bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantifying Attractor Morphing for High-Sensitivity Detection of Parameter Variations by Point Cloud Averaging
Authors: Hashmi Ali I. , Epureanu Bogdan I.
Published: June 2008

A novel method of damage detection for systems exhibiting chaotic dynamics is presented. The algorithm reconstructs variations of system parameters without the need for explicit system equations of motion, or knowledge of the nominal parameter values. The concept of a Sensitivity Vector Field (SVF) is developed. This construct captures geometrical deformations of the dynamical attractor of the system in state space. These fields are collected by the means of Point Cloud Averaging (PCA) applied to discrete time series data from the system under healthy (nominal parameter values) and damaged (variations of the parameters) conditions. Test variations are reconstructed from an optimal basis of the SVF snapshots which is generated by means of proper orthogonal decomposition. The method is applied to two system models, a magneto-elastic oscillator and an atomic force microscope. The method is shown to be highly accurate, and capable of identifying multiple simultaneous variations. The success of the method as applied to an atomic force microscope (AFM) and a magneto-elastic oscillator (MEO) indicates a potential for highly accurate sample readings by exploiting recently observed chaotic vibrations.
Parametric Identification of Chaotic Systems Via a Long-Period Harmonic Balance
Authors: Liang Yang , Feeny B. F.
Published: June 2008

Hyperbolic chaotic sets are composed of a countable infinity of unstable periodic orbits (UPOs). Symbol dynamics reveals that any long chaotic segment can be approximated by a UPO, which is a periodic solution to an ideal model of the system. Treated as such, the harmonic balance method is applied to the long chaotic segments to identify model parameters. Ultimately, this becomes a frequency domain identification method applied to chaotic systems.
On Performance Enhancement of Parallel Kinematic Machine
Authors: Zhang Dan , Wang Lihui
Published: June 2008

This paper proposes a spatial three degrees of freedom parallel kinematic machine enhanced by a passive leg and a web-based remote control system. First, the geometric model of the three degrees of freedom parallel kinematic machine is addressed; in the mechanism, a fourth kinematic link — a passive link connecting the base center to the moving platform center — is introduced. This last link is used to constrain the motion of the tool (located in the moving platform) to only three degrees of freedom, as well as to enhance the global stiffness of the structure and distribute the torque from machining. With the kinematic model, a web-based remote control approach is then applied. The concept of the web-based remote manipulation approach is introduced and the principles behind the method are explored in detail. Finally, an example of remote manipulation is demonstrated to the proposed 3-DOF structure using web-based remote control concept before conclusions.
Modeling and Visualization of the Requirements and System for Supporting System Development
Authors: Niwa Takashi , Aoyama Kazuhiro
Published: June 2008

Various process models have been proposed for system development, which represent all stages from requirements analysis to implementations and tests. However, these process models focus not on improvement of the model of the system itself but on the development of processes to adapt to the properties of the requirements in system development. First, we arranged the features of system development. Then, we modeled the requirements and a system, and propose here a design method by which the customer and designer can always check requirements by introducing not plural design methods using various conventional design model figures but a unified multiphase design method, even if the designer does not implement the system. The customer and designer can check the requirements using the animations of the scenarios described as requirements. Finally, we present an example of execution, which designs a system using the proposed model, and describe avenues for future work.
Experimental Validation of a Numerical Model for the Simulation of Tramcar Vehicle Dynamics
Authors: Cheli Federico , Corradi Roberto , Diana Giorgio , Facchinetti Alan
Published: June 2008

Tramcar vehicles significantly differ from traditional railway vehicles both for the adopted structural configuration and design solutions and for the operating conditions. For this reason, a new numerical model specific for the analysis of tramcar dynamics has been developed by Politecnico di Milano. Before the numerical model can be adopted as a useful mean to analyse tramcar operational problems, the capability of the model to reproduce the actual tramcar dynamic behaviour has to be verified. The paper deals with the validation of the developed numerical model by means of comparison with experimental data.
Application of a Transfer Function, Obtained by Variation Principles for a Steam Turbine Journal Failure Analysis Based on “DOE” and Optimization Techniques
Authors: Ventura Gabriel , Di´az Carlos , Morales Hugo
Published: June 2008

There are many engineering situations where is not necessary to analyze whole domain of a physical model. According with these situations we demonstrate that is possible, with a transfer matrix and variation principles, to obtain an equivalent bilinear form using Lax-Milgram theorem with an orthogonal form applied to turbomachinery. This transfer matrix solves a problem in shorter time than the Traditional DOE-FEA (design of Experiments) (Finite Element Analysis) Method. In this method we consider a solution sub-space that contents generalized forces in a given location and maximum displacements in other location of the same domain, which may cause a failure, Kij = a(vhj*,uhi) is the transfer matrix, with a small range. The coefficients in matrix are obtained by n runs, (where n is the number of variables to be consider), with FEA, applying unitary forces in n directions. With the Traditional DOE-FEA method, FEA runs require great computational efforts because this method shall need 2n runs, on the basis of this fact, this proposal can be 75 and up to 99% (n/2n) shorter in time to obtain the transfer function and apply it into the FEA than the Traditional DOE-FEA method. Analysis in short time helps to confront many fields’ problems. In this paper we will analyze the case of a steam turbine journal, where was possible to find the amount of the limit loads that cause its failure, under prescribed displacements.
A Study of the Wheel Geometry Effect on the Dynamic Behavior of Railroad Vehicles
Authors: Shabana Ahmed A. , Tobaa Mahmoud , Zaazaa Khaled E.
Published: June 2008

The effect of the geometry of a wheel profile that allows only a single point of contact between the wheel and the rail is investigated in this study. The local geometric properties of this profile are compared with the local geometric properties of a profile that allows for two-point contacts in order to understand the basic differences between the two profiles. A simple model is first used to examine the effect of the profile geometry on the stability and nonlinear dynamics of a suspended wheel set. The results obtained in this paper show that the wheel profile can significantly alter the critical speed. Using surface parameters that define the wheel and rail geometry, the global representations of the positions of the points on the wheel and rail surfaces are obtained and used to define the conditions of the contact between the wheel and the rail. Numerical results are presented for a full railroad vehicle model and the effect of the wheel profile on the vehicle stability is investigated. A comparison between the results obtained using the two wheel profiles in the case of wheel climb scenarios is presented.
A New Approach to Probabilistic Risk Analysis in Concurrent and Distributed Design of Aerospace Systems
Authors: Farhang Mehr Ali , Tumer Irem Y.
Published: June 2008

NASA’s space exploration vehicles, like any other complex engineering system, are susceptible to failure and ultimately loss of mission. Researchers, therefore, have devised a variety of quantitative and qualitative techniques to mitigate risk and uncertainty associated with such low-volume high-cost missions. These techniques are often adopted and implemented by various NASA centers in the form of risk management tools, procedures, or guidelines. Most of these techniques, however, aim at the later stages of the design process or during the operational phase of the mission and therefore, are not applicable to the early stages of design. In particular, since the early conceptual design is often conducted by concurrent engineering teams (and sometimes in distributed environments), most risk management methods cannot effectively capture different types of failure in both subsystem and system levels. The current risk management practice in such environments is mostly ad-hoc and based on asking “what can go wrong?” from the team members. As such, this paper presents a new approach to risk management during the initial phases of concurrent and distributed engineering design. The proposed approach, hereafter referred to as Risk and Uncertainty Based Integrated Concurrent Design (or RUBIC-Design), provides a solid rigor for using functional failure data to guide the design process throughout the design cycle. The new approach is based on the functional model of space exploration systems (or any other mission-critical engineering system for that matter) and has the capability of adjusting in real-time as the overall system evolves throughout the design process. The application of the proposed approach to both single-subsystem and multi-subsystem designs is demonstrated using a satellite reaction wheel example.
A Dynamical Model for Studying the Stability of Thermo-Solutal Convection Under the Effect of Vertical Vibration
Authors: Razi Y. P. , Mojtabi M. , Maliwan K. , Charrier-Mojtabi M. C. , Mojtabi A.
Published: June 2008

This paper concerns the thermal stability analysis of porous layer saturated by a binary fluid under the influence of mechanical vibration. The linear stability analysis of this thermal system leads us to study the following damped coupled Mathieu equations: BH¨+B(π2+k2)+1H˙+(π2+k2)−k2k2+π2RaT(1+Rsinω*t*)H=k2k2+π2(NRaT)(1+Rsinω*t*)Fε*BF¨+Bπ2+k2Le+ε*F˙+π2+k2Le−k2k2+π2NRaT(1+Rsinω*t*)F=k2k2+π2RaT(1+Rsinω*t*)H where RaT is thermal Rayleigh number, R is acceleration ratio (bω2/g), Le is the Lewis number, k is the dimensionless wave-number, ε* is normalized porosity and N is the buoyancy ratio (H and F are perturbations of temperature and concentration fields). In the follow up, the non-linear behavior of the problem is studied via a generalization of the Lorenz model (five coupled non-linear differential equations with periodic coefficients). In the presence or absence of gravity, the stability limit for the onset of stationary as well as Hopf bifurcations is determined.
Optimizing Distributed-Contact Friction in Ring Dampers
Authors: Tangpong X. W. , Wickert J. A. , Akay A. , Karpenko Yuri
Published: June 2008

This paper describes the vibration analysis and optimization of a base structure and a beam-like attached damper sub-system that couple in vibration through distributed-contact friction damping. The objective is to tune the characteristics of the damper sub-system to maximize energy dissipation, and therefore to control vibration of the base structure. Applications of the concept to noise and vibration phenomena associated with automotive disk brake rotors are discussed. Per-cycle energy dissipation is examined as a function of damper preload for two classes of sub-systems: dampers that are split rings, and dampers that are continuous rings. End-effects and the manner in which energy dissipation is distributed spatially along the damper are also discussed. Of potential technological application, for a given excitation frequency, the damper sub-system’s design can be optimized to reduce vibration of the base structure.
Modelling and Identification of a Six Axes Industrial Robot
Authors: Waiboer Rob , Aarts Ronald , Jonker Ben
Published: June 2008

This paper deals with the modelling and identification of a six axes industrial Sta¨ubli RX90 robot. A non-linear finite element method is used to generate the dynamic equations of motion in a form suitable for both simulation and identification. The latter requires that the equations of motion are linear in the inertia parameters. Joint friction is described by a friction model that describes the friction behaviour in the full velocity range necessary for identification. Experimental parameter identification by means of linear least squares techniques showed to be very suited for identification of the unknown parameters, provided that the problem is properly scaled and that the influence of disturbances is sufficiently analysed and managed. An analysis of the least squares problem by means of a singular value decomposition is preferred as it not only solves the problem of rank deficiency, but it also can correctly deal with measurement noise and unmodelled dynamics.
Dynamic Modeling of Synchronous Belt-Drives Using an Explicit Finite Element Code
Authors: Wasfy Tamer M. , Leamy Michael J.
Published: June 2008

A time-accurate explicit time-integration finite element code is used to simulate the dynamic response of synchronous belts-drives. The belt is modeled using beam or truss elements. The sprockets are modeled as cylindrical rigid bodies. Normal contact between the belt and a sprocket is modeled using the penalty technique and friction is modeled using an asperity-based approximate Coulomb friction model. The belt teeth/grooves are assumed to be located at the belt nodes (every fixed number of belt nodes). The nodes in-between teeth are subjected to the normal contact and tangential friction forces. The belt and sprocket teeth are assumed to be trapezoidal. The equivalent belt-sprocket tooth stiffness and damping coefficients in the normal tooth contact direction are used to calculate a normal tooth contact force at the belt teeth nodes. The tooth contact model also includes the effect of the tooth engagement tolerance. For validation purposes, a two-sprocket drive is modeled and a comparison is made between tooth loads predicted by the finite element model and experimental data available in the literature. Reasonable agreement between the simulation and experimental results is found of the drive’s tooth loads. Also, the dynamic response of a hybrid sprocket – flat pulley belt-drive is studied.
Comparison of Three-Dimensional Flexible Beam Elements for Dynamic Analysis: Finite Element Method and Absolute Nodal Coordinate Formulation
Authors: Schwab A. L. , Meijaard J. P.
Published: June 2008

Three formulations for a flexible spatial beam element for dynamic analysis are compared: a finite element method (FEM) formulation, an absolute nodal coordinate (ANC) formulation with a continuum mechanics approach and an ANC formulation with an elastic line concept where the shear locking of the asymmetric bending mode is suppressed by the application of the Hellinger–Reissner principle. The comparison is made by means of an eigenfrequency analysis on two stylized problems. It is shown that the ANC continuum approach yields too large torsional and flexural rigidity and that shear locking suppresses the asymmetric bending mode. The presented ANC formulation with the elastic line concept resolves most of these problems.
Capturing Creativity: Using a Design Repository to Drive Concept Innovation
Authors: Bohm Matt R. , Vucovich Jayson P. , Stone Robert B.
Published: June 2008

This paper describes how a design repository can be used as a concept generation tool by drawing upon archived function-based design knowledge. Modern design methodologies include several types of activities to formally generate design concepts. Typical concept generation methods range from open-ended creative brainstorming activities to quantitative function-component analysis. A combination of two such methods—the Chi Matrix and Morphological Matrix techniques—is the basis for this work. Building on existing functionality of the design repository, desired product functions can be specified in a search of stored design knowledge, returning a Morphological Matrix of artifacts solving the specified functions. Such a search is termed a Morphological Search. The repository Morphological Search feature is evaluated against concepts generated in a previous original design project. Results of the Morphological Search return are then compared to ten of the original concept variants generated during the design project. This comparison shows that 76% of the specified subfunctions return results and that, on average, 61.35% of the components used in the hand-generated concepts can be derived by using the Morphological Search feature.
Semantics-Based Design Knowledge Annotation and Retrieval
Authors: Li Zhanjun , Liu Min , Anderson David C. , Ramani Karthik
Published: June 2008

Nowadays computer aided tools have enabled the creation of the electronic design documents on an unprecedented scale, while determining and finding what can be reused is like searching a “needle in a haystack.” One of the primary reasons for this is that the design knowledge behind the physical design is not properly represented and indexed. With the large amount of designs available, design engineers need to retrieve suitable ones, so that a knowledge-based unified reuse environment can be realized. In this paper, we describe our approach to intelligently annotating and retrieving designs by using ontology engineering and natural language processing. We use the design documents from an engineering design class as the first case study.
Computation and Stability Analysis of Solutions of Periodic Delay Differential Algebraic Equations
Authors: Verheyden Koen , Lust Kurt , Roose Dirk
Published: June 2008

This paper is concerned with the numerical computation, continuation and stability analysis of periodic solutions of periodic delay differential algebraic equations. We consider systems with a time-periodic right hand side function and time-periodic delays. We introduce numerical algorithms based on collocation to compute periodic solutions and their stability. The presented methods combine knowledge from numerical methods for delay equations and differential algebraic equations. Our algorithms are illustrated with numerical results for two models.
Tolerance-Maps Applied to a Point-Line Cluster of Features
Authors: Ameta Gaurav , Davidson Joseph K. , Shah Jami J.
Published: June 2008

In this paper, groups of individual features, i.e. a point, a line, and a plane, are called clusters and are used to constrain sufficiently the relative location of adjacent parts. A new mathematical model for representing geometric tolerances is applied to a point-line cluster of features that is used to align adjacent parts in two-dimensional space. First, tolerance-zones are described for the point-line cluster. Then, a Tolerance-Map®, a hypothetical volume of points, is established which is the range of a mapping from all possible locations for the features in the cluster. A picture frame assembly of four parts is used to illustrate the accumulations of manufacturing variations, and the T-Maps provide stackup relations that can be used to allocate size and orientational tolerances. This model is one part of a bi-level model that we are developing for geometric tolerances. At the local level the model deals with the permitted variations in a tolerance zone, while at the global level it interrelates all the frames of reference on a part or assembly.
Automated Concept Generation: A Co-Evolutionary Approach
Authors: Li Wei , Jin Yan
Published: June 2008

Conceptual design is a key early activity in product development. However, limited understanding of the conceptual design process and lack of quantitative information at this stage of design pose difficulties for effective design concept generation and evaluation. In this paper, we propose a hierarchical co-evolutionary approach to supporting design concept generation and evaluation. The approach adopts a zigzag process in which grammar rules guide function decomposition and functions and means co-evolve at each level of decomposition hierarchy. It provides an automatic computational solution to complex conceptual design systems. In this paper, the details of the approach are described, and an example of designing a mechanical personal transporter is presented to show the effectiveness of the proposed approach.
A New Method for Vibration Mode Analysis
Authors: Chelidze David , Zhou Wenliang
Published: June 2008

In this paper, a new modal analysis method based on a novel multivariate data analysis technique called smooth orthogonal decomposition (SOD) is proposed. The development of the SOD and its main properties are described. The mathematical justification for the application in modal analysis is also provided. The proper orthogonal decomposition (POD) and its application in modal analysis are provided for comparison. Numerical simulations of discrete and continuous systems are used in this comparison. It is demonstrated that the SOD-based analysis overcomes main deficiencies of the POD. The SOD identifies linear normal modes and corresponding frequencies without requiring any a priori information about the distribution of mass in the system.
A Controversial Study of the Aerodynamics of a Baseball
Authors: Mitiguy Paul , Woo Michael
Published: June 2008

Projectile motion under idealized conditions has been well understood for centuries. However, once aerodynamic forces (drag and lift) are introduced, the motion becomes significantly more difficult to analyze and predict. This paper compares two aerodynamic models on the flight of a baseball — the first by Robert Adair and the second by Greg Sawicki, Mont Hubbards, and William Stronge. Applied to the distance traveled by a baseball, the two models predict substantially different results. The results of the models were further examined through interactive computer simulations using Working Model and Autolev.
A Hybrid Method Using Response Surface and Pattern Search for Design Optimization
Authors: Zhang T. , Choi K. K. , Rahman S.
Published: June 2008

This paper presents a new method to construct response surface function and a new hybrid optimization method. For the response surface function, the radial basis function is used for a zeroth-order approximation, while new bases is proposed for the moving least squares method for a first-order approximation. For the new hybrid optimization method, the gradient-based algorithm and pattern search algorithm are integrated for robust and efficient optimization process. These methods are based on: (1) multi-point approximations of the objective and constraint functions; (2) a multi-quadric radial basis function for the zeroth-order function representation or radial basis function plus polynomial based moving least squares approximation for the first-order function approximation; and (3) a pattern search algorithm to impose a descent condition. Several numerical examples are presented to illustrate the accuracy and computational efficiency of the proposed method for both function approximation and design optimization. The examples for function approximation indicate that the multi-quadric radial basis function and the proposed radial basis function plus polynomial based moving least squares method can yield accurate estimates of arbitrary multivariate functions. Results also show that the hybrid method developed provides efficient and convergent solutions to both mathematical and structural optimization problems.
Acquisition of Product Design Guidelines Considering User Kansei Data Pertaining to Product Environments
Authors: Yoshimura Masataka , Nishimura Tsutomu , Izui Kazuhiro
Published: June 2008

Recently, almost all industrially manufactured consumer goods have a high level of engineering excellence, and product designers face an increasingly difficult task of creating products that will stand out in a competitive marketplace. At present, users tend to base their purchasing decisions on the product’s degree of fitness to their preferences, not the degree of functional fulfillment that the product offers. The development of products that are more attractive to users requires the consideration of human preferences and sensibilities, so-called “Kansei,” as well as the skillful application of these factors to the design sequence. The process of identifying and clarifying Kansei suggests that personal preferences concerning a given product are strongly influenced by both the person’s environment and the circumstances in which the product will be used. Analyzing both of these clarifies the influence that subconscious desires and human nature have on the expression of Kansei. This paper proposes a method for extracting the Kansei of potential customers and applying it to product designs that aim to maximize their human appeal, rather than their technical superiority.
Designing Product Families for a Changing Market Space
Authors: Kulkarni Rakesh S. , Allen Janet K. , Mistree Farrokh
Published: June 2008

The Product Platform Constructal Theory Method (PPCTM) provides designers with an approach for synthesizing multiple modes of managing customization in the development of product platforms. An assumption underlying PPCTM is that the extent of the market space is known and is fixed. In this paper, we introduce PPCTM-RCM (Robust to Changes in Market) that facilitates designing product platforms when the extent of the market space is expected to change. The PPCTM-RCM is illustrated via example problem, namely, the design of a product platform for a line of customizable pressure vessels. Our focus in this paper is on highlighting features of the method rather than results per se.
Limitations of Parametric Operators for Supporting Systematic Design
Authors: Bettig Bernhard , Bapat Vikram , Bharadwaj Balaji
Published: June 2008

Computers are being used extensively in the manufacturing industry to design and analyze products. In spite of the power of existing CAD systems and potential power of current Design Automation systems, we believe that they possess an inherent limitation that keeps them from aligning with and fully supporting the design process. Specifically, all of these systems are based on using parametric operators to generate valid designs. This paper examines the limitations of parametric operators for CAD and design automation and shows how “variational” methods could be used. An approach using variational methods is compared with traditional CAD and design automation methods. The paper also proposes a language of objects and relationships to represent design requirements. This work is a step towards realizing an interactive design synthesis system that can represent and satisfy design requirements.
Hierarchical Modularity: Decomposition of Function Structures With the Minimal Description Length Principle
Authors: Wang Bingwen , Antonsson Erik K.
Published: June 2008

In engineering design and analysis, complex systems often need to be decomposed into a hierarchical combination of different simple subsystems. It’s necessary to provide formal, computable methods to hierarchically decompose complex structures. Since graph structures are commonly used as modeling methods in engineering practice, this paper presents a method to hierarchically decompose graph structures. The Minimal Description Length (MDL) principle is introduced as a measure to compare different decompositions. The best hierarchical decomposition is searched by evolutionary computation methods with newly defined crossover and mutation operators of tree structures. The results on abstract graph without attributes and a real function structure show that the technique is promising.
Structural Topology Optimization Using Frame Elements Based on the Complementary Strain Energy Concept for Eigen-Frequency Maximization
Authors: Takezawa Akihiro , Nishiwaki Shinji , Izui Kazuhiro , Yoshimura Masataka
Published: June 2008

This paper discuses a new topology optimization method using frame elements for the design of mechanical structures at the conceptual design phase. The optimal configurations are determined by maximizing multiple eigen-frequencies in order to obtain the most stable structures for dynamic problems. The optimization problem is formulated using frame elements having ellipsoidal cross-sections, as the simplest case. Construction of the optimization procedure is based on CONLIN and the complementary strain energy concept. Finally, several examples are presented to confirm that the proposed method is useful for the topology optimization method discussed here.
A Method for Inferring the Optimization Cost Function of Experimentally Observed Motor Strategies
Authors: Bottasso Carlo L. , Croce Alessandro , Sartirana Stefano , Prilutsky Boris I.
Published: June 2008

We propose a computational procedure for inferring the cost functions that, according to the Principle of Optimality, underlie experimentally observed motor strategies. This work tries to overcome the need to hypothesize the cost functions, extracting this non-directly observable information from experimental data. Optimality criteria of observed motor tasks are here indirectly derived using: a) a mathematical model of the bio-system; and b) a parametric mathematical model of the possible cost functions, i.e. a search space constructed in such a way as to presumably contain the unknown function that was used by the bio-system in the given motor task of interest. The cost function that best matches the experimental data is identified within the search space by solving a nested optimization problem. This problem can be recast as a non-linear programming problem and therefore solved using standard techniques. The proposed methodology is tested on representative examples.
LMI Tools for Stability Analysis of Fractional Systems
Authors: Moze Mathieu , Sabatier Jocelyn , Oustaloup Alain
Published: June 2008

The main point when dealing with Linear Matrix Inequalities (LMI) is convexity. However, with state space representation of fractional systems, the stability domain for a fractional order 0 < ν < 1 is not convex. The classical stability condition thus cannot be extended to fractional systems. In this paper, three LMI based methods are used to characterize stability. The first is based on the second Lyapunov method and provides a sufficient but non-necessary condition. The second and new method provides a sufficient and necessary condition, and is based on a geometric analysis of a fractional system stability domain. The third method is more conventional but involves non strict LMI. A comparison of the first two methods is provided.
Adaptive Customization of User Interface Design Based on Learning Styles and Behaviors: A Case Study of a Heritage Alive Learning System
Authors: Kim Yong Se , Kim Sungah , Cho Yun Jung , Park Sun Hee
Published: June 2008

The computer mediated education in the 21st century knowledge-based society calls for an intelligent learning environment which is adaptive to learner’s various needs and changing situations in a learning process. Such an intelligent learning environment can be embodied by having intelligent features such that the user interfaces are adaptive to user’s learning style. The learner model is introduced as a main component for designing adaptive features. The learner modeling makes it possible to create a highly effective learning environment by allowing the development of tutoring media, interface design, and the design of learning strategy tuned to the perception style, input, processing, and understanding of learning information. In order to come up with a more accurate and reliable learner model, the system should be able to record interactions between the learner and the learning system so that their interrelations with the leaning situations can be analyzed and reflected to the learner model. The learner model is to be updated according to the analysis in a dynamic manner to provide the adaptive learning environment tailored to each learner. In this paper, such a learning system is demonstrated through the implementation of a heritage alive learning system.
Studies on Onset of Ratcheting in Pipe Bends
Authors: Shanmuga Sundaram K. , Thanigaiyarasu G. , Palaniswamy Manoj Kumar
Published: June 2008

This paper intends to provide an overview of various possibilities of ratcheting in pipelines subjected to cyclic thermal and mechanical loadings. The present work deals with review on results from the studies of research papers providing experimental data and analytical study on ratcheting. There has been no well-defined material model and analysis procedure to predict this phenomenon accurately. An analysis carried out on 2-inch NPS SS304 pipe bends with different thickness (Schedule 40 and Schedule 80) using ABAQUS, non-linear FEA software to predict the strain accumulation and their influences on ratcheting failure is presented. Also, a theoretical analysis to identify the onset of ratcheting in pipe bends using the modified equation of Edmunds and Beer is presented. The results and their inferences are included.
Modeling, Motion and Vibration Control for Flexible Rotor Supported by Active Magnetic Bearings
Authors: Nakajima Yuichi , Sagane Takahito , Tajima Hiroshi , Watanabe Toru , Seto Kazuto
Published: June 2008

This paper proposes a new modeling technique and control system design for flexible rotors using active magnetic bearings (AMB) to pass through many critical speeds and fulfill high-speed rotation. To achieve this purpose, it is necessary to control not only motion but also many modes of bending vibration. For the purpose, an extended reduced order physical model that is able to express simultaneously the motion and bending vibration of the flexible rotor, is proposed. Furthermore, a new controller combined PID with LQ control is adapted to control the flexible rotor. Effectiveness of the proposed modeling and control approach for the flexible rotor is verified through simulations and experiments.
Methods for Discrete Design Optimization
Authors: Pettersson Marcus , Andersson Johan , Krus Petter
Published: June 2008

One area in design optimization is component based design where the designer has to choose between many different discrete alternatives. These types of problems have discrete character and in order to admit optimization an interpolation between the alternatives is often performed. However, in this paper a modified version of the non-gradient algorithm the Complex method is developed where no interpolation between alternatives is needed. Furthermore, the optimization algorithm itself is optimized using a performance metric that measures the effectiveness of the algorithm. In this way the optimal performance of the proposed discrete Complex method has been identified. Another important area in design optimization is the case of optimization based on simulations. For such problems no gradient information is available, hence non-gradient methods are therefore a natural choice. The application for this paper is the design of an industrial robot where the system performance is evaluated using comprehensive simulation models. The objective is to maximize performance with constraints on lifetime and cost, and the design variables are discrete choices of gear boxes for the different axes.
Modal Reduction Method for Vibrational Analysis of Structures Partially Filled With Internal Liquids
Authors: Schotte´ Jean-Se´bastien , Ohayon Roger
Published: June 2008

In the framework of the vibrational analysis of structures, we propose a method to take into account the internal liquids (like fuel) in the structure modelling. Since the “classical” added-mass hydroelastic model cannot be used for slender and flexible structures such as space launchers or civil aircraft wings (because the decoupling assumption of sloshing and hydroelasticity is not valid for such structures), we propose here a revised hydroelastic formulation which takes this coupling into account. Since this model introduces in the system a great number of degrees of freedom for the fluid, we will present a reduction method using the Ritz-Galerkin projection onto the fluid sloshing modal basis. A discretization of the reduced equations by the finite element method will be proposed and the convergence rate of this modal reduction method will be discussed on an application example.
Nonstationary Sliding Mode Control Using Time-Varying Switching Hyperplane for Transverse Vibration of Elevator Rope
Authors: Otsuki Masatsugu , Ushijima Yumiko , Yoshida Kazuo , Kimura Hiroyuki , Nakagawa Toshiaki
Published: June 2008

The excitation of transverse vibration of an elevator rope is caused by the resonance with the building-sway by an earthquake or wind-induced vibration, hence, a useful active solution for its issue is demanded. In this paper, therefore, the vibration suppression for the elevator rope with the nonstationary sliding mode control using a time-varying switching hyperplane is performed by moving the rope directly near its boundary by use of a control device with gaps between actuator and rope. The nonstationary sliding mode controller has the effectiveness for the control of the object with time-varying characteristics and the robustness for the nonlinearity of the control device. The performance and robustness of the proposed controller are verified through the numerical calculation for the practical case, consequently, the good results are obtained.
DYC and SMC Combined New Tracking Control Based on Nonholonomic Constraints for Skidding Cars
Authors: Saito Shinjiro , Nonaka Kenichiro
Published: June 2008

A car running on a low friction road skids off easily and falls into a spin. In general, it is technically difficult for normal drivers to recover a car into stable state. If the car obeys non-holonomic constraints, which corresponds to the case without side skidding, the steering controller based on exact linearization assures exponential stability to the desired trajectory. To keep these constraints, we have proposed a driving force controller based on the sliding mode control that drastically reduces the deviations from constraints. In this study, we combine “direct yaw moment control” and sliding mode control to show that our controller is effective to prevent undesired tracking errors. Additionally, the chattering phenomena caused by the driver’s and our controller’s inputs is smoothed by proper interior division of them related to transverse direction speeds of each tire. The advantage of our controller is verified through an interactive driving simulation.
On the Placement of Active Bars and Optimal Feedback Gain in Random Adaptive Structures for Vibration Suppression
Authors: Yang F. , Sedaghati R. , Younesian D. , Esmailzadeh E.
Published: June 2008

This paper addresses active vibration control of adaptive structures using piezoelectric active structural elements with built-in sensing and actuation function. Optimal placement and feedback gain of these active members are important issues, which are discussed in this study. An efficient optimal placement strategy has been developed using minimum control energy dissipating over infinite time interval. Optimal location of active members has been found through minimization of total control energy dissipating over infinite time interval using Simulated Annealing (SA) algorithm. Moreover, the effect of structural randomness and random load in optimal feedback gain has been investigated. To accomplish this, a mathematical model with reliability constraints on the stress and displacement is developed and the optimal velocity feedback gain of active members, using probabilistic optimization technique, is obtained. Illustrative examples are presented to demonstrate the effectiveness of this methodology. It is shown that deterministic approach can not provide reliable optimum design values.
Multi-Field Characterization of Single Wall Nano-Tube Composites for Hydrogen Storage
Authors: Michopoulos John G. , Lambrakos Sam G. , Tran Nick E.
Published: June 2008

The goal of the present work is three fold. Firstly to create the forward continuum model of a multi-species diffusing system under simultaneous presence of chemical reactivity and temperature as the general case of all hydrogen storage systems. Secondly, cast the problem of hydrogen storage in a pragmatic product-design context where the appropriate design parameters of the system are determined via appropriate optimization methods that utilize extensive experimental data encoding the behavior of the system. Thirdly, demonstrate this methodology on characterizing certain systemic parameters. Thus, the context of the work presented is defined by a data-driven characterization of coupled heat and mass diffusion models of hydrogen storage systems from a multiphysics perspective at the macro length scale. In particular, a single wall nanotube (SWNT) based composite is modeled by coupled partial differential equations representing spatio-temporal evolution of distributions of temperature and hydrogen concentration. Analytical solutions of these equations are adopted for an inverse analysis that defines a non-linear optimization problem for determining the parameters of the model by objective function minimization. Experimentally acquired and model produced data are used to construct the system’s objective function. Simulations to demonstrate the applicability of the methodology and a discussion of its potential extension to multi-scale and manufacturing process optimization are also presented.
FMDesign: A Tool and Interchange Format for Product Concept Designs
Authors: Johansson Olof , Krus Petter
Published: June 2008

This paper presents a formalized approach to design product models in the product concept evaluation phases, and exchange the models with other engineering tools using open formats like XML and relational database tables. FMDesign is used for designing product concepts with the aid of integrated stakeholder trees, requirement trees, function-means trees, product concept trees, and implementation trees. It has its foundation in systems engineering and design methodology, and presents a formalization and integration with theory from software engineering that enable similar engineering tools to be implemented with automated model driven software implementation techniques that support the Unified Modeling Language (UML). The paper provides an overview of the theory behind the tool, its user interface, interchange formats and the formal software specification as an UML class diagram.
Piston Ring Behaviour Simulation Considering Mixed-Lubrication and Flexibility
Authors: Senatore Adolfo , D’Agostino Vincenzo
Published: June 2008

An important portion of the total power loss in a modem automotive engine is due to piston ring/cylinder bore friction. This paper introduces the results of simulations about the interaction of a SI engine piston ring taking into account the mixed lubrication regime, the ring flexibility in presence of piston approaching motion to the cylinder liner. The friction force calculations show a visible difference between the ring portion interacting with the two cylinder sides (Thrust and Anti-Thrust) due to specific oil film wedges caused by flexibility and piston lateral motion. The effects of engine speed, radial tension, surface roughness and ring shape are also investigable.
Identification and Control of Hysteresis in Rolling Element Guideways
Authors: Al-Bender F. , Symens W.
Published: June 2008

Rate independent hysteresis seems to be the dominant frictional characteristic found in many machine elements in common engineering use, such as plain and rolling element guideways. The study of the non-linear dynamics caused by such elements becomes imperative if we wish to achieve improved design and, in particular, effective control of such machines. This paper reviews systematic analysis, which we have carried out to characterize the dynamics of rolling element guideways. The dependency of hysteresis characteristics on the bearing design parameters is first investigated and the notion of ‘equivalent’ dynamic quantities, namely stiffness and damping, is introduced. Secondly, a frequency domain, harmonic analysis method for mass-“hysteresis spring” systems, via application of the Describing Function method, is developed and discussed. We checked the validity and applicability of this approach by direct numerical simulation as well as by experiment. The results showed that the (amplitude dependent) Frequency Response Maps invariably contain an “anomalous” region where the response is very sensitive to systems parameter variations. This manifests itself in practice in jump-like phenomena, which thus appear to be inherent features of this type of system. Finally, appropriate control structures for systems with this type of hysteresis elements are proposed and discussed.
Structural Finite Element Modeling of Electromechanical Interaction in Rotordynamics of Electrical Machines
Authors: Laiho Antti N. , Holopainen Timo P. , Klinge Paul , Arkkio Antero
Published: June 2008

In this work the electromechanical interaction in electrical machines is studied. The eccentric rotor motion distorts the electromagnetical fields in the air-gap between the stator and rotor of the machine inducing a total force, the unbalanced magnetic pull, exerted on the rotor shaft. In order to study the phenomenon a parametric electromagnetic force model is coupled with finite element structural model of the machine. The main objective of the work is to study the effects of the electromechanical interaction on vibration characteristics of electrical machines.
Automatic Multi-Axis Slicing Based on Centroidal Axis Computation
Authors: Ruan Jianzhong , Eiamsa-ard Kunnayut , Liou F. W.
Published: June 2008

A multi-axis adaptive slicing algorithm which can generate optimal slices to achieve deposition without support structures for multi-axis layered manufacturing is presented in this paper. Different from current adaptive slicing, this technique varies not only in layer thickness but also in slicing direction. Aware of potential problems of previous research on slicing, the work in this paper studied an innovative geometry reasoning and analysis tool-centroidal axis. Similar to medial axis, it contains geometry and topological information but is much computationally cheaper. Using a centroidal axis as a guide, the multi-axis slicing procedure is able to generate a “3-D” layer or change slicing direction as needed automatically to build the part with better surface quality. This paper presents various examples to demonstrate the feasibility and advantages of centroidal axis and its usage in the multi-axis slicing process.
A Time-Stepping Scheme for Quasistatic Multibody Systems
Authors: Trinkle J. C. , Berard Stephen , Pang J. S.
Published: June 2008

Two new instantaneous-time models for predicting the motion and contact forces of three-dimensional, quasistatic multi-rigid-body systems are developed; one linear and one nonlinear. The nonlinear characteristic is the result of retaining the usual quadratic friction cone in the model. Discrete-time versions of these models provide the first time-stepping methods for such systems. As a first step to understanding their usefulness in simulation and manipulation planning, a theorem defining the equivalence of solutions of a time-stepping method for the nonlinear model and a global optimal solution of a related convex optimization problem is given. In addition, a Proposition giving necessary and sufficient conditions for solution uniqueness of the nonlinear time-stepping method is given. Finally, a simple example is discussed to help develop intuition about quasistatic systems and to solidify the reader’s understanding of the theorem and proposition.