Ra Hyde

A comparison of different scheduling techniques for H-infinity controllers

Several approaches to designing schedule H-infinity control systems are compared. These include a controller switching approach and also parameter scheduling of an observer representation of the controller. They are illustrated by application to a Generic VSTOL Aircraft Model (GVAM) supplied by The Royal Aerospace Establishment (RAE) at Bedford. The switched design has been tested on the simulator at RAE Bedford. The linear H-infinity designs make use of a loop-shaping followed by robust stabilisation to additive perturbations of a normalised coprime factorisation of the shaped plant. The different scheduling approaches are compared with respect to achieved robust stability levels, performance and complexity of implementation.

Development of a Robust Flight Control Law for a VSTOL Aircraft

Abstract A flight control law is being developed for a VSTOL aircraft. Extensive design studies have already been carried out on a Generic VSTOL Aircraft Model (GVAM) developed by the Defence Research Agency (D.R.A.), and subsequently tested on the D.R.A. motion simulator at Bedford. This paper describes further development of these designs with a view to future implementation on the D.R.A. research Harrier. The transition between powered lift and wingborne flight considerably complicates both closed-loop control design and flight mode-design, and as such provides a very interesting design example. For linear design, the longitudinal motion of the aircraft is treated as a multivariable system, and linear controllers are designed for different operating points using the loop-shaping plus H∞ robust stabilisation procedure of Glover and McFarlane. The controllers are then scheduled using the unique observer structure associated with this design formulation. Results are presented of non-linear simulation of the controller on the GVAM model.

DEVELOPMENT OF A ROBUST FLIGHT CONTROL LAW FOR A VSTOL AIRCRAFT

A flight control law is being developed for a VSTOL aircraft. Extensive design studies have already been carried out on a Generic VSTOL Aircraft Model (GVAM) developed by the Defence Research Agency (D.R.A.), and subsequently tested on the D.R.A. motion simulator at Bedford. This paper describes further development of these designs with a view to future implementation on the D.R.A. research Harrier. The transition between powered lift and wingborne flight considerably complicates both closed-loop control design and flight mode-design, and as such provides a very interesting design example. For linear design, the longitudinal motion of the aircraft is treated as a multivariable system, and linear controllers are designed for different operating points using the loop-shaping plus H∞ robust stabilisation procedure of Glover and McFarlane. The controllers are then scheduled using the unique observer structure associated with this design formulation. Results are presented of non-linear simulation of the controller on the GVAM model.

Flight control system design for VSTOL aircraft using switched H∞ controllers

This is a design study on a Generic VSTOL Aircraft Model (GVAM) supplied by the Royal Aerospace Establishment, Bedford. Widely varying dynamics requires some form of gain scheduling or switching. The approach taken is to switch between linear controllers designed on linearisations of the non-linear model. The linear designs make use of an open-loop singular-value shaping technique developed by McFarlane and Glover (1988) and McFarlane, (1988) which optimises the system robustness to perturbations of the normalised c oprime factors of the plant. Switching between controllers is achieved using a technique proposed by Hanus, (1987) which permits smooth transition between controllers. A more detailed account of the design here can be found in Hyde, et al. (1990)..