Study And Development Of Hybrid Electric Vehicle's Powertrain Control System

Hybrid Electric Vehicle (HEV) has won extensive attention by the world's majorautomobile manufacturers for its good power performance, better fuel consumption and loweremissions, will play an important role for a long period of time in the future. Based on theanalysis of parallel-serial HEV powertrain composition and the working principle of its majorcomponents, this paper determines the overall scheme of the control system. According to thescheme, the powertrain has three driven mode, they are pure electric driven mode, enginedriven mode and co-driven mode. It constructs a CAN network, and co-control each componentby communicating with its control unit via the CAN bus. To control the ouput power of theGasoline engine, an electronic throttle is used to replace the original mechanical throttle.Itrealizes the switching function of vehicle driven mode through the control of wet clutchs'separation and connection which are executed by regulating the solenoid valve of the powercoupler's hydraulic system. It designs a vehicle control strategy, defines a communicationprotocol, develops the vehicle controller hardware, fullfills its software and control algorithmsbased on the deep analysis of the various working mode. At last it testes the control system onthe bench and prototype vehicle.In the design of control strategy, it considers the best engine working range and battery'sstate of charge (SOC) as the major parameters. On the basis of analyzing vehicle's variousoperating conditions and their working modes, it divides the work area of the engine, sets thework scope of the battery's SOC, and identifies the intention of the driver's operation, designs acontrol strategy using a method called rule-based logic threshold.On the basis of the CAN network architecture constructed, it developes the CAN network'sapplication layer protocol of communication, tests and evaluate its performance. Realise adiagnose network based on the unified diagnostic service (UDS). For electronic throttle control,it arise a fuzzy PID control method which combines the PID control and fuzzy algorthim on thebasis of insufficient analysis of the traditional PID control method. And the method has goodperformance in both static and dynamic response. It puts forward with a control method ofswitching power coupling system's different driven mode on the basis of the analyzing themechanical and hydraulic system's working principle.On the hardware side, a vehicle controller (HCU) based on Freescale's dual-coremicro-controller MC9S12XEP100CAG is developed. The HCU includes a minimum system ofthe micro-controller, power management, communication interface, input signals regulating andcomplex driver circuits based on the analysis of system control requirements. Considering theautomotive environment requirement, it also takes some measures that helps improve the anti-jamming performance and the stability in the hardware.On the software side, a detailed division of vehicle controller's embedded softwarearchitecture is done. It optimizes the operating system to ensure the control system real-timeperformance, as well as reducing the CPU load. In addition, it also builds a monitoring softwaremodule for the system's functions, drivers, signals and others in case of fault and failure.Takingcertain anti-interference measures to enhance the system's operation stability under the complexenvironment.After the completion of all design, it integrates the control system developed in hybridelectric vehicle powertrain, and carries on bench and prototype vehicle testing. The powertrainin the testing process switches smoothly between different working modes, and the systemworks stablily. This indicates that the control system can effectively coordinate the control ofthe various components in the powertrain, thus achieves the desired design goals.