bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of the Impact Model on Vibration Response of Discrete and Continuous Systems
Authors: Brake M. R.
Published: September 2013

Impact is a phenomenon that is ubiquitous in mechanical design; however, the modeling of impacts in complex systems is often a simplified, imprecise process. In many high fidelity finite element simulations, the number of elements required to accurately model the constitutive properties of an impact event is impractical. As a result, rigid body dynamics with approximate representations of the impact dynamics are commonly used. These approximations can include a constant coefficient of restitution, an artificially large penalty stiffness, or a single degree of freedom constitutive model for the impact dynamics that is specific to the type of materials involved (elastic, plastic, viscoelastic, etc.). In order to understand the effect of the impact model on the system’s dynamics, simulations are conducted to investigate a single degree of freedom, two degrees of freedom, and continuous system each with rigid stops limiting the amplitude of vibration. Five contact models are considered: a coefficient of restitution method, a penalty stiffness method, two similar elastic-plastic constitutive models, and a dissimilar elastic-plastic constitutive model. Frequency sweeps show that simplified contact models can lead to incorrect assessments of the system’s dynamics and stability. In the worst case, periodic behavior can be predicted in a chaotic regime. Additionally, the choice of contact model can significantly affect the prediction of wear and damage in the system.
Conceptual Design and Modelling of a Self-Adaptive Compliant Parallel Gripper for High-Precision Manipulation
Authors: Hao Guangbo , Kong Xianwen
Published: September 2013

To meet the need of advanced compliant parallel grippers (CPGs), this paper deals with the conceptual design and modelling of a novel self-adaptive CPG for high-precision manipulation. A self-adaptive CPG is proposed by using a cymbal-type amplifier and two parallelogram modules at first. The self-adaptive grasping function ensures the mobility of one jaw if another jaw is constrained. Then the displacement amplification ratio and the force-displacement equations of the self-adaptive CPG are derived and compared with the FEA results. Finally, the variations, especially the case with a bistable mechanism as the jaw, are discussed. The self-adaptive grasping function of the proposed CPG is unique compared with the existing CPGs driven by only one linear actuator. Other good performance characteristics of the proposed self-adaptive CPG include: large-stroke, no stress-concentration, minimized parasitic rotation of the jaw, actuator isolation, and a simple and compact configuration.
Potentialities of a Light Three-Wheeled Vehicle for Sustainable Mobility
Authors: Cossalter Vittore , Doria Alberto , Ferrari Marco
Published: September 2013

Electric and hybrid vehicles with narrow track are very suited to sustainable urban mobility. A particular tilting three-wheeled vehicle has been developed at Padova University. It is composed of a tilting front module (one wheel) and a non-tilting rear module (two wheels). The lower part of the front module is connected to the upper part of the rear module by means of four revolute joints and two rockers. Therefore, the two modules of the vehicle and the two rockers make a four-bar linkage. A specific code for kinematic, dynamic and electric analysis of this vehicle has been developed, with the aim of showing the effects of linkage set-up and mass distribution on the handling and stability characteristics. Some numerical results are presented. This particular three-wheeled vehicle is well suited both to advanced electric and hybrid propulsion systems. A section of this paper shows the characteristics of an electric version for fast urban mobility, that is named E-Snake. The performances of E-Snake were assessed by means of many road tests and were confirmed when it participated in Formula Electric and Hybrid Italy: in 2008 E-Snake was the winner of its category. The last section of the paper deals with Hy-Snake, a new version of the three-wheeled vehicle for sustainable urban and sub-urban mobility. The principal feature of Hy-Snake is the series hybrid propulsion system. Some numerical results show the effectiveness of the integration between mechanical and electrical design. The propulsion system gives good performances and a proper set-up of the four-bar linkage makes the vehicle stable and easy to ride.
Geometric Mistuning Identification of Integrally Bladed Rotors Using Modified Modal Domain Analysis
Authors: Bhartiya Yasharth , Sinha Alok
Published: September 2013

Modified Modal Domain Analysis (MMDA) is a novel method for the development of a reduced-order model of a bladed rotor with geometric mistuning. This method utilizes proper orthogonal decomposition (POD) of Coordinate Measurement Machine (CMM) data on blades’ geometries, and sector analyses using ANSYS and solid modeling. In a recent paper, MMDA has been extended to use second order Taylor series approximations of perturbations in mass and stiffness matrices (δM and δK) instead of exact δM and δK. Taylor series expansions of deviations in mass and stiffness matrices due to geometric mistuning give a direct approach for generating the reduced order model from the components of POD features of spatial variations in blades’ geometries. Reversing the process, algorithms for mistuning identification based on MMDA are presented in this paper to calculate the geometric mistuning parameters. Two types of algorithm, one based on modal analyses and the other on the forced responses, are presented. The validity of these methods are then verified through a mistuned academic rotor.
Vibration Mode Structure of Cyclically Symmetric Centrifugal Pendulum Vibration Absorber Systems
Authors: Shi Chengzhi , Parker Robert G.
Published: September 2013

This work develops an analytical model of centrifugal pendulum vibration absorber systems with equally-spaced, identical absorbers and uses it to investigate the structure of the modal vibration properties. The planar model admits two translational and one rotational degree-of-freedom for the rotor and a single arclength degree-of-freedom for each absorber. The gyroscopic effects from rotor rotation are taken into account. Examination of the associated eigenvalue problem reveals well-defined structure of the vibration modes resulting from the cyclic symmetry of the absorbers. The vibration modes are classified into rotational, translational, and absorber modes. Characteristics of each mode type are analytically proved.
Toplogy Design and Optimization of Nonlinear Metamaterials
Authors: Manktelow Kevin L. , Leamy Michael J. , Ruzzene Massimo
Published: September 2013

We consider topology optimization of lumped and continuous nonlinear metamaterial systems. Structures that consist of alternating layers of material with high impedance contrast are a simple example of a continuous phononic crystal that may exhibit nonlinearity. Analysis of this system, subject to prescribed constraints, shows that optimal design for a bilayered system consists of a thin nonlinear layer. Optimal, in this context, refers to a design which maximizes the frequency shift (and thus bandgap shift) at the edge of the first Brillouin Zone for the acoustic branch. Computer simulations of this system validate the predicted dispersion behavior. Optimization of two-dimensional arrays is presented using lumped-parameter models with nonlinear spring elements. Pattern-search algorithms identify topology (discrete mass distributions) that produce large increases in complete bandgap width. The analytical expression used in calculating nonlinear frequency shifts reveals that the largest contributions to the frequency shift are primarily produced from the resonant components of the system. Optimizing continuous multidimensional unit cells using a commercial finite-element code is briefly addressed.
Multiple-Target Selective Disassembly Sequence Planning With Disassembly Sequence Structure Graphs
Authors: Smith Shana , Chen Wei-Han
Published: September 2013

Modern green products must be easy to disassemble. Selective disassembly is used to access and remove specific product components for reuse, recycling, or remanufacturing. Early related studies developed various heuristic or graph-based approaches for single-target selective disassembly. More recent research has progressed from single-target to multiple-target disassembly, but disassembly model complexity and multiple constraints, such as fastener constraints and disassembly directions, still have not been considered thoroughly. In this study, a new graph-based method using disassembly sequence structure graphs (DSSGs) was developed for multiple-target selective disassembly sequence planning. The DSSGs are built using expert rules, which eliminate unrealistic solutions and minimize graph size, which reduces searching time. Two or more DSSGs are combined into one DSSG for accessing and removing multiple target components. In addition, a genetic algorithm is used to decode graphical DSSG information into disassembly sequences and optimize the results. Using a GA to optimize results also reduces searching time and improves overall performance, with respect to finding global optimal solutions. Case studies show that the developed method can efficiently find realistic near-optimal multiple-target selective disassembly sequences for complex products.
Modeling and Identification for Rotary Geometric Errors of Five-Axis Machine Tools With R-Test Measurement
Authors: Hsu Yung-Yuan , Chang Chih-Hsiang , Tsai You-Tern
Published: September 2013

The main purpose of this study is to use an R-test measurement device to estimate the geometric location error of the axis of rotation of five-axis machine tools. The error model of CNC machine tool describes the relationship between the individual error source and its effects on the overall position errors. This study based ISO230 to construct a geometric error model used to measure errors in the five-axis machine tools for the R-test measurement device. This model was then used to reduce the five-axis geometric error model based solely on the location error of the axis of rotation. Moreover, based on the simplified model and the overall position errors measured by the R-test with path K4, the location errors of rotary axes and ball position errors can be estimated very accurately with the least square estimation method. Finally, paths K1 and K2 were used as testing paths. The results of the test showed that the model built in this study is accurate and is effective in estimating errors.
Kinematics of a Novel Single-Loop Under-Actuated Wrist
Authors: Di Gregorio Raffaele
Published: September 2013

A novel type of parallel wrist (PW) is proposed which, differently from previously presented PWs, features a single-loop architecture and only one nonholonomic constraint. Due to the presence of a nonholonomic constraint, the proposed PW type is under-actuated, that is, it is able to control the platform orientation in a three-dimensional workspace by employing only two actuated pairs, one prismatic (P) and the other revolute (R); and it cannot perform tracking tasks. Position analysis and path planning of this novel PW are studied. In particular, all the relevant position analysis problems are solved in closed form, and, based on these closed-form solutions, a path-planning algorithm is built.
Design Optimization of a 3-D Three Cable Driven Manipulator
Authors: Bahrami Arian , Aghbali Behnam , Bahrami Mansour Nikkhah
Published: September 2013

This paper presents simulation and optimization of a 3-D three cable driven manipulator. For some specific paths in the workspace volume, motions of the robot before optimization are simulated and tension in the cables and stiffness of the cable robot for various points on the paths are determined. By selecting a function which is related to the stiffness matrix of the robot and considering it as the objective function of genetic algorithm, vertical positions of the connection points on the base platform as the optimization variables for each point on the paths can be determined in a way that the related function of the robot is optimized and a tension reduction in all the cables can be observed for most of the paths. Finally, the results of using different kinds of objective functions derived from the stiffness matrix are presented for three different criteria: workspace volume, kinematic performance indices and actuating energy of the robot. The results indicate which function has the largest workspace volume with tension reduction property in all the three cables, which has the highest values for the kinematic performance indices and which has the lowest actuating energy.
Research on Mechanism Model of Fixture Location Errors Analysis
Authors: Wu Yuguang , Li C. G.
Published: September 2013

A new methodology using mechanism to model fixture location error (FLE) is proposed. Typically, there are four elements related to accumulation and propagation of FLE in workpiece-fixture system (WFS), which are machining feature, process datum, location datum and locators, and the relative position variations among them correspond to various FLEs. In this research, the four elements are treated as link mechanism components, the concatenation between location datum and locators is represented by contact pair, which is transformed to kinematic pair in equivalent mechanism, and geometry & dimension tolerances are simulated by link mechanisms. The rules mapping from FLE elements to their equivalent mechanisms are established, and by which the WFS is transformed into an equivalent mechanism model system. The method is studied that the process parameters of WFS are calculated by the structure parameters and kinematic parameters of equivalent mechanism. Thus, the solution of location error can be realized by means of the position analysis methods of mechanism.
Dependency Modeling and Model Management in Mechatronic Design
Authors: Qamar Ahsan , Paredis Christiaan J. J.
Published: September 2013

Mechatronic design is traditionally supported through domain-specific design activities throughout the product development process. The partitioning into domain-specific problems leads to a situation where product properties influence each other, hence giving rise to dependencies. These dependencies play a key role in prediction of properties and as a result, in the decision making process. The important question is: how to manage the dependencies for an efficient and effective decision making? The aim of this paper is threefold. Firstly, we investigate the nature of dependencies and study how to model them. The paper proposes appropriate language constructs taking into account synthesis and analysis nature of properties and dependencies. The concepts related to the dependency modeling are then illustrated through a simple robot design example, where the creation and importance of a dependency model are explained. Secondly, we study practical approaches for consistency management and model management in the presence of dependencies. Six levels-of-detail in modeling dependencies are presented; emphasizing that modeling at higher level-of-detail ensures that more inconsistencies are avoided. Available languages such as OMG SysML™ are evaluated for a possible creation of the dependency models leading towards executable dependency networks. However, at present, SysML does not provide sufficiently rich language constructs to model dependencies. Thirdly, we compare our dependency modeling approach to the other state-of-the-art approaches such as dependency modeling with a Design Structure Matrix, and highlight the benefits of the language constructs proposed in this paper. We aim to convince the reader that there is a substantial value in modeling dependencies explicitly, especially to avoid inconsistencies, which is not the current state of the practice. However, an overall value from dependency modeling can only be obtained if the cost of creating the dependency model is reasonable. Issues such as human interaction/effort and model management through PLM are discussed.
Characterization of Task Specific Force Systems and the Rational Selection of A-Frame Ladders
Authors: Barnett Ralph L.
Published: September 2013

Because it is inexpensive, an A-Frame ladder is routinely chosen to perform specific aerial work tasks. Presently, these death defying activities cannot be evaluated a priori using information furnished by ladder manufacturers relative to the resistance of their ladders or by trade organizations who cannot define the reasonably foreseeable load environment for various construction tasks. This paper proposes a methodology for rationally evaluating the safety of A-Frame ladders for specific overhead work tasks. A force-plate, normally used in gait testing, is used to safely support workers engaged in a specific work task. The force-plate output can be used to characterize the loading environment for a menu of important operations such as tuck pointing, painting, installation of lighting fixtures, speakers, and ceiling fans. Using statics, the loading menu may be accessed to simulate the forces applied to any ladder under any user profile. The overturning resistance of A-Frame ladders must be established by testing; static stability calculations are unconservative. When the loading environment associated with the installation of a typical ductwork detail was compared to the resistance of a special duty A-Frame ladder, the applied forces sometimes exceeded its lateral resistance. This is consistent with our field experience involving six death cases of sheet metal workers.
Role of Combined Thermo-Mechanical Loading on the Nonlinear Response of a Skin Panel
Authors: Ling Yu , Shukla Amit
Published: September 2013

The goal of this paper is to understand transient dynamics of an aero-structure under combined loading. In this study, a nonlinear finite element model of a representative panel is used to evaluate the effect of combined thermal and mechanical loading on nonlinear response with specific focus on severe aerodynamic heating and fluctuating pressure. This results in nonlinear response behavior including thermal buckling, snap-through and snap-buckling. A snap-through boundary is presented in the space of combined loading parameters. Relationship between the frequency of snap-through and loading magnitude is also discussed. Some observations are presented on transient behavior as well as the asymmetric response. It is demonstrated that boundary conditions can be utilized to enhance the design of such structural panels.
A Robust Technique for Lumped Parameter Inverse Boundary Value Problems
Authors: Venkataraman P.
Published: September 2013

A natural approach to the inverse coupled nonlinear lumped parameter problem is to use a continuous approximation of the data and its derivatives using Bezier functions. The method is robust and does not need regularization or other transformation to convert the inverse problem to a well-posed one. The Bezier function technique first identifies continuous Bezier functions to represent the measured data using a recursive Bezier filter. These Bezier functions also provide information on the derivatives of the functions over the range of the independent variable. This is used in two ways. First, the residuals of the differential equations now depend on the distributed parameters alone. Second, the boundary conditions for a reduced range of the independent variable are easily generated. The lumped parameters are determined through two applications of standard unconstrained optimization. The first application identifies the parameters by minimizing the sum of the least squared error in the residuals over the range of the data. This also provides a robust initial guess for the second optimization. In the second optimization, the parameters are determined once again using a collocation technique to integrate the solution and reduce the sum of the absolute error with respect to the smooth representation of the data. Fluid flow in a long vertical channel with fluid injection is used to illustrate the procedure. The measured data is simulated using random perturbations about the smooth solution to the forward problem. The results show that the Bezier function technique can identify a solution even with severe perturbations in the data. It is also shown that using the information from a clipped region can lead to a well-posed problem.
An Overview on Continuous Contact Force Models for Multibody Dynamics
Authors: Flores Paulo , Lankarani Hamid M.
Published: September 2013

The nature of the constitutive contact force law utilized to describe contact-impact events plays a crucial role in predicting the dynamic response of multibody systems. The main goal of this work is present a survey of the literature on the most relevant penalty-force based approaches for multibody dynamic simulations. In this process, the fundamental characteristics of the purely elastic and the dissipative contact force models are analyzed, namely the models which have been developed based on the Hertz contact law. In particular, the different models are compared in this study for a simple impact problem for the sole purpose of comparison of the models and examining their validity compared to those from experiments. Results obtained for a classical ball impact on a massive surface are presented and used to discuss the main assumptions and procedures associated with the different penalty-force approaches. The force models are found to be quite well representative of the contact forces in an impact, and that they can be applied for the analysis of impact in more complex systems a such as the ones in planar and spatial multibody mechanical systems.
A Pilot Study of Engineering Design-Decision Methods in Practice
Authors: Nichols Aaron , Olewnik Andrew
Published: September 2013

Numerous engineering design-decision methods have been developed to assist groups of engineers in making choices within a design problem. However, while there are a variety of methods to choose from, there is no empirical data that exhibits which decision-method is best for specific phases of the design process, or that designers are willing to adopt particular decision methods. Due to this lack of empirical data, industry may not use certain engineering design methods since they do not have the resources or time to investigate which method would work best for them. This work presents the development of a framework to examine various engineering design-decision methods in practice. The framework is used in a pilot study with undergraduate engineering students which compares usage of Pugh’s Controlled Convergence (PuCC) and the Group Hypothetical Equivalent and Inequivalent Method (G-HEIM) to the results of an “informal” method (a group decision that is made without a formalized decision method). Results of the pilot study include documenting the emergence of decision “traps” within each group, assessing student perceptions about using formalized design-decision methods through interviews and surveys (critical to understanding potential barriers to adoption of formal methods), and insight into where formal decision methods are most appropriate within a design process. Finally, a number of changes and additions to the framework and study protocol are identified for future work focused on repeating the study with more participants and potentially in industrial settings.
Design of a 2 DOF Prosthetic Ankle Using Coupled Compliance to Increase Ankle Torque
Authors: Huang Shuguang , Schimmels Joseph M.
Published: September 2013

Current passive prosthetic ankles are lighter, simpler, and less expensive than powered prosthetic ankles. These current passive designs, however, do not provide adequate torque at the instant when it is needed to propel the body forward. This paper presents a novel 2 degree of freedom (DOF) passive compliant prosthetic ankle that uses a network of conventional springs. One DOF allows the lower leg component to compress when the weight of the amputee is applied during walking. The second DOF allows rotation about the prosthetic ankle joint. The force generated along the leg during walking is converted into ankle torque used to propel the body forward during push-off. An optimization routine is used to select the stiffness values and connection locations of the springs used in the compliant mechanism. The optimization yields a design that generates a torque-deflection profile that is very similar to that of a natural ankle. The mechanism demonstrates apparent active behavior (negative spring constant) at the ankle during push-off without using active components.
An Approach Toward Developing Metrics to Predict Performance and Creativity of Final Products in Project-Based Design Class
Authors: Takai Shun , Midha Ashok , Esterman Marcos
Published: September 2013

This paper investigates metrics to predict performance and creativity of final products at the early stages of product design, i.e., at concept selection and proof-of-concept (POC) prototyping. Three deliverables (concept sketches, POC prototypes, and final products) in a project-based design class are evaluated using Creative Product Semantic Scale (CPSS). Then, CPSS scores are analyzed using correlation analysis to find CPSS of concept sketches or POC prototypes that significantly correlate with CPSS or performance of final products. The preliminary results of this paper indicate that CPSS subscales may be used to predict performance and creativity of final products; that the earlier the stage of the design process is, the more difficult it is to predict performance of final products; and that building fully-functional prototypes is important to test performance of design concepts.
Disassembly Sequence Planning for Product Maintenance
Authors: Luo Yongtao , Peng Qingjin
Published: September 2013

Environmental and sustainable issues have brought more and more attention to industries in product design and manufacturing. It is important for a product to meet its lifecycle requirements in repairing, replacing and recycling. Disassembly is required in product maintenance and recycling. An efficient disassembly plan can reduce the cost of product maintenance and minimize the product repair time. This paper introduces an efficient method for selective disassembly planning for the need of product maintenance and recycling to reduce the product operation time and cost. The method is based on an efficient product representation and effective sequence searching. It considers the product structure, removing direction of components, operation constraints and complex in the product representation and sequencing planning. An example is used to verify the proposed method. Challenges and further work are also discussed.
Aligning Operational Decisions to Enterprise Objectives Through a Dynamic Enterprise Architecture Approach
Authors: Chadha B. , Pemberton M. , Crockett A. , Sharkey J. , Sacks J. , McKenna S.
Published: September 2013

As the rate of change in both business models and business complexity increases, enterprise architecture can be positioned to supply decision support for executives. The authors propose a dynamic enterprise architecture framework that supports business executive needs for rapid response and contextualized numerical decision support. The classic approaches to business decision making are both over simplified and insufficient to account for the dynamic complexities of reality. Recent failures of historically sound businesses demonstrate that a more robust mathematical approach is required to establish and maintain the alignment between operational decisions and enterprise objectives. We begin with an enterprise architecture (EA) framework that is robust enough to capture the elements of the business within the structure of a meta model that describes how the elements will be stored and tested for completeness and coherence. We add to that the analytical tools needed to innovate and improve the business. Finally, dynamic causal and agent layers are added to account for the qualitative and evolutionary elements that are normally missing or over simplified in most decision systems. This results in a dynamic model of an enterprise that can be simulated and analyzed to answer key business questions and provide decision support. We present a case study and demonstrate how the models are used within the decision framework to support executive decision makers.
Stiffness Modeling of Robotic-Manipulators Under Auxiliary Loadings
Authors: Klimchik Alexandr , Pashkevich Anatol , Caro Stéphane , Chablat Damien
Published: September 2013

The paper focuses on the extension of the virtual-joint-based stiffness modeling technique for the case of different types of loadings applied both to the robot end-effector and to manipulator intermediate points (auxiliary loading). It is assumed that the manipulator can be presented as a set of compliant links separated by passive or active joints. It proposes a computationally efficient procedure that is able to obtain a non-linear force-deflection relation taking into account the internal and external loadings. It also produces the Cartesian stiffness matrix. This allows to extend the classical stiffness mapping equation for the case of manipulators with auxiliary loading. The results are illustrated by numerical examples.
Design of Reflex Actions for Compensating High Amplitude Disturbances to Digital Controllers
Authors: Kim Won Young , Pochiraju Kishore
Published: September 2013

When a system controlled by a low-frequency digital feedback controller experiences a sudden large disturbance such as an impact, its dynamic performance and stability may deteriorate. Inspired by various reflex actions in human body, analog reflex actions are designed to compensate the effects of large disturbances to digital controllers. The human reflexes are triggered by motor neurons as soon as sensory neurons detect stimuli above a threshold without any decision process involving the brain. In this approach, large disturbances are attenuated more rapidly by external sensor-actuator modules connected with only analog components. A series of simulations is performed to design the reflex actions and its findings are articulated in this paper. The system performance is evaluated by measuring the peak error and the settling time. The paper presents a discussion on various techniques to determine appropriate reflex actions with only minimal information about the disturbance profiles.
Finite Element Analysis Over Tangled Meshes
Authors: Danczyk Josh , Suresh Krishnan
Published: September 2013

In finite element analysis (FEA), tasks such as mesh optimization and mesh morphing can lead to overlapping elements, i.e., to a tangled mesh. Such meshes are considered ‘unacceptable’ today, and are therefore untangled using specialized procedures.

Here it is shown that FEA can be easily extended to handle tangled meshes. Specifically, by defining the nodal functional space as an oriented linear combination of the element shape functions, it is shown that the classic Galerkin formulation leads to a valid finite element formulation over such meshes.

Patch tests and numerical examples illustrate the correctness of the proposed methodology.
An Ensemble Empirical Mode Decomposition-Based Lossy Signal Compression Method for a Remote and Wireless Bearing Condition Monitoring System
Authors: Tse Peter W. , Guo Wei
Published: September 2013

Rolling bearings are one of the most widely used and most likely to fail components in the vast majority of rotating machines. A remote and wireless bearing condition system allows the bearings to be inspected in remote or hazardous environments and increases the machine reliability. To minimize the transmission loads of enormous vibration data for accurate bearing fault diagnosis, a lossy compression method based on ensemble empirical mode decomposition (EEMD) method was proposed for bearing vibration signals in this paper. The EEMD method inherits the advantage of the popular empirical mode decomposition (EMD) method and can adaptively decompose a multi-component signal into a number of different frequency bands of signal components called intrinsic mode functions (IMFs). After applying the EEMD method to the vibration signal, the impulsive signal component related to the faulty bearing is extracted. The noise and irrelevant signal components that are often embedded in the collected vibration signals were removed. In the bearing signal, the distribution for most of the extremes is around zero. Almost all meaningful extremes related to the defect are concentrated in a small fraction of the samples. Hence, this signal compression provides high compression ratio for the bearing vibration signal.

To verify the effectiveness of this method, raw vibration signals were collected from an experimental motor and a real traction motor. The proposed lossy signal compression method was applied to these vibration signals to extract the bearing signals and compress them. A comparison of this compression method with the popular wavelet compression method was also conducted. Wirelessly transmitting these compressed data demonstrates that the proposed signal compression method provides high compression performance for bearing vibration signals. Furthermore, the fault diagnosis using the reconstructed signal indicates that most of the impulses relating to the bearing fault are retained, including their periodicity and amplitudes, which are vital for accurate bearing fault diagnosis. Therefore, the compression of the bearing vibration signal contributes not only on the decreases of the file size and the transmission time, but also on the extraction of faulty bearing features to improve the accuracy in signal analysis.

With the help of this method, wireless data communication for the remote and wireless bearing condition monitoring system becomes highly efficient, even in a limited bandwidth environment and maintains accurate bearing fault detection without loss of features and the need of transmitting a large amount of vibration data.
Optimization Method of Location for Cooperative Lifting of Two Mobile Cranes
Authors: Wang Xin , Liu Yuanyuan , Liu Fang
Published: September 2013

Dual-crane lifting has been generally used with the need of erection and installation of large equipment. Choosing proper locations for two mobile cranes is an important work as well as a difficulty in design of heavy lifting plan. So, this paper proposes an optimization method of location for cooperative lifting of dual-crane. This approach starts with determining search field and maximum step length, and then finds out load’s possible initial locations by bisection method; secondly calculates work envelope of dual-crane which will be dispersed to find all dual-crane’s possible locations; after this, it puts cranes in their respective possible locations corresponding to each load’s location and simulates the whole lifting course while carries out collision detection to exclude crash happened locations; finally, creates weighted optimization function, uses enumeration method to traverse all collision-free locations, and gains optimal location of dual-crane and load. At last, this approach has been used in an actual engineering case and optimal location is got, from which we can see its feasibility and validity.
Novel Detection of Dynamics Effects in the Transverse Acceleration Field of a Hole in Aluminum Plate Platform of an Aircraft Engine
Authors: Georgiou Ioannis T. , Kintzios Nikolaos
Published: September 2013

Presented is a novel technique for damage detection in a monolithic plate platform containing a small through-the-thickness slightly elliptic hole in addition to precision drilled holes to support an aircraft engine. Partially cantilevered, the plate is interrogated by a hammer-generated impulsive force applied sequentially over points on spanning interrogation lines. The impulse-induced transverse acceleration is sampled simultaneously by three sensors placed at the apexes of a local triangle in a selected sensing area. Dynamics effects of the presence of the hole (damage) are extracted by decomposing the three local collocated acceleration databases into their intrinsic proper orthogonal decomposition (POD) modes. The POD spatial modulations of the three collocated databases are smooth and reflect in a clear manner symmetries of the interrogation lines. We find that the dynamic effect of the presence of the hole is reflected as robust destruction of symmetry in all POD spatial modulations. This result holds for a large number of local sensing areas covered by the triangular formation of the three sensors. The technique has promising potential to extract robust and highly indicative spatial patterns of damage in coupled machinery-structural systems of complex geometry.
A Virtual Testing Framework for Engineering Product Development
Authors: Jung Byung C. , Youn Byeng D. , Kim Ji Sun
Published: September 2013

Virtual testing is a new engineering development trend to design, evaluate, and test new engineered products. This research proposes a virtual testing framework for new product development using three successive steps: (i) statistical model calibration, (ii) hypothesis test for validity check and (iii) virtual qualification. Statistical model calibration first improves the predictive capability of a computational model over a calibration domain. Next, the hypothesis test is performed under limited observed data to see if a calibrated model is sufficiently predictive for virtual testing of a new design. A u-pooling metric is employed for the hypothesis test to measure the degree of mismatch between predicted and observed results while considering uncertainty in the u-pooling metric due to the lack of experimental data. The calibrated model can be rejected only when the measured metric of the calibrated model strongly suggest that the null hypothesis—the calibrated model is valid—is false. If the null hypothesis is accepted, the virtual qualification process can be executed with a qualified model for new product developments. The qualification process builds a design decision matrix to aid in rational decision-making on the product developments. A computational model of a tire tread block was used to demonstrate the effectiveness of the proposed framework.
Modeling and Free Vibration Analysis of a Complex Cable-Stayed Bridge
Authors: Cao D. Q. , Song M. T. , Zhu W. D.
Published: September 2013

A complex cable-stayed bridge that consists of a simply-supported four-cable-stayed deck beam and two rigid towers is studied. The nonlinear and linear partial differential equations that govern the motions of the cables and segments of the deck beam, respectively, are derived, along with their boundary and matching conditions. The undamped natural frequencies and mode shapes of the linearized model of the cable-stayed bridge, which includes both the transverse and longitudinal vibrations of the cables, are determined. Numerical analysis of the natural frequencies and mode shapes of the cable-stayed bridge is conducted for a symmetrical case with regards to the sizes of the components of the bridge and the initial sags of the cables. The results show that there are very close natural frequencies and localized mode shapes.
Independent Modal Control of Beams With Spatially Distributed Orthogonal Photostrictive Actuators
Authors: Jiang Jing , Yue Hong-Hao , Cheng Wen-Xiu , Deng Zong-Quan , Tzou Horn-Sen
Published: September 2013

High-energy light regulated photostrictive actuators provide a new wireless and non-contact precision actuation mechanism. For PLZT actuators with 0–3 polarization, the electrode shape can be designed to achieve desired modal control effects. In this paper, the photonic control of flexible shells using shaped photostrictive actuators is investigated. Spatially distributed and shaped 0–3 polarized PLZT actuators are selected to achieve independent control of various natural modes of a simply supported beam. Constitutive equations which define the time history response of photo-induced strain for 0–3 polarized PLZT actuator are presented. Based on experimental observation and theoretical analysis, the relationships of saturated photovoltage and time constant with actuator thickness and light intensity are formulated. Based on the orthogonality of the mode shape function, distributed orthogonal modal actuators designed for a simply supported beam are proposed. In order to realize the actuator shape design, paired spatially shaped photostrictive actuators are segmented and respectively placed on the top and bottom surfaces of the beam and the light direction of each segment actuator is regulated. Their control effectiveness with constant light intensity control is evaluated and the time history analysis is presented.
Acoustic Surface Perception for Improved Mobility of Legged Robots
Authors: Ozkul Mine Cuneyitoglu , Saranli Afsar , Yazicioglu Yigit
Published: September 2013

A dynamically dexterous legged robot has the distinct property that the legs are continuously interacting with the environment. During walking and running, this interaction generates acoustic signals that carry considerable information about the surface being traversed, state of the robot legs and joint motors as well as the stability of the locomotion. Extracting a particular piece of information from this convolved acoustic signal however is an interesting and challenging area of research which we believe may have fundamental benefits for legged robotics research. For example, the identification of the surface that the robot travels on gives us the ability to dynamically adapt gait parameters hence improve dynamic stability. In the present paper, we investigate this particular sub-problem of surface identification using naturally occurring acoustic signals and present our results. We show that a spectral energy based feature set augmented by time derivatives and an average zero crossing rate carries enough information to accurately classify a number of commonly occurring indoor and outdoor surfaces using a popular higher dimensional vector quantizer classifier. Our experiments also suggest that VQ surface models may be velocity dependent. These initial results with a carefully collected but relatively limited dataset indicate a promising direction for our future research on improving outdoor mobility for dynamic legged robots.
Enhancing Audio-Haptic Enabled Novel Dental Training Platform Performance
Authors: Deshpande Sameer , Nahavandi Saeid , Mullins James , Khan Muhammad B. , Creighton Douglas
Published: September 2013

Existing haptic and non-haptic dental simulators do not eliminate the problem of hand instability while using the haptic devices for training purpose. This paper reports an audio-haptic dental training platform, which uses a Hand Stability System to reduce the effect of nervousness and hand instability for trainee dental students. Maintaining the ease of implementation, application customizability and the cost factor, the proposed platform increases the training efficiency by enhancing the immersive haptic experience with hand stability. This haptic platform includes multiple angle viewing techniques, audio feedback and session recording for after action review. Trials using this preliminary platform reduced the effect of human nervousness and hand instability due to the customized design.
A Variable Stiffness Joint by Granular Jamming
Authors: Jiang Allen , Ataollahi Asghar , Althoefer Kaspar , Dasgupta Prokar , Nanayakkara Thrishantha
Published: September 2013

We propose a novel, high degree of freedom variable stiffness joint for use in a miniature snake-like robot for minimally invasive surgeries via granular jamming. By pulling granule filled membrane-columns under vacuum, the columns and joint stiffen as the granular matter begin to jam. In our experiments, we achieved a four-fold increase in stiffness, and the stiffness can be achieved while the columns are straight or bent. Current flexible manipulators in industrial and medical robotics have followed two dominating methods of actuation and stiffness control. The first method is the continuum manipulator, which utilizes tendons or rods to bend the manipulator in a continuous fashion. The second method is classified as the highly articulated robot, where the manipulator is comprised of multiple segments linked by motor-driven universal joints. Like the latter, our manipulator is highly articulated, however stiffness of each joint can be independently controlled by the granular jamming principle. This paper studies the effect of grain type and vacuum pressure for stiffness tuning. We found that granules with a matte surface were able to achieve higher stiffnesses, with a cube shape exhibiting the highest stiffness, but at the cost of high levels of hysteresis.
Feasibility of a 5x Speedup in System Development due to META Design
Authors: de Weck Olivier L.
Published: September 2013

The main goal of META design is to achieve a factor five (5x) improvement in product development speed for cyber-electro-physical systems compared to current practice. The method claims to achieve this speedup by a combination of three main mechanisms:

1. The deliberate use of layers of abstraction. High-level functional requirements are used to explore architectures immediately rather than waiting for downstream level 2, 3, 4 … requirements to be defined.

2. The development and use of an extensive and trusted component (C2M2L) model library. Rather than designing all components from scratch, the META process allows importing component models directly from a library in order to quickly compose functional designs.

3. The ability to find emergent behaviors and problems ahead of time during virtual Verification and Validation (V&V) and generating designs that are correct-by-construction allows a more streamlined design process and avoids costly design iterations that often lead to expensive design changes.

This paper quantifies the impact of these main META mechanisms with a sophisticated System Dynamics (SD) model that allows simulating development projects over time. META compares favorably against a simulation of a traditional design process due to the generation of late engineering changes in a traditional design-build-test-redesign environment. The benchmark case analyzed in this paper contained 3,000 requirements, and the results show a dramatic improvement for project completion schedule with a demonstrated speedup factor of 4.4 (70 months versus about 16 months). In the simulated META process we used 3 layers of abstraction, 50% novelty and a model library integrity of 80% with 70% of problems are caught early. The results were also validated against data from the B777 Electric Power System (EPS) design project at UTC where a speedup factor of 3.8 was demonstrated. The paper contains a useful sensitivity analysis that helps establish requirements and bounds on the META process and tool-chain itself that should enable the desired 5x speedup factor.