G Papageorgiou

Guaranteed multi-loop stability margins and the gap metric

The gap metric and nu-gap metric have many appealing properties for assessing the uncertainty in a plant in a feedback configuration. This short paper addresses the question of relating these generalised stability margins to more traditional single-loop and multiloop robustness measures. In particular we show that when a system is controlled by a controller which provides a stability margin of /spl epsiv/ in the gap metric for the weighted plant then if the weighting matrices are diagonal the plant will have robust stability to easily interpreted simultaneous gain and phase variations at all the inputs and outputs.

Taking robust LPV control into flight on the VAAC Harrier

Describes the application of a multivariable control system design procedure, linear parameter-varying (LPV) H/sub /spl infin// loop shaping, to design a flight controller for the pitch dynamics of the vectored thrust aircraft advanced flight control (VAAC) Harrier. The particular LPV design procedure used was developed by Papageorgiou and Glover (2000) and is an advancement of the H/sub /spl infin// design method successfully flight tested in 1993 on the VAAC Harrier in that the control laws are automatically scheduled over the flight envelope. Automatically scheduled control laws are a strong and very likely candidate for the next generation of flight control systems (FCS). The flight test of the LPV controller described here is the first of its kind in the international aerospace community and is recognised as a key milestone in the general development of next generation FCS design methods.

A systematic procedure for designing non-diagonal weights to facilitate /spl Hscr//sub /spl infin// loop shaping

The first step of the /spl Hscr//sub /spl infin// loop shaping design procedure is to specify desired closed loop performance by shaping the singular values of the nominal plant with a pre- and/or a post-compensator. Designers usually choose diagonal weighting functions but it is not always possible to obtain the desired loop shape with diagonal weights. This paper develops a systematic procedure for designing nondiagonal pre- and post-compensators. Such nondiagonal weighting functions enable the designer to shape each singular value of the nominal plant separately. To illustrate the procedure an /spl Hscr//sub /spl infin// loop shaping controller is designed for a plant whose singular values can not be shaped accurately using diagonal weights.

Design, development and control of the HIRM wind tunnel model

The flight envelope and configuration of fighter aircraft is changing, and designing flight controllers for the next generation fighters will be a challenging problem. A wind tunnel model has been built to help develop and evaluate flight control laws. The rig design and its simulation model are described in some detail. A linear time-invariant controller is designed for the rig using H/sub /spl infin// loop shaping. The controller is flight tested and very satisfactory performance is achieved.