Research on Control Algorithm for Automatic Tracking System of ship-borne Satellite Antenna

As the multi-DOF ship motion in the ocean, the ordinary satellite antenna can not be normal used on the ship. A ship-borne automatic tracking system is introduced in this paper. First, the MCU will calculate the satellite antenna pointing solution according to GPS and electronic compass, and then will drive the motors to specified angle according to the azimuth, pitch angle and polarization angle. Finally, the antenna system will track the satellite automatically according to three-axis gyro sensor signals. In order to overcome the sensor drift and get better satellite tracking precision, a conical scan algorithm is used in the tracking system. Stabilized Platform[1] is used to maintain a stable position relative to a device, its unique feature is to keep isolation from the carrier movement. Synchronous communication satellite systems is in the near 35000km above the earth in geosynchronous orbit. It's stationary relative to the ground. Receiver on the ground can get a stable satellite signal as long as the appropriate pitch angle, azimuth and polarization angle. However, the movement of ships in the ocean has six degrees of freedom, which are decomposed into forward, horizontal drift, fluctuations, turning, horizontal roll, and portrait roll[2]. Therefore, in order to receive the satellite signals stably on the ship in movement, there need to design a stable platform, which is also called ship-borne satellite antenna tracking system. The automatic tracking system has two difficulties in the design: 1) the initial antenna point. The ship's motion state changes, making the theoretical point different with practical point. 2) antenna tracking. Because of the change of ship state, the satellite antenna should automatically adjust its posture and keep aligned with the satellite.