Vibration Mitigation With a Multi-Axial Magnetorheological Mount

Abstract

This paper presents a multi-axial magnetorheological (MMR) mount. An MMR mount has been developed for use with hydraulic hybrid vehicles (HHV). Like hybrid electric vehicles (HEV), HHV provides better fuel economy. An inherent problem to hydraulic hybrid vehicles is vibration of the hydraulic pump-motor (P/M). This vibration can be classified as shock loading for initial start-up, and periodic vibration over a large frequency range. The latter vibration opportunity can be classified as having large displacement at low frequency and small displacement at high frequency. This requires a stiff mount for the low frequency response and a soft mount for the high frequency response. A single axis magnetorheological (MR) mount has previously been developed and studied by the same group. This was done to develop an understanding of the MR fluid and to discover the limitations of such a mount. Models to predict the experimental results have also been generated. These models show a good correlation to the experimental results. Then, the model has been enhanced from the single axis mount to a multi-axial. This was done by examining the 3-D CAD model to develop the different boundary conditions for the simulation. With a multi-axial magnetorheological mount, damping and stiffness can be altered to yield acceptable transmissibility over the frequency range. This is achieved through the use of an inertia track paired with a pseudo-decoupler. These features are commonly found in a passive hydraulic mount; however through the use of MR fluid, the downfalls of the hydraulic mount can be mitigated, e.g. performance deterioration outside of notch frequency. Additionally, a magnetorheological mount is semi-active so there is an inherent stability to the mount. The MMR mount uses elastomer and MR fluid to achieve the static stiffness to support the P/M and achieve low dynamic stiffness for the high frequency response, which is necessary for a good isolator. The advantages of the use of a multi-axial magnetorheological mount are as follows: fewer mounts are required, stability when compared to an active mount, less power required when compared to an active mount, better isolation when compared to pure elastomeric and passive hydraulic mounts. A model for a multi-axial magnetorheological mount has been developed and simulated. For the purposes of this study, elastomer has been considered to have a linear dynamic response. Additionally, the shock response of the mount has not been considered. Future work includes manufacturing a multi-axial MR mount to verify the simulation results.