Abstract: The configuration of a new semi-active hydraulic mount with variable-stiffness decoupling membrane is analyzed, and the dynamic characteristics are tested. Based on the theory of engineering hydromechanics, a nonlinear lumped-parameter-model (LPM) is set up to reflect the external and internal characteristics. Based on the fixed points on dynamic stiffness in-phase, the bulk stiffness of upper chamber and the effective pump area of main rubber when the air chamber closed or connecting to atmosphere are identified. The identified results show that the bulk stiffness changes significantly in two different states because of the change of decoupling membrane stiffness. The dynamic characteristics are simulated and the samples are tested, the simulated results agree well with the experimental ones, so the LPM is reasonable and the parameters are correct. Then a single-degree-of-freedom system is modeled, the vibration isolation performance at some typical conditions such as at low frequency, high frequency and the impacted transient response are simulated, the control methods to minimize the force transfer ratio are proposed, which is helpful for the development of semi-active hydraulic mount and powertrain vibration isolation and noise reduction.

Key words: automotive, lumped parameter model, semi-active hydraulic mount, variable-stiffness decoupling membrane, vibration isolation