Aircraft Deck Motion Compensation Design

Deck Motion Compensation (DMC) is the process of adapting the flight guidance and control commands provided to a flight control system to account for the motion of the ship and the total effective delay of the system from sensors through computation and communication to control surface actuation. The motion has historically only been compensated (1) in the vertical direction, (2) for purely translational motion of the touch down point (TDP), and (3) using a constant-gain lead-lag filter. These limitations lead to practical weaknesses in existing DMC methods. This is because, as the ship pitches (rotates with fore and aft moving vertically), the aft portion of the ship heaves up and down significantly more than the TDP. Landing aircraft are required to pass above the ramp with at least 10 ft of vertical clearance. The use of a constant-gain lead-lag filter limits the effectiveness of DMC for ship motion beyond the specific frequency spectrum for which the filter was tailored. The approach set forward in this proposal involves replacing the open loop lead compensation with a closed loop compensating approach which makes use of an adaptive ship motion prediction method in conjunction with the aircraft's linear model phase lag.