag the Kinetic energy variable prom the Variables tab into the graphic window Fig 42 Plot kinetic energy vs time 3 Run the simulation by the Integration button in the bottom of the inspector In our test the energy value decreases to the value lower than 1 J after 7 seconds of simulation Fig 42 1 e the TV 1s nearly the equilibrium 4 Start the pause mode after 7 s of simulation by the button in the window of integration process parameters or by the Esc button Save the final values of coordinates in the xv file with any name by the Save button in the bottom of the pause window Break simulation by the Interr
18. nding box 3 Number of track links is 108 Universal Mechanism 6 0 7 Getting started UM Caterpillar 1 4 Adding suspension Structure Track Suspension Type of suspension torsion bar wheel we Generate Number of subsystems Parameter Value Fig 5 Uninitialized values of suspension geometry parameters Open the Parameters Suspension tab Fig 6 1 As we have pointed out six suspension units subsystems the table of geometrical parameters of suspension contains the same number of longitudinal coordinates of the subsystems Xcl Xc6 Besides the road wheel radius R and width W must be set in this table All parameters are in meters The suspension unit type is specified on the same tab as torsion_bar_wheel 1 e the default value Structure Track Suspension Type of suspension torsion bar wheel We Generate Number of subsystems Parameter Value Fig 6 Value of suspension geometry parameters for the MT L transporter Following the data in Fig 2 fill in cells of the tab as in Fig 6 Note that the origin of SCO in the X direction is located on the level of the sprocket center Fig 7 First variant of suspension 2 Click the Generate button to create the suspension according to the specified parameters the suspension appears in the animation window Fig 7 Universal Mechanism 6 0 8 Getting started UM Caterpillar Parameters Position Identifiers Left track hole list Sprocket Idler
19. of tracked vehicle TV in UM The model which development is discussed is shown in Fig 1 It is assumed that the user has already studied the document devoted to introduction in UM file es UM pdf and can create and analyze simple models This document does not contain complete information about simulation of TV in UM More detailed information can be found in Chapter 18 of the users manual file 18_UM_Caterpillar pdf The ready TV model considered in this document is located in the directory Path to UM Samples Tracked vehicle gsTV 1 http www umlab ru download 50 rus gs_um pdf Universal Mechanism 6 0 4 Getting started UM Caterpillar 1 Development of TV model 1 1 Prototype Fig 2 Data on prototype of TV A Russian light crawler transporter is considered as the prototype of the model Fig 2 shows some geometric data related to the tracks 1 We would remind that this document is developed to help the user in studying UM Caterpillar module That is why we will not follow the exact design data of the prototype Universal Mechanism 6 0 5 Getting started UM Caterpillar 1 2 Creating new object and track subsystem Object UmObj0 a Object a a Curves A Vanables abe Attributes _ included amp amp Joints F A external A Bipolar forces H wheelset Be Scalartorques GE Linear FEM subsystem E Linear forces 85 Bearing i Contact forces Mil 7 Caterpillar a E
20. pisgL Harmonic irregularities A sin 2 pi pexd0 L Amplitude A r Wave length Lim 20 00 Phase shittx0 of wave for lett track Fig 58 Parameters of sinusoidal road profile 2 Use the Tracked vehicle Options Irregularities tab to set parameters of sinusoidal irregularities Fig 58 By x0 0 the irregularities for the left and right tracks are equal by x0 gt 0 the left road curve passes ahead of the right one Use the k4 button to visualize the curves Fig 59 Irregularities for left track Irregularities for right track TO Qn Puc 59 Sinusoidal irregularities for the left thick and right tracks es Animation window OK B 6 e HI d H coordinate system n Ferspectve vw Smoothing Simplified drawing _ Background color Cal Window parameters J Orientation b Z Grid gt PE ay Rotation style SCO r 3 82 1 11 1 44 m 4 23 gsty Hull Modes of cede images O Save animation Camera follows Hull Fig 60 Setting camera motion 3 Open an animation window and assign the camera motion mode to keep the TV within the window Move the mouse cursor to the hull image click the right mouse button and select the Camera follows Hull command Fig 60 Universal Mechanism 6 0 34 Getting started UM Caterpillar Solver Identifiers Initial conditions Objectvariables S ii gst Latest identifier file FaBHoBecHe pAr whole list Mame Expression V
21. preview the sprocket Fig 14 Note the sprocket radius is computed automatically by the link length t t ratio and number of teeth so that the final variant can differ from the current one Universal Mechanism 6 0 11 Getting started UM Caterpillar pai Sprocket view Fig 15 Adding sprocket 4 Addthe sprocket to the model by the Generate button Fig 15 Universal Mechanism 6 0 12 Getting started UM Caterpillar 1 6 Adding idler Rollers Sprocket Idler Type of idler with tension mechanism idler_crank_simple y P n cere Fig 16 Parameters of idler Open the Parameters Idler tab Fig 16 1 Select a simplified model of the idler on a crank idler_crank_simple 2 Set geometrical parameters of the idler in meters as in Fig 16 radius width and coordinates of the center 3 Add the idle to the model by the Generate button Fig 17 1999990 Fig 17 Adding idler with tension device Universal Mechanism 6 0 13 Getting started UM Caterpillar 1 7 Adding track chain Structure Track Suspension Track envelope Length of envelope 14072 Estimation of link length 0 11166 Estimation of error in length 0 0008 Current error in length 0 0002 Track link tracklink_bushing Jointtype ORigid Flexible Parallel press Profile ee a oc Puc 18 Tack chain parameters Open the Parameters Track tab Fig 18 e Use trac
22. rag in it the test variables which are circular velocities of sprockets Fig 55 Universal Mechanism 6 0 32 Getting started UM Caterpillar variables B sprocket Lett track Ws sprocket Right track Circular velocities imi 5 0 1 2 3 4 E Fig 56 Circular sprocket velocities vs time 3 Run the test The plot of circular sprocket velocities vs time is shown in Fig 56 4 Confirm saving the results after finishing the test The values of coordinates and velocities of all he bodies are saved in the 50 tvv file and will be used in any main dynamic test in which the TV speed differs from zero 2 3 Straight motion of TV This is the main test for analysis of dynamics of a TV by straight motion without turn Here we consider two examples of such the test 2 3 1 Motion on sinusoidal road profile Options Resistance Tools Identification Tests Straight motion test v Parameters Variables Mode of mation C Run off const O v tlAv s Numeric parameters Amplification 100000 Fig 57 Test parameter 1 Select the corresponding type of the test Fig 57 The test parameter is used in control of the speed history which will be constant in our test The amplifier is not used if the Run off speed mode 1s set Universal Mechanism 6 0 So Getting started UM Caterpillar Options Resistance Tools Identification Tests MITPITTITITERI TI TITTI eee eee un uni File A sin 2
23. rmonic vertical force Fig 51 EAE Parameters Variables Vertical force Suspension movement Fig 52 Test variables 2 Open a graphic window and drag in it the test variables Fig 52 Lay off the suspension movement as abscissa Universal Mechanism 6 0 31 Getting started UM Caterpillar Load KN Vertical movement mm 20 40 60 a0 100 120 140 Fig 53 Test result Load vs vertical movement 3 Run the test The results are shown in Fig 53 Increase of the suspension stiffness corresponds to the vertical movement exceeding the road wheel dynamic travel 110 mm parameterized by the identifier f_dyn Fig 40 2 2 4 Test initial velocities The test is necessary for automatic computation of initial velocities of TV bodies by the given value of the TV speed when one of the main dynamic tests is executed As a rule it is enough to create a file of initial conditions corresponding to one speed e g 5 m s With this file the program computes start velocities for any speed of TV using a scale factor Options Resistance Tools Identification Tests Parameters Variables Numeric parameters Target vehicle speed Time of acceleration Fig 54 Test parameters 1 Select the corresponding type of the test assign the target speed and time interval for acceleration Fig 54 Parameters Variables sprocket Lett track sprocket Right track Fig 55 Test variables 2 Open a graphic window and d
24. track links are still located under the zero level in the vertical direction in fact they are under the ground Fig 34 To avoid intensive transient processes by simulation it is recommended to shift the TV model upwards on the link height whale list n vi mum New identifier Ins ULI QUI Add from subsystems nn roodo Insert identifier Shift Ins i A EStidentifier gt GOG Delete identifier Del La DE Copy value to clipboard Ctl c gauge 2 6 Copy table to clipboard Ctrl Ins Show elements including identifier List of unused identifiers New sheet Refresh object Identifiers Eg A iz_crank d_tension_angle 0 pretension_torgque 500 c_torsional 11250 Itracklink 0 1116 wtracklink 0 3 htr acklink 0 03 n_lug w_lug 0 05 ae a B E Fig 35 Adding an identifier from subsystem Universal Mechanism 6 0 22 Getting started UM Caterpillar At first note that by default the track link height is set by the identifier htracklink which 1s defined in track subsystems and not visible in the head part of the TV model It is recommended to add an identifier with the same name in the head part Fig 35 e click by the right mouse button on the list of identifiers and select the Add from subsystems command e select the htracklink identifier in one of the track subsystems and click on it e make sure that the identifier appears in the list ci CDI da
25. track tension must be 20 kN The corresponding bushing preload is approximately 26 6 KN Universal Mechanism 6 0 30 Getting started UM Caterpillar Options Resistance Tools Identification Tests General Iregularities Macrogeometry sprocket rotation 5 2262 HA 5 2163 A Mass of TY iti 12 29 Mass of hull ft 0 00 Elongation of tension rod mm Preload in joint kN Fig 50 Setting joint preload for the further use Break the pause mode and set the found preload value in the Tracked vehicle Options General for use in other tests 6 Now we must solve the last problem Positions of TV bodies for the given track tension must be computed and stored e set the Equilibrium test e run test during 7 seconds e save coordinates in the pause mode by the Save button break simulation read the saved coordinates on the Initial conditions tab set zero values for velocities and save the coordinates by the i button Use this coordinates any time when the test requires an equilibrium state of the TV by the given value of the track tension 2 2 3 Vertical harmonic loading The test allows the user to get nonlinear vertical characteristics of the suspension by a slow harmonic excitation Options Resistance Tools Identification Tests Vertical harmonic loading Parameters Variables Numeric parameters Fig 51 Test parameters 1 Select the corresponding type of the test and set parameters of the ha
26. upt button f p TELES S w7 Universal Mechanism 6 0 21 Getting started UM Caterpillar Fig 43 Track before and after the equilibrium test 5 Read the saved file by the amp button on the Initial conditions Coordinates tab of the inspector Set zero values for velocities by the button It is recommended to save the found coordinates in a file by the ll button for the next tests Positions of track bodies before and after the test are shown in Fig 43 Remember that the necessary track tension is still not set 2 2 2 Track tension Options Resistance Tools Identification Tests Tension by joint preload Parameters Variables Identifiers Elongation of tension rod Lett track Lett track track_tension 0 Elongation of tension rod Right tracki Righttracktrack_tension 0 Numeric parameters PStart kN PFinish kN PY kisi Puc 44 Parameters of the test 1 Select the Tension by joint preload test In this test a value of the preload force in bushings can be found which gives the desired value of the track tension Note that there exists a test Track tension where the tension value is obtained by elongation of the tensions rod but this method is usually used for track links with rigid joints Test parameters are presented in Fig 44 First identifiers of preload force in bushing models are specified in the Identifiers group Increase of the value of these identifiers leads to t
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