bluuebunny/crossref_metadata_2025 huggingface dataset:
Increasing System Robustness Through a Utility-Based Analysis
Authors: Baxter Benjamin , Malak Richard
Published: February 2014

Robustness is an important aspect of complex engineered systems. However, ambiguity in its definition can generate uncertainty among engineers about how to be sure that it is accounted for in their design. In this paper, robustness is defined as a property that allows a system to maintain its functions against anticipated internal and external perturbations. The important aspect of this definition is the focus of robustness on a per-function basis. A modified utility-based design approach is presented that provides a step by step implementation to help engineers ensure their designed systems meet their preferences and contain robust characteristics. The approach focuses on generating functional models of the proposed system. The functional models provide designers with insight into which internal and external perturbations should be included within the system model. An example case study is included to illustrate the steps of the modified utility-based design approach. The case study examines the entry, descent and landing of a Mars rover. The system and subsystems are modeled using black box models and EMS (Energy, Material, Signal) function structures. This allows the relevant internal and external perturbations to be modeled in the system model. The case study shows how using a utility-based analysis can produce a robust system.
Micro Cantilever Electrostatic Energy Harvester
Authors: Hammad Bashar K. , Abdel-Rahman Eihab M. , Mahmoud Mohamed A. E.
Published: February 2014

In this paper, we present a SDOF model of an energy harvester made up of microcantilever beams with tip mass. We investigate performance utilizing electrostatic actuation mechanism resulted from an electret layer patterned underneath the tip mass. The excitation force is transferred to cantilever beams through the vibration of the fixed end, i.e. the base of the beam. The model accounts for the mechanical and electric parameters as well as the coupling between them, and it includes design parameters by lumping them into nondimensional quantities, thereby allowing an easier understanding of their effects and the interaction between the mechanical and electric forces. We study the static behavior of deflection and electric charge as a function of the DC static voltage. In addition, we simulate the dynamic response, generate the frequency-response curves for a variety of conditions, and notice nonlinear effects.
Surface Electromyographic Control of a Humanoid Robot
Authors: Grammar Alex W. , Williams Robert L.
Published: February 2014

This paper details the development of an open-source surface electromyographic interface for controlling 1-DOF for the DARwIn-OP humanoid robot. This work also details the analysis of the relationship between surface electromyographic activity of the Biceps Brachii muscle and the angle of the elbow joint for the pseudo-static unloaded arm case. The human arm was mechanically modeled for a two link system actuated by a single muscle. The SEMG activity was found to be directly proportional to joint angle using a combination of custom joint angle measuring hardware and a surface electromyographic measuring circuit. This relationship allowed for straightforward control of the robot elbow joint directly. The interface was designed around the Arduino Microcontroller; another open-source platform. Software for the Arduino and DARwIn-OP were drawn from open source resources, allowing the entire system to be comprised of open-source components. A final surface electromyographic measuring and signal conditioning circuit was constructed. Data recording and processing software was also coded for the Arduino, thus achieving control of the robotic platform via surface electromyography.
Safe Human Robot Interaction by Using Exteroceptive Sensing Based Human Modeling
Authors: Morato Carlos , Kaipa Krishnanand , Zhao Boxuan , Gupta Satyandra K.
Published: February 2014

In this paper, we propose an exteroceptive sensing based framework to achieve safe human-robot interaction during shared tasks. Our approach allows a human to operate in close proximity with the robot, while pausing the robot’s motion whenever a collision between the human and the robot is imminent. The human’s presence is sensed by a N-range sensor based system, which consists of multiple range sensors mounted at various points on the periphery of the work cell. Each range sensor is based on a Microsoft Kinect sensor. Each sensor observes the human and outputs a 20 DOF human model. Positional data of these models are fused together to generate a refined human model. Next, the robot and the human model are approximated by dynamic bounding spheres and the robot’s motion is controlled by tracking the collisions between these spheres. Whereas most previous exteroceptive methods relied on depth data from camera images, our approach is one of the first successful attempts to build an explicit human model online and use it to evaluate human-robot interference. Real-time behavior observed during experiments with a 5 DOF robot and a human safely performing shared assembly tasks validate our approach.
On the Effects of Blade-Disk Interface Mistuning on the Response of Integrated Bladed Rotors
Authors: Avalos Javier , Murthy Raghavendra , Wang X. Q. , Mignolet Marc P.
Published: February 2014

The response of blades in bladed disks can be represented as a sum of modal contributions from their cantilevered modes and a component induced by the motion of the disk and its interface with the blades. This last contribution referred to here as the disk-induced blade motions is generally considered to be tuned when performing mistuning analysis of bladed disks. Yet, as most of the blade properties, its structural coupling to the disk is likely to be uncertain, for example due to variations in thickness at the blade filet. One thus expects a mistuning of the interface stiffness and mass matrices in particular. The effect of this mistuning on the blade response, which does not appear to have received significant attention, is the focus of the present investigation. A Craig-Bampton methodology is introduced to highlight the disk-blade interface and a mistuning modeling of its stiffness matrix is introduced following the nonparametric modeling method. The analysis with various mistuning models is carried out on a 15-blade impeller finite element model at several resonances. It is found that a small mistuning of the disk-induced blade does not alter notably the mistuned response of the blades.
Design of a Compliant Underactuated Robotic Finger With Coordinated Stiffness
Authors: Nelson Carl A. , Dessauw Etienne , Saiter Jean-Marc , Benzohra Mohamed
Published: February 2014

In this paper, we propose an underactuated robotic finger whose grasp behavior is modulated by the design of its superelastic joints. Using shape-memory alloy, the finger joints can be given specific stiffness and pre-form shapes such that a single-cable actuation rather than opposing-pair actuation can be used; this also allows the grasping motions of the phalanges to be synchronized in the free phase and then adaptive once contact is made. A default-closed pre-tensioned configuration allows grasp forces to be maximal for larger objects and still keeps control components such as tendons out of the grasp workspace. The simplicity of the design lends itself to the possibility of integrated joint angle and surface pressure sensing on the finger itself. The details of design, prototyping and testing are described.
Design and Fabrication of an Arm Exoskeleton for Aim Stabilization
Authors: Baechle Daniel M. , Wetzel Eric D. , Agrawal Sunil K.
Published: February 2014

Accurately aiming and firing a pistol requires a steady hand. While many devices can steady a shooter’s arm or hand by restricting movement or degrees-of-freedom, few devices actively reduce involuntary tremors while allowing larger voluntary aiming movements. This paper details the design and fabrication of an arm exoskeleton that can actively damp arm tremors while allowing voluntary aiming movements. The device allows five degrees-of-freedom and is very lightweight due to its cable-driven architecture and use of carbon fiber composite materials. Tremorous movement is filtered out from voluntary motion, and an adaptive algorithm provides a tremor-cancelling signal to the cable control motors.
An Experimental Investigation Into the Performance of a T-Shaped Piezoelectric Flow Energy Harvester
Authors: Jain P. B. , Cacan M. R. , Leadenham S. , De Marqui C. , Erturk A.
Published: February 2014

The harvesting of flow energy by exploiting aeroelastic and hydroelastic vibrations has received growing attention over the last few years. The goal in this research field is to generate low-power electricity from flow-induced vibrations of scalable structures involving a proper transduction mechanism for wireless applications ranging from manned/unmanned aerial vehicles to civil infrastructure systems located in high wind areas. The fundamental challenge is to enable geometrically small flow energy harvesters while keeping the cut-in speed (lowest flow speed that induces persistent oscillations) low. An effective design with reduced cut-in speed is known to be the T-shaped cantilever arrangement that consists of a horizontal piezoelectric cantilever with a perpendicular vertical beam attachment at the tip. The direction of incoming flow is parallel to the horizontal cantilever and perpendicular to the vertical and symmetric tip attachment. Vortex-induced vibration resulting from flow past the tip attachment is the source of the aeroelastic response. For a given width of the T-shaped harvester with fixed thickness parameters, an important geometric parameter is the length ratio of the tip attachment to the cantilever. In this paper we investigate the effect of this geometric parameter on the piezoaeroelastic response of a T-shaped flow energy harvester. A controlled desktop wind tunnel system is used to characterize the electrical and mechanical response characteristics for broad ranges of flow speed and electrical load resistance using different vertical tip attachment lengths for the same horizontal piezoelectric cantilever. The variations of the electrical power output and cut-in speed with changing head length are reported along with an investigation into the electroaeroelastic frequency response spectra.
Low Voltage Electrostatic Actuation for MEMS Actuator Using Frequency Modulation
Authors: Park Sangtak , Khater Mahmoud , Abdel-Rahman Eihab
Published: February 2014

In this paper, we derive and present an analytical model of the parallel-plate electrostatic actuator coupled with the resonant drive circuit when it is driven by a frequency-modulated input signal. Using this analytical model, we determine the stability of the fixed points of the actuator without linearization process. Furthermore, we study the effect of parasitic capacitance and the quality factor of the resonant drive circuit on the operation range and stability of the electrostatic actuator.
Estimation of Probability of Failure With Dependent Variables Using Copulas and Support Vector Machines
Authors: Jiang Peng , Missoum Samy
Published: February 2014

This paper presents an approach to estimate probabilities of failure in the case of dependent random variables. The approach is based on copulas and support vector machines (SVMs). A copula is used to generate dependent Monte Carlo samples and an SVM is used to construct the explicit boundary of the failure domain. It is shown that this construction of the failure boundary cannot be made in the original space due to the lack of “isotropy” of the probability densities. In this work the SVM is built in the uncorrelated standard normal space and refined using an adaptive sampling scheme. A transformation is used to map SVM training points and Monte-Carlo samples between the original space and the uncorrelated standard normal space. Because SVM is a classification-based approach, it can handle discontinuous responses and, more importantly, several limit states using one single SVM. Several analytical examples are used to demonstrate the methodology.
Manifold Conjugation and Discrete Gear Design
Authors: Yu Bowen , Ting Kwun-lon
Published: February 2014

This paper presents a new conjugation theory and a new design methodology for the advanced conjugation design based on CAD (computer aided design) and CAE (computer aided engineering). A general conjugation theory called manifold conjugation is established based on the classic conjugation theory and manifold theory. It leads to both smooth conjugation modeling and discrete conjugation modeling. The former one has been studied in the previous work for design optimization of analytical conjugation properties. The latter one is a desirable methodology for the conjugation design based on CAE simulation. The paper brings up a new perspective towards conjugation representation theory, leading to a new design process. Contrary to the traditional idea that CAD has to be known before and separated from CAE, the new theory suggests using discrete manifold to bridge CAD and CAE. Furthermore, discrete modeling techniques from CG (computer graphics) such as subdivision can be employed for conjugation modeling and design. Two planar examples that minimize gear PPTE (peak to peak transmission error) show that the methodology is capable of and effective in conjugation optimization.
Virtual Contact Dynamics Behaviour in Haptic Interfacing
Authors: Amin Sara Shayan , Kovács László L. , Kövecses József
Published: February 2014

The key element in haptic interfacing is the virtual contact representation that connects the virtual environment to the human via the haptic device. The properties of virtual contact can determine the quality of the haptic interfacing. In this work, we particularly investigate how the mechanical and structural properties can influence the virtual contact behaviour. To this end, representative models are incorporated, where the effective parameters are directly connected to physical and structural properties of the system. Virtual contact behaviour is then investigated via parametric stability analysis, and corresponding spectral radius of the transition matrix is selected as a performance indicator. It is shown that structural flexibility plays an important role in the quality of the haptic interfacing. As an example, rendering virtual walls with different impedances are considered and for each case the optimum effective parameters of the model is obtained for fidelity improvement.
Fast Far-Field Potential Evaluation in Multibody-Based Simulations of Biopolymers
Authors: Poursina Mohammad , Anderson Kurt S.
Published: February 2014

A novel algorithm to approximate the long-range potential field in multiscale simulations of biopolymers is presented. These models contain various domains including single particles, as well as regions with coarse-grained clusters in which high frequency modes of motion are suppressed. Herein, coarse-grained regions are formed via treating groups of atoms as rigid and/or flexible bodies/clusters connected together via kinematic joints, and as such, multibody dynamic techniques are used to form and solve the equations of motion. In such simulations with n particles, the evaluation of the potential field with computational complexity of O(n2), if not performed wisely, may become a bottleneck. This paper presents the approximation of the potential field due to the interaction between a charged particle and a body containing charged particles. This approximation is expressed in terms of physical and geometrical properties of the bodies such as the entire charge of the cluster and a pseudo-inertia tensor. Further, a divide-and-conquer scheme is introduced to implement the presented far-field potential evaluations. In this scheme adjacent charged bodies are combined together to form new bodies. The mathematical framework to create these new assemblies is presented. Then the potential of the resulting bodies on the charged particles which are far from them are recursively calculated.
A Study of Engineering Design Project Complexity and Risk Indicators
Authors: Yim Rachel L. , Castaneda Jason M. , Doolen Toni L. , Tumer Irem Y. , Malak Richard J.
Published: February 2014

Engineering design projects can be characterized by three dimensions: duration, budget, and scope. As projects grow in any of these three dimensions, there will be increased opportunity for uncertainty, and subsequently, increased risk. This study explored the relationship between the number of project activities and the presence of risk indicators. A risk indicator is a particular state of affairs that has potential predictive power about the likelihood of a risk occurring during the course of a project. This study was completed by examining eleven projects that were conducted within one division of a large engineering design firm. Projects were divided into groups according to the number of activities associated with each project, and interviews were conducted with employees, who worked in a variety of positions. A comparative analysis of risk indicators was then completed to identify potential “watch” areas and provide a basis for risk mitigation planning. The study provided conclusive evidence that the most frequently occurring risk indicators vary with the number of activities involved in a project. Project managers can use this information to create more specific risk management plans tailored to the types of risk indicators most frequently associated with the number of activities within a project.
Comparison of Cylindrical Wrapping Geometries to Via Points for Modeling Muscle Paths in the Estimation of Sit-to-Stand Muscle Forces
Authors: Norman-Gerum Valerie , McPhee John
Published: February 2014

To better understand the complexities of rising from a seated to a standing position, a model of the human has been created. Sit-to-stand kinematics as well as ground reaction forces were measured experimentally and are used in an inverse dynamics analysis to estimate nine muscle forces during motion.

Calculated muscle forces are sensitive to assumptions made when modeling muscle paths. Changes in the line of action of a muscle due to interaction with anatomical constraints are often accounted for by including fixed via points in a model. Here an alternate approach of representing anatomical constraints using three-dimensional cylindrical geometries is derived and presented. In this mathematical model the course of the muscle is determined as the minimum-length path where the muscle is allowed to wrap freely over the surface of the cylinder.

Muscle forces are estimated for sit-to-stand by resolving net joint torques using an objective function giving preference to solutions minimizing both muscle stresses and abrupt changes in muscle forces. This is the first time muscle forces have been presented for sit-to-stand using a musculoskeletal model with included anatomical constraints represented using cylindrical wrapping geometries alone. A comparison of calculated muscle force patterns using fixed via points and wrapping points versus three-dimensional wrapping surfaces is made with reference to electromyographic phase data. For the sit-to-stand motion, the inclusion of anatomical constraints as three-dimensional cylindrical geometries results in calculation of muscle forces more true to the experimental data and more consistent with the belief that gradual motions are created by gradual changes in muscle force over time.
Basic Optimization Methodology for the Design of Friction Damping in Blade Shrouds
Authors: Hajžman Michal , Pešek Luděk , Brůha Jan , Zeman Vladimír , Rychecký Drahomír
Published: February 2014

This paper is focused on the optimization of friction element parameters in blade shrouds for various types of excitation. In order to create and validate a proper modelling methodology an experimental stand and a numerical simulation of blades interaction by means of a friction element placed in the shrouds were prepared. Mathematical models are based on the finite element method combined with rigid bodies. The interaction of the friction element and blades is described by normal contact and tangential friction forces derived for particular geometrical parameters of the studied mechanical system. The models can be analyzed both in frequency domain (by the harmonic balance method) or in time domain (by the numerical integration). The results of the optimization of friction element parameters with respect to the bending vibration suppression are documented in the paper. Another contact modelling approach intended for more complex contact surfaces is based on the decomposition of a contact surface into a set of elementary areas and on the expression of contact and friction forces between these areas. All methodologies are implemented in the MATLAB system and the results for the chosen test cases are compared with the results obtained by a measurement or by the ANSYS software.
Efficient Hyper-Volumetric Contact Dynamic Modelling of the Foot Within Human Gait Simulations
Authors: Shourijeh Mohammad Sharif , McPhee John
Published: February 2014

This study describes the development of a multi-body foot contact model consisting of spherical volumetric models for the surfaces of the foot. The developed model is two-dimensional, and consists of two segments, the hind-foot, mid-foot, and forefoot as one rigid body and the phalanges collectively as the second rigid body. The model has four degrees of freedom: ankle x, y, hind-foot orientation, and metatarsal joint angle. Both ankle and metatarsal joints are assumed to be revolute joints. Three different types of contact elements are targeted: Kelvin-Voigt, linear volumetric, and nonlinear volumetric. The models are kinematically driven at the ankle and the metatarsal joints, and simulated horizontal and vertical ground reaction forces as well as center of pressure location are compared against the measured quantities within a complete human gait cycle. The hyper-volumetric foot contact model was found to be a suitable choice for foot/ground interaction modelling within human gait simulations.
Early-Stage Design of Rheologically Complex Materials via Material Function Design Targets
Authors: Bharadwaj N. Ashwin , Allison James T. , Ewoldt Randy H.
Published: February 2014

Rheological material properties are high-dimensional function-valued quantities, such as frequency-dependent viscoelastic moduli or non-Newtonian shear viscosity. Here we describe a process to model and optimize design targets for such rheological material functions. For linear viscoelastic systems, we demonstrate that one can avoid specific a priori assumptions of spring-dashpot topology by writing governing equations in terms of a time-dependent relaxation modulus function. Our approach embraces rheological design freedom, connecting system-level performance to optimal material functions that transcend specific material classes or structure. This technique is therefore material agnostic, applying to any material class including polymers, colloids, metals, composites, or any rheologically complex material. These early-stage design targets allow for broadly creative ideation of possible material solutions, which can then be used for either material-specific selection or later-stage design of novel materials.
Small Low Cost Unmanned Aerial Vehicle Lithium-Polymer Battery Monitoring System
Authors: Podhradsky Michal , Bone Jarret , Jensen Austin M. , Coopmans Calvin
Published: February 2014

Lithium-Polymer (LiPo) batteries are becoming a popular choice for electric small low cost Unmanned Aerial Vehicles (UAVs). In case of a multirotor UAVs, a battery failure means a certain loss of the air frame. To fully utilize their potential and maintain mission safety, a monitoring system predicting battery behaviour is required. In this study a change in battery dynamics during discharge, and its effect of thrust produced by actuators is measured. Experiments simulating flight conditions are performed, and measured data are interpolated with double exponential and polynomial curves. An obvious similarity between the battery state-of-charge and produced thrust is observed. Due to conventional altitude controllers’ inability to cope well with changes in battery dynamics, a controller invariant to those changes is presented.
An Integrated Model Approach for Quantifying Carbon Emissions From Residue-Based Biofuel Production
Authors: Abodeely Jared M. , Muth David J. , Koch Joshua , Bryden Kenneth M.
Published: February 2014

This paper presents an agricultural residue removal decision framework that couples the environmental process models WEPS, RUSLE2, SCI, and DAYCENT. One of the goals of this integrated model is to quantify the impacts of land management strategies on soil organic carbon and CO2 emissions. Soil, climate, and land management practices are considered in determining sustainable residue removal rates using wind- and water-induced soil erosion and qualitative soil organic carbon constraints and to quantify the long-term impacts of sustainable residue removal on soil organic carbon and greenhouse gas emissions. Using this integrated model sustainable residue removal for four crop rotations, three tillage regimes, and four soil types representing nearly 70% of the arable acres in Boone County, Iowa are examined. Each scenario was performed for a twenty-year period. Soil organic carbon and CO2 emission results are aggregated by soil type using crop rotation and tillage statistics. The soil type results are aggregated using a normalized percentage area to provide a county level estimate of soil organic carbon changes and CO2 emissions. Results show that for the largest sustainable residue removal rate that soil organic carbon increased 3.53–6.63 Mg/ha over the 20 year simulation and that CO2 emissions ranged from 3.50–4.23 Mg/ha across the four soil types resulting in an average increase of soil organic carbon of 4.85 Mg/ha and CO2 emission of 3.77 Mg/ha at the county level.
Antenna-Like Tactile Sensor for Thin-Film Piezoelectric Micro-Robots
Authors: Rudy Ryan , Cohen Adam J. , Pulskamp Jeffrey S. , Polcawich Ronald G. , Oldham Kenn R.
Published: February 2014

Terrestrial and other millimeter-scale autonomous micro-robots face significant challenges in surveying their environment, due to small power budgets and payload capacities. One low-power, low-mass form of obstacle detection is tactile sensing of contact with other surfaces. In this-paper, a tactile sensor inspired by insect antennae is described, based on thin-film lead-zirconate-titanate (PZT) transduction. Thin-film piezoelectric materials permit actuation and sensing mechanisms to be coupled in very small, compact structures, as well as complement previously developed microrobotic leg mechanisms. Key design parameters for the tactile sensor are introduced and analyzed in terms of sweep frequency and range of motion, and signals from sensor impact are predicted. Experimental results with partially-released prototype actuators show respectable agreement with modeled behavior for dynamic motion, though impact detection is hampered by large feedthrough disturbances. Completed sensors range from 2 to 4 mm in length and are approximately 500 μm in width, with a sweep range of nearly 1 mm demonstrated from a 2 mm long prototype.
Advanced Motion Control Design for Longitudinal Web Dynamics in Roll-to-Roll Systems: Velocity or Position Control?
Authors: Martz Y. , Frechard J. , Knittel D.
Published: February 2014

Roll-to-Roll systems handling web material such as papers, polymers, textiles or metals are very common in the industry. One of the main objectives in web handling plant is to reach an expected web speed while maintaining the web tension within an acceptable range around the tension reference in the entire processing line. In the recent years, several works have focused on the topic of web tension control using H∞ approaches. In the traditional way, each motor driven roller is controlled in speed and the web tension control is ensured by an external loop. This paper proposes to compare, for the first time, the traditional control strategy with a control strategy including position control rather than speed control. In fact, position control is commonly used in printing industry. The comparison will be ensured in frequency and time domain and take into account the reference tracking performances and the robustness to web elasticity variations.
Comparison of Hip Torque and Radial Forcing Effects on Locomotion Stability and Energetics
Authors: Shen Zhuohua , Larson Peter , Seipel Justin
Published: February 2014

Hip torque and radial forcing along the leg are two common actuation methods for legged robots. However, hip torque and radial forcing have not been compared as potential alternative strategies of actuation. The respective advantages and disadvantages of hip torque and radial forcing are not well known. In this paper, we compare hip torque and radial forcing actuation through the simulation of two models: a Rotary-forced Spring-Loaded Inverted Pendulum and a Radially Forced Spring-Loaded Inverted Pendulum. Both actuation methods can produce fully asymptotically stable locomotion. Interestingly, it is found that they improve locomotion stability in different ways: hip torque first destabilizes locomotion when initially introduced but greatly stabilizes locomotion when it keeps increasing; radial forcing always stabilizes locomotion, but in a moderate way.
Modeling and Optimization of a Miniature Elastomeric Compliant Mechanism Using a 3-Spring Pseudo Rigid Body Model
Authors: Vogtmann Dana , Gupta Satyandra K. , Bergbreiter Sarah
Published: February 2014

This paper extends a previously developed Pseudo Rigid Body (PRB) analytical model for miniature elastomeric joints by introducing correction factors for joints with geometry not previously considered. Inclusion of these correction factors has resulted in an increase in the accuracy of the model from 20% to within 3% in bending and from 25% to within 7% in tension, when compared to equivalent Finite Element Analysis (FEA) models. Additionally, using the PRB model, a robotic leg with four elastomeric joints has been modeled, resulting in a maximum error of 12% when compared to an equivalent FEA model. Finally, the PRB model was used to optimize the robotic leg for minimum motor torque required to drive a hexapedal robot with six identical legs.
Control and Tension Estimation of a Cable Driven Mechanism Under Different Tensions
Authors: Kosari Sina Nia , Ramadurai Srikrishnan , Chizeck Howard Jay , Hannaford Blake
Published: February 2014

This paper proposes a method to estimate and compensate for the changes of cable tension in the control of cable driven mechanisms. Cable tension may depend on various factors, including mechanism design, fabrication and operation. In many systems it is also an adjustable parameter that affects the performance of the control system. An implementation of the unscented Kalman filter is used for the simultaneous estimation of the states and parameters of a cable driven mechanism. Changes in cable tension are captured in the estimated parameters which, along with system states, are used by a model predictive controller to generate appropriate control actions. The method is described and its effectiveness is shown for a single degree of freedom cable driven robot. In addition, the correlation between the cable tension and the estimated robot parameters provides a way of estimating the tension. It is shown that cable tension can be inferred from one of the estimated robot parameters, namely cable stiffness.
Online-Applicable Temperature Prediction Model for EV Battery Pack Thermal Management
Authors: Kim Tae Jin , Youn Byeng D. , Kim Hyun Jae
Published: February 2014

Lithium-ion (Li-ion) batteries may fail through thermal runaway caused by increased temperature. It is thus important to monitor battery temperature for prevention of the battery failure. Currently, thermal monitoring of the battery for electric vehicles (EVs) is being conducted by multiple thermostats. As the size of battery system increases and the cells are closely packed to exploit high power density, the number of thermostats is also increased to monitor the battery system. However, this increased number of sensors enhances the probability of the sensor malfunction, which prevents robust thermal monitoring, and causes increased maintenance cost and customer complaints. This paper thus proposes an online applicable temperature prediction model for EV battery pack while minimizing the number of sensors and keeping the monitoring capability. This was possible with three ideas: (a) devising battery thermal characterization test under various operating conditions, (b) development of the online-applicable temperature prediction model using artificial neural network (ANN), and (c) validation of the temperature prediction model. The proposed temperature prediction model was demonstrated with the EV battery pack that consists of twelve battery modules.
Exploring the Effects of the Design Prompt on Students’ Design Cognition
Authors: Williams Christopher B. , Lee Yoon , Gero John , Paretti Marie C.
Published: February 2014

Engineering design educators often provide their students a task (or “prompt”) to guide their design projects. Similarly, engineering design educational researchers also provide research participants with a design task to guide their activity during experimental sessions. In both contexts, there is a fundamental underlying assumption that the design task has no significant effect on the students’/participants’ design cognition. Specifically, the authors test the hypothesis that a design task does affect a student’s design experience. Failing to disprove this hypothesis could significantly impact both design education practice and design education experimental research.

To determine the effect of a design task on students’ design cognition, experimental sessions were conducted wherein student design teams worked together to solve a speculative design task. The student teams were presented with two nearly identical design tasks; however, one featured an additional design requirement. A task-independent protocol analysis method grounded in the Function-Behavior-Structure design ontology is performed on audio and video recordings of the design sessions to provide a common basis for comparing the two groups. Differences in design cognition are identified by analyzing and comparing the percent occurrences of the design issues and design processes and the Problem-Solution indices.
Modal-Based Finite Elements for Efficient Wave Propagation Analysis
Authors: Capuano German , Ruzzene Massimo , Rimoli Julian J.
Published: February 2014

This paper presents an extension to the Geometric Multi-Scale Finite Element Method (GMsFEM) developed by Casadei et al. to predict the dynamic response of heterogeneous materials and structures. The proposed approach introduces elements enriched by the natural modes over their own domain. When heterogeneities are present, the auxiliary fine-scale mesh from GMsFEM is used to calculate the modes numerically. The enrichment scheme is also chosen in such a way that it automatically satisfies continuity across boundaries. The computational efficiency of the method is compared to that of traditional finite element formulations through selected benchmark problems.
Statics Analysis of Clemen’s Linkage for Robotic Applications
Authors: Lahr Derek , Hong Dennis
Published: February 2014

Robotic manipulators can be categorized as either parallel, serial, or in some cases a combination of the two. Among others, a notable drawback of serial manipulators in dynamic applications is the large inertia created by typically heavy electromechanical actuators at the distal end of the manipulator. In addition, compact packaging of multiple actuators in a multi-degree of freedom (DOF) joint, as is often necessary with serial manipulators, can be difficult. These difficulties can be alleviated should a means be found to relocate actuators across one or more degrees of freedom. In this paper, we investigate a constant velocity (CV) linkage, the Clemen’s linkage, that may be used to relocate an actuator across a one DOF revolute joint to an adjacent link while maintaining a serially actuated architecture. This can be very advantageous in some applications such as a humanoid robot ankle. The linkage is analyzed for both its range of motion and torque capacity for such applications given limitations of currently available bearing hardware.
Actuated Slip Model of Human Running With an Elastically-Suspended Load
Authors: Potwar Karna , Ackerman Jeffrey , Seipel Justin
Published: February 2014

An elastically-suspended load can reduce the peak forces acting on the body and the energetic cost of human walking compared to a rigidly-attached load. However, limited knowledge exists on how elastically-suspended loads affect the biomechanics of human running. We develop a variant of an Actuated SLIP (Spring Loaded Inverted Pendulum) model to analyze human running with an elastically-suspended load. This model consists of a suspended load attached to the body mass of an Actuated SLIP model with approximate human parameters. The model enables the investigation of the coupled dynamics of the load and the human body and shows that the stride frequency of running is affected by the load suspension stiffness. The model also shows that the peak forces of the load acting on the body are reduced compared to a rigidly-attached load when the load suspension stiffness is minimized. However, the energetic cost of running with an elastically-suspended load is shown to increase compared to a rigidly-attached load. Further, the peak forces and the energetic cost of running are maximized when the natural frequency of the load suspension is tuned near the stride frequency. This model could lead to a better understanding of human running with elastically-suspended loads and may enable the design of load suspension systems that are optimized to reduce stress on the human body while running with a load.
Configurable Compliance for Series Elastic Actuators
Authors: Orekhov Viktor , Lahr Derek , Lee Bryce , Hong Dennis
Published: February 2014

Variable compliance has been a growing topic of interest in legged robotics due to recent studies showing that animals adjust their leg and joint stiffness to adjust their natural dynamics and to accommodate changes in their environment. However, existing designs add significant weight, size, and complexity. Series Elastic Actuators, on the other hand, are designed with a set stiffness usually tuned for actuator performance. We propose a new concept for implementing a physical spring in series with a linear SEA using a cantilevered spring. A movable pivot is used to adjust the stiffness by changing the effective length of the cantilever. While the proposed design does not allow for variable compliance, it does retain many of the benefits of passive spring elements such as absorbing impacts, storing energy, and enabling force control. The primary advantage of the design is the ability to adjust the stiffness of each joint individually without the increased weight and complexity of variable stiffness designs. This paper introduces the motivation for configurable compliance, describes the proposed design concept, explains the design methods, and presents experimental data from a completed prototype.
Modeling and Simulation of a Multiple-Regime Plug-In Hybrid Electric Vehicle
Authors: Cheng Rui , Dong Jian , Dong Zuomin
Published: February 2014

In recent years, the automotive industry has devoted considerable resources to the research and development of hybrid vehicles. Plug-in hybrid electric vehicles (PHEV) present to be the next generation hybrid vehicles that offer the advantages in reducing fossil fuel consumption and lowering emissions without sacrifice vehicle performance, and the ability to utilize renewable energy through charge from the electric grid.

In this work, the powertrain model of a series-parallel, multiple-regime plug-in hybrid electric vehicle (SPMR-PHEV) was introduced. As one of the several parallel powertrain modeling, simulation and control system design approaches at University of Victoria, the presented SPMR-PHEV model was developed using rule-based load-leveling energy management strategy (EMS) under the MATLAB/Simulink and SimDriveline environment. In order to validate the model and evaluate the fuel consumption and performance of SPMR-PHEV, a Simulink based Prius model and two different PHEV powertrain models have also been built using Autonomie — a vehicle simulation tool developed by DOE’s Argonne National Laboratory, using the default control logics. Fuel consumption from the three different models were compared using a test drive case consisting of eight times of the US06-City drive cycle. Under the static modeling and simulation method and different control strategies, the SPMR-PHEV model in Simulink/SimDriveline and rule-based load-leveling EMS showed 12.02% fuel economy and powertrain efficiency improvements over the Autonomie model. The new powertrain system model developed using Simulink and SimDrivline could also be used as a generic, modular and flexible vehicle modeling platform to support the integration of powertrain design and control system optimization.
Krylov Subspace Methods for Rigid Bodies With Compliant Contact and Cohesion
Authors: Mazhar Hammad
Published: February 2014

Using particle based methods to simulate the behavior of compliant material is a complex task. When investigating the behavior of compliant terrain with hundreds of thousands of bodies in contact, millions of unknowns need to be determined. The size of problems solvable using traditional methods such as Jacobi or Gauss Seidel are severely limited due to the poor rate of convergence. This rate of convergence is typical when the equations of motion are posed as a differential variational inequality (DVI) problem that captures contact events between rigid bodies. The methods used for this framework rely on iterative krylov subspace methods such as Conjugate Gradient and Minimum Residual, which show good convergence for large problems. However, this class of iterative algorithms is not generally suitable for solving DVI problems for dynamics simulation. This document will show that these methods, while not specifically designed to solve rigid body dynamics problems, are very capable of doing so and converge very quicky.
Loading and Design Parameter Uncertainty in the Dynamics and Performance of High-Speed-Parallel-Helical Stage of a Wind Turbine Gearbox
Authors: Alemayehu Fisseha M. , Ekwaro-Osire Stephen
Published: February 2014

The Wind Turbine Gearboxes (WTGs) are highly subjected to variable torsional and non-torsional loads. In addition, the manufacturing and assembly process of these devices results in uncertainty in the system. These gearboxes are reported to fail in their early life of operation, within three to seven years as opposed to the expected twenty years of operation. Their downtime and maintenance process is the most costly of any failure of subassembly of wind turbines. The objective of this work is to perform a probabilistic multibody dynamic analysis (PMBDA) of the high-speed-parallel-helical stage of the gearbox of wind turbine that considers uncertainty of generator side torque loading and the input shaft speed, assembly errors and design parameter uncertainty. System reliability, probability of failure, and probabilistic sensitivities of all the input variables towards several performance functions have been measured and conclusions have been drawn. PMBDA has demonstrated a new dimension of design and installation of wind turbine gearboxes than traditional deterministic approach. In addition to revealing system reliability or under-performance through probability of failure, the method will also help designers to consider certain variables critically through the sensitivity results.
Preliminary Modeling of an Intracochlear Piezoelectric Microphone
Authors: Manson Robert D. , Shen I. Y.
Published: February 2014

A preliminary model of an intracochlear piezoelectric microphone is proposed that mimics the structure of stereocilia in the cochlea. Its purpose is to determine the crucial system parameters prior to fabrication of an actual testing set up via a mathematical model. As a first approximation, the system is modeled as a 1-D, periodic beam with N identical substructures. Each one consists of a nanorod grown on an Si substrate, a bottom electrode, piezoelectric thin film, and two top electrodes. The model consists of: a finite element analysis of a single substructure to obtain its flexibility matrix and differential voltage (DV) under unit loads; and a mapping of these results through the structure to predict displacement and DV of each substructure. A parametric study is then conducted based on this model. It was determined that the nanorod length was the most critical parameter in improving sensitivity. By increasing the amount of drag force on the nanorods the sensitivity grows. Substructures near fixed boundaries generate higher DV thus leading to better sensitivity too. The number of substructure in the microphone would also affect signal-to-noise ratio.
Frequency-Domain Analysis of a Two-Stage Planetary Gear With Combined Backlash and Tooth Damage Nonlinearities
Authors: Wu Xi , Fang Brian , Meagher Jim , Sommer Andrew
Published: February 2014

Being compact and efficient power transmissions, planetary gears are widely used in helicopters, wind turbines and spacecraft. Due to the nonlinearity introduced by the combination of backlash and different teeth damage at different locations, however, the complicated dynamic behaviors of the planetary gears are less understood and investigated. Unfortunately, since the dynamic behavior of the system is highly dependent on the changing point-to-point contact forces between gear pairs, it is nearly impossible to simulate a damaged planetary gear with theoretical models. Therefore, very few research results are published. In this paper, a practical two-stage planetary gear with various types of teeth damage is designed using CAD and analyzed with the multi-body dynamics software ADAMS. The region of point-to-point contact along the involute profile is modeled elastically and accounts for teeth flexibility. Several important parameters such as the stiffness, force exponent, penetration depth, and damping coefficients are carefully chosen based on practical modeling experience. Constraints, bearing resistant torques, and some key parameters are applied to emulate realistic operation conditions. Comprehensive frequency-domain analysis of dynamic contact forces will reveal unique vibration spectra called modulated sidebands, at distinct frequencies around the stage mesh frequencies, and sub- and super-synchronous frequencies. These spectral lines comprise a substantial portion of the vibration and are closely related to the complicated nonlinear dynamics induced by the interaction between backlash and damaged teeth at different locations on different components of the transmission system. The results may serve as the useful fault indicators of the planetary gears. In addition, joint time-frequency analysis (JTFA) is performed on the two-stage damaged planetary gear analysis based on transient start-up conditions, and demonstrates how the frequency content of the contact force evolves over time. As an effective detection tool utilized by industry, JTFA health monitoring is simulated for the first time using a damaged two-stage planetary gear in this paper.