Applied research on diesel engine SCR system with the variable structure control theory

As one of the selective technology for meeting the demand of diesel engine emission standard, SCR technology has been applied in China & Abroad widespreadly. In order to meet the stricter technical requirements and standard, it´s more necessary to adopt the optimal SCR technology based on close-loop control system comparing the insufficient open-loop control system. This paper deals with a new research of the close-loop control on the SCR system. Considering the demand of SCR transient control, We have designed a variable structure controller based on the variable structure control theory and use the ETC transient experimental test data on a vehicle with SCR system, and a simulation is made for the controller at last. The simulation results indicate that the variable structure controller has a good robustness and quick-response capability and can adjust urea injecting quantity quickly in specified time, also it can ensure the NO_x emission and the NH₃ leakage within the specified range to meet the emission standard.