An Output Feedback Approach for Regulation of 5-DOF Offshore Cranes With Ship Yaw and Roll Perturbations

In practice, offshore cranes are effective transportation tools used on ships. Different from land-fixed cranes, offshore cranes work in the noninertial frame, which are usually affected by different disturbances. Therefore, the control problem of offshore cranes is much more difficult. Till now, only few control methods have been proposed for offshore cranes, which are usually designed for planar offshore cranes, while the more practical three-dimensional (3-D) movements are ignored. Considering these facts, in this article, we focus on the control problem of a 5 degrees of freedom (DOF) offshore crane in 3-D space with persistent ship yaw and roll perturbations and propose an effective output feedback control method. Specifically, we first present an elaborate coordinate transformation method to deal with ship perturbations. Then an energy-like function is constructed based on the transformed model, and then by designing some auxiliary signals, an output feedback method is designed with rigorous mathematical analysis to prove the closed-loop asymptotic stability results. As far as we know, the proposed method is the first control method designed for 5-DOF offshore cranes without any linearization, which only uses output signals. Finally, experimental results are included to verify the performance of the proposed method.