Criteria for the Static Balancing of Compliant Mechanisms

2010 ◽  
Author(s):  
Juan A. Gallego ◽  
Just L. Herder
Keyword(s):  
Energy Storage ◽  
Rigid Body ◽  
Strain Energy ◽  
Compliant Mechanisms ◽  
Design Methods ◽  
Static Balancing ◽  
Torsion Springs

Compliant mechanisms achieve their mobility through the deformation of their members, this means that part of the energy transmitted from the input to the output of the mechanisms will be stored in the mechanisms as strain energy. This energy storage in some cases is not a desired characteristic and a way to solve this problem is by static balancing the behavior of the mechanisms. Here five criteria are presented that can be used in the static balancing of compliant mechanisms. The criteria are combined in a systematic way with design methods for compliant mechanisms as an exercise to find feasible combinations for the development of design methods for statically balanced compliant mechanisms. The feasibility of the combination between criteria and design methods for compliant mechanisms is demonstrated by using rigid body mechanisms with torsion springs, roughly emulating their compliant counterpart.

Application of Rigid-Body-Linkage Static Balancing Techniques to Reduce Actuation Effort in Compliant Mechanisms

2015 ◽  
Vol 8 (2) ◽  
Author(s):  
Sangamesh R. Deepak ◽  
Amrith N. Hansoge ◽  
G. K. Ananthasuresh
Keyword(s):  
Rigid Body ◽  
General Framework ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Small Length ◽  
Element Analysis ◽  
Static Balancing ◽  
Free Length ◽  
First Order ◽  
Taylor’S Series

There are analytical methods in the literature where a zero-free-length spring-loaded linkage is perfectly statically balanced by addition of more zero-free-length springs. This paper provides a general framework to extend these methods to flexure-based compliant mechanisms through (i) the well know small-length flexure model and (ii) approximation between torsional springs and zero-free-length springs. We use first-order truncated Taylor's series for the approximation between the torsional springs and zero-free-length springs so that the entire framework remains analytical, albeit approximate. Three examples are presented and the effectiveness of the framework is studied by means of finite-element analysis and a prototype. As much as 70% reduction in actuation effort is demonstrated. We also present another application of static balancing of a rigid-body linkage by treating a compliant mechanism as the spring load to a rigid-body linkage.

Compliant Wireform Mechanisms

2008 ◽  
Vol 130 (12) ◽  
Author(s):  
Tyler M. Pendleton ◽  
Brian D. Jensen
Keyword(s):  
Rigid Body ◽  
Compliant Mechanisms ◽  
Finite Element Models ◽  
Simplified Models ◽  
New Class ◽  
Body Model ◽  
Single Piece ◽  
Rigid Body Model ◽  
Torsion Springs ◽  
Torsion Bar

This paper presents an alternative to fabrication methods commonly used in compliant mechanisms research, resulting in a new class of compliant mechanisms called wireform mechanisms. This technique integrates torsional springs made of formed wire into compliant mechanisms. In this way the desired force, stiffness, and motion can be achieved from a single piece of formed wire. Two techniques of integrating torsion springs are fabricated and modeled: helical coil torsion springs and torsion bars. Because the mechanisms are more complex than ordinary springs, simplified models, which aid in design, are presented, which represent the wireform mechanisms as rigid-body mechanisms using the pseudo-rigid-body model. The method is demonstrated through the design of a mechanically tristable mechanism. The validity of the simplified models is discussed by comparison to finite element models and, in the case of the torsion-bar mechanism, to experimental measurements.

A Generalized Loop-Closure Theory for the Analysis and Synthesis of Compliant Mechanisms

1994 ◽  
Author(s):  
Larry L. Howell ◽  
Ashok Midha
Keyword(s):  
Energy Storage ◽  
Rigid Body ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Mechanism Analysis ◽  
Model Concept ◽  
Loop Closure ◽  
Body Model ◽  
Rigid Body Model ◽  
Analysis And Synthesis

Abstract Compliant mechanisms gain at least some of their motion from flexible members. The combination of large-deflection beam analysis, kinematic motion analysis, and energy storage makes the analysis of compliant mechanisms difficult. The design of mechanisms often requires iteration between synthesis and analysis procedures. In general, the difficulty in analysis has limited the use of compliant mechanisms to applications where only simple functions and motions are required. The pseudo-rigid-body model concept promises to be the key to unifying the compliant and rigid-body mechanism theories. It simplifies compliant mechanism analysis by determining an equivalent rigid-body mechanism that accurately models the kinematic characteristics of a compliant mechanism. Once this model is obtained, many well known concepts from rigid-body mechanism theory become amenable for use to analyze and design compliant mechanisms. The pseudo-rigid-body-model concept is used to develop a generalized loop-closure method for the analysis and synthesis of compliant mechanisms. Synthesis is divided into two major categories: (i) rigid-body replacement synthesis, wherein only kinematic constraints are considered, and (ii) synthesis for compliance, wherein considerations of the energy storage and input/output force/torque characteristics of compliant mechanisms are utilized. The method allows compliant mechanisms to be designed for tasks that would have earlier been assumed to be unlikely, if not impossible, applications of compliant mechanisms. Examples of function, motion, and path generation of compliant mechanisms are presented for the first time.

Pseudo-Rigid-Body Models of Compliant DNA Origami Mechanisms

2015 ◽  
Author(s):  
Lifeng Zhou ◽  
Alexander E. Marras ◽  
Carlos E. Castro ◽  
Hai-jun Su
Keyword(s):  
Rigid Body ◽  
Strain Energy ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Mechanical Energy ◽  
Energy Landscape ◽  
Thermal Fluctuations ◽  
Dna Origami ◽  
Double Stranded Dna ◽  
Flexible Parts

In this paper, we introduce the strategy of designing and analyzing compliant nanomechanisms fabricated with DNA origami which we call compliant DNA origami mechanism (CDOM). The rigid, compliant and flexible parts are constructed by a bunch of double-stranded DNA (dsDNA) helices, fewer dsDNA helices and single-stranded DNA (ssDNA) strands respectively. Just like in macroscopic compliant mechanisms, a CDOM generates its motion via deformation of at least one structural member. During the motion, strain energy is stored and released in the mechanism. These CDOM can suppress thermal fluctuations due to the internal mechanical energy barrier for motion. An example of compliant hinge joint and a bistable four-bar CDOM fabricated with DNA origami are discussed at the end of this paper. The classic pseudo-rigid-body (PRB) model for compliant mechanism is successfully employed to the analysis of these DNA origami nanomechanisms. This PRB model has been used to guide the design of a bistable CDOM for a desired energy landscape.

Design of Compliant Mechanisms for Minimizing Input Power in Dynamic Applications

2006 ◽  
Vol 129 (10) ◽  
pp. 1064-1075 ◽  
Author(s):  
Tanakorn Tantanawat ◽  
Sridhar Kota
Keyword(s):  
Energy Storage ◽  
Rigid Body ◽  
Power Flow ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Input Power ◽  
Power Requirement ◽  
Effective Manner ◽  
Flapping Mechanism

In this paper, we investigate power flow in compliant mechanisms that are employed in dynamic applications. More specifically, we identify various elements of the energy storage and transfer between the input, external load, and strain energy stored within the compliant transmission. The goal is to design compliant mechanisms for dynamic applications by exploiting the inherent energy storage capability of compliant mechanisms in the most effective manner. We present a detailed case study on a flapping mechanism, in which we compare the peak input power requirement in a rigid-body mechanism with attached springs versus a distributed compliant mechanism. Through this case study, we present two approaches: (1) generative-load exploitation and (2) reactance cancellation, to describe the role of stored elastic energy in reducing the peak input power requirement. We propose a compliant flapping mechanism and its evaluation using nonlinear transient analysis. The input power needed to drive the proposed compliant flapping mechanism is found to be 50% less than a rigid-link four-bar flapping mechanism without a spring, and 15% less than the one with a spring. This reduction of peak input power is primarily due to the exploitation of elasticity in compliant members. The results show that a compliant mechanism can be a better alternative to a rigid-body mechanism with attached springs.

Synthesis Methods in Compliant Mechanisms: An Overview

2009 ◽  
Author(s):  
Juan A. Gallego ◽  
Just Herder
Keyword(s):  
Rigid Body ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Design Methods ◽  
Synthesis Methods ◽  
Starting Point ◽  
Rigid Body Model ◽  
Wide Perspective ◽  
Conceptual Overview ◽  
Compliant Mechanism Design

Compliant mechanisms are rapidly gaining importance, yet their design remains challenging. A great variety of methods are being developed as it is reported in a growing stream of publications. However, so far no review of this body of literature is available. This paper provides a comprehensive and conceptual overview of the main notions behind the most relevant design methods for compliant mechanisms. Rigid-Body-Replacement methods including the Pseudo-Rigid-Body model and the FACT approach are covered, as well as Building Block approaches. In addition an introduction and explanation on Topology Optimization and Shape Optimization is provided, including their most common parameterizations and formulations. This work aims to serve as an introduction into compliant mechanism design methods and as a reference work for more experienced scholars and professionals. It is intended to be a starting point for the exploration of the literature, as well as a guide to specific papers about a particular design problem one may have. For this reason, the paper presents the methods in a wide perspective, emphasizing the conceptual ideas behind every method and refers to literature for details and advanced features.

Static Balancing of Four-Bar Linkages With Torsion Springs by Exerting Negative Stiffness Using Linear Spring at the Instant Center of Rotation

2020 ◽  
Author(s):  
Jorge A. Franco ◽  
Juan A. Gallego ◽  
Just L. Herder
Keyword(s):  
Compliant Mechanisms ◽  
Negative Stiffness ◽  
Path Generation ◽  
Static Balancing ◽  
Center Of Rotation ◽  
Straight Path ◽  
Body Model ◽  
Rigid Body Model ◽  
Linear Spring ◽  
Torsion Springs

Abstract A design approach for the quasi-static balancing of four-bar linkages with torsion springs is proposed. Such approach is useful on the design of statically balanced compliant mechanisms by setting the stiffness of the Pseudo-Rigid-Body-Model. Here the positive stiffness exhibited by torsion springs at the R-joints is compensated by a negative stiffness function. The negative stiffness is created by a non-zero-free-length linear spring connected between the coupler link and the ground, and where both connecting points trace a line directed to the coupler link’s instant center of rotation. An example of the static balancing of the Burmester’s linkage for straight path generation is developed, where actuation energy is reduced in 94% for a range of motion of 80 degrees for the input link.

Compliant Mechanisms Formed From Shaped Wire

2007 ◽  
Author(s):  
Tyler M. Pendleton ◽  
Brian D. Jensen
Keyword(s):  
Rigid Body ◽  
Compliant Mechanisms ◽  
Helical Coil ◽  
Finite Element Models ◽  
Simplified Models ◽  
Body Model ◽  
Single Piece ◽  
Rigid Body Model ◽  
Torsion Springs ◽  
Torsion Bar

This paper presents an alternative to fabrication methods commonly used in compliant mechanisms research. This method integrates torsional springs made of formed wire into compliant mechanisms. In this way the desired force, stiffness, and motion can be achieved from a single piece of formed wire. Two techniques of integrating torsion springs are fabricated and modeled: helical coil torsion springs and torsion bars. Because the mechanisms are more complex than ordinary springs, simplified models, which aid in design, are presented which represent the wireform mechanisms as rigid body mechanisms using the pseudo-rigid-body model. The method is demonstrated through the design of a mechanically tristable mechanism. The validity of the simplified models is discussed by comparison to finite element models and, in the case of the torsion bar mechanism, to experimental measurements.

Static Balancing of Four-Bar Compliant Mechanisms With Torsion Springs by Exerting Negative Stiffness Using Linear Spring At the Instant Center of Rotation

2021 ◽  
Vol 13 (3) ◽  
Author(s):  
Jorge A. Franco ◽  
Juan A. Gallego ◽  
Just L. Herder
Keyword(s):  
Compliant Mechanisms ◽  
Negative Stiffness ◽  
Path Generation ◽  
Static Balancing ◽  
Center Of Rotation ◽  
Straight Path ◽  
Body Model ◽  
Rigid Body Model ◽  
Linear Spring ◽  
Torsion Springs

Abstract A design approach for the quasi-static balancing of four-bar linkages with torsion springs is proposed. Such an approach is useful in the design of quasi-statically balanced fully compliant mechanisms by tuning the stiffness of the pseudo-rigid-body-model. Here, the positive stiffness exhibited by torsion springs at the R-joints is compensated by a negative stiffness function. The negative stiffness is created by a non-zero-free-length linear spring connected between the coupler link and the ground, and where both connecting points trace a line directed to the coupler link’s instant center of rotation. A full example of the static balancing of two compliant linkages for approximate straight path generation is developed, where actuation energy of the compliant designs is reduced in 66% and 54%, respectively.

Multistability of Compliant Sarrus Mechanisms

2012 ◽  
Author(s):  
Guimin Chen ◽  
Shouyin Zhang
Keyword(s):  
Rigid Body ◽  
Compliant Mechanisms ◽  
Spatial Motion ◽  
Deployable Structures ◽  
Static Balancing ◽  
Compliant Joints ◽  
Body Method

Although there are many examples of multistable compliant mechanisms in the literature, most of them are of planar configurations. Considering that a multistable mechanism providing spatial motion could be useful in numerous applications, this paper explores the multistable behavior of the overconstrained spatial Sarrus mechanisms with compliant joints (CSMs). The kinetostatics of CSMs have been formulated based on the pseudo-rigid-body method. The kinetostatic results show that a CSM is capable of exhibiting bistability, tristability, and quadristability. Possible applications of multistable CSMs include deployable structures, static balancing of human/robot bodies and weight compensators.

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