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An efficient direct/indirect transcription approach for singular optimal control
Author(s) -
AndrésMartínez Oswaldo,
FloresTlacuahuac Antonio,
Kameswaran Shivakumar,
Biegler Lorenz T.
Publication year - 2019
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.16487
Subject(s) - singular control , invertible matrix , optimal control , mathematical optimization , regularization (linguistics) , mathematics , nonlinear system , interval (graph theory) , nonlinear programming , control theory (sociology) , computer science , control (management) , physics , quantum mechanics , combinatorics , artificial intelligence , pure mathematics
It is very common in chemical engineering applications to find optimal control problems whose optimality conditions do not provide information about the control over an interval. This type of problems is called partially singular, as the control switches between nonsingular and singular arcs. When direct transcription is applied, the resulting nonlinear programming problem is ill conditioned. Some mesh refinement and rigorous iterative methods have been developed to determine the control profile and switching points. This work presents a practical alternative that quickly produces accurate state and control profiles without adding nonconvex terms. The problem is first solved with a large number of equally spaced finite elements. Then, unnecessary elements are removed while keeping the solution structure. Finally, direct and indirect approaches are combined to apply a regularization scheme only to the singular part. Seven examples were solved to test our strategy. Results provide good approximations to the analytical switching points . © 2018 American Institute of Chemical Engineers AIChE J , 65: 937–946, 2019