Analytical control laws for interplanetary solar sail trajectories with constraints

An indirect method is used to obtain an analytical control law for a spacecraft with a low-thrust propulsion system which is constituted by a solar sail coupled with a solar electric thruster. Constraints on the control inputs for such as the system need to be taken into account for the design of a control law to avoid reducing control performance, even though the solar electric thruster is employed as an auxiliary system capable of increasing the thrust magnitude of the sailcraft. The aim of this paper is to derive an analytical control law for a system with input constraints. A barrier function is used to analytically obtain a control law without a computationally expensive iterative algorithm. Therefore, using the analytic method presented, a transfer orbit can be readily calculated with an onboard computer. Pontryagin's maximum principle is also used to obtain an optimal control law to compare with the proposed control law. The proposed control law is demonstrated as suitable for an example transfer problem between circular and coplanar orbits