bluuebunny/crossref_metadata_2025 huggingface dataset:
SLAM Using 3D Reconstruction via a Visual RGB and RGB-D Sensory Input
Authors: Wurdemann Helge A. , Georgiou Evangelos , Cui Lei , Dai Jian S.
Published: June 2012

This paper investigates simultaneous localization and mapping (SLAM) problem by exploiting the Microsoft Kinect™ sensor array and an autonomous mobile robot capable of self-localization. The combination of them covers the major features of SLAM including mapping, sensing, locating, and modeling. The Kinect™ sensor array provides a dual camera output of RGB, using a CMOS camera, and RGB-D, using a depth camera. The sensors will be mounted on the KCLBOT, an autonomous nonholonomic two wheel maneuverable mobile robot. The mobile robot platform has the ability to self-localize and preform navigation maneuvers to traverse to set target points using intelligent processes. The target point for this operation is a fixed coordinate position, which will be the goal for the mobile robot to reach, taking into consideration the obstacles in the environment which will be represented in a 3D spatial model. Extracting the images from the sensor after a calibration routine, a 3D reconstruction of the traversable environment is produced for the mobile robot to navigate. Using the constructed 3D model the autonomous mobile robot follows a polynomial-based nonholonomic trajectory with obstacle avoidance. The experimental results demonstrate the cost effectiveness of this off the shelf sensor array. The results show the effectiveness to produce a 3D reconstruction of an environment and the feasibility of using the Microsoft Kinect™ sensor for mapping, sensing, locating, and modeling, that enables the implementation of SLAM on this type of platform.
A Novel Search Algorithm for Interactive Automated Conceptual Design Generator (ACDG)
Authors: Rai Rahul , Kilaru Pranay , Vallepalli Ravi , Campbell Matthew I.
Published: June 2012

Automated concept generation is non-trivial task. The complexity of this problem is mainly due to lack of formal representation frameworks that lend themselves easily to a computational approach. Generative grammar has emerged as a potential solution to this problem and presents a number of different possibilities for conceptual design automation. This paper presents a novel search method that has been developed specifically for search trees defined by a special class of generative grammar in which rules of the grammar have parameters associated with them. A novel feature of the proposed search is ‘Human in the loop’ approach in which learning about the search space is achieved by querying the user. The user fatigue restricts the maximum number of comparisons of candidate solutions (30–50). From the data gathered from the comparisons, a stochastic decision making process proposed in this paper quickly converges to a region of design space which best meet the user’s preference. The method is implemented and applied to a grammar for shampoo bottle concept generation. It is shown through multiple user-guided and automated experiments that the method has ability to learn and adopt through human computer interaction process. The implications of the proposed search method for automated conceptual design are expounded on in the conclusions.
Command Strategies for Tele-Operation of Mobile-Manipulator Systems via a Haptic Input Device
Authors: Wrock Michael R. , Nokleby Scott B.
Published: June 2012

Tele-operation of mobile-manipulator systems (MMS) is typically done by modeling both the manipulator and mobile base as a single system combined with the use of various redundancy resolution techniques to achieve coordinated motion. In this work, the Omnibot MMS is controlled by a 3-DOF (degrees-of-freedom) haptic joystick. The base is a holonomic platform having 3-DOF supporting a 3-DOF manipulator capable of position control within its workspace. By controlling the base and manipulator individually, redundancy resolution techniques are not required because the master has equal DOF to the device it is controlling at any given time. Two command strategies are proposed herein for automatic switching of control between the manipulator and base. The first command strategy is a virtual wall method that uses haptic forces to make the operator feel like they are pushing against a wall at the edge of the manipulator’s workspace, resulting in the base moving. The second command strategy is a two state approach in which each state controls a different device and switching between the two is done by breaking through the workspace limits. With the help of haptic forces, the operator has the sensation of breaking through a compliant surface when switching states. The two proposed strategies were implemented and tested on the Omnibot MMS and both subjective and objective data was used to evaluate and compare the two methods.
Towards Parallel Cable-Driven Pantographs
Authors: Perreault Simon , Cardou Philippe , Gosselin Cle´ment
Published: June 2012

We propose a new class of pantographs, i.e., of mechanisms that allow the reproduction of the displacements of an input link, the master, with an output link, the slave. The application we envision for these devices is the telemanipulation of objects from small distances, at low cost, where magnetic fields or other design constraints prohibit the use of electromechanical systems. Despite the long history of pantographs, which were invented in the 17th century, the class of pantographs proposed here is new, as it relies on parallel cable-driven mechanisms to transmit the motion. This allows the reproduction of rigid-body displacements, while previous pantographs were limited to point displacements. This important characteristic and others are described in the paper. One important challenge in the design of the proposed systems is that the cables must remain taut at all time. We address this issue by introducing nonlinear springs that passively maintain a minimum tension in the cables, while approximating static balancing of the mechanism over its workspace. Approximating static balancing allows the forces applied at the slave to reflect more accurately at the master, and vice versa. As a preliminary validation, a two-degree-of-freedom parallel cable-driven pantograph is designed. A prototype of this apparatus that does not include approximate static balancing is built, which demonstrates the working principle of these mechanisms.
Structural-Acoustic Simulations of Naval Vehicles Using an Energy Finite Element Method
Authors: Vlahopoulos Nickolas
Published: June 2012

Simulation methods can be used for meeting both the new stealth initiatives for surface ship silencing, and the stringent limits on acceptable hull vibration. Additionally, interior noise concerns must be considered due to habitability and operational readiness. The pursuit of innovative ship designs, utilization of new materials, and the increasingly demanding performance requirements, dictate a more broadly focused thrust for addressing noise and vibration issues due to multiple sources of excitation during the design process. This expanded technical view also requires that the types of tools utilized for these assessments also improve and that they can provide results within a short enough time that can affect the design cycle. An Energy Finite Element Analysis (EFEA) formulation has been developed for computing efficiently the vibration of complex vehicles and the associated radiated noise at frequencies beyond the limits of conventional finite element methods. In this paper, the main theoretical aspects of the EFEA will be presented first. Results are presented for two 1/8th scale structures representing an advanced double hull design and a conventional hull design of a surface ship. Results for the structural vibration induced on the outer bottom part of the structures are compared to available test data.
Friction Stir Welding Process Parameter Effects on Workpiece Warpage due to Residual Strains
Authors: Michopoulos John G. , Lambrakos Samuel , Iliopoulos Athanasios
Published: June 2012

An important performance measure of the quality of a weld is the permanent deformation developed during welding processes due to the thermally activated residual strains. This paper presents the results of a sensitivity analysis that determines the effects of processing parameters — such as the speed of rotation and the traveling speed of a rotating friction stir welding (FSW) tool — on the resulting residual strain fields. The problem has been modeled as a thermostructurally coupled problem via Finite Element Analysis of an elastoplastic workpiece under the influence of heat generated from the stirring process and taking into account the temperature dependent yield strength of the material. Results are presented and discussed in the context of our future plans.
Reconstruction Synthesis of the Lost Subsystem for the Planetary Motions of Antikythera Mechanism
Authors: Yan Hong-Sen , Lin Jian-Liang
Published: June 2012

The mechanism for the planetary motions contained in the lost subsystem of Antikythera mechanism is a strict challenge of the reconstruction design and attracts many scholars’ attentions. In the modern time, Edmunds and Morgan, and Wright successively presented the design concepts, even the solid reconstruction models. To focus on the study of lost mechanisms, this work provides a systematic procedure of the reconstruction design to synthesize all feasible designs describing the planetary motion in the lost subsystem. And all synthesized designs agree with the science and technology standards of the subject’s time period. Based on the kinematic analysis of the planetary theories in the time of Antikythera mechanism, the anomaly planetary motions that could be demonstrated by a pin-in-slot device are completely understood. By the mechanism analysis and the design concept with the minimum numbers of the members, two types of the feasible topological structures and the corresponding design specifications are obtained: Type 1 is a four-bar mechanism with five joints; Type 2 is a five-bar mechanism with seven joints. In addition, the relations of the teeth for the inferior and superior planets are discussed in each possible combination of the planet gears. Moreover, through the study of the historical literature, the astronomical theories and the existing designs, the required design constraints are concluded further. For Type 1 and Type 2 reconstruction designs, one, the design by Edmunds and Morgan, and three feasible designs are respectively synthesized in accordance with the concepts of generalization and specialization. And all feasible designs are identified further for the suitable planets through the identifications of the input types. In conclusion, all generated designs are consistent with the scientific theories and techniques of the subject’s time period and match the surviving evidences.
Comparison of Linear and Nonlinear Electromagnetic Coupling Models for a Linear Oscillator
Authors: Owens Benjamin A. M. , Mann Brian P.
Published: June 2012

This paper examines the modeling and behavior of two forms of electromagnetic coupling with a linear oscillator. With coupling as either a linear or a nonlinear term dependent on position, analytical results were derived and numerical simulations performed for the mechanical and electrical system response. Analytical models were found to correlate well with their respective simulations. Linear coupling showed wider power bandwidth at certain excitation levels and higher theoretical power output than nonlinear beyond an excitation threshold. Nonlinear models showed increasingly complex harmonic current response at high excitation amplitudes and increased peak power at low amplitude excitation levels for certain offset coil positions.
An Energy Approach to the Design of Single Degree of Freedom Gravity Balancers With Compliant Joints
Authors: Rijff Boaz L. , Herder Just L. , Radaelli Giuseppe
Published: June 2012

A gravity balancer is a mechanism that compensates the weight of a mass over a range of motion. When no friction is present, this gives an energy efficient mechanism and little effort is required to move an object. Conventional mechanisms have drawbacks due to the use of conventional rigid joints. Compliant joints do not have these disadvantages, can be made from fewer parts and can increase performance compared to rigid body joints. The goal of this paper is to develop a new method for the design of single degree of freedom gravity balancers where all the rigid joints are replaced with compliant joints. The method is based on connecting rigid links with compliant joints. With a constant potential energy as an objective, the method allows new gravity balancers to be designed. The second goal is to construct a demonstrator as proof of principle. It can be concluded that for the first time a gravity balancer has been constructed where all the rigid joints are replaced with compliant joints. The gravity balancer had a peak moment reduction of 93%. The presented method is extensible and allows others to understand and further develop gravity balancers with compliant joints for other applications.
A Controller Design for Flexible Multibody System by the Use of Absolute Nodal Coordinate Formulation
Authors: Sugawara Yoshiki , Kobayashi Nobuyuki
Published: June 2012

In the past decade, Absolute Nodal Coordinate Formulation (ANCF), which is kind of a finite element method, has been developed for flexible multibody systems with large deformation and large rotation. Almost all studies for ANCF are dedicated to the development of expression ability of flexible multibody system’s behaviors, for example, a study of expansion of ANCF to three dimensional beam, the improvement of computational performance for numerical analysis and so on. On the other hand, there are few studies which extract controllers from the mathematical expressions derived by ANCF. The main aim of this study is to propose a controller design procedure by the use of the mathematical expression which is derived by ANCF. A flexible beam is introduced as a controlled object and the control torque is applied to the one end of the beam. Control objective is to rotate the beam to the desired position and suppress the residual vibration of the beam. In order to derive the mathematical expression for controller design, a kind of ANCF which uses continuum mechanics approach is employed. It is shown that some assumptions and manipulations of the mathematical expression derived by that method result in the linear equation of motion with some uncertainties and the resultant equation has a form suitable for controller design based on μ synthesis framework which is one of the robust control design method. Using μ synthesis framework, controllers are derived for some design parameters and the derived controllers are applied to the controlled object. The validity of the procedure for controller design is shown by numerical simulations and the possibilities and future works of the proposed controller design procedure by the use of mathematical expression by ANCF is discussed.
Error Estimations in Linear Inverse Problems With a Priori Information
Authors: Yagola Anatoly G. , Korolev Yury M.
Published: June 2012

We consider an inverse problem for an operator equation Az = u. The exact operator A and the exact right-hand side u are unknown. Only their upper and lower estimations are available. We provide techniques of calculating upper and lower estimations for the exact solution belonging to a compact set in this case, as well as a posteriori error estimations. We obtain approximate solutions with an optimal a posteriori error estimate. We also make use of a priori information about the exact solution, e.g. its monotonicity and convexity. The developed software package was applied to solving practical ill-posed problems.
Mutual Information Based Feature Selection From Data Driven and Model Based Techniques for Fault Detection in Rolling Element Bearings
Authors: Kappaganthu Karthik , Nataraj C.
Published: June 2012

This paper proposes a novel technique combining datadriven and model-based techniques to significantly improve the performance in bearing fault diagnostics. Features that provide best classification performance for the given data are selected from a combined set of data driven and model based features. Some of the common data driven techniques from time, frequency and time-frequency domain are considered. For model based feature extraction, recently developed cross-sample entropy is used. The ranking and performance of each of these feature sets are studied, when used independently and when used together. Mutual information based technique is used for ranking and selection of the optimal feature set. Using this method, the contribution to performance and redundancy of each of the data driven features and model based features can be studied. This method can be used to design an effective diagnostic system for bearing fault detection.
A Generalized Component Mode Synthesis Approach for Multibody System Dynamics Leading to Constant Mass and Stiffness Matrices
Authors: Gerstmayr Johannes , Pechstein Astrid
Published: June 2012

A standard technique to reduce the system size of flexible multibody systems is the component mode synthesis. Selected mode shapes are used to approximate the flexible deformation of each single body numerically. Conventionally, the (small) flexible deformation is added relatively to a body-local reference frame, which results in the floating frame of reference formulation (FFRF). The coupling between large rigid body motion and small relative deformation is nonlinear, which leads to computationally expensive non-constant mass matrices and quadratic velocity vectors. In the present work, the total (absolute) displacements are directly approximated by means of mode shapes, without a splitting into rigid body motion and superimposed flexible deformation. As the main advantage of the proposed method, the mass matrix is constant, the quadratic velocity vector vanishes and the stiffness matrix is a co-rotated constant matrix. Numerical experiments show the equivalence of the proposed method to the FFRF approach.
Parallel Efficiency of Lagrange Multipliers Based Divide and Conquer Algorithm for Dynamics of Multibody Systems
Authors: Malczyk Paweł , Fra¸czek Janusz
Published: June 2012

Efficient dynamics simulations of complex multibody systems are essential in many areas of computer aided engineering and design. As parallel computing resources has become more available, researchers began to reformulate existing algorithms or to create new parallel formulations. Recent works on dynamics simulation of multibody systems include sequential recursive algorithms as well as low order, exact or iterative parallel algorithms. The first part of the paper presents an optimal order parallel algorithm for dynamics simulation of open loop chain multibody systems. The proposed method adopts a Featherstone’s divide and conquer scheme by using Lagrange multipliers approach for constraint imposition and dependent set of coordinates for the system state description. In the second part of the paper we investigate parallel efficiency measures of the proposed formulation. The performance comparisons are made on the basis of theoretical floating-point operations count. The main part of the paper is concetrated on experimental investigation performed on parallel computer using OpenMP threads. Numerical experiments confirm good overall efficiency of the formulation in case of modest parallel computing resources available and demonstrate certain computational advantages over sequential versions.
Nonlinear Bifurcation Analysis of a Robotic Arm Subject to Digital Position Control
Authors: Habib Giuseppe , Rega Giuseppe , Stepan Gabor
Published: June 2012

Precision and stability in position control of robots are critical parameters in many industrial applications where high accuracy is needed. It is well known that digital effect is destabilizing and can cause instabilities. In this paper, we analyze a single DoF system and we present the stability limits in the parameter space of the control gains. Furthermore we introduce a nonlinearity relative to the saturation of the control force in the model, reduce the dynamics of the nonlinear map to its local center manifold, study the bifurcation along the stability border and identify conditions under which a supercritical or subcritical bifurcation occurs. The obtained results explain some of the typical instabilities occurring in industrial applications. We verify the obtained results through numerical simulations.
Design Considerations for an Aeroelastic Micro-Power Generator
Authors: Bibo Amin , Li Gang , Daqaq Mohammed F.
Published: June 2012

In two recent studies [1; 2], the authors have presented the concept and the analytical modeling framework for a scalable wind micro-power generator. The device transforms wind energy into electricity via the self-excited oscillations of a piezoelectric reed embedded within a cavity. Based on the model developed in [2], this effort utilizes the Routh-Hurwitz criterion and numerical algorithms to understand the influence of the design parameters on the device’s response with the goal of minimizing the cut-on wind speed and maximizing the output power. Results indicate that, for a beam of certain design parameters, there exists an optimal chamber volume that minimizes the cut-on wind speed of the device. This optimal volume is inversely proportional to the beam’s first modal frequency. Results also indicate that the cut-on wind speed can be decreased significantly as the aperture’s width is decreased. However, due to the reduced strain rate in the piezoelectric layer, it is observed that minimizing the cut-on wind speed does not always correspond to an increase in the output power. As such, in an attempt to study the influence of the design parameters on the output power, design charts were constructed to select the optimal design parameters for a known average wind speed. Experimental results are also presented to qualitatively verify the theoretical trends.
A Unified Method for Computing Position and Orientation Workspaces of General Stewart Platforms
Authors: Bohigas Oriol , Ros Llui´s , Manubens Montserrat
Published: June 2012

The workspace of a Stewart platform is a complex six-dimensional volume embedded in the Cartesian space defined by six pose parameters. Because of its large dimension and complex shape, such workspace is difficult to compute and represent, so that comprehension on its structure is being gained by studying its three-dimensional slices. While successful methods have been given to determine the constant-orientation slice, the computation and appropriate visualization of the constant-position slice (also known as the orientation workspace) has proved to be a challenging task. This paper presents a unified method for computing both of such slices, and any other ones defined by fixing three pose parameters, on general Stewart platforms involving mechanical limits on the active and passive joints. Additional advantages over previous methods include the ability to determine all connected components of the workspace, and any motion barriers present in its interior.
Dedicated Infrastructure for Academic Courses Related to Embedded Systems Design Supporting Students in Distance Learning Programs
Authors: Balog Peter , Kramer Michael , Beneder Roman , Brejcha Philipp
Published: June 2012

According to labor market needs even fresh graduates from undergraduate programs have to have not only profound knowledge but also extensive practical experiences especially when it comes to software design for Embedded Computing Systems. Didactic approaches like problem-based learning and project-based learning with a high degree of hands-on training using state of the art hardware, software, and tools have proven to achieve this learning outcome. Even though hands-on training using industry relevant equipment works fine with full-time students, the desired practical skills have to be obtained in a different way with part-time or distance-learning students. This is because of the significantly reduced training hours at dedicated university labs. This paper focuses primarily on a concrete setup and mix of dedicated learning infrastructures (“Remote-Lab” and “Hardware/Software Co-Simulation”) suitable for courses dealing with Embedded Systems (Software) Design to support students, participating in part-time or distance-learning degree programs, in developing their required skills.
Energy Dissipation by Micro-Slip in an Assembly, Analytic and Experimental Approach
Authors: Peyret N. , Dion J.-L. , Chevallier G. , Argoul P.
Published: June 2012

In structural dynamics, the problem of damping remains the biggest challenge. This paper deals with the energy losses caused by micro-slip in a planar interface of a structure. Taking into account friction in the joints during the analysis of dynamic systems remains a complex task. This paper proposes an analytical and experimental study of flexural vibrations of a clamped-clamped beam with innovative position of the interfaces. First, the benchmark is described and the choice of the position of the interface is justified. The displacement and stress fields are defined during each phase of the loading process in the joints under the assumption of quasi static motion. The energy dissipated by friction in the interface is calculated during a loading cycle. This leads to a definition of the dissipated energy, thus, to a non linear loss factor. The dynamic response of the beam is calculated using this non linear loss factor and a dissipative force is defined and used to predict the dynamic behaviour of the structure. In the last part of the paper, we present the experimental bench, and the dynamic behaviour of this structure. We propose to illustrate the mechanism of energy losses by micro-slip by making a comparison between the behaviour of the “monolithic” beam and the sectioned beam. Finally, we confront the loss factor calculated analytically and the measured one.
On Teaching Functionality and Functional Modeling in an Engineering Curriculum
Authors: Nagel Robert L. , Bohm Matt R.
Published: June 2012

This paper reviews functional representation and modeling across multiple domains of engineering as well as function recognition and modeling in the engineering design field. Various modeling techniques are presented along with approaches to model realization published in common engineering design text books. Specifically, within the field of engineering design, seven published approaches for modeling function are presented: 1.) Glass Box Method; 2.) Function Analysis System Technique; 3.) Systematic Processes; 4.) Enumeration; 5.) Zen Approach; 6.) Reverse Engineering; and 7.) Function-Means Trees. Through discussion of the modeling approaches the authors pose questions on how function should be taught in undergraduate engineering curriculum. Finally, the potential benefits of function-based design approaches are reviewed and discussed.
Modeling Uncertainty in Through-Life Costing at the Early Design Stages: I
Authors: Saravi Mohammad , Goh Yee Mey , Newnes Linda , Mileham Antony , Morton Karen , Beedall Duncan
Published: June 2012

Estimating the Through Life Cost (TLC) of a product or service is one of the major challenges for industry. If the products involved are complex and are long-life this increases the challenge. Although industry attempts to estimate the TLC of such products as early as possible, lack of information makes it very difficult. To assist in this process uncertainty within the estimate and the estimation process is normally considered. The research presented in this paper proposes an approach for the consideration and management of the uncertainties in terms of the data and alternative scenarios. First the issue of how to deal with this uncertainty from the conceptual stage of design for different phases of product life cycle is explained. From this an approach for identifying and understanding the scenario uncertainty at each phase of the lifecycle is then presented. An industrial case study is then used to explain how to map the costing process for scenario uncertainty in different phases of product life cycle including; development, manufacturing, in-service and disposal. Finally, the next phase of the research activity is discussed.
A MATLAB-Based Application Development Using a 3D PMD Camera for a Mobile Robot
Authors: Chami Mohammad , Voos Holger
Published: June 2012

Three-dimensional sensing is a vital field in mobile robotic applications. This work proposes an application of a Time-of-Flight 3D Photonic Mixer Device (PMD) camera for the navigation of an Omni-directional mobile robot. The 3D PMD camera enables real time distance detection as well as the capturing of grayscale images. In our framework, the application of the 3D PMD camera is aimed at solving the problem of environmental perception in mobile robotics. In this paper, we present the development of a MATLAB-based kit for the control of an Omni-directional mobile robot supported by a data acquisition board. The communication interface of the camera, used to close the system’s control loop, has been also developed. We further present results of different experiments including online obstacle detection and avoidance. In addition, an adaptive pose determination for the robot is proposed.
Effects of Median Filtering on Fractional Processes
Authors: Sheng Hu , Chen YangQuan
Published: June 2012

Median filtering, an effective non-linear signal enhancement technique, has been successfully used for the suppression of impulsive noise and extracting features from noisy signals. Although median filtering can effectively preserve the sharp changes in signals, some signal distortion may be introduced and some features of signals may be lost. In this research, we investigate the effects of median filtering on fractional processes which are characterized by the heavy-tailed distribution or the long-range dependence (LRD). The effects of median filtering on heavy-tailed distribution characteristic of α-stable processes, and on LRD property of long-range dependent processes are investigated, respectively. Besides, the effects of median filtering on both the heavy tailed distribution and the LRD properties of fractional autoregressive integrated moving average (FARIMA) with stable innovations time series are studied. The analysis results show that the heavy-tailed distribution and the LRD properties of fractional processes are evidently affected by median filtering.
Resonances in an Infinitely Long Cable on a Tensionless Non-Smooth Foundation: A Numerical Analysis
Authors: Demeio L. , Lancioni G. , Lenci S.
Published: June 2012

When a semi-infinite cable resting on a bed of unilateral springs is subjected to a harmonic excitation, the motion of the touch-down-point (TDP), i.e., the point which separates the detached part of the cable from the laid part, and which is assumed to be unique in this paper, exhibits interesting resonant phenomena. These phenomena are studied numerically by means of a self-made finite element (FEM) code, and the effects of the non-linearity of the problem, such as, e.g., the bending of the resonance curves and the secondary resonances, are investigated in detail.
Development and Comparison of Shaft-Gear Models for the Computation of Gear Misalignments due to Power Transmission
Authors: Roda-Casanova Victor , Iserte-Vilar Jose L. , Sanchez-Marin Francisco , Fuentes-Aznar Alfonso , Gonzalez-Perez Ignacio
Published: June 2012

Gear misalignments cause transmission errors, the shift of the bearing contact and may reduce substantially the life of gears. Some gear misalignments are caused directly by shafts misalignments but others are mainly related with the torque transmission and shaft bending. Even for perfectly aligned gear drives, shaft bending due to power transmission causes the shifting of the bearing contact towards the edge of the gear tooth surfaces for those non-modified gear drives with theoretical lineal contact. In this paper, four different models (two based on the Bernoulli’s beam theory and two based on the finite element method) have been proposed for shaft and gear modeling in order to estimate misalignments of gears due to power transmission in a conventional spur gear transmission. The influence of transmitted torque, length of shafts and relative position of gears over the shafts on the errors of alignment has been investigated.
How Dynamic is Dynamic Walking? Human vs. Robotic Gait
Authors: Mummolo Carlotta , Kim Joo H.
Published: June 2012

For design and control of biped walking robots, it is important to quantify the different level of dynamicity. We propose the Dynamic Gait Measure (DGM) that quantifies the dynamicity of a given biped walking motion. The DGM is associated with the gait stability, and quantifies the effects of inertia in terms of the Zero-Moment Point (ZMP) and the ground projection of center of mass (GCOM). Also, DGM takes into account the stance foot dimension and the relative threshold between static and dynamic walking. Human-like and robotic walking motions are generated for a planar biped system from an optimization problem. The resulting DGMs demonstrate their dependence on the stance foot dimension as well as the walking motion. The DGM results verify the dynamic nature of normal human walking. For a given gait motion, smaller foot dimension results in increased dynamicity. Moreover, the DGMs for normal human walking are greater than those for robotic walking. The proposed results will benefit the development of walking robots.
PipeSynth: An Algorithm for Automated Topological and Parametric Design and Optimization of Pipe Networks
Authors: Patterson William R. , Campbell Matthew I.
Published: June 2012

This paper describes a design automation approach that combines various optimization research and artificial intelligence methods for synthesizing fluid networks. Unlike traditional software tools available today, this approach does not rely on having any predefined network topology to design and optimize its networks. PipeSynth generates its designs by using only desired port locations, and the desired fluid properties at each of those ports. An ideal network is found by optimizing the number and connectivity of pipes and pipe fittings, the size and length of each pipe, and the size and orientation of each fitting. A Uniform-Cost-Search is used for topology optimization along with a combination of non-gradient based optimization methods for parametric optimization. PipeSynth demonstrates how advances in automated design can enable engineers to manage much more complex fluid network problems. PipeSynth uses a unique representation of fluid networks that synthesizes and optimizes networks one pipe at a time, in three-dimensional space. PipeSynth has successfully solved several problems containing multiple interlaced networks concurrently with multiple inputs and outputs. PipeSynth shows the power of automated design and optimization in producing solutions more effectively and efficiently than traditional design approaches.
Bioreactor Improvement Based on Design for Assembly in Virtual Environments
Authors: Li Wen , Peng Qingjin , Xing Malcolm
Published: June 2012

A Bioreactor is a device used in tissue engineering to simulate the physiological environment required for cell growth, attachment, and immigration. The existing bioreactor is not user-friendly and difficult to operate. A great care has to be paid in the device application, such as assembly and disassembly in the operation. This research seeks to use design for assembly (DFA) methods to analyze and improve the design of the current bioreactor. Product difficulty levels are introduced to the DFA analysis. A new design is proposed to ease operation, save time and increase the application efficiency. The proposed solution is evaluated in a virtual environment using 3D assembly modeling and simulation.
A Function Based Approach for Product Integration
Authors: Kalyanasundaram Vishwa , Lewis Kemper
Published: June 2012

Reconfigurable and multifunctional products are breeds of products that cater to the increased diversification of customer needs. Unlike single-state static products which can perform only one primary function, these products cater to different customer needs by performing more than one function with or without changing their configuration. However, there is a lack of systematic methods to support the conceptual task of combining two existing single-state products into an integrated product that provides multiple functions. In this paper, a function based approach is proposed which provides more rigorous support to assess the feasibility of integrating two products. The function structures of the existing products are combined to obtain the overall function structure of the reconfigurable product. Function sharing, based on quantified functional similarity, is proposed and applied to identify functions that can be shared by the same component. The information obtained from the function structure is then mapped to the components of two existing products to analyze their roles in the final reconfigurable product architecture. A case study illustrates the proposed approach by analyzing the integration of a power drill and a dust buster.
Detecting Design Trends Using Perceptive Tests Based on an Interactive Genetic Algorithm
Authors: Poirson Emilie , Petiot Jean-Franc¸ois , Be´nabe`s Julien , Boivin Ludivine , Blumenthal David
Published: June 2012

To avoid flops, the control of the risks in product innovation and the reduction of the innovation cycles require valid and fast customer’s assessments. An Interactive Genetic algorithm is proposed for eliciting user’s perceptions concerning the shape of a product, in order to stimulate creativity and detecting design trends. Interactive users’ assessment tests are conducted on virtual products, for capturing and analyzing users’ responses. The IGA is interfaced with a CAD software (CATIA V5) and allows the creation in real time of a set of parameterized designs, which are presented iteratively by a graphical interface to the user for evaluation. After a description of the IGA, we present a study on the convergence of the IGA, according to the tuning parameters of the algorithm and the size of the design problem. An experiment was carried out with a set of 20 users on a particular product, table glasses. We describe the implementation of the perceptive tests and an analysis of the results. These results show how the IGA can be used to elicit user perception and detecting design trends.
On Calculation Methods and Results for Straight Cylindrical Roller Bearing Deflection, Stiffness, and Stress
Authors: Krantz Timothy L.
Published: June 2012

The purpose of this study was to assess some calculation methods for quantifying the relationships of bearing geometry, material properties, load, deflection, stiffness, and stress. The scope of the work was limited to two-dimensional modeling of straight cylindrical roller bearings. Preparations for studies of dynamic response of bearings with damaged surfaces motivated this work. Studies were selected to exercise and build confidence in the numerical tools. Three calculation methods were used in this work. Two of the methods were numerical solutions of the Hertz contact approach. The third method used was a combined finite element surface integral method. Example calculations were done for a single roller loaded between an inner and outer raceway for code verification. Next, a bearing with 13 rollers and all-steel construction was used as an example to do additional code verification, including an assessment of the leading order of accuracy of the finite element and surface integral method. Results from that study show that the method is at least first-order accurate. Those results also show that the contact grid refinement has a more significant influence on precision as compared to the finite element grid refinement. To explore the influence of material properties, the 13-roller bearing was modeled as made from Nitinol 60, a material with very different properties from steel and showing some potential for bearing applications. The codes were exercised to compare contact areas and stress levels for steel and Nitinol 60 bearings operating at equivalent power density. As a step toward modeling the dynamic response of bearings having surface damage, static analyses were completed to simulate a bearing with a spall or similar damage.
Output Only Modal Analysis of a Nonuniform Beam Experiment by Using Decomposition Methods
Authors: Caldwell Rickey A. , Feeny Brian F.
Published: June 2012

This work explores the application of reduced-order mass-weighted proper orthogonal decomposition (RMPOD), state variable modal decomposition (SVMD), and smooth orthogonal decomposition (SOD) for extracting approximations of linear normal modes (LNMs) of a free vibrating thin lightly damped nonuniform beam experiment. The application of these decomposition methods involves organizing sensed outputs into ensemble matrices. The ensemble matrices are utilized to create correlation matrices, which are used in solving an eigenvalue problem. This is realized experimentally by sensing a thin nonuniform cantilevered beam, a saw blade, with eleven equally spaced accelerometers, during free vibration. The first mode was filtered out since its frequency was below the threshold of reliable accelerometers performance. RMPOD was able to extract the second, third, and fourth mode as implied by modal assurance criterion (MAC) in a comparison with an analytical approximation of the nonuniform Euler-Bernoulli beam modes. SVMD was able to extract an approximation to the LNMs and natural frequencies for the second, third, and fourth modes. SOD was able to extract the second, third, and fourth modes and natural frequencies successfully.
Multi-Objective Optimization of a Segmented Lunar Wheel Concept
Authors: Faragalli Michele , Pasini Damiano , Radzizsewski Peter
Published: June 2012

The goal of this work is to develop a systematic method for optimizing the structural design of a segmented wheel concept to improve its operating performance. In this study, a wheel concept is parameterized into a set of size and shape design variables, and a finite element model of the wheel component is created. A multi-objective optimization problem is formulated to optimize its directional compliance and reduce stress concentrations, which has a direct affect on the efficiency, traction, rider comfort, maneuverability, and reliability of the wheel. To solve the optimization problem, a Matlab-FE simulation loop is built and a multi-objective genetic algorithm is used to find the Pareto front of optimal solutions. A trade-off design is selected which demonstrates an improvement from the original concept. Finally, recommendations will be made to apply the structural optimization framework to alternative wheel conceptual designs.
Damped Transition of a Strongly Nonlinear System of Coupled Oscillators Into a State of Continuous Resonance Scattering
Authors: Andersen David , Wang Xingyuan , Starosvetsky Yuli , Remick Kevin , Vakakis Alexander , Mane Mercedes , Hubbard Sean , Bergman Lawrence
Published: June 2012

We examine analytically and experimentally a new phenomenon of ‘continuous resonance scattering’ in an impulsively excited, two-mass oscillating system. This system consists of a grounded damped linear oscillator with a light, strongly nonlinear attachment. Previous numerical simulations revealed that for certain levels of initial excitation, the system engages in a special type of response that appears to track a solution branch formed by the so-called ‘impulsive orbits’ of this system. By this term we denote the periodic (under conditions of resonance) or quasi-periodic (under conditions of non-resonance) responses of the system when a single impulse is applied to the linear oscillator with the system being initially at rest. By varying the magnitude of the impulse we obtain a manifold of impulsive orbits in the frequency-energy plane. It appears that the considered damped system is capable of entering into a state of continuous resonance scattering, whereby it tracks the impulsive orbit manifold with decreasing energy. Through analytical treatment of the equations of motion, a direct relationship is established between the frequency of the nonlinear attachment and the amplitude of the linear oscillator response, and a prediction of the system response during continuous scattering resonance is provided. Experimental results confirm the analytical predictions.
Noise and Contact in Dynamic AFM Operations
Authors: Chakraborty Ishita , Balachandran Balakumar
Published: June 2012

In this article, the authors study the effects of Gaussian white noise on the dynamics of an atomic force microscope (AFM) cantilever operating in a dynamic mode by using a combination of numerical and analytical efforts. As a representative system, a combination of Si cantilever and HOPG sample is used. The focus of this study is on understanding the stochastic dynamics of a micro-cantilever, when the excitation frequencies are away from the first natural frequency of the system. In the previous efforts of the authors, period-doubling bifurcations close to grazing impacts have been reported for micro-cantilevers when the excitation frequency is in between the first and the second natural frequencies of the system. In the present study, it is observed that the addition of Gaussian white noise along with a harmonic excitation produces a near-grazing contact, when there was previously no contact between the tip and the sample with only the harmonic excitation. Moment evolution equations derived from a Fokker-Planck system are used to obtain numerical results, which support the statement that the addition of noise facilitates contact between the tip and the sample.
Optimization of Fixture and Joint Positions in Sheet Metal Assembly: The Effect of Fixture Numbers and Constraints
Authors: Hajikolaei Kambiz Haji , Wang G. Gary
Published: June 2012

Assembly process is widely used in the manufacturing processes. Fabrication processes such as machining, casting and metal forming are not perfect and introduce variation in the components. Variations of components and tools accumulate and cause the assembly variation. In this paper, after reviewing the literature and presenting sheet metal assembly variation analysis, an optimization method is used to minimize the assembly variation by optimizing the location of joints and fixtures. The model is constructed in ANSYS with three fixtures and two joints. When a black-box function calculated numerically in software is used as the objective function, using deterministic methods for optimization is not suitable because the deterministic methods need knowledge of the objective functions. Also, using stochastic methods such as genetic algorithm is not suitable because of the large number of function evaluations they normally need. In this paper, an optimization algorithm based on mode-pursuing sampling (MPS) method is used to minimize the assembly variation. The optimization method is explained and after implementing the method, results are presented. It is learned that, in addition to the number of fixtures, the constraints on neighboring fixture locations also affect the optimal fixture layout, as well as the final assembly stiffness and spring-back.