Research And Development Of SCR Electronic Control System For Diesel Engine Based On MBD

Diesel engine is widely applied because of its many advantages,such as high power and wide torque range,but it also brings exhaust pollution problem.With the increasingly stringent emission regulations,aftertreatment technology has become an indispensable part of the diesel engine.SCR(Selective Catalytic Reduction)technology has been used as the mainstream aftertreatment technology in our country because of its good fuel economy and so on.This technology has a significant effect on purifying diesel exhaust pollutant NO_X.At present,in the SCR system market,especially the electronic control system,the foreign enterprises occupy most of the share,without the core technology,the domestic still have no mature and stable products to compete.Therefore,the research and development of electronic control system for SCR system and its core components are great significant.The main work of this article is as follows:1、The SCR system is built.On the basis of investigating the application and research of SCR system at home and abroad,the air auxiliary and non-air auxiliary SCR system are compared.The SCR system is built based on the urea pump developed by this project group.In order to improve the stability of the system,the system structure is optimized.The working principle of the system is analyzed,and the system parts are discussed in detail.2、The hardware circuits of the controller are designed.The requirement of the SCR system is analyzed.Based on the NXP 16 bit MCU MC9S12XEP100,the whole frame of the hardware circuit and the circuit design of the function modules are carried out.The specific circuit design mainly includes the selection of the main control chip,the design of the power supply circuit,the design of the input signal conditioning circuit,the design of CAN(Controller Area Network)communication circuit and the design of output driver circuit.3、The strategy is studied and the software is designed.Based on the principle of modularization and referring to the AUTOSAR(Automotive Open System Architecture)standard,the SCR system software is divided into the bottom layer,the middle layer and the application layer.Based on Simulink&Stateflow,the SCR system strategy and application layer software are developed,including the system coordination control module,the urea demand calculation module,the low temperature heating module and the OBD(On-Board Diagnostic)fault diagnosis module.Due to the disadvantages of traditional software development,such as low efficiency,large amount of work and difficulties in writing code,this topic is based on the SCR system control algorithm and uses the MBD(Model-Based Design)development process to build the model of system algorithm,simulate and validate of models and automatically generate C codes from model.4、Experiments and tests are carried out.In the CodeWarrior IDE,the application layer code generated is integrated with the underlying and middle level code.Then it is downloaded into the controller,and related experiments and tests are carried out.The urea pump experiment platform is set up in the laboratory environment.The verification of the urea pump’s function and the metering injection precision is carried out.The experimental results show that the developed urea pump can operate normally and the precision of the metering injection is high.In the bench test environment,the ESC and ETC test of diesel engine with a SCR system developed by this project is completed.The test results show that the NO_X emission values under ESC and ETC standards are 1.606g/(kWh)and 1.527g/(kWh)respectively,which can reach the five emission limit level of the state.