Research On Vehicle Control Unit For Electric Vehicles With Battery-Ultracapacitor Dual Energy Sources

There are two big challenges that are resource shortage and environmentpollution in the world. Electric vehicle (EV) with advantages of non-pollution, lownoise, high energy efficiency and simple structure becomes an importantdevelopment direction of new energy vehicle. The combined energy of a chemicalbattery with an ultra-capacitor considered as key component is a futuredevelopment direction of on-board storage power sources system for EV, it cansatisfy the EV to have higher specific power and specific energy, reducerequirement for single battery, extend cruising range, and also make for commercialpromoting and applying for EV. The vehicle control unit (VCU) is a corecomponent in EV control system, its advantages or disadvantages directly impacton the whole vehicle power, economy, reliability and other performance. Therefore,developing the VCU with combined energy of a chemical battery with anultra-capacitor and mastering key technologies have an important practical meaningfor EV industry.In the paper, the scheme of whole vehicle control system with combined energyis made from two aspects of power system structure and network structure, and thecharacteristics of combined energy are analysis. The whole vehicle control strategyis determined, and EV control models are established in MATLAB/Simulinksimulation environment. In terms of functional and design requirements of VCU, itshardware and software are designed with MC9S12DG128B control chip, and theEV application layer communication protocol is determined based on the SAEJ1939protocol and actual communication requirements. The CAN buscommunication system is tested based on the CANoe/MATLAB co-simulationplatform.A hardware-in-the-loop (HIL) simulation test for developed VCU is donebased on dSPACE by using development methods of modern control system.The simulation results show that the whole vehicle control strategy determinedcan make the motor control unit (MCU) respond to commands the VCU transfersbetter to achieve software control function of VCU. Combined energy managementcontrol strategy determined exert ultra-capacitor’s advantages of high efficiency inprocess of fast charging and discharging, which effectively protects battery toextend cruising range. The CANoe/MATLAB co-simulation results show that CAN bus communication system designed is able to complete communication with othercontrol units and meet the real-time needs of bus, reach requirements of datatransferred for EV communication system. The HIL simulation results show that theVCU developed can exactly reflect driver’s intention, achieve real-timecommunication of data and commands with other control units, and achievefunction of driving control, regenerative braking energy feedback andcommunication.