become much more acute when one attempts to deal withsystems which, like most of those encountered in this book,involve human behaviour as an essential component. It maybe that only a qualitative analysis is appropriate, or evenpossible, in this context.

Nevertheless, the book succeeds in illustrating how thequantitative methods of optimisation theory can be usefullyapplied even in such areas. A welcome feature, also, is theinterdependence established between many of the chapters,despite their varied authorship, so that, for example, thefinal article draws on those preceding it for much of its illustra-tive material. Knowing from personal experience the difficultiesof achieving coherence in a multi-authored work of this kind,I feel that the Editor deserves congratulation.

P.A. COOK

Elements of computer process control with advanced controlapplicationsP.B. Deshpande and R.H. AshInstrument Society of America, 1981, 382 pp., £21.35ISBN: 87664-449-3

From the title, one would be expecting this book to give areasonably well balanced review of all aspects of computercontrol in the process industries. However, a very brief scanthrough the book reveals a heavy bias towards mathematicalanalysis and less emphasis on the hardware and softwareaspects of computer control.

To be more specific, the opening chapter gives a briefreview of classical control; to appreciate this and subsequentchapters, a good working knowledge of Laplace transformsis essential. Chapter 2 covers hardware and software, whilethe following ten chapters cover what is best described assampled-data control theory; the final five chapters comingin part II, devoted to 'advanced control concepts'.

The essentials of the hardware and software are coveredin chapter 2, and much of the 'jargon' is introduced; un-fortunately, it is crammed into a mere 36 pages althoughthe book has some 380 pages. There is insufficient treatmentof the software organisation associated with online computercontrol systems, and the whole chapter lacks depth. I wouldhave expected at least half of the book to have been devotedto the hardware and software aspects.

The section of the book covering sampled-data theoryand system analysis can be found in a number of other texts(which are referenced). However, it does give a more practicalviewpoint than is found in most other texts. Throughout itrefers to 'PID control', the mainstay algorithm of the processindustries, together with guidelines on selection of samplingrates, a discussion on digital filtering and dead-time algorithms,including the Smith predictor.

Part II examines process modelling and identification,together with a discussion of feedforward and cascade control.This section gives a good review of these standard techniquesas applied in the process industries. However, it has not beenwritten with particular reference to computer control andcould equally well apply to conventional analogue control.

This book would give the reader unfamiliar with computercontrol concepts in the process industries a good appreciationof the factors involved. It would be suitable for final yearstudents, and the industrial user wishing to delve further intothe theory. However, it cannot be considered a completetext on computer control in the process industries becauseof its scant treatment of the hardware and software aspects.

D. ROBINSON

Modelling of dynamical systems Vol. 1H. Nicholson (Ed.)Peter Peregrinus, 1980, 227 pp., £24.25ISBN: 0-906048-38-9This book is the first of two volumes on the subject ofmathematical modelling of dynamical systems. The systemsconcerned arise from a wide range of research interests, butthey all have one common attribute: that of being modelled interms of sets of ordinary or partial differential equations.

The mathematical modelling of systems requires consider-able understanding of the processes involved; hence it may atfirst be thought by the reader that a book on the subjectwould be difficult to read and understand. This possibilityappears to have been recognised by the contributors to thisvolume, for each chapter carries its own introduction to theunderlying principles in the modelling methods presented.

There are seven chapters in the book. The first chapter givesan introduction to the principles of model building in general,covering such aspects as material and energy balances, lumped-parameter modelling analogues, distributed systems, processtime and transport delays, linearisation techniques and systemidentification. The treatment is necessarily short, but manyreferences are given for further reading.

The next five chapters are devoted to the modelling ofvarious engineering systems, and the last chapter is concernedwith biological system modelling. The categories covered inthe contributions on engineering systems represent a very goodcross-section of the types of modelling problem one couldcome across in engineering. Chapter two concerns the modellingof chemical process plant, and the application to severalchemical engineering unit operations is concerned. The maincharacteristic evident in this type of model is the distributednature of the systems concerned. This leads to considerationof the use of linearisation to yield suitable transfer functions,and incidentally, to check the 'goodness' of plant design.

The third chapter, modelling of refrigeration and air-conditioning systems, gives the reader an introduction to theproblems of modelling two-phase flow dynamics applied toevaporators and condensers in refrigeration plant. The secondpart of the chapter covers the modelling of a complete air-conditioning system followed by discussion of the problemsof modelling the air conditioning of buildings.

Chapter four concerns the modelling of the spatial kineticsof neutron flux and power density in a somewhat idealisednuclear reactor. This is a distributed-parameter system thatdiffers from the chemical plant systems discussed earlier, inseveral important respects:

(a) More than one space dimension is considered.(b) The assumption of an axis of symmetry allows use of

polar co-ordinates for a cylindrical representation of thereactor.

(c) More than one type of symmetry can be considered.These complications ensure that the modelling of nuclearreactors in this way is very different from other distributedsystems.

A very important area of mathematical modelling is coveredin the fifth chapter, namely the treatment of the dynamics ofcontrolled flight. A glossary of terms is given to try to coverthe lengthy terminology involved, and the reader is takenthrough the stages of applying the traditional two-partmodelling process to various examples of aerospace systems.By contrast, the sixth chapter deals with marine systems.Although there is similarity with the previous chapter, con-cerning a rigid body moving through a fluid, the effect ofnonlinearities has to be taken much more into account if goodmodelling results are to be obtained. There is also some dis-cussion of the problems to be faced in using system identifi-cation techniques.

IEEPROC, Vol. 129, Pt. D, No. 4, JULY 1982 143

The final chapter of the book is very different from therest. The modelling of biological systems is probably the mostdemanding modelling task that could be undertaken, sincethere is no engineering design to serve as a starting point, andthere is a great deal of interaction of one biological subsystemwith another, usually in a highly nonlinear way, and thiscauses problems of trying to divorce a subsystem under studyfrom others around it. The examples presented show theproblems of achieving good identification of the model par-ameters from a variety of measurements, and of the use of thedata obtained in forming an adequate model of the biologicalprocess being studied. It is a pity that more space could nothave been devoted to biological modelling, but a long referencelist seeks to remedy the deficiency.

Although the spectrum of modelling applications discussedin this book is wide, there are notable omissions from thematerial covered, namely the modelling of economic andsocial systems. The use of dynamical system modelling isgrowing in these areas, and it must be said in conclusion that itis to be hoped that the omissions will be rectified in thesecond volume of the series.

Self-tuning and adaptive control: theory and applicationsC.J. Harris and S.A. Billings (Eds.)Peter Peregrinus, 1981,333 pp., £13.50ISBN: 0-906048-62-1

The main objective of this compendium of articles is toprovide an overview of existing techniques of self-tuning andmodel-reference control and their relevance to industrialimplementation. It is the outcome of the first Oxford IEEAdaptive Control Workshop held in March 1981. The papersnow published are rather better than what was available at theWorkshop, but nevertheless the Conference itself was verysuccessful in attracting industrialists, which was reflected inthe pragmatism of the ensuing discusssion. Some flavour ofthis happily comes through into the publication, which shouldencourage further industrial application of adaptive control.The book provides a comprehensive review of the state of playbut largely of a tutorial nature. Industrialists may questioneven now whether the technique of self tuning is yet in a fitstate for full-scale implementation. Certainly some preproduc-tion work remains to be done, raising the awkward question ofwho is to pay for this.

The book quite rightly does not try to answer this knottyproblem, but provides a fully documented background for theserious student wishing to get into the modern and attractiveforms of adaptive control, such as self-tuners, that have nowbecome economically viable thanks to the advent of cheap andreliable microelectronics.

The introductions to adaptive control and self-tuners arecomprehensive and pitched at an appropriate level. These arefollowed by a number of more specialised topics dealt with ingreater length in separate chapters on subjects such as stabilityand convergence of adaptive systems, generalisation into multi-variable self tuners, model-reference adaption and design withvariable structures. Included is an excellent chapter on practicalimplementation of self-tuning controllers with hints concerningthe importance of efficient programming and the significanceof numerical stability in the use of estimation algorithms withsmall word-length computers. The whole is rounded off withlessons from a briefly reviewed range of applications.

A sensible proportion of the chapters are devoted to goodaccounts of some real applications of self-tuning given inreasonable practical detail. Topics covered in this way includecontrol of distillation column compositions, control of gasturbine engines, course keeping and manoeuvring of surfaceships and dynamic positioning of ships.

In summary, the volume represents a useful statement on a

topic of rising interest at a relevant level of presentation. Thechapters split more or less equally between introductorytheory, specialist topics and specific applications, there beingabout five of each. For a topic that has been around for a longtime but has suddenly achieved a new lease of life thanks tomodern electronic hardware, this forms a useful and balancedstatement. In view of the fact that each chapter is written by adifferent set of authors, the book hangs together surprisinglywell, which is a credit to the editors. For those who feel theremight after all be something in this adaptive control stuff buthave not the time to winkle out the detailed story fromproceedings, this volume performs a valuable service inpresenting a reasoned collation of material. Students wishingto get in the topic could do worse than start here.

J.H. WESTCOTTPrinciples of automatic control (3rd edn.)M. HealeyHodder & Stoughton, 1980, 352 pp., £3.75ISBN: 0-340-176717

This textbook has been available in one form or another for anumber of years and has been accepted on many courses as aninexpensive standard elementary text for students of automaticcontrol. The book is aimed essentially at the introductory leveland concentrates on the traditional classical approach to linearcontrol systems, with chapters on differential equations,transfer functions, frequency-response methods, stability andelementary systems design. Chapters are also included onnonlinear systems, elementary statistics and digital controlsystems. Here again, as one might expect, emphasis is placedon traditional topics such as the sinusoidal describing function,phase-plane methods and z-transforms analysis. Most of theessentials are adequately covered, but it is a pity that theopportunity was not taken to expand the section of digitalcontrol to provide a more comprehensive treatment of thisincreasingly important topic.

In this recent edition, the introductory section has beenextended to provide a good practical background for the newstudent of the subject. In my view this is important, as manystudents have the impression that control is a very theoreticalsubject with little practical application, and it is vital at anearly stage to emphasise the important engineering reasonswhy one must undertake the subsequent analytical studies.The section on multivariable systems has also been extended,with some emphasis on state-space analysis, and topics such asobservability, controllability, and the state transition matrixare also included. The coverage here is of course necessarilybrief but is adequate for the level at which the text is aimed.

The last section of the book is concerned with furtherpractical engineering aspects and a brief description of a rangeof control components including servomechanisms, analogueamplifiers, synchros, resolvers and hydraulic servomechanisms.The overall treatment in the book is thus very conprehensiveand the author endeavors to simplify any analysis and presentit in a form suitable for students at second year university orHND/HNC level. Unfortunately, in a text of this length someof the more important sections must receive an abbreviatedtreatment and it is indeed a pity that a number of workedexamples have not been included in each section. This in asense is one of the main failings in the textbook, and thus theonus will be on the lecturer to provide worked examples fromthe range of problems given in the text.

This is a textbook which has been successfully used for anumber of years in British universities and technical colleges.In its latest form it still represents excellent value for moneyand can be readily recommended to new students as a textwhich will provide the introductory basics on which the moreadvanced terms of control system design can be built.

J.O. GRAY

144 IEEPROC, Vol. 129, Pt. D, No. 4, JULY 1982