COMPARISON BETWEEN MINIMUM AND NEAR MINIMUM TIME OPTIMAL CONTROL OF FLEXIBLE SLEWING SPACECRAFT

In this paper. muiitruun and near-minimum time optimal control laws are developed and compared for a rigid space platforn: with flc:Tible links duriru] an orientating nuuieuuer with a Im .gr; angle of rotation. The control conuiuuid« m e considered as typical l!!Lng-bang with muliip!« symmetrical suntclies, the time optimal control solution for the Tigid-body mode is obtained as a bangbang function and applied to the .fle:rible system after smoothening the control inpnt.s to avoid stimulation of the .flexilile modes. This will also reflect practical limitations in erertuu; bang-I)(lT/,g actuator jorces/torques due to delays and non-zero time constants of eiisiiru; actuation elements. The smoothness of the uiuut. commasul is obtained by ncshaping its profile based on consuieration of addiiion.a! derioaiiue constraints. the optimal control problem is converted into parameter optimization problem. The steps of tlu solution procedure and numerical algorithm. to obt.aiti the time optinuil control input are discussed next: The developed control law is applied to a given satellite duriiu; a slewing maueuuer. The simulation results show that the couirol input with just a few switching times can significantly lessen the vibrating motion of the jieribie appendage. which reneols the merits of the developed control law. The modified realistic optimal input compared to the liang-bang solution goes well with the practical Iiniitations and alleviates the vibrating motion of the flexible appendage. which reveals therneriis of the new developed control law.