Dynamic modeling is the basis of gear system dynamics research. From the perspective of gear dynamics, the cutting part of shearer can be regarded as a rocker gear box. The rocker box is a hollow cantilever structure, which will produce three-dimensional large deformation under the heavy load and strong impact of the roller load. The cutting transmission system is located in the rocker arm box, generally two-stage fixedplus two-stage planetary gear train, or three-stage fixed shaft gear plus one-stage planetary gear train, which will produce multi-point and multi frequency meshing excitation. The cutting transmission system has the characteristics of low speed and heavy load, and the gear teeth will produce large deformation, which makes the actual meshing interval of the gear pair different from the theoretical meshing interval. The deformation of the rocker box will change the gear meshing state, and the gear meshing excitation will be transmitted to the rocker box through the gear shaft and bearing. Therefore, in order to accurately grasp the dynamic service characteristics of shearer cutting part, it is necessary to fully consider the coupling effect of multi-stage gear transmission and rocker box, and accurately simulate the meshing excitation of support system and gear teeth under the condition of large deformation.
At present, the academic circles have established the meshing excitation models under the conditions of large deformation of support system and gear teeth respectively, but they are limited to plane problems, and the three-dimensional problems have not been studied. The modeling process of dynamic substructure method is complex, and there are few reports about the modeling of complex gear system except for the application of commercial software.
Taking the cutting part of shearer as the object, the dynamic modeling method of multi-stage gear system under the condition of large deformation is studied. On the one hand, a three-dimensional gear dynamic model is proposed, which can be used to support system and gear teeth with large deformation at the same time. The model considers the influence of the large deformation of the system on the actual meshing process. The meshing angle and the actual meshing interval in the model are functions of the system deformation, which improves the accuracy of gear dynamics simulation under the condition of large deformation. On the other hand, an efficient modeling method is proposed to solve the problem of complicated dynamic modeling process of multi-stage gear system. Based on the dynamic substructure method, this method systematically combs the key steps of substructure decomposition, substructure assembly, local / global degree of freedom number conversion, and derives the normalized matrix operation form of substructure assembly.
Finally, taking the cutting part of a mg1200 shearer as an example, the multi-stage gear transmission box coupling dynamic model of the cutting part is established, which comprehensively considers the motor, fixed shaft gear, planetary gear, drum, gear shaft, bearing and rocker box, which lays the foundation for the follow-up research of this paper.