Abstract: A manipulation variable generating unit 7 for generating a target air-fuel ratio KCMD to converge the output of an oxygen concentration sensor 5 disposed downstream of a catalytic converter 3 in an exhaust system E as a plant to a given target value has a plurality of estimators for generating data indicating estimated values of the output of the oxygen concentration sensor after a dead time of the exhaust system E or a total dead time which is the sum of the dead time of the exhaust system E and a dead time of a system comprising an engine control unit 8 and an internal combustion engine 1, according to respective different algorithms. The manipulation variable generating unit 7 generates the target air-fuel ratio KCMD according to an adaptive sliding mode control process using a value selected from the estimated values or a combined value representing a combination of the estimated values.

Abstract: A control system for a plant is disclosed. In this control system, a model parameter vector of a controlled object model which is obtained by modeling said plant, is calculated. A sliding mode controller is included in the control system. The sliding mode controller controls the plant using the identified model parameter vector. A damping input is calculated according to a speed of change in an output of the plant, and an element of the model parameter vector. A control input form the sliding mode controller to the plant includes the calculated damping input.

Abstract: A control system for a throttle valve actuating device is disclosed. The throttle valve actuating device includes a throttle valve of an internal combustion engine and an actuator for actuating the throttle valve. The control system includes a predictor for predicting a future throttle valve opening and controls the throttle actuating device according to the throttle valve opening predicted by the predictor so that the throttle valve opening coincides with a target opening.

Abstract: A control system for a plant, includes a sliding mode controller for controlling the plant with a sliding mode control. The sliding mode controller controls the plant using a switching function defined as a linear function of a deviation between an output of the plant and a control target value, and changes the switching function according to at least one of a parameter indicative of the output of the plant and a parameter indicative of an amount of change in the output of the plant.

Abstract: A control system for a plant is disclosed. According to this system, a model parameter vector of a controlled object model which is obtained by modeling the plant, is identified. A controller controls the plant using the identified model parameter vector. An identifying error of the model parameter vector is calculated, and the calculated identifying error is limited in a predetermined range. An updating vector is calculated according to the limited identifying error. The model parameter vector is calculated by adding the updating vector to a reference vector of the model parameter vector.

Abstract: A control system for a plant is disclosed. According to this system, a model parameter vector of a controlled object model which is obtained by modeling the plant, is identified. A controller controls the plant using the identified model parameter vector. An identifying error of the model parameter vector is calculated, and an updating vector is calculated according to the identifying error. The updating vector has at least one first element which is relevant to an input or an output of the plant, and a second element which is irrelevant to the input and the output of the plant. The updating vector is corrected by multiplying a past value of at least one first element of the updating vector by a predetermined value which is greater than “0” and less than “1”, and multiplying a past value of the second element of the updating vector by “1”. The model parameter vector is calculated by adding the corrected updating vector to a reference vector of the model parameter vector.

Abstract: A state determining apparatus for an exhaust gas recirculation system is provided for appropriately determining the state of an exhaust gas recirculation system including an EGR passage. An exhaust gas recirculation system is arranged in an exhaust system of an internal combustion engine including an EGR passage for recirculating a portion of exhaust gases to an intake system in accordance with an operating state of the internal combustion engine. The state determining apparatus comprises a humidity sensor arranged in the EGR passage for detecting a humidity within the EGR passage, and an ECU for determining the state of the exhaust gas recirculation system based on a result detected by the humidity sensor.

Abstract: An adsorbent state determining apparatus is provided for accurately determining the state of an adsorbent including a deterioration as well as for allowing for recovery of the adsorbent if its adsorbent performance can be restored. The adsorbent state determining apparatus determines the state of an adsorbent for adsorbing hydrocarbons contained in exhaust gases. An upstream and a downstream temperature sensor are provided at upstream and downstream locations of the adsorbent in an exhaust system for detecting temperatures of exhaust gases upstream and downstream of the adsorbent. An engine water temperature sensor detects an operating state of the engine. An ECU estimates the temperature of the exhaust gas which should be detected downstream of the adsorbent during adsorption of the adsorbent based on the upstream temperature detected by the upstream temperature sensor and an engine water temperature of the engine detected by the engine water temperature sensor.

Abstract: A control system for a throttle valve actuating device is disclosed. The throttle valve actuating device includes a throttle valve of an internal combustion engine and an actuator for actuating the throttle valve. At least one model parameter of a controlled object model which is obtained by modeling the throttle valve actuating device is calculated. A learning value of a throttle valve opening at which an actuating characteristic of the throttle valve changes, is calculated. The throttle valve actuating device is controlled using the learning value so that an opening of the throttle valve coincides with a target opening.

Abstract: A control system for a plant is disclosed. The control system includes a response specifying type controller for controlling the plant with a response specifying type control. The response specifying type controller calculates a nonlinear input according to a sign of a value of a switching function and an output of the plant. The switching function is defined as a linear function of a deviation between the output of the plant and a control target value. A control input from the response specifying type controller to the plant includes the nonlinear input.

Abstract: A control system for a plant is disclosed. According to this system, a value of a switching function which is defined as a linear function of a deviation between the output of the plant and a control target value, is calculated. A reaching mode input is calculated. The reaching mode input contributes to placing a deviation state quantity which is defined based on the deviation, onto a switching straight line on which the value of the switching function becomes zero. The reaching mode input is corrected according to the value of the switching function. A control input to the plant is calculated with a response specifying type control, and the control input includes the reaching mode input. The plant is controlled with the calculated control input.

Abstract: The temperature of an exhaust gas flowing through an exhaust passage 3 is estimated or detected, and the temperature of an active element of an exhaust gas sensor 8 (O2 sensor) is controlled at a predetermined target temperature by a heater using the estimated or detected temperature of the exhaust gas. For estimating the temperature of the exhaust gas in the vicinity of the exhaust gas sensor 8, the exhaust passage 3 extending up to the exhaust gas sensor 8 is divided into a plurality of partial exhaust passageways 3a through 3d, the temperatures of the exhaust gas in the partial exhaust passageways 3a through 3d are estimated successively from an exhaust port 2 of an engine 1. The temperature of the exhaust gas is estimated according to an algorithm which takes into account a heat transfer between the exhaust gas and passage-defining members 6a, 6b, 7 which define the exhaust passage 3 and a heat radiation from the passage-defining members into the atmosphere.

Abstract: A system controls the air-fuel ratio in an exhaust gas supplied from an internal combustion engine to a catalytic converter in order to keep an output voltage Vout of an O2 sensor disposed downstream of the catalytic converter at a predetermined target value Vop. In the system, the temperature of an active element of the O2 sensor is controlled at a predetermined temperature such that the output voltage of the O2 sensor at an inflection point of output characteristics thereof is substantially the same as the target value Vop.

Abstract: There are provided an adsorption amount sensor which is capable of accurately detecting an amount of hydrocarbons or water adsorbed by a zeolite of a hydrocarbon adsorber, even during operation of an engine, as well as a coking sensor which is capable of accurately detecting an amount of coke deposition on inner surfaces of a pipe of an internal combustion engine, even during operation of an engine. The adsorption amount sensor has a plurality of electrodes arranged in the vicinity of the hydrocarbon adsorber in a manner opposed to each other and each carrying a zeolite thereon. The amount of hydrocarbons adsorbed is detected by using a parameter indicative of changes in at least one of a resistance value between the electrodes and an electrical capacitance between the electrodes. The coking sensor has a plurality of electrodes arranged within the pipe of the engine in a manner opposed to each other and each having a surface thereof coated with an insulating material.

Abstract: A control system for a plant is disclosed. The control system includes a controller which controls the plant based on a controlled object model which is obtained by modeling the plant. The controlled object model is modeled using an input and an output of the plant which are sampled at intervals of a period which is longer than a control period of the controller. The controller carries out a control process of the plant at intervals of the control period.

Abstract: A control system for a plant is provided. This control system can control the plant more stably, when the model parameters of the controlled object model which are obtained by modeling the plant, which is a controlled object, are identified and the sliding mode control is performed using the identified model parameters. The model parameter identifier (22) calculates a model parameter vector (&thgr;) by adding an updating vector (d &thgr;) to a reference vector (&thgr; base) of the model parameter. The updating vector (d &thgr;) is corrected by multiplying a past value of at least one element of the updating vector by a predetermined value which is greater than “0” and less than “1”. The model parameter vector (&thgr;) is calculated by adding the corrected updating vector (d &thgr;) to the reference vector (&thgr; base).

Abstract: A failure determination device that detects the humidity of exhaust gases from an internal combustion engine and a control system for an exhaust passage changeover valve, which can switch the changeover valve with appropriate timing, thereby enabling sufficient purification of exhaust gases. An operating condition of the engine is detected. Based on the detected operating condition of the engine, it is determined whether the engine is in an operating condition in which failure determination of the humidity sensor can be executed. It is determined whether the humidity sensor has failed, based on a result of detection by the humidity sensor, when it has been judged that the failure determination of the humidity sensor can be executed.

Abstract: A target air-fuel ratio KCMD for an exhaust gas upstream of a catalytic converter is sequentially determined to converge the output VO2/OUT of an O2 sensor downstream of the catalytic converter to a target value VO2/TARGET, and the amount of fuel supplied to an internal combustion engine is controlled to converge the output KACT of an air-fuel ratio sensor to the target air-fuel ratio KCMD. While the amount of fuel supplied to the internal combustion engine is being thus controlled, the value of a deterioration linear function &sgr; whose variable components are represented by time-series data of the output VO2/OUT of the O2 sensor is determined. A central value of the square &sgr;2 of the value of the deterioration linear function &sgr; is determined as a deterioration evaluating parameter. A deteriorated state of the catalytic converter is evaluated on the basis of the value of the deterioration evaluating parameter.

Abstract: A control system for an internal combustion engine having a catalyst arranged in the exhaust system is disclosed. In the control system, catalyst temperature rise accelerating control is executed by increasing the intake air amount immediately after starting of the engine and retarding the ignition timing to make the rotational speed of the engine coincide with a target rotational speed. The air-fuel ratio of an air-fuel mixture supplied to the engine is controlled to a lean region with respect to the stoichiometric ratio immediately after starting of the engine. The degree of making the air-fuel ratio leaner is suppressed when the retard amount of the ignition timing during the execution of the catalyst temperature rise accelerating control is less than a predetermined retard amount.

Abstract: A control system for an internal combustion engine having at least one control device that affects an air-fuel ratio of an air-fuel mixture to be supplied to the engine, is disclosed. An air-fuel ratio correction coefficient is calculated for correcting an amount of fuel to be supplied to the engine so that the detected air-fuel ratio coincides with a target air-fuel ratio. An air-fuel ratio affecting parameter indicative of a degree of influence that an operation of the control device exercises upon the air-fuel ratio, is calculated. A correlation parameter which defines a correlation between the air-fuel ratio correction coefficient and the air-fuel ratio affecting parameter is calculated using a sequential statistical processing algorithm. A learning correction coefficient relating to a change in characteristics of the control device is calculated using the correlation parameter. The air-fuel ratio is controlled using the air-fuel ratio correction coefficient and the learning correction coefficient.