| Extended-range electric vehicle,as a plug-in hybrid electric vehicle,combines the advantages of pure electric vehicle and hybrid vehicle.It has extended range and environmental protection and energy saving characteristics,and it is of great significance for the promotion and application of electric vehicles.This thesis is focused on the design and research of the auxiliary power unit control system for the extended-range electric vehicle.The function and definition of the auxiliary power unit(APU)are analyzed on the vehicle level.Taking the electric city bus as prototype,the APU system components,such as engine,generator,power battery,parameter matching method are studied.The control scheme of the APU controller is designed by studying the vehicle control strategy which the vehicle controller(VCU)used to control the APU system.On the basis of the traditional APU operation scheme based on the best fuel economy point and the best fuel economy line,a new operation scheme based on APU efficiency is designed.According to the overall demands of APU controller,the design of APU controller hardware and software is completed.The hardware design includes the selection of the APU controller MCU and the design of the minimization system.The input and output signals of the APU control system are analyzed and the corresponding processing circuit is designed.Through the analysis of the system power supply logic,the design of the system wiring diagram is completed.The software design adopts the modular programming method to design the sub-modules first,and finally completes the design of the main program of the software.Through the study of the engine speed control sub-module and the engine start submodule,the engine speed control based on the feedforward-feedback PID and the engine starting control based on the generator speed control are designed.The experimental of the engine starting process and the engine heat process was carried out using the APU system test bench.The general rule of the engine starting process and the starting speed are obtained by the engine starting test.The rise curve of the cooling water temperature at a specific speed was obtained by the engine heat test.In addition,the comparison between the feedback PID speed control and the feedforward-feedback PID speed control of the engine is carried out by the test bench,and a proper method for high dynamically demanding engine speed PID control is obtained. |
