טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentLiat Bar-Shimon
SubjectA Varying-Bandwidth Homing Estimator
DepartmentDepartment of Aerospace Engineering
Supervisor Full Professor Oshman Yaakov


Abstract

This research studies the estimation problem in maneuvering ballistic missile scenarios. Tactical ballistic missiles' high reentry speed enables maneuver capabilities. Making use of the maneuverability potential does not involve exceptional technological capabilities and, therefore, it is expected that defense systems will have to deal with highly maneuvering targets in the future. The ability to intercept non-maneuvering tactical ballistic missiles has already been established. The THAAD, PAC-3 and ARROW weapon systems have recently demonstrated hit-to-kill performance against tactical ballistic missiles .


Existing guidance laws were derived assuming perfect information, including the knowledge of target acceleration at any moment. In practice, from the defense point of view, the target acceleration is random; it cannot be measured directly and, thus, it needs to be estimated. The purpose of the estimator is to estimate the target acceleration from noisy measurements in order to improve guidance accuracy. The filtering process is not immediate. The estimator’s convergence rate and estimation accuracy depend on the scenario, the measurements noise level, and on the quality of the target's dynamic model .


The homing performance of interceptor missiles is measured by the miss distance achieved at the end of interception. Previous research shows that the main reasons for large miss distance are low interceptor/target maneuver ratio, and the delay in estimating the target acceleration. Currently, the interceptor/target maneuver ratio is low and, therefore, a fast and accurate estimation of the target acceleration is required to ensure reasonable interception probability. In order to obtain fast estimation, a high bandwidth estimator is needed. On the other hand, accurate estimation requires a low bandwidth estimator .


The objective of this research is to improve homing performance against a maneuvering target using an estimator with time-varying bandwidth . The influence of constant estimator bandwidth on homing performance is investigated numerically. A varying-bandwidth estimator is proposed to reduce the response time to changes and, at the same time, to reduce miss distances achieved at the end of interception . The homing performance achieved by applying the proposed estimator using a differential game-based guidance law is tested by Monte Carlo simulation runs. The proposed estimator is compared to other, existing, methods. The results of this investigation show that the homing performance is improved relative to that of existing state-of-the-art methods .