Closed-Form Time-to-Go Estimation for Proportional Navigation Guidance Considering Drag

A closed-form analytical method for estimating the time-to-go of a proportional guidance law guided missile is proposed. This method is effective for both stationary and maneuvering targets. It divides the missile flight process into a constant drag-lift ratio flight phase and a constant drag coefficient flight phase, so that the influence of drag can be fully considered when calculating the time-to-go. In this article, the time-to-go estimation for a stationary target is given first. Then, the maneuvering target is transformed into a stationary target by reasonably setting a fictitious target related to the target motion state and a preliminary estimation of the time-to-go for the maneuvering target is obtained. To further improve the accuracy of the time-to-go estimation for the maneuvering target, a compensation item is designed on the basis of the preliminary estimation. The simulation results show that the method proposed in this article can accurately estimate the time-to-go for various targets, and cooperative attacks can be realized by applying the time-to-go estimation to a specific cooperative guidance law.