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.

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

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.

A Simple and Accurate Method for Determining Large Deflections in Compliant Mechanisms Subjected to End Forces and Moments

1998 ◽  
Vol 120 (3) ◽  
pp. 392-400 ◽  
Author(s):  
A. Saxena ◽  
S. N. Kramer
Keyword(s):  
Rigid Body ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Elliptic Integral ◽  
Beam Equation ◽  
Large Deflections ◽  
Euler Beam ◽  
Body Model ◽  
Rigid Body Model ◽  
Analysis And Synthesis

Compliant members in flexible link mechanisms undergo large deflections when subjected to external loads. Because of this fact, traditional methods of deflection analysis do not apply. Since the nonlinearities introduced by these large deflections make the system comprising such members difficult to solve, parametric deflection approximations are deemed helpful in the analysis and synthesis of compliant mechanisms. This is accomplished by representing the compliant mechanism as a pseudo-rigid-body model. A wealth of analysis and synthesis techniques available for rigid-body mechanisms thus become amenable to the design of compliant mechanisms. In this paper, a pseudo-rigid-body model is developed and solved for the tip deflection of flexible beams for combined end loads. A numerical integration technique using quadrature formulae has been employed to solve the large deflection Bernoulli-Euler beam equation for the tip deflection. Implementation of this scheme is simpler than the elliptic integral formulation and provides very accurate results. An example for the synthesis of a compliant mechanism using the proposed model is also presented.

A Simple and Accurate Method for Determining Large Deflections in Complaint Mechanisms Subjected to End Forces and Moments

1998 ◽  
Author(s):  
A. Saxena ◽  
Steven N. Kramer
Keyword(s):  
Rigid Body ◽  
Numerical Integration ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Beam Equation ◽  
Integration Scheme ◽  
Large Deflections ◽  
Body Model ◽  
Rigid Body Model ◽  
Analysis And Synthesis

Abstract Compliant members in flexible link mechanisms undergo large deflections when subjected to external loads for which, traditional methods of deflection analysis do not apply Nonlinearities introduced by these large deflections make the system comprising such members difficult to solve Parametric deflection approximations are then deemed helpful in the analysis and synthesis of compliant mechanisms This is accomplished by seeking the pseudo-rigid-body model representation of the compliant mechanism A wealth of analysis and synthesis techniques available for rigid-body mechanisms thus become amenable to the design of compliant mechanisms In this paper, a pseudo-rigid-body model is developed and solved for the tip deflection of flexible beams for combined end loads with positive end moments A numerical integration technique using quadrature formulae has been employed to solve the nonlinear Bernoulli-Euler beam equation for the tip deflection Implementation of this scheme is relatively simpler than the elliptic integral formulation and provides nearly accurate results Results of the numerical integration scheme are compared with the beam finite element analysis An example for the synthesis of a compliant mechanism using the proposed model is also presented.

The Mixed-Body Model: A Method for Predicting Large Deflections in Stepped Cantilever Beams

2021 ◽  
pp. 1-18
Author(s):  
Brandon Sargent ◽  
Collin Ynchausti ◽  
Todd G Nelson ◽  
Larry L Howell
Keyword(s):  
Large Deflections ◽  
Cantilever Beams ◽  
Element Analysis ◽  
Body Model ◽  
Minimal Error ◽  
Small Deflection ◽  
Rigid Body Model ◽  
Expected Values ◽  
Deflection Theory ◽  
Sample Set

Abstract This paper presents a method for predicting endpoint coordinates, stress, and force to deflect stepped cantilever beams under large deflections. This method, the Mixed-Body Model or MBM, combines small deflection theory and the Pseudo-Rigid-Body Model for large deflections. To analyze the efficacy of the model, the MBM is compared to a model that assumes the first step in the beam to be rigid, to finite element analysis, and to the numerical boundary value solution over a large sample set of loading conditions, geometries, and material properties. The model was also compared to physical prototypes. In all cases, the MBM agrees well with expected values. Optimization of the MBM parameters yielded increased agreement, leading to average errors of <0.01 to 3%. The model provides a simple, quick solution with minimal error that can be particularly helpful in design.

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