Adaptive sliding‐mode control for spacecraft relative position tracking with maneuvering target

Abstract

SummaryThis paper considers the adaptive sliding‐mode control (ASMC) problem of spacecraft relative position tracking with maneuvering target in the presence of external disturbance and unknown mass property. Integrated with the spacecraft absolute orbit dynamics, the line‐of‐sight–based relative position motion model is established; further, the problem is formulated in the general mechanical second‐order form with unknown mass parameter and matching disturbance, which makes it convenient to use some useful physical properties in the control law design. As a stepping‐stone, the traditional ASMC law is proposed without prior knowledge of uncertainty/disturbance bound. Then, incorporated with the smooth‐projection algorithm and equivalent‐control‐dependent gain method, the modified control law is proposed, which can force the mass estimate to remain in a desired domain and efficiently overcome the drawback of the overestimation of the disturbance in the traditional ASMC law. Within the Lyapunov frame, the bounded stability is presented in the real case that the sign function is replaced by the hyperbolic tangent function. Finally, three different simulation cases are presented to show fine performance of the modified ASMC law.