SDRE based impact angle control guidance law considering seeker's field-of-view limit

The terminal impact-angle-control guidance problem of a homing missile with a physical constraint on seeker's field of view (FOV) limit is considered. The problem is formulated as an infinite horizon non-linear regulator problem with a state constraint, and solved using an extension of the State Dependent Riccati Equation (SDRE) method: first a baseline SDRE controller is designed without taking into account the state constraint, and then a SDRE regulator is designed augmenting the cost functional to take into account the state constraint and the base-line performance. In our design, the state weighting matrix Q is chosen to be a function of time-to-go to include the distance information between the missile and target, and the input weighting matrix R is designed to be a function of the distance of the constrained state to the allowable boundary. Numerical simulations are carried out for different impact angles and seeker's FOV limits, the results of which verify the effectiveness of the proposed guidance approach.