4569846498

3
Multibody systems simulation software
3.1 Overview
There exists a range of commercial computer packages that can be used to
solve problems in multibody systems analysis. In addition to the commercial
packages that may be licensed there are also programs developed by academic
institutions that may be available, albeit without the level of development and
support that would be expected when buying the software from an established
program developer. The features described in this chapter are from
MSC.ADAMS but in principle will equip the reader to understand the capabilities
of other multibody systems analysis programs used in vehicle dynamics.
General-purpose MBS programs are able to address a large set of problems
across a wide range of engineering industries and are not restricted to the
applications in vehicle dynamics discussed here. The main use of MSC.
ADAMS within the automotive industry is to simulate the performance of
subsystems and full vehicles. Models are increasingly being used for large
amplitude non-linear vibration problems such as powertrain isolation and
driveline oscillations. The analyst will often wish to validate the performance
of a suspension model over a range of displacements between full bump to
rebound before the assembly of a full vehicle model that may be used for
ride, handling and durability studies. A detailed model may include representations
of the body, subframes, suspension arms, struts, anti-roll bars,
steering system, engine, drivetrain and tyres.
The main analysis code consists of a number of integrated programs that
perform three-dimensional kinematic, static, quasi-static or dynamic analysis
of mechanical systems. These programs may be thought of as the core
solver. In addition there are a number of auxiliary programs, which can be
supplied to link with the core solver. These programs can be used to model
vehicle tyre characteristics, automatically generate vehicle suspensions and
full vehicle models, or model the human body. Once a model has been
defined the core solver will assemble the equations of motion and solve them
automatically. It is also possible to include differential equations directly in
the solution, which allows the modelling of a variety of control systems.
The software can link or interface with CAD systems, finite element programs,
software used for advanced visualization or additional software
modules such as those used for tyre modelling. The combined use of these
systems can lead to the development of what may be referred to as virtual
prototypes, that is computer models that can simulate the tests and conditions
that a real prototype would be subject to during the development of a new
engineering product. The extent of these interfaces involving MSC.ADAMS
is illustrated in Ryan (1993) and reproduced here in Figure 3.1.
Note that although the software has been continually developed since this
publication Figure 3.1 is still a useful illustration of the integration of MBS
software in a CAE environment.