Elastodynamic behavior of balanced closed-loop mechanisms: numerical analysis of a four-bar linkage

Meccanica ◽  
2013 ◽  
Vol 49 (3) ◽  
pp. 601-614 ◽  
Author(s):  
Alberto Martini ◽  
Marco Troncossi ◽  
Marco Carricato ◽  
Alessandro Rivola
Keyword(s):  
Numerical Analysis ◽  
Closed Loop ◽  
Four Bar Linkage

Kinematics Synthesis of Linkage Mechanisms With Cam Integrated Joints for Controlled Harmonic Content of the Output Motion

2004 ◽  
Vol 126 (1) ◽  
pp. 135-142 ◽  
Author(s):  
Lifang Yuan ◽  
Jahangir S. Rastegar
Keyword(s):  
Closed Loop ◽  
Vibrational Excitation ◽  
High Harmonic ◽  
Harmonic Component ◽  
Primary Source ◽  
Effective Length ◽  
Linkage Mechanism ◽  
Function Generation ◽  
Harmonic Content ◽  
Four Bar Linkage

A new method is presented for the modification of the output motion of linkage mechanisms with closed-loop chains using cams positioned at one or more of its joints. As an example and to present the basic concept, the method is applied to a four-bar linkage mechanism that is synthesized for function generation for the purpose of eliminating the high harmonic component of the output link motion. By eliminating the high harmonic component of the output motion of a mechanism, the potential vibrational excitation that the mechanism can impart on the overall system, including its own structure, is greatly reduced. The resulting system should therefore be capable of operating at higher speeds and with increased precision. For mechanisms with rigid links, the primary source of high harmonics in the output motion is the nonlinearity of the kinematics of their closed-loop chains. With the present method, a selected range or ranges of high harmonic motions generated due to such nonlinearities may be eliminated by integrating appropriately designed cams that are used to vary the effective length of one or more of the links during the motion. A numerical example is provided together with a discussion of the related topics of interest.

Dynamic Modeling and Numeration of Flexible Multi-Body System with Closed Loop

2010 ◽  
Vol 44-47 ◽  
pp. 1519-1524
Author(s):  
Shu Qing Liu ◽  
Xing Song Wang
Keyword(s):  
Dynamic Model ◽  
Closed Loop ◽  
Narrow Range ◽  
Null Space ◽  
Orthogonal Basis ◽  
Natural Coordinates ◽  
Body System ◽  
Multi Body ◽  
Four Bar Linkage ◽  
Flexible Linkage

The dynamic model of flexible multi-body system with closed loop is described with natural coordinates. The method is formulaic and especially appropriate to the modeling of system with repetitive substructures, but Lagrange multipliers as unknown variables are contained in the model. The dynamic model is reduced to a system with minimum dimensions by means of null-space orthogonal basis of constraint Jacobin. The result is correspondence with the dynamic model of rigid multi- body system while the rigid and flexible coupling is considered. The numerical method and the simulation steps are given in detail. Numerical example dealing with a flexible parallel four-bar linkage widely used in engineering illustrates the performance of the proposed method. The dynamic response of the angle between flexible linkage and horizontal axis are presented. The results indicate that there are clearly fluctuation in the angular velocity and acceleration of crank. The motion of connecting linkage contains not only translation but also narrow range rotation especially in the start instant.

Linkage Mechanisms With Cam-Integrated Joints for Controlled Harmonic Content of the Output Motion: Theory and Application

2007 ◽  
Vol 130 (1) ◽  
Author(s):  
L. Yuan ◽  
J. Rastegar ◽  
J. Zhang
Keyword(s):  
Closed Loop ◽  
Vibrational Excitation ◽  
High Harmonic ◽  
Harmonic Component ◽  
Linkage Mechanism ◽  
Mechanism Synthesis ◽  
Cam Mechanism ◽  
Harmonic Content ◽  
Harmonic Components ◽  
Four Bar Linkage

In a recent study, the authors presented a systematic method for the modification of the output motion of linkage mechanisms with closed-loop chains using cams positioned at one or more joints of the mechanism. In this paper, the method is applied to the design of a linkage mechanism with an integrated cam mechanism to eliminate high harmonic component of the output motion. The mechanism may be synthesized using any existing linkage mechanism synthesis technique. In the present study, a cam mechanism is synthesized to eliminate all high harmonic components of the output link motion of a four-bar linkage mechanism to illustrate the potentials of the present approach. The mechanism is then constructed and successfully tested. With the present method, selected ranges of high harmonic motions generated due to the mechanisms kinematics nonlinearity can be eliminated by integrating appropriately designed cams, thereby significantly reducing the potential vibrational excitation that the mechanism can impart on the overall system, including its own structure. Such systems should therefore be capable of operating at higher speeds and with increased precision.

A New Approach for the Reduction of Vibrational Excitation in Kinematics Synthesis of High Speed Linkages

2000 ◽  
Author(s):  
L. Yuan ◽  
J. Rastegar
Keyword(s):  
High Speed ◽  
Closed Loop ◽  
Vibrational Excitation ◽  
High Harmonic ◽  
Harmonic Component ◽  
Primary Source ◽  
Linkage Mechanism ◽  
New Approach ◽  
Function Generation ◽  
Four Bar Linkage

Abstract A new method is presented for the modification of the output motion of linkage mechanisms with closed-loop chains using cams positioned at one or more of its joints. In particular, the method is applied to a four-bar linkage mechanism that is synthesized for function generation for the purpose of eliminating the high harmonic component of the output link motion. By eliminating the high harmonic component of the output motion of a mechanism, the potential vibrational excitation that the mechanism can impart on the overall system, including its own structure, is greatly reduced. The resulting system should therefore be capable of operating at higher speeds with increased precision. For mechanisms with rigid links, the primary source of high harmonic motions is the nonlinearity of the kinematics of closed-loop chains. With the present method, the higher harmonic motions generated due to such nonlinearities are eliminated by the integration of appropriately designed cams that are used to vary the effective link lengths. A numerical example is provided together with a discussion of the related topics of interest.

On the Relationship Between the Harmonic Amplitudes of the Output Motion of Closed-Loop Linkage Mechanisms

2008 ◽  
Author(s):  
Jahangir Rastegar ◽  
Dake Feng ◽  
Lin Hua
Keyword(s):  
Closed Loop ◽  
High Harmonic ◽  
Constant Input ◽  
Vibration Excitation ◽  
Basic Characteristics ◽  
Harmonic Components ◽  
Input Motion ◽  
Four Bar Linkage ◽  
The Relationship

It is well known that due to the nonlinearity of the kinematics of linkage mechanisms, their output motion contains harmonics of the input motion. In most mechanisms, the generated high harmonic components in the output motion are the main source of vibration excitation that the mechanism imparts on the overall system, including its own structure. For simple linkage mechanisms such as slider-cranks and four-bar linkage mechanisms, the amplitudes of the harmonics of the output motion for constant input rotation have been derived. In the present study, it is shown that certain relationships exist between the amplitudes of the harmonic of the output motions. In particular, odd and even harmonic amplitudes are shown to be related through an inequality relationship. These relationships are due to the basic characteristics of the linkage mechanisms motions, which are significantly simplified for certain linkage geometries. The relationships between the amplitudes of the output velocity harmonics are derived for slider-crank and four-bar linkage mechanisms.

scholarly journals Numerical Analysis of General Trends in Single-Phase Natural Circulation in a 2D-Annular Loop

2008 ◽  
Vol 2008 ◽  
pp. 1-10 ◽  
Author(s):  
Gilles Desrayaud ◽  
Alberto Fichera
Keyword(s):  
Natural Convection ◽  
Numerical Analysis ◽  
Single Phase ◽  
Closed Loop ◽  
Dynamic Properties ◽  
Natural Circulation ◽  
Flow Behavior ◽  
Pitchfork Bifurcation ◽  
Chaotic Flow ◽  
Over The Top

The aim of this paper is to address fluid flow behavior of natural circulation in a 2D-annular loop filled with water. A two-dimensional, numerical analysis of natural convection in a 2D-annular closed-loop thermosyphon has been performed for various radius ratios from 1.2 to 2.0, the loop being heated at a constant flux over the bottom half and cooled at a constant temperature over the top half. It has been numerically shown that natural convection in a 2D-annular closed-loop thermosyphon is capable of showing pseudoconductive regime at pitchfork bifurcation, stationary convective regimes without and with recirculating regions occurring at the entrance of the exchangers, oscillatory convection at Hopf bifurcation and Lorenz-like chaotic flow. The complexity of the dynamic properties experimentally encountered in toroidal or rectangular loops is thus also found here.

Numerical analysis of photovoltaic solar panel cooling by a flat plate closed-loop pulsating heat pipe

Solar Energy ◽  
2020 ◽  
Vol 206 ◽  
pp. 455-463
Author(s):  
Hossein Alizadeh ◽  
Mohammad Alhuyi Nazari ◽  
Roghayeh Ghasempour ◽  
Mohammad Behshad Shafii ◽  
Aliakbar Akbarzadeh
Keyword(s):  
Numerical Analysis ◽  
Flat Plate ◽  
Heat Pipe ◽  
Closed Loop ◽  
Solar Panel ◽  
Pulsating Heat Pipe

Singularity-Based Four-Bar Linkage Mechanism for Impulsive Torque With High Energy Efficiency

2015 ◽  
Vol 7 (3) ◽  
Author(s):  
Tomoaki Mashimo ◽  
Takateru Urakubo ◽  
Takeo Kanade
Keyword(s):  
Energy Efficiency ◽  
Closed Loop ◽  
High Energy ◽  
Linkage Mechanism ◽  
High Acceleration ◽  
Short Period ◽  
Torque Generation ◽  
High Energy Efficiency ◽  
Singular Configuration ◽  
Four Bar Linkage

We propose a mechanism that exploits the singular configuration in a closed-loop four-bar linkage that can produce a high impulsive torque (a high torque for a short period in time) at the start of motion and high angular velocity during the successive motion. Such characteristics make the mechanism suitable for executing with high energy efficiency a certain class of tasks, such as lifting heavy objects. In this paper, we define the singularity-based linkage mechanism (SLM), analyze its characteristics of torque generation and energy efficiency theoretically, and then confirm them experimentally by using an SLM prototype. The performance of the SLM is compared with that of a comparable size parallelogram mechanism (PM). It is shown that the energy efficiency of the SLM comes from the fact that it achieves the high acceleration of the output link in the neighborhood of the singular configuration by providing energy with low current and high voltage to the motor; whereas the typical PM requires high current to produce the comparable impulsive torque.

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