IN FLIGHT ESTIMATION OF ELASTIC FREQUENCIES OF MISSILES USINGEXTENDED KALMAN FILTER

摘要

Interceptor missiles, being slender, have low and lightly damped structural elastic modes. Toprevent the controller from exciting them, notch filters are usually used to remove thefrequency content of the controller's output around these frequencies. Preflight estimates ofthese frequencies (based on physical models of the interceptor or ground tests) have limitedparameter certainty; therefore the notch filters must be relatively wide which, in turn, resultsin a significant phase loss in the control loop. This article proposes a real time, in-flightmethod of estimation based on the IMU measurements. The method is comprised of pre-filtering,Kalman filtering and WLSE line-fitting. The result is an accurate estimation of thesefrequencies that enables the design of a "slimmer" notch, thus reducing phase loss.