Vibration Isolation Analysis And Design Optimitation Of Vehicle Powertrain Mounting System

Engine vibration is one of the main sources of vehicle vibration which affecting vehicle's comfort and NVH(Noise, Vibration and Harshness)performance. The NVH of a vehicle represents an overall evaluation of a vehicle's quality and refinement, and it is also the key question which in the vehicle high-quality process must be solved.A rational design of a vehicle powertrain mounting system can significantly isolate vibration from being transmitted to the vehicle body. Effective isolation will increase a vehicle comfort and extend the durability and lifespan of the engine and other vehicle components.This paper studies the powertrain mounting system vibration isolation for a domestic vehicle. The primary work includes the following aspects.First, the paper examines the research and development progress of powertrain mount and mounting system design optimization world wide; studies the fundamental theory and design method of the powertrain mounting system; determines the powertrain mounting system excitation force; deduces dynamics equation of powertrain mounting system from LaGrange equation and constructs non-linear mathematic models by utilizing mechanical and hydro-elastic equations for both conventional rubber mounts and hydraulic mounts. Based on the combined simulation techniques, the paper simulates the mounting system's vibration performance under different mounts and different working conditions. The results were analyzed and compared with the experimental data.Second, the paper analyzes vibration characteristics of the powertrain mounting system from system natural frequency collocating and vibration decoupling point of view; examines mechanical system and sensitivity design optimization methods to improve system modal decoupling and achieve optimal design for vehicle powertrain mounting system; uses Monte Carlo technique to compare the original design and the modified one for robustness. The result shows that the design optimization study for powertrain mounting system will improve the system vibration isolation, stability and reliability. The result also demonstrates the effectiveness in engineering applications of mount design by using Monte Carlo method and mount parameters sensitivity analysis.Finally, the paper constructs a MBD(Multi-Body Dynamics) simulation model with the powertrain and vehicle system; compares vehicle model in terms of final natural frequency changes for powertrain system in primary excitation directions. The vehicle simulation study demonstrates that the mounting system will reduce the transmissibility after the optimizing parameters of the system and verifies the correctness and reliability of the optimization results. It concludes the vehicle simulation model could be used as a method for powertrain mounting system design and optimization and guide vehicle NVH study in the future.