THE HYBRID CONTROL OF AN ORBITING FLEXIBLE TETHERED ANTENNA REFLECTORSYSTEM

In order to improve the performance and ensure stability for a tethere d antenna/reflector system, the longitudinal vibration of the tether s hould be considered. The frequencies of the longitudinal modes are qui te high; direct measurement of the vibration is not easily implemented . Therefore, a passive damper is designed for possible use. The damper is mounted in the subsatellite at the end of the tether. The system w ithout the damper is neutrally stable in the gravitational field. But the in-plane subsystem will be asymptotically stable with the proper d amper design parameters. It is found that only the tether longitudinal vibration and the axisymmetric modes of the shell are effectively dam ped by the passive damper. Therefore, attitude and shape control is as sumed to result from the combination of active actuators, the tether t ension and passive damper. The LQR technique is employed to synthesize the control laws.