Mass Properties Identification of a Rigid Body Using Modal Analysis

In performing vibration analysis of the car engine on the engine support, it is necessary to know the mass properties of the engine including mass, position of the center of mass and mass inertia moments. Because the car engine has a relatively complex geometric shape and is composed of different components with different densities, determining its mass properties faces many challenges. There are various methods to determine the mass properties of a car engine, one of the most common of which is the use of modal analysis (mass line method). In this paper, the mass line method is presented in order to find the mass properties of rigid bodies. In order to evaluate the efficiency and accuracy of the method, dynamic modeling of a rigid body with known mass properties is performed in MSC Adams software. So according to the theory of mass line, the rigid body is hung from a soft suspension and a force is applied to it in different locations. Then, by performing Adams simulations, the corresponding acceleration values ​​are extracted at various points. After that, the mass line method is coded in MATLAB software and the applied forces and accelerations obtained from Adams in the time domain are entered as input to the MATLAB code and by executing the MATLAB code, the mass properties of the rigid body are calculated. Finally, the values ​​of the mass characteristics obtained from the MATLAB code are compared with the actual values ​​of the rigid body simulated in Adams, and the accuracy of the mass line method in finding the mass properties is evaluated.