Dynamic Modeling of Relative Motion for Disturbance-Free-Payload Spacecraft

In the disturbance-free-payload (DFP) spacecraft, the relative motion between the payload-module (PM) and support-module (SM) should be researched to meet the requirements of the non-contact actuators. In this paper, the six-degrees-of-freedom relative dynamics model between the PM and SM is established. Focusing on the DFP spacecraft with a hexapod cubic DFP interface, the forces and torques acting on the PM and SM are analyzed. Then, the rotational dynamic model of the SM relative to the PM and the translational dynamics model of the PM relative to the SM are established considering the characteristics of the relative motion between the PM and SM. Furthermore, the control system of the DFP spacecraft is designed based on the proportional differential (PD) control. The simulation results show that the relative motion of the DFP spacecraft can satisfy the requirement of the non-contact actuators, whether it is pointing or maneuvering. This illustrates that the non-contact actuators can separate the PM and SM and control the PM simultaneously, and reveals the significance of the dynamic modeling of the relative motion for investigating the DFP spacecraft.