Robust Control of an Actuated Coupling Device for Autonomous mid-air Coupling

Abstract

The probe-and-drogue method has numerous practical applications like in-air-capturing and aerial refuelling, where automating the docking procedure can enable a fully autonomous coupling maneuver in the future. A simplified system model of an actuated coupling device was derived by combining the aerodynamic forces of control surfaces and the drogue body through superposition. Wind tunnel tests and CFD simulations were conducted to identify the aerodynamic coefficients, which were then used for model-based controller design. Robust control strategies such as sliding mode control, super twisting control, and PID control, which served as a baseline, were implemented and tested in a comprehensive probe-and-drogue simulation under various external disturbances. A super twisting disturbance observer was added to enhance the controllers' performance. Furthermore, all tested control architectures were modified by adding incremental nonlinear dynamic inversion to reduce perturbation rejecting controller gains while preserving control performance. The derived system model and the implemented controllers were shown to be effective for this control problem. Specifically, the application of incremental nonlinear dynamic inversion can lead to reduced control input variation without compromising control performance.