Predictive control of teleoperation rendezvous with large time delay

Abstract

Teleoperation rendezvous and docking (RVD) means the RVD mission to be performed is at a distance from the controllers, which can be used as a backup for autonomous rendezvous for an unmanned spacecraft or for guiding the chaser docking with an uncooperative target. However, due to the time delays caused by distance and computer processing at spacecraft and ground stations, stability and control performance of the teleoperation rendezvous system are seriously affected. For spacecraft in a low earth orbit, the time delays may approach 6s. To eliminate the effect of time delay, a predictive control algorithm is investigated in this paper. The control issue of teleoperation RVD is described first, and the composing of time delay is analyzed. Then a predictive model is built based on the Clohessy-Whiltshire equations, and the processed measure information through time delay is utilized to correct the predictive relative states of the spacecraft. After that, a phase plane control method is introduced to teleoperate the chaser rendezvous and dock with the target. At last, a semi-physical simulation system is developed, and experiments are carried out with different time delays to verify the methods presented in this paper. The results show that the predictive control is effective on alleviating the time delay during the process of teleoperation RVD, and the success probability and control precision can be improved. Teleoperation RVD using this method can be applied as a useful backup for autonomous RVD.