Study And Optimization On Control Strategy For High Pressure Common-rail Diesel Engine Based On Models

With the increasing demand of energy saving and emission reduction,the direction of the diesel engine is turning to low pollution and energy consumption.And thanks to the rapid development of electronic technology,the flexible control in full operating range has come true:Electronic Control Unit(ECU)can calculate the amount of oil,rail pressure,injection timing and quantity according to the current state of the engine with the help of hardware and software.In this case,the development and optimization of control strategy has become the main bottleneck to restrict the actual effect of the engine.In order to break this bottleneck,this paper was devoted to the study of ECU control strategy development based on models,verified the superiority and effectiveness of the development process by optimizing the rail pressure and idle control strategy for Common-rail diesel engine.First,this paper analyzed the V mode development process and AUTOSAR standard.Second,this paper introduced the functional structure,software system of diesel engine and real-time task scheduling based on AUTOSAR OS.Then,in order to improve the precision of the rail pressure control,the pressure control strategy on application layer was modeled and optimized by the Matlab/Simulink tool.After the analysis of the adverse effects on rail pressure caused by actuator,Double-level closed-loop control algorithm based on pressure signal and current signal on fuel meter valve was designed;feed-forward control and feedback control were optimized to improve the accuracy and the transient response of rail pressure control.Finally,the Simulink Coder was used to accomplish the automatic generation of the software code,and the portability of the control software was enhanced.The experiment was carried out on the oil pump bench and the engine bench.The results showed that the steady state and transient deviation of this method could meet the new requirements of the rail pressure control of vehicle diesel engines.On the basis of the rail pressure optimization,this paper introduced the composition and calibration system of the test engine,and studied the optimization of the idle speed condition aim at the stability of rotating speed.The possible problems in the transient state of high pressure common rail diesel engine were analyzed.The idle speed instability after a cold start was solved by building integral separation PID and feed-forward plus feedback control strategy models.After the verification,feed-forward plus feedback strategy was chosen.And the stability of the idle speed after the sharp deceleration was optimized by the oil volume compensation method.The test results proved its rationality and realized the stability and smoothness of idle speed control.The optimization process and results of rail pressure and idle control strategy showed that ECU software could be developed by using models.This kind of development was efficient and maintainable.When there's a problem,the engineer could optimize the models and codes again and again easily,This kind of development met the current needs of the development of ECU diesel engine.