Braking control law for a barbell Electric Sail

摘要

The Electric Sail is investigated here with a focus on tether deployment. The Electric Sail is envisioned to deploy multiple greater than 1 km tethers connected to a central confluence point. The barbell Electric Sail which contains two satellites and two tethers connected to a central confluence point is investigated here. The deployment process is complex and has a high likelihood of creating unnecessary vibrations. In order to deploy the satellites, kinetic energy must be introduced into the system to separate the satellites. This kinetic energy must be removed without creating significant axial vibrations or the remainder of the mission will be compromised. Creating axial vibrations will impart a significant amount of fatigue on the system or could cause the entire system to collapse on itself. A braking mechanism is envisioned to be used to remove the kinetic energy via friction. The force vs time curve of the brake is the focus of this paper by investigating different braking control laws for the barbell Electric Sail. It is shown through simulation that using a Gaussian distribution for the braking force results in the lowest residual energy in the system. This is shown by using a previously derived multibody nonlinear simulation tool coupled to a visco elastic tether bead model.