bluuebunny/crossref_metadata_2025 huggingface dataset:
A Design Exploration of Genetically Engineered Myosin Motors
Authors: Egan Paul F. , LeDuc Philip R. , Cagan Jonathan , Schunn Christian
Published: June 2012

As technology advances, there is an increasing need to reliably output mechanical work at smaller scales. At the nanoscale, one of the most promising routes is utilizing biomolecular motors such as myosin proteins commonly found in cells. Myosins convert chemical energy into mechanical energy and are strong candidates for use as components of artificial nanodevices and multi-scale systems. Isoforms of the myosin superfamily of proteins are fine-tuned for specific cellular tasks such as intracellular transport, cell division, and muscle contraction. The modular structure that all myosins share makes it possible to genetically engineer them for fine-tuned performance in specific applications. In this study, a parametric analysis is conducted in order to explore the design space of Myosin II isoforms. The crossbridge model for myosin mechanics is used as a basis for a parametric study. The study sweeps commonly manipulated myosin performance variables and explores novel ways of tuning their performance. The analysis demonstrates the extent that myosin designs are alterable. Additionally, the study informs the biological community of gaps in experimentally tabulated myosin design parameters. The study lays the foundation for further progressing the design and optimization of individual myosins, a pivotal step in the eventual utilization of custom-built biomotors for a broad range of innovative nanotechnological devices.
Probability of User Fit for Spatially Optimized Products
Authors: Garneau Christopher , Parkinson Matthew
Published: June 2012

This study offers a new method for understanding the likelihood of acceptable fit for users of adjustable products and environments and is a useful tool for aiding the designer in making decisions about problems involving human variability. Accommodation, which describes the ability of a user to interact with a device or environment in a preferred way, is a key product performance metric. Methods that offer a better understanding of accommodation of broad user populations would allow for the design of products that are more cost-effective, safer, and/or lead to greater levels of customer satisfaction. This work uses parametric studies to explore the characteristics of a target user population and the probability of accommodating individuals of a given body size. Performance regions are identified in both the problem’s design space (the product dimensions under consideration) and the anthropometry space of the target population (the relevant body dimensions of product users). The existence of probability contours is a result of outcome uncertainty due to anthropometry-independent user preference, and the analysis is achieved by assessing binary accommodation of individuals using a “virtual fit” method with many iterations. Two case studies, one univariate and one bivariate in both performance and anthropometry spaces, are presented. An important outcome of the decision making framework described in this work is the ability to intuitively gauge who in the population of target users will be disaccommodated by a design and how to improve overall accommodation.
On Stability of a Nonlinear, Periodically Time Varying, Rotating Blade
Authors: Wang Fengxia
Published: June 2012

This paper discusses the stability of a periodically time-varying, spinning blade with cubic geometric nonlinearity. The modal reduction method is adopted to simplify the nonlinear partial differential equations to the ordinary differential equations, and the geometric stiffening is approximated by the axial inertia membrane force. The method of multiple time scale is employed to study the steady state motions, the corresponding stability and bifurcation for such a periodically time-varying rotating blade. The backbone curves for steady-state motions are achieved, and the parameter map for stability and bifurcation is developed. Illustration of the steady-state motions is presented for an understanding of rotational motions of the rotating blade.
Optimization of Parabolic Heliostat Focal Lengths in a Mini-Tower Solar Concentrator System
Authors: Hamza Karim , Gandhi Umesh , Saitou Kazuhiro
Published: June 2012

Solar tower with heliostat mirrors is one of the established setups for utility-scale solar energy harvesting. Advantages of the setup include the capability to reach high temperature, modularity and ease of maintenance for the heliostats, containment of the high temperature zone atop the tower, as well as overall low cost per unit energy. However, downscaling to medium or small scale applications often does not turn out economically feasible with flat mirror heliostats that are the norm in utility-scale systems. This is mainly due to the need to preserve the solar concentration ratio, which in turn means the number of flat mirrors cannot be reduced. Use of parabolic mirrors instead can significantly reduce the required number of mirrors for smaller scale systems, but comes with new challenges. Unlike flat mirrors that have infinite effective focal length, the effective focal length of parabolic mirrors changes with the angle of incidence, which in turn, changes throughout the day and season. The design challenge tackled in this paper is that of optimal selection of the focal lengths of the heliostats in order to maximize the yearly harvested energy while maintaining the concentration ratio within desirable limits. A parameterized system model is developed and a genetic algorithm is implemented for the optimization task. The model is then applied to a demonstration case study of a 10 kW solar concentrator. Results of the study demonstrate the proposed design approach as well as show the promise for effective downscaling of tower and heliostat systems.
LCA Study and Comparison of Two Multispeed Blenders
Authors: Hawthorne Bryant D. , Ameta Gaurav
Published: June 2012

Many Americans have a variety of small kitchen appliances. Among this collection a blender is typically present. The diversity of the blender selection is great and can range from economical to industrial quality. However, the average American is not in need of an industrial blender and leans more towards the economical approach. In addition, depending on the individual, a blender can go months unused. Therefore, environmental effects of a blender are mainly due to material extraction, manufacturing, distributing, and disposal. To the best of the author’s knowledge, there are no formal life cycle analysis (LCA) studies of a blender published in the literature. This paper describes a LCA of two economical blenders from the same manufacturer. This allows for a direct comparison between the LCAs to determine how the design changes and materials used contribute to environmental effects.
Encouraging Environmentally Conscious Behaviour Through Product Design: The Principle of Discretization
Authors: Srivastava Jayesh , Shu L. H.
Published: June 2012

Lead user methods were applied to develop product design principles that encourage environmentally conscious behaviours in individuals. Old Order Mennonites (OOMs) were chosen as lead users because of their low resource consumption lifestyles. Ethnographic analysis revealed that discretizing resource consumption facilitates and encourages conservation behaviours in OOMs. An experimental study demonstrated the effectiveness of discretization in reducing water consumption. We postulate several distinct ways in which discretization encourages conservation behaviours. We conclude with insights on how discretization can be integrated into the design of modern products to encourage environmentally conscious behaviour in the general population.
A Two Degree of Freedom Nanopositioner With Electrothermal Actuator for Decoupled Motion
Authors: Kim Yong-Sik , Dagalakis Nicholas G. , Gupta Satyandra K.
Published: June 2012

Building a two degree-of-freedom (2 DOF) MEMS nanopositioner with decoupled X-Y motion has been a challenge in nanopositioner design. In this paper a novel design concept on making the decoupled motion of the MEMS nanopositioner is suggested. The suggested nanopositioner has two electrothermal actuators and employs a fully nested motion platform with suspended anchors. The suggested MEMS nanopositioner is capable of delivering displacement from the electrothermal actuator to the motion platform without coupled motion between the two X-Y axes. The design concept, finite element analysis (FEA) results, fabrication procedures and the performance of the 2 DOF nanopositioner is presented. In order to test the nanopositioner moving platform decoupled motion, one actuator moves the platform by 60 μm, while the other actuator is kept at the same position. The platform position cross talk error was measured to be less than 1 μm standard deviation.
A Distributed Pool Architecture for Highly Constrained Optimization Problems in Complex Systems Design
Authors: Pandey Vijitashwa , Mourelatos Zissimos P.
Published: June 2012

The design of complex systems design is challenging because of the presence of numerous design variables and constraints. Dynamic changes in design requirements and lack of complete knowledge of subsystem requirements add to the complexity. A recently proposed pool architecture has been shown to aide distributed solving of optimization problems. The approach not only saves solution time but also has other benefits like resiliency against failures of some processors. We apply this approach in this paper, to highly constrained design problems, with dynamically changing constraints, where finding a feasible solution is challenging. This task is distributed between the processors in the methodology we propose. We demonstrate the efficacy of our method using an MINLP-class of mechanical design optimization problem. We demonstrate the computational savings and the resistance to partial failures in the processors. In addition, we show how the optimization approach can adapt to dynamic changes in design constraints.
Hybrid Adaptive Rotor Imbalance Vibration Control via Passive Autobalancer and Active Bearing Actuation
Authors: Jung DaeYi , DeSmidt Hans
Published: June 2012

Many researchers have explored the use of active bearings, such as non-contact Active Magnetic Bearings for example, to control imbalance vibration in rotor systems. This paper develops a new hybrid adaptive imbalance vibration control approach based on an active bearing augmented with a passive automatic balancing device (ABD) to enhance the balancing and vibration isolation capabilities. Essentially, an ABD or “autobalance” consists of several freely moving eccentric balancing masses mounted on the rotor, which, at supercritical operating speeds, act to cancel the rotor’s imbalance at steady-state. This “automatic balancing” phenomena occurs as a result of nonlinear dynamic interactions between the balancer and rotor wherein the balancer masses naturally synchronize with the rotor with appropriate phase to cancel the imbalance. Since the ABD acts directly on the rotor in the rotating frame, rotor whirl amplitudes are passively reduced without any forces transmitted between rotor and bearing. Therefore, this hybrid ABD/active bearing approach enables increased rotor balancing capability and reduced steady-state control power consumption. However, due to the inherent nonlinearity of the autobalancer, the potential for other, non-synchronous limit-cycle behavior exists. In such situations, the balancer masses do not reach their desired synchronous balanced steady-state equilibrium positions resulting in increased rotor vibration. To address this, a new adaptive active control algorithm for the rotor/bearing/ABD system is derived based on the Lyapunov approach which guarantees global asymptotic stability of the synchronous balanced condition. This approach enables the controller to cope with both the system nonlinearity introduced by the passive ABD and with the rotor imbalance uncertainty. Here, the controllability of system is established through an accessible distribution Lie bracket operational analysis. The simulation results demonstrate the advantages of the hybrid ABD/active bearing system. In particular, it is shown that the balanced equilibrium can be made globally attractive under the action of the adaptive bearing control law, and that the steady-state power levels are significantly reduced via the addition of the ABD. These findings are relevant to limited power applications such as in satellite reaction wheels or flywheel energy storage batteries.
Design of a Multi-Contact-Aided Compliant Mechanism
Authors: Aguirre Milton E. , Frecker Mary
Published: June 2012

This work is part of a multidisciplinary project developing design and manufacturing methods for narrow-gauge surgical instruments intended for advanced minimally invasive surgery. The instruments are designed specifically for Penn State’s lost mold rapid infiltration forming process, which is capable of fabricating hundreds of freestanding meso-scale parts. In previous work, a 1 mm diameter forceps case study demonstrated the design and fabrication process. The forceps is a monolithic compliant mechanism (CM) that relies on contact to re-distribute maximum stresses to generate larger elastic tip deflections; a phenomenon defined here as contact stress-relief. Prototypes were developed and evaluated in an end user surgical simulator. Feedback from 11 clinicians identified the total jaw opening of the forceps must be increased in the next generation of prototypes. This paper focuses on exploiting the benefits of contact-aided compliant mechanism (CCM) design to obtain larger elastic tip deflections and thus jaw openings. Using the commercially available finite element software package ANSYS to model large deformation and contact, an optimization problem is developed to determine the effects of incorporating additional contact elements in a CCM design on maximizing elastic tip deflection. Results show that designs with multiple contact elements generate larger elastic tip deflections due to a multi-stage contact stress-relief profile.
Optimal Error-Clamping Design for Position-Based Visual Servoing of a 2-DOF Model Helicopter
Authors: Alizadeh M. , Ratanasawanya C. , Mehrandezh M. , Paranjape R.
Published: June 2012

A vision-based servoing technique is proposed for a 2 degrees-of-freedom (dof) model helicopter equipped with a monocular vision system. In general, these techniques can be categorized as image- and position-based, where the task error is defined in the image plane in the former and in the physical space in the latter. The 2-dof model helicopter requires a configuration-dependent feed-forward control to compensate for gravitational forces when servoing on a ground target. Therefore, a position-based visual servoing deems more appropriate for precision control. Image information collected from a ground object, with known geometry a priori, is used to calculate the desired pose of the camera and correspondingly the desired joint angles of the model helicopter. To assure a smooth servoing, the task error is parameterized, using the information obtained from the linearaized image Jacobian, and time scaled to form a moving reference trajectory. At the higher level, a Linear Quadratic Regulator (LQR), augmented with a feed-forward term and an integrator, is used to track this trajectory. The discretization of the reference trajectory is achieved by an error-clamping strategy for optimal performance. The proposed technique was tested on a 2-dof model helicopter capable of pitch and yaw maneuvers carrying a light-weight off-the-shelf video camera. The test results show that the optimized controller can servo the model helicopter to a hovering pose for an image acquisition rate of as low as 2 frames per second.
Pseudo Standing, Forward Falling, and Pulling Simulation for Pregnant Women
Authors: Zou Qiuling , Yang Jingzhou James
Published: June 2012

This paper presents an optimization-based dynamic simulation for pregnant women pseudo standing, forward falling, and pulling tasks. Based on anatomy of pregnant women a digital pregnant woman model is developed. The model has 55 degrees of freedom (DOFs) including 6 global DOFs and 49 body DOFs. Recursive dynamic algorithm is used to formulate the equations of motion. Human motion can be formulated as a non-linear optimization problem. Control points of B-spline curves that represent joint angle profiles are design variables. The joint angles, angular velocities and angular accelerations, will be obtained from the control points. The summation of all joint actuator torque square acts as the objective function. Besides some common constraints, different constraints are adopted for standing, falling, and pulling, respectively. Three cases, non-pregnancy, 6-month, and 9-month pregnancy, are investigated. For the pulling task, 2N, 100N or 200N external load is applied as the pulling force. Determinant joints (hip, knee and ankle) are plotted to analyze the simulation results. The simulation results show the effects of pregnancy on human movement kinematics and dynamics. The average computational time for each case is close to 3.5 minutes in a Dell computer with 3.25 GB of RAM and 3.16 GHz.
APIX: Analysis From Pixellated Inputs in Early Design Using a Pen-Based Interface
Authors: Murugappan Sundar , Vinayak  , Ramani Karthik , Yang Maria C.
Published: June 2012

Product development is seeing a paradigm shift in the form of a simulation-driven approach. Recently, companies and designers have started to realize that simulation has the biggest impact when used as a concept verification tool in early stages of design. Early stage simulation tools like ANSYS™ Design Space and SIMULIA™ DesignSight Structure help to overcome the limitations in traditional product development processes where analyses are carried out by a separate group and not the designers. Most of these commercial tools still require well defined solid models as input and do not support freehand sketches, an integral part of the early design stage of product development. To this extent, we present APIX (acronym for Analysis from Pixellated Inputs), a tool for quick analysis of two dimensional mechanical sketches and parts from their static images using a pen-based interface. The input to the system can be offline (paper) sketches and diagrams, which include scanned legacy drawings and freehand sketches. In addition, images of two-dimensional projections of three dimensional mechanical parts can also be input. We have developed an approach to extract a set of boundary contours to represent a pixellated image using known image processing algorithms. The idea is to convert the input images to online sketches and use existing stroke-based recognition techniques for further processing. The converted sketch can now be edited, segmented, recognized, merged, solved for geometric constraints, beautified and used as input for finite element analysis. Finally, we demonstrate the effectiveness of our approach in the early design process with examples.
Design and Fabrication of Differential Scanning Nanocalorimeter for Biological Applications
Authors: Zuo Lei , Chen Xiaoming , Lu Ming
Published: June 2012

This paper describes the design, fabrication, and characterization of a differential scanning nanocalorimeter that has potential to significantly reduce the sample volume to microliter and improve the temperature sensitivity to 10 μK. The nanocalorimeter consists of a polymeric freestanding membrane, four high-sensitive low-noise thermistors based on the silicon carbide (SiC), and a platinum heater and temperature sensor. With the integrated heater and sensors, temperature scanning and power compensation can be achieved for calorimetric measurement. Temperature sensing SiC film was prepared by using sintered SiC target and DC magnetron sputtering under different gas pressure and sputtering power. The SiC sensing material is characterized through the measurement of current-voltage curves and noise levels. Thermal performance of a fabricated nanocalorimeter is studied in simulation and experiment. The results indicate the device has a nano watt thermal power sensitivity, 10 μK temperature sensitivity, and long time constant to hold thermal energy, which leads to low-volume ultra sensitive nanocalorimetry for biological process, such as protein folding and ligand binding.
A Model for Highly Strained DNA in a Cavity
Authors: Hirsh Andrew D. , Lillian Todd D. , Perkins N. C.
Published: June 2012

A single DNA molecule is a long and flexible biopolymer that contains the genetic code. Building upon the discovery of the iconic double helix over 50 years ago, subsequent studies have emphasized how its biological function is related to the mechanical properties of the molecule. A remarkable system which high-lights the role of DNA bending and twisting is the packing and ejection of DNA into and from viral capsids. A recent 3D reconstruction of bacteriophage φ29 reveals a novel toroidal structure thought to be 30–40 bp of highly bent/twisted DNA contained in a small cavity below the capsid. Here, we extend an elastic rod model for DNA to enable simulation of the toroid as it is compacted and subsequently ejected from a small volume. We compute biologically-realistic forces required to form the toroid and predict ejection times of several nanoseconds.
An Automatic Injection Device for Precise Cement Delivery During Osteoporotic Bone Augmentation
Authors: Kutzer Michael D. , Basafa Ehsan , Otake Yoshito , Armand Mehran
Published: June 2012

Augmentation of osteoporotic bone with polymethylmethacrylate (PMMA) bone cement has been shown to be effective in reducing the risk of bone fracture. Injection of the highly viscous bone cement, however, is challenging mainly due to high injection forces required to maintain the nominal injection rates. Also, effective placement of the cement requires precise planning and execution. We are developing a surgical workstation for planning and executing proximal femur augmentation. As a crucial part of the framework, we have designed and fabricated a prototype automatic injection device that provides the substantial forces while maintaining the planned injection rates. Design parameters were determined based on the criteria available in the literature and our preliminary tests. Intended features for the device included high injection force capability, precisely controllable injection and ease of use. A number of calibration experiments were performed to ensure that the device meets the intended criteria. The device can be quickly set up before the surgical operation and can operate in manual or automatic placement configurations. The automatic injection device can also be used for a range of other orthopaedic applications involving direct augmentation of the bones or screws fixated in the bones.
Limit-Cycle Analysis of Planar Rotor/Autobalancer System Supported on Hydrodynamic Journal Bearing
Authors: Jung DaeYi , DeSmidt Hans
Published: June 2012

In recent years, there has been much interest in the use of so-called automatic balancing devices (ABD) in rotating machinery. Essentially, ABDs or “autobalancers” consists of several freely moving eccentric balancing masses mounted on the rotor, which, at certain operating speeds, act to cancel rotor imbalance at steady-state. This “automatic balancing” phenomena occurs as a result of nonlinear dynamic interactions between the balancer and rotor wherein the balancer masses naturally synchronize with the rotor with appropriate phase and cancel the imbalance. However, due to inherent nonlinearity of the autobalancer, the potential for other, undesirable, non-synchronous limit-cycle behavior exists. In such situations, the balancer masses do not reach their desired synchronous balanced steady-state positions resulting in increased rotor vibration. Such automatic behavior has been widely studied and is well understood for rotor systems on idealized bearings with symmetric supports. This paper presents a comprehensive study into automatic balancing behavior of an imbalanced planar rigid rotor/ABD system mounted in two different widely-used types of hydrodynamic bearings; i) the short journal bearing with asymmetric stiffness, damping and cross-coupling terms and ii) a so-called tilting-pad bearing. In this study the non-dimensional characteristic curves of stiffness and damping of these two fluid film bearings are employed and the rotor/bearing/ABD system autobalancing behavior is studied as a function of rotor speed, bearing eccentricity and bearing journal radial clearance. These two essential bearing parameters in turn are directly determined by the rotor static loading, bearing structure, and oil viscosity. Consequently, this research focuses on the connectivity between the bearing parameters and the corresponding synchronous balancing and non-synchronous limit-cycle behavior of the system. Here, solutions for rotor limit-cycle amplitudes and corresponding autobalancer ball speeds are obtained via a harmonic balance and numerical continuation solution approach. Furthermore, an exact solution for the limit-cycle is obtained for the special case of symmetric support stiffness together with a so-called Alford’s force cross-coupling term. In each case, the limit-cycle stability is assessed via a perturbation and Floquet analysis and the coexistence of the stable balanced synchronous limit-cycle and undesired non-synchronous limit-cycle is studied. It is found that for certain combinations of bearing parameters and operating speeds, the non-synchronous limit-cycle can be made unstable thus guaranteeing global asymptotic stability of the synchronous balanced condition. Finally, the analysis is validated through numerical time-domain simulation. The findings in this paper yield important insights for researchers wishing to utilize automatic balancing devices in practical rotor systems.
Understanding Innovation: A Study of Perspectives and Perceptions in Engineering
Authors: Krager Jarden , Wood Kristin L. , Crawford Richard H. , Jensen Dan , Cagan Jonathan , Schunn Christian D. , Linsey Julie S. , White Christina K.
Published: June 2012

Well developed innovation processes are essential components for continued success of product and systems design throughout industry. Such processes build upon research advancements in innovation techniques and methods. To create such techniques and methods, studies are needed to examine the current state-of-the-art, as well as the corresponding teaching of such innovation processes in higher education. This paper contributes to this effort by studying a specific group of innovation researchers, teachers, and practitioners. The study was created to probe this group of leaders in the engineering design domain using technical, demographic, and short answer questions. Various analysis methods are used to obtain a fundamental view of the answers to these questions with respect to the demographics of the participant group. Two deductive analysis methods are used, in addition to an inductive approach, consisting of a correlation analysis to compare responses to questions and understand trends across the participants. Results from the analyses emphasize the current perceptions of innovation by the participants and opportunities to refine research in improving innovation practices.
Real-Time Explicit Flexible Multibody Dynamics Solver With Application to Virtual-Reality Based E-Learning
Authors: Wasfy Tamer M. , Wasfy Hatem M. , Peters Jeanne M.
Published: June 2012

A flexible multibody dynamics explicit time-integration parallel solver suitable for real-time virtual-reality applications is presented. The hierarchical “scene-graph” representation of the model used for display and user-interaction with the model is also used in the solver. The multibody system includes rigid bodies, flexible bodies, joints, frictional contact constraints, actuators and prescribed motion constraints. The rigid bodies rotational equations of motion are written in a body-fixed frame with the total rigid body rotation matrix updated each time step using incremental rotations. Flexible bodies are modeled using total-Lagrangian spring, truss, beam and hexahedral finite elements. The motion of the elements is referred to a global inertial Cartesian reference frame. A penalty technique is used to impose joint/contact constraints. An asperity-based friction model is used to model joint/contact friction. A bounding box binary tree contact search algorithm is used to allow fast contact detection between finite elements and other elements as well as general triangular/quadrilateral rigid-body surfaces. The real-time solver is used to model virtual-reality based experiments (including mass-spring systems, pendulums, pulley-rope-mass systems, billiards, air-hockey and a solar system) for a freshman university physics e-learning course.
Fault Tolerant Control of a Quadrotor Helicopter Using Model Reference Adaptive Control
Authors: Sadeghzadeh Iman , Mehta Ankit , Zhang Youmin
Published: June 2012

This paper proposes a useful approach to Fault Tolerant Control (FTC) based on the Model Reference Adaptive Control (MRAC) technique with application to a quadrotor helicopter Unmanned Aerial Vehicle (UAV) in hovering as well as trajectory tracking flight in order to control and keep the desired height and trajectory of the quadrotor helicopter in both normal conditions and in the presence of faults in one or more actuators. A Linear Quadratic Regulator (LQR) controller is used in cooperation with the MRAC to control the pitch and roll attitude of the helicopter. Three cases of fault are considered: 1) simulated fault in all the four actuators; 2) simulated fault in back and right motors; 3) a physical damage of 23% of one of the four propellers during autonomous flight. It can be seen from the test results that under the faulty and damage conditions MRAC controller provided a good response of the quadrotor UAV and result in safe landings of the quadrotor.
Tooth Contact Analysis and Manufacture on Multi-Tasking Machine of Large-Sized Straight Bevel Gears
Authors: Kawasaki Kazumasa , Tsuji Isamu , Gunbara Hiroshi
Published: June 2012

Straight bevel gears are widely used in the plant of large-sized power generation when the gears have large size. The purpose of this study is to manufacture the large-sized straight bevel gears with equi-depth on multi-tasking machine. The manufacturing method has the advantages of arbitrary modification of the tooth surface and machining of the part without the tooth surface. For this study, first the mathematical model of straight bevel gears by complementary crown gears considering manufacture on multi-tasking machine is proposed, and the tooth contact pattern and transmission errors of these straight bevel gears with modified tooth surfaces are analyzed in order to clarify the meshing and contact of these gears. Next, the numerical coordinates on the tooth surfaces of the bevel gears are calculated and the tooth profiles are modeled using a 3D-CAD system. 5-axis control machines were utilized. The gear-work was machining by a swarf cutting using a coated carbide end mill. After rough cutting, the gear-work was heat-treated, and it was finished based on a CAM process through the calculated numerical coordinates. The pinion was also machined similarly. The real tooth surfaces were measured using a coordinate measuring machine and the tooth flank form errors were detected using the measured coordinates. As a result, the obtained tooth flank form errors were small. In addition, the tooth contact pattern of the manufactured large-sized straight bevel gears was compared with those of tooth contact analysis. As a result, there was good agreement.
Thermal Modeling for Control of Friction Stir Welding Process in Automated Manufacturing
Authors: Mantegh Iraj
Published: June 2012

Friction stir welding is a patented joining process invented in 1991 at The Welding Institute in Cambridge, UK, and further developed to the stage suitable for production. In this process, a wear resistant rotating tool is used to join sheet and plate with different materials such as aluminum, copper, lead, magnesium, zinc, and titanium. This work studies the thermal characteristics of this process and provides a modeling technique based on Neural Network that can be used for real-time control. A thermal feed-back control method is presented to control the process. Using some thermal modeling for the heat distribution during friction stir welding process, this paper displays the complexity of obtaining an accurate design for the thermal feed back control. A three-dimensional transient heat transfer model is developed here for a sequential joining process (Friction Stir Welding-FSW) applied on aluminum parts. A neural network is created based on a set of experiments to predict the spatial and temporal variations in the temperature over the weld seam for different set of input variables. The model includes the dynamic and friction behavior of the rotating spindle and the thermal behaviors of the weld components involved. The significance of this modeling approach is that it captures the movement of the spindle, simulating a sequential joining process along a continuous weld seam. The modeling results are compared with experimental data obtained by thermocouples and infrared camera, and accurately predict the trend of variations in weld temperature. A fuzzy-logic based controller is proposed to regulate the FSW process parameters to maintain the weld temperature within the margin required to ensure the weld quality. This modeling and control system can have applications in manufacturing aluminum parts in automotive and aerospace industry.
Development of an Omnidirectional Walking Engine for Full-Sized Lightweight Humanoid Robots
Authors: Song Seungmoon , Ryoo Young-Jae , Hong Dennis W.
Published: June 2012

In this paper, we propose and demonstrate an omnidirectional walking engine that achieves stable walking using feedback from an inertial measurement unit (IMU). The 3D linear inverted pendulum model (3D-LIPM) is used as a simplified model of the robot, the zero moment point (ZMP) criterion is used as the stability criterion, and only the feedback from the IMU is utilized for stabilization. The proposed walking engine consists of two parts; the omnidirectional gait generator, and the stability controller. ZMP equations, derived based on the 3D-LIPM, are used in the omnidirectional gait generator. The solutions of the differential equations are directly used which reduces the computation cost compare to other existing methods. Two kinds of feedback controllers are implemented for the stability controller; one is the indirect reference ZMP controller, and the other is the indirect joint controller. The walking engine is tested on a lightweight, full-sized, 21-degree-of-freedom (DOF) humanoid robot CHARLI-L (Cognitive Humanoid Autonomous Robot with Learning Intelligence, version Lightweight) which stands 141 cm tall and weighs only 12.7 kg. The design goals of CHARLI-L are low development cost, lightweight, and simple design, which all match well with the proposed walking engine. The results of the experiments present the efficacy of our approach.
A Low Cost Micro Scale Cyclone Microparticle Separator - Design and CFD Analysis
Authors: Pandya Deval A. , Dennis Brian H.
Published: June 2012

Microparticle separation process has a variety of application varying from application in biological and biomedical industries for analysis and diagnosis, in biogas manufacturing to separate phases as well as in defense sector for detection of biological weapons like anthrax. Available electrical, magnetic, acoustic and various other methods are either very costly or not portable. The proposed design of micro scale cyclone separator is low cost as well as portable and easy to manufacture. Huge cyclone separators are widely used in various industries since decades but due to lack of research in micro scale cyclones no direct and sufficient data is available. This research attempts to develop a microscale cyclone separator and study the effect of parameters like inlet velocity on pressure drop in a micro scale cyclone separator. It further studies the effect of particle size on collection efficiency through Computational Fluid Dynamics (CFD) approach. CFD analysis has been proved very efficient for calculations in larger cyclones and hence is used as a tool in this study as well, though experimental verification is recommended. Computational experiments were performed using FLUENT. The results obtained are compared with various empirical relations developed for huge cyclone separators and similarities and dissimilarities in trends are analyzed. Finally a multi-cyclone model is proposed to obtain higher collection efficiency.
Computational Modeling of Hypoplastic Left Heart Syndrome (HLHS) in Newborn Babies
Authors: Jalali Ali , Nataraj C. , Jones Gerard F. , Licht Daniel J.
Published: June 2012

Hypoplastic left heart syndrome (HLHS) is a congenital heart defect (CHD) in which left side of the heart is severely underdeveloped. To better understand this unique physiology, a computational model of the hypoplastic heart was constructed on the basis of compartmental analysis. Lumped parameter model of HLHS is developed based on the electrical circuit analogy. Model is made up of three parts: hypoplastic heart, pulmonary circulation and systemic circulation. Plots of blood pressure and flow for various parts of body show great match between predicted values and what we expected for the case of HLHS babies. Influence of patent ductus arteriosus (PDA) and ASD resistances on cardiac output and pulmonary to systemic flow was also studied. Results show that by increasing the PDA resistance causes more flow to pulmonary compartments and so the ratio increases. Blood flow increases by decreasing of pulmonary artery resistant. Increasing the PDA resistance causes decrease the cardiac output because of more resistance against blood occurs. Saturation increases by decreasing of pulmonary artery resistant.
Coupled-Oscillator Model of Locomotion Stability With Elastically-Suspended Loads
Authors: Ackerman Jeffrey , Seipel Justin
Published: June 2012

Elasticity is a fundamental property of dynamic locomotion and is generally thought to affect the efficiency and stability of motion. In particular, it is becoming increasingly apparent that elastically-suspended loads are common in biology and useful for carrying loads. For example, the Suspended Load Backpack reduces the peak forces and energy cost during locomotion. In this paper, we present a simple model of locomotion to examine the effect of elastically-suspended loads on the peak forces, energy cost, and stability during locomotion. The results from the model show that elastically-suspended loads reduce the peak forces, energy cost, and stability of locomotion compared to rigidly-attached loads, thus indicating that a tradeoff exists between the decreased stability of locomotion and the reduction of peak forces and energy cost. We discuss this tradeoff and the implications of reduced stability on locomotion over rough terrain and the maneuverability of a system.
Delayed Car-Following Dynamics for Human and Robotic Drivers
Authors: Orosz Ga´bor , Moehlis Jeff , Bullo Francesco
Published: June 2012

A general class of car-following models is analyzed where the longitudinal acceleration of a vehicle is determined by a nonlinear function of the distance to the vehicle in front, their velocity difference, and the vehicle’s own velocity. The driver’s response to these stimuli includes the driver reaction time that appears as a time delay in governing differential equations. The linear stability of the uniform flow is analyzed for human-driven and computer-controlled (robotic) vehicles. It is shown that the stability conditions are equivalent when considering ring-road and platoon configurations. It is proven that time delays result in novel high-frequency oscillations that manifest themselves as short-wavelength traveling waves. The theoretical results are illustrated using an optimal velocity model where the nonlinear behavior is also revealed by numerical simulations. The results may lead to better understanding of multi-vehicle dynamics and allow one to design cooperative autonomous cruise control algorithms.
Visual Synthesis of RRR- and RPR-Legged Planar Parallel Manipulators Using Constraint Manifold Geometry
Authors: Purwar Anurag , Gupta Aditya
Published: June 2012

In this paper, we present our ongoing work on development of a visual design tool for designing planar parallel manipulators that satisfy a given rational motion. Although in this paper, we have restricted ourselves to RRR- and RPR-type legs, the approach presented here is general enough to accommodate other leg topologies. The basic idea is to represent the kinematic constraint of such parallel manipulators as an algebraic manifold and the given motion as a one-parameter curve in the image space of planar displacements. The algebraic manifold is projected in the three-dimensional space and a simple set of relationships are obtained that couple the geometry of the projected manifold to the design parameters of the parallel manipulators. Simple geometric transformations in the projected space allow a user to visually contain the image curve inside the manifold, thus satisfying the kinematic constraints. This interactive process, at the end, gives the dimensions of the links of the legs and the location of the fixed and moving frames. This is an extension of our previous work on the dimensional synthesis of planar 6R closed chains.
A Behavior Based Approach to Cellular Self-Organizing Systems Design
Authors: Chen Chang , Jin Yan
Published: June 2012

Multi-agent systems (MAS) have been considered a potential solution for developing adaptive systems. The design of MAS however is difficult because the global effect emerges from local actions and interactions that can be hard to specify and control. In order to achieve high level resilience and robustness of MAS and retain the capability of specifying desired global effects, we propose a cellular self-organizing (CSO) system framework and a biologically inspired behavior based design approach (BDA) and a field based regulative control mechanism (FBR). The BDA approach links global functional requirements with the local behavior design of a CSO system. FBR is a real-time, dynamical, distributed mechanism that regulates the emergence process for CSOs to self-organize and self-reconfigure in complex operation environments. BDA and FBR together extend the system adaptability without imposing global control over local agents. This paper describes the models of CSO, BDA and FBR and demonstrates their effectiveness by presenting simulation based case studies in which CSO agents explore an unknown environment and move an object to designated locations.
On the Classification of Compliant Mechanisms and Synthesis of Compliant Single-Strip Mechanisms
Authors: Midha Ashok , Kolachalam Sharath K. , Annamalai Yuvaraj
Published: June 2012

Compliant mechanisms, unlike rigid-body mechanisms, are devices that derive some or all of their mobility due to the deformation of their flexible members. The knowledge of existing rigid-body mechanism synthesis techniques is very useful in designing compliant mechanisms. In rigid-body mechanisms, a four-bar is treated as the basic mechanism that can transfer motion, force or energy. In this paper, a compliant single-strip continuum is introduced as the basic compliant mechanism that can transfer motion, force or energy. A classification of compliant mechanisms is presented herein. A methodology for compliant single-strip mechanism synthesis for energy, force or torque specifications is developed in this research as our second objective. The synthesis types, the governing equations, and the variables involved are enumerated.
On a Gearing Problem in Conventional Harmonic Drives With Involute Toothed Gear Set
Authors: Routh Bikash , Maiti Rathindranath
Published: June 2012

Circular pitches of flex spline teeth of a ‘Strain Wave Gearing’, also known as a ‘Harmonic Drive’, are deformed when the Strain Wave Generating Cam is inserted into the flex spline cup. In the present work the deformed pitch distances considering that flex spline teeth remain rigid while the rim deforms, are estimated. No applied load is considered. It is also shown that if the cam is elliptical then the pitch curve is not an ellipse and vice versa. Geometries of such curves can be defined following the analysis presented in this paper. Cases of both undeformed flex spline with circular spline and deformed flex spline with circular spline, with involute teeth, are considered to find out tooth positions. Geometries of involute teeth profiles in mesh are examined and compared considering oval shaped (on deformation) base drum of flex spline where as base circle of circular spline remained circular.
An Asymmetric Dimension-Adaptive Tensor-Product Method for Reliability Analysis
Authors: Hu Chao , Youn Byeng D.
Published: June 2012

Reliability analysis plays an essential role in the development of structural systems. However, commonly used reliability analysis methods suffer from either the curse of dimensionality or the lack of accuracy in many structural problems. This paper presents an asymmetric dimension-adaptive tensor-product (ADATP) method to resolve the difficulties of existing reliability analysis methods. The proposed method leverages three ideas: (i) an asymmetric dimension-adaptive scheme to efficiently build the tensor-product interpolation considering both directional and dimensional importance, (ii) a hierarchical interpolation scheme using either piecewise multi-linear basis functions or cubic Lagrange splines, (iii) a hierarchical surplus as an error indicator to automatically detect the highly nonliner regions in a random space and adaptively refine the collocation points in these regions. The proposed method has three distinct features for reliability analysis: (a) automatically detecting and adaptively reproducing tri- and higher-variate interactions, (b) greatly alleviating the curse of dimensionality, and (c) no need of response sensitivities. Several mathematical and engineering problems involving high nonlinearity are used to demonstrate the effectiveness of the ADATP method.
Analytic-Holistic Two-Segment Model of Quadruped Back-Bending in the Sagittal Plane
Authors: Seipel Justin E.
Published: June 2012

Back-bending in the sagittal plane is common in many animals during legged locomotion and could be useful for robots. However, to our knowledge, there exists no analytical mechanistic model of sagittal-plane back bending legged locomotion of quadrupeds. Such a mechanistic model and knowledge derived from it is expected to enable direct analysis and insight into back bending locomotion and can be applied to the study of biomechanics or the design of robots. Here a whole-body mechanistic model is developed and governing equations of motion are derived to provide insight into the mathematical structure of the system dynamics. The model is energy conserving, consisting of massless elastic legs pinned to two body segments. The two body segments are pin-joined together with a rotational spring. The massless legs are returned to a resting angle relative to the body during swing phase. We discover: 1) Whole-body configuration variables simplify the resulting equations of motion. 2) The sagittal-plane back-bending two-segment model of legged locomotion yields stable periodic gaits.