Data-driven method for impact time control based on proportional navigation guidance

A data-driven impact-time-control guidance (DD-ITCG) method based on proportional navigation guidance (PNG) is presented in this study, in which the assumption of constant velocity adopted in previous reports is not necessary, and it is applicable to cases with significant velocity changes. The motivation of the presented DD-ITCG is that, for a given flight state vector (FSV, including position and velocity) and a given target position, the PNG trajectory from this FSV to this target as well as the corresponding PNG time-to-go (TGO) are determined. Based on this fact, a database including input FSV and output of PNG TGO is built. At a time instant in DD-ITCG, there are two TGO quantities, one is PNG TGO of PNG trajectory, and the other one is the required TGO. Hence there is a TGO error between PNG TGO and required TGO. Then a TGO error rate with opposite sign of TGO error is set to decrease the TGO error to zero. The relation between the TGO error rate and the DD-ITCG commands is analyzed, based on which the DD-ITCG commands are computed by virtue of the database. Case studies of a hypersonic flight vehicle impact time control show the performances of the presented DD-ITCG method, and some observations in these case studies are discussed.