Linear
model predictive control
is popular since the 70s of the past
century and by now widely employed in practice. The 90s have witnessed
a steadily increasing attention from control theoreticians as well as
control practitioners in the area of nonlinear model predictive
control (NMPC) and over the past decade significant theoretical as
well as implementational advances in the area of NMPC have been
achieved. The focus of this workshop/mini course is twofold. Besides an
in
depth introduction to the basic ideas and principles of (nonlinear)
predictive control current application and research issues in NMPC
spanning from stability and robustness, output-feedback, efficient
numerical solution as well as implementation aspects are
discussed. For this purpose the course is split up in six parts. The
first part provides an introduction as well as a historical review of
(nonlinear) predictive control, often also referred to as receding
horizon control or moving horizon control. Part two focuses on how to
achieve nominal stability of the closed-loop using NMPC. In part three
the robustness as well as the robust design of NMPC are
discusses. Part four provides an overview on output-feedback in
conjunction with NMPC. The efficient numerical solution and
implementation of NMPC is discussed in depth in part five. Part six
discusses existing applications as well as application aspects of
NMPC. The workshop/mini course is concluded by a short wrap up, summary
and
outlook.
The
course starts with an
elementary level before moving to the more advanced
topics. It is accompanied by copies of the slides
and suplementary material provided by the lecturers.
The
main focus in this lecture is laid on an introduction and historical
perspective of (nonlinear) predictive control. Specifically we outline
the basic principle of predictive control, reasons for the huge success
of linear model predictive control and the key advantages,
disadvantages and challenges inherent in NMPC.
Nonlinear
model predictive control is based on the repeated solution of
a
(finite) horizon open-loop optimal control problem subject to system
dynamics and input and state constraints. However, as is well known by
now, optimality does not automatically imply stability in the case of
finite prediction horizons. Different approaches to achieve closed-loop
stability using finite horizon lengths exist. The main purpose of this
lecture is to review the underlying main ideas and theoretical
foundations for these approaches and to provide a unified view on
nominally stabilizing NMPC schemes.
Nonlinear
model predictive control is based on the repeated solution of
a
(finite) horizon open-loop optimal control problem subject to system
dynamics and input and state constraints. However, as is well known by
now, optimality does not automatically imply stability in the case of
finite prediction horizons. Different approaches to achieve closed-loop
stability using finite horizon lengths exist. The main purpose of this
lecture is to review the underlying main ideas and theoretical
foundations for these approaches and to provide a unified view on
nominally stabilizing NMPC schemes.
The
introduction of uncertainty in the system description raises the
question of robustness. In this lecture we present several
approaches to the study of robustness. The first is concerned with the
robustness analysis of closed-loop systems, designed using a nominal
model. The second attempts to achieve robustness in the context of
conventional model predictive control by consideration of a min-max
open-loop model predictive control. The third one addresses the
robustness problem by introducing feedback in the min-max optimal
control problem solved on-line.
Nonlinear
model predictive control is inherently a state feedback control scheme.
Often, however, the full state information is not available and a
suitable state observer must be used for state estimation.
Since
the well known separation principle does not apply for nonlinear
systems, it is not guaranteed that a combination of
a
stabilizing NMPC state feedback controller with a stable state
estimator does lead to a stabilizing output-feedback control scheme. In
this lecture we review results and conditions on output-feedback NMPC
schemes that guarantee stability of the closed loop.
This
lecture presents
state-of-the-art methods for numerical solution of the
optimal control problems arising in NMPC. After first giving
a
brief overview of different solution approaches to optimal control we
focus on direct shooting methods and collocation, in conjunction with
nonlinear programming techniques. In particular, we discuss the direct
multiple shooting method, an algorithm suitable for nonlinear
problems with complex constraints that is often used in NMPC
applications, and show ways to deal with limited time for on line
computation.
This
lecture provides an introduction in the development of practical
model-based control approaches that can be supported in an industrial
environment. The importance of the judicious compromise between,
modeling, sensors, estimation and optimization are assessed.
Academic NMPC approaches are confronted with industrial methods
through several example processes with contouring current trends toward
potential applications in biotechnology, polymer, pharmaceutical and
microelectronics industry.
17:45-18:00
Wrap
up,
summary and outlook
Provided
material:
Copies
of the
slides
and supplementary material will be provided to the registered
participants.
In
case of
additional questions or requests please feel free to contact:
Rolf
Findeisen Institute
for
Systems Theory in Engineering University
of
Stuttgart Pfaffenwaldring
9 70550
Stuttgart,
Germany Tel.
+49-711-685-7748 Fax.
+49-711-685-7735 findeise@ist.uni-stuttgart.de
Frank
Allgöwer is professor
in the mechanical engineering department of the University of Stuttgart
and director of the Institute for Systems Theory in
Engineering.
Besides his interests in predictive control, he is active in the areas
of nonlinear and robust control, identification of nonlinear
systems and application of modern systems and control theoretical
methods in engineering and biology. He is Editor for the
journal Automatica, Associate Editor of the
Journal of Process Control and the European Journal of Control and is
on the
editorial board of several further journals. He is organizer
or
co-organizer of several
international
conferences and has published over 100 scientific articles.
Selected
publications
relevant to the workshop:
F.
Allgöwer and A.Z. Zheng. Nonlinear Model
Predictive
Control: Assessment and Future Directions for Research. Progress in
Systems and Control Series, Birkhäuser Verlag, Basel. 2000.
F. Allgöwer,
R. Findeisen, and
C. Ebenbauer.
Nonlinear model predictive control.
Encyclopedia for Life Support Systems (EOLSS) article contribution
6.43.16.2, 2003.
H. Chen and F.
Allgöwer. A quasi-infinite horizon
nonlinear model predictive control scheme with guaranteed stability.
Automatica. Vol. 34, issue. 10, S. 1205-1218, 1998.
Moritz
Diehl is mathematics
lecturer at the Interdisciplinary Center for Scientific Computing (IWR)
of the University
of Heidelberg. His main research interests are:
algorithms for dynamic optimization, nonlinear model predictive
control, parameter- and state estimation; applications e.g. in chemical
engineering, medicine, robotics, power engineering. He serves as
reviewer for "Automatica", "Automatisierungstechnik", "Computational
Optimization and Applications", "Computers and Chemical Engineering",
"Optimization and Engineering", "Journal of Process Control".
Selected
publications
relevant to the workshop:
M. Diehl, H.G.
Bock, J.P. Schlöder, R. Findeisen,
Z.
Nagy,
and F. Allgöwer: Real-time optimization and nonlinear model
predictive
control of processes governed by differential-algebraic equations
. Journal of Process Control 12, pp. 577-585, 2002.
M. Diehl, R.
Findeisen, S. Schwarzkopf, Ilknur Uslu, F.
Allgöwer, H.G. Bock, E. D. Gilles, J.P. Schröder: An
Efficient
Algorithm for Optimization in Nonlinear Model Predictive Control of
Large-Scale Systems.
Automatisierungstechnik 12/2002 and 1/2003.
M. Diehl, I. Uslu,
S. Schwarzkopf, F. Allgöwer,
H.G.
Bock, R. Findeisen, E.D. Gilles, A. Kienle, J.P. Schlöder, and
E.
Stein: Real-Time Optimization for Large Scale Processes: Nonlinear
Model Predictive Control of a High Purity Distillation Column
In Groetschel, Krumke, Rambau (eds.): Online Optimization of Large
Scale Systems: State of the Art, Springer, 2001.
Rolf
Findeisen is researcher and lecturer at the Institute for
Systems Theory in Engineering at the University of Stuttgart. His main
research areas are: nonlinear model predictive control, output feedback
control, optimization based control and state estimation, differential
algebraic systems, nonlinear control, system theoretical methods in
biomedical engineering and biological systems; and the application of
these methods in chemical, biological and mechanical systems.
He
serves as reviewer for various journals and conferences including
Automatica, IEEE Transaction on Automatic Control, SIAM Journal on
Control and Optimization, Computers and Chemical Engineering,
System and Control Letters, Journal of Process Control.
Selected
publications
relevant to the workshop:
R. Findeisen, F.
Allgöwer, and C. Ebenbauer. Nonlinear model predictive
control. Encyclopedia for
Life Support Systems (EOLSS) article contribution 6.43.16.2. 2005.
M. Diehl, R.
Findeisen, and F. Allgöwer. A stabilizing real-time
implementation of nonlinear model
predictive control. In L. Biegler, O. Ghattas, M. Heinkenschloss, D.
Keyes, and B. van
Bloem Wanders, editors, Real-Time PDE Optimization, New York, 2005.
Springer-Verlag. To appear.
R. Findeisen,
L. Imsland,
F. Allgöwer, and
B.A. Foss.
Output feedback stabilization for constrained systems with nonlinear
model predictive control.
Int. J. of Robust and Nonlinear Control, 13(3-4):211-227, 2003.
R. Findeisen,
L. Imsland,
F. Allgöwer, and
B.A. Foss.
State and output feedback nonlinear model predictive control: An
overview.
Europ. J. Contr., 9(2-3):190-207, 2003.
R. Findeisen,
L. Imsland,
F. Allgöwer, and
B.A. Foss.
Towards a sampled-data theory for nonlinear model predictive control.
In C. Kang, M. Xiao, and W. Borges, editors,
New Trends
in Nonlinear Dynamics and Control, and their Applications, Lecture
Notes in Control and Information Sciences, 295, pages 295-313, New
York, 2003. Springer-Verlag.
Lalo
Magni got his PhD in
Electronic and Computer Engineering in 1998 with the dissertation
:"Nonlinear Receding Horizon Control: Theory and Application".
Currently he is Assistant Professor at the University of Pavia, Italy.
His research in model predictive control is witnessed by 20 papers
appeared in the main international journals of the field. He has been
Guest Editor of the Special Issue "Control of nonlinear systems with
Model Predictive Control" in the International Journal of Robust and
Nonlinear Control. He serves as an Associate Editor of the IEEE
Transactions on Automatic Control.
Selected
publications relevant to the workshop:
Fontes F.A.C.C.
and L. Magni, Min-max Model Predictive
Control of
Nonlinear Systems using Discontinuous Feedbacks, IEEE Transactions on
Automatic Control,48,pp. 1750-1755, 2003.
Magni L., G. De
Nicolao, R. Scattolini and F.
Allgöwer,
Robust
Model predictive Control of nonlinear discrete-time systems,
International Journal of Robust and nonlinear control, 13, Issue 3-4,
pp. 229-246, 2003.
Magni L., H.
Nijmeijer and A.J. Van Der Schaft, A
receding-horizon approach to the nonlinear H Inf. Control problem,
Automatica, 37(3), pag. 429-435, 2001.
Zoltan
K. Nagy received his
Ph.D. in chemical engineering, from the "Babes-Bolyai" University of
Cluj, Romania in 2001, where he holds a lecturer position. In 2001-2003
he was a research associate and lecturer at the University of Illinois
at Urbana-Champaign, USA. He is currently with the University of
Stuttgart, working on an industrial project with BASF and ABB related
to a feasibility study of industrial NMPC. His research interests
include: nonlinear model predictive control, batch process control,
uncertainty analysis, robust optimal control, mathematical modeling of
chemical processes. He received the outstanding reviewer award for
Automatica in 2003, and serves as reviewer for McGraw-Hill and for
several journals and conferences including, Journal of Process Control,
IEE Proceedings on Control Theory and Applications, Chemical
Engineering
Communications.
Selected
publications
relevant to the workshop:
Z.
K. Nagy and R. D.
Braatz, Robust nonlinear model
predictive control of batch processes, AIChE J., 49 (7), 1776-1786,
2003.
Z.
K. Nagy, R. D. Braatz,
Worst-case and Distributional Robustness Analysis of Finite-time
Control Trajectories for Nonlinear Distributed Parameter Systems, IEEE
Transaction on Control Systems Technology, 11 (5), 694-704, 2003.
Z.
K. Nagy and R. D.
Braatz, Open-loop and closed-loop robust
optimal control of batch processes using distributional and worst-case
analysis, Journal of Process Control, 14, 411-422, 2004.