Fast Terminal Sliding Mode Control for the Soft Landing of a Space Robot on an Asteroid Considering a Barycentric Gravitational Model

This study aims to control a space robot s soft-landing trajectory on the asteroid EROS433 considering a weak, yet effective gravitational field. As the research innovation, the study employs a fast terminal sliding mode control (FTSMC) to manage the landing trajectory and enhance the dynamic tracking performance for the soft landing of the space robot on the asteroid. This controller can ensure that the system modes are positioned on the sliding surface within a limited time. As an advantage over the PD sliding mode controller, the proposed controller raises the speed and improves the accuracy of tracking the desired trajectory and enhances the robustness of the control system. The study further compares the results of simulations performed in MATLAB to evaluate the proposed controller design. The results show that the absolute error value for FTSMC is significantly lower than the PD sliding mode controller, and when the sign function is replaced by a hyperbolic tangent, it makes the system behavior smoother and reduces the oscillations.