Numerical calculation and experimental study of the influence of solid lubrication coating on the contact stiffness of planetary gears

• A computational model integrating extended Hertz theory and potential energy method accurately predicts dynamic characteristics of time-varying meshing stiffness in solid-lubricated coated gears, validated via experiments and FEM. • Coating elastic modulus and thickness significantly affect gear stiffness: higher modulus increases stiffness and reduces fluctuations, while thickness inversely impacts stiffness trends for hard (modulus ratio >1) vs. soft coatings (ratio <1). • Experiments show coatings effectively regulate stiffness fluctuations, enhancing dynamic stability and reducing meshing irregularities under complex conditions. • This study offers a theoretical basis for optimizing solid lubrication coatings in aerospace planetary gears, enabling improved reliability and precision under extreme environments via scientific material selection. This study focuses on the stability and control precision issues faced by planetary gear transmission systems in the aerospace field under complex operating conditions, with a particular emphasis on investigating the regulatory mechanism of solid lubrication coatings on gear contact stiffness and dynamic performance. Based on the extended Hertz contact theory and potential energy method, coupled with the elastohydrodynamic model, an analysis model for the coating gear contact stiffness was developed, and its validity was verified through finite element simulation. The theoretical and simulation results showed high consistency in terms of periodic characteristics and stiffness trends. Two solid lubrication coatings with different preparation processes (such as molybdenum disulfide and manganese phosphate coatings) were compared with uncoated gears in the experiment. Using a custom-designed planetary gear test rig, vibration signals were collected and frequency domain analysis was conducted to reveal the effect of coatings on gear meshing stiffness. The study indicates that the coating significantly improves the dynamic stability of gear contact stiffness by regulating the elastic modulus and thickness of the contact area. This study combines theoretical modeling with engineering experiments to systematically elucidate the regulatory mechanisms of coating properties on gear contact stiffness. It provides theoretical support for the surface modification design and life prediction of high-reliability transmission systems in spacecraft, especially in optimizing structural stability under extreme environments.