Control strategies for a series-parallel hybrid electric vehicle

Living in the era of rising environmental sensibility and increasing gasoline prices, the development of a new environmentally friendly generation of vehicles becomes a necessity. Hybrid electric vehicles are one means of increasing propulsion system efficiency and decreasing pollutant emissions. In this paper, the series-parallel power-split configuration for Michigan Technological University\u27s FutureTruck is analyzed. Mathematical equations that describe the hybrid power-split transmission are derived. The vehicle\u27s differential equations of motion are developed and the system\u27s need for a controller is shown. The engine\u27s brake power and brake specific fuel consumption, as a function of its speed and throttle position, are experimentally determined. A control strategy is proposed to achieve fuel efficient engine operation. The developed control strategy has been implemented in a vehicle simulation and in the test vehicle. Simulation and experimental results are presented and discussed. The control strategy leads to a series hybrid vehicle behavior at low speeds and parallel hybrid vehicle behavior at highway speeds. Furthermore, the strategy ensures charge sustaining vehicle operation