Study On Control System Of EGR Valve Driven By DC Motor

Using diesel fuel has been a trend of modern automobile engine. The rearrangement direction of automobile industry policy is harmoniously developed with domestic environment during Eleventh Five-Year Plan. Choosing diesel engine technique as the energy-saving method at the present stage is a big concern for domestic automobile development.With the deep realization of energy crisis and environmental issue, people start to concern the economical efficiency and discharging of diesel engine for automobile. And the emissions regulations are more and more strict. Emissions technology is endowed with higher value of research for achieving the higher emissions requirements which is called Green Technology of internal combustion engine. The implement mode of Green Technology of internal combustion engine is divided into two types; one is purification technology inside machine, the other is cake layer purification technology. The purification technology inside machine is to optimize combustion process and reduce emission pollutants by improving the quality and combustion status of combustible mixture in fuel combustion chamber. The cake layer purification technology is to inject the polluted gas out of fuel combustion chamber into the atmosphere after purifying treatment by additional device outside machine. In the practical applications, these two techniques are complementary each other. Since the existing of combustion environment for combustion engine, NOx and PM could be creating in inverse proportion. Therefore the EGR+DPF technology proved to be a feasible way to solve this problem.It is in this thesis that EGR valve and electronic control system are studied and developed. EGR valve is an important component and the executed part in EGR control system. It further developed into more control precision, faster response speed and higher EGR ratio. The EGR valve of electrically control type become the mainstream market which replace the EGR valve of mechanical type and of vacuum type step by step in the market. And the electrically control EGR valve contains stepping motor driven type, proportional solenoid drive type and DC motor drive type.In this thesis, research object is EGR valve driven by DC motor in the project, designed the electronic control unit of EGR control system which based on MCU named MC9S12XD256MAL produced by Freescale Semiconductor. The similarities and differences of EGR valve driven by DC motor were analyzed. The principle of PWM control DC motor was described. At last, designed DC motor driver circuit used Infineon TLE6209R motor control chip. Introduced the principle of PID control and fuzzy control theory, and designed incremental PID control algorithm and fuzzy adaptive tuning PID control algorithm. The control program was written by C language, and completed control system development of EGR valve driven by DC motor.Proceeded response method off test stand separately with the EGR valve control system driven by DC motors. Analyzed the effectiveness of control system through actual emissions effect with which comparing the emission test on stand. The results indicated that the strategy of fuzzy self-adaptive PID controller is superior to the incremental PID controller. Neither with what off stand valve response speed or overshoot size is, nor with what on stand control effect or closeness degree of target value. Therefore it provided factual basis for choosing the control algorithm of EGR valve control system driven by DC motors in this thesis.