1. Universal Mechanism Simulation of Tracked Vehicle Dynamics with
This presentation is devoted to the problems of simulation of tracked vehicle dynamics with UM. The program has been developed at Laboratory of Computations Mechanics, Bryansk State Technical University, Russia

2. Examples of tracked vehicle (TV) models Main components of TV models
Contents
Examples of tracked vehicle (TV) models
Main components of TV models
Development of a model of TV
Models of force elements
Simulation of TV dynamics

3. Examples of TV models TV of different types Tank Crawler transporter
371 bodies, 1916 d.o.f.
Crawler transporter
263 bodies, 1332 d.o.f.
D.o.f. means ‘degrees of freedom’
Excavator
138 bodies, 128 d.o.f.

4. Examples of TV models
Jump by speed 15 m/s

5. Examples of TV models Model developed in 2003
The model has been developed in2003 with the help of the first version of the UM Caterpillar module for simulation of TV dynamics
Model developed in 2003

6. Examples of TV models

7. Examples of tracked vehicle (TV) models
Main components of TV models
Development of a model of TV
Models of force elements
Simulation of TV dynamics

8. Main components of TV model
Sprocket
Idler with tension device
Rollers
Track links
Suspension and road wheels
UM generates a track model automatically with help of a database of main elements in figure. A rear drive TV is shown.
Components of a track model
Main system of coordinates for TV model

9. Main components of TV model
Torsion bar suspension
Suspension bogie
For types of standard suspensions from UM database are shown on slide.
Suspension torsion bogie
Fixed suspension
Standard suspensions as subsystems

10. Main components of TV model
Simplified model of idler on a crank
Advanced model of idler on a crank
Idler on a slider
Three types if idler with tensioner from UM database.
The tension device is used for setting a desired tension of the track, as well as for absorption of impacts. The tensioner spring has a definite preload, which exceeding leads to the compression of the spring.
Standard models of idler with tension device

11. Main components of TV model
A pin toothing is implemented in UM
Sprocket radius is computed according to the number of teeth and distance between the track link joints
Sprocket

12. Main components of TV modelRo r Rs h
μ/2  Ro
μ/2 h Rs LJ RT RP r
The most frequently used tooth profiles are generated automatically according to specified geometric parameters
Generator of sprocket tooth profile

13. Main components of TV model
Main menu command for call the tooth generator
Generator of tooth profiles

14. Main components of TV model
Track link with rigid joint
Track link with flexible joint (bushing)
Track link with two parallel bushings (double pin)
In case of track link with one pin, the link is modeled be one rigid body. Two rigid bodies are .
Bushings can be both linear and nonlinear
Standard track link models

15. Main components of TV model
A support roller is a rigid body with one rotationsl degree of freedom
Support roller

16. Main components of TV model
The user can develop his own components of TV such suspension subsystem, idler or track link, and add it to the UM database. The new component should be registered on the local computer
User defined components
Registration of a new component of TV

17. Examples of tracked vehicle (TV) models
Main components of TV models
Development of a model of TV
Models of force elements
Simulation of TV dynamics

18. Development of TV model
Track is generated automatically with the help of components from the database
The track structure includes
- position of the track Left/Right
- number of suspension units
- number of rollers (can be zero)
- number of track links
Step.1 Setting track structure

19. Development of TV model
Step.2 Suspension
The user set geometric parameters such as coordinates of torsions, length of torsion arm etc.

20. Development of TV model
Step.3 Adding sprocket
The user sets the tooth profile, the number of teeth, sprocket/track step ratio as well as geometric parameters.

21. Development of TV model
Step.4 Adding idler
The user selects a type of the tension mechanism from the drop-down box and sets geometrical parameters of the idler.

22. Development of TV model
Step.5 Creation the track chain. Enveloping curve
The user selects the type of track link, assigns the pin profile, length of track link and othe parameters.
According to the geometrical data for positions of all the wheels and their radii, UM computes the enveloping curve and generates track links with joints in their exact positions along the track.

23. Development of TV model
Step.6 Completion of track model. Adding dampers
Dampers
Characteristics of shock absorber
Some elements must be added to the model to complete its development. In particular, shock absorbers must be added.

24. Development of TV model
Set.7 Adding a hull
A hull image is often imported from a CAD software such as SolidWorks, Autodesk Inventor, Pro/E, UG atc.

25. Development of TV model
Set.8 Adding the second track
The second track can be added by a single copying the first one. Sometimes, the tracks have different geometric parameters; in this case the parameters of the second track can be modified.

26. Examples of tracked vehicle (TV) models
Main components of TV models
Development of a model of TV
Models of force elements
Simulation of TV dynamics

27. Models of force elements
Pin-sprocket interactions
Contact interactions of track pins with sprocket teeth transfers traction and brake torque to the track. Positions of contact points are computed according to positions of the bodies taking into account exact profiles of pin and tooth.

28. Models of force elements
Pin-sprocket interaction
A compliant contact model is used. Contact forces depend on penetration of pin and tooth profiles and produce two components: the normal force N and the friction force F. The normal component is the linear function of the penetration and its derivative.
Compliant contact model

29. Models of force elements
Wheel-link interaction S R  δ
Normal contact force is proportional to the area S of penetration

30. Models of force elements
Wheel-link interaction
Force versus penetration model
Here δ0 is the deflection under the load P;
c(δ) is the stiffness versus penetration law

31. Models of force elements
Wheel-link interaction
The obtained relations are generalized for a contact of a wheel with a polyline corresponding to the track chain.

32. Models of force elements
Restrictive force and moment C ht T y x y αx
The force and moment prevent the lateral shift and rotation of a link

33. Models of force elements
Track-ground interaction
Two main model of the ground:
Spring-damper model without sinkage
Soil with sinkage
Contact point
One contact point is automatically assigned to each of the links. It is planned to implement a user-defined set of contact points for each of the links

34. Models of force elements
Bekker ground model
Here p is the normal link-ground pressure
b is the minimal size on the contact patch b (length of a track link)
n, kc , k are the model parameters
z is the sinkage depth

35. Models of force elements
Examples of terrain models
Normal force versus sinkage depth for different soils

36. Models of force elements
Loading
Unloading/ Reloading
Example of track load force versus sinkage by loading and unloading/reloading processes

37. Модели силовых взаимодействий
Tangential strength
(Janosi, Hanamoto)
Here j is the shear displacement of the link since the first contact with soil
p is the normal pressure
c is the cohesion
 is the angle of internal friction
K is an empirical constant
The tangential stress model is used for computation of friction forces in interaction of a link with the soil.

38. Модели силовых взаимодействий
Database of terrain parameters
The user can add terrain models to the database

39. Examples of tracked vehicle (TV) models
Main components of TV models
Development of a model of TV
Models of force elements
Simulation of TV dynamics

40. Simulation of TV dynamics
Dynamic analysis of TV as a set of tests
List of auxiliary tests:
Equilibrium
Track tension
Computation of initial velocities
List of main tests:
Vertical harmonic loading
Straight motion
Open loop steering
Test with driver:
2D curve
3D testing area

41. Simulation of TV dynamics
Test: equilibrium
This is an auxiliary test intended for finding coordinates of bodies in the TV equilibrium state. The test is necessary because positions of bodies in the TV model after its development in the UMInput are specified approximately.
The user stops the test when the kinetic energy value becomes small enough.

42. Simulation of TV dynamics
Test: track tension
This is an auxiliary test, which is used for setting a desired track tension.
The main result of the test is the plot of tension force vs. elongation of the tension rod or a preload in the bushings.

43. Simulation of TV dynamics
Test: Computation of 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.

44. Simulation of TV dynamics
Test: Vertical harmonic loading
The test allows the user to get nonlinear vertical characteristics of the suspension by a slow harmonic excitation

45. Simulation of TV dynamics
Test: straight motion
Harmonic irregularities in opposite phase

46. Simulation of TV dynamics
Test: straight motion
Тест: движение по прямой
In-phase harmonic irregularities

47. Simulation of TV dynamics
Test: straight motion
Jump

48. Simulation of TV dynamics
Test: straight motion
Trench

49. Simulation of TV dynamics
Test: straight motion
Barrier

50. Simulation of TV dynamics
A simplified modeling a gunshot is made by application of a definite impulse.
Click the picture by the mouse to get an animation
Gunshot

51. Simulation of TV dynamics
Click the picture by the mouse to get an animation

52. Simulation of TV dynamics
Click the picture by the mouse to get an animation

53. Simulation of TV dynamics
Click the picture by the mouse to get an animation

54. Simulation of TV dynamics. Open steering test
Longitudinal speed 8 m/s
Difference in sprocket speeds 0.7 m/s
If a driveline is not included in the model of TV, the open lop control of TV is set as the difference in circular speeds of the left and right sprockets

55. Simulation of TV dynamics. Open steering test
Longitudinal speed 0 m/s
Difference in sprocket speeds 0.7 m/s

56. Simulation of TV dynamics
Driver model: closed loop control for TV turning
Desired path TV Lp x y
Driver model: the track speed difference is proportional to the deviation y of a point with preview Lp from the desired path with a reaction delay dt.
Closed loop control

57. Simulation of TV dynamics: test with driver
Test: motion on a 2D curve

58. Simulation of TV dynamics: testing area
Testing area is created in one of the CAD programs (SolidWorks, Inventor, PRO/E…)
A set of routes is specified by the user
Speed along the route can be variable
A testing area (TA) is a surface with a set of testing obstacles. The TV model overcames the obstacles according to a route defined by the user. The image of TA is created in one of the CAD programs and imported to UM format in the standard manner.

59. Simulation of TV dynamics: test with driver
Testing area
Speed history along the route

60. Simulation of TV dynamics: test with driver
Motion of an excavator along the route

61. Simulation of TV dynamics
Excavator manipulations

62. Simulation results
Any kinematic variables (trajectories, velocities, accelerations of any point, angles of rotation, angular velocities and accelerations of bodies)
Plots of applied forces
Plots of reaction forces
Plots of special variables related to TV dynamics
Animation files
Special tools for multivariant calculations and processing of their results
Factorial experiments

63. Special variables in the wizard of variables
Animation of hystograms

64. Processor requirements
UM implements parallel computation of TV dynamics with the help of multithreading
It is strongly recommended to use
multi-core processors
The highest performance is achieved on
eight-core processors
(four physical + four logical cores)

65. Universal Mechanism Simulation of Tracked Vehicle Dynamics with