Suresh P. Sethi Optimal Control Theory Applications to Management Science and Economics Third Edition Optimal Control Theory Suresh P. Sethi Optimal Control Theory Applications to Management Science and Economics Third Edition 123 SureshP.Sethi JindalSchoolofManagement,SM30 UniversityofTexasatDallas Richardson,TX,USA ISBN978-3-319-98236-6 ISBN978-3-319-98237-3 (eBook) https://doi.org/10.1007/978-3-319-98237-3 LibraryofCongressControlNumber:2018955904 2ndedition:©Springer-VerlagUS2000 ©SpringerNatureSwitzerlandAG2019 Thisworkissubjecttocopyright. AllrightsarereservedbythePublisher,whetherthewholeorpartof thematerialisconcerned,specificallytherightsoftranslation,reprinting,reuseofillustrations,recitation, broadcasting, reproductiononmicrofilmsorinanyotherphysicalway, andtransmissionorinformation storageandretrieval, electronicadaptation, computersoftware, orbysimilarordissimilarmethodology nowknownorhereafterdeveloped. Theuseofgeneraldescriptivenames,registerednames,trademarks,servicemarks,etc. inthispublication doesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfromtherelevant protectivelawsandregulationsandthereforefreeforgeneraluse. Thepublisher,theauthorsandtheeditorsaresafetoassumethattheadviceandinformationinthisbook arebelievedtobetrueandaccurateatthedateofpublication. Neitherthepublishernortheauthorsorthe editorsgiveawarranty,expressorimplied,withrespecttothematerialcontainedhereinorforanyerrorsor omissionsthatmayhavebeenmade. Thepublisherremainsneutralwithregardtojurisdictionalclaimsin publishedmapsandinstitutionalaffiliations. ThisSpringerimprintispublishedbytheregisteredcompanySpringerNatureSwitzerlandAG Theregisteredcompanyaddressis:Gewerbestrasse11,6330Cham,Switzerland This book is dedicated to the memory of my parents Manak Bai and Gulab Chand Sethi Preface to Third Edition The third edition of this book will not see my co-author Gerald L. Thompson, who very sadly passed away on November 9, 2009. Gerry and I wrote the first edition of the 1981 book sitting practically side by side, and I learned a great deal about book writing in the process. He was also my PhD supervisor and mentor and he is greatly missed. After having used the second edition of the book in the classroom for many years, the third edition arrives with new material and many improvements. Examples and exercises related to the interpretation of the adjoint variables and Lagrange multipliers are inserted in Chaps.2– 4. Direct maximum principle is now discussed in detail in Chap.4 along with the existing indirect maximum principle from the second edition. Chattering or relaxed controls leading to pulsing advertising policies are introduced in Chap.7. An application to information systems involving chattering controls is added as an exercise. The objective function in Sect.11.1.3 is changed to the more popular objectiveofmaximizingthetotaldiscountedsociety’sutilityofconsump- tion. Further discussion leading to obtaining a saddle-point path on the phasediagramleadingtothelong-runstationaryequilibriumisprovided in Sect.11.2. For this purpose, a global saddle-point theorem is stated in Appendix D.7. Also inserted in Appendix D.8 is a discussion of the Sethi-Skiba points which lead to nonunique stable equilibria. Finally, a new Sect.11.4 contains an adverse selection model with continuum of the agent types in a principal-agent framework, which requires an appli- cation of the maximum principle. Chapter 12 of the second edition is removed except for the material on differential games and the distributed parameter maximum principle. The differential game material joins new topics of stochastic Nash differ- ential games and Stackelberg differential games via their applications to marketing to form a new Chap.13 titled Differential Games. As a result, Chap.13 of the second edition becomes Chap.12. The material on the distributed parameter maximum principle is now Appendix D.9. The exposition is revised in some places for better reading. New exercises are added and the list of references is updated. Needless to say, the errors in the second edition are corrected, and the notation is made consistent. vii viii Preface to Third Edition Thanks are due to Huseyin Cavusoglu, Andrei Dmitruk, Gustav Fe- ichtinger, Richard Hartl, Yonghua Ji, Subodha Kumar, Sirong Lao, Hel- mut Maurer, Ernst Presman, Anyan Qi, Andrea Seidl, Atle Seierstad, Xi Shan, Lingling Shi, Xiahong Yue, and the students in my Optimal Control Theory and Applications course over the years for their sug- gestions for improvement. Special thanks go to Qi (Annabelle) Feng for her dedication in updating and correcting the forthcoming solution manual that went with the first edition. I cannot thank Barbara Gordon and Lindsay Wilson enough for their assistance in the preparation of the text, solution manual, and presentation materials. In addition, the meticulous copy editing of the entire book by Lindsay Wilson is much appreciated. Anshuman Chutani, Pooja Kamble, and Shivani Thakkar are also thanked for their assistance in drawing some of the figures in the book. Richardson, TX, USA Suresh P. Sethi June 2018 Preface to Second Edition The first edition of this book, which provided an introduction to op- timalcontroltheoryanditsapplicationstomanagementsciencetomany students in management, industrial engineering, operations research and economics, went out of print a number of years ago. Over the years we have received feedback concerning its contents from a number of instruc- tors who taught it, and students who studied from it. We have also kept up with new results in the area as they were published in the literature. For this reason we felt that now was a good time to come out with a new edition. While some of the basic material remains, we have made several big changes and many small changes which we feel will make the use of the book easier. The most visible change is that the book is written in Latex and the figures are drawn in CorelDRAW, in contrast to the typewritten text and hand-drawn figures of the first edition. We have also included some problems along with their numerical solutions obtained using Excel. The most important change is the division of the material in the old Chap.3, into Chaps.3 and 4 in the new edition. Chapter 3 now contains models having mixed (control and state) constraints, current value formulations, terminal conditions and model types, while Chap.4 covers the more difficult topic of pure state constraints, together with mixed constraints. Each of these chapters contain new results that were not available when the first edition was published. Thesecondmostimportantchangeistheexpansionofthematerialin the old Sect.12.4 on stochastic optimal control theory and its becoming the new Chap.13. The new Chap.12 now contains the following ad- vanced topics on optimal control theory: differential games, distributed parameter systems, and impulse control. The new Chap.13 provides a brief introduction to stochastic optimal control problems. It contains formulations of simple stochastic models in production, marketing and finance, and their solutions. We deleted the old Chap.11 of the first edition on computational methods, since there are a number of excellent referencesnowavailableonthistopic. Someofthesereferencesarelisted in Sect.4.2 of Chap.4 and Sect.8.3 of Chap.8. ix x Preface to Second Edition The emphasis of this book is not on mathematical rigor, but rather on developing models of realistic situations faced in business and man- agement. For that reason we have given, in Chaps.2 and 8, proofs of the continuous anddiscretemaximumprinciplesbyusingdynamicprogram- ming and Kuhn-Tucker theory, respectively. More general maximum principles are stated without proofs in Chaps.3, 4 and 12. One of the fascinating features of optimal control theory is its ex- traordinarily wide range of possible applications. We have covered some of these as follows: Chap.5 covers finance; Chap.6 considers production and inventory problems; Chap.7 covers marketing problems; Chap.9 treats machine maintenance and replacement; Chap.10 deals with prob- lems of optimal consumption of natural resources (renewable or ex- haustible); and Chap.11 discusses a number of applications of control theory to economics. The contents of Chaps.12 and 13 have been de- scribed earlier. Finally, four appendices cover either elementary material, such as the theory of differential equations, or very advanced material, whose inclusion in the main text would interrupt its continuity. At the end of the book is an extensive but not exhaustive bibliography of relevant material on optimal control theory including surveys of material devoted to specific applications. We are deeply indebted to many people for their part in making this edition possible. Onur Arugaslan, Gustav Feichtinger, Neil Geismar, RichardHartl,SteffenJørgensen,SubodhaKumar,HelmutMaurer,Ger- hard Sorger, and Denny Yeh made helpful comments and suggestions about the first edition or preliminary chapters of this revision. Many students who used the first edition, or preliminary chapters of this revi- sion, also made suggestions for improvements. We would like to express our gratitude to all of them for their help. In addition we express our appreciation to Eleanor Balocik, Frank (Youhua) Chen, Feng Cheng, Howard Chow, Barbara Gordon, Jiong Jiang, Kuntal Kotecha, Ming Tam, and Srinivasa Yarrakonda for their typing of the various drafts of the manuscript. They were advised by Dirk Beyer, Feng Cheng, Sub- odha Kumar, Young Ryu, Chelliah Sriskandarajah, Wulin Suo, Houmin Yan, Hanqin Zhang, and Qing Zhang on the technical problems of using LATEX. We also thank our wives and children—Andrea, Chantal, Anjuli, Dorothea, Allison, Emily, and Abigail—for their encouragement and un- derstanding during the time-consuming task of preparing this revision. Preface to Second Edition xi Finally, while we regret that lack of time and pressure of other du- ties prevented us from bringing out a second edition soon after the first editionwentoutofprint,wesincerelyhopethatthewaithasbeenworth- while. In spite of the numerous applications of optimal control theory which already have been made to areas of management science and eco- nomics, we continue to believe there is much more that remains to be done. We hope the present revision will rekindle interest in furthering such applications, and will enhance the continued development in the field. Richardson, TX, USA Suresh P. Sethi Pittsburgh, PA, USA Gerald L. Thompson January 2000