Controller and control method for internal combustion engine

A controller for an internal combustion engine, the controller controlling a flow rate of exhaust gas of the internal combustion engine which flows to a turbocharger, by operating an actuator to adjust an opening of a valve, and

• the controller comprising at least one microprocessor comprising:
• a target supercharging pressure computing unit configured to compute a target supercharging pressure, based on an operating state of the internal combustion engine;
• a required target opening computing unit configured to compute a required target opening of the valve that allows the target supercharging pressure computed by the target supercharging pressure computing unit to match with an actual supercharging pressure detected by a supercharging pressure sensor configured to detect a pressure of intake air of the internal combustion engine, which has been supercharged by the turbocharger;
• a reference position learning unit configured to set, as a fully closed position learning value, an actual position of the valve detected by a position sensor, when the valve is located in a fully closed position;
• an actual opening computing unit configured to compute an actual opening of the valve, based on the actual position detected by the position sensor and the fully closed position learning value which has been set by the reference position learning unit;
• a restricted target opening computing unit configured to compute a restricted target opening of the valve, based on the fully closed position learning value which has been set by the reference position learning unit and a restricted target position which has been set, in advance, to have a value between an opening side upper limit position of the actuator and an opening side stopper position of the actuator, wherein the opening side upper limit position corresponds to an upper limit value of the required target opening, and the opening side stopper position corresponds to a position at which an output shaft of the actuator contacts an opening side stopper of the valve;
• a target opening restricting unit configured to set, as a target opening of the valve, the smaller of:
• the required target opening computed by the required target opening computing unit;
• and the restricted target opening computed by the restricted target opening computing unit;
• an operation quantity computing unit configured to compute an operation quantity to operate the actuator, so that the actual opening computed by the actual opening computing unit follows the target opening which has been set by the target opening restricting unit;
• and
• a driving unit configured to operate the actuator in accordance with the operation quantity computed by the operation quantity computing unit.