Dynamic Modeling and Control of Disturbance-Free Payload Spacecraft

Disturbance-Free Payload (DFP) concept is a novel configuration of spacecraft. The DFP spacecraft is separated into two modules called payload and platform respectively, which are connected by non-contact electromagnetic actuators (NCEAs) and sensors. The two modules are mechanically decoupled so that most of the vibration can be isolated and the pointing accuracy of the payload can be improved. However, the relative position control between the two modules is necessarily taken into consideration. This paper addresses a relative position dynamics of the DFP spacecraft and proposes a relative position control law based on sliding mode control which effectively avoids the collision of the two modules. A PD controller is designed for the attitude tracking control of the payload. To realize the attitude maneuver of the DFP spacecraft, another PD control law is designed for the relative attitude control of the two modules. Simulation results are presented to illustrate the performance of the proposed control law.