Studies Of The Design Of Medium Pressure Common Rail Multiple-System And The Control Strategy For Diesel Engine

As fuel consumption and environment laws and regulations are more and more stringent, attention has been paid to electronic technology applied in Diesel engine. Common-rail injection system is one of the best and the most hopeful fuel injection systems, and the electronically controlled variable valve system becomes important too. So a new double-pressure Common-rail system, which uses the lubricating oil in the Diesel engine as the actuating medium, is presented.First, an experimental bench with the hydraulic system^ fuel injection systeiru electronic control unit and simulated Diesel engine is built.Next, a set of control strategies covering all conditions of the Diesel engine is presented. The experimental results of the program on the bench show that the control strategies in the program are reasonable and feasible.After that, due to the importance of the control of the common-rail pressure, three control methods named PID control, Fuzzy control and Fuzzy-PID control are studied. In the research on PID control, a method, which weakens integral when the control value exceeds the limit, is introduced. A new method combining the experiential and the orthogonal method is used to determine the parameters of PID, which can reduce the amount of experiment. The results of the pressure control are acceptable. In the Fuzzy control method, a PI Fuzzy control with nested control table is studied. Experimental results show that the static error and the oscillation can be reduced. In the Fuzzy-PID method, one kind of Fuzzy-PID control combining the advantages of both the PID control and the Fuzzy control is studied. Experimental results indicate that the control of the pressure in most of conditions is rapid, and the over-regulating is small. It is confirmed that the control system is stable.Finally, because high-speed power solenoid valve is one of the most important executive parts in the electronic control Diesel engine and the performances of Diesel engine are strongly related to the solenoid valve, the response performance of the solenoid valve is investigated. The response performance of the solenoid is influenced by many factors, such as driving voltage, electric driving unit etc. In order to have high excitation voltage andinlow maintaining voltage, a high-low voltage electric driving unit is designed, and in order to make the solenoid valve close more rapidly, an active free-wheeling circuit and a bootstrapping circuit are designed in the electric driving unit, too. In the high-low electric driving unit, high voltage and low voltage are supplied by the DC-DC device and by the accumulator respectively. Based on the high-low voltage electric driving unit, a new electric driving unit is built, which not only has the advantages of the high-low voltage electric driving unit but also has the advantage of obtaining high limiting current and low maintaining current easily. Using self-excitation chopper circuit, the electric driving unit is good efficient, and the heat creating from the solenoid is small.