Shape-Morphing Using Bistable Triangles With Dwell-Enhanced Stability

2018 ◽  
Author(s):  
Rami Alfattani ◽  
Craig Lusk
Keyword(s):  
Compliant Mechanism ◽  
Isosceles Triangle ◽  
Vertex Angle ◽  
The Novel ◽  
Shape Morphing ◽  
Compliant Joints ◽  
Cube Corner ◽  
The Stability ◽  
Bistable Mechanism ◽  
Novel Design

This paper presents a new design concept for a morphing triangle-shaped compliant mechanism. The novel design is a bistable mechanism that has one changeable side. These morphing triangles may be arrayed to create shapemorphing structures. The mechanism was based on a six-bar dwell mechanism that can fit in a triangle shape and has stable positions at the motion-limit (dead-center) positions. An example of the triangle-shaped compliant mechanism was designed and prototyped: an isosceles triangle with a vertex that changes from 120 degrees to 90 degrees and vice versa. Three of these in the 120-degree configuration lie flat and when actuated to the 90-degree configuration become a cube corner. This design may be of use for folding and packaging assistance. The force analysis and the potential energy analysis were completed to verify the stability of the triangle-shaped compliant mechanism. Because of its dead-center motion limits the vertex angle cannot be extended past the range of 90 degrees to 120 degrees in spite of the mechanism’s compliant joints. Furthermore, because it is a dwell mechanism, the vertex angle is almost immobile near its stable configurations, although other links in the mechanism move. This makes the stable positions of the vertex angle robust against stress relaxation and manufacturing errors. We believe this is the first demonstration of this kind of robustness in bistable mechanisms.

scholarly journals Shape-Morphing Using Bistable Triangles With Dwell-Enhanced Stability

2020 ◽  
Vol 12 (5) ◽  
Author(s):  
Rami Alfattani ◽  
Craig Lusk
Keyword(s):  
Compliant Mechanism ◽  
Isosceles Triangle ◽  
Vertex Angle ◽  
The Novel ◽  
Shape Morphing ◽  
Compliant Joints ◽  
Cube Corner ◽  
Manufacturing Errors ◽  
Bistable Mechanism ◽  
Novel Design

Abstract This paper presents a new design concept for a morphing triangle-shaped compliant mechanism. The novel design is a bistable mechanism that has one changeable side. These morphing triangles may be arrayed to create shape-morphing structures. The mechanism design was based on a six-bar dwell mechanism that can fit in a triangle shape and has stable positions at the motion-limit (dead-center) positions. An example of the triangle-shaped compliant mechanism was designed and prototyped: an isosceles triangle with a vertex that changes from 120 deg to 90 deg and vice versa. Three of these in the 120-deg configuration lie flat and when actuated to the 90-deg configuration become a cube corner. This design may be of use for folding and packaging assistance. The mechanism was designed using geometric constraint programming. Force and potential energy analyses characterize the triangle mechanism’s stability. Because of its dead-center motion limits, the vertex angle of the triangle cannot be extended past the range of 90–120 deg, in spite of the mechanism’s compliant joints. Furthermore, because it is a dwell mechanism, the vertex angle is almost immobile near its stable configurations, although other links in the mechanism move. This makes the stable positions of the vertex angle robust against stress relaxation and manufacturing errors. We believe this is the first demonstration of this kind of robustness in bistable mechanisms.

scholarly journals Design of Compliant Joints for Large Scale Structures

2020 ◽  
Author(s):  
Angela Nastevska ◽  
Jovana Jovanova ◽  
Mary Frecker
Keyword(s):  
Large Scale ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Small Scale ◽  
Nonlinear Bending ◽  
Large Scale Structures ◽  
Compliant Joints ◽  
Scale Structures ◽  
High Level ◽  
Novel Design

Abstract Large scale structures can benefit from the design of compliant joints that can provide flexibility and adaptability. A high level of deformation is achieved locally with the design of flexures in compliant mechanisms. Additionally, by introducing contact-aided compliant mechanisms, nonlinear bending stiffness is achieved to make the joints flexible in one direction and stiff in the opposite one. All these concepts have been explored in small scale engineering design, but they have not been applied to large scale structures. In this paper the design of a large scale compliant mechanism is proposed for novel design of a foldable shipping container. The superelasticity of nickel titanium is shown to be beneficial in designing the joints of the compliant mechanism.

Towards Statically Balanced Compliant Joints Using Multimaterial 3D Printing

2014 ◽  
Author(s):  
Arnaud Bruyas ◽  
François Geiskopf ◽  
Pierre Renaud
Keyword(s):  
3D Printing ◽  
Range Of Motion ◽  
Elastic Material ◽  
Geometry Optimization ◽  
Compliant Joints ◽  
Stiffness Properties ◽  
Large Joint ◽  
Hyper Elastic ◽  
Bistable Mechanism ◽  
Novel Design

Compliant joints are widely used in mechanisms when accurate movements are required. With no assembly requested, they are also a great tool for mesoscale robotics, a field in which compactness and large joint amplitudes are necessary features. In this paper, an original multi-material compliant revolute joint is presented. Taking advantage of multi-material 3D printing, it exhibits a novel design with the integration of an hyper-elastic material. Thanks to a helical shape design, a large range of motion is obtained, and the incompressibility of the hyper-elastic material is used to improve the stiffness properties of the joint while keeping it compact. The spring effect of compliant joints makes mechanism actuation more difficult. The proposed joint is therefore designed with an integrated static balancing system in order to minimize actuation torques. The balancing system is composed of a bistable mechanism, which geometry optimization is presented. Experimental assessment demonstrate that the joint possesses a range of motion of 120°, and the balancing system reduces actuation moments by almost 60%.

scholarly journals A bistable mechanism with linear negative stiffness and large in-plane lateral stiffness: design, modeling and case studies

2020 ◽  
Vol 11 (1) ◽  
pp. 75-89 ◽  
Author(s):  
Zhanfeng Zhou ◽  
Yongzhuo Gao ◽  
Lining Sun ◽  
Wei Dong ◽  
Zhijiang Du
Keyword(s):  
Vibration Isolation ◽  
Compliant Mechanism ◽  
Dynamic Stiffness ◽  
Negative Stiffness ◽  
Analytical Models ◽  
Lateral Stiffness ◽  
Constant Force ◽  
The Novel ◽  
Stiffness Characteristic ◽  
Bistable Mechanism

Abstract. To overcome the limitations of conventional bistable mechanisms, this paper proposes a novel type of bistable mechanism with linear negative stiffness and large in-plane lateral stiffness. By connecting the novel negative-stiffness mechanism in parallel with a positive-stiffness mechanism, a novel quasi-zero stiffness compliant mechanism is developed, which has good axial guidance capability and in-plane lateral anti-interference capability. Analytical models based on a comprehensive elliptic integral solution of bistable mechanism are established and then the stiffness curves of both conventional and novel bistable mechanisms are analyzed. The quasi-zero stiffness characteristic and High-Static-Low-Dynamic-Stiffness characteristic of the novel compliant mechanism are investigated and its application in constant-force mechanism and vibration isolator is discussed. A prototype with adjustable load-carrying capacity is designed and fabricated for experimental study. In the two experiments, the effectiveness of the proposed quasi-zero stiffness mechanism used in the field of constant-force output and vibration isolation is tested.

In-Parallel Passive Compliant Coupler for Robot Force Control

2000 ◽  
Author(s):  
T. A. Dwarakanath ◽  
Carl D. Crane ◽  
Joseph Duffy ◽  
Chad Tyler
Keyword(s):  
Mechanism Design ◽  
Force Control ◽  
Parallel Mechanism ◽  
Quality Index ◽  
Compliant Mechanism ◽  
Signal To Noise Ratio ◽  
The Novel ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Novel Design

Abstract This paper describes the design of a Passive Compliant Coupler for Force Control (PCCFC) based on an in-parallel mechanism. The optimal synthesis of the mechanism is performed with the objective of achieving a good quality index. The novel design of the connector (also termed as the leg), a crucial element of the mechanism, is one of the important features of the paper. The shape optimization of connectors of an in-parallel mechanism is obtained by satisfying compliant requirements and considering maximization of signal to noise ratio criteria. The various design aspects of sizing, sensing the displacement, and implementation of the connector are discussed. The in-parallel compliant mechanism for force control is obtained by optimizing the signal to noise ratio at various stages of the mechanism design.

Novel Nanolipoidal Systems for the Management of Skin Cancer

2020 ◽  
Vol 14 (2) ◽  
pp. 108-125
Author(s):  
Apoorva Singh ◽  
Nimisha
Keyword(s):  
Skin Cancer ◽  
Survival Rates ◽  
Cancer Therapeutics ◽  
The Body ◽  
Surgical Removal ◽  
The Novel ◽  
Skin Cancers ◽  
Recent Developments ◽  
Abnormal Cells ◽  
The Stability

: Skin cancer, among the various kinds of cancers, is a type that emerges from skin due to the growth of abnormal cells. These cells are capable of spreading and invading the other parts of the body. The occurrence of non-melanoma and melanoma, which are the major types of skin cancers, has increased over the past decades. Exposure to ultraviolet radiations (UV) is the main associative cause of skin cancer. UV exposure can inactivate tumor suppressor genes while activating various oncogenes. The conventional techniques like surgical removal, chemotherapy and radiation therapy lack the potential for targeting cancer cells and harm the normal cells. However, the novel therapeutics show promising improvements in the effectiveness of treatment, survival rates and better quality of life for patients. Different methodologies are involved in the skin cancer therapeutics for delivering the active ingredients to the target sites. Nano carriers are very efficient as they have the ability to improve the stability of drugs and further enhance their penetration into the tumor cells. The recent developments and research in nanotechnology have entitled several targeting and therapeutic agents to be incorporated into nanoparticles for an enhancive treatment of skin cancer. To protect the research works in the field of nanolipoidal systems various patents have been introduced. Some of the patents acknowledge responsive liposomes for specific targeting, nanocarriers for the delivery or co-delivery of chemotherapeutics, nucleic acids as well as photosensitizers. Further recent patents on the novel delivery systems have also been included here.

Achieving Multistability Through Use of a Single Bistable Compliant Mechanism

2010 ◽  
Author(s):  
Guimin Chen ◽  
Yanjie Gou ◽  
Aimei Zhang
Keyword(s):  
Stable Equilibrium ◽  
Compliant Mechanism ◽  
Power Input ◽  
Successful Operation ◽  
New Approaches ◽  
Reconfigurable Robots ◽  
Bistable Mechanism

A compliant multistable mechanism is capable of steadily staying at multiple distinct positions without power input. Many applications including switches, valves, relays, positioners, and reconfigurable robots may benefit from multistability. In this paper, two new approaches for synthesizing compliant multistable mechanisms are proposed, which enable designers to achieve multistability through the use of a single bistable mechanism. The synthesis approaches are described and illustrated by several design examples. Compound use of both approaches is also discussed. The design potential of the synthesis approaches is demonstrated by the successful operation of several instantiations of designs that exhibit three, four, five, and nine stable equilibrium positions, respectively. The synthesis approaches enable us to design a compliant mechanism with a desired number of stable positions.

Bistable Compliant Four-Bar Mechanisms With a Single Torsional Spring

2006 ◽  
Author(s):  
Adarsh Mavanthoor ◽  
Ashok Midha
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Mechanism Design ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Stored Energy ◽  
Element Analysis ◽  
Bistable Behavior ◽  
Torsional Spring ◽  
Bistable Mechanism

Significant reduction in cost and time of bistable mechanism design can be achieved by understanding their bistable behavior. This paper presents bistable compliant mechanisms whose pseudo-rigid-body models (PRBM) are four-bar mechanisms with a torsional spring. Stable and unstable equilibrium positions are calculated for such four-bar mechanisms, defining their bistable behavior for all possible permutations of torsional spring locations. Finite Element Analysis (FEA) and simulation is used to illustrate the bistable behavior of a compliant mechanism with a straight compliant member, using stored energy plots. These results, along with the four-bar and the compliant mechanism information, can then be used to design a bistable compliant mechanism to meet specified requirements.

Calculation and Measurement of the Stiffness and Damping Coefficients for a Low Impedance Hydrodynamic Bearing

1997 ◽  
Vol 119 (1) ◽  
pp. 57-63 ◽  
Author(s):  
M. J. Goodwin ◽  
P. J. Ogrodnik ◽  
M. P. Roach ◽  
Y. Fang
Keyword(s):  
Experimental Data ◽  
Dynamic Stiffness ◽  
Perturbation Technique ◽  
The Novel ◽  
Oil Film ◽  
Hydrodynamic Bearing ◽  
Damping Coefficients ◽  
Stiffness And Damping ◽  
Film Stiffness ◽  
Novel Design

This paper describes a combined theoretical and experimental investigation of the eight oil film stiffness and damping coefficients for a novel low impedance hydrodynamic bearing. The novel design incorporates a recess in the bearing surface which is connected to a standard commercial gas bag accumulator; this arrangement reduces the oil film dynamic stiffness and leads to improved machine response and stability. A finite difference method was used to solve Reynolds equation and yield the pressure distribution in the bearing oil film. Integration of the pressure profile then enabled the fluid film forces to be evaluated. A perturbation technique was used to determine the dynamic pressure components, and hence to determine the eight oil film stiffness and damping coefficients. Experimental data was obtained from a laboratory test rig in which a test bearing, floating on a rotating shaft, was excited by a multi-frequency force signal. Measurements of the resulting relative movement between bearing and journal enabled the oil film coefficients to be measured. The results of the work show good agreement between theoretical and experimental data, and indicate that the oil film impedance of the novel design is considerably lower than that of a conventional bearing.

scholarly journals A novel flexible tool with rotary ultrasonic spindle for fine grinding of tungsten carbide

2018 ◽  
Vol 185 ◽  
pp. 00018
Author(s):  
Albert Wen-Jeng Hsue ◽  
Yi-Zhong Zheng
Keyword(s):  
Tungsten Carbide ◽  
The Novel ◽  
Machining Processes ◽  
Flexible Tool ◽  
Operational Conditions ◽  
Cnc Grinding ◽  
Grinding Conditions ◽  
Novel Design ◽  
Conventional Machining ◽  
Tungsten Steel

Tungsten carbide is a typical difficult-to-cut material by conventional machining processes. In this paper, a novel design of flexible abrasives tool combined with a rotary ultrasonic machining (RUM) spindle is conducted to reduce the labor force significantly. The newly designed flexibility of tool-tip is aimed at preventing overcutting from the CNC grinding. The grinding conditions with resulted surface morphology of the tungsten steel were investigated through Taguchi design of experiment and ANOVA analysis. The machining capability of the novel flexible tool is compared with conventional tools through specific grinding paths under proper operational conditions.

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