Abstract

The purpose of this research is the development of design concepts and models of large-angle, compliant, multistable, revolute joints. This research presents evidence of the capability of these models and concepts by presenting a case study in which the miniaturization of revolute joints are examined. Previous attempts at multistable revolute joints can be categorized into two categories: compliant and non-compliant mechanisms. Non-compliant multistable revolute joints are typified by a combination of pin-in-slot joints, springs, and detents. Due to factors inherit in design, noncompliant joints often succumb to friction, wear, and undesirable motion, that leads to a decline in performance. Compliant multistable joints, such as those discussed in this work, negate these issues by allowing deflection in one or more of their members. However, compliant mechanisms have challenges associated with large-angle revolutions, stress concentration, and, historically, they perform poorly in compression. The literature has been lacking information on the fabrication of compliant multistable revolute joints having more than two stable positions. This work develops a truly multistable compliant revolute joint that is capable of multiple stable positions, the multistable compliant rolling-contact element(CORE). A CORE is a contact-aided complaint mechanism that eliminates friction and wear by allowing two surfaces to roll on each other. Furthermore, the contact eliminates problems such as poor performance in compression, typically associated with compliant mechanisms. The device uses minima in potential energy to achieve multi-stability, through one of six mechanisms. The use of minima in the potential energy eliminates the need for detents and other fatigue prone devices. Multistability may be achieved by placing the CORE flexure into tension or using flexible segments attached to the foci; or by changing the initial curvature of the flexure, curvature of the CORE surface, cross sectional area of the flexure (both protagonistically or antagonistically), or material properties. The stability methods are evaluated via a Pugh scoring matrix and the most promising concept, stability through tension in the CORE flexures, examined further. The utility of mathematical models, developed in this work, that predict stress, strain, and activation force, are demonstrated via a case study. This work also demonstrates that the device is capable of large angle deflections (360) and that the provided models permit efficient engineering design with COREs.

Degree

College and Department

Ira A. Fulton College of Engineering and Technology; Mechanical Engineering

Rights

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