Method and system for controlling EGR rate in diesel engines

A method for controlling EGR rate of an internal combustion engine, such engine having an intake throttle for controlling mass flow to an intake of the engine and an EGR valve for controlling flow from the exhaust of the engine back to the intake of the engine along with air passing through the intake throttle, such method comprising:

• measuring a mass air flow passing to the intake throttle;
• comparing such measured mass air flow with a desired mass air flow;
• producing an error signal representative of a difference between the measured mass air flow and the desired mass air flow;
• producing a pair of control signals in response to such produced error signal;
• using one of the pair of control signals to adjust the intake throttle to control mass air flow through such intake throttle;
• using the other one of the pair of control signals to adjust EGR rate through the EGR valve;
• and
• wherein the pair of control signals operate to drive the throttle to a closed position only when such error signal is unable to be driven towards the null solely from adjustment by the EGR valve.

A controller for controlling EGR rate of an internal combustion engine, such engine having an intake throttle for controlling mass flow to an intake of the engine and EGR valve for controlling flow from the exhaust of the engine back to the intake of the engine along with air passing through the intake throttle, such controller being programmed to:

• measure a mass air flow passing to the intake throttle;
• compare such measured mass air flow with a desired mass air flow;
• produce an error signal representative of a difference between the measured mass air flow and the desired mass air flow;
• produce a pair of control signals in response to such produced error signal;
• wherein one of the pair of control signals is used to adjust the intake throttle to control mass air flow through such intake throttle;
• wherein the other one of the pair of control signals is used to adjust EGR rate through the EGR valve;
• and
• wherein the pair of control signals operate the intake throttle and the EGR valve to drive the error signal towards a null.

A controller for controlling EGR rate of an internal combustion engine, such engine having an intake throttle for controlling mass flow to an intake of the engine and an EGR valve for controlling flow from the exhaust of the engine back to the intake of the engine along with air passing through the intake throttle, such controller being programmed to:

• measure a mass air flow passing to the intake throttle;
• compare such measured mass air flow with a desired mass air flow;
• produce an error signal representative of a difference between the measured mass air flow and the desired mass air flow;
• produce a pair of control signals in response to such produced error signal;
• and
• wherein one of the pair of control signals is used to adjust the intake throttle to control mass air flow through such intake throttle;
• wherein the other one of the pair of control signals is used to adjust EGR rate through the EGR valve;
• and
• wherein the pair of control signals operate to drive the throttle to a closed position only when such error signal is unable to be driven towards the null solely from adjustment by the EGR valve.

An article of manufacture, comprising:

• a computer storage medium having a program encoded therein for controlling EGR rate of an internal combustion engine, such engine having an intake throttle for controlling mass flow to an intake of the engine and an EGR valve for controlling flow from the exhaust of the engine back to the intake of the engine along with air passing through the intake throttle, such storage medium comprising:
• code for measuring a mass air flow passing to the intake throttle;
• code for comparing such measured mass air flow with a desired mass air flow;
• code for producing an error signal representative of a difference between the measured mass air flow and the desired mass air flow;
• code for producing a pair of control signals in response to such produced error signal, one of the pair of control signals being used to adjust the intake throttle to control mass air flow through such intake throttle and the other one of the pair of control signals being used to adjust EGR rate through the EGR valve;
• and
• wherein the pair of control signals is used to operate the intake throttle and the EGR valve to drive the error signal towards a null.

An article of manufacture, comprising:

• a computer storage medium having a program encoded therein for controlling EGR rate of an internal combustion engine, such engine having an intake throttle for controlling mass flow to an intake of the engine and an EGR valve for controlling flow from the exhaust of the engine back to the intake of the engine along with air passing through the intake throttle, such medium comprising:
• code for measuring a mass air flow passing to the intake throttle;
• code for comparing such measured mass air flow with a desired mass air flow;
• code for producing an error signal representative of a difference between the measured mass air flow and the desired mass air flow;
• code for producing a pair of control signals in response to such produced error signal;
• wherein one of the pair of control signals is used to adjust the intake throttle to control mass air flow through such intake throttle;
• wherein the other one of the pair of control signals is used to adjust EGR rate through the EGR valve;
• and
• wherein the pair of control signals operate to drive the throttle to a closed position only when such error signal is unable to be driven towards the null solely from adjustment by the EGR valve.