Model Reference Adaptive Control for Net-Based Debris Towing

Tether-net-based debris removal missions are deemed promising, but the postcapture control of net-enveloped targets by a chaser is understudied. In fact, existing studies on postcapture control are limited to open-loop thrust control or to feedback controllers designed for simplified models that do not consider the presence of a flexible net. To bridge this gap, advancements in closed-loop control algorithms are necessary for this critical phase. In this work, two tether elongation control algorithms are developed based on model reference adaptive control (MRAC) algorithms to stabilize the full coupled chaser-tether-net-debris system, with the flexible net completely modeled in simulation. These algorithms, named MRAC-1 and MRAC-2, are designed to modify the dynamics of the net-based system so that it behaves similarly to an ideal and stable reference model. The proposed MRAC-1 algorithm requires lower effort for initial parameter selection, while MRAC-2 benefits from greater adaptability. Compared to a proportional–integral–derivative control baseline, both MRAC algorithms demonstrate improved transient behavior in a nominal towing scenario and achieve convergence 68% faster. Results from 90 simulations with varying initial debris states, inertial properties, and imperfect measurements show that the proposed algorithms are generally robust across different conditions, enabling the net-based debris removal system to achieve the desired steady and safe behavior in the postcapture phase.