Study On Control Strategy Of Diesel High Pressure Common-Rail Electronic Fuel Injection System

With the development of human society,the awareness of energy conservation and emission reduction in various countries in the world is also gradually increasing,thus putting more stringent requirements on the performance of diesel engines.With its outstanding flexible control characteristics,the high pressure common-rail electric fuel injection system occupies a great advantage in improving the performance of diesel engines and becomes the mainstream direction of fuel injection technology research and development.In order to achieve the best control effect,the fuel injection parameters must be flexibly controlled under all working conditions.Besides the perfect hardware and software system,the fuel injection system control strategy and control algorithm are the important contents of the study.In the dissertation,supported by Zhejiang Provincial Key R&D Projects and the National Natural Science Foundation of China,the control strategy of high pressure common-rail electric fuel injection system is studied through the combination of modeling,simulation and experimental verification.The main contents are as follows.(1)The basic composition and principle of diesel engine body and high pressure common-rail electric fuel injection system are briefly described.Based on the diesel engine test data and its own structural parameters,an average model of diesel engine body and fuel injection system is established by using MATLAB / Simulink.(2)The control strategy of common-rail pressure,fuel injection amount,fuel injection timing and fuel injection rate are researched and analyzed under different operating conditions.The overall framework of fuel injection system control strategy is determined.In MATLAB / Simulink software environment,Simulation model of Control Unit of fuel injection system is established.(3)Combined with conventional PID control and T-S fuzzy control,the T-S fuzzy PID controller is analyzed.According to the adaptive neural control theory and common-rail pressure test data,A common-rail pressure control algorithm based on T-S Adaptive Neuro-Fuzzy Inference System(ANFIS)and PID controller is proposed.The simulation results show that the algorithm overshoots about 5% when the output step changes,and the steady-state time-consuming time is less than 1s.When the pulse disturbance is applied,the fluctuation is only half that of the conventional PID control and resumes stability after 0.2s.(4)The common-rail pressure control algorithm is embedded in the control unit simulation model to realize the joint simulation of the diesel simulation model and the control unit model.The simulation results show that the fuel injection amount and fuel injection timing basically meet the system requirements at start-up and idling conditions The common-rail pressure fluctuates slightly from start to idle and transient conditions.However,the simulation results are in accordance with the expected rail pressure trend.And the designed control algorithm overshoot is smaller than the conventional PID algorithm,achieving a shorter stabilization time.(5)The rationality of control strategy further is verified through diesel engine bench test.Test data show that the starting pressure can reach 20 Mpa after starting for 0.4s,and injecting oil for 30 mg/cyc is started.When the rotation speed is increased to 750 r / min,the rail pressure switches to the closed-loop mode,and it stabilizes near the idle target value with a deviation of 5MPa after 1.25 s.The rail pressure control process basically matches its control strategy.Under ransient conditions,rail pressure and fuel injection response time is not more than 0.5s,and good followability.After 1s it can be restored to stability,their overshoot control below 10%.Under steady-state conditions,the rail pressure increased gradually,the fuel injection advance angle and fuel injection pulse width decreased nonlinearly,and all the parameters changed normally.Thus ensuring a good the fuel injection,combustion conditions.Therefore,the study of fuel injection system control strategy in the dissertation is of great significance to improve its control effect and improve the overall performance of diesel engine.