Adaptive Control System for Steering the Ship Along the Desired Trajectory - Based on The Optimal Control and Filtering Theory

Abstract The paper presents the synthesis of the system for the steering the ship along the trajectory defined as a sequence of adjacent lines. The system enables the steering according to the required value of the velocity. That value belongs to the full range of accessible velocities including Dynamic Positioning case (velocity equals zero). Three main aspects of the synthesis are considered. The separation of high-frequency motions (induced by wave and wind's gusts) from low-frequency motions (used by controllers) is solved by using the extended Kalman filters cooperating with adaptive filters for estimation of high-frequency motions. The synthesis of a nonlinear optimal controller is presented. The quadratic performance index is formulated. Also the problem of a proper modification of set points for controllers is considered. In particular it is important during the turn manoeuver (the change of the trajectory section). Assuming the redundancy of a thruster system the decomposition of tasks is presented (thruster logic allocation). That method takes into account the differences in thrusters' characteristics. The results of computer simulation are included.