TABLE OF CONTENTS This chapter describes how multvariable control has been applied to the Defence Evaluation and Research Agency (DERA) Bedford Harrier and flight tested [1] The work was carried out as a research study at Cambridge University Engineering Department [1-3] between 1988 and 1993. At that time there were significant advances in the so-called H ? (pronounced H-infinity) control design method [4]. The advent of numerically well-conditioned solutions to the H ? optimisation problem such as Reference [4], and the increase in computing power made the design technique a very viable alternative to more classical methods. However, there was a huge gap between the elegant theory and producing a control law suitable for implementation on an aircraft. In particular, the linear controllers produced were high order, and it was not clear how to gain schedule them with flight condition. The aim of the research programme was to narrow this theory-practice gap. The first phase investigated the design and implementation issues associated with multivariable optimal controllers, and resulted in a control law for the DERA generic VSTOL aircraft model (GVAM). Based on the success of this, DERA and the Science and Engineering Research Council (SERC) funded a two-year follow-on phase at Cambridge University to develop a control law suitable for flight testing on the DERA research Harrier under the vectored thrust aircraft advanced flight control (VAAC) programme.
The H ? method is what is known as a robust multivarible design method. The term multivarible...
