Study On Air-fuel Ratio Control Strategy Based On Fuzzy PI

In recent years,cars have been entered into ordinary family as advanced transportation.It not only gave rise to a comfortable life,but also led to problems such as environmental pollution,energy shortages,traffic congestion etc.In order to solve these problems,people have done a lot of research.The result showed thatthe most effective way to reduce the engine exhaust emission is to combineelectronic-controlled injector fueland Three-way Catalyst?TWC?.The key is to achieve precise control of critical air-fuel ratio?AFR?.So this article has proposed the AFR control strategy combined fuel compensated feedforward control and feedback control.Through simulation and bench test,the effect of ARF control strategy is verified.Based on the average model theory proposed by Hendricks,the engine mathematical expressions of air passage sub-models,fuel passage sub-model and dynamic sub-model has been presented.By analyzing of these mathematical expressions,the article has selected en-DYNA engine model as the control object of simulation.The engine model of en-DYNA requires fuel passage sub-model.The x₁?_ff fuel passage sub-model has been discretized to f_?f_?model.The f_?f_?model can be simplified to f_?model.Then discrete model has been generalized to mathematical expression of Auto-Regressive and Moving Average Model?ARMA?.A parameter identification algorithm based on time-varying forgetting factor has been proposed.The ARMA parameter can be identified by the parameter identification algorithm.The f_?f_?model Simulation results show that the parameter identification algorithm is effective.The f_?model Simulation results are used to design fuel compensated feedforward controller.According to the absolute value of the deviation between excess air ratios detected by the oxygen sensor and?,feedback controller based on fuzzy PI can be designed.Air-fuel ratio controllersimulation model founded by MATLAB is integrated in en-DYNA for simulation.ThenHM479Q-BA engine Electronic Control Unit?ECU?has been developed,the air-fuel ratio control strategy is integrated in ECU to perform bench test.Simulation results show that fuel compensated feedforward controller can minimize fuel transport lag and feedback controller based on fuzzy PI can reduce steady-state erroreffectively.Bench testresults show that the deviation of ARF has been controlled into 8%after the addition of air-fuel ratio control strategy.Therefore,air-fuel ratio control strategy proposed by the work can achieve precise control of ARF.