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.

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.

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.

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.

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

2004 ◽  
Author(s):  
L. Yuan ◽  
J. Rastegar
Keyword(s):  
Closed Loop ◽  
Vibrational Excitation ◽  
High Harmonic ◽  
Harmonic Component ◽  
Primary Source ◽  
Linkage Mechanism ◽  
Output Link ◽  
Mechanism Synthesis ◽  
Constant Input ◽  
Cam Mechanism

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 of the mechanism joints. In this paper, the method is applied to the design of a linkage mechanism with an integrated cam mechanism for the purpose of eliminating the high harmonic component of the output link motion. The mechanism may be synthesized using well-developed linkage mechanism synthesis techniques for the intended application. Based on this method, a cam mechanism is synthesized for a prescribed output link motion while limiting the output motion to a simple harmonic motion with the frequency of its constant input velocity. The mechanism is constructed and tested. In mechanisms with relatively 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. 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.

A Systematic Method for Optimal Integration of Smart Materials Into the Structure of High Speed Mechanisms

1999 ◽  
Author(s):  
L. Yuan ◽  
J. Rastegar
Keyword(s):  
Smart Materials ◽  
High Speed ◽  
Closed Loop ◽  
Vibrational Excitation ◽  
High Harmonic ◽  
Harmonic Component ◽  
Primary Source ◽  
Linkage Mechanism ◽  
Constant Input ◽  
Systematic Method

Abstract A systematic method is presented for the integration of smart (active) materials based actuators into the structure of mechanical systems in general and mechanisms with closed-loop chains in particular for the purpose of modifying the output motion of the system. In the resent study, the method is applied to a four-bar linkage mechanism with a constant input velocity 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 and 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 the closed-loop chain. The usually less prominent high harmonic motions due to joint and/or structural flexibility may be eliminated in a similar manner and will be addressed in future publications.

Reduction of Induced Vibration Using Motion-Doubling Linkage Mechanisms

2006 ◽  
Author(s):  
J. Rastegar ◽  
J. Zhang
Keyword(s):  
High Speed ◽  
High Harmonic ◽  
Full Rotation ◽  
Rocking Motion ◽  
Points Of View ◽  
Harmonic Components ◽  
Input Motion ◽  
And Control ◽  
Special Case ◽  
Input Torque

In recent studies, the authors presented a special class of planar and spatial linkage mechanisms in which for a continuous full rotation or continuous rocking motion of the input link, the output link undergoes two continuous rocking motions. Such linkage mechanisms were referred to as the “motion-doubling” linkage mechanisms. It was also shown that in a special case of such mechanisms, the fundamental frequency of the input motion is doubled. This class of mechanisms generally has dynamics advantage over regular mechanisms designed to achieve similar gross output motions. In the present study, it is shown that in general and for the same gross output motion, motion-doubling mechanisms require lower input torques, and that the high harmonics of the input torque have smaller amplitudes. The high harmonic components present in the input torque are the main source of vibration and control problems in the system or device that the mechanism operates and its own structure. It is therefore concluded that when vibration and motion precision is of concern, such as in high-speed and precision machinery, motion-doubling mechanisms are generally more suitable from the potential vibration excitation and control points of view and actuating torque requirements.

scholarly journals Automated Axis Alignment for a Nanomanipulator inside SEM and Its Error Optimization

Scanning ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-8
Author(s):  
Chao Zhou ◽  
Lu Deng ◽  
Long Cheng ◽  
Zhiqiang Cao ◽  
Shuo Wang ◽  
...  
Keyword(s):  
Average Method ◽  
Closed Loop ◽  
Alignment Method ◽  
Visual Servo ◽  
End Effector ◽  
Axis Alignment ◽  
Deposition Effect ◽  
Relationship Of ◽  
The Relationship ◽  
Error Optimization

In the motion of probing nanostructures, repeating position and movement is frequently happing and tolerance for position error is stringent. The consistency between the axis of manipulators and image is very significant since the visual servo is the most important tool in the automated manipulation. This paper proposed an automated axis alignment method for a nanomanipulator inside the SEM by recognizing the position of a closed-loop controlling the end-effector, which can characterize the relationship of these two axes, and then the rotation matrix can be calculated accordingly. The error of this method and its transfer function are also calculated to compare the iteration method and average method. The method in this paper can accelerate the process of axis alignment to avoid the electron beam induced deposition effect on the end tips. Experiment demonstration shows that it can achieve a 0.1-degree precision in 90 seconds.

A Modified Monte-Carlo Potts Model for Dynamic Recrystallization

2015 ◽  
Vol 1096 ◽  
pp. 280-287 ◽  
Author(s):  
Jian Fu ◽  
Bi You Peng ◽  
Bin Xie ◽  
Yi Gen Ye
Keyword(s):  
Monte Carlo ◽  
Dynamic Recrystallization ◽  
Potts Model ◽  
Metallic Materials ◽  
Stored Energy ◽  
Modified Model ◽  
Grain Sizes ◽  
Basic Characteristics ◽  
Evolution Modeling ◽  
The Relationship

In order to improve the microstructure evolution modeling of dynamic recrystallization (DRX) in agreement with physical experiment, a modified Monte-Carlo (MC) Potts model for simulating DRX process was proposed in this paper under the consideration of the inhomogeneous stored energy distribution related to grain sizes, the nucleation criteria related to critical dislocation density, the site energy change related to grain preferred-growth, the combination of macroscopic thermo-mechanical parameters and microscopic material parameters, and the relationship between MC calculation steps and real DRX time. The results show that the modified model can better simulate the basic characteristics of dynamic recrystallization of metallic materials during forging, which the recrystallized grains nucleate mainly in the deformed regions with high stored energy and preferentially grow up by merging adjacent deformed grains with high stored energy.

KINETOSTATIC ANALYSIS FOR FOUR-BAR LINKAGE MECHANISM OF PROSTHETIC KNEE JOINT

2019 ◽  
Vol 19 (04) ◽  
pp. 1950018 ◽  
Author(s):  
XUHUI LIU ◽  
TIANTIAN GUO ◽  
JIAHAO ZHANG ◽  
GUANG YANG ◽  
LUCHAN SUN ◽  
...  
Keyword(s):  
Knee Joint ◽  
Group Method ◽  
Linkage Mechanism ◽  
Analysis Software ◽  
Prosthetic Knee ◽  
Damping Effect ◽  
D’Alembert Principle ◽  
Prosthetic Knee Joint ◽  
Four Bar Linkage ◽  
The Relationship

In this paper, a mathematical model of four-bar linkage mechanism is built to investigate the prosthetic knee joint, by means of the bar group method, and the motion of the prosthetic knee joint is simulated by motion analysis software. In the state of motion of the four linkage mechanism, to the moving component of the mechanism, the relationship between the moving displacement, velocity and acceleration are obtained. On the basis of the above investigation, dynamic statics analysis for the moving component of four-bar linkage mechanism are completed by the ‘D’Alembert principle. The research results show that, with the change of the rotating angle of the active part, the counter-force of rotating pair and the balance torque on active component are all changeable, which will provide a theoretical basis for the design of prosthetic knee joint mechanism with longer life and better damping effect.

scholarly journals The prediction of braking noise in regenerative braking system using closed-loop coupling disk brake model

2019 ◽  
Vol 233 (14) ◽  
pp. 3721-3735
Author(s):  
Pu Gao ◽  
Jiageng Ruan ◽  
Yongchang Du ◽  
Paul D Walker ◽  
Nong Zhang
Keyword(s):  
Closed Loop ◽  
Coupled Model ◽  
Regenerative Braking ◽  
Bench Test ◽  
Disk Brake ◽  
Coupling Stiffness ◽  
Braking Force ◽  
The Impact ◽  
The Relationship ◽  
Brake Noise

Aiming at improving regenerative braking ability in electric vehicles without compromising any safety, two different regenerative braking strategies are proposed in this study. The impact of continuously varying braking force distributions between front/rear wheel and electric/friction corresponding in two different strategies on braking noise are investigated. Based on the closed-loop coupling disk brake model, the relationship between the contact coupling stiffness and the braking force is established by considering the stationary modal test, the nonlinear optimization, and the relationship between brake-line pressure and braking force. The continuously varying braking force is initially transformed to continuously varying contact coupling stiffness, then, the brake noise tendency at each frequency band is calculated in closed-loop coupled model. The predicted result shows good consistency with the result recorded in bench test, verifying the reliability and effectivity of the presented method. The comparison of the two different electric braking strategies shows that the second braking strategy is superior to the first braking strategy in terms of suppressing the brake noise tendency.

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