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.

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.

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 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.

scholarly journals Design, Analysis and Testing of a New Compliant Compound Constant-Force Mechanism

Actuators ◽  
2018 ◽  
Vol 7 (4) ◽  
pp. 65 ◽  
Author(s):  
Xiaozhi Zhang ◽  
Guangwei Wang ◽  
Qingsong Xu
Keyword(s):  
Maximum Stress ◽  
Contact Process ◽  
Constant Force ◽  
Force Output ◽  
Element Analysis ◽  
Input Force ◽  
Force Structure ◽  
Force Mechanism ◽  
Design And Testing ◽  
Constant Force Mechanism

This paper presents the design and testing of a novel flexure-based compliant compound constant-force mechanism (CCFM). One uniqueness of the proposed mechanism lies in that it achieves both constant-force input and constant-force output, which is enabled by integrating two types of sub-mechanisms termed active and passive constant-force structures, respectively. Unlike conventional structures, the active constant-force structure allows the reduction on input force requirement and thus the enlargement of motion stroke provided that the maximum stress of the material is within allowable value. While the passive one offers a safe environmental interaction during the contact process. Analytical model of the proposed CCFM is derived which is verified by simulation study with finite element analysis (FEA). A prototype mechanism is fabricated by a 3D printer to demonstrate the performance of the proposed CCFM design. Experimental results reveal the effectiveness of the reported CCFM.

Simplified modelling and development of a bi-directionally adjustable constant-force compliant gripper

2016 ◽  
Vol 231 (11) ◽  
pp. 2110-2123 ◽  
Author(s):  
Guangbo Hao ◽  
John Mullins ◽  
Kevin Cronin
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Negative Stiffness ◽  
Displacement Curve ◽  
Constant Force ◽  
Force Output ◽  
Element Analysis ◽  
Force Mechanism ◽  
Bistable Mechanism ◽  
Constant Force Mechanism

This paper proposes the design of a wholly mechanical constant-force gripper that can accommodate the imprecise manipulation of brittle/delicate objects by the actuation. This was achieved by designing a constant-force mechanism as the jaw that allowed a constant force to be applied to the grasping objects regardless of the displacement of the mechanism. The constant-force mechanism is attached to the end effector of the gripper via a parallelogram mechanism which ensures that the jaws remain in parallel. The constant-force mechanism combines the negative stiffness of a bistable mechanism and the positive stiffness of a linear spring to generate a constant force output. By preloading the positive stiffness mechanism, the magnitude of the constant force can be adjusted to be as low as zero. The constant-force mechanism has been fully modelled and simulated using finite element analysis. A normalised force-displacement curve has been developed that allows to obtain the simplified analytical negative stiffness of the bistable mechanism. The design formulation to find the optimal configuration that produces the most constant force has been developed. Illustrated experiments prove the concept of the design although the discrepancies between finite element analysis results and testing results exist due to bistable beam manufacturing error.

Design of a Single-Acting Constant-Force Actuator Based on Dielectric Elastomers

2008 ◽  
Author(s):  
Giovanni Berselli ◽  
Rocco Vertechy ◽  
Gabriele Vassura ◽  
Vincenzo Parenti Castelli
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Compliant Mechanism ◽  
Structural Parameters ◽  
Dielectric Elastomer ◽  
Constant Force ◽  
Element Analysis ◽  
Body Model ◽  
Rigid Body Model ◽  
Supporting Frame

The interest in actuators based on dielectric elastomer films as a promising technology in robotic and mechatronic applications is increasing. The overall actuator performances are influenced by the design of both the active film and the film supporting frame. This paper presents a single-acting actuator which is capable of supplying a constant force over a given range of motion. The actuator is obtained by coupling a rectangular film of silicone dielectric elastomer with a monolithic frame designed to suitably modify the force generated by the dielectric elastomer film. The frame is a fully compliant mechanism whose main structural parameters are calculated using a pseudo-rigid-body model and then verified by finite element analysis. Simulations show promising performance of the proposed actuator.

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.

On the Design of a Long-Stroke Beam-Based Compliant Mechanism Providing Quasi-Constant Force

2019 ◽  
Author(s):  
Pietro Bilancia ◽  
Alessandro Geraci ◽  
Giovanni Berselli
Keyword(s):  
Compliant Mechanism ◽  
Design Method ◽  
Reaction Force ◽  
Constant Force ◽  
Physical Prototype ◽  
Flexible Behavior ◽  
Improved Design ◽  
The One ◽  
Long Stroke ◽  
Integrated Software

Abstract In this paper the design of a linear long-stroke quasi-constant force compliant mechanism (CM) is presented and discussed. Starting from a flexure-based slider-crank mechanism, providing the required constant force within a rather limited deflection range, the paper reports about the shape optimization carried out with the specific aim of extending the available CM operative range. The proposed device is suitable in several precision manipulation systems, which require to maintain a constant-force at their contact interface with the manipulated object. Force regulation is generally achieved by means of complex control algorithms and related sensory apparatus, resulting in a flexible behavior but also in high costs. A valid alternative may be the use of a purposely designed CM, namely a purely mechanical system whose shape and dimensions are optimized so as to provide a force-deflection behavior characterized by zero stiffness. In the first design step, the Pseudo-Rigid Body (PRB) method is exploited to synthesize the sub-optimal compliant configuration, i.e. the one characterized by lumped compliance. Secondly, an improved design alternative is evaluated resorting to an integrated software framework, comprising Matlab and ANSYS APDL, and capable of performing non-linear structural optimizations. The new embodiment makes use of a variable thickness beam, whose shape and dimensions have been optimized so as to provide a constant reaction force in an extended range. Finally, a physical prototype of the beam-based configuration is produced and tested, experimentally validating the proposed design method.

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