Research On Rail Pressure Control Strategy Of High Pressure Common Rail Diesel

With the increasingly stringent energy saving and environmental protect, high pressurecommon rail system (CRS) has been widely applied. Rail pressure control strategy is thepremise of high pressure and multi-times injection of CRS.An electronic control unit (ECU) based on MC9S12XEP100single chip microcomputerhas been developed, with a large number of simulation, tests and analysis.Firstly, the one-dimensional simulation model of Bosch CRS2.0is established, usingAMESim, according to the working principle of the key components, including common rail,injector and high pressure pump. Injector fuel injection, return characteristics and highpressure pump plunger leakage characteristics are analyzed to provide reference for theestablishment of rail pressure control strategy. A simplified model is set up to satisfy "V"development mode of electric control system.Secondly, a control model of CRS rail pressure is built using MATLAB/Simulink,including open loop switching module, target rail pressure calculation, feedforward flowcalculation, the PID feedback flow calculation, duty ratio module, etc. A control structurecontains feedforward and feedback is determined.Thirdly, a pump test bench driven by frequency variable motor is established andpreliminary calibration is finished. The signal processing, task scheduling and output driverare improved with CodeWarrior IDE, making the rail pressure control strategy workingnormally under the overall framework of the ECU. Finally, further calibration is done on thecomplete engine test bench.The results show that: the return quantity is related to the injection pulse width andtarget rail pressure, and the growth is almost a straight line in the range studied; growthregularity of injector fuel injection and return are similar, and the two parameters can be usedas one feedforward MAP; high pressure pump plunger leakage is associated with the targetrail pressure, and it can be used as another feedforward MAP; after careful calibration, with open and closed loop selecting switch, based on control structure contains feedforward andfeedback, the rail pressure control strategy can play a good control effect, namely smallfluctuations and fast responses on the steady and transient states, satisfying the need of highpressure common rail diesel engine in starting, idling, normal, acceleration, deceleration andother conditions.