Device, method, and program recording medium for control of air-fuel ratio of internal combustion engine

An apparatus for controlling the air-fuel ratio of an internal combustion engine having an exhaust gas sensor disposed downstream of a catalytic converter disposed in an exhaust passage of the internal combustion engine, for detecting the concentration of a particular component in an exhaust gas which has passed through the catalytic converter, identifying means for sequentially identifying the value of a predetermined parameter of a predetermined model of an exhaust system, which ranges from a position upstream of said catalytic converter to said exhaust gas sensor and including said catalytic converter, for expressing a behavior of the exhaust system which is regarded as a system for generating the output of said exhaust gas sensor from the air-fuel ratio of the exhaust gas which enters said catalytic converter, manipulated variable generating means for sequentially generating a manipulated variable to determine an air-fuel ratio of the exhaust gas which enters said catalytic converter using the identified value of the parameter of said model to converge the output of said exhaust gas sensor to a predetermined target value, and air-fuel ratio manipulating means for manipulating the air-fuel ratio of an air-fuel mixture to be combusted by the internal combustion engine depending on the manipulated variable, wherein:

• said identifying means comprises means for identifying the value of said parameter according to an algorithm for minimizing an error between the output of said exhaust gas sensor in the model of said exhaust system and an actual output of said exhaust gas sensor;
• wherein said apparatus further comprising:
• flow rate data generating means for sequentially generating data representative of a flow rate of the exhaust gas flowing through the catalytic converter;
• and
• means for variably setting the value of a weighted parameter of the algorithm of said identifying means depending on the value of the data generated by said flow rate data generating means.

A method of controlling the air-fuel ratio of an internal combustion engine, comprising the steps of sequentially identifying the value of a predetermined parameter of a predetermined model of an exhaust system, which ranges from a position upstream of a catalytic converter disposed in an exhaust passage of the internal combustion engine to an exhaust gas sensor disposed downstream of the catalytic converter for detecting the concentration of a particular component in an exhaust gas, and includes said catalytic converter, for expressing a behavior of the exhaust system which is regarded as a system for generating the output of said exhaust gas sensor via at least a dead time element from the air-fuel ratio of the exhaust gas which enters said catalytic converter, and sequentially generating a manipulated variable to determine an air-fuel ratio of the exhaust gas which enters said catalytic converter using the identified value of the parameter of said model in order to converge the output of said exhaust gas sensor to a predetermined target value, said internal combustion engine having air-fuel ratio manipulating means for manipulating the air-fuel ratio of an air-fuel mixture to be combusted by the internal combustion engine depending on the manipulated variable, said method comprising the steps of:

• sequentially generating data representative of a flow rate of the exhaust gas flowing through the catalytic converter, and sequentially setting a set dead time as the dead time of a dead time element of the model of said exhaust system depending on the value of the data representative of the flow rate of the exhaust gas, wherein said step of identifying the parameter of the model of said exhaust system identifies the value of said parameter using the value of said set dead time.

A method of controlling the air-fuel ratio of an internal combustion engine, comprising the steps of sequentially identifying the value of a predetermined parameter of a predetermined model of an exhaust system, which ranges from a position upstream of a catalytic converter disposed in an exhaust passage of the internal combustion engine to an exhaust gas sensor disposed downstream of the catalytic converter for detecting the concentration of a particular component in an exhaust gas, and includes said catalytic converter, for expressing a behavior of the exhaust system which is regarded as a system for generating the output of said exhaust gas sensor from the air-fuel ratio of the exhaust gas which enters said catalytic converter, and sequentially generating a manipulated variable to determine an air-fuel ratio of the exhaust gas which enters said catalytic converter using the identified value of the parameter of said model in order to converge the output of said exhaust gas sensor to a predetermined target value, wherein the air-fuel ratio of an air-fuel mixture to be combusted by the internal combustion engine is manipulated depending on the manipulated variable, wherein:

• said step of identifying the parameter of the model of said exhaust system comprises the step of identifying the value of said parameter according to an algorithm for minimizing an error between the output of said exhaust gas sensor in the model of said exhaust system and an actual output of said exhaust gas sensor;
• said method further comprising the steps of:
• sequentially generating data representative of a flow rate of the exhaust gas flowing through the catalytic converter, and variably setting the value of a weighted parameter of said algorithm for identifying the parameter of said model depending on the value of the data representative of the flow rate of the exhaust gas.

A recording medium readable by a computer and storing an air-fuel ratio control program for enabling said computer to perform a process of sequentially identifying the value of a predetermined parameter of a predetermined model of an exhaust system, which ranges from a position upstream of a catalytic converter disposed in an exhaust passage of the internal combustion engine to an exhaust gas sensor disposed downstream of the catalytic converter for detecting the concentration of a particular component in an exhaust gas, and includes said catalytic converter, for expressing a behavior of the exhaust system which is regarded as a system for generating the output of said exhaust gas sensor via at least a dead time element from the air-fuel ratio of the exhaust gas which enters said catalytic converter, a process of sequentially generating a manipulated variable to determine an air-fuel ratio of the exhaust gas which enters said catalytic converter using the identified value of the parameter of said model in order to converge the output of said exhaust gas sensor to a predetermined target value, and a process of manipulating the air-fuel ratio of an air-fuel mixture to be combusted by the internal combustion engine depending on the manipulated variable, wherein said program comprising:

• said air-fuel ratio control program includes a program for enabling the computer to perform a process of sequentially generating data representative of a flow rate of the exhaust gas flowing through the catalytic converter, and sequentially setting a value of said set dead time as the dead time of a dead time element of the model of said exhaust system depending on the value of the data representative of the flow rate of the exhaust gas, and
• said program for enabling the computer to identify the parameter of the model of said exhaust system identifies the parameter using the value of said set dead time.

A recording medium readable by a computer and storing an air-fuel ratio control program for enabling said computer to perform a process of sequentially identifying the value of a predetermined parameter of a predetermined model of an exhaust system, which ranges from a position upstream of a catalytic converter disposed in an exhaust passage of the internal combustion engine to an exhaust gas sensor disposed downstream of the catalytic converter for detecting the concentration of a particular component in an exhaust gas, and includes said catalytic converter, for expressing a behavior of the exhaust system which is regarded as a system for generating the output of said exhaust gas sensor from the air-fuel ratio of the exhaust gas which enters said catalytic converter, a process of sequentially generating a manipulated variable to determine an air-fuel ratio of the exhaust gas which enters said catalytic converter using the identified value of the parameter of said model in order to converge the output of said exhaust gas sensor to a predetermined target value, and a process of manipulating the air-fuel ratio of an air-fuel mixture to be combusted by the internal combustion engine depending on the manipulated variable, wherein:

• the program of said air-fuel ratio control program for enabling the computer to perform the process of identifying the value of the parameter of the model of said exhaust system identifies the value of said parameter according to an algorithm for minimizing an error between the output of said exhaust gas sensor in the model of said exhaust system and an actual output of said exhaust gas sensor;
• and
• said air-fuel ratio control program includes a program for enabling the computer to perform a process of sequentially generating-data representative of a flow rate of the exhaust gas flowing through the catalytic converter, and a process of variably setting the value of a weighted parameter of said algorithm for identifying the parameter of said model depending on the value of the data representative of the flow rate of the exhaust gas.