A Study For The Air-Fuel-Ratio Control Strategy And Modeling For Corresponding Sensors Of A Pre-Mixed LPG Engine

Advanced control theory is used for LPG engine AFR control and it is helpful for improving LPG engine's running performance and fully representing gas fuel's low emission superiority. Study on Modeling for Corresponding Sensors and Air-Fuel-Ratio Control Strategies of A LPG Engine is a key content in analysis and designing process of LPG engine control system, it is a base for optimally designing electronic control unit and control system simulation model.This dissertation mainly about:Firstly, the static and dynamic calibration experiment of MAP sensor was completed on a calibration experiment stage which was designed by us. its static linear models be achieved on the basis of experimental data;its dynamic linear models be achieved on the basis of different directions and different magnitude step response signals.Then, the static and dynamic calibration experiment of exhaust gas oxygen sensor was completed on a engine calibration experiment stage and studying its static and dynamic characteristic of EGO sensors of different temperatures. The static models of EGO sensors for different temperature were built up using sectioned polynomial based on the least square. For the influence of temperature to EGO sensor's output, its nonlinear regression models which include temperature's modifying term be achieved. Its dynamic Hammerstein nonlinear models are achieved on the basis of different directions and different magnitude step response signals.According to relationship between temperature and delay time, achieved a dynamic Hammerstein nonlinear models which delay time are revised by temperature.Thirdly, a large numbers of static calibration experiments of LPC engine were performed. The mean value model aimed to air-fuel ratio control was founded using velocity-density method on the basis of the experiment data. The forward model is used to produce the practical querying table for controlling the opening position of the gas valve and the air valve by means of simulation calculation. This work is used to provide basic control parameters for designing electronic control unit.Finally, on the basis of the forward and feedback control scheme, its static AFR control simulation study is performed on the LPG engine. Forward part is controlled by model ,feedback part is controlled by PID> fuzzy-control methods and revised PID-fuzzy control methods. The results of the simulation suggested that the strategies using both PID and fuzzy-control can be effective in well controlling the A/F ratio of LPC engine, while the controlling effect of the fuzzy-self-adaptive-PID strategy was the best.