Relaxation Systems and Cyclic Monotonicity
Thomas Chaffey, Henk J. van Waarde, Rodolphe J. Sepulchre · 2023
It is shown that an LTI system is a relaxation system if and only if its Hankel operator is cyclic monotone. Cyclic monotonicity of the Hankel operator implies the existence of a storage function whose gradient is the Hankel operator. This storage is a function of past inputs alone, is independent of the state space realization, and admits a generalization to nonlinear circuit elements.