Discussion Of Dynamic Characteristics And Modeling Methods Of Automotive Engine Hydraulic Mount

Passive hydraulic mount is a new type of automotive engine vibration isolator. Because its dynamic stiffness and damping can be frequency- and amplitude-dependent, it can provide a better performance than conventional elastomeric mounts. Hydraulic mount are used widely in China. This paper analyses the typical structure, working principle and characteristics of two hydraulic mounts, addresses in detail the modeling methods of engine hydraulic mounts.In order to understand such a passive device, using the laws of physics, a complex nonlinear mathematical model with lumped mechanical and fluid elements is proposed. More nonlinear aspects are considered, such as the effect of static deflection, oscillatory flows, and air volume in the top portion of the upper chamber. Compared with measured signals under sinusoidal testing conditions of mount 1, the model predicts time and frequency domain responses reasonably well. Based on the computer simulation, the effects of the parameter values on the low-frequency performances are studied and the choice of mount design parameters optimal vibration isolation performance is discussed.The complex nonlinear model developed above is directly related to the structure of the engine mounts. It is too complex to be used in the modeling and simulation of vehicle ride dynamics. Based on the result of sensitivity analyses of the parameter vales, an 11-parameter-simplifying-low-frequency-model is set up by omitting unimportant aspects.System identification is another modeling method in common use. Several methods of identification were attempted in a previous study, but the results were disappointing owing to the complicated behavior of the hydraulic mount. A routine for identifying the model parameters in this paper is based on the simplifying low-frequency model, differential evolution algorithm and sinusoidal testing. When compared with measured signals of mount2, the identifying model predicts time and frequency domain responses reasonably well. So the identification procedure described in this paper was successful.