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The chassis are subject to both road profile and engine or pump/motor vibration when a vehicle is moving on the road. The suspension is developed to reduce the effect of the road conditions to the chassis. The vibration from engine or pump/motor of hydraulic hybrid vehicles (HHV) will be also transmitted to the chassis and needs to be isolated. A mixed mode magnetorheological (MR) fluid mount is presented to isolate force vibration for a two degree of freedom (DOF) model based on quarter car concept. The MR fluid mount is designed to work in flow mode and squeeze mode separately and simultaneously. The skyhook control for the MR fluid mount is also been designed and simulated. Both displacement transmissibility and force transmissibility for each mode and for combined modes have been obtained. These simulation results present a basis for designing a more effective controller to control both the displacement transmissibility and force transmissibility.

Gasoline-electric hybrid vehicles are becoming popular due to their high fuel efficiency and lower emission. While this technology has proven effective for passenger cars and light SUVs, it is not as effective for heavier vehicles. Hydraulic hybrid vehicles offer an alternative hybridization technology for heavier vehicles. This alternative technology is especially effective for frequent-stop vehicles including city buses, delivery vehicles, and refuse trucks. This paper, using simulations, investigates the noise and vibration problem of hydraulic hybrid vehicles. The noise and vibration is mainly caused by the moving parts of the pump/motor, which is the main component of hydraulic hybrid systems. The variable speed motion of the pump/motor inner parts takes place under time-varying levels of hydraulic high pressure. The proposed solution consists of magnetorheological (MR) mounts isolating the hybrid system from the vehicle chassis.

The paper presents the design and control aspects of a magnetorheological (MR) fluid based mount. The proposed design yields a high static stiffness and a low dynamic stiffness in the working frequency range of the mount, enhancing the vibration isolation capabilities of the mount compared to existing hydraulic mounts. Vertical vibrations, namely displacement/force transmissibility, can be isolated or significantly reduced, in real time, by controlling the fluid yield stress through an applied electric current. The mount governing equations are derived and the effectiveness of the mount is evaluated for two cases: low frequency-high displacement and at high frequency-low displacement. These cases correspond to the operation of the mount in squeeze mode and in flow mode, respectively. Preliminary results on the implementation of a skyhook control strategy are also presented.