Constraint-Based Synthesis of Shape-Morphing Structures in Virtual Reality

2010 ◽  
Author(s):  
Judy M. Vance ◽  
Denis Dorozhkin
Keyword(s):  
Virtual Reality ◽  
Rigid Body ◽  
Method Development ◽  
Compliant Mechanisms ◽  
Design Method ◽  
Shape Change ◽  
The Body ◽  
Motion Path ◽  
Primary Methods ◽  
Shape Morphing

This manuscript outlines a novel approach to the design of compliant shape-morphing structures using constraint-based design method. Development of robust methods for designing shape-morphing structures is the focus of multiple current research projects, since the ability to modify geometric shapes of the individual system components, such as aircraft wings and antenna reflectors, provides the means to affect the performance of the corresponding mechanical systems. Of particular interest is the utilization of compliant mechanisms to achieve the desired adaptive shape change characteristics. Compliant mechanisms, as opposed to the traditional rigid link mechanisms, achieve motion guidance via the compliance and deformation of the mechanism’s members. The goal is to design a single-piece flexible structure capable of morphing a given curve or profile into a target curve or profile while utilizing the minimum number of actuators. The two primary methods prevalent in the design community at this time are the pseudo-rigid body method (PRBM) and the topological synthesis. Unfortunately these methods either tend to suffer from a poor ability to generate potential solutions (being more suitable for the analysis of existing structures) or are susceptible to overly-complex solutions. By utilizing the constraint-based design method (CBDM) we aim to address those shortcomings. The concept of CBDM has generally been confined to the Precision Engineering community and is based on the fundamental premise that all motions of a rigid body are determined by the position and orientation of the constraints (constraint topology) which are placed upon the body. Any mechanism motion path may then be defined by the proper combination of constraints. In order to apply the CBDM concepts to the design and analysis of shape-morphing compliant structures we propose a tiered design method that relies on kinematics, finite element analysis, and optimization. By discretizing the flexible element that comprises the active shape surface at multiple points in both the initial and the target configurations and treating the resulting individual elements as rigid bodies that undergo a planar or general spatial displacement we are able to apply the traditional kinematics theory to rapidly generate sets of potential solutions. The final design is then established via an FEA-augmented optimization sequence. Coupled with a virtual reality interface and a force-feedback device this approach provides the ability to quickly specify and evaluate multiple design problems in order to arrive at the desired solution.

Kinematic Synthesis of Planar, Shape-Changing Compliant Mechanisms Using Pseudo-Rigid-Body Models

2012 ◽  
Author(s):  
Kai Zhao ◽  
James P. Schmiedeler ◽  
Andrew P. Murray
Keyword(s):  
Rigid Body ◽  
Shape Matching ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Shape Change ◽  
Flexible Beam ◽  
Beam Model ◽  
Flexible Beams ◽  
Multi Objective Genetic Algorithm ◽  
Optimization Loop

This paper presents a procedure using Pseudo-Rigid-Body Models (PRBMs) to synthesize partially compliant mechanisms capable of approximating a shape change defined by a set of morphing curves in different positions. To generate a single-piece compliant mechanism, flexural pivots and flexible beams are both utilized in the mechanism. New topologies defined by compliant mechanism matrices are enumerated by modifying the components that make up a single degree-of-freedom (DOF) rigid-body mechanism. Because of the introduction of the PRBM for flexural pivots and the simplified PRBM for flexible beams, torsional springs are attached at the characteristic pivots of the 1-DOF rigid-body mechanism in order to generate a corresponding pseudo-rigid-body mechanism. A multi-objective genetic algorithm is employed to find a group of viable compliant mechanisms in the form of candidate pseudo-rigid-body mechanisms that tradeoff minimizing shape matching error with minimizing actuator energy. Since the simplified beam model is not accurate, an optimization loop is established to find the position and shape of the flexible beam using a finite link beam model. The optimal flexible beams together with the pseudo-rigid-body mechanism define the solution mechanism. The procedure is demonstrated with an example in which a partially compliant mechanism approximating two closed-curve profiles is synthesized.

Using Rigid-Body Mechanism Topologies to Design Shape-Changing Compliant Mechanisms

2015 ◽  
Vol 8 (1) ◽  
Author(s):  
Kai Zhao ◽  
James P. Schmiedeler
Keyword(s):  
Rigid Body ◽  
Shape Matching ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Shape Change ◽  
Mesh Network ◽  
Adaptive Antenna ◽  
Optimal Size ◽  
Dimensional Synthesis ◽  
Element Analysis

This paper uses rigid-body mechanism topologies to synthesize fully distributed compliant mechanisms that approximate a shape change defined by a set of morphing curves in different positions. For a shape-change problem, a rigid-body mechanism solution is generated first to provide the base topology. This base topology defines a preselected design space for the structural optimization in one of two ways so as to obtain a compliant mechanism solution that is typically superior to the local minimum solutions obtained from searching more expansive design spaces. In the first strategy, the dimensional synthesis directly determines the optimal size and shape of the distributed compliant mechanism having exactly the base topology. In the second strategy, an initial mesh network established from the base topology is used to generate different topologies (in addition to the base), and an improved design domain parameterization scheme ensures that only topologies with well-connected structures are evaluated. The deformation of each generated compliant mechanism is evaluated using geometrically nonlinear finite element analysis (FEA). A two-objective genetic algorithm (GA) is employed to find a group of viable designs that trade off minimizing shape matching error with minimizing maximum stress. The procedure's utility is demonstrated with three practical examples—the first two approximating open-curve profiles of an adaptive antenna and the third approximating closed-curve profiles of a morphing wing.

Design and Prototyping of a Shape-Changing Rigid-Body Human Foot in Gait

2018 ◽  
Author(s):  
Tanner N. Rolfe ◽  
Andrew P. Murray ◽  
David H. Myszka
Keyword(s):  
Rigid Body ◽  
Compliant Mechanisms ◽  
Shape Change ◽  
Dynamic Change ◽  
A Priori ◽  
External Loading ◽  
Loading Conditions ◽  
Kinematic Synthesis ◽  
Human Foot

Traditional ankle-foot devices such as prostheses or robotic feet seek to replicate the physiological change in shape of the foot during gait using compliant mechanisms. In comparison, rigid-body feet tend to be simplistic and largely incapable of accurately representing the geometry of the human foot. Rigidbody mechanisms offer certain advantages over compliant mechanisms which may be desirable in the design of ankle-foot devices, including the ability to withstand greater loading, the ability to achieve more drastic shape-change, and the ability to be synthesized from their kinematics, allowing for realistic functionality without a priori characterization of the external loading conditions of the foot. This work focuses on applying the methodology of shape-changing kinematic synthesis to design and prototype a multi-segment rigid-body foot device capable of matching the dynamic change in shape of the human foot in gait.

Computational Design of Active Lattice Structures for 4D Printed Pneumatic Shape Morphing

2019 ◽  
Author(s):  
Cosima du Pasquier ◽  
Pascal Koller ◽  
Tino Stankovic ◽  
Kristina Shea
Keyword(s):  
Complex Shape ◽  
Lattice Structure ◽  
Design Method ◽  
Shape Change ◽  
Computational Design ◽  
Digital Fabrication ◽  
Computational Effort ◽  
Shape Morphing ◽  
Actuator Placement ◽  
Shape Changes

Abstract With advances in 3D printing and digital fabrication an opportunity is presented to realize highly customized designs whose shape can change and adapt to facilitate their functionality. A computational design method to determine the configuration of 2D pneumatic shape morphing lattices using a direct search method is implemented and assessed. The method is tested using a Kagome unit cell lattice structure, which is particularly well suited for shape morphing. To achieve shape change, beams are replaced by linear actuators such as those found in pneumatic 4D printing, whose number and placement are optimized to replicate a given target shape. The actuator placement and deformation accuracy are given for four main curvature changes: linear, convex, concave and the transition from one to the other. The results are assessed in terms accuracy of deformation and computational effort. It is shown that the method proposed produces structures that can replicate complex shape changes within 1% of the desired shape. Reducing the number of actuators for robustness purposes is shown to affect the results minimally.

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.

Using Rigid-Body Mechanism Topologies to Design Shape-Changing Compliant Mechanisms

2013 ◽  
Author(s):  
Kai Zhao ◽  
James P. Schmiedeler
Keyword(s):  
Rigid Body ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Shape Change ◽  
Adaptive Antenna ◽  
Dimensional Synthesis ◽  
Element Analysis ◽  
Initial Element ◽  
Multi Objective Genetic Algorithm ◽  
Improved Design

This paper uses rigid-body mechanism topologies to synthesize distributed compliant mechanisms that approximate a shape change defined by a set of morphing curves in different positions. A single-actuator compliant mechanism is synthesized from a single degree-of-freedom rigid-body mechanism’s base topology in one of two ways. In one case, the base topology is directly evaluated through dimensional synthesis to determine the compliant mechanism’s optimal dimensions. In the second, the base topology establishes an initial element network for an optimization routine that determines topologies and dimensions simultaneously, and an improved design domain parameterization scheme ensures that only topologies with well-connected structures are evaluated. A multi-objective genetic algorithm is employed to search the design space, and the deformation is evaluated using geometrically nonlinear finite element analysis. The procedure’s utility is demonstrated with two practical examples — one approximating open-curve profiles of an adaptive antenna and the other closed-curve profiles of a morphing wing.

scholarly journals A Virtual Reality Interface for the Design of Compliant Mechanisms

2009 ◽  
Author(s):  
Utkarsh Seth ◽  
Hai-Jun Su ◽  
Judy M. Vance
Keyword(s):  
Virtual Reality ◽  
Design Process ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Current Method ◽  
Motion Path ◽  
User Centered Design ◽  
Design Algorithm ◽  
Constraint Sets ◽  
User Centered

The objective of this research is to develop an immersive interface and a design algorithm to facilitate the synthesis of compliant mechanisms from a user-centered design perspective. Compliant mechanisms are mechanical devices which produce motion or force through deflection or flexibility of their parts. Using the constraint-based method of design, the design process relies on the designer to identify the appropriate constraint sets to match the desired motion. Currently this approach requires considerable prior knowledge of how non-linear flexible members produce motion. As a result, the design process is based primarily on the designer’s previous experience and intuition. A user-centered methodology is suggested where the interface guides the designer throughout the design process, thus reducing the reliance on intuitive knowledge. This methodology supports constraint-based design methods by linking mathematical models to support compliant mechanism design in an immersive virtual environment. A virtual reality (VR) immersive interface enables the designer to input the intended motion path by simply grabbing and moving the object and letting the system decide which constraint spaces apply. The user-centered paradigm supports an approach that focuses on the designer defining the motion and the system generating the constraint sets, instead of the current method which relies heavily on the designer’s intuition to identify appropriate constraints. The result is an intelligent design framework that will allow a broader group of engineers to design complex compliant mechanisms, giving them new options to draw upon when searching for design solutions to critical problems.

Direct Displacement Synthesis Method for Shape Morphing Skins Using Compliant Mechanisms

2010 ◽  
Author(s):  
Luke A. Berglind ◽  
Joshua D. Summers
Keyword(s):  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Shape Change ◽  
Synthesis Method ◽  
Bending Stiffness ◽  
Optimization Techniques ◽  
Synthesis Methods ◽  
Specific Load ◽  
Shape Morphing ◽  
Continuum Structure

This paper presents a direct displacement synthesis method for the design of shape morphing skin structures using compliant mechanisms. The objective of this method is to design a skin structure that will deform to a desired final shape when acted on by a specific load. The method utilizes a ground structure geometry which can facilitate variable bending stiffness along the length of the skin using compliant spring members. Synthesis procedures involve the use of direct displacement to determine how the bending stiffness of the skin must vary to produce the desired shape change. The direct displacement synthesis method differs from other compliant mechanism synthesis methods found in literature, such as pseudo-rigid-body and continuum structure optimization, in the approach taken to solve for the unknown variables in the system. By using direct displacement to determine how the structure must respond to a specific load to achieve the desired shape change, the unknown variables within the system can be extracted directly without the use of optimization techniques.

scholarly journals Using Singularities of Parallel Manipulators to Enhance the Rigid-Body Replacement Design Method of Compliant Mechanisms

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Lennart Rubbert ◽  
Stéphane Caro ◽  
Jacques Gangloff ◽  
Pierre Renaud
Keyword(s):  
Rigid Body ◽  
Degrees Of Freedom ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Design Method ◽  
Synthesis Method ◽  
Parallel Manipulators ◽  
Replacement Method ◽  
Stiffness Properties ◽  
Parallel Structures

The rigid-body replacement method is often used when designing a compliant mechanism. The stiffness of the compliant mechanism, one of its main properties, is then highly dependent on the initial choice of a rigid-body architecture. In this paper, we propose to enhance the efficiency of the synthesis method by focusing on the architecture selection. This selection is done by considering the required mobilities and parallel manipulators in singularity to achieve them. Kinematic singularities of parallel structures are indeed advantageously used to propose compliant mechanisms with interesting stiffness properties. The approach is first illustrated by an example, the design of a one degree of freedom compliant architecture. Then, the method is used to design a medical device where a compliant mechanism with three degrees of freedom is needed. The interest of the approach is outlined after application of the method.

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