bluuebunny/crossref_metadata_2025 huggingface dataset:
Finite Element Analysis of Wavy Composites
Authors: Pratt William F.
Published: June 2008

Wavy composite is a new form of constrained layer damping that uses opposing pairs of in-plane sinusoidal fiber patterns, and viscoelastic materials to create a composite structure that exhibits both high damping and stiffness. This paper reports on the author’s development of a specialty Finite Element Analysis code capable of modeling and predicting performance of wavy composite tubes and foam core samples using MathWorks’ Matlab® development software. The main use of the code has been to characterize various material combinations and correlate the results to material test results. The FEA code has been shown to be surprisingly accurate and fast and because it was developed in Matlab®, takes advantage of the numerous powerful matrix manipulation routines to perform analyses.
A Study of Linear Joint and Tool Models in Spindle-Holder-Tool Receptance Coupling
Authors: Burns Timothy J. , Schmitz Tony L.
Published: June 2008

The dynamics of a spindle-holder-tool (SHT) system during high-speed machining is sensitive to changes in tool overhang length. A well-known method for predicting the limiting depth of cut for avoidance of tool chatter requires a good estimate of the tool-point frequency response (FRF) of the combined system, which depends upon the tool length. In earlier work, a combined analytical and experimental method has been discussed, that uses receptance coupling substructure analysis (RCSA) for the rapid prediction of the combined spindle-holder-tool FRF. The basic idea of the method is to combine the measured direct displacement vs. force receptance (i.e., frequency response) at the free end of the spindle-holder (SH) system with calculated expressions for the tool receptances based on analytical models. The tool was modeled as an Euler-Bernoulli (EB) beam, the other three spindle-holder receptances were set equal to zero, and the model for the connection with the tool led to a diagonal matrix. The main conclusion of the earlier work was that there was an exponential trend in the dominant connection parameter, which enabled interpolation between tip receptance data for the longest and shortest tools in the combined SHT system. Thus, a considerable savings in time and effort could be realized for the particular SHT system. A question left open in the earlier work was: how general is this observed exponential trend? Here, to explore this question further, an analytical EB model is used for the SH system, so that all four of its end receptances are available, and the tool is again modeled as a free-free EB beam that is connected to the SH by a specified connection matrix, that includes nonzero off-diagonal terms. This serves as the “exact” solution. The approximate solution is once again formed by setting all but one SH receptance equal to zero, and the connection parameters are determined using nonlinear least squares software. Both diagonal and full connection matrices are investigated. The main result is that, for this system, in the case of a diagonal connecting matrix, there is no apparent trend in the dominant connecting spring stiffness with tool overhang length. However, in the full connecting matrix case, a general constant trend is observed, with some interesting exceptions.
Functional Classification of Computational Services in an Internet-Based Distributed Modeling Environment
Authors: Cao Qing , Senin Nicola , Wallace David R.
Published: June 2008

New emerging modeling and simulation environments have the potential to provide easy access to design models and simulations over the Internet, much as the World Wide Web (WWW) has provided easy access to information. Parametric simulation models accessible through such Internet-based environments can be seen as providers of computational services. As Internet-based computational services become more common, an effective mechanism for identifying functionally appropriate computational services will be necessary to support distributed simulation-based design. There are ongoing efforts to develop ontological descriptions of computational services, with the goal of explicitly defining the functional or semantic role of a computational service. However, much in the way web search engines operate, the goal of this work is to use patterns found within the syntactic information in interfaces for computational model services to identify functional roles. Typical, pre-existing syntactic information expected to be available—such as model and parameters names, parameter units, and input/output structure—are identified. Given a model with a known functional role, a Fuzzy Attributed Relational Graph representation of its syntactic interface information is used as a pattern or template for this known role. Then, using a graph-matching algorithm based on attribute similarity metrics, the interface information from other models can be classified against the functional template. New information from functionally equivalent model interfaces that have been found can be incorporated into the original template, thereby both generalizing the pattern for the functional role and strengthening the most critical aspects of the pattern. Test results for a prototype implementation of the proposed algorithm are provided.
Student System Level Design Activities: An Empirical Pilot Study on Improving Design Outcomes
Authors: Ruder Joshua , Sobek Durward K.
Published: June 2008

Previous studies have indicated that system level design (SLD) has a positive association with the outcome of engineering design projects. However, the causal relationship has not been established. This pilot study will explore the feasibility of implementing a laboratory experiment on design process and attempt to demonstrate a causal relationship between SLD and design outcome quality. Using outcome data from the pilot student laboratory exercise, a comparison between design processes that used SLD activities and those that did not are made using simple statistical testing methods. The results of this comparison support previous indications that SLD has an effect on outcome quality. The difficulties of constraining students performing SLD activities gave rise to an alternative method of analyzing SLD activities and lead us to conclude that our protocol is insufficient to test design process but is suitable for testing the application of a specific tool.
Analysis of Information Complexity During Product Development
Authors: Ko K. H. , Yu C. , Pochiraju K. , Manoochehri S.
Published: June 2008

The product development process is a series of asynchronous process steps in which the geometry, the materials, and the manufacturing processes are defined to meet the performance and cost requirements. During the product design, information about a product is initially sparse and becomes more detailed as the process matures. In this paper, we apply a systems complexity analysis methodology to track the evolution of information complexity for several design process workflows. We used a frame-slot based model to store parametric design information, defined the size and link complexity measures for the design information and tracked the evolution of the knowledge-base complexity throughout the design process. Product design through injection molding is taken as an example to illustrate the utility of our approach and the static and dynamic aspects of the complexity of design information are analyzed.
Design of Functionally Graded Structures for Enhanced Thermal Behavior
Authors: Blouin Vincent Y. , Oschwald Martin , Hu Yuna , Fadel Georges M.
Published: June 2008

Multi-material structures take advantage of beneficial properties of different materials to achieve an increased level of functionality. In an effort to reduce the weight of vehicle components such as brake disk rotors, which are generally made of cast iron, light materials such as aluminum alloys may be used. These materials, however, may lead to unacceptable temperature levels. Alternatively, functionally graded structures may offer a significant decrease in weight without altering thermal performance. The design of such structures is not trivial and is the focus of this paper. The optimization combines a transient heat transfer finite element code with a genetic algorithm. This approach offers the possibility of finding a global optimum in a discrete design space, although this advantage is balanced by high computational expenses due to many finite element analyses. The goal is to design a brake disk rotor for minimum weight and optimal thermal behavior using two different materials. Knowing that computational time can quickly become prohibitively high, strategies, such as finite element grouping to reduce the number of design variables and local mesh refinement, must be employed to efficiently solve the design problem. This paper discussed the strengths and weaknesses of the proposed design method.
A Method for Inferring Design Rules With Explicit Bounds of Applicability
Authors: Rawson Kevin , Stahovich Thomas F.
Published: June 2008

We present a two-step technique for learning reusable design procedures from observations of a designer in action. This technique is intended for the domain of parametric design problems in which the designer iteratively adjusts the parameters of a design so as to satisfy the design requirements. In the first step of the two-step learning process, decision tree learning is used to infer rules that predict which design parameter the designer will change for any particular state of an evolving design. In the second step, decision tree learning is again used, but this time to learn explicit termination conditions for the rules learned in the first step. The termination conditions are used to predict how large of a parameter change should be made when a rule is applied. The learned rules, and termination conditions, can be used to automatically solve new design problems with a minimum of human intervention. Initial experiments with this technique suggest that it is considerably more efficient than the previous technique which was incapable of learning explicit rule termination conditions. In particular, the rule termination conditions allow a program to automatically solve new design problems with far fewer iterations than required with the previous approach.
A Bayesian Identification Methodology for Selection Among Pareto Optimal Structural Models Using Modal Residuals
Authors: Christodoulou K. , Papadimitriou C.
Published: June 2008

The structural parameter estimation problem based on measured modal data is formulated as a multi-objective optimization problem in which modal metrics measuring the fit between measured and model predicted groups of modal properties are simultaneously minimized to obtain all Pareto optimal structural models consistent with the measured data. Equivalently, the multiple Pareto optimal models can be obtained by minimizing a single metric formed as a weighted average of the multiple metrics. The Pareto optimal models are obtained by varying the values of the weights. The optimal values of the parameters are sensitive to the values of the weighting factors. A Bayesian statistical framework is used to provide a rational choice of the optimal values of the weight factors based on the available data. It is shown that the optimal weight values for each group of modal properties are asymptotically, for large number of data, inversely proportional to the optimal prediction errors of the corresponding modal group. Two algorithms are proposed for obtaining simultaneously the optimal weight values and the corresponding optimal values of the structural parameters. The proposed framework is illustrated using simulated data from multi-DOF spring-mass chain structure. In particular, compared to conventional parameter estimation techniques that are based on pre-selected values of the weights, it is demonstrated that the optimal structural models proposed by the methodology are significantly less sensitive to large model errors or bad measured modal data, known to affect optimal selection.
Order Reduction of Nonlinear Systems With Periodic-Quasiperiodic Coefficients
Authors: Redkar Sangram , Sinha S. C.
Published: June 2008

In this work, some techniques for order reduction of nonlinear systems involving periodic/quasiperiodic coefficients are presented. The periodicity of the linear terms is assumed non-commensurate with the periodicity of either the nonlinear terms or the forcing vector. The dynamical evolution equations are transformed using the Lyapunov-Floquet (L-F) transformation such that the linear parts of the resulting equations become time-invariant while the nonlinear parts and forcing take the form of quasiperiodic functions. The techniques proposed here construct a reduced order equivalent system by expressing the non-dominant states as time-modulated functions of the dominant (master) states. This reduced order model preserves stability properties and is easier to analyze, simulate and control since it consists of relatively small number of states. Three methods are proposed to carry out this model order reduction (MOR). First type of MOR technique is a linear method similar to the ‘Guyan reduction’, the second technique is a nonlinear projection method based on singular perturbation while the third method utilizes the concept of ‘quasiperiodic invariant manifold’. Order reduction approach based on invariant manifold technique yields a unique ‘generalized reducibility condition’. If this ‘reducibility condition’ is satisfied only then an accurate order reduction via invariant manifold is possible. Next, the proposed methodologies are extended to solve the forced problem. All order reduction approaches except the invariant manifold technique can be applied in a straightforward way. The invariant manifold formulation is modified to take into account the effects of forcing and nonlinear coupling. This approach not only yields accurate reduced order models but also explains the consequences of various ‘primary’ and ‘secondary resonances’ present in the system. One can also recover all ‘resonance conditions’ obtained via perturbation techniques by assuming weak parametric excitation. This technique is capable of handing systems with strong parametric excitations subjected to periodic and quasi-periodic forcing. These methodologies are applied to some typical problems and results for large-scale and reduced order models are compared. It is anticipated that these techniques will provide a useful tool in the analysis and control system design of large-scale parametrically excited nonlinear systems.
Conceptual Design Knowledge Management and the Semantic Web
Authors: Kopena Joseph B. , Cera Christopher D. , Regli William C.
Published: June 2008

The early stages of engineering design are critical, as the decisions made at this point have the most impact on the final product. However, little software is available to support engineers during the initial, conceptual design phase. In addition, at this and all other stages of design, engineers are increasingly tasked with utilizing unwieldy collections of data such as databases of legacy designs and catalogs. This work addresses both of these issues. A conceptual design interface with several advancements crucial to industrial deployment is developed and used to aid design. Among these are provisions for real-time collaboration and security. A representation of mechanical devices based on intended function is developed and used by the conceptual design interface to capture design semantics. This representation is defined using a description logic, enabling automated reasoning. The descriptions created using the conceptual design interface can thus be employed to annotate designs, create search queries, and to organize collections of designs. Further, this work incorporates Semantic Web technology, enabling conceptual design knowledge to be published and accessed effectively on the World Wide Web. New applications of design repositories are made possible by this but new issues must be investigated and addressed, as discussed here.
A Group Technology Based Representation for Product Portfolios
Authors: Jordan Robert L. , Van Wie Mike , Stone Robert B. , Wang Jiachuan , Terpenny Janis
Published: June 2008

Repository based applications for portfolio design offer the potential for leveraging archived design data with computational searches. Toward the development of such search tools, we present a representation for product portfolios that is an extension of an existing Group Technology (GT) coding scheme. Relevance to portfolio design is treated with a case study example of a hand held grinder design. Results of this work provide a numerical coding representation that captures function, form, material and manufacturing data for systems. This extends the current GT line work by combining these four types of design data and clarifying the use of the functional basis in a GT code. The results serve as a useful starting point for the development of portfolio design algorithms, such as genetic algorithms, that account for this combination of design information.
Dynamic Stability of Ring-Based MEMS Gyroscopes
Authors: Cho Jihyun , Asokanthan Samuel F.
Published: June 2008

Dynamic stability of ring-based MEMS gyroscopes subjected to harmonic perturbations in input angular rate is examined using an asymptotic approach. The governing equations that represent the transverse and tangential in-plane motion of the ring are derived via Hamilton’s principle. The equations of motion, after discretization and suitable linearization, represent a two-degree-of-freedom time-varying linear gyroscopic system. Such a system can exhibit instability behaviour characterized by exponential growth in response amplitudes. Employing the method of averaging, conditions for instability are obtained in closed-form. Instability boundaries for the ring in the excitation intensity-frequency space are then established for small excitation amplitudes. In addition, effects of damping, input angular rate variations, and the effect of imperfection due to the ring asymmetry are discussed.
Pipe Route Design Using Variable Topography Distance Transforms
Authors: Kristinsson Hlynur , Jonsson Magnus Thor , Jonsdottir Fjola
Published: June 2008

In this paper the Variable Topography Distance Transform method (VTDT) is used to find optimal paths across physical landscapes for pipelines carrying a two-phase geothermal fluid. The method incorporates constraints such as obstacles, land costs, building costs, variable gradients, height, and environmental issues in the route selection process. The method is an expanded form of Distance Transform algorithms that are used in image processing. It offers a way to look at land surfaces as a slope-adjusted 2-D model rather than as a more complex and computationally intensive 3-D model. The VTDT method works with a digital representation, called a Digital Elevation Model (DEM), of the landscape in question. The method is then tested on the route design for pipelines carrying a two-phase geothermal fluid at the Hellisheidi Power Plant in Iceland, which is currently (early 2005) in the design and construction phase.
Heuristic Gradient Projection for 3D Space Frame Optimization
Authors: Abd El Malek Maged R. , Senousy Mohamed S. , Hegazi Hesham A. , Metwalli Sayed M.
Published: June 2008

The purpose of this work is to develop a novel optimization process for the design of space frames. The main objective is to minimize the space frame volume and consider stress constraints satisfaction. A finite element program is devised to synthesize 3D-space frames and aid in its topology optimization. The program is verified through different elementary problems with known analytical solutions as well as with commercial packages. A Midi-Bus frame is modeled with about 300 members and analyzed for a severe road model condition. The optimization effectively uses the devised Heuristic Gradient Projection (HGP) technique to synthesize the optimum Midi-Bus frame. Results indicate a marked improvement over available designs and remarkably faster convergence over other optimization techniques. This technique can thus be effectively applied to other large 3D space frame synthesis and optimization.
Fuzzy Logic Based Vehicle Stability Enhancement Through Active Rear Steering
Authors: Ghaffari A. , Ahmadi J. , Kazemi R.
Published: June 2008

This paper introduces an investigation of a steering intervention system based on active rear steering system (RWS) which uses rear steer angle as control input. The induced yaw moment on the vehicle affects handling states, there by increasing the steering performance. The steering function achieved through RWS can then be used to assist the driver in severe maneuvers that most drivers are not familiar with. Because of the high nonlinearities and uncertainties that exist in vehicle handling behavior a fuzzy logic inference system is developed to explore RWS feasibility and capability. Computer simulations using nonlinear seven degree of freedom vehicle model show the remarkable enhancements of RWS vehicle.
A Parametric Study on the Friction-Induced Vibration of a Brake Model During Decelerated Sliding
Authors: Tan Chin An , Li Jinsha
Published: June 2008

In this paper, the friction-induced vibration of a simple disc brake model during decelerated sliding is investigated. A three-degree-of-freedom physical model of a disc brake system is considered; the brake pads are modeled as rigid blocks interacting with a rigid translating strip (rotor) through friction. This model simulates the transient dynamics of the longitudinal motions (in the direction of sliding) of the pads during braking. A Coulomb-type friction model is adopted, with the coefficient of friction approximated by an analytical function of the sliding speed at the rotor-pads interface. The coupled equations of motion for the longitudinal vibrations of the sliding strip and the pads are solved simultaneously. Effects of the friction model and other physical parameters on the transient dynamics and instability of the system are examined through the numerical results. Implication of these results to brake squeal generation is also discussed.
A Hybrid Geometric Modeling Method for Large Scale Conformal Cellular Structures
Authors: Wang Hongqing , Chen Yong , Rosen David W.
Published: June 2008

This paper presents a hybrid geometric modeling method to create CAD models of large-scale conformal cellular structures effectively and efficiently. Cellular material structures can be engineered at the mesoscopic scale for high performance and multi-functional capabilities. One type of cellular structure is conformal lightweight truss. A simple method of constructing models of uniform trusses is to pattern unit cells linearly within a CAD system. However, by orienting strut directions and adjusting strut sizes, such trusses can be optimized to achieve superior strength, stiffness, and weight characteristics. For large truss structures, computational and storage complexities cause difficulties in CAD system modeling. In this paper, a new hybrid geometric modeling approach of directly creating tessellated models is developed to automate the geometric modeling process of conformal truss structures efficiently. This modeling approach is intended to support the design, analysis, optimization, and manufacture of conformal truss structures. Examples are presented and the computational efficiency of the hybrid method is compared with the approach of creating the complete solid model of cellular structures.
Estimation of Critical Value of Friction Coefficient for Brake Squeal Analysis
Authors: Huang Jinchun , Krousgrill Charles M. , Bajaj Anil K.
Published: June 2008

Automotive brake squeal which is generated during brake application has become a major concern in automotive industry. Warranty costs for brake noise have been greatly increasing in recent years. Brake noise and vibration control are important for the improvement of vehicle quietness and passenger comfort. In this work, the mode coupling instability mechanism is discussed, and a method to estimate the critical value of friction coefficient is presented to predict the onset of brake squeal. A modal expansion method is developed to calculate eigenvalue and eigenvector sensitivities. Different types of mode couplings and their relationships with squeal are discussed. A reduced-order characteristic equation method based on the statically coupled eigenvalues and their derivatives is presented to estimate the critical value of friction coefficient. The significance of this method is that the critical value of friction coefficient can be predicted accurately without the need for a full complex eigenvalue analysis, making it possible to determine the sensitivity of system stability with respect to design parameters directly.
Design Space Exploration for Rapid Product Realization
Authors: Devanathan Srikanth , Cunningham Robert , Peters Christopher , Ramani Karthik
Published: June 2008

In this work, a product centric view of the design process is used in capturing the process and the design knowledge of complex, hierarchical engineering systems. The use of individual product configurators expedites redesign and further exploration of the design space. The notion of concept representation is introduced to mathematically formulate the various aspects of a product concept. This representation also enhances the understanding of the overall objectives, allowing for design sensitivity analyses, pre-computation of the engineering design spaces and multi-disciplinary constraint management between modules. Product configurators are developed in a distributed framework to enable rapid design across different platforms. The Purdue Formula SAE vehicle is used as an example case in developing the configuration problem.
Concise Interactions and Effective Management of Shared Design Spaces: Moving Beyond Strategic Collaboration Towards Co-Design
Authors: Ferna´ndez Marco Gero , Panchal Jitesh H. , Allen Janet K. , Mistree Farrokh
Published: June 2008

Often, design problems are coupled and their concurrent resolution by interacting stakeholders is required. The ensuing interactions are characterized predominantly by degree of interdependence and level of cooperation. Since tradeoffs, made within and among sub-systems, inherently contribute to system level performance, bridging the associated gaps is crucial. With this in mind, effective collaboration, centered on continued communication, concise coordination, and non-biased achievement of system level objectives, is becoming increasingly important. Thus far, research in distributed and decentralized decision-making has focused primarily on conflict resolution. Game theoretic protocols and negotiation tactics have been used extensively as a means of making the required tradeoffs, often in a manner that emphasizes the maximization of stakeholder (personal) payoff over system level performance. More importantly, virtually all of the currently instantiated mechanisms are based upon the a priori assumption of the existence of solutions that are acceptable to all interacting parties. No explicit consideration has been given thus far to ensuring the convergence of stakeholder design activities leading up to the coupled decision and the associated determination of values for uncoupled and coupled design parameters. Consequently, unnecessary and costly iteration is likely to result from mismatched objectives. In this paper, we advocate moving beyond strategic collaboration towards co-design. We present an alternative coordination mechanism, centered on sharing key pieces of information throughout the process of determining a solution to a coupled system. Specifically, we focus on (1) establishing and assessing collaborative design spaces, (2) identifying and exploring regions of acceptable performance, and (3) preserving stakeholder dominion over design sub-system resolution throughout the duration of a given design process. The fundamental goal is to establish a consistent framework for goal-oriented collaboration that (1) more accurately represents the mechanics underlying product development and (2) facilitates interacting stakeholders in achieving their respective objectives in light of system level priorities. This is accomplished via improved utilization of shared resources and avoidance of unnecessary reductions in design freedom. Comparative performance of the proposed method is established using a simple example, involving the resolution of a tradeoff with respect to a system of non-linear equations.
Structural-Acoustic Optimization of Sandwich Panels
Authors: Franco Francesco , Cunefare Kenneth A. , Ruzzene Massimo
Published: June 2008

Sandwich panels, comprising face sheets enclosing a core, are increasingly common structural elements in a variety of applications, including aircraft fuselages and flight surfaces, vehicle panels, lightweight enclosures, and bulkheads. The design flexibility associated with such composite structures provides significant opportunities for tailoring the structure to the load and dynamic response requirements for the particular application. Design flexibility encompasses the details of the face sheets and the core. This paper deals with the numerical optimization of different sandwich configurations for the purposes of achieving reduced structural acoustic response. Laminated face sheets and core geometries, comprising honeycomb and truss-like structures, are considered. The relative importance of the mass and stiffening properties of the core and face sheets are discussed. The optimization work is carried out using commercial codes. Benefits and limits of using an optimization algorithm based on gradient methods are highlighted.
Effect of Safety Measures on Reliability of Aircraft Structures Subjected to Damage Growth
Authors: Kale Amit A. , Haftka Raphael T.
Published: June 2008

This paper demonstrates the effect of various safety measures used to design aircraft structures for damage tolerance. In addition, it sheds light on the effectiveness of measures like certification tests in improving structural safety. Typically, aircraft are designed with a safety factor of 2 on the service life in addition to other safety measures, such as conservative material properties. This paper demonstrates that small variation in material properties, loading and errors in modeling damage growth can produce large scatter in fatigue life, which means that quality control measures like certification tests are not very effective in reducing failure probability. However, it is shown that the use of machined cracks in certification can substantially increase the effectiveness of certification testing.
Jump Avoidance Conditions for Piecewise Linear Vibration Isolator
Authors: Deshpande Sagar , Mehta Sudhir , Nakhaie Jazar G.
Published: June 2008

Piecewise linear systems being highly non-linear, standard perturbation methods cannot produce an analytical expression for the frequency response. Hence, an adapted averaging method is employed to obtain an implicit function for frequency response of a bilinear system under steady state. This function is examined for jump-avoidance and a condition is derived which when met ensures that the undesirable phenomenon of ‘Jump’ does not occur and the system response is functional and unique.
A Virtual Engineering Tool for Product Design Using High Fidelity CFD Analysis Models
Authors: Huang Gengxun , Xiao Angran , Bryden Kenneth M.
Published: June 2008

Product design optimization is a complex decision-making process requiring intensive interactions between designers and the designed product. However, most current optimization tools do not support this type of direct interaction. Typically, resolving a converged result with an optimization tool takes a long solution time and high computing cost. However, designers are not involved in the optimization process and cannot control the quality of the so-called optimal result. In this paper, we introduce a virtual engineering design tool that expands the application scope of virtual reality from visualization to interaction and decision support. This design tool allows designers to easily experiment with different product designs using high fidelity CFD solver and observe the effects in an almost real-time manner. This can help designers understand the nature of the product and make superior decisions. Most importantly, the design tool enables designers to control the optimization computing process by selecting superior starting points or changing an obviously unpromising search direction. Hence, by adding human creativity and experience into the optimization process, designers can resolve the design optimization problem more efficiently. A coal pipe design and optimization scenario is presented to demonstrate the efficacy of this virtual engineering design tool. The goal of this tool is to enable a designer to modify the size and shape of a coal pipe to obtain evenly distributed coal at the outlet. In this tool after the initial population was chosen, a standard evolutionary algorithm was used to find the most superior pipe design within a much shorter time.
An Analysis of Risk and Function Information in Early Stage Design
Authors: Van Wie Michael , Grantham Katie , Stone Robert , Barrientos Francesca , Tumer Irem
Published: June 2008

The concept of function offers a high potential for thinking and reasoning about designs as well as providing a common thread for relating together other design information. This paper focuses specifically on risk data by examining how this information is addressed for a design team conducting early stage design for space missions. Sample risk information is decomposed into a set of key attributes which are then used to scrutinize the risk information using three approaches from the pragmatics sub-field of linguistics: i) Gricean, ii) Relevance Theory, and iii) Functional Analysis. Based on the deficiencies identified in this analysis, the concepts of functional templates and a risk worksheet are used to suggest corrective actions for improving treatment of risk data by explicitly accounting for five risk attributes developed in this work.
Towards Computer-Aided Conceptual Design of Mechatronic Devices With Multiple Interaction-States
Authors: Xu Changxin , Gupta Satyandra K. , Yao Zhiyang , Gruninger Michael , Sriram Ram
Published: June 2008

In multiple interaction-state mechatronic devices the interactions between elements of use-environment and elements of the device can have different qualitative structures depending upon the modes of the device operation and the states of the use-environment. This paper describes a modeling framework to support conceptual design of such devices using state transition diagrams. We define the primitives and operators needed in the modeling framework, and illustrate the conceptual design process using these primitives and operators. We believe that the framework described in this paper will provide the underlying foundations for constructing the next generation software tools for the conceptual design of mechatronic devices.
A Parallel Grammar for Simulation-Driven Mechanical Design Synthesis
Authors: Starling Alex C. , Shea Kristina
Published: June 2008

This research investigates the use of quantitative measures of performance to aid the grammatical synthesis of mechanical systems. Such performance measures enable search algorithms to be used to find designs that meet requirements and optimize performance by using automatically generated performance feedback, including behavioral simulation, as a guide. The work builds on a new type of production system, a parallel grammar for mechanical systems based on a Function-Behavior-Structure representation, to generate an extensive variety of designs. Geometric and topological constraints are used to bound the design space, termed the language of the grammar, to ensure the validity of designs generated. The winding mechanism of an electromechanical camera is examined as a case study using the behavioral modeling language Modelica. Behavioral simulations are run for parametric models generated by the parallel grammar and this data is used, in addition to geometric performance metrics, for performance evaluation of generated alternative designs. Multi-objective stochastic search, in the form of a hybrid pattern search developed as part of this research, is used to generate Pareto sets of optimally directed designs of winding mechanisms, showing the design of the camera chosen for the case study to be optimally directed with respect to the design objectives considered. The Pareto sets generated illustrate the range of simulation-driven solutions that can be generated and simulated automatically as well as their performance tradeoffs.
An Overview on a Nonideal System With Three and a Half Degrees of Freedom
Authors: Guilherme Karen de Lolo , Balthazar Jose´ Manoel , Gardel Kurka Paulo Roberto , Tsuchida Masayoshi
Published: June 2008

The present paper studies a system comprised of two blocks connected by springs and dampers, and a DC motor with limited power supply fixed on a block, characterizing a non-ideal problem. This DC motor exciting the system causes interactions between the motor and the structure supporting it. Because of that, the non-ideal mathematical formulation of the problem has one and a half extra degree of freedom than the ideal one. A suitable choice of physical parameters leads to internal resonance conditions, that is, its natural frequencies are multiple of each other, by a known integer quantity. The purpose here is to study the dynamic behavior of the system using an analytical method based on perturbation techniques. The literature shows that the averaging method is the more flexible method concerning non-ideal problems. Summarizing, an steady state solution in amplitude and phase coordinates was obtained with averaging method showing the dependence of the structure amplitudes with the rotation frequency of the motor. Moreover, this solution shows that on of the amplitude coordinates has influence in the determination of the stationary rotation frequency. The analytical solution obtained shows the presence of the rotation frequency in expressions representing the oscillations of the structure, and the presence of amplitude coordinates in expressions describing the dynamic motion of the DC motor. These characteristics show the influence not only of the motor on structure but also of the response of the structure on dynamical behavior of the motor.
An Extended Integrated Development Environment Strategy for the Enterprise
Authors: Streit Paul A.
Published: June 2008

This document outlines a Rockwell Collins initiative currently underway to establish an eXtended Integrated Development Environment (XIDE) throughout its enterprise. The strategies contained in this document are either based on steps already complete or steps that are planned. We begin with a description of the XIDE vision followed by the major attributes of an XIDE and their importance. Several approaches to XIDE tool integration are described and a tool integration framework technology is selected based on the goals of scalability and modularity, available components for tool integration, and platform portability characteristics. A strategic migration plan is then outlined by identifying steps necessary to implement the XIDE vision. The implementation steps are then explored further along with reasons why they’re necessary and guidance on how to approach them. The final section explores Eclipse in much greater detail, including its history as an open source tool, the Eclipse Foundation, and justification for its selection for the XIDE framework. Also included are guidelines for the use of open source, and a review of several scenarios where contributing to open source can make sound business sense.
Predictabilty of Change in Engineering: A Complexity View
Authors: Eckert Claudia , Clarkson John , Earl Chris
Published: June 2008

Design changes can be surprisingly complex. We examine the problems they cause and discuss the problems involved in predicting how changes propagate, based on empirical studies. To assist this analysis we distinguish between (a) a static background of connectivities (b) descriptions of designs, processes, resources and requirements and (c) the dynamics of design tasks acting on descriptions. The background might consist of existing designs and subsystems, or established processes used to create them. The predictability of design change is examined in terms of this model, especially the types and scope of uncertainties and where complexities arise. An industrial example of change propagation is presented in terms of the background (connectivity) - description - action model.
Reliable Control System Design Despite Byzantine Actuators
Authors: Kulathumani Vinodkrishnan , Arora Anish , Kim Young Man , Shankar Praveen , Yedavalli Rama K.
Published: June 2008

Sensor-actuator networks are increasingly being used in distributed control of large scale systems. Often these applications are mission-critical and are required to maintain satisfactory performance in the presence of component failures. On the one hand, sensor-actuator network components are becoming inexpensive but they also tend to be unreliable, especially when deployed in harsh or unpredictable environments. The various component failures can manifest themselves in the form of arbitrary actuator behavior in which case their effect on the underlying systems can be severe. In this paper we focus our attention on applications of sensor networks in control of linear systems and show how to deal with Byzantine faults of actuators. We first describe a fault-tolerant control scheme using locally redundant actuators. We then relax the requirement on actuators to be at the same location and design a fault-tolerant scheme where the actuator redundancies are further reduced as well. We demonstrate our methodologies using a beam vibration control application as a case study.
Crack Position and Depth Identification in Rotating Shafts: Part 1— Theoretical Model
Authors: Bachschmid Nicolo` , Pennacchi Paolo , Vania Andrea
Published: June 2008

This paper presents a model based transverse crack identification method in rotating shafts suitable for industrial machines. The identification method and the relative theory is fully discussed, by presenting the breathing mechanism of the crack, the equivalent system of forces, which excites the vibrations of rotating shafts, the way to localize the crack position along the shaft and finally to identify the depth of the crack. This is obtained by using standard finite element models of the machine and the vibration measured in the bearings only, as usual in industrial machines. The proposed method will be validated by means of experimental results which are described in detail in the second part of the paper.
Vibration Damping Using Low-Wave-Speed Media: Complex Wavenumber and Energy Approximations
Authors: Varanasi Kripa K. , Nayfeh Samir A.
Published: June 2008

Significant damping of structural vibration can be attained by coupling to the structure a low-density medium (such as a powder or foam) in which the speed of sound propagation is relatively low. We describe a set of experiments in which flexural vibration of aluminum beams over a broad frequency range is damped by introduction of a layer of lossy low-wave-speed foam. At frequencies high enough to set up standing waves through the thickness of the foam, loss factors as high as 0.05 can be obtained with a foam layer whose mass is 3.9% of that of the beam. In our prior studies [1,2], we modeled the foam as a continuum in which waves of dilatation and distortion can propagate and obtained approximate solutions for the frequency response of the system by means of a modal expansion. However, these modal expansion models are cumbersome for design and quick calculation. In this paper, we develop a simple approximation for the system loss factor based on the complex wavenumber associated with wave propagation, and find that the damping estimates are in close agreement with measured responses and those predicted by modal expansion methods and strain energy approximations. Finally, we extend this approach to longitudinal vibration in a bar coupled to foam and obtain estimates for the system loss factor.
A Plug-and-Contract Mechanism for a Robust Assessment of Design Concepts
Authors: Yannou Bernard , Awedikian Roy
Published: June 2008

Starting from a need and a set of functional requirements (FRs), a designer is often perplexed to assess the potential of a given concept to fit these requirements. He is even more perplexed when several concepts are candidates. This paper proposes a definition of a concept in a practical way as a parameterized model linking a set of design variables (DVs) to a set of performance variables (PVs). This set of PVs is supposed to be the same for any concept candidate to fulfill a need. This is why our model propose to “plug” a card of FRs into candidate concepts in order to lead concurrent reasonings on competing concepts until one or several of them appear to be of poor interest. The plugging mechanism is implemented by constraint programming techniques (evolved interval arithmetics) that immediately contract the performance and design variable domains to provide an outer approximation of the solution (or design) space. Two sets of comparison operators between solution spaces are proposed: operators for comparing the relative potential of two concepts submitted to the same FRs, and operators for comparing two successive stages of solution spaces of a given concept. These last operators provide the way to tackle the robustness of design decision making under uncertainty. All the mentioned features: plugging mechanism, contraction of domains and design space representation, comparison operators and robustness considerations have been experimented on an example of a pair of candidate concepts of truss structures.
Automatic Fairing of Two-Parameter Rational B-Spline Motion
Authors: Purwar Anurag , Chi Xiaoyi , Ge Qiaode Jeffrey
Published: June 2008

This paper deals with the problem of automatic fairing of two-parameter B-Spline spherical and spatial motions. The concept of two-parameter freeform motions brings together the notion of the analytically determined two-parameter motions in Theoretical Kinematics and the concept of freeform surfaces in the field of Computer Aided Geometric Design (CAGD). A dual quaternion representation of spatial displacements is used and the problem of fairing two-parameter motions is studied as a surface fairing problem in the space of dual quaternions. By combining the latest results in surface fairing from the field of CAGD and computer aided synthesis of freeform rational motions, smoother (C3 continuous) two-parameter rational B-Spline motions are generated. The results presented in this paper are extensions of previous results on fine-tuning of one-parameter B-spline motions. The problem of motion smoothing has important applications in the Cartesian motion planning, camera motion synthesis, spatial navigation in visualization, and virtual reality systems. Several examples are presented to illustrate the effectiveness of the proposed method.