The invention relates to a model-based
urea emitting amount control method. The method includes the following steps that S1, according to the actual
urea emitting amount, based on an SCRF model, a first
ammonia storage value in an SCRF is calculated; S2, based on an SCR model, a second
ammonia storage value in an SCR is calculated; S3, the first
ammonia storage value obtained in the step S1 and the second
ammonia storage value obtained in the step S2 are subject to weighted treatment to obtain an actual
ammonia storage value; S4, a difference is obtained from the actual
ammonia storage value obtained in the step S3 and an actual storage setting value, and a closed-cycle correction
ammonia nitrogen ratio is obtained through a
PID controller; and S5, the sum of the closed-cycle correction
ammonia nitrogen ratio obtained in the step S4 and a feedforward
ammonia nitrogen ratio is obtained to be finally converted into the needed
urea emitting amount. According to the model-based urea emitting amount control method, a model-based closed-
cycle control strategy is adopted, accurate control over urea emitting can be achieved, the engine emission requirements can be met,
standardization work can be reduced, and the problem about
crystallization can be solved.