Rail pressure control strategy based on pumping characteristics for the common rail fuel system

Abstract

The control of rail pressure is quite important in the common rail fuel system. Generally, the rail pressure control strategy is a combination of feedforward control and proportional–integral–derivative feedback control. A lumped parameter model of the common rail fuel system is built. Theoretically, the three main factors that affect the rail pressure are engine speed, rail pressure, and fuel injection. With these factors as the control parameters, the feedforward control logic is established. Then, with the basic fuel amount as the proportional–integral–derivative control parameter, the feedback control strategy is improved. The feedforward control is used to determine the basic fuel amount; the proportional–integral–derivative feedback control is used to fine-tune the basic fuel amount based on the deviation of target rail pressure and real rail pressure. Compared with only proportional–integral–derivative feedback control, the computation load of feedback control is reduced and the response speed is increased. In addition, experiments based on a common rail fuel system test rig are completed. The results show that the fuel efficiency of common rail fuel pump decreases with pump speed, and rail pressure increases. The steady-state rail pressure fluctuations are effectively reduced and the dynamic control precision of the common rail fuel system increases when the optimized control method is adopted.