A Comprehensive Instantaneous Power Loss Calculation Method of Planetary Gear System Considering Tooth Surface Microtopography

Abstract Accurately calculating the instantaneous power losses of the planetary gear system provides theoretical guidance for optimizing the system's structure and enhancing its energy efficiency. Existing power loss calculation methods neglect the influence of tooth surface microtopography and lubrication conditions and are unable to accurately capture the time-varying characteristics of power losses. Moreover, there is a lack of research specifically addressing the coupled dynamics of planetary gear–bearing systems. To address this issue, a time-varying mesh stiffness calculation model has been established using elastohydrodynamic lubrication theory and fractal theory. On this basis, a novel bending-torsional coupled dynamic model of a planetary gear–bearing system was established, which incorporates the effects of tooth surface microtopography and lubrication conditions. The dynamic responses are obtained by solving the dynamic model. Based on the dynamic responses, a new method was proposed to calculate multiple forms of instantaneous power losses, enabling the evaluation of their time-varying characteristics. Finally, the accuracy of the proposed method was validated through test bench experiments. The results show that the proposed approach can more accurately and physically represent power loss behavior. Furthermore, the influence of surface fractal dimension and initial dynamic viscosity on power losses was investigated.