Dynamic and thermal control of an electromagnetic formation flight testbed

Abstract

Formation flight of multiple spacecraft is an emerging method for completing complex space missions in an efficient manner. A limitation found in maintaining such formations is the need for precise control at all times. Using traditional thruster propulsion systems can be costly and life-limiting since the propellant is consumed during the mission. An alternative method for providing this relative position control is to use electromagnetic interaction between the vehicles of the formation to provide forces and torques. This method uses electricity alone, which is a renewable resource in space, to provide all actuation to control the formation. The Space Systems Laboratory at MIT is developing this concept with a project called Electromagnetic Formation Flight (EMFF). A two-dimensional testbed has been developed to demonstrate the ability to control vehicle position and attitude using only electromagnetic forces and reaction wheels. A thorough description of this system is given, focusing on the development of its thermal and dynamic control. Innovations to the thermal system, used to cool the superconducting wire of the electromagnet, are described. All systems involved with dynamic control of an EMFF vehicle are identified and the methods used to develop control algorithms are explained. Simulations demonstrating the stability achieved by these controllers are presented and successful experimental results from the testbed are examined. Finally, the test results are used to refine the parameters used in the simulation and a more accurate dynamic model of the system is determined.