Research Papers

Mobility and Constraint Analysis of Interconnected Hybrid Flexure Systems Via Screw Algebra and Graph Theory

[+] Author and Article Information
Frederick Sun

Mechanical and Aerospace Engineering,
University of California, Los Angeles,
Los Angeles, CA 90095
e-mail: frederis@seas.ucla.edu

Jonathan B. Hopkins

Mechanical and Aerospace Engineering,
University of California, Los Angeles,
Los Angeles, CA 90095
e-mail: hopkins@seas.ucla.edu

1Corresponding author.

Manuscript received November 23, 2016; final manuscript received January 20, 2017; published online March 27, 2017. Assoc. Editor: Larry L. Howell.

J. Mechanisms Robotics 9(3), 031018 (Mar 27, 2017) (12 pages) Paper No: JMR-16-1363; doi: 10.1115/1.4035993 History: Received November 23, 2016; Revised January 20, 2017

This paper introduces a general method for analyzing flexure systems of any configuration, including those that cannot be broken into parallel and serial subsystems. Such flexure systems are called interconnected hybrid flexure systems because they possess limbs with intermediate bodies that are connected by flexure systems or elements. Specifically, the method introduced utilizes screw algebra and graph theory to help designers determine the freedom spaces (i.e., the geometric shapes that represent all the ways a body is permitted to move) for all the bodies joined together by compliant flexure elements within interconnected hybrid flexure systems (i.e., perform mobility analysis of general flexure systems). This method also allows designers to determine (i) whether such systems are under-constrained or not and (ii) whether such systems are over-constrained or exactly constrained (i.e., perform constraint analysis of general flexure systems). Although many flexure-based precision motion stages, compliant mechanisms, and microarchitectured materials possess topologies that are highly interconnected, the theory for performing the mobility and constraint analysis of such interconnected flexure systems using traditional screw theory does not currently exist. The theory introduced here lays the foundation for an automated tool that can rapidly generate the freedom spaces of every rigid body within a general flexure system without having to perform traditional computationally expensive finite element analysis. Case studies are provided to demonstrate the utility of the proposed theory.

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Grahic Jump Location
Fig. 1

Flexure system categories (a); interconnected hybrid system examples (b)

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Fig. 2

Parameters that define a twist vector (a) and a wrench vector (b); DOFs (c), freedom space (d), and constraint space (e) of a blade; DOFs (f), freedom space (g), and constraint space (h) of a wire (see figure online for color)

Grahic Jump Location
Fig. 3

Parallel system (a), elements' constraint spaces (b), system's constraint space (c), system's freedom space (d), elements' freedom spaces (e); serial system (f), subsystems' freedom spaces (g), system's freedom space (h), system's constraint space (i), and subsystems' constraint spaces (j) (see figure online for color)

Grahic Jump Location
Fig. 4

Hybrid system (a); its freedom space (b); interconnected hybrid system (c) (see figure online for color)

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Fig. 5

Joint freedom spaces (a); independent twists within spaces (b); system graph (c); two independent paths (d); and freedom spaces of the system's bodies (e) (see figure online for color)




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