A centralized hydraulic system for passenger cars

The majority of passenger vehicles use separate hydraulic circuits to drive and control high-power components such as the braking and steering systems . While this approach is acceptable, it is possible for significant improve ments in efficiency to be achieved using a centralized system. In order to establish the advantages and disadvantages of the distributed and centraliz ed approaches, a simulation-based feasibility study of the pressure, flow a nd power requirements of the individual engine cooling, anti-lock braking s ystem (ABS), semi-automatic transmission, active roll control and power ass isted steering subsystems was carried out. Using a realistic drive and load cycle together with simulation models acco unting for component non-linearities and dynamics, the flow requirements of an integrated hydraulic system were established. It was shown that the ste ering and roll control suspension requirements were complementary. The stee ring system requires high flow at low forward speeds, while the suspension requires high flow during conditions of high speed. In addition it was show n that, although the peak flow requirements of an integrated system were hi gh, the mean how was moderate and the high demands could be met using small accumulator units, suggesting that the system would be feasible for use in passenger cars. Finally, an energy efficient integrated hydraulic circuit including some degree of safety back-up is proposed.