Control of a Urea SCR Catalytic Converter System for a Mobile Heavy Duty Diesel Engine

An advanced controller for a urea SCR (Selective Catalytic Reduction) catalytic converter system for a mobile heavy-duty diesel engine is presented. The after-treatment system is composed of the injecting device for urea solution and a single SCR catalytic converter. The control strategy consists of three parts: A primary feedforward controller, a surface coverage observer, and a feedback controller. A nitrogen oxide (NO_x) gas sensor with non-negligible cross-sensitivity to ammonia (NH₃) is used for a good feedback control performance. The control strategy is validated with ESC and ETC cycles: While the average NH₃ slip is kept below 10 ppm, the emission of NO_x is reduced by 82%.