Robust optimal control for reconfiguration of Coulomb spacecraft formations along invariant manifolds

This paper addresses the challenge of maintaining Coulomb thrusting, a propellant-free propulsion method, in close-formation spacecraft platforms subject to perturbations such as Earth’s J 2 effect and solar radiation pressure. Although Coulomb formations offer advantages such as low propellant consumption, rapid throttling, and plume avoidance, their performance is highly sensitive to dynamic disturbances. To overcome these limitations, this paper proposes a robust optimal sliding mode control framework that reconfigures deputy spacecraft along invariant manifolds through active charge modulation of the chief spacecraft. By integrating a linear quadratic regulator with sliding-mode control, the method synthesizes a hybrid feedback law to suppress disturbances and address thruster saturation. Additionally, a Poincaré map is employed to design low-energy transfer trajectories utilizing the geometric properties of stable/unstable manifolds near collinear equilibrium points. Extensive simulations demonstrate centimeter-level tracking precision and minimal thrust requirements under charge constraints, validating the method’s robustness, optimality, and applicability to space missions.