Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – With indicator or control of power plant
Reexamination Certificate
1999-12-17
2001-07-24
Dolinar, Andrew M. (Department: 3747)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
With indicator or control of power plant
C060S276000, C700S030000, C700S052000
Reexamination Certificate
active
06266605
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plant control system.
2. Description of the Prior Art
The applicant of the present application has proposed an air-fuel ratio control system having an exhaust gas sensor for detecting the concentration of a certain component of an exhaust gas that has passed through a catalytic converter such as a three-way catalytic converter disposed in the exhaust passage of an internal combustion engine, such as an O
2
sensor for detecting the concentration of oxygen in the exhaust gas, the exhaust gas sensor being disposed downstream of the catalytic converter. The system controls the air-fuel ratio of the internal combustion engine, more accurately, the air-fuel ratio of an air-fuel mixture to be combusted by the internal combustion engine, in order to converge an output of the O
2
sensor, i.e., the detected value of the oxygen concentration, to a predetermined target value for enabling the catalytic converter to have a desired purifying ability irrespective of the aging of the catalytic converter. See, for example, U.S. patent application Ser. No. 09/311353, now U.S. Pat. No. 6,188,953 U.S. Pat. No. 6,112,517 and Japanese patent application No. 11-93740 (U.S. Pat. No. 6,079,205).
According to the disclosed technology, a manipulated variable for manipulating the air-fuel ratio of the internal combustion engine, specifically, a target air-fuel ratio or a quantity defining such a target air-fuel ratio, is successively generated in given control cycles in order to converge the output of the O
2
sensor to its target value based on a feedback control process. An exhaust gas sensor (hereinafter referred to as an “air-fuel ratio sensor) for detecting the air-fuel ratio of the exhaust gas that enters the catalytic converter, specifically, the air-fuel ratio of the air-fuel mixture that has been burned by the internal combustion engine, is disposed upstream of the catalytic converter. The amount of fuel supplied to the internal combustion engine is regulated so as to converge the output of the air-fuel ratio sensor, i.e., the detected value of the air-fuel ratio, to a target air-fuel ratio defined by the manipulated variable for thereby controlling the air-fuel ratio of the internal combustion engine at the target air-fuel ratio.
Such air-fuel ratio control for the internal combustion engine is capable of converging the output of the O
2
sensor disposed downstream of the catalytic converter to its target value for thereby enabling the catalytic converter to have a desired purifying ability.
In the above proposed air-fuel ratio control system, the feedback control process using the output of the air-fuel ratio sensor disposed upstream of the catalytic converter is carried out for controlling the air-fuel ratio of the internal combustion engine at the target air-fuel ratio. However, it is also possible to control the air-fuel ratio of the internal combustion engine at the target air-fuel ratio according to a feed-forward control process by determining the amount of fuel supplied to the internal combustion engine from the target air-fuel ratio using a map or the like.
In the above air-fuel ratio control system, the O
2
sensor is used as the exhaust gas sensor disposed downstream of the catalytic converter. However, the exhaust gas sensor may comprise an NOx sensor, a CO sensor, an HC sensor, or another exhaust gas sensor. It is possible to enable the catalytic converter to have a desired purifying ability by controlling the air-fuel ratio of the internal combustion engine so as to converge the output of such an exhaust gas sensor to a suitable target value.
In the above conventional air-fuel ratio control system, the exhaust system, including the catalytic converter, which ranges from a position upstream of the catalytic converter to the O
2
sensor downstream of the catalytic converter may be considered to be a plant for generating the output of the O
2
sensor from the air-fuel ratio of the internal combustion engine (the air-fuel ratio as detected by the air-fuel ratio sensor). The internal combustion engine may be considered to be an actuator for generating an exhaust gas having an air-fuel ratio to be supplied to the plant. Thus, the air-fuel ratio control system may be expressed as a system for generating a manipulated variable to control the input (air-fuel ratio) to the plant (=an output from the actuator) to converge the output of the O
2
sensor as the output of the plant to a given target value, and controlling operation of the internal combustion engine as the actuator based on the manipulated variable.
The catalytic converter generally has a relatively long dead time which tends to adversely affect the control process of converting the output of the O
2
sensor to the target value. In the air-fuel ratio control system, the behavior of the exhaust system including the catalytic converter and ranging from the position upstream of the catalytic converter to the O
2
sensor downstream of the catalytic converter is modeled. The output of the O
2
sensor after the dead time of the exhaust system is successively estimated according to an algorithm constructed on the basis of the model of the exhaust system. The manipulated variable is generated using the estimated value of the output of the O
2
sensor (specifically, the manipulated variable is generated in order to converge the estimated value of the output of the O
2
sensor to the target value) for thereby compensating for the effect of the dead time.
In modeling the exhaust system including the catalytic converter, the exhaust system is regarded as a system for generating the difference between the output of the O
2
sensor and its target value with a response delay and the dead time, from the difference (hereinafter referred to as a “differential air-fuel ratio”) between the air-fuel ratio of the air-fuel mixture combusted by the internal combustion engine, i.e., the air-fuel ratio detected by the air-fuel ratio sensor, and a predetermined constant reference value with respect to the air-fuel ratio. The algorithm for estimating the output of the O
2
sensor after the dead time of the exhaust system is constructed on the basis of the model of the exhaust system.
With the input (differential air-fuel ratio) to the exhaust system that is modeled and the output thereof (the difference between the output of the O
2
sensor and its target value) being expressed as differences, the algorithm for estimating the output of the O
2
sensor after the dead time of the exhaust system can be simplified.
The applicant has also proposed a technique for compensating for not only the dead time of the exhaust system, but also the effect of dead times of the internal combustion engine and a controller (hereinafter referred to as an “engine controller”) which controls operation of the internal combustion engine based on the manipulated variable, in U.S. patent application Ser. No. 09/311353. This process is proposed because the dead times of the internal combustion engine and the engine controller may adversely affect the control process of converting the output of the O
2
sensor to the target value, depending on an operating state of the internal combustion engine (more specifically, the state of the rotational speed thereof) for which the control process of converting the output of the O
2
sensor to the target value is carried out.
According to the above proposed technique, the exhaust system is modeled as described above, and a system comprising the internal combustion engine and the engine controller is modeled as a system for generating an air-fuel ratio to be given to the exhaust system, with only the dead time of the air-fuel ratio control system, from the manipulated variable, i.e., a system in which the air-fuel ratio to be given to the exhaust system is uniquely defined by the manipulated variable prior to the dead time. According to an algorithm constructed on the basis of these models, the output of the O
2
sensor after a total dead time represe
Akazaki Shusuke
Iwaki Yoshihisa
Sato Tadashi
Ueno Masaki
Yasui Yuji
Arent Fox Kintner Plotki & Kahn, PLI
Dolinar Andrew M.
Honda Giken Kogyo Kabushiki
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