Model-based speed governing for variable-pitch propeller

A system for controlling a variable-pitch propeller of an aircraft, the system comprising:

• a sensor for sensing a current rotational speed of the variable-pitch propeller;
• an actuator for adjusting a pitch angle of blades of the variable-pitch propeller;
• and
• one or more controllers operatively connected to the sensor and to the actuator, the one or more controllers being configured to, when the variable-pitch propeller is operating in a current forward thrust condition including the current rotational speed:
• determine a speed error between the current rotational speed of the variable-pitch propeller and a set point rotational speed for the variable-pitch propeller;
• determine a power coefficient of the variable-pitch propeller at the current forward thrust condition;
• determine an advance ratio of the variable-pitch propeller at the current forward thrust condition;
• determine a gain for a feedback control loop, the gain being scheduled based on the power coefficient of the variable-pitch propeller and the advance ratio of the variable-pitch propeller;
• and
• use the feedback control loop to adjust the pitch angle of the blades of the variable-pitch propeller based on the speed error and the gain to reduce the speed error.

A power plant for propelling an aircraft, the power plant comprising:

• a variable-pitch propeller configured to propel the aircraft;
• an actuator for adjusting a pitch angle of blades of the variable-pitch propeller;
• a source of motive power configured to drive the variable-pitch propeller;
• and
• a propeller controller operatively connected to the variable-pitch propeller and configured to, when the variable-pitch propeller is operating in a current operating condition including a current rotational speed:
• determine a speed error between the current rotational speed of the variable-pitch propeller and a set point rotational speed for the variable-pitch propeller;
• determine a power coefficient of the variable-pitch propeller at the current operating condition;
• determine an advance ratio of the variable-pitch propeller at the current operating condition;
• determine a gain for a feedback control loop, the gain being scheduled based on the power coefficient of the variable-pitch propeller and the advance ratio of the variable-pitch propeller;
• and
• use the feedback control loop to adjust the pitch angle of the blades of the variable-pitch propeller based on the speed error and using the gain to reduce the speed error.