Autopilot nonlinear compensation

An autopilot nonlinear compensation system for stabilizing autopilot control of an aircraft, comprising:

• an autopilot controller adapted to transmit an autopilot command to a servo for positioning a control surface of the aircraft;
• a sensor adapted to provide a measured position of a pilot interface;
• and
• a primary flight controller adapted to receive the autopilot command and to receive the measured position of the pilot interface for determining a ratio of a desired aerodynamic moment to a total aerodynamic moment based on the autopilot command and the measured position, the primary flight controller further adapted to adjust the autopilot command with a corrective command based on the ratio, thereby stabilizing the aircraft.

An autopilot nonlinear compensation method, comprising:

• providing a measured control-wheel position;
• providing an autopilot command for executing a roll of an aircraft;
• determining a perfected control-wheel position based on the measured control-wheel position and the autopilot command;
• determining a predicted spoiler position based on the perfected control-wheel position;
• determining a spoiler rolling moment based on the predicted spoiler position;
• determining a predicted aileron position based on the autopilot command;
• determining a desired rolling moment based on the predicted aileron position;
• determining a total rolling moment based on the spoiler rolling moment and the desired rolling moment;
• determining a ratio of the desired rolling moment to the total rolling moment;
• and
• adjusting the autopilot command based on the ratio, thereby compensating for any additional unwanted rolling moment over the desired rolling moment.