Experimental Validation of Positive Adaptive-Control Approach for Spacecraft Proximity Maneuvers

In this study, we propose a positive adaptive control approach for spacecraft in proximity. The new control law aims to track a predefined path under various uncertainties, such as physical parameters of the vehicle and others persisting in the external environment. Besides, the proposed method also considers the divergent performance and the nature of monodirectionality of the thrusters to ensure each control command is strictly nonnegative. In other words, the proposed method is capable of not only compensating for various uncertainties but also automatically allocating active thrusters with strictly positive manners. The numerical simulation results demonstrate the potential of the proposed algorithm by comparing the magnitude of fluctuation of the states concerning the activation of the adaptive scheme. Considering the findings, we attempt to perform a hardware experiment by utilizing the recently developed air-bearing-based hardware-in-the-loop spacecraft test facility. The results of the experiment clearly suggest the practical effectiveness of the proposed controller by showing that individual thrust magnitudes are manipulated based on the estimation of scale factor errors and other external uncertainties under their boundaries.