Study On A New Inertial Parameter Testing System And Vibration Isolation Optimization Of Powertrain Mounting System

Powertrain mounting system is one of the major vibration systems which affect the vibration and noise performance of a vehicle. This paper studies two key issues of engine powertrain mounting system isolation design currently, one is inertial parameter identification of powertrain, and the other is vibration isolation optimization of powertrain mounting system which considering the elastic foundation of the vehicle body. The main content includes following aspects:This paper develops a new powertrain inertial parameter testing system. The moment of inertia and product of inertia parameters of powertrain is reversed by testing the six orders rigid modal frequencies of the powertrain mounting system, which the mounting position, angle and stiffness of mounts are known. Based on the modal analysis equation of powertrain mounting system, the inertial parameter reverse method and the initial values of iteration solving are brought out, and then the natures of solution of the method are studied. By using FORTRAN language the powertrain inertial parameter reverse software is compiled, and then a theoretical numerical reverse example and an experimental modal testing reverse example of powertrain inertial parameters are carried out and researched, which verify the correctness and feasibility of the inertial parameter reverse method.Before the powertrain inertial parameter reverse calculation, the mass and the centroid of powertrain must be measured. This paper develops a measurement method and facility for mass and centroid measuring, and the mass and centroid is calculated by measuring the weight distribution and the position of reference points relative to the testing platform of any two or more different postures of the measured powertrain. The mass and centroid projection on testing platform computational formula are deduced, the centroid position transform relationship in engine coordinate system and testing platform coordinate is put forward. A mass and centroid measuring software and a mass and centroid testing facility for powertrain are developed. At last, the mass and centroid of the 4D20 engine body and cylinder combined structure are measured, verify the validity of the method and the software.In order to study the vibration isolation optimization of powertrain mounting system, taking a mine dump truck as the research object, by using Lagrange dynamics equation a powertrain mounting system-entire vehicle modal synthesis model is established, which considers the elastic foundation of the truck body. Modal analysis of the dump truck body is carried out by ANSYS software, and the low order mode information of the dump truck body is extracted for participation the entire vehicle modal synthesis. A dynamic analysis program for the modal synthesis model is developed in the MATLAB environment, and then the modal analysis of the modal synthesis model is conducted. The modal analysis results of modal synthesis model are compared with those of the entire vehicle finite element model in ANSYS; results show that the modal synthesis method is correct and reasonable. The modal frequencies of powertrain mounting system of entire truck is compared with those of 6-DOF powertrain mounting system, the results indicate that powertrain mount system has vibration coupling with the elastic foundation, which leads to the designed frequency of 6-DOF mounting system do not tally with the actual mounting situation on truck, and the frequency error may reaches 1-2Hz.Finally, a vibration isolation analysis and optimization study based on the powertrain mounting system-entire vehicle modal synthesis model is put forward. Comparing with the entire vehicle finite element model, the degree of freedom of modal synthesis model is reduced greatly, and the computational efficiency is improved. The dynamic response of powertrain mounting system is simulated based on the modal synthesis model, and the time-domain and frequency-domain results are compared to those results of transient analysis by ANSYS finite element model, to verify the rationality and the validity of the model and method. On this basis, vibration isolation analysis of powertrain mounting system is carried out, and then a mathematical model for vibration isolation optimization is brought out and solved by sequential quadratic programming algorithm, which obviously improves vibration isolation performance of the original powertrain mounting system.Furthermore, this study closely related engineering practice, has a good theory significance and practical application value.