bluuebunny/crossref_metadata_2025 huggingface dataset:
Edge Effects in the Energy Dissipation of Jointed Structures
Authors: Brink Adam , Quinn D. Dane
Published: September 2013

Many models of reduced complexity have been theorized to predict energy dissipation due to micro-slip in mechanical joints, including Iwan models. This class of reduced-order models is is based on a spring element combined with a frictional slider, known as a Jenkin’s element. Critical for their use, Jenkin’s elements have been shown to satisfy Masing’s hypothesis, which builds a full hysteresis loop from only a monotonic backbone curve. This paper will show that an edge effect, derived from the height of the joint geometry being analyzed, precludes realistic joint geometries from following the Masing hypothesis. A brief derivation of Iwan models and their association to Masing’s hypothesis is presented. A closed-form, 1-D continuum model is presented to establish a baseline for joint behavior without explicit height effect. To show the edge effect that joint height introduce, a finite element model was analyzed. It is shown that as the joint member height increases, the more prevalent the edge effect is, and the more quickly energy dissipation falls away from the power-law relationship predicted by 1-D models.
Influence of Charge Transfer Interconnection Topology on State of Charge Performance in Battery Packs: Simulation Results
Authors: Quinn D. Dane , Hartley Tom T.
Published: September 2013

The performance of a battery pack, composed of multiple connected cells, can be increased with the additional of a charge balancing system. This work explores the dynamic performance of charge balancing systems and how their ability to equilibrate the state of charge depends on the design of the underlying charge balancing network. The performance of the charge balancing system is shown through simulation studies to be related to the properties of the underlying graph of the balancing connections.
Analysis and Design of Multiple Order Centrifugal Pendulum Vibration Absorbers
Authors: Vidmar Brendan J. , Shaw Steven W. , Feeny Brian F. , Geist Bruce K.
Published: September 2013

We consider nonlinear interactions in systems of order-tuned torsional vibration absorbers. These absorbers, which consist of centrifugally driven pendulums fitted to a rotor, are used to reduce engine-order torsional vibrations in rotating machines, including automotive engines, helicopter rotors, and light aircraft engines. In all current applications, absorber systems are designed to reduce torsional vibrations at a single order. However, when two or more excitation orders are present and absorbers are introduced to address different orders, undesirable nonlinear interactions become possible under certain resonance conditions. Under these conditions, a common example of which occurs for orders n and 2n, crosstalk between the absorbers, acting through the rotor inertia, can result in instabilities that are detrimental to system response. In order to design absorber systems that avoid these interactions, we develop predictive models that allow one to select proper tuning and sizing of the absorbers. These models are based on perturbation methods applied to the system equations of motion, and they yield system response features, including absorber and rotor response amplitudes and stability, as a function of parameters of interest. The model-based analytical results are compared against numerical simulations of the complete nonlinear equations of motion, and are shown to be in good agreement. These results are useful for the selection of absorber parameters for desired performance. For example, they allow for approximate closed form expressions for the ratio of absorber masses at the two orders that yield optimal performance.
Reasoning: Source of Variability in the Boothroyd and Dewhurst Assembly Time Estimation Method
Authors: Namouz Essam , Summers Joshua D. , Mocko Gregory M.
Published: September 2013

This paper evaluates the effect of making a subjective decision in a design for assembly time analysis. An example is found in the first set of questions for estimating handling time of a part the user chose “parts are easy to grasp and manipulate” as opposed to “parts present handling difficulties”. The subjectivity is explored through a study of assembly time estimates generated by a class of mechanical engineering students in the time analysis of a clicker pen based on the Boothroyd and Dewhurst estimation method. The assembly times calculated by the class ranged from a minimum of 23.64 seconds to a maximum of 44.89 seconds (range of 21.25 seconds). This large range in results serves as motivation in determining the effect that answering a subjective decision has on the resulting assembly time estimate. Initial results indicate that not answering the first level of subjective questions will result in assembly time estimate within 15% of the time had the subjective question been answered. The probability density plots of the time estimates also indicates that 63% of the time, the estimated assembly time without making the subjective decision will fall within the normal distribution had the subjective decision been made. This provides evidence that there is an opportunity to reduce the amount of subjective questions that a user must answer to estimate the assembly time of a product.
Enabling Decision-Based Design Using Solution Trajectory Correction and Backtracking Rules
Authors: Pandey Vijitashwa , Mourelatos Zissimos P. , Majcher Monica
Published: September 2013

Optimization is needed for effective decision based design (DBD). However, a utility function assessed a priori in DBD does not usually capture the preferences of the decision maker over the entire design space. As a result, when the optimizer searches for the optimal design, it traverses (or ends up) in regions where the preference order among different solutions is different from the actual order. For a highly non-convex design space, this can lead to convergence to a grossly suboptimal design depending on the initial design. In this article, we propose two approaches to alleviate this issue. First, we map the trajectory of the solution as generated by the optimizer and generate ranking questions that are presented to the designer to verify the correctness of the utility function. We then propose backtracking rules if a local utility function is very different from the initially assessed function. We demonstrate our methodology using a mathematical example and a welded beam design problem.
Real-Time Estimation of Glenohumeral Joint Rotation Center With CAREX: A Cable-Based Arm Exoskeleton
Authors: Mao Ying , Jin Xin , Agrawal Sunil K.
Published: September 2013

In the past few years, the authors have proposed several prototypes of a Cable-driven upper ARm EXoskeleton (CAREX) for arm rehabilitation. The key advantages of CAREX over conventional exoskeletons are: (i) It is nearly an order of magnitude lighter. (ii) It does not have conventional links and joints, hence does not require joint axes alignment and segment lengths adjustment. (iii) It does not limit the natural degrees-of-freedom of the upper limb. (iv) The structure of the exoskeleton is novel as the cables are routed from the proximal to the distal segments of the arm. Preliminary experimental results with CAREX on a robotic arm and on healthy subjects have demonstrated the effectiveness of the exoskeleton within “assist-as-needed” training paradigm. In this paper, we propose a novel approach to estimate the glenohumeral joint rotation center (GH-c) using measurements of shoulder joint angles and cable lengths. This helps in locating the glenohumeral joint rotation center appropriately within the kinematic model. As a result, more accurate kinematic model can be used to improve the training of human users. An estimation algorithm is presented to compute the GH-c in real-time. The algorithm was implemented on the latest prototype of CAREX which controls four degrees-of-freedom of the shoulder and elbow. Preliminary experiments were performed on two healthy subjects under two different scenarios: (i) GH-c was assumed to be a fixed point and (ii) GH-c was estimated using the proposed algorithm. Experimental results are presented to compare the two scenarios.
Natural Language Processing Applications in Requirements Engineering
Authors: Lash Alex , Murray Kevin , Mocko Gregory
Published: September 2013

In the design process, the requirements serve as the benchmark for the entire product. Therefore, the quality of requirement statements is essential to the success of a design. Because of their ergonomic-nature, most requirements are written in natural language (NL). However, writing requirements in natural language presents many issues such as ambiguity, specification issues, and incompleteness. Therefore, identifying issues in requirements involves analyzing these NL statements. This paper presents a linguistic approach to requirement analysis, which utilizes grammatical elements of requirements statements to identify requirement statement issues. These issues are organized by the entity—word, sentence, or document—that they affect. The field of natural language processing (NLP) provides a core set of tools that can aid with this linguistic analysis and provide a method to create a requirement analysis support tool. NLP addresses requirements on processing levels: lexical, syntactic, semantic, and pragmatic. While processing on the lexical and syntactic level are well-defined, mining semantic and pragmatic data is performed in a number of different methods. This paper provides an overview of these current requirement analysis methods in light of the presented linguistic approach. This overview will be used to identify areas for further research and development. Finally, a prototype requirement analysis support tool will be presented. This tool seeks to demonstrate how the semantic processing level can begin to be addressed in requirement analysis. The tool will analyze a sample set of requirements from a family of military tactical vehicles (FMTV) requirements document. It implements NLP tools to semantically compare requirements statements based upon their grammatical subject.
Product-Service Systems Design With Business Model Strategy Integrated: A Case Study of Urban Umbrella Rental Service System
Authors: Kim Yong Se , Lee Sang Won , Kim Jin Hui , Jeong Heji , Lee Ji Hwan , Hong Yoo S.
Published: September 2013

The value creation paradigm in industry has recently been shifting toward value creation through Product-Service Systems (PSS) where product and service elements are tightly integrated as systems to provide functional fulfillment. A successful PSS should satisfy economical, ecological and experience values. A systematic design method for PSS has been developed where activities of stakeholders are designed to support those values reflecting diverse context elements. Also business model aspects of PSS are considered using the category of the business model canvas together with strategies and protocols obtained from various real world cases. To illustrate the PSS design method with business model strategy integrated, a case of urban umbrella rental service system is presented.
An Interactive Tool for the Participatory Design of Product Interface
Authors: Barbieri Loris , Angilica Agostino , Bruno Fabio , Muzzupappa Maurizio
Published: September 2013

The importance of participatory design (PD) is progressively increasing thanks to its capacity to explore a wide variety of concepts, thus increasing the opportunity to create a successful product. In fact the design process should not be a solo activity, as designers often need inputs and other points of view, especially from end-users.

According to the ultimate idea of PD, end-users are actively involved in the various activities of the product development to ensure that their needs and desires are satisfied.

This paper presents a novel approach to the participatory design of product interfaces in a user-centered design (UCD) process. The approach is based on an interactive tool that allows end-users to design custom user interfaces of household appliances taking advantage of their own needs and experiences.

The tool incorporates the analytical and more abstract knowledge of the designers codified in the form of aesthetical, technological and manufacturing constraints (i.e., limitations in the number and geometry of interface components, a limited number of colors, a discretization of the area where interface widgets are placed). This solution allows the end-users to directly design their favorite interface without the interference of any other subject. Through an accurate analysis of the choices done by the users, the designers are able to access to the deepest level of the users’ expression in order to catch their latent needs and tacit knowledge.

The tool has been designed in order to make possible to immediately perform usability tests on the designed interface by using a Mixed Reality prototype.

The paper describes the development of the tool and proposes a methodology that has been specifically addressed to include this tool in a design process based on UCD principles. Both the tool and the methodology are presented through the description of a case-study related to the redesign of a washing machine dashboard. Experimental results show that the proposed tool can be an effective support to design product interfaces during PD sessions.
Finite Element Analysis of Piezoelectric Strips for Modifying Ankle Torques in Active Prosthetic Feet: A Pilot Study
Authors: Powelson Thomas , Yang Jingzhou (James)
Published: September 2013

Over the last fifty years there has been a steady advance in prosthetic foot technologies. These advances have primarily focused on more accurately mimicking the biologic foot for amputees. One field of research currently being explored is active/powered prosthetic feet in which the movement of the foot is actively controlled through the use of electric motors. Some of these feet also seek to reproduce the ankle torques seen in the biologic foot. This paper proposes a novel method for more accurately reproducing these ankle torques through the use of piezoelectrics in conjunction with the electric motors. FEA software is used to simulate the modification of ankle torques through the use of piezoelectric bending actuators in a general case. A number of different configurations for the piezoelectric strips are examined to test the versatility of the piezoelectrics in this application. The general trends of the ankle torque vs gait cycle found in the literature have been reproduced in the simulations.
Experimental Research of Vibration and Noise of Rolling Cylinder on Plane
Authors: Bucinskas Vytautas , Urbanavicius Robertas , Mitrouchev Peter
Published: September 2013

This experimental research is intended to research on noise generation of rolling surfaces. This problem is important in bearings, railroad transport and many technical applications. Experimental research was performed in such a way that noise and vibration from any technical equipment didn’t interfere; only ambient vibration and noise influenced measurement. Tests were performed on special setup, which is described in the paper. Parameters of vibrations on steady plane and noise in surroundings of rolling cylinder were registered. For this purpose three sets of test surfaces with different roughness parameters were performed. It was experimentally proven that dry and lubricated surfaces generate different noise sound frequencies, found some interest dependencies on connection between generated vibrations and sound. The proposed technique can be applicable to bearing noise evaluation, especially when special materials are used. Research brings useful results, which can be used to estimate noise in newly designed devices. Finally, conclusions on results are made.
Synthesizing Load Impedance to Frequency-Tune an Electro-Mechanical Vibration Energy Harvester
Authors: Bowden James , Burrow Stephen G. , Cammarano Andrea , Mitcheson Paul D.
Published: September 2013

Energy harvesters based upon resonant mass-spring-damper systems can only generate useful power over a narrow range of excitation frequencies. This is a significant limitation in applications where the vibration source frequency changes over time. In this paper an active electrical load is presented which can overcome the bandwidth limitations by parametrically tuning the overall harvester system. The electrical tuning technique synthesizes an optimum reactive load with high-efficiency switch-mode electronics, which also provides rectification, feeding power harvested into a DC store. The method is shown to be effective at increasing the power frequency bandwidth of resonant type harvesters, and offers the capability of autonomous operation. The theoretical basis for the technique is presented, and verified with experiment results. The paper illustrates the challenges of implementing the power electronic converter for a low quiescent power overhead and in choosing the control architecture and tuning algorithms.
Increasing the Utility of Sustainability Assessment in Product Design
Authors: Eastlick Dane D. , Haapala Karl R.
Published: September 2013

Design engineers are seeking effective ways to make informed decisions regarding product sustainability. Several attempts have been made to identify sustainability metrics, assess sustainability impacts, or support decisions based on sustainability, but none fully support product designers in a way that provides for robust sustainable manufacturing decisions. Sustainability assessments can provide quantitative performance data for design variants, but in many cases, the most sustainable alternative remains uncertain. Adequate support for sustainable manufacturing activities should address each step in the decision making process with enough detail to accurately capture manufacturing impacts. The methods selected throughout the process should consider the specific needs of sustainability related issues and provide transparent, easily understood, efficient solutions. A process is outlined to assist product designers, and a demonstration of the process is given for the production of a titanium component to discuss its utility.
Incorporating Heterogeneous Customer Preferences With Dirichlet Process Mixture Model for Product Positioning in Environmentally Conscious Design
Authors: Zhao Yuan , Thurston Deborah
Published: September 2013

Increased environmental protection legislation forces manufacturers to employ environmentally conscious design and manufacturing methods. In addition, customer preferences for energy efficient and environmentally sustainable products influence manufacturers design strategies. In order to influence customer buying behaviors for environmentally friendly products, manufacturers need to understand customer preferences first. Manufacturers can make optimal design decisions based on inference on customers’ decision making models. It is recognized that consumers are heterogeneous in their response to different attributes for any given type of product or service. In this paper, we proposed a framework for incorporating heterogeneous customer preferences with Dirichlet Process mixture model for product positioning in environmentally conscious design. The uncertainty about the functional form of the customer preference distribution can be expressed by using a nonparametric prior, in which the number of clusters grows without bound as the amount of data grows. An automobile design case study is used here to demonstrate the proposed approach.
Managing Dilemmas Embodied in 21st Century Engineering
Authors: Ahmed Salman , Xiao Minting , Panchal Jitesh H. , Allen Janet K. , Mistree Farrokh
Published: September 2013

In this session we describe in four parts the pedagogy and out-comes of a course Designing for Open Innovation designed to empower 21st century engineering students to develop competencies associated with innovating in an inter-connected technologically flat world:

1. Competencies for Innovating in the 21st Century, [1].

2. Developing Competencies In The 21st Century Engineer, [2].

3. Identifying Dilemmas Embodied in 21st Century Engineering, [3].

4. Managing Dilemmas Embodied in 21st Century Engineering - this paper.

In the first paper we describe the core characteristics of the engineering in an interconnected world and identify the key competencies and meta-competencies that 21st century engineers will need to innovate and negotiate solutions to issues associated with the realization of systems.

In the second paper, we describe our approach to fostering learning and the development of competencies by an individual in a group setting. We focus on empowering the students to learn how to learn as individuals in a geographically distanced, collaborative group setting.

We assert that two of the core competencies required for success in the dynamically changing workplace are the competencies to first identify and then to manage dilemmas. In the third paper, we illustrate how students have gone about identifying dilemmas and in the fourth paper how they have attempted to manage dilemmas. In papers three and four students have briefly described the challenges that they faced and their takeaways in the form of team learning and individual learning.

In this the last of four papers in this session, we focus on how students learned to manage dilemmas associated with the realization of complex, sustainable, socio-techno-eco systems, namely, energy policy design. The example involves the identification of a bridging fuel that balances environmental, economic and socio-cultural concerns. The principal outcome is clearly not the result attained but a student’s ability to learn how to learn as illustrated through the development of personal competencies in a collaborative learning framework and environment.
Computer-Aided Generation of Modular Designs Considering Component End-of-Life Options: Implications for the Supply Chain
Authors: Philip Nirup , Okudan Gül E. , Haapala Karl R. , Kim Kyoung-yun
Published: September 2013

Given the growing demand for product customization, modularization is a viable way to reduce the complexity of new product development. This study presents a framework to incorporate component end-of-life options through modularization during the early design stages, to simultaneously account for supply chain factors as well as evaluating design variants. In order to accomplish this, we extend an existing software framework; this software is aimed at creating a computational design tool to aid designers in developing new modular products, by taking into account design for assembly (DfA) and design for variety (DfV). We present an extension to that work where the user has the ability to generate modular designs considering component end-of-life options, and to optimize relevant supplier selections, either to minimize costs or carbon footprint. We compare the results of this modularization with the widely used decomposition approach (DA). Overall, this computational tool enables users to understand the trade-offs between product design and supply chain performance, and the presented investigation on the two modularization methods (DA and Green DA) attests to the implications of design decisions throughout the supply chain and across the product life cycle.
The Creation of Design Modules for Use in Engineering Design Education
Authors: Foster Garrett , Holland Micah , Ferguson Scott , Deluca William
Published: September 2013

Industry demands that graduating engineers possess the ability to solve complex problems requiring multidisciplinary approaches and systems-level thinking. Unfortunately, current curricula often focus on analytical approaches to problem solving. Further, adding courses focused solely on engineering design is often unachievable due to the large amount of material covered in today’s undergraduate engineering curricula. Combined, these prevent a comprehensive focus on engineering design education from being realized. To overcome these time and resource constraints, this paper proposes the use of computational modules within current courses. The investigators hypothesize that the modules would eliminate the repetitive analysis barrier in design problems, thus allowing for design-related experiences to be included earlier in the curricula as opposed to postponing it to a capstone experience. Four major hurdles that hinder successful integration of modules in current engineering courses are: a) engaging students such that they will want to use the modules; b) ensuring the modules are easy to use; c) reducing the complexity of deploying the modules into the classroom; and d) providing educational value. To address these issues, this paper treats the design of the modules as a product design problem. This paper presents the redesign process followed to improve two different design modules planned for implementation in the engineering curriculum at North Carolina State University. Additionally, this research indicates that using a formal redesign process enhances a module’s ability to overcome the hurdles listed above.
A Novel Approach to Algebraic Fitting of a Pencil of Quadrics for Planar 4R Motion Synthesis
Authors: Ge Q. J. , Zhao Ping , Purwar Anurag , Li Xiangyun
Published: September 2013

The use of the image space of planar displacements for planar motion approximation is a well studied subject. While the constraint manifolds associated with planar four-bar linkages are algebraic, geometric (or normal) distances have been used as default metric for least-squares fitting of these algebraic manifolds. This paper studies the problem of using algebraic distance for least-squares fitting of quadrics defining the constraint manifolds associated with Planar 4R mechanisms. It shows that the problem can be solved by fitting a pencil of quadrics with linear coefficients to a set of image points of a given one dimensional set of displacements. This linear formulation leads to a simple and fast algorithm for kinematic synthesis in the image space.
Identification of Platform Variables in Product Family Design Using Sensitivity Analysis
Authors: Hume Chad , Rosen David W.
Published: September 2013

Product family design strategies based on a common core platform have emerged as an efficient and effective means of providing product variety. The main goal in product platform design is to maximize internal commonality within the family while managing the inherent loss in product performance. Therefore, identification and selection of platform variables is a key aspect when designing a family of products. Based on previous research, the Product Platform Constructal Theory Method (PPCTM) provides a systematic approach for developing customizable products, while allowing for multiple levels of commonality, multiple product specifications, and balancing the tradeoffs between commonality and performance. However, selection of platform variables and the modes for managing product variety are not guided by a systematic process in this method. When developing a platform with more than a few variables, a quantitative method is needed for selecting the optimal platform variable hierarchy. In this paper we present an augmented PPCTM which includes sensitivity analysis of platform variables, such that hierarchical rank is conducted based on the impact of the variables on the product performance. This method is applied to the design of a line of customizable finger pumps.
Kinematic Synthesis and Dynamic Analysis of the Dual-Rod Slider Rocker Mechanism: An Application to Modular Robotics
Authors: Moubarak Paul M. , Ben-Tzvi Pinhas , Ma Zhou , Alvarez Eric J.
Published: September 2013

In mechanism theory and design, no work has been reported on the kinematic synthesis and dynamic analysis of the dual-rod slider rocker mechanism. By definition, this system is equivalent to two traditional slider-rocker mechanisms that share a common rocker, where the two sliders translate along two opposite directions of motion. Unlike a single slider-rocker mechanism, the dual-rod-based mechanism exhibits unique kinematic characteristics in which the two sliders do not travel the same distance for the same rocker rotation. This paper presents an optimal analysis that outlines the early investigations on the kinematic design and dynamic analysis of the dual-rod slider rocker mechanism. Because of the translation difference that exists between the two sliders, an expression for the relative position error is derived. This error is integrated as a cost function in an optimization problem which calculates the optimal rod length that allows the two sliders to meet terminal boundary conditions. These kinematics are validated experimentally through a case-study application in modular robotic docking.
Numerically Stable Design Optimization With Price Competition
Authors: Morrow W. Ross , Mineroff Joshua , Whitefoot Kate S.
Published: September 2013

Researchers in Decision-Based Design have asserted that business objectives, e.g. profits, should replace engineering requirements or performance metrics as the objective for engineering design. Using profits as the objective for engineering design, however, requires modeling consumer preferences and competition between firms. Game theoretic “design-then-pricing” models—i.e. product design with price competition—provide an important framework for integrating consumer preferences and competition when design decisions must be made before prices are decided by a firm or by its competitors. This article proposes a method for solving design-then-pricing problems that exhibits improved efficiency and reliability, relative to existing methods. Numerical results for a vehicle design example using three solvers—matlab, KNITRO, and SNOPT—to validate this claim. We also highlight the importance of checking the Second-Order Sufficient Conditions in design-then-pricing problems that use Mixed Logit models of demand.
Designing Products for Optimal Collaborative Performance With Application to Engineering-Based Poverty Alleviation
Authors: Wasley Nicholas S. , Lewis Patrick K. , Mattson Christopher A.
Published: September 2013

Collaborative products are created by combining components from two or more products to result in an additional product that performs previously unattainable tasks. The resulting reduction in cost, weight, and size of a set of products needed to perform a set of functions makes collaborative products useful in the developing world. In this paper, a method for designing a set of products for optimal individual and collaborative performance is introduced. This is accomplished by: (i) characterizing the collaborative design space of the product set and collaborative product, (ii) defining areas of acceptable Pareto offset, (iii) identifying the combinations of designs that fall within the defined areas of acceptable Pareto offset for each product, and (iv) selecting the optimal set of product designs. An example is provided to illustrate this method and demonstrate its usefulness in designing collaborative products for both the developed and developing world. We conclude that the presented method is a novel, and useful, approach for balancing the inherent trade-offs between the performance of collaborative products and the product sets used to create them.
Collective Transport by Multiple Molecular Motors
Authors: Nam Woochul , Epureanu Bogdan I.
Published: September 2013

Kinesin is a processive molecular motor that transports various cellular cargoes by converting chemical energy into mechanical movements. Although the motion of a single molecule has been characterized in several studies, the dynamics of collective transports remains unresolved. Since the fluctuating load acting on each motor is an important factor in the collective transport, the relation between the varying force and the chemical reaction of kinesin is considered using a stochastic mechanistic model. Several metrics are developed to measure the correlation among the motion of the motors, the force distribution, and the power loss. It is shown that both large external load and stiff cargo linkers cause highly correlated motions of motors. However, these correlated motions do not lead to faster collective transport.
Using GPUs for Realtime Prediction of Optical Forces on Microsphere Ensembles
Authors: Bista Sujal , Chowdhury Sagar , Gupta Satyandra K. , Varshney Amitabh
Published: September 2013

Laser beams can be used to create optical traps that can hold and transport small particles. Optical trapping has been used in a number of applications ranging from prototyping at the microscale to biological cell manipulation. Successfully using optical tweezers requires predicting optical forces on the particle being trapped and transported. Reasonably accurate theory and computational models exist for predicting optical forces on a single particle in the close vicinity of a Gaussian laser beam. However, in practice the workspace includes multiple particles that are manipulated using individual optical traps. It has been experimentally shown that the presence of a particle can cast a shadow on a nearby particle and hence affect the optical forces acting on it. Computing optical forces in the presence of shadows in real-time is not feasible on CPUs. In this paper, we introduce a ray-tracing-based application optimized for GPUs to calculate forces exerted by the laser beams on microparticle ensembles in an optical tweezers system. When evaluating the force exerted by a laser beam on 32 interacting particles, our GPU-based application is able to get a 66-fold speed up compared to a single core CPU implementation of traditional Ashkin’s approach and a 10-fold speedup over its single core CPU-based counterpart.
Experimental Optimization of a Discrete Robot Exhibiting Hysteresis
Authors: Kirsch Karl , Kean Michael , Cipra Raymond J.
Published: September 2013

Discrete joint manipulators are a potential alternative to common continuous joint robots used in industry today. Applications of a discrete joint manipulator include proximity positioning tasks, space exploration, camera placement, and automation systems. Discrete robots are potentially useful for small scale robots because it is difficult to implement sensors and motors at small scales. This work discusses the results obtained with an experimental 7 link robot designed for an 8 × 12 inch grid.

Results show that a discrete robot can successfully be used for proximity positioning tasks. The performance depends on the location of discrete points relative to the desired points and also on the repeatability of the experimental manipulator. Results obtained via a vision system demonstrate the potential capabilities of the planar discrete manipulator. Results include subsets of end-effector positions in the gridspace and training results.
Finite Element Modeling and Simulation Analysis of a Portable Roll-Up Sign
Authors: Yang Qiwei , Tate Derrick , Bae Sang-Wook
Published: September 2013

Although a large number of crash tests have been performed between passenger cars and rigid fixed traffic signs, the number of real tests focusing on crashworthiness of portable roll-up signs is still limited. Because a standard, portable roll-up sign contains at least three kinds of dissimilar materials, such as steel for the base, fiberglass for the batten, vinyl for the sign, and because the sign’s configuration is more complicated than a rigid fixed sign, it is important to simulate the behavior of portable roll-up signs in collision. In this paper, a fine-mesh finite element model precisely representing the portable roll-up sign was created and used together with a car model to simulate the process of impact with 0 and 90 degree orientation. The simulation was performed using LS-DYNA software. Techniques for creating the finite element model were discussed. Afterwards this finite element model, being validated and verified through real tests, can be used for parametric and/or robust design.
Nonlinear Modeling and Analysis of Electromagnetic Bearings With Permanent Magnets for Bias
Authors: Naseradinmousavi Peiman , Nataraj C. , Frank Matthew
Published: September 2013

This article describes high fidelity modeling of electromagnetic (EM) bearings with permanent magnets (PM) used to supply bias current. We analyze both the PM and EM parts of the system. Magnetic circuit theory is first used to gain insight into the magnetic forces and allows for the dynamic analysis of a rigid rotor coupled with the magnetic bearings. The results reveal that the magnetic forces are a strong nonlinear function of the rotor offsets from its equilibrium position. Next, the validity of the simplifying assumptions is examined with the aid of the finite element method. Comparisons of the magnetic forces are presented and discussed.
Higher-Pair Reuleaux-Triangle in Square and its Derived Mechanisms
Authors: Figliolini Giorgio , Rea Pierluigi , Grande Salvatore
Published: September 2013

This paper deals with the formulation of a mathematical procedure for the motion analysis of mechanisms, which are derived by the higher-pair Reuleaux-triangle in square, which curve-triangle shows a rounded vertex.

In particular, the trajectory of the center of the modified Reuleaux triangle, the fixed and moving centrodes, the trajectory of any moving point, with particular reference to the center of the rounded corner of the curve-triangle, have been obtained in algebraic form. Exact square trajectories can be also obtained for specific rounded corners.
Predicting Energy Consumption in Humans Using Joint Space Methods
Authors: Roberts Dustyn P. , Kim Joo H.
Published: September 2013

Humans act as transducers that transform chemical energy from food, water, and air into mechanical work and the thermal energy of heat loss. Although this energy expenditure can be experimentally measured, methods of predicting energy expenditure have not been broadly studied. This work introduces a new formulation of metabolic energy consumption based on muscle physiology and the equations of motion for the human body. Kinematic and kinetic data from a gait experiment and an over-arm throwing simulation are used to illustrate and validate this new model. The results extend the capabilities of dynamic human modeling to include metabolic energy prediction in general tasks. This novel formulation is useful for the investigation of human performance with applications in physical therapy, rehabilitation, and sports.
A Proposed Platform to Simplify the Integration of Electronics Into a Mechanical Engineering Design Course
Authors: Skaloud Brett A. , Chandrasegaran Senthil K. , Ramani Karthik
Published: September 2013

The interdisciplinary nature of engineering design and the pervasiveness of electronics in most products has made it necessary for practitioners of “design thinking” to understand electronics and embedded systems, in order to expand their concept exploration space. This poses a significant challenge for mechanical engineers, whose knowledge of electronics is typically limited. A course in mechatronics is available to enhance this knowledge, however it is taught separate from product design and CAD/Toy Design, and students often do not get the opportunity to combine these elements. With an open source microcontroller platform (Arduino™) that allows for easy programming, we see an oppportunity to blend design thinking into a larger domain of engineering. In this paper, we propose a platform that would simplify the incorporation of electronics into a design. The proposed platform will utilize the Arduino™, along with a modular architecture for designing electronic systems, as well as modular program segments for controlling these systems which can be easily customized to meet student requirements. This will enable students in a toy design course to integrate electro-mechanical systems into their designs, while at the same time providing useful electronic knowledge which can be used in their future careers. The toy design projects utilize a Problem-Based Learning [1, 2] approach that will allow students to familiarize themselves with the synthesis and programming of these systems. We describe two student test teams that were introduced to this electronic integration in an existing toy design course, and we use our observations to inform the design of the proposed platform.
Investigation Into the Effect of Mode Shape Errors on Validation Experiments for Experimental-Analytical Substructuring
Authors: Rohe Daniel P. , Allen Matthew S.
Published: September 2013

Experimental-to-Analytical Substructuring has been investigated as a way to avoid potentially costly tests and analysis on large systems by performing smaller, subcomponent-level tests. However, this has proven more difficult to implement than expected because the substructuring calculations can be sensitive to modal truncation and experimental noise and require the measurement of rotational motions at the interface. These issues seem to have led to decreased confidence in substructuring calculations, causing it to remain underutilized in industry. In recent work, the authors have proposed performing a small, inexpensive validation test to give confidence or reveal flaws in an experimentally-derived model. This work explores whether such an approach might be used to characterize the uncertainty in a substructure model due to measurement errors. Substructuring is simulated on a finite element model of a beam structure whose modal parameters have been contaminated with noise to simulate measurement errors and cross axis sensitivity. The beam is then coupled to a validation fixture, and the modal parameters of the validation experiment are investigated in a Monte-Carlo experiment to determine the correlation of a validation test to the actual application for different levels and types of errors in the measured mode shapes.
Tolerance Allocation for Structures Subject to Various Loading Events
Authors: Barari Ahmad
Published: September 2013

Although allocation of design tolerances for parts and components is typically based on the prediction of geometric and dimensional deviations resulting by the inherent errors of production, this process cannot be conducted unconstrained. Concurrent to studying the manufacturing and assembly uncertainties in tolerance allocation, it is highly important to evaluate the total combination of the allocated tolerances and the deformations due to various loading on the final product. This ensures that parts and components in their working condition meet their essential requirements for functionality, form and fit. This process is optimized only if the minimum geometric zone that covers the evaluated deformations is studied properly. In addition, the minimum deformation zones for various types of loading in an assembly of parts and components need to be studied and the tolerances should be selected after considering the requirements for all possible events. Using this concept, a unified methodology is developed to find the optimum tolerances for the geometric parameters of mechanical structures which are under various loading condition. Validity of the developed procedure is studied by conducting case studies and variety of experiments. The developed methodology can be employed efficiently during detailed design process of mechanical parts and assemblies.
Graphical Synthesis of Fourbar Mechanisms by Three-Position, Instant-Center Specification
Authors: Thompson Thomas J.
Published: September 2013

In four-bar mechanism synthesis, solutions to both the three-position and four-position synthesis problems are well-known. However, certain practical synthesis problems also require consideration of the instantaneous center of velocity for one of the precision positions. Examples are the double-wishbone front suspension of an automobile (camber in jounce and rebound, along with roll center), and four-bar prosthetic knee (standing stability, flexion length, and sitting cosmetic advantage).

Because specifying the location of the instant center constrains the solution by one free choice per dyad, it reduces the number of free choices available in a three-position problem from two to one. Thus, center point and circle point solutions to the three-position, instant center specified synthesis (TPICS) problem are located along point-pair solution curves similar to the Burmester curves in four-position synthesis.

The purpose of this paper is to present a direct, graphical method for finding pivot locations in three-position, instant-center synthesis of four-bar mechanisms. The method uses pole triangle theory to determine pivot locations along center point and circle point curves. A summary of a previously-presented computational method is included.

As an example, both the graphical and the computational method are used to generate TPICS center-point curves for an automotive front suspension.
Representation: Metrics for Analyzing Sketches — A Critical Survey
Authors: Joshi Shraddha , Summers Joshua D.
Published: September 2013

Sketches are used in design research experiments by various researchers to draw inferences with respect to creativity, representation use, solution quality, and other research goals. Numerous different metrics, such as quantity, sketch quality, and solution quality, are used by the researchers to analyze sketches. This paper presents a survey of the metrics used in the design research community. Characteristics developed by the authors to evaluate these metrics are used to compare the metrics. Further, an initial attempt to identify a relation between type of research approach and characteristics of the metrics is then reported to test the hypothesis that a mature research field would include canonically accepted metrics for experimental studies. The findings indicate that current literature does not provide any formal definition of metrics that are widely accepted in the community. The findings from correlations indicate a general trend of using objective metrics for qualitative research and subjective metrics for mixed method approach. Ultimately, this work lays the foundation for a more systematic approach to evaluating engineering design sketches through critical selection of metrics.
Simulation and Testing of a 6-Story Structure Incorporating a Coupled Two Mass Nonlinear Energy Sink
Authors: Wierschem Nicholas E. , Luo Jie , AL-Shudeifat Mohammad , Hubbard Sean , Ott Richard , Fahnestock Larry A. , Quinn D. Dane , McFarland D. Michael , Spencer B. F. , Vakakis Alexander , Bergman Lawrence A.
Published: September 2013

The nonlinear energy sink (NES) is a passive device used to rapidly direct energy into higher modes of vibration and locally dissipate a significant portion of the impulsive shock energy induced in the primary, linear structure to which it is attached. The Type III NES is a two degree-of-freedom device comprised of two lightweight masses coupled together through an essentially nonlinear element. The lower mass in this two-mass arrangement is coupled to the linear structure through another essentially nonlinear element. This modification has been found to dramatically improve the performance of the NES to mitigate the shock when compared to a one degree-of-freedom NES device. The measure of effective damping of the linear structure indicates the ability of the NES to dissipate energy and reduce the response of the structure across a wide range of energies. Experimental tests have been performed to verify the numerical findings. Good agreement between numerical predictions and experimental observations validates the identified model of the NES.