Abstract: According to a sliding mode control method, a hyperplane for a sliding mode control process is established with a linear function having as variables a plurality of state quantities of an object to be controlled. The state quantities are converged onto the hyperplane, and also converged toward a balanced point on the hyperplane while the state quantities are being converged onto the hyperplane, thereby to control the state quantities at target state quantities represented by the balanced point. The hyperplane are variably established depending on the manner in which the state quantities are converged onto the hyperplane.

Abstract: An air-fuel control system for use with an internal combustion engine has a catalytic converter disposed in an exhaust system of the engine, for purifying an exhaust gas emitted from the engine, a first exhaust gas sensor disposed in the exhaust system for detecting an air-fuel ratio of the exhaust gas upstream of the catalytic converter, a second exhaust gas sensor disposed in the exhaust system for detecting the concentration of a component of the exhaust gas which has passed through the catalytic converter, downstream of the catalytic converter, and a control unit for controlling an air-fuel ratio of the engine based on outputs from the first exhaust gas sensor and the second exhaust gas sensor.

Abstract: A control system is provided in an internal combustion engine in which a valve timing such as an opening time point and lift amount of an intake valve can be switched to a low-speed or high-speed valve timing within a lean-burn control range established in accordance with the operational state, such as an intake pipe internal absolute pressure and an engine revolution number of the engine, wherein an air-fuel ratio of an air-fuel mixture supplied to the internal combustion engine is enriched for a predetermined time when the valve timing is switched from the low-speed valve timing to the high-speed valve timing while carrying out a lean-burn control.

Abstract: An air-fuel control system for use with an internal combustion engine has a catalytic converter in an exhaust system of the engine, for purifying an exhaust gas emitted from the engine, a first exhaust gas sensor in the exhaust system for detecting an air-fuel ratio of the exhaust gas upstream of the catalytic converter, and a second exhaust gas sensor in the exhaust system for detecting the concentration of a component of the exhaust gas which has passed through the catalytic converter, downstream of the catalytic converter. A sliding mode controller determines a correction quantity at a first period to correct the air-fuel ratio of the engine so as to equalize the concentration of the component downstream of the catalytic converter to a predetermined appropriate value, according to a sliding mode control process based on the output from the second exhaust gas sensor.

Abstract: An air-fuel control system for use with an internal combustion engine has a catalytic converter, a first exhaust gas sensor, and a second exhaust gas sensor. A sliding mode controller determines a correction quantity to equalize the concentration of the component downstream of the catalytic converter to a predetermined appropriate value based on the output from the second exhaust gas sensor. A feedback controller determines a correction quantity to converge the concentration of the component downstream of the catalytic converter toward the predetermined appropriate value, and feed-back controls the rate at which fuel is supplied to the engine with the determined correction quantity.

Abstract: An air-fuel ratio control system for an internal combustion engine having a fuel injection valve for each cylinder and an electronic air control valve (EACV) for controlling intake air bypassing the engine throttle valve. When the target air-fuel ratio is switched over from a rich value to a lean value, the amounts of fuel injected into the cylinders, for example, #1, #2, #3 and #4 cylinders are controlled so that they are sequentially decreased at predetermined intervals, and the EACV is controlled to be opened stepwise. This causes a decrease in engine torque generated by the switching-over of the target air-fuel ratio to be offset by an increase in engine torque generated by an increase in amount of air drawn, thereby preventing the generation of a torque shock. At this time, the target opening degree of the EACV is corrected based on the magnitude of the interval and the magnitude of a loading of the internal combustion engine, thereby further effectively preventing the generation of the torque shock.