bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Study of an Acoustic System Coupled to a Nonlinear Membrane Under Multi-Frequency Forcing
Authors: Bellizzi Sergio , Côte Renaud , Pachebat Marc
Published: February 2014

In this paper, an experimental study of the coupling of a 2 degree-of-freedom acoustic medium to a nonlinear visco-elastic membrane under multi-frequency forcing is presented. When the excitation is sinusoidal, we observe classical results: non-linear effects tend to damp pressure in the linear system. When the excitation is quasi-periodic with two frequencies, various aspects of quasi-periodic regimes are observed. Some regimes exhibit only the two excitation frequencies in their spectrum, other display a more complicated, but mostly discrete, spectrum. These stable quasi-periodic regimes can disappear leaving to Strongly Modulated Quasi-Periodic Responses (SMQPR). Various structures have been extracted from SMQPRs using signal processing tools (RMS analysis, Fourier analysis, histogram analysis). They are compared with theory and the NES efficiency is assessed. The system behaves in general as expected: the periodic, quasi-periodic or SMQPR regimes correspond to theoretical findings.
Measurement of Damping due to Bolted Joints
Authors: Goyder Hugh , Ind Philip , Brown Daniel
Published: February 2014

The damping of a structure assembled from subsystems (a built-up structure) is commonly assumed to be due to frictional effects in the joints. This paper attempts to investigate this hypothesis. A built-up beam with 10 bolted links and a plate with 27 bolts were tested. The procedure was to measure the damping and then remove a link or a bolt and then to repeat the measurement and remove a further link or bolt. This continued until all the links or bolts were removed. If the hypothesis is correct an analysis of the data was expected to show a correlation between the number of bolts and the damping. No such simple correlation was evident. One possibility is that the effect of joint damping is smaller than the effect of other sources of damping such as material damping. Other possibilities are also discussed.
Closed Form Expressions for Higher Derivatives of Screw Systems
Authors: Müller Andreas
Published: February 2014

A central element in the kinematic analysis is the determination of partial derivatives of the twist of a member in a serial kinematic chain with respect to the joint parameters (angles, translations). This requires partial derivatives of the screw system, generated by a given ordered set of joint screws. While the closed form expression of first and second order derivatives are widely known in terms of screw products, and even the derivatives up to fifth order have been reported, a general closed form expression for derivatives of arbitrary order remained an open issue. Such a closed form expression of partial derivatives of the joint screws for any order is reported in this paper. The final result for the n-th partial derivative involves n-fold nested Lie bracket (screw products) of the joint screws. The crucial observation that gives rise to the closed form expression is that the derivative is given as a sum of terms with complementary joint index ranges.
A Z-Score-Based Method to Synthesize Anthropometric Datasets for Global User Populations
Authors: Nadadur Gopal , Parkinson Matthew B.
Published: February 2014

Globalized marketplaces are necessitating the consideration of the needs of users from a variety of national and international regions. Relevant body dimensions are known to play a key role in influencing users’ physical interactions with products. The main challenge in designing these products is the unavailability of comprehensive anthropometric databases for detailed analyses and decision-making. This paper presents a new method to this end. Z-scores are computed for each body measure of every individual in a reference population; this can be any population for which a comprehensive database is available. Next, descriptive statistical information (e.g., means, standard deviations, by-percentile values) from numerous studies and surveys are used to estimate distributions of the required body dimensions. Finally, the z-score values from the reference population are utilized to sample from the aforementioned distributions in order to synthesize the requisite virtual target population of users. The z-score method is demonstrated in the context of two existing populations: U.S. military in the late 1980s (ANSUR) and Japanese youth from the early 1990s. Despite certain stated limitations, which are topics of future work in this line of research, the method is shown to be accurate, easy-to-apply, and robust in terms of underlying assumptions.
A Model-Based and Simulation Driven Design Approach for Haptic Devices
Authors: Ahmad Aftab , Andersson Kjell , Sellgren Ulf
Published: February 2014

The output from a design process of high precision and reliable haptic devices for surgical training like bones and teeth is a complex design. The complexity is largely due to the multi-criteria and conflicting character of the functional requirements. These requirements include high stiffness, large workspace, high manipulability, small inertia, low friction, and high transparency. The requirements are a basis for generating design concepts. The concept evaluation relies to a large extent on a systematic usage of kinematic, dynamic, stiffness, and friction models. The design process can benefit from a model-based and simulation driven approach, where one starts from an abstract top-level model that is extended via stepwise refinements and design space exploration into a complete realization of the system. Such an approach is presented and evaluated through a test case where a haptic device, based on a Stewart platform, has been designed and realized. It can be concluded, based on simulation and experimental results that the performance of this optimally designed haptic device satisfies the stated user requirements. This indicates that the methodology can support the development of an optimal haptic device. However, more test cases are needed to further verify the presented methodology.
A Simple Multibody Dynamic Model of Cross-Country Ski-Skating
Authors: Bruzzo John , Schwab A. L. , Mikkola Aki , Ohtonen Olli , Linnamo Vesa
Published: February 2014

The purpose of this paper is to present the development of a simple multibody dynamic model matching the observed movements of the center of mass of a skier performing the skating technique in cross-country skiing. The formulation of the equation of motion was made using the Euler–Lagrange equations applied to a multibody tree-type system in three dimensions. The description of the lower limb of the skier and the ski was completed by employing three bodies, one representing the ski, and two representing the natural movements of the leg of the skier. This simple model is able to show an approximation of the movement of the center of mass of the skier and its velocity behavior allowing to study the effect of the key parameters used to build the model.
Gear Noise Diagnosis System for Automobile Transmission Using Artificial Intelligence (Effect of Number of Intermediate Layers on Judgement Performance)
Authors: Nakamura Morimasa , Nishiyama Masahiko , Moriwaki Ichiro
Published: February 2014

The present paper describes a digitizing method for the measured gear noise and a construction of a neural network system for gear noise diagnosis.

Gear noise emitted from automobile transmissions should be evaluated by gear noise experts. Although quietness performance estimates from measured noise levels of the transmissions on some production lines, the estimation must be very difficult. There is not a certain relationship between the measured noise levels and the evaluations by the gear noise experts. Therefore, the estimation should be severe. As a result, such an automatic gear noise diagnosis system must yield transmissions with over-quality.

The present study deals with a new gear noise diagnosis system to which an artificial intelligence, that is, a neural network system is applied. The previous evaluations by the new gear noise diagnosis system were good when the statistical property of the teacher signals from which the neural network system learned was similar to that of population. This fact means that many teacher signals are necessary on the practical use.

Proposed digitizing method of gear noise levels provided good evaluations of neural network system even when the statistical properties of the teacher signals were not similar to that of the population. In addition, a new method, “Moment method” for determining the construction of the neural network system was introduced instead of “Back Propagation Method”. The Moment Method contributed to the improvement of the system judgments.

The neural network system constructed using the Moment Method brought good performance. And the number of intermediate layers in the neural network system could be small enough to obtain good performance. It was found that the Moment method provided good learning because of connecting weights update function. When the Moment method was used for determining the connection weights between neurons in the neural network system, the developed gear noise diagnosis system achieved high and stable correct answer ratio. And the number of intermediate layers in the neural network system was only one enough for obtaining good performance of the system. Four intermediate layers, which was the maximum in this paper, did not provide much good performance.
Experimental Assessment of the Clique Problem in FlexRay
Authors: Horauer Martin , Schuster Harald , Balog Peter
Published: February 2014

The FlexRay bus protocol recently adopted by the automotive industry provides both a time- and event-triggered communication paradigm, combined with communication via two independent channels, as well as optional bus-guardians in order to meet the bandwidth and reliability requirements by present and future emerging automotive applications.

Despite the benefits and improvements, when compared to traditional bus systems (e.g., CAN), rare faults may still occur. In this regard, this paper presents an experimental investigation of the clique problem, where a FlexRay network gets partitioned into multiple functional domains. In such a scenario the nodes within a domain may still be able to communicate with each other, however, not across domain boundaries. As a result affected applications that rely on information from nodes of either domain may be impaired in their intended functionality as long as such a clique exists. Such an impairment affecting critical applications like the braking system may result in hazardous situations.
Numerical Computation of Nonlinear Normal Modes of Nonconservative Systems
Authors: Renson L. , Kerschen G.
Published: February 2014

Since linear modal analysis fails in the presence of non-linear dynamical phenomena, the concept of nonlinear normal modes (NNMs) was introduced with the aim of providing a rigorous generalization of linear normal modes to nonlinear systems. Initially defined as periodic solutions, numerical techniques such as the continuation of periodic solutions were used to compute NNMs. Because these methods are limited to conservative systems, the present study targets the computation of NNMs for non-conservative systems. Their definition as invariant manifolds in phase space is considered.

Specifically, the partial differential equations governing the manifold geometry are considered as transport equations and an adequate finite element technique is proposed to solve them. The method is first demonstrated on a conservative nonlinear beam and the results are compared to standard continuation techniques. Then, linear damping is introduced in the system and the applicability of the method is demonstrated.
Hobbing of Bevel and Hypoid Gears
Authors: Dooner David B.
Published: February 2014

The paper presents a hyperboloidal hob cutter similar to a cylindrical hob cutter used to fabricate spur and helical gear elements today. This hyperboloidal cutter can be used to manufacture bevel and hypoid gear elements using an existing CNC hobbing machine. These bevel and hypoid gear elements can be either spur or spiral. This hyperboloidal hob cutter is entirely different from the circular face cutters today as part of face hobbing. A brief overview of the existing circular face cutting technology is presented along with some of its geometric limitations. Subsequently, concepts of the hyperboloidal hob cutter are presented. These concepts include crossed hyperboloidal gears, cutter spiral angle, invariant speed relations, and cutter coordinates. Two illustrative examples are presented to demonstrate the concept of the hyperboloidal hob cutter. The first example is a spur bevel gear pair and the second example is a spiral hypoid gear pair. Virtual models of the cutter in mesh with the gear elements are presented.
State-Dependent Delay Influenced Drill String Dynamics and Stability Analysis
Authors: Liu Xianbo , Vlajic Nicholas , Long Xinhua , Meng Guang , Balachandran Balakumar
Published: February 2014

In this paper, the authors present a discrete system model to study the coupled axial-torsional dynamics of a drill string. In this model, nonlinearities such as dry friction, loss of contact, and state-dependent time delay are taken into consideration. Simulations are carried out by using a 32-segment model with 128 states. Bit bounce is observed through time histories of axial vibrations, while stick-slip phenomenon is noted in the torsion response. The normal strain contours of this spatial-temporal system demonstrate the existence of strain wave propagation along the drill string. The shear strain wave shows the wave node and wave loop along the drill string, which indicates that the torsion motion has the properties of a standing wave. By varying the penetration rate, qualitative changes are observed in the system response, which includes chaotic and hyperchaotic behavior. Stability analysis shows a stable region for the degenerated one-segment model, while the stable region becomes infinitesimally small, as the resolution of spatial discretization is increased. This finding suggests the drill string motions are always likely to be self-exited in practical drilling operations.
Computerized Systematic Approach to Fault Tree Analysis Based on Quantity Dimension Indexing
Authors: Murakami Tamotsu , Ishii Toshiyuki
Published: February 2014

Fault tree analysis (FTA) is an effective method of ensuring the security and safety of the product by identifying all the possible causes of the problem and fixing them. However, it is not easy for a designer to construct a complete fault tree about various physical phenomena without any misunderstanding or oversight, and some computerized method of managing (i.e., storing, searching and utilizing) knowledge about FTA is needed. To solve the problem, the authors have proposed and studied a method and software tool for knowledge management of FTA based on quantity dimension indexing as a design knowledge management method to avoid ambiguity of literal expression about physical phenomena. In the previous method and software, however, fault values of quantities were limited as just above- and below-normal, and dynamic phenomena such as oscillation could not be described. In this paper, the authors introduce a systematically classified definition of fault values as above/below normal, one-side/both-sides, constant/varying, monotonic/non-monotonic and sudden/gradual, and expand the computerized systematic approach to FTA. Feasibility of the method was examined by applying it to fault tree examples made in a company.
Improving Overlapping Between Testing and Design in Engineering Product Development Processes
Authors: Tahera Khadija , Earl Chris , Eckert Claudia
Published: February 2014

Testing components, prototypes and products comprise essential, but time consuming activities throughout the product development process particularly for complex iteratively designed products. To reduce product development time, testing and design processes are often overlapped. A key research question is how this overlapping can be planned and managed to minimise risks and costs. The first part of this research study investigates how a case study company plans testing and design processes and how they manage these overlaps. The second part of the study proposes a significant modification to the existing process configuration for design and testing, which explicitly identifies virtual testing, that is an extension to Computer Aided Engineering which mirrors the testing process through product modelling and simulation, as a distinct and significant activity used to (a) enhance and (b) replace some physical tests. The analysis shows how virtual testing can mediate information flows between overlapping (re)design and physical tests. The effects of virtual testing to support overlap of test and (re)design is analysed for the development phases of diesel engine design at a case study company. We assess the costs and risks of overlaps and their amelioration through targeted virtual testing. Finally, using the analysis of the complex interactions between (re)design, physical and virtual testing, and the scope for replacing physical with virtual testing is examined.
Analysis of Influence Factors of Virtual Human Real-Time Driven Accuracy and its Optimization in Virtual Reality Environment
Authors: Qiu Shiguang , Jing Xu , Fan Xiumin , He Qichang , Wu Dianliang
Published: February 2014

In the case that a real operator drives a virtual human in real-time using the motion capture method and performs complex products assembling and disassembling simulation, a very high driven accuracy is needed to meet the quality requirements of interactivity and simulation results. In order to improve the driven accuracy in virtual reality environment, a method is put forward which analyzes the influence factors of virtual human real-time driven accuracy and optimize the factors. A systematical analysis of factors affecting the accuracy is given. The factors can be sorted into hardware factors and software factors. We find out that the software factors are the main ones affecting the accuracy, and it is very hard to analyse their influence separately. Therefore, we take the virtual human kinematic system as a fuzzy system and improve the real-time driven accuracy using an optimization method. Firstly, a real-time driven model is built on dynamic constraints and body joint rotation information and supports personalized human driven. Secondly, a function is established to describe the driven error during interactive operations in the virtual environment. Then, based on the principle of minimum cumulative error, we establish an optimization model with a specified optimization zone and constraints set according to the standard Chinese adult dimensions. Next, the model is solved using genetic algorithm to get the best virtual human segment dimensions matching the real operator. Lastly, the method is verified with an example of auto engine virtual assembly. The result shows that the method can improve the driven accuracy effectively.
A Hybrid Energy-Efficient Itinerary Planning for Mobile Agents in Wireless Sensor Networks
Authors: Chou Yu-Cheng
Published: February 2014

Wireless sensor networks (WSNs) are limited to resources including computing power, storage capacity, and especially energy supply. Thus, energy consumption of sensor nodes has become a dominant performance index for a WSN. In addition, data transmission between sensor nodes is a main energy consumer of WSNs. This paper presents a method called immune genetic algorithm based multiple-mobile-agent itinerary planning (IGA-M2IP) that addresses issues of energy consumption in large-scale WSNs. The IGA-M2IP preserves a GA’s advantages, and further improves a GA’s efficiency by restraining possible degenerative phenomena during the evolutionary process.
Integration of Realtime Finite Element Analysis and Haptic Feedback for Hands-On Learning of the Mechanical Behavior of Materials
Authors: Ferrise Francesco , Bordegoni Monica , Fiorentino Michele , Uva Antonio E.
Published: February 2014

The paper describes a novel application of real-time finite element analysis controlled by a haptic device. The user can impose displacement constraints to a virtual structure using a probe and sense in real-time the response in terms of forces on her/his hand. In addition, conventional color map results are visualized on a desktop monitor. The application has been developed with the aim of simplifying the teaching of the mechanical behavior of materials in engineering schools by transforming the learning phase into an enactive process. A set of examples commonly used in the mechanical engineering courses have been implemented and tested. The paper describes and discusses the system implementation, the potentialities and the issues of such approach.
Homography-Based Low-Cost Gaze Estimation and its Application to the Usability Assessment of Digital Prototypes of Information Appliances
Authors: Kanai Satoshi , Date Hiroaki
Published: February 2014

Recently 3D digital prototypes of information appliances have been proposed for efficient user acceptance tests of user-interface (UI) usability. The purpose of this research is to develop a gaze estimation system based on Homography and to fully integrate it with a 3D digital prototype of the information appliances in order to obtain information more useful for usability assessment. The estimation system consists only of four infrared LEDs and a USB camera and is low-cost. The gaze estimation enables the system not only to record a gaze point on the prototype but to identify the UI objects which the user is looking for in real time during the test session. A gaze-based index was newly introduced to identify the misleading UI objects and to quantify the irrelevance of the UI design. A case study suggested that the integration of the gaze estimation with the 3D digital prototype and the proposed index were useful for automatically identifying which irrelevant UI objects misled the users’ operations which could not yet be captured in previous simple event logging of the user inputs.
Three Dimensional Bushing Element Based on the Absolute Nodal Coordinate Formulation
Authors: Mohamed Abdel-Nasser A. , Liu Jeff
Published: February 2014

In addition to the load transmission, the rubber bushings play an important role in the noise and vibration reduction. This paper presents a new three dimensional bushing element based on the absolute nodal coordinate formulation (ANCF). This element is used to simulate the torsional and axial bushing stiffness between two fully parameterized ANCF nodes. Tangent frame of reference is used to define local coordinates at each node. Rodrigues’ formula is used to define the angle and the axis of rotation between the two coordinates. Linear relationship, between the bushing forces and the relative deflections between the coordinates attached to the two ANCF nodes, is assumed. The numerical implementation of the proposed ANCF bushing element is validated by comparing with the expected results.
Design Tool for Prediction of Thermal Synchronous Instability
Authors: Kirk R. Gordon , Guo Zenglin
Published: February 2014

The investigation of thermal synchronous instability has been active since the mid 1990’s and the number of machines experiencing this type of instability continues to rise. The initial design threshold speed criteria was developed and compared to available case studies during 1998–2001. Further advances were made from 2002–2007 in the prediction of the bearing journal thermal hot spot in addition to improved pre and post processing capability. These improvements made the design tool more useful for prediction of thermal synchronous instability for shaft overhangs. More recent work reported in 2011, extended the theory to treat rotor center-span instability, but the interest in shaft overhang instability is still dominant from a practical view. This paper will document a new threshold speed criteria being used in a modified design tool that is considered to be more realistic for a wider range of operating speed conditions. The paper will discuss the improved threshold criteria and illustrate why it is a more reliable design tool.
A Decision Support Approach for Modeling Sustainability Consequences in an Aerospace Value Chain
Authors: Hallstedt Sophie , Thompson Anthony W. , Isaksson Ola , Larsson Tobias C. , Ny Henrik
Published: February 2014

Next generation jet engine technologies are typically driven by performance, value and environmental challenges, and appropriate technologies are developed in international research programs. One on-going engine component technology project at an aerospace component manufacturer aims to develop an engine with less fuel consumption. A likely consequence is higher pressure in the core engine, which leads to higher temperature. One way to handle the higher temperature is using a more advanced Ti-alloy for the product component, which will render a different sustainability profile. One weakness in current decision situations is the inability to clarify and understand the “value” and “sustainability” implications compared to e.g. performance features of concepts. Both “value” and “sustainability” include a rich set of features important for successful introduction of new products and product-service solutions to the market. The purpose with this research is to provide decision support for companies in early development phases for assessment of value and sustainability consequences over product-service system lifecycles.

A workshop was held with the aerospace component manufacturer and a value chain partner focusing on material handling, to: i) get a better understanding of activities, flows and ownership related to the studied materials at the two companies, ii) to understand the companies’ perspective at new suggested scenarios with regard to these materials, and iii) define relevant scenarios to look into more in depth from a sustainability and value perspective. Three different scenarios were developed with differences in ownership, responsibilities and value streams. It is therefore essential to be able to quickly assess and optimize consequences of such alternative scenarios.

Based on the workshop experiences and scenarios, a modeling and simulation approach to assess sustainability and value consequences for the scenarios is proposed. The sustainability consequences are based on a sustainability life cycle assessment and a risk assessment. Key features of the proposed tool include: consideration of the time dimension, societal sustainability consequences, risk assessment, company value assessment, and cost/revenue perspectives.
Unified Inverse Dynamics of Variable Topologies of a Metamorphic Parallel Mechanism Using Screw Theory
Authors: Gan Dongming , Dias Jorge , Seneviratne Lakmal D.
Published: February 2014

This paper presents the topology variation of a 3(rT)PS metamorphic parallel mechanism which can change its mobility from 3 to 6. The reconfiguration stems from a reconfigurable (rT)PS limb of which the two phases can be unified by taking one as a special case of the other. Based on this, unified inverse kinematics is solved and a unified dynamics modeling is built using screw theory which naturally represents the geometric constraint and actuation forces in the same manner. The obtained modeling covers all the topologies of the parallel mechanism. A numerical example demonstrates the theoretical results which provide basis for this metamorphic parallel robot with applications in reconfiguration-required environment.
A Comparative Study of Friction Estimation and Compensation Using Extended, Iterated, Hybrid, and Unscented Kalman Filters
Authors: Ahmad Aftab , Andersson Kjell , Sellgren Ulf
Published: February 2014

Transparency is a key performance evaluation criterion for haptic devices, which describes how realistically the haptic force/torque feedback is mimicked from a virtual environment or in case of master-slave haptic device. Transparency in haptic devices is affected by disturbance forces like friction between moving parts. An accurate estimate of friction forces for observer based compensation requires estimation techniques, which are computationally efficient and gives reduced error between measured and estimated friction. In this work different estimation techniques based on Kalman filter, such as Extended Kalman filter (EKF), Iterated Extended Kalman filter (IEKF), Hybrid extended Kalman filter (HEKF) and Unscented Kalman filter (UKF) are investigated with the purpose to find which estimation technique that gives the most efficient and realistic compensation using online estimation. The friction observer is based on a newly developed friction smooth generalized Maxwell slip model (S-GMS). Each studied estimation technique is demonstrated by numerical and experimental simulation of sinusoidal position tracking experiments. The performances of the system are quantified with the normalized root mean-square error (NRMSE) and the computation time. The results from comparative analyses suggest that friction estimation and compensation based on Iterated Extended Kalman filter both gives a reduced tracking error and computational advantages compared to EKF, HEKF, UKF, as well as with no friction compensation.
Bi-State Bifurcation Control of a Shaped-Comb Parametric Resonator
Authors: Guo Congzhong , Fedder Gary K.
Published: February 2014

This work employs behavioral modeling to develop a bi-state control technique capable of servoing at the onset of the microelectromechanical parametric resonant bifurcation setpoint. The parametric resonance features a sharp “turn-on” in oscillation amplitude at the bifurcation, enhancing sensitivity to resonance frequency change. A bi-state controller is constructed to servo at this sharp jump point. It has two states of operation: one state is within the instability tongue where the oscillation amplitude builds up exponentially; another state resides outside of the tongue where the oscillation turns off. The rapid turn on and off of the parametric resonance keeps the resonant amplitude small and circumvents the slow build-up time. Both the simulated and experimental loop transient responses are presented.
Does an Experiential Based Project Improve Design Education?
Authors: Hodges Timothy M. , Sullivan Gerald A.
Published: February 2014

Students of engineering can significantly improve their comprehension of the theoretical and mathematical topics of design education if they are coupled with hands-on design and build projects. In this paper, several projects are discussed that are used to promote experiential learning in the Design of Mechanical Systems course. Projects implemented include natural frequency analysis of a cantilever beam and a buckling analysis. Each of the projects utilize a paradigm in which computational methods are used to reinforce analytical findings presented in class, followed by a design challenge for which students are required to design, build and then experimentally validate the performance of the design. The design challenge is structured such that analytical results give insight as to what features of the design could be changed to get the intended result, but, require the use of computational tools like ANSYS to obtain solutions due to the complex geometries involved. Once the design is complete, students fabricate it in the machine shop and then experimentally measure how closely the performance of their design came to the intended goals of the design challenge. Preliminary results indicate that students prefer these types of lab projects and that the retention of concepts covered with experiential project based labs is actually better than the retention of concepts observed in conventional labs.
Towards Multiphysics Modeling of Chlorine Dilution
Authors: Iliopoulos Athanasios , Michopoulos John G. , DeGiorgi Virginia
Published: February 2014

Electrodes of Impressed Current Cathodic Protection systems used to inhibit corrosion of ship hulls, are areas where Chlorine is produced. It has been observed that certain concentrations of such oxidants can lead to the reduction or even reversal of the accumulation of biological fouling on ship hulls. In this paper a multiphysics modeling and simulation framework of such a process is developed and applied for a typical electrolytic cell. The framework is based on a coupled chemical reaction – electric currents – convection – diffusion and electromigration model aiming at providing transient solutions of the Chlorine species concentration in the volume of the cell. Finite element analysis results are presented for the relevant partial differential equations of the spatio-temporal evolution of the involved species and current density for the geometry of the electrolytic cell.
Accuracy Analysis and Validation of the Mars Science Laboratory (MSL) Robotic Arm
Authors: Collins Curtis L. , Robinson Matthew L.
Published: February 2014

The Mars Science Laboratory (MSL) Curiosity Rover is currently exploring the surface of Mars with a suite of tools and instruments mounted to the end of a five degree-of-freedom robotic arm. To verify and meet a set of end-to-end system level accuracy requirements, a detailed positioning uncertainty model of the arm was developed and exercised over the arm operational workspace. Error sources at each link in the arm kinematic chain were estimated and their effects propagated to the tool frames. A rigorous test and measurement program was developed and implemented to collect data to characterize and calibrate the kinematic and stiffness parameters of the arm. Numerous absolute and relative accuracy and repeatability requirements were validated with a combination of analysis and test data extrapolated to the Mars gravity and thermal environment. Initial results of arm accuracy and repeatability on Mars demonstrate the effectiveness of the modeling and test program as the rover continues to explore the foothills of Mount Sharp.
Reducing Gear Windage Losses From High Speed Gears and Applying These Principles to Actual Running Hardware
Authors: Winfree Don D.
Published: February 2014

Windage losses in gearboxes account for a large portion of the total power loss in high-speed drive trains. Very little actual data has been collected specifically quantifying these losses. Traditional techniques to measure the effects of baffles in high speed gearing applications have been done by trial and error on very complex systems. This trial and error technique is used throughout the gearing industry to solve problems without isolating each individual gear windage effect. These solutions are usually sub-optimum. They cause time-consuming delays and cost overruns in many programs. This paper describes two gear baffle test rigs that were built to quantify and minimize the gear windage losses in high-speed drive trains. The intent of the first gearbox baffle test rig was to isolate and measure the windage effects on a single high-speed bevel gear with various baffle configurations. The results of these tests were used to define a basic set of ground rules for designing baffles. This set of ground rules was then applied to another rig replicating the F-35 Liftfan gear box configuration. Immediate benefits were seen. Without this work Lockheed Martin’s X-35 STOVL aircraft would not have been able to operate.
A Lookup Table-Based Approach for Spatial Analysis of Contact Problems
Authors: Machado Maria Margarida , Flores Paulo , Ambrósio Jorge
Published: February 2014

The aim of this work is to present an efficient methodology to deal with general 3D-contact problems. This approach embraces three steps: geometrical definition of 3D-surfaces; detection of the candidate contact points; evaluation of the contact forces. The 3D-contact surfaces are generated and represented by using parametric functions due to their simplicity and easiness to handle freeform shapes. This task is carried in preprocessing, performed preliminarily to the implementation of the multibody code. The preprocessing procedure can be condensed into four steps: a regular and representative surface collection of points is extracted from the 3D-parametric surface; for each point the tangent vectors to the u and v directions of the parametric surface and the normal vector are computed; the geometrical information on each point is saved in a lookup table, including the parametric point coordinates, the corresponding Cartesian coordinates and the Cartesian components of the normal, tangent and binormal vectors; the lookup table is rearranged such that the u-v mapping is converted into a 3D-matrix form. In the last step, the surface data is saved as a direct access file. Regarding the detection of the contact points, the relative distance between the candidate contact points are computed and used to check if the bodies are in contact. The actual contact points are selected as those that correspond to the maximum relative indentation. The contact forces are determined as functions of the indentation, impact velocity and geometric and material properties of the contacting surfaces. In general, lookup tables are used to reduce the computation time in dynamic simulations. However, the application of these schemes involves an increase of memory needs. Within the proposed approach, the amount of memory used is significantly reduced, as a result of a partial upload into memory of the lookup table. A slider-crank mechanism with a cup on the top of the slider and a marble ball is used as demonstrative example. A contact pair is considered between a cup and a marble ball, being the contact forces computed using a dissipative contact model.
Design of Hybrid-Electric Vehicle Architectures Using Auto-Generation of Feasible Driving Modes
Authors: Bayrak Alparslan Emrah , Ren Yi , Papalambros Panos Y.
Published: February 2014

Several hybrid-electric vehicle architectures have been commercialized to serve different categories of vehicles and driving conditions. Such architectures can be optimally controlled by switching among driving modes, namely, the power distribution schemes in their planetary gear (PG) transmissions, in order to operate the vehicle in the most efficient regions of engine and motor maps. This paper proposes a systematic way to identify the optimal architecture for a given vehicle drive cycle, rather than parametrically optimizing one or more pre-selected architectures. An automatic generator of feasible driving modes for a given number of PGs is developed. For a powertrain consisting of one engine, two motors and two PGs, this generator results in 1116 modes. A heuristic search is then proposed to find a near-optimal pair of modes for a given driving cycle and vehicle specification. In a study this process identifies a dual-mode architecture with an 8% improvement in fuel economy compared to a commercially available architecture over a standard drive cycle.
Topology Optimization of Fluid Channels Using Generative Graph Grammars
Authors: Hooshmand Amir , Campbell Matthew I.
Published: February 2014

This paper presents a new technique for topology optimization of fluid channels using generative design methods. The proposed method uses the generative abilities of graph grammars with simulation and analysis power of conventional CFD methods. The graph grammar interpreter GraphSynth is used to carry out graph transformations, which define different topologies for a given multi-inlet multi-outlet problem. The generated graphs are first transformed into meaningful 3D shapes. These solutions are then analyzed by a CFD solver to find the optimum. The effectiveness of the proposed method is checked by solving a variety of available test problems and comparing them with those found in the literature. Furthermore by solving complex problems the robustness and effectiveness of the method is tested.
A Scalable Preference Elicitation Algorithm Using Group Generalized Binary Search
Authors: Ren Yi , Scott Clayton , Papalambros Panos Y.
Published: February 2014

We examine the problem of eliciting the most preferred designs of a user from a finite set of designs through iterative pairwise comparisons presented to the user. The key challenge is to select proper queries (i.e., presentations of design pairs to the user) in order to minimize the number of queries. Previous work formulated elicitation as a blackbox optimization problem with comparison (binary) outputs, and a heuristic search algorithm similar to Efficient Global Optimization (EGO) was used to solve it. In this paper, we propose a query algorithm that minimizes the expected number of queries directly, assuming that designs are embedded in a known space and user preference is a linear function of design variables. Besides its theoretical foundation, the proposed algorithm shows empirical performance better than the EGO search algorithm in both simulated and real-user experiments. A novel approximation scheme is also introduced to alleviate the scalability issue of the proposed algorithm, making it tractable for a large number of design variables or of candidate designs.
Heterogeneous Tissue Layer Deformation With Haptic Feedback
Authors: Vaughan Neil , Dubey Venketesh N. , Wee Michael Y. K. , Isaacs Richard
Published: February 2014

A volumetric graphics model of deformable human tissue with layers of varying stiffness was developed. The model uses spring-mass-damper to calculate haptic force feedback from various layers of tissue. A haptic epidural needle insertion simulation is developed with real-time tissue deformation when external forces are exerted. Voxelization is used to fill surface meshes with grids of spring-mass-damper assemblies. The modeled tissues include all the layers traversed during an epidural procedure, including skin, subcutaneous fat, Supraspinous and interspinous ligaments, ligamentum flavum and the epidural space. Tissue is modeled with volumetric information describing the stiffness and density of each layer. Spring-mass-damper modeling enables the calculation of compression and extension of springs between tissue masses, to simulate tissue stretching and relaxation movement. A haptic force feedback device is used to interact with the tissue model with a virtual needle. The resulting simulation gives a different feeling for each tissue layer. The haptic device allows the user to insert a needle though the modeled tissue layers feeling the various physical properties of each tissue layer during needle insertion. Tissues can be viewed in cross-section to see the progress and depth of the needle. Force feedback graphs were produced to compare the force from the operator’s thumb to the resultant force feedback from the device.
A Framework for Adaptive Multibody Modeling of Biopolymers
Authors: Khan Imad M. , Poursina Mohammad , Laflin Jeremy , Anderson Kurt
Published: February 2014

Due to the challenges involved with modeling complex molecular systems, it is essential that computationally intelligent schemes be produced that put the computational effort where and when it is needed to capture important phenomena, and maintain needed accuracy at minimum costs. In this work, we investigate and propose some key issues for the adaptive modeling and simulation of the dynamic behavior of highly complex multiscale processes. This is accomplished through the appropriate use of an adaptive hybridization of existing, newly developed, and proposed advanced multibody dynamics algorithms and modeling strategies for forward dynamic simulation. The adaptive multiscale simulation technique discussed here benefits from the highly parallelizable structure of the divide and conquer (DCA) framework for modeling multibody systems. These algorithms include Flexible Divide and Conquer Algorithm (FDCA), Orthogonal Complement Divide-and-Conquer Algorithm (ODCA) and generalized momentum approaches for modeling discontinuous changes in the system. These algorithms permits a large complex molecule (or systems of molecules) to be seamlessly treated using a hierarchy of reduced order models ranging from atomistic to the continuum scale.
Diagnostics of Rolling Element Bearings for the Traction System of High Speed Trains: Experimental Evidences
Authors: Chatterton S. , Pennacchi P. , Ricci R. , Borghesani P.
Published: February 2014

Monitoring of the integrity of rolling element bearings in the traction system of high speed trains is a fundamental operation in order to avoid catastrophic failures and to implement effective condition-based maintenance strategies. Diagnostics of rolling element bearings is usually based on vibration signal analysis by means of suitable signal processing techniques. The experimental validation of such techniques has been traditionally performed by means of laboratory tests on artificially damaged bearings, while their actual effectiveness in industrial applications, particularly in the field of rail transport, remains scarcely investigated. This paper will address the diagnostics of bearings taken from the service after a long term operation on a high speed train. These worn bearings have been installed on a test-rig, consisting of a complete full-scale traction system of a high speed train, able to reproduce the effects of wheel-track interaction and bogie-wheelset dynamics. The results of the experimental campaign show that suitable signal processing techniques are able to diagnose bearing failures even in this harsh and noisy application. Moreover, the most suitable location of the sensors on the traction system is also proposed.
A Cable-Driven Grasping Mechanism With Lock/Unlock Constraints
Authors: Abyaneh Soroush , Saber Omid , Zohoor Hassan
Published: February 2014

The application of manipulators is becoming more and more popular in object handling especially when it is desired to have access to remote areas in destructive or hazardous taskspaces. For this purpose, a hand-like mechanism must be designed to be used as an end-effector, which can grasp objects. In this paper a cable driven grasping mechanism has been presented. In the proposed mechanism each finger consists of three phalanxes which are actuated by a single motor. Locking and unlocking constraints are used in the mechanism in order to generate an anthropomorphic motion, in which, the order of reaching phalanxes to the object is sequential. In this way, each phalanx starts moving toward the object when the previous phalanx had already made its contact. The gripping motion of the mechanism has been classified into five steps according to each phalanx’s status as being locked or unlocked. For each step, dynamics equations are derived involving kinematic parameters of the mechanism as well as the tension in the cables. Finally a numerical example is provided to obtain tensions in the gripper cables.
A Probabilistic Graphical Model for Evaluating Variable Energy Consumption During the Use Stage of a Product’s Lifecycle
Authors: Telenko Cassandra , Seepersad Carolyn
Published: February 2014

Although energy consumption during use can cause a majority of a product’s environmental impact, the relationship between a product’s usage context and its environmental performance is rarely considered in design evaluations. Probabilistic graphical models (PGMs) provide the capability of evaluating uncertainty and variability of product use in addition to correlating the results with aspects of the usage context. This research demonstrates a method for representing the usage context as a PGM through the use of a lightweight vehicle design example. The demonstration PGM is constructed from factors such as driver behavior, alternative driving schedules, and residential density, which are related to local conditional probability distributions derived from publicly available data sources. Unique scenarios are then assembled from sets of conditions on these factors to provide insight into sources of variance in lifetime energy use. The vehicle example demonstrates that implementation of realistic usage scenarios via a PGM can provide a much higher fidelity investigation of energy savings during use than commonly found in the literature and that distinct scenarios can have significantly different implications for the effectiveness of lightweight vehicle designs.