Tube-based Nonlinear MPC of an Over-actuated Marine Platform for Navigation and Obstacle Avoidance using Control Barrier Functions

This paper presents the design of a robust tube-based nonlinear Model Predictive Control (MPC) law for a triangular marine platform, that is over-actuated with three rotating jets. The goal is safe navigation and dynamic positioning of the platform under realistic wind and wave environmental disturbances, as well as real-time obstacle avoidance employing Control Barrier Functions (CBF) as constraints in the robust MPC strategy. Extensive Monte Carlo simulations have been conducted under a control allocation scheme, taking into account the actuator thrust and rotation dynamics, sensor noise, as well as additional state and input constraints. The simulation results show that the nonlinear controller ensures robust and safe navigation with obstacle avoidance and accomplishes accurate positioning of the floating platform at a given goal pose, while satisfying the actuator limits.