Simulation And Test Research On Dynamic Characteristics Of The Passenger Car Torsion Beam Rear Suspension System

When the car is traveling at a moderate speed, the main factor causing interior vibration is the interaction between tire and road. The excitation comes from uneven road will cause wheel vibration, which is buffered and absorbed by suspension system, and finally spreads to the body causing structural vibration and noise. In the engineering practice, significant noise in the process of moving at a moderate speed has become an universal problem for FF passenger cars which apply torsion beam rear suspension. How to improve vehicle NVH performance by optimizing the suspension system design caused widespread concern in the industry.The torsion beam suspension system widely used in affordable passenger cars has been chosen as research object, combining simulation and test for further study on dynamic characteristics and analyzing vehicle vibration based on the dynamic characteristics of rear suspension system. The stiffness of the rubber bushings which are used to connect suspension system and body has been selected as the influence factor, in order to identify the effect law for the purpose of improving the modal distribution of the suspension system and reducing the vibration response of chassis.For the sake of revealing the inherent characteristics and the vibration transmission characteristics of the suspension system. This paper conducted a comprehensive test analysis of dynamic characteristics for torsion beam suspension system through various NVH experiments. The experimental modal parameters, function transfer of vibration (VTF) and characteristic parameters of each elastic damping elements have been obtained. All of above-mentioned parameters also provide experimental data for simulation modeling and model validation of the suspension system.According to finite element theory, this paper conducted a simulation analysis of dynamic characteristics for torsion beam suspension system based on a simulation platform offered by Hyper Works. Which focus on the characteristics equivalent expression of each components and simple simulation principle of each boundary constraint during the modeling. An equivalent method for the dynamic stiffness of bushings has been put forward and an iron tooling has been used to replace complex tire acting as boundary of suspension system. Then, the validity and accuracy of the above-mentioned conclusions has been verified by the test results to get a fine FE model.Based on the FE model of torsion beam suspension system, this paper conducted a sensitivity analysis. The stiffness in each direction of the install bushing which is used to connect suspension and body has been chosen as a single variable, and the lower order modal frequencies of the suspension system as analysis objects. The correspondence between one direction of the bushing stiffness and one order modal shape of the suspension system has been discussed. Then, the law of suspension system modal distribution changes with bushing stiffness has been revealed. Accroding to the study, the front three modes of vibration for suspension system are mainly in the Z and X directions, so the modal frequencies are also mainly affected by both directions.Another project is to add some subsystems besidefangxs rear suspension subsystem for a vehicle parametric model including front suspension subsystem, steering subsystem, tires and body subsystem. The stiffness of the install bushing has been chosen as analysis object, to discuss the influence on the vertical vibration acceleration response of the vehicle chassis.Through the real vehicle test to verify the validity of the above law. Study shows that it advantageous to reduce low-frequency vibration in the car by reducing the stiffness of the install busing in the Z direction.In summary, this paper reveals the dynamic characteristics of torsion beam suspension system from various aspects, as well as the influence law of each key factor on it. Another focus of discussion is the effect of bushing stiffness on vehicle vibration. All of these provide guidance for the reducing vibration work which comes from road surface excitation and spreads to body via suspension system and thus enhances vehicle NVH performance.