Adaptive Sliding Mode Guidance Law with Three-Dimensional Terminal Line-of-Sight Angle Constraint

This paper investigates the problem of missile interception guidance in three-dimensional space, where the missile is required to intercept a maneuvering target at a prescribed line-of-sight (LOS) angle. To address the nonlinear relative motion of the missile-target system, an adaptive sliding mode guidance law based on <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathcal{K}_{\infty}$</tex> class functions is proposed. The proposed guidance law guarantees the convergence of the LOS angle to the desired value at the interception moment without relying on target acceleration information. Furthermore, to overcome the challenges of excessive initial control input and chattering in conventional sliding mode guidance laws, saturation constraints are introduced into the adaptive gain, effectively mitigating large initial control efforts. Numerical simulations conducted under various LOS angle constraints verify the effectiveness of the proposed approach, demonstrating its capability to achieve precise target interception while ensuring LOS angle convergence. Additionally, the proposed guidance law significantly reduces control gain while maintaining interception accuracy.