Non-Time-to-Go Estimation Polynomial Guidance with Impact Angle Constraint

Aiming at the difficulty in estimating the remaining flight time when aircraft adopt guidance laws with impact angle constraints, a guidance law based on position polynomials is proposed. First, the aircraft's position is set as a variable-order polynomial, and the boundary conditions are determined based on the hitting accuracy requirements and impact angle constraints. Subsequently, through kinematic derivation, the analytical expressions of the polynomial coefficients are obtained. These expressions can represent the flight path angle and the variation of the line-of-sight angle solely based on the lateral position coordinates. Based on this, the acceleration command is derived. This polynomial guidance relies on position measurements that are easily obtainable in practical scenarios, avoiding the need for estimating the remaining flight time, thereby offering better practicality. The new guidance can also achieve zero terminal acceleration. Finally, numerical simulations are conducted, the results demonstrate that the proposed guidance law ensures precise terminal impact while achieving impact angle constraints, with no requirement for estimating the remaining flight time.