Research On The Operation Modal Identification Method And Experiment Of Dump Truck Frame

The frame of the special engineering dump truck is the main supporting body of the vehicle, with assemblies and components, like power system, driving cab, carriages, axle and hydraulic lifting system, directly installed on the frame. In the process of the vehicle movement, frame needs to withstand a variety of load cases caused by external road roughness, and incentives by internal engine, transmission power and power transmission device. The frame will occur resonance when the inherent frequences of frame are coupled with the external incentive. It will reduce the dynamic accuracy of the vehicle and affect its performance and may even cause fatigue and the failure of the structures and component. The vibration of the frame will be passed to the relevant assemblies, and then affect the performance and reliability various assembly. Therefore, the dynamic characteristic of the frame has a very important influence on the comfort and reliability of the vehicle.The operational modal analysis of the frame can reflect the resonance frequency of the frame and the deformation under the dynamic load instantly, accurately and effectively and it is very important for the evaluation of the structural rationality and the arrangement design. However, when the special engineering dump truck works in the typical working roads, the vibration of the frame and response is very complex because of road excitation and inner vibration. As vibration signal contains much noise, the traditional working mode identification method is difficult to gain accurate results. The frame is subjected to various constraints and needs to install many parts in the vehicle environment, and the dynamic characteristics of the frame can be significantly changed due to external factors such as constraints and additional quality, so the actual working status of motivation is also very complex.Therefore, the design process of frame is not only to meet the requirements of strength but also to give full consideration of the dynamic characteristic. For the frame and related assemblies and components, the rationality of the design needs to be evaluated in the vehicle operation status, instead of paying attention to the intrinsic characteristics of the single parts offline. So it is necessary to establish the evaluation method of dynamic characteristics of frame and related assemblies in the vehicle operation status. The characteristic parameters of the frame and other assemblies and components in working status were utilized to make an analysis and evaluation of the rationality of assembly parts, especially the frame and parts directly installed on the frame, thus the integration of optimization design can be done to enhance the arrangement of the related assemblies and improve vehicle ride comfort and reliability.Some research was carried out in the thesis, which includes the identification of working modes, the evaluation of dynamic characteristic and the arrangement of related assemblies of engineering dump truck working in some typical operating status.The main contents and conclusions are outlined as follows:(1) Working characteristics and vibration response of the dump truck working in some typical roads are analyzed. The research shows that signal-to-noise ratio of the vibration signal is small and the components are complex. It is hard to gain the dynamic characteristic of truck frame just from the frequency spectrum. This paper presents an operational modal method to evaluate the dynamic characteristic of the frame.(2) As the signal-to-noise ratio of the response signal of the dump truck was too small, the average correlation function was used to suppress the noise. According to DC-ERA algorithm, the original signal was replaced by the correlation function, thus covariance-driven stochastic subspace identification algorithm was improved. Average reference based covariance-driven stochastic subspace identification(Cov-SSI/AR) was introduced in this thesis and the robustness of the algorithm used in status of the non-stationary excitation was indicated through simulation and test.(3) Operational modalof the frame of the DT002 dump truck, working in the construction site, were identified based on Cov-SSI/AR. Evaluation strategy of the rationality and dynamic characteristic was proposed, the content of which is to find the stress concentration part and the resonance frequency of operational modalof the frame and evaluate the system accurately.(4) The matching of the driving cab was evaluated according to whether there is resonance frequency between operational modal of the frame and the cab. So did the mounting system. Moreover, the lightweight design of the driving cab was carried out based on the matching. In addition, the mounting system was analyzed and optimized to increase the vibration isolation performance and after the optimization, the decoupling rate and vibration isolation performance were better than before and the ride comfort and reliability of the vehicle were improved.This thesis was supported by the graduate excellent innovation project of Shanxi province of China with grant No.2012-3025 and the high technology industrialization project of Shanxi province of China with grant No. 2011-2368.