Design Considerations, Analysis and Practical Experience with an Adaptive Ship's Autopilot

The paper describes an adaptive autopilot. The autopilot is based on a mathematical model which uses a priori information to find initial parameter estimates. The autopilot also includes a model of wave induced law-motion. The estimates of the oscillating yaw components are used to minimize their influence on the rudder motions. It is shown in the paper that a Kalman filter gain for a vessel of unit length can be computed once and for all. Based upon this unit vessel Kalman filter gain, formulas for computing the gain for a general vessel are given. A vector of variable forgetting factors are introduced. This completely eliminates the blow up problem. The autopilot is tested on board the coastal steamer M/s MIDNATSOL and results from these tests are given.