MBSOFT: a symbolic/numerical multibody program for analysing mechanical and mechatronic systems

The field of multibody dynamics has been the subject of a multitude of theoretical developments over the last 10 years (1990-2000). The resulting multibody programs have been widely used in various fields. With respect to other disciplines like structural analysis or fluid mechanics, a high degree of generality is a difficult challenge for a multibody program since the possible applications have their own modelling specificities which require a particular computer implementation. In such a context, there are two possibilities: (i) the development of a general purpose multibody code which aims at covering most of the multibody families of applications; (ii) the development of a toolbox multibody program which gives the user the possibility to build his own specific model by introducing himself his own functions and modules, on the basis of multibody tools such as kinematic and/or dynamic equations in symbolic form. We have opted for the latter philosophy in the MBSOFT program by distinguishing the symbolic generation for the modelling phase from the numerical treatment for the analysis phase (performed in MATLAB syntax). The symbolic generation is based on the ROBOTRAN program and allows the user to automatically obtain the dynamic equations of the multibody structure, but also to put various symbolic equations and models at his disposal in order to (for instance): generate some user kinematic constraints; generate a particular result, such as the force at a given point expressed in a given frame; generate some kinematic chains for the modelling of a given force constitutive equation; compute any kinematic quantities.Anglai