Non-Singular Fast Terminal Sliding Mode Attitude Control for Rocket First Sub-Stage Parafoil Recovery

In this paper, the non-singular fast terminal sliding mode attitude controller is proposed for the parafoil recovery of the rocket first sub-stage separator. Non-singular fast terminal sliding mode control (NFTSMC) is widely applied in nonlinear systems that require high-precision control and rapid convergence. It combines the advantages of sliding mode control (SMC) and fast terminal sliding mode control (FTSMC), addressing the limitations caused by singularities. As a result, NFTSMC is an effective control strategy well-suited for parafoil system that provides robustness and fast response without encountering the instability issues typical of singular points. This paper designs a non-singular fast terminal sliding surface and provides a detailed derivation of the attitude controller for the parafoil system. The stability of this control method is demonstrated using Lyapunov stability theory. and finally, compared with the traditional SMC through digital simulation, the simulation results show that the controller designed in this paper possesses smaller error, faster convergence speed, and better control effect, which verifies the feasibility of the controller and superiority of the design.