bluuebunny/crossref_metadata_2025 huggingface dataset:
Load-Effective Dynamic Motion Planning for Redundant Manipulators
Authors: Kim Joo H. , Yang Jingzhou , Abdel-Malek Karim
Published: May 2009

The robotic motion planning criteria has evolved from kinematics to dynamics in recent years. Many research achievements have been made in dynamic motion planning, but the externally applied loads are usually limited to the gravity force. Due to the increasing demand for generic tasks, the motion should be generated for various functions such as pulling, pushing, twisting, and bending. In this presentation, a comprehensive form of equations of motion, which includes the general external loads applied at any points of the system, is derived and implemented. An optimization-based algorithm is then developed to generate load-effective motions of redundant manipulators (single-loop and tree-structured chains) that guarantee the execution of the generic tasks under limited actuator capacities. It is shown that if the external loads are not incorporated in the motion planning formulation, then the generated motions do not always guarantee the execution of the task, especially when a large load is desired. By using our algorithm, the load-effective motions can be found that are executable for given external loads. The proposed method is also applicable in predicting realistic dynamic human motions. Some dual-arm human tasks are simulated to show different motions to sustain different amounts of external loads. Our formulation for general external loads will further advance the current motion planning methods for redundant manipulators.
Stiffness Modeling and Force Distribution for the All-Terrain Hex-Limbed Extra-Terrestrial Explorer (ATHLETE)
Authors: Collins Curtis L.
Published: May 2009

The All-Terrain Hex-Limbed Extra-Terrestrial Explorer (ATHLETE) is a six limbed vehicle designed for both mobility and manipulation. Each limb has six active degrees-of-freedom, plus a powered wheel. Along the axis if each wheel is a mechanical interface that allows the integration of tools that can make use of the wheel actuator. Thus each limb can act as a leg for walking, an active suspension for a driven wheel, or a manipulator with an actuated tool. Fundamental to the operation of the system is the ability to control limb pose, overall body pose, as well as regulate limb forces. Joint torques are estimated from the difference between the incremental and absolute encoder readings on each joint. Forces are then computed from joint torques and force regulation is performed by modifying the limb positions. Force regulation allows the vehicle to lift larger payloads and traverse terrain while actively complying to terrain features.
A Shear-Lag Model for Nanotube Reinforced Piezoelectric Polymeric Composites Subjected to Electro-Thermo-Mechanical Loadings
Authors: Salehi-Khojin Amin , Jalili Nader
Published: May 2009

Understanding the stress transfer between nanotube reinforcements and surrounding matrix is an important factor in determining the overall mechanical properties of nanotube-reinforced composites. An efficient load transfer from the polymer matrix to the nanotube through interface is required to take the advantage of very high Young’s modulus and strength of carbon nanotubes in the composites. On the other hand, considerable energy dissipation can be obtained by interfacial slippage in the interface of nanotube and matrix which is beneficial in term of structural damping. In order to obtain a composite structure with tunable properties ranges from stiffer structure to better damper, we propose a semi-active control approach. In this method, applied electrical loading to piezoelectric polymeric matrix such as Polyvinylidene Fluoride (PVDF) reinforced with nanomaterials results in radial displacement of piezoelectric polymer corresponding to the direction and magnitude of electrical load. This leads to control of restriction effect of nanotube on the polymer segments, and consequently results in tunable interfacial adhesion between piezoelectric polymer and nanomaterials with faster response time. According to the concept of semi-active control, a shear lag model is obtained for a nanotube reinforced piezoelectric polymer under electro-thermo-mechanical loadings. As the adhesion in carbon nanotube (CNT) composite is universally present in the form of van der Waals interaction, and is the focus of this study, the shear stress and the axial displacement of nanotube and matrix in the interface zone can not be equal. This makes mathematical modeling of interface region more difficult. To solve this complexity, we propose to obtain the relative axial displacement between nanotube and polymer in the interface according to the Lennard-Jones potential function. Results indicate that as the electrical load increases, the relative displacement between nanotube and polymer increases which mean the possibility for slippage increases. Furthermore, results indicate that stiffer structures have more potential to show more switch stiffness capability.
Design and Development of a Fused Vision Force Controller for Nanofiber Grasping and Manipulation
Authors: Saeidpourazar Reza , Jalili Nader
Published: May 2009

This paper presents the design and development of a fused vision force feedback robust controller for a nanomanipulator used in nanofiber grasping and nano-fabric production applications. The RRP (Revolute Revolute Prismatic) manipulator considered here utilizes two rotational motors with 0.1 μrad resolution and one linear Nanomotor® with 0.25 nm resolution. Weighing just about 30g and having short lever arms (<5cm), the manipulator is capable of achieving well-behaved kinematic characteristics without the backlash in addition to atomic scale precision to guarantee accurate manipulation at the nanoscale. A mathematical model of the nanomanipulator is formulated and both direct and inverse kinematics of the system as well as dynamic equations are presented. A fused force vision feedback based modified optimal robust controller with perturbation estimation for nanomanipulator positioning is then derived and analyzed extensively. Unlike typical macroscale manipulator models and controllers, the controller development is not trivial here due to nanoscale movement and forces, coupled with unmodeled dynamics, nonlinear structural dynamics and mainly lack of position and velocity feedback in this nanomanipulator. Following the development of the fused force vision robust controller, numerical simulations of the proposed controller are preformed to demonstrate the positioning performance capability in nanofiber grasping applications.
Experimental and Theoretical Investigation of New Capacitive Switches Activated by Mechanical Shock and Acceleration
Authors: Alsaleem Fadi M. , Younis Mohammad I. , Miles Ronald , Su Quang
Published: May 2009

This paper presents experimental and theoretical investigation into the characteristics and performance of a new class of switches (triggers) actuated at or beyond a specific level of mechanical shock or acceleration. The principle of operation of the switches is based on dynamic pull-in instability induced by the combined interaction between electrostatic and mechanical shock forces. Two commercial off-the-shelf capacitive accelerometers operating in air are tested under mechanical shock and electrostatic loading. A single-degree-of-freedom model accounting for squeeze-film damping, electrostatic forces, and mechanical shock is utilized for the theoretical investigation. Good agreement is found between the simulation results and experimental data. Our results indicate that designing these new switches to respond quasi-statically to mechanical shock makes them robust against variations in shock shape and duration. More importantly, this makes the switches insensitive to variations in damping conditions. This can be promising to lower the cost of packaging for these switches since they can operate in atmospheric pressure with no hermetic sealing or costly package required.
Nonlinear Vibrations of a Piezoelectrically-Driven Microcantilever for Biologically-Induced Surface Stress Sensing
Authors: Mahmoodi S. Nima , Afshari Mana , Jalili Nader
Published: May 2009

In this paper, nonlinear vibrations of a piezoelectrically-driven microcantilever beam in presence of a biological monolayer are investigated and the corresponding equations of motion are derived and simulated. A part of the microcantilever beam surface is covered by a piezoelectric layer, which acts as an actuator. Inextensibility condition and the coupling between electrical and mechanical properties in piezoelectric materials are considered in the bending vibrations of the beam. The adsorbed biological layer is considered to be a monolayer and its adsorption induced surface stress is formulated from the molecular viewpoint. The nonlinear terms in the governing equations of motion of the beam appear in the form of quadratic due to presence of piezoelectric layer, and cubic due to geometry of the beam and the adsorbed biological layer. Through extensive numerical simulations, it is demonstrated that the nonlinear effect of piezoelectric layer is significant in the microcantilever resonance sensing range. It is also shown that the effect of intermolecular attraction/repulsion on the surface stress is less dominant than other sources of surface stress (e.g., the electrostatic forces). Finally, it is observed that piezoelectrically-actuated microcantilever provides the ability of indirect measurement of vibrations and frequency response characteristics, instead of using bulky laser sensor.
Transient Shear Wave Propagation in a Viscoelastic Gel Cylinder: Comparison of Theory to MRI-Based Measurements
Authors: Sabet A. , Genin G. M. , Zatlin B. , Christoforoue E. , Bayly P. V.
Published: May 2009

Shear strain patterns in a cylindrical gelatin sample under transient angular acceleration were measured by tagged magnetic resonance imaging (MRI). Measured strain fields were compared to theoretical strain fields obtained by finite element (FE) simulation. Agreement between theory and experiment is very good. The current results support the utility of the experimental approach for tasks such as measurement of shear waves in brain tissue during angular acceleration of the skull. The results also show that a simple viscoelastic model is suitable to describe rapid shear deformation of a gel biomaterial.
A Sensitivity Study on Static and Dynamic Detection Modes of Adsorption-Induced Surface Stress in Microcantilever Biosensors
Authors: Afshari Mana , Jalili Nader
Published: May 2009

Microcantilever biosensors may be utilized as a platform for the adsorption induced surface stress measurements. This can be done by measuring either the static deflection of the microcantilever after the adsorption or the adsorption induced shift in its resonance frequency. This paper presents a new method of formulating the adsorption induced surface stress as a function of the static deflection of the microcantilever. Most of the previous works in this area are based on the Stoney’s simple equation. In the proposed method, the molecular interactions of the adsorbed biological species are modeled based on the Lennard-Jones attraction/repulsion potential. As a result, the sensitivity of the static detection mode (based on the proposed method) is compared to that of the dynamic mode. It is shown that the dynamic mode of biosensing is much more sensitive to the change in the properties of the adsorbed biological species, when compared to conventional static mode detection mechanism.
A Geometric Approach to Constraint Stabilization for Holonomic Lagrangian Systems
Authors: Yoshimura Hiroaki
Published: May 2009

In this paper, we develop a geometric approach to constraint stabilization for holonomic mechanical systems in the context of Lagrangian formulation. We first show that holonomic mechanical systems, for the case in which a given Lagrangian is hyperregular, can be formulated by using the Lagrangian two-form, namely, a symplectic structure on the tangent bundle of a configuration manifold that is induced from the cotangent bundle via the Legendre transformation. Then, we present an idea of geometric constraint stabilization and we show that a holonomic Lagrangian system with geometric constraint stabilization can be formulated by the Lagrange-d’Alembert principle, together with its local coordinate expression for the sake of numerical computations. Finally, we illustrate the numerical verification that the proposed method enables to stabilize constraint violations effectively in comparison with the Baumgarte and Gear–Gupta–Leimkuhler methods together with an example of a linkage mechanism.
Haptic Interface for Real-Time Evaluation and Modification of Shape Design
Authors: Bordegoni Monica , Cugini Umberto
Published: May 2009

The paper presents the results of a research project aiming at developing an innovative framework for conceptual design of products based on innovative haptic interfaces. The framework consists of a CAD (Computer Aided Design) system enhanced with intuitive interaction tools and modalities for modeling, modification and evaluation of shapes. The system aims at exploiting designers’ skills in modeling products, improving the products design process by reducing the necessity to build several physical models for evaluating and testing the product designs. The system proposes an emotional engineering approach by supporting product designers in translating their sensibility into physical design factors, allowing easy and fast creation and evaluation of diverse shape solutions. The system requirements have been defined after observing designers during their daily work and translating the way they evaluate and modify shapes using hands and craft tools into specifications for the modeling system and the haptic tool. The system prototype has been tested by designers who have found it intuitive and effective to use.
Explicit Solutions for Nonlinear Partial Differential Equations Using Bezier Functions
Authors: Venkataraman P. , Michopoulos J. G.
Published: May 2009

This paper presents a methodology for generating solutions of non linear partial differential equations through Bezier functions. These functions define corresponding Bezier surfaces using a bipolynomial Bernstein basis function. The solution, or essentially the coefficients, is identified through design optimization. The set up is direct, elegantly simple, and involves minimizing the error in the residuals of the differential equations over the domain. No domain discretization is necessary. The procedure is not problem dependent and is adaptive through the selection of the order of the Bezier functions. Two examples: (1) the laminar flow over a flat plate; and (2) displacement of an ionic polymer-metal composite membrane are solved. Alternate solution to these problems is referenced in the paper.
Synthesis of Demand Signals for High Speed Operation of a Packaging Mechanism
Authors: Sahinkaya M. Necip , Rayner Robert M. C. , Vernon Geoff , Shirley Graham , Aggarwal Raj K.
Published: May 2009

The aim of the work described in this paper is to improve the dynamic performance of a one-degree-of-freedom packaging mechanism through demand signal shaping to minimize the peak to peak motor torque. This enables the mechanism to operate at higher speeds with lower vibration and noise levels, and hence with higher accuracy. Initial experimental tests have shown the motion of the Woodpecker mechanism to suffer from dynamic, vibration problems synonymous with a mechanism possessing large amounts of harmonic content in its output motion. The dynamics of the Woodpecker mechanism and the accompanying servo system are developed and the likely causes of the dynamic issues experienced are identified. A computer model of the complete system drive unit is developed utilizing experimental data. The intention is to use the model in further detailed analytical work to shape the velocity demand signal passed to the system. Inverse dynamics are used to derive the variation in driving torque, which must be exerted on the mechanism crank by the drive motor for the mechanism to achieve a constant speed over the complete cycle. Based on the computer model, a novel technique to shape the speed demand signal is developed and it is shown that significant performance improvements can be achieved without re-synthesizing the mechanism or altering the existing industrial controller.
Decomposition Strategies for the Synthesis of Single Input-Single Output and Dual Input-Single Output Compliant Mechanisms
Authors: Kim Charles
Published: May 2009

In this paper a new method for the synthesis of compliant mechanism topologies is presented which involves the decomposition of motion requirements into more easily solved sub-problems. The decomposition strategies are presented and demonstrated for both single input-single output (SISO) and dual input-single output (DISO) planar compliant mechanisms. The methodology makes use of the single point synthesis (SPS) which effectively generates topologies which satisfy motion requirements at one point by assembling compliant building blocks. The SPS utilizes compliance and stiffness ellipsoids to characterize building blocks and to combine them in an intelligent manner. Both the SISO and DISO problems are decomposed into sub-problems which may be addressed by the SPS. The decomposition strategies are demonstrated with illustrative example problems. This paper presents an alternative method for the synthesis of compliant mechanisms which augments designer insight.
Algorithms for Extraction of Nanowires Attributes From Optical Section Microscopy Images
Authors: Peng Tao , Balijepalli Arvind , Gupta Satyandra K. , LeBrun Thomas W.
Published: May 2009

Optical tweezers have emerged as a unique tool for micro and nanomanipulation. In an optical tweezers-based assembly cell, components are usually suspended in a fluidic medium and undergo constant random Brownian motion. Automated assembly using optical tweezers requires online monitoring of components in the assembly workspace. Nanowires are very important building blocks for constructing nanoscale devices. This paper presents algorithms for estimating length, location, and orientation of nanowires in the workspace using images obtained by optical section microscopy. The images are first segmented to locate general areas of interest which are then analyzed to determine discrete nanowire parameters. We use image gradient based techniques as well as feature extraction techniques to identify parameters of nanowire image patterns. These parameters are then used to estimate length, location, and orientation of nanowires.
Vibration-Based Energy Harvesting With Essential Nonlinearities
Authors: Quinn D. Dane , Vakakis Alexander F. , Bergman Lawrence A.
Published: May 2009

The implementation of energy harvesting devices enables and extends the operational capabilities of a wide variety of devices, including portable electronics and inaccessible sensors. While linear energy harvesting devices have been shown to be effective for power generation in some environments, they must be tuned to the single dominant frequency of the excitations. In contrast, this work investigates the energy harvesting capabilities of attachments based on essentially nonlinear elements. Although primarily a numerical study, the results suggest that the use of essentially nonlinear attachments for harvesting energy low-level broadband vibration sources is not only possible but also efficacious, leading to performance gains that may be orders of magnitude superior to that of corresponding linear devices for broadband low-frequency excitations.
Design and Testing of the Frontal Impact Attenuator for a Formula SAE Vehicle
Authors: Braghin Francesco , Gottardi Diego , Morandi Fabio , Tartaglia Mattia
Published: May 2009

According to FSAE rules ([1]), the frontal impact attenuator, when mounted on the front of a vehicle with a total mass of 300kg that is run into a solid, non-yielding impact barrier with a velocity of impact of 7.0 m/s, has to give an average deceleration of the vehicle not to exceed 20 g. Thus, FSAE teams have to design and test, either experimentally or numerically, their frontal impact attenuator and submit an “Impact Attenuator Calculations” form. Several different frontal impact attenuator solutions were numerically tested and the best one in terms of deceleration, compactness and weight was experimentally tested using a very simple catapult thus allowing to validate the numerical models.
Including Preference in Anthropometry-Driven Models for Design
Authors: Garneau Christopher J. , Parkinson Matthew B.
Published: May 2009

In the design of artifacts that interact with people, the spatial dimensions of the user population are often used to size and engineer the artifact. The variability in body dimensions (called “anthropometry”) is used to indicate how much adjustability or how many sizes are required to accommodate the intended user population. However, anthropometry is not the only predictor of these kinds of interactions. For example, two vehicle drivers with similar body dimensions might have very different preferred locations for the seat. The variability not predicted by body dimensions can be considered “preference”. Well-conceived models considering all sources of variability can can facilitate the application of design automation tools such as optimization and robust design methodologies, resulting in products that are safer, cost effective, and more accessible to broader populations (including people with disabilities). In contrast, poor models and those that fail to include a preference component can produce misleading results that under- or over-approximate accommodation and prescribe inappropriate amounts of adjustability. This paper reviews common methods of designing for human variability, demonstrating the use and strengths and weaknesses of each. This is done in the context of a simple, univariate case study to determine the appropriate allocation of adjustability to achieve a desired accommodation level.
Representation and Analysis Challenges in Design for Part-Reuse: An Automotive Case Study
Authors: Kintner Hallie J.
Published: May 2009

Product Platform and Product Family Design is reshaping the way that many companies develop products. But how well are the CAD and PLM technologies keeping pace with this advancement? This paper presents data from a three month ethnographic study of an expert automotive body engineer. His assignment is to modify the design of an existing body structural member for use in the next-generation vehicle. The modification was necessitated by manufacturability issues. Observations and subsequent interviews revealed that manipulation time, model reuse and representation of part interfaces (such as welds) presented challenges to the body engineer and collaborating analysis engineers. Despite re-use of a physical part, the engineer had to create a new CAD model. The redesign involved breaking the original part into two pieces. The engineer sketched initial design concepts on paper because manipulation time in the CAD system was so lengthy. After determining the design concept, the engineer created a new CAD model, including new weld locations, and passed it along to analysis engineers for stiffness and crashworthiness FEA testing. Hand-offs between design and analysis engineers were challenged by the PLM system. The paper ends by making recommendations for improving CAD and PLM tools.
An Alternate Geometry for a Piezoelectric MEMS Microphone, Part I: Design and Analysis
Authors: Littrell Robert , Cheng Lei , Grosh Karl
Published: May 2009

Microphones fabricated using microelectromechanical systems (MEMS) technology are one of the fastest growing applications of MEMS. While most commercial MEMS microphones are sensed capacitively, piezoelectric MEMS microphones require less accompanying electronics and offer increased linearity. Currently, piezoelectric MEMS microphones suffer from high noise levels, limiting their applicability. This paper presents an alternative sensor geometry consisting of a cantilever beam electrostatically clamped to the center of a diaphragm that both favorably concentrates stress from the applied acoustic load and eliminates the deleterious effects of residual stress in the piezoelectric material. A complete analysis of the sensitivity and noise characteristics of the electromechanical design (including the amplifying electronics) is performed and compared to a design employing a piezoelectric layer on a diaphragm. The analysis has shown that the proposed geometry can be used to build microphones sensed via aluminum nitride with noise levels around 48 dBA while similar materials and sizes result in noise levels around 57 dBA using the standard geometry.
Efficient Methodology for Multibody Simulations With Discontinuous Changes in System Definition
Authors: Mukherjee Rudranarayan M. , Anderson Kurt S.
Published: May 2009

A new algorithm is presented for accurately and efficiently simulating multi-scale multibody systems with discontinuous changes in system definitions as encountered in adaptive switching between models with different resolutions as well as models with different system topologies. An example of model resolution change is a transition of a system from a discrete particle model to a reduced order articulated multi-rigid body model. An example of model topology change is the transition of a system from a serial chain to closed kinematic loop topology or vice versa. An impulse-momentum formulation is implemented in a Divide and Conquer scheme which conserves the generalized momentum of the system and preserves the essential dynamics of the system. This process couples together the impulse-momentum equations of the individual bodies to formulate and solve the corresponding equations for the whole system using the boundary conditions. This results in an inherently substructured form of equations within the formulation making it highly conducive to adjusting / modifying model types within a substructure. The algorithm is applicable to general systems with either tree or closed loop topologies. This method maintains linear and logarithmic complexity in serial and parallel implementations respectively.
Design Sensitivity Analysis of Nonlinear Multidisciplinary Multibody Systems in the MIXEDMODELS Platform
Authors: Vaze Shilpa A. , Krishnaswami Prakash , DeVault James
Published: May 2009

Most state-of-the-art multibody systems are multidisciplinary and encompass a wide range of components from various domains such as electrical, mechanical, hydraulic, pneumatic, etc. The design considerations and design parameters of the system can come from any of these domains or from a combination of these domains. In order to perform analytical design sensitivity analysis on a multidisciplinary system (MDS), we first need a uniform modeling approach for this class of systems to obtain a unified mathematical model of the system. Based on this model, we can derive a unified formulation for design sensitivity analysis. In this paper, we present a modeling and design sensitivity formulation for MDS that has been successfully implemented in the MIXEDMODELS (Multidisciplinary Integrated eXtensible Engine for Driving Metamodeling, Optimization and DEsign of Large-scale Systems) platform. MIXEDMODELS is a unified analysis and design tool for MDS that is based on a procedural, symbolic-numeric architecture. This architecture allows any engineer to add components in his/her domain of expertise to the platform in a modular fashion. The symbolic engine in the MIXEDMODELS platform synthesizes the system governing equations as a unified set of non-linear differential-algebraic equations (DAE’s). These equations can then be differentiated with respect to design to obtain an additional set of DAE’s in the sensitivity coefficients of the system state variables with respect to the system’s design variables. This combined set of DAE’s can be solved numerically to obtain the solution for the state variables and state sensitivity coefficients of the system. Finally, knowing the system performance functions, we can calculate the design sensitivity coefficients of these performance functions by using the values of the state variables and state sensitivity coefficients obtained from the DAE’s. In this work we use the direct differentiation approach for sensitivity analysis, as opposed to the adjoint variable approach, for ease in error control and software implementation. The capabilities and performance of the proposed design sensitivity analysis formulation are demonstrated through a numerical example consisting of an AC rectified DC power supply driving a slider crank mechanism. In this case, the performance functions and design variables come from both electrical and mechanical domains. The results obtained were verified by perturbation analysis, and the method was shown to be very accurate and computationally viable.
Attractive Force Based on Fractional Potential in Dynamic Motion Planning for Mobile Robot
Authors: Melchior Pierre , Metoui Brahim , Poty Alexandre , Najar Slaheddine , Oustaloup Alain , Abdelkrim Mohamed Naceur
Published: May 2009

In path planning, potential fields introduce force constraints to ensure curvature continuity of trajectories and thus to facilitate path-tracking design. In previous work, a path planning design by fractional (or generalized) repulsive potential has been developed to avoid fixed obstacles. A fractional road was determined by taking into account danger of each obstacle. Danger level of each obstacle is characterized by the fractional order of differentiation. Then a new attractive force based on fractional potential was introduced, with the aim to extend the method to dynamic obstacles characterized by fractional potential fields. In this paper a comparison between each classical attractive force is presented. Then the new attractive force based on fractional potential is introduced. Finally, this attractive force is applied on an example and compare with the Ge and Cui method which is the classical potential fields for motion planning of mobile robots in a dynamic environment.
Automated Fault Tree Analysis for Engineering Design Optimization
Authors: Shao Tiefu , Lin Zongfang , Krishnamurty Sundar , Grosse Ian R. , Osterweil Leon J.
Published: May 2009

This paper presents an automated fault tree analysis for engineering design optimization process. Specifically, a novel approach is presented in which Little-JIL, a process programming language, is applied to create a process model of engineering optimization. The process model uses a graphical language in the form of easy-to-understand block diagrams for defining processes that coordinate the activities of autonomous agents and their use of resources during the performance of a task. The use of Little-JIL facilitates agent coordination in the design optimization process and helps to model the order of and the communications between units of sub-processes. The resulting process model is easy to debug and is rigorous for simulation and formal reasoning in engineering design optimization. Furthermore, it enables the development of a clear and precise design optimization process model at different levels of granularity as perhaps preferred by the user. Moreover, since the process model allows for generation of fault trees automatically, it can be expected to be less errorprone than manually generated ones. A case study is shown to demonstrate the effectiveness and efficiency of the automated fault tree approach to design optimization and its usefulness in engineering decision making and in improving reliability of engineering design process.
Lower Order Tetrahedral Finite Elements With Rotational Degrees of Freedom for Solid Modelling
Authors: To Cho W. S. , Hua Xiao
Published: May 2009

The investigation reported in this paper is concerned with the development of efficient, conceptually simpler, mathematically rigorous and physically meaningful three-dimensional (3D) finite elements for solid modelling. A mixed variational principle based on the hybrid strain formulation has been adopted for the derivation of element stiffness matrices of two lower order tetrahedral finite elements. Explicit expressions for element matrices have been derived with a combination of hand manipulation and computer algebraic package, MAPLE. Each of the two finite elements has four nodes. Every one of the latter has six degrees of freedom (DOF). These include three translational and three rotational DOF. Element performance is evaluated with benchmark problems. For brevity, only two benchmark problems are included in this paper. It is shown numerically that the results converge to the true solution and have superior accuracy compared with those previously published in the literature. Mathematically, the elements being proposed are simple and frame invariant. Computationally, they are very efficient compared with higher order tetrahedral finite elements and other lower order tetrahedral finite elements.
Investigation of Boundary Conditions for Flexible Multibody Spacecraft Dynamics
Authors: MacLean John R. , Huynh An , Quiocho Leslie J.
Published: May 2009

In support of both the Space Shuttle and International Space Station programs, a set of generic multibody dynamics algorithms integrated within the Trick Simulation Environment have addressed a variety of on-orbit manipulator simulation requirements for engineering analysis, procedures development and crew familiarization/training at the NASA Johnson Space Center (JSC). Enhancements to these dynamics algorithms are now being driven by a new set of Constellation program requirements for flexible multibody spacecraft simulation. One particular issue that has been discussed within the NASA community is the assumption of cantilever-type flexible body boundary conditions. This assumption has been commonly utilized within manipulator multibody dynamics formulations as it simplifies the computation of relative motion for articulated flexible topologies. Moreover, its use for modeling of space-based manipulators such as the Shuttle Remote Manipulator System (SRMS) and Space Station Remote Manipulator System (SSRMS) has been extensively validated against flight data. For more general flexible spacecraft applications, however, the assumption of cantilever-type boundary conditions may not be sufficient. This paper describes the boundary condition assumptions that were used in the original formulation, demonstrates that these equations can be augmented to accommodate systems in which the assumption of cantilever boundary conditions no longer applies, and verifies the approach through comparison with an independent model previously validated against experimental hardware test data from a spacecraft flexible dynamics emulator.
Robust Product Family Consolidation and Selection Using the Hypothetical Equivalents and Inequivalents Method
Authors: Dolan Bryan R. , Lewis Kemper E.
Published: May 2009

The design and development of effective product lines is a challenge in modern industry. Companies must balance diverse product families that satisfy wide ranging customer demands with practical business needs such as combining manufacturing processes and using similar materials, for example. In this paper, the issue of consolidating an existing product family is addressed. Specifically, the Hypothetical Equivalents and Inequivalents Method (HEIM) is utilized in order to select an optimal product family configuration. In previous uses, HEIM has been shown to assist a decision maker in selecting one concept from a set when concept attributes conflict with each other. In this extension of HEIM, the optimization problem’s constraints are formulated using two different value functions, and common solutions are identified in order to select an optimal family of staplers. The result is then compared with the result found using a multi-attribute utility theory (MAUT) based approach. While each method has its advantages and disadvantages, and MAUT provides a necessary first step for product family consolidation and selection, a robust solution is achieved through HEIM.
Visualizing Energy: How BIM Influences Design Choices
Authors: Hedges Keith E. , Denzer Anthony S.
Published: May 2009

This paper investigates how the infusion of a parametric object-based Building Information Modeling (BIM) methodology has influenced the design responses of engineering students in architectural design studios. BIM provides students with an opportunity to explore the consequences of design alternatives through three-dimensional representation in addition to two-dimensional abstraction during the schematic design phase. The authors qualitatively evaluate data in the participant observation tradition garnered from two architectural design studios in an architectural engineering program. The purpose is to explore how students respond when offered opportunities to visualize energy performance in concert with architectural design. The results indicate that BIM provides more time for realizing the design idea, thereby inducing a higher level of intellectual behavior where the students visually evaluate multiple conditions of design iterations in a qualitative manner while bringing to life the numerical application and analysis procedures of quantitative theory. The engineering students make relatively sophisticated choices regarding building orientation, passive solar heating, daylighting, and envelope design and materials selection.
The Use of Really Simple Syndication (RSS) Feeds for Improved Information Communication in Decentralized Decision Systems
Authors: Gurnani Ashwin P. , Lewis Kemper
Published: May 2009

In today’s global product development environment, the design of large scale systems is completed by distributing design tasks to various subsystems that are located in different parts of the world. Though such a process reduces the product development time (due to concurrent completion of design tasks), there also exists the possibilities of errors due to information communication and handling among the distributed subsystems. Errors in information communication get amplified when there exist a large number of subsystems with high coupling between them. Causes for errors in design information communication include loss of design information emails, corruption of attachments that include product data, duplication of files at multiple locations, different software being used to complete the same design task, etc. All these factors contribute to delays in the product development process. In this paper, a new approach for design information communication that utilizes Really Simple Syndication (RSS) feeds is proposed. Most information providing websites provide their users with RSS feeds that include the latest available news. In this paper, the same process is incorporated for design information communication within decentralized design through the use of a web-based design environment. The design of a golf driver head by two subsystems is used as a case study.
An Approach to Improved Decentralized Design: The Modified Approximation-Based Decentralized Design (MADD) Framework
Authors: Gurnani Ashwin P. , Lewis Kemper
Published: May 2009

The design of large scale complex engineering systems requires interaction and communication between multiple disciplines and decentralized subsystems. One common fundamental assumption in decentralized design is that the individual subsystems only exchange design variable information and do not share objective functions or gradients. This is because the decentralized subsystems can either not share this information due to geographical constraints or choose not to share it due to corporate secrecy issues. Game theory has been used to model the interactions between distributed design subsystems and predict convergence and equilibrium solutions. These game theoretic models assume that designers make perfectly rational decisions by selecting solutions from their Rational Reaction Set (RRS), resulting in a Nash Equilibrium solution. However, empirical studies reject the claim that decision makers always make rational choices and the concept of Bounded Rationality is used to explain such behavior. In this paper, a framework is proposed that uses the idea of bounded rationality in conjunction with set-based design, metamodeling and multiobjective optimization techniques to improve solutions for convergent decentralized design problems. Through the use of this framework, entitled Modified Approximation-based Decentralized Design (MADD) framework, convergent decentralized design problems converge to solutions that are superior to the Nash equilibrium. A two subsystem mathematical problem is used as case study and simulation techniques are used to study the impact of the framework parameters on the final solution. The discipline specific objective functions within the case study problem are unconstrained and continuous — however, the implementation of the MADD framework is not restricted to such problems.
Use of Random Excitation to Develop Pod Based Reduced Order Models for Nonlinear Structural Dynamics
Authors: Kumar Nishant , Burton Thomas D.
Published: May 2009

This paper considers use of Proper Orthogonal Decomposition (POD), also known as the Karhunen-Loeve (K-L) method, to obtain reduced order dynamic models of nonlinear structural systems. The study applies POD to simulated time series data to extract dominant “modes” that describe the system behavior. The “POD modes” are used to formulate reduced order differential equation models (ROM’s) of the structure in which the dependent variables are the POD modal coordinates. Two example systems are considered: 1) a clamped beam whose tip is placed between attracting magnets; POD analysis of this system was done by Feeny and Kerschen [1] using harmonic excitation to excite chaotic motions, which were analyzed to develop the POD modes for reduced order modeling, and 2) a chain of oscillators having an isolated nonlinear Duffing element. Our approach is to generate the POD modes for model reduction by using strong, band limited random excitation to excite vibratory motions. The richness of this type of excitation is intended to provide responses whose POD-based reduced models can be used with reasonable accuracy for system parameters that differ from those used to generate the reduced order model (this is the central issue in using POD to generate reduced order nonlinear models of structures). Our results indicate that, due to the spectral richness of the random excitation, this type of excitation can be used with reasonable accuracy for conditions that differ from those used to generate the reduced order model. The method works well for the chain of oscillator system, but less well for the magnetic beam system, due to the presence of multiple stable equilibria in this system. A useful result of this work is the finding that the number of POD modes required to achieve accurate reduced order differential equation models may be considerably larger than the number of POD modes needed to accurately project the full model responses onto a subspace defined by dominant POD modes. Also, it is shown that for the clamped beam problem with multiple equilibria, we require more modes to develop a reduced order model than we require for a chain of oscillators.
Path Planning for Origami Carton Folding With a Multi-Fingered Robotic System
Authors: Yao Wei , Dai Jian S.
Published: May 2009

This paper investigates the algorithm of origami carton folding with a multi-fingered robotic carton-packaging system. The equivalent mechanism structure of origami cartons is developed by modeling carton boards as links and creases as revolution joints. The trajectories of carton folding are analyzed by the mechanism model. Particularly the vertex of the carton is identified as a spherical linkage. A path planning algorithm is then generated based on the trajectory that is passed on to the tip of a five-bar robotic finger and the finger configuration space is identified. A test rig with two robotic fingers was developed to demonstrate the principle.
Evolution Based Synthesis of Metamorphic Mechanisms
Authors: Zhang Liping , Wang Delun , Dai Jian S.
Published: May 2009

A new methodology for configuration design of metamorphic mechanisms is developed based on genetic evolutionary operation with biological building blocks. The goal is to conceive the appropriate source-metamorphic-mechanism configuration given the multiple phases of kinematic functions in motion specifications. The key enabler of configuration synthesis is the method of capturing the metamorphic configuration characteristics and the genetic evolutionary criteria and of developing genetic evolution in modeling and design. With the unique characteristics of achieving multiple working-phase functions, the metamorphic mechanisms possess two features: one, the ametabolic feature referring to the specified sub-working phases that can be accomplished by traditional mechanisms; two, the metamorphic feature occurring transition between different working phases resulting change of topology of the mechanism. Based on this transition between phases, the concept of mechanism evolution is for the first time introduced in this paper based on biological building blocks in the form of metamorphic cells and associated inner elements as the metamorphic gene. This leads to development of cell evolution and genetic aggregation forms with mechanism decomposition and evolution formulation based on mapping from the source-metamorphic-mechanism to multi-phases working configurations. Examples are given to demonstrate the concept and principles.
Wear Prediction of Total Hip Prostheses Due to Common Activities
Authors: Onisoru Justin , Enescu Nicolae , Iarovici Aron , Capitanu Lucian
Published: May 2009

The wear prediction of artificial joints is a very difficult task due to several factors. First, one could notice a large domain of joint loading due to the wide spectrum of common activities. Secondary, to account for the evolution of contact conditions due to wearing could imply a high level of nonlinearity and time-consuming algorithms in order to solve. The authors tried to overcome all these difficulties by using a complex predictive model that combines statistical evaluation, nonlinear mechanical analyses of load transfer by the contact interface and tribological estimations of the wear characteristics. After a theoretical description of the predictive model, one could notice an application for an artificial Total Hip Prosthesis — a frictional CoCr alloy on ultra high molecular weight polyethylene (UHMWPE) couple. Several loading regimes are considered as characteristic for the common activity of the patient (normal walking, stair ascending and descending). For every regime a dynamic Finite Element simulation of the frictional contact was performed establishing the contact traces and the contact pressure distribution. Those characteristics combined with the frequencies of the activities considered are input data for computing a special point function which distribution over the contact surface could be a good measure of the wearing regime, qualitatively as quantitatively.