Emulating Scaled Clohessy–Wiltshire Dynamics on an Air-Bearing Spacecraft Simulation Testbed

摘要

This work addresses the problem of experimentally reproducing the orbital relative motion on a planar floating spacecraft simulator testbed. Floating spacecraft simulators are characterized by double-integrator dynamics on their three degrees of freedom. In this paper, the Clohessy–Wiltshire planar dynamics is scaled down, and it is emulated using an autonomous floating vehicle actuated using compressed-air thrusters. The dynamics scaling criteria are determined through the use of the Pi theorem; subsequently, the problem of accurate actuation of the equivalent transport acceleration and Coriolis acceleration is solved. Three different thrust modulation strategies (namely, pulse-width modulation, delta sigma modulation, and hybrid pulse-width delta sigma modulation) have been used to achieve an accurate conversion of the requested continuous-thrust time histories into sequences of actuated fixed-thrust pulses. The performances of the resulting system are evaluated through a set of simulations by comparing the nominal spacecraft trajectories with the correspondent equivalent floating simulator trajectories. Finally, a set of experimental results is presented.