Development of phase plane attitude control algorithms for nanosatellite rendezvous applications

Nanosatellite rendezvous missions can enable diagnostics and servicing of disabled spacecraft on a miniaturized, low-cost, and rapid response platform. However, this technology is still under development as the state of the art continues to overcome the challenges associated with maintaining high levels of capability on highly constrained spacecraft platforms. The University of Texas (UT) at Austin is participating in this endeavor through the Air Force University Nanosatellite Program (UNP) and is designing ARTEMIS, an ambitious mission to demonstrate autonomous rendezvous of two nanosatellites.The Guidance, Navigation, and Control (GNC) system architecture required for this capability is an active research field because the algorithms must be equipped with the necessary features to be efficient with limited resources and yet remain robust against inherent uncertainties. ARTEMIS is used as a baseline mission profile to facilitate the design of a prototype GNC system for autonomous nanosatellite rendezvous. A robust attitude control architecture has been devised to work in conjunction with the guidance and navigation modules. The proposed attitude control architecture leverages industry standard phase plane methods in order to utilize a full thruster actuation system and to provide precision pointing with limited fuel expenditures. Several phase plane algorithms have been developed and simulated to study the trades between algorithm architectures, control parameters, and performance measures. The results of these studies demonstrate that the modified phase plane approach with optimal jet selection logic and coupled actuation can provide settling times on the order of 25 seconds, pointing precision on the order of 2 degrees, and total propellant expenditure on the order of 3 newtons.