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This paper presents a computer generated model of a hydraulic circuit that is typically seen in hybrid hydraulic vehicles (HHV's). HHV's have shown considerable potential for increasing fuel economy and decreasing emissions for mid-size and commercial trucks that exhibit urban driving habits. The aim of the present model is to aid in further optimizing the performance of the hybrid powertrain and serve as a baseline for future studies into the noise and vibration (NV) associated with the system. The model simulates the regenerative braking process of a parallel type hybrid hydraulic propulsion system. Regenerative braking captures and stores otherwise lost energy into an accumulator. This stored energy can then later be used to propel the vehicle, thus reducing the vehicle's reliance on a conventional internal combustion engine (ICE). This model will serve as a baseline for future developments and will be expanded and validated experimentally in ensuing research.

The primary purpose of this paper is to evaluate how various time-domain system identification techniques, which have been successfully used for different dynamic systems, can be applied for identifying heavy truck dynamics. System identification is the process by which a model is constructed from prior knowledge of a system and a series of experimental data. The parameters obtained from the identification process can be used for developing or improving the mathematical representation of a physical system. In contrast to lighter vehicles, heavy trucks have considerably more flexible frames. The frame can exhibit beaming dynamics in a frequency range that is within the range of interest for evaluating the ride and handling aspects of the truck. Understanding the dynamic contributions of the truck frame is essential for improving the ride characteristics of a vehicle. This understanding is also needed for designing new frame configurations for the existing or new production trucks.

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.