Research On Vibration Reduction Of ATV

ATV (All-terrain vehicle) is three- and four- wheeled vehicle with over-sized, low-pressure tires, over-rode style, handlebar steering designed for all-purpose vehicle by a single rider. The problem of ATV's vibration not only badly influences its vibration comfort, control stability, safety, but also can arose ATV's structural fatigue destroy. Moreover, with the higher demand for ATV's performance, it becomes important to do the research about ATV's vibration. For modal analysis aims to gain structural modal parameters, it has widely used for the analysis of vibration reduction. ATV's body is defined as ATV's frame with engine, as the key assembly of ATV, its dynamic characteristic directly determines the whole ATV's vibration. Therefore, it's necessary to do modal analysis of ATV's body for obtaining its modal parameters. Then we can find out dynamic defects in the body and suitably modify them to improve vibration accordingly.The main aim of the dissertation is to resolve the bad vibration of a certain type ATV150 at 50km/h. Firstly, the modal parameters of ATV's frame and body were obtained by calculated modal analysis, then by experimental modal analysis the calculated models were proved. From the view of the matching between the dynamic characteristic of ATV's body and engine excitation, its dynamic defects were analyzed and pointed out. Finally, based on body's finite element model, in order to improve its dynamic characteristic for resolving the problem of ATV's vibration, some structural improvements were done suitably. Concrete contents as follows:â‘ Utilizing the reverse engineering technology and the 3D modeling software CATIA, the geometry model of ATV's frame was established, then the finite element model of ATV's frame and body were set up with FEA (finite element analysis) pre processing software MSC.Patran. At last, by importing the finite element models into the solution software MSC.Nastran,the front six modal parameters of ATV's frame and body were obtained.â‘¡With the LMS modal analysis testing system, the EMA (experimental modal analysis) of the ATV's frame and body was done and the front six experimental modal parameters of ATV's frame and body were obtained.â‘¢Through comparing with the results of FEA and EMA, it was showed that the calculated modes were very close to the experimental modes, so the finite element models can be considered correct and accurate. Then the matching analysis between the dynamic characteristic of ATV's body and engine excitation was done. As a result, it's found that the ATV's bad vibration was caused by the body's resonance vibration in respect that the engine excitation frequency was closed to the body's inherent modal frequency.â‘£According to the vibration reduction theory, three kinds of vibration reduction method were proposed. Then taking the practicability into account, the method of improving dynamic characteristic of ATV's body was chosen. When the method was implemented, the improvement of the ATV's frame and the link between the engine and the frame was done separately. At last, the results was showed that the improvement for the ATV's frame to heighten inherent frequency and improve mode shapes was not obvious, however, the improvement for the link between the engine and the frame was obvious. Accordingly resonance vibration was avoided and the problem of this ATV's bad vibration at 50km/h resolved.