To establish an exercise in open muscular chain rehabilitation (OMC), it is necessary to choose the type of kinematic chain of the mechanical / biomechanical system that constitutes the lower limbs in interaction with the robotic device. Indeed, it’s accepted in biomechanics that a rehabilitation exercise in OMC of the lower limb is performed with a fixed hip and a free foot. Based on these findings, a kinematic structure of a new machine, named Reeduc-Knee, is proposed, and a mechanical design is carried out. The contribution of this work is not limited to the mechanical design of the Reeduc-Knee system. Indeed, to define the minimum parameterizing defining the configuration of the device relative to an absolute reference, a geometric and kinematic study is presented.
This work is about the validation of a Common Rail (CR) injector model. The model describes injector internal behavior in a detailed way, validation is done using dosage measurements and needle lift traces.
The model contains fluid dynamic, mechanic and electro-magnetic parts describing all important internal processes. To compare the modelling results against measurement data, three test cases were chosen on a medium duty test engine to represent a wide range of operation points. Dosage measurements were done by averaging the injected mass of 1500 injections, each measurement repeated three times. Needle displacement was measured using an injector equipped with a needle lift sensor in the same operating points. The results of the simulated injector and the measured values showed good conformity both in needle displacement and injected fuel mass, so the model can be a basis for further injector and combustion analyses.
Electrostatic actuators have major role in many MEMS devices, e.g. sensors, actuators. The amount of applied voltage to an electrostatic micro-actuator has a direct impact on the amplitude of deflection throughout the cantilever. This research aims to study the effect of the electrode length and the applied voltage on the amplitude of deflection of the micro-cantilever. Also, the resonant frequency for the cantilever was computed for full length and compared with simulation results. Finite element method, ANSYS was used as a simulation tool.
Ayoub Ayadi, Kamel Meftah, Lakhdar Sedira and Hossam Djahara
In this paper, the earlier formulation of the eight-node hexahedral SFR8 element is extended in order to analyze material nonlinearities. This element stems from the so-called Space Fiber Rotation (SFR) concept which considers virtual rotations of a nodal fiber within the element that enhances the displacement vector approximation. The resulting mathematical model of the proposed SFR8 element and the classical associative plasticity model are implemented into a Fortran calculation code to account for small strain elastoplastic problems. The performance of this element is assessed by means of a set of nonlinear benchmark problems in which the development of the plastic zone has been investigated. The accuracy of the obtained results is principally evaluated with some reference solutions.
The paper presents a four-node tetrahedral solid finite element SFR4 with rotational degrees of freedom (DOFs) based on the Space Fiber Rotation (SFR) concept for modeling three-dimensional solid structures. This SFR concept is based on the idea that a 3D virtual fiber, after a spatial rotation, introduces an enhancement of the strain field tensor approximation. Full numerical integration is used to evaluate the element stiffness matrix. To demonstrate the efficiency and accuracy of the developed four-node tetrahedron solid element and to compare its performance with the classical four-node tetrahedral element, extensive numerical studies are presented.
Abdelkrim Merah, Ridha Kelaiaia and Faiza Mokhtari
The Taylor-Couette flow between two rotating coaxial cylinders remains an ideal tool for understanding the mechanism of the transition from laminar to turbulent regime in rotating flow for the scientific community. We present for different Taylor numbers a set of three-dimensional numerical investigations of the stability and transition from Couette flow to Taylor vortex regime of a viscous incompressible fluid (liquid sodium) between two concentric cylinders with the inner one rotating and the outer one at rest. We seek the onset of the first instability and we compare the obtained results for different velocity rates. We calculate the corresponding Taylor number in order to show its effect on flow patterns and pressure field.
Salah Guerbaai, Mouna Touiker, Kamel Meftah and Abdeslam Omara
A numerical study is performed to analyze steady state forced convection fluid flow through a confined porous square cylinder. The Darcy-Brinkman-Forchheimer model is adopted for the porous region. The finite volume method and the iterative SIMPLE algorithm are used to solve the governing equations. The results obtained are presented for the streamlines, variation of Nusselt number and drag coefficient for the range of conditions as 5 ≤ Re ≤ 40 and 10−2 ≤ Da ≤ 10−6.
El Hadi Boussaha, Samia Aouici, Hamdi Aouici and Abida Bahloul
A continuous CO2 laser (10.6 µm wavelength) was adopted to investigate the influence of powder particle sizes on microstructural and morphological characteristics of laser claddings.
To study the potential of powder in controlling the incident laser energy, different average particle sizes of Ni-base powder were deposited on an austenitic stainless steel X3CrNi18-10 substrate. The energy value necessary to melt a mass m of powder was calculated. The results indicate that this energy decreases with particle sizes.
The claddings obtained with small particle sizes revealed a good morphological aspect and a low dilution of the cladding layer in the substrate, yet enough to create a very good metallurgical bond. The residual stress state was also influenced. Concerning modeling, we have elaborated residual stress model in the case of laser cladding by exploiting the response surface methodology (RSM), using a quadratic regression model. Combined effects of three laser cladding parameters on the residual stress is explored by a statistical analysis of variance (ANOVA). Results show that the residual stress is influenced principally by the power delivered by laser beam and by the scanning speed. It is also indicated that the size of powder particle is the dominant factor affecting the residual stress.
The classification and detection of defects play an important role in different disciplines. Research is oriented towards the development of approaches for the early detection and classification of defects in electrical drive systems. This paper, proposes a new approach for the classification of induction motor defects based on image processing and pattern recognition. The proposed defect classification approach was carried out in four distinct stages. In the first step, the stator currents were represented in the 3D space and projected onto the 2D space. In the second step, the projections obtained were transformed into images. In the third step, extraction of features whereas the Histogram of Oriented Gradient (HOG) is used to construct a descriptor based on several sizes of cells. In the fourth step, a method of classifying the induction motor defects based on the Support Vector Machine (SVM) was applied. The evaluation results of the developed approach show the efficiency and the precision of classification of the proposed approach.
This paper presents a numerical algorithm for determining the minimum dwell time constraint for switched linear ℋ∞ fault detection filters. When applying switched systems, ensuring the stability is a crucial target, which can be guaranteed, when we switch slowly enough between the subsystems, more precisely when the intervals between two consecutive switching instants, called dwell time, are large enough. The problem formulation is based on multiple Lyapunov functions and is expressed through a special form of linear matrix inequalities (LMIs), which include a nonlinear term of the dwell time. This represents a multivariable, time dependent optimization problem. As a result, the task cannot be treated as a simple feasibility problem involving a LMI solver as it is widely used in applications of the linear control. To solve these special LMIs, we propose a numerical algorithm, called 𝒯d-iteration, which combines the procedure of interval halving with an LMI solver. The algorithm implemented in MATLAB shows its applicability as well as suggest further benefits for the switched linear control and filter synthesis.