Method and system for controlling a fuel-metering device

A method for controlling a fuel metering device with a movable metering element for a combustion chamber of an aircraft turbomachine, this method comprising at least two iterations of the following steps:

• a—a step of detecting a possible change in the operating state of a position sensor among a first position sensor and a second position sensor measuring the position of the metering element, each position sensor being either operating or malfunctioning;
• b—if the two position sensors are operating, a first step of determining the position of the metering element from an average between a first position measurement of the first position sensor and a second position measurement of the second position sensor;
• c—if one of the two position sensors is malfunctioning, the other position sensor remaining in operation, a second step of determining the position of the metering element from a position measurement of the position sensor remaining in operation;
• d—a step of determining a flow rate setpoint of fuel to be provided to the combustion chamber from a power setpoint of the turbomachine and a power measurement of the turbomachine;
• e—a step of converting the determined flow rate setpoint into a position setpoint of the metering element;
• f—a step of determining a command of displacement of the metering element from the position setpoint of the metering element and the position determined for the metering element;
• g—a step of controlling the position of the metering element according to the determined displacement command;
• wherein, if a change in the operating state of one of the first and second position sensors is detected during step a), the method further comprises before step d) of determining a flow rate setpoint of the current iteration:
• h—a step of calculating a first instantaneous flow rate of fuel delivered by the metering device to the combustion chamber from the position of the metering element determined in step b) or c) of the current iteration according to the operating state of the position sensors;
• i—a step of calculating a second instantaneous flow rate of fuel delivered by the metering device to the combustion chamber from the position of the metering element determined in step b) or c) of the previous iteration according to the operating state of the position sensors during the previous iteration;
• j—a step of determining a fuel flow rate deviation between the first instantaneous fuel flow rate calculated in step h) and the second instantaneous fuel flow rate calculated in step i),
• and following the step of determining a flow rate setpoint of the current iteration:
• a step of correcting the flow rate setpoint determined in step d) taking into account the flow rate deviation determined in step j), so as to match the position setpoint of the metering element with the position of the metering element determined in step b) or c) of the current iteration according to the operating state of the position sensors.