Method and apparatus for controlling EGR

An apparatus for controlling exhaust gas recirculation (EGR), the apparatus comprising:

• an engine including a speed sensor and an air flow meter;
• an actuator configured to control opening degrees of an inhalation pressure control valve and an EGR valve;
• and
• an engine control unit configured to
• obtain data about an operation state of the engine from the engine including rpm, a fuel supply quantity, and an inhalation air quantity of the engine,
• calculate an actual EGR rate and a demand EGR rate based on the obtained data and a pre made target EGR rate map, and
• transmit a control signal to the actuator when there is a difference between the actual EGR rate and the demand EGR rate as a result of the calculation,
• wherein the engine control unit makes a current EGR rate follow the demand EGR rate by changing a recirculation quantity of exhaust gas by adjusting a pressure of an inhalation side of supply gas according to the difference,
• wherein the current EGR rate is calculated based upon a difference between the inhalation air quantity and a non-EGR air quantity divided by the non-EGR air quantity,
• wherein the non-EGR air quantity is matched with the rpm in a pre-made non-EGR air quantity table, and
• wherein the engine control unit is configured to perform by mutually adjusting an opening degree of an inhalation pressure control valve, which is provided at an inhalation side of the supply gas and adjusts an inhalation negative pressure, and an opening degree of an EGR valve, which is provided at a discharge side of the exhaust gas and introduces the exhaust gas to the inhalation side of the supply gas.