REAL-TIME FORECASTING OF FUTURE SHIP MOTION

THE DESIGN, DEVELOPMENT, AND IMPLEMENTATION OF A REAL-TIME METHOD TO FORECAST FUTURE QUIESCENT INTERVALS IN SHIP MOTION IS PROPOSED FOR V/STOL AIRCRAFT RECOVERY OPERATIONS ABOARD AIR-CAPABLE SHIPS. THE METHOD USES ONLY MEASURED SHIP MOTIONS AND PROVIDES A RATIONAL BASIS IN TIME-OPTIMAL CONTROL THEORY FOR ESTABLISHING REQUISITE FORECASTING INTERVALS. THE FORECASTING TECHNIQUE IS BASED ON CONTINUOUS REAL-TIMEIDENTIFICATION OF THE SINUSOIDAL AMPLITUDES AND PHASE ANGLES IN THE RANGE OF FREQUENCIES THAT CHARACTERIZE THE ENCOUNTERED MODAL PERIOD OF MOTIONS, REPEATED SAMPLING OF SHIP MOTIONS, AND FAST-TIME INTEGRATION OF SEVERAL HIGHER DERIVATIVES OF MOTION COUPLED WITH MEASURED INITIAL CONDITIONS. THE MOTION FORECAST METHOD HAS BEEN VALIDATED IN THE LABORATORY IN REAL TIME WITH RECORDED TIME HISTORIES OF ACTUAL SHIP MOTIONS. THE NECESSARY SHIP MOTION MEASURING TECHNIQUES, SENSORS, AND COMPUTER PROGRAMS FOR OPERATIONAL REAL-TIME SHIP MOTION FORECASTING ARE DESCRIBED. A PROGRAM IS PROPOSED FOR ASSESSING THE ACCURACY OF THE FORECASTING AS A FUNCTION OF THE PREDICTION INTERVAL, THE ACCURAY OF THE ESTIMATED SINUSOIDAL AMPLITUDES AND PHASE ANGLES IN THE RANGE OF FREQUENCIES THAT CHARACTERIZE THE ENCOUNTERED MODAL PERIOD, AND THE ACCURACY OF THE SENSED AND SAMPLED SHIP MOTIONS.