bluuebunny/crossref_metadata_2025 huggingface dataset:
Discrete Time Linear Quadratic Tracking Controller for Omni-Directional Mobile Robots
Authors: Hashemi Ehsan , Ghaffari Jadidi Maani
Published: June 2012

The purpose of this investigation is to suggest and examine a trajectory follower control system for linear discrete dynamic model of omni-directional mobile robots to reach a controller with optimal inputs for drivers. Introducing optimal controllers for multi input-multi output control systems in acceleration and deceleration maneuvers to track a specified path is one of essential subjects for motion study of omni-directional mobile robots. Regulated drivers’ rotational velocities and torques greatly affect the ability of these robots to perform trajectory planner tasks. Moreover, environmental influencing factors shall also be considered in such robot models for accurate path planning. Presented tracking control system in this article provides an optimal solution to minimize differences between reference trajectory and system output in the lately developed simulated model. Trajectory following system together with implemented kinematic and dynamic modeling for an optimal controller to satisfy the path planning prerequisites is mainly discussed in this paper in several sections. Main topics presented and discussed in this article are considerable improvements in simulation of the newly optimized controller by Linear Quadratic Regulator and Tracking. Utilizing the new approach on tracking controller design results in the more precise and appropriate tracking behavior of omni-directional mobile robots as the simulation and experimental results confirm this issue.
An Alternative Formulation of Motion Equations in Redundant Coordinates for the Inverse Dynamics of Constrained Mechanical Systems
Authors: Mu¨ller Andreas
Published: June 2012

The basis for any model-based control of dynamical systems is an efficient formulation of the motion equations. These are preferably expressed in terms of independent coordinates. In other words the coordinates of a constrained system are split into a set of dependent and independent ones. It is well-known that such coordinate partitioning is not globally valid. A remedy is to switch between different possible sets of minimal coordinates. This drastically increases the numerical complexity and implementation effort, however. In this paper a formulation of the motion equations in redundant coordinates is presented for general non-holonomic systems. This gives rise to a redundant system of differential equations. The formulation is valid in any regular configuration. Because of the singular mass matrix it is not directly applicable for solving the forward dynamics but is tailored for solving the inverse dynamics. An inverse dynamics solution is presented for general full-actuated systems.
Modeling Heat Transfer in Heterogeneous Media Using Fractional Calculus
Authors: Sierociuk Dominik , Dzielin´ski Andrzej , Sarwas Grzegorz , Petras Ivo , Podlubny Igor , Skovranek Tomas
Published: June 2012

The paper presents the results of modeling the heat transfer process in heterogeneous media with the assumption that part of the heat flux is dispersed in the air around the beam. The heat transfer process in solid material (beam) can be described by integer order partial differential equation. However, in heterogeneous media it can be described by sub- or hyperdiffusion equation which results in fractional order partial differential equation. Taking into consideration that the part of the heat flux is dispersed into the neighbouring environment we additionally modify the main relation between heat flux and the temperature, and we obtain in this case the heat transfer equation in the new form. This leads to the transfer function which describes the dependency between the heat flux at the beginning of the beam and the temperature at the given distance. The article also presents the experimental results of modeling real plant in the frequency domain basing on the obtained transfer function.
Complex Motions in Horizontal Impact Pairs With a Periodic Excitation
Authors: Guo Yu , Luo Albert C. J.
Published: June 2012

In this paper, the horizontal impact pair with a periodic excitation is studied from the theory of discontinuous dynamical system. Analytical conditions for motion switching are obtained. From generic mappings, analytical prediction of periodic motion is presented, and the corresponding stability and bifurcation analysis are carried out. Periodic and chaotic motions are illustrated numerically.
Chaos and Diffusion in Dynamical Systems With Periodic Impulses
Authors: Luo Albert C. J.
Published: June 2012

In this paper, quasi-periodic motion and chaotic diffusion in impulsive systems are discussed. The impulsive system is as a special switching system. Thus, switching systems are discussed first. The quasi-periodic flows and chaotic diffusion of impulsive systems are illustrated to demonstrate flow regularity and complexity of switching systems.
Synchronization Dynamics of Two Gyroscope Systems
Authors: Min Fuhong , Luo Albert C. J.
Published: June 2012

In this paper, the synchronization dynamics of two gyroscope systems is discussed by the theory of discontinuous dynamical systems. The necessary and sufficient conditions of such synchronization are obtained. The non-synchronization, partial and full synchronizations of two gyroscope systems are illustrated for the analytical conditions of synchronization.
Modeling and Parameter Study of Bistable Spherical Compliant Mechanisms
Authors: Smith Chester L. , Lusk Craig P.
Published: June 2012

The Bistable Spherical Compliant Mechanisms (BSCM) is a novel device capable of large, repeatable, out-of-plane motion, characteristics that are somewhat difficult to achieve with surface micro-machined MEMS. An improved pseudo-rigid-body model to predict the behavior of the BSCM is presented. The new model was used to analyze seven different versions of the device, each with a different compliant joint length. The new model, which adds torsion, is compared with a Finite-Element beam model. The new model more closely approximates the results yielded by FEA than previous models used to analyze the BSCM. Future work is needed to quantify stress-stiffening interactions between bending and torsion. Both FEA and the current model show that increasing the length of the compliant segment decreases the amount of force required to actuate the device.
An Elastic Rod Representation for the LacI-DNA Loop Complex
Authors: Lillian Todd D.
Published: June 2012

The well-recognized Lac repressor protein (LacI) regulates transcription by bending DNA into a loop. In addition to the known role of DNA flexibility, there is accumulating evidence suggesting that the flexibility of LacI also plays a role in this gene regulation. Here we extend our elastic rod model for DNA (previously used to model DNA only) to represent LacI. Specifically, we represent sites of concentrated flexibility in the protein with flexible elastic rod domains; and we represent relatively rigid domains of the protein with stiff elastic rod domains. Our analysis shows the sensitivity of looping energetics to the degree of flexibility within the protein over a large range of DNA lengths. In addition, we show that the predicted energetically dominant binding topology (A) remains upon introducing protein flexibility.
A Method for Designing Collaborative Products With Application to Poverty Alleviation
Authors: Morrise Jacob S. , Lewis Patrick K. , Mattson Christopher A. , Magleby Spencer P.
Published: June 2012

Collaborative products are created when physical components from two or more products are temporarily recombined to form another product capable of performing additional tasks. In this paper, a method for designing collaborative products is introduced. The method identifies a set of products capable of being recombined into a collaborative product. These products are then designed to allow for this recombination. Collaborative products are particularly useful in reducing the cost, weight, and size of poverty-alleviating products—reductions that are valued in the developing world. A simple example of a cabinet maker’s tool shows that a collaborative block plane created from a chisel and sanding block can account for reductions in cost, weight, and size of 44%, 38%, and 44% respectively, when compared to a typical wooden block plane, chisel, and sanding block. Additionally, an example of a collaborative apple peeler is provided to demonstrate scalability of the method. The authors conclude that the method introduced herein provides a new and useful tool to design collaborative products and to assist in engineering-based poverty alleviation.
Theoretical and Numerical Analysis on Material-Stiffness Characteristics for Thin-Walled Beams on Vehicles
Authors: Han Xiao , Hou Wenbin , Hu Ping
Published: June 2012

In order to study the lightweight effect of different materials on vehicle, we first took the two-end-fixed thin-walled beam as the research object and the Stiffness Mass Efficient as the corresponding criterion. According to the FEM simulation with four different materials conducted on thin-walled beam, the theoretical conclusion was proved coincident with the numerical one. Focusing on vehicle body-in-white, its material of beams was chosen as a variable in FEM analysis, and the relation between material attributes and body stiffness was acquired. It is noted that the magnesium-silicon alloy and the Pan-Base Carbon Fiber Reinforced Composite can achieve better lightweight effect than that of mild steel, while the classic aluminum alloy can not realize lightweight without necessary structural optimization.
Experimental Investigation of Low Frequency Noise Reduction Using a Nonlinear Vibroacoustic Absorber
Authors: Bellizzi Sergio , Cochelin Bruno , Herzog Philippe , Matte´i Pierre-Olivier , Pinhe`de Ce´dric
Published: June 2012

This work deals with the energy pumping phenomenon for acoustical applications. The concept of energy pumping is to passively reduce the vibrations of a primary system by attaching to it an essentially nonlinear damped oscillator also named Nonlinear Energy Sink (NES) creating a strongly nonlinear coupling which localizes and dissipates the vibrational energy. In the context of acoustics, a vibroacoustic coupling is used. In an earlier work, we showed experimentally that a loudspeaker used as a Suspended Piston (SP) working outside its range of linearity can be used as a NES. In this work, the performance and efficiency of a SP NES is studied numerically and experimentally. The considered acoustic medium is a resonant pipe. The coupling between the pipe and the NES is ensured acoustically by a small acoustic compliance (the air in a coupling box). Various observed aspects of energy pumping are presented: behavior under sinusoidal forcing, pumping threshold, resonance capture and transient response. As a SP NES technology permits an easy control of the moving mass of the NES, the effect of this parameter is also studied.
A Novel Inflatable Tendon Driven Manipulator With Constant Volume
Authors: Voisembert Se´bastien , Mechbal Nazih , Riwan Alain , Barraco Andre´
Published: June 2012

Tensegrity and cable driven systems are used in robotics when lightness and stiffness are required. Inflatable structures are well known as tensegrity structures. In this case the skin is the tension member and the air is the compression member. Such structures have already been used in robotics to create cable driven arms made of inflatable links separated by mechanical joints. In this paper we propose a novel inflatable manipulator in which the joints are fully integrated to the inflatable structure. This design allows us to make inflatable robots with a constant and continuous pressurized volume with no loss of strength at the joints. A mechanical model has been developed and validated by experiments. We also present an appropriate cable-based actuation system that controls the joints without coupling.
Assessment of the Vibration Excitation and Optimization of Cylindrical Gears
Authors: Ho¨hn Bernd-Robert , Heider Michael , Stahl Karsten , Otto Michael , Bihr Jens
Published: June 2012

Vibration and noise generation of gear stages is mainly caused by the excitation of the gear mesh. This excitation is significantly influenced by geometry of the tooth. Here, both the macro-geometry (main geometry) and the micro-geometry (flank corrections) of the teeth are important. Corrections of the tooth flanks usually have to meet the requirements of low excitation and high load capacity. Furthermore it is oftenly necessary, especially for transmissions with variable speed, to account for the dynamic effects (e.g. resonance behavior) of noise excitation. The computer program DZP (Dynamic Tooth Force Program) provides extensive calculation methods for analyzing mesh excitation and transmission dynamics. The frame program DZPopt provides extensive possibilities to determine an optimum excitation flank correction based on the calculation capabilities of DZP.
Towards a Holistic Workflow Pattern for Using VR for Design Decisions: Learning From Other Disciplines
Authors: Aust Matthias , de Clerk Matthias , Blach Roland , Dangelmaier Manfred
Published: June 2012

In their respective design processes automobile manufacturers use more and more virtual prototyping. Today, even some design decisions are made, based on purely digital vehicle models. This is a report of a recent study, which was done with a German car manufacturer, that has looked into different academic disciplines besides computer science, to find new ways to vitalize and stage digital vehicle models. Usability engineering, psychology, dramatics, and theater teaching were consulted. As a result a novel workflow pattern is proposed, exemplarily conceptualized for Design Reviews of automobiles. It embeds the use of Virtual Reality (VR) or Mixed Reality (MR) between Briefing and Debriefing phases, to give the users a chance for preparing and postprocessing the digital experience. This workflow pattern and its pragmatic conception are introduced in this paper.
Identification of Product Family Platforms Using Pattern Recognition
Authors: Freeman Dane , Lim Dongwook , Garcia Elena , Mavris Dimitri
Published: June 2012

In product family design the goal is to generate a set of lowest cost products that target specific market niches. Sharing components, called platforms, between different products can minimize duplication of effort, thereby lowering family costs. However, if the products’ requirements are too dissimilar, sharing components may compromise the end product; such variance will lead to lower end products being overdesigned and/or higher end products being underdesigned. It is important to identify which components are similar enough, so that sharing does not compromise the individual products’ performances. Most existing product family design methods make decisions a priori about platforms; constraining platforms to be used by every product in the family, or not at all. Methods that simultaneously optimize component sharing and design variable settings have the potential to find better families because product subsets may be more similar to each other than to other subsets of products. Allowing components to be shared between any subset of family members leads to a very large combinatorial problem, and considering large product families can be computationally prohibitive. This paper proposes a method to identify possible sets of product family platforms by using the pattern recognition technique of fuzzy c-means clustering on component subspaces. Component subspaces are taken from a database of generated design points for the whole family. If components from different products are similar enough to be grouped into the same cluster, then those components could possibly become the same platform. Fuzzy equivalence relations can be extracted from the cluster membership functions that show the binary relationship from one products’ component to a different products’ component. Ultimately, this method can be used as a platform identification heuristic in a larger product family design methodology. This method is demonstrated by applying it to find possible common components in a family of universal electric motors.
Comparative Studies in Traction Concepts
Authors: Mathieson James L. , Thompson Matthew , Satterfield Heather , Satterfield Zachary , Kraus Elisabeth , Summers Joshua D.
Published: June 2012

The interaction between tires and soft soils is a complex process that has not yet been fully understood. Attempts to create analytical models which realistically simulate these interactions have proven to be exceedingly time consuming for each tire model and have achieved only limited success. Thus, the exploration and evaluation of traction concepts by analytical means is impractical. This paper posits that significantly more reliable, rapid, and cost effective development is achieved through the prototyping and experimental evaluation of traction concepts. Here, three traction prototypes are developed and evaluated by undergraduate teams in the course of an academic semester. These concepts explore the performance of grousers, inverted geometry (dimples), and cellular materials respectively using a wheel endurance and soft-soil traction testing system at Clemson University. Each concept is tested at different acceleration rates from 0–10km/h and at different loads while measuring the slip between the tire and soil surfaces. The results of experimental evaluation indicate that cellular materials present a unique slip profile which is superior to that of the two other purely geometric concepts studied. The worst performance was seen on the inverse geometry concept which presented a behavior of steadily increasing slip with respect to wheel velocity regardless of acceleration. Grousers also presented this behavior but only at higher accelerations. This suggests that not only that prototyping is preferable, but that traditional soft-soil traction approaches may be in error.
Redesign of a Gearbox for 5MW Wind Turbines
Authors: Giger Urs , Arnaudov Kiril
Published: June 2012

Wind turbines with gearboxes must regain the highest possible reliability as fast as possible. This can occur with improved gearbox designs. Epicyclic gear drives with multiple planet gears would be technically correct to solve this torque transmission problem. A maximal compactness and lightweight construction is thus achieved. In order to also meet with the requirements regarding the increase of the rotational speed to a correspondingly efficient value of the generator, several coupled epicyclic trains are necessary. This technically demanding objective is sensibly solved by the proposed gearbox solution. The following article presents the patented new design [WO 2008/104258 A1] and determines it from a scientific standpoint.
Parametric Resonance Based Piezoelectric Micro-Scale Resonators: Modeling and Theoretical Analysis
Authors: Ghaderi Pooya , Dick Andrew J.
Published: June 2012

In this study, a two-component auto-parametric resonator utilizing piezoelectric actuation is proposed. The resonator consists of a plate component which serves as the exciter and a beam component which serves as the oscillator. When an electric signal is applied, the plate component experiences in-plane oscillations which serve to provide axial excitation to the beam component. The system is designed to operate in auto-parametric resonance with a plate to beam principal frequency ratio of 1:2. Due to the oscillations of the beam component, a dynamic force and a moment are applied to the plate and can cause out-of-plane oscillations of the plate component. Internal-resonance can also exist between the beam oscillations and the out-of-plane vibrations of the plate component. A model is derived in order to describe these three motions and the coupling between them. By assuming single mode behavior for each motion, the model is discretized and represented with a three degree-of-freedom model. The model is solved analytically by using the method of multiple scales. Results of the perturbation method agree well with the numerical simulation. The results for the system with strong and weak coupling between the resonator components are presented and compared.
Identification of Contact Failures in Multi-Layered Composites
Authors: Abreu L. A. , Orlande H. R. B. , Naveira-Cotta C. P. , Quaresma J. N. N. , Cotta R. M. , Kaipio J. , Kolehmainen Ville
Published: June 2012

This paper deals with the solution of an inverse heat conduction problem, aiming at the identification of contact failures in composites formed by layers of different materials. The inverse problem is solved within the Bayesian framework, with a Markov chain Monte Carlo method. The effects of the prior models, for the unknown contact conductance at the interface of a plate with two layers, are examined. The solution of the inverse problem is performed with simulated temperature measurements.
Battery Sizing as a Function of Powertrain Component Efficiencies for Various Drive Cycles
Authors: Gantt Lynn R. , Alley R. Jesse , Nelson Douglas J.
Published: June 2012

The market segment of hybrid-electric and full function electric vehicles is growing within the automotive transportation sector. While many papers exist concerning fuel economy or fuel consumption and the limitations of conventional powertrains, little published work is available for vehicles which use grid electricity as an energy source for propulsion. Generally, the emphasis is put solely on the average drive cycle efficiency for the vehicle with very little thought given to propelling and braking powertrain losses for individual components. The modeling section of this paper will take basic energy loss equations for vehicle speed and acceleration, along with component efficiency information to predict the grid energy consumption in AC Wh/km for a given drive cycle. An electric-only range target is established as part of the vehicle technical specifications. This set range along with component characteristics will impact the sizing of the energy storage subsystem. To demonstrate the usefulness in understanding powertrain losses, the energy use is described in propelling, braking, idle, and charging cases. A simulation focusing on battery sizing to meet power and range requirements shows the impacts of friction brakes, regenerative braking fraction, and average motor efficiency. Vehicle characteristics such as, but not limited to, a range extender application, electric-only vehicle range, and acceleration performance are explained as well. The model is correlated to real world vehicle data for a custom-built plug-in hybrid electric vehicle. By using the Virginia Tech Range Extended Crossover (VTREX) and collecting data from testing, the parameters that the model is based on will be correlated with real world test data. The paper presents a propelling, braking, and net energy weighted drive cycle averaged efficiency that can be used to calculate the losses for a given cycle. In understanding the losses at each component, not just the individual efficiency, areas for future vehicle improvement can be identified to reduce petroleum energy use and greenhouse gases.
Low Cost Output Feedback Controllers for Small UAVs
Authors: Asthana Chandra B. , Bhat Seetharama M.
Published: June 2012

This article demonstrates that many general forms of pre-compensators can be included in a Multi-Input-Multi-Output (MIMO) plant with a very general state-space description and the augmented plant can be reduced to static output feedback (SOF) form that is required for optimal design. The main contribution lies in solving very cumbersome algebraic matrix equations, for each configuration, to separate the unknown parameters after the optimal static output feedback gain matrix is achieved. Once the designers see that such configurations with chosen pre-compensators can be dealt with, they would be motivated to consider a suitable configuration for the specific application and finally achieve low cost controllers that are simple to implement and require low computational power.
Improving Adhesion Density and Coverage Uniformity of Antibody-Antigen Binding on a Sensor Surface Using U-Type, T-Type and W-Type Microfluidic Devices
Authors: Wu Chia-Che , Tseng Ping-Kuo , Tsai Ching-Hsiu
Published: June 2012

Usually microorganisms, molecules, or viruses in the fluidic environment are at very low Reynolds numbers because of tiny diameters. At very low Reynolds numbers, viscous forces of molecules and viruses will dominate. Those micro- or nanoparticles will stop moving immediately when flows cease and drag forces disappear, those phenomena were discovered by the fluorescent particle experiment. Of course, molecules and viruses are still subject to Brownian motion and move randomly. In order to increase the adhesion density of micro- and nanoparticles on sensor’s surface, designs of the flow movements in microfluidic channel is proposed. Adhesion density of linker 11-mercaptoundecanoic acid (MUA) and Turnip yellow mosaic virus (TYMV) with specific quantum dots were measured by confocal microscope. Fluorescent intensity and coverage of quantum dots are used to identify the adhesion density quantitatively. Results show that TYMV and MUA layers disperse randomly by dipping method. Fluorescent intensity of quantum dots; i.e. relative to the amount of MUA and TYMV; were 2.67A.U. and 19.13A.U., respectively, in W-type microfluidic devices to contrast just 1.00A.U. and 1.00A.U., respectively, by dipping method. Coverage of MUA and TYMV were 80∼90% and 70∼90%, respectively, in W-type microfluidic channel to contrast just 20∼50% and 0∼10%, respectively, by dipping method.
Evaluation and Comparison of Two Design for Assembly Methods: Subjectivity of Information Inputs
Authors: Owensby Eric , Shanthakumar Aravind , Rayate Vikrant , Namouz Essam , Summers Joshua D.
Published: June 2012

This paper presents a comparison study on two design for assembly (DFA) tools, Boothroyd and Dewhurst’s Design for Manufacturing and Assembly software and the Mathieson-Summers connective-complexity algorithm, focusing on the amount of information required from the designer to complete the analysis and the subjectivity of this information. The Boothroyd Dewhurst software requires the user to answer a set of questions about each part and how it is assembled to estimate an assembly time, assembly cost, and to suggest design improvements. The connective-complexity method predicts assembly times based on the physical connectivity between parts within an assembly. The methods are applied to three consumer products and evaluated and compared through five criteria: approximate time to conduct the analysis, predicted assembly time, amount of required input information, amount of subjective information, and number of redesign features provided to the user. The results show that the DFMA software requires the user to go through eight types of information answering a total of forty nine questions per part. Sixteen of these questions are based on subjective information making the analysis nearly a third subjective. The connectivity method requires only two types of information and a total of five questions per part to complete the analysis, none of it being subjective. The predicted assembly times from the connective-complexity DFA method ranged from 13.11% to 49.71% lower than the times predicted by the DFMA software. The results from this comparison can be used to bench mark DFA methods so that their weaknesses can be identified and improved.
On a Control Design to an AFM Microcantilever Beam, Operating in a Tapping-Mode, With Irregular Behavior
Authors: dos Santos Rodrigues Kleber , Balthazar Jose´ Manoel , Tusset Angelo Marcelo , Pontes Ju´nior Bento Rodrigues
Published: June 2012

In last decades, control of nonlinear dynamic systems became an important and interesting problem studied by many authors, what results the appearance of lots of works about this subject in the scientific literature. In this paper, an Atomic Force Microscope micro cantilever operating in tapping mode was modeled, and its behavior was studied using bifurcation diagrams, phase portraits, time history, Poincare maps and Lyapunov exponents. Chaos was detected in an interval of time; those phenomena undermine the achievement of accurate images by the sample surface. In the mathematical model, periodic and chaotic motion was obtained by changing parameters. To control the chaotic behavior of the system were implemented two control techniques. The SDRE control (State Dependent Riccati Equation) and Time-delayed feedback control. Simulation results show the feasibility of the both methods, for chaos control of an AFM system.
Application of a Lightweight Engineering Tool: Lazy Parts Analysis and Redesign of a Remote Controlled Car
Authors: Griese David , Namouz Essam , Shankar Prabhu , Summers Joshua D. , Mocko Gregory
Published: June 2012

The objective of this study was to implement the Lazy Parts Indicator Method (LPIM) in the analysis of a remote control (RC) car to identify potential parts for mass reduction. In addition, an example of how the method can be used in conjunction with a part redesign process has been shown through topology optimization of an identified part. The LPIM, which was originally developed for the analysis of automobiles, serves as a set of guidelines for novice designers to identify components that have potential for mass reduction. By successfully using the method on a RC car, the method can be shown to be applicable on smaller scale. The analysis of the RC car consisted of using indicators to identify lazy parts, weighing of those parts, and estimation of mass reduction percentages. From this, it was estimated that approximately 5% of the vehicle’s weight could be reduced. Once the lazy analysis was completed on the car, a component with a high potential for mass reduction was selected for redesign. Topology optimization using ANSYS Mechanical was done to suggest a new design, which contained regions of material removal. After creating a redesigned part, a new mass was measured and used to validate the original mass reduction estimates from the LPIM. The new part design was also validated through physical experimentation in which the part was fabricated and tested. This paper outlines an entire process for lightweight design from start to finish, beginning with an identification of parts with mass reduction using the Lazy Parts Indicator Method.
Viscoelasticity Measurement and Identification of Viscoelastic Parametric Models
Authors: Renaud Franck , Chevallier Gael , Dion Jean-Luc , Lemaire Re´mi
Published: June 2012

Generally speaking, the behaviour of viscoelastic material is more complicated than the behaviour proposed by classical models as Voigt, Maxwell or Zener. The stiffness of such materials is a frequency dependent complex function. Above 1000Hz, classical measurements techniques are unable to achieve accurate measurements of the stiffness. In this paper, a new Dynamical Mechanical Analysis (DMA) tester is presented. It allows the characterization of the shear stiffness of preloaded viscoelastic materials between 200 and 3500Hz and without using frequency-temperature equivalences. Then the Generalized Maxwell model is used to describe behaviours measured with the DMA tester. A new iterative identification method of the parameter of the Generalized Maxwell model is described. This identification method is based on the asymptotes of the model.
A Middleware for Integrating Components of Modern Distributed Virtual Reality Systems
Authors: Kharitonov Vasily Y.
Published: June 2012

Distributed virtual reality systems (DVR systems) represent one of the most intensively developing branches of distributed simulation technology to date. Examples of such systems include various human-in-the-loop applications for training, educational and entertainment purposes. Modern DVR systems require sophisticated data exchange mechanisms to provide consistent and at the same time responsive interaction of a large number of heterogeneous components. While many DVR systems have been implemented in the past decade, there is still exists a lack of universal, easily deployable and extensible framework that enables rapid creation of complete systems from scratch. In this work we present the TerraNet framework which is a middleware allowing an application developer to easily implement and deploy medium-sized DVR systems for specific tasks without direct low-level network programming. TerraNet framework provides a high-level application programming interface to create, manage and distribute objects in a shared virtual environment. In paper we discuss overall framework system architecture, its basic features and functionality, as well as possible practical applications.
An Approach to Automated Conversion From Design Feature Model to Analysis Feature Model
Authors: Cao Weijuan , Chen Xiaoshen , Gao Shuming
Published: June 2012

An approach to automatically converting a design feature model to an analysis feature model for downstream finite element analysis is proposed. The analysis feature model is a mixed-dimensional model with shell features representing thin regions and solid features representing thick regions. In the approach, the design feature model is first decomposed into a set of remnants of additive features, each of which represents part of an additive feature’s volume that remain in the final volume of the design model. The remnant of each additive feature is then decomposed into swept bodies and non-swept bodies. After that, the thin regions of each swept body are effectively recognized based on its sketch information. These detected thin regions can be wrongly recognized, which, together with potentially missing ones are thus detected and corrected by a synthesization process. Finally, the analysis features and their relative interfaces are generated, which ultimately gives the corresponding analysis feature model to the input design feature model. Experimental results are also shown to demonstrate the proposed method’s effectiveness.
IRSBot-2: A Novel Two-DOF Parallel Robot for High-Speed Operations
Authors: Germain Coralie , Briot Se´bastien , Glazunov Victor , Caro Ste´phane , Wenger Philippe
Published: June 2012

This paper presents a novel two-degree-of-freedom (DOF) translational parallel robot for high-speed applications named the IRSBot-2 (acronym for IRCCyN Spatial Robot with 2 DOF). Unlike most two-DOF robots dedicated to planar translational motions, this robot has two spatial kinematic chains which confers a very good intrinsic stiffness. First, the robot architecture is described. Then, its actuation and constraint singularities are analyzed. Finally, the IRSBot-2 is compared to its two-DOF counterparts based on elastostatic performances.
Symptoms of Misaligned Worn Journal Bearings in Rotor Response Under External Excitation by a Magnetic Bearing
Authors: Chasalevris Athanasios , Dohnal Fadi , Markert Richard
Published: June 2012

The defect of wear in journal bearings appears usually after long-time operation of rotating systems and the main symptom is the decrease in the bearing load carrying capacity. Wear in aligned or misaligned pattern can result in higher eccentricities of whirling and changes the properties of stiffness and damping of the fluid film. In this work the operation of worn journal bearings is investigated by incorporating a radial active magnetic bearing (AMB) on the same shaft which acts as a collocated sensor/actuator unit. This combination offers a possibility to identify and observe the characteristic symptoms that the wear provokes under external excitation and without disturbance from the nominal operation conditions of the system. Under specific electromagnetic excitation the harmonic components that are introduced due to wear are detected. A simple rotor mounted in two worn journal bearings is used and the response at steady operational speed and at transient electromagnetic external excitation with linearly varying frequency (chirp) is analyzed in the time and frequency domains. The occurrence of additional sub- and super-harmonic components is observed when the external frequency lies in the region of the first natural frequency of the operating system. The time-frequency analysis discloses the onset of additional frequency components, especially in the sub-harmonic domain. This offers a distinct detection of wear if wear depth becomes higher than 20% of the radial clearance. An experimental test rig is outlined for future studies in order to benchmark the observations from the present numerical calculations.
A Review of Microstructural Effects on Pitting Corrosion in Stainless Steels
Authors: Qidwai Siddiq M. , DeGiorgi Virginia G. , Leung Alan C.
Published: June 2012

A vast literature can be found on pitting corrosion addressing the initiation and propagation of pits due to localized corrosion. However, most of is the work to date is devoted to the electrochemical and metallurgical aspects of the phenomenon. In this paper, we provide a brief review of the recent progress in characterizing and analyzing the effects of various microstructural features on pitting corrosion. The scope of the paper is limited to stainless steels in chloride-containing solutions. The review shows that initiation of pitting corrosion in stainless steels is affected by such microstructural features on the exposed surface as the crystallographic orientation, phase and grain boundaries, beside the well-known and much characterized sulphide inclusions. Similarly, pit growth kinetics and evolution has been shown to depend upon the presence of precipitates and secondary phase particles, grain boundaries, and other material interfaces. One outcome of the review is the identification of the need to complement the recent computational studies incorporating fully-coupled electrochemical, mass transfer and momentum field equations at the macroscale with similar modeling and analysis at microscale to fully understand the effects of microstructural features on stable pit growth.
Bistable Threshold Sensor With Mechanically Nonlinear Self-Limiting Suspension and Electrostatic Actuation
Authors: Rabanim Shila , Amir Emil , Krylov Slava
Published: June 2012

We report on the operational principle, modeling, fabrication and characterization of an electrostatically actuated force/acceleration sensor with mechanically nonlinear stiffening suspension. The suspension incorporates initially curved beams oriented in such a way that both the electrostatic and inertial forces applied to the beam’s ends are directed predominantly along the beam. Since the stiffness of the curved beam is significantly lower than that of the straightened beam, the force-displacement dependence of the suspension is of the self-limiting type while the suspension itself serves as a compliant constraint. Application of a softening electrostatic force, provided by a parallel-plate transducer, results in pull-in instability followed by the steep increase in the suspension stifftness and the appearance of an additional stable configuration of the device. In accordance with the model results the dependence between the acceleration and the shift of the pull-in voltage induced by the acceleration is nearly linear and the pull-in voltage monitoring can be used for the measurement of the acceleration. Model results show that using the suggested approach significantly improves device resolution, extends dynamic range, and improves reliability by eliminating contact. Devices of several configurations were fabricated from a silicon on insulator (SOI) substrate using a deep reactive ion etching (DRIE) based process. Preliminary experimental results imply that the suggested approach is feasible.
Indoor Vibration Testing for High-Frequency Modal Characterization of Tyres
Authors: Rocca G. , Kindt P. , Middelberg J. M. , Gonza´lez Di´az C. , Peeters B. , Van der Auweraer H.
Published: June 2012

The driver subjective perception of a vehicle is strongly determined by its Noise, Vibration and Harshness (NVH) behavior. Consequently, the NVH performance has become an important design and marketing criterion for vehicle manufacturers. The low-frequency (0–500Hz) noise and vibration perceived by a passenger are mainly determined by the dynamic behavior of rolling tyres. Besides the increasing awareness for the problems associated with road traffic noise has lead to the demand for more quiet tyres and road surfaces. Computer aided engineering tools play an important role for improving the vehicle vibration behavior at the earliest step of the design. In order to carry out precise modeling of the vehicle and its subsystems, an accurate tyre model is a key element in predicting the performance of the vehicle system with respect to ride comfort, NVH, durability, safety (braking manoeuvre) and tyre/road interaction. To obtain the best possible performance from a tyre model, a number of different measurements are required to support the tyre model parameter identification process. Although tyre vibration and noise behavior has been studied for several decades, there are still some missing links in the process of accurately predicting and controlling the overall tyre/road noise and vibration linked to the difficulty of performing modal testing on a tyre when rotating. This paper deals with the main test benches, experimental activities and modal analysis techniques available nowadays for characterizing the dynamic behavior of a static (unloaded tyre on a fixed hub and loaded tyre on a fixed hub) and a rotating tyre under different boundary conditions. The main results arising from modal analysis of a static and dynamic test on a tyre are highlighted and compared. In particular the effect of rolling speed, inflation pressure, preload, temperature and excitation amplitude on the dynamic response of a rolling tyre will be discussed.
Variable Screening Using Restricted Maximum Likelihood Kriging Method With Application to Gunner Joint Stiffness Variables
Authors: Dong Guang , Ma Zheng-Dong , Hulbert Gregory , Kikuchi Noboru , Arepally Sudhakar , Vunnam Madan , Lou Ken-An
Published: June 2012

Complex and computationally intensive modeling and simulation of real-world engineering systems can include a large number of design variables in the optimization of such systems. Consequently, it is desirable to conduct variable screening to identify significant or active variables so that a simpler, more efficient, yet accurate optimization process can be achieved. This paper proposes a variable screening method based on a Kriging model with Restricted Maximum Likelihood criterion. The Kriging metamodeling method is more reliable for highly nonlinear systems than the traditional response surface method, and the Restricted Maximum Likelihood criterion makes the variable screening process more efficient. In this work, three different sampling methods, namely, Latin Hypercube, Improved Distributed Hypercube and D-optimally selected Latin Hypercube sampling methods, are compared when used with the proposed variable screening method. The new variable screening method is evaluated using a standard benchmark nonlinear numerical example that employs 20 factors. The variable screening method then is applied to a gunner restrain system design problem. Starting with a set of eight of the most important gunner’s joints variables in a wide open property space, the Improved Hypercube space filling sampling technique is used to screen the joints variables and the variable screening method based on the Kriging method with the restricted maximum likelihood criterion is used to determine the most important joints properties for gunner’s performance.
A Pseudo-Rigid-Body Model Approach for the Design of Compliant Mechanism Springs for Prescribed Force-Deflections
Authors: Leishman Levi C. , Colton Mark B.
Published: June 2012

Compliant mechanism springs offer a variety of benefits for applications where nonlinear force responses are desired. Designing a compliant mechanism spring with a prescribed force response is a unique challenge with many design variables. This paper introduces a method, based on the Pseudo-Rigid-Body Model (PRBM) for large beam deflections, to synthesize three- and four-link compliant mechanisms that exhibit prescribed force-deflection responses. The designer prescribes the target force-deflection curve, the number of links the spring is to have, and bounds for the spring’s link lengths and torsional spring constants. The method uses a genetic algorithm routine to search for promising designs and a direct search method to further refine the configuration to achieve the desired force-deflection curve. Experimental results illustrate the methods ability to generate springs whose force-deflection curves approximate the target curves. The results also suggest that inclusion of more complex configurations may lead to more accurate designs. It is shown how the method can be used to design springs that closely mimic the behavior of zero-free-length springs, and a discussion of how the method can be extended to design springs that behave similarly to pre-tensioned springs is presented.
1/2-Order Subharmonic Resonances in Horizontally Supported Jeffcott Rotor
Authors: Yoshida Nao , Takano Tomoyuki , Yabuno Hiroshi , Inoue Tsuyoshi , Ishida Yukio
Published: June 2012

A Rotary machine is a significant component of many mechanical systems. It is important to clarify the dynamic characteristics in several conditions. This study deals with nonlinear dynamics of a horizontally supported Jeffcott rotor. The equations of motion are derived by considering the effects of gravity and the cubic nonlinearity of restoring force by the support condition. These effects produce the difference between the linear natural frequencies in the vertical and horizontal directions and make the stiffness in the vertical direction unsymmetric. It is theoretically and experimentally shown that due to such effects, the 1/2-order subharmonic resonances are produced in the cases when the rotational speed is in the neighborhood of twice the natural frequencies in the horizontal and vertical directions, and the frequency response curve of the resonance near twice the horizontal natural frequency is hardening-type, while near twice the vertical natural frequency is softening-type.