Memory Elements: A Paradigm Shift in Lagrangian Modeling of Electrical Circuits

TL;DR

This paper introduces a novel Lagrangian modeling approach for meminductors and memcapacitors using integrated charges and fluxes, enabling a variational formulation for nonconservative circuit elements.

Contribution

It proposes a new configuration space with integrated charges/fluxes, allowing Lagrangian and dual variational principles for mem-elements.

Findings

Derived Euler-Lagrange equations yield integrated Kirchhoff laws.

Included memristive losses via a scalar action function.

Provided mechanical analogs to explain mem-elements.

Abstract

Meminductors and memcapacitors do not allow a Lagrangian formulation in the classical sense since these elements are nonconservative in nature and the associated energies are not state functions. To circumvent this problem, a different configuration space is considered that, instead of the usual loop charges, consist of time-integrated loop charges. As a result, the corresponding Euler-Lagrange equations provide a set of integrated Kirchhoff voltage laws in terms of the element fluxes. Memristive losses can be included via a second scalar function that has the dimension of action. A dual variational principle follows by considering variations of the integrated node fluxes and yields a set of integrated Kirchhoff current laws in terms of the element charges. Although time-integrated charge is a somewhat unusual quantity in circuit theory, it may be considered as the electrical analogue of a mechanical quantity called absement. Based on this analogy, simple mechanical devices are presented that can serve as didactic examples to explain memristive, meminductive, and memcapacitive behavior.