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.

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.

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.

An Adjustable Constant-Force Mechanism for Adaptive End-Effector Operations

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Yi-Ho Chen ◽  
Chao-Chieh Lan
Keyword(s):  
Compliant Mechanism ◽  
Displacement Curve ◽  
Constant Force ◽  
Force Output ◽  
Control Effort ◽  
End Effector ◽  
Linear Spring ◽  
End Effectors ◽  
Force Mechanism ◽  
Constant Force Mechanism

Force regulation is a challenging problem for robot end-effectors when interacting with an unknown environment. It often requires sophisticated sensors with computerized control. This paper presents an adjustable constant-force mechanism (ACFM) to passively regulate the contact force of a robot end-effector. The proposed ACFM combines the negative stiffness of a bistable mechanism and positive stiffness of a linear spring to generate a constant-force output. Through prestressing the linear spring, the constant-force magnitude can be adjusted to adapt to different working environments. The ACFM is a monolithic compliant mechanism that has no frictional wear and is capable of miniaturization. We propose a design formulation to find optimal mechanism configurations that produce the most constant-force. A resulting force to displacement curve and maximal stress curve can be easily manipulated to fit a different application requirement. Illustrated experiments show that an end-effector equipped with the ACFM can adapt to a surface of variable height, without additional motion programming. Since sensors and control effort are minimized, we expect this mechanism can provide a reliable alternative for robot end-effectors to interact friendly with an environment.

A Primal Treatise of Constant-Force, Compliant Segments and Mechanisms

2020 ◽  
Author(s):  
Ashok Midha ◽  
Vamsi Lodagala ◽  
Pratheek Bagivalu Prasanna ◽  
Jyothi Komatireddy
Keyword(s):  
Energy Storage ◽  
Range Of Motion ◽  
Design Optimization ◽  
Compliant Mechanisms ◽  
Axial Loading ◽  
Constant Force ◽  
Rigid Link ◽  
Torsional Spring ◽  
Natural Energy

Abstract The evolution of constant-force mechanisms is propelled by a growing interest in being able to exert constant or near-constant force in various applications. Compliant mechanisms have recently received much attention in the design of constant-force mechanisms because of their several advantages, e.g. fewer parts, compact construct, natural energy storage, no backlash, among many others. There have been many research efforts in developing various techniques to design these mechanisms for applications in diverse fields. Several of these techniques require design optimization to generate a constant force over a desired range of motion. There is generally a lack of understanding of the mechanics of the generation of constant force. This paper presents the hypothesis that simple arrangements, such as a rigid link with a torsional spring, or compliant segments, under axial loading are capable of producing constant force. Three compliant segment types are considered herein: fixed-free, pinned-pinned, and fixed-guided beams under axial loading, to demonstrate that they can exert near-constant force, without the need for a design optimization. This paper further exemplifies that the proposed theory is the kernel to generating constant force by different mechanism configurations.

A Load-Adjustable Constant-Force Mechanism

2018 ◽  
Author(s):  
Steven Hasara ◽  
Craig Lusk
Keyword(s):  
Reaction Force ◽  
Longitudinal Axis ◽  
Degree Of Freedom ◽  
Constant Force ◽  
Force Output ◽  
Constant Output ◽  
Force Mechanism ◽  
Constant Force Mechanism ◽  
Novel Design ◽  
Second Degree

This paper outlines the design of a compliant crank slider with adjustable constant-force output. Constant-force mechanisms (CFM) are used to maintain a constant output reaction force throughout a large range of compressive motion. This novel design improves on existing CFM by introducing a second degree of freedom that adjusts the mechanism’s output without changing its kinematic structure. This second degree of freedom is the rotation of a compliant beam about its longitudinal axis as it is constrained to the initial plane of bending. The resulting change in the beam’s stiffness allows for adjustment to a specifiable range of constant-force outputs.

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