Appointed-time-control-based three-dimensional parallel approaching guidance for intercepting maneuvering target

This study presents an improved guidance method consisting of the parallel approaching guidance (PAG) and the appointed-time-control-based guidance for addressing the challenge of the three-dimensional guidance with maneuvering target. The relative kinematic equations of the guidance system are divided into the line-of-sight (LOS) angle subsystem and the relative velocity subsystem. For the LOS angle subsystem, the nonsingular finite-time backstepping control (NFTBC) based guidance method is proposed to converge the LOS angles to achieve the PAG. To solve the issue of the singularity and ensure the continuity of the guidance law, a segmented function is designed to obtain the virtual control and further derive the NFTBC. For the relative velocity subsystem, the appointed-time-control-based guidance method is applied with the utilization of the time-to-go to achieve the successful interception at an appointed time for the missile against the target. Besides, the finite-time nonlinear disturbance observer is developed to estimate the target maneuvers. Furthermore, the Lyapunov stability theory is utilized to demonstrate the stability of the closed-loop guidance system. Finally, the simulations of the three-dimensional guidance system are implemented to verify the effectiveness of the proposed method.