Closed loop control method for SCR (Selective Catalyst Reduction) system of all-working-condition diesel engine

The invention discloses a closed loop control method for an SCR (Selective Catalyst Reduction) system of an all-working-condition diesel engine. The method is carried out according to the following steps of: (1) establishing a novel three-dimensional matrix of the adding amount of reducing agent for the SCR system based on exhaust temperature and exhaust backpressure of the all-working-condition diesel engine; and (2) forming a precise control mode of a closed loop of the SCR system of the all-working-condition diesel engine by utilizing a nitrogen oxide sensor and a PID (Proportion Integration Differentiation) controller. By using the closed loop control method for the SCR system of the all-working-condition diesel engine in the invention, the acquisition of working-condition parameters of the diesel engine can not depend on an electronic control unit (ECU) of the diesel engine, the technical obstacle that the current home and abroad SCR systems are only suitable for electrically controlling the diesel engine is broken through, and an approach for reducing the discharging amount of NOx is provided for vehicles assembled with light, middle and heavy non-electric control diesel engines.