The inerter: a retrospective

Abstract

The paper provides an introduction and overview of the inerter concept and device. Careful attention is given to the distinction between the inerter as an ideal modelling element and devices that approximate the ideal behaviour. The background is given to the formal definition of the inerter as a mechanical one-port with terminal forces proportional to the relative acceleration between them. Four major methods of construction are described and modelled. The discussion focuses particularly on: the notion of terminals; the distinction between a device and an effect; sign reversals; back-driving in geared systems; the conceptual aspects of the modelling step for inerter embodiments; the problem of reverse engineering to discover a purpose. The paper includes an analysis and discussion of the rotational inerter. A brief review of the ideas of passive network synthesis that led to the inerter concept are provided. A discussion and analysis is given on several examples of integrated mechanical devices. The article concludes with an imaginary dialogue between the author and an interlocutor on the understanding and purpose of the inerter.