Model Of Air-fuel Ratio Feedback Control For GDI Gasoline Engine Based On Dual Oxygen Sensor

With the rapid development of automobile industry, car ownership increased, but the ensuing energy consumption, environmental issues are increasingly attracted people’s attention. Many countries lay down appropriate emission regulations according to their own circumstances. As the most important parameters of the engine, the accuracy of air-fuel ratio control affect the economy and emission performance of the engine seriously. For this reason, scholars at home and abroad continued to do air-fuel ratio control research and made a series of achievements. On this basis, using ASCET software, a GDI(gasoline direct injection) engine air-fuel ratio feedback control model, which is based on dual oxygen sensor, was built and simulated in this text.The first to introduce in this article is the development and operation mode of GDI engine. The paper analyse the causes of major pollutants generated by the engine, and then make an explanation on the exhaust aftertreatment system for GDI engine, such as the structure and working principle of three-way catalytic converter and oxygen sensor. Secondly, it introduces the air-fuel ratio feedback control strategy and ASCET software which is based on the V-shaped development process.The module of air-fuel ratio feedback control consists of signal detection and processing module and a feedback control module. In order to meet stringent emission regulation, dual oxygen sensors are used in the air-fuel ratio feedback control. So, there are two modules in signal detection and processing module, they are main sensor module, linear oxygen sensor which is located in the upsteam of front catalyst, and a secondary sensor module, switch-type oxygen sensor which is located in the downsteam of main catalyst. Because of the influence of manufacturing tolerances or aging factors, the characteristic line of LSU will have shifted during use, so the design of feedback controller joined the LSU offset adaptation module, which includes a air-fuel ratio control module downstream main catalyst and LSU offset calculation module. In addition, it also contains air-fuel ratio continuous modulation and control module, whose fuction are modulate air-fuel ratio based on the oxygen storage capacity of catalyst and track the target respectively.