Adaptation is Unnecessary in L1-"Adaptive" Control

TL;DR

This paper demonstrates that the recently proposed L1-adaptive control architecture is essentially equivalent to a classical full-state feedback proportional-integral controller with a decaying disturbance, challenging claims of novelty.

Contribution

It clarifies that the so-called L1-adaptive control architecture is not fundamentally new but matches a well-known classical control method.

Findings

L1-adaptive control is equivalent to a classical PI controller with disturbance.

The supposed novelty of L1-adaptive control is unfounded.

Classical control methods suffice for the scenarios addressed by L1-adaptive control.

Abstract

We show in the paper that the, so--called, "new architecture of L_1-Adaptive Control" is, indeed, different from classical model reference adaptive control. Alas, it is not new, since it exactly coincides with a full--state feedback, linear time--invariant proportional plus integral controller (with a decaying additive disturbance).