Research On Rail Pressure Control Algorithm Of Direct Injection Gasoline Engine

With the increase of Car Parc,cars bring much more convenience while they also bring energy crisis and environmental pollution.Facing these problem,low emission and excellent power of GDI engine emerged at the historic moment.The high pressure pump and injector of GDI engine are connected to the common rail pipeline,the high pressure pump oil fluctuation and the engine working cycle frequency are high,makes it difficult to control the large fluctuation of rail pressure of GDI engine.The rail pressure of GDI engine directly affects the injection pressure.For example,the fluctuation of rail pressure will lead to the instability of injection pressure,which will reduce the working efficiency of GDI engine and may even damage the engine.As a result,the rail pressure control has become one of the core control technologies of GDI engine.The goal of GDI engine rail pressure control is to make the rail pressure fluctuation much smaller and the tracking accuracy much higher.In this paper,the non-model-based fuzzy PI control algorithm is studied to control the rail pressure of GDI engine under multiple operating conditions.Secondly,aiming at the characteristics of uncertain oil leakage and huge disturbance of GDI engine,a backstepping synovium control algorithm based on the model was studied to achieve rail pressure control.Finally,the comparison of two algorithms in Simulink.The main work of this paper is as follows:(1)A brief introduction of mechanical structure and working principle of GDI engine,and establishing the pressure differential equation mathematical model of high pressure pump-track-injector according to the fluid mechanics theory.The mathematical modeling of common rail system in Simulink.In addition,the simulation and verification of the high pressure pump,common rail pipe,injector sub-module and the overall rail pressure model are carried out.Finally,simplify the mathematical model ignoring the effects of fuel injection performance and temperature on gasoline density.Finally,simplifying the common rail system into a second-order nonlinear mathematical model in the form of state space.(2)Aiming at the complex problem of traditional PI parameter tuning,a three-dimensional fuzzy PI control algorithm which is not based on the system model is studied in the nonlinear and strongly coupled rail pressure control system.According to the information of reference rail pressure,reference rail pressure change rate and rail pressure error,we can adjust the PI parameters under various working conditions by fuzzy reasoning to meet the requirements of self-tuning of PI parameters under different working conditions for reference rail pressure,reference rail pressure change rate and error.Finally,Fuzzy PI improves the tracking accuracy and stability of the system.(3)Considering the strong nonlinear characteristics,and the disturbance of uncertain and unmeasured oil leakage of GDI engine system mode,the backstepping synovium control algorithm based on the model is studied to improve the rail pressure control performance.The traditional backstepping method needs to feedback accurate oil leakage rate information to the input.The backstepping synovial control law can suppress the disturbance by estimating the upper bound of the oil leakage rate.Finally,The backstepping sliding mode control algorithm can improve the tracking accuracy of the system and the ability of the system to suppress disturbances.(4)In view of the stringent requirements for the simplicity and accuracy of the algorithm in practical engineering applications,the linear auto disturbance rejection control for rail pressure that does not depend on the model is studied,and the linear auto disturbance rejection controller is implemented for each subsystem of the high pressure common rail system Research design.Finally,in the Simulink simulation software,The non-model-based linear rail pressure auto-disturbance rejection controller and the model-based backstepping sliding mode controller have similar simulation effects,and the non-model-based linear auto-disturbance rejection controller has practical value.This paper mainly studies the model-based backstep sliding film control algorithm and the model-free fuzzy PI control algorithm and the auto-disturbance rejection control algorithm.The three algorithms are respectively simulated by software and analyzed and compared to provide theories for the application of the algorithm basis.