115 results found
Chachuat B, Sager S, 2018, Introduction to the Special Issue on Global and Robust Optimization of Dynamic Systems, Optimal Control Applications and Methods, ISSN: 0143-2087
Quek V, Shah N, Chachuat B, 2018, Modeling for design and operation of high-pressure membrane contactors in natural gas sweetening, Chemical Engineering Research and Design, ISSN: 1744-3598
Over the past decade, membrane contactors (MBC) for CO2 absorption have been widely recognized for their large intensification potential compared to conventional absorption towers. MBC technology uses microporous hollow-fiber membranes to enable effective gas and liquid mass transfer, without the two phases dispersing into each other. The main contribution of this paper is the development and verification of a predictive mathematical model of high-pressure MBC for natural gas sweetening applications, based on which model-based parametric analysis and optimization can be conducted. The model builds upon insight from previous modeling studies by combining 1-d and 2-d mass-balance equations to predict the CO2 absorption flux, whereby the degree of membrane wetting itself is calculated from the knowledge of the membrane pore-size distribution. The predictive capability of the model is tested for both lab-scale and pilot-scale MBC modules, showing a close agreement of the predictions with measured CO2 absorption fluxes at various gas and liquid flowrates, subject to a temperature correction to account for the heat of reaction in the liquid phase. The results of a model-based analysis confirm the advantages of pressurized MBC operation in terms of CO2 removal efficiency. Finally, a comparison between vertical and horizontal modes of operation shows that the CO2 removal efficiency in the latter can be vastly superior as it is not subject to the liquid static head and remediation strategies are discussed.
Bernardi A, Nikolaou A, Meneghesso A, et al., 2017, Semi-empirical modeling of microalgae photosynthesis in different acclimation states - Application to N. gaditana, JOURNAL OF BIOTECHNOLOGY, Vol: 259, Pages: 63-72, ISSN: 0168-1656
Houska B, Chachuat B, 2017, Global optimization in Hilbert space, Mathematical Programming, Pages: 1-29, ISSN: 0025-5610
© 2017 The Author(s) We propose a complete-search algorithm for solving a class of non-convex, possibly infinite-dimensional, optimization problems to global optimality. We assume that the optimization variables are in a bounded subset of a Hilbert space, and we determine worst-case run-time bounds for the algorithm under certain regularity conditions of the cost functional and the constraint set. Because these run-time bounds are independent of the number of optimization variables and, in particular, are valid for optimization problems with infinitely many optimization variables, we prove that the algorithm converges to an (Formula presented.)-suboptimal global solution within finite run-time for any given termination tolerance (Formula presented.). Finally, we illustrate these results for a problem of calculus of variations.
Houska B, Li JC, Chachuat B, 2017, Towards rigorous robust optimal control via generalized high-order moment expansion, Optimal Control Applications and Methods, ISSN: 0143-2087
© 2017 The Authors. Optimal Control Applications and Methods published by John Wiley & Sons, Ltd. This study is concerned with the rigorous solution of worst-case robust optimal control problems having bounded time-varying uncertainty and nonlinear dynamics with affine uncertainty dependence. We propose an algorithm that combines existing uncertainty set-propagation and moment-expansion approaches. Specifically, we consider a high-order moment expansion of the time-varying uncertainty, and we bound the effect of the infinite-dimensional remainder term on the system state, in a rigorous manner, using ellipsoidal calculus. We prove that the error introduced by the expansion converges to zero as more moments are added. Moreover, we describe a methodology to construct a conservative, yet more computationally tractable, robust optimization problem, whose solution values are also shown to converge to those of the original robust optimal control problem. We illustrate the applicability and accuracy of this approach with the robust time-optimal control of a motorized robot arm.
Peric ND, Villanueva ME, Chachuat B, 2017, SENSITIVITY ANALYSIS OF UNCERTAIN DYNAMIC SYSTEMS USING SET-VALUED INTEGRATION, SIAM JOURNAL ON SCIENTIFIC COMPUTING, Vol: 39, Pages: A3014-A3039, ISSN: 1064-8275
Rajyaguru J, Villanueva ME, Houska B, et al., 2017, Chebyshev model arithmetic for factorable functions, JOURNAL OF GLOBAL OPTIMIZATION, Vol: 68, Pages: 413-438, ISSN: 0925-5001
Sun M, Villanueva ME, Pistikopoulos EN, et al., 2017, Robust Multi-Parametric Control of Continuous-Time Linear Dynamic Systems, IFAC-PapersOnLine, Vol: 50, Pages: 4660-4665
© 2017 We extend a recent methodology called multi-parametric NCO-tracking for the design of parametric controllers for continuous-time linear dynamic systems in the presence of uncertainty The approach involves backing-off the path and terminal state constraints based on a worst-case uncertainty propagation determined using either interval analysis or ellipsoidal calculus. We address the case of additive uncertainty and we discuss approaches to handling multiplicative uncertainty that retain tractability of the mp-NCO-tracking design problem, subject to extra conservatism. These developments are illustrated with the case study of a fluidized catalytic cracking (FCC) unit operated in partial combustion mode.
Villanueva ME, Li JC, Feng X, et al., 2017, Computing Ellipsoidal Robust Forward Invariant Tubes for Nonlinear MPC, IFAC PAPERSONLINE, Vol: 50, Pages: 7175-7180, ISSN: 2405-8963
This paper is concerned with tube-based model predictive control (MPC) for both linear and nonlinear, input-affine continuous-time dynamic systems that are affected by time-varying disturbances. We derivea min-max differential inequality describing the support function of positive robust forward invariant tubes, which can be used to construct a variety of tube-based model predictive controllers. These constructions are conservative, but computationally tractable and their complexity scales linearly with the length of the prediction horizon. In contrast to many existing tube-based MPC implementations, the proposed framework does not involve discretizing the control policy and, therefore, the conservatism of the predicted tube depends solely on the accuracy of the set parameterization. The proposed approach is then used to construct a robustMPCscheme based on tubes with ellipsoidal cross-sections. This ellipsoidal MPC scheme is based on solving an optimal control problem under linear matrix inequality constraints. We illustrate these results with the numerical case study of a spring-mass-damper system.
Adi VSK, Cook M, Peeva LG, et al., 2016, Optimization of OSN Membrane Cascades for Separating Organic Mixtures, Editors: Kravanja, Bogataj, Publisher: ELSEVIER SCIENCE BV, Pages: 379-384
Baroukh C, Steyer JP, Bernard O, et al., 2016, dynamic Flux Balance Analysis of the Metabolism of Microalgae under a Diurnal Light Cycle, 11th IFAC Symposium on Dynamics and Control of Process Systems including Biosystems, Publisher: ELSEVIER SCIENCE BV, Pages: 791-796, ISSN: 2405-8963
Bernard O, Mairet F, Chachuat B, 2016, Modelling of Microalgae Culture Systems with Applications to Control and Optimization, Editors: Posten, Chen, Publisher: SPRINGER-VERLAG BERLIN, Pages: 59-87
Mathematical modeling is becoming ever more important to assess the potential, guide the design, and enable the efficient operation and control of industrial-scale microalgae culture systems (MCS). The development of overall, inherently multiphysics, models involves coupling separate submodels of (i) the intrinsic biological properties, including growth, decay, and biosynthesis as well as the effect of light and temperature on these processes, and (ii) the physical properties, such as the hydrodynamics, light attenuation, and temperature in the culture medium. When considering high-density microalgae culture, in particular, the coupling between biology and physics becomes critical. This chapter reviews existing models, with a particular focus on the Droop model, which is a precursor model, and it highlights the structure common to many microalgae growth models. It summarizes the main developments and difficulties towards multiphysics models of MCS as well as applications of these models for monitoring, control, and optimization purposes.
Bernardi A, Nikolaou A, Meneghesso A, et al., 2016, High-Fidelity Modelling Methodology of Light-Limited Photosynthetic Production in Microalgae, PLOS ONE, Vol: 11, ISSN: 1932-6203
Bernardi A, Nikolaou A, Meneghesso A, et al., 2016, High-Fidelity Modelling Methodology of Light-Limited Photosynthetic Production in Microalgae (vol 11, e0152387, 2016), PLOS ONE, Vol: 11, ISSN: 1932-6203
Faust JMM, Fu J, Chachuat B, et al., 2016, Optimization of dynamic systems with rigorous path constraint satisfaction, Editors: Kravanja, Bogataj, Publisher: ELSEVIER SCIENCE BV, Pages: 643-648
Nikolaou A, Booth P, Gordon F, et al., 2016, Multi-Physics Modeling of Light-Limited Microalgae Growth in Raceway Ponds, IFAC PAPERSONLINE, Vol: 49, Pages: 324-329, ISSN: 2405-8963
Nikolaou A, Hartmann P, Sciandra A, et al., 2016, Dynamic coupling of photoacclimation and photoinhibition in a model of microalgae growth, JOURNAL OF THEORETICAL BIOLOGY, Vol: 390, Pages: 61-72, ISSN: 0022-5193
Paulen R, Villanueva ME, Chachuat B, 2016, Guaranteed parameter estimation of non-linear dynamic systems using high-order bounding techniques with domain and CPU-time reduction strategies, IMA JOURNAL OF MATHEMATICAL CONTROL AND INFORMATION, Vol: 33, Pages: 563-587, ISSN: 0265-0754
Peric ND, Villanueva ME, Chachuat B, 2016, Set-valued integration of uncertain dynamic systems with sensitivity analysis capability, Editors: Kravanja, Bogataj, Publisher: ELSEVIER SCIENCE BV, Pages: 1165-1170
Sun M, Chachuat B, Pistikopoulos EN, 2016, Design of multi-parametric NCO tracking controllers for linear dynamic systems, COMPUTERS & CHEMICAL ENGINEERING, Vol: 92, Pages: 64-77, ISSN: 0098-1354
Sun M, Villanueva ME, Chachuat B, et al., 2016, Strategies towards the robust multi-parametric control of continuous-time systems, Pages: 355-357
Ulmasov D, Baroukh C, Chachuat B, et al., 2016, Bayesian Optimization with Dimension Scheduling: Application to Biological Systems, Publisher: ELSEVIER SCIENCE BV
Bernardi A, Nikolaou A, Meneghesso A, et al., 2015, A Framework for the Dynamic Modelling of PI Curves in Microalgae, 12TH INTERNATIONAL SYMPOSIUM ON PROCESS SYSTEMS ENGINEERING AND 25TH EUROPEAN SYMPOSIUM ON COMPUTER AIDED PROCESS ENGINEERING, PT C, Vol: 37, Pages: 2483-2488, ISSN: 1570-7946
Bernardi A, Nikolaou A, Meneghesso A, et al., 2015, Using Fluorescence Measurements to Model Key Phenomena in Microalgae Photosynthetic Mechanisms, ICHEAP12: 12TH INTERNATIONAL CONFERENCE ON CHEMICAL & PROCESS ENGINEERING, Vol: 43, Pages: 217-222, ISSN: 1974-9791
Chachuat B, Houska B, Paulen R, et al., 2015, Set-Theoretic Approaches in Analysis, Estimation and Control of Nonlinear Systems, 9th IFAC Symposium on Advanced Control of Chemical Processes ADCHEM 2015, Publisher: ELSEVIER SCIENCE BV, Pages: 981-995, ISSN: 2405-8963
Fu J, Faust JMM, Chachuat B, et al., 2015, Local optimization of dynamic programs with guaranteed satisfaction of path constraints, AUTOMATICA, Vol: 62, Pages: 184-192, ISSN: 0005-1098
Houska B, Villanueva ME, Chachuat B, 2015, STABLE SET-VALUED INTEGRATION OF NONLINEAR DYNAMIC SYSTEMS USING AFFINE SET-PARAMETERIZATIONS, SIAM JOURNAL ON NUMERICAL ANALYSIS, Vol: 53, Pages: 2307-2328, ISSN: 0036-1429
Nikolaou A, Bernardi A, Meneghesso A, et al., 2015, A model of chlorophyll fluorescence in microalgae integrating photoproduction, photoinhibition and photoregulation, JOURNAL OF BIOTECHNOLOGY, Vol: 194, Pages: 91-99, ISSN: 0168-1656
Nikolaou A, Chachuat B, 2015, 427331 Scaling-up microalgae production systems: Inferring biomass productivity in raceway ponds using numerical simulation, Pages: 453-456
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