Integrated Line of Sight and Model Predictive Control for Path Following and Roll Motion Control Using Rudder

Roll motion control and path following are two representative marine control problems that have been traditionally treated separately. However, these two problems are closely coupled, as roll motion could cause negative effects on marine surface vessels during path following in seaways and path following actions could cause undesirable roll motion. In this article, an optimal controller is proposed for the integrated path following and roll motion control problem. The rudder, whose actuation amplitude and rate are both limited, is the only control input, while the cross-track error, heading angle, roll rate, and roll angle are the outputs that collectively define the performance of the system. This leads to a classic underactuated problem. Model predictive control is the natural choice for the solution, given its capability in dealing with constraints and multi-input multi-output system, and its design will be pursued in this article. Line of sight technique is used to extend the straight-line path following to arbitrary path following. A four degrees of freedom high-fidelity model is implemented as the simulation model, and the simulation results verify the effectiveness of the proposed controller. The influences of the control design parameters on system performance are investigated and the trade-offs between two key attributes, namely, the roll reduction and path following, are explored.