Engine air-fuel ratio control
AssigneeNissan Motor Co., Ltd.
InventorHiroshi Katoh
Life of this patent
Estimating the term…
Abstract
A state quantity σ(n) of a switching function is calculated based on a predetermined target air-fuel ratio TGABF, a detected air-fuel ratio AFSAF detected by a sensor (16), and a state equation derived from a transfer function Geng(q) of a secondary discrete system, representing the correlation between an air-fuel ratio of an air fuel mixture in a combustion chamber (1A) and the detected air-fuel ratio (S14). The air-fuel ratio is feedback corrected by applying a sliding mode control process based on the difference between the target air-fuel ratio TGABF and the detected air-fuel ratio AFSAF, and the state quantity σ(n) (S14-S21). The response and robustness of the air-fuel ratio control are enhanced by using a physical model of the secondary discrete system.
Claims16
An air-fuel ratio control device for an engine with a combustion chamber for burning a mixture of air and fuel, comprising:
- a mechanism which regulates an air-fuel ratio of the mixture;
- an air-fuel ratio sensor which detects the air-fuel ratio of the mixture from a composition of an exhaust gas of the engine;
- and
- a programmable controller programmed to:
- calculate a state quantity σ(n) of a switching function based on a preset target air-fuel ratio TGABF, a detected air-fuel ratio AFSAF detected by the sensor, a state equation derived from a transfer function Geng(q) of a secondary discrete system representing the correlation between the air-fuel ratio of the mixture in the combustion chamber and the detected air-fuel ratio, and a predetermined switching function gain mat S;
- calculate a non-linear input unl(n) for a sliding mode control process based on the state quantity σ(n) of the switching function, the predetermined switching function gain mat S, a predetermined non-linear gain η and a predetermined disturbance input β(n);
- calculate a linear input ueq(n) for the sliding mode control process based on a difference between the target air-fuel ratio TGABF and the detected air-fuel ratio AFSAF, and the switching function gain mat S;
- calculate an air-fuel ratio feedback correction value ALPHA from the non-linear input u1(n) and the linear input ueq(n);
- and
- feedback control the air-fuel ratio regulating mechanism based on the air-fuel ratio feedback correction value ALPHA.
An air-fuel ratio control device for an engine with a combustion chamber for burning a mixture of air and fuel, comprising:
- means for regulating an air-fuel ratio of the mixture;
- means for detecting the air-fuel ratio of the mixture from a composition of an exhaust gas of the engine;
- means for calculating a state quantity σ(n) of a switching function based on a preset target air-fuel ratio TGABF, a detected air-fuel ratio AFSAF detected by the detecting means, a state equation derived from a transfer function Geng(q) of a secondary discrete system representing the correlation between the air-fuel ratio of the mixture in the combustion chamber and the detected air-fuel ratio, and a predetermined switching function gain mat S;
- means for calculating a non-linear input unl(n) for a sliding mode control process based on the state quantity σ(n) of the switching function, the predetermined switching function gain mat S, a predetermined non-linear gain η and a predetermined disturbance input β(n);
- means for calculating a linear input ueq(n) for the sliding mode control process based on a difference between the target air-fuel ratio TGABF and the detected air-fuel ratio AFSAF, and the switching function gain mat S;
- means for calculating an air-fuel ratio feedback correction value ALPHA from the non-linear input unl(n) and the linear input ueq(n);
- and
- means for feedback controlling the air-fuel ratio regulating means based on the air-fuel ratio feedback correction value ALPHA.
An air-fuel ratio control method for an engine with a combustion chamber for burning a mixture of air and fuel, the engine comprising a mechanism which regulates an air-fuel ratio of the mixture, the method comprising:
- detecting the air-fuel ratio of the mixture from a composition of an exhaust gas of the engine;
- calculating a state quantity σ(n) of a switching function based on a preset target air-fuel ratio TGABF, a detected air-fuel ratio AFSAF, a state equation derived from a transfer function Geng(q) of a secondary discrete system representing the correlation between the air-fuel ratio of the mixture in the combustion chamber and the detected air-fuel ratio, and a predetermined switching function gain mat S;
- calculating a non-linear input unl(n) for a sliding mode control process based on the state quantity σ(n) of the switching function, the predetermined switching function gain mat S, a predetermined non-linear gain η and a predetermined disturbance input β(n);
- calculating a linear input ueq(n) for the sliding mode control process based on a difference between the target air-fuel ratio TGABF and the detected air-fuel ratio AFSAF, and the switching function gain mat S;
- calculating an air-fuel ratio feedback correction value ALPHA from the non-linear input unl(n) and the linear input ueq(n);
- and
- feedback controlling the air-fuel ratio regulating means based on the air-fuel ratio feedback correction value ALPHA.
Dependencies are inferred from the claim text.