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 presents the design and experimental validation of a robust control system for hybrid-powered robots in forms of unmanned aerial vehicles intended for firefighting and support operations in dangerous and hazardous marine environments. Flight maneuvers are actuated by integrated thrusts from four downward water nozzles and four horizontal propellers. The primary lift is generated by high-pressure water expelled throught the former, while the latter aerial propellers provide attitude control and horizontal stabilization, enabling fully controllable flight. The fabrication of the flying robot is first presented. Then, a robust integral sliding mode control (ISMC) strategy is proposed, with an integral term of tracking errors incorporated into the sliding surface, to achieve required flight maneuvers, enhance disturbance rejection and handle system uncertainties. Lyapunov-based analysis guarantees the asymptotic stability of the proposed system. Experimental results in attitude tracking scenarios show that the proposed ISMC provides superior tracking performance in comparison to other controllers, namely conventional sliding mode and proportional-integral-derivative (PID). Therefore, the fabricated robot configuration proves its feasibility, and the proposed control system operates effectively.