Study And Development Of Vehicle Control Unit For Hybrid Electric Bus

With two challenges of energy sources shortage and environment pollution to global vehicle industry, new energy concept vehicle should be researched right now. Compared to traditional ICE vehicle, hybrid electric vehicle has not only characters of ICE vehicle, but also advantages of electric vehicle, and HEV has much perspective to improve fuel economics and reduce emission. At present, HEV has been developed much widely in Japan, Europe and American, and in China HEV also has been developed very a pace. As HEV needs engine, motor and battery to work harmoniously, all the components often change their work mode under the control strategy, all these require a more rigorous condition in the hardware and software for the Hybrid Control System.Hybrid Control Unit (HCU) is the core control component of HEV. It can calculate parameters required such as engine output power, motor and generator torque etc. By the input signals such as driver attempts, accelerate pedal position, gear and brake pedal position and the State of Charge (SOC) of battery. So, it can make the power components cooperate and ensure the HEV to run normally. Besides, it can reach to the high efficiency by running charging and braking regeneration etc. Therefore, the design of HCU will directly influence the power, fuel economy, reliability and other performances.A pattern of control unit was designed for a parallel hybrid electric bus according to the characteristic and work principle of MCU and the method of electro-magnetic compatibility design. According to hardware design plan, hardware design was mainly divided into MC9S12XDT512 least system design, A/D conversion circuit design, D/A conversion circuit design, RS232 serial communication circuit design, I/O interface circuit design, power design and CAN communication circuit design. MC9S12XDT512 least system included Reset circuit design and clock circuit design and so on.According to different requirements for communication in the vehicle, vehicle control network was built up based on CAN bus technology. The communication protocol and messages content of the VCU were designed. Message acknowledgment mechanism based on the PRI of ID was put forward to meet the vehicle communication requirement. The development and testing system of vehicle CAN bus network was designed and analyzed. It could simulate the function of the vehicle network and perform experiments to test the baud rate of network and correctness and veracity of messages to validate the design. The simulation model could be modified and optimized through adjusting the parameters of CAN communication. It offers the gist for the installation and debug of the CAN network in parallel hybrid electric bus.The performance of the system was testified by hardware-in-the-loop simulations. The simulation results showed that the HCU system worked in a stability condition. It was reliable and can meet the commands of the vehicle control function.