Dynamics and advanced active disturbance rejection control of tethered UAV

Due to its vast potential for applications in agricultural harvesting, the tethered unmanned aerial vehicle (UAV) has garnered considerable interest. However, the anti-disturbance control of this system remains fraught with obstacles, stemming primarily from its inherent nonlinearity, unpredictable airflow disturbances, unmeasurable tether tension, and the changes in the center of gravity during operation. We propose a comprehensive dynamic model for the operational tethered unmanned aerial vehicle with considering the center of gravity shift. Because of obstructions caused by branches and leaves, the tethered UAV can't reach fruits inside the tree. Therefore, two deformation functions of the tethered quadcopter are considered. Additionally, in order to enhance the effectiveness of traditional Active Disturbance Rejection Control, we present an optimized controller combining a phase compensation algorithm with a nonlinear function. The proposed Controller is validated in a high-fidelity simulation environment, considering internal interference, wind field interference and reactive force from produces. Besides, the simulation is specifically developed for picking operation, The results underscore the better observation capabilities of the enhanced controller proposed in this study. Moreover, when deployed in a simulated picking environment, the improved controller exhibits remarkable resistance to the interference and significantly mitigates chattering issues.