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.

Nowadays, the demand for high-precision devices is becoming more intense, thanks to the growing complexity and sophistication of modern technology and applications, including microscopy, nanomeasurement and analysis instruments. However, challenges arise because environmental factors such as vibration negatively affect their performance. An active vibration isolation system (AVIS) is one of the most recent solutions for that, but the high degree-of-freedom (DoF) nature results in it strongly suffering from unwanted interactions. Hence, in this paper, a robust decoupling controller is designed to handle the mentioned disadvantages. The system model is first presented, followed by the proposed decoupling techniques, and then, a feedback controller is designed by applying the mixed-sensitivity $H_{\infty }$ control framework. Experimental studies are conducted to investigate the effectiveness of the proposed AVIS and compare it with other systems, namely, a passive vibration isolation system, a proportional–derivative (PD)-controlled AVIS, and a robust controlled AVIS. The robustness and decoupling performance of the proposed controller are guaranteed by suppressing external vibrations and isolating interactions, and, therefore, stabilizing the system.

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.

Active vibration isolation system (AVIS) is one of the latest applications for improving the working performance of high-precision devices, which are easily affected by environmental vibrations. Additionally, a major challenge with such a high degree-of-freedom (DoF) system is the interaction among individual movements. Therefore, this paper introduces the design of a robust decoupling controller for the 6-DoF AVIS. The mathematical model of the system is presented; the decoupling process is outlined; and the mixed sensitivity HSUB∞/SUB control framework is used to develop the robust decoupling controller. The effectiveness of the proposed system is demonstrated by comparing simulation results of its velocities and control efforts with the results of an uncontrolled system, a PID control system, and a robust control system. The designed controller ensures robustness and decoupling performance through the suppression of external vibrations, isolation of interactions, and stabilization of the system.

In this study, the control system design problem of a novel flying type fire fighting system (flying robot) is presented. A proposed system can provide very effective fire fighting such that the safety in work is occupied. The proposed fire fighting system is flying and approaching to the fire point as the target by using water source propulsion systems which consist of four water jet actuators. Controling the propulsion forces made by actuators, the 6DOF motions of flying robot are controlled such that the system approaches to the target point. For this purpose, the authors design a control system for the flying robot. Two control schemes are provided for evaluating the control performances. The simulation results show the superiority and reliability of the proposed control system.

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.