scholarly journals Compliant Mechanisms that use Static Balancing to Achieve Dramatically Different States of Stiffness

2020 ◽  
pp. 1-9
Author(s):  
Reinier Kuppens ◽  
Miguel Bessa ◽  
Just L. Herder ◽  
Jonathan Hopkins
Keyword(s):  
Compliant Mechanisms ◽  
Static Balance ◽  
Constant Force ◽  
Bistable Switch ◽  
Static Balancing ◽  
Constant Torque ◽  
Single Piece ◽  
Force Mechanism ◽  
First Time ◽  
Additional Device

Abstract Stiffness in compliant mechanisms can be dramatically altered and even eliminated entirely by using static balancing. This requires elastic energy to be inserted before operation, which is most often done with an additional device or preloading assembly. Adding such devices contrasts starkly with primary motivations for using compliant mechanisms, such as part count reduction, increased precision and miniaturization. However, statically balanced compliant mechanisms with a fully monolithic architecture are scarce. In this paper we introduce two novel statically balanced compliant mechanisms with linear and rotary kinematics that do not require preloading assembly, enabling miniaturization. Static balance is achieved by the principle of opposing constant force and extended to a rotational device by using opposing constant torque mechanisms for the first time. A constant force mechanism based on existing work is used and inspired a novel constant torque mechanism. A single piece device is obtained by monolithically integrating a bistable switch for preloading, which allows static balance to be turned on and off. The linear device reduces stiffness by 98.5 % over 10 mm, has significantly reduced device complexity and doubled relative range of motion from 3.3 % to 6.6 % compared to the state of the art. The rotary device reduces stiffness by 90.5 % over 0.35 rad.

Crank-Slider With Spring Constant Force Mechanism

2004 ◽  
Author(s):  
Bart D. Frischknecht ◽  
Larry L. Howell ◽  
Spencer P. Magleby
Keyword(s):  
Energy Storage ◽  
Compliant Mechanisms ◽  
Behavioral Model ◽  
Constant Force ◽  
Spring Element ◽  
Translational Spring ◽  
And Performance ◽  
Force Mechanism ◽  
Constant Force Mechanism ◽  
Opening Up

This paper explores the development and performance of new constant-force compliant mechanisms that involve the addition of a translational spring element to slider-crank constant force mechanisms. The translational spring element has the additional requirement that, similar to a slider, it resists off-axis loads sufficiently to permit translation along only one axis. Geometric and energy storage parameters have been determined by optimization for five classes of mechanisms. The results of the optimization are values for geometric and energy storage parameters for each mechanism class for various levels of the translational spring parameter and various levels of constant-force behavior. The new configurations experience decreasing performance with increasing translational spring stiffness. The potential to implement a translational spring that also acts as a slider link provides the motivation for the new configurations. Such a spring would have the potential to completely remove friction from the mechanism and provide a constant-force solution that could replace current solutions such as hydraulic or pneumatic devices. The new configurations also have the potential to be manufactured as one piece or in layers, opening up new arenas for compressive constant-force mechanisms. Prototyping and testing of one of the new configurations are included as an example to demonstrate the use of the behavioral model.

Dimensional Synthesis of Compliant Constant-Force Slider Mechanisms

1994 ◽  
Author(s):  
Larry L. Howell ◽  
Ashok Midha ◽  
Morgan D. Murphy
Keyword(s):  
Compliant Mechanisms ◽  
Design Procedure ◽  
Constant Force ◽  
Dimensional Synthesis ◽  
Model Concept ◽  
Output Force ◽  
Rigid Body Model ◽  
Constant Output ◽  
Force Mechanism ◽  
Constant Force Mechanism

Abstract Constant-force mechanisms produce a constant output force for a range of input displacements. Such mechanisms are important in applications with a varying displacement but a constant resultant force required. Constant-force mechanism designs have been limited to rigid-link mechanisms, but the design of compliant, or flexible link, constant force mechanisms could increase the number of applications by taking advantage of the unique characteristics of compliant mechanisms. Murphy (1993) developed type-synthesis theories for compliant mechanisms and applied them to generate possible configurations for compliant constant-force slider mechanisms. This paper concentrates on the dimensional synthesis of several of the resulting topologies. Optimization and the pseudo-rigid-body-model concept are employed in the design procedure. An example application as an electrical connection for use in electronic chip carriers is also illustrated.

Synthesis of Single-Input and Multiple-Output Port Mechanisms with Springs for Specified Energy Absorption

1994 ◽  
Vol 116 (3) ◽  
pp. 937-943 ◽  
Author(s):  
J. G. Jenuwine ◽  
A. Midha
Keyword(s):  
Energy Absorption ◽  
Output Port ◽  
Constant Force ◽  
Plane Symmetry ◽  
Multiple Precision ◽  
Linear Spring ◽  
Single Input ◽  
Force Mechanism ◽  
Closure Method ◽  
Constant Force Mechanism

A means of synthesis of single-input and multiple-output port mechanisms for specified energy absorption is formulated for multiple precision points. The synthesis presented makes use of an extension of the loop closure method which includes expressions for energy absorption by linear spring elements. The configuration considered locates spring elements at two output ports of a multi-loop, planar mechanism. Economies realized for the symmetric mechanism are discussed for both one- and two-plane symmetry. Synthesis examples are included for both the general and symmetric mechanism. Special applications presented include synthesis of a constant force mechanism and synthesis of a mechanism suited to the energy absorption requirements of an automotive crashworthiness system.

The Design and Analysis of a Compliant Constant-Force Mechanism

2016 ◽  
Author(s):  
Zhongtian Xie ◽  
Lifang Qiu
Keyword(s):  
Compliant Mechanism ◽  
Reaction Force ◽  
Constant Force ◽  
Element Analysis ◽  
Fea Model ◽  
Electrical Connector ◽  
Force Mechanism ◽  
Input Motion ◽  
Operational Range ◽  
Constant Force Mechanism

Compliant constant-force mechanisms (CFM) are a type of compliant mechanism which produce a reaction force at the output port that does not change for a large range of input motion. This paper describes a new compliant CFM, introduces its design and configuration-improvement process. A finite element analysis (FEA) model of the compliant CFM was created to evaluate its constant force behavior. The FEA result shows that when the displacement is Δ = 4 mm, the compliant CFM maintains a nearly constant force in the operational displacement range of 1.31 mm to 4 mm with an error of 5.05%. The operational range accounts for 67% of the total motion. This compliant CFM can be used to regulate the contact force of a robot end-effector or as an electrical connector.

A Two-Dimensional Adjustable Constant-Force Mechanism

2019 ◽  
Vol 142 (6) ◽  
Author(s):  
Yu-Ling Kuo ◽  
Chao-Chieh Lan
Keyword(s):  
Limited Range ◽  
Two Dimensions ◽  
Working Environment ◽  
Design Parameters ◽  
Constant Force ◽  
Two Dimensional ◽  
Output Force ◽  
Constant Output ◽  
Force Variation ◽  
Force Mechanism

Abstract Constant-force mechanisms (CFMs) can produce an almost invariant output force over a limited range of input displacement. Without using additional sensor and force controller, adjustable CFMs can passively produce an adjustable constant output force to interact with the working environment. In the literature, one-dimensional CFMs have been developed for various applications. This paper presents the design of a novel CFM that can produce adjustable constant force in two dimensions. Because an adjustable constant force can be produced in each radial direction, the proposed adjustable CFM can be used in applications that require two-dimensional force regulation. In this paper, the design formulation and simulation results are presented and discussed. Equations to minimize the output force variation are given to choose the design parameters optimally. A prototype of the two-dimensional CFM is tested to demonstrate the effectiveness and accuracy of adjustable force regulation. This novel CFM is expected to be used in machines or robots to interact friendly with the environment.

Design and Evaluation of a Passive Constant Force Mechanism for a Cardiac Ablation Catheter

2020 ◽  
Vol 15 (2) ◽  
Author(s):  
Werner W. P. J. van de Sande ◽  
Awaz Ali ◽  
Giuseppe Radaelli
Keyword(s):  
Contact Force ◽  
Effective Range ◽  
Constant Force ◽  
Ablation Catheter ◽  
Cardiac Ablation ◽  
Element Analysis ◽  
Average Force ◽  
And Performance ◽  
Force Mechanism ◽  
Constant Force Mechanism

Abstract Contact force management has been proven to have a positive effect on the outcome of cardiac ablation procedures. However, no method exists that allows maintaining a constant contact force within a required and effective range. This work aims to develop and evaluate such a constant force mechanism for use in an ablation catheter. A passive constant force mechanism was designed based on a tape loop. The tape loop consists of two tapered springs that work in parallel. A finite element analysis was carried out to verify the behavior and performance of the design. A design based on requirements for a constant force ablation tip showed an average force of about 7.8×10−2 N±8×10−3 N over 20 mm in simulation. A scaled prototype was built and evaluated to prove the validity of the concept; this prototype provides an average force of 1.3×10−1 N±1.6×10−2 N over 35 mm. The mechanism allows for controlled delivery of contact force within a desired and effective range. Based on these findings, it can be concluded that the approach is successful but needs to be optimized for future applications. Being able to control the delivery of contact force in a constant range may increase the effectivity of cardiac ablation procedures and improve clinical outcomes.

Application of Rigid-Body-Linkage Static Balancing Techniques to Reduce Actuation Effort in Compliant Mechanisms

2015 ◽  
Vol 8 (2) ◽  
Author(s):  
Sangamesh R. Deepak ◽  
Amrith N. Hansoge ◽  
G. K. Ananthasuresh
Keyword(s):  
Rigid Body ◽  
General Framework ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Small Length ◽  
Element Analysis ◽  
Static Balancing ◽  
Free Length ◽  
First Order ◽  
Taylor’S Series

There are analytical methods in the literature where a zero-free-length spring-loaded linkage is perfectly statically balanced by addition of more zero-free-length springs. This paper provides a general framework to extend these methods to flexure-based compliant mechanisms through (i) the well know small-length flexure model and (ii) approximation between torsional springs and zero-free-length springs. We use first-order truncated Taylor's series for the approximation between the torsional springs and zero-free-length springs so that the entire framework remains analytical, albeit approximate. Three examples are presented and the effectiveness of the framework is studied by means of finite-element analysis and a prototype. As much as 70% reduction in actuation effort is demonstrated. We also present another application of static balancing of a rigid-body linkage by treating a compliant mechanism as the spring load to a rigid-body linkage.

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.

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