On determining unknown functions in differential systems, with an application to biological reactors.

Éric Busvelle; Jean-Paul Gauthier

ESAIM: Control, Optimisation and Calculus of Variations (2010)

  • Volume: 9, page 509-551
  • ISSN: 1292-8119

Abstract

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In this paper, we consider general nonlinear systems with observations, containing a (single) unknown function φ. We study the possibility to learn about this unknown function via the observations: if it is possible to determine the [values of the] unknown function from any experiment [on the set of states visited during the experiment], and for any arbitrary input function, on any time interval, we say that the system is “identifiable”. For systems without controls, we give a more or less complete picture of what happens for this identifiability property. This picture is very similar to the picture of the “observation theory” in [7]: Contrarily to the case of the observability property, in order to identify in practice, there is in general no hope to do something better than using “approximate differentiators”, as show very elementary examples. However, a practical methodology is proposed in some cases. It shows very reasonable performances.
As an illustration of what may happen in controlled cases, we consider the equations of a biological reactor, [2,4], in which a population is fed by some substrate. The model heavily depends on a “growth function”, expressing the way the population grows in presence of the substrate. The problem is to identify this “growth function”. We give several identifiability results, and identification methods, adapted to this problem.

How to cite

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Busvelle, Éric, and Gauthier, Jean-Paul. "On determining unknown functions in differential systems, with an application to biological reactors.." ESAIM: Control, Optimisation and Calculus of Variations 9 (2010): 509-551. <http://eudml.org/doc/90709>.

@article{Busvelle2010,
abstract = { In this paper, we consider general nonlinear systems with observations, containing a (single) unknown function φ. We study the possibility to learn about this unknown function via the observations: if it is possible to determine the [values of the] unknown function from any experiment [on the set of states visited during the experiment], and for any arbitrary input function, on any time interval, we say that the system is “identifiable”. For systems without controls, we give a more or less complete picture of what happens for this identifiability property. This picture is very similar to the picture of the “observation theory” in [7]: Contrarily to the case of the observability property, in order to identify in practice, there is in general no hope to do something better than using “approximate differentiators”, as show very elementary examples. However, a practical methodology is proposed in some cases. It shows very reasonable performances.
As an illustration of what may happen in controlled cases, we consider the equations of a biological reactor, [2,4], in which a population is fed by some substrate. The model heavily depends on a “growth function”, expressing the way the population grows in presence of the substrate. The problem is to identify this “growth function”. We give several identifiability results, and identification methods, adapted to this problem. },
author = {Busvelle, Éric, Gauthier, Jean-Paul},
journal = {ESAIM: Control, Optimisation and Calculus of Variations},
keywords = {Nonlinear systems; observability; identifiability; identification.; identification},
language = {eng},
month = {3},
pages = {509-551},
publisher = {EDP Sciences},
title = {On determining unknown functions in differential systems, with an application to biological reactors.},
url = {http://eudml.org/doc/90709},
volume = {9},
year = {2010},
}

TY - JOUR
AU - Busvelle, Éric
AU - Gauthier, Jean-Paul
TI - On determining unknown functions in differential systems, with an application to biological reactors.
JO - ESAIM: Control, Optimisation and Calculus of Variations
DA - 2010/3//
PB - EDP Sciences
VL - 9
SP - 509
EP - 551
AB - In this paper, we consider general nonlinear systems with observations, containing a (single) unknown function φ. We study the possibility to learn about this unknown function via the observations: if it is possible to determine the [values of the] unknown function from any experiment [on the set of states visited during the experiment], and for any arbitrary input function, on any time interval, we say that the system is “identifiable”. For systems without controls, we give a more or less complete picture of what happens for this identifiability property. This picture is very similar to the picture of the “observation theory” in [7]: Contrarily to the case of the observability property, in order to identify in practice, there is in general no hope to do something better than using “approximate differentiators”, as show very elementary examples. However, a practical methodology is proposed in some cases. It shows very reasonable performances.
As an illustration of what may happen in controlled cases, we consider the equations of a biological reactor, [2,4], in which a population is fed by some substrate. The model heavily depends on a “growth function”, expressing the way the population grows in presence of the substrate. The problem is to identify this “growth function”. We give several identifiability results, and identification methods, adapted to this problem.
LA - eng
KW - Nonlinear systems; observability; identifiability; identification.; identification
UR - http://eudml.org/doc/90709
ER -

References

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  13. R.M. Hirschorn, Invertibility of Nonlinear Control Systems. SIAM J. Control Optim.17 (1979) 289-297.  
  14. P. Jouan and J.-P. Gauthier, Finite singularities of nonlinear systems. Output stabilization, observability and observers. J. Dynam. Control Systems2 (1996) 255-288.  
  15. W. Respondek, Right and Left Invertibility of Nonlinear Control Systems, edited by H.J. Sussmann. Marcel Dekker, New-York, Nonlinear Control. Optim. Control (1990) 133-176.  
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