Simulation And Experiment Of Electronic Control Unit For Urea-Scr System In Diesel Engine Meeting National Emission Standard Ⅳ

In order to control the atmosphere pollution and protect our home earth, many countries have their emission standards for motor vehicle.Among the current exhaust control techniques for diesel engines, the Urea Selective Catalytic Reduction is presently considered as the best way to diminish NOx originating and to meet National Emission StandardⅣin China. In order to control the Urea Selective Catalytic Reduction System, an Electronic Control Unit of Urea-SCR system used in Diesel Engine was designed based on the requirement of Urea-SCR system in this thesis. According to the modularization design method, the structures and functions of Urea-SCR system was researched and analyzed, every module of ECU was designed. The following research jobs have been finished:1. By investigating the many successful SCR systems used in diesel engine, and with a view to National Emission StandardⅣ, we made the blue print of the Urea Selective Catalytic Reduction System.2. After analyzing the requirement of SCR system and economy, we use the appropriate microcontroller MC9S12 and other electronic components to design the ECU. The modules of ECU,including micro-controller module, sensor signal processing module, power supply module, solenoid driving module and communication interface module were designed. And by optimization design, we improved the stability and durability of the ECU.3. Based on National Emission StandardⅣ, a economical and practical control strategy was devised. Then we designed the driver of each module the ECU, include initialization, variable definition, memory assignment, Input/Output, Analog-to-Digital, Pulse-Width Modulator, Real-Time Interrupt, CAN communication etc.4. Based on CAN calibration protocol, CAN driver and CCP driver was designed for data monitoring and calibration system.5. We have done the experiment of ECU and bench test with SCR system equipped on diesel engine. The bench test show that this ECU has powerful function and high reliability. In the emission test, the NOx have been reduced 74.7%, meet National Emission StandardⅣ.