Model With Variable Parameter And Simulation Of Scr System

With more and more extensive application of SCR(selective catalytic reduction)technology in the field of ship and automobile and environmental problems becoming increasingly prominent,emission standards are more and more stringent.The open-loop control strategy based on MAP is the present strategy for SCR system,with the upgrade of the regulations,the open-loop control strategy will be difficult to meet emission standards.And for all control problems,system modeling and parameter identification are the basic work.When the structure and model parameters of the system are determined,many mature design and analysis methods of control system could be used.But for SCR system,most of the models are based on the chemical reaction mechanism,which is of great help to the analysis of ammonia storage characteristics and conversion efficiency but of little help to the control algorithm design of the system.This paper is aimed to determine the model structure of SCR system,establish the model of diesel engine SCR system and identify the parameters of the system model through the experimental study on some engine,and set up multi variable parameter model of SCR system through statistical modeling method.The accuracy of the model is verified in the software platform,and the model is used to validate the control strategy.The main research contents are as follows:(1)Design the step response test,identify the parameters of SCR system model under various conditions based on the experimental data and establish the parameters collection.Use control variables method to deeply analyse each parameter of the model from the perspective of test data.Study on the factors that affect the parameters and propose the concept of multi variable parameters.(2)Describe the reaction process of SCR system,analyse the essential reason of model parameters affected by multiple factors from the aspect of the reaction mechanism and the test data.(3)Fit the coefficients of multiple linear regression equation of each parameter by using multiple linear regression method.Analyse the fitting results and partial correlation according to the correlation between variables.(4)Assume the nonlinear multivariate function of the parameters with the mechanism analysis result and find out the the highest related nonlinear factors to parameters through correlation analysis and the final form of each parameter.Identify the unknown coefficients of the functions with MATLAB software and verify the results with offine data of ESC cycle.(5)Establish the simulation model of SCR system in Matlab/Simulink platform,design and complete the simulation and verification platform with Matlab/GUI tool,which can verify the reliability of control algorithm and predict the control results.