Design of Small-Scale Statically Balanced Compliant Joints

2011 ◽  
Author(s):  
Brian D. Jensen ◽  
Cesare H. Jenkins
Keyword(s):  
Viscous Friction ◽  
Small Scale ◽  
Dynamic Force ◽  
Compliant Joints ◽  
Stiffness Design ◽  
Rigid Body Model ◽  
Compliant Joint ◽  
Internal Forces ◽  
Low Stiffness ◽  
Torsion Bar

This paper demonstrates a low stiffness compliant joint design obtained by balancing the energy stored within individual components of the mechanism. As a step toward a fully-compliant zero-stiffness joint, this paper presents the design of a partially-compliant joint. A wireform torsion bar partially compliant joint was optimized using a pseudo rigid body model. A low stiffness design was obtained by balancing the energy stored within individual components of the mechanism. The joint was then fabricated using piano wire, polypropylene and Delrin®. During testing it was found that friction in the joint was greater than any internal forces allowing the joint to be neutrally stable in all positions. Dynamic force deflection data on the joints was collected in order to investigate the friction characteristics. The Delrin® joint exhibited only Coulomb friction while the polypropylene model exhibited both Coulomb and viscous friction.

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.

scholarly journals Routes to Dissipation under Different Dynamical Conditions

2015 ◽  
Vol 45 (8) ◽  
pp. 2149-2168 ◽  
Author(s):  
Nils Brüggemann ◽  
Carsten Eden
Keyword(s):  
Energy Flux ◽  
Velocity Component ◽  
Functional Relationship ◽  
Baroclinic Instability ◽  
Viscous Friction ◽  
Ocean Model ◽  
Global Ocean ◽  
Small Scale ◽  
Ocean Energy ◽  
Global Estimate

AbstractIn this study, it is investigated how ageostrophic dynamics generate an energy flux toward smaller scales. Numerical simulations of baroclinic instability are used with varying dynamical conditions ranging from quasigeostrophic balance to ageostrophic flows. It turns out that dissipation at smaller scales by viscous friction is much more efficient if the flow is dominated by ageostrophic dynamics than in quasigeostrophic conditions. In the presence of ageostrophic dynamics, an energy flux toward smaller scales is observed while energy is transferred toward larger scales for quasigeostrophic dynamics. Decomposing the velocity field into its rotational and divergent components shows that only the divergent velocity component, which becomes stronger for ageostrophic flows, features a downscale flux. Variation of the dynamical conditions from ageostrophic dynamics to quasigeostrophic balanced flows shows that the forward energy flux and therefore the small-scale dissipation decreases as soon as the horizontal divergent velocity component decreases. A functional relationship between the small-scale dissipation and the local Richardson number is estimated. This functional relationship is used to obtain a global estimate of the small-scale dissipation of 0.31 ± 0.23 TW from a high-resolution realistic global ocean model. This emphasizes that an ageostrophic direct route to dissipation might be of importance in the ocean energy cycle.

scholarly journals Design and Analysis of a Rigid-Flexible Parallel Mechanism for a Neck Brace

2019 ◽  
Vol 2019 ◽  
pp. 1-20
Author(s):  
Jingfang Liu ◽  
Yanxia Cheng ◽  
Shuang Zhang ◽  
Zhenxin Lu ◽  
Guohua Gao
Keyword(s):  
Parallel Mechanism ◽  
Rotational Degree ◽  
Compliance Matrix ◽  
Body Model ◽  
Rotation Measurement ◽  
Rigid Body Model ◽  
Compliant Joint ◽  
Spherical Parallel Mechanism ◽  
Rotation Function ◽  
Flexion And Extension

A rigid-flexible parallel mechanism called 3-RXS mechanism as a neck brace for patients with head drooping symptoms (HDS) is presented. The 3-RXS neck brace has a simple and light structure coupled with good rotation performance, so it can be used to assist the neck to achieve flexion and extension, lateral bend, and axial torsion. Firstly, to prove that the X-shaped compliant joint has a rotational degree of freedom (DoF) and can be used in the 3-RRS spherical parallel mechanism (3-RRS SPM), the six-dimensional compliance matrix, axis drift, and DoF of the X-shaped compliant joint have been systematically calculated. Secondly, the 3-RXS mechanism and its pseudo-rigid-body model (PRBM) are obtained by replacing the revolute pair with the X-shaped compliant joint in the 3-RRS SPM. The rotation workspace of the 3-RXS mechanism is also performed. Finally, to verify the rotation function and effect of 3-RXS mechanism for neck-assisted rehabilitation, the kinematics simulations of the 3-RXS and 3-RRS mechanisms are carried out and compared with the theoretical result, and a primary experiment for rotation measurement of 3-RXS mechanism prototype is carried out. All results prove the feasibility of the 3-RXS mechanism for a neck brace.

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.

Design of a Compact Actuated Compliant Elbow Joint

2014 ◽  
Vol 14 (08) ◽  
pp. 1440030 ◽  
Author(s):  
Johannes Gerard Kleinjan ◽  
Alje Geert Dunning ◽  
Justus Laurens Herder
Keyword(s):  
Smart Materials ◽  
Performance Indicators ◽  
Elbow Joint ◽  
Large Deflection ◽  
Rotational Axis ◽  
Half Cycle ◽  
Compliant Joints ◽  
Compliant Joint ◽  
Cycle Efficiency

Compactness is a valuable property in designs of assistive devices and exoskeletons. Current devices are large and stigmatizing in the eyes of the users. The cosmetic appearance will increase by reducing the size. The users want a device that is small enough to be worn underneath the clothes, so it becomes unnoticeable. The goals of this paper are (1) to provide an overview of the shape-changing-material-actuated large-deflection compliant rotational joints, (2) provide new introduced performance indicators that evaluate the designs on performance with respect to volume or weight and (3) design a compact active assistive elbow device as a case study. In order to reach these goals, two evolving fields of study are brought together that have great potential to reduce the size of exoskeletons: smart materials and compliant rotational joints. Smart materials have the ability to change their shape, which make them suitable as actuators. Compliant joints can be compact, since they are made out of one piece of material. An overview of shape-changing-material-actuated large-deflection compliant rotational joints is presented. Performance indicators are proposed to evaluate the existing designs and the prototype. As a case study a compact actuated rotational elbow joint is presented. An antagonistic actuator made from shape memory alloy wires is able to carry an external load and to actuate to move the arm to different positions. The compliant joint is optimized to balance the weight of the arm and to auto-align with the rotational axis of the human elbow joint. A prototype is able to generate a volume specific stall torque of 5.77 ⋅ 103 Nm/m3, produces a work density of 7.27 ⋅ 103 J/m3 based on volumes including isolation covers and the half-cycle efficiency of the device is 3.6%. The prototype is able to balance and actuate a torque of 1.1 Nm.

Design of a Contact-Aided Compliant Notched-Tube Joint for Surgical Manipulation in Confined Workspaces

2017 ◽  
Vol 10 (1) ◽  
Author(s):  
Kyle W. Eastwood ◽  
Peter Francis ◽  
Hamidreza Azimian ◽  
Arushri Swarup ◽  
Thomas Looi ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Compliant Mechanism ◽  
Surgical Instruments ◽  
Minimally Invasive Neurosurgery ◽  
Fem Simulations ◽  
Trade Off ◽  
Compliant Joints ◽  
Compliant Joint ◽  
Joint Mechanism ◽  
Surgical Manipulation

This work presents a novel miniature contact-aided compliant joint mechanism that can be integrated into millimeter-sized manual or robotic surgical instruments. The design aims to address the trade-off between notched-tube compliant joints' range of motion and stiffness, while also ensuring a compact form factor. The mechanism is constructed from a nitinol tube with asymmetric cutouts and is actuated in bending by a cable. The innovative feature of this design is the incorporation of a contact aid into the notched-tube topology, which acts to both increase the stiffness of the joint and change the shape that it undertakes during bending. Using finite element modeling (FEM) techniques, we present a sensitivity analysis investigating how the performance of this contact-aided compliant mechanism (CCM) is affected by its geometry, and derive a kinematics and statics model for the joint. The FEM simulations and the kinematic and static models are compared to experimental results. The design and modeling presented in this study can be used to develop new miniature dexterous instruments, with a particular emphasis on applications in minimally invasive neurosurgery.

Preliminary design of a revolute to prismatic morphing compliant joint

2020 ◽  
Vol 44 (4) ◽  
pp. 481-491
Author(s):  
Nicolas Mouazé ◽  
Lionel Birglen
Keyword(s):  
Preliminary Design ◽  
Finite Element Analyses ◽  
Hand Tools ◽  
Body Model ◽  
Performance Indexes ◽  
Rigid Body Model ◽  
Compliant Joint ◽  
Potential Applications ◽  
Variable Topology ◽  
End Effectors

The reduction of weight and size of mechanisms are important and difficult challenges considering portability, energy efficiency, and simplicity of fabrication. One of the solutions to address these issues consists of mechanisms with variable topology for which the mobility of the output is a succession of several simpler elementary motions. This change of mobility allows for achieving complex motions without necessitating a complicated design where many actuators or types of mechanical transmissions are required. Indeed, these variable topology mechanisms, also referred to as morphing mechanisms, have the ability to change their output motion throughout their workspace. Hand tools, medical devices, and aerospace robotic end-effectors are potential applications of this technology. In this paper, conceptual designs of such a revolute to prismatic morphing joint and its implementation using compliant hinges are proposed. Additionally, performance indexes pertaining to the desired output motion are proposed. First, a pseudo-rigid body model of a design candidate is presented, and simulations of this model are compared with finite element analyses to ensure accuracy. Then, several design features are quantitatively evaluated to propose improvements for future versions of the design. Finally, an early prototype illustrates the potential and feasibility of the proposed design as well as a possible application. Video

scholarly journals A Review on Compliant Joint Mechanisms for Lower Limb Exoskeletons

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Miguel A. Gálvez-Zúñiga ◽  
Alejandro Aceves-López
Keyword(s):  
Human Body ◽  
Lower Limb ◽  
Mathematical Description ◽  
Rapid Development ◽  
Revolute Joints ◽  
Close Interaction ◽  
Compliant Joint ◽  
Internal Forces ◽  
Human Joints

Lower limb exoskeletons are experiencing a rapid development that may suggest a prompt introduction to the market. These devices have an inherent close interaction with the human body; therefore, it is necessary to ensure user’s safety and comfort. The first exoskeletal designs used to represent the human joints as simple revolute joints. This approximation introduces an axial misalignment issue, which generates uncontrollable internal forces. A mathematical description of the said misalignments is provided to better understand the concept and its consequences. This review will only focus on mechanisms aiming to comply with its user.

scholarly journals Modeling and Parameter Study of Bistable Spherical Compliant Mechanisms

2011 ◽  
Author(s):  
Chester L. Smith ◽  
Craig P. Lusk
Keyword(s):  
Compliant Mechanisms ◽  
Current Model ◽  
Plane Motion ◽  
Parameter Study ◽  
Beam Model ◽  
New Model ◽  
Novel Device ◽  
Rigid Body Model ◽  
Compliant Joint ◽  
Motion Characteristics

The Bistable Spherical Compliant Mechanisms (BSCM) is a novel device capable of large, repeatable, out-of-plane motion, characteristics that are somewhat difficult to achieve with surface micro-machined MEMS. An improved pseudo-rigid-body model to predict the behavior of the BSCM is presented. The new model was used to analyze seven different versions of the device, each with a different compliant joint length. The new model, which adds torsion, is compared with a Finite-Element beam model. The new model more closely approximates the results yielded by FEA than previous models used to analyze the BSCM. Future work is needed to quantify stress-stiffening interactions between bending and torsion. Both FEA and the current model show that increasing the length of the compliant segment decreases the amount of force required to actuate the device.

Design of Large-Displacement Compliant Joints

2004 ◽  
Vol 127 (4) ◽  
pp. 788-798 ◽  
Author(s):  
Brian P. Trease ◽  
Yong-Mo Moon ◽  
Sridhar Kota
Keyword(s):  
Range Of Motion ◽  
Parametric Models ◽  
Stress Concentrations ◽  
Concentration Effects ◽  
Element Analysis ◽  
Compliant Joints ◽  
Joint Range Of Motion ◽  
Stiffness Properties ◽  
Compliant Joint ◽  
Joint Range

This paper investigates the drawbacks of typical flexure connectors and presents several new designs for highly effective, kinematically well-behaved compliant joints. A revolute and a translational compliant joint are proposed, both of which offer great improvements over existing flexures in the qualities of (1) a large range of motion, (2) minimal “axis drift,” (3) increased off-axis stiffness, and (4) a reduced stress-concentrations. Analytic stiffness equations are developed for each joint and parametric computer models are used to verify their superior stiffness properties. A catalog of design charts based on the parametric models is also presented, allowing for rapid sizing of the joints for custom performance. A joint range of motion has been calculated with finite element analysis, including stress concentration effects.

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