Synthesis and Experimental Validation of a Fuel Injection Pressure Controller in a Common Rail System

Abstract

Electronics has greatly contributed to the development of internal combustion engines. This progress has resulted in reducing environmental degradation, and yet continuing to support improvements in performance. Regarding gasoline engines, a considerable step forward has been achieved by CR technology able to exactly regulate the injection pressure during the entire engine speed range. As a consequence, the injection of a fixed amount of fuel is more precise and it is possible to perform multiple injections for combustion cycle. To obtain this goal a closed loop control must regulate the average of fuel pressure into the rail so to mitigate unavoidable negative effects that the motion of three lobes mechanical pump and multiple injections can have on it. In order to assist the Engine Management System design, through a better performance of GDI engine and the common rail system, in this chapter we present the synthesis and experimental validation of a model-based gain-scheduling controller aimed to regulate the fuel pressure and to track demanded pressure trajectories. By exploiting the simple but effective control oriented model described in the Chap. 3, we get a pressure regulator formed by a closed loop integral action coupled to a feedforward static compensator where both control actions are scheduled in function of the engine speed and battery voltage as well. Rail pressure controller has been experimentally validated for a wide range of working conditions confirming the effectiveness of the proposed control algorithm in regulating the mean value rail pressure independently from engine speed and duration of injection with limited design effort. The resulting controller is simple enough to be effectively implemented in commercial ECUs.