Energy consumption and exhaust emissions of hybrid vehicles strongly depend on their configuration, power ratios of the components and applied control strategy.
Recent developments of new hydrostatic units, which are characterized by high power density, low weight, low noise and high efficiency over a wide range of operation, make hydraulic technology look promising for the application in passenger cars. The prototype models of hydraulic hybrid vehicles HHVs that have been built, especially in applications of SUVs and larger vehicles have demonstrated their ability to significantly reduce fuel consumption and CO2 emissions. The introduced hydraulic hybrid vehicle can compete with current electric hybrid vehicles. The paper presents a simulation study in the DSHplus environment and a power management strategy for the novel series hydraulic hybrid vehicle, known as the Hydrid, along with an explanation of system operation and control that allows energy recuperation in a hydro-pneumatic accumulator during vehicle braking to use it back during propulsion. The general architecture of the Hydrid was introduced by the Dutch organization Innas BV, replacing the mechanical transmission with a distinct series hydraulic transmission which includes innovative components such as a thee port-plate hydraulic transformer, a fixed displacement pump and in-wheel hydro-motors designed on the new high efficiency floating cup principle. However, more than in any other drivetrain, the robustness of the applied power and control strategy is dependent on the driving cycles which may include aggressive or smooth patterns. Therefore, three standardized drive cycles are applied in the simulation model, such as the European NEDC, the American FTP-75 and the Japanese 10/15-mode cycles. Operation performance, system variables behavior, fuel consumption and CO2 emissions will be evaluated for each cycle. The simulation results indicate that the introduced drivetrain exhibits low fuel consumption and CO2 emissions compared to a conventional baseline mid-sized vehicle. The good fuel economy is a result of forcing the engine that is decoupled from the vehicle wheel to run only at medium to high loads as well as shutting-off the engine at idle and braking modes.
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