Adaptive Polynomial Guidance With Impact Angle Constraint Under Varying Velocity

Considering the velocity of the missile cannot remain constant in most applications due to the effect of aerodynamic drag and thrust, a feasible adaptive impact angle control guidance law under varying velocity is proposed. The design of the guidance command is transformed into the design of the flight path angle, which is proposed as a general polynomial function of time-to-go with unknown coefficient. In addition, the unknown coefficient can be acquired from the boundary condition of the position. To cope with unpredictable disturbances, the adaptive scheme to initialize and recalculate the control parameter at each time step is also adopted. First, the guidance law is proposed with constant velocity. Then the law is extended to a more practical situation by considering varying velocity, and the estimation of time-to-go under varying velocity is proposed. Different simulations are carried out to verify the performance of the proposed guidance law.