Diesel engine two-stage SCR aftertreatment control method and system

The invention provides a diesel engine two-stage SCR aftertreatment control method and system, and relates to the technical field of diesel engine aftertreatment systems.The method comprises the steps that the basic urea injection amount of a preceding stage is determined according to the first molar concentration of the preceding stage, and the basic urea injection amount of a backward stage is determined according to the second molar concentration of the backward stage; performing fuzzy control on the preceding-stage target ammonia coverage degree according to the backward-stage carrier temperature and the backward-stage NOx conversion efficiency so as to correct the preceding-stage target ammonia coverage degree; fuzzy PID control is conducted on the difference value of the corrected preceding-stage target ammonia coverage degree and the corrected preceding-stage actual ammonia coverage degree, so that the basic spraying amount of preceding-stage urea is corrected; and fuzzy PID control is carried out on t