A STUDY ON TETHERED LANDER FOR SOFT LANDING ON A CLASS OF PLANETS WITH ATMOSPHERE

摘要

This paper studies a tethered lander which is applied to soft landing on a class of planets with atmosphere. The lander is comprised of two parts: Assisted Decelerating Module (ADM) equipped with thrusters, engines and tether system, and Payload Assembly Module (PAM) such as rovers and crew vehicles. The PAM is attached to the ADM by a tether enwinding around a windlass. The ADM suspends the PAM from above and lowers it to the surface via the tether. The dynamics of tethered lander is modeled under some assumptions. Two controllers based on fuzzy control and variable structure control theories are designed respectively to command the decelerating engines' on or off and to regulate the tether's tension. In order to illustrate a representative soft landing on planets with atmosphere, the surface wind is also considered. Numerical simulations for soft landing on the Mars are fulfilled. The results show that the proposed controllers applied to the tethered lander can prevent the lander from damaging by rocks and ejecta of engines due to ground interference, the PAM could be lowered to the Martian surface safely, and the ADM is sacrificed at a site far from the PAM. Therefore, it is feasible that the tethered lander would be adopted for soft landing on a class of planets with atmosphere.