Study On The Key Problems Of Torsional Vibration Modeling Of Automobile Powertrain

Automobile powertrain, which carries the power from the engine, through the crankshaft,flywheel,clutch,transmission,drive shafts and the drive axles, to the wheels. All of these flexible shafts and rotational inertia of components form a torsional vibration system. When the external torque frequency from the engine,the road,or the self-excited vibration is equal with the inherent frequency of automobile powertrain torsional vibration, which will lead to torsional resonance. This will seriously affect automobile ride comfort, comfort and powertrain components'life. It is necessary to know torsional vibration characteristics of automobile powertrain. Sometimes, torsional vibration characteristics can be measured appropriately through experimental data. But more often, they can not be measured, only estimate them by a series of simplified model and calculation. Therefore, how to establish precise models of torsional vibration and seek appropriate methods of calculation, which are extremely necessary.The study of the model of automobile powertrain torsional vibration is still the traditional theoretical analysis. That is, in accordance with focusing on quality-oriented model, according to the principle that the kinetic and potential energy of the system before and after simplifying remains unchanged, the actual torsional vibration system will be simplified into equivalent mechanical models composed of inelastic inertia disk and flexible shaft without quality. Based on these mechanical models, further establish mathematical models and methods of calculation to solve torsional vibration problems. In this regard, the domestic and foreign scholars have established a lot of models and methods of calculation, but they are not perfect and there are some limitations.To address this issue of torsional vibration modeling of automobile powertrain, this paper will conduct in-depth study and find a better way to solve automobile powertrain torsional vibration problems. Firstly, through theoretical study, based on the finite element idea, the model of torsional vibration of automobile powertrain is established. Secondly, the main excitation which arouses torsional vibration of automobile powertrain-engine excitation will be carried out detailed analysis. Thirdly, on the basis of the existing research, and further expatiates the classic Holzer's method that solves Shafts torsional vibration problems. Finally, based on finite element idea and Holzer's method to solve specific automobile powertrain torsional vibration problems, which verifies the modeling and algorithm's correctness, and furthermore obtain the torsional vibration's response curve under the engine's excitation. The detail of the work is below:(1) The importance and situation of the research of automobile powertrain torsional vibration is summarized. Particularly, the existing modeling and calculation methods of automobile powertrain torsional vibration are introduced.(2) On the basis of equivalent mechanical model, based on the innovative finite element idea, the discrete models and mathematical model are further founded. At the same time, based on the software of MATLAB, compiles the procedures of finite element modeling are compiled, and the procedures are generic.(3) Comprehensively referencing to the relevant literatures of Engine excitation, these forming factors of the engine excitation are summarized. Through rigorous analysis and derivation, the model of engine excitation was established. On the basis of the single cylinder, the excitation of cylinders of In-Line Engine is further analyzed.(4) On the basis of the existing research, the Holze's computer arithmetic of the direct and the branch torsional vibration systems are developed. Classical Holze's method was further refined. On the platform of MATLAB, the corresponding arithmetic is compiled.(5) Rely on the powerful matrix's Operational functions of MATLAB, the natural vibration mathematical models (Matrix equations) based on the finite element idea are direct calculated. Further, based on mode analysis method, the forced vibration response is calculated, corresponding algorithm is constructed.(6) Based on the Holzer's computer method, two specific straight-equivalent system and branch equivalent system'natural vibration is calculated. The results show that: the results of the Holzer's method solving the natural vibration of straight-equivalent system was a bit of precise, but the result of solving branch equivalent system was unstable, and it is difficult to compile uniform procedures.(7) Based on the finite element idea, the mathematical models of the two specific equivalent systems are established, and they are direct calculated to obtain the inherent modes. Compared the results with the results of the Holzer's method and the relevant literatures, they are very accurate. And any branch system can use a common process to model and solve. Furthermore, on the platform of MATLAB, the torsional vibration's response curves are drawn under the engine's excitation.