control of fuel rail pressure

Pressure within the fuel rail 12 of an internal combustion engine is generated by electrically driven fuel pump 15, 16. A set-point fuel pressure 21 is provided and the average fuel flow through the system is estimated. A feed forward signal 23 having a set of fuel pump motor control parameters is generated at 22 based upon the set-point fuel pressure and the average fuel flow. Fuel rail pressure is measured by pressure sensor 18, compared to the set-point fuel pressure at 24, and an error value 25 corresponding to the difference between the pressures is generated. Feed back controller 26 receives the error value 25 and generates a feed back control signal 27 which modifies the feed forward control signal 23 to generate a motor controller signal 29, 31. An adaptive learning controller may optimise the operation of feed forward controller 22 and the average fuel flow may be estimated from pulses in the pressure signal generated by a pressure sensor adjacent the fuel pump with the fuel pressure signal being derived from the same sensor by low pass filtering.