bluuebunny/crossref_metadata_2025 huggingface dataset:
Haptic Interface on Measured Data for Epidural Simulation
Authors: Vaughan Neil , Dubey Venketesh N. , Wee Michael Y. K. , Isaacs Richard
Published: September 2013

This paper presents a haptic device with 3D computer graphics as part of a high fidelity medical epidural simulator development program. The haptic device is used as an input to move the needle in 3D, and also to generate force feedback to the user during insertion. A needle insertion trial was conducted on a porcine cadaver to obtain force data. The data generated from this trial was used to recreate the feeling of epidural insertion in the simulator. The interaction forces have been approximated to the resultant force obtained during the trial representing the force generated by the haptic device. The haptic device is interfaced with the 3D graphics for visualization. As the haptic stylus is moved, the needle moves on the screen and the depth of the needle tip indicates which tissue layer is being penetrated. Different forces are generated by the haptic device for each tissue layer as the epidural needle is inserted. As the needle enters the epidural space, the force drops to indicate loss of resistance.
Distributed Modal Signals of Conical Shells Based on Flexoelectric Effect
Authors: Li H. , Hu S. D. , Tzou H. S.
Published: September 2013

Flexoelectricity is known as the electromechanical coupling effect between the strain gradient and the polarization. It is the only contribution of polarization from inhomogeneous mechanical deformation in nonpiezoelectric materials. Conical shells are commonly used as injectors, sprays and rocket nozzles, etc, which are generally clamped at the minor end and free at the major end when mounted. In this study, a flexoelectric layer is laminated on conical shells with clamped-free boundary conditions (BCs) to monitor the natural modal signal distributions. The direct flexoelectric effect defined in a tri-orthogonal coordinate system is presented first, followed by the sensing mechanism of a generic flexoelectric sensor patch. The mode shape functions of conical shells obtained by using the Rayleigh-Ritz method are briefly reviewed. The spatially distributed microscopic sensing signal with respect to position coordinates is evaluated in detail to reveal the modal signal distributions. Due to the gradient effect, the bending strain component is the only contribution to the total sensing signal. The total signal consists of two components resulting from the two bending strain components: circumferential bending strains and longitudinal bending strains. Analytical results show that, the flexoelectric sensing signal induced by the circumferential bending strain is the dominant contribution to the total signal for lower order modes. The optimal location of flexoelectric sensors is discussed for selected vibration modes.
Jerk-Continuous Trajectories for Cyclic Tasks
Authors: Boscariol Paolo , Gasparetto Alessandro , Vidoni Renato
Published: September 2013

Planning smooth trajectories is a crucial task for most advanced robotic applications. Poorly planned trajectories can be inefficient under many aspects, since they might require long execution time and induce unnecessary vibration on the end-effector of the robot as well as high solicitation on its mechanical structure and actuators. In this paper a novel trajectory planning methods for robotic manipulators is introduced, named “5455”. This method is based on an interpolation of a sequence of via points using a combination of 4th and 5th order polynomial functions. This technique allows to obtain a continuous-jerk trajectory for improved smoothness and minimum excitation of vibration. Such method allows also to impose an arbitrary value of jerk at the first and last via-point. This feature can be effectively used to produce a smooth trajectory for repetitive tasks, trough an innovative optimization algorithm which is introduced in this paper. Both numerical and experimental results are provided for a 3 d.o.f. Cartesian robot, but the techniques provided here can be applied to any industrial manipulator.
Dimensional Mobility Criteria of Planar 6T-9R Paradoxical Chains
Authors: Lee Chung-Ching , Lee Jeng-Hsiung , Lee Po-Chih
Published: September 2013

Focusing on the structural type of 6 ternary links and 9 revolute pairs (denoted 6T-9R), which stems from the commercialized Expanda-Triangles construction toy, we conduct in-depth study on the mobility constraints of the generalized planar 6T-9R paradoxical chains. According to Grübler criterion, the degree of freedom (DoF) of the chains of this type is minus 3 and they should have no constrained motion. However, due to the special dimensional constraints (Euclidean metric), some of such paradoxical mechanisms can still have the full-cycle mobility. To identify the dimensional constraints of mobility algebraically, we adopt a simple direct algebraic elimination approach to attain an eliminant of sixth-order polynomial in one variable only. The identity of polynomial whose coefficients are merely function of link lengths and structural angles produces six necessary dimensional constraints for movable 6T-9R paradoxical chain. One new and two existing paradoxical chains are revealed and their numerical examples are illustrated to show the correctness and validity of the proposed dimensional constraints. A novel generalized form of planar 6-bar paradoxical chain is disclosed too.
Best Practices for Engineering Design Project in Undergraduate Student Education With Eco-Friendly Vehicle Design
Authors: Lim Hong Wee , Goh Kim Hoo , Lu Wen Feng
Published: September 2013

With the recommendation from ABET, each engineering student should go through a major engineering design experience and understand how to go from design specifications to a final artifact. The Department of Mechanical Engineering at the National University of Singapore (NUS) started automotive design projects including competition vehicles and proof of concept vehicles for its undergraduate students many years ago. These projects aim to provide practical engineering education to the students through vehicle design and fabrication with hands-on experience. The project lifecycle usually does not last longer than one year as it is governed by the competition and the academic cycle. With many years of experience supervising students, the best practice of guiding students learning through this engineering design project within one academic year is developed. Before each project, students will first go through training and apprenticeship. Such project usually starts with problem formulation that studies the requirements of vehicle for the competition and the resources available. The team of students will go from design specifications to a final vehicle prototype with generating alternatives, synthesizing, analyzing, fabrication, testing and evaluating. This method allows sustainability in vehicle design projects. NUS Eco-car project is used as a case study to illustrate the best practice. Our past experience showed that students trained in this project have strong practical and analytical skills and are able to manage and communicate in a team well.
Numerical Research on Efficiency Performance of the Propulsion System for an Innovative Airship
Authors: Ilieva Galina I. , Páscoa José C. , Dumas Antonio , Trancossi Michele
Published: September 2013

The current work deals with the methodology and results for the numerical modeling, research and implementation of an unconventional propulsion system for an airship with an innovative shape. It is a part of a global study (European Project MAAT) that investigates the possibilities of using the cruiser/feeders concept for passengers and cargo transportation.

Based on an initial research for the airship shape, aerodynamic features at given altitudes, and the propulsion needs, were analyzed by means of numerical simulations for different flow conditions and propulsion concepts. The propulsion system is a set of air-jets, distributed in a circular row around the airship. The air-jets are working with an ambient air that is sucked/blowned from channels positioned in the upper and bottom sides of the airship body. These jets generate thrust to drive the airship in horizontal direction.

The flow is modeled using the RANS equations with an appropriate model for turbulence effects simulation. The environmental conditions are varied in order to be representative of several altitude positions for the airship. Boundary zones that were set are “pressure far field”, “mass flow inlet”, “wall” and “fluid”.

Attention is focused on the performance of the air-jets working with high mass flow rates and low jet flow speeds. They should also work in different combinations to ensure the needed thrust and direction of flight.

The results provide opportunities for future developments of these propulsion concepts for airships.
Fault Symptoms of Rolling Element Bearings Under Variable Operating Conditions: A Multi Domain Analysis
Authors: Borghesani P. , Ricci R. , Chatterton S. , Pennacchi P.
Published: September 2013

Diagnostics of rolling element bearings have been traditionally developed for constant operating conditions, and sophisticated techniques, like Spectral Kurtosis or Envelope Analysis, have proven their effectiveness by means of experimental tests, mainly conducted in small-scale laboratory test-rigs. Algorithms have been developed for the digital signal processing of data collected at constant speed and bearing load, with a few exceptions, allowing only small fluctuations of these quantities. Owing to the spreading of condition based maintenance in many industrial fields, in the last years a need for more flexible algorithms emerged, asking for compatibility with highly variable operating conditions, such as acceleration/deceleration transients.

This paper analyzes the problems related with significant speed and load variability, discussing in detail the effect that they have on bearing damage symptoms, and propose solutions to adapt existing algorithms to cope with this new challenge. In particular, the paper will i) discuss the implication of variable speed on the applicability of diagnostic techniques, ii) address quantitatively the effects of load on the characteristic frequencies of damaged bearings and iii) finally present a new approach for bearing diagnostics in variable conditions, based on envelope analysis. The research is based on experimental data obtained by using artificially damaged bearings installed on a full scale test-rig, equipped with actual train traction system and reproducing the operation on a real track, including all the environmental noise, owing to track irregularity and electrical disturbances of such a harsh application.
Virtual Reality Based Enhanced Visualization of Epidural Insertion
Authors: Vaughan Neil , Dubey Venketesh N. , Wee Michael Y. K. , Isaacs Richard
Published: September 2013

This paper outlines an approach to create stereoscopic 3D computer graphics for visualization of epidural insertions. The graphics are built from several 3D vertex models of the anatomical structures including the vertebrae, tissue layers and the skin, subcutaneous fat, supraspinous ligament, interspinous ligament, ligamentum flavum and epidural space. The 3D models are wrapped with full color textures and vertex edges are rounded. The objects are stored in object files and are rendered as 3D by a custom OpenGL application. Graphics drivers calculate the angles and offset for the two separate stereo images and render both in 3D. The stereoscopic images are viewed through a visor containing two OLED micro-displays in stereo using the page-flipped method. The completed stereo simulation allows depth to be perceived so that the operator can judge depth of the needle tip in relation to tissue layers and bones, which aids to the location of the epidural space. Applying stereoscopic vision to epidural simulators will help the operator to visualize the depths required for correct needle placement in the epidural space.
Designing Resource-Efficient Military Base Camps From a Holistic Perspective
Authors: Putnam Nathan H. , Seepersad Carolyn C. , Webber Michael E.
Published: September 2013

The U.S. Department of Defense (DoD) has recently shown an interest in incorporating resource efficiency into decision-making processes, including decisions that pertain to Forward Operating Military Base Camp (FOB) equipment. Often deployed in environments without access to grid utilities, FOBs require costly deliveries by land or air of resources such as fuel and fresh water. Resource-efficient FOB designs have the potential to reduce supply costs, but competing objectives and uncertain operational conditions complicate the design process. For example, integration of solar photovoltaic panels into existing designs has the potential to reduce the need to burn fuel in generators, however solar panels have up-front logistical and monetary costs that limit widespread use. There are also uncertainties associated with available solar energy and camp electrical loads. The research described here uses computer modeling and simulation of a real FOB subsystem under different operational scenarios to develop configurations of solar panels and batteries that, when integrated with an existing FOB design, maximize resource savings but minimize logistical and monetary costs, showing the benefit of a holistic design strategy that accounts for scenario variation. This research will also show that while different hardware configurations prove most efficient under different scenarios and objectives, certain hardware configurations provide good performance under all scenarios and objectives.
Al-Mg Micro-Features Using Micro-EDM Milling
Authors: Modica F. , Marrocco V. , Moore P. , Fassi I. , Wiens G.
Published: September 2013

Aluminum alloys offer many machining advantages, such as excellent machinability and finish degree, outstanding tool life, and good corrosion resistance. They also display an elevated thermal exchange and weight reduction, which lead to easier handling compared to steels and make them good candidates for applications in the automotive and aerospace industry and in the field of mould production. Despite these recognized features, the machining accuracy, in particular in the micro-electro discharge machining (micro-EDM) process, needs further improvement. Revealing the nature of the Al alloys in EDM machining, some papers report of resolidifying layers in Al alloys appearing after the EDM process and grain compositions hugely affecting surface roughness. In particular, it has been observed that a thin and strong insulating layer due to the oxidation of the aluminum workpiece after machining leads to frequent tool breakage. In practice, this makes the micro-EDM process harder when micro-tools are meant to be used. However, to the best of our knowledge, the investigation of micro-EDM process performances of Al-Mg has not yet been fully explored. In this work, micro-EDM Al-Mg machining is presented: different energy levels were tested to find the proper parameter combination feasible to process micro-features. The machining geometrical limits are also investigated, putting in relation the energy levels to different electrode tool diameters. The experimental results are discussed on the basis of the evaluation of material removal rate (MRR), tool wear ratio (TWR), surface roughness and sparking gap. The machining of a micro-shaft housing component featuring high aspect ratio (HAR) is also shown as demonstrator to prove the effectiveness of the micro-EDM parameters selected from the previous trials.
Emergence System of Pattern Design Showing Natural Impression
Authors: Kamahara Yuki , Aoyama Hideki , Oya Tetsuo
Published: September 2013

In recent years, design is becoming increasingly important due to advancement of product function, which makes it increasingly difficult to differentiate product quality. Coupled with the growing demands for shorter product development lead time, systems which can create design plans effectively at the initial stage of design are indispensable. The objective of this study is to develop a system which can create designs with natural impression by quantifying natural phenomenon, mainly pattern designs like polka dots and leaf designs. The authors constructed the system using a neural network simulating the structure of the human brain and genetic algorithms simulating the heredity of living things. The effectiveness of the system was validated by using it to create design examples.
A Dynamic Model of a Belt Driven Electromechanical XY Plotter Cutter
Authors: Prisco Joseph V. , Voglewede Philip A.
Published: September 2013

Currently, models for XY plotter cutters specific to industrial and arts and crafts applications are not publicly available. This paper mathematically models the XY motion control for a commercial plotter cutter. In this particular application, the Y motion is controlled by media feed and the X motion is controlled by a gantry arm. A dynamic, electromechanical model consisting of a governing system of differential equations for the gantry arm is developed and simulated using Matlab. Once the model is developed, it will be used to decrease development time and optimize performance parameters.
The Combination of Empirical Mode Decomposition and Minimum Entropy Deconvolution for Roller Bearing Diagnostics in Non-Stationary Operation
Authors: Ricci R. , Borghesani P. , Chatterton S. , Pennacchi P.
Published: September 2013

Diagnostics is based on the characterization of mechanical system condition and allows early detection of a possible fault.

Signal processing is an approach widely used in diagnostics, since it allows directly characterizing the state of the system. Several types of advanced signal processing techniques have been proposed in the last decades and added to more conventional ones. Seldom, these techniques are able to consider non-stationary operations. Diagnostics of roller bearings is not an exception of this framework.

In this paper, a new vibration signal processing tool, able to perform roller bearing diagnostics in whatever working condition and noise level, is developed on the basis of two data-adaptive techniques as Empirical Mode Decomposition (EMD), Minimum Entropy Deconvolution (MED), coupled by means of the mathematics related to the Hilbert transform.

The effectiveness of the new signal processing tool is proven by means of experimental data measured in a test-rig that employs high power industrial size components.
An IBIS Based Approach for the Analysis of Non-Functional Requirements
Authors: Dai Weili , Aurisicchio Marco , Armstrong Gareth
Published: September 2013

The design of complex systems is based on the needs and expectations of multiple stakeholders. Analysing such elements and transforming them into a rigorous system specification is a long and demanding task. This research is interested in supporting engineers and other stakeholders in the specification of system requirements with a focus on requirement analysis. The paper presents an approach to conduct analysis of non-functional requirements in a way that benefits both the engineers involved in the development of the current system, and those who will need to make improvements to it. The approach includes suggestions towards a tool, a representation, and a method. The tool is a software tool that specialises in capturing decision rationale known as Decision Rationale editor (DRed); the representation is adopted from the IBIS notation; the method is based on a model synthesised from literature on requirement analysis.
Use Scenarios for Design Space Exploration With a Dynamic Multiobjective Optimization Formulation
Authors: Curtis Shane K. , Hancock Braden J. , Mattson Christopher A.
Published: September 2013

In a recent publication, we presented a new strategy for engineering design and optimization, which we termed formulation space exploration. The formulation space for an optimization problem is the union of all variable and design objective spaces identified by the designer as being valid and pragmatic problem formulations. By extending a computational search into this new space, the solution to any optimization problem is no longer predefined by the optimization problem formulation. This method allows a designer to both diverge the design space during conceptual design and converge onto a solution as more information about the design objectives and constraints becomes available. Additionally, we introduced a new way to formulate multiobjective optimization problems, allowing the designer to change and update design objectives, constraints, and variables in a simple, fluid manner that promotes exploration. In this paper, we investigate three use scenarios where formulation space exploration can be utilized in the early stages of design when it is possible to make the greatest contributions to development projects. Specifically, we look at s-Pareto frontier generation in the formulation space, formulation space boundary exploration, and a new way to perform inverse optimization. The benefits of these methods are illustrated with the conceptual design of an impact driver.
GPU-Based Local Tone Mapping in the Context of Virtual Night Driving
Authors: Bonner Erik , Berssenbruegge Jan
Published: September 2013

Virtual Prototyping of automotive headlights requires a realistic illumination model, capable of rendering scenes of high contrast in fine detail. Due to the high dynamic range nature of headlight beam pattern data, which is projected onto the virtual road, high dynamic range illumination models are required. These are used as the basis for illumination in simulations for automotive headlight Virtual Prototyping.

Since high dynamic range illumination models operate on brightness ranges commensurate with the real world, a post-processing operation, known as tone mapping, is required to map each frame into the device-specific range of the display hardware.

Algorithms for tone mapping, called tone mapping operators, can be classified as global or local. Global operators are efficient to compute at the expense of scene quality. Local operators preserve scene detail, but, due to their additional computational complexity, are rarely used with interactive applications. Local tone mapping methods produce more usable visualization results for engineering tasks.

This paper proposes a local tone mapping method suitable for use with interactive applications. To develop a suitable tone mapping operator, a state of the art local tone mapping method was accelerated using modern, work-efficient GPU algorithms. Optimal performance, both in terms of memory and speed, was achieved by means of General-Purpose GPU programming with CUDA.

A prototypic implementation has shown that the method works well with high dynamic range OpenGL applications. In the near future, the tone mapper will be integrated into the virtual night driving simulator at our institute.
A Literature Survey of Biodynamic Models for Whole Body Vibration and Vehicle Ride Comfort
Authors: Bhagwan Kumbhar Prasad , Xu Peijun , Yang Jingzhou (James)
Published: September 2013

Vehicle ride comfort plays an important role in the vehicle design. Human body is very sensitive to whole body vibration. Vehicle ride comfort has brought lots of concerns in recent years due to requirement of better ride comfort performance for newly developed vehicles. Vehicle ride comfort has a direct effect on driver’s performance and will result in overall customer satisfaction. Various papers have reported vehicle ride comfort and various biodynamic models have been built in the literature. However, there is a lack of a comprehensive literature survey to summarize all biodynamic models for whole body vibration and vehicle ride comfort. The purpose of this paper is to have a literature review of biodynamic models. So this paper initially focuses on various health issues due to whole body vibrations. Whole body vibration transfers environmental vibration to human body through a large contact area. Vibration evaluation methods such as weighted root mean square (r.m.s.) acceleration method, fourth power VDV method are discussed. Along with that the paper will focus on various biodynamic response functions. Human models in the literature are divided into three main groups: lumped parameter (LP), finite element model (FE), and multibody model (MB). In the LP model, human body is represented by several concentrated masses which are connected by springs and dampers. The FE model considers that human body consists of numerous finite elements. And in MB model, human body is made of several rigid bodies connected by bushing element for both translational and rotational motion. So this paper thoroughly summarizes various models developed to reduce human body vibration. At the end, four different approaches of assessing ride comfort are summarized. These four approaches are ride measurement in vehicles, ride simulator test, shaker table test and subjective ride measurement.
Global Stability Study of a Compliant Double-Inverted Pendulum Based on Hamiltonian Modeling
Authors: Spyrakos-Papastavridis Emmanouil , Medrano-Cerda Gustavo , Dai Jian S. , Caldwell Darwin G.
Published: September 2013

This paper presents a dynamical model of a compliant double-inverted pendulum that is used to approximate the physical structure of the compliant humanoid (COMAN) robot, using both the Hamiltonian and the Lagrangian approaches. A comparison between the two aims at providing insight into the various advantages and/or disadvantages associated to each approach. Through manipulation of the resulting formulae, it is shown that the Hamiltonian equations possess certain characteristics, such as the allowance of the tracking of global stability, that render this method of representation suitable for legged robotics applications. Finally, an asymptotically stabilizing control scheme is presented together with simulation results.
Evaluation of SSVEP as Passive Feedback for Improving the Performance of Brain Machine Interfaces
Authors: Wang Shaocheng , Esfahani Ehsan Tarkesh , Sundararajan V.
Published: September 2013

Research in brain-computer interfaces have focused primarily on motor imagery tasks such as those involving movement of a cursor or other objects on a computer screen. In such applications, it is important to detect when the user is interested in moving an object and when the user is not active in this task. This paper evaluates the steady state visual evoked potential (SSVEP) as a feedback mechanism to confirm the mental state of the user during motor imagery. These potentials are evoked when a subject looks at a flashing objects of interest. Four different experiments are conducted in this paper. Subjects are asked to imagine the movement of flashing object in a given direction. If the subject is involved in this task, the SSVEP signal will be detectable in the visual cortex and therefore the motor imagery task is confirmed. During the experiment, EEG signal is recorded at 4 locations near visual cortex. Using a weighting scheme, the best combination of the recorded signal is selected to evaluate the presence of flashing frequency. The experimental result shows that the SSVEP can be detected even in complex motor imagery of flickering objects. The detection rate of 85% is achieved while the refreshing time for SSVEP feedback is set to 0.5 seconds.
Motion Controller Design for a Biped Humanoid Robot
Authors: Dezfouli Siavash , Daniali Mohsen M.
Published: September 2013

This paper addresses design of a motion controller for a teen sized biped robot, Archie. The main goal is to develop a motion controller for a cost oriented robot to assist human in daily life. The proposed real-time controller enables each joint individually to receive reference speed and position to provide a smooth motion. In this scheme, action commands are transmitted via Control Area Network (CAN) bus from a PC to robot. Aim of using such a communicator is to provide error process mechanism with a message priority concept. The main advantage of this method is to synchronize the motion of all joints necessary for biped walking motion. Finally test and implementation results are presented to demonstrate the good performance.
Predicting the Thermal Performance for the Multi-Objective Vehicle Underhood Packing Optimization Problem
Authors: Katragadda Ravi Teja , Gondipalle Sreekanth Reddy , Guarneri Paolo , Fadel Georges
Published: September 2013

The ever increasing demands towards improvement in vehicle performance and passenger comfort have led the automotive manufacturers to further enhance the design in the early stages of the vehicle development process. Though, these design changes enhance the overall vehicle performance to an extent, the placement of these components under the car hood also plays a vital role in increasing the vehicle performance. In the past, a study on the automobile underhood packaging or layout problem was conducted and a multi-objective optimization routine with three objectives namely, minimizing center of gravity height, maximizing vehicle components accessibility and maximizing survivability (for army vehicles) has been setup to determine the optimal locations of the underhood components. The previous study did not consider thermal performance as an objective. This study asserts the necessity of including thermal performance as an objective and makes an assessment of the several available thermal analyses that are performed on the automotive underhood to evaluate the thermal objective. A Neural Network approximation of the CFD analysis conducted over the automotive underhood is presented in this paper. The results obtained from the Neural Network are compared with the CFD results, showing good agreement. The Neural Network model is included in the multi-objective optimization routine and new layout results are obtained. A non-deterministic evolutionary multi-objective algorithm (AMGA-2) is used to perform the optimization process.
Vortex-Induced Vibration of a Sprung Rigid Circular Cylinder Augmented With a Nonlinear Energy Sink
Authors: Tumkur Ravi Kumar R. , Calderer Ramon , Masud Arif , Bergman Lawrence A. , Vakakis Alexander F. , Pearlstein Arne J.
Published: September 2013

We study the nonlinear fluid-structure interaction of an elastically supported rigid circular cylinder in a laminar flow. Periodic shedding of counter-rotating vortices from either side of the cylinder results in vortex-induced vibration of the cylinder. We demonstrate the passive suppression of the limit cycle oscillation (LCO) of the cylinder with the use of an essentially nonlinear element, the nonlinear energy sink (NES). The computational study is performed at a Reynolds number (Re) of 100; Re is defined based on the cylinder diameter and inlet velocity. The variational multiscale residual-based stabilized finite-element method is used to compute approximate solutions of the incompressible Navier-Stokes equations. The NES is comprised of a small mass, an essentially nonlinear spring, and a linear damper. With appropriate values for the NES parameters, the coupled system of flow-cylinder-NES exhibits resonant interactions, resulting in targeted energy transfer (TET) from the flow via the cylinder to the NES, where the energy is dissipated by the linear damper. The NES interacts with the fluid via the cylinder by altering the phase relation between the lift force and the cylinder displacement; this brings about significant reduction in the LCO amplitude of the cylinder for several set of values of the NES parameters.
Efficient Coupling of Absolute Nodal Coordinate Formulation Flexible Bodies With an Existing Multibody Dynamics Code
Authors: Liu Jeff , Mohamed Abdel-Nasser A.
Published: September 2013

A couple of issues are identified in the process to embed absolute nodal coordinate formulation (ANCF) flexible bodies in an existing multibody dynamics code. (1) The generalized coordinates of ANCF must be solved together with those of the rest of the mechanism in a combined system of the equations of motion. (2) The various constraints, joints, and forces elements supported in the multibody dynamics code must be extended to the ANCF flexible bodies without major code restructuring. This paper describes two novel techniques that were devised to solve these issues. The first is the idea of interface triad. We will demonstrate how to construct the interface triad such that all exiting constraints, joints, and forces elements are automatically supported. The second idea is to represent the equations of motion of the ANCF body as a user-defined subroutine element representing a set of implicit general state equations subroutine (GSESUB). By treating each ANCF body modularly as a user-defined subroutine, not only all existing integration options of its host solver, e.g., HHT or DAE index-1, 2, and 3, etc., are automatically supported, but also the existing features such as parallel computing and sparse matrix solution of the existing multibody dynamics software are supported with minimum programming. Numerical examples are presented to demonstrate the efficiency and the success of these two techniques.
Detection of Non-Metallic Cords Using Synthetic Aperture Acoustic Imaging
Authors: Judge John A. , Vignola Joseph F. , Glean Aldo A. J. , Ryan Teresa J. , Good Chelsea E. , Gugino Peter M. , Bishop Steven S. , Soumekh Mehrdad
Published: September 2013

Synthetic aperture acoustic (SAA) imaging is a technique for remotely obtaining information about the location, geometry, and mechanical properties of objects based on the way they scatter incident acoustic energy. Results are presented for an experimental investigation of the use of SAA imaging to detect non-metallic cords of different sizes laid in various configurations on the ground surface in an outdoor urban environment. Interest in this application of SAA stems from the fact that non-metallic cords are not readily detectable with synthetic aperture radar (SAR) and that the SAA imaging approach represents a relatively inexpensive alternative or supplement to SAR. The measurement system is comprised of a mobile acoustic transceiver (a speaker and microphone) that broadcasts a burst chirp with a bandwidth of 2–15 kHz. The recorded signal is used to form a two-dimensional image of the distribution of acoustic scatterers within the scene. For this study, five different diameters (2–15mm) of nylon cord laid on the ground were imaged in different configurations. These measurements were made in the presence of urban ambient noise of varying levels. The goal of this study was to identify the effect of environmental noise and other parameters on detectability. The results demonstrate that non-metallic cords can be detected acoustically if the angle to the transceiver path is sufficiently small.
Interaction Model for Products and Services Using Affordance
Authors: Kim Yong Se , Hong Yeon Koo
Published: September 2013

A human activity interacting with products or with services involves the steps of perception, judgment and action. Affordances provided by products or services induce human activities. A model of interaction with products and services will be presented with examples of affordances and affordance features for products and services.
Energetics of a Circular Membrane Subjected to a Sudden Eccentric Circular Areal Constraint
Authors: AlSahlani Assaad , Mukherjee Ranjan
Published: September 2013

We investigate the energetics of a freely vibrating circular membrane subjected to a sudden eccentric circular areal constraint. The membrane is assumed to be fixed at its outer boundary and the constraint is assumed to be applied at an arbitrary time during the motion of the membrane. The constraint is applied instantaneously such that immediately after application of the constraint, the geometry of the membrane outside the area of the constraint remains unchanged and the constrained area comes to rest. The change in total energy after constraint application is investigated for different sizes and locations of the constraint and time of application of the constraint. The results show that the energy can decrease or increase depending on the time of application of the constraint. The condition for maximum energy reduction is presented and simulation results based on this condition show that sequential application and removal of the constraint reduces the total energy rapidly. This provides the opportunity for active control of membrane vibration through direct physical interaction with a small area of the membrane.
Composite Material Testing Data Reduction to Adjust for the Systematic 6-DoF Testing Machine Aberrations
Authors: Iliopoulos Athanasios , Michopoulos John G. , Hermanson John C.
Published: September 2013

This paper describes a data reduction methodology for eliminating the systematic aberrations introduced by the unwanted behavior of a multiaxial testing machine, into the massive amounts of experimental data collected from testing of composite material coupons. The machine in reference is a custom made 6-DoF system called NRL66.3 and developed at the NAval Research Laboratory, that consists of multiple sets of hexapod configurations essentially forming a recursive synthesis of multiple parallel mechanisms. Hexapod linkages, the grips, and other deformable parts of the machine absorb energy. This is manifested in an either reversible or irreversible manner, thus introducing a parasitic behavior that is undesirable from the perspective of our ultimate goal of the material constitutive characterization. The data reduction focuses both on the kinematic (pose of the grip) and the reaction (forces and moments) that are critical input quantities of the material characterization process. The kinematic response is reduced by exploitation of the kinematics of the dots used for full field measurements. A correction transformation is identified by solving an inverse problem that minimizes the known displacements at the grips as given by the full field measurements and those given by the machine’s displacement sensors. A Procrustes problem formalism was introduced to exploit a known material behavior tested by the testing machine. Consequently, a correction transformation was established and was applied on the load cell data of the machine in order to eliminate the spurious responses appearing in the force and moment data.
Improvement of Convergence Properties for Ritz Formulations of Acousto-Elasticity Problems
Authors: McPherson Patrick , Cadogan Elizabeth , Ferri Al
Published: September 2013

Many applications require the analysis of structures with cavities filled with fluids or gases. In many cases the fluid domains can be ignored, and we can safely assume that the structure’s in vacuo properties apply. Sometimes, however, resonances in the fluid can couple with structural resonances to yield acousto-elastic modes of response. The most popular approach to these problems is to describe the trapped fluid in terms of a finite number of eigenmodes of a geometrically identical cavity with rigid boundaries. Then, the structural and fluid domains are coupled by matching the pressure across the wetted surface. However, for light structures with embedded cavities of relatively heavy fluids such as water, this technique may not be satisfactory because the interior rigid-cavity modes are poor candidates to satisfy the “natural boundary conditions” that exist at the fluid-structure boundary. This paper explores the use of an expanded set of Ritz functions for the fluid domain, to include a number of functions that explicitly allow for motion along the wetted surface. The method is applied to a two-dimensional rectangular acoustic cavity, with rigid boundaries on all sides except for a flexible membrane on the top surface. Through comparisons with the “exact solution,” it is shown that the solution using the expanded set of Ritz functions converges more quickly than do solutions employing rigid cavity modes. The convergence trends of the first few natural frequencies are computed for a number of different physical and geometric system properties.
Helicopter Ground Resonance Phenomenon With Blade Stiffness Dissimilarities: Experimental and Theoretical Developments
Authors: Sanches Leonardo , Michon Guilhem , Berlioz Alain , Alazard Daniel
Published: September 2013

Recent works study the ground resonance in helicopters under the aging effects. Indeed, the blades lead-lag stiffness may vary randomly with time and be different from each other (i.e.: anisotropic rotor). The influence of stiffness dissimilarities between blades on the stability of the ground resonance phenomenon is determined through numerical investigations on the periodical equations of motion, treated by using Floquet’s theory. Stability chart highlights the appearance of new instability zones as function of the perturbation introduced on the lead-lag stiffness of one blade. In order to validate the theoretical results, a new experimental setup is designed and developed. The ground resonance instabilities are investigated for different types of rotor configurations (i.e.: isotropic and anisotropic rotors) and the boundaries of stability are determined. A good correlation between both theoretical and experimental results is obtained and the new instability zones, found in asymmetric rotors, are verified experimentally. The temporal responses of the measured signals highlight the exponential divergence at the instability regions.
Configuration Space Analysis and Synthesis of Planar Variable Kinematic Joints
Authors: Slaboch Brian J. , Voglewede Philip A.
Published: September 2013

This paper presents a new approach to the analysis and synthesis of planar variable kinematic joints using a configuration space approach. The advantage of this approach is that the configuration space representation contains both the joint topology and the configuration variables. Based on the same configuration space, different combinations of higher pair equivalent revolute and prismatic joints can be used to analyze and synthesize planar variable kinematic joints. Two practical examples will be presented to illustrate the proposed method.
Does Using Different Concept Generation Techniques Change the Design Cognition of Design Students?
Authors: Gero John S. , Jiang Hao , Williams Christopher B.
Published: September 2013

This paper presents the preliminary results of protocol studies to determine the effects of teaching different concept generation techniques to engineering students on their design cognition.

Twenty-two mechanical engineering students were given instructions in the three concept generation techniques of brainstorming, morphological analysis and TRIZ as part of their undergraduate education at a large land grant university. After the instruction for each concept generation technique, the students were formed into the same teams of two. Each team was given the same set of three design tasks, one for each concept generation technique, while their verbalization and gestures were videoed as they designed for a period of 45 minutes.

Students’ design cognition was examined by protocol analysis using the FBS ontologically-based coding scheme. Preliminary results indicate that statistically significant differences in students’ design cognition were observed when using different concept generation techniques.
Stochastic Modal Models of Slender Uncertain Curved Beams Preloaded Through Clamping
Authors: Avalos Javier , Richter Lanae A. , Wang X. Q. , Murthy Raghavendra , Mignolet Marc P.
Published: September 2013

This paper addresses the stochastic modeling of the stiffness matrix of slender uncertain curved beams that are forced fit into a clamped-clamped fixture designed for straight beams. Because of the misfit with the clamps, the final shape of the clamped-clamped beams is not straight and they are subjected to an axial preload. Both of these features are uncertain given the uncertainty on the initial, undeformed shape of the beams and affect significantly the stiffness matrix associated with small motions around the clamped-clamped configuration. A modal model using linear modes of the straight clamped-clamped beam with a randomized stiffness matrix is employed to characterize the linear dynamic behavior of the uncertain beams. This stiffness matrix is modeled using a mixed nonparametric-parametric stochastic model in which the nonparametric (maximum entropy) component is used to model the uncertainty in final shape while the preload is explicitly, parametrically included in the stiffness matrix representation. Finally, a maximum likelihood framework is proposed for the identification of the parameters associated with the uncertainty level and the mean model, or part thereof, using either natural frequencies only or natural frequencies and mode shape information of the beams around their final clamped-clamped state. To validate these concepts, a simulated, computational experiment was conducted within Nastran to produce a population of natural frequencies and mode shapes of uncertain slender curved beams after clamping. The application of the above concepts to this simulated data led to a very good to excellent matching of the probability density functions of the natural frequencies and the modal components, even though this information was not used in the identification process. These results strongly suggest the applicability of the proposed stochastic model.
A Hybrid Approach to 3D Porous Microstructure Reconstruction via Gaussian Random Field
Authors: Jiang Zhen , Chen Wei , Burkhart Craig
Published: September 2013

Obtaining an accurate three-dimensional (3D) structure of a porous microstructure is important for assessing the material properties based on finite element analysis. While directly obtaining 3D images of the microstructure is impractical under many circumstances, two sets of methods have been developed in the literature to generate (reconstruct) 3D microstructure from its 2D images: one characterizes the microstructure based on certain statistical descriptors, typically two-point correlation function and cluster correlation function, and then performs an optimization process to build a 3D structure that matches those statistical descriptors; the other method models the microstructure using stochastic models like a Gaussian random field (GRF) and generates a 3D structure directly from the function. The former obtains a relatively accurate 3D microstructure, but the optimization process can be very computationally intensive, especially for problems with a large image size; the latter generates a 3D microstructure quickly but sacrifices the accuracy. A hybrid optimization approach of modeling the 3D porous microstructure of random isotropic two-phase materials is proposed in this paper, which combines the two sets of methods and hence maintains the accuracy of the correlation-based method with improved efficiency. The proposed technique is verified for 3D reconstructions based on silica polymer composite images with different volume fractions. A comparison of the reconstructed microstructures and the optimization histories for both the original correlation-based method and our hybrid approach demonstrates the improved efficiency of the approach.
Constraint and Singularity Analysis of the Exechon Tripod
Authors: Zlatanov Dimiter , Zoppi Matteo , Molfino Rezia
Published: September 2013

The paper discusses mobility and singularities of the Exechon three-degree-of-freedom (dof) parallel mechanism (PM) on which a family of parallel kinematic machines is based. Exechon designs are used by a number of machine-tool makers. A new version of the manipulator has been developed as a component of a mobile self-reconfigurable fixture system within an inter-European project. The PM has two UPR (4-dof) legs, constrained to move in a common rotating plane, and an SPR (5-dof) leg. The paper focuses on the constraint and singularity analysis of the mechanism. The screw systems of end-effector freedoms and constraints are identified. The singular configurations are classified in detail and their geometric interpretation is discussed. The velocity kinematics and the Jacobian operator are formulated via a screw-system approach. A fully parameterized package of Maple tools has been developed and used to visualize singularities and their consequences.