Estimation Enhancement by Trajectory Modulation for Homing Missiles

For bearing-only measurements used in the guidance of homing missiles, guidance laws based upon the separation of estimation and guidance do not seem to be adequate. To enhance observability, the trajectory of a bank-to-turn missile is modulated by minimizing the trace of the Fisher information matrix. The calculations for constructing this performance index are greatly reduced by noting that the required transition matrix can be obtained in closed form because, in a relative rectangular coordinate system, the missile-target engagement dynamics are linear. To show significant improvement in estimation performance, the extended Kalman estimator is tested along both the enhanced observability trajectory and a proportional navigation trajectory. A Monte Carlo analysis is performed showing that, even for large initial estimation errors in range, range-rate and target acceleration, convergence for the enhanced observability trajectory occurred within the homing period, whereas no convergence occurred for the proportional navigation path.