Gear-Shifting Control Strategy for Parallel Hybrid Electric Truck in Starting Process

The aim of an overall control strategy of a hybrid vehicle is to coordinate the operation of various subsystems by improving fuel economy and reducing exhaust emissions. On the upper level, the supervisory control problems are regarded as power management ones. In earlier studies, many supervisory control strategies were developed to solve the problem on gear-shifting with engine and motor as the driving source at the same time. In view of a parallel hybrid electric truck with super capacitor as its energy storage, the vehicle can be driven only by the motor under frequent start and stop driving conditions. Aimed at improving fuel economy, the global starting control strategy for hybrid electric truck under normal driving conditions can be deduced based on dynamic programming. The obtained control law as well as the rule-based control strategy is implemented on the test bench. Test results according to UDDS, NEDC and HWFET standard driving cycles have shown effectiveness of the obtained gear-shifting control strategy under pure electric driving mode during starting process.