Coupling characteristics analysis for the disturbance free payload spacecraft

In the Disturbance-Free-Payload (DFP) architecture spacecraft, the payload-module (PM) and support-module (SM) are mechanically separated such that the disturbances and vibrations from the SM can be perfectly suppressed. However, the back-Electromotive-Force (back-EMF) of the non-contact actuators and the stiffness of the cables connecting the PM and SM can cause the coupling between the PM and SM. This paper analyzes the coupling characteristics in detail. To understand the coupling essentially, the coupling dynamics model of the DFP spacecraft is established using the combination of the Newton-Euler method with the Lagrange formulation. Then, the displacement transfer function from the SM platform to the PM platform is derived by considering the coupling dynamics equation as a second-order non-proportionally damped system, and a numerical example is developed to analyze the coupling characteristics in the time and frequency domain. The results illustrate that cross coupling exists between the PM and SM, and the low-frequency excitation on the SM will affect the PM obviously. In addition, the larger back-EMF coefficient can cause the more obvious coupling effect on the PM, while the coupling effect caused by the cables is related to the frequency of the excitation on the SM.