| The thesis deals with the use of kinematic GPS for an automatic berthing system. Building a berthing system requires precise measurements of the ship's position, velocity, attitude (roll, pitch, and heading or yaw) and angular velocity (attitude rate) in real time, at the time of approach to the wharf. The berthing maneuver is the most delicate and difficult phase of navigation. To reduce the work load of crews and avoid the accidents, automation of berthing is required.; The objectives of the research are to use GPS to feed the necessary and precise information into the controller of a berthing system, and to assess the navigation solution obtained by a GPS-based system.; Rapid and reliable GPS phase ambiguity resolution provides the ultimate accuracy for GPS positioning and attitude determination. Algorithms have been developed for the GPS-based system with single frequency receivers, which make synergetic use of all the GPS observations and the characteristics of ship's berthing. Velocity and attitude rate can be directly determined using instantaneous Doppler or temporal difference of phase measurement. The use of Doppler measurements and phase difference were compared. A simulation study on attitude determination was conducted to find optimal antenna configurations for the ship's berthing application. The quality of the navigation solution was verified on land and at sea, using an optimal configuration of 4 antennas on board whose baseline lengths were about 1m.; Different data sets were processed and analyzed: (1) the precision of position is better than ±5 cm, (2) the precision of velocity is better than ±1 cm/s with phase difference, (3) the precision of attitude angles with an optimal configuration, in which antenna separation is about 1 m, varies between ±0.1° and ±0.4°, and (4) the precision of yaw rate is ca. ±0.2°/s with differential phase observations and ±0.6°/s with Doppler measurements. The results show that the onboard GPS-based system would satisfy the sensor requirements for ship's berthing (with baseline lengths between onboard antennas of about 5 m) and they confirmed the potential of GPS for a berthing system. |
