Analysis And Optimization Of Automotive Powertrain MRF Mount Based On Flexible Foundation

With the development of national economy and the improvement of living standards, people hold higher requirements for the driving comfort of automotive. The driving comfort of automotive is directly related to the vehicle's NVH(Noise, Vibration and Harshness) performance, and the vibration isolation effect of the engine mount system will directly affect the NVH performance of automotive. It is how to design the mount system that can reduce and isolate vibration that the engine transmit to the frame or the body that is the key point to improve the NVH performance and the driving comfort of automotive, also is the emphasis of this paper.Basing on the FEM and Multi-body Dynamics Theory, this dissertation establish a magnetorheological fluid mount system's rigid flexible coupling model to analyze the influence that the flexible foundation upon mount system by use of the ADAMS and ANSYS software platform, and then the Mount Components are optimized based on the rigid flexible coupling model. The research contents of this dissertation are summarized as follows:By counseling the relevant literature, this dissertation analyzes the current research on the power train mounting components, mount system optimization design, introduces the modern automobile engine power train mount system optimization design theory and methods, and then presents the main significance and the purpose of this study to provide theoretical guidance for the optimization of the design based on the flexible foundation.This dissertation introduces magnetorheological mount structure and principle; establish the mechanics and mathematical model to analyze the dynamic characteristics of magneto theological fluid mount through the bond graph theory. The dynamic characteristic equation of the internal structure parameters of the mount of the low frequency and high frequency were established, which lay the foundation for the following simulation analysis and optimization design.Before the establishment of the system model, firstly this dissertation analyzes of the vibration reason of the engine and Power train vibration isolation theory. By Step by step modeling method, establishing power assembly mounting system model accord to multi-body dynamics theory, establishing the flexible frame model which can be used to exert rigid flexible coupling with the help of finite element analysis software ANSYS, creating the suspension and the tire subsystem in Adams, simplifying the body as a rigid ball. Finally, under the Adams/view module, the rigid flexible coupling based on flexible foundation system was established.Firstly this dissertation introduces several evaluation indexes of vehicle vibration isolation, analyzes their advantages and disadvantages, and finally selects the vibration level drop as the evaluation method of this paper. With the help of Adams/vibration module, this dissertation analyzes dynamic characteristics of rigid flexible coupling system. Through the calculation of natural frequency and frequency response curve and vibration level difference curve, this dissertation analyzes influence that the flexible foundation upon mount system. At the same time, four kinds of working conditions are carried out, and the differences between the power train on the rigid foundation and the flexible foundation are analyzed.By using of the rigid flexible coupling model established in ADAMS, the magnetorheological fluid mounting elements are optimized. Using the mount's at the junction dynamic response amplitude changes and engine centroid displacement and acceleration changes to verify the correctness of the optimization.