Dual-system methods in dynamical analysis. Part 1: Variational principles and their application to nonlinear-network theory

The feedback connection of a dynamical system and its dual, through nonlinear coupling elements, is shown to generate a pair of fundamental stationary principles. These provide a unified basis for both the classical Lagrangian and Hamiltonian treatments of dynamical systems aud modern work on nonlinear network theory and linear optimal-control theory.