Global positioning system receiver tracking-loop optimisation via an H∞ approach

The application of H_∞ optimal control theory to global positioning system receiver tracking loops is investigated. The design of an H_∞ controller for the receiver tracking-loop is presented. The H_∞ controller is particularly attractive because it is a robust design in the sense that small disturbances lead to small tracking errors. Furthermore, it easily accommodates the inclusion of plant uncertainties as part of the plant model. By adding unstructured or structured perturbations to the plant model, it is possible to design controllers that ensure stability robustness and performance robustness of the closed-loop system. In order to apply the H_∞ optimal design, the GPS receiver tracking loop is rewritten into a two-input two-output generalised plant model. Various levels of disturbances are derived using a software-based GPS L5 signal generator which are then used as test inputs to evaluate the performance of the proposed tracking loop.