On the ship course-keeping control system design by using robust and adaptive control

The paper considers a problem of ship autopilot design based on the input-output feedback linearization method combined with the robust and adaptive control approaches. At first, the nonlinear ship model of Norrbin type is linearized with the use of the simple system nonlinearity cancellation. Next, as exact values of the model parameters are not known, the ensuing inaccuracies are taken as disturbances acting on the system. Thereby we obtain a linear system with an extra term representing the uncertainty that can be treated by using robust, H_∞ optimal control techniques. In the final step, to enhance the overall system performance, the system parameters are additionally tuned in adaptive way. The performed simulations of ship course-changing process confirmed a high performance of the proposed controller despite the assumed considerable errors of its parameters.