Research On Hardware Design And Simulation Of Electronic Control Unit For Gasoline Direct Injection Engine

Gasoline Direct Injection?GDI?is an important branch of current engine research,and is also the foundation for realizing Homogenous Charge Compression Ignition technology and ultra-thin technology in cylinder.Electronic control unit is the foundation for direct injection in cylinder.It is very important to study the key circuits of ECU and ameliorate these key circuits to improve performance of ECU.This paper focuses on in-depth research on temperature sensor interface circuit,pressure sensor interface circuit,crankshaft position sensor interface and fuel injector drive circuit,and improves circuit topology,and the performance of these key circuits is optimized.The specific work is as follows:1)Measuring signal resolution ratio of the tandem-temperature-measuring-circuit is different in different temperature intervals,and some temperature intervals are highly resolution ratio and,some temperature intervals are lowly resolution ratio.Aiming at this problem,R-T function model of temperature sensor is established by using a×e^b×x+c×e^d×x model and a function of measuring signal and temperature,pull-up resistance is established.Based on maximum resolution ratio of measurement signal within the temperature range of the sensor is the optimization target,to improve temperature sensor interface circuit.Improved interface circuit achieves the maximum resolution ratio of measurement signal.2)Dynamic response of the pressure sensor is slowly and can not respond to pressure signal in the intake manifold quickly.The zero-pole-placement-method is used to improve dynamic characteristics of the sensor.Through time constant of the first-order model of the pressure sensor to determine zeroe of needed elimination and spectrum analysis of pressure signals in the manifold are determined to determine the poles required.A compensation transfer function is established and RC active compensation filter is retrieved by the transfer function.Improved interface circuit compensation pressure sensor can significantly improve dynamic response speed of the sensor.3)The output signal amplitude of crankshaft position sensor is greatly influenced by speed,which brings great difficulty to signal shaping.Interference causes partial loss or increase of crankshaft signal and brings large phase error.Aiming at these problems,a differential-filter-difference scheme is used to improve the interface circuit of the crankshaft position sensor.Improved circuit can complete the signal shaping and overcome the problem of increasing the crankshaft signals,phase error can be controlled within 0.5 degrees,but the problem of crankshaft signals loss can not be eliminated and the phase error is not linear with the engine speed.4)The fuel injector needs different current changing rate at different stages when injector injecting,single current freewheeling loop can not meet the demand of current changing rate.In view of this problem,the driver circuit topology of the injector is improved by introducing different current freewheeling circuits at different stages.The first,third stage adopts the Buck type current circuit,and the second stage adopts the D type current circuit,a new control strategy is designed.The improved driving circuit can reduce the calorific value of the solenoid valve of the injector,save energy and reduce the opening and closing time of the injector.5)The design of other sensor signal acquisition interface circuits and the design of igniter and electronic throttle driving circuit are completed.