What is a Multibody System

The modern way to check ideas and to convince others is computer simulation. There, a computer model of the system under investigation is established and all kinds of studies and measurements are made on this model. The art of transforming a complex mechanical system into a computer model is covered by the rather young discipline computational mechanics. 

This description of the mechanical system is used by special multibody programs to automatically transform it into a set of mathematical equations, mostly ordinary differential equations (ODEs). 

Often the engineer using such a tool is not interested in the mathematical description of his problem. He asks for a machinery inside the multibody program which handles these equations in a numerically appropriate way and gives answers to his questions. In the above example the critical speed of the vehicle might be such an answer. 

However, it cannot be expected that the numerical methods implemented in multibody programs run satisfactory for any multibody problem. A particular model might cause problems such as the fascinating error message corrector could not 

Then it becomes necessary for the engineer to know something about the numerical machinery inside multibody programs. There are usually a lot of varieties how to model a system. The choice of the model and the mathematical formulation have a large impact on the simulation performance. Let us take a simulation of a truck as an example Which coordinates are taken for the description What about the friction models  

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