Synthesis of Planar Compliant Mechanisms

2007 ◽  
Author(s):  
Tewodros E. Mengesha ◽  
Kerr-Jia Lu
Keyword(s):  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Design Method ◽  
Computing Time ◽  
Structural Connectivity ◽  
Solution Space ◽  
Repair Process ◽  
Discrete Topology ◽  
Topology Optimization Problem ◽  
Path Representation

This paper introduces a compliant mechanism design method that guarantees structural connectivity and planarity of the resulting design. The structural connectivity is ensured by a path-representation, while a coin-optimization process is introduced to verify the planarity of the design. A non-planar design can be “planarized” by a coin-repair process, thus all non-planar designs can be effectively excluded from the solution space. The discrete topology optimization problem is incorporated in a genetic algorithm. The resulting topology is further processed through size and shape optimization for improved stress distribution. The results from two benchmarking design examples showed that the proposed method is capable of producing planar mechanisms in a reasonable amount of computing time. The presented design method will be incorporated into an on-going research in the design of biomimetic wings for Micro-Aerial Vehicles (MAVs).

The Uncertainty Elimination in Discrete Topology Optimization of Compliant Mechanisms

2013 ◽  
Author(s):  
Hong Zhou ◽  
Satya Raviteja Kandala
Keyword(s):  
Topology Optimization ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Optimization Process ◽  
Design Domain ◽  
Discrete Topology ◽  
Optimization Strategy ◽  
Hybrid Discretization ◽  
Ambiguous Point

Topology uncertainty leads to different topology solutions and makes topology optimization ambiguous. Point connection and grey cell might cause topology uncertainty. They are both eradicated when hybrid discretization model is used for discrete topology optimization. A common topology uncertainty in the current discrete topology optimization stems from mesh dependence. The topology solution of an optimized compliant mechanism might be uncertain when its design domain is discretized differently. To eliminate topology uncertainty from mesh dependence, the genus based topology optimization strategy is introduced in this paper. The topology of a compliant mechanism is defined by its genus which is the number of holes in the compliant mechanism. With this strategy, the genus of an optimized compliant mechanism is actively controlled during its topology optimization process. There is no topology uncertainty when this strategy is incorporated into discrete topology optimization. The introduced topology optimization strategy is demonstrated by examples with different degrees of genus.

A Two-Stage Design Method for Compliant Mechanisms Having Specified Non-Linear Output Paths

2006 ◽  
Author(s):  
Masakazu Kobayashi ◽  
Hiroshi Yamakawa ◽  
Shinji Nishiwaki ◽  
Kazuhiro Izui ◽  
Masataka Yoshimura
Keyword(s):  
Topology Optimization ◽  
Shape Optimization ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Design Method ◽  
Two Stage ◽  
Traditional Methods ◽  
Stage Design ◽  
Second Stage ◽  
Additional Constraints

Compliant mechanisms generated by traditional topology optimization methods have linear output response, and it is difficult for traditional methods to implement mechanisms having non-linear output responses, such as nonlinear deformation or path. To design a compliant mechanism having a specified nonlinear output path, a two-stage design method based on topology and shape optimization is constructed here. In the first stage, topology optimization generates an initial and conceptual compliant mechanism based on ordinary design conditions, with “additional” constraints that are used to control the output path at the second stage. In the second stage, an initial model for the shape optimization is created, based on the result of the topology optimization, and the additional constraints are replaced by spring elements. The shape optimization is then executed, to generate a detailed shape of the compliant mechanism having the desired output path. In this stage, parameters that represent the outer shape of the compliant mechanism and the properties of spring elements are used as design variables in the shape optimization. In addition to configuration of the specified output path, executing the shape optimization after the topology optimization also makes it possible to consider the stress concentration and large displacement effects. This is an advantage offered by the proposed method, since it is difficult for traditional methods to consider these aspects, due to inherent limitations of topology optimization.

On Optimal Design of Compliant Mechanisms for Specified Nonlinear Path Using Curved Frame Elements and Genetic Algorithm

2006 ◽  
Author(s):  
Ashok Rai ◽  
Anupam Saxena ◽  
Nilesh D. Mankame ◽  
Chandra Shekhar Upadhyay
Keyword(s):  
Genetic Algorithm ◽  
Compliant Mechanisms ◽  
Beam Theory ◽  
Topology Design ◽  
Size Optimization ◽  
Discrete Topology ◽  
Topology Optimization Problem ◽  
Young’S Moduli ◽  
Design Variables ◽  
Out Of Plane

This paper discusses topology, shape and size optimization of fully compliant mechanisms for path generation applications using curved frame elements and genetic algorithm. The topology optimization problem is treated as a discrete ‘0-1’ problem wherein the elastic modulus is chosen as 0 or some pre-specified value, and no intermediate value in between. As the Young’s moduli are discrete topology design variables, function based genetic algorithm is employed for optimization. The size optimization variables are the lengths, in-plane widths and out-of-plane thicknesses of frame elements. Shape optimization is performed using the end slopes. Kirchhoff’s shallow arch beam theory is employed along with co-rotational geometrically nonlinear formulation. Synthesis examples are presented to demonstrate the applicability of min-max criterion proposed to achieve a curved path specified using precision points.

Hinged Beam Elements for the Topology Design of Compliant Mechanisms Using the Ground Structure Approach

2006 ◽  
Author(s):  
Deepak S. Ramrkahyani ◽  
Mary I. Frecker ◽  
George A. Lesieutre
Keyword(s):  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Topology Design ◽  
Ground Structure ◽  
Topology Optimization Problem ◽  
Beam Elements ◽  
New Type ◽  
Beam Type ◽  
Compliant Mechanism Design ◽  
Ground Structure Approach

The design obtained from a topology optimization problem can largely depend on the type of the ground structure used. A new type of ground structure containing hinged beam elements is described in this paper that reduces the dependence of the optimal design on the ground structure. Apart from the beam and truss elements that have traditionally been used, two new types of elements are introduced: 1) a beam with a hinge on one end and a solid connection on the other end, 2) beam element with hinges on both ends. These elements are particularly useful when applied to a compliant mechanism design using a truss/beam type ground structure. A couple of compliant mechanism problems are solved to demonstrate the effectiveness of these elements.

Distributed Shape Optimization of Compliant Mechanisms Using Intrinsic Functions

2007 ◽  
Author(s):  
Chao-Chieh Lan ◽  
Yung-Jen Cheng
Keyword(s):  
Stress Concentration ◽  
Shooting Method ◽  
Abrupt Change ◽  
Compliant Mechanisms ◽  
Optimization Problems ◽  
Compliant Mechanism ◽  
Design Method ◽  
Geometry Optimization ◽  
Systematic Design ◽  
Body Type

A compliant mechanism transmits motion and force by deformation of its flexible members. It has no relative moving parts and thus involves no wear, lubrication, noise, and backlash. Compliant mechanisms aims to maximize flexibility while maintaining sufficient stiffness so that satisfactory output motion can be achieved. When designing compliant mechanisms, the resulting shapes sometimes lead to rigid-body type linkages where compliance and rotation is lumped at a few flexural pivots. These flexural pivots are prone to stress concentration and thus limit compliant mechanisms to applications that only require small-deflected motion. To overcome this problem, a systematic design method is presented to synthesize the shape of a compliant mechanism so that compliance is distributed more uniformly over the mechanism. With a selected topology and load conditions, this method characterizes the free geometric shape of a compliant segment by its rotation and thickness functions. These two are referred as intrinsic functions and they describe the shape continuously within the segment so there is no abrupt change in geometry. Optimization problems can be conveniently formulated with cusps and intersecting loops naturally circumvented. To facilitate the optimization process, a numerical algorithm based on the generalized shooting method will be presented to solve for the deflected shape. Illustrative examples will demonstrate that through the proposed design method, compliant mechanisms with distributed compliance will lessen stress concentration so they can be more robust and have larger deflected range. It is expected that the method can be applied to design compliant mechanisms that have a wide variety of applications from precision instruments to biomedical devices.

Multi-material topology optimization of large-displacement compliant mechanisms considering material-dependent boundary condition

2021 ◽  
pp. 095440622110361
Author(s):  
Jinqing Zhan ◽  
Yu Sun ◽  
Min Liu ◽  
Benliang Zhu ◽  
Xianmin Zhang
Keyword(s):  
Boundary Condition ◽  
Topology Optimization ◽  
Optimization Problem ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Impedance Matching ◽  
Large Displacement ◽  
Thermal Impedance ◽  
Output Displacement ◽  
Topology Optimization Problem

Multi-material compliant mechanisms design enables potential design possibilities by exploiting the advantages of different materials. To satisfy mechanical/thermal impedance matching requirements, a method for multi-material topology optimization of large-displacement compliant mechanisms considering material-dependent boundary condition is presented in this study. In the optimization model, the element stacking method is employed to describe the material distribution and handle material-dependent boundary condition. The maximization of the output displacement of the compliant mechanism is developed as the objective function and the structural volume of each material is the constraint. Fictitious domain approach is applied to circumvent the numerical instabilities in topology optimization problem with geometrical nonlinearities. The method of moving asymptotes is applied to solve the optimization problem. Several numerical examples are presented to demonstrate the validity of the proposed method. The optimal topologies of the compliant mechanisms obtained by the proposed method can satisfy the specified material-dependent boundary condition.

scholarly journals Integrated Multi-Step Design Method for Practical and Sophisticated Compliant Mechanisms Combining Topology and Shape Optimizations

2007 ◽  
Vol 19 (2) ◽  
pp. 141-147
Author(s):  
Masakazu Kobayashi ◽  
◽  
Shinji Nishiwaki ◽  
Hiroshi Yamakawa ◽  
◽  
...  
Keyword(s):  
Topology Optimization ◽  
Shape Optimization ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Design Method ◽  
Traditional Methods ◽  
Second Stage ◽  
Spring Element ◽  
Design Variables ◽  
Additional Constraints

Compliant mechanisms designed by traditional topology optimization have a linear output response, and it is difficult for traditional methods to implement mechanisms having nonlinear output responses, such as nonlinear deformation or path. To design a compliant mechanism having a specified nonlinear output path, we propose a two-stage design method based on topology and shape optimizations. In the first stage, topology optimization generates an initial conceptual compliant mechanism based on ordinary design conditions, with “additional” constraints used to control the output path in the second stage. In the second stage, an initial model for the shape optimization is created, based on the result of the topology optimization, and additional constraints are replaced by spring elements. The shape optimization is then executed, to generate the detailed shape of the compliant mechanism having the desired output path. At this stage, parameters that represent the outer shape of the compliant mechanism and of spring element properties are used as design variables in the shape optimization. In addition to configuring the specified output path, executing the shape optimization after the topology optimization also makes it possible to consider the stress concentration and large displacement effects. This is an advantage offered by the proposed method, because it is difficult for traditional methods to consider these aspects, due to inherent limitations of topology optimization.

Multi-Stage Design Method for Practical Compliant Mechanisms by Topology and Shape Optimizations and Shape Conversion Method Utilizing Level Set Method

2008 ◽  
Author(s):  
Masakazu Kobayashi ◽  
Shinji Nishiwaki ◽  
Masatake Higashi
Keyword(s):  
Topology Optimization ◽  
Shape Optimization ◽  
Level Set Method ◽  
Level Set ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Design Method ◽  
Stage Design ◽  
Conversion Method ◽  
Multi Stage

This paper proposes a multi-stage design method for a design of practical compliant mechanisms. The proposed method consists of topology and shape optimizations and a shape conversion method that incorporates two optimizations. In the 1st stage, an initial and conceptual compliant mechanism is created by topology optimization. In the 2nd stage, an initial model of shape optimization is created from the result of topology optimization by the shape conversion method based on the level set method. In the 3rd stage, the shape optimization yields a detailed shape of the compliant mechanism by considering non-linear deformation and stress concentration. Execution of the shape optimization after the topology optimization enables evaluation of stress concentration and large deformation effect that are normally difficult for the traditional topology optimization. On the other side, the precise conversion from the model by topology optimization to the one for the shape optimization becomes possible by the shape conversion method that is utilizing the level set method. Using the proposed multi-stage method, a practical compliant mechanism can be designed with the designer’s minimum efforts that are indications of design conditions of the topology and shape optimizations and several parameters and threshold values of the shape conversion method.

A Material Selection and Design Method for Multi-Constraint Compliant Mechanisms

2016 ◽  
Author(s):  
John Sessions ◽  
Nathan Pehrson ◽  
Kyler Tolman ◽  
Jonathan Erickson ◽  
David Fullwood ◽  
...  
Keyword(s):  
Performance Metrics ◽  
Compliant Mechanisms ◽  
Material Selection ◽  
Compliant Mechanism ◽  
Design Method ◽  
Solar Array ◽  
Multiple Constraints ◽  
Systematic Method ◽  
Electrically Conductive ◽  
Compliant Mechanism Design

One of the challenges often encountered in compliant mechanism design is managing material selection given the need to meet multiple constraints. Many methods have been offered previously to systematically facilitate that decision process. However, these methods struggle to incorporate a systematic method for material selection in multi-functional compliant mechanisms. This work seeks to address this gap by generically implementing a new Ashby-based material selection and design method for compliant mechanisms with multi constraint design criteria. To help demonstrate the method, the design of an electrically conductive lamina emergent torsion (LET) joint used for a back-packable solar array is explored. The methodology described here can be used to create other compliant mechanism performance metrics to address the design of specific compliant mechanisms.

Bench Top Test of a Droop Nose With Compliant Mechanism

2015 ◽  
Author(s):  
Johannes Riemenschneider ◽  
Srinivas Vasista ◽  
Bram van de Kamp ◽  
Hans Peter Monner
Keyword(s):  
Wind Tunnel ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Full Range ◽  
Leading Edge ◽  
Optimization Methods ◽  
Load Path ◽  
Future Design ◽  
Linear Motors ◽  
Path Representation

Morphing is a technology with high potential to reduce emissions in aviation, since it enables wings to adapt their shape to operate at a higher efficiency over the full range of flight conditions. This paper is presenting a concept to adapt camber by drooping the nose. The scope is the setup and bench top testing of a full scale wing tip leading edge wind tunnel model with a morphing droop nose. The complete model features a span of 1.3 m and a strong taper from the root to the tip. For completeness, the design approach is covered as well. The design comprises a GFRP skin to be drooped by two compliant mechanisms, which are driven by linear motors. The compliant morphing devices are “designed-through-optimization”, with the optimization algorithms including Simplex optimization for composite compliant skin design, continuum-based and load path representation topology optimization methods for compliant internal substructure design. The compliant mechanism is manufactured by nickel-titanium alloy to allow high strains in the order of several percent, which is shown to be critical in the design of such compliant mechanisms. In order to validate the models, strains within the mechanisms are measured while drooping the nose in the bench top test. This is done after installing the mechanisms into the leading edge skin. It can be shown, that the simulation for the inboard mechanism is close to the experimental results. The comparison of strain levels in the skin and in the mechanism during droop reveals that the stiffness distribution between these two components is quite different. As a result this ratio can be taken into account in future design processes in order to distribute strains more evenly. Moreover the 3D shapes of the morphed and clean skin are measured and their comparison with the target shapes is presented as well. Finally, the bench top tests are a proof of concept for the overall concept and design which resultes in a “go” for the following low speed subsonic wind tunnel tests.

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