Stabilization control of 3-DOF parallel vessel-borne platform with dynamic uncertainties and unknown disturbances

Abstract

The wave-induced vessel motions inevitably affect and even menace the operation of onboard equipment, such as excavators, cranes and drilling configurations. Vessel-borne stabilization platforms as a vessel motion compensation device can provide a good solution scheme for the safe offshore operation in tough environmental conditions. To compensate the wave-induced vessel motions in roll, pitch and heave degrees of freedom, this paper proposes a novel stabilization control scheme for a three degrees of freedom parallel vessel-borne platform with dynamic uncertainties and unknown time-varying disturbances. Here the conventional super-twisting algorithm is innovatively modified to mitigate its inherent chattering whereby a new adaptive super-twisting extended state observer (STESO) is constructed to realize the finite-time estimates of the total disturbances lumped by dynamic uncertainties and unknown time-varying disturbances of the vessel-borne platform without relying on any prior knowledge of its upper bounds. Further, a novel adaptive super-twisting sliding mode (STSM) control law with the adaptive STESO is designed to stabilize vessel-borne platforms at a desired position and orientation in the inertial space. The simulation results on a benchmark platform indicate that the wave-induced vessel motions can be compensated by the platform for more than 98% in both 0.5m and 2.5m significant wave heights, such that the workability and safety during offshore activities in tough environmental conditions is increased.