Research Of Closed-loop Control Strategy Of Urea-SCR System Based On D2P Platform

With the rapid development of China's automobile industry,automobile production and sales have been ranked first in the world.The diesel engine is a kind of internal-combustion engine with high efficiency and fuel economy,and has been attracting more and more attention,with the proportion of vehicles propelled by diesel engines increasing continually.Consequently,the diesel engine NOx emissions causes serious environmental pollution problems.SCR technology can efficiently reduce NOx emissions.A crucial issue regarding the use of SCR as the key technology in this regard is to develop a reasonable urea injection control strategy.This dissertation focuses on how to reduce NOx emissions as well as how to deal with the NH3 leakage problem more efficiently through a closed-loop control strategy research on a Urea-SCR system by means of Rapid Control Prototype(RCP).A kind of closed-loop control strategy of Urea-SCR system based on NH3 feedback,comprising feedforward control strategy and closed-loop control strategy has been studied in this paper based on the D2 P platform.The PID control algorithm was used for the NH3 feedback closed-loop control,with the purpose of tuning the PID parameters.In this study,tuning the PID parameters was achieved by using the self-tuning function of the PID module.This way,it was possible to obtain a fast response and robustness with good effect.Furthermore,it was possible to debug PID parameters online through the Rapid Control Prototype technique,facilitating the realization of the real-time adjustment of PID parameters.As a consequence,this could meet the actual environmental control requirements,and ultimately leading to a greatly improved offline optimization of the parameters and the actual.The study focused on how to use the nonlinear least squares method for urea SCR control strategy and model parameter identification,including SCR catalytic converter temperature model and SCR catalyst chemical reaction model.This study mainly used the lsqnonlin function of Matlab to identify the parameters of the model based on the principle of nonlinear least square method.An experiment shows that the identification results were very good for satisfying the actual working conditions of the model.The control strategy was verified using the hardware-in-loop based on the D2 P platform.This mainly included the following steps: design of experiments;establishing the model and setting up the D2 P test platform.After debugging the model in loop real-time,the experimental results were better than that of the offline simulation.Additionally,the NOx emission was further reduced on the basis of meeting the country's five emission standards,with the NH3 leakage control also meeting the five emission standards in the country.This paper studies the closed-loop control strategy based on NH3 feedback.The control strategy model was built using Matlab-Simulink,after which the model was transferred to the D2 P MotoHawk platform.By ESC and ETC cycle test,hardware-in-the-loop simulation test results showed that by adopting the proposed control strategy,the NOx emission of the diesel engine could meet the stipulated emission standards with the NH3 emissions also falling within the scope of the stipulated provisions.