Accuracy and precision: a new view on kinematic assessment of solid-state hinges and compliant mechanisms

TL;DR

This paper introduces a novel, eigenvalue-based method to quantitatively assess the accuracy and precision of compliant mechanisms, addressing ambiguities in traditional evaluation criteria by leveraging concepts from measurement theory.

Contribution

It proposes a new approach using eigenvalue analysis of hinge stiffness to evaluate compliant mechanisms' quality, improving clarity over existing methods.

Findings

Eigenvalue analysis effectively quantifies accuracy and precision.

The method reduces ambiguities in traditional assessment criteria.

It provides a more objective evaluation of compliant mechanisms.

Abstract

Compliant mechanisms are alternatives to conventional mechanisms which exploit elastic strain to produce desired deformations instead of using moveable parts. They are designed for a kinematic task (providing desired deformations) but do not possess a kinematics in the strict sense. This leads to difficulties while assessing the quality of a compliant mechanism's design. The kinematics of a compliant mechanism can be seen as a fuzzy property. There is no unique kinematics, since every deformation need a particular force system to act; however, certain deformations are easier to obtain than others. A parallel can be made with measurement theory: the measured value of a quantity is not unique, but exists as statistic distribution of measures. A representative measure of this distribution can be chosen to evaluate how far the measures divert from a reference value. Based on this analogy, the concept of accuracy and precision of compliant systems are introduced and discussed in this paper. A quantitative determination of these qualities based on the eigenvalue analysis of the hinge's stiffness is proposed. This new approach is capable of removing most of the ambiguities included in the state-of-the-art assessment criteria (usually based on the concepts of path deviation and parasitic motion).