柴油机主-从双微元Urea-SCR系统非线性状态观测器设计与分析

Design and analysis of nonlinear state observer for master-slave two cell Urea-SCR system of diesel engine

针对Urea-SCR状态反馈控制系统存在不可测状态变量的问题,首先,分析了SCR系统的化学反应机理,为了描述SCR系统的分布参数特性,给出了包含上游-下游(主-从)两个单元的SCR系统双核动力学模型;其次,利用Urea-SCR系统下游氨浓度及氮氧化物浓度的测量值,设计了非线性降维观测器估计上游氨浓度、上下氨覆盖率等不可测的状态变量,同时在Lyapunov稳定性框架下,分析了观测器的稳定性,并据此给出了保证观测器稳定的观测器增益的取值范围;最后,在发动机动力学仿真软件enDYNA中,通过FTP75循环测试工况仿真测试,验证了该方法的有效性。

As one of the effective approaches to reduce NOxemission of diesel,Urea Selective Catalytic Reduction（Urea-SCR）can catalytically convert toxic NOx emission to nitrogen and water by accurately controlling the amount of ammonia injection.However,there still exists problem such as non-measurable states in Urea-SCR.To resolve this problem in the Urea-SCR feedback control system,first,the chemical reaction mechanism of DCR system is analyzed and a model containing both upstream and downstream（master-slave）elements is introduced.Second,a nonlinear reducedorder observer is designed to observe the non-measurable states by utilizing the concentration measurement downstream ammonia and NOx,meanwhile,the stability of the observer is analyzed and the value range of the observer parameter is calculated based on stability analysis.Finally,theeffectiveness of the proposed approach is testified by simulation in enDYNA employing FTP75 cycle test procedure.