| Environmental pollution and energy shortages enormous pressure greatly promoted the development of electric vehicles, however, because of electric vehicle are faced with higher costs and short running mileage bottleneck problems, make Extended-Range Electric Vehicles become the more realistic solutions. Extended-Range Electric Vehicles auxiliary power unit (engines-generators, APU) is used to coordinate the distribution of energy, according to the state and the vehicle work mode, provided drive motor energy or charged the battery, and engine’s control is the key to ensure APU stable, efficient and low-pollution operation.This paper based on design requirements of APU systems control unit (ECU), completed ECU design improve and control from hardware, software and background calibration software three aspects based on the early development of control systems, solved problems exposed in the original system and unresolved issues. The main contents are as follows:(1) Based on vehicle performance design requirements of Extended-Range Electric Vehicles, made a specific parameter matching for powertrain part, and determined the appropriate motor, battery and specific parameters of Auxiliary Power Unit system.(2) Improved hardware design of ECU. Complemented signal conditioning circuit which include generator voltage, battery voltage and switching oxygen sensor, designed ignition modules, oxygen heating drive circuit, add fuel pump relay, starter relay and generator control relay driver circuit, In order to achieve ignition digital control, closed loop air-fuel ratio control, APU automatic start-stop control and battery charge control.(3) Improved software design of ECU. Based on μC/OS-Ⅱ real-time operating system and task scheduling mechanism, interrupt service system, developed ECU software system, which includes sensor input signal acquisition, analysis and physical conversion task, closed loop air-fuel ratio control, ignition control task, throttle position drive control tasks, auxiliary power system start-stop control tasks and communication protocols and so on. On the basis of APU constant speed control mode added the constant voltage control mode to achieve the generator voltage feedback control. (4) ECU calibration system development. Based on Visual Basic development environment, developed this calibration software. Based on CAN bus communication, could online settings engine operation control parameter, real-time monitoring the state of engine operation parameters and has MAP data upload, modify, store, downloads and other features.Completed generator voltage feedback control and throttle control experiment in the engine pedestal, the results showed, ECU hardware and software worked reliably and achieved the desired results. |
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