Method and device for determining an internal combustion engine intake air flow rate based on the measurement of the oxygen concentration in the gaseous mixture taken in by the engine

A method and a device for controlling the exhaust gas recirculation in an internal-combustion engine (1) are described herein. The engine (1) is provided with an air-intake system (2), a gas-exhaust system (4), and an exhaust-gas-recirculation system (5). A linear oxygen sensor (25) is arranged along the air-intake system (2) in a section traversed, in use, by the air/recirculated-exhaust-gas mixture, for measuring the oxygen concentration in the mixture itself. An electronic control unit is connected to the oxygen sensor (25) and to the exhaust-gas-recirculation system (5) for controlling the flow rate of recirculated exhaust gases on the basis of the oxygen concentration in the mixture taken in by the engine (1). In particular, the oxygen sensor is a UHEGO probe (25).