Predictive guidance for interceptors with time delays

Predictive guidance equations for systems with time delays are developed using optimal control theory to obtain interceptor steering gains. Previously, predictive guidance and proportional navigation, which are essentially the same, employed a steering policy based on instantaneous interceptor response. In this paper the time response of the interceptor is approximated by a linear first order time lag, and the optimal steering gain is evaluated using a quadratic penalty function. The optimal control for interception is determined to be a linear function of the predicted position error and the acceleration error. The gains are functions of only the time-to-go and the interceptor time constant. An application with computer simulations is included for interception of a non-maneuvering target. The simulations demonstrate a significant improvement of interceptor performance using the optimum gains in comparison to the conventional gain of proportional navigation.