Practical Time-Synchronized Model Predictive Control for Energy-Efficient Dynamic Positioning of Fully Actuated Surface Vehicles

For the robust dynamic positioning (DP) of the fully actuated electric vessel, this paper presents the first practical time-synchronized (TS) Lyapunov-based model predictive control (LMPC) scheme, guaranteeing the practical TS stability and the optimal energy consumption. To ensure TS convergence of vessel states, a slack variable vector of ratio persistence is introduced into the stage cost of LMPC. To guarantee the stability of the presented scheme, a practical TS auxiliary controller based on a TS disturbance observer and adaptive compensators is designed to construct the contractive constraint for LMPC. A chattering-reduction thrust allocation algorithm is designed to smooth the thrust force commands. Supported by theoretical analyses of the feasibility and stability, all states of the closed-loop DP control system under the proposed scheme converge to their desired values with a synchronized settling time. Consequently, the vessel under the proposed scheme can precisely maneuver with optimized trajectories and reduced thruster power consumption. Comparative hardware-in-the-loop simulations on a model-scale electric vessel demonstrate the precise DP performance and the energy-saving capability of the proposed scheme.