The application of eigenstructure assignment to the design of flight control systems

Modem control methods have often been advocated by academics as able to solve fairly complex control engineering design problems in the aircraft industry. However, evidence suggests that practicei s still gearedt owardsu sing classicalt echniques,e ven on the most modem fighter aircraft which are open-loop unstable. This thesis stems from a need to understand the reasons for this. Modem methods are examined in order to determine their strengths and weaknesses when applied to industrial problems. As a representative situation, a modem control method, eigenstructure assignment, is examined. One objective of the research described in the thesis is to improve the application oriented aspects of the methodology of eigenstructure assignment. The purpose of this is that every facet of the method can then be explained in terminology that is familiar to the aircraft control engineer. Furthermore, the theory is developed such that it is compatible with easily understandable controller structures and control design strategies, to provide a control system with good performance and robustness characteristics. The design of a robust controller for a civil aircraft model developed by the GARTEUR (Group for Aeronautical Research and Technology in Europe) demonstrates the utility of eigenstructure assignment and culminates in suggestions as to when and where the method has its greatest strengths and weaknesses.