Time-varying line-of-sight rate estimator with a single modified tracking index for RF homing guidance

Abstract

A practical time-varying line-of-sight (LOS) rate estimator is proposed for surface-to-air missile (SAM) guidance using an RF seeker. The range-dependant LOS rate dynamics and variances of boresight error (BSE) measurements constitute the Kalman filtering problem associated with the timevarying matrix differential Riccati equation (DRE). Since the conventional gain-scheduled steady-state Kalman filter derived by solving an algebraic Riccati equation (ARE) cannot fully consider the timevarying nature of LOS rate dynamics, it might not be appropriate for volatile missile-target engagement scenarios. This motivates us to investigate a pseudo-analytic solution to the time-varying Kalman filtering problem based on the algebraic transform of the given DRE. Apart from the previous works, the explicit form of time-varying Kalman gain is expressed in terms of a single filter design parameter, called modified tracking index. The proposed time-varying filter is not only able to effectively handle the time-varying LOS rate dynamics but is also affordable for real-time implementation. Adjoint analysis results for a homing guidance loop show that the proposed LOS rate estimator could improve guidance performance and be an excellent choice for SAM applications.

Robust finite-time line-of-sight angular rate estimation in missile guidance

“…To further improve the performance of the results in Faruqi et al. 10 and Rusnak, 11 Ra and Whang 12 derived a new pseudo-analytic LOS angular rate estimation filter, whose gain was a function of the sole design parameter.…”

“…Since the LOS dynamics is highly time varying for air-to-surface missile, where conventional gain-scheduled steady-state Kalman filter 8,9 is usually not feasible, the authors 10,11 proposed a pseudo-timevarying Kalman filtering algorithm to overcome this problem. To further improve the performance of the results in Faruqi et al 10 and Rusnak, 11 Ra and Whang 12 derived a new pseudo-analytic LOS angular rate estimation filter, whose gain was a function of the sole design parameter.…”