Adaptive Ship Steering Autopilot Design with Saturating and Slew Rate Limiting Actuator

Abstract The proposed adaptive ship steering autopilot is based on the internal model control method, which is characterized by a model-based design approach that provides clear connections between the structure of the controller and that of the ship model. Specifically, the controller parameters depends explicitly on the ship model parameters and on a design parameter that specifies the closed-loop system response speed. Once the ship model parameters are estimated on-line, the controller parameters are adjusted accordingly to adapt to different operating conditions. A key feature of the proposed approach being that the rudder limit and rudder rate limit are directly taken into the adaptation design consideration. Specifically, a reference conditioning technique that modifies the reference input in such a way that the rudder command is always equal to the actual rudder input into the plant. This allows the controller to exert its full power without attempting to take on values beyond the bounds imposed by the rudder limit and rudder rate limit. Consequently, under different operating conditions, rapid course-changing maneuvers are achievable without introducing possible instability problem caused by the controller integrator wind-up.