Common rail pressure controller for diesel engines using an empirical model

This paper proposes a common rail pressure controller based on an empirical rail pressure model for passenger car diesel engines. The controller consists of pressure control valve (PCV) control algorithm and metering unit (MeUn) control algorithm. The PCV control algorithm controls the leakage fuel flow of the common rail based on the empirical rail pressure model. The proposed rail pressure model describes the relation between the common rail pressure and the driving current of the PCV as a quadratic function. This model is applied to the feedforward part of the PCV control algorithm. The MeUn control algorithm is designed to control the inlet fuel flow of the common rail. This algorithm is composed of a feedforward and feedback parts. The feedforward action is effective to reduce the rail pressure variation in a steady operating condition, and the feedback action reinforces the tracking performance of the rail pressure controller. In order to validate the proposed control algorithm, engine experiments were performed. The experiments include step change tests of the desired rail pressure and engine operating condition and the new European driving cycle test. The test results show that the empirical model based rail pressure controller is effective for the desired pressure tracking and reduction of pressure variation in the steady state.