bluuebunny/crossref_metadata_2025 huggingface dataset:
Adaptive Moving Least-Squares Surfaces for Multiple Point Clouds Registration
Authors: Huang Yunbao , Zhang Linchi , Tan Zhihui , Wang Qifu , Chen Liping
Published: June 2012

In this paper, we propose an Adaptive Moving Least-Squares (AMLS) surface based approach for multi-view or multi-sensor point cloud ICP registration. The core idea of this approach is to reconstruct a smooth and accurate surface, e. s. AMLS surface, from a point cloud, without data segmentation and surface model selection, resulting in an accurate point-to-AMLS surface ICP registration. The major difference between AMLS and traditional MLS is that the width of Gaussian kernel is adaptively scaled with the principle curvature, which is defined through local integral invariant analysis. Experimental results of both synthetic data and scanned data from a mechanical part show that the presented approach is more accurate and robust on sensor noise and sample density.
Some Initial Findings From an Investigation of Engineering Students’ Choices and Motivations
Authors: Smith Warren F.
Published: June 2012

Engineering is a technical profession that seeks to solve open problems. The practice of engineering spans design, manufacture, operation and maintenance and these in themselves offer wide ranging opportunities for routine and novel approaches. In preparing engineering students through a university education, it has been observed that they have differing reactions to open ended project activities intended to model their chosen profession. For example, not all mechanical or even automotive engineering students desire to be involved in a Formula SAE Team. If students engaged in their engineering education are preparing to deal with future issues not yet perceived (open problems), why do students make the choices they do and what motivates them? Why have they chosen an engineering pathway and what do they find exciting about this prospect? With a view to strengthening educational outcomes, some initial findings from an investigation of student choices and motivations are presented.
The Applicability of the Floating-Frame Based Component Mode Synthesis to High-Speed Rotors
Authors: Pechstein Astrid , Reischl Daniel , Gerstmayr Johannes
Published: June 2012

The floating frame of reference formulation (FFRF) together with modal reduction is a standard method in multibody system dynamics. As an advantage of the FFRF, fully nonlinear coupling of small flexible deformations superimposed to arbitrarily large rigid body motion is considered. The idea of the present paper is to apply the FFRF with component mode synthesis to an electromagnetically levitated high-speed rotor, in which large tilting angles may occur, which are not accounted for in classical rotor dynamics. The applicability of FFRF to rotor dynamics, especially close to bending resonance, is not studied in detail in the literature. Thus, fully nonlinear and transient finite element computations are compared to different FFRF-based simulations. In exhaustive numerical studies of a flexible two-disc rotor, comparing FFRF and fully nonlinear transient computations, it is shown that the choice of reference frames and the rotation parameterization influence accuracy of results and CPU-performance.
PLM Architecture for Optimization of Geometrical Interfaces in a Product Platform
Authors: Levandowski Christoffer , Edholm Peter , Ekstedt Fredrik , Carlson Johan , So¨derberg Rikard , Johannesson Hans
Published: June 2012

Product platforms can be used as an enabler for offering a wide variety of products to the market, while keeping the development cost down. Reusing knowledge in new designs is a key concept of product platforms, whether it is about reusing entire parts, or reusing ideas and concepts. The Configurable Component (CC) concept is one way of describing a product platform, and is based on autonomous subsystems that are not fixed, but have a bandwidth within which they can vary. These systems are configured to fit the set of requirements resulting in product variants. Product Lifecycle Management (PLM) as a complementing business strategy deals with integrating processes, information, systems and people across the product lifecycle to support the development of complex products. This paper describes a case study where the CC concept is successfully implemented in a PLM environment to allow configuration of the systems in relation to each other. The focal point of this paper is configuration of the geometrical interfaces between sub systems. A car door from a Swedish car manufacturer, known for the tight fit in assembly, is used as an example. In this case, there are two requirements on the assembly. First, the assembly cannot be far from nominal, thus requiring robust interfaces between the ingoing parts. Second, the window must be mountable. The result is a PLM architecture with a Product Data Management (PDM) system, a Computer Aided Design (CAD) tool, two Computer Aided Engineering (CAE) tools and a configurator, all integrated.
Wrench Capability Analysis of Cable-Driven Parallel Mechanisms
Authors: Zou Yu , Zhang Yuru
Published: June 2012

The maximum wrench capabilities of the cable-driven parallel mechanisms are investigated in this paper. Focusing on accuracy and efficiency, two methods, an optimization-based method and a hybrid method based on optimization and geometry, are presented for determining the wrench capability of the cable-driven parallel mechanisms. Both methods are applied to a 6-DOF cable-driven parallel mechanism with eight cables to compute the maximum isotropic force and maximum isotropic moment. Comparison of the two methods is made. The results show that the hybrid method proposed is more accurate and computationally efficient.
Autoparametric Resonances of Elastic Structures Coupled With Two Sloshing Modes in a Square Liquid Tank
Authors: Ikeda Takashi , Takashima Masaki , Harata Yuji
Published: June 2012

Nonlinear vibrations of an elastic structure coupled with liquid sloshing in a square tank subjected to vertical sinusoidal excitation are investigated. Previous studies examined the vibrations of a structure coupled with only one sloshing mode in a rectangular tank. However, square tanks are expected to work more efficiently as a vibration suppression device (Tuned Liquid Damper, TLD) because two sloshing modes, (1,0) and (0,1) modes, simultaneously appear when the internal resonance ratio 2:1:1 is satisfied. In reality, it is impossible to build a perfectly square tank. Therefore, a nearly square liquid tank is also considered when the tuning condition is slightly deviated. In the theoretical analysis, the fluid in the tank is assumed to be perfect. The modal equations of motion for seven sloshing modes are derived using Galerkin’s method, considering the nonlinear terms. The linear damping terms are then incorporated into the modal equations to consider the damping effect of sloshing. The frequency response curves are determined using van der Pol’s method (based on the harmonic balance method). From these response curves, the influences of the liquid level, the aspect ratio of the tank cross section, and the deviation of the tuning condition are investigated. For a square tank it is found that (1,0) and (0,1) modes are nonlinearly coupled. When the liquid level is high, there are three patterns for sloshing: (I) both (1,0) and (0,1) sloshing modes appear at identical amplitudes; (II) these two modes appear at different amplitudes; and (III) either (1,0) or (0,1) mode appears. Compared with the performance of a rectangular TLD, a square TLD works more efficiently when the liquid level is low. Small deviations of the tuning condition may cause amplitude modulated motion to appear. Bifurcation sets are also calculated to illustrate the influence of the system parameters on the performance of the TLD. Experiments were also conducted in order to confirm the validity of the theoretical results. These results were in good agreement with the experimental data.
Dynamic Analysis of a Direct-Driven Permanent Magnet Generator Drive Train Including Flexible Turbine Blades
Authors: Heikkinen Janne E. , Sopanen Jussi T. , Ruuskanen Vesa V. , Nerg Janne K.
Published: June 2012

The dynamic torque of a wind turbine drive train with a direct-driven permanent magnet synchronous generator is analyzed in this paper. A simplified multi-mass model for the whole drive train — from the flexible turbine blades to the rotor of the generator — is presented. Dynamic torque is analyzed for both steady state and transient cases. In the mechanical model, torsional electromagnetic forces called “cogging torque” and “torque ripple” are used as excitation forces. The magnitude of electromagnetic excitation is highly related to the shape and placement of the magnets. Four different permanent magnet installations are analyzed. It can be noticed that during start-up only cogging torque affects the generator rotor. Allowable cogging torque in this case is 1.5–2 percent of the rated torque even when the corresponding resonance frequency does not occur in the operational speed range of the wind turbine. Furthermore, it was perceived that the resonance caused by the excitation torque should occur at the lowest possible speed to minimize dynamic torque during the start-up. Several excitations, both cogging torque and torque ripple harmonics, occur in the operational speed range. However, it was detected that the dynamic responses in the operational speed range are not critical to the operation of the wind turbine.
Simultaneous Requirement and Design Optimization of an Industrial Robot Family Using Multi-Objective Optimization
Authors: Wa¨ppling Daniel , Feng Xiaolong , Andersson Hans , Pettersson Marcus , Lunden Bjo¨rn , Westro¨m Jakob
Published: June 2012

Simultaneous development of an industrial robot family, consisting typically of 2–10 robots, has been an engineering practice in robotics industry. In this process, significant scenario studies on defining product requirement specifications and associated design change are conducted. This implies that understanding the relation between product requirements and design of the robot family is of critical importance. However, in the current engineering practice, any change in requirement specification results in tremendous efforts in the re-design of the robot family. This discloses the need for efficient methodology and tools for simultaneously optimizing product requirements and design of an industrial robot family. In this work, methodology and tools have been successfully developed for simultaneously optimizing product requirements and design of an industrial robot family in a fully automated way. This problem is formulated to a multi-objective optimization problem and solved using multi-objective genetic algorithm (MOGA). Results of this work have demonstrated clearly the efficiency of this approach and the insight obtained on the relation between product requirement and product design. The developed methodology and results of simultaneous requirement specification and design optimization will be detailed in this paper. In addition, research experience and future work will also be discussed. To our best knowledge, the simultaneous optimization of product requirement and product design has not been widely investigated and explored in academia. The trade-off information explored by such approach is crucial in product development in industrial practice. Such approach will further increase the complexity of traditional design optimization approach where product requirement is normally pre-defined and used as constraint. It is certain that discussions of the addressed problem and developed methodology will contribute to promoting the significance of efforts in the research society of multi-objective design optimization, multi-objective design optimization of product families, and design automation.
A New Approach to Trust and Reputation Based Rights Management in Product Development Collaboration
Authors: Vo¨lz Diana , Schu¨le Anselm
Published: June 2012

In times of globalization the importance of cross-company collaboration has significantly increased. An appropriate example is the automotive industry where Original Equipment Manufacturers (OEM) need to collaborate with several globally distributed suppliers to develop innovative high-tech cars. In this case, sharing information with the collaboration partner is a complex and risky process for the company but nevertheless an essential factor for development projects to be successful. Knowledge is the most important resource in today’s economy, especially in specific branches [I]. However, the damage caused by industrial espionage and product piracy has continually increased [2]. Thus, the protection of IP (intellectual property) during data exchange within the product development process is challenging and highly depends on trust between the collaboration partners. Usually, rights management in data exchange is mainly based on user groups and roles as well as by objects and projects. This classification does not meet the requirements of rights management in this paper. A new approach is introduced to manage data exchange rights by trust and reputation in product development collaboration.
Comparing the Performance of a Nonlinear Energy Harvester in Mono- and Bi-Stable Potentials
Authors: Masana Ravindra , Daqaq Mohammed F.
Published: June 2012

The quest to develop broadband vibratory energy harvesters (VEHs) has recently motivated researchers to explore introducing nonlinearities into the harvester’s design. Some research efforts have demonstrated that this new class of nonlinear harvesters can outperform their traditional linear (resonant) counterparts; some others however concluded that nonlinearities can diminish the harvester’s transduction. Through this effort, we compare the performance of a nonlinear VEH operating in mono- and bi-stable potentials. With that objective, we consider an axially-loaded clamped-clamped piezoelectric beam which functions as an energy harvester in the mono-stable (pre-buckling) and bistable (post-buckling) configurations. For the purpose of fair performance comparison, the oscillation frequency around the stable equilibria of the harvester is tuned to equal values in both configurations. The harvester is then subjected to harmonic base excitations of different magnitudes and a slowly-varying frequency which spans a wide range around the tuned oscillation frequency. The output voltage measured across an arbitrarily chosen electric load is used as a relative performance measure. Both numerical and experimental results demonstrate that the shape of the potential function plays an essential role in conjunction with the magnitude of the base excitation to determine whether the bi-stable harvester can outperform the mono-stable one and for what range of frequencies.
Consensus Based Formation Control of Multiple Small Rotary-Wing UAVs
Authors: Xu Yaojin , Di Long , Chen YangQuan
Published: June 2012

Small unmanned aerial vehicles (UAVs) can provide facilities in various applications. Compared with single UAV system, small UAVs based cooperative UAV system can bring advantages such as higher efficiency and safety. Therefore, it is necessary to design a robust multi-agent cooperative flight controller to coordinate a group of small UAVs for stable formation flights. This paper investigates the problem of consensus-based formation control for a multi-UAV system. Firstly, We choose a simplified model with nonholonomic constraints for UAV dynamics. Secondly, using the algebraic theory and backstepping technique, we design consensus protocols for multi-UAV systems under the strongly connected topology. Then based on that, we propose a multi-UAVfromation control strategy. Finally, we extend our results to the directed topology case which is still effective by simulation.
The Integration of Sustainability, Systems, and Engineering Design in the Engineering Curriculum at James Madison University
Authors: Nagel Robert L. , Pierrakos Olga , Pappas Eric C. , Ogundipe Adebayo
Published: June 2012

In order for our future engineers to be able to work toward a sustainable future, they must be versed not only in sustainable engineering but also in engineering design. An engineering education must train our future engineers to think flexibly and to be adaptive as it is unlikely that their future will have them working in one domain. They must, instead, be versatilists. The School of Engineering at James Madison University has been developed from the ground up to provide this general engineering training with an emphasis on engineering design, systems thinking, and sustainability. Students take courses in math and science, business and liberal arts, engineering science, sustainability, and design. In this paper, we discuss how sustainability is taught in a multi-context perspective through the School’s curriculum and pedagogy. We do not mean to present the School’s approach as an all or nothing model, but instead as a collection of approaches of which hopefully one or more may be appropriate at another university.
Autonomous Flying Under 500 USD Based on RC Aircraft
Authors: Di Long , Chen YangQuan
Published: June 2012

Radio control (RC) aircrafts have been favorite toys of aviation hobbyists for years. Because of their simple configurations and low expense, they can also be used for reconnaissance and surveillance with information-gathering devices under commands of a skillful human pilot. However, control with human in the loop not only degrades the reliability of the flight performance, but also bring restrictions in endurance and accuracy. In order to resolve these issues and extend the usage of RC aircrafts, getting them capable of autonomous navigation is a preferred solution. This paper reports our approach by designing and integrating an autonomous system on a regular RC aircraft to achieve full autonomy while keeping the additional costs almost equivalent to the cheap RC platform. The current platform will be briefly presented, the system architecture and major components will be introduced, and detailed autonomous demonstration flight results will be provided at the end.
Global Product Family Design: A Mathematical Model for Simultaneous Decision of Module Commonalization and Supply Chain Configuration
Authors: Fujita Kikuo , Amaya Hirofumi , Akai Ryota
Published: June 2012

Today’s manufacturing has become global at all aspects of marketing, design, production, distribution, etc. While product family design has been an essential viewpoint for meeting with the demand for product variety, its meaning is becoming more broad and complicated with linking product design with issues on market systems, supply chain, etc. This paper calls such a design situation ‘global product family design,’ and firstly characterizes its components and complexity. Following them, this paper develops a mathematical model for the simultaneous decision problem of module commonalization strategies under the given product architecture and supply chain configuration through selection of manufacturing sites for module production, assembly and final distribution as an instance of the problems. This paper demonstrates some numerical case studies for ascertaining the validity and promise of the developed mathematical model with an optimization method configured with a genetic algorithm and a simplex method. Finally, it concludes with some discussion on future works.
Fractal Characterisation of Inhomogeneous Rough Surfaces
Authors: Burbridge Daniel J. , Howell-Smith Sebastian , Teodorescu Mircea S.
Published: June 2012

Load bearing conjunctions are never perfectly flat. They are covered by surface features, which may be either unintentional roughness inherent in the manufacturing process or a combination of such roughness with intentionally introduced surface texture. In either case, only a small proportion of load bearing surfaces are in contact and carry load. This depends on the surface topography, material properties and contacting conditions. Simple surface roughness characterisation parameters such as Ra, Rp etc. although commonly used do not give an adequate description, particularly where surfaces are deliberately textured. Furthermore Imaged surface topographies commonly exhibit features below the resolution of the imaging apparatus. We demonstrate the application of a fractal geometry analysis to honed internal combustion engine cylinder liners, imaged by Atomic Force Microscopy and Confocal Laser Scanning Microscopy. This method enables anisotropic surfaces to be characterised by five parameters which can then be used to generate model surfaces whose characteristics follow very closely those of the measured surface. Analysis of the structure function allows the determination of length scales and roughness features relevant at a given contact length. The reconstruction of anisotropic surfaces is demonstrated. Results from modelled contacts between these surfaces reveal the likely asperity contact geometry to be used in modelling contact and friction in these interfaces.
Impulse Response of a Generalized Fractional Second Order Filter
Authors: Jiao Zhuang , Chen YangQuan
Published: June 2012

The impulse response of a generalized fractional second order filter of the form (s2α + asα + b)−γ is derived, where 0 < α ≤ 1, γ > 0. The asymptotic properties of the impulse responses are obtained for two cases, and similar properties are shown for these two cases when we change the value of γ. It is shown that only when (s2α + asα + b)−1 has the critical stability, the generalized fractional second order filter (s2α + asα + b)−γ has different properties as we change the value of γ. Finally, numerical examples to illustrate the impulse response are provided to verify the proposed concepts.
Tuning Fractional Order Proportional Integral Controllers for Time Delayed Systems With a Fractional Pole
Authors: Malek Hadi , Luo Ying , Chen YangQuan
Published: June 2012

First order plus time delay model is widely used to model systems with S-shaped reaction curve. Its generalized form is the use of a single fractional pole to replace the first order (single-time constant) model, which is believed to better characterize the reaction curve. Using time delayed system model with a fractional pole as the starting point, in this paper, designing fractional order controllers for this class of fractional order systems is investigated. The novelty of this paper is on designing the integer order PID and fractional order PI and [PI] controllers for these class of systems. The simulation and lab experimental results are both included to illustrate the effectiveness of the proposed tuning method. By comparing the results of PID controller, fractional order PI and [PI] controllers, the advantages of the fractional order controller are clearly demonstrated in the case of controlling the single fractional pole plants with constant time delay.
Multifractional Property Analysis of Human Sleep EEG Signals
Authors: Sheng Hu , Chen YangQuan
Published: June 2012

Electroencephalogram (EEG), the measures and records of the electrical activity of the brain, exhibits evidently nonlinear, non-stationary, chaotic and complex dynamic properties. Based on these properties, many nonlinear dynamical analysis techniques have emerged, and much valuable information has been extracted from complex EEG signals using these nonlinear analysis techniques. Among these techniques, the Hurst exponent estimation was widely used to characterize the fractional or scaling property of the EEG signals. However, the constant Hurst exponent H cannot capture the the detailed information of dynamic EEG signals. In this research, the multifractional property of the normal human sleep EEG signals is investigated and characterized using local Holder exponent H(t). The comparison of the analysis results for human sleep EEG signals in different stages using constant Hurst exponent H and the local Ho¨lder exponent H(t) are summarized with tables and figures in the paper. The analysis results show that local Ho¨lder exponent provides a novel and valid tool for dynamic assessment of brain activities in different sleep stages.
Determining the Sub-Surface Stresses in a Graded-Elastic Solid Using Fourier Series Decomposition
Authors: Chidlow Stewart , Teodorescu Mircea , Vaughan Nick
Published: June 2012

This paper describes a fully analytic solution method for the displacements and sub-surface stresses within a graded elastic layered solid. This method can be utilised to predict the local deformation of nano or micro-scale depositions under contacting conditions. The solid consists of two distinct layers which are considered to be perfectly bonded and comprise of a graded elastic coating whose shear modulus varies exponentially with the depth coordinate and an infinitely deep homogeneously elastic substrate. The solution given in this paper is generic and easily utilised to solve real problems as it requires only known physical characteristics of the solid under study and an applied surface pressure. As a result, this model is very cheap to use and can be easily integrated into tribological codes to predict local deflections.
Practical Stability of Systems in a Dynamical Integrity Perspective
Authors: Lenci Stefano , Rega Giuseppe
Published: June 2012

The effects of the dynamic excitation on the practical stability of mechanical systems are investigated with reference to an archetypal model which permits to highlight the main ideas without spurious mechanical complexities. First, the effects of the excitation on periodic solutions are analyzed, focusing on bifurcations entailing their disappearance. Then, attractor robustness (i.e., large magnitude of the safe basin) is shown to be necessary but not sufficient to have global safety under dynamic excitation. In fact, the excitation strongly modifies the topology of the safe basins, and a dynamical integrity perspective accounting for the magnitude of the solely compact part of the safe basin must be considered. By means of extensive numerical simulations, robustness/erosion profiles of dynamic solutions/basins for varying axial load and dynamic amplitude are built, respectively. These curves permit to appreciate the practical reduction of system load carrying capacity and, upon choosing the value of residual integrity admissible for engineering design, the practical stability. Dwelling on the effects of the interaction between axial load and lateral dynamic excitation, this paper highlights the fundamental role played by global dynamics as regards a reliable estimation of the practical stability of mechanical systems.
Level of Modularity at Different Levels of System Granularity
Authors: Chiriac Noemi , Ho¨ltta¨-Otto Katja , Lysy Dusan , Suh Eun Suk
Published: June 2012

All system development projects involve analysis of the system architecture. However, it has been assumed thus far that there is some correct system decomposition that can be used in the architectural analysis. The sensitivity of the results to the chosen level of decomposition has not been considered. We represent forty eight idealized system architectures and a real complex system as a Design Structure Matrix at two different levels of decomposition. We analyze these architectures for their degree of modularity. We find that the degree of modularity can vary for the same system when the system is represented at the two different levels of granularity. For example, the printing system used in the case study is considered slightly integral at a higher level of decomposition and quite modular at a lower level of decomposition. We further find that even though the overall results can be different depending on the level of decomposition, the direction of change toward more modular or more integral can be calculated the same regardless of the level of decomposition. Level of decomposition can distort the results of architectural analysis and care must be taken in defining the system decomposition for any analysis.
Accuracy Analysis Considering Clearances and Elastic Deformations in Parallel Manipulators
Authors: Aginaga Jokin , Altuzarra Oscar , Macho Erik , Olza Jon
Published: June 2012

Clearances at joints and deformability of links produce a loss of accuracy when positioning a mechanism. End-effector pose error depends on the mechanism configuration, the applied external wrenches, the nature and magnitude of clearances and the rigidity of the mechanical components. Clearance magnitudes and elastic deformations are much smaller than other dimensions and consequently they are assumed to be infinitesimal, which leads to a linear analysis. Under this assumption, velocity equations can be utilized instead of position ones, and they can be easily expressed by using screw coordinates. A general methodology for analyzing the pose accuracy of a parallel manipulator is presented, making use of the example of a 5R planar mechanism along a pick-and-place trajectory.
Refined Design of a Measuring Wheel
Authors: Gobbi Massimiliano , Previati Giorgio , Mastinu Giampiero
Published: June 2012

The measurement of the contact forces between road and tires is of fundamental importance while designing road vehicle control systems. In this paper, the detail design of a measuring wheel (smart wheel) for a small two-seater vehicle is presented. The smart wheel concept design is based on a patented three-spoke structure connected to the wheel rim. The spokes are instrumented by means of strain gauges and the smart wheel is able to measure the three forces and the three moments acting at the interface between the tire and the road. The main objective of the design process presented in the paper is improving the sensibility and the accuracy of the measuring system while limiting its mass complying with maximum stress constraints. An iterative process is undertaken by employing both simple (analytical) and complex (finite element) models of the smart wheel to evaluate its performance and the structural stress levels during vehicle running. The complex model includes a finite element model of the tire to accurately apply the loads on the rim while operating. The simple design, the good performance, in terms of accuracy, dynamic behaviour, limited mass and the low cost represent the main features of the designed system.
Novel Form-Finding of Tensegrity Structures Using Ant Colony Systems
Authors: Chen Yao , Feng Jian , Wu Yongfen
Published: June 2012

Tensegrity structures are drawing the attention of architects and engineers due to their remarkable configurations. They have inextensional mechanisms, yet they are stable. The determination of connectivity patterns of the compression bars and tension cables is a key to design tensegrity structures. In this paper, a discrete optimization model for the form-finding of tensegrity structures was developed, and converted into a modified travelling salesman problem (TSP). The ant colony system (ACS) was used to search for feasible solutions, where all the given nodes were taken as different cities in the network. To obtain optimized shapes of tensegrity structures with stable equilibriums and adequate stiffness, an objective function was introduced. Examples based on the geometries of some polyhedra were carried out using the proposed technique. Many different configurations of the assemblies which consist of cables and bars are transformed into interesting tensegrity structures. It concludes that this novel algorithm could be applicable to the form-finding of both regular and nonregular tensegrity structures.
Reduced State Space Model for the Substructuring of Nonlinear Multibody Mechanisms
Authors: Gubitosa Marco , Anthonis Jan , De Cuyper Joris , Desmet Wim
Published: June 2012

In the work presented in this paper we introduce a novel approach for reducing nonlinear models of mechanical systems organized in an open kinematic chain topology. Starting from the Equation of Motion (EoM) of a constrained mechanical system including different sources of non-linearities, and assuming that the location and type of the non-linear behavior is known, a state space realization is obtained through linearization and standard matricial computation. Hints to generate this distinction are here given and basis towards a general procedure are suggested. Singular perturbation is hence adopted to purge the non-linearly behaving states and to reduce the model’s configuration parameters. The nonlinear portion is maintained in the MB environment, finally linked in a coupled simulation with the reduced first order system.
Model-Based Embedded System Design Methodology for Automotive Applications
Authors: Luo Wei , Chen Bo
Published: June 2012

The ever increasing complexity of embedded systems is driving the change in embedded software development from traditional approaches to model-based design methodology. The model-based design approach provides a number of benefits such as reducing software development time and cost, improving software quality through computationally intensive modeling, and real-time verification. This paper presents model-based embedded system design using a rapid prototyping system called Mototron. Models for individual components and the control strategies are developed in a simulation environment with MotoHawk, Simulink, and Stateflow software tools. The developed control algorithms and parameters are then tested using a calibration tool (MotoTune) that is connected to embedded system hardware. An electronic throttle control example is given in the paper to illustrate the major steps of model-based embedded system design using Mototron system.
Detecting Loosening of Bolted Connections in a Pipeline Using Changes in Natural Frequencies
Authors: He K. , Zhu W. D.
Published: June 2012

Loosening of bolted connections in a structure can significantly reduce the load-bearing capacities of the structure. Detecting loosening of bolted connections at an early stage can avoid failure of the structure. Due to the complex geometry of a bolted connection and the material discontinuity between the clamped components, it is difficult to detect loosening of a bolted connection using conventional non-destructive test methods. A vibration-based method that uses changes in natural frequencies of a structure to detect the locations and extent of damage can be used to detect loosening of bolted connections, since the method focuses on detecting a stiffness reduction, which can result from loosening of the bolted connections. Experimental and numerical damage detection using the vibration-based method was conducted to detect the loosening of the bolted connections in a fullsize steel pipeline with bolted flanges. With the recent development of a predictive modeling technique for bolted connections in thin-walled structures, an accurate physics-based finite element model of the pipeline that is required by the vibration-based damage detection method is developed. A trust-region search strategy is employed to improve the damage detection method so that convergence of the damage detection algorithm can be ensured for under-determined systems, and the robustness of the algorithm can be enhanced when relatively large modeling error and measurement noise are present. The location and extent of the loosened bolted connections were successfully detected in experimental damage detection using changes in the natural frequencies of the first several modes; the exact location and extent of the loosened bolted connections can be detected in the numerical simulation where there are no modeling error and measurement noise.
Interactive Modular Optimization Strategy for Layout Problems
Authors: Be´nabe`s Julien , Poirson Emilie , Bennis Fouad , Ravaut Yannick
Published: June 2012

Layout design optimization has a significant impact in the design and use of many engineering products and systems. Real-world layout problems are usually considered as complex problems because of the geometry of components, the problem density and the great number of designer’s requirements. Solving these optimization problems is a hard and time consuming task. This paper proposes an interactive modular optimization strategy which allows the designer to find optimal solutions in a short period of calculation time. This generic strategy is based on a genetic algorithm, combined with specific optimization modules. These modules improve the global performances of the algorithm. This approach is adapted to multi-objective optimization problems and interactivity between the designer and the optimization process is used to make a final choice among design alternatives. This optimization strategy is tested on a real-world application which deals with the search of an optimal spatial arrangement of a shelter.
Upper Level Engineering Design Instruction Using a Product Archaeology Paradigm
Authors: Lewis Kemper , Moore-Russo Deborah
Published: June 2012

Historically, the teaching of design theory in an engineering curriculum was relegated to a senior capstone design experience. Presently, however, engineering design concepts and courses can be found through the entirety of most engineering programs. Educators have recognized that engineering design provides a foundational platform that can be used to develop educational strategies for a wide array of engineering science principles. More recently, educators have found that product archaeology provides an effective platform to develop scalable learning materials, strategies, and educational innovations across these design courses. In this paper, we focus on the upper level design experience and present a set of innovative strategies aimed at teaching design in a global perspective. Moreover, this approach facilitates meeting the challenging requirements of ABET’s Outcome h. The effectiveness of the strategies is assessed using a benchmark national survey on the Engineer of 2020. Results demonstrate a significant increase in student perception across a number of skill and knowledge areas, which are critical to the next generation of engineers.
Optimization of Wind Turbine Placement in Offshore Wind Farms
Authors: Li Simeng , Alexander J. Iwan D.
Published: June 2012

In this paper, a Genetic Algorithm is used to find optimized spatial configurations of wind turbines in offshore or flat terrain wind farms. The optimization is made by obtaining maximizing power output per unit cost. A wake model which permits the calculation of single wakes, multiple wakes and wake interactions is employed to estimate wind speeds at each turbine for a given external wind distribution function and a given spatial configuration. The optimization is applied to cases of unidirectional wind, variable direction winds and variable wind speed. The placement of a turbine can be set at any location following the approach of Mittal et al. Results are obtained for different spacing limits between turbines and wind farms of different sizes. The results for some patterns of optimized placements of wind turbines are discussed in the context of the wind distributions and the wake model employed.
Feature Cluster Algebra for Geometric Tolerancing
Authors: Shen Yadong , Shah Jami J. , Davidson Joseph K.
Published: June 2012

The ASME Y14.5.1 companion to the Geometric Dimensioning and Tolerancing (GD&T) standard gives an exhaustive tabulation of active and invariant degrees of freedom (DOF) for Datum Reference Frames (DRF). These DRFs are entity clusters of points, lines, and planes with different geometric relations to each other (coincident, parallel, perpendicular etc.). This paper investigates the systematic derivation of DRF & target clusters’ DOFs and associates them with tolerance classes. A vector representation of geometric entities and Boolean operations are proposed. This algebra was validated by applying it to all cases in the Y14.5.1 tabulation; the results were identical to those in the standard. Only translational and rotational DOFs were considered since size dimensions are independent of this analysis. Of course, only a handful of DRF cases in the standard have practical use. Based on the algebraic calculation of DOF in each DRF cluster, the general rules regarding how target entities are constrained by diverse DRF clusters are discussed in this paper. Target entities are associated with specific DRF and tolerance or composite tolerances.
Visually Exploring a Design Space Through the Use of Multiple Contextual Self-Organizing Maps
Authors: Richardson Trevor , Winer Eliot
Published: June 2012

Understanding relationships amongst n-dimensional design spaces has long been a problem in the engineering community. Many visual methods previously developed, although useful, are limited to comparing three design variables at a time. Work described in this paper builds off the idea of a self-organizing map in order to visualize n-dimensional data on a two dimensional map. By using the contextual self-organizing map, current work shows that more design space information can be gleaned from map nodes themselves. By breaking the final visualization up into three maps containing separate contextual information, an investigator can quickly obtain information about the overall behavior of a design space. Tests run on well-known optimization functions show that information such as modality and curvature may be quickly suggested by these maps, and that they may provide enough information for a designer to choose a function to proceed with formal optimization of a given data set.
Non-Cleanroom Fabrication of Carbon Nanotube-Based MEMS Force and Displacement Sensors
Authors: Cullinan Michael A. , Panas Robert M. , Daniel Cody R. , Gafford Joshua B. , Culpepper Martin L.
Published: June 2012

Traditional microelectromechanical MEMS fabrications such photolithography and deep reactive ion etching (DRIE) are expensive and time consuming. This limits the types and designs of MEMS devices that can be produced cost effectively since in order to overcome the high startup costs and times associated with traditional MEMS fabrication techniques tens of thousands of each type of MEMS device must be produced and sold. In this paper, we will present a method for placing carbon nanotube (CNT) based piezoresistive sensors onto metallic flexural elements that are created via micromachining. This method reduces the fabrication time from over 3 months to less than 3 days. In addition, the fabrication cost is reduced form over $500 per device to less than $20 per device. This flexible, low cost fabrication method enables rapid prototyping of MEMS devices which is an important step in the design and development process for electromechanical systems. Also, the development of this type of low cost fabrication method will help to make low volume manufacturing of MEMS devices feasible from a cost prospective. In this fabrication method, a micromill is used to fabricate the flexure beams. Electron beam evaporation is then used to deposit (1) an insulating ceramic thin film layer and (2) metal traces on the flexure. A shadow mask is used to define the wire patterns. Either a tungsten wire or a focused ion beam (FIB) is used to define a 1–5 μm gap in the wire traces. Dielectrophoresis is then used to orient/position the CNT sensors across the gap. Finally, the structure is coated with a thin ceramic layer to protect the sensor and mitigate noise. When the flexure element is deflected, the CNTs strain which results in a measurable change in resistance. Several meso-scale test devices were produced using this fabrication method. The devices that were fabricated using a FIB to create the gap in the wire traces have the same strain sensitivity as devices fabricated using traditional cleanroom based techniques. However, the devices that were fabricated using the tungsten wire have a strain sensitivity that is almost 7 times lower than the devices fabricated using traditional cleanroom based fabrication techniques. This is because the gap size for the tungsten wire fabrication method is about an order of magnitude larger than for the FIB cut or lithography based gap fabrication methods. Therefore, the CNT are not able to stretch across the entire gap. This creates CNT-CNT junctions in the electrical pathway of the sensors which significantly increases the sensor resistance and decreases the strain sensitivity of the sensor. Overall, these results show that functional CNT-based piezoresistive MEMS sensors may be fabricated without conventional integrated circuit (IC) microfabrication technologies but that tight control over the gap size is needed in order to ensure that the sensor performance is not degraded.
The Effect of Interface Delays in Substructuring Experiments
Authors: Marsico Maria Rosaria , Wagg David J. , Neild Simon A.
Published: June 2012

Normally, for feasibility reasons, tests must be conducted on scaled structures, although scaling can introduce other issues. An alternative solution is to experimentally test the part of the structure that is of particular interest, at full or closer to full scale, while numerically modeling the remainder of the structure. This method is termed real-time dynamic substructuring or hybrid testing. To complete the substructure interaction the forces required to impose the displacements on the physical model are measured and applied to the model in real-time. One of the key challenges is to compensate for the dynamics associated with the actuators that are imposing the displacements on the physical test-piece. Ideally these actuators would act instantaneously however even with sophisticated control techniques interface errors are inevitable. We used an example system to study the effects of interface error modeled as a delay, on the accuracy of the overall substructuring technique.
Lagrangians With Linear Velocities Within Hilfer Fractional Derivative
Authors: Baleanu Dumitru , Agrawal Om P. , Muslih Sami I.
Published: June 2012

Fractional variational principles started to be one of the major area in the field of fractional calculus. During the last few years the fractional variational principles were developed within several fractional derivatives. One of them is the Hilfer’s generalized fractional derivative which interpolates between Riemann-Liouville and Caputo fractional derivatives. In this paper the fractional Euler-Lagrange equations of the Lagrangians with linear velocities are obtained within the Hilfer fractional derivative.