Design of a modern pitch pointing control system

The development of a pitch pointing control system for an advanced high performance fighter aircraft using eigenstructure assignment and command generator tracking schemes is presented. A desired eigenstructure is first chosen to achieve a desired decoupling (i.e., pitch attitude and flight path angle), and to obtain a desired damping and rise time. The command generator tracker is next used to ensure zero steady-state error-to-step commands. The stability robustness to the parameter variations of the closed-loop system is evaluated in the sense of the conditioning of the achieved eigenstructure by using singular value analysis technique. The analysis and synthesis techniques for the pitch pointing control system are illustrated by applying the techniques to F-15 aircraft as a part of the NASA/USAF program named ACTIVE (Advanced Controls for integrated Vehicles)     

Gravity modeling in aerospace applications

The science of inertial navigation has evolved to the point that the traditional gravity model is a principal error source in advanced, precise systems. Specifically, the unmodeled vertical deflections of the earth's gravitational field are a major contributor to CEP (circular error probable) divergence in precise terrestrial inertial navigation systems (INS). Over the years, several studies have been undertaken to the development of advanced techniques for accurate, real-time compensation of gravity disturbance vectors. More complex on-board gravity models which compute vertical deflection components will reduce the CEP divergence rate, but imperfect modeling due to on-board processing limitations will still cause residual vertical deflection errors. In order to eliminate or reduce gravity-induced errors in the INS requires measurement of gravity disturbance values and in-flight compensation to the inertial navigator. It is assumed in this paper that gravity disturbance values have been measured prior to the airborne mission and various techniques for compensation are to be considered. As part of a screening process in this study, several gravity compensation techniques (both deterministic and stochastic models) were investigated. The screening process involved identification of gravity models and algorithms, and developments of selection criteria for subsequent screening of the candidates.     

Tracking an incoming ballistic missile using an extended interval Kalman filter

The important tracking problem by radar of an incoming ballistic missile system, which contains uncertainty in modeling and noise in both dynamics and measurements, is studied. The classical extended Kalman filter (EKF) is no longer applicable to such an uncertain system, and so a new extended interval Kalman filter (EIKF) is developed for tracking the missile system. Computer simulation is presented to show the effectiveness of the EIKF algorithm for this uncertain and nonlinear ballistic missile tracking problem.