An Improved Design of Gravity Compensators Based on the Inverted Slider-Crank Mechanism

2019 ◽  
Vol 11 (3) ◽  
Author(s):  
Vigen Arakelian ◽  
Yang Zhang
Keyword(s):  
Literature Review ◽  
Potential Energy ◽  
Mechanical Systems ◽  
Input Energy ◽  
Principal Mechanism ◽  
Suggested Approach ◽  
End Effector ◽  
Improved Design ◽  
The Masses ◽  
Crank Mechanism

The static balancing of mechanical systems is an important issue because it allows one to significantly decrease the size of actuators for equivalent displacements of the end effector. Indeed, the actuators do not have to produce the required input energy to counterbalance the variation of the potential energy of the robot. However, the literature review shows that in many cases the gravity balancing of mechanical systems is carried out by neglecting the masses of auxiliary links associated with the principal mechanism. For many balancing schemes, it is a source of errors.This paper deals with an improved solution for gravity compensators based on the inverted slider-crank mechanism considering the masses of the coupler and the spring. To achieve this, the torques are determined due to auxiliary links. Subsequently, they are introduced into the balancing equation for minimization of the residual unbalance. Hence, a more accurate balancing of gravity compensators based on the inverted slider-crank mechanism can be achieved. The efficiency of the suggested approach is illustrated by numerical simulations.

Improvement of the Balancing Accuracy in Gravity Compensators Based on the Inverted Slider Crank Mechanism

2018 ◽  
Author(s):  
Vigen Arakelyan ◽  
Yang Zhang
Keyword(s):  
Literature Review ◽  
Numerical Simulations ◽  
Mechanical Systems ◽  
Principal Mechanism ◽  
Suggested Approach ◽  
Static Balancing ◽  
The Masses ◽  
Crank Mechanism

The static balancing of mechanical systems is an important issue because it allows significant reduction of torques. However the literature review shows that in many cases the gravity balancing of mechanical systems is carried out by neglecting the masses of auxiliary links associated to the principal mechanism. For many balancing schemes it is the source of errors. This paper deals with an improved solution for gravity compensators based on the inverted slider crank mechanism considering the masses of the rocker and the spring. For this purpose, the torques due to auxiliary links are determined. Then, they are introduced into the balancing equation for minimization of the residual unbalance. In this way, a more accurate balancing of gravity compensators is achieved. The efficiency of the suggested approach is illustrated by numerical simulations.

Investigation of Parametric Resonance Instability in a Flexible Rod Slider Crank Mechanism

1991 ◽  
Author(s):  
David G. Beale ◽  
Shyr-Wen Lee
Keyword(s):  
Potential Energy ◽  
Parametric Resonance ◽  
Variational Approach ◽  
Equations Of Motion ◽  
Monodromy Matrix ◽  
Bending Energy ◽  
Constrained Equations ◽  
Beam Bending ◽  
Floating Frame ◽  
Crank Mechanism

Abstract A direct variational approach with a floating frame is presented to derive the ordinary differential equations of motion of a flexible rod, constant crank speed slider crank mechanism. Potential energy terms contained in the derivation include beam bending energy and energy in foreshortening of the rod tip (which were selected because of the importance of these terms in a pinned-pinned rod parametric resonance). A symbolic manipulator code is used to reduce the constrained equations of motion to unconstrained nonlinear equations. A linearized version of these equations is used to explore parametric resonance stability-instability zones at low crank speeds and small deflections by a monodromy matrix technique.

scholarly journals Some Aspects Concerning The Impact Of The End Of Stroke On Hydraulic Cylinders

2015 ◽  
Vol 21 (3) ◽  
pp. 821-824
Author(s):  
Niculai Hauk
Keyword(s):  
Numerical Simulation ◽  
Mechanical Systems ◽  
Hydraulic Cylinder ◽  
Important Variable ◽  
Mechanical Impact ◽  
Hydraulic Cylinders ◽  
The Masses ◽  
The Impact ◽  
Simulation Systems ◽  
Classical Calculation

Abstract The increase of speeds for mechanical systems operated with hydraulic cylinder raises risks of mechanical impact of the end of the race. We are considering a number of measures to limit the impact intensity. Its size is estimated according to the masses in motion, to work pressures and to the geometry of the mechanism. Elasticity of the components is also an important variable. This paper presents a method which combines the classical calculation with numerical simulation systems.

Modeling and Analysis of Spatial Flexible Mechanical Systems With a Spherical Clearance Joint Based on the LuGre Friction Model

2019 ◽  
Vol 15 (1) ◽  
Author(s):  
Xiao Tan ◽  
Guoping Chen ◽  
Hanbo Shao
Keyword(s):  
Mechanical Systems ◽  
Beam Element ◽  
Friction Model ◽  
Lugre Friction Model ◽  
Clearance Joint ◽  
Lugre Friction ◽  
Computational Methodology ◽  
Crank Mechanism ◽  
Flexible Components

Abstract A computational methodology for modeling spatial flexible mechanical systems with stick-slip friction in a spherical clearance joint is presented. A modified three-dimensional (3D) absolute nodal coordinate formulation based shear deformable beam element with two nodes is proposed and employed to discretize the flexible components. To avoid locking problems, we employed an enhanced continuum mechanics approach to evaluate the beam element elastic forces. The strain components εyz, εyy, and εzz are approximated using linear interpolation to improve the computational efficiency while the loss of accuracy is acceptable. The contact and friction forces in a spherical clearance joint were evaluated by the hybrid contact and LuGre friction models, respectively. Three numerical examples are presented and discussed. A simple pendulum was utilized to prove the correctness of the modified beam element. A classical slider–crank mechanism was employed to validate the computational methodology. A spatial rigid–flexible slider–crank mechanism with a spherical clearance joint was used to investigate the effect of link flexibility and joint clearance on the dynamic behavior of mechanical systems. Using the LuGre friction model, we reproduced the Stribeck effect as it is expected in real world settings. The components with appropriate stiffness play the role of suspension for spatial mechanical systems with imperfect joints. The vibrations of the flexible components play an active role of intensifying the collision in kinematic joint with clearance.

scholarly journals GERAKAN MAHASISWA DI INDONESIA DALAM BINGKAI KEKUASAAN ORDE BARU (1966-1998)

2014 ◽  
Vol 14 (1) ◽  
pp. 15-32
Author(s):  
Mohammad Maiwan
Keyword(s):  
Information Technology ◽  
Literature Review ◽  
Economic Crisis ◽  
Qualitative Method ◽  
Descriptive Analysis ◽  
Student Movement ◽  
New Order ◽  
Internal Factors ◽  
New Ideas ◽  
The Masses

This study discusses the dynamics of Indonesian student movement in the New Order era between 1966 until 1998. It also analyses the responses of the authority to their movement and its impact. This research uses the qualitative method of literature review and interviews where the arguments are presented in descriptive analysis. Based on Antonio Gramsci’s concept of hegemony, this study has uncovered the hegemonic means utilized by the authority to undermine student movement. The description of how this social formation was defragmented, justified and then integrated into bureaucratic processes where their existence was then consented as a subordinated class. In reality, the student movement under the New Order government was closely related to the situation of socio-politics and character of the regime. Nevertheless, the Asian economic crisis jolted the revival of the student movement to its initial vibrant state which brought down Suharto’s regime in 1998. This study has proven that hegemonic process also has a shelf-life as the masses will eventually see through the regime’s political construction. This eventuality was due to external and internal factors such as development of information technology, the rise of cyber-power, international politics and the emergence of new ideas.

Dynamic Behavior of a Revolute Clearance Joint in Multibody Mechanical Systems

2003 ◽  
Author(s):  
P. Flores ◽  
H. M. Lankarani ◽  
J. Ambro´sio ◽  
J. C. P. Claro
Keyword(s):  
Mechanical Systems ◽  
Force Model ◽  
Continuous Contact ◽  
Revolute Clearance Joint ◽  
Regular Motion ◽  
Clearance Joint ◽  
Contact Force Model ◽  
The Coefficient Of Friction ◽  
The Impact ◽  
Crank Mechanism

This work describes the influence of the clearance size and the coefficient of friction on the dynamic response of a revolute clearance joint in multibody mechanical systems. When there is a clearance in a revolute joint, impacts between the journal and the bearing can occur, and consequently, local deformations take place. The impact is internal and the response of the system is performed using a continuous contact force model. The friction effect due to the contact between joint elements is also modeled. The clearance size and friction effects are analyzed separately. Through the use of Poincare´ maps both periodic and chaotic responses of the system are observed. The results predict the existence of the periodic or regular motion at certain clearance sizes and friction coefficients and chaotic or nonlinear in other cases. A detailed discussion of the results relative to a planar slider-crank mechanism with a revolute clearance joint is presented.

Joint Clearances With Lubricated Long Bearings in Multibody Mechanical Systems

1999 ◽  
Vol 122 (4) ◽  
pp. 484-488 ◽  
Author(s):  
P. Ravn ◽  
S. Shivaswamy ◽  
B. J. Alshaer ◽  
Hamid M. Lankarani
Keyword(s):  
Mechanical Systems ◽  
Steady Motion ◽  
Joint Clearance ◽  
Hydrodynamic Theory ◽  
Viscous Effects ◽  
Analysis And Design ◽  
Joint Clearances ◽  
The Impact ◽  
Crank Mechanism ◽  
Hydrodynamic Theory Of Lubrication

Proper modeling of joint clearance is of great importance in the analysis and design of multibody mechanical systems. The clearance may be due to wear or imperfection in manufacturing. When there is no lubricant in the clearance, solid-to-solid contact occurs. The impulse due to contact between the links is transmitted throughout the system. The presence of a lubricant avoids such contact, as the hydrodynamic forces developed by the lubricant film support the loads acting on the bodies and prevent the bodies from coming into contact. In this paper, an analysis of revolute joint clearances in multibody mechanical systems with and without lubricant is presented. Squeeze as well as viscous effects are considered utilizing the hydrodynamic theory of lubrication in long bearings. Unlike the traditional machine design approach, the instantaneous lubricant forces are the unknown and evaluated in terms of the known geometrical position and velocity of the journal and bearing. In the case of analysis of a joint clearance with no lubricant, a modified Hertzian relation is used to model the impact or contact between the journal and bearing, which includes a hysteresis damping term to account for the energy dissipation during impact. The methodology is applied for the analysis of a slider-crank mechanism having a clearance in the piston pin. The simulations are carried out with and without lubricant and the results are compared. It is shown that the lubricant results in a steady motion with fewer peaks in the required cranking moment for the system. [S1050-0472(00)01804-3]

Closed Refrigerated Display Cabinets

2019 ◽  
pp. 1-23
Author(s):  
Onrawee Laguerre ◽  
Nattawut Chaomuang
Keyword(s):  
Literature Review ◽  
Potential Energy ◽  
Product Quality ◽  
Energy Saving ◽  
Temperature Profile ◽  
Food Quality ◽  
Field Studies ◽  
Air Infiltration ◽  
Potential Energy Saving ◽  
Determining Factor

The use of closed refrigerated display cabinets in supermarkets is in progression because of the potential energy saving compared to the open ones with an air infiltration at the front. However, the influence of the presence of doors on product temperatures (determining factor of product quality) is much less studied. For better understanding the interest of the use of closed display cabinets, this chapter presents the state of the art of field studies, the airflow and temperature profile in the closed display cabinet, the influence of the presence of doors/the frequency of door openings and the room temperature. Finally, a literature review of studies on food quality in the closed display cabinet is presented.

scholarly journals Multiple pilomatrixomas: Case report and literature review

2008 ◽  
Vol 87 (4) ◽  
pp. 230-233 ◽  
Author(s):  
Shashidhar Sadda Reddy ◽  
Swarupa A. Gadre ◽  
Patrick Adegboyega ◽  
Arun K. Gadre
Keyword(s):  
Differential Diagnosis ◽  
Case Report ◽  
Literature Review ◽  
Lymph Nodes ◽  
Black Woman ◽  
Clinical Examination ◽  
Surgical Excision ◽  
Hair Matrix ◽  
The Masses ◽  
Epithelial Neoplasm

Pilomatrixoma is a rare, benign, circumscribed, calcifying epithelial neoplasm that is derived from hair matrix cells. Multiple pilomatrixomas are uncommon. We describe a case of multiple pilomatrixomas in a 23-year-old black woman who presented with lesions on her face and back. Based on the results of the clinical examination, she was provisionally diagnosed with either calcified sebaceous cysts or calcified lymph nodes. She underwent surgical excision of the masses. On histopathology, the lesions were identified as pilomatrixomas. We attribute our original failure to diagnose this condition to our lack of familiarity with it. We discuss the presentation, differential diagnosis, and other characteristics of pilomatrixomas.

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