Development of Control System for Parallel Hybrid System with Turbo Engine 2023-01-0547

This paper describes a new control technology that coordinates the operation of multiple actuators in a new hybrid electric vehicle (HEV) system consisting of a turbocharged engine, front and rear electric motors, two clutches, and a 6-speed automatic transmission. The development concept for this control technology is to achieve the driver’s desired acceleration G with a natural feeling engine speed. First, to realize linear acceleration G even while the engine is starting from EV mode, clutch hydraulic pressure reduction control is implemented. Furthermore, the engine start timing is optimized to prevent delayed drive force response by predicting the required maximum power during cranking. Second, to realize linear acceleration, this control selects the proper gear position based on the available battery power, considering noise and vibration (NV) restrictions and turbocharging response delays. Finally, to precisely control engine speed when the clutch is not directly connected, feedforward (F/F) controller and feedback (F/B) controller are implemented. The F/B controller for the engine was specially designed for response and stability considering the dead-time of engine torque response and disturbances. When disturbances occur, this controller reduces both the overshoot and settling time to the target value as compared to using a simple PI controller. These control technologies achieve shorter engine start time by 20%, powerful acceleration at low engine speed, and precise engine speed control. These contribute to driving pleasure of the new parallel hybrid system.