Nonlinear torsional vibration analysis of shearer semi-direct drive cutting transmission system subjected to multi-frequency load excitation

The cutting transmission system is always subjected to multi-frequency load excitation due to the complicated working conditions of shearer. Under this condition, the multi-frequency load excitation not only affects the torsional vibration response of the transmission system, but also induces various resonance cases. Thus, the oversimplification of excitation may lead to large errors in the dynamic response of the transmission system and further result in the inaccuracy of the torsional vibration analysis. According to the Lagrange principle, a simplified two-inertia electromechanical coupling torsional vibration model for the rotor system is established considering the electromagnetic excitation as well as the multi-frequency load excitation. Then, the resonance response of the rotor system is solved by the multiple scales method, and a parametric study is conducted to reveal the effects of electromagnetic excitation and load excitation on the amplitude-frequency response, respectively. In addition, other possible resonance cases (combination resonance and combination subharmonic resonance) are also discussed in this research. Finally, by utilizing the Runge-Kutta method, the numerical simulation is carried out to verify the validity of the analytical solutions and the reliability of the proposed dynamic model. The results indicate that the presence of the multi-frequency load excitation introduces the interaction between various harmonic excitations, which significantly change the vibration behaviors of shearer semi-direct drive cutting transmission system.