The Analysis And Optimization Of Light Truck NVH Vibro-acoustics Character On Transfer Path Method

As the main domestic short distance carrier, Light truck’s NVH performance can affect the driver’s mood and health, severe car vibration and noise can accelerate the driver’s fatigue, prone to traffic accident. In order to improve the NVH performance of a light truck, this paper starts from matching and optimization of the powertrain mounting system, using the finite element theory of rubber material, transfer path analysis, powertrain mounting system mechanics modeling theory, genetic algorithm of optimization theory and experimental analysis theory, systematically researching the improvement method and process of the vehicle NVH performance according to the optimization theory of the suspension systems.First,through the method of rubber material uniaxial tensile and compression testing, it established the rubber material of the VAN_DER_WAALS hyperelastic constitutive model. By using the finite element method it analyses the front and rear rubber suspension’s static and dynamic stiffness in the direction of U, V, W. Using method of the transmission path analysis, comparing three important load identification methods, including direct measurement method, inverse matrix method and suspension stiffness method, this paper uses the inverse matrix method to calculate the impact of each pass path on the vehicle vibration.According to the method and theory of model establishing in the powertrain mounting system, using the parameters in the rubber mount finite element method, the suspension stiffness calculating, the pendulum method using to identify the dynamic assembly center of mass, moment of inertia, product of inertia and other, this chapter establishes the powertrain mounting system of a mechanical model. By using the matching optimization genetic algorithm theory of mounting system, it writes the suspension system decoupled optimization program, two sets of programs are take out: optimizing the stiffness only; optimizing stiffness and rear position and installation angle by the parameters of mounting system vibration energy distribution matrix, modal distribution range, powertrain attitude and each suspended static displacement and stress it verifies that two sets of programs can significantly improve the suspension matching performance. Finally, the optimized suspension stiffness is used as improvement scheme.This paper varied the method of optimization suspension stiffness by testing. Under the four conditions that stationary of constant speed, stationary engines plus speed, road uniform and road transport acceleration, it respectively tests the vibration acceleration signal of the active and passive side at the four powertrain mounting system, the driver and passenger’s seat rail and the noise signal of driver’s right ear. Through calculation and comparison of vibration transmission rate, it is indicated that the vibration transmission rate of the suspension system is reduced, especially the vibration in the direction Y is descended by 90%, and the vibration isolation effect is improved. Through the comparison of vibration and noise signals, it is showed that the vibration amplitude of the driver’s seat and the passenger seat is reduced, and the noise value is reduced by 1-2dB(A), and the passengers’ riding comfort of vehicle is improved.