bluuebunny/crossref_metadata_2025 huggingface dataset:
Design Margins as a Key to Understanding Design Iteration
Authors: Eckert Claudia M. , Isaksson Ola , Earl Chris F.
Published: January 2015

Design processes are subject to many uncertainties. Changes resulting from the need to respond to external uncertainties are one of the main drivers of engineering change and therefore for iteration in design processes. Another important cause of iteration in design processes arises from the dependencies in design information which is being generated as part of the design process itself. At the beginning of the design process engineers need to make an informed guess about the values of parameters that they need and can achieve. These values are passed on to others, who base their decisions on them. Design decisions are distributed and iterative among design teams, customers and suppliers. Communicated parameter values are uncertain in two different but related ways. First, there is the confidence, precision and commitment that the designers have in the values they specify. Second there are uncertainties in the values that can be achieved with the technology the new design employs. These issues become particularly challenging when they span design teams, customers and suppliers as they iterate to converge on a mutually effective solution. This paper looks at this type of convergent iteration through an example from the aerospace industry, which illustrates how uncertainty in operating temperature at the beginning of the design process requires a thorough understanding of the temperature ranges that solution alternatives, at different degrees of maturity, can operate under. This paper argues that the key to managing convergent iterations lies in communicating the available ranges of parameter values and in understanding how design margins have arisen in existing technologies. These margins on product parameters provide potential performance which exceeds immediate functional requirements. The paper develops and formalizes the concept of design margins and argues that margins are included into products for a variety of reasons that are not always transparent to different team members. Analysis of margins enables design companies to reason in terms of ranges of values describing the scope for design change in meeting customer and supplier requirements without being forced into unplanned iteration loops.
Partial Bi-Invariance of SE(3) Metrics
Authors: Chirikjian Gregory S.
Published: January 2015

In a flurry of articles in the mid to late 1990s, various metrics for the group of rigid-body motions, SE(3), were introduced for measuring distance between any two reference frames or rigid-body motions. During this time it was shown that one can choose a smooth distance function that is invariant under either all left shifts or all right shifts, but not both. For example, if one defines the distance between two reference frames to be an appropriately weighted Frobenius norm of the difference of the corresponding homogeneous transformation matrices, this will be invariant under left shifts by arbitrary rigid-body motions. However, this is not the full picture — other invariance properties exist. Though the Frobenius norm is not invariant under right shifts by arbitrary rigid-body motions, for an appropriate weighting it is invariant under right shifts by pure rotations. This is also true for metrics based on the Lie-theoretic logarithm. This paper goes further to investigate the full invariance properties of distance functions on SE(3), clarifying the full subsets of motions under which both left and right invariance is possible.
A Low Voltage Electrostatic Micro Actuator for Large Out-of-Plane Displacement
Authors: Towfighian Shahrzad , He Siyuan , Ben Mrad Ridha
Published: January 2015

An electrostatic actuator is designed to move a 1 mm mirror, 58 μm out of plane at 25 volts. Large out-of-plane displacement is obtained from repulsive forces generated on four sets of comb drive fingers attached to the mirror plate in the middle. The proposed actuator is a customized design of a previous study for low voltage applications. The static modeling of the actuator was performed using a coupled-field finite element model of the actuator, including mechanical and electrical domains. Low voltage operation is achieved by decreasing the finger width and the lateral spacing, which increased the generated repulsive force at a specified voltage in a unit cell of the actuator. Decreasing the lateral spacing also enabled increasing the number of fingers, which could increase the repulsive-force, and consequently the torque and the rotation angles when the vertical gap between moving and fixed fingers is small. However, the redesigned actuator has a lower stiffness compared to the previous design. The actuator is optimized for auto-focusing applications in cell phone cameras that require voltages below 30 Volts for user safety. In the intended auto-focusing module, the actuators do not carry the lens and auto-focusing is obtained by moving the mirror attached to the actuators.
Development of a Search Tool to Identify Structural Design Principles for Bioinspired Materials Design
Authors: Tsenn Joanna , Linsey Julie S. , McAdams Daniel A.
Published: January 2015

Natural materials are often more efficient and tend to have a wider range and combination of properties than do present-day engineered materials. Biological materials are composed from a limited set of components, but are able to achieve great diversity in their properties. The variation in properties is largely due to the different arrangements of the materials components, which form unique structures. We believe that there are underlying structural design principles, relating material structure to material properties, that commonly appear in biological materials. Because nature itself achieves highly effective design solutions, the utilization of these natural design principles could similarly improve the effectiveness of engineered materials. Materials scientists need a way to abstract relevant structural design principles from the myriad of biological materials articles for the development of bioinspired materials.

This research involves the development of a data mining tool that will quickly identify potential structural design principles of biological materials with respect to a chosen material property or combination of properties. This paper presents the first stage of this process: information retrieval. An algorithm is developed to extract structural design principles’ key terms and relevant passages for specified material properties from a corpus of materials journal articles. The development of this search tool is explained beginning with the determination of search term categories and appropriate search terms and continuing to the refinement of the program algorithm. An evaluation of the tool is also described comparing the program’s results to those of a manual search for the structure-property relationships. The program identified 98% of the manually found structural design principle key terms, although many unanticipated passages were returned as well. Finally, the future work needed to improve the program is presented.
Evaluation of System Reconfigurability Based on Usable Excess
Authors: Allen Jeffrey D. , Watson Jason D. , Mattson Christopher A. , Ferguson Scott M.
Published: January 2015

The challenge of designing complex engineered systems with long service lives can be daunting. As customer needs change over time, such systems must evolve to meet these needs. This paper presents a method for evaluating the reconfigurability of systems to meet future needs. Specifically we show that excess capability is a key factor in evaluating the reconfigurability of a system to a particular need, and that the overall system reconfigurability is a function of the system’s reconfigurability to all future needs combined. There are many examples of complex engineered systems; for example, aircraft, ships, communication systems, spacecraft and automated assembly lines. These systems cost millions of dollars to design and millions to replicate. They often need to stay in service for a long time. However, this is often limited by an inability to adapt to meet future needs. Using an automated assembly line as an example, we show that system reconfigurability can be modeled as a function of usable excess capability.
Quantitative Methodology for Knee Exoskeleton Design
Authors: Jun Seungkook , Zhou Xiaobo , Ramsey Daniel K. , Krovi Venkat N.
Published: January 2015

Traditionally, the design of exoskeletons (from choice of configuration to selection of parameters) as well as the process of fitting this exoskeleton (to the individual user/patient) has largely depended on intuition and/or practical experience of a designer/physiotherapist. However, improper exoskeleton design and/or incorrect fitting can cause buildup of significant residual forces/torques (both at joint and fixation site). Performance can be further compromised by the innate complexity of human motions and need to accommodate the immense individual variability (in terms of patient–geometries, motion–envelopes and musculoskeletal–strength). In this paper, we propose a systematic and quantitative methodology to evaluate various alternate exoskeleton designs using twist- and wrench-based modeling and analysis. This process is applied in the context of a case-study for developing optimal configuration and fixation of a knee brace/exoskeleton. An optimized knee brace is then prototyped using 3D printing and instrumented with 6–DOF force-torque transducer. Knee brace is then physically tested together with a saw-bones knee model in a scaled knee bracing test. Preliminary results of the physical testing of the knee brace show promise and are discussed.
InTenso+ System: Measured Centre of Gravity Locations and Inertia Tensors of Road Vehicles
Authors: Gobbi Massimiliano , Mastinu Giampiero , Pennati Mario , Previati Giorgio
Published: January 2015

The InTenso+ system has been developed at Politecnico di Milano (Technical University of Milan) for the measurement of the centre of gravity location and of the inertia tensor of vehicles and their components (such as gearboxes and engines). The test rig is basically a multi-bar pendulum carrying the body under investigation and oscillating from well-known initial conditions. By means of a proper mathematical procedure, the mass properties of the body are accurately measured within a very short time.

The InTenso+ System has been employed for a number of measurements of the mass properties of road vehicles. In this paper, the measured data are collected and analyzed.

Formulas for the estimation of the mass properties (mass, centre of gravity location and inertia tensor) from easily accessible vehicle data are proposed and tested against the measured values. It is confirmed that the mass properties coming from the considered estimations are useless if accurate simulations of the dynamic behavior of a vehicle have to be performed.
Modeling Evolution of Uncertainty in Sustainable Product Design
Authors: Afshari Hamid , Peng Qingjin
Published: January 2015

Although a large number of research activities have been conducted for sustainable product development, it is not easy to find a practical method applied in sustainable product design as there are many uncertain factors existed in particular problems faced in different phases of product development. Based on reviewed literature, it is found that it is necessary to have an optimization metric accompanied with uncertainty effects in product development. A model is proposed in this research to evaluate the effects of uncertainty in product life cycle. The goal is to quantify various types of uncertainty from internal and external sources to assess the design efficiency for mitigating undesirable effects of uncertainty. The design phase is aimed in the research to look at product parameters that are subject to change in the design process. Inaccuracy, indecision and imprecision are selected as information uncertainty levels to quantify the evolution of uncertainty. Using the proposed concept, the discrete-event simulation (DES) is used to model and evaluate scenarios to minimize design phase duration of a sustainable wheelchair. Suggested improvements are compared to search the optimal solution. The analysis and comparison of scenarios show ways to reduce design time by (1) revision of the design process, (2) breaking down the product into design details, and (3) providing a clear and technical definition of uncertainty to be mitigated. The model is also used to locate areas for sustainability improvement in the studied case.
Relationship Between Product Aesthetic Subject Preference and Quantified Gestalt Principles
Authors: Lugo José E. , Schmiedeler James P. , Batill Stephen M. , Carlson Laura
Published: January 2015

Birkhoff proposed that order divided by complexity is a formula for aesthetic measurement. In that context, this work proposes to measure order with a method to quantify Gestalt principles. These principles establish how humans visually group elements of a shape together, and they have been used in architecture, product design and art as guidelines for good design. A human subject study was conducted to test the hypothesis that if complexity is held constant, Gestalt can serve as a direct measurement of aesthetics. In a survey, subjects were asked to evaluate their preference for multiple individual 2-D representations of automotive wheel rims from a variety of styles. The wheel rims within each style were designed in pairs, one pair with lower and one pair with higher Gestalt. Complexity was held constant by only comparing subject ratings within wheel rim styles. The results show that a positive change in Gestalt has a positive effect on aesthetic subject preference and that preferences are not significantly different for designs differing in geometry but having the same Gestalt. The implications of these results for designers and for future work are discussed.
Type Synthesis of 4-DOF and 5-DOF Parallel Mechanisms Considering Passive Constraining Limbs
Authors: Guo Wentao , Guo Weizhong , Gao Feng
Published: January 2015

Passive limbs can be introduced into the design of parallel mechanisms to provide constraints, generate decoupled configuration, bear full or partial weights and/or payloads, separate constraints from the actuations, decrease the required actuating forces of active limbs, and even increase the stiffness and accuracy of the whole system. Currently, there is still no systematic study on the utilization of passive limbs. The available parallel mechanisms having one passive limb were developed mainly based on intuition and ingenuity. In this paper 4-DOF and 5-DOF parallel mechanisms with passive limbs are investigated in terms of type synthesis. Based on the distribution of wrench system among the active limbs and passive limbs, a full-scale criterion is developed for effectively and efficiently synthesizing all kinds of 4 & 5-DOF parallel mechanisms with one or more passive limbs. All 9 categories of the 4-DOF and 2 categories of 5-DOF parallel mechanisms with passive limbs are synthesized and exemplified through kinematic diagrams merely using independent constraints. Several nonoverconstrained 4 or 5-DOF parallel mechanisms with one or two constraining passive limb are presented.
Analytic Models in Game Based Productive Systems
Authors: Kosmadoudi Zoe , Lim Theodore , Ritchie James , Liu Ying , Sung Raymond C. W.
Published: January 2015

Current computer-aided design (CAD) applications deliver limited user experience due to their complex functionality and step-by-step evolution; on the contrary, games offer memorable and formative experiences to their users. Hence, the article focuses on the architecture characteristics of games and CAD with a particular interest in developing and evaluating a CAD system embedded with game mechanics for mechanical engineering design. To establish the benefit of game-enriched engineering design ecosystem preliminary experiments were conducted to investigate engineer affect whilst carrying out parametric design tasks in a game-based CAD UI. By analysing their psycho-physiological signals and action log data an interaction model was established to identify which feedback game mechanics contributed the most in the user’s design experience.
Using SysML to Elicit a Value Model in Multi-Stakeholder Value-Driven System Design
Authors: Broadwell Douglas , Paredis Christiaan J. J.
Published: January 2015

In recent years, a formal, mathematically rigorous, value-based approach to system design has been proposed within the systems engineering community. This approach stands in contrast to the traditional requirements based approach to system design because of its foundations in decision theory. One of the crucial first steps in the value-based approach is the elicitation of information about all the elements that influence a design or acquisition decisions, namely, all actors, system properties and behavior, preferences, and concerns. This elicitation step requires a formalized, model-based method for capturing these elements of the value network, the basis of the decision maker’s value function. In this paper, we examine previous work in the area of elicitation in system design and define a set of elements necessary to effectively elicit a meaningful value network. We then consider a domain-specific profile as an extension of SysML to formally capture the essential elements of a value network. To illustrate the modeling approach, the profile is applied to a case study of the design of a heads-up display system (iHUD) in order to test the depth of the profile as well as to show the value of the model-based approach in the elicitation process.
An Evaluation of Moreau’s Time-Stepping Scheme for the Simulation of a Legged Robot
Authors: Gehring Christian , Diethelm Remo , Siegwart Roland , Nützi Gabriel , Leine Remco I.
Published: January 2015

A state-of-the-art simulation technique that solves the equations of motion together with the set-valued contact and impulse laws by the time-stepping scheme of Moreau is introduced to the legged robotics community. An analysis is given that shows which of the many variations of the method fits best to legged robots. Two different methods to solve the discretized normal cone inclusions are compared: the projected over-relaxed Jacobi and Gauss-Seidel iteration. The methods are evaluated for an electrically-driven quadrupedal robot in terms of robustness, accuracy, speed and ease of use. Furthermore, the dependence of the simulation speed on the choice of the generalized coordinates is examined. The proposed technique is implemented in C++ and compared to a fast and simple approach based on compliant contact models. In conclusion, the introduced method with hard contacts is very beneficial for the simulation of legged robots.
Design and Experimental Validation of a Two-Degree-of-Freedom Force Illusion Device
Authors: Pedemonte Nicolò , Berthiaume Frédérik , Laliberté Thierry , Gosselin Clément
Published: January 2015

In this paper, a new hand-held haptic device that aims at producing the illusion of an external force is presented. This device is based on a planar two-degree-of-freedom parallel mechanism that can be programmed to produce the force illusion in any direction of the plane. Two tests are proposed to a group of people, in order to evaluate the device’s capabilities. The results obtained from the tests are analyzed and shown to be promising. Finally, modifications to the device are proposed in order to further improve the effectiveness of the system. The device proposed in this work is envisioned as a guidance tool for visually impaired people.
Ideal Compliant Joints and Integration of Computer Aided Design and Analysis
Authors: Hamed Ashraf M. , Jayakumar Paramsothy , Letherwood Michael D. , Gorsich David J. , Recuero Antonio M. , Shabana Ahmed A.
Published: January 2015

This paper discusses fundamental issues related to the integration of computer aided design and analysis (I-CAD-A) by introducing a new class of ideal compliant joints that account for the distributed inertia and elasticity. The absolute nodal coordinate formulation (ANCF) degrees of freedom are used in order to capture modes of deformation that cannot be captured using existing formulations. The ideal compliant joints developed can be formulated, for the most part, using linear algebraic equations, allowing for the elimination of the dependent variables at a preprocessing stage, thereby significantly reducing the problem dimension and array storage needed. Furthermore, the constraint equations are automatically satisfied at the position, velocity, and acceleration levels. When using the proposed approach to model large scale chain systems, differences in computational efficiency between the augmented formulation and the recursive methods are eliminated, and the CPU times resulting from the use of the two formulations become similar regardless of the complexity of the system. The elimination of the joint constraint equations and the associated dependent variables also contribute to the solution of a fundamental singularity problem encountered in the analysis of closed loop chains and mechanisms by eliminating the need to repeatedly change the chain or mechanism independent coordinates. It is shown that the concept of the knot multiplicity used in computational geometry methods, such as B-spline and NURBS (Non-Uniform Rational B-Spline), to control the degree of continuity at the breakpoints is not suited for the formulation of many ideal compliant joints. As explained in this paper, this issue is closely related to the inability of B-spline and NURBS to model structural discontinuities. Another contribution of this paper is demonstrating that large deformation ANCF finite elements can be effective, in some MBS application, in solving small deformation problems. This is demonstrated using a heavily constrained tracked vehicle with flexible link chains. Without using the proposed approach, modeling such a complex system with flexible links can be very challenging. The analysis presented in this paper also demonstrates that adding significant model details does not necessarily imply increasing the complexity of the MBS algorithm.
Enhanced Running Using a Jet Pack
Authors: Kerestes Jason , Sugar Thomas G.
Published: January 2015

A Jet Pack was designed to augment the physical ability of a person running. The Jet Pack is a light weight back pack style device that produces a forward and upward thrust propelling the user forward. The external force is produced by two variable speed, electric ducted fans, which unlike other running assistive devices, allows for completely unrestricted movement as the device does not connect to the user’s joints or leg segments. The Jet Pack has shown successful running augmentation by significantly increasing a runner’s overall speed while decreasing their heart rate in 200 meter time trials as well as 1 mile time trials when comparing running with the device versus running with no device.
Effect of Expert Data Variability in the Change Prediction Method
Authors: Von Hagel Kayla A. , Ferguson Scott M.
Published: January 2015

The Change Prediction Method is an approach that has been proposed in the literature as a way to assess the risk of change propagation. This approach requires experts to define the elements of the design structure matrix and provide both impact and likelihood values for each subsystem interaction. The combined risk values produced by the Change Prediction Method indicate where high probabilities of propagation may exist, but the results rely heavily on the supplied expert data. This study explores how potential variability in expert data impacts the rank order of returned risk values from the Change Prediction Method. Results are presented that indicate significant changes in rank order, highlighting both the importance of expert data accuracy and the insights that can be gained from the Change Prediction Method as a design tool.
Crowd-Sourcing the Evaluation of Creativity in Conceptual Design: A Pilot Study
Authors: Green Matthew , Seepersad Carolyn Conner , Hölttä-Otto Katja
Published: January 2015

Creativity is often considered to be a critical aspect of engineering innovation and successful product design. Many methods have been proposed for enhancing creativity, originality, and innovation. When these methods are tested, the experiment often generates large numbers of concepts that must be evaluated by experts in a time-consuming process. Similarly, the increased use of crowd-sourcing for generating concepts often leads to a plethora of alternatives that must be evaluated. Accordingly, engineering design practitioners and researchers alike often find themselves evaluating large numbers of concepts. In this paper, the feasibility of using non-experts to evaluate engineering creativity is investigated. Dozens of students at two universities are asked to rate the originality of several different solutions to a design problem, for which validated expert ratings are available. Results indicate that it is possible to extract expert-level ratings from the non-expert student raters by focusing on the student raters with excellent inter-rater agreement amongst themselves and by training the students with example problems prior to the rating exercise. These results suggest that it may be possible to evaluate originality reliably with a large set of novice raters, perhaps with a Mechanical Turk type of approach.
Developing CAD/CAM Techniques for Machining Unexpanded Honeycomb Core
Authors: Yip-Hoi Derek
Published: January 2015

Composites parts manufacture is an increasingly important part of aerospace production. A wide range of techniques are in practice for fabricating composite structures. Structural fillers are commonly used, one of these being honeycomb core. In addition to providing the structural strength and stiffness, they also contribute to reducing weight and can impart other desirable properties such noise and vibration damping, and the ability to absorb impacts from equipment failure. When the shape of the core needs to be accurately controlled, it is fixtured in its expanded form and machined using 5-axis routers with specialized cutters. For large parts such as wing edges or helicopter rotor blades, this requires machines with larger tables to accommodate the size of the work piece. There are definite capital equipment savings, operation and maintenance savings, floor space reductions and possibly machining time reductions to be achieved by machining core in its unexpanded form, when it occupies a fraction of the expanded length. This is difficult to do for all but the simplest surfaces because of challenges predicting and controlling excess material and gouging of the part. The paper motivates the development of CAD/CAM techniques for this domain by introducing approaches for modeling the collapsed core of a part from its expanded form. It further investigates the machining errors that can occur from tool paths generated by common CAM systems using NC verification technology.
3D Reconstruction of the Left Ventricle From Four Echocardiographic Projections
Authors: Rajan Navaneetha Krishnan , Song Zeying , Hoffmann Kenneth R. , Belohlavek Marek , McMahon Eileen M. , Borazjani Iman
Published: January 2015

The left ventricle (LV) of a human heart receives oxygenated blood from the lungs and pumps it throughout the body via the aortic valve. Characterizing the LV geometry, its motion, and the ventricular flow is critical in assessing the heart’s health. An automated method has been developed in this work to generate a three-dimensional (3D) model of the LV from multiple-axis echocardiography (echo). Image data from three long-axis sections and a basal section is processed to compute spatial nodes on the LV surface. The generated surfaces are output in a standard format such that it can be imported into the curvilinear-immersed boundary (CURVIB) framework for numerical simulation of the flow inside the LV. The 3D LV model can be used for better understanding of the ventricular motion and the simulation framework provides a powerful tool for studying left ventricular flows on a patient specific basis. Future work would incorporate data from additional cross-sectional images.
MBS Motion Equation Without Explicit Definition of Body-Fixed Reference Frames
Authors: Müller Andreas
Published: January 2015

Any description of rigid body motions requires body-fixed RFRs since the latter kinematically represent the bodies and are necessary to define their inertia properties. Consequently there is no formulation without RFR. Nevertheless this does not necessarily mean that the definition of body-fixed RFRs is an indispensable step in MBS modeling.

A formulation without body-fixed reference frames is one that does not involve explicit definition of body-fixed frames to express the kinematics and the inertia data of an MBS. In this paper a formulation is presented that only requires a single spatial inertial frame to model all kinematic and dynamic properties of the MBS. It only requires the joint kinematics (axis and position vector) as well as the inertia tensors w.r.t. the spatial inertial frame in a reference configuration the MBS. That is, the inertia tensors of all rigid bodies are expressed w.r.t. a virtual body-fixed references frame that coincides with the spatial inertia frame in the reference configuration.

Avoiding the explicit introduction of body-fixed reference frames significantly simplifies the MBS modeling. This is not only beneficial for manual modeling but also gives rise to much simpler MBS codes. The approach is discussed for tree-topology MBS as well as for closed loop systems. It is demonstrated for a planar slider-crank examples.
Development of a 3-Spring Pseudo Rigid Body Model of Compliant Joints for Robotic Applications
Authors: Venkiteswaran Venkatasubramanian Kalpathy , Su Hai-Jun
Published: January 2015

Compliant mechanisms achieve motion utilizing deformation of elastic members. However, analysis of compliant mechanisms for large deflections remains a significant challenge. In this paper, we will develop a 3-spring pseudo-rigid-body model for 2D beams that are often used in compliant joints in robots. First, we utilize the Timoshenko beam theory to calculate the tip deflection for a large range of loading conditions. An optimization process is then carried out to calculate the values of the parameters of the PRB model. The errors in the model will be analyzed and compared to the beam model. An example based on a robotic grasper finger is provided to demonstrate how the model can be used in analysis of such a system. This model will provide a much simpler approach for the analysis of compliant robotic mechanisms.
Effects of Bearings and Housing on Mode Localization of a Nearly Cyclic Symmetric System
Authors: Chen Y. F. , Shen I. Y.
Published: January 2015

This paper is to study how flexible bearings and housing affect mode localization of a nearly cyclic symmetric system with mistune. A finite element analysis is first conducted on a reference system that consists of a circular disk and 24 blades with mistune. The disk is annular with an inner rim and an outer rim. A fixed boundary condition is imposed at the inner rim, while the 24 blades with mistune are evenly attached to the outer rim and subjected to a free boundary condition. As a result of the mistune, the reference system presents 26 localized torsional modes as well as 24 localized in-plane modes in its blade vibration. When the fixed inner rim is replaced by a bearing support (i.e., an elastic boundary condition), not only the localized torsional modes can change their natural frequencies and mode shapes but also the number of the localized torsional modes may be increased to 28 in some range of bearing stiffness. Similarly, when the bladed-disk reference system is mounted on a stationary housing via a bearing support, the number of the localized in-plane modes can change from 24 to 33 modes. Moreover, localized mode shapes change significantly, and some of them involve significant housing deformation. To understand this phenomenon theoretically, we first demonstrate that the presence of bearing and housing provides additional degrees of freedom, which, in turn, allow the bladed-disk system to have additional disk modes. When the bearing and housing stiffness is properly tuned, some of these additional disk modes may possess significant torsional or in-plane displacement components in the blades. If these additional modes happen to have a natural frequency that is close to those of the localized modes of the reference system, these additional modes will join the localized modes to form new localized modes. As a result, the number of localized modes increases and the mode shapes change significantly.
Torsional Vibration Analysis of Multiple Driving Mode Hybrid Bus Drivetrain
Authors: Tehrani Mohammad Gerami , Sopanen Jussi
Published: January 2015

Several hybrid electric driveline topologies have been introduced for vehicles in order to reduce emissions and improve energy efficiency in the transportation sector. This study introduces a novel configuration for a hybrid electric bus driveline. The designed driveline is capable of operating in pure electric, series and parallel hybrid modes. The torsional vibration analysis of the proposed drivetrain is performed for different driving mode configurations. The finite element method is applied to solve the torsional natural frequencies and mode shapes of the driveline. The model contains mass-elastic data of drive shafts, a diesel engine, a permanent magnet generator and a traction motor, as well as clutches and couplings. Different modelling strategies are discussed, and a sensitivity analysis is performed in order to determine the effect of different modelling parameters on the system’s torsional frequencies and mode shapes. Different excitation frequencies arising from the diesel engine and electric drives are identified and compared to the natural frequencies.
Chrono::Render: A Graphical Visualization Pipeline for Multibody Dynamics Simulations
Authors: Kaczmarek Daniel , Bartholomew Aaron , Gutierrez Felipe , Mazhar Hammad , Negrut Dan
Published: January 2015

This paper describes a web-enabled tool capable of generating high quality videos and images from multibody dynamics simulation results. This tool, called Chrono::Render, uses the Blender modeling software as the front end with Pixars RenderMan used to create high quality images. Blender is a free and open source tool used to create and visualize 3D content and provides a robust plugin framework which Chrono::Render leverages. To produce the final image, the Blender front end passes data to a RenderMan compliant rendering engine. Along with Pixars PhotoRealistic RenderMan (PRMan), several open source options such as Aqsis, JrMan, or Pixie can be used. Preprocessing is performed on the client side, where the front end generates a work order for the RenderMan compliant rendering engine to process. This work order, which contains several scripts that define the visualization parameters, along with the pre-processed simulation data and other user-defined geometry assets is uploaded to a remote server hosted by the Simulation Based Engineering Lab. This server contains more than a thousand CPU cores used for high performance computing applications, which can be used to render many frames of an animation in parallel. Chrono::Render is free and open source software released under a BSD3 license.
A Confidence-Based Adaptive Sampling Approach for Dynamic Reliability Analysis
Authors: Wang Zequn , Wang Pingfeng
Published: January 2015

Dynamic reliability is defined as the probability that an engineered system successfully performs the predefined functionality over a certain period of time considering time-variant operation condition and component deterioration. In practice, it is still a major challenge to conduce dynamic reliability analysis due to the prohibitively high computational costs. In this study, a confidence-based meta-modeling approach is proposed for efficient sensitivity-free dynamic reliability analysis, referred to as double-loop adaptive sampling (DLAS). In DLAS a Gaussian process (GP) model is constructed to approximate extreme system responses over time, so that Monte Carlo simulation (MCS) can be employed directly to estimate dynamic reliability. A qualitative confidence measure is proposed to evaluate the accuracy of dynamic reliability estimation while using the MCS approach based on developed GP models. To improve the confidence, a double-loop adaptive sampling scheme is developed to efficiently update the GP model in a sequential manner, by considering system input variables and time concurrently in double sampling loops. The model updating process can be terminated once the user defined confidence target is satisfied. The DLAS approach does not require computationally expensive sensitivity analysis, thus substantially improves the efficiency of dynamic reliability assessment. Two case studies are used to demonstrate the effectiveness of DLAS for dynamic reliability analysis.
A Self-Cognizant Dynamic System Approach for Health Management: Lithium-Ion Battery Case Study
Authors: Bai Guangxing , Wang Pingfeng
Published: January 2015

Safe and reliable operation of lithium-ion batteries as major energy storage devices is of vital importance, as unexpected battery failures could result in enormous economic and societal losses. Accurate estimation of the state-of-charge (SoC) and state-of-health (SoH) for an operating battery system, as a critical task for battery health management, greatly depends on the validity and generalizability of battery models. Due to the variability and uncertainties involved in battery design, manufacturing, and operation, developing a generally applicable battery physical model is a big challenge. To eliminate the dependency of SoC and SoH estimation on battery physical models, this paper presents a generic self-cognizant dynamic system approach for lithium-ion battery health management, which integrates an artificial neural network (ANN) with a dual extended Kalman filter (DEKF) algorithm. The ANN is trained offline to model the battery terminal voltages to be used by the DEKF. With the trained ANN, the DEKF algorithm is then employed online for SoC and SoH estimation, where voltage outputs from the trained ANN model are used in DEKF state-space equations to replace the battery physical model. Experimental results are used to demonstrate the effectiveness of the developed self-cognizant dynamic system approach for battery health management.
Multi-Scale, Heterogeneous CAD Representation for Metal Alloy Microstructures
Authors: Rosen David W.
Published: January 2015

Most heterogeneous CAD representations in the literature represent materials using a volume fraction vector, which may not by physically realizable or meaningful. In contrast, the multi-scale, heterogeneous CAD representation presented here models materials using their microstructure. For the specific metal alloys of interest in this work, the material model is a probabilistic model of grain characteristics, represented as cumulative distribution functions. Several microstructure reconstruction algorithms are presented that enable different alloy grain structures to be reconstructed in a part model. Reconstructions can be performed at any desired size scale, illustrating the multi-scale capability of the representation. A part rendering algorithm is presented for displaying parts with their material microstructures. The multi-scale, heterogeneous CAD representation is demonstrated on two Inconel alloys and is shown to be capable of faithfully reconstructing part representations consistent with the probabilistic grain models.
Parallel Strategy of FMBEM for 3D Elastostatics and its GPU Implementation Using CUDA
Authors: Xia Zhaohui , Wang Qifu , Huang Yunbao , Yixiong Wei , Yingjun Wang
Published: January 2015

Finite Element Method (FEM1) is pervasively used in most of 3D product design analysis, in which Computer Aided Design (CAD) models need to be converted in to mesh models first and then enriched with some material features and boundary conditions data, etc. The interaction between CAD models and FEM models is intensive. Boundary Element Method (BEM) has been expected to be advantageous in large-scale problems in recent years owing to its reduction of the dimensionality and its reduced complexity in mesh generation. However, the BEM application has so far been limited to relatively small problems due to the memory and computational complexity for matrix buildup are O(N2). The fast multipole BEM (FMBEM) combined with BEM and fast multipole method (FMM) can overcome the defect of the traditional BEM, and provides an effective method to solve the large-scale problem. Combining GPU parallel computing with FMBEM can further improve its efficiency significantly. Based on the three-dimensional elastic mechanics problems, the parallelisms of the multipole moment (ME), multipole moment to multipole moment (M2M) translation, multipole moment to local expansion (M2L) translation, local expansion to local expansion (L2L) translation and near-field direct calculation were analyzed respectively according to the characteristics of the FMM, and the parallel strategies under CUDA were presented in this paper. Three main major parts are included herein: (1) FMBEM theory in 3D elastostatics, (2) the parallel FMBEM algorithm using CUDA, and (3) comparison the GPU parallel FMBEM with BEM, FEM and FMBEM respectively by engineering examples. Numerical example results show the 3D elastostatics GPU FMBEM not only can speed up the boundary element calculation process, but also save memory which can be effective to solve the large-scale engineering problems.
Investigating the Use of Large-Scale Immersive Computing Environments in Collaborative Design
Authors: Rosenberg Meisha , Vance Judy M.
Published: January 2015

Successful collaborative design requires in-depth communication between experts from different disciplines. Many design decisions are made based on a shared mental model and understanding of key features and functions before the first prototype is built. Large-Scale Immersive Computing Environments (LSICEs) provide the opportunity for teams of experts to view and interact with 3D CAD models using natural human motions to explore potential design configurations. This paper presents the results of a class exercise where student design teams used an LSICE to examine their design ideas and make decisions during the design process. The goal of this research is to gain an understanding of (1) whether the decisions made by the students are improved by full-scale visualizations of their designs in LSICEs, (2) how the use of LSICEs affect the communication of students with collaborators and clients, and (3) how the interaction methods provided in LSICEs affect the design process. The results of this research indicate that the use of LSICEs improves communication among design team members.
Image Matching Assessment of Attainable Topology via Kriging-Interpolated Level-Sets
Authors: Guirguis David , Aly Mohamed , Hamza Karim , Hegazi Hesham
Published: January 2015

Level-set methods are domain classification techniques that are gaining popularity in the recent years for structural topology optimization. Level sets classify a domain into two or more categories (such as material and void) by examining the value of a scalar level-set function (LSF) defined in the entire design domain. In most level-set formulations, a large number of design variables, or degrees of freedom is used to define the LSF, which implicitly defines the structure. The large number of design variables makes non-gradient optimization techniques all but ineffective. Kriging-interpolated level sets (KLS) on the other hand are formulated with an objective to enable non-gradient optimization by defining the design variables as the LSF values at few select locations (knot points) and using a Kriging model to interpolate the LSF in the rest of the design domain. A downside of concern when adopting KLS, is that using too few knot points may limit the capability to represent complex shapes, while using too many knot points may cause difficulty for non-gradient optimization. This paper presents a study of the effect of number and layout of the knot points in KLS on the capability to represent complex topologies in single and multi-component structures. Image matching error metrics are employed to assess the degree of mismatch between target topologies and those best-attainable via KLS. Results are presented in a catalogue-style in order to facilitate appropriate selection of knot-points by designers wishing to apply KLS for topology optimization.
Simulation Based Machine Learning for Fault Detection in Complex Systems Using the Functional Failure Identification and Propagation Framework
Authors: Papakonstantinou Nikolaos , Proper Scott , O’Halloran Bryan , Tumer Irem Y.
Published: January 2015

Fault detection and identification in mechatronic systems with complex interdependencies between subsystems is a very active research area. Various alternative quantitative and qualitative methods have been proposed in the literature for fault identification on industrial processes, making it difficult for researchers and industrial practitioners to choose a method for their application. The Functional Failure Identification and Propagation (FFIP) framework has been proposed in past research for risk assessment of early complex system designs. FFIP is a versatile framework which has been extended in prior work to automatically evaluate sets of alternative system designs, perform sensitivity analysis, and event trees generation from critical event scenario simulation results. This paper’s contribution is an FFIP extension, used to generate the training and testing data sets needed to develop fault detection systems based on data driven machine learning methods. The methodology is illustrated with a case study of a generic nuclear power plant where a fault or the location of a fault within the system is identified. Two fault detection methods are compared, based on an artificial neural network and a decision tree. The case study results show that the decision tree was more meaningful as a model and had better detection accuracy (97% success in identification of fault location).
A Nonlinear Constraint Formulation for Direct and Inverse Vehicle Dynamics Modelling
Authors: Jarzębowska Elżbieta M. , Vantsevich Vladimir V.
Published: January 2015

The paper presents an analysis of holonomic and non-holonomic material/non-material constrains that may be used in wheeled vehicle dynamics. Based on this analysis, a modified approach to the formulation of vehicle motion constraints is proposed. Specifically, a non-material constraint that limits vehicle kinematic parameters to a required motion, i.e. to a programmable motion that corresponds to required vehicle operational properties including turnability and stability of motion, is introduced.

The new concept of constraints put upon wheeled vehicle dynamics makes the resulting direct and inverse dynamic models more oriented towards required vehicle performance and facilitate the control design. The new constraint concept is illustrated by an example of a required vehicle acceleration performance.
Dynamics of a System of Two Coupled Oscillators Which are Driven by a Third Oscillator
Authors: Lazarus Lauren , Rand Richard
Published: January 2015

Analytical and numerical methods are applied to a pair of coupled nonidentical phase-only oscillators, where each is driven by the same independent third oscillator. The presence of numerous bifurcation curves defines parameter regions with 2, 4, or 6 solutions corresponding to phase locking. In all cases, only one solution is stable. Elsewhere, phase locking to the driver does not occur, but the average frequencies of the drifting oscillators are in the ratio of m:n. These behaviors are shown analytically to exist in the case of no coupling, and are identified using numerical integration when coupling is included.