An internal combustion engine control device 110 includes a mass flux calculation unit F2, an opening area calculation unit F3, an effective opening area calculation unit F4, and a passing gas flow rate calculation unit F5. The mass flux calculation unit F2 calculates a mass flux MF of gas passing through a throttle valve 125 based on an upstream gas temperature Tu, an upstream gas pressure Pu, and a downstream gas pressure Pd of the throttle valve 125. The opening area calculation unit F3 calculates an opening area A of the throttle valve 125 based on an opening degree θ of the throttle valve 125. The effective opening area calculation unit F4 calculates an effective opening area EA of the throttle valve 125 based on the upstream gas pressure Pu, the downstream gas pressure Pd, the opening degree θ, and the opening area A. The passing gas flow rate calculation unit F5 calculates a gas flow rate GF passing through the throttle valve 125 based on the mass flux MF and the effective opening area EA.

There is provided an airflow control device of an internal combustion engine comprising: a plasma actuator provided in an intake passage, a fuel injector for port injection provided in the intake passage so as to inject fuel toward the plasma actuator and a control unit for controlling them. The control unit is configured to actuate the plasma actuator after valve opening of an intake valve, in addition to causing the fuel injector to perform an operation of fuel injection, and causing the plasma actuator to perform an operation in a part of a valve closing period of the intake valve. Furthermore, the control unit includes a determination unit to determine whether or not water has adhered to the plasma actuator, and makes port injection operation and plasma actuator operation be performed only when water has adhered.

In exemplary embodiments, methods, and systems for multivariable torque control of a vehicle are provided. The method includes configuring a processor disposed of in a multivariable controller to determine a set of references associated with Exhaust Gas Recirculation (EGR) by implementing an algorithm based on engine temperature and at least one reference associated with the EGR to generate commands for the control of a set of actuators; Optimizing at least one cam phase position by the control based on a generated command to apply an appropriate level of engine torque for vehicle propulsion; Restricting an allowable range of cam phases associated with operations of an EGR valve for a set of cams based on amounts of humidity and EGR introduced by the EGR valve during an internal combustion phase of vehicle operation; and providing an amount of propulsion torque by an engine in accordance with instructions provided by the processor.

Methods and systems are provided for an engine including a humidity sensor. Degradation of the humidity sensor may be determined based on a change in intake air relative humidity as compared to a change in intake air temperature or pressure, under selected conditions. An amount of exhaust gas recirculated to an engine intake is adjusted differently based on whether the humidity sensor is degraded or functional.

A method of operating an engine is provided. The method includes determining a temperature and a pressure of intake air, and a temperature and a pressure of exhaust generated by the engine. The method includes determining a work performed by the engine based at least on an engine speed of the engine, and determining heating losses of the engine. The method includes determining an enthalpy of the intake air based at least on the work, the heating losses, a heating value of a fuel used for combustion within the engine, and the temperature and the pressure of the exhaust. The method includes determining a humidity value of the intake air based on the enthalpy, temperature and pressure of the intake air and determining an amount of NOx based on the humidity value. The method further includes controlling an operation of the engine based on the determined amount of NOx.

Embodiments for diagnosing a humidity sensor are provided. One example method comprises, responsive to a humidity sensor test cycle, pumping air conditioning and windshield washer gas flows past a humidity sensor, and indicating humidity sensor degradation based on a response of the humidity sensor to the air conditioning and windshield washer gas flows. In this way, degradation of the humidity sensor may be indicated if the humidity sensed by the humidity sensor does not change responsive to the humidity sensor test cycle being initiated.

Methods and systems for operating an engine during conditions where ambient humidity changes over time are presented. In one non-limiting example, an engine air flow limit is adjusted to increase engine air flow during high humidity conditions such that an engine may provide equivalent torque output during the high humidity conditions as compared to when the engine is operated during low humidity conditions.

Methods and systems are provided for adjusting engine operation based on wirelessly received weather data in conjunction with engine sensor outputs. In one example, a method may comprise receiving a first measurement of a weather parameter from one or more engine sensors and a second measurement of the weather parameter from weather data, the weather data provided by a wireless weather service. The method may further comprise determining accuracies for the first and second measurements, generating an estimate of the weather parameter based on the accuracies of the first and second measurements, and adjusting at least one engine operating parameter based on the generated estimate.

A technique is provided for compensating an untrimmed oxygen (O.sub.2) sensor utilized in operation of an exhaust gas recalculation (EGR) system associated with an engine. The technique includes, in one implementation, receiving a measurement from the O.sub.2 sensor at a known pressure, where the O.sub.2 sensor is positioned on an intake side of an engine system. Humidity compensation and pressure compensation are then determined for the O.sub.2 sensor measurement, where the pressure compensation is based in part on the humidity compensation. The EGR system is controlled using the untrimmed O.sub.2 sensor measurement that has been compensated for pressure and humidity.

A controller calculates a specific humidity of an intake air based on a relative humidity of the intake air, an intake air temperature, and an intake air pressure. Then the controller calculates a water vapor amount in the intake air based on the specific humidity and a mass flow rate of the intake air obtained from an air intake rate. By calculating the water vapor amount in the intake air based on information that directly represents the status of the intake air, this water vapor amount may be calculated more accurately. As a result, a generation amount of condensed water may be estimated more accurately. Therefore, accumulation of condensed water may be suppressed while recirculating as much of a low pressure exhaust gas as possible, and thus fuel economy may be sufficiently improved.