A state observer design based on EKF for diesel engine Urea-SCR system

Urea-Selective catalytic reduction(Urea-SCR) method is an effective way to reduce the NO x emissions for diesel engine, and the closed-loop state feedback control strategy is widely studied by many researchers. In order to estimate the un-measurement state, this paper uses extended Kalman filter(EKF) to design a state observer for Urea-SCR system. Firstly, a two-cell Urea-SCR model is given. Secondly the two-cell Urea-SCR model is dispersed by Backward Euler method at each sampling instant. Thirdly, tailpipe NO x and ammonia concentration are chosen as the output of the Urea-SCR system and then used by EKF to estimate state variables of the upstream and downstream catalyst. At last, the effectiveness of the observer is validated by simulations under FTP75 driving cycles in enDYNA.