Parameter estimation and control of an automatic balancing system for CubeSat research and applications

Abstract

Deployed for purposes of GPS, defense, atmospheric and space research, environmental monitoring, broadcasting, and communication, Earth observation satellites are complex systems that require the design of highly reliable control and estimation algorithms. A satellite's attitude determination and control system (ADCS) must be able to operate accurately, in a robust manner against unexpected conditions, especially in missions that demand more intricate tasks. The desire for optimal and robust performance in satellites has been the driving factor behind decades of attitude control research. With computers, the performance of spacecraft subject to some mission can be simulated to test new control methods, but the availability of real satellites to researchers for testing these algorithms is very limited. To solve this issue, attitude control simulators have been developed, such that algorithms and hardware can be tested inexpensively in a lab environment, while maintaining a high level of accuracy to the environment it emulates. The Nanosatellite Attitude Control Simulator (NACS) has been developed at McMaster University for this purpose. Consisting of a mock 1U CubeSat, an air-bearing configuration, and an automatic balancing system (ABS), rotational attitude control experiments are conducted in-lab without deployment, simulating the zero-gravity of space. The mechanism responsible for environment simulation is the ABS, which minimizes residual torque due to gravity by influencing the center of mass (CoM) of the system, thereby improving control performance and efficiency. The performance of the ABS in a balancing task is presented, where system parameters of inertia and CoM are estimated from response data. Three filtering strategies are investigated for this purpose, providing varying degrees of accuracy and computational cost.