bluuebunny/crossref_metadata_2025 huggingface dataset:
Complex System Design Verification Using Assumption Generation
Authors: Mehrpouyan Hoda , Giannakopoulou Dimitra , Brat Guillaume , Tumer Irem Y. , Hoyle Chris
Published: February 2014

In the era of large complex systems with continuous and discrete event components, it is critical to establish a complete design verification strategy to determine whether a system satisfies certain safety properties. However, traditional approaches for the verification of such a complex system lack the ability to take into account all possible system states, efficiently model all component interactions, and accurately quantify the risks and uncertainties. This paper presents a methodology for system-level design of complex systems verification based on compositional model checking. This methodology relies on assumption generation and on the domain independent compositional rules for correctness proof of the design of physical systems. The objective is to present a case study for applying the existing automated compositional verification techniques and observing the characteristics of the verification model. The main advantage of this method is that it enables the designer to verify the safety properties of the system without requiring the detail knowledge of the internal actions of the system. The under-approximate context model of the system design is constructed and, in an iterative approach, its safety properties are analyzed until a violation of a property is found and an execution trace called a counter example is produced. In the case of safety requirements violation, the early generation of counter examples leads to faster design verification.
Electroelastic Finite Element Modeling and Experimental Validation of Structurally-Integrated Piezoelectric Energy Harvester
Authors: Aridogan Ugur , Basdogan Ipek , Erturk Alper
Published: February 2014

Vibration-based energy harvesting has attracted interest of researchers from various disciplines over the past decade. In the literature of piezoelectric energy harvesting, the typical configuration is a unimorph or a bimorph cantilevered piezoelectric beam located on a vibrating host structure subjected to base excitations. As an alternative to cantilevered piezoelectric beams, piezoelectric layers structurally integrated on thin plates can be used as vibration-based energy harvesters since plates and plate-type structures are commonly used in aerospace, automotive and marine applications. The aim of this paper is to present experiments and electroelastic finite element simulations of a piezoelectric energy harvester structurally integrated on a thin plate. The finite element model of the piezoceramic patch and the all-edges-clamped plate are built. In parallel, an experimental setup is constructed using a thin PZT-5A piezoceramic patch attached on the surface of all-edges-clamped rectangular aluminum plate. The electroelastic frequency response functions relating voltage output and vibration response to forcing input are validated using the experimentally obtained results. Finally, electrical power generation of the piezoceramic patch is investigated using the experimental set-up for a set of resistive loads. The numerical predictions and experimental results show that the use of all-edge-clamped flexible plate as host structure for piezoelectric energy harvester leads to multimodal vibration-to-electricity conversion.
Epistemic and Aleatoric Uncertainty in Modeling
Authors: Segalman Daniel J. , Brake Matthew R. , Bergman Lawrence A. , Vakakis Alexander F. , Willner Kai
Published: February 2014

One major difficulty that exists in reconciling model predictions of a system with experimental measurements is assessing and accounting for the uncertainties in the system. There are several enumerated sources of uncertainty in model prediction of physical phenomena, the primary ones being: 1) Model form error, 2) Aleatoric uncertainty of model parameters, 3) Epistemic uncertainty of model parameters, and 4) Model solution error. These forms of uncertainty can have insidious consequences for modeling if not properly identified and accounted for. In particular, confusion between aleatoric and epistemic uncertainty can lead to a fundamentally incorrect model being inappropriately fit to data such that the model seems to be correct. As a consequence, model predictions may be nonphysical or nonsensical outside of the regime for which the model was calibrated. This research looks at the effects of aleatoric and epistemic uncertainty in order to make recommendations for properly accounting for them in a modeling framework.
Initial Steps Toward an Analogy Retrieval Tool Based on Performance Specification
Authors: Ngo Peter , Viswanathan Vimal , Turner Cameron J. , Linsey Julie
Published: February 2014

In design-by-analogy, inventors draw inspiration from natural and man-made systems to create new, often innovative engineering products. Though methods exist to aid concept generation through design-by-analogy, they are not built on fundamental knowledge of how inventors inherently use analogies. Such a foundation is critical for developing effective analogy-finding tools and methods. In this research, we pursue an empirical product study to guide the creation of a computational tool that presents relevant analogies based on designers’ objectives. Using an inductive approach, we studied 57 design-by-analogy products and their inspiring analogs to identify how analogies entered the design process. We developed classification schemes that characterize the analogies and their design contexts, which includes the inventors’ field of work and design objectives. Findings emerged from identifying patterns in the classification results. When comparing academic and commercial inventors, we found differences in how they use analogies to find new product functions or gain better performance. We gained insight into how knowledge-driven and problem-driven analogy usage cases differ. Most intriguingly, we found that products commonly borrow critical functions directly from analog systems, but we also discovered instances of critical function inversion, where the sense of the critical function is reversed between the analog and the product. For example, this occurred with the ECO-Auger Tidal Turbine (critical function: “Convert fluid flow into rotation”) which was inspired by screw conveyors (“Convert rotation into material flow”). This discovery implies that a computational search for analogs should expand from a designers’ function specification to include analogs with inverted critical functions, thus widening the space of possible inspiration sources.
Application of Regional Strain Energy in Topology Optimization With Inertia Relief Analysis
Authors: Song Wei , Gea Hae Chang , Yang Ren-Jye , Chuang Ching-Hung
Published: February 2014

In finite element analysis, inertia relief solves the response of an unconstrained structure subject to constant or slowly varying external loads with static analysis computational cost. It is very attractive to utilize it in topology optimization to design structures under unbalanced loads, such as in impact and drop phenomena. In this paper, regional strain energy formulation and inertia relief is integrated into topology optimization to design protective structure under unbalanced loads. For background, the equations of inertia relief are introduced and a commonly used solving method is revisited. Then the regional strain energy formulation for topology optimization with inertia relief is proposed and its sensitivity is derived from the adjoint method. Based on the solving method, the sensitivity is evaluated term by term to simplify the results. The simplified sensitivity can be calculated easily using the output of commercial finite element packages. Finally, the effectiveness of this formulation is shown in the first example and the proposed regional strain energy formulation for topology optimization with inertia relief are presented and discussed in the protective structure design examples.
Optimization of Electrode Structure for Effective Particle Separation in a Micro-Fluidic Chip
Authors: Chen Yun , Manoochehri Souran
Published: February 2014

This paper presents the optimization of electrode structure for effective particle separation in a micro fluidic chip. The purpose of electrodes in the micro fluidic chip is to generate the DEP (dielectrophoresis) force that is perpendicular to the micro channel direction to separate both nDEP and pDEP particles of the same sizes. The particles will experience DEP force when passing through the electric field which is created by electrode arrays located in different positions in the channel. In this study, we optimize the electrode structure by investigating different shapes and dimensions using numerical simulation and modeling. The optimized electrode structure can provide better separation effect due to larger effective area of DEP force and relative small variation of electric field gradient as demonstrated in this study.
Parallel Algorithm for Constrained Multi-Rigid Body System Dynamics in Generalized Topologies
Authors: Mukherjee Rudranarayan
Published: February 2014

This paper presents an algorithm for modeling the dynamics of multi-rigid body systems in generalized topologies including topologies with closed kinematic loops that may or may not be coupled together. The algorithm uses a hierarchic assembly disassembly process in parallel implementation and a recursive assembly disassembly process in serial implementation to achieve highly efficient simulation turn-around times. The kinematic constraints are imposed using the formalism of kinematic joints that are modeled using motion spaces and their orthogonal complements. A mixed set of coordinates are used viz. absolute coordinates to develop the equations of motion and internal or relative coordinates to impose the constraints. The equations of motion are posed in terms of operational inertias to capture the nonlinear coupling between the dynamics of the individual components of the system. Einstein’s notation is used to explain the generality of the approach. Constraint impositions at the acceleration, velocity and configuration levels are discussed. The application of this algorithm in modeling a complex micro robot with multiple coupled closed loops is discussed.
Strategies for Analyzing Random Vibration of Jointed Structures
Authors: Segalman Daniel J. , Starr Michael J. , Guthrie Michael A.
Published: February 2014

Development of mathematical models for built-up structures, particularly those with many interfaces, is still primitive. This limitation is particularly evident when complex loads and load histories are considered, an example of which is random vibration.

Two steps in simplifying this problem are explored here. First, the system response is approximated as that of the superposition of numerous decoupled modes, the coordinates of which evolve according to a constitutive model designed to capture the nonlinearity of the structure. Second, because among the categories of load for which dynamic analysis on nonlinear structures is particularly difficult is that of random loads and the resulting random vibration, and given the previous approximation, it is natural to apply the method of stochastic equivalent linearization to the governing equation of each mode. Both of these approximations are explored for the case where the nonlinear behavior of the interfaces is represented by a Masing-Prandtl-Ishlinskii-Iwan model employing a Palmov kernel.
Investigating the Relationship Between Product Design Complexity and FDA for Medical Device Development
Authors: Medina Lourdes A. , Jankovic Marija , Okudan Kremer Gül E.
Published: February 2014

Product complexity has been studied as an important factor to decrease the cost and time of the development process. With this purpose, prior research has included the development of design complexity metrics as a method to assess and decrease complexity. Recent studies have also focused on the comparison of complexity metrics for the particular case of medical devices development (MDD). However, the major issue relevant to MDD has not been addressed; the relationship between FDA regulations and the device complexity is not clarified. Therefore, to increase MDD safety and decrease the time to market, we must understand the regulatory decision process and rules. In this paper, we investigate the relation between different complexity metrics and FDA’s decision time using a sample of 100 hip replacement devices. Bayesian network learning is used to explore in detail local relationships between different variables, both complexity measures and product variables. This relationship was found significant for the first two clusters of the analysis. However, for a third cluster it is speculated that FDA decision time does not depend solely upon the degree of medical device complexity. Company or organization relevant variables could be playing a greater role than just complexity. Additional questions are drawn based on the results that must be investigated.
Environmental Burdens and the Light-Weighting of Rockets
Authors: Romaniw Yuriy , Bras Bert
Published: February 2014

The overarching goal of the research is to determine the relationship between light-weighting and the life cycle environmental burdens of a rocket system. Light-weighting is done by replacing traditionally metal components with carbon fiber reinforced polymer components. This paper documents a preliminary analysis of the environmental burdens of a rocket, considering rockets of different sizes and propellant combinations. The purpose of the analysis is to first determine if such a relationship exists, and second to determine which components of the rocket most significantly influence the life cycle environmental burdens. The analysis found that a small change of about 0.15–0.3% in the structural mass can decrease embodied energy and carbon dioxide of the rocket by about 5.2% and 5.0%, respectively. Furthermore, the overall propellant load of the rocket decreases by 5.7%, while the overall structural mass decreases by 6.4%. Though there are small differences as to the extent to which light-weighting reduces environmental burdens depending on propellant combination, it is shown that there is a general reduction in life cycle environmental burdens when a rocket is light-weighted.
Massively Parallel Discrete Element Modeling of Wheeled Mobility on Granular Terrain
Authors: Houlihan Ryan , Mukherjee Rudranarayan
Published: February 2014

Quantitatively understanding wheeled mobility on granular terrain such as sand or gravel is critical for design and operations of ground vehicles for terrestrial or extra-terrestrial applications. While the Bekker-Wong theory of wheeled mobility and its derivatives have been used in many applications, the static nature of these formulations are limiting in understanding mobility in deformable terrain under dynamic mobility conditions. Single wheel hardware experiments in laboratory settings and detailed modeling of wheel-terrain interactions are two avenues currently being actively pursued to develop quantitative understanding of wheeled mobility. In this paper, we present findings of massively parallel discrete element modeling of wheeled mobility on granular media such as sand. We present a brief overview of the underlying methodology and then focus on the results of the simulation. In these simulations, we model the inter-granular interactions and interactions between the wheel and the granules with an objective of using high fidelity first-principles approach to capture emergent behavior in these complex and highly dynamic phenomena. These simulations typically model millions of granules and use highly scalable software and parallel computing resources to overcome the severe complexity of the problem. We present results of parametric studies with varying levels of both wheel penetration and mobility conditions. These have been modeled to present a quantitative perspective of the diverse behaviors encountered in wheeled mobility on granular terrain. We have retained the full complexity of the problem by simulating granules of the size encountered in real terrain to overcome the fidelity limited issues of other comparable methods that use much larger granules.
Automated Navigation of Method Time Measurement Tables for Automotive Assembly Line Planning
Authors: Renu Rahul , Peterson Matthew , Mocko Gregory , Summers Joshua
Published: February 2014

Assembly process sheets are formal documents used extensively within automotive original equipment manufacturers (OEMs) to document and communicate assembly procedure, required tooling, contingency plans, and time study results. These sheets are authored throughout the vehicle life-cycle. Further, various customers use these sheets for training, analyzing the process, and line-balancing. In this research, the primary focus is the time studies analysis that is completed using knowledge contained within the assembly process sheets. In this research, a method and software tool are developed to utilize coupling between part descriptions and process descriptions for assembly time studies. The method is realized through the development of a standardized vocabulary for describing work instructions, a mapping from work instructions to MTM codes, and a tool for extracting relevant part information from CAD models. The approach enables process planners to establish part-process coupling, author work instructions using the controlled vocabulary, to estimate assembly time. A prototype system is developed and tested using examples from an automotive OEM.
A Recursive Body-Body Formulation for Reducing the Computational Cost of Pairwise Coulomb Force Computation for Modeling and Simulation of Biopolymers, Using a Multibody Approach to Model Reduction
Authors: Laflin Jeremy , Anderson Kurt
Published: February 2014

This work presents a method for recursively assembling tensor-like quantities that parameterize the charge distribution of rigid bodies, which result from model reduction of biopolymeric systems using an articulated multibody approach. This is done with the goal of reducing the computational cost associated with the pairwise force determination encountered in molecular dynamics simulations. To achieve a linear computational cost complexity of the force determination, with respect to the number of bodies in the system (N), a recursive assembly and disassembly (evaluation) sweep is proposed. This work proposes assembling these tensor quantities (pseudo-inertia tensors), which are associated with the body’s charge distribution, with a method that uses the standard parallel axis theorem to shift these tensors to a common point so they may be summed.

This work presents a preliminary numerical example that examines the accuracy of the force and moment computation using a pseudo-inertia tensor resulting after one level of recursive assembly. The Coulomb force and associated moment on a target body due to the assembled body is computed. The test problem approximates a system that is highly negatively or positively charged. The orientation of the bodies that are assembled is varied, along with the distance between the assembly and the target body. The preliminary results presented herein suggest that this is a viable method of efficiently representing the charge distribution of an assembly. The numerical example presented determines the Coulomb force and the associated moment, as a function of distance and the pseudo-inertia tensor. However, the approximation can be used for any force that is of the form 1/rs, where s is any power.
Smooth Projective Nonlinear Noise Reduction
Authors: Chelidze David
Published: February 2014

Many nonlinear or chaotic time series exhibit an innate broad spectrum, which makes noise reduction difficult. Locally projective noise reduction is one of the most effective tools. It is based on proper orthogonal decomposition (POD), and works for both map-like and continuously sampled time series. However, POD only looks at geometrical or topological properties of data and does not take into account the temporal characteristics of time series. Here we present a new smooth projective noise reduction method. It uses bundles of locally reconstructed trajectory strands and their smooth orthogonal decomposition (SOD) to identify smooth local subspaces. Restricting trajectories to these subspaces imposes temporal smoothness on the filtered time series. It is shown that SOD-based noise reduction significantly outperforms the POD-based method for continuously sampled noisy time series.
Ceramic Matrix Composite Materials by Design Using Robust Variable Fidelity Optimization
Authors: Khadke Kunal R. , An Weigang , Tovar Andrés
Published: February 2014

Ceramic matrix composites (CMC) have been widely studied to tailor desired properties at high temperatures. However, research applications involving design tool development for multi-phase material design are at an early stage of development. While numerical CMC modeling provides significant insight on the material performance, the computational cost of the numerical simulations and the type of variables involved in these models are a hindrance for the effective application of design methods. This technical challenge heightens with the need of considering the uncertainty of material processing and service. For this reason, few design researchers have addressed the design paradox that accompanies the rapid design space expansion in CMC material design.

The objective of this research is to establish a tractable approach for CMC design considering uncertainty. Traditionally, surrogate models of statistical data are incorporated in the design strategy. An alternative to surrogate modeling is the use of lower fidelity models, which captures some of the physics of the problem and avoids the generation of uncertainty quantification. A variable fidelity optimization (VFO) management framework is incorporated in this research. In the proposed VFO method, a high-fidelity, cohesive, finely meshed finite-element model guides the coarsely meshed, low-fidelity model towards the optimal material design. Uncertainty in CMC material processing (multiphase nucleation and growth) is quantified using a stochastic material microstructural lattice model. The lattice model is verified with laboratory processed microstructures.

Dimension reduction for reduction of the number of random variables under consideration. Linear data transformation and principal component analysis (PCA) is traditionally used in dimension reduction. However, nonlinear dimension reduction techniques are better handle complex nonlinear data. This work incorporates Maximum Variance Unfolding (MVU) that preserves global properties of the original data in the low-dimensional representation.

The proposed methodology is applied to the optimal distribution of the matrix and the disperse phases in the composite structure. Results are demonstrated in the design of silicon carbide (SiC) fibers in a silicon-nitride (Si3N4) matrix for maximum fracture energy. The results provide a reference for SiC-Si3N4 nanocomposite.
Stochastic Kriging for Random Simulation Metamodeling With Finite Sampling
Authors: Wang Bo , Bai Junqiang , Gea Hae Chang
Published: February 2014

As a metamodeling method, Kriging has been intensively developed for deterministic design in the past few decades. However, Kriging is not able to deal with the uncertainty of many engineering processes. By incorporating the uncertainty of data, Stochastic Kriging methods has been developed to analyze and predict random simulation results, but the results cannot fit the problem with uncertainty well. In this paper, deterministic Kriging are extended to stochastic space theoretically, where a novel form of Stochastic Kriging that fully considers the intrinsic uncertainty of data and number of replications is proposed on the basis of finite inputs. It formulates a more reasonable optimization problem via a stochastic process, and then derives the spatial correlation models underlying a random simulation. The obtained results are more general than Kriging, which can fit well with many uncertainty-based problems. Three examples will illustrate the method’s application through comparison with the existing methods: the novel method shows that the results are much closer to reality.
A Novel Combinatorial Algorithm for Determining the Generic/Topological Mobility of Planar and Spherical Mechanisms
Authors: Shai Offer , Müller Andreas
Published: February 2014

Structural mobility criteria, such as the well-known Chebychev-Kutzbach-Grübler (CKG) formula, give the correct generic mobility of a linkage (possibly of a certain class, e.g. planar, spherical, spatial) provided that it is not topologically overconstrained. As a matter of fact all known structural mobility criteria are prone to topological redundancies.

In this paper a combinatorial algorithm is introduced that determines the correct generic/topological mobility of any planar and spherical mechanism. The algorithm also yields a set of independent links that can be used as input, as well as the redundantly constrained sub-linkages. A mathematical proof of the algorithm and the underlying mathematical concept is presented. The proposed method relies on an established algorithm developed within combinatorial rigidity theory, called pebble game, originally developed for checking the rigidity/immobility of constraint graphs. A novel theorem is introduced and later proved in the paper which in turn enables applying the algorithm to any holonomic planar or spherical mechanism with higher and lower kinematic pairs and multiple joints. A further important result of applying this algorithm is that it gives rise to a decomposition into Assur graphs, which is briefly discussed in this paper.
An Approach for Understanding Action Origami as Kinematic Mechanisms
Authors: Bowen Landen A. , Grames Clayton L. , Magleby Spencer P. , Lang Robert J. , Howell Larry L.
Published: February 2014

Action origami is a field of origami dealing with models that are folded so that in their final, deployed state they exhibit motion. Hundreds of action origami models exist, many of which use complicated kinematics to achieve motion in their deployed state. Understanding the kinematics of action origami could result in a new source of concepts for deployable, movable engineering solutions. This paper presents an approach for evaluating and classifying the mechanisms that enable action origami motion. Approximately 300 action origami models are studied. Although disguised with artistic elements, it is found that most action origami models are based on a few fundamental mechanisms. A classification scheme is proposed, and a previously unused class of action origami is identified as an area for future origami art.
Compensated Conjugation and Gear Tooth Modification
Authors: Yu Bowen , Ting Kwun-lon
Published: February 2014

This paper rigorously presents a new theory called compensated conjugation for gear transmission error balance. The proposed theory is a systematic study based on conjugation equation and transmission function. The basic idea is that conjugation is essentially impaired by loading condition but can be compensated by modifying transmission function. In contrast to the traditional method which is mainly applicable for planar involute gears, the new idea generally applies for all conjugation types based on the same concept of transmission. Multiple Concepts of conjugation and transmission are rigorously modeled and defined by screw theory. A theorem about the continuity of motion and conjugate geometries is presented and proved in order for desirable modification. The proposed theory is consistent with the standard manufacturing process for tooth modification. Tooth geometries and cutter geometries can be obtained after the theoretical transmission error function is designed. For the most important application — planar involute gear design, a practically convenient method with a direct rack-cutter modification is proposed and rigorously analyzed by kinematics and differential geometry. Examples show the effectiveness of the methodology.
Vibration of Spinning Cantilever Beams Undergoing Coupled Bending and Torsional Motion
Authors: Cooley Christopher G. , Parker Robert G.
Published: February 2014

This study investigates the vibration of a spinning cantilever beam with a rigid body attached to its free end undergoing coupled bending and torsional motion. The rotation axis is perpendicular to the beam (like a helicopter blade). The governing equations of motion are cast in a structured way using extended variables and extended operators. With this structure the equations represent a classical gyroscopic system and Galerkin discretization is readily applied where it is not for the original problem. The natural frequencies and vibration modes are investigated over a wide range of rotation speeds.
Sliding Mode Based LMI Criterion for Robust Stabilization of Uncertain Fractional Order Nonlinear Systems
Authors: Dadras Sara , Chen YangQuan
Published: February 2014

A robust sliding mode control (SMC) technique is introduced in this paper for a class of fractional order (FO) nonlinear dynamical systems. Using the sliding mode control technique, a sliding surface is determined and the control law is established. A new LMI criterion based on the sliding mode control law is derived to make the states of the FO nonlinear system asymptotically gravitate toward the origin which can work for any order of the system, 0<q<2. The designed control scheme can also control the uncertain FO nonlinear systems, i.e. the controller is robust against the system uncertainty and guarantees the property of asymptotical stability. The advantage of the method is that the control scheme does not depend on the order of systems model and it is fairly simple. So, there is no complexity in the application of our proposed method. An illustrative simulation result is given to demonstrate the effectiveness of the proposed robust sliding mode control design.
Modeling Energy Dissipation in Atomic Force Microscopy
Authors: Huang Wei , Dick Andrew J.
Published: February 2014

Atomic force microscopy is an important research tool in micro- and nano-scale science because of its high resolution and versatility. Many different operation methods have been developed and more are being developed. In numerical studies, a nonlinear interaction force model is recognized as a necessary part to achieve accurate results. However, the energy dissipation in the system is still generally modeled only by structural and viscous damping which are proportional to velocity, and the non-conservative interaction force models for numerical simulations are limited and frequently not used. In this work, the authors investigate the importance of using a non-conservative interaction force model in numerical simulations. Some modeling methods are discussed and the simulation results for resonant excitation are compared. The response magnitude at the first harmonic is determined to be significantly affected by the modeling approach when the dissipative level in the tip-sample interaction and the structural and viscous damping are high.
Recurring and Unresolved Problems in Sustainable Design
Authors: Bras Bert
Published: February 2014

Much progress has been made in sustainable design over the past 20 years since the first publications on design for the environment started to appear in the mechanical engineering literature. Engineering design methods now attempt to include environmental considerations and Life-Cycle Analysis is a commonly used approach nowadays. Nevertheless, some fundamental problems seem to be recurring and remain unresolved. More so, some of these problems can have significant effects on the efficacy of design methods. Without consideration or even acknowledgement of these problems, proposed sustainable design methods may not bring us closer to sustainability at all. In this paper, we highlight a few of these recurring problems. Although true sustainable design should also include social and financial considerations, we will focus primarily on the environmental issues in this paper.
Constrained Multibody Dynamics With Python: From Symbolic Equation Generation to Publication
Authors: Gede Gilbert , Peterson Dale L. , Nanjangud Angadh S. , Moore Jason K. , Hubbard Mont
Published: February 2014

Symbolic equations of motion (EOMs) for multibody systems are desirable for simulation, stability analyses, control system design, and parameter studies. Despite this, the majority of engineering software designed to analyze multibody systems are numeric in nature (or present a purely numeric user interface). To our knowledge, none of the existing software packages are 1) fully symbolic, 2) open source, and 3) implemented in a popular, general, purpose high level programming language. In response, we extended SymPy (an existing computer algebra system implemented in Python) with functionality for derivation of symbolic EOMs for constrained multibody systems with many degrees of freedom. We present the design and implementation of the software and cover the basic usage and workflow for solving and analyzing problems. The intended audience is the academic research community, graduate and advanced undergraduate students, and those in industry analyzing multibody systems. We demonstrate the software by deriving the EOMs of a N-link pendulum, show its capabilities for LATEX output, and how it integrates with other Python scientific libraries — allowing for numerical simulation, publication quality plotting, animation, and online notebooks designed for sharing results. This software fills a unique role in dynamics and is attractive to academics and industry because of its BSD open source license which permits open source or commercial use of the code.
Dynamical Structural Modification for Rotordynamic Application
Authors: Birchfield Neal , Singh Kumar Vikram , Singhal Sumit
Published: February 2014

In the field of rotordynamics, the critical speeds of a rotating system have a wide range of implications throughout industry as the operating speeds for current machine design are pushed to the limit. Moreover, interaction or coupling of a rotordynamic system with the base and/or auxiliary structures influences the dynamic behavior as well as the critical speeds for the coupled system. In order to ensure that the critical speeds of the coupled system is not excited, structural modification of primary structures (e.g. rotordynamic, foundation, auxiliary units etc.) and/or of the coupling parameters may be necessary by passive or active means. The modeling of these coupled systems, as well as the coupling mechanism, may lead to approximation errors. These errors may deteriorate the desired dynamic response of the coupled system. In order to avoid such modeling errors, this paper investigates structural modification and control strategies that are purely based on the transfer functions of the individual subsystems of the overall coupled system. The proposed concept is demonstrated by numerical examples, in which the receptance transfer functions are used to guide structural modifications; for example, to change the critical speed of a coupled rotordynamic system to a desired value. Coupling of turbine-generator assembly and rotordynamic system with flexible base is considered here.
Targeted Energy Transfer for Suppressing Regenerative Instabilities in a 2-DOF Machine Tool Model
Authors: Nankali Amir , Lee Young S. , Kalmar-Nagy Tamas
Published: February 2014

We study targeted energy transfer (TET) mechanisms by applying a nonlinear energy sink (NES) to suppress regenerative instabilities in a 2-DOF planar machine tool model. With the help of a numerical continuation tool, DDEBIFTOOL, we show that the tool instability is generated through a subcritical Hopf bifurcation in this simplified tool model. Studying modal energy exchanges reveals that only one of the DOFs is predominant, which may lead to the standard single-DOF machine tool model. Then, we apply an ungrounded NES to the 2-DOF tool model such that the NES interacts only with the dominant mode, which turns out to be more efficient than applying the NES to the other insignificant mode. Simple numerical simulations and bifurcation analysis demonstrate that the three typical TET mechanisms can be identified — That is, recurrent burstouts and suppression, and partial and complete suppression of tool instability.
Suppression of Aeroelastic Instabilities due to Freeplay Nonlinearity
Authors: Chen Heng , Medina Cory , Lee Young S.
Published: February 2014

We explore the triggering mechanism of aeroelastic instability due to freeplay in a 2-dimensional rigid airfoil with a control surface. This 3-DOF aeroelastic model is mounted on a cubic nonlinear stiffness in heave and pitch, with the freeplay being piecewise linear (i.e., nonsmooth); and the quasisteady aerodynamic theory is considered. Similar to the 2-DOF aeroelastic model, the LCO triggering consists of a series of resonance captures and escapes from resonances. Furthermore, the nonlinear modal interactions become more complicated for full LCO development due to nonsmooth dynamics introduced when the angular displacement of the control surface reaches the clearance limit. Understanding such LCO triggering, we apply a nonlinear energy sink (NES) such that the NES can interact primarily with the heave mode to prevent its initial triggering from being developed further, and also that it can engage in attenuating the pitch mode response. Three distinct suppression mechanisms by means of targeted energy transfers can be identified: recurrent burstouts and suppressions, partial suppression and complete elimination of aeroelastic instability. We explore the respective mechanisms extensively by numerical methods such as a numerical continuation method and wavelet transform spectra.
A Human-Inspired Method for Mobile Robot Navigation
Authors: Heidari Fatemeh , Fotouhi Reza
Published: February 2014

A new method for real-time navigation of mobile robots in complex and mostly unstructured environment is presented. This novel human-inspired method (HIM) uses distance-based sensory data from a laser range finder for real-time navigation of a wheeled mobile robot in unknown and cluttered settings. The approach requires no prior knowledge from the environment and is easy to be implemented for real-time navigation of mobile robots. HIM endows the robot a human-like ability for reasoning about the situations to reach a predefined goal point while avoiding static and moving or unforeseen obstacles; this makes the proposed strategy efficient and effective. Results indicate that HIM is capable of creating smooth (no oscillations) paths for safely navigating the mobile robot, and coping with fluctuating and imprecise sensory data from uncertain environment. HIM specifies the best path ahead, according to the situation of encountered obstacles, preventing the robot to get trapped in deadlock and impassable conditions. This deadlock detection and avoidance is a significant ability of HIM. Also, this algorithm is designed to analyze the environment for detecting both negative and positive obstacles in off-road terrain. The simulation and experimental results of HIM is compared with a fuzzy logic based (FLB) approach.
Study on Life Cycle Assessment of Servo Press With Comparison to Flywheel Press
Authors: Yu Suiran , Liu Yu , Li Lu , Peng Qingjin
Published: February 2014

Heavy duty machines consume a tremendous amount of energy during their life cycle. Therefore, designing an energy efficient machine is of great importance. This paper presents a method for the comparative life cycle assessment (LCA) of two different types of press machines: servo press and flywheel press to understand quantitatively the environmental emissions during their life cycles. To make a fair comparison of the two machines, the same amount of production is used as the basis for comparison. Assessment scopes and boundaries are defined first, then detailed product structures and manufacturing processes are investigated. After data collection from visiting enterprises, related project reports, academic papers, and commercial software databases, analysis of the life cycle inventory is performed. Comparative inventory tables for each life cycle stages and whole life cycle are presented. The results of the study can be used for decision making during the product purchase, planning and design process.
Measuring the Maintainability of Commercial Off-the-Shelf (COTS) Based System Deployments: A Network-Based Approach
Authors: Smith Michael W. , Tate Derrick , Lawson William D.
Published: February 2014

This paper proposes a diagnostic approach to quantify the maintainability of a Commercial Off-the-Shelf (COTS)-based system (CBS) by analyzing the complexity of the deployment of the system. The approach integrates architectural dependencies and the system’s concept of operations to derive a network-based representation of the software system. A greater understanding of the deployment complexity is gained by comparing the in-degree distribution of the derived network to the power-law distribution. The resultant measure is useful in evaluating the maintainability of the operational system while the system is being designed and throughout the lifetime of the system. The measure is applied to deployed production systems with known maintainability histories to validate the approach.
A Numerical Averaging Algorithm for Rapid Simulation of Multiscale Damage Dynamics
Authors: Roy Arjun , Cusumano Joseph P.
Published: February 2014

We study the nonlinear dynamics of damage evolution under periodic loading using a new numerical approach based on the method of averaging. The algorithm can reduce the computational time required for multiscale life-cycle simulations by many orders of magnitude. We use the algorithm to study a previously-developed finite element multiscale continuum damage model, and derive an approximate autonomous rate law for the damage elements. This permits us to efficiently study space-time failure statistics using large ensembles of simulations starting from random initial damage states. The algorithm derivation and simulations illustrate how increased dynamical brittleness reduces the need for higher-order damage terms in the rate laws. We show how localized initial damage gives rise to low-dimensional autonomous rate laws: the geometry of the resulting averaged damage phase space can be used understand the likelihood of different failure modes.
Machining Feature Modeling and Process Intermediate Model Generation in Process Planning
Authors: Zhang Xu , Liang Chao , Si Tiedong , Ding Ding
Published: February 2014

In process planning of machined part, machining feature recognition and representation, feature-based generative process planning, and the process intermediate model generation are the key issues. While many research results have been achieved in recent years, the complete modeling of machining features, process operations, and the 3D models in process planning are still need further research to make the techniques to be applied in practical CAPP systems. In this paper, a machining feature definition and classification method is proposed for the purpose of process planning based on 3D model. Machining features are defined as the surfaces formed by a serious of machining operation. The classification scheme of machining features is proposed for the purpose of feature recognition, feature-based machining operations reasoning, and knowledge representation. Recognized from B-Rep representation of design model, machining features are represented by adjacent graph and organized by feature relations. The machining process plan is modeled as operations and steps, which is the combination and sequencing of machining feature’s process steps. The process intermediate models (PIM) are important for process documentation, analysis and NC programming. An automatic PIM generation approach is proposed using local operations directly on B-Rep model. The proposed data structure and algorithm is adopted in the development of CAPP tool on solid modeler ACIS/HOOPS.
Model Based Biomass System Design of Feedstock Supply Systems for Bioenergy Production
Authors: Cafferty Kara G. , Muth David J. , Jacobson Jacob J. , Bryden Kenneth M.
Published: February 2014

Engineering feedstock supply systems that deliver affordable, high-quality biomass remains a challenge for the emerging bioenergy industry. Cellulosic biomass is geographically distributed and has diverse physical and chemical properties. Because of this feedstock supply systems that deliver cellulosic biomass resources to biorefineries require integration of a broad set of engineered unit operations. These unit operations include harvest and collection, storage, preprocessing, and transportation processes. Design decisions for each feedstock supply system unit operation impact the engineering design and performance of the other system elements. These interdependencies are further complicated by spatial and temporal variances such as climate conditions and biomass characteristics. This paper develops an integrated model that couples a SQL-based data management engine and systems dynamics models to design and evaluate biomass feedstock supply systems. The integrated model, called the Biomass Logistics Model (BLM), includes a suite of databases that provide 1) engineering performance data for hundreds of equipment systems, 2) spatially explicit labor cost datasets, and 3) local tax and regulation data. The BLM analytic engine is built in the systems dynamics software package Powersim™. The BLM is designed to work with thermochemical and biochemical based biofuel conversion platforms and accommodates a range of cellulosic biomass types (i.e., herbaceous residues, short-rotation woody and herbaceous energy crops, woody residues, algae, etc.). The BLM simulates the flow of biomass through the entire supply chain, tracking changes in feedstock characteristics (i.e., moisture content, dry matter, ash content, and dry bulk density) as influenced by the various operations in the supply chain. By accounting for all of the equipment that comes into contact with biomass from the point of harvest to the throat of the conversion facility and the change in characteristics, the BLM evaluates economic performance of the engineered system, as well as determining energy consumption and green house gas performance of the design. This paper presents a BLM case study delivering corn stover to produce cellulosic ethanol. The case study utilizes the BLM to model the performance of several feedstock supply system designs. The case study also explores the impact of temporal variations in climate conditions to test the sensitivity of the engineering designs. Results from the case study show that under certain conditions corn stover can be delivered to the cellulosic ethanol biorefinery for $35/dry ton.
Consistency Management System Between Product Design and the Lifecycle
Authors: Fukushige Shinichi , Matsuyama Yuki , Kunii Eisuke , Umeda Yasushi
Published: February 2014

Within the framework of sustainability in manufacturing industry, product lifecycle design is a key approach for constructing resource circulation systems of industrial products that drastically reduce environmental loads, resource consumption and waste generation. In such design, designers should consider both a product and its lifecycle from a holistic viewpoint, because the product’s structure, geometry, and other attributes are closely coupled with the characteristics of the lifecycle. Although product lifecycle management (PLM) systems integrate product data during its lifecycle into one data architecture, they do not focus on support for lifecycle design process. In other words, PLM does not provide explicit models for designing product lifecycles. This paper proposes an integrated model of a product and its lifecycle and a method for managing consistency between the two. For the consistency management, three levels of consistency (i.e., topological, geometric, and semantic) are defined. Based on this management scheme, the product lifecycle model allows designers to evaluate environmental, economic, and other performance of the designed lifecycle using lifecycle simulation.