Experiments with a Robust Formation Controller for Underactuated Autonomous Surface Vessels

D. Schoerling, C. Van Kleeck, F. Fahimi, R. Koch (Canada), A. Ams, and P. Löber (Germany)


Formation Control, Sliding Mode Control, UnderactuatedSurface Vessels, Trajectory Tracking Control, UnmannedSurface Vessels.


A nonlinear robust model-based sliding mode formation controller is proposed and tested. For the operation of arbitrary formation configurations two leader-follower control schemes are needed. To design these controller schemes three degrees-of-freedom (DOF) of surge, sway, and yaw are assumed in the planar motion of the surface vessels. Further, each vessel only is equipped with two actuators; therefore, the vessels are underactuated and due to the lack of a kinematic constraint, surface vessels are holonomic systems. Further, it is shown that the internal dynamics of this underactuated system is stable, i.e. the follower vehicle does not oscillate about its control point during the formation maneuvers. As the yaw-angle of the underactuated vessel is not directly controlled this oscillatory motion might occur. During operation the proposed formation controller relies only on the inertial information obtained from the immediate neighbors of the vessel and the vessel itself. Simulations and outdoor field experiments have illustrated the effectiveness and robustness of these control laws in the presence of parameter uncertainty and environmental disturbances. The experiments were performed on a large lake in British Columbia, Canada, using a small test vessel.

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