Abstract: A downstream exhaust system controller generates a target value for the output of an upstream O2 sensor disposed between first and second catalytic converters for converging the output of a downstream O2 sensor disposed downstream of the second catalytic converter to a target value while taking into account the dead time of a downstream exhaust system. An upstream exhaust system controller generates a target air-fuel ratio for an internal combustion engine for converging the output of the upstream O2 sensor to a target value while taking into account the dead time of an upstream exhaust system. A fuel processing controller controls the air-fuel ratio of the internal combustion engine at the target air-fuel ratio according to a feedback control process.

Abstract: Even when a reaction delay time of an A/F ratio detection device changes, an A/F ratio controller prevents an A/F ratio feedback control from being disturbed. The controller is programmed to calculate an A/F ratio feedback coefficient by proportional term control and integration term control, and to set length of time for said integration term to be carried out in accordance with an operating state of the engine. It is programmed to calculate the integration term based on the set time and to set a proportional term for shifting said A/F ratio feedback coefficient. It is further programmed to detect a deviation between a first A/F ratio feedback coefficient before the integration term is carried out and a second A/F ratio feedback coefficient after the integration term is carried out and the coefficient is shifted by the proportional term set by said means for setting the proportional term. Based on the detected deviation, the length of time for the integration term to be carried out is corrected.

Abstract: A method is provided for accommodating the purge vapors from an evaporative emission control system of an automotive vehicle. The method includes a purge compensation model to identify the concentration of purge vapor entering the intake manifold of the engine of the automotive vehicle, identifying the source of the vapor as from the vapor collection canister or the fuel tank using a characteristic mapping of maximum concentration as a function of instantaneous flow and accumulated flow through a canister and uses this information to predict variations in vapor concentrations as a function of purge flow. The method also includes a purge control model which uses mode logic to identify an appropriate time to initiate a purge cycle, provides the flow conditions necessary for a learning portion of the purge compensation model and increases purge flow rates after the learning is complete to deplete the contents of the canister.

Abstract: An improved closed-loop feedback fuel control with a model-based A/F ratio estimator, wherein the estimator, controller and portions of the model are updated on a fixed time interval basis, thereby minimizing the impact of the control on event-based throughput. Engine transport delays and oxygen sensor dynamics are modeled to estimate the sensed A/F ratio, and the estimate is compared with the sensed A/F ratio to adaptively adjust the model and to develop a closed-loop adjustment of the commanded fuel amount. The engine transport delay model is carried out on an engine event basis, but the sensor dynamics model is carried out on a time basis to accurately reflect the analog nature of the sensor. The estimator and the controller are also carried out on a time basis to reduce throughput requirements at higher engine speeds, and the control gain is scheduled to account for differences between the engine event and time update rates.

Abstract: An apparatus for controlling air-fuel ratio in an engine provided with a fuel vapor purging system. The purging system sends the fuel vapor in a fuel tank to an intake passage. The actual air-fuel ratio is computed from the oxygen concentration of the exhaust gas. An electronic control unit (ECU) adjusts the amount of fuel injected from an injector. The ECU sets a feedback correction coefficient FAF to correct the difference between the actual air-fuel ratio and a predetermined target air-fuel ratio. The feedback correction coefficient FAF is feedback controlled. The ECU further considers fluctuations of the air-fuel ratio caused by the purging system in accordance with the operating state and operating history of the engine.

Abstract: A plant control system has a reference value setting unit for variably setting a reference value for an air-fuel ratio to be given to an exhaust system including a catalytic converter, depending on a component based on an adaptive control law of a manipulated variable of the air-fuel ratio generated by a controller according to an adaptive sliding mode control process in order to converge an output of an O2 sensor disposed downstream of the catalytic converter to a target value. The manipulated variable generated by the controller represents the difference between the air-fuel ratio and the reference value, required to converge the output of the O2 sensor to the target value.

Abstract: An air-fuel ratio control apparatus adapted for an internal combustion engine equipped with a purge system. The air-fuel ratio control apparatus estimates the amount of fuel vapor present in a fuel tank from a balance between an estimated produced vapor amount and an estimated purged amount of fuel vapor. When the estimated amount of fuel vapor present is small, the concentration of fuel vapor to be purged is low, so that a base air-fuel ratio feedback coefficient is learned in a period where the estimated value is small. As a result, the base air-fuel ratio feedback coefficient is appropriate learned. Even if the base air-fuel ratio feedback coefficient is learned incorrectly, the air-fuel ratio control apparatus can correct the feedback coefficient. Accordingly, the concentration of the fuel vapor to be purged into the intake air can be detected accurately, thus permitting the base air-fuel ratio feedback coefficient to be maintained at a more appropriate value.

Abstract: An improved fuel control in which the transfer function of a wide-range exhaust gas oxygen sensor is automatically and periodically learned or re-learned in the course of vehicle operation. The oxygen sensor is calibrated at two different operating conditions: at a stoichiometric air/fuel ratio, and at a fuel cut-off or free-air ratio. The first operating condition occurs during steady state operation when a switching sensor disposed in the exhaust gas stream downstream of the catalytic converter indicates that the engine is being fueled at the stoichiometric air/fuel ratio. The second operating condition occurs when engine fuel is shut off, either during vehicle deceleration, or when the engine is turned off. Once both calibration points have been determined, the transfer function of the wide range sensor is adjusted to match the stored voltages, and engine fueling is thereafter based on the adjusted transfer function.

Abstract: An object system for generating an output signal of an O2 sensor from a target air-fuel ratio is expressed as a model including a response delay element and a dead time element. Data of identified values of parameters of the model are sequentially generated by an identifier. Data of an estimated value of the output signal of the O2 sensor after a dead time of the object system is sequentially generated by an estimator. The target air-fuel ratio is generated according to an adaptive sliding mode control process performed by a sliding mode controller using the data of the identified and estimated values. The air-fuel ratio of an internal combustion engine is manipulated on the basis of the target air-fuel ratio according to a feed-forward control process.

Abstract: A plant control system has an actuator for generating an input to the plant, a first sensor for detecting an output from the plant, a manipulated variable determining unit for sequentially determining a manipulated variable which determines the input to the plant to equalize the output from the first sensor to a predetermined target value, an actuator controller for controlling operation of the actuator based on the manipulated variable determined by the manipulated variable determining unit, and an estimator for sequentially generating data representing an estimated value of the output from the first sensor after a total dead time which is the sum of a first dead time of the plant and a second dead time of a system which comprises the actuator and the actuator controller. The manipulated variable determining unit determines the manipulated variable based on the data generated by the estimator.

Abstract: When a pulse width limitation control is carried out, an air-fuel ratio feedback correction control such as O2 feedback or an A/F (air-fuel ratio) learning correction control is prohibited or limited. When the pulse width limitation control is carried out, various kinds of factors for carrying out a basic injection amount are made a prohibition condition or a limitation condition, and when other operation conditions arise, the operability is not damaged.

Abstract: An air-fuel ratio control apparatus for an internal combustion engine calculates a purge rate from a purge amount and an engine operating state, calculates a purge air density from the purge rate and an air-fuel ratio correcting coefficient, and calculates a purge air density correcting coefficient based on the purge rate and the purge air density. Further, the air-fuel ratio control apparatus calculates a learned air-fuel ratio feedback correction value from the air-fuel ratio feedback correcting coefficient, calculates a fuel injection amount based on the air-fuel ratio feedback correcting coefficient, the learned air-fuel ratio feedback correction value and the purge air density correcting coefficient, and alternately switches over the learning of the air-fuel ratio feedback correction and the learning of the purge air density.

Abstract: A method is provided for accommodating the purge vapors from an evaporative emission control system of an automotive vehicle. The method includes a means of learning the bank-to-bank distribution of purge vapors within the engine manifold. As such, the fuel to air ratio delivered from various injectors can be selectively controlled to accommodate the purge vapor at that bank of the engine and maintain the desired fuel to air ratio.

Abstract: Air/fuel and ignition control of engine are used to more rapidly heat-up a catalytic converter. A control system generates a fuel command for fuel delivery to the engine based upon at least an amount of air inducted into the engine. The fuel command is corrected by a correction value so that the exhaust gas mixture is shifted more closely to the preselected air/fuel ratio. Correction values are adaptively learned during warm engine operation from a feedback signal derived from an exhaust gas oxygen sensor. Initial warm correction values are stored in a reference table. At engine shut-off the difference between the warm correction values and the reference table are stored in an offset correction table. This offset correction table is then used during the next engine cold start to schedule the open-loop air/fuel ratio by using the cold adaptive table values which have been modified by the values stored in the corresponding cells of the offset correction value table.

Abstract: An air-fuel ratio control system for an automotive internal combustion engine equipped with a fuel injector valve. The control system comprises a sensor for detecting a ratio between air and fuel which form air-fuel mixture in the engine. A controller is provided to control the ratio between air and fuel, and includes a section for calculating the ratio between air and fuel, in accordance with an engine operating condition. A section is provided for calculating a quantity of fuel to be supplied through the fuel injector valve, in accordance with the calculated ratio between air and fuel. A section is provided for calculating a coefficient relating to a feedback control for the ratio between air and fuel, in accordance with the calculated quantity of fuel to be supplied. The feedback control is made in accordance with the ratio between air and fuel detected by the sensor.

Abstract: An improved individual cylinder fuel control method based on sampled readings of a single oxygen sensor responsive to the combined exhaust gas flow of several engine cylinders. The oxygen sensor output is sampled in synchronism with the engine firing events, a stored non-volatile table of offset values is used to correlate the sampled oxygen sensor values with individual engine cylinders, and a new offset value is determined and stored in place of a current offset value when the current offset value fails to reduce a measure of air/fuel ratio maldistribution among the engine cylinders. In systems having an oxygen sensor of the switching type, the measure of air/fuel ratio maldistribution is determined by filtering and integrating the oxygen sensor signal, and the new offset value is determined by repeatedly incrementing the stored offset value, and fueling the individual cylinders of the engine based on the incremented offset value, until the measure of air-fuel ratio maldistribution decreases.

Abstract: An air/ratio control system and method for an internal combustion engine coupled to a fuel vapor recovery system simultaneously maps a difference between a desired air/fuel ratio and a measured air/fuel ratio to fueling errors and a purge vapor flow. This system and method maximizes the ability to purge the vapor recovery system while maintaining the ability to diagnose fuel errors.

Abstract: A control system for a plant includes a sensor for detecting an output from the plant, an adaptive controller for controlling a manipulated variable applied to control of the plant in such a manner that an output from the sensor becomes equal to a desired value, and an adaptive parameter-adjusting device for adjusting adaptive parameters used by the adaptive controller. The adaptive parameter-adjusting device has an identification error-calculating device for calculating an identification error of the adaptive parameters and generating an identification error signal indicative of the calculated identification error, and an adjusting device for adjusting the adaptive parameters based on the calculated identification error. The adaptive parameter-adjusting device includes a non-linear filter for generating an output of 0 or approximately 0 in response to the identification error signal when the identification error is within a predetermined range.

Abstract: A fuel injection control system of an engine includes: (a) an intake air quantity estimation unit for estimating the quantity of intake air; (b) an intake fuel quantity estimation unit for estimating the quantity of intake fuel; (c) an estimated air-fuel ratio calculation unit for calculating an estimated air-fuel ratio; (d) a target air-fuel ratio setting unit for setting a target air-fuel ratio; (e) a feedback control unit for providing a fuel injection signal to the engine, which fuel injection signal is outputted also to the intake fuel quantity estimation unit as one of the predetermined signals; and (f) an actual air-fuel ratio deviation estimation unit for estimating a deviation of an actual air-fuel ratio or a factor correlated thereto from a predetermined level, which unit is programmed to output a deviation signal based on predetermined signals.

Abstract: A fuel injection system for small engines. A controller is provided to monitor manifold absolute pressure, engine RPM and engine oxygen levels. Fuel injector pulses are synchronized to minima in the manifold absolute pressure signal. The width of the pulses is varied depending upon the manifold absolute pressure, the engine RPM, and the oxygen level. In addition, a plurality of correction factors are available to adjust the pulse width depending on engine performance.

Abstract: A method for monitoring the performance of a catalytic converter (34) computes the oxygen storage capacity and desorption capacity of a catalyst within the catalytic converter (34). An engine control unit (10) receives mass flow rate information of air from a mass air flow rate sensor (12) and an injector driver (24), and receives electrical signals from an upstream exhaust gas sensor (28) and a downstream exhaust gas sensor (30). A rate modifier is determined from excess air ratios and an adaptation parameter. The engine control unit (10) calculates normalized air fuel ratios for the exhaust gas entering and leaving the catalytic converter (34) and performs numerical integration using the rate modifier to determine the oxygen storage capacity of the catalyst in the catalytic converter (34). The calculated oxygen storage capacity of the catalyst can be compared with threshold values to determine the performance of the catalytic converter (34).

Abstract: For proper treatment of NOx released from NOx absorbent catalyst as well as HC and CO in exhaust gas, a measure of A/F of exhaust gas downstream of the NOx absorbent is used as the input to a feedback control loop. The feedback control loop alters a feedback correction factor (or coefficient) of a fuel control command applied to each fuel injector in such a direction to decrease a deviation of the actual A/F input from a target A/F (stoichiometry or rich) When the measure of A/F has switched the side to rich, a measure of A/F of exhaust gas upstream of the NOx absorbent catalyst is used as the input to perform usual feedback control loop to maintain lean combustion mode.

Abstract: A learning value of a multiplication term for correcting a basic injection amount and a learning value of an addition term for correcting the basic injection amount are stored in a memory. The learning value of the addition term is converted to a proportion relative to the basic injection amount, and these learning values are modified such that the sum of the proportion and the multiplication term lies within a predetermined range. The proportion of the total learning values relative to the basic injection amount is thereby suppressed to a constant level so that the effect of incorrect learning on air-fuel ratio control is also suppressed.

Abstract: A plant control system controls a plant modeled as a discrete-system model including an element relative to a response delay of the plant. The plant control system includes an actuator for generating an input to the plant, a first detector detecting an output from the plant, and a second detector for detecting the input to the plant which is generated by the actuator. An identifier identifies parameters to be established of the discrete-system model based on data representing an output of the first detector and data representing an output of the second detector. A manipulated variable determining unit determines a manipulated variable which determines the input to the plant to control operation of the actuator such that the output from the first detector will be equalized to a predetermined target value, according to a predetermining algorithm using the parameters of the discrete-system model which are identified by the identifier.

Abstract: An air/ratio control system and method for an internal combustion engine coupled to a fuel vapor recovery system simultaneously maps a difference between a desired air/fuel ratio and a measured air/fuel ratio to fueling errors and a purge vapor flow. This system and method maximizes the ability to purge the vapor recovery system while maintaining the ability to diagnose fuel errors.

Abstract: To optimally operate a NOx-occluded type catalytic converter installed in an exhaust passage of an internal combustion engine, there are employed an air/fuel ratio sensor for detecting an exhaust air/fuel ratio of the exhaust gas downstream of the converter; and a control device for controlling an air/fuel ratio of a combustible mixture fed to the engine. The control device comprises a first section for causing the converter to effect NOx-reduction treatment by making the air/fuel ratio of the combustible mixture richer and/or stoichiometric; and a second section for learning and correcting the condition of the NOx-reduction treatment, based on the exhaust air/fuel ratio detected by the sensor under the NOx-reduction treatment.

Abstract: An Air/Fuel mixture control system for an internal combustion engine which uses a closed loop controller for varying an air/fuel mixture in response to the voltage output of the engine's exhaust gas oxygen sensor. The oxygen sensor will produce a voltage output which is classified in a range extending from very rich, net rich, net lean or very lean depending upon the sensed voltage output in milli-volts. The controller responds to an onset of a lean or rich exhaust signal, representative of either too much or too little oxygen, by instructing the fuel injectors to either increase or decrease the fuel delivery rate to a predetermined rich step value or lean step value. The delivery rate at the rich or lean step value is maintained until the onset of either a rich or lean exhaust indication or until a predetermined rich or lean step duration expires.

Abstract: A plant control system for controlling a plant includes an actuator for generating an input to the plant and a first detector for detecting an output from the plant. A manipulated variable determining unit determines a manipulated variable which determines the input to the plant according to a sliding mode control process such that an output from the first detector will be equalized to a predetermined target value. The manipulated variable determining unit determines the manipulated variable to converge a plurality of state quantities, which comprise differences between a plurality of present and previous time-series data of the output of the first detector and the target value, onto a balanced point on a hyperplane for the sliding mode control process, which is defined by a linear function having variables represented respectively by the state quantities.

Abstract: Automotive internal combustion engine fuel volatility is estimated during cold start operations by stabilizing air admission to the engine and analyzing engine speed over a modeling period following an engine coldstart after engine speed has stabilized and prior to closed-loop engine operation. If engine speed deviates significantly away from an expected engine speed for the current engine intake air and fuel, a fuel volatility deviation is diagnosed. The magnitude of the fuel volatility deviation away from a nominal fuel volatility is determined as a function of the magnitude of the engine speed deviation. A fuel volatility correction value is updated as a function of the engine speed deviation and is applied throughout an ignition cycle, including during the modeling period to compensate for the fuel volatility deviation.

Abstract: A plant control system controls a plant modeled as a discrete-system model including an element relative to a response delay of the plant and an element relative to a dead time of the plant. The plant control system includes an actuator for generating an input to the plant, a first detector for detecting an output from the plant, and a second detector for detecting the input to the plant. An estimator generates data representing an estimated value of an output of the first detector after the dead time, based on data representing the output of the first detector and data representing an output of the second detector. A manipulated variable determining unit determines a manipulated variable which determines the input to the plant, based on the estimated value, represented by the data generated by the estimator, of the output of the first detector after the dead time.

Abstract: A system for controlling fuel vapors of an internal combustion engine having a fuel supply system including a fuel tank for supplying fuel to an air intake system such that an air-fuel mixture flows to a combustion chamber, including a canister purge mechanism for purging the stored fuel vapors into the air intake system of the engine through a purge line. A purged fuel amount supplied to the combustion chamber of the engine is calculated and a fuel injection amount to be supplied to the engine is determined based on the calculated purged fuel amount and a basic fuel inject-on amount. In the system, the purged fuel amount is calculated based on the estimated amount of the fuel vapors in response to a transport delay of the purged fuel vapors.

Abstract: The apparatus for correcting air-flow sensor output includes an air-flow sensor sensing an air-flow in an intake of an engine, and other sensors sensing operating conditions of the engine. An electronic control unit determines whether the engine is operating in one of a first and second state based on the sensed operating conditions, and reads a correction factor from a data map based on the sensed operating conditions when the engine is operating in the first state. Also, the electronic control unit calculates a new correction factor based on the sensed operating conditions and stores the new correction factor in the data map when the engine is operating in the second state. Then, the electronic control unit determines a corrected air-flow quantity based on the sensed air-flow and one of the read correction factor and the calculated correction factor.

Abstract: An engine control system in which a plurality of engine control data values corresponding to respective values of a predetermined engine operating parameter are previously stored in a read only memory, correction data indicative of a correction value for correcting errors of the engine control data values stored in the read only memory is stored in a rewritable memory, and one of the engine control data values corresponding to a detected value of the predetermined engine operating parameter is read out from the read only memory, while the correction data stored in the rewritable memory is read out to obtain the correction value, whereby the read engine control data value is corrected by using the correction value in order to control the engine based on the corrected engine control data value.

Abstract: A method is provided for accommodating the purge vapors from an evaporative emission control system of an automotive vehicle. The method includes a means of learning changes in the mass of a purge vapor collection canister such that a mass of purge vapor in the canister can be determined. The canister model uses the output of a strategic adaption routine to learn the loading of the canister. Thereafter, the canister model uses the learned loading of the canister and tank flow rate from a tank model to compute the mass balance of purge vapor exiting and entering the canister. The concentration level is compared to the calibrated maximum in an open loop surface to determine the level of canister loading. Based on the current loading of the canister, the open loop surface of canister concentration as a function of flow rate and accumulated flow is used to predict how the concentration will change as the flow rate through the canister changes.

Abstract: An air/fuel ratio control system controls the supply of fuel to an internal combustion engine to achieve a target air/fuel ratio, based on the output of an air/fuel ratio sensor. The system may determine whether there is an abnormality in the air/fuel ratio sensor based on a comparison between a change of an air/fuel ratio correction coefficient, used to drive the air/fuel ratio to the target value, and a change of the target air/fuel ratio if the target air/fuel ratio has sharply changed.

Abstract: When fuel supply system abnormality diagnosis conditions are satisfied, the abnormality of a fuel supply system is diagnosed by comparing an air/fuel ratio deviation index value with a lean/rich abnormality determination value by diagnosis means. At this time, a hot lean abnormality determination value KHL is set leaner than an ordinary lean abnormality determination value KLL, and a hot rich abnormality determination value KHH is set richer than an ordinary rich abnormality determination value KLH by abnormality determination value setting means when the engine compartment temperature is high. As a result, it is possible to diagnose whether or not the fuel supply system is abnormal (i.e., an abnormal deviation in the air/fuel ratio) while preventing the mistake even when the engine compartment temperature is high, so that the early discovery of the abnormality and the prevention of the mistaken diagnosis are made compatible.

Abstract: A control system for a plant includes a sensor for detecting an output from the plant, an adaptive controller for controlling a manipulated variable applied to control of the plant in a manner such that an output from the sensor becomes equal to a desired value, and an adaptive parameter vector-adjusting mechanism for adjusting an adaptive parameter vector used by the adaptive controller. The adaptive parameter vector-adjusting mechanism is constructed such that an updating component for updating the adaptive parameter vector is added to an initial value of the adaptive parameter vector, and updates the adaptive parameter vector by multiplying at least part of preceding values of the updating component by a predetermined coefficient which is larger than 0 but smaller than 1.

Abstract: An air-fuel ratio control system for a multi-cylinder engine is provided. An air-fuel ratio sensor is arranged in an exhaust system of the engine for detecting an air-fuel ratio of a mixture supplied to the engine and for generating an output indicative of the air-fuel ratio of the mixture. An adaptive controller determines an amount of fuel to be supplied to the engine with a first predetermined repetition period in a manner such that the output from the air-fuel ratio sensor becomes equal to a desired value. An adaptive parameter-adjusting mechanism adjusts adaptive parameters used by the adaptive controller. In the adaptive parameter-adjusting mechanism, the adaptive parameters are calculated with a second predetermined repetition period longer than the first predetermined repetition period, and output data indicative of results of the calculation is generated.

Abstract: An air-fuel ratio control system for an internal combustion engine includes an air-fuel ratio sensor arranged in the exhaust system of the engine, for detecting the air-fuel ratio of exhaust gases from the engine. An ECU calculates an adaptive control amount, based on an output from the air-fuel ratio sensor, by using an adaptive controller having an adaptive parameter-adjusting mechanism, such that the air-fuel ratio of a mixture supplied to the engine is converged to a desired air-fuel ratio, and controls the air-fuel ratio of the mixture in a feedback manner, according to the adaptive control amount. When a particular engine operating condition in which the adaptive controller can become unstable in operation is detected, the adaptive parameters are initialized according to the adaptive control amount.

Abstract: Feedback correction of an air-fuel ratio is performed, a feedback correction amount is learned, and applied as a learning value on the next occasion that control is performed. It is determined whether or not an engine is in a high load state, and when the high load state continues for a predetermined time, the feedback correction amount is fixed at a predetermined value. The learning value is fixed at its value based on the feedback correction amount before fixing. The predetermined time is set such that the learning value in the high load state converges within this time. By applying open loop control using this learning value, surging of the vehicle due to the air-fuel ratio feedback control in the high engine load state is prevented, while the air-fuel ratio in this state is controlled precisely to the stoichiometric air-fuel ratio.

Abstract: A method and apparatus for controlling the air-fuel ratio in an internal combustion engine wherein, when the operating condition of the internal combustion engine has shifted between learning zones, a learning control updates a correction value after the shift is made in accordance with a stand-by function of a control unit to reduce the occurrence of mislearning, perform the correction value updating learning control efficiently and effect the purification of exhaust gases. In the air-fuel ratio controlling method for the internal combustion engine, when the operating condition of the engine has shifted between learning zones, a learning control updates a correction value in accordance with a stand-by function.

Abstract: A control system for a plant includes a sensor for detecting an output from the plant, an adaptive controller for controlling a manipulated variable applied to control of the plant in a manner such that an output from the sensor becomes equal to a desired value, and an adaptive parameter-adjusting device for adjusting adaptive parameters used by the adaptive controller. The adaptive controller is configured in a manner adapted to a predetermined dead time shorter than an actual dead time which the plant and the detection means possess. Sampling timing of an input vector input to the adaptive parameter-adjusting device corresponds to the actual dead time.

Abstract: An air-fuel ratio in an engine provided with an air-fuel ratio control unit is controlled, by using an oxygen sensor disposed in an exhaust gas passage in operative association with the air-fuel ratio control unit, by the steps of setting a feedback control mode for detecting states of the exhaust gas by using the oxygen sensor, operating the engine in one of a plurality of operating areas which are sectioned in accordance with an engine operational conditions such as engine revolution speed, determining a correction value of the air-fuel ratio in accordance with the engine operation with respect to a set value, and calculating another correction value of the air-fuel ratio in another operating area on the basis of the correction value previosly determined.

Abstract: In an engine air-fuel ratio controller, a target frequency of an air-fuel ratio oscillation is set to a value different from a natural vibration frequency of a drive mechanism, and an air-fuel ratio feedback correction coefficient is set so that the air-fuel ratio oscillation frequency coincides with the target frequency, and the air-fuel ratio is rich for a longer time than the time for which it is lean. In this way, resonance of the air-fuel ratio oscillation frequency with the natural vibration frequency of the drive system is prevented, the air-fuel ratio is prevented from remaining lean in the high load region for a long period of time, and decline of driving performance is avoided.

Abstract: An air-fuel ratio control using an A/F sensor which outputs a current representing an air-fuel ratio in response to a voltage applied thereto. If the A/F sensor is still in a state prior to activation and the actual air-fuel ratio is different from an air-fuel ratio represented by a current of the sensor in the state prior to activation when the engine is started, that is, if the air-fuel ratio is put on the rich side by an increased amount of fuel injected at a start of an internal combustion engine at a low temperature or other causes, for example a CPU employed in an ECU, determines whether the difference between the .lambda.-conversion value of the current of the A/F sensor and a target air-fuel ratio is equal to or greater than a predetermined value. If the determination is YES, a feedback control of the air-fuel ratio is started.

Abstract: An electronic engine control system for a lean burn engine includes a unit for detecting an amount Qa of intake air fed into a cylinder of the engine, a unit for detecting an engine speed Ne, a unit for calculating a basic fuel injection pulse width TPbas on the basis of the intake air amount Qa and the engine speed Ne, and a unit for determining control parameters containing any of at least an air-fuel ratio, an ignition timing, a fuel injection timing, a throttle opening and an EGR rate in accordance with an operating state of the engine in optimum. A reference TPref having the same dimension as the basic fuel injection pulse width TPbas and which is a function of an accelerator operating amount determined on the basis of the accelerator operating amount is determined as a load parameter used upon determination of the control parameters of the engine in operation with a lean air-fuel ratio.

Abstract: An air/fuel ratio control system controls the supply of fuel to an internal combustion engine to achieve a target air/fuel ratio, based on the output of an air/fuel ratio sensor. The system may determine whether there is an abnormality in the air/fuel ratio sensor based on a comparison between a change of an air/fuel ratio correction coefficient, used to drive the air/fuel ratio to the target value, and a change of the target air/fuel ratio if the target air/fuel ratio has sharply changed.

Abstract: In an engine fuel supply system, the difference between the actual and target air-fuel ratios, an air-fuel ratio feedback correction coefficient and a learned correction amount are added as a parameter for diagnosing the fuel supply system. The diagnostic parameter is smoothed and the smoothed value is compared with a diagnosis reference value, thereby detecting a malfunction in the fuel supply system. Even if the learned correction amount is not updated, the malfunction in the fuel supply system can be promptly detected from the difference between the actual and target air-fuel ratios and the air-fuel ratio correction coefficient. The diagnosis reference value is determined variably in accordance with engine operating parameters such as the amount of intake air.

Abstract: An air-fuel ratio control system for an internal combustion engine includes an air-fuel ratio sensor for detecting the air-fuel ratio of exhaust gases from the engine. An ECU estimates the air-fuel ratio of a mixture supplied to each of the cylinders cylinder by cylinder in response to an output from the air-fuel ratio sensor, by using an observer based on a model representative of the behavior of the exhaust system. Cylinder-by-cylinder air-fuel ratio control amounts corresponding respectively to the cylinders are calculated for carrying out feedback control of the air-fuel ratio of the mixture such that each of the estimated air-fuel ratio is converged to a desired value.

Abstract: An apparatus for controlling operation of an engine is disclosed. The apparatus includes a passage for supplying air to the engine and a fuel injection valve. The engine burns air-fuel mixture to produce torque. A valve adjusts the quantity of air supplied to the engine. An ECU actuates the valve based on the driving state of the engine. The ECU feedback controls the air-fuel ratio by altering the position of the valve to prevent torque shocks caused by changes in the air supply. The feedback control employs two correction factors, the first of which is representative of the air-fuel ratio of the mixture, and the second of which is representative of an average deviation of the first factor from a stoichiometric air-fuel ratio value. The air-fuel ratio of the mixture is feedback controlled as a function of both correction factors.