Dynamics modeling and trajectory tracking control of space tether system

The tethered sub-satellite for long distance deployment is researched, the dynamic equations of a space tether system in inertial frame are established using Newtonian mechanics principle, which takes the features of control mechanism and elasticity and mass of the tether into consideration. The nominal trajectory and nominal tension control law is achieved by employing optimization theory, and in order to track the nominal trajectory, a proportional and differential controller based on the consideration of control restrictions is designed to adjust the tension. This method is tested by numerical simulation based on the long distance deployment missions, and the motion laws of tether vibration and sub-satellite moving are analyzed during tether deployment. Simulation results demonstrate that the model efficiently reflects the dynamic characteristics of space tether systems, and the controller enables tether deployment to track the nominal trajectory accurately. These results may provide ideas on control and release strategy for long space tether systems.