Distributed autonomous control of multiple spacecraft during close proximity operations

Abstract

This research contributes to multiple spacecraft control by developing an autonomous distributed control algorithm for close proximity operations of multiple spacecraft systems, including rendezvous and docking scenarios. The proposed control algorithm combines the efficiency of the Linear Quadratic Regulator (LQR) and the robust collision avoidance capability of the Artificial Potential Function (APF) method. The LQR control effort serves as the attractive force toward goal positions, while the APF-based repulsive functions provide collision avoidance for both fixed and moving obstacles. The combination of the LQR and APF control logics, referred to as the LQR/APF control algorithm, yielded promising results as demonstrated by the numerous multiple spacecraft maneuver simulations reported in this dissertation. In order to validate the proposed control approach, a multiple spacecraft model validation and visualization technique was developed using a versatile MATLABSatellite Toll Kit (STK) interface to propagate the spacecraft models, compare against STK generated ephemeris, and animate for analysis. The MATLAB-STK interface efficacy was demonstrated during the evaluation and analysis of the innovative LQR/APF multiple spacecraft control algorithm. The LQR/APF multiple spacecraft close proximity control algorithm was developed, refined, and thoroughly simulated using high fidelity six Degree of Freedom (DOF) spacecraft models. In order to evaluate the stability and robustness of the control approach a Monte-Carlo simulations set was run. The LQR/APF control algorithm was further evaluated by virtual hardware-in-the-loop implementation at the NPS Spacecraft Robotics Laboratory. The laboratory hosts the Autonomous Docking and Spacecraft Servicing testbed which allows for on-the-ground testing of close proximity multiple spacecraft control concepts.