Study On The Dynamic Characteristics Of Harmonic Drive System Considering Lubricating Oil Film

The subject of this paper comes from the key research and development project of Chongqing artificial intelligence technology innovation major theme "robot collaborative research and development and industrialization for 3C industry"(cstc2017rgzn zdyf0027).As a kind of transmission method different from traditional gear,harmonic gear transmission has the advantages of larger transmission ratio,smaller volume,simpler structure,lighter weight,greater bearing capacity and higher transmission accuracy,which can meet the urgent requirements and characteristics for the development of aerospace,robot and other industries.Therefore,it is widely used in various fields of high-precision equipment.The research of its dynamic characteristics is of great significance to the improvement of accuracy and the extension of service life.In this paper,the harmonic gear is taken as the research object,the comprehensive curvature radius,load and entrainment speed at the meshing point are derived,and the finite line contact elastohydrodynamic lubrication model of harmonic gear is established.The numerical calculation method is used to solve the oil film thickness and pressure distribution in the lubrication area,and the influence of rotating speed and temperature on the lubrication characteristic parameters such as contact load ratio,film thickness ratio and oil film stiffness in the meshing area are quantitatively analyzed.Furthermore,the system dynamics model and equation considering the lubricant film are established to analyze the influence of the existence of the oil film on the dynamic characteristics of the system.The main contents of this paper are as follows:1.This paper introduces the basic operation principle of harmonic gear drive,and establishes the elastohydrodynamic lubrication model of the finite line contact of harmonic gear with comprehensive consideration of load,radius of curvature and entrainment speed.In order to simplify the solution and improve the calculation efficiency,the established lubrication equations are treated dimensionless and discretized respectively,and then the numerical simulation method is analyzed to draw up the lubrication solution flow.2.According to the established lubrication model,the oil film thickness and pressure distribution in the meshing area are analyzed and calculated by using numerical calculation method,and the variation trend of oil film pressure and film thickness in the meshing area under different loads and suction speeds is studied.Then,the film thickness ratio and the contact load ratio are used as the evaluation indexes to analyze the change rule of the lubrication characteristics of the system under different temperature and speed conditions.3.On the basis of lubrication calculation,this paper introduces several oil film stiffness analysis methods,calculates the oil film stiffness under different methods,analyzes the oil film stiffness values obtained by several algorithms under different loads,entrainment speeds and roughness,and verifies the accuracy of the algorithm.Then,the oil film stiffness values in the meshing area of harmonic gears under different speed and temperature conditions are compared and analyzed to obtain the specific change rule with the working conditions,which lays the foundation for the follow-up study of the influence of oil film on the dynamic characteristics of the system.4.The system dynamics model is established,and the system dynamics equation is established considering the factors such as dynamic transmission error and gear comprehensive stiffness under the action of lubricating oil film.The changes of parameters such as harmonic gear system comprehensive stiffness,dynamic meshing force,dynamic transmission error and displacement under the action of lubricating oil film are compared and analyzed,and the influence rule of oil film on the dynamic characteristics of the system is analyzed.