1. Universal Mechanism software
Simulation of dynamics of road vehicles in
Universal Mechanism software

2. Road vehicle as a mechanical system Creating models
Contents
Background
Road vehicle as a mechanical system
Creating models
Simulation of vehicle dynamics
Verification

3. Road vehicle components
Background
Road vehicle components
Kinematics of cars

4. Engine

5. Off-road vehicle

6. Transmission components
Differential
Cardan shaft

7. Author: Vlad Govorov, BSTU, Bryansk, Russia
Grader
Grader GS by
Bryansk factory of road machines.
Velocity: 40 km/h
Pavement: asphalt in satisfactory condition
Author: Vlad Govorov, BSTU, Bryansk, Russia

8. Dynamic test: vertical load
VAZ 2109
Dynamic test: vertical load
Here you can see a quasi-static test. Slow force of high amplitude acts on the car body that causes large displacements of the car body and gives us a possibility to determine summary stiffness of the suspension including changing geometry of the suspension.

9. UM Caterpillar Simulation results
Tracked vehicle in the test range with irregularities in staggered order
Simulation results

10. UM Caterpillar Simulation results
Tracked vehicle on a vertical obstacle
Simulation results

11. Truck/trailer SAE lane change, V=88 km/h
SAE lane change (Society of Automotive Engineers, 1993) maneuver, V=88 km/h. It is used for estimating rearward amplification and several other safety related performance measures. When the test is conducted in the field, several variables are recorded during the manoeuvre for later processing; the main ones being the lateral acceleration of the centre of the steer axle and the lateral acceleration of the center of gravity of the sprung mass of the rearmost trailer.

12. Low-speed 90º turn, V=10 km/h, R=11.25 m
B-double
Low-speed turn (closed-loop path following simulation) for estimating low-speed offtracking
Low-speed 90º turn, V=10 km/h, R=11.25 m

13. Pulse steer Pulse steer, V=100 km/h
Моделирование динамики грузовика с прицепом при совершении маневра «рывок руля».
Pulse steer, V=100 km/h

14. Step steer
Step steer, V=100 km/h

15. Three-wheeled light vehicle (1)
Double lane change, V=14 km/h

16. Three-wheeled light vehicle (2)
Double lane change, V=14 km/h

17. Single-cylinder engine
Student work
Single-cylinder engine

18. Student work: cart
Police turn

19. Student work: police turn

20. Student work: drifting

21. Road vehicle as a mechanical system Creating models
Contents
Background
Road vehicle as a mechanical system
Creating models
Simulation of vehicle dynamics
Verification

22. Simulation workflow
Real mechanical system or its prototype 1
Preparing input data and conception of a model 2
Describing
kinematical model 3
Describing
dynamical model 4 5
Automatic generation of equations of motion
Researches starts from problem statement and obtaining the source data (steps 1, 2). After that the model of the mechanical system is prepared (steps 3, 4) and its equations of motion are automatically generated. Numerical simulation of these equations gives us dynamical behavior of the model.
Analyzing model’s dynamical performances 6

23. Technical objects as multibody systems
Bodies +
Joints
Force elements
All mechanical systems are represented in the program as a set of rigid or flexible bodies interconnected by means of joints and force elements.

24. Rigid body: Image Inertial parameters Rigid bodies
Once again: any model is a set of bodies, joint and force elements. Rigid bodies has its inertia parameters and graphical image. Inertia parameters are mass, moments of inertia and position of the center of mass.

25. Joints Joints Translational Rotational 2 - 6 d.o.f. joints Quaternion
“Universal Mechanism” software supports using joints of various types that allow to describe all practically feasible kinematical pairs.
2 - 6 d.o.f. joints
Quaternion
Rod

26. For Hendrickson Pacific Ltd.
Force elements
Bushing
Air spring
Bushing
Different heavy vehicle suspension in this slide demonstrate variety of built-in types of force elements in “Universal Mechanism”. Bushings, air springs, dampers – all these elements can be successfully modeled in UM.
Damper
For Hendrickson Pacific Ltd.

27. Force elements Airspring Damper
Shown here an airspring and a damper are modeled its non-linear force diagram.

28. Heavy vehicle suspension
Cobblestone pavement, V=100 km/h.

29. UM FEM: Flexible bodies
For Hendrickson Pacific Ltd.
Finite-element model of the leaf spring

30. UM FEM: principle of operation
Simulation of hybrid system
(system of rigid and flexible bodies)
Import of dynamic and static modes from FEM software
(ANSYS, MSC.NASTRAN)
FEM-model
from
ANSYS,
MSC.NASTRAN
Rigid body model
from
Universal
Mechanism
Hybrid model in
Universal
Mechanism + =
To include a flexible body into your hybrid model in UM you need first to develop its model in external FEM software

31. Durability analysis Workflow
Workflow of the durability analysis module

32. Kompass 3D –> Universal Mechanism interface

33. SolidWorks –> Universal Mechanism interface
Here you can see an example of data import from SolidWorks. In the top figure you can see the model in SolidWorks, in the bottom one – the same model in Universal Mechanism.

34. Autodesk Inventor –> Universal Mechanism interface
Import from Autodesk Inventor

35. Matlab/Simulink interface
Example 1. Stabilization of the inverted pendulum
The UM Control module allows to import Matlab/Simulink models to UM models. Here you can see the classical model of the control of an inverted pendulum. UM model includes a cart and the inverted pendulum on it. Control system is modeled in Matlab/Simulink. The control system takes an angle of declination of pendulum as an input and calculates a force F, that should be applied to a cart to stabilize a pendulum in upper unstable position, as an output.

36. Matlab/Simulink interface
Example 1. Stabilization of the inverted pendulum
Slide shows the examples of moving the inverted pendulum with turned on and off control system.
Free motion
Controlled motion

37. Matlab/Simulink interface: ABS simulation
ABS model in Matlab/Simulink

38. Braking coefficient / Slip diagram
Kienhöfer, F.W., Cebon, D. Improving ABS on Heavy Vehicles Using Slip Control 38

39. Simulation results: vehicle speed
with ABS
without ABS
Vehicle speed

40. Simulation results: with ABS
Angular r velocity of wheels
Longitudinal slip

41. Simulation results: without ABS
Angular velocity
Longitudinal slip

42. Simulation in Matlab

43. Road vehicle as a mechanical system Creating models
Contents
Background
Road vehicle as a mechanical system
Creating models
Simulation of vehicle dynamics
Verification

44. Creating models (UM Input)
Tree of elements
Program package Universal Mechanism consists of two programs: UM Input for model description and UM Simulation for analysis of its dynamics. Please have a look at the main window of UM Input program that is shown in this slide.
Identifiers
Inspector
Screen shot of UM Input program

45. Automatic generation of equations of motion
Deriving equations in symbolic form using a built-in computer algebra system (C, Pascal codes)
Numeric-iterational generation
………………………………………………………….
_Frc_Vctr[1] := _._ap[3]*_.ix+_._ap[3]*_.mass*_._c2* _._c3*_.length*_.length+_._ap[3]*_.mass*_._c3*_.length*_.length-_._ap[3]*_.mass*_.length*_.length* _._s2*_._s3+ _._ap[3]*_.mass*_.length*_.length * _._ap[3]*_.mass*_._c2*_._c3*_.length *_._ap[3]*_.mass*_._c3*_.length * _._ap[3]*_.mass*_.length*_._s2*_._s * _._ap[3]*_.mass*_.length *_._ap[3]*_.mass
+2*_._ap[2]*_.ix+_._ap[2]*_.mass*_._c2* _._c3* _.length*_.length+2*_._ap[2]*_.mass*_._c3*_.length* _.length +2*_._ap[2]*_.mass*_._c2*_.length *_.length-_._ap[2]*_.mass*_.length*_.length*_._s2*_._s3
Elements of equations are computed on each step of numeric integration
After describing the model the step of the generation of equations of motions. Universal Mechanism supports two such methods: symbolic and numeric-iterative. Let us consider them more detailed.
Symbolic method assumes generation equations of motion as source files in C or Pascal with posterior their compilation by one of the supported external compilers. As a result of compilation the UMTask.dll appears. This *.dll is used by UM Simulation program for numerical integration of equations of motion.
Numeric-iterative method assumes generation of equations of motion on each step of numerical integration directly in UM Simulation program.
Let us consider advantages and disadvantages of both methods. In terms of CPU efforts the symbolic method is faster. It provides decreasing CPU efforts up to 10-30% for complex (more than degrees of freedom) models. For rather simple models CPU efforts for both methods are roughly the same. The symbolic method during generation of source code fulfils its optimization from the point of view of CPU-efforts. On the other hand the symbolic method of generation of equations of motion expects any external compiler to be installed on the same computer. Universal Mechanism supports Borland Delphi, Borland C++ Builder, Microsoft Visual C++ as external compilers. At the same time the numeric-iterative method does not suppose explicit steps of generation and compilation of equations of motion and seems to be simpler in usage.
also implemented in UM (sometimes very useful)
very fast!
Generation of equation in symbolic form and the following compiling them as DLL is one of the reason why UM is faster that many other software

46. Road vehicle as a mechanical system Creating models
Contents
Background
Road vehicle as a mechanical system
Creating models
Simulation of vehicle dynamics
Verification

47. Analysis of Models (Simulation Module)
Here you can see the main window of the UM Simulation program. There are animation and graphical windows.
Screenshot: Simulation Module
Any number of animation and plot window

48. Simulation: on-line visual representation of results
3D animation of motion
3D animation of vectors (forces, velocities, accelerations)
3D animation of trajectories
plots (coordinates, velocities, accelerations, applied and reaction forces etc.)
Animation of motion of mechanical system takes place simultaneously with plotting results. This is very useful at the stage of checkout a model when faults in the model are visible right after simulation starts.
Expander: direct dynamic problem

49. Processing of Variables
Simulation tools
Processing of Variables
Every computed variable from graphical window or from list of variables can be processed with
Table processor
Window of statistics
Important role for effective analysis of dynamics of mechanical systems plays facility of postprocessor for analyzing obtained results. Built-in table processor and statistical tool let the user a possibility to carry out such analysis quickly and effectively.

50. Simulation tools Original Filtered
There are possibilities to export any graph to Microsoft Excel as a diagram or to filter the process as it is shown in this slide.
Original
Filtered

51. Steering wheels
Cobblestone pavement, V=100 km/h.

52. UM Automotive: tire models, library of suspensions
Pacejka Magic Formula
FIALA tire
model
Tabular and experimental tire models
Road excitations
Pointwise input
(for measured data)
Analytical expressions
Synthesis of the road profile based on its spectral power density
Superposed pointwise/analytical/generated by spectral power density road profile
UM Automotive widens the functionality of UM Base configuration and includes program tools for description of a mathematical models of tires, road plan, road excitations, as well as … (see the next slide)
Library of spectral power density of typical road surfaces

53. UM Automotive: maneuvers
Maneuvers with closed-loop steer control
Trajectory +
Driver model
(MacAdam’s model, Second order preview model)
… and mathematical models of drivers and tools for maneuver description.

54. Eigenmodes
0,40 Hz
0,82 Hz
1,10 Hz
1,39 Hz

55. Road vehicle as a mechanical system Creating models
Contents
Background
Road vehicle as a mechanical system
Creating models
Simulation of vehicle dynamics
Verification

56. National road transport commission of Australia
Heavy Vehicles
National road transport commission of Australia
Model 2: Truck-trailer
Model 1: B-double
ADAMS CAR
UMTRI’s Yaw/Roll
AUTOSIM
Universal Mechanism
To compare and determine if there is acceptable agreement between simulations from Universal Mechanism and other computer-based modeling packages special verification was done. Two test models of heavy vehicles were created in different modeling programs and results of simulation their dynamics were obtained. National road transport commission of Australia carried out numerical experiments in ADAMS/CAR, UMTRI’s constant velocity Yaw/Roll program and AUTOSIM and our laboratory did the same in Universal Mechanism. Computer models of a truck/trailer and a B-double are considered. In total four simulations were devised that would test and compare a range of features in the models. Pulse steer and step steer inputs were used in the two simulations that employed open-loop steer control, and closed-loop control was used in path following tasks of a high-speed lane change and a low-speed 90° turn.
Results of comparison are presented in next slides.
SAE Lane change, 88 km/h

57. Simulation results: pulse steer
ADAMS
Yaw/Roll
AUTOSIM UM
Comparison of reports shows very good agreement between Universal Mechanism and other modeling packages.

58. Simulation results: pulse steer
ADAMS
Yaw/Roll
AUTOSIM UM

59. Thanks for your kind attention
Simulation of dynamics of road vehicles in
Universal Mechanism software