Prescribed-Time Chattering-Free Sliding Mode Guidance Law With Terminal Angle Constraint Based on Periodic Delayed Feedback

This article proposes a prescribed-time chattering-free sliding mode guidance law with terminal angle constraint based on periodic delayed feedback. First, a prescribed-time sliding mode guidance law is presented based on a periodic delayed sliding mode surface, which can ensure the prescribed-time convergence of both the line-of-sight angular rate and the line-of-sight angle. Second, a prescribed-time extended state observer is proposed to acquire the precise disturbance estimation within the prescribed settling time. In contrast to other finite-time or fixed-time disturbance observer, the convergence time of the proposed observer is concise and easy for tuning. Finally, by incorporating the estimated disturbance into the original prescribed-time sliding mode guidance law, a composite guidance law with prescribed-time convergence is developed, where chattering is completely eliminated. In particular, the convergence time of the proposed prescribed-time extended state observer and prescribed-time sliding mode guidance law can be arbitrarily assigned and prescribed in advance. A series of numerical simulations are carried out to verify the efficacy of the proposed guidance law.