Research On Control Method Of High Pressure Common Rail System Based On Active Disturbance Rejection

The high-pressure common rail system comprises various components,including the high-pressure oil pump,common rail pipe,fuel injector,high-pressure oil pipe,and others.This system is a complex nonlinear system that integrates electromagnetic,mechanical,hydraulic,and other multi-physics coupling.To ensure stability and reliability of the highpressure common rail system,it is crucial to have smooth control of the pressure,which acts as a buffer device for the pressure pulsation supply of the high-pressure oil pump and the intermittent injection of the injector.When using the traditional rail pressure closed-loop control method,the dynamic performance of the system is poor when the diesel engine’s working conditions change.It becomes challenging to achieve accurate control of the rail pressure of the high-pressure common rail control system throughout all working conditions.Furthermore,due to the strong nonlinearity of the high-voltage common rail system,it is difficult to establish an accurate full-working simulation model.Therefore,this paper proposes a rail pressure control method using model-independent active disturbance rejection control.The primary research contents of the paper are as follows:Firstly,this study clarifies the control requirements for rail pressure based on the working process of the high-pressure common rail fuel injection system.The closed-loop control principle of Active Disturbance Rejection Control(ADRC)for rail pressure is analyzed and compared with traditional control methods.The appropriate control strategy is then selected for different working conditions.Based on this analysis,a rail pressure control scheme using active disturbance rejection is designed to provide theoretical support for subsequent rail pressure control.This study analyzes the pumping process of the high-pressure oil pump and the injection process of the injector.Simulation calculation models for the high-pressure oil pump and injector are built separately.Subsequently,a simulation model for the high-pressure common rail system is constructed based on its working principle and the adjustment requirements of the common rail pressure.The stability of the model is analyzed,and the critical stability gain of the system is determined to be K≤11.5.Secondly,a rail pressure control scheme for a high-pressure common rail system based on active disturbance rejection is proposed.The control parameters,including the tracking differentiator,extended state observer,and nonlinear feedback control law,are determined for the control unit.The dynamic performance of the control system is analyzed,and the results indicate that the set rail pressure is 80 MPa,120 MPa,and 180 MPa for single working conditions,and the set rail pressure is stepped from 80 MPa to 160 MPa for multiple working conditions.The rail pressure settling time is less than 0.25 s,and the system overshoot and adjustment time are smaller than those of the traditional high-pressure common rail control system.This approach has a better control effect,which can effectively regulate the rail pressure of the high-pressure common rail system,and also can meet the control needs of the system under different working conditions.Finally,this study compares the anti-interference ability and robust performance of the active disturbance rejection rail pressure closed-loop control system and the traditional rail pressure closed-loop control system under different working conditions and injector injection processes,based on the pressure fluctuation caused by the high-pressure common rail system.The comparison is conducted for different rail pressures,fuel injection pulse widths,and noise interference.The results indicate that the active disturbance rejection control system effectively improves the dynamic performance,steady-state performance,and antiinterference performance.Additionally,the study addresses the differential tracking problem of rail voltage signal by comparing the advantages and disadvantages of two different functions and solving the issue of slow tracking of tracking differential signal.Furthermore,the study addresses the interference problem of noise signal to the system by adopting two different functions to solve the problem of large oscillation of the output signal caused by the noise interference signal in the extended state observer.These improvements allow the controller to better adapt to the control of the system,resulting in better control results.