bluuebunny/crossref_metadata_2025 huggingface dataset:
Large Deformation Analysis of Elastic Cosserat Continua by FEM
Authors: Sharbati Ehsan , Naghdabadi Reza
Published: September 2008

Based on the non linear terms appearing in the strain tensor in classical continuum mechanics, two expressions for large strain in the Cosserat continuum are proposed. The generalized form of principal of virtual work together with the constitutive equations for an isotropic elastic Cosserat continuum are used to derive the finite element formulations for elastic large deformation analysis based on the Cosserat theory. The finite element formulations are then applied to a four-node quadrilateral element with three degrees of freedom at each node including two translational and one rotational degrees of freedom. The tension of a semi-infinite plate with a circular whole in the center is solved using the Cosserat finite element formulation and the results are compared with those obtained by the classical theory. Also, pure bending and shear of a cantilever beam are done and the differences of the results obtained based on the two proposed formulations of large strains are investigated.
Design of Trajectories With Physical Constraints for Very Lightweight Single Link Flexible Arms
Authors: Ramos Francisco , Feliu Vicente , Payo Ismael
Published: September 2008

This communication deals with feedforward control of light, flexible robotic arms. In particular we develop a new, objective method to design a family of trajectories that can be used as modified inputs which cancel the tip vibrations during the robot manoeuvres. This method takes into account the constraints encountered in real actuators (motors), such as a maximum motor torque, and those due to the mechanical limits of the link, such as the maximum deflection before reaching the elastic limit of the link. Parameters of the internal control of the actuators are also derived from the design process, gaining the fastest performance without saturating the motor. Lastly, we show some experimental results which clearly demonstrate the benefits of the new trajectories by comparing them to a linear one.
The Effects of Obstacle and Vent Position on Particle Removal From an Enclosure
Authors: Hendijanifard M. , Saidi M. H. , Taeibi-Rahni M.
Published: September 2008

This paper reports the results of a study of the transient removal of contaminant particle from enclosures. These results are the basic instruments for finding a model for contaminant particle removal from an enclosure containing an obstacle. A numerical CFD code is developed and validated with different cases, then proper two- and three-dimensional cases are modeled and improvements are done. The improvements are done by proper positioning the inlet/outlet vents. The size and position of the obstacle affect the order of magnitude of the convection-diffusion terms in the Navier-Stokes equations, hence results in different phenomena while removing the particles. One of these phenomena, the step effect, is more detailed in reference [41]. The results of these two papers may be compacted into one whole theory, describing the particle removal efficiency from an enclosure as a function of obstacle position and size.
Development of a Thermodynamic Model to Study the Behaviour of Reciprocating Air Compressor With Disc Valve Used in Automotive Braking System
Authors: Venkatesan J. , Kumar S. , Anandram V. , Saikishan S. , Vijaymanikandan J.
Published: September 2008

Mathematical modeling is the process of designing a model of a real system and conducting experiments with it for the purpose of understanding the behaviour of the system. Mathematical simulation is widely used for investigating and designing the compressors. Investigations of the processes of reciprocating compressors using mathematical models is an effective tool by high development of computing technique, which enables complicated problems to be solved with a minimal number of simplifying assumptions. A considerable number of previous works has been done on the mathematical modeling and simulation. The aims of the present work are to construct a model which is easy to understand, easy to detect errors in the process of building a model and easy to compute a solution. This project presents a simplified and effective mathematical model for the estimation of reciprocating compressor performance using personal computers that can be easily handled. The effect of various physical parameters, like, clearance volume, cylinder diameter, connecting rod length, crank radius, valve lift and other dimensions, etc., and operating parameters, like, discharge pressure, compressor speed, etc., on thermodynamic behaviour of compressor in working condition has been analysed. The model has been developed for obtaining cylinder pressure, cylinder volume, cylinder temperature, valve lift and resultant torque at different crank angles and free air delivered and indicated power of the compressor.
A Pulsating Flow in a Pipe and the Visualized Flow Pattern of the Jet From the Pipe
Authors: Ikeda Daisuke , Iwamoto Junjiro
Published: September 2008

The high-speed pulsating flow is found in the exhaust system of the reciprocating internal combustion engine, the piping system connected to reciprocating compressor, etc., and has various features which never exist in the steady flow. This work is concerned with an experimental study of the high-speed pulsating flow in a straight pipe and the jet discharged by the pipe. In order to express quantitatively the intensity of compression wave in the pipe, the “intensity of compression wave” is defined and discussed. The shock formed in vortex ring in the issuing jet from the pipe is found to be due to Laval nozzle effect. The schlieren pictures taken with optical path inclined to the jet axis shows that the decay of vortex ring depends on the speed of the rotary valve.
Body Force Method for Flamant Problem Using Complex Potentials
Authors: Manjunath B. S. , Ramakrishna D. S.
Published: September 2008

Body force method is a method based on principle of superposition. In the body force method the actual condition is treated as an imaginary condition i.e. the semi-infinite plate with hole is treated as a plate without hole; the actual hole is regarded as imaginary on whose periphery boundary forces are applied. The problem is solved by superimposing the stress fields of the boundary forces and concentrated force acting at an arbitrary point to satisfy the prescribed boundary conditions so that the stress condition of the actual plate is approximately equal to that of the imaginary plate. The flamant problem with hole is shown below in Fig. 1.The complex variable method of stress analysis is a versatile technique for stress analysis Problem. The formulas for flamant problem are derived and described. Complex potentials are used for stress analysis. In the present paper, semi-infinite plate with hole is considered for analysis by body force method.
Fuzzy-Based Roll Control for a Single Unit Heavy Vehicle
Authors: Boada Maria Jesu´s L. , Boada Beatriz L. , Gauchia Antonio , Di´az Vicente
Published: September 2008

In this paper a fuzzy-based controller to improve the roll stability in a single unit heavy vehicle is proposed. The controller, consisting of active anti-roll bars, provides the adequate roll moments to the vehicle to improve its performance. The main advantages of fuzzy method are its simplicity, its good performance to control non-linear systems and it is a free-model control. Simulation results show the effectiveness of the proposed control system during different manoeuvres (J-turn and change line).
A Co-Robotic Positioning Device for Carrying Surgical End-Effectors
Authors: Frumento Silvia , Michelini Rinaldo C. , Konietschke Rainer , Hagn Ulrich , Ortmaier Tobias , Hirzinger Gerd
Published: September 2008

The development of a remotely operated, Co-Robotic Positioning Device (CRPD) for instrumental backing and optimal base position to robotic arms in tele-surgery is discussed. To optimise the setting of robotic operating rooms (ROR) by reducing the structures’ size around the patient and by selecting task-driven layouts, the design of a hanging servo-carrier coming from the ceiling is chosen, rather than a device located on the floor. The present study prospects a split-duty approach, distinguishing the Co-Robotic Positioning Device, CRPD, from the front-end effectors, each subsystem hierarchically controlled by remote location, in keeping with optimal protocols. The attention is focused on the slave-carrier, to establish an optimal design of the CRPD, based on the characteristics of robotic effectors and the surgical task. The CRPD is conceived to support (up to four) robotic effectors, each one equipped with proper tools (endoscope, scalpels, scissors, suture needles, etc.). The CRPD, actually, by optimally positioning the robotic arms, avoids the need of manual deployment, in current setups often necessary to avoid singularities or collisions. The Automatic Changing Device for Surgical Tools, ACD-ST, is another significant device of the conceived slave-carrier. It allows the tele-operating surgeon to change the tools (scalpels, scissors, etc.) by a direct command from his console. Example applications aim at ticklish endoscopic/tomic operations that require high accuracy with low involved forces such as cardio-thoracic-surgery, abdominal surgery, spine-surgery, microsurgery (neurosurgery, hand-surgery, ophthalmic-surgery, ear-nose-throat surgery), say, the typical domains of MIRS, where robotic surgery is quickly expanding.
Camera Based Concept for Enhancement of IRB Accuracy Using Fixed Features and SLAM
Authors: Andersson Lars A. A. , Berglund Marcus
Published: September 2008

A standard IRB (Industrial Robot) of today is not capable of positioning itself to within better than 2–5mm relative to a given structure or object. In order to be able to perform high precision manufacturing, the requirement is less than 0.5mm. Existing solutions for 6DOF measurements to enhance the accuracy are not only expensive but also lack flexibility. An affordable, accurate concept for IRB closed loop position feedback is presented here. This article proposes a method for using a camera together with fixed features to enhance the accuracy of an IRB in industrial manufacturing processes. The method is based on SLAM (Simultaneous Localization and Mapping), used to structure collected information about the features (mapping), and for the IRB to locate itself among the features (localization). The concept covers a scenario in which a set of features are placed within the working area. A camera is mounted on the IRB to observe (measure) the relative pose of the feature set. When the system is running observation of only one feature increases accuracy. However, in normal operation more features are observed which will increase accuracy further. The system setup is a standard IRB, ABB4400, on which a single camera with IR flash is mounted and used as sensor. The features are made out of reflectors that are placed in the production cell. The camera is also equipped with an IR filter to improve the signal to noise ratio, simplifying image processing and accelerating execution. The execution time is critical since the goal is to sample at such a rate that as to cover the dynamics of the robot.
Validation of a Navier-Stokes Solver for CFD Computations of Transonic Compressors
Authors: Biollo Roberto , Benini Ernesto
Published: September 2008

The progress of numerical methods and computing facilities has led to using Computational Fluid Dynamics (CFD) as a current tool for designing components of gas turbine engines. It is known, however, that a sophisticated numerical model is required to well reproduce the many complex flow phenomena which characterize compression systems, such as shock waves and their interactions with boundary layers and tip clearance flows. In this work, the flow field inside the NASA Rotor 37, a well known test case representative of complex three-dimensional viscous flow structures in transonic bladings, was simulated using a commercial CFD code based on the 3-D Reynolds-averaged Navier-Stokes equations. In order to improve the accuracy of predictions, different aspects of the numerical model were analyzed; in particular, an attempt was made to understand the influence of grid topology, number of nodes and their distribution, turbulence model, and discretization scheme of numerical solution on the accuracy of computed results. Existing experimental data were used to assess the quality of the solutions. The obtainment of a good agreement between computed and measured performance maps and downstream profiles was clearly shown. Also, detailed comparisons with experimental results indicated that the overall features of the three-dimensional shock structure, the shock-boundary layer interaction, and the wake development can be calculated very well in the numerical approach for all the operating conditions. The possibility for a numerical model to better understand the aerodynamic behaviour of existing transonic compressors and to help the design of new configurations was demonstrated. It was also pointed out that the development of an accurate model requires the knowledge of both the physical phenomena place within the flow field and the features of the code which model them.
Quantitative Evaluation of Surface Roughness of Flat Metal Surfaces Using Computer Vision System
Authors: Inamdar Kedar H. , Joshi S. G.
Published: September 2008

In this paper, a method of quantitative evaluation of surface roughness based on computer vision system is presented. A low cost computer vision system consisting of flat bed desktop scanner connected to personal computer (PC) is used. A large number of surface specimens such as EN-8, EN-9, cast iron, copper, brass, aluminium, C-20, C-45 steel etc. were carefully prepared by using various machining processes like planing, shaping, turning, milling, grinding, polishing etc. to generate a database of surface specimens with different lay-types and surface roughness values. This database is evaluated for conventional surface roughness parameters like Rt, Ra, Rq and for RGB colour component values at each pixel over the digital images of these produced surfaces. By using the technique of multiple linear regression analysis, the conventional roughness values and colur component values were correlated with each other to form a multiple linear regression equation for Rt. The value of surface roughness Rt obtained for a given specimen using this equation was then crosschecked and confirmed with the results obtained by using conventional method for the same specimen. When any test surface is introduced for surface roughness evaluation, the developed method relates the colour component values obtained from its surface image, to the conventional values like Rt, Ra, Rq. In addition to this, surface topographical representation and summits are also presented. Using this method even the evaluation of the surface roughness in the nano-metre level can be carried out to fulfill the requirements of experimental field of 0.001 to 50 microns.
Design of Planetary Exploration Vehicles
Authors: Genta Giancarlo
Published: September 2008

The exploration, both robotic and human, of the Moon and the planets requires the use of vehicles to carry instrumentation and later people from the landing site or the outpost to the places to be explored. The aim of the present paper is to consider the design requirements of planetary exploration vehicles, both manned and robotic, mainly for what mobility on the planetary surface is concerned. The objective is to identify technologies that can be transferred from the automotive field, and to show the relevant differences and similarities of operation in so different environments.
Prediction of Dry-Friction Whirl and Whip Between a Rotor and a Stator
Authors: Childs Dara W. , Bhattacharya Avijit
Published: September 2008

This paper addresses recent test results for dry-friction whip and whirl. Authors of these publications suggest that predictions from Black’s 1968 paper are deficient in predicting their observed transition speeds from whirl to whip and the associated precession frequencies of whirl and whip motion. Predictions from Black’s simple Jeffcott-rotor/point-mass stator are cited. This model is extended here to a multi-mode rotor and stator model with an arbitrary axial location for rotor-stator rubbing. Predictions obtained from this new model are quite close to experimental observations in terms of the transition from whip to whirl and observed precession frequencies. Paradoxically, nonlinear numerical simulations using Black’s model fail to produce the whirl and whip solutions. The Coulomb friction force in Black’s model has a fixed direction, and Bartha showed in 2000 that by making the friction-force direction depend on the relative sliding velocity, nonlinear simulations would produce the predicted whirl solutions. He also showed that Black’s proposed whip solution at the upper precession-frequency transition from whirl to whip was unstable. Results presented here show that Black’s whirl solutions are unstable for all whirl precession frequencies, not just the whirl-whip transition frequency. The multi-mode extension of Black’s model predicts a complicated range of whirl and whip possibilities; however, nonlinear time-transient simulations (including the sgn function definition for the Coulomb force) only produce the initial whirl precession range, the initial whirl-whip transition, and the initial whip frequency. Simulation results for these values agree well with predictions. However, none of the predicted higher-frequency whirl results are obtained. Also, the initial whip frequency persists to quite high running speeds and does not (as predicted) transition to higher frequencies. Hence, despite its deficiencies, correct and very useful predictions are obtained from a reasonable extension of Black’s model.
A Realistic Model for Visco-Elastic Contact Between Spherical Particles
Authors: Bordbar Mohammad Hadi , Hyppanen Timo
Published: September 2008

The contact force model is very important to describe the grain collision process accurately. In this research, the linear/nonlinear contact force models and normal coefficient of restitution in different impact velocities has been studied. A new contact force model for describing the normal collision between two visco-elastic spherical particles has been suggested and the ability of this new model in predicting the correct behavior of normal contact has been confirmed. The constitutive equations of this model have been solved numerically and the result shows a better conformity with experimental result reported by Bridge et al. [1] than the previous models, such as the model presented by Brilliantov et al. [2]. By using the suitable finite elements model, the stress and deformation of particles during the collision has been obtained and the result of the finite elements model shows a good conformity with our new suggested contact force model in the case of elastic and visco-elastic contact. The behavior of normal coefficient of restitution in multisize spherical particles in different impact velocities and effect of the size on it has been experimentally studied. In addition to our more suitable contact force model, we achieved some nice conclusions from our experimental data about the loss of energy during the multisize collision and effect of size difference on this loss.
Manufacturing Tolerance Analysis of a Robot Manipulator’s Joint Axis Orientation Employing Single Monte-Carlo Simulation
Authors: Choi Dong Hwan , Yoo Hong Hee
Published: September 2008

The operation error of a robot manipulator that occurs inevitably due to the manufacturing tolerance needs to be controlled within a certain range to achieve proper performance. The reduction of manufacturing tolerance, however, increases the manufacturing cost in return. Therefore, system design engineers try to solve the problem of maximizing the tolerance to reduce the manufacturing cost while minimizing the operation error to satisfy the performance requirement. In the present study, a revolute joint model considering the variation of joint axis orientation due to joint clearance is employed to perform a tolerance analysis of the robot manipulator operation. This paper presents a hybrid method which employs the sensitivity-based analytic method and the single Monte-Carlo simulation. The proposed method provides rapid implementation and the accurate statistical properties using the only single integration or single iteration for one sample set, whereas the Monte-Carlo method necessitates integrations as the number of samples and cases. Significant reduction of computing time can be achieved with the proposed method. The present method is especially effective if sensitivity information is hard to be obtained for the analysis.
A Sequential Approach for Hybridizing Conventional Vehicles and an Approval Example
Authors: Esfahanian Mohsen , Khanipour Ahmad , Nabi Ali , Fazeli Amir Mohammad , Amiri Meisam
Published: September 2008

Hybridization of conventional vehicles is considered an important step to achieve high fuel economy and low emissions. In this study, principle considerations involved in a hybridizing process are discussed and consequently, a sequential approach for designing hybrid components for both series and parallel configurations has been introduced. The so called approach has then been applied to one of the productions of Iran-Khodro Company called SAMAND. Having designed the hybrid components, the conventional SAMAND and its series and parallel hybrid configurations were defined and evaluated using the ADvanced VehIcle SimulatOR (ADVISOR) software. It is observed that compared to the conventional vehicle, a reduction in fuel consumption by about 51% in the series configuration and about 34% in the optimized parallel configuration is achievable.
Development of Energy Management System for a Parallel Hybrid Electric Vehicle Using Fuzzy Logic
Authors: Fazeli Amir Mohammad , Nabi Ali , Rajaei Salmasi Farzad , Amiri Meisam
Published: September 2008

In this paper a fuzzy power controller for a parallel hybrid passenger car is developed in order to minimize its fuel consumption and optimize its components efficiencies. This is done by controlling the engine operating points in its optimal region and maintaining the SoC of batteries and electric motor operating point at the highest possible efficiency. Of course the designed control strategy must be able to obey the driver’s commands and achieve the PNGV regulations. The controller implemented in this paper is a Mamdani fuzzy logic controller which takes the batteries SoC, electric motor’s speed, ICE speed and the total demanded torque as its input variables and gives the ICE torque as its output. This controller has been simulated using the ADvanced VehIcle SimulatOR (ADVISOR) and its results have been compared to the default fuel mode fuzzy controller of ADVISOR. Simulation results show considerable improvement in the efficiency of the ICE and consequently, fuel consumption and acceleration performances.
The Cruise and Active Suspension Control for High Speed Train
Authors: Lin Chih-Jer , Xu Wan-Quan
Published: September 2008

This paper presents a complete analysis of the cruise control and the active suspension control for the high speed train (HST). For a train system, the system are designed to being safe and reliable with high efficiency and fault tolerance; however, users require faster, more stable and more comfort transportation. To make sure the safety at such high speed, automatic train control (ATC) is needed and used for the modern HST to guarantee the safety and monitor the cruise status. For HST, the conventional (passive) suspension techniques have reached the limit of its optimization and development; therefore, the active suspension system is necessary for HST to obtain better comfort. In this paper, the extended sliding mode control is studied and applied to the cruise and active suspension of the HST.
CO2 Capture for Power Plants: An Analysis of the Energetic Requirements by Chemical Absorption
Authors: Diaz Ana R.
Published: September 2008

The tendency in the world energy demand seems clear: it can only grow. The energetic industry will satisfy this demand-despite all its dialectic about new technologies-at least medium term mostly with current fossil fuel technologies. In this picture from an engineer’s point of view, one of the primary criterions for mitigating the effects of increasing atmospheric concentration of CO2 is to restrict the CO2 fossil fuel emissions into the atmosphere. This paper is focused on the analysis of different CO2 capture technologies for power plants. Indeed, one of the most important goal to concentrate on is the CO2 capture energy requirements, as it dictates the net size of the power plant and, hence, the net cost of power generation with CO2 avoidance technologies. Here, the Author presents a critical review of different CO2 absorption capture technologies. These technologies have been widely analyzed in the literature under chemical and economic points of view, leaving their impact on the energy power plant performance in a second plan. Thus, the central question examined in this paper is the connection between abatement capability and its energetic requirements, which seriously decrease power generation efficiency. Evidencing that the CO2 capture needs additional technical effort and establishing that further developments in this area must be constrained by reducing its energy requirements. After a comprehensive literature revision, six different chemical absorption methods are analyzed based on a simplified energetic model, in order to account for its energetic costs. Furthermore, an application case study is provided where the different CO2 capture systems studied are coupled to a natural gas cogeneration power plant.
Vehicle Sideslip Angle Estimation Through Neural Networks: Application to Numerical Data
Authors: Melzi Stefano , Resta Ferruccio , Sabbioni Edoardo
Published: September 2008

Aim of this paper is to evaluate the possibility of estimating the vehicle sideslip angle through a non-structured algorithm based on neural networks. Results reported are relevant to a numerical investigation of the network performance which can be regarded as preliminary stage for the application on a real vehicle. A numerical model is used to describe the vehicle dynamics and to generate the inputs for the neural network; with an appropriate set of manoeuvres for network training the non-structured algorithm provides reliable results when applied to a complete series of handling manoeuvres carried out with different tire-road friction coefficients.
Function-Driven Product Design in Virtual Teams Through Methodical Structuring of Requirements and Components
Authors: Kreimeyer Matthias , Herfeld Ulrich , Deubzer Frank , Dequidt Cyrille , Lindemann Udo
Published: September 2008

Today’s development process is mainly geometry driven and executed by a component-based organization of design departments (in automotive development e.g. one department for body design, one for interior design etc.). Yet, design departments developing complex products depend more and more on support from other departments. Therefore, these component-based organizational structures are not fully adequate. The product developed in these departments is — from the customer’s point of view — a set of functions that meet his needs, requiring the incorporation of different compromises from different aspects of design for X. Typically, the individual functions do not have a direct, one-on-one relation with single components or assemblies but overlap with several components and assemblies. Therefore, at least two perspectives coexist in the design of a product and particularly with respect to collaboration between embodiment design engineers and simulation engineers, that of functions and that of components. Hence, a manageable approach is needed to map components and functions. This paper proposes an approach to methodically compose function-oriented teams between embodiment design and simulation departments. These are meant to support cross-departmental communication to raise efficiency in the development process. The approach is implemented by interrelating components and functional requirements. To do so, the methodologies of design structure and domain mapping matrices are used. The mapping provides the engineering departments with several opportunities: First of all, it provides transparency of the product’s functions as specified by the requirements and their interrelation with the product’s topology. This offers the embodiment design engineers a possibility to understand the involvement of “their” parts into the total product and the simulation engineer the possibility to find all parts involved in a function to be simulated. Thus it serves as a means to structure communication between the involved engineers. Furthermore, it allows conclusions to compose adequate roles and teams within the design process. Adapting the approach of so-called “communities of practice”, a team structure across design and simulation departments is proposed to form function-driven teams that are able to work together efficiently and target-oriented. This establishes well-defined channels of communication to foster efficient exchange of information among different departments such as embodiment design and simulation department.
Vibration Signature Analysis of Real and Virtual Damaged Gears
Authors: Barbato David , Barsanti Michele , Forte Paola , Manconi Salvatore , Melani Gabriele , Vitali Michele , Saroglia Maurizio
Published: September 2008

A high performance rig designed to test gears (materials and geometries) in extreme load and speed conditions as in aerospace applications was used to test diagnostic systems by the only vibration analysis. The authors of the present report have implemented, in addition to some standard signal analysis techniques, some advanced methodologies (e.g. NA4, NB4), which are applied to the synchronously averaged signal to detect the smallest fault related variations in the tested gear vibration signature. The different techniques have been tested and compared on the signals of a gear that underwent failure, showing the good performance of the latter approaches compared to the more conventional ones. A numerical simulation of the gear meshing was carried out to support the experimental campaign and the benchmarking of the diagnostic tools. The stiffness computed by a FEM code was employed to simulate the gear system dynamic behavior with a lumped model, which was finally tuned using the experimental signals, to obtain indications on the crack evolution.
Modelling and Simulation of Fluid Power Systems in Object-Oriented Programming Environment
Authors: Grossschmidt Gunnar , Harf Mait , Sallaste Taavi
Published: September 2008

The paper deals with principles of computer modelling and simulation of behaviour of fluid power systems in object-oriented programming environment. The approach is based on using multi-pole models and signal-flow graphs of functional elements, that enables methodical, graphical representation of mathematical models of large and complicated chain systems. In this way we can be convinced in the correct composing of models. A high-level programming environment NUT is used as a tool for building modelling and simulation systems. Several modelling and simulation systems have been developed using approach described above. Different simulation tasks have been solved on these modelling systems. Methodology described in the paper has several advantages and novelties.
Development of Membrane Contactors for Greenhouse Climate Control
Authors: Lo Presti Giulio M. , Malvicino Carloandrea , Mola Stefano , Mastrodomenico Nunzio , Rostagno Matteo M.
Published: September 2008

Cultivation in greenhouse requires high water quantity for irrigation and sometimes for internal climate conditioning. Water resource is becoming more and more poor. The proposed system allows making greenhouses self-sufficient from the point of view of water needs and self-conditioned at a very low energy cost. Moreover it could allow cultivation in areas where drinkable water is scarce, since it can use as primary source saline or brackish water. This is a new concept of greenhouse, patented by Centro Ricerche FIAT (CRF), in which membranes, waterproof but permeable to vapor, are used in order to improve a cooling system. The management of membrane contactors allows, with lower energy expense with respect to standard air conditioning systems, allows to control both temperature and lowest humidity level inside the greenhouse, thus reducing water need. Saline water is used upstream for cooling and clean water is obtained, by means of downstream condensation.
Hygro-Thermal Performance of Ventilated Underground Cavities
Authors: Brunello Pierfrancesco , Del Col Davide
Published: September 2008

The risk assessment regarding overheating in underground structures is becoming quite common among the designers, when internal heat gains are severe or they occur for a long time. Typical is the case of subway tunnel networks, but many other recent examples may be easily found. Quite often however, not only the air temperature pattern is relevant, but also humidity may play an important role, especially if underground water infiltrations are not negligible. In fact, water evaporation or condensation may significantly affect the temperature profiles; on the other hand, high humidity ratios may hamper some activities performed in the cavities. The present paper aims to present a design tool to simulate the hygro-thermal behaviour of ventilated underground cavities. The model can be used to simulate steady-state or transient conditions: it solves the heat and mass transfer equations in the cavity, providing also a criterion for the evaluation of the fog in the air.
CFD Methodology to Predict Demisting Phenomena on the Car Windows
Authors: Mattiello Fabrizio , Croce Giulio , De Angelis Alessandra
Published: September 2008

The vehicle HVAC systems have a fundamental role for demisting operation, eventually even more important than assuring thermal comfort because it guarantees the correct visibility for the drivers in the respect of the global security, towards the passengers and the pedestrians. Fiat Auto regulation follows the Standard CEE 78/317 performance test that the HVAC systems must respect to assure windshield demisting. The performance is evaluated by means an experimental test in climatic chamber. This test usually requires either waste of time and of money, since it has to be performed in climatic chambers. Only afterwards, if this first test is satisfied, thermal comfort performances of the vehicle are analysed. The goal of the present work is to describe the CFD virtual model developed to predict the demist performance of an HVAC system coupled with the virtual vehicle cabin, once the cabin CAD surfaces are available (draft surfaces are enough), and not after the vehicle manufacturing. A suite of routines for the prediction of environment moist condensation and evaporation on solid surfaces is presented. The physical problems require the solution of the air flow field along a (cold) solid surface, the evaluation of the unsteady conduction through the solid itself, and the development of a suitable model for the heat and mass transfer within the thin water layer on the fogged surface. The routines for the unsteady simulation of the water layer evolution are designed as a purely interfacial procedure, minimizing the exchange of information with the flow and conductive solver. This allows the coupling with different solvers. Here, the model is used in connection with a commercial CFD solver, in order to predict the defogging process of a car windshield. The water layer is modelled as a collection of closely packed tiny droplets, leaving a portion of dry area among them. The effect of the contact angle is taken into account, and physical assumptions allow to define the local ratio between wet and dry surface for both the fogging and defogging process. The model for the misted layer simulation is derived from a numerical method developed for the aeronautical de-icing systems. Fluid domain, solid domain and liquid film are simultaneously solved, and the problem of the conjugated thermal exchange through solid-fluid domains is carried out by means of opportune interpolations and information exchange on the boundary conditions. Finally this model has been successfully validated with respect to the experimental results.
Pneumatic Vehicular Suspension With a Controllable Stiffness Spring
Authors: Ferraresi Carlo , Franco Walter , Quaglia Giuseppe , Morello Andrea , Pierucci Domenico
Published: September 2008

This paper deals with the design of a new vehicular pneumatic suspension. It presents an innovative scheme of suspension, using a special 3-membrane deformable fluid spring. The spring is provided with three internal chambers, supplied by a compressible fluid. Each chamber presents a different volume gradient versus the stroke; a proper variation of the connection between the chambers, that may be performed in few milliseconds, determines a stiffness variation of the air spring. The spring structure and the related mathematical models are presented. Afterwards the process of adaptation of the component to a specific mid-low class car model, in order to achieve a prototypal phase, is described. Finally the results of some dynamic simulations of the car behavior are shown.
A Model for Bone Resorption
Authors: Johansson Lars , Edlund Ulf , Fahlgren Anna , Aspenberg Per
Published: September 2008

In the present paper a model for the resorption of bone, such as that observed at the interface between surgical implants and bone tissue, is developed. While there are many previous studies where models for bone remodelling calculations are proposed, these have been based on the stress or strain state of the bone tissue itself as the driving force for bone remodelling. We, instead, develop a constitutive model based on observations in recent experiments where it seems that fluid pressure, or possibly fluid flow velocity, is a major factor in the bone resorption process.
Modeling of Closed Loop Pulsating Heat Pipes by Neural Networks
Authors: Shokouhmand Hossein , Gharib Nima , Bahrami Hafez
Published: September 2008

Pulsating heat pipes (PHPs) are devices that their performance strongly depends on many factors such as filling ratio, working fluid, internal diameter, and etc. Therefore, variety of such parameters must be considered in experimental data or an accurate model must be used to characterize the behaviors of PHPs. In this study, a two layers neural network model is used to predict the behaviors of the PHPs. The effects of filling ratio and heat power input and working fluid on thermal resistance of PHPs are considered. The obtained results are in good agreement with available data and can be appropriate for predicting the trend of effective parameters on PHPs performance.
Development of an Interferometric Method for Measurement of Thermal Conductivity of a Transparent Medium
Authors: Sobhan Choondal B. , Kurian Renju
Published: September 2008

Interferometric methods are non-intrusive optical measurement techniques, which find extensive use in flow and heat transfer visualization. The present work originates from the idea that by a suitable experimental system and data analysis method, the interferometric technique can be used to estimate its thermal conductivity. A method is developed to obtain the thermal conductivity of a transparent medium using the optical technique of differential interferometry. The basis is of this method is the measurement of the local interference fringe shift values along an isothermal flat plate surrounded by the medium to visualize the heat transfer field. The local Nusselt number distribution along the plate is estimated from fringe shift and compared with theoretical local Nusselt number distribution along an isothermal plate, and this comparison is used to estimate the thermal conductivity of the medium.
Overtaking Stationary and Moving Obstacles for Autonomous Ground Vehicles
Authors: Javid Ghasem Amini , Durali Mohammad , Kasaaizadeh Alireza
Published: September 2008

In this paper, a method for overtaking stationary and moving obstacles will be introduced. The method consists of designing a desired trajectory for lateral motion of the vehicle and then using a lateral motion controller for tracking this desired trajectory. The desired trajectory is a sigmoid exponential function of relative distance between the vehicle and the obstacle and guarantees overtaking the obstacle, if tracked exactly, despite of lateral and longitudinal motions of the obstacle. Lateral acceleration of the vehicle should not exceed safety limits during tracking desired trajectory. This matter has been used as a decision criterion for determining feasible and unfeasible desired trajectories. A neural network has been trained for predicting maximum lateral acceleration (MLA) during overtaking maneuver. The lateral motion controller is a sliding mode controller which has been designed to be robust to uncertainties existing in lateral dynamic model of the vehicle. A virtual test environment has been developed as a design tool for developing new control strategies for autonomous vehicles. The lateral controller has been tested extensively using this virtual test environment and has shown satisfactory performance in controlling the vehicle, even in existence of noises and disturbances.
Transient Radiative Heat Transfer Analysis of a Polypropylene Layer Using Hottel’s Zonal Method
Authors: Safavisohi Babak , Sharbati Ehsan , Aghanajafi Cyrus , Khatami Firoozabadi Seyed Reza
Published: September 2008

Polymer films possess excellent optical properties, such as high transparency, and thermal characteristics, like low heat conductivity, as well as further polymer specific advantages. Consequently, polymer films have an outstanding potential for many solar applications. They are already used for encapsulation of photovoltaic (PV) cells, as convection barrier in solar collectors and as substrate or adhesive layers for glazing. In translucent polymers, energy can be transferred internally by radiation in addition to conduction. Since radiant propagation is very rapid, it can provide energy within the layer more quickly than diffusion by heat conduction. Thus, the transient thermal response of a layer for combined radiative and conduction may be extremely different from that of conduction alone. In this paper, the behavior of a heat conducting, absorbing, and emitting layer of Polypropylene is investigated during the transient interval when both conductive and radiative heat transfer are considered. The governing differential equations include the equation of radiative heat transfer within the material coupled to the transient energy equation, which contains both radiative and conductive terms. The solution procedure is based on nodal analysis and Hottel’s zonal method extended by the ray tracing method. The transient energy equation including the radiative internal energy source is solved using a time marching finite difference procedure with variable space and time increments. In addition, effects of variable parameters including optical thickness and thermal conductivity of the layer are investigated carefully.
Delayed Feedback Control in Bilateral Teleoperation
Authors: Zafer Naci
Published: September 2008

Stabilization of time delay systems is currently a mainstream of research. In this paper, a delayed feedback controller is considered for internet-based teleoperation, where the master and the slave manipulators are bilaterally connected through a communication channel. A frequency based approach is employed for the stability analysis of teleoperation in spite of varying time delays. The derived approach is exact in telling weather the system is stable, whenever the system parameters including the delay are prescribed. The analysis formulates the stability intervals as delay varies. It is also shown how delayed negative feedback is able to stabilize oscillatory system dynamics. The results are illustrated with numerical examples.
Adaptive Control of the Closed Loop Behaviour of Manufacturing Processes
Authors: Wilkin Tim , Frayman Yakov , Rolfe Bernard
Published: September 2008

An open problem in manufacturing control is the design of controllers with guaranteed closed loop performance on plants subject to unmeasurable disturbances and changing dynamics. Existing methods for Adaptive Control of these plants typically rely on system identification techniques, which lead to a multi-objective optimisation task that offers no explicit guarantee regarding the stability of the closed loop system or the quality of its output. Robust Control design guarantees stability in the presence of unmeasured disturbances, although at the expense of sub-optimal control performance. We propose a control architecture and methodology for online adaptation of the process behavior that does not require explicit identification of the plant or disturbance dynamics. An arbitrary function approximator is used for control of the plant and the closed loop behaviour of this coupled system is adapted to that of a generic performance target. No exogenous signal is required for excitation of the adaptation, which instead used the inherent variability in the plant output. The use of a closed loop performance target for adaptation is practical, simple to implement and does not require a knowledge of either the plant dynamics or the disturbances acting on the process, since the controller is only concerned with maintaining transient process behavior within acceptable bounds. The resulting controller is capable of achieving a specified closed loop performance in the presence of unmeasurable, bounded disturbances, making the proposed scheme a viable candidate for disturbance rejection tasks.
Universiti Tenaga Nasional Short Duration Hypersonic Test Facility: Calibration and Verification
Authors: Al-Falahi Amir , Yusaf T. , Yusoff M. Z.
Published: September 2008

The first phase of this paper is aimed to develop a standard test procedure for short-duration hypersonic test facility that build at the Universiti Tenaga Nasional “UNITEN” in Malaysia. The facility has been designed, built, and commissioned for different values of diaphragm pressure ratios. A theoretical model was developed to evaluate the Mach number values as a function of diaphragm pressure ratio for different working fluids. The second phase is to run experimental tests for different operating conditions. The calculated parameters which are pressure, temperature and velocity were very comparable to the practical results. A high precision in house made thermocouple was used to measure the temperature profile during the facility operation. A numerical transient heat transfer mathematical model was developed to evaluate the heat flux from the surface temperature history. The principle of operation and the reasoning behind building such a facility are explained, and the governing equations for the shock tube are presented.
A Control Strategy for Optimization of Power Losses in Series Hybrid Electric Vehicles Considering the Extension of Battery Life
Authors: Amiri Meisam , Salmasi Farzad R. , Esfahanian Vahid
Published: September 2008

Series hybrid electric vehicles (SHEVs) use an electric generator together with battery pack to feed the vehicle traction system. Control system of a hybrid vehicle has a fundamental role in its drivability and performance. Therefore, satisfying the drivers demand while optimizing the power-train efficiency is the key goal in designing the control strategy. An optimization based control strategy for SHEVs has been proposed in order to optimize power-train efficiency while taking the minimization of the losses caused by reducing the battery life into account. Simulation results verify the proposed method.