Abstract: As a mature modeling technology, the block diagram is widely applied. MATLAB/SimMechanics use this technology to model and simulate multibody mechanical systems. However, SimMechanics is obviously insufficient for flexible and large multibody mechanical systems requiring high modeling precision and real time simulation. While DARTSM software package can perform high precision and real time simulation of spacecraft mechanical system. This paper deeply analyzes underlying modeling technology of the two softwares, then designs the detailed method for model conversion according to the equivalence relationship of modeling information, and finally develops the model conversion program through C++ to convert the SimMechanics model of spacecraft multibody systems to DARTSM model. Through the model conversion method and program in this paper, the advantages of the two different softwares can be combined. So that SimMechanics indirectly obtain the ability to handle flexible body and real time simulation. Similarly, it also resolves the problem that DARTSM software package lacks graphical modeling interface, which has important engineering application value.

Key words: flexible multibody spacecraft, multibody system modeling, Simulink/SimMechanics, model conversion method