Moment-Dependent Pseudo-Rigid-Body Models for Straight Beams

2010 ◽  
Author(s):  
Diego A. Espinosa ◽  
Craig P. Lusk
Keyword(s):  
Rigid Body ◽  
Rational Function ◽  
Statistical Significance ◽  
Horizontal Displacement ◽  
Vertical Displacement ◽  
Beam Model ◽  
Characteristic Radius ◽  
Rigid Body Model ◽  
The Moment ◽  
Key Parameter

This paper introduces a parametric beam model for describing the kinematics and elastic properties of ortho-planar compliant beams subject to specific buckling loads. This model uses an approach similar to the Pseudo-Rigid-Body Model but differs that in a key parameter, the characteristic radius factor, is not a constant, but a rational function of the moment. The rational function coefficients are determined by least squares, along with the statistical significance of the coefficients. Results are calculated for straight beams for two cases: a vertical displacement and a horizontal displacement.

Preliminaries for a Spherical Compliant Mechanism: Pseudo-Rigid-Body Model Kinematics

2007 ◽  
Author(s):  
Saurabh Jagirdar ◽  
Craig P. Lusk
Keyword(s):  
Rigid Body ◽  
Compliant Mechanism ◽  
Beam Angle ◽  
Body Model ◽  
Spherical Mechanisms ◽  
Characteristic Radius ◽  
Rigid Body Model ◽  
Limiting Case

The kinematic portion of a pseudo-rigid-body model (PRBM) is developed as a generalization from planar to spherical mechanisms. The topology of the spherical compliant segment and its rigid-body equivalent are derived from planar models by analogy. The nomenclature for the spherical PRBM is chosen to facilitate comparison with the planar PRBM. The motion of the compliant segment is calculated using FEA and PRBM parameters are determined. The characteristic radius and parametric angle coefficient are found to decrease as the angle subtended by the beam increases. The parameterization limit increases with increasing beam angle. The spherical PRBM is identical to the planar PRBM in the limiting case when beam angles become very small.

The Analysis of a Simplified 2R Pseudo-Rigid-Body Model with Moment Load

2012 ◽  
Vol 224 ◽  
pp. 18-23
Author(s):  
Yun Jiao Zhang ◽  
Guo Wu Wei ◽  
Jian Sheng Dai
Keyword(s):  
Rigid Body ◽  
Objective Function ◽  
Compliant Mechanisms ◽  
Three Dimensional ◽  
Body Model ◽  
Design Variables ◽  
Characteristic Radius ◽  
Rigid Body Model ◽  
Analysis And Synthesis ◽  
Moment Load

Pseudo-rigid-body model (PRBM) method, which simplifies the geometrical nonlinear analysis, has become an important tool for the analysis and synthesis of compliant mechanisms. In this paper, a simplified 2R PRBM with two rigid links and two torsion springs is proposed. The characteristic radius factor and stiffness coefficients are selected as the design variables; in order to be better to simulate the tip point and tip slope, a three-dimensional objective function is formulated to optimize the new pseudo-rigid-body model. It is revealed in this paper that the precision of the tip point simulation can be improved when the coefficient of the tip slope error in the objective function is reduced.

A Pseudo Rigid Body Model of a Single Vertex Compliant-Facet Origami Mechanism (SV-COFOM)

2016 ◽  
Author(s):  
Jelle Rommers ◽  
Giuseppe Radaelli ◽  
Just Herder
Keyword(s):  
Rigid Body ◽  
Computational Cost ◽  
Element Model ◽  
Design Tool ◽  
Single Vertex ◽  
Starting Point ◽  
Rigid Body Model ◽  
Cost Efficient ◽  
The Moment ◽  
Planar Fabrication

Recently, there has been an increased interest in origami art from a mechanism design perspective. The deployable nature and the planar fabrication method inherent to origami provide potential for space and cost efficient mechanisms. In this paper, a novel type of origami mechanisms is proposed in which the compliance of the facets is used to incorporate spring behavior: Compliant Facet Origami Mechanisms (COFOMs). A simple model that computes the moment characteristic of a Single Vertex COFOM has been proposed, using a semi-spatial version of the Pseudo-Rigid Body (PRB) theory to model bending of the facets. The performance of this PRB model has been evaluated numerically and experimentally, and showed performance comparable to a Finite Element model with 122 elements. The PRB model is a potential starting point for a design tool which would provide an intuitive way of designing this type of mechanisms including their spring behavior, with very low computational cost.

A Pseudo-Rigid-Body Model for Spherical Mechanisms: The Kinematics and Stiffness of a Compliant Curved Beam

2008 ◽  
Author(s):  
Alejandro Leo´n ◽  
Saurabh Jagirdar ◽  
Craig P. Lusk
Keyword(s):  
Rigid Body ◽  
Curved Beam ◽  
Beam Angle ◽  
Element Analysis ◽  
Body Model ◽  
Spherical Mechanisms ◽  
Characteristic Radius ◽  
Rigid Body Model ◽  
Spherical Mechanism ◽  
Spherical Motion

A pseudo-rigid-body model (PRBM) which describes a class of curved compliant beams in terms of spherical mechanism kinematics was developed. The topology of the spherical compliant segment and its rigid-body equivalent were chosen to be analogous to planar models. The nomenclature for the spherical PRBM was also chosen to facilitate comparison with planar models. The motion of the compliant segment was calculated Finite Element Analysis and the PRBM parameters were determined. The characteristic radius and parametric angle coefficient were found to decrease as the angle subtended by the beam increases. The kinematic and elastic parameterization limits of the model increase with increasing beam angle. The stiffness of the beam is described by two separate spring elements, which describe the appropriate combination of moment and force which produces spherical motion. A previous planar PRBM is shown to be the small angle limit of the new spherical PRBM.

Pseudo-Rigid-Body Model for the Flexural Beam With an Inflection Point in Compliant Mechanisms

2017 ◽  
Vol 9 (3) ◽  
Author(s):  
Shun-Kun Zhu ◽  
Yue-Qing Yu
Keyword(s):  
Rigid Body ◽  
Inflection Point ◽  
Compliant Mechanisms ◽  
Angular Displacement ◽  
Flexible Beam ◽  
Body Model ◽  
Numerical Result ◽  
Characteristic Radius ◽  
Rigid Body Model ◽  
Flexural Beam

The pseudo-rigid-body model (PRBM) used to simulate compliant beams without inflection point had been well developed. In this paper, two types of PRBMs are proposed to simulate the large deflection of flexible beam with an inflection point in different configurations. These models are composed of five rigid links connected by three joints added with torsional springs and one hinge without spring representing the inflection point in the flexural beam. The characteristic radius factors of the PRBMs are determined by solving the objective function established according to the relative angular displacement of the two rigid links jointed by the hinge via genetic algorithm. The spring stiffness coefficients are obtained using a linear regression technique. The effective ranges of these two models are determined by the load index. The numerical result shows that both the tip locus and inflection point of the flexural beam with single inflection can be precisely simulated using the model proposed in this paper.

Development of a 3-Spring Pseudo Rigid Body Model of Compliant Joints for Robotic Applications

2014 ◽  
Author(s):  
Venkatasubramanian Kalpathy Venkiteswaran ◽  
Hai-Jun Su
Keyword(s):  
Rigid Body ◽  
Compliant Mechanisms ◽  
Large Range ◽  
Beam Theory ◽  
Beam Model ◽  
Significant Challenge ◽  
Body Model ◽  
Compliant Joints ◽  
Rigid Body Model ◽  
Robotic Applications

Compliant mechanisms achieve motion utilizing deformation of elastic members. However, analysis of compliant mechanisms for large deflections remains a significant challenge. In this paper, we will develop a 3-spring pseudo-rigid-body model for 2D beams that are often used in compliant joints in robots. First, we utilize the Timoshenko beam theory to calculate the tip deflection for a large range of loading conditions. An optimization process is then carried out to calculate the values of the parameters of the PRB model. The errors in the model will be analyzed and compared to the beam model. An example based on a robotic grasper finger is provided to demonstrate how the model can be used in analysis of such a system. This model will provide a much simpler approach for the analysis of compliant robotic mechanisms.

Design and Analysis of Compliant Rotary Joint

2013 ◽  
Vol 372 ◽  
pp. 467-470 ◽  
Author(s):  
Thanh Phong Dao ◽  
Shyh Chour Huang
Keyword(s):  
Rigid Body ◽  
Compliant Mechanisms ◽  
Virtual Work ◽  
Compliant Mechanism ◽  
Horizontal Displacement ◽  
Flexure Hinge ◽  
Rotary Joint ◽  
Rigid Body Model ◽  
Future Work ◽  
The Relationship

Unlike rigid-body mechanisms, compliant mechanisms (CMs) gain some or all of their motion from relative flexibility of their joints. This paper presents a pseudo-rigid-body model (PRBM) method and virtual work to design and analyze kinematics and dynamics for compliant rotary joints or flexure hinges in the processing of compliant mechanisms. The stress at flexible pivot, the nonlinear-large deflection of flexure hinge, the relationship between displacement and force and/or torque, stress were taken into account in this work based on PRBM. A numerical software package, ANSYS, was exploited to illustrate schematic diagram of the stress versus to horizontal displacement of free end AB of flexure hinge. A mechanism with the desired structure is that one of the most popular aspects, which is needed to take into account in the design phase in advance. The results revealed that the proposed effective approach can be further easily applied in compliant mechanism structures. Future work will focus on multi-objective structural optimization of the flexure hinge.

Vertical and horizontal barbell kinematics indicate differences in mechanical advantage between using an arched or flat back posture in the barbell bench press exercise

2021 ◽  
pp. 174795412098295
Author(s):  
Brendan L Pinto ◽  
Clark R Dickerson
Keyword(s):  
Repeated Measures ◽  
Bench Press ◽  
Glenohumeral Joint ◽  
Statistical Significance ◽  
Vertical Displacement ◽  
Moment Arm ◽  
Mechanical Advantage ◽  
Strength Performance ◽  
Flat Back ◽  
And Training

Employing an arched back posture during the bench press exercise is increasingly popular. Vertical displacement of the barbell is commonly believed to be the key difference influencing strength performance between an arched and flat back bench press technique. However, comparisons between these back postures using a free weight barbell are lacking. Directly comparing performance between each posture is confounded by many variables such as proficiency and fatigue. This investigation aimed to investigate whether changing back posture alone can influence barbell kinematics, to indirectly assess potential performance differences. Twenty males performed one repetition of the bench press exercise using either an arched or flat back posture, at 25%, 50% and 75% of their one repetition maximum, in a repeated measures study design. Statistical significance was considered at p < 0.05. Changing back posture alone, reduced vertical displacement (approximately 11% average difference across all load conditions) and barbell to glenohumeral joint moment arm (approximately 20% difference) in the arched posture compared to the flat posture. These changes occurred without any specific cueing of the barbell motion and may increase the potential for lifting higher loads and decrease cumulative joint exposure. Additional cueing and training may be required to maximize the mechanical advantage available with each back posture. The arched posture appears to have an increased potential for further improvements in vertical displacement and moment arm through specific cueing. Future comparisons should consider if each back posture’s potential mechanical advantage has been maximized when assessing differences between techniques.

scholarly journals Influence of rigidity of retainers on dynamic behavior of implant-supported removable partial dentures

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Toshifumi Nogawa ◽  
Masayasu Saito ◽  
Naomichi Murashima ◽  
Yoshiyuki Takayama ◽  
Atsuro Yokoyama
Keyword(s):  
Dynamic Behavior ◽  
Horizontal Displacement ◽  
Vertical Displacement ◽  
Denture Base ◽  
Second Molar ◽  
Mechanical Simulation ◽  
Computed Tomography Images ◽  
Significant Difference ◽  
Abutment Teeth ◽  
Distal Extension

Abstract Background Implant-supported removable partial dentures (ISRPDs) are an effective treatment for partially edentulous patients. ISRPDs improve patients’ satisfaction and oral function to a greater extent than RPDs by improving denture stability and enhancing support. However, the effect of a type of direct retainer on displacement of the abutment teeth and dentures in ISRPDs remains unclear. Therefore, we made a resin mandibular model of unilateral mandibular distal-extension partial edentulism for mechanical simulation and compared the dynamic behavior of the abutment teeth and the denture base among different tooth-borne retainers with various rigidities for RPDs and ISRPDs. Methods A resin mandibular model for mechanical simulation that had unilateral mandibular distal-extension edentulism and was missing the first molar, second molar, first premolar, and second premolar, and a denture fabricated from the patient’s computed tomography images were used. Three types of direct retainers with different connecting rigidities were evaluated. The vertical displacement of the denture base and buccal and lingual sides and the mesial displacement of the abutment teeth were measured. Results Regardless of the rigidity of the direct retainers and loading positions, the displacement of the denture bases in the ISRPDs was significantly smaller than that in the RPDs (P < 0.001). There was no significant difference in vertical displacement of the denture bases among direct retainers with various connecting rigidities in the ISRPDs. Conversely, horizontal displacement of the abutment teeth in both the RPDs and ISRPDs tended to be larger with the cone crown telescope, which has high rigidity, than with the cast cingulum rest and wire clasp, which have much lower rigidities. Conclusion Our results suggested that cast cingulum rest and wire clasps as direct retainers are appropriate ISRPDs to minimize denture movement and suppress displacement of the remaining teeth in patients with unilateral mandibular distal-extension partial edentulism.

Sign in / Sign up

Export Citation Format

Share Document