H ∞ Aerospace Control Design: A VSTOL Flight Application

220 Pages·1995·4.87 MB·English

by  Richard Alden Hyde

Advances in Industrial Control
Springer
Berlin
Heidelberg
New York
Barcelona
Budapest
Hong Kong
London
Milan
Paris
Tokyo
Other titles published in this Series:
Parallel Processing for Jet Engine Control
Haydn A. Thompson
Iterative Learning Control for Deterministic Systems
Kevin L. Moore
Parallel Processing in Digital Control
D. Fabian Garcia Nocetti and Peter J. Fleming
Intelligent Seam Trackingfor Robotic Welding
Nitin Nayak and Asok Ray
Identification of Multivariable Industrial Processes for Simulation,
Diagnosis and Control
Yucai Zhu and Ton Bacla
Nonlinear Process Control: Application of Generic Model Control
Edited by Peter L. Lee
Microcomputer-Based Adaptive Control Applied to Thyristor-Driven
D-CMotors
Ulrich Keuchel and Richard M. Stephan
Expert Aided Control System Design
Colin Tebbutt
Modeling and Advanced Control for Process Industries:
Applications to Paper Making Processes
Ming Rao, Qijun Xia and Yiqun Ying
Robust Multivariable Flight Control
Richard J. Adams, James M. Buffington,
Andrew G. Sparks and Siva S. Banda
Modelling and Simulation of Power Generation Plants
Andrzej W. Ordys, Andrew W. Pike, Michael A. Johnson,
Reza Katebi and Michael J. Grimble
Model Predictive Control in the Process Industry
E.F. Camacho and C. Bordons
R.A. Hyde
Hoc
Aerospace
Control Design
A VSTOL Flight Application
With 139 Figures
, Springer
Dr Richard Alden Hyde, MA, PhD
Cambridge Control Limited, Newton House, Cambridge Business Park,
Cowley Road, Cambridge CB4 4WZ. UK
Covu lIlustrtltion: Ch. 3 Fig.l. GV AM in transition to wing-borne rught
British LibruyCataloguing in Publication Data
Hyde. Richard Alden
H":Aerospace Control Design: VSTOL Flight Application. - (Advances in Industrial
Control Series) I. Title II. Series
6a9.13Sa
ISBN 978-1·4471·3051-2 [SBN 978-1-4471·3049·9 (eDoo};:)
00110.1007/978-1.-4471-3049-9
Library of Congress Cataloging in Public.ation Data
A catalog r«Ord for this book is avaibble from the Libury of Congress
Apart from any fair dealing for the purposes of research or priVllte study, or criticism or
review, as permitted under the Copyright, Designs and PatenU Act 1988, this publication
may only be reproduced, stored or transmitted, in any form, or by any means, with the
prior permiSllion in writing of the publishers, or in the cast of reprographic reproduction
in accordance with the terms oflicenct5 issued by the Copyright Licensing Agency.
Enquiries concerning reproduction ouUide those terms should be senl to the publishen.
C Springer-Verlag London Limited 1995
Softcowr ~I of the hardrovu ",I edition '995
The pu'>lisher makes no representation, expreSll or implied, with regard to the accuracy of
the information conlained in thb book and cannot accept any legal fetponsibility or
liability fOf any errors or omissions that may be made.
Typesetting: Camera ready byauthor
69/.)8lo-S43110 Printed on acid-free paper
To my parents, my brother Jon, Karen and Liz
SERIES EDITORS' FOREWORD
The series Advances in Industrial Control aims to report and encourage
technology transfer in control engineering. The rapid development of control
technology impacts all areas of the control discipline. New theory, new
controllers, actuators, sensors, new industrial processes, computer methods,
new applications, new philosophies, ... , new challenges. Much of this
development work resides in industrial reports, feasibility study papers and
the reports of advanced collaborative projects. The series offers an opportunity
for researchers to present an extended exposition of such new work in all
aspects of industrial control for wider and rapid dissemination.
The present text considers the application of one of the most successful of
the new generation multivariable control design techniques. The Hoo design
approach was partly stimulated by the need of the aerospace industry where
robustness issues and safety aspects are of particular importance. The
uncertainties in aircraft systems arise both from the variations in the system
description at different operating conditions and the disturbances affecting
the system.
Flight control system design for VSTOL aircraft is even more difficult than
for usual applications. Control of the aircraft in manoeuvres from hover to
wing borne flight pose particularly difficult multivariable highly interacting
design problems. For an effective design the system must be properly analysed
and appropriate models developed. The text introduces the basic components
of the flight control and engine systems and describes the models for the
different sub-systems.
An Hoo loop shaping robust design procedure is described and the resulting
system properties and results are analysed. Practical issues of controller
implementation such as control switching and scheduling through different
flight conditions are also considered. Problems of wind-up and the difficulties
introduced by of the complexity of the solution are discussed. The resulting
solution therefore satisfies both design requirements and can be implemented
in practice.
In Part II the implementational problems are considered further, including
the discretization process, handling limitations on actuators and the
nonlinearities in the system. This text then goes further than most in being able
to provide both piloted simulation and flight testing results.
viii Series Editors' Foreword
The Monograph is of interest not only to flight control engineers but to
designers in general industries which require a complete overview of procedures
to be followed when applying one of the latest multivariable design techniques.
M.J. Grimble and M.A. Johnson
Industrial Control Centre
Glasgow, Scotland, U.K.
PREFACE
Recent developments in 1£00 theory have produced a highly attractive design
approach. However, a large gap between theory and practice has emerged,
there being as yet very few design examples applied to real industrial con
trol problems. The work described in this monograph aims to narrow this
gap, and to address implementation issues associated with multivariable 1£00
controllers. An 1£00 control law has been developed for the DRA Bedford
research Harrier and is presented. This control law has recently undergone
preliminary flight testing.
Future aircraft are likely to have many more control surfaces than current
aircraft. To fully utilise these surfaces the pilot will have to rely increasingly
on automatic control. Conventional design techniques do not provide a sys
tematic way of designing for systems with multiple inputs and outputs. The
paradigm of 1£00 is one way of directly designing for this type of system with
out the need for successive loop closing. The Harrier provides a particularly
good design example in that it has both aerodynamic and vectored thrust
controls which result in a 3-input system. Each of these three inputs has sig
nificant coupling to each of the controlled outputs. Thus demonstrating the
1£00 technology on the Harrier gives confidence that it could be applied to
future aircraft for which a multi variable design approach may be necessary
to extract maximum performance.
Early 1£00 design examples were based on optimisation using weighted
closed-loop transfer functions. The control law presented here uses weight
ing of the open-loop frequency response to specify the desired performance,
followed by an 1£00 robustness optimisation. The optimisation uses the nor
malised coprime factor uncertainty description. A weighting selection proce
dure is developed for this design approach. Then, given a set of linear designs
which cover the flight envelope, the problem of moving from one design to
the next as the flight envelope is traversed is addressed. Conventional con
trollers typically gain schedule proportional and integral gains. Two methods
are considered for multi variable 1£00 controllers, one based on switching and
one on gain interpolation of an observer implementation of the control law.
Anti-windup schemes are also investigated, and a novel combination of using
observers and the Hanus desaturation scheme is proposed.
x
A common criticism of 11.00 is that it produces high order controllers
which are complex to implement. A design study has been carried out using
parametric optimisation of a fixed structure controller in order to investigate
the performance/complexity trade-off. The control law which was flight tested
was model reduced using balanced truncation methods.
The control law developed for the DRA research Harrier XW175 is one
of several control laws being evaluated by DRA Bedford under the Vectored
thrust Aircraft Advanced flight Control (VAAC) programme. The VAAC
Harrier and the DRA Large Motion Simulator (LMS) enable fast testing of
new control law technologies. In the simulator the same non-linear model as
used for design is flown with the control law by pilots. Once the control law
is sufficiently mature, it can then be implemented on the VAAC Harrier.
The 11.00 control law gives full authority longitudinal control for airspeeds
between the hover and 300 knots. Non-linear simulation, piloted simulation
and flight test results are presented. The development of the control law
is described in some detail, and it is intended that the text should have
some tutorial value. It is hoped that the exposition of the control law in this
monograph will help the reader apply 11.00 control to other real engineering
applications.
Richard Alden Hyde
Girton College
Cambridge
28th December 1993
Acknowledgements
The material presented in this monograph is the result of five years re
search carried out at Cambridge University Engineering Department. For
the first three years I was studying for my doctorate, and much of Part I
originates from my thesis. For the past two years I have been a Research
Associate, and all of Part II dates from this period. Funding was provided
by the Science and Engineering Research Council, and the Defence Research
Agency provided both simulation facilities and time on their XW175 research
Harrier.
The direction of my work was greatly influenced by my PhD supervi
sor, Keith Glover. Keith's encouragement and advice have been invaluable,
and the success of the project owes much to his support. I would also like
xi
to mention Steve Williams who originally motivated my interest in control
when he supervised me as an undergraduate. It was Steve who set up the
research programme between the DRA and Cambridge University. Glenn Vin
nicombe, with whom I shared an office, imparted much helpful advice when
I was designing for flight testing. All of my colleagues in the control group at
Cambridge also deserve a special mention.
I would like to thank DRA Bedford for their involvement in the project,
and providing us with access to their simulation facilities. They also provided
us with a very rare opportunity, that of actually flight testing our control law
design. The Deutsche Institut fUr Luft und Raumfahrt also very kindly gave
me the opportunity to visit them for a few months and to tryout their
software on the VSTOL design.