Path Following with Roll Constraints for Marine Surface Vessels in Wave Fields.
Zhen Li · Deep Blue (University of Michigan) · 2009
Ways to improve maneuverability of marine surface vessels through judicious application of advanced control theory are explored. Although for years the problem of marine vessel maneuvering has been addressed in many publications, the control design to achieve path following with roll constraints in wave fields remains to be an open problem. This is the exclusive focus of this research. A ship dynamical model, together with path following error dynamics, is first introduced to facilitate the control design. A numerical test-bed combining the ship dynamics and wave effects on vessels is also developed to provide a platform for evaluating the performance of ship motion control systems in wave fields. A novel Feedback Dominance Back-Stepping (FDBS) controller is then designed and tuned to achieve path following without roll constraints. This controller is promising for industrial applications, in terms of easy implementation and robustness against model uncertainties and disturbances. The path following capability and robustness of the FDBS controller are demonstrated through theoretical analysis, numerical simulations, and experimental validations. The need to enforce roll constraints and the fact that the rudder actuation is limited in both amplitude and rate make the Model Predictive Control (MPC) approach a natural choice for the design of the path following controller. The simulation results are presented to verify the effectiveness of the resulting controller and a simulation-based tuning process for the controller is also presented. Meanwhile, through simulations, issues associated with roll constraint violation and successive feasibility have been identified for the standard MPC path following controller in wave fields. Several mitigating strategies, such as constraint tightening and softening and gain re-tuning, are proposed to meet the state constraints of the path following for marine surface vessels in wave fields. Motivated by the constraint violation and feasibility issues of the standard MPC in the presence of disturbances, a novel disturbance compensating MPC (DC-MPC) algorithm is developed to guarantee the state constraint satisfaction. The satisfactory performance of DC-MPC algorithm is validated by numerical simulations of ship heading control. The limitations of the DC-MPC scheme are discussed along with potential future work.