bluuebunny/crossref_metadata_2025 huggingface dataset:
A Mereotopology-Based Approach for Integrated Assembly Modeling and Planning
Authors: Demoly Fre´de´ric , Matsokis Aristeidis , Kiritsis Dimitris
Published: June 2012

This paper describes a novel approach for integrated assembly modeling and planning. The main objective is to make assembly information accessible and exploitable by data management systems and computer-aided X tools. Product information and knowledge as well as the related assembly sequence require a logical foundation in order to be managed consistently and processed proactively. In this context, the authors consider and describe product-process relationships in the part-whole theory supported by mereology and its extension, mereotopology. Firstly, past and current research work is presented on: concurrent product design and assembly sequence planning approaches; existing assembly relational models; and spatio-temporal mereotopology. Then, a mathematical description of product relationships based on mereotopology and temporal relationships is introduced. The long term aim is the representation of the outcomes in a formal ontology, in order to allow reuse and collaborative exploitation of the assembly knowledge in the different product lifecycle phases.
Transient Response Control by Fractional-Order PI Controllers
Authors: Hamamci Serdar Ethem , Obuz Serhat
Published: June 2012

Consideration of the transient response is one of the key topics in control system design for time delay systems. In this paper, an efficient method to control the transient response of the first order plus time delay stable (FOPTD) systems using the fractional-order PI (PIλ) controllers is presented. The main characterization of the method is first to construct the global stability region in the (kp, ki)-plane for any fixed value of λ and then to obtain ts and Mp curves corresponding to special settling time and maximum overshoot values in this region. Finally, by intersection of these curves, the Dλ-stability region in the (kp, ki)-plane is found. Changing the value of λ in the range of (0, 2), a set of Dλ-stability regions is obtained. These regions involve the controller parameters providing the closed loop settling time and maximum overshoot specifications together in the acceptable values. Therefore, the designer can easily decide to the selection of suitable values of kp, ki and λ. The simulation results indicate that the presented transient response control method is effective and practically useful in the analysis and control of the stable FOPTD systems by means of fractional-order PI controllers.
Design of a Robotic Endoscope for Mini Invasive Surgery
Authors: Zazzarini Cynthia C. , Pansini Alberto , Cerveri Pietro , Zaltieri Renzo , Lavizzari Damiano
Published: June 2012

Natural orifice transluminal endoscopic surgery (NOTES) is a novel surgical technique which uses endoscopic tools to perform mini invasive abdominal operations through natural orifices. The main limitation for a secure use of this technique is the lack of a proper surgical device, since it is still performed by non rigid endoscopes designed for diagnostic applications. Robot Assisted Surgery is the ideal solution to perform this kind of surgical operations. This research project is a preliminary study for the design of an endoscope, with variable stiffness in effort to provide the surgeons with a device which meets specific clinical requirements. The body is composed of a series of robotic modules connected by joints capable of two different movements: an axial rotation and a longitudinal bending. The movements are servo commanded and carried out by two brushless DC electric motors and an encoder. A force sensor is mounted on each module in order to provide a haptic feedback to the surgeon. The end point of the robot is equipped with a high definition camera which is able to perform zoom, autofocus and image stabilization. Illumination is provided by a power led system. A CAN bus ensures the communication between the modules, the camera and the haptic interface.
A Study of Gear Root Strains in a Multi-Stage Planetary Wind Turbine Gear Train Using a Three Dimensional Finite Element/Contact Mechanics Model and Experiments
Authors: Prueter Phillip E. , Parker Robert G. , Cunliffe Frank
Published: June 2012

Wind energy has received a great deal of attention in recent years in part due to its minimal environmental impact and improving efficiency. Increasingly complex wind turbine gear train designs, well-known failures in gear train rolling element bearings, and the constant push to manufacture more reliable, longer lasting systems generate the need for more advanced analysis techniques. The objectives of this paper are to examine the mechanical design of an Orbital2 flexible pin multi-stage planetary wind turbine gear train using a three dimensional finite element/contact mechanics model and to compare to full system experiments. Root strain is calculated at multiple locations across the facewidth of ring gears from the computational model and compared to experimental data. Gear misalignment and carrier eccentricity are also considered. Design recommendations for improving load distribution across gear facewidths are also discussed.
Design of Circularly Towed Cable-Body Systems
Authors: Gottimukkala Varma , Rahn Christopher D.
Published: June 2012

Circularly towed cable-body systems can be used to pickup and deliver payloads, provide surveillance, and tow aerial and marine vehicles. To provide a stable operating platform, the body or end mass should have a unique and stable steady state solution with small diameter so that it travels at a much slower speed than the tow vehicle. In this paper, the minimum damping is calculated that ensures the stable single valued steady state solutions as a function of non-dimensional system parameters including cable length and end mass. Steady state solutions are found using the numerical continuation and bifurcation analysis and Galerkin’s method provides the linearized vibration equations that determine stability. Bifurcation analysis is also used to find the minimum achievable end mass radius. A design algorithm is presented and demonstrated using an example.
Multi-Terrain Vehicle Active Suspension Control Modeling and Design
Authors: Masood Jawad , Zoppi Matteo , Molfino Rezia
Published: June 2012

This paper presents the progress of work toward state of art design and development of active suspension low level impedance control for high speed (> 80km/h) multi-terrain vehicles. We have used a quarter car suspension model for mechanical system modeling. The system utilizes hydraulic actuation to change the impedance at joints. The control strategy is designed such that the excitation force or disturbance from the environment is balanced such that the system follows ideal impedance parameters. Control synthesis is performed on the position control scheme for the analysis of sensitivity, robustness and performance. In the end different control tuning techniques are used to improve the impedance control performance under environmental conditions.
Mapping Problem and Requirements to Final Solution: A Document Analysis of Capstone Design Projects
Authors: Joshi Shraddha , Morkos Beshoy , Summers Joshua D.
Published: June 2012

Formulating and solving engineering problems and designing solutions that meet the established requirements are important skills that graduating engineering students need to possess. However, there are noticeable gaps in the literature with respect to understanding how the formulation of design problems and establishment of requirements affect the final design solution in undergraduate design education. This paper is an initial step to understand the influence of level of detail of problem statement and requirements on the level of detail of final solution in capstone design projects. In doing so, a document analysis of final reports from capstone design class collected over a period of ten years, 1999 to 2008, is conducted. A data compression approach is developed to allow for the mapping of level of detail of problem statement and requirements to the level of detail of final solution. The findings of this research indicate that a low level of detail problem statement and requirements leads to no greater than a medium level of detail in the final solution. A high level of detail of final solution is more likely to result from either a high or medium level of detail of problem statement and requirements. Additionally, it was found that a high level of detail final solution is more likely to result in a high percentage of requirements satisfied. These findings are used to make several recommendations to improve the level of detail of the problem statement and requirements so a high level of detail final solution is developed while satisfying a great number of requirements. This assists in ensuring that students possess the skills needed before entering the professional workforce.
Complexity as a Surrogate Mapping Between Function Models and Market Value
Authors: Mathieson James L. , Shanthakumar Aravind , Sen Chiradeep , Arlitt Ryan , Summers Joshua D. , Stone Robert
Published: June 2012

The purpose of this paper is to investigate if early stage function models of design can be used to predict the market-value of a commercial product. In previous research, several metrics of complexity of graph-based product models have been proposed and suitably chosen combinations of these metrics have been shown to predict the time required in assembling commercial products. By extension, this research investigates if this approach, using new sets of combinations of complexity metrics, can predict market-value. To this end, the complexity values of function structures for eighteen products from the Design Repository are determined from their function structure graphs, while their market values are procured from different vendor quotes in the open market. The complexity and value information for fourteen samples are used to train a neural net program to define a predictive mapping scheme. This program is then used to predict the value of the final four products. The results of this approach demonstrate that complexity metrics can be used as inputs to neural networks to establish an accurate mapping from function structure design representations to market values to within the distribution of values for products of similar type.
Metamodeling in Product and Process Design
Authors: Turner Cameron J.
Published: June 2012

As computational capabilities have increased, so too has our ability to apply engineering simulations to problems of ever increasing complexity. Unfortunately, while our desire to apply engineering analysis to problems of increasing complexity; the computational burden of these analysis tools often precludes their direct use on design problems where iteration is the norm. Not only does design entail iteration, the practice of design optimization relies upon iterative methods to arrive at an optimal and or robust design solution. Surrogate models, often called metamodels or models of models, are a common solution to this challenge. Numerous metamodeling techniques are available to the engineering designer. However, all metamodels face common issues in the acquisition of sufficient data to support the metamodel, algorithms to fit the metamodel to the data, and methods to exploit the metamodel for tasks such as design space visualization, analysis and optimization. This paper reviews the state of the art in metamodeling as a tool for product and process design. In addition to reviewing the various types of metamodels in use, discussions of current research issues in data acquisition, modeling the design space and using metamodels in product and process design are discussed. This review is intended to define the foundation for other papers within the conference session.
DC Motor Selection for Hybrid and Electric Vehicles Using an Infinitely Variable Transmission
Authors: Groen Benjamin C. , Todd Robert H.
Published: June 2012

Demand for more fuel efficient and less polluting vehicles has motivated development of the electric and hybrid power-trains. Unfortunately, some components used in these vehicles are expensive and complex. This research summarizes DC motor types, DC speed control methods and the use of an Infinitely Variable Transmission (IVT) to reduce the cost of the vehicle. A safe, low cost and repeatable laboratory setup was designed and documented for educational use. Motor testing revealed that field weakening can be a low-cost speed-control method but has limited range of control and must be supplemented. Additionally it was determined that a mechanical differential can be used as an IVT by varying the speed of the input motors. An innovative concept is presented using one DC motor as a power or traction motor, while another motor acts as a vehicle speed controller. This concept eliminates the need for expensive complex AC motor controllers, improves safety and efficiency, and reduces battery management requirements by lowering the operating voltage of the system.
A Method for Inferring Conditional Stochastic Failure Rates From the Time-History of Observed Failures
Authors: Thompson David , Pe´bay Philippe
Published: June 2012

Observed failures, rather than first principles, are used to estimate fatigue rates probabilistically conditioned on operating conditions. The method developed assumes that a normal random variable may be used to approximate the damage limit (remaining lifetime) of components subjected to cumulative damage and that when a component fails, its damage limit has vanished at a rate proportional to the amount of time spent at each operating condition experienced during its lifetime. By considering differences in cumulative damage between pairs of failed components, we obtain the relative rates at which damage is accumulated for each observed operating condition. When the differences in component lifetimes are dominated by variations in experienced conditions, it is possible to estimate absolute rates. Otherwise, variations in initial damage limits dominate and it is only possible to estimate the mean and variance of this distribution. We demonstrate the procedure on synthetic data, including a test for the dominant source of lifetime variations.
An Approach Toward Making a Design Decision Based on Future Demand Prediction
Authors: Takai Shun , Razu Swithin S. , Yang Tae G.
Published: June 2012

This paper presents an approach for modeling uncertainty of future demand according to a forecast of an influential exogenous variable, which serves as the first step toward making a product design decisions based on future demand prediction. Optimum product design that maximizes expected profit or expected utility of profit depends on future demand influenced by future exogenous variables (i.e., economic, societal, and political variables beyond designers’ control). For example, an optimum design among gasoline, hybrid, electric, and fuel cell vehicles may depend on economic variables such as future gasoline prices, societal variables such as future climate change, and political variables such as future government standards for fuel-efficient vehicles. However, in particular for large-scaled and complex products, designers quite often make design decisions many years before the product is introduced to the marketplace without knowing future exogenous variables. To enable designers to make design decisions according to predicted demands, this study proposes to link demand distributions with exogenous variables and update demand distributions based on exogenous variable forecasts and their degrees of accuracies. An illustrative example is used to demonstrate impacts of exogenous variable forecasts and their accuracies on future demand prediction and expected profit calculation of a fuel cell vehicle.
Reduced Order Modeling of a Bladed Rotor With Geometric Mistuning via Estimated Deviations in Mass and Stiffness Matrices
Authors: Bhartiya Yasharth , Sinha Alok
Published: June 2012

This paper deals with further development of Modified Modal Domain Analysis (MMDA), which is a breakthrough method in the reduced order modeling of a bladed rotor with geometric mistuning. The main focus of this paper is to show that deviations in mass and stiffness matrices due to mistuning, estimated by Taylor series expansions in terms of independent Proper Orthogonal Decomposition variables representing geometric variations of blades, can be used for MMDA. This result has rendered Monte Carlo simulation of the response of a bladed rotor with geometric mistuning to be easy and computationally efficient.
Control of Constrained Systems Described by Lagrangian DAEs
Authors: Frye Jason P. , Fabien Brian C.
Published: June 2012

In this paper, a nonlinear controller design for constrained systems described by Lagrangian differential algebraic equations (DAEs) is presented. The controller design utilizes the structure introduced by the coordinate splitting formulation, a numerical technique used for integration of DAEs. In this structure, the Lagrange multipliers associated with the constraint equations are eliminated, and the equations of motion are transformed into implicit differential equations. Making use of this, a feedback linearizing controller can be chosen for successful motion tracking of the constrained system. Numerical examples demonstrate the controller design can be successfully applied to fully actuated and underactuated systems.
Measuring Effective Modulus With Bifurcation Based Atomic Force Microscope Method
Authors: Huang Wei , Dick Andrew J.
Published: June 2012

The atomic force microscope (AFM) is a high-resolution measurement tool for sample topography and material properties in nano-scale and micro-scale research. The dynamics of the cantilever probe in AFM is affected by the intrinsically nonlinear interaction between the probe tip and the sample. Previous works have shown that in off-resonance excited intermittent-contact AFM, a period-doubling bifurcation occurs as a result of the nonlinearity. The sub-harmonic amplitude of the response is used as the source of contrast to measure the effective modulus of the sample. This paper further investigates the performance of this proposed measurement method on more complicated 1-D samples and 2-D samples. The nonlinear relationship between the sub-harmonic amplitude and the tip-sample separation raises new challenges to the traditional PI controller. The design of the controller is revisited and modified in this paper to improve measurement accuracy.
Cost-Effective Measurements of Piezoelectric Coefficient d33 of Thin-Film PZT Using a Mini Force Hammer
Authors: Guo Qing , Cao G. Z. , Shen I. Y.
Published: June 2012

Lead Zirconate Titanate (PbZrxTi1−xO3 or PZT) is a piezoelectric material widely used as sensors and actuators. For microactuators, PZT often appears in the form of thin films to maintain proper aspect ratios. One major challenge encountered is accurate measurement of piezoelectric coefficients of PZT thin films. In this paper, we present a simple, low-cost, and effective method to measure piezoelectric coefficient d33 of PZT thin films through use of basic principles in mechanics of vibration. We use a small impact hammer with a tiny tip to generate an impulsive force acting perpendicularly to the surface of a PZT film. In the meantime, we measure the impulsive force via a load cell and the responding charge of the PZT thin film via a charge amplifier. Then the piezoelectric coefficient d33 is obtained from the measured force and charge based on piezoelectricity and a finite element modeling. We also conduct a thorough parametric study to understand the sensitivity of this method on various parameters, such as substrate material, boundary conditions, specimen size, specimen thickness, thickness ratio, and PZT thin-film material. To demonstrate the feasibility, we calibrate the new method via a PZT thick film disk resonator with a known d33. Experimental results show that d33 measured via this method is as accurate as those from the manufacturer’s specifications within its tolerance. We then apply the new method to PZT thin films deposited on silicon substrate, and successfully measure the corresponding piezoelectric coefficient d33.
Fabrication of Pillared PLGA Microvessel Scaffold Using Femtosecond Laser Ablation
Authors: Wang Hsiao-Wei , Cheng Chung-Wei , Li Ching-Wen , Wang Gou-Jen
Published: June 2012

One of the continuing, persistent challenges confronting tissue engineering is the lack of intrinsic microvessels for the transportation of nutrients and metabolites. An artificial microvascular system can be a feasible solution to this problem. In this study, the femtosecond laser ablation technique was implemented for the fabrication of pillared microvessel scaffolds in PLGA. This novel scaffold enable the conventional cell seeding process to be implemented and the progress of cell growth to be observed in vitro by an optical microscopy. Hence, the milky and completely opaque problems of the conventional PLGA scaffold after cell seeding can be resolved. Currently, PLGA microvessel scaffolds consisting of 30μm×200μm pillared branches have been produced. Cell cultural results of BECs demonstrate that cells can well adhere and grow surrounding each branch of the proposed pillared microvessel networks. The promising results reveal that an artificial microvessel networks for tissue engineering can be completely realized.
Equivalent Standard Deviation to Convert High-Reliability Model to Low-Reliability Model for Efficiency of Sampling-Based RBDO
Authors: Lee Ikjin , Choi Kyung K. , Gorsich David
Published: June 2012

This study presents a methodology to convert an RBDO problem requiring very high reliability to an RBDO problem requiring relatively low reliability by increasing input standard deviations for efficient computation in sampling-based RBDO. First, for linear performance functions with independent normal random inputs, an exact probability of failure is derived in terms of the ratio of the input standard deviation, which is denoted by δ. Then, the probability of failure estimation is generalized for any random input and performance functions. For the generalization of the probability of failure estimation, two coefficients need to be determined by equating the probability of failure and its sensitivity with respect to the standard deviation at the current design point. The sensitivity of the probability of failure with respect to the standard deviation is obtained using the first-order score function for the standard deviation. To apply the proposed method to an RBDO problem, a concept of an equivalent standard deviation, which is an increased standard deviation corresponding to the low reliability model, is also introduced. Numerical results indicate that the proposed method can estimate the probability of failure accurately as a function of the input standard deviation compared to the Monte Carlo simulation results. As anticipated, the sampling-based RBDO using the surrogate models and the equivalent standard deviation helps find the optimum design very efficiently while yielding relatively accurate optimum design which is close to the one obtained using the original standard deviation.
Combined Nodal and Non-Conformal Contact Approach for the Analysis of Turnout Negotiations of Multibody Railroad Vehicles
Authors: Sugiyama Hiroyuki , Sekiguchi Takuto , Matsumura Ryosuke , Yamashita Shunpei , Suda Yoshihiro
Published: June 2012

In this investigation, a numerical procedure that can be used for solving complex wheel/rail contact problems in turnout is proposed. In particular, a combined nodal and non-conformal contact approach is developed such that significant jumps in contact points are detected using the nodal search, while the exact location of contact point is then determined with continuous surface parameterizations using non-conformal contact equations. With this combined nodal and non-conformal contact approach for the contact geometry analysis of vehicle/turnout interactions, multiple look-up contact tables can be generated in an efficient way without losing accuracy. Since detailed contact search is performed offline to obtain look-up contact tables, significant changes in contact points in turnout can be efficiently predicted online with tabular data to be interpolated in a standard way. Several numerical examples are presented in order to demonstrate the use of the numerical procedure developed in this investigation.
Static Modes Switching: On-Line Variable Static Augmentation for Efficient Flexible Multibody Simulation
Authors: Tamarozzi Tommaso , Heirman Gert H. K. , Desmet Wim
Published: June 2012

This paper discusses and further investigates a new methodology, “Static Modes Switching” (SMS), improving computational efficiency for elastic multibody (EMBS) systems. This method focuses on mechanisms in which loading is possible in many degrees of freedom, but only few of them are simultaneously loaded at a given moment in time (e.g. sliding elements, gear contact, etc.). The methodology adapts during simulation the mode set used to represent component flexibility, by judiciously choosing only those static modes that are contributing actively to the body deformation. First, the general methodology is presented, then the current work and its original contributions are discussed; namely SMS is tested on a 3D mechanism including multiple flexible bodies on which sliding elements are present. Moreover, as opposed to previous studies, the locations where external excitation is acting is not known a priori. Finally, some limitations of the proposed methodology are treated with focus on the numerical discontinuities introduced by the switching of the modal base and their propagation to neighbouring bodies.
Deviations of Visual Expectation From Somatosensory Experience in Emotional Quality: Effects of Surface Characteristic in Context of “Lifting Object”
Authors: Yanagisawa Hideyoshi , Yuki Norihito
Published: June 2012

A deviation of reality from our prior expectation causes positive or negative emotions such as unexpected pleasure or disappointment depending on the condition. Although recognition of this psychological phenomenon has much potential in the design of a product’s emotional quality, i.e., that which evokes the customer’s specific feelings, impressions, or emotions, this factor is largely unexplored. In the transition from prior expectation to posterior experience, we often observe switching sensory modalities, such as from vision to touch. In this paper, we discuss the differences in emotional quality between different sensory modalities in the context of shifting from visual expectation to somatosensory experience. As a case study, we investigate the effects of an object’s surface characteristics on the deviation from visual expectation in the context of “lifting an object”. In this context, the sensory modality shifts from vision to touch and vision, i.e., we see and then lift a target object. We conducted an experiment using cylinder-shaped objects of equal weight with different surface characteristics such as brightness, roughness and gloss. The experiment consists of three phases. 1) We asked eight participants to give their impressions by only looking at the object using adjectives and onomatopoeias, 2) we asked them to lift the objects and recorded their grip force, and 3) we conducted the same evaluation as the first phase except that the participants were allowed to pick up the objects. The results show that the deviation from visual prediction regarding object massiveness and surface roughness can be observed using redundant grip force differences, and that this deviation affects a posteriori tactile emotional qualities such as tactile feelings. With the result, we discuss the need to consider such deviations in emotional quality design.
Eccentricity Effect Analysis in Right-Angle Gear Dynamics
Authors: Peng Tao , Lim Teik C. , Yang Junyi
Published: June 2012

Geometric eccentricity here refers to the radial deviation (radial runout) of pinion or gear geometric center off its rotational center or axis. Such a typical manufacturing or assembly error in gear transmission exhibits inherent effects on the gear dynamic responses. Modeling of eccentricity has rarely been done for high speed right-angle gears such as hypoid or spiral bevel gears. In this paper, two modeling methods are proposed to quantitatively represent the eccentricity in the hypoid/bevel gear dynamic analysis. The first method is based on the loaded tooth contact analysis (LTCA) for a long shaft period. The LTCA results are then used to synthesize the corresponding roll angle dependent varying mesh model parameters. A second simpler method using translational kinematic transmission error (TE) modification is proposed to reduce the computational time. The effects of eccentricity on the gear dynamic responses are then investigated. The eccentricity excited low frequency shaft order dynamics is found to affect not only the overall level of vibration but also the high frequency mesh order responses. The sideband responses are simulated and characterized. This study is expected to improve the right-angle gearing system dynamic analytical capability and assist in guiding the manufacturing or assembly error tolerance specification.
Fuzzy Dynamic Fault Tree Analysis of Hydraulic System of CNC Machining Center
Authors: Li Yan-Feng , Sun Jian , Li Haiqing , Huang Hong-Zhong , Liu Yu
Published: June 2012

Fault tree analysis (FTA), as an effective reliability assessment tool, is a widely used in analyzing the risk and reliability of large scale and complex engineering systems. Dynamic fault tree analysis (DFTA) extends the static fault tree by defining additional gates to model the complicated interactions, and in most case, Markov models can be used to solve dynamic gates. In many real systems, it is quite difficult to evaluate the probability of failure events preciously due to many uncertainty factors. To account for the uncertainty resulting from the lack of sufficient data or the subjective adjustments from experts, a fuzzy dynamic fault tree model is proposed to assess the system reliability when acquiring precious probability of failure event is impossible. With the aim of obtaining the membership function of the fuzzy probability of the top event, the extension principle is employed. The proposed method and algorithm are demonstrated by a case study of the hydraulic system of a specific CNC machining center.
Reciprocal Screw-Based Force-Closure of Cable-Driven Closed Chains
Authors: Mustafa Shabbir Kurbanhusen , Agrawal Sunil Kumar
Published: June 2012

Extensive research has been conducted in force-closure analysis of single rigid-bodied cable-driven platforms, and very recently of cable-driven open chains. However, force-closure analysis of cable-driven closed chains is still an open question. For the case of an n-DOF closed chain driven by cables, two important questions arise: (i) How can force-closure analysis be carried out for a given cable routing configuration while retaining the geometric insights of the problem? (ii) Are n+1 cables sufficient to fully constrain the entire closed chain? This paper will address these issues and propose a systematic and novel approach based on the reciprocal screw theory. The proposed methodology can analyze closed chains with arbitrary cable routings and the analysis shows that an n-DOF closed chain requires a minimum of n+1 cables to fully constrain it.
An Approach for Analysis of Load Sharing in Planetary Gear Drives With a Floating Sun Gear
Authors: Tsai Shyi-Jeng , Ye Siang-Yu , Huang Guan-Lin
Published: June 2012

The goal of the paper is to propose an approach for analysis of load sharing in the planetary gear drives with a floating sun gear based on a stiffness model for multiple gear-pair contact under consideration of the mesh stiffness of the engaged teeth, as well as the tooth gaps due to manufacturing errors and deviated position of the sun gear. The tooth stiffness of gears is expressed analytically considering the bending deflection and the contact deformation. The relations for tooth gaps due to various errors are derived from the mesh relations of gears based on the exact involute gear geometry. The balanced position of the floating sun gear is solved iteratively by using the load equilibrium conditions and the shared loads at the corresponding position of the sun gear. Finally some numerical examples are illustrated. The results calculated by the proposed approach have, an acceptable agreement with those by using FEM.
Nonlinear Vibration Analysis of Nano to Micron Scale Beams Under Electric Force Using Nonlocal Theory
Authors: Pasharavesh Abdolreza , Alizadeh Vaghasloo Y. , Ahmadian M. T. , Moheimani Reza
Published: June 2012

Electrostatically actuated beams are fundamental blocks of many different nano and micro electromechanical devices. Accurate design of these devices strongly relies on recognition of static and dynamic behavior and response of mechanical components. Taking into account the effect of internal forces between material particles nonlocal theories become highly important. In this paper nonlinear vibration of a micro\nano doubly clamped and cantilever beam under electric force is investigated using nonlocal continuum mechanics theory. Implementing differential form of nonlocal constitutive equation the nonlinear partial differential equation of motion is reformulated. The equation of motion is nondimentioanalized to study the effect of applied nonlocal theories. Galerkin decomposition method is used to transform governing equation to a nonlinear ordinary differential equation. Homotopy perturbation method is implemented to find semi-analytic solution of the problem. Size effect on vibration frequency for various applied voltages is studied. Results indicate as size decreases the dimensionless frequency increases for a cantilever beam and decreases for a doubly clamped beam. Size effect is specially significant as the beam size tends toward nano scale in the analysis.
Static Analysis of Electrically Actuated Nano to Micron Scale Beams Using Nonlocal Theory
Authors: Alizadeh Vaghasloo Y. , Pasharavesh Abdolreza , Ahmadian M. T. , Fallah Ali
Published: June 2012

In this paper, size dependent static behavior of micro and nano cantilevers actuated by a static electric field including deflection and pull-in instability, is analyzed implementing nonlocal theory. Euler-bernoulli assumptions are made to model the relation between deflection of the beam and bending moment. Differential form of the constitutive equation of nonlocal theory is used to find the revised equation for bending moment and substituting in the equilibrium equation of electrostatically actuated beams final nonlinear ordinary differential equation is arrived. Also the boundary conditions for solving the equation are revised and to analyze the size effect better governing equation is nondimetionalized. The one parameter Galerkin method is used to transform this equation to a nonlinear algebraic equation. Arrived algebraic equation is solved utilizing Newton-Raphson method. Size effect on the maximum deflection and deflection shape for various applied voltages is studied. Also effect of beam size on the static pull-in voltage is studied. Results indicate that the dimensionless beam deflection decreases as size decreases while the pull-in voltage increases and specially change of deflection and pull-in voltage is significant for nanobeams.
Discrete Fractional Calculus: Non-Equidistant Grids and Variable Step Length
Authors: Podlubny Igor , Skovranek Tomas , Petras Ivo , Verbickij Viktor V. , Chen YangQuan , Vinagre Jara Blas M.
Published: June 2012

In this paper we further develop Podlubny’s matrix approach to discretization of integrals and derivatives of arbitrary real order. Numerical integration and differentiation on a set of non-equidistant nodes is described and illustrated by several examples of numerical solution of fractional differential equations. In this paper, for the first time, we present a variable step length approach that we call “the method of large steps”, since it is applied in combination with the matrix approach for each “large step”. This new method is also illustrated by an example. The presented approach allows fractional order differentiation and integration of non-uniformly sampled signals, and opens the way to development of variable and adaptive step length techniques for fractional differential equations.
An Early-Stage Tool to Evaluate the Product Redesign Impact
Authors: Raffaeli Roberto , Mengoni Maura , Germani Michele
Published: June 2012

In order to face the rapid changing market requirements, companies need methods and tools in order to implement flexibility over the whole product development process, from ideation to manufacturing. The proposed approach targets the development of a method to support decision making in product redesign activities. Design alternatives and product modifications can be rapidly evaluated in terms of feasibility, cost and time. The approach is based on a product structure multilevel representation, where functions, modules, assemblies and components are strictly interrelated. The representation allows criteria and rules in order to efficiently connect the elements within the same level and among levels. Such connections will contain the values to estimate the impact of analyzed product changes. In this way the structure will serve as evaluation tool in the early redesign phases. In order to manage and interact with the structure a software tool has been developed, called Modulor. This system allows modeling the product representation and rapidly evaluating the consequences in terms of change propagation. The tool was tested within the R&D department of a large sized company producing household appliances. Pilot studies have revealed shorter redesign cycles thanks to a broader understanding of implications while deciding among several implementation solutions.
CFD Modelling of Moisture Content, Air Velocity and Thermal Patterns in the Tombs of Horemeheb in Valley of Kings
Authors: Khalil Essam E.
Published: June 2012

Airflow characteristics in ventilated and air-conditioned spaces play an important role to attain comfort and hygiene conditions. This paper utilizes a 3D Computational Fluid Dynamics (CFD) model to assess the airflow and relative humidity characteristics in ventilated and air-conditioned archaeological tomb of Horemheb in the Valley of the Kings in Luxor, Egypt. It is found that the best airside design system can be attained, if the airflow is directed to pass all the enclosure areas before the extraction with careful selection of near wall velocities to avoid any wear or aberration of the tomb-wall paintings. Still all factors and evaluation indices have the shortage to describe the influence of the recirculation zones on the occupancy zone of the visitors and also on the fresh supplied air. The mode of evaluation should assess the airflow characteristics in any tomb passage according to its position in the enclosure and the thermal pattern and air quality.
Flow Regimes and Thermal Comfort Around Spectators in Air Conditioned Squash Courts
Authors: A. Munem Hesham S. , Abou El Kassem ElSayed K. , Khalil Essam E.
Published: June 2012

Although there are still a number of squash arenas that are not air-conditioned or heated; Air conditioning of squash courts has become a trend when design and establishing new squash courts as well as other sporting arena. The current paper numerically investigates the influence of location and number of air conditioning supply and extracts openings on air flow properties in spectators’ area within a squash area. The present work focuses on predicting air flow patterns and thermal behaviour through investigating of the air flow regimes and moisture content inside the spectators’ area. Furthermore, the work investigates the heat transfer behaviour through analysing temperature and relative humidity profiles within the area. Moreover, carbon dioxide dispersion is investigated in order to recommend design features that aid to achieve the thermal comfort environment inside the studied area. The present investigation made use of Computational Fluid Dynamics (CFD) simulation techniques as embedded in the commercially available code (FLUENT 6.2).
The Use of the Fixed Points Method for Optimal Damping of Harmonically Forced Cantilever Beams
Authors: Issa Jimmy S.
Published: June 2012

The use of viscous dampers for vibration attenuation in harmonically forced cantilever beams is studied. The system considered is a cantilever beam with a point harmonic force applied at a given location and a viscous damper attached to it from one end, and grounded from the other. An assumed mode model of the system is derived using the first two transverse modes of the beam. For any given positions of the point force and damper, the optimal damping constant which minimizes the maximum of the frequency response function at the tip of the beam is determined analytically. It is shown that the objective function passes through a number of points independent of the damping constant. These inevitable points are used in the determination of the maximum allowable value of the objective function. As the locations of the point force and damper are varied separately from the fixed end of the beam to its tip, a two dimensional region plot is generated illustrating the different regions where each of these points is the highest. The optimal damping constant is determined analytically by forcing the frequency response function to pass horizontally through the highest fixed point which is referred to as the active peak. Four different damping ratios are determined and depending on the positions of the force and damper, the two dimensional map is consulted in the selection of the correct optimal damping ratio. The solution obtained is unique except when the active peak is the static fixed point. In this case, the solution is made unique by modifying the objective function to further enhance the solution at high frequencies.
Fractional Variable Structure Control
Authors: Machado J. A. Tenreiro
Published: June 2012

This paper studies fractional order variable structure control algorithms. For that purpose the fractional order of the sliding mode is varied and its effect upon the system performance is evaluated. The test bed is constituted by a simple mechanical manipulator. Both the system response and the control effort are analysed. The results show that the fractional order provides an extra method for adjusting the closed loop system response.
Partitioned Model vs Parallelized Solver
Authors: Mikelsons Lars , Menager Nils , Schramm Dieter
Published: June 2012

Nowadays, engineers still search for more efficient methods in order to decrease simulation times. However, most simulation environments do not use the full power provided by modern PCs. Even though every modern computer is equipped with a multicore processor, only very few simulation environments use more than one core for simulations. There are various possibilities to parallelize simulations. One approach is to partition the model into several submodels. Using adequate solvers for each submodel can result in lower computation times, especially if there is a significant difference in the time constants of the submodels. Other approaches are based on parallelization of the ODE solver. For example, it is possible to parallelize the linear algebra methods inside the solver. Parallelization of the solver itself is another way to use the multicore architecture. From the modeling and simulation point of view, the latter approach is more interesting. Consequently, the question is whether it is beneficial to partition the model or to use a parallelized solver. In this paper this question is answered at least for an example system. However, the more efficient approach may not be the better approach for the usage inside a simulation environment. Therefore, it is discussed which approach can be automated and integrated easier into a simulation environment.
Managing Uncertainty in Multiscale Systems via Simulation Model Refinement
Authors: Sinha Ayan , Panchal Jitesh H. , Allen Janet K. , Mistree Farrokh
Published: June 2012

The motivating question for this article is: ‘How should a system level designer allocate resources for auxiliary simulation model refinement while satisfying system level design objectives and ensuring robust process requirements in multiscale systems? Our approach consists of integrating: (i) a robust design method for multiscale systems (ii) an information economics based approach for quantifying the cost-benefit trade-off for mitigating uncertainty in simulation models. Specifically, the focus is on allocating resources for reducing model parameter uncertainty arising due to insufficient data from simulation models. A comprehensive multiscale design problem, the concurrent design of material and product is used for validation. The multiscale system is simulated with models at multiple length and time scales. The accuracy of the simulated performance is determined by the trade-off between computational cost for model refinement and the benefits of mitigated uncertainty from the refined models. System level designers can efficiently allocate resources for sequential simulation model refinement in multiscale systems using this approach.
Leveraging Symbolic Programming in Engineering Courses: An Example
Authors: Venkataraman P.
Published: June 2012

Symbolic programming, available through software packages, is a useful resource for teaching and learning in upper level professional courses in the undergraduate engineering curriculum. It positively impacts both knowledge and comprehension. The knowledge of required mathematics, previously learnt but easily forgotten, is now available at the fingertips. Symbolic programming makes it accessible through a single line of code. The comprehension is encouraged by visually illustrating the mathematical results through simple graphic commands. Increased knowledge and comprehension improves student’s academic ability, confidence, and maturity. These are necessary drivers of innovation. It takes only a small collection of software commands to deliver these significant improvements in student learning. In this paper we showcase some examples that demonstrate how symbolic programming can be used to service the basic course in aerodynamics. We also highlight the small collection of commands. It is anticipated that every other course in the engineering curriculum that uses mathematics can be completely supported in a similar fashion.
A User Study to Evaluate the Function Model and Function Interaction Model for Concept Generation
Authors: Ramachandran Raveesh , Caldwell Benjamin W. , Mocko Gregory M.
Published: June 2012

Function modeling is often performed during the conceptual design phase to identify what the product must do in a solution independent form. However, function-based design approaches do not adequately enable designers to capture and analyze the non-functional requirements, interactions between the product of interest and other products and interactions between the product of interest and human users. This paper presents the results of a user study to evaluate how two models: (1) traditional function models (FM) and (2) the function interaction model (FIM), relate to functional and non-functional engineering requirements, and how they affect the creation of design solutions. Forty students were divided into two groups and asked to generate solutions for a design problem using either the function model (FM) or the function interaction model (FIM). The concepts were then evaluated in terms of quantity and quality by an external panel. Results from this study indicate that the quantity of solutions generated by the function model (FM) group is greater than the function interaction model (FIM) group. However, the quality of design concepts from the function interaction model (FIM) group is greater than the function model (FM) group. Further, nonfunctional requirements that are important to the design solutions cannot be captured in function model and thus are not reflected in the associated solution concepts.