Unified Practical Finite-Time and Prescribed Performance Attitude Control for Hypersonic Flight Vehicles

This paper presents a unified practical finite-time and prescribed performance attitude control scheme for the attitude tracking of hypersonic flight vehicles (HFVs). To achieve the integrated performance without introducing additional design complexity, a unified control law is constructed utilizing the super-twisting sliding mode technique. By embedding the discontinuous terms within the integral action, the continuity of the control signal is maintained. The parameter conditions for the practical finite-time tracking and the prescribed performance tracking are established based on the Lyapunov theory and the positive system theory, respectively. Particularly, the prescribed performance tracking is achieved by guaranteeing the non-negativity of the distance vectors from the tracking error to the performance boundaries, and a simple framework is established for the non-negativity analysis of these distance vectors. Numerical simulations substantiate the effectiveness of the proposed control scheme, demonstrate its advantages compared to the existing ones, and evaluate its robustness with respect to the underestimation of uncertainty bounds and actuator saturations. Note to Practitioners - The attitude control of hypersonic flight vehicles (HFVs) necessitates rapid command tracking while satisfying state constraints to ensure flight safety. To address this challenge, this paper presents a low-complexity unified practical finite-time and prescribed performance control scheme. Based on the super-twisting sliding mode technique, the proposed controller guarantees the continuity of control signals. Furthermore, by leveraging the positive system theory, the scheme circumvents the singularity issue inherent in conventional transformation-based prescribed performance control (PPC) approaches. The primary merit of this scheme lies in its simplicity and flexibility; practitioners can tune parameters to ensure either convergence speed, prescribed performance, or both, according to specific mission demands. Similar to existing positive system theory-based PPC approaches, the proposed scheme relies on the prior knowledge of initial conditions; if the initial state is uncertain, it is advisable to set relatively conservative performance envelopes. While presented in the context of HFV attitude control, this scheme is equally applicable to other engineering systems characterized by strict state constraints and rapid tracking demands.