Dynamics and Control of Tethered Antennas/Reflectors in Orbit

摘要

A momentum exchange controller where the time rate of change of the flexiblemomentum relative to the rigid body motion is used as a part of a feedback control law for maneuvers and flexible vibration suppression is introduced. This control concept is applied to: (1) a model of a rigid hug (based) with a canti-levered flexible appendage undergoing a single axis maneuver; and (2) as a component of an adaptive feedback control strategy for the retrieval of an orbiting tethered antenna/reflector system. The optimal linear quadratic Gaussian (LQG) digital control of the orbiting tethered antenna/reflector system is analyzed. The flexibility of both the antenna and the tether are included in this high order system model. With eight point actuators optimally positioned together with tether tension modulation it is seen that the degree of controllability is very high. A method of measuring tether transverse motions is proposed and is required to guarantee system observability. An analytical formulation for the modelling of the solar radiation disturbance on the tethered antenna/reflector system is introduced. A control law based on tension modulation where the gains are based on the linear quadratic regulator theory is able to maintain satisfactory pointing accuracy for low and moderate altitude orbits under the influence of solar pressure. For the higher altitudes a combination of tether tension modulation together with active (actuator) control will be required. Dynamics and control; Orbiting/reflector.