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Collocation software for boundary value differentialalgebraic equations
 SIAM J. Sci. Comput
, 1994
"... We describe the methods and implementation of a generalpurpose code, COLDAE. This code can solve boundary value problems for nonlinear systems of semiexplicit differentialalgebraic equations (DAEs) of index at most 2. Fully implicit index1 boundary value DAE problems can be handled as well. The ..."
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Cited by 17 (2 self)
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We describe the methods and implementation of a generalpurpose code, COLDAE. This code can solve boundary value problems for nonlinear systems of semiexplicit differentialalgebraic equations (DAEs) of index at most 2. Fully implicit index1 boundary value DAE problems can be handled as well. The code COLDAE is an extension of the package COLNEW (COLSYS) for solving boundary value ODEs. The implemented method is piecewise polynomial collocation at Gaussian points, extended as needed by the projection method of AscherPetzold. For general semiexplicit index2 problems, as well as for fully implicit index1 problems, we define a selective projected collocation method, and demonstrate its use. The mesh selection procedure of COLSYS is modified for the case of index2 constraints. We also discuss shooting for initial guesses. The power and generality of the code are demonstrated by examples.
A Boundary Value Problem Approach to the Optimization of Chemical Processes Described by DAE Models
, 1997
"... An efficient and robust technique for the optimization of dynamic chemical processes is presented. In particular, we address the solution of large, multistage optimal control and design optimization problems for processes described by DAE models of index one. Our boundary value problem approach (a ..."
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Cited by 4 (0 self)
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An efficient and robust technique for the optimization of dynamic chemical processes is presented. In particular, we address the solution of large, multistage optimal control and design optimization problems for processes described by DAE models of index one. Our boundary value problem approach (a simultaneous solution strategy) is based on a piecewise parametrization of the control functions and a multiple shooting discretization of the DAEs, combined with a specifically tailored SQP technique. The inherent problem structure is exploited on various levels in order to obtain an efficient overall method. In addition, the formulation lends itself well to parallel computation. Unlike other simultaneous strategies based on collocation, direct use is made of existing advanced, fully adaptive DAE solvers. An implementation of this strategy is provided by the recently developed modular optimal control package MUSCODII. Apart from a difficult DAE test problem with control and path constrain...
Optimization Strategies for Dynamic Systems
 In C. Floudas, P. Pardalos (Eds), Encyclopedia of Optimization
, 1999
"... Introduction and Problem Statement Interest in dynamic simulation and optimization of chemical processes has increased significantly during the last two decades. Common problems include control and scheduling of batch processes; startup, upset, shutdown and transient analysis; safety studies and th ..."
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Cited by 3 (0 self)
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Introduction and Problem Statement Interest in dynamic simulation and optimization of chemical processes has increased significantly during the last two decades. Common problems include control and scheduling of batch processes; startup, upset, shutdown and transient analysis; safety studies and the evaluation of control schemes. Chemical processes are modeled dynamically using differentialalgebraic equations (DAEs). The DAE formulation consists of differential equations that describe the dynamic behavior of the system, such as mass and energy balances, and algebraic equations that ensure physical and thermodynamic relations. The general dynamic optimization problem can be stated as follows: min z(t);y(t);u(t);t f ;p '(z(t f ); y(t f ); u(t<F8
Optimization Framework for the Synthesis of Chemical Reactor Networks
, 1998
"... The reactor network synthesis problem involves determining the type, size, and interconnections of the reactor units, optimal concentration and temperature profiles, and the heat load requirements of the process. A general framework is presented for the synthesis of optimal chemical reactor networks ..."
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Cited by 2 (1 self)
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The reactor network synthesis problem involves determining the type, size, and interconnections of the reactor units, optimal concentration and temperature profiles, and the heat load requirements of the process. A general framework is presented for the synthesis of optimal chemical reactor networks via an optimization approach. The possible design alternatives are represented via a process superstructure which includes continuous stirred tank reactors and cross flow reactors along with mixers and splitters that connect the units. The superstructure is mathematically modeled using differential and algebraic constraints and the resulting problem is formulated as an optimal control problem. The solution methodology for addressing the optimal control formulation involves the application of a control parameterization approach where the selected control variables are discretized in terms of time invariant parameters. The dynamic system is decoupled from the optimization and solved as a func...
Optimal Operation of Alternating Activated Sludge Processes
"... The study presents dynamic optimisation of a small size single basin wastewater treatment plant. The objectives are to determine an optimal sequence of aeration/nonaeration times so that for a typical diurnal pattern of disturbances, the e#uent constraints are respected, the plant remains in peri ..."
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Cited by 1 (0 self)
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The study presents dynamic optimisation of a small size single basin wastewater treatment plant. The objectives are to determine an optimal sequence of aeration/nonaeration times so that for a typical diurnal pattern of disturbances, the e#uent constraints are respected, the plant remains in periodical steady state, and energy consumption is minimised.
A Novel Approach to Dynamic Optimization of ODE and DAE Systems as HighIndex Problems
, 1995
"... Solution of many problems in plant operations requires determination of optimal control profiles subject to state constraints for systems modeled by ordinary differential equations (ODEs) or differentialalgebraic equations (DAEs). For example, optimal temperature and/or feed rate profiles are im ..."
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Solution of many problems in plant operations requires determination of optimal control profiles subject to state constraints for systems modeled by ordinary differential equations (ODEs) or differentialalgebraic equations (DAEs). For example, optimal temperature and/or feed rate profiles are important for the operation of many batch reactions. Similar observations apply to reflux policies for batch distillation, and feedstock changeover in oil refineries. Currently there are two different classes of methods for determining optimal control profiles for DAEs. Control parameterization techniques rely on the discretization of the control variables to reduce the optimal control problem to an NLP. These methods require repeated integration of the DAEs and some variational equations, which effectively discretizes the state variables within the numerical integrator. Path constraints are typically handled by the master NLP solver, and can force the NLP solver to call for a large nu...
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"... and other research outputs The properties of differentialalgebraic equations representing optimal control problems Journal Article ..."
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and other research outputs The properties of differentialalgebraic equations representing optimal control problems Journal Article