bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental and Numerical Investigations of an Untethered, Nonlinear Spherical Buoy in a Wave Tank
Authors: Ballard Zach , Mann Brian
Published: June 2012

The horizontal and vertical motions of a spherical buoy, excited by synthetic ocean waves within a wave flume, is numerically and experimentally investigated. First, fluid motion in the wave tank is described using Airy’s theory, and the forces on the buoy are determined using a modified form of Morison’s equation. The system is then studied statically in order to determine the effects of varying system parameters. Numerical simulations then use the governing equations to compare predicted motions with experimentally observed behavior.
A New Approach to Obtaining Closed-Form Solutions for Higher Order Tetrahedral Finite Elements Using Modern Computer Algebra Systems
Authors: McCaslin Sara E. , Shiakolas Panos S. , Dennis Brian H. , Lawrence Kent L.
Published: June 2012

Closed-form solutions for straight-sided tetrahedral element stiffness matrices used in finite element analysis have been proven more efficient than numerically integrated solutions. These closed-form solutions are symbolically integrated using computer algebra systems such as Mathematica or Maple. However, even with memory and processing speed available on desktop computers today, major hindrances exist when attempting to symbolically evaluate the stiffness matrices for high order elements. This research proposes a new approach to obtaining closed-form solutions. Results are presented that demonstrate the feasibility of obtaining the stiffness matrices for high order tetrahedral elements through p-level 9 by use of parallel processing tools in Mathematica 7. Comparisons are made between serial and parallel approaches based on memory required to generate a solution. The serial approach requires more memory and can only generate closed-form solutions up to 7th order. The parallel processing approach presented requires less memory and can generate solutions up to 9th order.
A Systematic Approach to Designing Multi-Material Miniature Compliant Mechanisms
Authors: Vogtmann Dana E. , Gupta Satyandra K. , Bergbreiter Sarah
Published: June 2012

A new process has been developed for realizing multimaterial miniature compliant hinges. This paper presents a systematic approach to the design of multi-material miniature compliant mechanisms based on the new process. A mechanism concept in the form of a skeleton diagram with force and motion constraints is provided as input, and the design results in a 3-D CAD model that incorporates all manufacturing constraints. The new fabrication process allows the utilization of multiple materials to realize compliant mechanisms. Therefore, material choice is an important component of the design approach in addition to shape selection, manufacturing constraints incorporation, and the final optimization. A sub-gram flapping mechanism used to characterize the performance of miniature wings is presented as a running example, illustrating the design process.
An In-Pipe Leak Detection Sensor: Sensing Capabilities and Evaluation
Authors: Chatzigeorgiou Dimitris M. , Khalifa Atia E. , Youcef-Toumi Kamal , Ben-Mansour Rached
Published: June 2012

In most cases the deleterious effects associated with the occurrence of leak may present serious problems and therefore leaks must be quickly detected, located and repaired. The problem of leakage becomes even more serious when it is concerned with the vital supply of fresh water to the community. In addition to waste of resources, contaminants may infiltrate into the water supply. The possibility of environmental health disasters due to delay in detection of water pipeline leaks has spurred research into the development of methods for pipeline leak and contamination detection. Leaks in water pipes create acoustic emissions, which can be sensed to identify and localize leaks. Leak noise correlators and listening devices have been reported in the literature as successful approaches to leak detection but they have practical limitations in terms of cost, sensitivity, reliability and scalability. To overcome those limitations the development of an in-pipe traveling leak detection system is proposed. The development of such a system requires a clear understanding of acoustic signals generated from leaks and the study of the variation of those signals with different pipe loading conditions, leak sizes and surrounding media. This paper discusses those signals and evaluates the merits of an in-pipe-floating sensor.
Analysis of a Flexibly Mounted Shaft Incorporating a Non-Constant Velocity Coupling With Dynamic Misalignment
Authors: Johnson David R. , Wang K. W.
Published: June 2012

Some shafting systems, such as those in certain types of rotorcraft, are mounted on flexible foundations. Since the foundation can deform, shaft segments are joined by flexible couplings to accommodate motion. Many of these couplings are non-constant velocity, meaning there is a difference in angular velocity between the input and output of the coupling, and this difference can lead to large motion in the shaft system. In this paper, a model is developed which allows the misalignment angle between the input and output shafts to vary dynamically with time, and this kinematic relationship creates a nonlinearity in the system. Through nonlinear analysis and accompanying simulation, this research explores some interesting and potentially harmful phenomena which occur at secondary resonances of such a shaft system. At particular shaft operating speeds, the shaft system may experience internal resonance, large and rapid amplitude growth, or chaotic motion, all of which can lead to destructive large amplitude vibration. This paper also shows that applying appropriate damping is an effective strategy for mitigating these effects.
Challenges for Managing Component Obsolescence in Long Life Products Through the Product Development Lifecycle
Authors: Brown Travis E. , Bartholomew Scott E. , Dragon Glen A. , Smykowski Aaron C. , Rojas Arciniegas Alvaro J. , Esterman Marcos
Published: June 2012

Producers of low volume, long life products must utilize the latest commercial, off the shelf (COTS) components in order to meet cutting edge technological needs. These COTS components often have a primary use in the high volume commercial markets (e.g. smart phones) which are characterized by short product lifecycles to satisfy consumer needs and remain competitive. Consequently, the two to three year lifecycles of these products tend to heavily influence the lifecycle of the components inside. Most tactical military products (as an example of low volume, long life products) have a very long design, production and support period that can often exceed ten years. Given the lifecycle mismatch between the products and components, an obsolescence management process is essential in order for a producer of low volume, long life products to effectively manage obsolescence in their product line. In this paper, the obsolescence management strategies are reviewed to identify best practices and recommendations that can improve a company’s ability to deal with obsolescence, sometimes called DMSMS (Diminishing manufacturing sources and material shortages), though the terms are not strictly interchangeable. This is achieved not only through a comprehensive literature review but also through a series of case studies from different companies. These validate findings from literature and provide a realistic perspective on the challenge to manage obsolescence, during the product development lifecycle.
Initialization of Fractional-Order Systems Using the Hankel Operator
Authors: Adams Jay L. , Veillette Robert J. , Hartley Tom T.
Published: June 2012

This paper demonstrates the use of the Hankel operator to characterize the initial-condition response of a fractional-order system. A general initial-condition response can be determined for any input applied before t = 0. Two techniques for approximating the Hankel operator are discussed. These approximation methods are applied to illustrative examples, demonstrating a general characterization of natural responses.
Optimization of Complex Dynamic Systems With Respect to Their Behavior in Time and Frequency Domain
Authors: Marx Matthias , Wei Chunsheng , So¨ffker Dirk
Published: June 2012

This paper describes an integrated optimization process of dynamic systems including design parameters and control algorithms. In contrast to known approaches the developed approach is based on an optimization loop including the evaluation of the dynamical behavior of technical systems with respect to the behavior and related properties in time and frequency domain. This includes as well the behavior of the system, the objective function as the formulation of the restrictions to be considered for the dynamical behavior (stationary and instationary). The proposed approach is declared in detail and will be illustrated using two typical technical applications as examples. The first application example is the optimization of the control system of an active magnetic bearing (AMB) rotor system. Hereby the modeling of the AMB rotor system is briefly introduced. An H∞ controller is designed for the control of the system. The performance both in time and frequency domain is optimized in parallel. The algorithm will be explained by simulation examples. The second example is the optimization of the pow-ermanagement system of a fuel cell/supercap-based hybrid electric powertrain. Hereby the modeling of the electric power flow within the powertrain system is demonstrated and its influence on certain system properties like availability, efficiency, and typical aging mechanisms is discussed. The proposed method leads to near-optimal results in a few steps for both of the systems introduced.
Market-Driven Positioning of Remanufactured Product for Design for Remanufacturing With Part Upgrade
Authors: Kwak Minjung , Kim Harrison M.
Published: June 2012

In a market with rapid changes in technology and customer preferences, technological obsolescence of end-of-life products poses a significant challenge to product end-of-life recovery. Remanufacturing with appropriate part upgrade can be a promising solution for overcoming obsolescence. This paper proposes a model for positioning a remanufactured product with an aim to support design for remanufacturing with part reuse and upgrade. By considering original product design, target market, and recovery economics (i.e., original design specifications, expected timing and quantity of end-of-life products, customer preferences and competing products, and expected remanufacturing cost and revenue), the model provides an estimate for appropriate selling price and specifications of a remanufactured product at which maximum recovery profit is expected. The developed model is illustrated with an example of desktop computer. Potential applications are also discussed with an emphasis on design for remanufacturing and recovery strategy planning.
A Novel Numerical Method to Solve the Inverse Kinematics of 3R Manipulators
Authors: Gonza´lez-Barbosa E. A. , Gonza´lez-Palacios M. A. , Aguilera-Corte´s L. A. , Bernal-Marti´nez C. A.
Published: June 2012

A new numerical method to solve the inverse kinematics solution problem of serial manipulators is developed in this paper. The proposed method is known as Differential Evolution (DE), a novel and efficient numerical method which has been adapted to solve the inverse kinematics solution of 3R serial manipulator of general geometry. Besides, the paper contains the complete structuring for the implementation of this new case in SnAP, a comprehensive software package for synthesis, analysis and simulation of serial manipulators. The DE method is stable since it converges to the solution with any initial values, and it is not sensitive to the singular configurations of serial manipulators. Simulation results are presented to show the performance benefits of the proposed algorithm. Computational efficiency of the method is shown based on the results, as well as in comparison with traditional methods used in this problem.
Evaluation of Deviation Zone Based on Maximum Conformance to Tolerances
Authors: Barari Ahmad
Published: June 2012

The accurate estimation of the geometric deviations is not possible only by manipulating the Euclidian distances of the discrete measured points from substitute geometry. The real geometric deviations of a measured surface need to be calculated based on the desired tolerance zone of the surface. This fact is usually neglected in common practices in the coordinate metrology of surfaces. The importance of considering the desired tolerance zone in estimation of the optimum deviation zone is demonstrated in this paper. Then a best fit method is presented which complies with the tolerance requirements of the designed surface. The developed fitting methodology constructs a substitute geometry to minimizes the residual deviations corresponding to the given tolerance zone and the needs of down-stream operations that use the results of the inspection process. It is shown how the developed objective function can be adopted for a case of closed-loop manufacturing process, when the under-cut residual deviations of the manufactured part can be corrected by a down-stream operation. In order to validate the proposed methodology, experiments are conducted. The results show a significant reduction of uncertainties in coordinate metrology of geometric surfaces. Implementation of this method directly results in increasing the accuracy of the entire tolerance evaluation process, and less uncertainty in quality control of the manufactured parts.
Process Integration and Design Optimization for Model-Based Systems Engineering With SysML
Authors: Min Byung I. , Kerzhner Aleksandr A. , Paredis Christiaan J. J.
Published: June 2012

Modern systems are difficult to design because they often involve the integration of multiple engineering domains, are constrained by competing objectives, include a multitude of stakeholders, and are inundated by large quantities of design information. As the complexity of systems design has grown, designers are using a diverse set of analyses during the design process. In this paper, we present an approach to help designers manage this spectrum of analyses and relate them to their systems design problems by integrating the Object Management Group’s Systems Modeling Language (OMG SysML™) with a process integration and design optimization (PIDO) framework. This allows designers to model their design problems and the related analyses within SysML. These related analyses can then be translated into the PIDO framework where they are executed and managed. The framework used in this paper is Phoenix Integration’s ModelCenter. Previous approaches have integrated SysML with a specific analysis tool, but these approaches are not sufficient because they allow designers to use only a few types of analyses. By integrating SysML with ModelCenter, this approach allows designers to tackle the design problems from several perspectives. ModelCenter provides existing integrations to a large number of analysis tools allowing users to handle multiple heterogeneous analyses in the same environment. The implementation of this approach and its usefulness during a design process is illustrated using the design of a horizontal acting hydraulic log splitter. The log splitter model is chosen as the example because it is a simple hydraulic system with well-defined composition and modular components and has several competing requirements to satisfy.
Analytical Solutions for Nonlinear Lateral Sloshing in Partially-Filled Elliptical Tankers
Authors: Younesian Davood , Askari Hassan , Saadatnia Zia , Esmailzadeh Ebrahim
Published: June 2012

Dynamic behavior of the large amplitude lateral sloshing is analytically studied in partially filled elliptical tankers. Theory of elliptical trammel pendulums is employed for modeling of the large oscillation of the fluid inside the elliptical container. Nonlinear governing equation of the motion is derived employing the Hamilton principle. Standard and modified Energy Balance Method (EBM) is adopted as the solution technique. Natural frequencies of the free oscillation are analytically obtained as a function of the initial amplitude. It is proved that the nonlinear dynamical system can behave mutually as a hardening and softening system based on the tanker aspect ratio. A number of numerical simulations are carried out and accuracy of the obtained analytical solution is evaluated.
Mass-Customization of Hip-Replacement Joint Design Using Shape Grammar
Authors: Nandi Soumitra , Siddique Zahed
Published: June 2012

Hip-replacement joints are designed to meet shape specifications for each individual patient. Because the height and shape of bones of every patient are different than the other, the shapes of hip-replacement joints need to be customized for each individual patient. Customizing for each individual patient will increase the overall cost of hip-replacement joint production and eventually the cost of whole surgery process. Mass-production is necessary to reduce the production cost for such products. A technique of mass-customization can address to both of these issues providing customization of individual design in mass format and in reasonably low production cost. In this paper we investigate the use of shape grammar to develop a common platform for mass-customization of hip-replacement joints. To capture the common shape used in regular hip replacement surgery, a set of rules is presented to define the shape grammar. The rules are then varied inside the limits and the variations of design are observed.
The Dynamics of MEMS Arches of Non-Ideal Boundary Conditions
Authors: Alkharabsheh Sami A. , Younis Mohammad I.
Published: June 2012

We present an investigation into the dynamics of MEMS arches when actuated electrically including the effect of their flexible (non-ideal) supports. First, the eigenvalue problem of a nonlinear Euler-Bernoulli shallow arch with torsional and transversal springs at the boundaries is solved analytically. Several results are shown to demonstrate the possibility of tuning the theoretically obtained natural frequencies of an arch to match the experimentally measured. Then, simulation results are shown for the forced vibration response of an arch when excited by a DC electrostatic force superimposed to an AC harmonic load. Shooting technique is utilized to find periodic motions. The stability of the captured periodic motion is examined using the Floquet theory. The results show several jumps in the response during snap-through motion and pull-in. Theoretical and experimental investigations are conducted on a microfabricated curved beam actuated electrically. Results show softening behavior and superharmonic resonances. It is demonstrated that non-ideal boundary conditions can have significant effect on the qualitative dynamical behavior of the MEMS arch, including its natural frequencies, snap-through behavior, and dynamic pull-in.
Simulation of Nonlinear Systems Having Series and Parallel Friction Elements
Authors: Ferri Al , Shahid Emad
Published: June 2012

The numerical response of a SDOF oscillator with a friction element and spring in series is investigated. The connection between the friction element and the spring is massless resulting in an ideal “Iwan element,” also termed an elastic/perfectly-plastic element. A methodology is proposed that avoids the complications caused by hysteresis, allowing the system to be simulated using relatively simple programming logic. A notable feature of the technique is that it yields a functional relation for the friction force that depends on the present value of the state vector, rather than on prior history of the motion. The method introduces a small, “fictitious” slider mass within the Iwan element. Simulations are presented to show how the relative size of the slider mass affects the trade off between accuracy and computational costs. It is seen that the results of the method are very accurate and easy to implement. It is also shown that the added numerical stiffness associated with the high-frequency dynamics of the slider mass can be alleviated through use of a switchable viscous damping term. The viscous damping term decreases the number of timesteps required for simulation without adversely affecting the accuracy. The paper considers SDOF systems having a single Iwan-element as well as multiple Iwan elements.
Type Synthesis of 3-DOF Parallel Manipulators With Both Planar and Translational Operation Modes
Authors: Kong Xianwen
Published: June 2012

Despite recent advances in the type synthesis of parallel manipulators with a mono-operation mode, such as translational parallel manipulators and spherical parallel manipulators, the type synthesis of parallel manipulators with multiple operation modes is still an open issue. This paper deals with the type synthesis of 3-DOF parallel manipulators with both planar and translational operation modes. The type synthesis of planar parallel manipulators, which refer to parallel manipulators in which the moving platform undergoes planar motion, is first dealt with using the virtual chain approach. Then, the types of 3-DOF parallel manipulators with both planar and translational operation modes are obtained. This work can be extended to the type synthesis of other classes of parallel manipulators with multiple operation modes.
Towards Industrial Implementation of Emerging Semantic Technologies
Authors: Breindel Jay T. , Grosse Ian R. , Krishnamurty Sundar , Altidor John , Wileden Jack , Trachtenberg Seth , Witherell Paul
Published: June 2012

Every new design, project, or procedure within a company generates a considerable amount of new information and important knowledge. Furthermore, a tremendous amount of legacy knowledge already exists in companies in electronic and non-electronic formats, and techniques are needed for representing, structuring and reusing this knowledge. Many researchers have spent considerable time and effort developing semantic knowledge management systems, which in theory are presumed to address these problems. Despite significant research investments, little has been done to implement these systems within an industrial setting. In this paper we identify five main requirements to the development of an industry-ready application of semantic knowledge management systems and discuss how each of these can be addressed. These requirements include the ease of new knowledge management software adoption, the incorporation of legacy information, the ease of use of the user interface, the security of the stored information, and the robustness of the software to support multiple file types and allow for the sharing of information across platforms. Collaboration with Raytheon, a defense and aerospace systems company, allowed our team to develop and demonstrate a successful adoption of semantic abilities by a commercial company. Salient features of this work include a new tool, the e-Design MemoExtractor Software Tool, designed to mine and capture company information, a Raytheon-specific extension to the e-Design Framework, and a novel semantic environment in the form of a customized semantic wiki SMW+. The advantages of this approach are discussed in the context of the industrial case study with Raytheon.
Evaluating Eco-Design Activities of Manufacturing Companies in a Developing Country
Authors: Akman Gu¨ls¸en , Pis¸kin Hamit , Okudan Kremer Gu¨l
Published: June 2012

Design for environment (DfE) is one of the design for X (DfX) strategies. Simplistically, DfE tries to lessen the effect of product design on the environment of a product. It takes into account the whole life cycle of a product. Eco-design is a tool of DfX. It includes paying attention to all the environmental effects of a product starting from the earliest stage of design process. It is defined as an activity that determines environmental influences of a product, and then systematically integrates these influences into product development process in the beginning of the design process. In order to reduce environmental effects of a product, factors such as function, cost, performance, quality, usage, reuse, refuse, waste and legal and technical aspects should be considered during the eco-design process. In this study, eco-design and its affecting factor was evaluated in automotive sub-contractor sector in Turkey. In order to determine standpoint of companies to eco-design, a survey was performed. 61 companies performing automotive subcontractor sector attended to the survey. The survey results were evaluated by using SPSS 17.0 statistical software.
A Fuzzy Approach for the Analysis of Rotor-Bearing Systems With Uncertainties
Authors: Rao Singiresu S. , Qiu Yazhao
Published: June 2012

The components of most structural and mechanical systems exhibit considerable variations or uncertainties in their properties and the performance characteristics of such systems are subject to uncertainties. In the case of a rotor bearing system, the nonlinear bearing restoring force is usually represented as a third or fourth power of displacement or as a piecewise linear function of displacement. The coefficients of these models are acquired from experiments and approximations, and will vary considerably during the operation of the bearing. Hence it is more reasonable to treat them as uncertain values. Other bearing parameters such as the inertial properties of concentrated disks, distributed mass and damping of the rotating assemblies are also uncertain due to manufacturing and assembly errors and imprecise operating conditions. It is known that the vibration response of a rotor is highly sensitive to small fluctuations or variations in the bearing parameters. Therefore, any realistic analysis and design of rotor-bearing systems must take the uncertainties into account. In this paper, a methodology is presented for the fuzzy analysis of nonlinear rotor-bearing systems along with numerical results to demonstrate the computational feasibility of the methodology.
Analyzing Overconstrained Design of Compliant Mechanisms
Authors: Aarts R. G. K. M. , Boer S. E. , Meijaard J. P. , Brouwer D. M. , Jonker J. B.
Published: June 2012

Whereas the use of compliant mechanisms is favorable for high precision applications, the constraints must be dealt with carefully. In an overconstrained design the actual natural frequencies and stiffnesses can differ considerably from their intended values. For this reason the awareness and possibly the avoidance of an overconstrained condition is important. We have developed a kinematic analysis with which under-constraints and overconstraints can be detected. A finite element based multibody approach is applied which offers a flexible beam element that is particularly suited to model the wire and sheet flexures frequently encountered in compliant mechanisms. For each element a fixed number of independent discrete deformations are defined that are invariant under arbitrary rigid body motions of the element. In the kinematic analysis only deformations associated with low stiffnesses are allowed, whereas the remaining deformations are prescribed zero. A singular value decomposition is used to determine the rank of the Jacobian matrix associated with the dependent nodal coordinates. Column and row rank deficiency indicate an underconstrained and overconstrained system, respectively. For an overconstrained system a statically indeterminate stress distribution can be derived from the left singular matrix. In this way the overconstraints can be visualized clearly as is illustrated with examples of compliant straight guidance mechanisms. The possible solutions to eliminate the overconstraints are found easily from the visualization.
Inverse Eigenmode Method for Identifying and Locating Added Mass in Mechanically Diverse Coupled Microresonantor Arrays
Authors: Glean Aldo A. J. , Judge John A. , Vignola Joseph F.
Published: June 2012

This paper summarizes a numerical analysis of an eigenmode-based approach for ultrasensitive mass detection via coupled microcantilevers. Mass detection using microcantilevers typically entails the observation of shifts in resonance frequency. Recently, detection systems have been proposed in which multiple cantilever sensors are coupled, either directly or by attachment to a single shuttle mass. Once sensors are coupled, however, mass adsorption on a single sensor alters all eigenmodes of the system. Thus, one disadvantage of the frequency-shift method in such cases is the need for strong mode localization, such that the shift of a single frequency can be associated with a mass change on a specific sensor. The consequent requirement for weak coupling limits the number of microcantilevers that can occupy a specific frequency band. The proposed eigenmode-based detection scheme involves solving the inverse eigenvalue problem to identify added mass, and can be used in cases where more than one eigenfrequency has shifted significantly. The method requires a single measured mode shape and corresponding natural frequency, selected from among those where a shift was observed. The fidelity of the identification of added mass and its location depends on the ability to accurately measure the mode shape, and on the amplitude with which each cantilever vibrates in the chosen mode (in modes without strong localization, multiple cantilevers respond with significant amplitude). Simulation results are presented that quantify, as a function of measurement noise, the ability of the method to accurately identify the cantilever(s) where mass adheres. In cases in which the resonance frequency-shift method is inappropriate due to non-localized modes, the inverse eigenvalue method proposed here can be used to identify both the amount and location of the added mass.
Closed-Form Solutions to the Kinematics of a Parallel Locomotion Mechanism With Actuated Spoke Wheels
Authors: Ren Ping , Hong Dennis
Published: June 2012

A parallel locomotion mechanism can be defined as “a mechanism with parallel configuration that has discrete contact with respect to the ground which renders a platform the ability to move”. The actuated spoke wheel robot IMPASS (Intelligent Mobility Platform with Active Spoke System) presented in this paper serves as an example of such locomotion mechanisms. The current prototype of IMPASS has two actuated spoke wheels and one passive tail with its lower portion designed as convex surface. The robot is considered as a mechanism with variable topologies (MVTs) because of its metamorphic configuration. Closed-form solutions to the kinematics of the variable topologies are developed and verified with numerical simulations. The analytical expressions to these solutions allow themselves to be used directly in the real-time motion planning and monitoring of the robot.
Development of Flight Guidance System of a Small Unmanned Aerial Vehicle (UAV)
Authors: Sasongko R. A. , Sembiring J.
Published: June 2012

This paper presents the development of a guidance system for a small Unmanned Aerial Vehicle (UAV) system which combines a waypoints following and an obstacle avoidance systems so that the UAV has a capability to operate in an environment whose ground condition is not completely known. The waypoints following system works by adopting the VOR-Hold approach, in which a correction command will be produced to reduce the angle difference between the desired path and the line connecting the actual UAV position and the subsequent destination point. An avoidance algorithm is developed and integrated with the path following system. In case of the UAV faces an obstacle lying on its flight path, then the avoidance system will generate a set of new waypoints for correcting the flight path, so that the UAV can avoid the obstacle and then returns to the previous flight path. The proposed avoidance approach bases its algorithm on the utilization of ellipsoid geometry for defining a restricted zone containing the obstacle, which is assumed to be already identified by the detection system. When the restricted ellipsoid zone has already been established, the algorithm then computes the locations of new waypoints on the edge of the ellipsoid. The algorithm then is simulated and evaluated in some cases representing situations when an UAV has to avoid obstacles during its flight to a predefined destination.
Reliable Kinetic Monte Carlo Simulation Based on Random Set Sampling
Authors: Wang Yan
Published: June 2012

To simulate the dynamic behaviors of large molecular systems, approaches that solve ordinary differential equations such as molecular dynamics (MD) simulation may become inefficient. The kinetic Monte Carlo (KMC) method as the alternative has been widely used in simulating rare events such as chemical reactions or phase transitions. Yet lack of complete knowledge of transitions and the associated rates is one major challenge for accurate KMC predictions. In this paper, a reliable KMC (R-KMC) mechanism is proposed to improve the robustness of KMC results, where propensities are interval estimates instead of precise numbers and sampling is based on random sets instead of random numbers. A multi-event algorithm is developed and implemented. The weak convergence of the multi-event algorithm towards traditional KMC is demonstrated with a proposed generalized Chapman-Kolmogorov Equation.
Construction and Use of the Frequency-Energy Plot for a System With Two Essential Nonlinearities
Authors: Hubbard Sean A. , Vakakis Alexander F. , Bergman Lawrence A. , McFarland D. Michael
Published: June 2012

We consider the problem of depicting possible periodic motions of a strongly nonlinear system in the frequency-energy plane. The particular case of a 2-degree-of-freedom, linear primary structure coupled to a 2-DOF, nonlinear attachment is examined in detail. While there exist numerical tools for the semiautomatic computation of such frequency-energy plots (FEPs), the presence of multiple essential (nonlinearizable) nonlinearities in the present system introduces new challenges in their application. Furthermore, the multiple degrees of freedom of the nonlinear subsystem allow the existence of complex nonlinear normal modes localized there but exhibiting more complicated resonances than those previously observed in the study of a single-DOF nonlinear attachment. The FEP generated for a laboratory-scale mechanical system is interpreted to explain the transitions and energy transfers that occur in the simulated transient response of the combined system following broadband shock excitation.
Exploring Heterogeneity of Customer Preference to Balance Commonality and Market Coverage
Authors: Turner Callaway , Ferguson Scott , Donndelinger Joseph
Published: June 2012

Offering increased variety in a market is one method of capturing greater market share. However, we generally observe diminishing marginal returns in share as the size of the product line is increased. Leveraging commonality is a means of offsetting this constraint as it leads to reductions in manufacturing costs and build complexity. Product platforms strive to capitalize on the naturally occurring phenomena that yield commonality in a product line. The structure of design variable values of individually optimized products create opportunities for commonality in a bottom-up platform, while a top-down platform discovers opportunities for commonality through similarity in customer preferences. This paper explores the effect of changing the number of products, and commonality between those products, on market share. Results from designing a varying number of products independently are leveraged to create a bottom-up product platform. A top-down product platform approach based on a heterogeneous discrete choice model and a multiobjective genetic algorithm is presented that allow commonality decisions and product configuration to occur simultaneously. Using the platforming techniques presented in this paper, it is shown that the top-down platforming approach allows for more well-informed platformed design by providing knowledge of the tradeoff between commonality and market share.
Molecular Replacement for Multi-Domain Structures Using Packing Models
Authors: Yan Yan , Chirikjian Gregory S.
Published: June 2012

Molecular replacement (MR) is frequently used to obtain phase information for a unit cell packed with a macromolecule of unknown structure. The goal of MR searches is to place a homologous/similar molecule in the unit cell so as to maximize the correlation with x-ray diffraction data. MR software packages typically perform rotation and translation searches separately. This works quite well for single-domain proteins. However, for multi-domain structures and complexes, computational requirements can become prohibitive and the desired peaks can become hidden in a noisy landscape. The main contribution of our approach is that computationally expensive MR searches in continuous configuration space are replaced by a search on a relatively small discrete set of candidate packing arrangements of a multi-rigid-body model. These candidate arrangements are generated by collision detections on a coarse grid in the configuration space first. The list of feasible arrangements is short because packing constraints together with unit cell symmetry and geometry impose strong constraints. After computing Patterson correlations of the collision-free arrangements, an even shorter list can be obtained using the 10 candidates with highest correlations. In numerical trials, we found that a candidate from the feasible set is usually similar to the arrangement of the target structure within the unit cell. To further improve the accuracy, a Rapidly-exploring Random Tree (RRT) can be applied in the neighborhood of this packing arrangement. Our approach is demonstrated with multi-domain models in silico for 3D, with ellipsoids representing both the domains of the model and target structures. Configurations are defined by sets of angles between the ellipsoids. Our results show that an approximate configuration can be found with mean absolute error (MAE) less than 5 degrees.
Creativity and Long-Term Potentiation: Implications for Design
Authors: Hallihan Gregory M. , Shu L. H.
Published: June 2012

An emerging research trend has seen concepts from cognitive psychology applied to enhance the creative design process through a more detailed understanding of the underlying cognitive mechanisms. However, the physiological processes by which the human element achieves creative solutions have only recently received significant attention. Understanding the mechanisms that allow the brain to change in response to experience may have implications for creative thought processes. Long-term potentiation (LTP) is one such mechanism, and has already been implicated in learning and memory development. This paper presents a theoretical-physiological explanation of creativity, implicating LTP as a modulator of neural networks. The proposed model is applied to explain existing creativity phenomena, including fixation, incubation, and obstacles in design-by-analogy. The model is then used to describe existing, and propose new methods for overcoming obstacles to creativity in design. The results of a study, which tested one application of the theory — the effect of physical activity on fixation, are also discussed.
Exploring Differences in Preference Heterogeneity Representation and Their Influence in Product Family Design
Authors: Sullivan Eric , Ferguson Scott , Donndelinger Joseph
Published: June 2012

When using conjoint studies for market-based design, two model types can be fit to represent the heterogeneity present in a target market, discrete or continuous. In this paper, data from a choice-based conjoint study with 2275 respondents is analyzed for a 19-attribute combinatorial design problem with over 1 billion possible product configurations. Customer preferences are inferred from the choice task data using both representations of heterogeneity. The hierarchical Bayes mixed logit model exemplifies the continuous representation of heterogeneity, while the latent class multinomial logit model corresponds to the discrete representation. Product line solutions are generated by each of these model forms and are then explored to determine why differences are observed in both product solutions and market share estimates. These results reveal some potential limitations of the Latent Class model in the masking of preference heterogeneity. Finally, the ramifications of these results on the market-based design process are discussed.
Subharmonic Resonance Cascades in a Class of Coupled Resonators
Authors: Strachan B. Scott , Shaw Steven
Published: June 2012

We consider a chain of N nonlinear resonators with natural frequency ratios of approximately 2:1 along the chain and weak nonlinear coupling of a form that allows energy to flow between resonators. Specifically, the coupling is such that the response of one resonator parametrically excites the next resonator in the chain, and also creates a resonant backaction on the previous resonator in the chain. This class of systems, which is being proposed for micro-electro-mechanical frequency dividers, is shown to have rich dynamical behavior. Of particular interest is the case when the high frequency end of the chain is resonantly excited, and coupling results in the potential for a cascade of sub-harmonic bifurcations down the chain. When the entire chain is activated, that is, when all N resonators have non-zero amplitudes, if the input frequency on the first resonator is Ω, then the terminal resonator responds with frequency Ω/2N. The details of the activation depend on the strength and frequency of the input, the level of resonator dissipation, and the mistuning in the chain. In this paper we present analytical results, based on perturbation methods, which provide useful predictions about these responses in terms of system and input parameters. Parameter conditions for activation of the entire chain are derived, along with results about other phenomena, such as bistability and partial activation of the chain. We demonstrate the utility of the predictive results by direct comparison with simulations of the equations of motion, and we also present samples of mechanical and electromechanical systems that realize the desired properties. These results will be useful for the design and operation of mechanical frequency dividers based on subharmonic resonances.
Design of an Electromagnetic Actuator Suitable for Production by Rapid Prototyping
Authors: Moses Matthew S. , Chirikjian Gregory S.
Published: June 2012

This paper presents a design for an electric motor that can potentially be produced by a personal 3D printer. The concept of a Cyclic Fabrication System — a network of tools, machines, and processes capable of producing all of its constituent components — is discussed in order to provide context for the various factors influencing the design. The motor is an axial-airgap permanent-magnet motor with a flat 2-layer coil. The coil pattern makes minimal use of crossovers or vias, and is well-suited to several methods for fabricating conductive structures that are currently under development. A versatile MATLAB script is presented which is used to generate the coil pattern. Coil geometry is controlled parametrically, and it is straightforward to generate a wide variety of coils, corresponding to different arrangements of magnets and desired coil spacings. The motor uses plastic roller bearings that are easily fabricated.
A Metric to Evaluate and Synthesize Distributed Compliant Mechanisms
Authors: Krishnan Girish , Kim Charles , Kota Sridhar
Published: June 2012

It is widely accepted that compliant mechanisms with stresses distributed evenly throughout its geometry have better load bearing ability and larger range of motion than mechanisms with compliance and stresses lumped at flexural hinges. In this paper, we present a metric to quantify how uniformly stresses and thus strain energy is distributed throughout the mechanism topology. The resulting metric is used to optimize the cross-sections of conceptual compliant topologies leading to designs with maximal distribution of stresses. This optimization framework is demonstrated for both single point mechanisms and single-input single-output mechanisms. It is observed that the optimized designs have a larger range of motion and perform more output work or store more strain energy before failure than their non-optimized counterparts. Furthermore, the nondimensional nature of the metric coupled with the physical insight enables an objective comparison of various topologies and actuation schemes based on how evenly stresses are distributed in the constituent members.
Characteristics of the Screw Transformation Matrix and Their Effect on Chasles’ Motion
Authors: Dai Jian S.
Published: June 2012

Rigid body displacement can be presented with Chasles’ motion by rotating about an axis and translating along the axis. This motion can be implemented by a screw transformation matrix in the form of either 3×3 dual number matrix or 6×6 transformation matrix that is executed with rotation and translation. This paper investigates characteristics of the screw transformation matrix, and decomposes the dual part of the transformation matrix into the part with an equivalent translation due to the effect of moving rotation axis and the part resulting from a pure translation. New results are presented and new formulae are generated. The analysis further reveals two new traces of the transformation matrix and presents the relation between the screw transformation matrix and the instantaneous screw, leading to the understanding of Chasles’ motion embedded in a normal body transformation. An algebraic and geometric interpretation of the screw transformation matrix is thus given, presenting an intrinsic property of the screw transformation matrix in relation to the finite screw. The paper ends with a case study to verify the theory and illustrate the principle.
Compliant Mechanism Road Bicycle Brake: A Rigid-Body Replacement Case Study
Authors: Olsen Brian M. , Howell Larry L. , Magleby Spencer P.
Published: June 2012

This paper demonstrates rigid-body replacement synthesis in the design a mechanism with known design objectives. The design of high-performance bicycle brakes is complicated by a variety of competing design objectives, including increased performance and low weight. But this challenge also provides a good case study to demonstrate the design of compliant mechanisms to replace traditional rigid-link mechanisms. This paper briefly reviews current road brake designs, demonstrates the use of rigid-body replacement synthesis to design a compliant mechanism, and illustrates the combination of compliant mechanism design tools. The resulting concept was generated from the modified dual-pivot brake design and is a partially compliant mechanism where one pin has the dual role of a joint and a mounting pin. The pseudo-rigid-body model, finite element analysis, and optimization algorithms are used to generate design dimensions, and designs are considered for both titanium and E-glass flexures. The resulting design has the potential of reducing the part count and overall weight while maintaining a performance similar to the benchmark.