bluuebunny/crossref_metadata_2025 huggingface dataset:
State Dependent Regenerative Delay in Milling Processes
Authors: Insperger Ta´mas , Ste´pa´n Ga´bor , Hartung Ferenc , Turi Janos
Published: June 2008

Traditional models of regenerative machine tool chatter use constant time delays assuming that the period between two subsequent cuts is a constant determined definitely by the spindle speed. These models result in delay-differential equations with constant time delay. If the vibrations of the tool relative to the workpiece are also included in the surface regeneration model, then the resulted time delay is not constant, but it depends on the actual and a delayed position of the tool. In this case, the governing equation is a delay-differential equation with state dependent time delay. Equations with state dependent delays can not be linearized in the traditional sense, but there exists linear equations that can be associated to them. This way, the local behavior of the system with state dependent delays can be investigated. In this study, a two degree of freedom model is presented for milling process. A thorough modeling of the regeneration effect results in the governing delay-differential equation with state dependent time delay. It is shown through the linearization of the nonlinear equation that an additional term arises in the linearized equation of motion due to the state-dependency of the time delay.
Experimental Research on Nonlinear Vibration Characteristics of Rotor Bearing System With Coupling Fault of Rub-Impact and Oil Whirl
Authors: Liu Changli , Zhang Yimin , Han Qing Kai , Wen Bangchun
Published: June 2008

An experimental rotor rig was developed to investigate nonlinear vibration characteristics of rotor bearing system with coupling fault of rub-impact and oil whirl. It was found that when the effect of oil film force on a rub-impact rotor system is comparatively weak, the rotor/stator rub-impact will cause the system to give rise to sub- and super-harmonic vibration components. In a rub-impact rotor system with oil whirl fault, super-harmonic vibration components were excited, when rotor/stator rub-impact happens before oil film whirl because of small rotor/stator clearance. When the rotor/stator clearance is comparatively large, the rub-impact happens after oil film whirl, and the effect of rub-impact on the rotor system will be very weak.
An Efficient Computation Method for Hopf Bifurcation of High Dimensional Systems
Authors: Zhu Songhui , Yu Pei , Jones Stacey
Published: June 2008

Normal form theory is a powerful tool in the study of nonlinear systems, in particular, for complex dynamical behaviors such as stability and bifurcations. However, it has not been widely used in practice due to the lack of efficient computation methods, especially for high dimensional engineering problems. The main difficulty in applying normal form theory is to determine the critical conditions under which the dynamical system undergoes a bifurcation. In this paper a computationally efficient method is presented for determining the critical condition of Hopf bifurcation by calculating the Jacobian matrix and the Hurwitz condition. This method combines numerical and symbolic computation schemes, and can be applied to high dimensional systems. The Lorenz system and the extended Malkus-Robbins dynamo system are used to show the applicability of the method.
A Novel Vibration Analysis of Stiff-Soft Structural Systems by the Method of Spectral Proper Orthogonal Decomposition
Authors: Georgiou Ioannis T. , Papadopoulos Christos I.
Published: June 2008

We have analyzed the computational dynamics of a complex one-dimensional structural system consisting of a number of alternating stiff and soft subsystems. In particular, the method of Proper Orthogonal Decomposition (POD) in the frequency domain has been applied to analyze the (single-frequency) steady state dynamics in terms of spectral amplitudes and spatial shapes of proper orthogonal modes. It is shown that the dominant POD modes of such a multi-body system are sensitive to imperfections. The processing of the computational dynamics by the spectral-POD method leads to a novel computation of the transfer function of the system.
Creation of Assembly Models to Support Automated Concept Generation
Authors: Rajagopalan Venkat , Bryant Cari R. , Johnson Jeremy , McAdams Daniel A. , Stone Robert B. , Kurtoglu Tolga , Campbell Matthew I.
Published: June 2008

This paper presents an assembly model process that fully characterizes the structural and flow interactions between artifacts in a product. Reverse engineering techniques were employed during the analysis of thirty-three existing consumer products to arrive at a concise standardization of the modeling process. During the product investigation, four different types of structural interactions were identified. These structural interactions, couple, secure, position and guide, were defined using a standardized vocabulary of functional terms. These four structural interactions are rigorously described in this paper in an effort to outline an assembly model method that is accurate and repeatable. Additionally, flow interactions between components are also characterized within the presented modeling technique. A rough representation of the artifact configuration of a product can also be achieved through placement of the component structures in the model. Analysis of the consumer product set also revealed that a new design tool can be generated using the structural interaction information contained in the described assembly models.
Using Q-Learning and Genetic Algorithms to Improve the Efficiency of Weight Adjustments for Optimal Control and Design Problems
Authors: Kamali Kaivan , Jiang Lijun , Yen John , Wang K. W.
Published: June 2008

In traditional optimal control and design problems, the control gains and design parameters are usually derived to minimize a cost function reflecting the system performance and control effort. One major challenge of such approaches is the selection of weighting matrices in the cost function, which are usually determined via trial and error and human intuition. While various techniques have been proposed to automate the weight selection process, they either can not address complex design problems or suffer from slow convergence rate and high computational costs. We propose a layered approach based on Q-learning, a reinforcement learning technique, on top of genetic algorithms (GA) to determine the best weightings for optimal control and design problems. The layered approach allows for reuse of knowledge. Knowledge obtained via Q-learning in a design problem can be used to speed up the convergence rate of a similar design problem. Moreover, the layered approach allows for solving optimizations that cannot be solved by GA alone. To test the proposed method, we perform numerical experiments on a sample active-passive hybrid vibration control problem, namely adaptive structures with active-passive hybrid piezoelectric networks (APPN). These numerical experiments show that the proposed Q-learning scheme is a promising approach for.
Twinkling a Random Search Algorithm for Design Optimization
Authors: Mekhilef Mounib
Published: June 2008

In this paper we are going to show that applying the twinkling technique on a naive random search algorithm is frequently more powerful than any algorithm using specific research techniques unless they use information provided by the gradient or the Hessian. In order to illustrate this result we have made the choice of the study of a mechanical system characterized by the non-linear nature of the optimization space. This system is basically an open kinematics chain that represents a robot which has to go through various different trajectories defined by a set of temporally equidistant points. In fact, we are going to show that the genetic algorithm, the simulated annealing algorithm, the particle swarm algorithm, the random search algorithm, need to use comparatively, a huge number of function evaluations in order to perform the same result quality.
Stability, Bifurcation and Jumping Phenomenon in a 2-D Model of Supersonic Lifting Surfaces
Authors: Yu Pei , Chen Zhen , Librescu Liviu , Marzocca Piergiovanni
Published: June 2008

This paper is concerned with the linear/nonlinear aeroelastic control of 2-D supersonic lifting surfaces. Its goal is to provide the feedback control mechanism enabling one to enlarge the flight envelope by increasing the flutter speed, and also to control the character, benign/catastrophic of the flutter instability boundary. Structural and aerodynamic nonlinearities are included in the aeroelastic governing equations, and linear and nonlinear feedback controls in both plunging and pitching are employed in conjunction with proportional velocity feedback controls. The attention of the paper is focused on multiple Hopf bifurcations. In particular, the jumping phenomenon found in our previous work will be further investigated to reveal the physical implications. It is found that such a jumping occurs when the system has multiple families of limit cycles bifurcating from a same set of parameter values with multiple solutions for frequencies. The case investigated in this paper is restricted to zero structure damping. Center manifold reduction and normal form theory are applied to consider the stability of post-flutter solutions and the associated jumping phenomenon. Numerical simulations are presented to show the implications of time delay in the considered controls.
Parametric Modeling Method for Conceptual Vehicle Design
Authors: Wan Jian , Wang Nanxin , Gomez-Levi Gianna
Published: June 2008

Early conceptual design is one of the most important stages in vehicle product development. At this stage, various iterations of design, analysis, validation, and confirmation need to be carried out with limited and constantly changing vehicle design information. To overcome this difficulty, computer aided design tools are widely used. Various parametric concept models are created and employed to increase the number of design iterations and reduce the design cycle time. However, two of the most common challenges still exist: 1) how to build a parametric model that is flexible and robust while maintaining adequate accuracy, and 2) how to easily manipulate the model based on limited dimensional and geometrical input available at early design stages. In this paper, a parametric modeling and controlling method is presented. It has been developed to generate and manipulate a parametric vehicle concept model for vehicle design at early design stages. This method greatly improves the flexibility and robustness of the parametric concept model, and allows easy modifications of the model based on the limited available input.
An Interval-Based Focalization Method for Decision-Making in Decentralized, Multi-Functional Design
Authors: Panchal Jitesh H. , Ferna´ndez Marco Gero , Allen Janet K. , Paredis Christiaan J. J. , Mistree Farrokh
Published: June 2008

Multi-functional design problems are characterized by strong coupling between design variables that are controlled by stakeholders from different disciplines. This coupling necessitates efficient modeling of interactions between multiple designers who want to achieve conflicting objectives but share control over design variables. Various game-theoretic protocols such as cooperative, non-cooperative, and leader/follower have been used to model interactions between designers. Non-cooperative game theory protocols are of particular interest for modeling cooperation in multi-functional design problems. These are the focus of this paper because they more closely reflect the level of information exchange possible in a distributed environment. Two strategies for solving such non-cooperative game theory problems are: a) passing Rational Reaction Sets (RRS) among designers and combining these to find points of intersection and b) exchanging single points in the design space iteratively until the solution converges to a single point. While the first strategy is computationally expensive because it requires each designer to consider all possible outcomes of decisions made by other designers, the second strategy may result in divergence of the solution. In order to overcome these problems, we present an interval-based focalization method for executing decentralized decision-making problems that are common in multi-functional design scenarios. The method involves propagating ranges of design variables and systematically eliminating infeasible portions of the shared design space. This stands in marked contrast to the successive consideration of single points, as emphasized in current multifunctional design methods. The key advantages of the proposed method are: a) targeted reduction of design freedom and b) non-divergence of solutions. The method is illustrated using two sample scenarios — solution of a decision problem with quadratic objectives and the design of multi-functional Linear Cellular Alloys (LCAs). Implications include use of the method to guide design space partitioning and control assignment.
A Computational Technique for Concept Generation
Authors: Bryant Cari R. , McAdams Daniel A. , Stone Robert B. , Kurtoglu Tolga , Campbell Matthew I.
Published: June 2008

Few computational tools exist to assist designers during the conceptual phase of design, and design success is often heavily weighted on personal experience and innate ability. Many well-known methods (e.g. brainstorming, intrinsic and extrinsic searches, and morphological analysis) are designed to stimulate a designer’s creativity, but ultimately still rely heavily on individual bias and experience. Under the premise that quality designs comes from experienced designers, experience in the form of design knowledge is extracted from existing products and stored for reuse in a web-based repository. This paper presents an automated concept generation tool that utilizes the repository of existing design knowledge to generate and evaluate conceptual design variants. This tool is intended to augment traditional conceptual design phase activities and produce numerous feasible concepts early in the design process.
Modal Synthesis Method for Poroelastic Fluid-Structure Coupled Problems Including Structural Damping
Authors: Penning Pascal , Ohayon Roger , Kehr-Candille Ve´ronique
Published: June 2008

At low frequency, modal synthesis is usually used to solve the vibrational fluid-structure interaction problem. The modal technique application for elasto-poro-acoustic complex structures requires a modal description of the poroelastic vibroacoustic behaviour. Some recent works concerning the application of modal techniques for the displacement pressure equation of the generalized Biot’s model were published. Dazel proposes a modal decomposition based on the use of complex modes. This work consists in projecting the poroelastic system on a truncated basis of damped and coupled modes. In the mode calculation, the author takes into account fluid-structure interaction, viscous and thermal dissipations but structural damping is neglected. This paper presents a modal approach allowing to reduce the size of the poroelastic matrix system and to predict more effectively the porous material vibroacoustic behaviour. Starting from Dazel’s works, this modal approach is based on complex modes, modal synthesis, modal projection and modal superposition techniques. The originality of this paper is to take into account the porous material structural damping in the poroelastic mode calculation.
Simulation of a MEMS RF Filter
Authors: Abdel-Rahman Eihab M. , Hammad Bashar K. , Nayfeh Ali H.
Published: June 2008

We simulate the motions in a MEMS bandpass Radio-Frequency (RF) filter. The filter model is obtained by discretizing the Lagrangian of the distributed-parameter system using a Galerkin procedure. The Euler-Lagrange equations are then used to obtain a two-degree-of-freedom model consisting of two non-linearly coupled ordinary-differential equations of motion. We use the model to study the transmission characteristics of a bandpass filter made up of two coupled resonators. Three distinct response regimes, separated by two critical amplification levels Vcr1 and Vcr2, are identified in the filter response. For amplification levels up to Vcr1, the pass signal is artifact free. Two types of artifacts due to the filter dynamics appear and distort the signal for amplification levels beyond Vcr1.
Dynamic Analysis of a Torsional MEMS Scanner Mirror: Part 2 — Sensitivity Analysis Framework
Authors: Meral Faik Can , Basdogan Ipek
Published: June 2008

Next generation optical Micro Electro Mechanical Systems (MEMS) such as micro mirrors and micro scanners will extend the resolution and sensitivity offered by their predecessors. It is advantageous to predict the performance of such systems early in the design stage. In this study, we developed a sensitivity analysis framework to investigate the effect of the modal and physical parameters on the performance of a torsional MEMS scanner. The sensitivity framework described in this paper is related to the disturbance analysis framework which was introduced in the first part of this study. Disturbance analysis framework uses the Lyapunov Approach to obtain root-mean-square (RMS) values of the mirror rotation angle under the effect of a disturbance torque. Analytical formulas were derived for the calculation of the modal parameter sensitivities and the results were verified by the finite difference method. The analytical formulas for the calculation of physical parameter sensitivities were described but they were found to be very inefficient due to the complexity and computational expense in calculating the eigenvalue and eigenvector derivatives included in these equations. Instead, the finite difference method was used to calculate the physical parameter sensitivities for the torsional MEMS scanner.
Application of Car Semi-Active Suspension Systems to Achieve Desired Performance on Decreasing Effect of Road Excitation on Human Health
Authors: Sharifi Sedeh Reza , Abdollahpour Rooholah , Ahmadian Mohamad Taghi , Sadati Nasser
Published: June 2008

Using passenger cars for daily traveling include advantages and disadvantages simultaneously; this daily traveling causes variety of road excitations in the form of vibration with different amplitude and acceleration to be imposed on body. Exceeding the standard limitations of these parameters results in fatigue, restlessness, and health problems. In this paper, a quarter-car model with semi-active suspension system is considered and three control approaches are applied to reduce these parameters in the limit of standard. Results show adaptive fuzzy optimal controller has better performance compared to others in controlling the critical health parameters, and can be easily used in future cars for minimizing unexpected hazards imposed on human body due to road excitations.
Online Case Studies and a Process Description for Product Platform Planning
Authors: Srinivasan Anand , Sahin Asli , Terpenny Janis P. , Simpson Timothy W. , Kumara Soundar R. T. , Shooter Steven B. , Stone Robert B.
Published: June 2008

Product Platform Planning is an emerging philosophy that calls for the planned development and deployment of families of related products. It is markedly different from the traditional product development process, which focuses on optimized designs for individual products. This is a relatively new development in engineering design, which is not typically a part of an engineer’s education. Furthermore, it is different from traditional engineering topics in that it requires an integration of principles from both management and engineering design. All this makes for a new and different topic for which educational material needs to be developed. To address these needs, an online resource has been developed. This resource includes a set of three cases, a tutorial, and a glossary in a multimedia format hosted on the Internet. The tutorial developed for the website presents the basic concepts as well as current research on planning and architecting families of products. The case study section has three cases based on a family of popular power tools. The cases present information in the form of function diagrams, assembly diagrams, customer needs and market-segment data. Links are provided to helpful sites, as well as to relevant sections in the tutorial. Although product platform planning is a relatively new development, a variety of approaches have been used by the research community and practitioners in industry. A need was felt for a comprehensive, coherent source of knowledge in this field on which to base the case studies, and also as a means to providing a single source of information to users of this resource. Accordingly, a literature review was conducted and an overall process description was developed. This paper presents and describes the online learning resource which was developed. In addition, the literature review and the process description of platform planning that were developed are also detailed.
Efficient Simulation of a Dynamic System With LuGre Friction
Authors: Do Nguyen B. , Ferri Aldo A. , Bauchau Olivier
Published: June 2008

Friction is a difficult phenomenon to model and simulate. One promising friction model is the LuGre model, which captures key frictional behavior from experiments and from other friction laws. While displaying many modeling advantages, the LuGre model of friction can result in numerically stiff system dynamics. In particular, the LuGre friction model exhibits very slow dynamics during periods of sticking and very fast dynamics during periods of slip. This paper investigates the best simulation strategies for application to dynamic systems with LuGre friction. Several simulation strategies are applied including the explicit Runge-Kutta, implicit Trapezoidal, and implicit Radau-IIA schemes. It was found that both the Runge-Kutta and Radau-IIA methods performed well in simulating the system. The Runge-Kutta method had better accuracy, but the Radau-IIA method required less integration steps.
Fuzzy Heuristic Gradient Projection for Frame Topology Optimization
Authors: Senousy Mohamed S. , Hegazi Hesham A. , Metwalli Sayed M.
Published: June 2008

In this paper, a new methodology to obtain an optimal structure size considering geometries nonlinearity is presented. This method makes use of Heuristic Gradient Projection method in addition to Fuzzy Logic. The Heuristic Gradient Projection (HGP) method, a previously developed method for 3D-frame design and optimization, utilizes mainly bending stress relations in order to simplify the process of iterations. HGP is based on comparing the resulting equivalent stress with the allowable stress value. The proposed Fuzzy Heuristic Gradient Projection (FHGP) approach incorporates both bending stress and axial stress when processing with the allowable stress value. The weighting factors of both axial and bending stresses are found using a Fuzzy Logic controller. Fuzzy logic is incorporated to reach an optimal solution with lesser number of function evaluations. A simple cantilever example, subjected to axial force and bending moment, is presented to illustrate this approach in addition to a 10-member planar frame that is used to prove the efficacy of the new method. FHGP approach generally results in faster convergence.
The Value of Using Imprecise Probabilities in Engineering Design
Authors: Aughenbaugh Jason Matthew , Paredis Christiaan J. J.
Published: June 2008

Engineering design decisions inherently are made under uncertainty. In this paper, we consider imprecise probabilities (i.e. intervals of probabilities) to express explicitly the precision with which something is known. Imprecision can arise from fundamental indeterminacy in the available evidence or from incomplete characterizations of the available evidence and designer’s beliefs. Our hypothesis is that, in engineering design decisions, it is valuable to explicitly represent this imprecision by using imprecise probabilities. We support this hypothesis with a computational experiment in which a pressure vessel is designed using two approaches, both variations of utility-based decision making. In the first approach, the designer uses a purely probabilistic, precise best-fit normal distribution to represent uncertainty. In the second approach, the designer explicitly expresses the imprecision in the available information using a probability box, or p-box. When the imprecision is large, this p-box approach on average results in designs with expected utilities that are greater than those for designs created with the purely probabilistic approach. In the context of decision theory, this suggests that there are design problems for which it is valuable to use imprecise probabilities.
Converting Molecular Meshes Into Smooth Interpolatory Spline Solid Models
Authors: Daniels Joel , Cohen Elaine , Johnson David
Published: June 2008

The study and understanding of molecules, once the domain of blackboards and stick-and-ball models, has become more and more exclusively linked to the use of computer-aided visualizations. Our project seeks to return the physical facsimile to the biologists, allowing the use of tactile senses while interacting with and manipulating a physical model, thus aiding educational and research endeavors. To increase the effectiveness of such a tool, the model is constructed such that multiple levels of information are viewable within the single physical form, stressing the interaction between the assorted components within the molecule. We use the term 3-D physical visualizations to refer to the fabricated model, to avoid confusion with the common usage of model as a virtual representation on the computer. To effectively combine multiple components into a smooth manufacturable physical visualization, all components of the model must be in a homogeneous format. Our research sets forth a method for converting triangulated mesh data, as provided by the molecular modeling packages, into spline models. Spline models have the attractive qualities that they are smooth without triangular facets, can be combined using traditional boolean operations (and, or, not), and can be directly fabricated using modern CAD/CAM techniques. Our method divides the polyhedral representation into multiple rectangular grids, then fits interpolatory spline surfaces to the data in each region, while focusing on smoothly stitching the boundaries and corners of the spline surfaces in order to create a near G1 continuous model.
Web Service Interfaces for Design Repositories
Authors: Shaffer Joshua , Kopena Joseph B. , Regli William C.
Published: June 2008

Reuse of design knowledge is an important goal in engineering design, and has received much attention. A substantial set of algorithms, methodology, and developed systems exist which support various aspects of this goal. However, the majority of these systems are built around a particular user interface, often some form of Web-based repository portal. The work described here presents search and other core functionality as web services rather than a monolithic repository system. These services may then be employed by a variety of applications, integrating them into interfaces familiar to the designer, extending functionality, streamlining their use, and enabling them to be employed throughout the design process. This paper demonstrates this approach by wrapping previously developed repository search algorithms as web services, and then using these within a plug-in for an existing commercial CAD environment. Based on issues encountered in developing this demonstration, this paper also discusses the challenges and potential approaches toward a more general, widespread application of web services in engineering design.
Distribution of Sub and Super Harmonic Solution of Mathieu Equation Within Stable Zones
Authors: Nakhaie Jazar G. , Mahinfalah M. , Rastgaar Aagaah M. , Mahmoudian N.
Published: June 2008

The third stable region of the Mathieu stability chart, surrounded by one π-transition and one 2π-transition curve is investigated. It is known that the solution of Mathieu equation is either periodic or quasi-periodic when its parameters are within stable regions. Periodic responses occur when they are on a “splitting curve”. Splitting curves are within stable regions and are corresponding to coexisting of periodic curves where an instability tongue closes. Distributions of sub and super-harmonics, as well as quasi-periodic solutions are analyzed using power spectral density method.
Gaussian Process Meta-Models for Efficient Probabilistic Design in Complex Engineering Design Spaces
Authors: Wang Liping , Beeson Don , Akkaram Srikanth , Wiggs Gene
Published: June 2008

Probabilistic design in complex design spaces is often a computationally expensive and difficult task because of the highly nonlinear and noisy nature of those spaces. Approximate probabilistic methods, such as, First-Order Second-Moments (FOSM) and Point Estimate Method (PEM) have been developed to alleviate the high computational cost issue. However, both methods have difficulty with non-monotonic spaces and FOSM may have convergence problems if noise on the space makes it difficult to calculate accurate numerical partial derivatives. Use of design and Analysis of Computer Experiments (DACE) methods to build polynomial meta-models is a common approach which both smoothes the design space and significantly improves the computational efficiency. However, this type of model is inherently limited by the properties of the polynomial function and its transformations. Therefore, polynomial meta-models may not accurately represent the portion of the design space that is of interest to the engineer. The objective of this paper is to utilize Gaussian Process (GP) techniques to build an alternative meta-model that retains the properties of smoothness and fast execution but has a much higher level of accuracy. If available, this high quality GP model can then be used for fast probabilistic analysis based on a function that much more closely represents the original design space. Achieving the GP goal of a highly accurate meta-model requires a level of mathematics that is much more complex than the mathematics required for regular linear and quadratic response surfaces. Many difficult mathematical issues encountered in the implementation of the Gaussian Process meta-model are addressed in this paper. Several selected examples demonstrate the accuracy of the GP models and efficiency improvements related to probabilistic design.
Nonlinear Dynamics of Closed Spherical Shells
Authors: Nayfeh Ali H. , Arafat Haider N.
Published: June 2008

We investigate the axisymmetric dynamics of forced closed spherical shells. The nonlinear equations of motion are formulated using a variational approach and surface analysis. First, we revisit the linear eigenvalue problem. Then, using the method of multiple scales, we assess the possibility of the activation of two-to-one internal resonances between the different types of modes. Lastly, we examine the shell’s nonlinear responses to an axisymmetric primary-resonance excitation and analyze their bifurcations.
An Internet Interface for Engineering Design Courseware
Authors: Brennan Robert W.
Published: June 2008

In this paper we focus on an approach to make web-based design engineering courseware accessible for the engineering education community. The proposed approach uses a distributed database driven web server where design courseware, or “CDEN Modules”, are organized by topic and tier. We provide a description of the basic architecture that is used for the web server and an example of an interface that is based on this approach.
Computational Methods Applied to Modelica Simulation Models in a Web Based Framework
Authors: Johansson Bjo¨rn
Published: June 2008

In this paper, it is illustrated how computational design methods such as design optimization and probabilistic analysis is applied to system simulation models in a web based framework. Special emphasis is given models defined in the Modelica modeling language. An XML-based information system for representation and management of design data for use together with Modelica models as well as other types of models is proposed. This approach introduces a separation between the model of the system and data related to the design of the product. This is important in order to facilitate the use of computational methods in a generic way. A web based framework for integration of simulation models and computational methods is further illustrated. The framework is based on open standards for distributed computing and enables so-called service oriented architecture. Finally, an example is presented, where design optimization and probabilistic analysis is carried out on a Modelica model of an aircraft actuation system using the proposed and implemented tools and methods.
Effects of Product Usage Context on Consumer Product Preferences
Authors: Green Matthew G. , Tan Junjay , Linsey Julie S. , Seepersad Carolyn C. , Wood Kristin L.
Published: June 2008

We present a framework for understanding product usage context and its impact upon customer needs and product preferences. We conduct customer interviews with two sets of representative products from the functional families of “mobile lighting” and “food boiling” products. Customer interviews lead to identification and characterization of distinct product usage contexts. Interactive surveys measuring customer product choice support the hypothesis that customer product preferences differ for each usage context identified. Further analysis shows that attributes of these chosen products are related to factors of the usage context (e.g. mass is related to transportation mode). These results demonstrate that valuable insight for product design is available through an understanding of usage context, and future work will refine and test methods to formally bring contextual information to bear on product design. These capabilities will be especially important for contexts in which needs assessment has traditionally been difficult, such as with latent needs and frontier design environments.
Product Configuration Design Based on Extensible Product Family for Mass Customization
Authors: Zhang Shuyou , Cheng Harry H.
Published: June 2008

A new product configuration design method based on extensible product family is presented in this paper. The extensible product family is a multi-layered model with extensible function, extensible principle, and extensible structure. Treating extensible element as a basic unit, the model can be used to associate extensible parts with reusable factors in the range from 0 to 1. The principle of configuration method has been implemented in software. Complicated rule editing and modification are handled by Ch, an embeddable C/C++ interpreter. Designers can establish and edit the configuration rules including formulas dynamically. According to the client requirements and nearest-neighbor matching, the results of the designed configuration can be obtained automatically. Furthermore, the multi-dimensional information about parameters and reusable factors can be displayed and analyzed graphically. If the client requirements or configuration rules are changed, the system can be easily re-configured to obtain designed results based on the new configuration quickly. The system has been successfully deployed and used to design complicated products with a large number of configurations and different specifications such as elevators, machine tools and smut-collectors.
On the Effect of Faults in Vibration Control of Fairing Structures
Authors: Kim Young Man , Arora Anish , Kulathumani Vinodkrishnan , Arumugam Umamaheshwaran , Kulkarni Sandeep
Published: June 2008

Sensor-actuator networks are increasingly being used in distributed control applications. The cost of sensors and actuators is dropping substantially and hence control by a large number of these components is now feasible. One such application is the damping of acoustic and structural vibration associated with the launch of a rocket. Reliability in the presence of faults is critical for such mission systems. These faults could be broken components, insecure or compromised components offering erroneous data to the control. The network itself could add unpredictable delays and data drop outs that could affect the control in potentially unanticipated ways. In this paper, we consider the Boeing Open Experimental Platform fairing control application for acoustic and structural vibration damping and study the effect of component level and network level faults. We identify several scenarios under which control performance is intolerable. This leads us to design an alternative control scheme. We design the application using a purely local on-off control scheme and compare its performance with that of the original system.
Crack Position and Depth Identification in Rotating Shafts: Part 2 — Experimental Results
Authors: Bachschmid Nicolo` , Pennacchi Paolo , Tanzi Ezio
Published: June 2008

This paper presents the experimental validation of a model based transverse crack identification method suitable for industrial machines, described in part 1. The method is validated by experimental results obtained on two test rigs, which were expressly designed for investigating the dynamical behavior of cracked horizontal rotors. On the first test rig, only one crack type is considered, while on the second one three different types of crack have been analyzed: the first is a slot, therefore not actually a crack since it has not the typical breathing behavior, the second a small crack (14% of the diameter) and the third a deep crack (47% of the diameter). The excellent accuracy obtained in identifying position and depth of different cracks proves the effectiveness and reliability of the proposed method. Moreover, the implementation of identification method operates on a PC and takes short time to run, therefore is suitable for industrial applications.
A Compromise Method for the Design of Parametric Polynomial Surrogate Models
Authors: George Pradeep , Ogot Madara
Published: June 2008

This study presents a compromise approach to augmentation of response surface (RS) designs to achieve the desired level of accuracy. RS are frequently used as surrogate models in multidisciplinary design optimization of complex mechanical systems. Augmentation is necessitated by the high computational expense typically associated with each function evaluation. As a result previous results from lower fidelity models are incorporated into the higher fidelity RS designs. The compromise approach yields higher quality parametric polynomial response surface approximations than traditional augmentation. Based on the D-optimality criterion as a measure of RS design quality, the method simultaneously considers several polynomial models during the RS design, resulting in good quality designs for all models under consideration, as opposed to good quality designs only for lower order models as in the case of traditional augmentation. Several numerical and an engineering example are presented to illustrate the efficacy of the approach.
Virtual Training Simulator for Atomic Force Microscopy
Authors: Heying Matthew J. , Oliver James H. , Sundararajan Sriram , Shrotriya Pranav , Zou Qingze
Published: June 2008

Training novice users how to operate an Atomic Force Microscope (AFM) is expensive due to the cost of equipment and the time required to train users in a hands-on learning environment. Training large groups of users simultaneously presents a problem because usually only one AFM is available for use. To alleviate this problem, a virtual training simulator for AFM training has been developed. The training simulator is a Windows-based software program designed to allow users to simulate basic AFM operation on a PC. Instructors can use this tool to demonstrate the exact same instruction that a user would receive in an AFM lab within the confines of a classroom or computer lab. The graphical user interface (GUI) of the simulator replicates the interface of one of the most popular commercial AFM models to aid learning transfer from the simulator to the actual AFM. The goal of this paper is to provide a brief overview of the work that has been completed towards creating this virtual training simulator. The virtual AFM simulator modeling, design, and implementation are described.
Experimental Compensation of Runout and High Order Harmonic Effects in Lorentz Force Type Integrated Motor-Bearing System
Authors: Park Sung-Ho , Lee Chong-Won
Published: June 2008

An integrated motor-bearing system integrates the functions of an active magnetic bearing and an electric motor into a single unit. Because this system requires the simultaneous generation of torque and radial control force, there will inevitably be undesired high order harmonic components in the rotating magnetic field, which will result in torque ripple and radial force distortion. Sensor target runout is a severe excitation source and, as such, causes a lot of vibration. In this paper, we propose an experimental compensation procedure for the oscillation and coupling of torque and radial force using a digital controller of the Lorentz force type integrated motor-bearing system in a dual disk rotor configuration. After the compensation of high order harmonics, the runout profile and rotor unbalance are identified by the extended influence coefficient method. The proposed scheme does not require complicated analysis or modeling of high order harmonic effects, and it can also compensate for manufacturing errors. The experimental results confirm that this compensation method effectively attenuates the rotor vibration throughout the operating range of rotational speeds.
A Study of Factor Effects in Data From Factorial Experiments
Authors: Li Xiang , Frey Daniel D.
Published: June 2008

This paper documents a meta-analysis of 113 data sets from published factorial experiments. The study quantifies regularities observed among factor effects and multi-factor interactions. Such regularities are known to be critical to efficient planning and analysis of experiments and to robust design of engineering systems. Three previously observed properties are analyzed — effect sparsity, hierarchy, and heredity. A new regularity is introduced and shown to be statistically significant. It is shown that a preponderance of active two-factor interaction effects are synergistic, meaning that when main effects are used to increase the system response, the interaction provides an additional increase. The potential implications for robust design are discussed.
Occupant Restraint System Design Under Uncertainty Using Analytical Uncertainty Propagation Via Metamodels
Authors: Fu Yan , Jin Ruichen
Published: June 2008

The effectiveness of using Computer Aided Engineering (CAE) tools to support design decisions is often hindered by the enormous computational demand of complex analysis models, especially when uncertainty is considered. Approximations of analysis models, also known as “metamodels”, are widely used to replace analysis models for optimization under uncertainty. However, due to the inherent nonlinearity in occupant responses during a crash event and relatively large numbers of uncertain variables and responses, naive application of metamodeling techniques can yield misleading results with little or no warning from the algorithms which generate the metamodels. Furthermore, in order to improve the quality of metamodels, a relatively large number of design of experiments (DOE) and comparatively expensive metamodeling techniques, such as Kriging or radial basis function (RBF), are necessary. Thus, sampling-based methods, e.g. Monte Carlo simulations, for obtaining the statistical quantities of system responses during the optimization loop may still be inefficient even for these metamodels. In recent years, analytical uncertainty propagation via metamodels is proposed by Chen et al. 2004, which provides analytical formulation of mean and variance evaluations via a variety of metamodeling techniques to reduce the computational time and improve the convergence behavior of optimization under uncertainty. An occupant restraint system design problem is used as an example to test the applicability of this method.
Packing Optimization by Enhanced Rubber Band Analogy
Authors: Dong Hong , Fadel Georges M. , Blouin Vincent Y.
Published: June 2008

In this paper, some new developments to the packing optimization method based on the rubber band analogy are presented. This method solves packing problems by simulating the physical movements of a set of objects wrapped by a rubber band in the case of two-dimensional problems or by a rubber balloon in the case of three-dimensional problems. The objects are subjected to elastic forces applied by the rubber band to their vertices as well as reaction forces when contacts between objects occur. Based on these forces, objects translate or rotate until maximum compactness is reached. To improve the compactness further, the method is enhanced by adding two new operators: volume relaxation and temporary retraction. These two operators allow temporary volume (elastic energy) increase to get potentially better packing results. The method is implemented and applied for three-dimensional arbitrary shape objects.
Cognitive Characteristics and Design Creativity: An Experimental Study
Authors: Kim Yong Se , Kim Mi Hyun , Jin Sun Tai
Published: June 2008

The objective of this research is to identify the relations between various cognitive characteristics and design creativity so that such relations could be exploited as a guide for design education. In this paper, an experimental study toward these goals is presented where various cognitive characteristics and abilities were evaluated for three groups of students whose exposure and education in design varies. Based on the experiment, constructive perception ability that combines perception and conception and basic ability in visual reasoning composed of visual analysis, synthesis and representation in iterative nature are equally related with creative design ability. However, the correlation between constructive perception and visual reasoning has not been identified in spite of some common aspects of the two.
Modal Identification of Multi-Degree-of-Freedom Mechanical Systems Endowed With Geometric Nonlinearities
Authors: Camillacci R. , Valente C. , Brancaleoni F.
Published: June 2008

An identification procedure for a sample class of mechanical system exhibiting non-linear behavior is presented and validated experimentally. The proposed procedure operates on the free-vibration response of the system and is able not only to extract the time-depended modal parameters, but also to identify the functional relationships between modal frequencies and modal amplitudes of oscillation. These relationships depend just on the mechanical characteristics of the system and thus, they characterize entirely the dynamic behavior. An experimental validation of the procedure performed on a physical laboratory system is presented and discussed. The experimental set-up was designed in order to allow for different configurations and hence for different levels of nonlinearity. The comparison between the identified results and the results of a proper analytical model of the system allows for highlighting the sensibility and effectiveness of the proposed procedure.