Research On Control Strategy For Transient Air Mass Flow Of Turbocharged GDI Engine With Dual VVT

Turbocharger,Downsizing,Dual VVT and Gasoline Direct Injection are the important technical means to realize energy saving and emission reduction of gasoline engines.Due to the inertia,turbocharger has the problem of response delay,while the dual VVT has a complex influence o n the intake air mass.The traditional gaso line engine control strategy uses the MAP based feed-forward and PID feedback controller to control the intake manifold pressure and boost pressure and thus adjusting the intake air mass which has the problem of being prone to overshoot,slow response and difficult to tuning the PID parameters.For the problems above,this paper presents a transient intake air mass control strategy for a turbocharged direct injection dual VVT gasoline engine to realize the fast and stable control of the intake air mass and require less calibration workload.First,a 1.0T three cylinder direct injection VVT gasoline engine is used as the research object,then build the experimental platform and design its control strategy to realize the stable operation of the engine.In order to develop the control strategy research,a GT-Power model for the gasoline engine is constructed and calibrated with experimental data.Second,design the transient intake air mass estimation algorithm and convert the desired intake air mass under transient condition into the desired intake manifold pressure and boost pressure and realized by the control of throttle and wastegate position.To consider the influence of dual VVT,a n algorithm based on the air charge efficiency model together with the closed loop correction with an observer is proposed.The simulation results show that,compared with the measured value of the direct air flow meter,the average error of intake air mass can be reduced by an average of 46.7% based on RMSE index.Experimental results show that the proposed method can reduce the maximum deviation of Lambda by 0.14~0.18 under empty load transient throttle condition and constant speed transient dual VVT phase condition,which demonstrates the validity of the algorithm.Thirdly,a throttle flow model based feed-forward and active disturbance rejection control algorithm is designed for the intake pressure control of the throttle,and the MAP with observer modification based feed-forward and active disturbance rejection feedback contro l algorithm is designed for the boost pressure control of the turbocharger.The optimal fuel consumption strategy is used to realize the smooth switching of the two pressure control loops,and avoid the fluctuation of the intake air mass.Simulation results show that the adjustment time of the intake air mass can be kept within 1.5s,the maximum overshoot is 3.6% under transient speed or load condition by the transient intake air mass control algorithm of the turbocharged direct injection dual VVT gasoline engine.The stability of intake air mass control and the dynamic response of the boost pressure control are both better than the traditional MAP plus PID control algorithm.The experiment results under medium and low load show that the transient intake air mass control algorithm can track fast with the desired intake air mass and intake manifold pressure.In summary,this transient intake air mass control strategy for the turbocharged direct injection dual VVT gasoline engine can realize fast and accurate estimation and fast and stable control of the intake air mass under transient conditions,and has some advantages on tracking accuracy,transient response and parameters tuning compared with the traditional control strategy.