When building the whole model, the dynamic analysis of each component can be carried out first, and the main mode set and constraint mode set can be established, at the same time, the degree of freedom of the substructure can be reduced. At the same time, compared with the overall structure of the excavator, the sub structure of the excavator has a much smaller span in the length direction. And the oil cylinder of excavator is the main component to ensure the stability of the whole structure. Therefore, the stiffness of the fixed interface substructure of the excavator is larger than that of the whole. Generally, the low order modes are mainly considered in the whole dynamic analysis, and ignoring the main mode set of the substructure with fixed interface will not cause much error to the whole analysis. Therefore, only the constrained mode set can be selected to reduce the degree of freedom of the substructure, which will further reduce the degree of freedom and simplify the calculation method.
After reducing the degree of freedom of the substructure, the global coordinate system and the local coordinate system can be calculated from the attitude angle to complete the modeling work.
