Sliding-Mode Tracking Control for Offshore Cranes Based on Time-Delay Estimator

The offshore crane is a kind of machinery used for the offshore lifting operation, the layout and recovery of underwater equipment, the transfer of goods between ships on the sea, the loading and unloading of port goods, the erection of submarine pipelines, etc. At present, compared with traditional crane systems, the design of the control method for offshore crane systems has many challenges. In practice, due to the ship motion, the dynamics of the system exhibits more complex nonlinearity and underactuated characteristics. This article uses sliding-mode technique to construct an effective tracking control method, further improving the robustness, achieving precise tracking control objectives, and ensuring effective suppression of the payload swing. By transforming the system model and designing an effective sliding surface, the control objective of payload swing suppression can be better achieved. At the same time, a time-delay estimator will be established to tackle system uncertainties, and then sliding-mode method is used to effectively deal with the estimation error. Through rigorous mathematical analysis, it has been proven that this method can achieve precise positioning of the payload. Finally, the experimental results demonstrate remarkable superiority of the proposed scheme.