Compliant Mechanism Synthesis Using Degree of Genus and Variable Width Curves

2014 ◽  
Author(s):  
Hong Zhou ◽  
Azher Hussain Naser Mohammed
Keyword(s):  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Structural Complexity ◽  
Joint Effect ◽  
Synthesis Process ◽  
Mechanism Synthesis ◽  
Shape Morphing ◽  
Optimizing Control ◽  
Material Layout ◽  
Shape And Size

Compliant mechanisms (CMs) utilize elastic deformations for mechanism functions. Their merits primarily come from jointless structures. The structure of a fully CM is a piece of elastic material and is defined by its topology, shape and size. Topology is the overarching material layout of a CM while shape and size are on its structural details, but topology is entangled with shape and size in the synthesis process of a CM because its elastic deformation is from the joint effect of topology, shape and size. Degree of freedom (DOF) and number of links used in rigid mechanism synthesis are not effective to guide the synthesis of CMs since any point of a fully CM can deform and its whole structure forms a single piece. Without effective synthesis guidance, the structural complexity of a synthesized CM can be undesirably high. In this paper, degree of genus (DOG) is introduced for topology guidance of CM synthesis. DOG of a CM is the number of holes and is actively controlled during its synthesis process. With DOG guidance, a synthesized CM will not have overcomplicated topology. Variable width curves (VWCs) are introduced in this paper for shape and size description. Any connection in a CM is defined as a VWC and the entire CM is modeled as a network of VWCs. With VWC description, a synthesized CM will not have unsmooth connection. Under DOG and VWC strategies, CM synthesis is systematized as optimizing control parameters of networks of VWCs. The proposed CM synthesis using DOG and VWC strategies is demonstrated by synthesizing shape morphing compliant mechanisms.

A Methodology for Compliant Mechanisms Design: Part I — Introduction and Large-Deflection Analysis

1992 ◽  
Author(s):  
A. Midha ◽  
I. Her ◽  
B. A. Salamon
Keyword(s):  
Large Deflection ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Companion Paper ◽  
Computational Techniques ◽  
Shooting Methods ◽  
Mechanism Synthesis ◽  
Calculation Algorithm ◽  
Deflection Analysis ◽  
Kinematic Properties

Abstract A broader research proposal seeks to systematically combine large-deflection mechanics of flexible elements with important kinematic considerations, in yielding compliant mechanisms which perform useful tasks. Specifically, the proposed design methodology will address the following needs: development of the necessary nomenclature, classification and definitions, and identification of the kinematic properties; categorization of mechanism synthesis types, both structurally as well as by function; development of efficient computational techniques for design; consideration of materials; and application and validation. Contained herein, in particular, is an introduction to the state-of-the-art in compliant mechanisms, and the development of an accurate chain calculation algorithm for use in the analysis of a large-deflection, cantilevered elastica. Shooting methods, which permit specification of additional boundary conditions on the elastica, as well as compliant mechanism examples are presented in a companion paper.

Design of Crashworthy Structures With Controlled Energy Absorption in the Hybrid Cellular Automaton Framework

2013 ◽  
Vol 135 (9) ◽  
Author(s):  
Punit Bandi ◽  
James P. Schmiedeler ◽  
Andrés Tovar
Keyword(s):  
Energy Absorption ◽  
Design Space ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Mechanism Synthesis ◽  
Load Paths ◽  
Fully Stressed Design ◽  
Novel Method ◽  
The Given ◽  
Synthesis Approach

This work presents a novel method for designing crashworthy structures with controlled energy absorption based on the use of compliant mechanisms. This method helps in introducing flexibility at desired locations within the structure, which in turn reduces the peak force at the expense of a reasonable increase in intrusion. For this purpose, the given design domain is divided into two subdomains: flexible (FSD) and stiff (SSD) subdomains. The design in the flexible subdomain is governed by the compliant mechanism synthesis approach for which output ports are defined at the interface between the two subdomains. These output ports aid in defining potential load paths and help the user make better use of a given design space. The design in the stiff subdomain is governed by the principle of a fully stressed design for which material is distributed to achieve uniform energy distribution within the design space. Together, FSD and SSD provide for a combination of flexibility and stiffness in the structure, which is desirable for most crash applications.

A Compliant Mechanism Design Methodology for Coupled and Uncoupled Systems, and Governing Free Choice Selection Considerations

2004 ◽  
Author(s):  
Ashok Midha ◽  
Yuvaraj Annamalai ◽  
Sharath K. Kolachalam
Keyword(s):  
Rigid Body ◽  
Design Methodology ◽  
Free Choice ◽  
Compliant Mechanisms ◽  
State Of The Art ◽  
Compliant Mechanism ◽  
Mechanism Synthesis ◽  
Strongly Coupled ◽  
Revolute Joints ◽  
Compliant Mechanism Design

Compliant mechanisms are defined as mechanisms that gain some, or all of their mobility from the flexibility of their members. Suitable use of pseudo-rigid-body models for compliant segments, and relying on the state-of-the-art knowledge of rigid-body mechanism synthesis types, greatly simplifies the design of compliant mechanisms. Assuming a pseudo-rigid-body four-bar mechanism, with one to four torsional springs located at the revolute joints to represent mechanism compliance, a simple, heuristic approach is provided to develop various compliant mechanism types. The synthesis with compliance method is used for three, four and five precision positions, with consideration of one to four torsional springs, to systematically develop design tables for standard mechanism synthesis types. These tables appropriately reflect the mechanism compliance by specification of either energy or torque. Examples are presented to demonstrate the use of weakly or strongly coupled sets of kinematic and energy/torque equations, as well as different compliant mechanism types in obtaining solutions.

Optimal Synthesis of Compliant Mechanisms to Satisfy Kinematic and Structural Requirements: Preliminary Results

1996 ◽  
Author(s):  
Mary I. Frecker ◽  
Noboru Kikuchi ◽  
Sridhar Kota
Keyword(s):  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Synthesis Method ◽  
Design Procedure ◽  
Problem Formulation ◽  
Mechanism Synthesis ◽  
Ground Structure ◽  
Design Problems ◽  
Structural Requirements ◽  
External Loads

Abstract Compliant mechanism synthesis is an automated design procedure which allows the designer to systematically generate the optimal structural form for a particular set of loading and motion requirements. The synthesis method presented here solves a particular class of design problems, where the compliant mechanism is required to be both flexible to meet motion requirements, and stiff to withstand external loads. A two-part problem formulation is proposed using mutual and strain energies, whereby the conflicting design objectives of required flexibility and stiffness are handled via multi-criteria optimization. The resulting compliant mechanism topologies satisfy both kinematic and structural requirements. The problem formulation is implemented using a truss ground structure and SLP algorithm. Several design examples are presented to illustrate this method.

On the Classification of Compliant Mechanisms and Synthesis of Compliant Single-Strip Mechanisms

2011 ◽  
Author(s):  
Ashok Midha ◽  
Sharath K. Kolachalam ◽  
Yuvaraj Annamalai
Keyword(s):  
Rigid Body ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Basic Mechanism ◽  
Governing Equations ◽  
Mechanism Synthesis ◽  
Synthesis Techniques ◽  
Single Strip

Compliant mechanisms, unlike rigid-body mechanisms, are devices that derive some or all of their mobility due to the deformation of their flexible members. The knowledge of existing rigid-body mechanism synthesis techniques is very useful in designing compliant mechanisms. In rigid-body mechanisms, a four-bar is treated as the basic mechanism that can transfer motion, force or energy. In this paper, a compliant single-strip continuum is introduced as the basic compliant mechanism that can transfer motion, force or energy. A classification of compliant mechanisms is presented herein. A methodology for compliant single-strip mechanism synthesis for energy, force or torque specifications is developed in this research as our second objective. The synthesis types, the governing equations, and the variables involved are enumerated.

Estimating Stress Bounds in Early-Stage Design of Distributed Compliant Mechanisms

2016 ◽  
Author(s):  
Sreekalyan Patiballa ◽  
John Francis Shanley ◽  
Girish Krishnan
Keyword(s):  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Early Stage ◽  
Functional Characterization ◽  
Stress Constraints ◽  
Design Stage ◽  
Synthesis Process ◽  
Early Design Stage ◽  
Computationally Intensive ◽  
Early Stage Design

Synthesis of distributed compliant mechanisms is often a two-stage process involving (a) conceptual topology synthesis, and a subsequent (b) refinement stage to meet stress and manufacturing specifications. The usefulness of a solution is ascertained only after the sequential completion of these two steps, which are in general computationally intensive. This paper presents a strategy to rapidly estimate final operating stresses even before the actual refinement process. This strategy is based on the uniform stress distribution metric, and a functional characterization of the different members that constitute the compliant mechanism topology. It enables selecting the best conceptual solution for further optimization, thus maximally avoiding refinement of topologies that inherently may not meet the stress constraints. Furthermore this strategy enables modifying topologies at the early design stage to meet final stress specifications, thus greatly accelerating the overall synthesis process.

Analysis of the Hex Cell Discretization for Topology Synthesis of Compliant Mechanisms

2007 ◽  
Author(s):  
Nilesh D. Mankame ◽  
Anupam Saxena
Keyword(s):  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Continuous Optimization ◽  
Elastic Response ◽  
Cell Design ◽  
Stable Convergence ◽  
Mechanism Synthesis ◽  
Single Node ◽  
Square Cell ◽  
The Ideal

We use non-linear finite element simulations to study the convergence behavior of the honeycomb or hex cell design discretization for optimization-based synthesis of compliant mechanisms in this paper. Adjacent elements share exactly one common edge in the hex cell discretization, unlike the square cell discretization in which adjacent elements can be connected by a single node. As the single node connections in bilinear quadrilateral plane stress elements allow strain-free relative rotations, compliant mechanism designs obtained from square cell discretizations with these elements often contain elements with single node connections or point flexures. Point flexures are sites of lumped compliance, and as such, are undesirable as they lead to compliant mechanisms designs which deviate from the ideal of distributed compliance. The hex cell design discretization circumvents the problem of point flexures without any additional computational expense (e.g. filtering, extra constraints, etc.) by exploiting the geometry of the discretization. In this work we compare the elastic response of a group of four cells in which two adjacent cells have the least connectivity in both: the square and the hex discretizations. Simulations show that the hex cell discretization leads to a more accurate modeling of the displacement, stress and strain energy fields in the vicinity of the least connectivity regions than the square cell discretization. Therefore, the hex cell discretization does not suffer from stress singularities that plague the square cell discretization. These properties ensure that continuous optimization-based compliant mechanism synthesis procedures that use the hex cell discretization, exhibit a faster and more stable convergence to designs that can be readily manufactured than those that use the square cell discretization.

Multivariate Parameter Sets for Optimal Synthesis of Compliant Mechanisms

2005 ◽  
Author(s):  
Alexander Shibakov ◽  
Stephen L. Canfield ◽  
Patrick V. Hull
Keyword(s):  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Mesh Size ◽  
Synthesis Process ◽  
Design Parameters ◽  
Control Points ◽  
Computationally Efficient ◽  
Alternative Approach ◽  
Multivariate Parameter ◽  
Simple Mapping

This paper will propose the use of control maps along with discretized elements or meshes in the design parameter set for optimizing compliant mechanisms. The use of control maps will be demonstrated to encode the motion of groups of nodes or control points defining the mesh with simple mapping rules. The technique will serve as an alternative to increased mesh size or node wandering techniques that have been proposed to increase the number of alternative design shapes that may be considered. As an alternative approach, the proposed control map parameterization has the significant benefit that it minimizes the number of design parameters necessary (parameters increase linearly with the mesh size) in describing a given design making it computationally efficient. A limited number of tiles can produce a map that has a significant effect on the final shape. If the tiles are chosen appropriately, the problems such as material overlap and non-convex mesh elements are avoided automatically. This paper will describe the implementation of these control maps and provide several examples showing their implementation in the compliant mechanism topology synthesis process.

A Conceptual Design Tool for Synthesis of Spatial Compliant and Shape Morphing Mechanisms

2018 ◽  
Author(s):  
Sreekalyan Patiballa ◽  
Kazuhiro Uchikata ◽  
Ramkumar Komanduri Ranganath ◽  
Girish Krishnan
Keyword(s):  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Shape Change ◽  
Design Guidelines ◽  
Design Tool ◽  
Three Dimensions ◽  
Shape Morphing ◽  
Compliant Surfaces ◽  
Flow Through ◽  
External Loads

Synthesis of spatial compliant mechanisms for morphing surfaces in three dimensions is challenging as it not only involves meeting the kinematic requirement for spatial shape change, but also providing support against external loads. In three dimensions, there are no existing insightful techniques for synthesis, and the computational approaches are rendered complex. This paper builds on a new insightful technique to synthesize compliant mechanism topologies by visualizing a kinetostatic field of forces that flow through the mechanism geometry. Such a framework when extended to three dimensions, enables a maximally decoupled synthesis framework of shape morphing compliant surfaces, where a primary mechanism meets the shape change requirement, and an auxiliary mechanism provides the required support under external loads. The preliminary design guidelines are implemented using an immersive Virtual Reality based design tool, and verified using finite element simulations for several spatial compliant mechanisms. This design framework is deemed useful for a larger class of shape morphing structures beyond the examples presented in the paper.

Design of Crashworthy Structures With Controlled Energy Absorption in the HCA Framework

2012 ◽  
Author(s):  
Punit Bandi ◽  
James P. Schmiedeler ◽  
Andrés Tovar
Keyword(s):  
Energy Absorption ◽  
Design Space ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Mechanism Synthesis ◽  
Load Paths ◽  
Fully Stressed Design ◽  
Novel Method ◽  
The Given ◽  
Synthesis Approach

This work presents a novel method for designing crashworthy structures with controlled energy absorption based on the use of compliant mechanisms. This method helps in introducing flexibility at desired locations within the structure, which in turn reduces the peak force at the expense of a reasonable increase in intrusion. For this purpose, the given design domain is divided into two subdomains: flexible (FSD) and stiff (SSD) subdomains. The design in the flexible subdomain is governed by the compliant mechanism synthesis approach for which output ports are defined at the interface between the two subdomains. These output ports aid in defining potential load paths and help the user make better use of a given design space. The design in the stiff subdomain is governed by the principle of a fully-stressed design for which material is distributed to achieve uniform energy distribution within the design space. Together, FSD and SSD provide for a combination of flexibility and stiffness in the structure, which is desirable for most crash applications.

Sign in / Sign up

Export Citation Format

Share Document