Abstract: For Stewart platform’s dynamic model in joint-space, its inertia matrix’s block diagonal dominance is analyzed. Firstly, the platform’s dynamic model is formulated by Lagrange method. Secondly, according to the platform’s geometry structure, it could be found that coupling of neighboring struts is most strong under normal circumstances, namely the inertia matrix is block diagonally dominant, and the corresponding index that indicates this inertia coupling characterization is defined. Finally, an approach for judging inertia matrix’s block diagonal dominance is proposed. Finite platform’s displacement points can be selected by using this approach, and the inertia matrix is block diagonally dominant in the given workspace if it is so on these points. As to the block diagonal dominance, the strong coupled struts could be considered integrally and the whole system is divided into three double inputs and double outputs subsystems. In such a way, the conventional single input and single output control method’s conservativeness is reduced.

Key words: Block diagonal dominant matrix, Dynamic coupling, Joint space, Stewart platform