Abstract: A sensor system includes a sensor element to which a control current is inputted, a DA converter to output the control current, and a control part configured to generate a control current instruction value and input the control current instruction value to the DAC, and further includes an instruction value generation part to sequentially generate an inspection current instruction value to be inputted to the DAC instead of the control current instruction value, an inspection current detection part to detect an inspection current value of an inspection current, an expected value calculation part to calculate an inspection current expected value, a difference value acquisition part to acquire a difference value between the inspection current value and the inspection current expected value, and a failure detection part to detect a failure of a bit in the DA converter, by frequency analysis of a temporal change of the difference value.

Abstract: Occlusion diagnosis of a vent passage is executed with high accuracy based on an estimated value of the volume of a sealed space. An occlusion diagnosis device includes a diagnosis unit for the diagnosis. An occlusion diagnosis unit of the diagnosis unit executes the occlusion diagnosis, based on whether or not an estimated volume of a sealed space of a fuel-vapor sealing system exceeds a volume threshold. The occlusion diagnosis determines that the vent passage is suspected of being occluded if the estimated volume is equal to or less than the volume threshold, while diagnoses that the vent passage is not occluded if the estimated volume exceeds the volume threshold. If it is determined that the vent passage is suspected of being occluded, the occlusion diagnosis unit causes the occlusion diagnosis of the vent passage to remain incomplete until a cumulative exhaust amount of fluid exceeds an exhaust amount threshold.

Abstract: A blockage detection device opens a purge valve in a state where a negative pressure pump is operated. The negative pressure pump is connected to a downstream side of a canister with respect to a fuel tank, and reduces pressure in a device internal space. The blockage detection device calculates gas information (volume V, for example) of the device internal space on the basis of variation of internal pressure before and after the purge valve is opened. The blockage detection device detects a blockage in a vent line using the calculated gas information.

Abstract: Disclosed is a fuel level estimation device including: an information acquiring unit acquiring information about a closed system internal pressure of a closed fuel vapor system including the fuel tank, a vent passage, and a canister; a flow rate controlling unit controlling, by actuating a negative pressure pump, a flow rate of fuel vapor-containing gas in the closed fuel vapor system; a fuel level estimating unit estimating a fuel level based on a total volume of the closed fuel vapor system and an occupied volume of the gas. The fuel level estimating unit estimates the occupied volume of the gas by using a change in a closed system internal pressure before and after the closed fuel vapor system is subjected to pressure-reducing treatment for a predetermined interval and a reference discharging rate when the gas is subject to the pressure-reducing treatment. An abnormality diagnostic apparatus is also disclosed.

Abstract: Occlusion diagnosis of a vent passage is executed with high accuracy based on an estimated value of the volume of a sealed space. An occlusion diagnosis device includes a diagnosis unit for the diagnosis. An occlusion diagnosis unit of the diagnosis unit executes the occlusion diagnosis, based on whether or not an estimated volume of a sealed space of a fuel-vapor sealing system exceeds a volume threshold. The occlusion diagnosis determines that the vent passage is suspected of being occluded if the estimated volume is equal to or less than the volume threshold, while diagnoses that the vent passage is not occluded if the estimated volume exceeds the volume threshold. If it is determined that the vent passage is suspected of being occluded, the occlusion diagnosis unit suspends the occlusion diagnosis of the vent passage until a cumulative exhaust amount of fluid at least exceeds an exhaust amount threshold.

Abstract: A blockage detection device opens a purge valve in a state where a negative pressure pump is operated. The negative pressure pump is connected to a downstream side of a canister with respect to a fuel tank, and reduces pressure in a device internal space. The blockage detection device calculates gas information (volume V, for example) of the device internal space on the basis of variation of internal pressure before and after the purge valve is opened. The blockage detection device detects a blockage in a vent line using the calculated gas information.

Abstract: Disclosed is a fuel level estimation device including: an information acquiring unit acquiring information about a closed system internal pressure of a closed fuel vapor system including the fuel tank, a vent passage, and a canister; a flow rate controlling unit controlling, by actuating a negative pressure pump, a flow rate of fuel vapor-containing gas in the closed fuel vapor system; a fuel level estimating unit estimating a fuel level based on a total volume of the closed fuel vapor system and an occupied volume of the gas. The fuel level estimating unit estimates the occupied volume of the gas by using a change in a closed system internal pressure before and after the closed fuel vapor system is subjected to pressure-reducing treatment for a predetermined interval and a reference discharging rate when the gas is subject to the pressure-reducing treatment. An abnormality diagnostic apparatus is also disclosed.

Abstract: An air-fuel ratio control apparatus includes an air-fuel ratio detector, an oscillation signal generator, an air-fuel ratio oscillation device, a sum/difference frequency component intensity calculator, a decision parameter calculator, and an imbalance failure determination device. The sum/difference frequency component intensity calculator is configured to calculate, while the air-fuel ratio oscillation device is in operation, at least one of a component intensity of a difference frequency and a component intensity of a sum frequency. The decision parameter calculator is configured to calculate, according to at least one of the component intensity of the difference frequency and the component intensity of the sum frequency, a decision parameter to determine a degree of imbalance of an air-fuel ratio. The imbalance failure determination device is configured to determine an imbalance failure in which the degree of imbalance of the air-fuel ratio exceeds an allowable limit using the decision parameter.

Abstract: An air-fuel ratio control system for an internal combustion engine, which, at the resumption of air-fuel ratio feedback control, is capable of setting the initial value of an integral term of the feedback control to a value properly learned in preceding feedback control, thereby enabling improvement of control accuracy. To feedback-control the output value of an O2 sensor to a target value, a target air-fuel ratio is calculated. During the feedback control, when it is determined that a predetermined condition in which it is estimated that exhaust gas air-fuel ratio upstream of the catalyst is excellently reflected on an exhaust gas air-fuel ratio at a location midway or downstream of the catalyst is satisfied, an adaptive law input calculated immediately before interruption of the feedback control is updated and stored as the initial value of an integral term for the following execution of the feedback control.

Abstract: An air-fuel ratio control apparatus for an internal combustion engine includes an air-fuel ratio detector, a fuel amount controller, an operational state parameter acquiring device, an extractor, a failure determination device, a variation state parameter calculator, and a determination stopping device. The operational state parameter acquiring device is configured to acquire at least one operational state parameter. The failure determination device is configured to execute failure determination of determining a failure in an air-fuel ratio control system of the internal combustion engine based on a specific frequency component extracted by the extractor. The variation state parameter calculator is configured to calculate a variation state parameter. The determination stopping device is configured to stop the failure determination if the variation state parameter calculated by the variation state parameter calculator is equal to or larger than a predetermined threshold value.

Abstract: An air-fuel ratio control system for an internal combustion engine has a perturbation control which oscillates the air-fuel ratio with a first frequency. A first difference signal is generated indicative of a difference between a present value and a first past value from an air-fuel ratio sensor detected at a timing of a first specific period which is set to reduce a specific frequency component corresponding to a specific frequency different from the first frequency. A first frequency component is extracted. A second difference signal is generated indicative of a difference between a present value and a second past value detected at a timing of a second specific period which is set to reduce the first frequency component. The specific frequency component is extracted. A failure of the control system is determined by a relationship between intensities of the first frequency component and the specific frequency component.

Abstract: An apparatus for controlling an air-fuel ratio of an internal-combustion engine includes an air-fuel ratio detector, a fluctuation signal generating device, an air-fuel ratio fluctuation device, a 0.5th-order frequency component strength calculator, a fluctuation frequency component strength calculator, a reference component strength calculator, and an imbalance fault determining device. The reference component strength calculator is configured to calculate strength of a reference component in accordance with strength of a first frequency component and strength of a second frequency component. The imbalance fault determining device is configured to make a determination of an imbalance fault in which air-fuel ratios of a plurality of cylinders vary beyond a tolerance limit on a basis of a relative relationship between strength of the 0.5th-order frequency component and the strength of the reference component.

Abstract: An abnormality determining apparatus includes an air-fuel ratio controller, an output change period parameter calculator, an output change amount extremum calculator, and an abnormality determining device. The abnormality determining device is configured to determine an abnormality of an air-fuel ratio sensor based on a relationship between an output change period parameter and an output change amount extremum.

Abstract: An air-fuel ratio control apparatus for an internal combustion engine includes an air-fuel ratio sensor having an output characteristic which is nonlinear with respect to the air-fuel ratio of exhaust gas. An output deviation converter is configured to convert an output deviation to a first predetermined value if an output value of the air-fuel ratio sensor is on a richer side of a predetermined target value and to a second predetermined value if the output value is on a leaner side of the target value. A control input calculator is configured to calculate a control input to feedback-control the output value of the air-fuel ratio sensor such that the output deviation converted by the output deviation converter is to be zero. An air-fuel ratio controller is configured to control the air-fuel ratio of exhaust gas using the control input calculated by the control input calculator.

Abstract: An abnormality determination device for an air-fuel ratio sensor includes a differential value calculator and an abnormality determiner. The differential value calculator is configured to calculate a differential value of an output value of the air-fuel ratio sensor which is configured to detect an air-fuel ratio of exhaust gas. The abnormality determiner is configured to determine abnormality of the air-fuel ratio sensor based on a result of comparison between a reference output value of the air-fuel ratio sensor and a predetermined threshold. The reference output value is obtained by the air-fuel ratio sensor when the differential value calculated by the differential value calculator becomes a predetermined value.

Abstract: An oscillation signal is generated to oscillate the air-fuel ratio with a set frequency which is different from a 0.5th-order frequency (half of the frequency corresponding to a rotational speed of the engine). Air-fuel ratio perturbation control is performed to oscillate the air-fuel ratio according to the oscillation signal. An intensity of the 0.5th-order frequency component and the set frequency component contained in the detected air-fuel ratio signal are calculated. A determination parameter applied to determining an imbalance degree of air-fuel ratios corresponding to the plurality of cylinders is calculated according to the two intensities and determines an imbalance failure that the imbalance degree of the air-fuel ratios exceeds an acceptable limit. A predicted imbalance value, indicative of a predicted value of the imbalance degree, is calculated, and an amplitude of the oscillation signal is set according to the predicted imbalance value.

Abstract: A plant controller includes a feedback controller configured to calculate a control input provided to a plant so that a control output of the plant matches a target value. The feedback controller includes a controller transfer function that is a transfer function of the feedback controller. The controller transfer function is expressed by a product of an inverse transfer function of a transfer function of a control target model obtained by modeling the plant and a disturbance sensitivity correlation function defined using a sensitivity function. The sensitivity function indicates sensitivity of a disturbance to be applied to the plant with respect to the control output. The sensitivity function is defined by using a response characteristic parameter that indicates a response characteristic of the plant.

Abstract: An air-fuel ratio control apparatus for an internal-combustion engine includes an air-fuel-ratio sensor, a control-input calculator, an air-fuel-ratio controller, and a gain calculator. The air-fuel-ratio sensor is disposed in an exhaust channel in the internal-combustion engine and is configured to detect an air-fuel ratio in exhaust gas. The control-input calculator is configured to calculate a control input in accordance with an output value of the air-fuel-ratio sensor. The air-fuel-ratio controller is configured to perform a feedback control using the control input such that the output value of the air-fuel-ratio sensor reaches a target value. The gain calculator is configured to calculate a gain in accordance with the output value when the output value is leaner than the target value. The gain is to be used in calculating the control input.

Abstract: An air-fuel ratio control apparatus includes an air-fuel ratio detector, an oscillation signal generator, an air-fuel ratio oscillation device, a sum/difference frequency component intensity calculator, a decision parameter calculator, and an imbalance failure determination device. The sum/difference frequency component intensity calculator is configured to calculate, while the air-fuel ratio oscillation device is in operation, at least one of a component intensity of a difference frequency and a component intensity of a sum frequency. The decision parameter calculator is configured to calculate, according to at least one of the component intensity of the difference frequency and the component intensity of the sum frequency, a decision parameter to determine a degree of imbalance of an air-fuel ratio. The imbalance failure determination device is configured to determine an imbalance failure in which the degree of imbalance of the air-fuel ratio exceeds an allowable limit using the decision parameter.

Abstract: An oscillation signal is generated to oscillate the air-fuel ratio with a set frequency which is different from a 0.5th-order frequency (half of the frequency corresponding to a rotational speed of the engine). Air-fuel ratio perturbation control is performed to oscillate the air-fuel ratio according to the oscillation signal. An intensity of the 0.5th-order frequency component and the set frequency component contained in the detected air-fuel ratio signal are calculated. A determination parameter applied to determining an imbalance degree of air-fuel ratios corresponding to the plurality of cylinders is calculated according to the two intensities and determines an imbalance failure that the imbalance degree of the air-fuel ratios exceeds an acceptable limit. A predicted imbalance value, indicative of a predicted value of the imbalance degree, is calculated, and an amplitude of the oscillation signal is set according to the predicted imbalance value.