Improved Estimation of Linear and Nonlinear Hydraulic Mount Models for Transient Responses

New procedures are proposed to estimate the amplitude-sensitive parameters of hydraulic engine mounts that typically exhibit many nonlinearities. The estimation is based on the premise that the analyst has access to limited dynamic stiffness test data (say up to 50 Hz), and the detailed laboratory work required for the nonlinear model development would be minimized. By using an analogous mechanical model, a 3^rd/2^nd type transfer function is suggested to curve-fit the empirical dynamic stiffness data. Key parameters (such as the inertia-augmented fluid damping and decoupler gap length) are approximated and the effects of some system nonlinearities (such as the vacuum-induced asymmetric chamber compliance) are quantified, leading to a quasi-linear model. For the sake of illustration, transient predictions for a free decoupler mount are made; simulations match well with measurements. Main simplifications and limitations of the method are briefly discussed.