A Comparative Study of Sensitivity Computations in ESDIRK-Based Optimal Control Problems

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Hauptverfasser: Andersen, Anders Hilmar Damm, Jørgensen, John Bagterp
Format: Preprint
Veröffentlicht: 2024
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author Andersen, Anders Hilmar Damm
Jørgensen, John Bagterp
author_facet Andersen, Anders Hilmar Damm
Jørgensen, John Bagterp
contents In this paper, we compare the impact of iterated and direct approaches to sensitivity computation in fixed-step explicit singly diagonally-implicit Runge-Kutta (ESDIRK) methods when applied to optimal control problems (OCPs). We use the principle of internal numerical differentiation (IND) strictly for the iterated approach, i.e., reusing the iteration matrix factorizations, the number of Newton-type iterations, and Newton iterates, to compute the sensitivities. The direct method computes the sensitivities without using the Newton schemes. We compare the impact of the iterated and direct sensitivity computations in OCPs for the quadruple tank system. We benchmark the iterated and direct approaches with a base case. This base case is an OCP that applies an ESDIRK method that refactorizes the iteration matrix in every Newton iteration and uses a direct approach for sensitivity computations. In these OCPs, we vary the number of integration steps between control intervals and we evaluate the performance based on the number of SQP and QPs iterations, KKT violations, and the total number of function evaluations, Jacobian updates, and iteration matrix factorizations. The results indicate that the iterated approach outperforms the direct approach but yields similar performance to the base case.
format Preprint
id arxiv_https___arxiv_org_abs_2402_04667
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle A Comparative Study of Sensitivity Computations in ESDIRK-Based Optimal Control Problems
Andersen, Anders Hilmar Damm
Jørgensen, John Bagterp
Systems and Control
In this paper, we compare the impact of iterated and direct approaches to sensitivity computation in fixed-step explicit singly diagonally-implicit Runge-Kutta (ESDIRK) methods when applied to optimal control problems (OCPs). We use the principle of internal numerical differentiation (IND) strictly for the iterated approach, i.e., reusing the iteration matrix factorizations, the number of Newton-type iterations, and Newton iterates, to compute the sensitivities. The direct method computes the sensitivities without using the Newton schemes. We compare the impact of the iterated and direct sensitivity computations in OCPs for the quadruple tank system. We benchmark the iterated and direct approaches with a base case. This base case is an OCP that applies an ESDIRK method that refactorizes the iteration matrix in every Newton iteration and uses a direct approach for sensitivity computations. In these OCPs, we vary the number of integration steps between control intervals and we evaluate the performance based on the number of SQP and QPs iterations, KKT violations, and the total number of function evaluations, Jacobian updates, and iteration matrix factorizations. The results indicate that the iterated approach outperforms the direct approach but yields similar performance to the base case.
title A Comparative Study of Sensitivity Computations in ESDIRK-Based Optimal Control Problems
topic Systems and Control
url https://arxiv.org/abs/2402.04667