SDRE guidance law for impact angle control against moving targets

In this paper, the terminal guidance problem of intercepting a moving target along a predetermined direction in the planar engagement scenario is considered. In this problem, two design specifications must be achieved: one is the minimum miss distance; and the other is the specified terminal impact angle. This problem is formulated as an infinite-horizon nonlinear regulator problem, and solved using the state-dependent Riccati equation (SDRE) method. To obtain a finite-horizon guidance law, a time-to-go based state weighting matrix is employed in the SDRE control scheme. In addition, to maintain the missile and the target in collision course and reduce the time-of-flight, the missile-target relative look angle is restricted using the SDRE control with a state constraint. Nonlinear simulations are performed to demonstrate the basic properties, applicability and robustness of the proposed guidance law.