2020-12-05T09:25:07Z
http://scientiairanica.sharif.edu/?_action=export&rf=summon&issue=271
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
5
Determining Maximum Load Carrying Capacity of Flexible Link Manipulators
M. H.
Korayem
R.
Haghighi
A.
Nikoobin
A.
Alamdari
A.H.
Korayem
Abstract. In this paper, an algorithm is proposed to improve the Maximum Load Carrying Capacity
(MLCC) of
exible robot manipulators. The maximum allowable load which can be achieved by a
exible
manipulator along a given trajectory is limited by the joints' actuator capacity and the end eector
accuracy constraint. In an open-loop approach, the end eector deviation from the predened path is
signicant and the accuracy constraint restrains the maximum payload before actuators go into saturation
mode. By using a controller, the accuracy of tracking will improve. The actuator constraint is not a major
concern and, therefore, the full power of the actuators, which leads to an increase in the Maximum Load
Carrying Capacity, can be used. In this case, the controller can play an important role in improving the
maximum payload, so a robust controller is designed. However, the control strategy requires measurement
of the elastic variables' velocity, which is not conveniently measurable. So, a nonlinear observer is designed
to estimate these variables. A stability analysis of the proposed controller and state observer is performed
on the basis of the Lyapunov Direct Method. In order to verify the eectiveness of the presented method,
simulation is done for a two link
exible manipulator. The obtained maximum payload for open and
closed-loop cases is compared, and the superiority of the method is illustrated.
Maximum Load
Boundary layer sliding mode
Nonlinear state observer
2009
10
01
http://scientiairanica.sharif.edu/article_3237_1d274849f6d5b328fca15dc91ed0b933.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
5
Eective Hamiltonian and Eective Penguin Model on b Quark Decays
H.
Mehrban
Abstract. In this research, we investigated b quark decays by two dierent approaches; rstly,
according to the structure of penguin decays, and secondly, based on an eective Hamiltonian theory.
Working with the standard model, the QCD penguin terms for various b and b decays are calculated. We
also studied decay rates of the matter-antimatter of b quark decays. The gluonic penguin of b decays,
b ! qkg ! qkqiqj , is studied through the Wilson coecients of the eective Hamiltonian. We obtained
the decay rates of the tree and penguin and magnetic dipole terms all together to compare them with
the eective Hamiltonian current-current and penguin operators. We described the eective Hamiltonian
theory and applied it to the calculation of current-current (Q1;2), QCD penguin (Q3; ;6) and magnetic
dipole (Q8) decay rates. Based on the eective penguin model, the simple coecients, d1; ; d6;8, are
dened according to the gluon penguin structure and used in the eective Hamiltonian theory. In the
other section of this research, the decay rates of processes like b ! cdc(b ! cdc), b ! csc(b ! csc),
b ! udu(b ! udu) and b ! usu(b ! usu) are obtained based on the Eective Hamiltonian (EH) and
Eective Penguin Model (EPM). Decay rates and branching ratios are very similar in all models, but in
the Eective Hamiltonian Magnetic Dipole, the total decay rate is about 10% larger than the simple tree or
Eective Hamiltonian. On the other hand, including the penguin induces matter-antimatter asymmetries.
These are largest in the rate decays b ! udu, the decay rate of which is about 7% smaller than the decay
rate b ! udu. Also, rate b ! suu is larger than rate b ! suu.
b quark
QCO Penguin
Eective Penguin model
Magnetic dipole
2009
10
01
http://scientiairanica.sharif.edu/article_3238_f3f961adf61821a847c98659ba736461.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
5
A New Method in Two Phase Flow Modeling of a Non-Uniform Grid
M.H.
Saidi
A.
Bohluly
Abstract. In this paper, a two dimensional numerical model for two phase
ow is presented. For
interface tracking, the FGVT-VOF (Fine Grid Volume Tracking-Volume Of Fluid) method is selected.
For momentum advection, an improved approach is used. In this scheme, a volume tracking step is coupled
with steps of computations for the advection of momentum. A Reynolds stress algebraic equation has been
implemented in the algorithm of turbulent modeling. Standard test cases are used for the verication of
interface tracking and hydrodynamic modeling in laminar and turbulent conditions. The test results show
that this methodology can be used in dierent applications of two-phase
ow modeling.
Two phase ow
Non-uniform grid
Volume tracking
Volume of uid
2009
10
01
http://scientiairanica.sharif.edu/article_3239_315c70be1cb293a0c931e350c4a7be4e.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
5
Estimation of Human Lower Extremity Musculoskeletal Conditions During Backpack Load Carrying
A.
Selk Ghafari
Gh. R.
Vossughi
A.
Meghdari
Abstract. This paper focuses on the biomechanical aspects of the human lower extremity loading
condition during backpack load carrying. A biomechanical framework was generated with the aim of
employing a block-oriented structure of Simulink integrated with the Virtual Reality Toolbox of MATLAB
software to provide a simulation study of the musculoskeletal system in a virtual environment. In this case,
a ten-degrees-of-freedom musculoskeletal model actuated with sixteen muscles in each leg was utilized to
simulate movement in the sagittal plane. An inverse dynamics based optimization approach was employed
to estimate the excitation level of the muscles. In addition, distributions of the mechanical power analysis
for lower extremity muscles were carried out to enhance the understanding of human leg morphology
and control mechanism to provide load support. Simulation results provide a biomechanical framework to
identify the muscles and joints, which are critically subjected to musculoskeletal injuries during the activity
under investigation. Analysis of the muscle activation patterns and their distribution of the mechanical
powers revealed the important role of the plantar
exors of the ankle and the extensors of the knee and
hip joints in supporting the body during backpack load carrying.
Lower extremity
Musculoskeletal
Backpack
Load carrying
Muscle activation
2009
10
01
http://scientiairanica.sharif.edu/article_3240_e4e405d25e2591964a90aee94b8bb874.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
5
A Harmonic Balance Approach for the Analysis of Flexible Rotor Bearing Systems on Non-Linear Support
M.A.
Rezvani
Abstract. The purpose of this article is to describe the theoretical background to the Harmonic
Balance approach; adopted and further developed for the analysis of general multi degree of freedom
rotor bearing systems with nonlinear supports. System equations of motion are prepared for dynamic
systems with any number of degrees of freedom. Nonlinear behaviour can be associated with any number
of these freedoms. A computer program which uses the harmonic balance method to solve the system
equations of motion is also written. These equations are partitioned into linear and nonlinear parts. The
nonlinear sets of equations need to be solved prior to solving the linear sets of equations. Verication of
the proposed method of solution is justied through two examples. The frequency response of a well known
rotor bearing, the so called Jefcott rotor, is examined and tested against data reported by some other
researchers. Also, the versatility of this method is tested by comparing the harmonic balance approach
with the transient solution and some experimental measurements involving the nonlinear squeeze lm
bearing supports, which have already been reported by this author. It is shown that by utilizing harmonic
balance with appropriate condensation, it is possible to considerably reduce the number of simultaneous
nonlinear equations inherent to such systems. The stability (linear) of the equilibrium solutions may be
conveniently evaluated using the Floquet theory.
Non-linear dynamics
Flexible rotor bearing systems
Squeeze lm bearings
Harmonic balance approach
Floquet theory
2009
10
01
http://scientiairanica.sharif.edu/article_3241_7699fe477afc35f6d3d56c873b101c9f.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
5
Dynamic Model of a Mobile Robot with Long Spatially Flexible Links
S. M.
Khorsandijou
H.
Zohoor
Abstract. Using some agent variables, the general structure of the dynamic model of a spatial mobile
robot with N long spatially
exible links and N revolute joints has been exposed. It is composed of a
set of 5N + 6 nonlinear coupled partial dierential motion equations under the in
uence of the boundary
conditions. Non-conservative forces/moments have been neglected. While being considered, the general
structure of the dynamic model will not change, but a few exciting/damping terms will arise within
the agent variables. The base of the robot is an unconstrained rigid body in space and the links as
3D Euler-Bernoulli beams undergo tension-compression, torsion and two spatial bendings while elastic
orientation is considerable and the nonlinear part of the geometric Green-Lagrange strain is ignored.
When the elastic orientation is neglected, the dynamic model of each link remains more accurate than
that of a nonlinear 3D Euler-Bernoulli beam within which the elastic orientation is actually negligible.
The obtained dynamic model is capable of creating the nonlinear 3D long Euler-Bernoulli beam and the
fully-enhanced/enhanced/generalized nonlinear 3D Euler-Bernoulli beam theories, considering a
ying or
a xed support.
Spatially exible link
Highly exible link
Mobile robot
Flying manipulator
2009
10
01
http://scientiairanica.sharif.edu/article_3242_2c06dddb327de578add90a5edfbdab59.pdf