Abstract: Taking a hybrid electric vehicle (HEV) as the research object, the three component modules of the control strategy, including driver intent interpretation, energy management and coordinated control of the powertrain system are studied in order to improve the reliability of hybrid electric vehicle control program. Considering the characteristic of the hybrid electric vehicle, and to meet diverse functional and performance requirements, a creative real-time and efficient software architecture composed of four functional layers, two data units, and one framework is worked out on the basis of the real-time embedded operating system (RTOS) µC/OS-II and the event-driven application framework for executing hierarchical state machines. Thus the different functions of the software are separated, and the coupling between modules is reduced, so as to facilitate concurrent and collaborative development, and to enhance the maintainability and portability of the software. The issue on how to implement the control strategy developed under the simulation model Matlab/Simulink/Stateflow into the electric control unit as convenient as possible under hand-coding mode is solved. The software is applied on the HEV undergoing lots of experiences on the road, and some typical experiences including process of power shift and regenerative braking are analyzed. Through systematical vehicle test and reliability verification, it is proved that the designed software can control the hybrid powertrain properly and steadily.

Key words: Control strategy, Hierarchical state machine, Hybrid systems, Quantum framework, Real-time operating system, Vehicle test