Robust Docking Control for Probe-and-Drogue Refueling System with Input Delay and Disturbances

In the probe-and-drogue refueling (PDR) docking phase, the probe with slow dynamics attempts to track the drogue with fast dynamics. Therefore, during this phase, it is crucial for the receiver to obtain the drogue position information and respond rapidly to control commands to guarantee successful docking. This paper considers the input delay caused by complex factors in PDR systems, such as sensors and controllers, and designs a control framework based on additive state decomposition (ASD). The ASD-based framework decomposes the PDR docking system with input delay into a primary system with disturbances and a secondary system with input delay. By combining classical control methods, the docking task of the primary system is completed using proportional-integral (PI) control, while the input-delay stabilization task of the secondary system is achieved through model predictive control. Simulation results show that the proposed comprehensive control method can effectively improve docking speed and enhance the system’s robustness against input delays, compared to the traditional PI control methods.