Interactive System Identification: Prospects and Pitfalls
The craft of designing mathematical models of dynamic objects offers a large number of methods to solve subproblems in the design, typically parameter estimation, order determination, validation, model reduc tion, analysis of identifiability, sensi tivi
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Torsten Bohlin
Interactive System Identification: Prospects and Pitfalls With 53 Figures
Springer-Verlag Berlin Heidelberg NewYork London Paris Tokyo Hong Kong Barcelona Budapest
Prof. TORSTEN BOHLIN Automatic Control Royal Institute of Technology S-lO044 Stockholm Sweden
ISBN 978-3-642-48620-3 DOl 10.1007/978-3-642-48618-0
ISBN 978-3-642-48618-0 (eBook)
This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifi cally the rights of translati on, reprinti ng, re-use ofi II ustrati ons, broadcasting, reprod ucti on on microfilms or in other ways, and storage in data banks. Duplication of this publication or parts thereof is only permitted underthe provisions ofthe German Copyright LawofSeptember9,1965,in its current version and a copyright fee must always be paid. Violations fall under the prosecution act of the German Copyright Law.
© Springer-Verlag Berlin, Heidelberg 1991
Softcover reprint of the hardcover 1st edition 1991 The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. 61/3020543210 - Printed on acid-free paper
To Birgitta
Preface
The craft of designing mathematical models of dynamic objects offers a large number of methods to solve subproblems in the design, typically parameter estimation, order determination, validation, model reduction, analysis of identifiability, sensi tivi ty and accuracy. There is also a substantial amount of process identification software available. A typical 'identification package' consists of program modules that implement selections of solution methods, coordinated by supervising programs, handling file administration, operator communication, and presentation of results. It is to be run 'interactively', typically on a designer's 'work station' . However, it is generally not obvious how to do that. Using interactive identification packages necessarily leaves to the user to decide on quite a number of specifications, including which model structure to use, which subproblems to be solved in each particular case, and in what order. The designer is faced with the task of setting up cases on the work station, based on apriori knowledge about the actual physical object, the experiment conditions, and the purpose of the identification. In doing so, he/she will have to cope with two basic difficulties: 1) The computer will be unable to solve most of the tentative identification cases, so the latter will first have to be form11lated in a way the computer can handle, and, worse, 2) even in cases where the computer can actually produce a model, the latter will not necessarily be valid for the intended purpose. The field of process identification is riddled with 'pitfalls', and recognizing that, the user must decide whether he/she can trust the result of the computer's calculations. Even with the best available program support ident
