An apparatus (200) for controlling the rail pressure of the high-pressure common-rail tube cavity of the high-pressure common-rail fuel system of an engine, comprising an operation condition acquiring device (202), which is used for acquiring operation conditions associated with the high-pressure common-rail fuel system of the engine; a fuel quantity metering valve equivalent cross-sectional area determining device (204) coupled with the operation condition acquiring device (202), which is used for determining an equivalent cross-sectional area of the fuel quantity metering valve (210) by a linear physical model (212) of fuel quantity metering valve equivalent cross-sectional area based on an acquired operation condition and a target value of the rail pressure of the high-pressure common-rail tube cavity; a signal generating device (206) coupled with the fuel quantity metering valve equivalent cross-sectional area determining device (204), which used for generating a driving signal (208) for controlling the equivalent cross-sectional area of the fuel quantity metering valve (210) based on the determined fuel quantity metering valve equivalent cross-sectional area. The apparatus can control the rail pressure of the high-pressure common-rail tube cavity precisely. A method for controlling the rail pressure of the high-pressure common-rail tube cavity of the high-pressure common-rail fuel system of an engine is also disclosed. An apparatus and a method for observing fuel pressure are further disclosed.

An apparatus (200) for controlling the rail pressure of the high-pressure common-rail tube cavity of the high-pressure common-rail fuel system of an engine, comprising an operation condition acquiring device (202), which is used for acquiring operation conditions associated with the high-pressure common-rail fuel system of the engine; a fuel quantity metering valve equivalent cross-sectional area determining device (204) coupled with the operation condition acquiring device (202), which is used for determining an equivalent cross-sectional area of the fuel quantity metering valve (210) by a linear physical model (212) of fuel quantity metering valve equivalent cross-sectional area based on an acquired operation condition and a target value of the rail pressure of the high-pressure common-rail tube cavity; a signal generating device (206) coupled with the fuel quantity metering valve equivalent cross-sectional area determining device (204), which used for generating a driving signal (208) for controlling the equivalent cross-sectional area of the fuel quantity metering valve (210) based on the determined fuel quantity metering valve equivalent cross-sectional area. The apparatus can control the rail pressure of the high-pressure common-rail tube cavity precisely. A method for controlling the rail pressure of the high-pressure common-rail tube cavity of the high-pressure common-rail fuel system of an engine is also disclosed. An apparatus and a method for observing fuel pressure are further disclosed.