Researches On Dynamic Characteristics Of Two Kinds Of Sensors Related To Automobile Engines

It is necessary to study the dynamic characteristics of sensors related to engines and establish their accurate dynamic models so as to improve the quality of the engine air-fuel ratio (AFR) control. Two kinds of key sensors, hot-film mass air flow (MAF) sensor and universal exhaust oxygen gas sensor, for the AFR control are fully studied in this paper.The non-linear dynamic model of the hot film MAF sensor must be built because the sensor possesses the nonlinear dynamic characteristics. The sensor static and dynamic experiments were conducted, and two kinds of nonlinear dynamic block-oriented models are built in Hammerstein and Wiener forms with the method of static-dynamic characteristic separation. The models can describe the non-linear dynamic characteristics of the sensor accurately.The response time of the hot-film MAF sensor can not meet the control requirements under certain conditions, and the nonlinearity will affect the control precision. In order to solve the problems the dynamic correctors were designed in Hammerstein and Wiener forms. A dynamic corrector was developed with dSPACE system, and its validity was verified by the results of simulation and experiment.A step response experimental scheme of the universal exhaust oxygen gas sensor was designed based on an automobile engine testing bench in order to identify the dynamic performance. The dynamic experiments were carried out in different exhaust temperatures and lambda values. Through analyzing and processing the experiment data, the proper input-output data were obtained for modeling. The prediction error method (PEM) was adopted to build the sensor dynamic model that adapts different operating conditions, and the performance indexes were obtained in time domain.The universal exhaust oxygen gas sensor cannot operate without a special controller. The controller will affect the performance of the sensor to a great extent. A controller was designed based on dSPACE system. Its measuring and controlling modules were developed by the software - ControlDesk. The parameters of the controlling module were tuned.