Abstract: An exhaust system is regarded as being equivalent to a system for generating an output of an O2 sensor or exhaust gas sensor from a combined air-fuel ratio that is produced by combining outputs of air-fuel ratio sensors associated with respective cylinder groups according to a filtering process of the mixed model type. With the equivalent system as an object to be controlled, an exhaust system controller determines a target value for the combined air-fuel ratio, and determines a target air-fuel ratio for the cylinder groups from the target combined air-fuel ratio. The outputs of the air-fuel ratio sensors are converted to the target combined air-fuel ratio under feedback control.

Abstract: A fuel property detecting system comprises a control unit coupled to a fuel injector and an air-fuel ratio sensor. The control unit is arranged to sample data of a response wave-form of an exhaust air-fuel ratio in response to an injected fuel quantity at a transient period, to identify a plant model as to fuel in use by controlling a parameter of a previously constructed plant model on the basis of the input and output data so as to decrease a prediction error between the plant model and a norm model, to calculate a cutoff frequency of the identified plant model, and to estimate a fuel property of the fuel in use from the calculated cutoff frequency of the identified plant model and data previous stored in the control unit.

Abstract: In a direct injection spark ignition engine which is operable in three operation modes including a stoichiometric air/fuel ratio operation mode, a pre-mixture combustion mode and a stratified combustion operation mode which are different in the desired air/fuel ratio and a single air/fuel ratio sensor installed downstream of the exhaust manifold, the sensor output is successively sampled and one from among the sampled data is selected based on the engine speed and engine load and selected one of the operation modes such that the air/fuel ratio at each cylinder can be accurately estimated for the selected operation mode under the engine operating conditions.

Abstract: In a stoichiometric operation mode after a lean operation mode, a control unit sequentially generates data representing an estimated value of an output VO2/OUT of an O2 sensor after the dead time of an exhaust system, and at the same time generates a target air-fuel ratio KCMD for an exhaust gas upstream of a catalytic converter in order to converge the estimated value to a predetermined target value. The air-fuel ratio of the exhaust gas is controlled at the target air-fuel ratio KCMD. In the stoichiometric operation mode, the reduced state of NOx in the catalytic converter is recognized based on the estimated value of the output of the O2 sensor, and whether the stoichiometric operation mode is to switch to the lean operation mode or not is determined depending on the reduced state of NOx in the catalytic converter.

Abstract: An internal combustion engine (10) has a plurality of cylinders which are arranged in two cylinder banks. A sensor (131, 132) is assigned to each of the two cylinder banks for determining the composition of the exhaust gas. A control apparatus is provided with which a control factor (fr1, fr2) can be determined for each of the two cylinder banks in dependence upon the output signals generated by the two sensors (131, 132). The fuel mass (ti1, ti2), which is to be injected into the two cylinder banks, can be influenced by the control factors. The two control factors (fr1, fr2) of the two cylinder banks can be compared to each other via the control apparatus. The control apparatus can distinguish between a cylinder-bank independent fault and a cylinder-bank dependent fault in dependence upon the two control factors (fr1, fr2).

Abstract: There is disclosed an apparatus in which changes of linear A/F sensor or engine response characteristics can be detected with high precision in a broad range during operation of an engine. The apparatus includes a controller 50 for controlling an air/fuel ratio of each cylinder of a multiple cylinder engine, and a linear A/F sensor 28 for emitting an output which is proportional to the air/fuel ratio of an exhaust tube assembly. The air/fuel ratio of a specific cylinder is changed by a predetermined amount, a vibration component amplitude or a frequency component based on an engine rotation number is extracted from a signal obtained from the linear A/F sensor 28, and the response characteristics of an air/fuel ratio detector or the engine are detected from the amplitude or a power of the frequency component.

Abstract: An air mass is supplied to the combustion chambers by an intake manifold (12) in an internal combustion engine (10). An underpressure store (18) of a servo system (20) can be subjected to an underpressure via this intake manifold (12). The air mass flow in the inlet region (30) of the intake manifold (12) is determined by a sensor (32) and is supplied to an electronic control unit (26) for the fill computation. The actuation of the servo system (20) is detected and the determined air mass flow is corrected with or directly after a detected actuation of the servo system (20).

Abstract: An air-fuel ratio detected by an air-fuel ratio sensor is estimated based on an estimation value of air-fuel ratio of an air-fuel mixture formed inside a cylinder, and based on an air-fuel ratio estimated as being detected by this air-fuel ratio sensor and the air-fuel ratio detected based on an output signal of the air-fuel ratio sensor, the estimation value of the cylinder air-fuel ratio is corrected and a fuel injection quantity is corrected based on the corrected cylinder air-fuel ratio.

Abstract: A diagnostic equipment for an exhaust gas cleaning apparatus installed for an engine, comprising a misfire detector which detects the misfire of the engine, and a secondary-air-system failure detector which detects the failure of a secondary air system. An index corrector corrects a deterioration index calculated by a deterioration-index calculator, in accordance with the detected result of the detector. A deterioration decision unit decides if the diagnostic equipment has failed, by the use of the corrected deterioration index. In a case where the extent of the misfire or the like is severe, a decision interrupter interrupts the decision of the deterioration decision unit. Thus, even when the misfire of the engine or the failure of the secondary air system has occurred, the detection of the deterioration of a catalyst does not err. It is therefore avoided to erroneously replace the catalyst which has not deteriorated yet, or to run the engine in spite of the deterioration of the catalyst.

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. A model-based observer is used to reproduce the imbalances of the different cylinders and a proportional-plus-integral controller is used for their elimination. Both the observer and the controller are formulated in terms of a periodic system. The observer input signal is preprocessed such that it reflects at each point of time the deviation from the current A/F-ratio mean value calculated over two engine cycles. Therefore, transient engine operating conditions do not harm the reconstruction of the cylinder imbalances dramatically. The control algorithm features process/controller synchronization based on table lookup and a mechanism to automatically adjust the mapping between the observer estimates and the corresponding cylinders if unstable control operation is detected.

Abstract: A method and system for optimizing performance of vehicle control systems based on the dynamics of the specific vehicle include a sensor for sensing a predetermined parameter associated with any one of the vehicle control systems during a predetermined trigger event. A control logic determines a critical vibration mode characteristic for the vehicle control system based on the sensed parameter and operates the vehicle control system based on the determined critical vibration mode characteristic.

Abstract: An engine control system includes an adaptive bias sub-system (100) that generates bias values for controlling the air-fuel ratio. The sub-system (100) includes an integral controller (118) that reads an error signal from a post-catalyst switching EGO sensor (112). A plurality of noise isolation integrators (122) filter any noise resulting from a particular engine operating condition (e.g. acceleration, deceleration, idling) from the integrated error signal and stores the signal in a corresponding keep-alive memory (124) as a bias value for that engine operating condition. In a preferred embodiment, the post-catalyst feedback loop includes a gated proportional controller 116 that turns on for a limited period of time after the post-catalyst switching EGO sensor (112) switches states.

Abstract: The invention is directed to an improved portable on-board mass emissions measuring system for internal combustion engines. In the preferred embodiment, the system is comprised of an exhaust analyzer (16), at least one sensor (18, 22 or 29) which may be temporarily attached to the engine for sensing parameters of the engine, and a processor (19) programmed to collect and manipulate data from the analyzer and the sensor, whereby the mass emissions of the engine may be calculated. The system may further comprise a display (20) for displaying the mass emissions of the engine and an engine-control interface (21). The sensor may be capable of sensing engine RPM, engine oil temperature, or intake manifold pressure. The exhaust analyzer may be capable of measuring concentrations of the engine exhaust constituents, particulates, aerosols, and gases in the engine emissions.

Abstract: A non-linear term UNL is computed as UNL=gain GNL×(air-fuel ratio detection value−target air-fuel ratio)/(|air-fuel ratio detection value−target air-fuel ratio|)+previous value UNL (OLD), and a linear term UL is computed as UL=gain GL×(air-fuel ratio detection value−target air-fuel ratio)/air-fuel ratio detection value. An addition of UNL and UL is set as an air-fuel ratio feedback correction coefficient to correct a fuel injection quantity. The gain GL is set a greater value as |air-fuel ratio detection value−target air-fuel ratio| becomes greater.

Abstract: An oxygen concentration detector includes an air-fuel ratio sensor, a heater that heats the air-fuel ratio sensor, a heater controller that supplies electric power to the heater such that the air-fuel ratio sensor reaches an activation temperature, and an element temperature detector that detects a temperature of an element of the air-fuel ratio sensor. The heater controller detects a rate of decrease in the temperature of the element of the air-fuel ratio sensor based on the temperature detected by the element temperature detector, and determines that the sensor element is wetted when the detected rate of decrease is greater than a reference value. The element temperature detector can detect the sensor element temperature based on an impedance of the element. The heater controller can prevent the supply of electric power to the heater if it is determined that the sensor element is wetted. The air-fuel ratio sensor can be provided in an exhaust passage of an engine.

Abstract: Method of reducing noxious or toxic exhaust emissions from an internal combustion engine (10) having a plurality of cylinders (12) cooperating with a crankshaft (13) to cause the crankshaft to rotate at a rotational speed when the cylinders (12) are provided with an air/fuel mixture having a lambda value and the mixture is ignited to generate pressure in the cylinders. The method includes measuring a parameter reflecting the pressure in a first cylinder during at least a part of a working stroke of the first cylinder when supplied with an air/fuel mixture having a first lambda value to thereby obtain a first parametric value. An air/fuel mixture is provided to a second cylinder, which air/fuel mixture has a second lambda value which is different to the first lambda value, to cause the second cylinder to perform a working stroke. A parameter is measured reflecting the pressure in the second cylinder during at least a part of the working stroke of the second cylinder to obtain a second parametric value.

Abstract: A control circuit of an exhaust probe has a microcontroller and an analog circuitry. Measured values which are recorded in a test chamber under predefined test conditions are stored in characteristic maps in a programmable read-only memory. These values are then used as a reference for a subsequent recalibration of a probe system.

Abstract: An allowable range (adaptive allowable range) for limiting a manipulated variable generated in order to converge the difference between an output from an O2 sensor disposed downstream of a catalytic converter and a target value thereof to “0” is sequentially updated depending on how the manipulated variable deviates from the allowable range.

Abstract: In order to improve estimation accuracy of estimating the value of the NOx exhaust concentration, the air fuel ratio control apparatus is adapted to estimate the NOx exhaust concentration from at least either one of a value depending on the air fuel ratio or a value depending on the exhaust gas recirculation quantity and a value depending to the ignition timing by means of the ECU 230.

Abstract: Cylinder-selective control of the air-fuel ratio in a multi-cylinder internal-combustion engine is provided, wherein a lambda probe arranged in the exhaust pipe system generates a voltage signal corresponding to an air-fuel ratio. The voltage signal is supplied to a computing unit which determines the air-fuel ratio for each individual cylinder. A fuel metering unit determines a fuel injection quantity at least as a function of a basic fuel injection value and the determined air-fuel ratios of the individual cylinders, and a fuel supply unit supplies the fuel injection quantity determined by the fuel metering unit to the cylinders of the internal-combustion engine. The computing unit crank-angle-synchronously detects the voltage signal and assigns it to a certain cylinder. A voltage deviation and corresponding injection quantity correction is determined for each cylinder in relation to the voltage signals of the adjacent cylinders.

Abstract: The method of operating an internal combustion engine, especially of a motor vehicle, having a combustion chamber (4), which is operable in a plurality of combustion cycles, includes feeding an air mass (42) and a fuel mass (3) into the combustion chamber (4) in each combustion cycle; adjusting a mixture composition lambda (&lgr;) of the air mass to the fuel mass for one of the combustion cycles so that &lgr;>1; determining a residual air portion present in the combustion chamber (4) due to combustion occurring in the combustion chamber in the combustion cycle in which the mixture composition lambda (&lgr;) is greater than one; and reducing the air mass to be supplied to the combustion chamber (4) in another combustion cycle following the one combustion cycle in which &lgr;>1 by about the residual air portion found in the one combustion cycle.

Abstract: Disclosed is a method to determine a failure status of a cylinder and for controlling an air fuel ratio for each cylinder by a simple method using a wide range oxygen sensor. When the engine in a car is in normal status, output values of the wide range oxygen sensor are determined. These measures detect the density of oxygen in the exhaust gasses during a predetermined cycle at specific crank angles, the ensemble average values are found, and the maximum and minimum values of the computed ensemble average values are detected. If the difference between the maximum and minimum values is greater than a set reference value, it is determined that there is a failure of a cylinder, and the position of the cylinder at the maximum or minimum value is determined.

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 plant control system also has an estimator for estimating the difference between an output of the O2 sensor after the dead time of the exhaust system and a target value therefor, using the difference between the set reference value and a detected value of the air-fuel ratio, and giving the estimated difference to the controller.

Abstract: An air-fuel ratio correction coefficient calculating component is provided to an air-fuel ratio controller for an engine having the wide range air-fuel ratio sensor. The air-fuel ratio correction coefficient calculating component can cope with a time lag in detection of an air-fuel ratio detected by the wide range air-fuel ratio sensor from the time when a mixed gas of the air-fuel ratio is supplied to the engine.

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: A method of minimizing torque disturbances in an internal combustion engine for a vehicle having a lean NOx trap that is periodically purged. The method includes the steps of generating feedforward values of first engine characteristics as a function of desired engine torque and generating feedback values of second engine characteristics as a function of intake manifold pressure. Target values are then calculated for predetermined engine variables based on the first and second engine characteristics. Engine variables are then set to the target values to compensate for torque disturbances resulting from the lean NOx trap purge cycle. According to the disclosed method, the feedforward path schedules the throttle, fuel rate and spark timing based on an engine model to produce a demanded engine torque. The feedback path then uses the values of fuel rate and spark timing to compensate for torque variations.

Abstract: The analog input of a sensor is connected to a 10-bit analog-to-digital converter. The converted is powered using a 5V supply. The A/D is interfaced with a microprocessor; however, only the least significant eight bits of the A/D output are connected to the microprocessor input. The microprocessor is used to adjust the fuel-air mixture used in engine combustion based on the output of the sensor. The use of the 10-bit A/D interfaced with only eight bits allows increased precision and increased computational speed. The increased precision allows more accurate adjustment of the fuel-air mixture to enable the engine to run closer to its stoichiometric point.

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: A separate irregular-running determination is carried out for each cylinder bank. Each ascertained irregular-running value is compared to a lower and an upper threshold value, the upper threshold value being set in such a way that all irregular-running values below it are not caused by combustion misses. A defect is signaled in one of the exhaust trains when, for at least one of the two cylinder banks, an irregular-running value is ascertained lying between the lower and the upper threshold value, and the difference between the irregular-running values of the two cylinder banks exceeds a threshold. This method makes it possible to ascertain a defect in one of the two cylinder banks very early.

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: The apparatus includes a sensor capable of delivering a voltage representative of the ratio between a reference oxygen pressure and the oxygen pressure in a volume of the sensor and provided with electrodes (12, 14) via which it is possible to pass a pumping current that controls said oxygen pressure in the volume, and monitoring and control means including a digital controller (26) receiving said representative voltage on an input and suitable for delivering the pumping current. The monitoring and control means deliver the pumping current in the form of a current that varies continuously and progressively, without interruptions, governed by the digital controller in such a manner as to servo-control the input voltage to a determined value.

Abstract: An apparatus for controlling an internal combustion engine has an amount-of-intake-air control unit for generating a command value for the opening of a flow control valve in an intake passage of the engine, which emits exhaust gases through a catalytic converter, so as to increase an amount of intake air introduced into a combustion chamber by a predetermined quantity greater when the engine operates in an idling mode after it has started to operate than when the engine operates in a normal idling mode, and controlling the opening of the flow control valve based on the generated command value, and an ignition timing control unit for controlling the ignition timing according to a feedback control process to correct the ignition timing so as to be retarded in order to converge the rotational speed of the engine to a predetermined target rotational speed while the amount of intake air is being increased.

Abstract: An apparatus and method for diagnosing the condition of a sensor in an internal combustion engine upstream from the catalytic converter. The diagnosis utilizes a signal from a second non-linear probe downstream from the catalytic converter. This signal is processed to give a signal that is filtered. The filtered signal is in turn compared with maximum and minimum values. The upstream probe is considered to be correct if the signal falls between these two values or faulty if it falls outside the values.

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: A gas concentration sensor voltage and current (in both heater on and heater off states) are detected and compared with predetermined thresholds, respectively, by a microcomputer. Based on a combination of the comparison results, the presence or absence of trouble in the system is detected and trouble location in the system is specified. In addition or alternatively, the sensor voltage is compared with thresholds to determine whether it is outside of a normal zone. The voltage may be actually detected or calculated. If the voltage is outside the normal zone, sensor voltage is reduced to zero or restricted to a predetermined limit.

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: A method for monitoring a catalytic converter includes ascertaining a measured variable at the catalytic converter and comparing it with a comparison value. The comparison value is ascertained in accordance with a model that uses at least one parameter of a comparison catalytic converter. The parameter of the comparison catalytic converter is adapted on the basis of a measured variable of the catalytic converter to be monitored.

Abstract: The invention is directed to a method for diagnosing an exhaust-gas probe mounted in the exhaust-gas system of an internal combustion engine for conducting the exhaust gas of the engine. The exhaust-gas probe is mounted downstream of the catalytic converter. The output signal of the exhaust-gas probe is monitored as the output signal changes in response to changes of the concentration of at least one of the components of the exhaust gas. The rate of the change is applied as a criterion as to the state of deterioration of the exhaust-gas probe.

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: 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: In a system using a gas concentration sensor such as an A/F sensor having a heater, a microcomputer detects an abnormality in a heater power supply control. After the detection of abnormality, the computer reduces the electric power to the heater to a minimum and determines whether the heater has restored its normal operation. The power supply to the heater is stopped and returned to the normal power supply control when it is determined that the detected abnormality continues and discontinues during the reduced power supply period, respectively.

Abstract: A diagnostic equipment for an exhaust gas cleaning apparatus installed for an engine, comprising a misfire detector which detects the misfire of the engine, and a secondary-air-system failure detector which detects the failure of a secondary air system. An index corrector corrects a deterioration index calculated by a deterioration-index calculator, in accordance with the detected result of the detector. A deterioration decision unit decides if the diagnostic equipment has failed, by the use of the corrected deterioration index. In a case where the extent of the misfire or the like is severe, a decision interrupter interrupts the decision of the deterioration decision unit. Thus, even when the misfire of the engine or the failure of the secondary air system has occurred, the detection of the deterioration of a catalyst does not err. It is therefore avoided to erroneously replace the catalyst which has not deteriorated yet, or to run the engine in spite of the deterioration of the catalyst.

Abstract: The present invention is concerned with a system and method for monitoring the exhaust emissions of combustion engines such as diesel engines equipment used in underground mining operations. The system comprises a gas analyzer capable of measuring the concentration of at least one exhaust gas from the exhaust emissions, the analyzer being coupled to a computer that processes the data collected from the gas analyzer. The processed data is then displayed to the operator on a computer screen, so that the monitoring is carried out in real time.

Abstract: A method of controlling the fuel/air ratio of an internal combustion engine in which the output signal of a first lambda probe which is arranged in the exhaust gas passage in front of a catalytic converter of the internal combustion engine is fed to a controller which has a proportional-and-integral (PI) characteristic. The controller gives off a setting variable for the fuel/air ratio. A further signal which is obtained from the output signal of a second lambda probe arranged behind the catalytic converter is fed to the controller and acts on the control circuit of the first lambda probe.In order to permit an accurate, adaptable control, the proportional portion of the output signal of the control circuit of the first lambda probe is modified as a function of the output signal of the second lambda probe.

Abstract: A method and apparatus that converts time-resolved sensor signals into frequency domain signals using Fast Fourier Transforms and power spectral densities. A signal, as a means to assess catalyst performance such as a signal based on sensing oxygen concentration in motor vehicle exhaust in accordance with the present invention is in the time domain and has multiple components at different frequencies. The use of Fast Fourier Transforms isolates the various spectral density which arise from different frequency components of the complex time domain signal. The analysis has been found to be substantially independent of operating conditions. The power spectral density has found to be a precise indication of oxygen storage and release of the catalyst and catalyst performance. The catalyst performance can be signaled to the vehicle operator for on board diagnostics (OBD) of the catalyst.

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.