Nonlinear Robust Heading Control for Sailing Yachts

In this paper, we present ℒ1 adaptive control theory to provide stabilization of the sailing yachts around any desired heading angle. The nonlinear heading model of the sailing yachts, which is presented in a recent paper, is expressed as a linear time-invariant system, i.e. the first-order Nomoto model, for which an ℒ1 adaptive heading controller is designed. A conventional PID heading controller is also constructed by pole-placement for the yacht system, and the previously presented backstepping controller is redesigned by adding an integral action. Afterwards, the performance achieved with the ℒ1 controller is compared with that obtained via the backstepping controller and the PID benchmark controller. Simulation results show that the ℒ1 heading controller ensures stable tracking and guarantees robustness. Furthermore, the performance of the ℒ1 surpasses that of the rest two controllers in terms of robustness when considering the unknown plant parameters, and energy saving is achieved by less rudder deflections in comparison to PID control.