Theoretical Study On Transmission Characteristics Of Differential Planetary Roller Screw

Differential planetary roller screw(DPRS)has been widely used in aerospace,weaponry,robots,automotive,high-precision machine tools,petrochemical industries and other key national development areas because of its advantages such as high precision,high efficiency,high load ratio,high reliability and high stability.However,currently DPRS has problems such as weak basic theoretical research and difficulty in high-quality and high-efficiency batch production.It is urgent to study the basic common technology of the DPRS.To this end,this article takes the DPRS as the research object,and uses a combination of theoretical analysis,numerical calculation and finite element simulation to systematically study the transmission characteristics under the combined action of multiple factors such as structural parameters,material characteristics,manufacturing errors and assembly errors.Its changing laws and related research results have important theoretical significance and engineering application value for key engineering issues such as DPRS accuracy maintenance,life extension and reliability improvement.The main research contents are as follows:(1)Based on the operating principle of the DPRS and the geometric relationship of the transmission,a mechanism analysis is performed to demonstrate the rationality of the transmission from the mathematical level.A DPRS kinematic analysis model is established to analyze the motion relationship between the components and the actual transmission lead of the screw.Based on the principle of space meshing,a DPRS space meshing geometry model is established.The numerical method is used to solve the position and contact area of the meshing point of the roller and the screw.And the influence of the axial tooth profiles of different rollers,key structural parameters,manufacturing errors and assembly errors on the meshing performance of the transmission pair are revealed.(2)The numerical calculation model of load distribution and load capacity of single roller thread tooth surface is established by Hertz contact theory,and compared with finite element simulation results and calculation results of existing literature,the accuracy of the model is verified.The sensitivity of roller load distribution to structural factors and threading errors is discussed,and its influence on the DPRS roller load distribution is obtained.A method for uniform load design of roller threads is proposed to improve the uneven load distribution of rollers.(3)Taking into account the actual contact between the roller and the screw,the Archard wear theory is revised,the accuracy loss prediction model of the DPRS is established,the accuracy loss rate of sliding wear is calculated,and the load distribution under the loss of accuracy is further revealed.The influence of structural parameters,screw speed and nut load on the accuracy loss of DPRS is analyzed,and methods to improve the accuracy loss of DPRS are proposed.(4)Based on the theory of tribology,the principle of the DPRS friction resistance is analyzed,and the DPRS rigid body dynamic model was established by Lagrange method.The dynamic friction torque and transmission efficiency solving equations during the transmission process are obtained.Based on the rigid body dynamics model and solving equations,the influences of structural parameters,screw speed and nut load on the dynamic characteristics of the DPRS are systematically analyzed,which give the design and use principles to improve the transmission efficiency of DPRS and extend the comprehensive service life of the DPRS.