Research On Control Strategy Of Common Rail Diesel

With more than one injection occurring per combustion cycle and with a variable number of injections per combustion cycle depending on the given operating point in modern common rail systems, the injected fuel quantity is no longer directly propor-tional to the torque generated. This new situation means that a simple linear conver-sion relationship between the injected new quantity and the resulting torque now no longer applies. The torque generated now depends not only on the injected fuel quan-tity, but also on the specific injection system in use and the given operating point. Otherwise, increasing demands on engine control and an increase in the functions al-ways require the torque currently generated as a control unit output variable. For this reason, this paper creates torque-based control algorithm of the CR diesel engines, the primary input variable is the driver command expressed by the angle-proportional position of the accelerator and engine speed, the resulting torque is converted into an injection quantity per cylinder for the respective injection system. The determined in-jection quantity is then, in turn, divided into individual injections, and their control start and duration is calculated.The main work of this paper is to establish a complete diesel engine electronic control system development platform based on the torque structure, follow the torque transmission path, so that all phases of development to effectively converge to im-prove development efficiency and the development level, saving time and reducing costs. And control parameters in the various functional modules can be adjusted, to make the performance of the system to achieve the best, to the maximum extent pos-sible to speed up the process of electronically controlled diesel ECU software devel-opment.Based on the torque transmission path, the torque structure divides into three modules for power train, engine system and fuel injection system, study the control strategy and simulate by MATLAB/Simulink respectively. Power train system module get the driver’s torque demand from the accelerator pedal opening degree at first, through gearbox, clutch, and the other driveline components, ultimately get the clutch torque, output torque of the crankshaft end, which also needs consider the im-pact of the cruise control and ESP intervention torque. The engine system module re-ceives the crankshaft-side output torque, added on the friction torque and the high pressure pump loss torque are indicated torque. The indicated torque is influenced by the temperature limitation, smoke limitation, speed limitation, and then the torque fil-ter into the ASD module. ASD module is designed to reduce the system excitation due to fast torque demand changes and engine speed oscillations, so it can effectively im-prove the vehicle’s driving comfort performance. ASD module output torque going through torque-fuel conversion, obtain the fuel injection quantity. The injection quan-tity cannot be applied to the start condition, and the start quantity requires specialized calibration. In addition, the engine system also focused on considering the idle condi-tion, its purpose is to maintain the stability of the high idle and low idle speed. The fuel injection system must guarantee the fuel injection quantity getting from the en-gine system torque conversion sprayed into the cylinder in the right rail pressure, the suitable injection timing, the suited injection numbers and the appropriate fuel injec-tion pulse width. And it focuses on the control strategy, on this basis, pilot injection and main injection were studied.This study is preliminary work for the development of practical engine control strategy and, more importantly, to propose and practice a more advanced design ideas, providing the theory and software support for the follow-up study, to further under-stand and master the structure of automotive torque design goal, and to shorten the development cycle, to play an actively role in the development of the diesel engine electronic control common rail system.