Vibration Analysis of Powertrain Mounting System with a Combination of Active and Passive Isolators with Spectrally-varying Properties

Most of the prior work on active mounting systems has been conducted in the context of a single degree-of-freedom even though the vehicle powertrain is a six degree-of-freedom isolation system. We seek to overcome this deficiency by proposing a new six degree-of-freedom analytical model of the powertrain system with a combination of active and passive mounts. All stiffness and damping elements contain spectrally-varying properties and we examine powertrain motions when excited by an oscillating torque. Two methods are developed that describe the mount elements via a transfer function (in Laplace domain). New analytical formulations are verified by comparing the frequency responses with numerical results obtained by the direct inversion method (based on Voigt type mount model). Eigensolutions of a spectrally varying mounting system are also predicted by new models. Complex eigenvalue problem formulation with spectrally-varying properties provides a closer match with experimental results than the real eigenvalue formulation with frequency-independent mounts. Given the spectral variance in the mount properties, a simple roll mode decoupling scheme is suggested for the powertrain isolation system. Then, the role of active path is clarified by comparison with no actuator operation. Multi-dimensional motions (especially coupling) are predicted and in particular the effects of active mount parameters such as the orientation angle, location and actuator input are investigated from the motion coupling perspective.