bluuebunny/crossref_metadata_2025 huggingface dataset:
Stability and Bifurcations in a Model of a Follower Loaded Rod
Authors: Gala´n-Vioque J. , Lago M. A. , Valverde J.
Published: June 2012

We analyse a continuous Cosserat model of a visco-elastic rod subjected to a combination of a conservative load and a follower term in one of the ends. The formalism takes into account the geometric non linearities that appear for large deformations from the straight solution. The resulting equation is a PDE whose solution can be analysed for special cases and the eigenvalues of the linearisation can be computed by a combination of numerical continuation and bifurcation results. We illustrate this method analysing the bifurcations of the straight solution of a rod subjected to a follower force. The dynamics and the bifurcation behaviour of the model are explored as the intensity of force is varied and as the mixture of conservative-follower terms varies continuously from the standard conservative case to the purely follower one. Special attention is paid to the corresponding transition from symmetry breaking pitchfork bifurcation (falling over mode) to the appearance of oscillations in a Hopf like bifurcation (if some material damping is included) or pure reversible Hamiltonian Hopf bifurcation in the absence of damping. After the onset of oscillations a complex dynamical behaviour frequently called flutter instability appears. The study is supplemented with the bifurcation analysis of the two elastically jointed follower pendula model as a simplified model of the continuous problem.
Dynamical Modeling of Flexible Linear Robots
Authors: Kilian F. Johannes , Gattringer Hubert , Bremer Hartmut
Published: June 2012

The production sector aims towards increasing capacity and energy efficiency. A possibility to achieve this is the usage of manipulators built of lightweight structures in order to raise the maximum velocity, acceleration and payload. This leads to an elastic robot that tends to vibrate. The main focus of this paper is the modeling of a fast moving, elastic robot with three linear axes. These axes are connected by four flexible links driven by synchronous motors with elastic gear racks and bearing elasticities. The Projection Equation in subsystem form is used to calculate the dynamic model. This equation in combination with a Ritz approximation for the flexible links, which are modeled as Rayleigh beams, leads to a set of highly nonlinear ordinary differential equations. The usage of the Projection Equation in subsystem form simplifies the modeling of this system and offers the possibility of a fast numerical integration supported by the Maple® packages SimCode2, SimSubs and SimRecursive. The subsystems of the elastic bodies are assembled by the kinematical chain. This leads to the possibility to evaluate the minimal accelerations of the system by a recursive scheme with O(n) efficiency. These results for the endpoint (position and acceleration) of the complete elastically modeled robot are compared to experimental measurements.
A Design Support System for Scenario-Based Lifecycle Design
Authors: Fukushige Shinichi , Kunii Eisuke , Yamamoto Kazuhiro , Umeda Yasushi
Published: June 2012

In order to solve global environmental issues, we should construct stable circular product lifecycle systems. For this purpose, lifecycle design plays a crucial role; especially, it is necessary to determine lifecycle strategies at the early stage of lifecycle design. In the current practice of eco-design, for example, a designer increases the disassemblability of a product for recycling, although the product is shredded without disassembling. For avoiding such a situation and realizing stable circular product lifecycle systems, appropriate lifecycle strategies should be determined and implemented by designing both a product and its processes. This paper proposes a method for supporting design of a product lifecycle. The main approach is to support a designer to determine a lifecycle strategy by describing a lifecycle scenario, at early stage of lifecycle design. We define a representational scheme of the lifecycle scenario and develop the support system based on the idea of cognitive design process model so that a designer can examine various possibilities of lifecycle strategy. After this stage of lifecycle design, the product and its lifecycle processes should be designed so as to realize the strategy. In order to embody the strategy in the later stages, the system derives requirements for the product and process design. A case study indicates that the lifecycle scenario is successfully represented on a computer and a designer can easily determine lifecycle strategies by using this system.
A Decision-Guided Energy Management Framework for Sustainable Manufacturing
Authors: Shao Guodong , Brodsky Alexander , Arinez Jorge , Menasce Daniel , Ammann Paul
Published: June 2012

A growing number of manufacturing industries are initiating efforts to address sustainability issues. According to the National Association of Manufacturers, the manufacturing sector currently accounts for about one third of all energy consumed in the United States [1]. Reducing energy costs and pollution emissions involves many areas within an industrial facility. Peak electric demands are a significant component in the cost of electricity. Electric demand management relates to electric tariff rates, new power generation, and incentives to curtail peak usages. Shifting some equipment/machine usage to the periods of lower cost or using stand-by local generators during the peak demand period can yield important savings. Analysis of these options is important to decision makers to avoid unnecessary high cost of energy and equipment. This paper proposes a Decision-Guided energy management in manufacturing (DG-EMM) framework to perform what-if analysis and make optimal actionable recommendations for a manufacturing facility both on (1) operational energy management including load shedding, curtailment, and local generation and (2) planning and investment decisions for introducing renewable technologies. The DG-EMM is based on the novel technology of the Decision-Guidance Query Language (DGQL), which is a tool for fast development and iterative extension of decision-guidance and optimization solutions. The proposed DG-EMM will support user-defined objectives for optimal recommendations, such as minimizing emissions and energy costs and maximizing Return on Investment (ROI). A case study of the peak demand control for an example manufacturing facility is discussed.
Noise Squeezing Control for Bifurcation Sensing in MEMS
Authors: Burgner Chris , Turner Kimberly , Miller Nick , Shaw Steve
Published: June 2012

This paper reports the development and implementation of a new method for tracking parameters at which dynamic bifurcations occur in MEMS. The underlying theory is developed for subcritical pitchfork bifurcations that occur near the subharmonic instability experienced near parametric resonance. The method relies on experimentally observed changes in response phase and amplitude just prior to the bifurcation, and these are used to forebode the bifurcation. These precursors are then employed in a feedback control scheme to stabilize a parametrically excited MEMS device at the edge of instability, making it highly sensitive to changes in device parameters. Implementation of the controller is shown through experimental validation. A comparison with the previous method of bifurcation detection for the same device shows that the new approach offers an improvement of over three orders of magnitude for the bifurcation point acquisition rate.
The Modified Quadrilateral Discretization Model for the Topology Optimization of Compliant Mechanisms
Authors: Zhou Hong , Killekar Pranjal P.
Published: June 2012

The modified quadrilateral discretization model for the topology optimization of compliant mechanisms is introduced in this paper. The design domain is discretized into quadrilateral design cells. There is a certain location shift between two neighboring rows of quadrilateral design cells. This modified quadrilateral discretization model allows any two contiguous design cells to share an edge whether they are in the horizontal, vertical or diagonal direction. Point connection is completely eliminated. In the proposed topology optimization method, design variables are all binary and every design cell is either solid or void to prevent grey cell problem that is usually caused by intermediate material states. Local stress constraint is directly imposed on each analysis cell to make the synthesized compliant mechanism safe. Genetic algorithm is used to search the optimum and avoid the need to select the initial guess solution and conduct sensitivity analysis. No postprocessing is needed for topology uncertainty caused by point connection or grey cell. The presented modified quadrilateral discretization model and the proposed topology optimization procedure are demonstrated by two synthesis examples of compliant mechanisms.
Using SysML for Conceptual Representation of Agent-Based Models
Authors: Sha Zhenghui , Le Qize , Panchal Jitesh H.
Published: June 2012

Agent-based modeling (ABM) is a technique used to simulate systems consisting of autonomous interacting entities called agents. It has shown great advantages in modeling complex systems with independent but interacting actors. ABM has been successfully applied to a variety of systems. Despite the availability of a large number of tools for ABM, there is limited support for the conceptual design of agent-based models. Further, the currently available tools capture both the model information and the tool-specific execution information in an integrated manner. This limits model reusability, which is an impediment to systematic validation of models. In this paper, we use the systems modeling language (SysML) for building conceptual models of agent-based models. We discuss how the different diagrams in the SysML language can be used to represent different aspects of agent-based models. Further, we propose an approach for automatically generating executable agent-based models from their conceptual SysML representations. The proposed approach is illustrated using a model of mass-collaborative processes as an example. The proposed approach for conceptual representation of agent-based models in SysML and automatic extraction of executable models has the potential to greatly improve reuse, reconfiguration, and validation of agent-based models.
NURBs for Robot Manipulator Trajectory Generation
Authors: Steuben John , Steele John , Turner Cameron J.
Published: June 2012

Modern applications of automation and robotic technologies require increasingly sophisticated control systems. One of the areas in which the control of these robotic systems can be improved is the generation of motion trajectories. We demonstrate that Non-Uniform Rational B-splines (NURBs) can be successfully adapted for use in producing trajectories for 6-DOF manipulators. We also discuss a methodology for fitting such splines to arbitrary geometries allowing for the generation of paths in cases where it is difficult or impossible to do so using less sophisticated methods. We demonstrate these techniques in simulation, where they are applied to a pair of complex industrial tasks. Several important properties of NURBs which offer advantages not present in other methods are also discussed. We conclude by discussing the future research needed to bring this technique to maturity, and potential opportunities that may be realized in its adoption.
Design of Small-Scale Statically Balanced Compliant Joints
Authors: Jensen Brian D. , Jenkins Cesare H.
Published: June 2012

This paper demonstrates a low stiffness compliant joint design obtained by balancing the energy stored within individual components of the mechanism. As a step toward a fully-compliant zero-stiffness joint, this paper presents the design of a partially-compliant joint. A wireform torsion bar partially compliant joint was optimized using a pseudo rigid body model. A low stiffness design was obtained by balancing the energy stored within individual components of the mechanism. The joint was then fabricated using piano wire, polypropylene and Delrin®. During testing it was found that friction in the joint was greater than any internal forces allowing the joint to be neutrally stable in all positions. Dynamic force deflection data on the joints was collected in order to investigate the friction characteristics. The Delrin® joint exhibited only Coulomb friction while the polypropylene model exhibited both Coulomb and viscous friction.
Impacts of Team Characteristics and Design Activities on Design Outcomes
Authors: Takai Shun
Published: June 2012

This paper presents an analysis of design team characteristics and design activities that are significantly associated with design outcomes (i.e., project performances) in sophomore-level project-based design courses. Besides efficient team work, a team needs to successfully perform three design activities: concept generation, concept selection, and prototyping. In the design course, teams are formed based on students’ choice of teammates as well as on instructor assigned teams which maximize cognitive mode diversity among members. A regression analysis is performed to find variables that are significantly associated with design outcomes. These variables include team size, teaming preference, diversity of cognitive modes among team members, the average number of power tools team members have used in the past, whether or not a team experienced a team-working difficulty, the number of concepts generated before and after using creativity techniques, whether or not a team had the most successful strategy (called “winning” concept in this study) in a set of concepts from which one concept is chosen for prototyping, and timing of selecting the winning concept (at concept selection, at proof-of-concept testing, or at final testing). Design strategies used by teams, the winning concepts, results of regression analysis (variables significantly associated with design outcomes) are discussed.
Methods of Describing Plastic Gear Geometry After a Temperature Change With Application to the Prediction of Gear Load Distribution
Authors: Kashyap Sumanth , Houser Donald R. , Smith Zan , Selvaraj Senthilvelan , Casella James M. , Bradway Jeffrey John
Published: June 2012

In Polymer gears, the rise in temperature not only influences gear rigidity but also tooth geometry. This paper presents methods to represent the influence of temperature by change in micro-geometry and macro-geometry parameters of the gear tooth. These macro and micro-geometry parameters of gear are entered into advanced gear analysis programs such as those for performing load distribution analysis and transmission error prediction. This theoretical model assumes linear thermal expansion of the material of the gear. This model is verified using a Finite Element Analysis (FEA) of the gear tooth. Two approaches were successfully used to model the thermal expansion of the material, one being to change the module of the gear and the other being to apply a pressure angle slope change to the tooth form. The profile change was verified by elevating the temperature of plastic gears of several materials and then measuring them on a Gear–Co-ordinate Measuring Machine. The two approaches were used in compatible load analysis programs that produced essentially identical transmission error predictions.
Modeling of Geometric Variations for Line-Profiles
Authors: Davidson Joseph K. , Shah Jami J.
Published: June 2012

The geometric variations in a tolerance-zone can be modeled with hypothetical point-spaces called Tolerance-Maps (T-Maps) for purposes of automating the assignment of tolerances during design. The objective of this paper is to extend this model to represent tolerances on line-profiles. Such tolerances limit geometric manufacturing variations to a specified two-dimensional tolerance-zone, i.e. an area, the boundaries to which are curves parallel to the true profile. The single profile tolerance may be used to control position, orientation, and form of the profile. In this paper, the Tolerance-Map (Patent No. 6963824) is a hypothetical volume of points that captures all the positions for the true profile, and those curves parallel to it, which can reside in the tolerance-zone. The model is compatible with the ASME/ANSI/ISO Standards for geometric tolerances. T-Maps have been generated for other classes of geometric tolerances in which the variation of the feature are represented with a plane, line or circle, and these have been incorporated into testbed software for aiding designers when assigning tolerances for assemblies. In this paper the T-Map for line-profiles is created and, for the first time in this model, features may be either symmetrical or non-symmetrical simple planar curves, typically closed. To economize on length of the paper, and yet to introduce a method whereby T-Maps may be used to optimize the allocation of tolerances for line-profiles, the scope of the paper has been limited to square, rectangular, and triangular shapes. An example of tolerance accumulation is presented to illustrate this method.
Comparative Study of Semi-Analytical Methods for the Stability Analysis of Delay Differential Equations
Authors: Tweten Dennis J. , Lipp Genevieve M. , Khasawneh Firas A. , Mann Brian P.
Published: June 2012

This paper describes and compares the zeroth-order semi-discretization, spectral element, and Legendre collocation methods. Each method is a technique for solving delay differential equations (DDEs) as well as determining regions of stability in the DDE parameter space. We present the necessary concepts, assumptions, and equations required to implement each method. To compare the relative performance between the methods, the convergence rate achieved and computing time required by each method are determined in two numerical studies consisting of a ship stability example and the delayed damped Mathieu equation. For each study, we present a stability diagram in parameter space and a convergence plot. The spectral element method is demonstrated to have the quickest convergence rate while the Legendre collocation method requires the least computing time. The zeroth-order semi-discretization method on the other hand has both the slowest convergence rate and requires the most computing time.
Optimization of the Spectral Kurtosis for Harmonic Component Detection
Authors: Dion J. L. , Chevallier G. , Peyret N. , Renaud F. , Festjens H.
Published: June 2012

This work is a contribution in the field of Operational Modal Analysis to identify the modal parameters of mechanical structures using only measured responses. The study deals with structural responses coupled with harmonic components amplitude and frequency modulated in a short range, a common combination for mechanical systems with engines and other rotating machines in operation. These harmonic components generate misleading data interpreted erroneously by the classical methods used in OMA. The present work attempts to differentiate maxima in spectra stemming from harmonic components and structural modes. The detection method proposed is based on the so-called Optimized Spectral Kurtosis and compared with others definitions of Spectral Kurtosis described in the literature. After a parametric optimization of the method, a critical study is performed on numerical simulations and then on an experimental structure in operation in order to assess the method’s performance.
An Adaptive Rapidly-Exploring Random Tree Algorithm for Assembly Path Planning in Complex Environments
Authors: Shang Wei , Liu Jian-hua
Published: June 2012

We present a refined Rapidly-exploring Random Tree (RRT) algorithm for assembly path planning in complex environments. This algorithm adapts its expansion automatically to explore complex environments with narrow passages and cluttered obstacles more efficiently. In this algorithm, the nodes in the tree are classified by various criterions and different extending values are assigned on them indicating the nearby environment and are used to control the future expansion. A series of tree extending schemes are designed and selectively used based on the attributes of the node and the extending result in each step. We show that the algorithm becomes greedy in constrained environments and promising nodes have higher priority to extend than the non-promising ones. The algorithm is evaluated and applied in assembly path planning. The results show significant performance improvement over the standard RRT planner.
Smooth Shutdown Control Strategy of Hybrid Engines for Commercial Vehicle Hotel Mode
Authors: Song Xubin
Published: June 2012

Long-haul commercial vehicles provide the hotel mode with a desirable comfort cabin for drivers to have rest. During this mode, sustainable power requirement on the on-board battery asks for occasional engine-on/off to maintain the battery SOC level, neither deeply charged nor overcharged. With the conventional engine-only-driven powertrains, there is a great challenge to deliver smooth engine on/off processes during the hotel mode in order to maintain the cabin as quiet and vibrationless as possible. But for the electric hybrid powertrain system, such a challenge can be addressed with the involvement of the hybrid motor/generator (M/G) to achieve smooth engine crank and shutdown. Apparently it is feasible to control M/G to mitigate discomfortable vibrations inside the cabin caused by periodic engine shutdowns for recharging the battery. In this paper, a pole placement control (PPC) with application of the hybrid M/G is developed to dampen out this kind of adverse vibrations which are transmitted from engine/gearbox to the cabin through the chassis structure and cabin mounts. More specifically, the PPC uses the motor speed as a feedback control signal to create a desirable motor torque command so that the vibration transmission could be abated. In the end of this paper, field testing data from a prototype hybrid truck will be presented to demonstrate the effectiveness of this innovative PPC strategy.
Identifiable Parameter Analysis for the Kinematic Calibration of a Hybrid Robot
Authors: Wang Yongbo , Wu Huapeng , Handroos Heikki
Published: June 2012

In this paper, a statistical method for the determination of the identifiable parameters of a hybrid serial-parallel robot IWR (Intersector Welding Robot) is presented. This method is based on the Markov Chain Monte Carlo (MCMC) algorithm to analyze the posterior distribution and correlation of the error parameters. Differential Evolution algorithm is employed to search a global optimizer as initial values for the random sampling of MCMC. The robot under study has ten degrees of freedom (DOF) and will be used to carry out welding, machining, and remote handing for the assembly of vacuum vessel of the international thermonuclear experimental reactor (ITER). In this paper, a kinematic error model which involves assembling and manufacturing error parameters is developed for the proposed robot. Based on this error model, the mean values of the unknown parameters are statistically analyzed and estimated using the proposed method. Computer simulations reveal that all the reduced independent kinematic parameters can be identified with the complete pose measurements. Results also demonstrate that the identification method is robust and effective with the given measurement noise.
Nonlinear Flutter Response of Tilting 4 Pad Bearings-Rotor System
Authors: Ying Jiayang , Jiao Yinghou , Chen Zhaobo , Kirk R. Gordon
Published: June 2012

Nonlinear analysis is increasingly applied in the dynamics analysis of rotor bearing systems. The use of tilting-pad bearings is now a standard feature of many types of rotor systems. The concern for oil film excitation of the rotor lowest natural frequency is eliminated by the use of the tilting pad journal bearings. For new higher speed or larger low speed applications, the possibility of the pad flutter instability still remains and most commonly used design tools do not consider the pad inertia as a standard feature. In this paper, taking the Jeffcott rotor supported by two 4 pad bearings as an example, the influence of pad inertia and journal diameter were studied. The influence of shaft diameter and pad inertia was determined by the transient response of a simple rotor-bearing system operating over a wide design speed range. The tilting pad journal bearing oil-film force was calculated by a database method. The resulting nonlinear transient vibration is discussed using bifurcation diagrams, orbits, frequency spectrum plots, phase trajectories, and Poincare maps. The results directly show that journal diameter and pad inertia greatly influence the nonlinear vibrations of the journal and rotor center.
Efficient Sensitivity Analysis for Multibody Dynamics Systems Using an Iterative Steps Method With Application in Topology Optimization
Authors: Dong Guang , Ma Zheng-Dong , Hulbert Gregory , Kikuchi Noboru , Arepally Sudhakar , Vunnam Madan , Lou Ken-An
Published: June 2012

Efficient and reliable sensitivity analyses are critical for topology optimization, especially for multibody dynamics systems, because of the large number of design variables and the complexities and expense in solving the state equations. This research addresses a general and efficient sensitivity analysis method for topology optimization with design objectives associated with time dependent dynamics responses of multibody dynamics systems that include nonlinear geometric effects associated with large translational and rotational motions. An iterative sensitivity analysis relation is proposed, based on typical finite difference methods for the differential algebraic equations (DAEs). These iterative equations can be simplified for specific cases to obtain more efficient sensitivity analysis methods. Since finite difference methods are general and widely used, the iterative sensitivity analysis is also applicable to various numerical solution approaches. The proposed sensitivity analysis method is demonstrated using a truss structure topology optimization problem with consideration of the dynamic response including large translational and rotational motions. The topology optimization problem of the general truss structure is formulated using the SIMP (Simply Isotropic Material with Penalization) assumption for the design variables associated with each truss member. It is shown that the proposed iterative steps sensitivity analysis method is both reliable and efficient.
GEO + ES Hybrid Optimization Algorithm Applied to the Parametric Thermal Model Estimation of a 200N Hydrazine Thruster
Authors: Galski Roberto Luiz , Patire Ju´nior Heitor , de Sousa Fabiano Luis , Hinckel Jose´ Nivaldo , Lacava Pedro , Ramos Fernando Manuel
Published: June 2012

In the present paper, a hybrid version of the Generalized Extremal Optimization (GEO) and Evolution Strategies (ES) algorithms [1], developed in order to conjugate the convergence properties of GEO with the self-tuning characteristics present in the ES, is applied to the estimation of the temperature distribution of the film cooling near the internal wall of a thruster. The temperature profile is determined through an inverse problem approach using the hybrid. The profile was obtained for steady-state conditions, were the external wall temperature along the thruster is considered as a known input. The Boltzmann’s equation parameters [2], which define the cooling film temperature profile, are the design variables. Results using simulated data showed that this approach was efficient in recuperating those parameters. The approach showed here can be used on the design of thrusters with lower wall temperatures, which is a desirable feature of such devices.
Towards a Framework for Holistic Ideation in Conceptual Design
Authors: Mohan Manikandan , Chen Ying , Shah Jami J.
Published: June 2012

The long term aim of this research is to develop a framework for holistic ideation. Towards that goal, we are investigating the components of ideation (both logical and intuitive), characterization of ideation states, ideation blocks and strategies used to overcome such blocks. One of the major contributions of this research is the method by which the experiential and the intuitive ideation methods are interlaced together, to support both creativity and functional quality. Another important part of the framework is the identification of creativity blocks and investigation of matching ideation strategies most likely to facilitate progress. This framework will also be used as a research tool to collect large amount of data from designers about their choice of ideation strategies used, and their effectiveness.
Improved Robotics Joint-Space Trajectory Generation With Via Point
Authors: Williams Robert L.
Published: June 2012

This paper presents novel fourth- and sixth-order polynomials to solve the problem of joint-space trajectory generation with a via point. These new polynomials use a single function rather than two polynomial functions matched at the via point as in previous methods. Another contribution of this paper is to expose the widespread, use of discontinuous acceleration functions in joint-space trajectory generation methods, which lead to unacceptable infinite spikes in jerk, the derivative of the acceleration.
A Model for Making Part Sourcing Decisions for Long Life Cycle Products
Authors: Prabhakar Varun J. , Sandborn Peter
Published: June 2012

Long life cycle products, commonly found in aviation, medical and critical infrastructure applications, are often fielded and supported for long periods of time (20 years or more). The manufacture and support of long life cycle products rely on the availability of suitable parts, which over long periods of time, leaves the parts susceptible to a number of possible supply chain disruptions such as suppliers exiting the market, counterfeit part risks, and part obsolescence. One solution to mitigating the supply chain risk is the strategic formulation of suitable part sourcing strategies (optimally selecting one or more suppliers from which to purchase parts over the life of the part’s use within a product or within an organization). Strategic sourcing offers one way of avoiding the risk of part unavailability (and its associated penalties), but at the possible expense of qualification and support costs for multiple suppliers. Existing methods used to study part sourcing decisions are procurement-centric where cost tradeoffs focus on part pricing, negotiation practices and purchase volumes. These studies are commonplace in strategic parts management for short life cycle products; however, conventional procurement-centric approaches offer only a limited view when assessing parts used in long life cycle products. Procurement-driven decision-making provides little to no insight into the accumulation of life cycle cost (attributed to the adoption and use of the part), which can be significantly larger than procurement costs in long life cycle products. This paper presents a new life cycle modeling approach to quantify risk that enables cost effective part sourcing strategies. The method quantifies obsolescence risk as “annual expected total cost of ownership (TCO) per part site” modeled by estimating the likelihood of obsolescence and using that likelihood to determine the TCO allowing sourcing strategies to be compared on a life cycle cost basis. The method is demonstrated for electronic parts in an example case study of linear regulators and shows that when procurement and inventory costs are small contributions to the part’s TCO, the cost of qualifying and supporting a second source outweighs the benefits of extending the part’s effective procurement life.
Analytical and Numerical Solutions of the Space and Time Fractional Bloch-Torrey Equation
Authors: Yu Q. , Liu F. , Turner I. , Burrage K.
Published: June 2012

Fractional order dynamics in physics, particularly when applied to diffusion, leads to an extension of the concept of Brownian motion through a generalization of the Gaussian probability function to what is termed anomalous diffusion. As MRI is applied with increasing temporal and spatial resolution, the spin dynamics are being examined more closely; such examinations extend our knowledge of biological materials through a detailed analysis of relaxation time distribution and water diffusion heterogeneity. Here the dynamic models become more complex as they attempt to correlate new data with a multiplicity of tissue compartments where processes are often anisotropic. Anomalous diffusion in the human brain using fractional order calculus has been investigated. Recently, a new diffusion model was proposed by solving the Bloch-Torrey equation using fractional order calculus with respect to time and space (see R.L. Magin et at, J. Magnetic Resonance, 190 (2008) 255–270). However effective numerical methods and supporting error analyses for the fractional Bloch-Torrey equation are still limited. In this paper, the space and time fractional Bloch-Torrey equation (ST-FBTE) is considered. The time and space derivatives in the ST-FBTE are replaced by the Caputo and the sequential Riesz fractional derivatives, respectively. Firstly, we derive an analytical solution for the ST-FBTE with initial and boundary conditions on a finite domain. Secondly, we propose an implicit numerical method (INM) for the ST-FBTE, and the stability and convergence of the INM are investigated. We prove that the implicit numerical method for the ST-FBTE is unconditionally stable and convergent. Finally, we present some numerical results that support our theoretical analysis.
Elastohydrodynamic Ball Bearing Optimization Using Genetic Algorithm and Heuristic Gradient Projection
Authors: Abbas Mohamed H. , Metwalli Sayed M.
Published: June 2012

Rolling element bearings operation depends on some variables contributing to the machine element performance. The present work attempts to improve the performance of rolling element bearings through the increase of fatigue life and the reduction of bearing wear. The formulation is based on Elastohydrodynamic to maximize the realistically evaluated minimum film thickness without significant increase in viscous friction torque. The multiobjective problem can then be stated as maximization of minimum film thickness and minimization of total friction torque. Design vectors are reduced in the present study relative to previous studies as some variables are considered as dependent variables. A new important parameter is introduced in this study as a design variable, which is the viscosity of lubricant (η0 (Pa.s)). Lubricant viscosity contributes drastically in either increasing minimum film thickness separation or increasing the frictional torque arising in bearing. A multi-objective optimization using Genetic Algorithm is used in order to evaluate Pareto optimal solutions. Another multi-objective problem has been formulated such as a two objective problem involving maximizing minimum film thickness, and minimizing the bearing elements size (i.e.: ball diameter and mean diameter) through subjecting the bearing to the maximum allowable compressive stress of the elements. Heuristic gradient projection method is used in solving such a problem, as it can efficiently seek the optimum point in less than five iterations. In such a case, the design variables are reduced to two variables, which are the ball diameter and mean diameter. Full design vector consideration is also performed.
Air Bubble Detection for Product Quality Inspection
Authors: Ito Teruaki
Published: June 2012

Product quality is one of the critical issues to be competitive in the global market place. Especially, food production companies are strongly required to control high product quality in their production lines. The contaminations such as metallic, or plastic, organic materials are harmful to human body and should be eliminate as much as possible. Therefore, machine inspections, such as X-ray or fluorescence spectrum methods work effectively to eliminate these contamination substances. However, the final inspections are taken care of by human inspectors to make sure the product quality kept in the required specifications. Contaminations are not perfectly eliminated by machine inspections and human inspections could cover some of them. That is not the only reason why the human inspector takes care of. Even though there is no contamination in the products, appearance of products may decrease the quality of the products. For example, even though air bubble has nothing to do with the taste of Tofu, customers do not purchase such Tofu which contains many air bubbles, whereas they would buy Tofu with some air bubble. Therefore, human inspectors review the Tofu package to check the defective products because of the air bubble, which is hard to be processed by machine inspection. This study proposes image processing-based air bubble detection method on Tofu packages to inspect the product quality without image sensor devices. Based on the results of air bubble detection on the Tofu package, the evaluation will be made on each package. The study applied an evaluation criterion based on the experiments. However, the results are not always identical to those by human inspection because of the disagreement of threshold value in evaluation. This paper presents the image-processing air bubble detection method to determine the quality of Tofu products and discusses the feasibility of this method in comparison with the human inspection results.
Application of a New Spherical Super Element in Predicting the Deformation of Biological Cells in Microinjection
Authors: Sarvi Masoud Nasiri , Ahmadian M. T.
Published: June 2012

Biological cell injection is a sensitive and important work which is implemented in injection of foreign materials into individual cells. Microinjection is significantly developed in the field of drug discovery and genetics so predicting the behavior of cell in microinjection is remarkably important because a tiny excessive manipulation force can destroy the tissue of the biological cell. There are a few analytical methods available to simulate the cell injection, hence the numerical methods such as FEM are suitable to be used to model the microinjection. In this study, a new spherical super element is presented to model the biological cells and deformation of a specific cell under an external force is performed. The relationship between the injection force and the deformation of biological cell is demonstrated by using super element formulations. For validating the model, results are compared with findings of analytical and experimental methods. The advantage of this element is that only a few super elements can predict the static behavior of biological cell in microinjection properly instead of implementing a large number of conventional elements, so using the super element to model the cell can decrease the run time with suitable accuracy.
The Selection of the Linearized Natural Frequency for the Second-Order Normal Form Method
Authors: Xin Zhenfang , Neild S. A. , Wagg D. J.
Published: June 2012

The normal form technique is an established method for analysing weakly nonlinear vibrating systems. It involves applying a simplifying nonlinear transform to the first-order representation of the equations of motion. In this paper we consider the normal form technique applied to a forced nonlinear system with the equations of motion expressed in second-order form. Specifically we consider the selection of the linearised natural frequencies on the accuracy of the normal form prediction of sub- and superharmonic responses. Using the second-order formulation offers specific advantages in terms of modeling lightly damped nonlinear dynamic response. In the second-order version of the normal form, one of the approximations made during the process is to assume that the linear natural frequency for each mode may be replaced with the response frequencies. Here we will show that this step, far from reducing the accuracy of the technique, does not affect the accuracy of the predicted response at the forcing frequency and actually improves the predictions of sub and superharmonic responses. To gain insight into why this is the case, we consider the Duffing oscillator. The results show that the second-order approach gives an intuitive model of the nonlinear dynamic response which can be applied to engineering applications with weakly nonlinear characteristics.
Teaching Manipulator Kinematics by Painting With Light
Authors: Shomin Michael , Fiene Jonathan
Published: June 2012

In this paper, we examine the creation and benefits of a new teaching platform to introduce and reinforce the key concepts of robotic manipulators in an introductory-level robotics course. This system combines a vintage PUMA 260 six-degree-of-freedom robotic arm with modern control circuitry and a Matlab API. The API operates as a servo controller for the robot, thereby allowing students to apply their knowledge of inverse kinematics to a real manipulator arm. To further motivate the exploration of manipulators, we have developed an open-ended project where students engage in the art of three-dimensional light painting. To facilitate this activity, a tricolor LED has been affixed to the end-effector of the robot. With a digital SLR camera, we take a long-exposure photograph as the robot is driven through a trajectory, effectively painting a picture with the end effector. We have also developed a method to quickly assemble pseudo-long-exposure photographs and videos using an inexpensive video camera. We believe this novel setup and project are an effective way to engage and motivate students to learn the underlying math and dynamics of robotic manipulators.
Towards Failure Free Design: An Analysis of Risk Mitigation Communication
Authors: Krus Daniel , Grantham Katie
Published: June 2012

In order to ensure that risk mitigation strategies are properly communicated to and understood by those who would use them in future designs, a common language of risk mitigation should exist. This paper focuses on a set of elements for describing risk mitigation strategies based on a linguistic analysis of the information such strategies must communicate to the design team. Sample strategies are then decomposed into these attributes and evaluated using the Gricean cooperation principle, relevance theory, and functional analysis theories from the pragmatics sub-field of linguistics. Using the deficiencies found from this analysis, a format for risk mitigation strategies using the six risk mitigation attributes is formulated.
Fractional PI Tuning Satisfying Gain and Phase Margin Constraints
Authors: Paridari Kaveh , Tavazoei Mohammad Saleh
Published: June 2012

In this paper, an algebraic tuning rule is presented for fractional PI controllers to control first order plus dead-time processes. By using the performance map (PM) method, this tuning rule is derived in order to set the gain margin of the control system close to 3 and the phase margin close to 60 degrees. The robustness and performance of this tuning rule are compared with some well-known PI tuning rules. Simulation results are brought to demonstrate the effectiveness and robustness of this tuning formula against process dynamic uncertainties in comparison with the other tuning methods.
Adjoint Design Sensitivity Analysis of Fracture Mechanics Using Molecular-Continuum Multiscale Approach
Authors: Kim Hyun-Seok , Jang Hong-Lae , Kim Min-Geun , Cho Seonho
Published: June 2012

We have developed a multiscale design sensitivity analysis method for transient dynamics using a bridging scale method by a projection operator for scale decomposition. Employing a mass-weighted projection operator, we can fully decouple the equations of motion into fine and coarse scales using the orthogonal property of complimentary projector to the mass matrix. Thus, independent solvers in response analyses can be utilized for the fine scale analysis of molecular dynamic (MD) and the coarse scale analysis of finite element analysis. To reduce the size of problems and to improve the computational efficiency, a generalized Langevin equation is used for a localized MD analysis. Through demonstrative numerical examples, it turns out that the derived sensitivity analysis method is accurate and efficient compared with finite difference sensitivity.
Some Experimental and Analytical Results on Self-Excited Vibration of a Dynamic Sliding System in the Case of Stribeck Law for Friction Coefficient
Authors: Le Rouzic Julian , Perret-Liaudet Joel , Carbonelli Alexandre , Le Bot Alain , Mazuyer Denis
Published: June 2012

The principal aim of this paper is to deal with friction-induced self-excited vibrations in the context of Stribeck law for friction coefficient. More precisely, the theoretical dynamic system under study consists of a single-degree-of-freedom mass-spring-damper oscillator subjected to a velocity-dependent frictional force as it slides on a conveyor belt, following a Stribeck law. We have analyzed the local stability of the static equilibrium and described the created periodic cycle using the averaging method. Numerical continuation with Matcont software is also used for qualitative analysis of this non linear system. In order to validate the theoretical analysis, an original experimental device, the named Lug test rig developed in our laboratory, was employed. For a glass/elastomer contact lubricated with water, friction force and dynamic displacement have been measured. The appearance of the instabilities is explained in relation to the friction measurements.
A Rolling Parallelogram Driven by a Crank-Rocker Mechanism
Authors: Liu Chang-huan , Yao Yan-an
Published: June 2012

Normally, one link of the four-bar linkage is fixed to the frame; another supplies the input; the motion of the third one with respect to the base is the output. A novel application of the four-bar linkage is proposed that a parallelogram mechanism is applied to be a rolling robot for which there is neither a constant base nor a constant output. Four sides take turns to be the support link and an adjacent link of the support one is regarded as the output in turn. The rolling motion is actuated by an internal angle change which is supplied by the rocker oscillation of a crank-rocker mechanism, not a motor directly. The unidirectional rotation of the motor simplifies the control system. A planar 4R parallelogram is suggested to roll straight under the driving of a planar 4R crank-rocker mechanism. For turning, a spatial RSRS quadrilateral is presented to roll and turn driven by a spatial RSUS crank-rocker mechanism. The principle of tipping and rolling are explained. Simulations testify the parameter design of the driving rank-rocker mechanism. An experimental prototype is fabricated to verify the feasibility of the concept.
Nonlinear Strain Energy Formulation to Capture the Constraint Characteristics of a Spatial Symmetric Beam
Authors: Sen Shiladitya , Awtar Shorya
Published: June 2012

In the past, a beam constraint model (BCM) that captures pertinent geometric nonlinearities associated with large displacements has been proposed for slender spatial beams with uniform and symmetric cross-sections. By providing closed-form parametric relations between the end-loads and end-displacements of the beam, the BCM quantifies the constraint characteristics of the beam in terms of stiffness variations, parasitic error motions, and the cross-axis coupling. This paper presents a nonlinear strain and strain energy formulation for the spatial symmetric beam, based on assumptions that are consistent with the BCM. This strain energy derivation, employing the Principle of Virtual Work, provides a simpler mathematical approach for the analysis of flexure mechanisms with multiple spatial beams. Using this formulation, we obtain the stiffness relations in the transverse bending directions, the constraint relations in the axial and torsional directions, and the overall strain energy expression in terms of the beam end-loads and end-displacements. These expressions, collectively the BCM, are in form that is suitable for the analysis of multi-beam flexure mechanisms.