Feed Forward Fuzzy PID Controller for Common-Rail Pressure Control of Diesel Engine

Abstract

The precise pressure control in common rail will directly influence the performance of common rail diesel engine, so it is very important to control it effectively. Because common rail pressure was nonlinear, time-variable and disturbed, it is difficult to realize accurate pressure control with traditional control methods. Conventional PID control can not meet the demand of precise diesel common rail pressure, especially when engine load changes largely and rapidly. In order to improve the performance of high pressure common rail system, the feed forward fuzzy PID controller has been designed; it consists of a combination of fuzzy PID control and feed forward control. According to every engine condition, the control method of pressure in common rail has been studied through theory and experiment. The experimental results show that: the overshoot of the new controller is much less than the conventional PID controller because of using fuzzy PID; and thanks to feed forward control, the disturbance of injection quality can be precontrolled, the new controller has quick velocity response and littler lag. At all engine conditions, the Feed forward fuzzy PID controller is better in effect, smaller in error, quicker in track speed and stronger in anti-jamming ability than conventional methods. It ensures the high pressure common rail engine meet the strict specification of the law.