Minimum-time optimal control of flexible spacecraft for rotational maneuvering

Space commercialization increasingly requires servicing, construction, and maintenance of space structures and satellites in orbit. A minimum-time optimal control law for a flexible spacecraft during an orientating maneuver with large angle of rotation is developed. The spacecraft is modeled as a linear undamped elastic system, which yields an appropriate model for analysis of planar rotational maneuvers. The control commands are considered as typical bang-bang with multiple symmetrical switches, and the optimal control problem is converted into parameter optimization problem. The steps of the solution procedure and numerical algorithm to obtain the time optimal control input are discussed next. The developed control law is applied on an Iranian satellite "Sepehr" during a slewing maneuver, and the simulation results show that the control input with just few switching times can significantly lessen the vibrating motion of the flexible appendage, which reveals the merits of the developed control law.