Multibody systems are the appropriate models for predicting and evaluating performance of a variety of dynamical systems such as spacecraft, vehicles, mechanisms, robots or biomechanical systems. This book adresses the general problem of analysing the behaviour of such multibody systems by digital simulation. This implies that pre-computer analytical methods for deriving the system equations must be replaced by systematic computer oriented formalisms, which can be translated conveniently into efficient computer codes for - generating the system equations based on simple user data describing the system model - solving those complex equations yielding results ready for design evaluation. Emphasis is on computer based derivation of the system equations thus freeing the user from the time consuming and error-prone task of developing equations of motion for various problems again and again.