The motion decomposition of power descent section of soft landing on small bodies based on sliding mode and PD control algorithm

In view of the power descent section of soft landing on small bodies, this paper had deduced the system dynamic models of the probe near small bodies under the body-fixed coordinate system. Through the analysis of the model, we decomposed this one phase of the movement into the out-of-plane movement and in plane movement based on the orbital plane. To the out-of-plane movement, a nominal height trajectory had been projected and variable structure control (VSC) with sliding mode had been designed to track the nominal trajectory. To the in plane movement, according to the coupling of movement and the desired final state, PD controllers are designed to eliminate the deviation of position and velocity. Finally, the effectiveness of algorithms were verified by numerical simulation.