Design of ship course-keeping system via robust adaptive approach

The paper considers the problem of ship autopilot design based on Bech's model of the vessel. Since the ship model is highly nonlinear and the state vector is not completely measurable, the control system synthesis is performed by means of output feedback linearization method combined with a state observer. Due to considerable parameter variations and other substantial uncertainties a robust-adaptive version of the method has been applied. The whole control system is able to ensure tracking performance on the H∞optimal attenuation level. This is the so-called H∞tracking problem in an adaptive system. Simulations of the ship course-changing process have confirmed a good performance of the proposed controller.