Document Type
Article
Publication Date
2024
DOI
10.1016/j.sysconle.2024.105783
Publication Title
Systems and Control Letters
Volume
187
Pages
105783
Abstract
Consider an input–output system where the output is the tracking error given some desired reference signal. It is natural to consider under what conditions the problem has an exact solution, that is, the tracking error is exactly the zero function. If the system has a well defined relative degree and the zero function is in the range of the input–output map, then it is well known that the system is locally left invertible, and thus, the problem has a unique exact solution. A system will fail to have relative degree when more than one exact solution exists. The general goal of this paper is to describe a decomposition of an input–output system having a Chen-Fliess series representation into a parallel product of subsystems in order to identify possible solutions to the problem of zeroing the output. For computational purposes, the focus is on systems whose generating series are polynomials. It is shown that the shuffle algebra on the set of generating polynomials is a unique factorization domain so that any polynomial can be uniquely factored modulo a permutation into its irreducible elements for the purpose of identifying the subsystems in a parallel product decomposition. This is achieved using the fact that this shuffle algebra is isomorphic to the symmetric algebra over the vector space spanned by Lyndon words. A specific algorithm for factoring generating polynomials into its irreducible factors is presented based on the Chen-Fox-Lyndon factorization of words.
Rights
© 2024. This manuscript version is made available under the CC-BY-NC-ND 4.0 license. https://creativecommons.org/licenses/by-nc-nd/4.0/
Original Publication Citation
Gray, W. S., Ebrahimi-Fard, K., & Schmeding, A. (2024). Decompositions of nonlinear input–output systems to zero the output. Systems & Control Letters, 187, Article 105783. https://doi.org/10.1016/j.sysconle.2024.105783
Repository Citation
Gray, W. Steven; Ebrahimi-Fard, Kurusch; and Schmeding, Alexander, "Decompositions of Nonlinear Input-Output Systems to Zero the Output" (2024). Electrical & Computer Engineering Faculty Publications. 439.
https://digitalcommons.odu.edu/ece_fac_pubs/439
Comments
This is the accepted manuscript version of the article, that has been made available under a Creative Commons License. The published version of the article is available at: https://doi.org/10.1016/j.sysconle.2024.105783