HHO-Based Cable Tension Control of Tethered UAV with Unknown Input Time Delay

A tethered Unmanned Aerial Vehicle (UAV) is a special type of UAV that is powered continuously through a cable, ensuring long-duration flight. However, the pulling interference of the cable significantly affects the UAV’s stability control, limiting its application and development. This paper addresses this issue by first analyzing the effect of cable tension on the UAV’s wind resistance capability and demonstrates the possibility of using cable tension to assist in wind resistance control. Building on this, a robust time-delay compensator is designed to address the problem of unknown external disturbance and unknown time delay in the cable control input. Sufficient conditions for system boundedness are provided using the Lyapunov–Krasovskii functional. Subsequently, to deal with the strong nonlinearity and strong coupling issues of the sufficient conditions, the Harris Hawks Optimization (HHO) algorithm is employed for intelligent optimization of the controller parameters. Simulation results indicate that the HHO-based robust time-delay compensator exhibits excellent robustness and fast response.