Hydraulic hybrid four wheel drive sport utility vehicle - utilizing the blended hybrid architecture

Improving the fuel economy of on-highway vehicles is of major concern to government agencies, consumers and industry leaders, that has caused an expanding interest in hybrid vehicles. Hydraulic hybrid vehicles show great potential due to their high power density, high efficiency in regenerative braking and low cost of materials. There are many different hydraulic hybrid architectures that allow for better engine management and regenerative braking. The focus for this work is the blended hydraulic hybrid. This transmission achieves high efficiency and response through the use of a hydrostatic power path, additionally a set of check valves enable regenerative braking and blending of engine power and stored power from the accumulator. A modified blended hybrid circuit was designed to allow for all time four wheel drive operation. Simulation was used to validate the design in four wheel drive turning events. Optimal control and dynamic simulation were used to understand how the sizing of main components affected the performance and efficiency of this transmission. The main components that were investigated are the hydraulic pump, the two hydraulic motors, the accumulator volume and minimum accumulator pressure, in addition this was compared to a statically sized transmission. This study resulted in the selection of A 100 cc/rev hydraulic pump, two 75 cc/rev hydraulic motors and a 32 liter accumulator was c. A 1999 Range Rover 4.0 Se was selected as the application vehicle, baseline measurements and empirical data were taken to build an appropriate vehicle dynamics model, and engine model to be used for simulation and control. With this information and results from the parameter study a complete blended hydraulic hybrid transmission was designed, and packaging was completed using 3D modeling. This design was implemented on the application vehicle and different operating modes of the blended hydraulic hybrid were demonstrated