Barge ships are designed to transport and assemble heavy and massive pieces of equipment at sea. Active propulsion systems are not installed in this type of ship, so the desirable motion and positioning of these ships can only be achieved with the assistance of several tugboats. In this study, the dynamical characteristics of barge conveying systems were formulated and robust control systems were designed to ensure efficient barge operation. To achieve these objectives, we first developed a mathematical model of a barge ship, which incorporated a novel conveying system configuration using tugboats. We then designed a robust controller for the tugboats that used the sliding mode law to deliver the desired barge motion performance. Finally, the usefulness of the proposed configuration and controller was verified via simulation studies using another system with an $H_{\infty }$ controller. The proposed sliding mode controller showed superiority, especially in terms of robustness against disturbances.

This paper introduces a novel approach to modeling and control system design for tugboat-assisted operations, such as the docking and rescue of marine vessels. In these scenarios, one or more tugboats push, pull, or guide large vessels to ensure precise and safe maneuvering. Their control systems ensure accurate coordination, vessel positioning, and overall stability, even in the presence of system uncertainties, imperfect control allocation, and ocean disturbances. To address these challenges, a mathematical model of a general tugboat-assisted system is first derived. Then, a new vector of variables is introduced, leading to a modified model representation where the mismatches from the allocation and lower-level tugboat controllers can be realized in the vessel’s motion equation. Thus, the design of a controller can take this aspect into account to enhance the overall system’s performance and stability. Thirdly, a control system design method is proposed, employing a centralized control framework and ensuring a mixed $H₂/H_{\infty }$ performance criterion. Finally, a case study is conducted with a particular tugboat-assisted configuration and the results validate the effectiveness of the control solution.

This paper introduces a novel approach to modeling and control system design for tugboat-assisted operations, such as docking and rescuing marine vessels. The control objective is to ensure effective positioning and movement of the vessels while maintaining overall system stability, even in the presence of system uncertainties, imperfect control allocation, and ocean disturbances. First, a mathematical model of a general tugboat-assisted system is derived. Second, a new vector of variables is introduced, leading to a modified model representation where the mismatches from the allocation and lower-level tugboat controllers can be realized in the vessel’s motion equation. Thus, the design of a supervisory controller for the vessel can take this aspect into account to enhance the overall system’s performance and stability. Then, a control system design method is proposed, employing a centralized control framework and ensuring a mixed H₂/H∞ performance criterion. Finally, a case study is conducted with a particular tugboat-assisted configuration and the results validate the effectiveness of the control solution.

This study presents the design of an intelligent robust controller for the 3-degree-of-freedom motion of an aerial robot using waterpower. The proposed controller consists of two parts: (1) an anti-windup super-twisting algorithm that provides stability to the system under actuator saturation; and (2) a fully adaptive radial basis function neural network that estimates and compensates for unexpected influences, i.e., system uncertainties, water hose vibration, and external disturbances. The stability of the entire closed-loop system is analyzed using the Lyapunov stability theory. The controller parameters are optimized such that the effect of these unexpected influences on the control system is minimized. This optimization problem is interpreted in the form of an eigenvalue problem, which is solved using the method of centers. Experiments are conducted where a proportional-integral-derivative controller and a conventional sliding mode controller are deployed for comparison. The results demonstrate that the proposed control system outperforms the others, with small tracking errors and strong robustness against unexpected influences.

In this paper, a hybrid flying robot that utilizes water thrust and aerial propeller actuation is proposed and analyzed, with the aim of applications in hazardous tasks in the marine field, such as firefighting, ship inspections, and search and rescue missions. For such tasks, existing solutions like drones and water-powered robots inherited fundamental limitations, making their use ineffective. For instance, drones are constrained by limited flight endurance, while water-powered robots struggle with horizontal motion due to the couplings between translational motions. The proposed hydro-aerodynamic hybrid actuation in this study addresses these significant drawbacks by utilizing water thrust for sustainable vertical propulsion and propeller-based actuation for more controllable horizontal motion. The characteristics and mathematical models of the proposed flying robots are presented in detail. A state feedback controller and a proportional–integral–derivative (PID) controller are designed and implemented in order to govern the proposed robot’s motion. In particular, a linear matrix inequality approach is also proposed for the former design so that a robust performance is ensured. Simulation studies are conducted where a purely water-powered flying robot using a nozzle rotation mechanism is deployed for comparison, to evaluate and validate the feasibility of the flying robot. Results demonstrate that the proposed system exhibits superior performance in terms of stability and tracking, even in the presence of external disturbances.

This paper investigates the controllability of vessel berthing systems assisted by multiple tugboats under actuator faults or failures. In such interconnected systems, a failure of an individual tugboat can potentially compromise the berthing operation, or even lead to the collapse of the entire system. To address this challenge, the dynamic model of the multi-tug-assisted vessel system is first derived, followed by a controllability analysis under various fault scenarios to identify tolerable fault configurations. Then, a robust controller is proposed, integrating an adaptive disturbance observer with finite-time sliding mode control. This design ensures effective rejection of maritime environmental disturbances, practical finite-time stability, and bounded trajectory tracking errors. To accommodate different fault conditions, a switching control allocation strategy is developed to redistribute control efforts among the remaining healthy tugboats, thereby maintaining system reliability and efficiency. Simulation results under various faulty conditions demonstrate the effectiveness and robustness of the proposed control approach.