Research On Dynamic Modeling For Spur Gear Transmission System

Gear transmission is widely used in machine systems, such as machine tools, automobiles,airplanes, for its advantage of steady transmission ratio and high efficiency. Because of gearmeshing and the complexity of shafting, gear transmission influences enormously on thedynamic characteristic of the entire machine system. However, there are many joints in geartransmission system, which make it very hard to build a dynamic model.To these problems,this article builds a dynamic model for bearing joint and gear meshing joint respectively.Combining the finite element method, a dynamics model for a gear transmission system isbuilt. Meanwhile, a method of identifying the dynamic parameter is proposed. Finally, agearbox test-piece is designed to verify the validity of the method.A simplified dynamic model for shaft-bearing-base system is built, based on which, aformula is derived to identify the stiffness of bearing joint. To identify the bearing jointstiffness of the test-piece, a modal test is designed on the gearbox with another shaft removed.Based on the formula and the test data, the bearing joint stiffness of the test-piece is identified,and the damping is calculated.Based on the model updating theory, a method to identify the gear meshing jointstiffness is proposed. A modal test is designed on the gearbox assembled, through which theresponse data are obtained. Based on the model updating method, sensitivity analysis isconducted to set the optimization objective. Final, the gear meshing joint stiffness of thetest-piece is identified, and the damping is calculated.According to the method proposed above, the dynamic model is built for the gearboxtest-piece. Modal analysis is conducted in Nastran, and the first five order parameter isobtained. Compared with analysis result based on test data, the natural frequency errorbetween the theoretical and experimental results is only3.8%，and the modal shapes agreewell．Furthermore, another dynamic model is built with method proposed by anotherresearcher, and the result illustrates the method in this article is more accurate.