Experimental Evaluation of Supervisory Switching Control for Unmanned Surface Vehicles

Abstract

In this paper, a method of incorporating multiobjective controller selection into a closed-loop control system is presented and validated using a full-sized unmanned surface vehicle. Three controllers are utilized to capture three 'behaviors' representative of typical maneuvers that would be performed in a port environment: 1) a nonlinear controller for transiting between locations using an underactuated thruster configuration; 2) a nonlinear controller for station-keeping at a setpoint heading and position using a fully actuated thruster configuration; and 3) a nonlinear controller for reversing using an underactuated thruster configuration. Given a trajectory to follow, a performance-based supervisory switching control system (PBSSC) dictates the switching between controllers to improve the closed-loop performance. Stability between controller switches is guaranteed through average dwell-time switching, and a novel method for determining minimum dwell-time between subsystems with transformed states is utilized. The proposed system was tested in field experiments on a physical platform against a nonlinear, gain-scheduled 'baseline' controller capable of adequately performing all three behaviors using a fully actuated thruster configuration. Using integral of absolute error (IAE) metrics, results demonstrate that positioning of the PBSSC system is 20% better than that of the fully actuated baseline controller. However, the orientation IAE of the baseline controller was 50% better than the other controllers, because the system uses a fully actuated thruster configuration along the entire experimental trajectory.