bluuebunny/crossref_metadata_2025 huggingface dataset:
Visualization of Urban Prediction Using Augmented Maps
Authors: Martedi Sandy , Callier Sébastien , Saito Hideo , Sanoamuang Pega , Muminović Milica
Published: December 2013

In this paper, we explore a visualization method using augmented maps for urban prediction. Our implementation allows users to determine the location for prediction in a paper map. As an application example, we examine an area before and after new train station is built. We use the difference between two maps for simulating the changes or predicting the impact if a new train station is built on a location in a paper map. In off-line phase, we gather knowledge data from several reference locations by comparing two aerial maps (before and after the train station is built). We then analyze the difference of green spaces between those two maps using color extraction. We observe that the green space around the new train station mostly decreases due to the area development. This information is then stored for prediction reference. In on-line phase, we use a monocular setup that consists of one camera and a monitor display. A paper map is captured using a web camera and tracked using its geometrical features. These features can be provided using the available data from Geographical Information Systems (GIS) or automatically extracted from the texture. The map is then matched with the reference map in database. When the map is matched, we can overlay the simulation on how the green space will change due to the existence of new train stations on a new location inputted by the user.
Validation of Turbulent Natural Convection in a Square Cavity for Application of CFD Modeling to Heat Transfer and Fluid Flow in a Data Center
Authors: Durand-Estebe B. , Lebot C. , Arquis E. , Mancos Jn.
Published: December 2013

Air flow management in a Data-center is a critical problem when designing HVAC (Heating, Ventilation and Air-Conditioning) system. Providing a sufficient cooling air volume at a designed temperature to all the informatics equipments, avoiding recirculation phenomenon, optimizing the installations in order to minimize the temperature difference between air exiting the CRAC (Computer Room Air Conditioning) and the air at the intake of the servers are parts of the multiples target that have to be reached in order to have the most efficient ventilation system.

In most of today’s data center, the IT (Information Technology) equipment dissipates between 12kW of heat for regular material, to up to 32kW for the recent high density server’s rack. Such a power release has to be cooled by efficient cooling system.

During this process the airflow temperature can increase by over 10K, and the air velocity can vary from 0.09m/s to more than 5m/s. Considering these large gradient of temperature and air speed several phenomenon must be taken into account, including turbulent natural convection.

To achieve these goals, we will use a CFD software to predict the airflow behaviour inside the Data-center. Therefore, the code must be able to accurately model turbulent airflow and heat transfers. We used the software (http/www.thetis.enscbp.fr) to simulate a 2D turbulent natural convection in a square cavity. The k-ε equations were solved to predict turbulent effects. The obtained results were compared to an experimental benchmark and are presented in the document.

In the last part of the paper we present the results of a 2D simulation representing a working server in a computer room cooled by a CRAC (Computer Room Air Conditioning) unit.

The airflow characteristics in the whole domain were determined using various dimensionless numbers in order to select the right physical and mathematical objects. Finally the results of a 3D simulation are presented and the cooling system performances are estimated.
Non-Dimensional Finite Element Formulation for Thermal Problems
Authors: Pashah Sulaman , Arif Abul Fazal M. , Zubair Syed M.
Published: December 2013

The use of dimensional analysis and dimensionless parameters is very common in the field of heat transfer; nevertheless the concept of non-dimensional finite element formulation has been applied to a limited type of thermo-fluid problems. The non-dimensional finite element method should provide the dimensionless solution for a given problem. The aim of present work is to develop a non-dimensional thermal finite element for getting dimensionless solution of the problems that do not have a closed form solution. An example is a fin (or extended surface) design. Fin efficiency is a performance characteristic that can be used as design criterion; thus closed form dimensionless solutions for fin efficiency are available in the literature. The results are for different geometry, single material fins. In case, if the fin problem has some geometric and/or material complexities then closed form solutions are not available and finite element approach can be used. However, the obtained finite element solution would not be in dimensionless form. For example, no closed form solutions are available for variable thickness composite fins (i.e. a fin having a base material with a coating over its surface), and the literature shows that finite element solution has been used to study thermal performance of the variable thickness composite fins. Therefore, non-dimensional finite element approach can be applied to directly obtain the dimensionless solution for the problem. The current work consists of presenting a non-dimensional finite element formulation for thermal problems. The element formulation is first validated by solving a test case study that has known closed form solution. The objective is to demonstrate the usefulness of the non-dimensional finite element approach by obtaining dimensionless finite element solutions for some applied problems that do not have a closed form solution.
Fluid-Dynamic Analysis of Earthquake Shaking Table Hydraulic Circuit
Authors: Cardone Massimo , Strano Salvatore
Published: December 2013

This paper presents a fluid-dynamic analysis of the hydraulic circuit of a shaking table for seismic tests; the model was developed adopting a commercial code. The aim of the study is to provide useful indications for the design of a new optimized control system. The model was developed taking into account all the components of the hydraulic circuit that is made of by the following main items: the axial piston pump, the pressure relief valve, the main control valve, the accumulators, the hydraulic cylinder with variable displacement and all the connecting pipes. Particular attention was given to the modelling of internal resistance of the hydraulic system, that can greatly affect the performance of the shaking table. It has also been accurately modelled the main valve dead zone to highlight its influence on the system dynamics. The results of numerical simulations obtained for different operational conditions are reported and compared with experimental data to show the validation and the performances of the developed model.
Dynamic Response of Piezoelectric Material Strips at High Frequencies
Authors: Ikenna-Agbeze N. , Oyadiji S. O. , Siores E. , Shah T.
Published: December 2013

This investigation is focused on the dynamic response of some commercially available piezoelectric materials which will be incorporated into textile materials for vibration control with a view of sports brassiere. Ceramic-based piezoelectric fiber composites (PFC), piezoelectric fiber composite bimorph (PFCB) and polymer-based polyvinylidene fluoride (PVDF) of various thicknesses have been chosen for this investigation. In a typical experiment, one end of each of the piezoelectric strips is fixed to the vibration table of an electrodynamic exciter while the other end is terminated at the cross-beam of a very stiff frame. The strip is placed under tension and made to undergo base excitation using pseudo-random signal from (0–2000) Hz using the electrodynamic shaker. The force output response is obtained using force transducers. The characterization of these piezoelectric materials will determine their behavior when embedded in the textile material for sports brassiere application.
EHD-Induced Flow in a Square Channel With Two-Stage Electrodes
Authors: Mazumder A. K. M. Monayem H. , Lai F. C. , Chou Y.-T.
Published: December 2013

In this study flow field inside a square channel with a two-stage electrohydrodynamic (EHD) gas pump has been critically examined by experimental measurement and numerical simulation. The EHD gas pump with 28 emitting electrodes in each stage is tested for a wide range of operating voltages starting from the corona threshold voltage up to 28 kV for further improvement in its performance over that of a single-stage. It has been shown that the two-stage EHD gas pump can produce and sustain gas flows with a maximum velocity of 5 m/s. Its maximum performance of 34 L/s/W is better than that of conventional cooling fans used in personal computers. The implication for its application in thermal management and heat transfer enhancement has also been discussed.
Combined Flow Fields (Serpentine-Interdigitated) for Improvement of a PEMFC Performance
Authors: Perez-Raya I. , Hernandez-Guerrero A. , Elizalde-Blancas F. , Ramos-Alvarado B. , Lorenzini-Gutierrez D.
Published: December 2013

This paper presents the results of an analysis that proposes a combined path for the gases distribution in a PEMFC. The combination takes into account two of the most common flow fields currently in use: serpentine and interdigitated. The objective of the study is to determine the optimal conditions related with the way of distributing the hydrogen with the aim to increase the fuel cell performance. Therefore the paper centers in modifying the geometry of the anode while keeping a conventional serpentine geometry for the geometry. The analysis shows the current density distribution, the pressure drop, and the power generated by a PEM operating under the proposed gas flow field. In order to compare the results, a conventional commercial geometry was also analyzed and then both geometries were compared via polarization and power curves. The model adopted for the analysis takes into account the effects of the electrochemical reactions that occur in the fuel cell, in this case, the electrons and protons movement, the species consumption, the water vapour production in the catalysts and the water transport through the membrane (electro-osmotic effect). The results show that the proposed geometry leads to an excellent species distribution allowing a more uniform current distribution and a good power generation.
Stability Analysis of 2D Flows by Numerical Tools Based on the Asymptotic Numerical Method: Application to the One and Two Sides Lid Driven Cavity
Authors: Cadou Jean-Marc , Guevel Yann , Girault Gregory
Published: December 2013

This work deals with the complete stability analysis in the case of two dimensional fluid flows searching for steady and Hopf bifurcations.

The stability analysis starts with the computation of steady bifurcations. It is realized by first considering the monitoring of an indicator which is a scalar function. The indicator is computed via a perturbation method: the Asymptotic Numerical Method. Steady bifurcation point corresponds to the zero of this indicator. From this singular point, all the steady bifurcated branches are computed by using the perturbation method.

Then the stability analysis is pursued with the computation of Hopf bifurcations by a hybrid method. This latter consists in coupling a continuation method with a direct Newton solver.

The continuation method allows the bifurcation indicator to be determined using alternating reduced order and full size steps resolution. The quantities coming from the bifurcation indicator are used as initial approximations for the direct method iterations.

Then an augmented system whose solutions are Hopf bifurcation is solved by a direct method of Newton kind.

The examples of the one side and two sides lid driven cavities show the reliability and the efficiency of the proposed numerical tools.
Robust Analysis of a Wireless Bistable Micro-Actuator
Authors: Zaidi Syed Sajid Hussain , Cherfi-Boulanger Zohra , Boudaoud Nassim , Pouille Philippe , Lamarque Frédéric
Published: December 2013

Nowadays, the integration of micro-actuators in the micro-systems poses a significant problem due to the complex designs as well as due to the contact power supply systems (e.g., via micro-batteries or via wires). A way to overcome this problem is to provide remote power supply and control to the bistable micro-actuators. It is mainly done by RF (radio-frequency) or optical means. As a consequence, the stability of the two positions of this kind of micro-actuators and the switching time evolution between them have to be studied to determine the robustness of the contactless bistable micro-actuators.

In this work, these system parameters were analysed by the ANOVA (Analysis Of Variance) method during a longlife test for 8 different configurations (Design of Experiments) of bistable micro-actuators controlled by laser. Transient and permanent regimes were observed for the stability of the positions, for the standard deviation around the positions and for the switching time as well. In each case, the transient regime represented only 3% of the total duration of the longlife test. A very good stabilisation was observed in the permanent regime whereas a decrease of the stroke was observed in the transient regime. As a consequence, during this regime, the switching time was reduced compared with the regular values (few seconds, optical power dependent). In the permanent regime, a progressive increase of this factor was noted that indicated the progressive fatigue of the bistable micro-actuator. A second indicator of the micro-actuator fatigue was given by the increase of the standard deviation of the stable position after cycle number 9000. Above this point, the micro-actuator was vibrating during the functioning even if the stability remained acceptable.
Adapting Ant-Colony Optimization to Design Problems in Mechatronics
Authors: Smaili Ahmad , Diab Nadim , Abdallah Samer
Published: December 2013

This paper adapts an Ant Colony intelligent Optimization algorithm (ACO) to four design problems important in Mechatronics applications: (1) Stress- and volume minimization of a helical compression spring subject to a set of geometrical and stress constraints for material volume minimization, (2) tuning the gains of a PID-controller for a second-order plant with a transport lag, (3) design of a planetary gear leg of a walking machine for a desired straight line trajectory and driving actuator torque, and (4) synthesis of four-bar mechanisms. A brief overview of the ACO algorithm is first presented and its adaptation to each design problem is explained and demonstrated by way of examples that have been solved by other optimization techniques for comparison. In all four examples, the ACO algorithm produced better results in terms of cost-function values while satisfying all necessary constraints.
Numerical Study of Fluid-Structure Interactions in Tube Bundles With Multiphase-POD Reduced-Order Approach
Authors: Pomadere Marie , Liberge Erwan , Hamdouni Aziz , Longatte Elisabeth , Sigrist Jean-François
Published: December 2013

Fluid-Structure Interactions are present in a large number of systems of nuclear power plants and nuclear on-board stoke-holds. Particularly in steam generators, where tube bundles are submitted to cross-flow which can lead to structure vibrations. We know that numerical studies of such a complex mechanism is very costly, that is why we propose the use of reduced-order methods in order to reduce calculation times and to make easier parametric studies for such problems.

We use the multiphase-POD approach, initially proposed by Liberge (E. Liberge; POD-Galerkin Reduction Models for Fluid-Structure Interaction Problems, PhD Thesis, Universite de La Rochelle, 2008). This method is an adaptation of the classical POD approach to the case of a moving structure in a flow, considering the whole system (fluid and structure) as a multiphase domain. We are interested in the case of large displacements of a structure moving in a fluid, in order to observe the ability of the multiphase-POD technique to give a satisfying solution reconstruction. We obtain very interesting results for the case of a single circular cylinder in cross-flow (lock-in phenomenon). Then we present the application of the method to a case of confined cylinders in large displacements too. Here again, results are encouraging.

Finally, we propose to go further presenting a first step in parametric studies with POD-Galerkin approach. We only consider a flowing-fluid around a fixed structure and the Burgers’ equation. A future work will consist in applications to fluid-structure interactions.
Vibration Suppression in Carbon Fiber Structures With Piezoelectric Actuators and Fiber Bragg Grating Sensors
Authors: Cazzulani Gabriele , Cinquemani Simone , Comolli Lorenzo , Gardella Andrea
Published: December 2013

Carbon fiber structures have become widespread in civil and mechanical field since they are claimed to offer several advantages such as contained mass and high stiffness. However, these structures are characterized by a very low mechanical damping and, therefore, they are easily subjected to potentially dangerous vibratory phenomenon. Active control techniques have been widely developed to suppress vibration and great progresses have been achieved. On the other hand the research on sensors and actuators to be used is still a research field of interest. The paper discusses the opportunity to use piezoelectric actuators (PZT) and Fiber Bragg Grating sensors (FBGs) to realize a smart structure including in itself both the sensing and the actuating devices. Such a structure is able to measure its state of excitation and to reduce the amplitude of vibration using the embedded actuators.
Effects of Actuators and Sensors Position on Independent Modal Control Performance
Authors: Cinquemani Simone , Resta Ferruccio
Published: December 2013

Independent modal control technique allows to change the eigenvalues of a system, without changing its eigenvectors. From a mechanical point of view, it means it is possible to modify the natural frequencies and the damping of a n-DoF system, letting modal shapes unchanged. Independent modal control can be profitably used in active vibration control increasing the damping of the system without changing its natural frequencies and vibration modes. A control of this type can improve the dynamic performance, reduce the vibratory phenomenon (and the resulting acoustic noise) and increase the fatigue strength of the system. This work demonstrates how the performance of the control depends on the number and position of sensors and actuators used besides, obviously, on the reduced model used to synthesize the control itself. Finally the paper suggests a simple optimum function to minimize the spillover effects due to unmodeled modes. Theoretical aspects are supported by numerical simulations.
Fuzzy Hybrid Control of Off-Road Vehicle Suspension Fitted With Magnetorheological Dampers
Authors: Ata W. G. , Oyadiji S. O.
Published: December 2013

The vibration caused by severe road excitation influences off-road vehicle suspension performance. The vibration control of the suspension system is a crucial factor for modern vehicles. Smart control devices (magnetorheological dampers) are proposed as a first step to handle a multiple suspension system of off-road vehicles. The magnetorheological (MR) dampers can be employed as smart dampers for vibration suppression of the suspension system; this is done by varying the produced damping force. In this paper an investigation is presented on the effectiveness of such smart dampers in attenuating the vibration of a multiple suspension system. This goal is accomplished by designing a new fuzzy hybrid controller and studying its effectiveness on the suspension performance. The multiple suspension system considered here comprises a chassis, five wheels and three MR dampers. The chassis is suspended over the five wheels through five compression springs. Three MR dampers are attached to the first, second and the fifth wheel. The stiffness of the wheels is represented by five compression springs. Only the bounce and the pitch of the chassis are considered. The assessment of the proposed model is carried out through a simulation scheme under bump and sinusoidal excitations in the time domain. The excitation of the five wheels is done independently. The simulation is accomplished using the MATLAB/SIMULINK software. The simulation results show the effectiveness and robustness of the new controller in conjunction with MR dampers in vibration suppression. Compared to the passive suspension, the body bounce, body displacement, angular acceleration and pitch angle can be well controlled.
Thermal Properties of Sintered Diamond Composites Used in Grinding
Authors: Moussa Tala , Garnier Bertrand , Peerhossaini Hassan
Published: December 2013

Sintered diamonds are used in grinding because they offer better mechanical properties than conventional materials (mineral or silicon carbide abrasives) and yield high grinding speed and long life. In addition, because of their thermal performance, they contribute to cooling the workpiece, avoiding excessive temperatures. Thus in order to choose the best material for the worktool, one often must know the thermal conductivity of sintered diamond. In this work, the thermal conductivity of sintered diamond is evaluated as a function of the volume fraction of diamond in the composite and for two types of metallic binders: hard and soft. The measurement technique is based on the flash method that associates heating and measurement devices without sample contact and on parameter estimation using a three-layer thermal model. With a hard metallic binder, the thermal conductivity of sintered diamond was found to increase up to 64% for diamond volume fraction increasing from 0 to 25%. The increase is much smaller for the soft binder: 35% for diamond volume reaching 25%. In addition, experimental data were found far below the value predicted by conventional analytical models for effective thermal conductivity. A possible explanation is that the thermal conductivity of such composites is affected by poor heat transfer at the diamond/binder interface, the thermal contact resistance between matrix and diamond particles being estimated at between 0.75 and 1.25 10−6 m2K.W−1.
Parametric Shape and Material Simulations for Optimized Parts Design
Authors: Bognet B. , Leygue A. , Chinesta F. , Bordeu F.
Published: December 2013

In this paper we consider a parametric model related to the elasticity problem in which many parameter describing he material and/or the geometry will considered as extra-coordinates, allowing for the construction, from a single solution, of an abaqus containing the solution for each choice of the parameters considered as extra-coordinates. In order to circumvent the curse of dimensionality related to the high number of dimensions considered in the model, a separated representation will be considered.
Experimental Study of Heat Transfer in Pulsation Flow in a Rectangular Duct
Authors: Shokouhmand H. , Safarifard M. , Emami S. M.
Published: December 2013

An experimental study was performed to investigate the heat transfer characteristics of the pulsation flow through a rectangular air duct with aspect ratio of 10. The test section was designed to have a constant heat flux. For pulsating flows, the surface temperatures, the temperature of air at the inlet and at the outlet of the test section, maximum velocity and minimum velocity of air in the test section and the frequencies of pulsation flow were measured and averaged local Nusselt numbers and averaged Nusselt numbers were calculated. The effect of pulsation amplitudes and pulsation frequencies on heat transfer were analyzed.
Toward an Affective Design of Products
Authors: Lu Weihua , Petiot Jean-François
Published: December 2013

The measurement and understanding of user emotions elicited by product appearance are critical elements of the product development process and have been interesting design challenges for many years. This paper proposes an original emotion measurement method, called Auditory Parameter Method. It is a non-verbal technique, which uses sounds and association tests for evaluating a set of products (given by their pictures). It provides an assessment of these products according to a series of emotional dimensions. We present a methodological framework to build the links between user’s emotional responses and geometrical features of product, by using a glasses frame 3D model as application case. Analysis of Variance techniques are employed to examine how various shape factors influence users’ emotional responses to 3D model. To demonstrate the effectiveness of our protocol, we compare the proposed method with the conventional Semantic Differential using Principal Component Analysis and Generalized Procrustes Analysis. The new protocol demonstrates interesting qualities to collect the intuitive emotions of user.
Mixed Experimental and Numerical Study of Steel Ferrule Forming by Low-Contact Deformation Process
Authors: Raujol-Veillé J. , Toussaint F. , Tabourot L. , Vautrot M. , Balland P.
Published: December 2013

The present work aims to develop a steel ferrule forming by a low-contact deformation process using numerical analysis. Two Finite Elements (FE) models have been developed within ABAQUS. The first one is a 3D model that can both calculate the forming geometry of the part and the forces applied on the roller. The second one is a 2D axisymmetric model allowing reducing the CPU time without important loss of accuracy on the final part geometry. We present in this paper a mixed experimental/numerical comparison performed with each model and discuss the results with measurements coming from a part manufacturing by the industrial partner.
Analysis of an Electromagnetically Actuated Pumping System
Authors: Nacy Somer M. , Sharif Montassar Aidi
Published: December 2013

In this paper a moderate technique has been developed to improve an electromagnetic actuation principle for pumping systems, thus obtaining pulsating flow. This work consists of two parts, namely, a numerical part, in which ANSYS software is adopted to simulate the pumping process, while the experimental part consists of the fabrication and testing of the computer controlled electromagnetic pumping system. The objective of this work is to enhance both flow rate and outlet pressure. This was achieved via two main parameters, namely, the electromagnetic pulse duration and the width of each electromagnet. Results show that flow rate and outlet pressure increase with decreasing the pulse duration and with increasing each electromagnet width.
Comparisons Between Dynamic Characteristics of Pneumatic, Magnetorheological, and Hydraulic Shock Absorbers
Authors: Salem A. M. , Oyadiji S. Olutunde
Published: December 2013

The dynamic performance of automotive vehicles is influenced by the suspension system design. Suspensions owing damping elements with a wide range of non-linear behaviour can provide higher mobility and better ride comfort performances. Pneumatic suspensions due to their inherent nonlinear behaviour can provide high mobility performance while suspensions with MR dampers can provide this nonlinearity through the controllable damping force produced by the control of the MR fluid. The pneumatic and MR suspension models are usually developed from experimental force-displacement and force-velocity characteristics.

The purpose of this paper is to measure and compare the dynamic characteristics of pneumatic, magnetorheological, and hydraulic shock absorbers. The study is carried out through measuring the characteristics of the different types of dampers at different frequencies and amplitudes using an Electro-Servo Hydraulic (ESH) testing machine. The shock absorber is subjected to sinusoidal excitation of frequency varying from 0 to 10 Hz, and amplitude varying from 0 to 10 mm. In the case of the MR damper, the tests are also done at different current levels of between 0 and 2 amp. The input displacement and acceleration to the shock absorber were measured using an LVDT (Linear Voltage Displacement Transducer) and an accelerometer, respectively while the input velocity was derived from the measured displacement and acceleration. This dual identification of the input velocity was done in order to ensure accurate representation of the velocity. The output force response of the shock absorber was measured by means of a force transducer. The force-displacement and force-velocity characteristics of each shock absorber were subsequently derived from the measured data. The results show the tunability of the MR damper characteristics in comparison to those of the pneumatic and hydraulic dampers.
A Novel Proper Generalized Decomposition (PGD) Based Approach for Non-Matching Grids
Authors: Nazeer S. Mohamed , Chinesta Francisco , Leygue Adrien
Published: December 2013

Proper Generalized Decomposition (PGD) is a recent model reduction technique, successfully employed to solve many multidimensional problems. This method is able to circumvent, or at least alleviate, the curse of dimensionality. This method is based on the use of separated representations. By avoiding the exponential complexity of standard grid based discretization techniques, the PGD circumvents the curse of dimensionality in a variety of problems. With the PGD, the problem’s usual coordinates (e.g. space, time), but also model parameters, boundary conditions, and other sources of variability can be viewed globally as coordinates of a high-dimensional space wherein an approximate solution can efficiently be computed at once. Non-matching grids are very common in advanced scientific computing (e.g. contact problems, sub-domains coupling,).In this framework, approximate solutions from one grid to a non-matching second grid needs to be projected. This approach poses substantial numerical complexity which increases when going from one to higher dimensional interfaces. In this paper, we try to simulate a domain, which has a coarse mesh on one side and a fine mesh on other side by PGD. We show that PGD can handle these non -matching grids by using a smooth transition of the separated representation description.
Predicting the Subjective Evaluation of Drivers in a Driving Simulator During Loss of Adherence
Authors: Denoual Thomas , Petiot Jean-François , Mars Franck , Kemeny Andras
Published: December 2013

This paper investigates the possibility of using objective indicators to predict the subjective evaluation of a driver in a simulator. Situations of loss of adherence (LOA) were controlled and modulated in intensity and duration on a static and on a dynamic simulator (with and without a motion base). Multiple regression analyses were performed using the subjective evaluation of participants as the dependent variable, and the objective physical variables of the interaction driver/vehicle as the independent variables. The results assigned the most contributive variables to the accuracy of the model’s prediction for each subjective item, lateral acceleration and yaw rate for “control feeling” for instance. They also underlined the consistency of our approach and the influence of motion rendering on the perception of LOA intensity. A similar method could be used to evaluate the perception of various configurations of electronic stability control (ESC) systems.
Payne Effect in Filled Nitrile Rubber Submitted to Cyclic Loadings
Authors: Garnier Pierre P. , Le Cam Jean-Benoît J. B. , Grédiac Michel M.
Published: December 2013

This study deals with the viscoelastic properties of filled nitrile rubber submitted to cyclic loading conditions. Classic strain amplitude sweeps were first carried out on both a filled and an unfilled nitrile rubber. Tests were performed at two temperatures ambient and 80 °C. Some specimens were then subjected to a high number of cycles to study the variations in the viscoelastic properties and the sensitivity of the Payne effect to cyclic loading tests at several given strain amplitudes.
Efficient Reduced Simulation of Shell Structures With a Full Description of the Thickness: Application to Composites
Authors: Pruliere Etienne
Published: December 2013

Numerical simulations of composite structures are generally performed using multi-layered shell elements in the context of the finite elements method. This strategy has numerous advantages like a low computation time and the capability to reproduce the comportment of composites in most of cases. The main restriction of this approach is that it has only a coarse description of strain and stresses variations in the thickness. This approximation is no more valid when increasing the thickness, near the boundary and loading conditions and when non linear phenomena like delamination occurs in the thickness. This paper explores an alternative to shell computation using the Proper Generalized Methods based on a separated representation. The idea is to solve the full 3D solid problem separating the in-plane and the out-of-plane spaces. Practically, a classical shell mesh is used to describe the in-plane geometry and a simple 1D mesh is used to deal with the out-of-plane space. This allows to represents complex fields in the thickness without the complexity and the computation cost of a solid mesh which is particularly interesting when dealing with multi-layer composite.
Optimized Design for the Knee Structure of a Humanoid Robot
Authors: Howard Thomas , Berviller Laurent , Zattarin Patrick , Abba Gabriel
Published: December 2013

The objective of this work is to design and to make a part of a humanoid robot, named HYDROÏD. The keynote is a development of a self-sufficient robot by minimizing energy inputs required for its activity. Currently humanoid robots have a power/weight ratio lower than human, as a consequence a limited autonomy. In this work we propose an innovative knee structure in order to reduce friction, and as a result, increase energy efficiency. In classic knee architectures, the rolling elements are balls in bearings with relatively small curvature radii. Here, the idea is to increase this curvature radius to minimize rolling friction. This new joint is realized by rolling between two pieces (femur and tibia) linked by ligaments, and thus get an architecture similar to that of a human knee. As such, the contact is made by rolling movement without sliding between two cylindrical surfaces with circular section, and for which we need find an innovative actuation mechanism. To take advantage of energy savings achieved, we must optimize the mass distribution so as to achieve the smallest global inertia of the mechanical system. In this work we propose various technological solutions for actuation mechanisms. A comparative study is performed between the different technological choices for actuator (cylinder or rotary actuator) and for transmission (connecting crank arm, belt, gearing, etc.). Of course, this new structure must be in accordance with specifications for the knee about size and weight, as well as amplitude and speed rotation of joint. In this work, our choice is to use electric actuators. These different solutions are evaluated according several criteria such as inertial characteristic (mass and inertia matrix), overall size, energy efficiency and the complexity of the system (number of used pieces). Initially, solutions with pulley and belt or rotary actuators and cables seem to have best performance those other systems with connecting crank arm or gearing. Results should be confirmed from a more accurate determination of transmission efficiency. For prospect, the future works will be about optimization of pieces geometry, and in particular as study the gain due to using curvilinear surfaces with elliptic section. Calculation of stresses in the materials by finite elements will provide more information about optimization of dimensions and shapes. Ultimately, energetic gains obtained with this architecture should be confirm through experimental tests.
Anisothermal Flow Control by Using Reduced-Order Models
Authors: Tallet Alexandra , Leblond Cédric , Allery Cyrille
Published: December 2013

Despite constantly improving computer capabilities, classical numerical methods (DNS, LES,…) are still out of reach in fluid flow control strategies. To make this problem tractable almost in real-time, reduced-order models are used here. The spatial basis is obtained by POD (Proper Orthogonal Decomposition), which is the most commonly used technique in fluid mechanics. The advantage of the POD basis is its energetic optimality: few modes contain almost the totality of energy. The ROM is achieved with the recent developed optimal projection [1], unlike classical methods which use Galerkin projection. This projection method is based on the minimization of the residual equations in order to have a stabilizing effect. It enables moreover to access pressure field. Here, the projection method is slightly different from [1]: a formulation without the Poisson equation is proposed and developed. Then, the ROM obtained by optimal projection is introduced within an optimal control loop. The flow control strategy is illustrated on an isothermal square lid-driven cavity and an anisothermal square ventilated cavity. The aim is to reach a target temperature (or target pollutant concentration) in the cavity, with an interior initial temperature (or initial pollutant concentration), by adjusting the inlet fluid flow rate.
Exact Null-Controllability of Abstract Evolution Equations With Boundary Input Operators by Smooth Control
Authors: Shklyar B.
Published: December 2013

The paper deals with exact null-controllability problem for a linear control system governed by smooth controls. Applications to the exact null-controllability for partial parabolic equations are considered.
Static and Dynamic Analysis of Electrostatically Actuated Microcantilevers Using the Spectral Element Method
Authors: Dileesh P. V. , Kulkarni S. S. , Pawaskar D. N.
Published: December 2013

The objective of this paper is to present the Spectral Element Method (SEM) as an accurate and efficient design tool for static and dynamic simulations of cantilever based MEMS devices. The microcantilever under consideration is modeled as a Timoshenko beam and discretized using the spectral element formulation that accounts for fringing field and the nonlinearity arising from the electrostatic driving force. The static analysis has been carried out using Picard’s iteration method and the static pull-in displacement and voltage have been calculated. An eigenvalue analysis of this beam is also carried out to determine its natural frequencies. In addition, the dynamics of this cantilever is studied using the explicit Newmark predictor-corrector method to generate the time history. In all cases, the results have been compared to the one-dimensional Finite Element Method and three-dimensional finite element method (implemented through the commercial package COMSOL Multiphysics) to examine the accuracy and computational speed of the proposed SEM. The results of the simulations were also compared to those obtained by experiments in the existing scientific literature.

These comparisons lead to the inference that the SEM is able to reproduce the static and dynamic response of the beam to a high degree of accuracy. It was also found that several numerical features inherent in the SEM lead to a significantly faster computation than the corresponding finite element method for equivalent degrees of freedom. This advantage was verified by using the SEM to carry out static and dynamic simulations of variable width microcantilevers.

We therefore propose that the SEM is a viable tool for the MEMS community to accurately and quickly determine the static and dynamic pull-in parameters, frequency eigenvalues, and static and dynamic behavior at the design stage.
Control Algorithms of the Longitude Motion of the Powered Paraglider
Authors: Aoustin Yannick , Martynenko Yuri
Published: December 2013

The design of remotely controlled and autonomous Unmanned Aerial Vehicles (UAVs) is an actual direction in modern aircraft development. A promising aircraft of this type is a powered paraglider (PPG). In this paper, a new mathematical model is suggested for the paraglider’s longitudinal motion aimed at the study of PPG dynamics and the synthesis of its automatic control. PPG under consideration is composed of a wing (canopy) and a load (gondola) with propelling unit. The PPG mechanical model is constructed as the system of two rigid bodies connected by an elastic joint with four degrees of freedom that executes a 2D motion in a vertical plane. The details of PPG’s motion characteristics including steady-states regimes and its stability have been studied. A nonlinear control law, based on the partial feedback linearization, has been designed for the thrust of PPG. Simulation results are analyzed. Simulation tests show that the internal dynamics are stable near the steady-state flight regime.
Improving Trajectory Tracking Performance of a 2 DOF Parallel Kinematic Manipulator With Flexible Links
Authors: Giberti Hermes , Cinquemani Simone , Ambrosetti Stefano
Published: December 2013

Flexible-link robots are an important class of manipulators which uses lightweight arms for assembly, civil infrastructure, bridge/vehicle systems and large-scale space structures. The wide spread of these systems in various application areas has ensured that the modeling of flexible elements and the control of vibration have received a great deal of attention in recent years.

In this work it is analyzed a two DOF parallel robot with two flexible links used for pick and place operations, developing a control strategy based on piezoelectric actuators and strain gauges or accelerometers embedded in the links.

The analysis of the robot behaviour and the development of the controller, have been carried out on an electromechanical model built in Matlab® and co-simulated with the multibody flexible model built in Adams®.

Results show positive confirmation of the study and encourage future tests on the real manipulator to validate the multibody model and the control strategy.
The Specific Accelerating Factor to Compare Brushless Motors
Authors: Giberti Hermes , Cinquemani Simone
Published: December 2013

This work is focused on the analysis of the parameter named “accelerating factor” and on its use in choosing the correct electric brushless motor and gearbox in automation field. The “accelerating factor” is analyzed from a phenomenological point of view, analyzing data available on catalogs of motor manufacturers, and from the point of view of the design of such devices, trying to find a relationship between the accelerating factor and the construction parameters of a brushless motor.

The result achieved in this paper is the definition of a specific value of the accelerating factor allowing a better comparison between different motors and helping the designer in the choice of the best motor for a given application.
Advanced Optimization of Industrial Large-Scale Roll-to-Roll Systems Under Parametric Uncertainties
Authors: Frechard J. , Knittel D.
Published: December 2013

In industrial plants some parameters can not be evaluated properly or they are varying with time. These parametric uncertainties has to be taken into account during the design process of industrial systems. In this work, the developped optimization approach is applied on an industrial roll-to-roll sytem. Such systems are commonly used to handle materials as polymer, metal, paper and textile. The key challenge is to move the web at the expected speed while maintaining the web tension in an acceptable range around its reference. Moreover, the Young’s modulus of the web is difficult to evaluate and it is varying with time due to temperature and moisture variations. This paper deals with the web tension controller synthesis on a large-scale roll-to-roll system with uncertain Young’s modulus. To synthesize web tension controllers, an H∞ approach is applied and adapted to the system with parametric uncertainties using multi-objective robust design optimization.
Nonlinear Modeling and Control of a 3 DOF Helicopter
Authors: Chriette A. , Plestan F. , Odelga M.
Published: December 2013

This paper presents a novel autopilot for a 3D helicopter. From desired trajectories defined by the user for elevation and travel angles, the autopilot is computing the desired trajectory of the pitch angle. Furthermore, the autopilot allows to decouple the system and to define “virtual” inputs in order to separately design controllers for each attitude angle. Travel and elevation controllers are based on adaptive version of super-twisting algorithm: this class of controllers keeps the robustness feature of sliding mode while reducing the well-known drawback of such control approach, the chattering, thanks to the online adaptation of the controller gain.
Workpiece Placement Optimization of Six-Revolute Industrial Serial Robots for Machining Operations
Authors: Dumas Claire , Caro Stéphane , Garnier Sébastien , Furet Benoît
Published: December 2013

Roboticists are faced with new challenges in robotic-based manufacturing. Up to now manufacturing operations that require both high stiffness and accuracy have been mainly realized by using computer numerical control machine tools. This paper aims to show that manufacturing finishing tasks can be performed with robotic cells knowing the process cutting phenomena and the robot stiffness throughout its Cartesian workspace.

It makes sense that the finishing task of large parts would be cheaper with robots. However, machining robots have not been adapted for such operations yet. As a consequence, this paper introduces a methodology that aims to determine the best placement of the workpiece to be machined knowing the cutting forces exerted on the tool and the elastostatic model of the robot. In this vein, a machining quality criterion is proposed and an optimization problem is formulated. The KUKA KR270-2 robot is used as an illustrative example throughout the paper.
Optimal Design and Experimental Validation of a Turgo Model Hydro Turbine
Authors: Anagnostopoulos John S. , Koukouvinis Phoevos K. , Stamatelos Fotis G. , Papantonis Dimitris E.
Published: December 2013

This work presents the development and application of a new optimal design methodology for Turgo impulse hydro turbines. The numerical modelling of the complex, unsteady, free surface flow evolved during the jet-runner interaction is carried out by a new Lagrangian particle method, which tracks a number of representative flow elements and accounts for the various hydraulic losses and pressure effects through special adjustable terms introduced in the particle motion equations. In this way, the simulation of a full periodic interval of the flow field in the runner is completed in negligible computer time compared to the corresponding needs of modern CFD software. Consequently, the numerical design optimization of runner geometry becomes feasible even in a personal computer and affordable by small and local manufacturers. The bucket shape of a 70 kW Turgo model is properly parameterized and numerically optimized using a stochastic optimization software to maximize the hydraulic efficiency of the runner. The optimal runner and the rest turbine parts are then manufactured and installed in the Lab for testing. Detailed performance measurements are conducted and the results show satisfactory agreement with the numerical predictions, thus validating the reliability and effectiveness of the new methodology.