Analysis method of natural properties of powertrain hydraulic mounting system in Laplace domain

In view of that the dynamic stiffness of hydraulic mount nonlinearly changes with excitation frequency, a Laplace domain analysis method is adopted to calculate the natural properties of powertrain hydraulic mounting system. Firstly a linear fluid model with lumped parameters for hydraulic mount is built, the steady state dynamic stiffness characteristics of powertrain mount in both low and high frequency bands are analyzed, and the dynamic stiffness expression for powertrain mount in a wide frequency range is obtained. Then a vibration model for powertrain mount is created in crankshaft coordinates and an analysis method of the natural properties of system is derived by directly applying dynamic stiffness expression of hydraulic mount in Laplace domain. Finally this new method is used to calculate the natural properties of a hydraulic mounting system. The results indicate that hydraulic mounting system has complex eigenvalues and complex modal vectors, in which eigenvalues contain information of the natural frequency and damping ratio of system. The type of mode can be judged according to damping ratio and the magnitude of complex modal vector, while the specific mode shapes can be determined based on phase information of complex modal vectors.