bluuebunny/crossref_metadata_2025 huggingface dataset:
Principles of Green Design: Analyzing User Activities and Product Feedback
Authors: Esposito Nicole , Linsey Julie
Published: September 2013

This study investigated the design principles applicable to environmentally friendly product design. An experimental approach was taken to examine principles that aid designers in producing an eco-friendly product that consumers will enjoy and use. Another important aspect to this study was to determine whether a user’s positive environmental attitude or a willingness to change for the environment relates to environmentally responsible behavior. Two hypotheses were developed for successful eco-friendly products and then appropriate products were purchased and modified to test these hypotheses. The activity hypothesis claims that if a product adds user activities, is less likely to be used. The feedback hypothesis states that a product that gives clear feedback is more likely to be used than a product that does not. Student participants took home products to use for one week, recorded each time they used the products, and then completed surveys afterword. For the activity hypothesis, we supposed that the product not adding user activities would be used more than the product adding activities. However, the experimental results have shown that this may not always be the case. For the feedback hypothesis, we speculated that visual reminder feedback and energy savings feedback both increase product usage. An increase in eco-friendly product usage would lead to a lessened negative impact that products are having on our environment. Experimental results indicate that there were errors in the experimental design, but these problems also aid in future work for this research.
Automated Indirect Optical Micromanipulation of Biological Cells Using Indirect Pushing for Minimizing Photo-Damage
Authors: Thakur Atul , Chowdhury Sagar , Svec Petr , Wang Chenlu , Losert Wolfgang , Gupta Satyandra K.
Published: September 2013

Precise micromanipulation of cells or other living systems is allowing for cell transport, sorting, characterization of mechanical properties, cell-cell interaction, migration studies, etc. In this paper, we report an automated indirect pushing-based approach for micromanipulation of cells using dielectric silica beads. In this approach, an optically actuated dielectric silica bead pushes on other bead that in turn pushes the cell, thereby minimizing photo-damage. We have defined three parametrized atomic maneuvers namely, push, align, and go behind the intermediate bead and used them to compose a feedback plan for in-direct pushing. We have developed a simplified dynamics model, which is used in the simulation of operations involving pushing of cells using optically trapped beads. We also present an optimization-based approach for automated tuning of maneuver parameters for different turning angles and measurement noise to increase the robustness of the developed feedback planner. Finally, we have tested the developed planner on a physical setup and obtained experimental results.
Effects of Non-Linear Wheel Suspension Bushing on Vehicle Response
Authors: Jerrelind Jenny , Arteaga Ines Lopez , Drugge Lars , Kari Leif
Published: September 2013

This work presents an analysis of the effects of non-linear characteristics of a top mount bushing in the wheel suspension of a vehicle when evaluating vehicle characteristics such as comfort and handling. The investigation is performed by comparing simulation results from a quarter car model when using a non-linear bushing model and an approximated linear bushing model. It is revealed when analysing the results that there are differences in the response when comparing measures such as sprung mass acceleration, rattle space ratio and tyre-ground contact force. The conclusion is that the more detailed bushing model mainly affects the acceleration levels especially at high frequencies where the linear model underestimates the acceleration. The rattle space ratio and tyre-ground contact force are also affected but not to the same extent.
A Spring-Loaded Inverted Pendulum Locomotion Model With Radial Forcing
Authors: Larson Peter , Seipel Justin
Published: September 2013

Recent locomotion models have demonstrated the benefits of hip torques on legged locomotion stability. Here, a simple constant radial forcing function along the leg of the Spring-Loaded Inverted Pendulum (SLIP) model is added. This model is analyzed in order to determine what effect such a radial force might have on the stability of locomotion versus the more commonly used hip-torque forcing. The model is found to be unstable for the vast majority of the parameter space studied, for any amount of added forcing and damping constants. This suggests that simple constant forcing along the leg does not produce stable locomotion, unlike the case where forcing happens via hip torque.
Load Transducer Design Using Inverse Method With Model Reduction
Authors: Gupta Deepak K. , Dhingra Anoop K.
Published: September 2013

This paper presents an inverse approach for estimating time varying loads acting on a structure from experimental strain measurements using model reduction. The strain response of an elastic vibrating system is written as a linear superposition of strain modes. Since the strain modes as well as the normal displacement modes are intrinsic dynamic characteristics of a system, the dynamic loads exciting a structure are estimated by measuring induced strain fields. The accuracy of estimated loads is dependent on the placement of gages on the instrumented structure and the number of retained strain modes from strain modal analysis. A solution procedure based on construction of D-optimal design is implemented to determine the optimum locations and orientations of strain gages. An efficient approach is proposed which makes use of model reduction technique, resulting in significant improvement in the dynamic load estimation. Validation of the proposed approach through a numerical example problem is also presented.
Adaptive Heliostat Solar Arrays Using Shape-Optimized Compliant Mirrors
Authors: Meng Li , Bilton Amy M. , You Zheng , Dubowsky Steven
Published: September 2013

In a Solar Power Tower (SPT) system, the ideal shape of a heliostat concentrator is a section of paraboloid which is a function of the location in the array and the incidence sun angle. This shape is difficult to achieve and limits the system efficiency. A shape-optimized compliant (SOC) design of parabolic heliostats is presented here to solve this problem. An approximation of the ideal shape is suggested to use an optimized stationary paraboloid shape which only varies with heliostat location in the array. A compliant structure design is proposed that to use a simple flat mirror with a two-dimensional tailored stiffness profile to form the required parabolic surface using adjustment mechanisms at each corner. This design is validated by numerical simulations including FEA tools, ray tracing, and classical nonlinear optimization. The annual performance shows that the SOC heliostat will substantially improve the efficiency and benefit the SPT system.
Towards Energy Efficient Follow Behaviors for Unmanned Ground Vehicles Over Rugged Terrains
Authors: Dabbeeru Madan M. , Langsfeld Joshua D. , Svec Petr , Gupta Satyandra K.
Published: September 2013

This paper focuses on the development of a follow behavior for an unmanned ground vehicle (UGV) in collaborative scenarios. The scenario being studied involves a human traveling over a rugged terrain on foot. The UGV follows the human. We present an approach for automatically generating a reactive energy-efficient follow behavior that maps the vehicle’s states into motion goals. We start by partitioning the state space that encodes the relationship between the state of the vehicle and the human’s state, and the environment. For each cell in the partitioned state space, we either directly generate the motion goal for the vehicle to execute or a function that produces the motion goal. The motion goal defines not only the location towards which the vehicle should move but also specifies a zero activity zone around the human within which the vehicle is supposed to slow down and remain stationary to save its energy until it gets outside the margin caused by the movement of the human. Our approach utilizes off-line simulations to assess the performance of the generated behavior. Our simulation results show that the automatically generated follow behavior significantly outperforms a simple conservative tracking rule in terms of distance traveled and violation of proximity constraints. We anticipate that the approach presented in this paper will ultimately enable us to implement energy efficient follow behaviors on physical UGVs.
Computing Nonlinear Normal Modes Using Numerical Continuation and Force Appropriation
Authors: Kuether Robert J. , Allen Matthew S.
Published: September 2013

Many structures can behave nonlinearly, exhibiting behavior that is not captured by linear vibration theory such as localization and frequency-energy dependence. The nonlinear normal mode (NNM) concept, developed over the last few decades, can be quite helpful in characterizing a structure’s nonlinear response. In the definition of interest, an NNM is a periodic solution to the conservative nonlinear equations of motion. Several approaches have been suggested for computing NNMs and some have been quite successful even for systems with hundreds of degrees of freedom. However, existing methods are still too expensive to employ on realistic nonlinear finite element models, especially when the Jacobian of the equations of motion is not available analytically. This work presents a new approach for numerically calculating nonlinear normal modes by combining force appropriation, numerical integration and continuation techniques. This method does not require gradients, is found to compute the NNMs accurately up to moderate response amplitudes, and could be readily extended to experimentally characterize nonlinear structures. The method is demonstrated on a nonlinear mass-spring-damper system, computing its NNMs up to a 35% shift in frequency. The results are compared with those from a gradient based algorithm and the relative merits of each method are discussed.
Stabilization of Electrostatic Actuators Through Variable Gain Amplifier
Authors: Park Sangtak , Abdel-Rahman Eihab
Published: September 2013

In the presence of high parasitic capacitance, conventional electrostatic actuation methods fail to drive an electrostatic actuator beyond its pull-in point. Although the resonant drive circuit is able to extend the operation range of an electrostatic actuator further at a much lower input voltage, an electrostatic actuator coupled with the resonant drive circuit also undergoes pull-in in the presence of high parasitic capacitance compared to the circuit’s quality factor. To improve its robustness to high parasitic capacitance, we design a variable gain amplifier that reduces voltage gain as an electrostatic actuator moves towards its bottom electrode: the increase in the impedance of the resonant drive circuit reduces voltage gain of a variable gain amplifier through its positive feedback loop, while its negative feedback stabilizes its operation.
A Line Geometric Approach to Kinematic Acquisition of Geometric Constraints
Authors: Wu Jun , Ge Q. J. , Gao Feng
Published: September 2013

This paper deals with the problem of geometrically defined planar motions using a line geometric approach. In a previous work, we have studied the problem of acquiring geometric constraints associated with a planar motion task using point geometric constraints. This paper extends this work from point geometric domain to line geometric domain.
Automated Silverware Sorting Using Vision Based Detection and Recognition Driving Pneumatically Actuated Mechanisms
Authors: Asmari Ali , Hoberock Lawrence L.
Published: September 2013

Manual Sorting of silverware pieces after being washed by a high-volume commercial dishwasher is a costly and time consuming process which can be improved by automation. This paper describes the design, construction, and testing of an automated silverware sorting process. The process employs machine vision with simple, but effective, high-volume mechanisms to detect the type and orientation of different types of silverware pieces and place them into different bins. The project was conducted in two major phases:

1) Design and Construction of the Mechanism: a simple and effective mechanism was designed to sort the pieces into separate bins off of a conveyor belt. Pneumatic actuators provided the key mechanical sorting.

2) Design of the Control System: a computer program was developed that detects the entrance of a piece into the machine and recognizes the type and orientation of each silverware piece using computer vision techniques. The software then commands the proper mechanical component at the proper time to actuate, so that each piece ends up in the designated bin.

The machine was tested with different silverware input sequences The accuracy of the software in identifying the type and direction of the pieces, the accuracy of the mechanical system in sorting the pieces, and the accuracy of the overall system were found to be 100%, 90.63% and 88.75% respectively.
Mobility Determination of Mechanisms Based on Rigidity Theory
Authors: Slavutin Michael , Shai Offer , Müller Andreas
Published: September 2013

Rigidity theory deals mostly with the topological computation in mechanical systems, i.e. it aims at making generic statements. Mechanism theory is mainly concerned with the geometrical analysis but again also with generic statements. Even more so for mobility analysis where one is interested in both the generic mobility and that of a particular mechanism. In rigidity theory the mathematical foundation is the topology representation using bar-joint and body-bar graphs, and the corresponding rigidity matrix. In this paper novel geometric rules for constructing the body-bar rigidity matrix are derived for general planar mechanisms comprising revolute and prismatic joints. This allows, for the first time, the treatment of general planar mechanisms with the body-bar approach. The rigidity matrix is also derived for spatial mechanisms with spherical joints. The bar-joint rigidity matrix is shown to be a special case of body-bar representation. It is shown that the rigidity matrices allow for mobility calculation as shown in the paper. This paper is aimed at supplying a unified view and as a result to enable the mechanisms community to employ the theorems and methods used in rigidity theory. An algorithm for mobility determination — the pebble game — is discussed. This algorithm always finds the correct generic mobility if the mechanism can be represented by a body-bar graph.
An Analysis of Complexity Measures for Product Design and Development
Authors: Crespo-Varela Josue R. , Okudan Kremer Gül E. , Tucker Conrad S. , Medina Lourdes A.
Published: September 2013

Complexity metrics have been developed for multiple applications such as consumer products, software, trajectory selection and assembly systems. Although existing complexity metrics were developed to reduce product design and development costs, their lack of simplicity in formulation and robustness has limited their applicability. This paper proposes a standard methodology for comparing and evaluating these metrics and introduces dimensions of complexity that should be considered towards the goal of developing a generalizable product complexity measure. To this end, this paper introduces variables that integrate multiple facets of complexity into a single metric.

A medical device case study is used to compare the efficiency and robustness of existing complexity measures. The medical device case study also serves as the motivation for the proposed complexity metric due to the complexity of the domain itself and the increasing importance of mitigating healthcare costs. Overall, product complexity metrics can aid medical device development by increasing the understanding about the design and its implications regarding development time and FDA approvals.
Non-Probabilistic Based Structural Design Optimization Under External Load Uncertainty With Eigenvalue-Superposition of Convex Models
Authors: Zhao Xike , Gea Hae Chang , Xu Limei
Published: September 2013

The non-probabilistic-based structural design optimization problems with external load uncertainties are often solved through a two-level approach. However there are several challenges in this method. Firstly, to assure the reliability of the design, the lower level problem must be solved to its global optimality. Secondly, the sensitivity of the upper level problem cannot be analytically derived. To overcome these challenges, a new method based on the Eigenvalue-Superposition of Convex Models (ESCM) is proposed in this paper. The ESCM method replaces the global optimum of the lower level problem by a confidence bound, namely the ESCM bound, and with which the two-level problem can be formulated into a single level problem. The advantages of the ESCM method in efficiency and stability are demonstrated through numerical examples.
Planar Trajectory Planning for Hopping and Swinging Along Designated Ground Contacts
Authors: Kean Michael , Cipra Raymond J.
Published: September 2013

The study of the dynamics of hopping robots has generated provably stable control algorithms for steady state hopping. Similar studies have been successfully undertaken for swinging from a handhold. The resulting controllers are capable of stable steady state motion. There is room in the literature for the planning of transient paths, where exact ground contacts become important.

This work introduces a path planning approach targeted at transient motion for hopping and swinging robots. The dynamic and kinematics of the robot are described. The construction of a nominal path between the ground contacts is detailed beginning with energy calculations and continuing to a sequence of ballistic flights between the ground contacts.

This work is aimed at online path planning where there is incomplete knowledge about the full path. Rules are introduced to adapt the nominal trajectories and select a specific set of trajectories based on current knowledge of the path. Example paths are included to demonstrate the successful application of the approach.
Robotic Device for 3D Imaging of Scour Around Bridge Piles
Authors: Fadool James C. , Francis Griffin , Clark Jonathan E. , Liu Guifeng , DeBrunner Victor
Published: September 2013

Bridge scour is an important concern for standing structures with piles footed underwater. The scour process that leads to the weakening of bridge foundations can result in (unexpected) loss of service, and can create unsafe conditions for the vehicles and persons using the bridge, particularly during flood conditions. Currently, stationary devices or divers are deployed to detect this condition; however these devices are expensive and diving in such conditions is inherently dangerous. Therefore, a need exists for an inexpensive and portable system that is able to determine and estimate the amount of scour around a pile. One approach is to use a sonar based scanning system, to construct a 3D image for interpretations and evaluations analysis. This paper details prototype development, image processing procedure, and initial experimental results of such a device.
Controlled Infeasibility for Physically Feasible Optimal Motion Planning of Manipulators
Authors: Kim Joo H. , Joo Chang B.
Published: September 2013

In this presentation, infeasible solutions of the optimal motion planning problems are treated through constraint prioritization and associated weight functions. The merit function and elastic mode of a sequential quadratic programming algorithm are used as main driving formulations. In the proposed multiple-loop iterative algorithm, constraints are first normalized according to the current values at every certain number of iterations and then the priority weights are assigned. The algorithm was demonstrated using a three-degree of freedom planar manipulator for two problems such as obstacle avoidance and excessive external load for static configuration and a dynamic motion. The results of those two examples show reliable and physically consistent manipulator configurations which demonstrate the valid formulation of the prioritized constraints.
Sensor-Based Navigation of Agricultural Autonomous Mobile Robots
Authors: Heidari F. , Vakil M. , Fotouhi R.
Published: September 2013

Investigation on development of autonomous mobile robots for agricultural use in a complex and mostly unstructured environment is studied. An approach that uses fuzzy-logic control and distance-based sensory data for real-time navigation of a mobile robot in an unknown farm setting is proposed. This approach requires no prior knowledge of the environment and adjusts a safety margin to cope with dynamic and unforeseen conditions. The simulation and experimental results indicate that the proposed strategy navigates robot in different conditions safely and efficiently. Comparing our results with vector field histogram and preference-based fuzzy approaches revealed that the approach suggested here produces shorter and smoother paths toward goal in almost all of the test cases examined.
Robot Task Planning and Trajectory Learning for Flexible Automation
Authors: Mantegh Iraj
Published: September 2013

A task planning method is presented to model and reproduce robot trajectories based on those captured from human demonstrations. In the framework of the Programming by Demonstration (PbD) approach, task planning algorithm is developed to determine the general type of trajectory pattern, its parameters, and its kinematic profile. The pattern is described independently of the shape of the surface on which it is demonstrated. Key pattern points are identified based on changes in direction and velocity, and are then reduced based on their proximity. The results of the analysis are provided are used inside a task planning algorithm, to produce robot trajectories based on the workpiece geometries. The trajectory is output in the form of robot native language code so that it can be readily downloaded on the robot.
Vibration Suppression in a Pinned-Pinned Nonlinear Rod Using a Frictionless Slider
Authors: Cai Tingli , Mukherjee Ranjan , Diaz Alejandro R.
Published: September 2013

We propose a new method for vibration suppression in a flexible structure using a frictionless sliding constraint. The constraint force applied by the slider is assumed known from measurements and the slider motion is prescribed to do negative work on the structure. The structure is modeled as a two-dimensional nonlinear rod with pinned-pinned boundary conditions and the slider is assumed to constrain the position of one point on the rod but not its slope. The problem is formulated using variable-length finite elements in the framework of Arbitrary Lagrange-Euler (ALE) description. The governing equations of motion are derived using the principle of virtual displacements and D’Alembert’s principle. Numerical simulation results are presented to demonstrate the effectiveness of the control strategy based on the idea of negative work. To meet the bandwidth requirement of the actuator, a nonlinear filter is placed in the feedback loop and asymptotic stability of the equilibrium configuration is established using Lyapunov stability theory.
Process Qualification for a Mobile Robotic Welding System Through Manipulability
Authors: Stacy Justin , Langley Daniel , Canfield Stephen L.
Published: September 2013

Advances in mobile robotics make these systems viable alternatives for developing new methods and techniques for manufacturing processes such as welding. When considering welding as a manufacturing process, the ability of the equipment to conduct the weld process must be verified. This step is called weld process validation and is generally conducted when a new machine or technique is introduced to the weld process. Traditionally, the weld validation process has focused on the electro-thermal aspects of the weld process, while the (human) welder qualification provides a certification step to ensure that an operator can perform the motion-control aspects of the weld operation while welding. The lack of industry standards for mechanized welding makes it difficult to introduce mobile robotic welding systems with validated performance in the market place. This paper will propose one approach to consider the motion control portion of the weld process validation for welding systems based on mobile robotic platforms. In particular, this paper will consider a skid-steer type mobile robot that is able to weld in flat, horizontal and vertical orientations. The paper will consider the motion-control portion of the weld validation process and will suggest a method that compares a mobile-robot-based welding process to a baseline (fixed-base track system) welding process through spanning manipulability ellipses. This approach allows general topologies of a mobile robotic welding system to be considered in a general way as a step to making mobile robotic welding a viable welding process.
Reconfigurable Foldable Spatial Mechanisms and Robotic Forms Inspired by Kinetogami
Authors: Gao Wei , Ramani Karthik , Cipra Raymond J.
Published: September 2013

In recent times, Origami has received an increasing research interest because of its capability to produce foldable tessellations and structures. This paper describes a new modular tetrahedral representation called “Kinetogami”. We embed the cuts and joining patterns into the crease pattern and create folded hinges across basic structural units (BSU), typically not done in Origami. We demonstrate sets of explicit 2D fabrication lay-outs and construction rules in order to fold reconfigurable structures and mechanisms in 3D by using a single flat paper sheet. The structural and combinatorial characteristics of Kinetogamic derivatives are further explored in a hierarchical manner. Inspired by Kinetogami, we design a family of multi-limbed tetrahedral robotic form that reconfigures and adapts. The kinematic properties of individual limbs are investigated and multiple gaits involving flipping, squatting/rising, squirming and slithering are synthesized for a representative hexapod robot. Our newly developed folding design paradigm provides affordances for a novel generation of robotic motion actuation and transformable reconfiguration.
Design of a 5-SS Spatial Steering Linkage
Authors: Plecnik Mark M. , McCarthy J. Michael
Published: September 2013

This paper presents the kinematic synthesis of a steering linkage that changes track, wheelbase, camber, and wheel height in a turn, while maintaining Ackermann geometry. Each wheel is controlled by a 5-SS platform linkage, which consists of a moving platform connected by five SS chains to the vehicle chassis. Ackermann steering geometry ensures all four wheels will travel on circular arcs that share the same center point. S denotes a spherical or ball-in-socket joint.

The kinematic synthesis problem is formulated using seven spatial task positions. The procedure computes the SS chains that guide the platform through the seven task positions, and examines all combinations of five that form a single degree-of-freedom linkage. A kinematic analysis identifies the performance of each design candidate, and eliminates functional defects.

In the design process, the task positions are modified randomly within constraints in order to find a useful mechanism design. Mechanisms are deemed useful if they travel smoothly through all seven task positions. Upon analyzing 1000 sets of task positions, only 10 useful mechanisms were found. A second iteration produced 22 useful mechanisms from 1000 task sets. An example of the design of a steering linkage is presented. A video of this linkage can be seen at http://www.youtube.com/watch?v=hEvbDiyQMiw.
Design of a Low-Cost Autoclave for Developing World Health Clinics
Authors: Tao Gregory D. , Cho Hallie S. , Frey Daniel , Winter Amos G.
Published: September 2013

Incidence of surgical site infection is 2–5 times higher in developing nations as compared to developed nations. A low-cost, easy to use autoclave was designed to address the unique technical, behavioral, and market challenges present in rural, health posts of the developing world. A thorough stakeholder analysis was performed very early in the design process to address non-technical needs for sustained user adoption as well as manufacturability and scalability. Twelve partnering clinics in Nepal trialed these autoclaves from July until December 2012. Usage statistics and follow-up observations highlight important factors for successful adoption. These findings were used to improve the autoclave design. The goal of this paper is to detail a case study and methodology to incorporate multiple stakeholder needs into the early design process.
A Method for Measuring Programmatic Dependency and Interdependency Between DoD Acquisition Programs
Authors: Christensen Matthew B. , Wirthlin J. Robert
Published: September 2013

Large and complex enterprises that are primarily involved in product development and design often must manage their development portfolios against a backdrop of competing demands and realities. Given an existing product development process, there is currently no accepted method for quantitative measurement of development program interdependency. While some methods exist for measuring dependency or interdependency at the component or system level, these methods do not translate well to program interdependency measurement. This paper presents a model for measuring development program interdependency accurately and quantitatively.

The model uses four Interdependency Factors to identify dependency relationships between programs. Specific Interdependency Levels are then used to measure the strengths of those dependencies. The model also accounts for measurement of dependencies upon programs that are not directly connected, i.e., programs that have a degree of separation from another program, and measurement of program criticality, or the extent to which a program is depended-upon by another program.

In this paper, a small portion of the US Air Force’s product development portfolio is examined and used to demonstrate these measures. The measurement model is applied to an example development program to measure program dependency characteristics. The results demonstrate that the model can be effectively used to identify and measure program dependencies. The model gives the program manager a quantitative tool to determine how much a program depends upon other programs and the potential impacts of those dependencies. With this information, program managers can better protect their programs from vulnerabilities associated with interdependency effects from other programs and portfolio managers are given new insights into the management of their portfolio in the product development processes of the enterprise.
Computational Synthesis for Nonlinear Dynamics Based Design of Planar Resonant Structures
Authors: Tripathi Astitva , Bajaj Anil K.
Published: September 2013

Nonlinear phenomena such as internal resonances have significant potential applications in Micro Electro Mechanical Systems (MEMS) for increasing the sensitivity of biological and chemical sensors and signal processing elements in circuits. While several theoretical systems are known which exhibit 1:2 or 1:3 internal resonances, designing systems that have the desired properties required for internal resonance as well as are physically realizable as MEMS devices is a significant challenge. Traditionally, the design process for obtaining resonant structures exhibiting an internal resonance has relied heavily on the designer’s prior knowledge and experience. However, with advances in computing power and topology optimization techniques, it should be possible to synthesize structures with the required nonlinear properties (such as having modal interactions) computationally. In this work, a preliminary method for computer based synthesis of structures consisting of beams for desired internal resonance is presented. The linear structural design is accompalished by a Finite Element Method (FEM) formulation implemented in Matlab to start with a base structure and iteratively modify it to obtain a structure with the desired properties. Possible design criteria are having the first two natural frequencies of the structure in some required ratio (such as 1:2 or 1:3). Once a topology of the structure is achieved that meets the desired criterion (i.e., the program converges to a definite structure), the linear mode shapes of the structure can be extracted from the finite element analysis, and a more complete Lagrangian formulation of the nonlinear elastic structure can be used to develop a nonlinear two-mode model of the structure. The reduced-order model is expected to capture the appropriate resonant dynamics associated with modal interactions between the two modes. The nonlinear response of the structure can be obtained by application of perturbation methods such as averaging on the two-mode model. Many candidate structures are synthesized that meet the desired modal frequency criterion and their nonlinear responses are compared.
Towards Automated Exploration and Assembly of Vehicle Design Models
Authors: Wrenn Ryan , Nagel Adam , Owens Robert , Yao Di , Neema Himanshu , Shi Feng , Smyth Kevin , vanBuskirk Chris , Porter Joseph , Bapty Ted , Neema Sandeep , Sztipanovits Janos , Ceisel Johanna , Mavris Dimitri
Published: September 2013

We describe the use of the Cyber-Physical Modeling Language (CyPhyML) to support trade studies and integration activities in system-level vehicle designs. CyPhyML captures integration interfaces across multiple design domains for system components, and generic design assembly rules given in terms of architecture alternatives. The CyPhyML tools support automated exploration of system-level architectural and parametric tradeoffs using a suite of design exploration tools that can be applied to models at different levels of fidelity and scale. Our overall approach includes exploration over the space of potential designs by evaluating structural combinations and then comparison of designs by simulating the dynamics of systems and subsystems with varying degrees of detail. In that flow, we use the DESERT toolkit for design tradeoffs that can be evaluated from the structure of the design model (i.e. interconnections of components and their parameters). DESERT extends a graphical modeling language with concepts and relations to define structural alternatives and constraints on system properties. Alternatives are given in an abstract way, decoupled from the details of the encoding of the combinatorial design space problem for the underlying binary decision diagram (BDD) solver. For desirable design instance models, the tools automatically assemble complete vehicle or subsystem computer-aided design (CAD) models from the associated component CAD models, and likewise create detailed finite-element structural analysis (FEA) models for selected component assemblies. Evaluation results are presented in a dashboard display which provides comparisons between different valid designs over all specified design metrics.
A Case Study of the Implementation and Maintenance of a Fee for Service Lighting System for a Rural Village in Sub Saharan Africa
Authors: Sloan Benjamin M. , McCorkle Douglas S. , Bryden Kenneth M.
Published: September 2013

Electricity is a critical need for the rural poor in developing countries. Often this need is met with disposable batteries. This results in high cost and problems with disposal. For example it was recently reported that an isolated rural village in West Africa with a population of 770 uses more than 21,000 disposable batteries per year and that purchase of these batteries accounts for 20–40% of household expense. As a result many organizations are seeking way to meet the need for village energy. This paper presents a case study of one such experience. In this study the efforts to meet the lighting needs of a cluster of eight rural villages with a population of approximately 8,000 people are discussed. A key aspect of this discussion is the challenge of creating a continuing and sustainable village lighting solution. In this case the technology chosen to implement a lighting system was a distributed micro-grid managed locally in each village. The success of this lighting grid has been in large part due to the continuing support of the local micro-grid system both financially and through continued engagement to maintain and upgrade the micro-grid systems.
Energy Harvesting From Broadband Random Vibrations: Comparison of Single-Mode and Multi-Mode Electroelastic Solutions
Authors: Zhao Sihong , Erturk Alper
Published: September 2013

Vibration-based energy harvesting has been heavily researched over the last decade with a primary focus on resonant excitation. However, ambient vibrational energy often has broader frequency content than a single harmonic, and in many cases it is entirely stochastic. As compared to the literature of deterministic energy harvesting, very few authors presented modeling approaches for energy harvesting from broadband random vibrations. These efforts have combined the input statistical information with the single-degree-of-freedom (SDOF) dynamics of the energy harvester to express the statistical electromechanical response characteristics. In most cases, the motion input (base acceleration) is assumed to be ideal white noise. White noise has a flat power spectral density (PSD) that might in fact excite higher vibration modes of an electroelastic energy harvester. In particular, piezoelectric energy harvesters constitute such continuous electroelastic systems with more than one vibration mode. This paper presents modeling and simulations of piezoelectric energy harvesting from broadband random vibrations based on distributed-parameter electroelastic solution. For white noise–type base acceleration of a given PSD level, first the general solution of the distributed-parameter problem is given. Closed-form representations are extracted for the single-mode case and these are analogous to the SDOF equations reported in the literature of energy harvesting. It is reported that the single-mode predictions might result in significant mismatch as compared to multi-mode predictions. Using the electroelastic solution, soft and hard piezoelectric power generators are compared under broadband random excitation. Shunt damping effect of power generation on the stochastic vibration response under broadband random excitation is also reported.
Grouping of Planetary Gear Modes With Significant Tooth Mesh Deflection
Authors: Ericson Tristan M. , Parker Robert G.
Published: September 2013

High natural frequencies of planetary gears tend collect into groups. The modes at these natural frequencies are characterized by motion of the planet gears with strain energy in the tooth meshes and planet bearings. Each group has one rotational, one translational, and one planet mode. The groups change in natural frequency together when system parameters are varied. The grouping behavior is disrupted with significant differences in planet-to-planet gear parameter values.
System Identification of a Vibro-Impact Beam With a View Toward Structural Health Monitoring
Authors: Kurt Mehmet , Chen Heng , Lee Young S. , McFarland D. Michael , Bergman Lawrence A. , Vakakis Alexander F.
Published: September 2013

We study the dynamics of a cantilever beam vibrating between two rigid stops of specified clearance at its free end by performing nonlinear system identification (NSI) based on the correspondence between analytical and empirical slow-flow dynamics. First, we perform empirical mode decomposition (EMD) on the acceleration responses measured at ten, almost evenly-spaced, spanwise positions along the beam, leading to sets of intrinsic modal oscillators governing the vibro-impact dynamics at different time scales. In particular, the EMD analysis can separate nonsmooth effects caused by vibro-impacts of the beam and the rigid stops from the smooth (elastodynamic) response, so that nonlinear modal interactions caused by vibro-impacts can be explored through the remaining smooth components. Then, we establish nonlinear interaction models (NIMs) for the respective intrinsic modal oscillators, determined from the intrinsic mode functions of the EMD, where the NIMs invoke slowly-varying forcing amplitudes that can be computed from empirical slow-flows. By comparing the spatio-temporal variations of the nonlinear modal interactions for the vibro-impact beam and those of the underlying linear model, we demonstrate that vibro-impacts significantly influence the lower frequency modes by introducing spatial modal distortions, whereas the higher frequency modes tend to retain their linear dynamics between impacts. Finally, we demonstrate that the proposed NSI method can extract spatio-temporal nonlinear modes, as further method development moves toward structural health monitoring and damage detection.
Generalized Theory of Electro-Mechanical Resonators With Fractal Electrodes
Authors: Jain Ankit , Alam Muhammad Ashraful
Published: September 2013

In this paper, we study the operation of electrostatically actuated electromechanical resonators having fractal electrodes. Using the spring-mass model, we establish the scaling relationships for pull-in instability ycy0=DFDF+1, voltage dependent resonance frequency ωω0=DF+1-DFy0y, and pull-in-voltage VPI∝y0DF+12, where DF is the fractal dimension of the electrode, y0 is the air-gap, ω0 and ω are the resonance frequency at zero and applied bias respectively, and y is the steady state position of the moving electrode. These scaling relationships reduce to the well known pull-in instability, and resonance frequency of resonators based on planar (DF = 2) and cylindrical (DF = 1) electrodes. The generality of the scaling relationships are confirmed by using electrodes based on array of cylinders, that allow us to continuously scan all fractal dimension in between planar and cylindrical electrodes (1 ≤ DF ≤ 2) simply by tuning the pitch of the array.
Design of Origami Sheets for Foldable Object Fabrication
Authors: Deng Dongping , Chen Yong
Published: September 2013

Reconfigurable structures that are enabled through the integration of multiple materials are important for future design and manufacturing practice. We investigate one of such reconfigurable structures — an origami sheet, which can be designed based on a 3D object and unfolded into a 2D sheet with complex creases. A fabrication approach based on a hybrid manufacturing process by integrating layer-based additive manufacturing and silicon molding techniques is developed. Related challenges on designing creases for given folding requirements and the related material properties are discussed. A novel structure design is presented to ensure the fabricated creases that are in soft materials can be folded and unfolded without failures. The design method can be applied to different scale levels. The origami sheets for test cases in different complexity have been tested. The experimental results illustrate that the designed and fabricated origami sheets can be folded and used for product components with reconfigurable shapes.
Iwan Models and Their Provenance
Authors: Segalman Daniel J. , Starr Michael J.
Published: September 2013

Iwan models have had some exposure recently in modeling the nonlinear response of individual joints. This popularity can be ascribed to their mathematical simplicity, their versatility, and their ability to capture the important responses of mechanical joints under unidirectional loads. There is a lot of history to this category of model. Masing explored kinematic hardening of metals with a model consisting of ten Jenkins elements in series. Soon after, Prandtl explored the behavior of a continuous distribution of such elements. Ishlinskii explored the mathematical structure of such continuous distributions. Much more recently, Iwan demonstrated practical application of such models in capturing various sorts of metal plasticity.

Among the features that make such models interesting is a simple relationship between the asymptotic nature of the integral kernel at small values and the power-law relation between force amplitude and dissipation per cycle in harmonic loading. Iwan provided several differential equations for deducing the kernel from force-displacement relations. Segalman and Starr devised methods for deducing kernels from force-displacement curves of arbitrary Masing models. This is illustrated to generate a BPII model equivalent to the Ramberg-Osgood plasticity model. The Segalman-Starr relationship is used to find relationships among several other plasticity models.
Identification of True State-Variable Decomposition Modes From Modal Coordinate Data
Authors: Farooq Umar , Feeny Brian F.
Published: September 2013

The recently developed state-variable modal decomposition method provides a quick and efficient way to estimate modal parameters from data for a multi-degree-of-freedom vibratory system without having the need to measure inputs. Associated with the decomposition method are the state-variable modal coordinates (SVMC), which can be used to determine the quality of decomposition. In present work, a systematic way is established to distinguish a true mode from a spurious one from features of the modal coordinates. In an approach similar, in principle, to the modal assurance criterion (MAC) for assessing mode shapes, a value is directly obtained by comparing the fast Fourier transform (FFT) of the impulse response of the modal coordinate, to the sampled ideal frequency response generated by the modal parameters obtained from the decomposition. Also, the norm of the difference between the FFT magnitude of the SVMC impulse response and the sampled identified ideal frequency response is used to distinguish the true modes. Various case studies using combinations of frequency and damping values are obtained in numerically simulated results. Actual modes are also distinguished from the spurious modes using test data from a uniform thin beam.
Asymmetric Interface and Interactions for Bimanual Virtual Assembly With Haptics
Authors: Vyawahare Vikram S. , Stone Richard T.
Published: September 2013

This paper discusses development of a new bimanual interface configuration for virtual assembly consisting of a haptic device at one hand and a 6DOF tracking device at the other hand. The two devices form a multimodal interaction configuration facilitating unique interactions for virtual assembly. Tasks for virtual assembly can consist of both “one hand one object” and “bimanual single object” interactions. For one hand one object interactions this device configuration offers advantages in terms of increased manipulation workspace and provides a tradeoff between the cost effectiveness and mode of feedback. For bimanual single object manipulation an interaction method developed using this device configuration improves the realism and facilitates variation in precision of task of bimanual single object orientation. Furthermore another interaction method to expand the haptic device workspace using this configuration is introduced. The applicability of both these methods to the field of virtual assembly is discussed.