Feedback Control for a Pursuing Spacecraft Using Differential Dynamic Programming

Near-optimal feedback controls for minimax-range pursuit-evasion problems between two constant-thrust spacecraft are generated by periodically resolving the differntial game based on the actual system state using a modified version of a first-order differential dynamic programming algorithm. Compared to a previously developed technique that requires the backward integration of a matrix Riccati differential equation, this new technique can be implemented in real time much more easily, and it requires only a rough estimate of the optimal controls to start it instead of a complete two-point boundary-value problem solution. Numerical results are presented which illustrate the advantages and limitations of this new technique.