The dynamic modeling method of multi-stage gear system under the condition of large deformation is studied. Taking the cutting part of a mg1200 shearer as the object, 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 arm box

① A gear dynamic model with high simulation accuracy under the condition of support system and large tooth deformation is proposed. The characteristics of the model are as follows

1) The lumped mass model with all spatial degrees of freedom can simulate any tooth surface error / modification by slicing the tooth along the tooth direction;

2) When calculating the micro element load of each slice, the influence of the large deformation of the system on the meshing angle and the actual meshing range is considered, and the meshing excitation under the condition of large deformation is accurately simulated;

3) The angular displacement is used as the generalized displacement, which is the sum of the angular displacement of rigid body and the angular displacement of vibration.

② A more general dynamic model of planetary gear train is established. The pure torsional dynamic model of the planetary gear system is established in the fixed coordinate system (rather than the planetary carrier follow-up coordinate system), and the generalized displacement in the model is angular displacement, so it is more convenient to couple with other substructure models of the gear system, and it is suitable for the simulation of variable speed process. In addition, a unified dynamic equation is derived for the case that the sun wheel may have forward and reverse rotation, which can be used to establish the dynamic model under the condition that the front and rear cutting parts of the shearer have opposite motor rotation.

③ Aiming at the problem of complicated and error prone dynamic modeling of multi-stage gear system, an efficient general modeling method is proposed. At present, when the dynamic substructure method is used to build the gear system model, it usually relies on manual substructure assembly, so the modeling is cumbersome and difficult to be applied to complex objects. In this paper, based on the standardized programming of the key steps of establishing the dynamic model of gear system by using the dynamic substructure method, the corresponding coupling matrix is derived according to the rigid, linear elastic or nonlinear connection mode between components, and the automatic assembly of substructures is realized. Taking the cutting part of shearer as the object, a multi-stage gear transmission box coupling dynamic model including 9 fixed shaft gears, 2-stage planetary gear train, 8 gear shafts, 1 rocker box, 1 cutting drum, 1 cutting motor, 12 nonlinear bearings and 3 elastic torque shafts was established by using this method.