KY Space Grant GF-22-045: Satellite Formation Control using Alternating Magnetic Fields

Satellite Formation Control using Alternative Magnetic Fields T. Michael Seigler Department of Mechanical Engineering University of Kentucky Electromagnetic formation flight (EMFF) is an actuation technology that uses magnetic forces to control the relative motions of a group of satellites. A primary motivation for EMFF is that the power source of electromagnetic actuators is renewable, whereas conventional propellant thrusters are eventually depleted. The foundational work on EMFF was provided by the NASA- SPHERES/RINGS program, which demonstrated EM actuation between two satellites aboard the International Space Station. However, EMFF is still an early-stage technology. There have been no experimental demonstrations for more than two satellites. One of the main challenges of EMFF is the coupling that occurs between the electromagnetic fields generated by all satellites. The magnetic force that is applied to an EMFF satellite is a nonlinear function of the magnetic moment generated by the individual satellite and those generated by every other satellite, as well as the relative positions and attitudes of all satellites. Thus, the system of satellites is nonlinear and completely coupled. Our recent work has made significant progress on the coupling challenges of EMFF using an approach called alternative magnetic field forces (AMFF). The fundamental principle of AMFF is that the average interaction between two satellites can be controlled using sinusoidal actuation signals. Thus, it is possible on average to prescribe forces between each satellite pair while eliminating interactions with other satellites. This approach naturally allows for a decentralized control architecture, where each satellite operates independently based on measured motions of neighboring satellites. We have conducted preliminary 1-DOF experiments to validate this approach, and we are currently conducting multi-satellite 3-DOF validation experiments using our flat-floor facility. The new feature of this proposal is the addition of attitude control. EMFF has previously only been considered for relative-position control, with the implication that a secondary attitude- control system is necessary to achieve attitude formation. Our recent work demonstrates that this approach does not take advantage of the full capabilities of EMFF. Specifically, the AMFF approach can also be used for relative-attitude formation control. Moreover, it is possible to achieve both relative-position and relative-attitude formation control using AMFF. The objective of this research proposal is to develop and demonstrate EMFF for relative position and relative attitude formation control. The proposed work, which includes fundamental research and development as well as proof-of-concept experiments, contributes to our research vision that culminates in a technology demonstration in orbit. We expect that this research effort will significantly advance the applicability of EMFF for small-satellite swarm technologies.