Sequences of Passively Stable Dynamic Equilibria for Hybrid Control of Reconfigurable Spacecraft

Abstract

This paper proposes a novel hybrid-control strategy to reconfigure modular spacecraft. This strategy utilizes passively stable system dynamics, which have the benefits of low control effort and a high degree of robustness. This approach treats reconfigurable spacecraft systems according to the theory of multibody kinematic mechanisms. It employs ambient force fields in the space environment (gravity gradient, magnetism, etc.), along with passively generated, non-contacting force fields on the spacecraft (such as those from permanent magnets), to drive the reconfiguration maneuver. The control strategy for reconfiguration in this paradigm consists of a selection of body incidences, joint Jacobians, and applied force fields that cause the multibody spacecraft system to evolve through passive dynamics to a new configuration. Many of these passive dynamical evolutions, chained together in stepwise fashion, allow the system to reach many possible desired configurations. All possible equilibrium configurations can be computed offline and uploaded to the spacecraft in a graph structure. The use of kinematic constraints and passive dynamics adds robustness to the system, while the stepwise nature of the reconfiguration maneuver provides many safe-hold points for verification regardless of transient dynamics.