Analysis of liquid fuel sloshing on free-floating robot dynamics under low-gravity condition

This paper analyses the impact of liquid fuel sloshing on the dynamics of a free-flying space robot, subject to low-gravity conditions. To date, no research and investigations were made to combine liquid fuel sloshing with free-floating robot dynamics. Thus, typical robotic motions for such a mission were analyzed and simulated first as rigid body motions. The satellite motion which results from the reaction to the robotic dynamic coupling was used as input for a dedicated computational fluid dynamics analysis (CFD). For slow motions, the results show relevant influence to the free-floating robot dynamics. However high dynamic motions, as they are needed for example for on-orbit dynamic identification, show a significant influence. Free-floating robot simulations with worst case configurations obtained from the CFD analysis showed a significant influence on the performance. Additionally a pendulum and a spring-mass model as equivalent mechanical model (EMM) were used for comparison with the CFD results. A nonlinear parameter identification was carried out to match the EMM models to obtain the same sloshing characteristics as the CFD results.