bluuebunny/crossref_metadata_2025 huggingface dataset:
The Realization of Desired Stiffness of Parallel Mechanism by Adding Redundantly-Actuated Limbs
Authors: Huang Shunzhou , Yu Jue , Wang Hao , Zhao Yong , Lai Xinmin
Published: November 2017

Stiffness performance is of importance for the use of parallel manipulators in the industrial applications. For this consideration, this paper proposes to realize the desired stiffness properties of parallel mechanism by adding redundantly-actuated limbs. Based on the stiffness mapping models of both the full-DOF and limited-DOF parallel mechanisms, the stiffness variation rules when redundant limbs is introduced into the mechanism are discussed. Moreover, an algorithm for designing the types and configurations of redundant limbs is studied. Two cases are investigated to validate the presented approach. One is about the stiffness decoupling of the Stewart platform, the other is focused on the enhancement of normal stiffness of a Tricept supporting mechanism used in a mirror milling machine designed by us. The result shows that the stiffness performance of Stewart platform can be decoupled when adding six redundantly-actuated limbs that are symmetric with the original active limbs. Besides, the normal stiffness of Tricept mechanism can be enhanced significantly by transforming the passive UP chain to be a redundant actuated chain.
Stress Analysis of a Touchdown Bearing Having an Artificial Crack
Authors: Neisi Neda , Sikanen Eerik , Heikkinen Janne E. , Sopanen Jussi
Published: November 2017

The active magnetic bearings (AMBs) are often the preferred bearing solution in high speed rotating machines. Even though AMBs have numerous advantages in comparison to normal bearings they are sensitive to the power shutdowns. In the absence of electromagnetic field, the rotor collides with touchdown bearing. The high contact forces occurring between the rotor and touchdown bearing might lead to a contact surface failure in the touchdown bearings. In this study, the simulation model has been used to study the stresses of the touchdown bearing with an artificial crack. Flexibility of the rotor is modelled using the finite element method and frictional contacts are defined between the rotor and touchdown bearing. Hertzian contact theory is used to model all internal contacts in the ball bearing type touchdown bearings. This makes it possible to obtain the Hertzian contact stresses in each ball of the touchdown bearing and evaluate the stress intensity factors for a crack propagation analysis. The results show that increase in the dynamic friction coefficient between the rotor and bearing as well as increase in the air gap leads to a higher maximum Hertzian stress. As a result of the higher contact stress the stress intensity factor will increase.
Field Isolation As a Basis for Modular Product Architecture
Authors: Niutanen Valtteri , Otto Kevin
Published: November 2017

Research into product modularity has created methods to partition a product system in to modules, including DSM algorithms to minimize various within- or between-module connectivity assumptions, as well as heuristic methods for combining functions into common modules, including dominant flow, convert-transmit, repeated elements, and branching flows. We here re-examine these methods in view of flows between field potentials. Fields are spatially defined scalar functions representing temperature, pressure, voltage, etc., each with associated flows such as heat, fluid, current, etc. It is hypothesized that isolation of elements to desired field values can form a physical basis for module definition. Product functional descriptions were examined from the literature. Those found sufficiently detailed with function structures, module definitions, part lists and subassembly definitions were studied here. Within these examples, there were 183 functions grouped into 51 modules. Of these, a statistically significant 67% of the modules had boundaries which isolated a field. For example, all elements within the module were at a high temperature and all elements outside the module were at a low temperature. Such agreement between actual modularity and field isolation provides evidence that an effective module definition strategy is to use field boundaries to separate into modules the necessarily high and low field values in the product structure. A second analysis considered how desired flows are designed to cross field boundaries. In 84% of the cases of flows crossing field boundaries, specific field separation functions were defined. Care was taken through specific functionality provision to ensure field boundary isolation. In summary, we find containing fields within a product can form a physics based guideline for defining product modularity.
Onboard Wind Speed and Road Grade Measurements for Determination of Model Coefficients on Cycling
Authors: Roa Sergio D. , Morales Mateo , Muñoz Luis E.
Published: November 2017

Different models for cycling power prediction have been presented and validated by different authors. The model validation processes have been performed in laboratory tests and field experimental tests. In field tests, different methods have been used, and in recent years, cycle-mounted power meters have been widely used for model validation and bicycle-cyclist set parameters determination. Field tests have been limited to the use of close spaces to avoid the high influence of external wind and to test in nearly flat surfaces. Although many studies have been carried out successfully in closed places, some advantages of the outdoor testing have not been exploited. This paper presents a methodology for performing outdoor tests while including the power delivered by the cyclist, the onboard measurement of wind speed and the accurate measurement of the road grade. The methodology seeks to determine the aerodynamic drag and rolling resistance coefficients based on experimental outdoor tests. A least squares method is used for identifying the model coefficients from the experimental data. A high correlation and significant similarity between the power measured and the power predicted by the model is found. These results suggest a good reliability of the wind speed measurement method and prove an improvement in the power prediction when including the onboard wind speed and road grade data. The coefficients found are in agreement with previous works presented in literature with similar bicycle-cyclist set characteristics.
A Fixed-Actuator Configuration for 3-Leg 6-DOF Robots
Authors: Nelson Carl A.
Published: November 2017

For many fully parallel robots, the number of legs is generally equal to the number of degrees of freedom, with one actuated joint per leg. However, another subset of robots exists in which there are fewer legs and more actuated joints per leg. This paper presents a method of mounting rotary actuators on the fixed platform such that no actuator mass is added to the moving links. Examples of 6-DOF parallel robot variants are given based on this technique, with inverse kinematics, and the scope of extensibility to other topologies is briefly described.
Identification of High Performance Regions of High-Dimensional Design Spaces With Materials Design Applications
Authors: Morris Clinton , Seepersad Carolyn C.
Published: November 2017

Design exploration methods seek to identify sets of candidate designs or regions of the design space that yield desirable performance. Commonly, the dimensionality of the design space exceeds the limited dimensions supported by standard graphical techniques, making it difficult for human designers to visualize or understand the underlying structure of the design space. With standard visualization tools, it is sometimes challenging to visualize a multi-dimensional Pareto frontier, but it is even more difficult to visualize the collections of design (input) variable values that yield those Pareto solutions. It is difficult for a designer to determine not only how many distinct regions of the design (input) space may offer desirable performance but also how those design spaces are structured. In this paper, a form of spectral clustering known as ε-neighborhood clustering is proposed for identifying satisfactory regions in the design spaces of multilevel problems. By exploiting properties of graph theory, the number of satisfactory design regions can be determined accurately and efficiently, and the design space can be partitioned. The method is demonstrated to be effective at identifying clusters in a 10 dimensional space. It is also applied to a multilevel materials design problem to demonstrate its efficacy on a realistic design application. Future work intends to visualize each individually identified design region to produce an intuitive mapping of the design space.
Frequency-Energy Dependence of the Bistable Nonlinear Energy Sink
Authors: AL-Shudeifat Mohammad A. , Saeed Adnan S.
Published: November 2017

Recently, the bistable attachment has been employed as a nonlinear energy sink (NES) for passive targeted energy transfer (TET) from linear structures. The bistable NES (BNES) has been coupled with a linear oscillator (LO) where the resulting LO-BNES system has been studied for passive TET. The nonlinear coupling force between the BNES and the associated LO comprises both negative and nonnegative linear and nonlinear stiffness components. Here, the dynamic behavior of the LO-BNES system on the frequency-energy plot is analyzed. The related FEP plot is obtained via numerical simulation techniques where the wavelet transform is imposed into the FEP for variety of initial conditions and damping content. It is found that the FEP has backbone branches at low energy levels associated with the oscillation of the bistable attachments about one of its stable equilibrium positions where passage through the unstable equilibrium position does not occur.
Effect of Initial Curvature on the Static and Dynamic Behavior of MEMS Resonators
Authors: Hajjaj Amal Z. , Alcheikh Nouha , Younis Mohammad I.
Published: November 2017

In this paper, we investigate experimentally and analytically the effect of the initial shape, arc and cosine wave, on the static and dynamic behavior of microelectromechanical (MEMS) resonators. We show that by carefully choosing the geometrical parameters and the shape of curvature, the veering phenomenon (avoided-crossing) between the first two symmetric modes can be activated. To demonstrate this concept, we study electrothermally tuned and electrostatically driven MEMS initially curved resonators. Applying electrothermal voltage heats up the beams and then increases their curvature (stiffness) and controls their resonance frequencies. While changing the electrothermal voltage, we demonstrate high frequency tunability of arc resonators compared to the cosine-configuration resonators for the first and third resonance frequencies. For arc beams, we show that the first resonance frequency increases up to twice its fundamental value and the third resonance frequency decreases until getting very close to the first resonance frequency triggering the veering phenomenon. Around the veering regime, we study experimentally and analytically, using a reduced order model based on a nonlinear Euler-Bernoulli shallow arch beam model, the dynamic behavior of the arc beam for different electrostatic forcing.
IoT Architecture for the Processing of Data Collected by a Central Vacuum Cleaner
Authors: Contigiani Marco , Pollini Rama , Sturari Mirco , Mancini Adriano , Frontoni Emanuele
Published: November 2017

The paper reports on a use case of vertical integration and predictive maintenance, two concepts that fall within the wider “Industry 4.0” domain. We designed an Internet of Things based-system for the collection, processing and management of data coming from central vacuum cleaners. The developed embedded system for data retrieval from the vacuum via MODBUS and for sending them to a cloud server via WiFi is described in detail. We also present the software techniques used to manage data and the application developed for the presentation of collected data to several types of users: administrators, customers and distributors. Finally, they are highlighted the advantages for using information stored in optimizing the assistance service, marketing opportunities and market analysis.
Risky Business: The Driving Factors of Creative Risk Taking Attitudes in Engineering Design Industry
Authors: Zheng Xuan , Miller Scarlett R.
Published: November 2017

Designing breakthrough products comes at a great cost to the design industry due to the risk and uncertainties associated with creative ideas. However, without creative ideas, there is no potential for innovation. As such, companies need to appropriately embrace the risk associated with creative concepts in the fuzzy front end of the design process in order to build their value. While previous research has linked risk taking attitudes to creative idea generation and selection in engineering design education, there has been limited research focused on engineering design professionals’ creative risk taking attitude and the corresponding driving factors. This is problematic because without this knowledge we do not know what factors inhibit or promote the flow of creative ideas in engineering design industry. In order to address this gap, a preliminary online survey was conducted with 46 design professionals from a global manufacturing company to understand the potential driving factors of creative risk taking, including educational training, job type (R&D, applied engineering, or management), and years of experience. The results suggest that there is a relationship between employee education level and years of experience and an engineering employee’s willingness to take risks on creative ideas in the fuzzy front end of the design process. Interestingly, the results also show that those individuals primarily responsible for the development (R&D) and selection (management) of creative ideas tend to be more financially risk averse than individuals in traditional engineering positions. These results contribute to the prediction of professionals’ design behaviors and have implications for the management of creative ideas in the early conceptual design stages of engineering design industry.
Finding Rigid Body Modes of Rigid-Foldable Origami Through the Simulation of Vertex Motion
Authors: Zimmermann Luca , Stanković Tino , Shea Kristina
Published: November 2017

Designing structures through the means of origami brings many advantages for engineering applications. In current research, the underlying origami principle is often selected based on experience out of a range of known patterns and then manually altered to fit the design problem. This tedious and time-consuming procedure, if automated through computational tools, has the potential to facilitate the design of origami engineering applications. This however requires efficient kinematic simulation of origamis that is also able to accommodate to design requirements specific to foldable structures. In this paper, a simulator is implemented that is able to model the motion of origami vertices without the need for mountain-valley assignments and with a path of deployment as activation. The formulation of constraint equations through these vertex positions does not restrict the system to certain folding configurations, which is why the approach is able to detect different rigid body modes resulting from single activations. Finding rigid body modes can be beneficial for the search of design alternatives conforming to certain input requirements. The results of the simulation show promise for the incorporation of the simulator within an automated procedure for the design of origamis.
Optimization of the Singularity Locus of a Novel Kinematically Redundant Spherical Parallel Manipulator
Authors: Landuré Jérôme , Gosselin Clément
Published: November 2017

This article introduces a new architecture of spherical parallel robot which significantly extends the workspace when compared to existing architectures. To this end, the singularity locus is studied and the design parameters are chosen so as to confine the singularities to areas already limited by other constraints such as mechanical interferences. First, the architecture of the spherical redundant robot is presented and the Jacobian matrices are derived. Afterwards, the analysis of the singularities is addressed from a geometric point of view, which yields a description of the singularity locus expressed as a function of the architectural parameters. Then, the results are applied to an example set of architectural parameters chosen in order to illustrate the advantages of the redundant architecture over current designs in terms of workspace.
A Reference Error Formulation for Multi-Fidelity Design Optimization
Authors: Bayoumy Ahmed H. , Kokkolaras Michael
Published: November 2017

We consider the problem of selecting among different computational models of various fidelity for evaluating the objective and constraint functions in numerical design optimization. Typically, higher-fidelity models are associated with higher computational cost. Therefore, it is desirable to employ them only when necessary. We introduce a reference error formulation that aims at determining whether lower-fidelity models (that are computationally cheaper) can be used in certain areas of the design space as the latter is being explored during the optimization process. The proposed approach is implemented using an existing trust region model management framework. We demonstrate the link between feasibility and fidelity and the key features of the proposed approach using the design example of a cantilever flexible beam subject to high accelerations.
Optimal Design of Topology and Gradient Orthotropic Material
Authors: Garland Anthony , Fadel Georges
Published: November 2017

The goal of this research is to optimize an object’s macroscopic topology and gradient material properties subject to multiple loading conditions. The gradient material is modeled as an orthotropic material where the elastic modulus in the x and y directions can change in addition to rotating the orthotropic material to align with the loading condition at each point. This orthotropic material is similar to a fiber-reinforced material where the number of fibers in the x and y-directions can change at each point as well as the overall rotation of the material at each point. Repeating cellular unit cells which form a mesostructure can also achieve these customized orthotropic material properties. Homogenization theory allows calculating the macroscopic averaged bulk properties of these celluar materials. The mesostructures are an order of magnitude smaller than the macro structure which then allows small variations in strain and stress to be averaged out. The average (homogenized) properties of a group of these mesostructures can be customized by carefully designing the topology of the repeating unit cell used to make the mesostructure. In the past, gradient material optimization coupled to optimal fiber optimization has been used to design material properties within a single part. By combining topology optimization with gradient material optimization and fiber orientation optimization, the algorithm significantly decreases the objective, which is to minimize the strain energy of the object. Additive manufacturing techniques enable the fabrication of these designs by selectively placing reinforcing fibers or by printing different mesostructures in each region of the design. Finally, this work shows a comparison of simple topology optimization, topology optimization with isotropic gradient materials, and topology optimization with orthotropic gradient materials.
Analysis and Design of an Active Self-Folding Antenna
Authors: Peraza Hernandez Edwin A. , Hartl Darren J. , Lagoudas Dimitris C.
Published: November 2017

Origami allows for novel approaches to the design of morphing structures. This paper presents a preliminary study on the analysis and design of a self-folding origami antenna. This preliminary study aims to develop and test novel origami analysis and design approaches for problems in morphing antennas. A parabolic dish antenna is considered. The objective is to design a planar sheet with a pattern of smooth folds (as opposed to creased folds generally encountered in the origami literature) that can fold via active material actuation towards the parabolic antenna shape. In the presented process, a mesh discretization of the parabolic shape is first determined. Subsequently, an origami design tool previously developed by the authors is utilized to obtain a planar sheet with a pattern of smooth folds that allows for folding towards the meshed parabolic shape. An origami structural analysis method is then used to simulate the shape memory alloy (SMA) actuation-driven folding of the determined sheet design from the planar reference configuration towards the parabolic configuration. The mesh discretization of the parabolic shape is parameterized and various discretizations are tested and compared considering certain performance outputs. The preliminary results presented here demonstrate the feasibility of active material-based origami in the development of morphing antennas.
Exploiting Nonlinear Behavior of MEMS Resonators for Filter Applications
Authors: Ilyas Saad , Younis Mohammad I.
Published: November 2017

We propose combining the hardening and softening nonlinearities of two resonators to realize a near flat pass band filter of almost zero roll-off. The device is composed of two near identical doubly clamped and laterally actuated microbeams made of Silicon. One of the resonators is buckled via thermal loading to produce softening resonance peak. It is then further tuned to create the desired overlap with the hardening resonance peak of the other resonator. This overlapping improves the filter’s pass band flatness and roll-off characteristics, which are highly desirable. This technique can be promising for future generation of filters with superior characteristics.
A Novel Threshold Pressure Sensor Based on Nonlinear Dynamics of MEMS Arches
Authors: Hasan Mohammad H. , Alsaleem Fadi M. , Ouakad Hassen M.
Published: November 2017

In this paper, we propose a new tunable pressure sensor based on the nonlinear snap-through instability of an electrically actuated shallow arch microbeam. The general concept of the sensor can be explained as follows: the shallow arch is excited to trigger dynamic snap-through instability yielding a high output amplitude, if the system operating pressure is below a threshold value. This state is interpreted as a digital logic 1. Once the varying pressure exceeds that threshold value, the arch gains its stability. Therefore, the new state would be interpreted as a digital logic 0 value. We show an example of an operation range of the proposed sensor by identifying the relationship between the excitation AC voltage and the critical cut-off pressure.
Optimal Paths for Polygonal Robots in SE(2)
Authors: Kennedy Monroe , Thakur Dinesh , Kumar Vijay , Hsieh M. Ani , Bhattacharya Subhrajit
Published: November 2017

We consider navigation for a polygonal, holonomic robot in an obstacle filled environment in SE(2). We denote the configuration space of the robot as C. In order to determine the free space, obstacles are represented as point clouds then transformed into C. The point-wise Minkowski sum of the robot and obstacle points is then calculated in C by adding the vertices and points on the convex hull of robot to obstacle points for different robot configurations. We then find a seed path using either a graph search or sample based planner. This seed path is then used in our novel method to determine overlapping convex regions for each consecutive chord of the seed path. Our proposed method represents the collision free, traversable region by defining overlapping convex corridors defined by a set of linear constraints. Within these corridors we find feasible trajectories that optimize a specified cost functional. The generated corridors along with the initial and desired poses are then used to determine an optimal path that satisfies the specified objective within the same homotopy group as the seed path. The key contributions is the proposed methods’ ability to easily generate a set of convex, overlapping polytopes that effectively represent the traversable free space. This in turn lends itself to (a) efficient computation of optimal paths, and (b) extending these basic ideas to non-Euclidean spaces such as SE(2). We provide simulated examples and implement this algorithm on the KUKA youBot omni-directional base.
A 3D Multi-Body Dynamics Model for Chain-Type Continuously Variable Unit
Authors: Hotait Mohammad A. , Singh Avinash
Published: November 2017

This paper presents a new 3-dimensional multi-body dynamic model of a chain-type continuously variable unit (CVU). The modeling requirements and assumptions are presented first. Then, the paper discusses the approaches developed to mathematically represent the chain, pulleys, and their interactions in terms of contact and friction. Three dimensional representation of the chain is given. Actual geometries of the pins and pulleys are captured, including crowning on either member. The model is then used to investigate the effects of different operating conditions, including speed ratio and torque, on the quasi-static performance of a CVU. Several metrics are discussed to characterize the behavior of an example CVU under practical operating conditions; these include torque capacity and the ratio of clamping forces. The predictions presented show the sensitivity of the model to these operating conditions. Finally, trends that describe the CVU quasi-static behavior are explained in context of the parameters studied.
Employing Multidimensional Data Visualization Tools to Assess the Impact of Constraint Uncertainties on Complex Design Problems
Authors: Stump Gary M. , Miller Simon W. , Yukish Michael A. , Farrell Christopher M.
Published: November 2017

A potential source of uncertainty within multi-objective design problems can be the exact value of the underlying design constraints. This uncertainty will affect the resulting performance of the selected system commensurate with the level of risk that decision-makers are willing to accept. This research focuses on developing visualization tools that allow decision-makers to specify uncertainty distributions on design constraints and to visualize their effects in the performance space using multidimensional data visualization methods to solve problems with high orders of computational complexity. These visual tools will be demonstrated using an example portfolio design scenario in which the goal of the design problem is to maximize the performance of a portfolio with an uncertain budget constraint.
Synthesis of Spatial 3R Chains With Configuration-Specific Twist System
Authors: Hassanzadeh Neda , Wegert Mason , Perez-Gracia M. Alba
Published: November 2017

Mixed-position synthesis of linkages has been used to define local contact conditions and for better adjusting a mechanism to its desired trajectory. In this work, multiple velocities are defined at a configuration in order to fully specify the subspace of twists of the end-effector at that point, and also to specify lower-dimensional subspaces of twists. This is applied to the spatial 3R chain, for which the equations are developed in detail.
Design of the I-BoomCopter UAV for Remote Sensor Mounting
Authors: McArthur Daniel R. , Chowdhury Arindam B. , Cappelleri David J.
Published: November 2017

This paper presents the design of the Interacting-BoomCopter (I-BoomCopter) unmanned aerial vehicle (UAV) for mounting a remote sensor package on a vertical surface. Critical to the design is the novel, custom, light-weight passive end-effector. The end-effector has a forward-facing sonar sensor and in-line force sensor to enable autonomous sensor mounting tasks. The I-BoomCopter’s front boom is equipped with a horizontally-mounted propeller which can provide forward and reverse thrust with zero roll and pitch angles. The design and modeling of the updated I-BoomCopter platform is presented along with prototype flight test results. A teleoperated wireless camera sensor mounting task examines the updated platform’s suitability for mounting remote sensor packages.
Amplitude-Dependent Stiffness Method for Studying Frequency and Damping Variations in Nonlinear Dynamical Systems
Authors: AL-Shudeifat Mohammad A.
Published: November 2017

A method is introduced here for extracting the fundamental backbone branches of the frequency energy plot in which the obtained nonlinear frequencies of the nonlinear dynamical system are plotted with respect to the nonlinear energy content. The proposed method is directly applied to the equations of motion where the solution is not required to be known a priori. The method is based on linearizing the nonlinear coupling force where a scaled amplitude-dependent coupling stiffness force is obtained to replace the original nonlinear coupling stiffness force. Accordingly, the backbone branches in the frequency-nonlinear-energy plot are extracted from the eigensolution of the mass-normalized amplitude-dependent global stiffness matrix of the nonlinear dynamical system. Moreover, the variations in the damping content under the effect of the nonlinear coupling stiffness are also studied. Interesting behavior of damping content under the effect of the amplitude-dependent stiffness has been observed and discussed.
Applications of Constraint Graphs and Assur Groups in Mechanism Analysis and Synthesis
Authors: Hahn Elad , Sljoka Adnan , Mueller Andreas
Published: November 2017

Assur groups and correspondingly Assur graphs have key attributes that make them important for the analysis and synthesis of linkages. The topology of linkages (more precisely the existence of constraints between links) in general can be represented by various types of constraint graphs. The concept of Assur graphs applies to any such graph and thus their peculiar features can be exploited. Despite of these potential benefits the relevant methods and tools are scattered in the literature. The aim of this paper is to provide an overview of the use of constraint graphs including recent results on the construction of Assur graphs.
Discovering Origami Fold Patterns With Optimal Actuation Through Nonlinear Mechanics Analysis
Authors: Gillman Andrew , Fuchi Kazuko , Bazzan Giorgio , Alyanak Edward J. , Buskohl Philip R.
Published: November 2017

The ability of origami fold patterns to transform two-dimensional sheets into complex three-dimensional structures provides utility for design and development of multifunctional devices. Recently, a topology optimization framework has been developed to discover fold patterns that realize optimal performance including mechanical actuation. This work incorporates an efficient nonlinear mechanics model into the topology optimization framework that accurately captures the geometric non-linearities associated with large rotations of origami facets. A nonlinear truss model, with accommodation for fold stiffness and large rotations, is implemented in both gradient and non-gradient optimization algorithms in this study. The ability of this framework to discover fold topology maximizing actuation motion is verified for the well known “Chomper” and “Square Twist” patterns. In particular, the performance of various optimization algorithms is discussed, and genetic algorithms consistently yield solutions with better performance.
Utilizing Node Interference Method and Complex Network Centrality Metrics to Explore Requirement Change Propagation
Authors: Htet Hein Phyo , Morkos Beshoy , Sen Chiradeep
Published: November 2017

Requirements play very important role in the design process as they specify how stakeholder expectations will be satisfied. Requirements are frequently revised, due to iterative nature of the design process. These changes, if not properly managed, may result in financial and time losses leading to project failure due to possible undesired propagating effect. Current modeling methods for managing requirements do not offer formal reasoning necessary to manage the requirement change and its propagation. Predictive models to assist designers in making well informed decisions prior to change implementation do not exist. Based on the premise that requirement networks can be utilized to study change propagation, this research will allow for investigation of complex network metrics for predicting change throughout the design process. Requirement change prediction ability during the design process may lead to valuable knowledge in designing artifacts more efficiently by minimizing unanticipated changes due to mismanaged requirements. Two research questions (RQs) described are addressed in this paper:

RQ 1: Can complex network centrality metrics of a requirement network be utilized to predict requirement change propagation?

RQ 2: How does complex network centrality metrics approach perform in comparison to the previously developed Automated Requirement Change Propagation Prediction (ARCPP) tool?

Applying the notion of interference, requirement nodes in which change occurs are virtually removed from the network to simulate a change scenario and the changes in values of select metrics of all other nodes are observed. Based on the amount of metric value changes the remaining nodes experience, propagated requirement nodes are predicted. Counting betweenness centrality, left eigenvector centrality, and authority centrality serve as top performing metrics and their performances are comparative to ARCPP tool.
Squat Lifting Motion Prediction With Heavy Load Considering Dynamic Strength of Knee Joint
Authors: Zaman Rahid , Xiang Yujiang
Published: November 2017

This paper studies the knee joint dynamic strength modeling and simulation for squat lifting with heavy loads. The dynamic strength is modeled as a three-dimensional function of joint angle and velocity based on experimental isometric and isokinetic strength data. Then the dynamic strength function is formulated as joint torque limits in an inverse dynamics based optimization formulation. By using this formulation, squat lifting is predicted with heavy loads. An enumeration procedure is introduced to predict maximum lifting weight under various lifting conditions by considering dynamic strength of knee joint. In addition, the effect of lifting speed on the maximum lifting weight is investigated. Several future research directions are identified.
Advancement of Contact Dynamics Modeling for Human Spaceflight Simulation Applications
Authors: Brain Thomas A. , Kovel Erik B. , MacLean John R. , Quiocho Leslie J.
Published: November 2017

Pong is a new software tool developed at the NASA Johnson Space Center that advances interference-based geometric contact dynamics based on 3D graphics models. The Pong software consists of three parts: a set of scripts to extract geometric data from 3D graphics models, a contact dynamics engine that provides collision detection and force calculations based on the extracted geometric data, and a set of scripts for visualizing the dynamics response with the 3D graphics models. The contact dynamics engine can be linked with an external multibody dynamics engine to provide an integrated multibody contact dynamics simulation. This paper provides a detailed overview of Pong including the overall approach, modeling capabilities, which encompasses force generation to computational performance, and example applications.
Comparison of Control Methods for Two-Link Planar Flexible Manipulator
Authors: Bowkett Joseph , Mukherjee Rudranarayan
Published: November 2017

While the majority of terrestrial multi-link manipulators can be considered in a purely kinematic sense due to their high stiffness, the launch mass restrictions of aerospace applications such as in-orbit assembly of large space structures result in low stiffness links being employed, meaning dynamics can no longer be ignored. This paper seeks to investigate the suitability of several different open and closed loop control techniques for application to the problem of end effector position control with minimal vibration for a low stiffness space based manipulator. Simulations of a representative planar problem with two flexible links are used to measure performance and sensitivity to parameter variation of: model predictive control, command shaping, and command shaping with linear quadratic regulator (LQR) feedback. An experimental testbed is then used to validate simulation results for the recommended command shaped controller.
Understanding Power Loss due to Mechanical Antagonism and a New Power-Optimal Pseudoinverse for Redundant Actuators
Authors: Cahill Nathan M. , Sugar Thomas , Holgate Matthew , Schroeder Kyle
Published: November 2017

Comparatively slow growth in power storage and generation makes power-efficient designs desirable for legged robot systems. One important cause of power losses in robotic systems is the mechanical antagonism phenomenon, i.e. one or more motors being used as brakes while the others exert positive energy. This two-part paper first develops a rigorous understanding of mechanical antagonism in multiactuator robotic limbs. We show that, for a 6-DoF robot arm, there exist 4096 distinct regions in the force-velocity space of the end effector (the regions are distinguishable by the sign of the actuator powers). Only sixty-four of these regions correspond with operating points where all actuators exert positive power into the system. In the second part of the paper, we formulate a convex optimization problem which minimizes mechanical antagonism in redundant manipulators. We solve the optimization problem which becomes the derivation for a new, power-optimal, pseudoinverse for non-square Jacobians. In fact, two such pseudoinverses are derived: one for statically determinate systems, such as serial manipulators, and one for statically indeterminate systems, such as parallel manipulators.
Influence of Altitude on the Performance of a Bicycle-Cyclist Set
Authors: Morales Mateo , Roa Sergio D. , Muñoz Luis E. , Ferreira Diego A. , Lopez Mejia Omar D.
Published: November 2017

There is a tradeoff between power delivery and aerodynamic drag force when cyclists ride at different altitudes. The result is particular to the characteristics of the bicycle as well as the aerobic fitness of the cyclist. This work proposes a methodology based on an integrated approach to the study of the influence of altitude on power output and aerodynamic drag over a particular bicycle-cyclist set. The methodology consists of an independent analysis for each of the effects, to conclude with an integration of results that allows estimating the overall effect of altitude on cycling performance.

A case study for the application of the methodology was developed, and the obtained results apply for the specific bicycle-cyclist set under analysis. First, the relationship between power and time was analyzed for a male recreational cyclist based on all-out effort tests at two different altitudes: 237 meters and 2652 meters above sea level (m.a.s.l). Second, the effects of environmental conditions on air density and drag area coefficient due to altitude changes were analyzed based on Computational Fluid Dynamics (CFD) simulations. It was found that for the bicycle-cyclist set under study, the sustainable power output for 1-hour cycling was reduced 45W for the high-altitude condition as a consequence of the reduction in the maximum oxygen uptake capacity. In addition, the aerodynamic drag force is reduced in greater proportion due to the change in air density than due to the change in drag coefficient. Finally, the results of both effects were integrated to analyze the overall influence of altitude on cycling performance. It was found that for the analyzed case study, the aerodynamic advantage at higher altitude dominates over the disadvantage of reduction in power output: despite delivering 45W less, the subject can travel an additional distance of 900 meters during a one hour ride for the high-altitude condition compared to that in low altitude.
An Electromagnetic Energy Harvester for Rotational Applications
Authors: Gunn Ben , Theodossiades Stephanos , Rothberg Steve , Saunders Tim
Published: November 2017

Many industrial applications incorporate rotating shafts with fluctuating speeds around a desired mean value. This often harmonic component of the shaft speed is generally undesirable, since it can excite parts of the system and can lead to large oscillations (potentially durability issues), as well as to excessive noise generation. On the other hand, the addition of sensors on rotating shafts for system monitoring or control poses challenges due to the need to supply power to the sensor and extract data from the rotating application. In order to tackle the requirement of powering sensors for structure health monitoring or control applications, this work proposes a nonlinear vibration energy harvester design intended for use on rotating shafts with harmonic speed fluctuations. The essential nonlinearity of the harvester allows for increased operating bandwidth, potentially across the whole range of shaft’s operating conditions.
Friction and Wear Properties of Halogen-Free and Halogen-Containing Ionic Liquids Used As Neat Lubricants, Lubricant Additives and Thin Lubricant Layers
Authors: Guo Hong , Liu Rui , Fuentes-Aznar Alfonso , Iglesias Victoria Patricia
Published: November 2017

The lubricating ability of one halogen-free and one halogen-containing phosphonium-based ionic liquids are investigated as neat lubricants, lubricant additives and thin lubricant layers in steel-steel contact. The use of the ionic liquids in any of the three lubricating methods reduced friction and wear compared to a base mineral oil. The halogen-free ionic liquid outperformed the halogen-containing ionic liquid in the three methods of lubrication. The highest friction and wear reduction were obtained when ionic liquids were used as neat lubricants. Under this condition, friction reductions of 37.21% and 25.73 %, and wear reduction of 47.12% and 41.18% compared to the based mineral oil were obtained for the halogen-free and halogen-containing ionic liquids respectively. The wear mechanisms and surface interactions are discussed in terms of ionic liquid-metal surface interactions from optical and SEM images and EDS analysis.
Creativity of Concept Ideation Methods As Affected by Team Personality
Authors: Berthelsdorf Friederich A. , Stone Robert B.
Published: November 2017

Prior work has shown that individual MBTI personality type influences the creative output of concept ideation methods [1,2]. In this paper, we present a pilot study that investigates the concept of team personality (defined as the average personality of the team along each MBTI spectrum) and the effect it has on ideation results, as measured by three creativity metrics; quantity, quality, and variety. We find evidence suggesting that a team whose average personality falls near the extremes of the Thinking-Feeling spectrum will produce more creative results, a team that is neutral along the Introversion-Extraversion spectrum can choose their method based on which creativity metric they wish to maximize, and that a team with high personality variance can choose to create either more variety or higher quantity of ideas based on their selected method.
Structural Optimization of Injection Molds With Lattice Cooling
Authors: Wu Tong , Upadhyaya Namrata , Acheson Douglas , Tovar Andres
Published: November 2017

Lattice cooling (LC) is a novel approach to improve the thermal and mechanical performance of an injection mold, thus challenging the traditional conformal cooling approach. By using current Additive Manufacturing (AM) technologies, LC with highly complex structures is possible. In this study, the design concept of LC is further improved by implementing a thermo-mechanical topology optimization method. This method utilizes porosity-dependent heat conduction, convection to dissipate internal heat generation, while maintaining mechanical stability of an injection mold. The porosity and shape of each lattice unit cell (LUC) in LC channels is determined by employing this method. A homogenization method is used to determine the porosity dependency of mechanical elasticity and heat conductivity, a surrogate model is used to determine the porosity dependency of heat convection and internal heat generation. The method firstly determines the porosity distribution of LUCs, then optimizing the bulk moduli of each LUC using inverse homogenization to improve the stability of LC. An example is presented to illustrate how to use the proposed approach to design LC sections for an injection mold with a given average porosity. The result shows, by applying the proposed approach, the thermal performance is improved 30 % compared to a uniform LC channel with the same average porosity, without decreasing the mechanical performance. The resulting optimized lattice made possible by utilizing Additive Manufacturing technologies.
A Friction Model for Non-Singular Complementarity Formulations for Multibody Systems With Contacts
Authors: Peiret Albert , Kövecses József , Font-Llagunes Josep M.
Published: November 2017

The dynamics of multibody systems with many contacts are frequently formulated as a Linear Complementarity Problem (LCP), for which several direct or iterative algorithms are available to solve it efficiently. These formulations rely on discretized friction models that approximate the friction cone of the Coulomb model to a pyramid. However, they produce rank-deficient LCPs even though the physical problem does not have constraint redundancy and has a unique solution. Here, a new discretized friction model is presented which results in an LCP formulation with a full-rank lead matrix. This model relies on an inertial term to couple the equations of the model, which behaves as close to the Coulomb model as the other discretized models. Moreover, it is shown through some simulations that some algorithms can be used with this formulation, which could not be used with the other rank-deficient LCP formulations.
Qualitative Analysis and Design of Mechanical Metamaterials
Authors: Patiballa Sreekalyan , Krishnan Girish
Published: November 2017

This paper presents a new mechanics-based framework for the qualitative analysis and conceptual design of mechanical meta-materials. The methodology is inspired by recent advances in the insightful synthesis of compliant mechanisms by visualizing a kinetostatic field of forces that flow through the mechanism geometry. The framework relates load flow behavior in the microstructure geometry to the global behavior of the materials, such as auxetic (negative poisson’s ratio), high bulk modulus, and high shear modulus. This understanding is used to synthesize and demonstrate novel planar microstructures that exhibit negative poisson’s ratio behavior. Furthermore, the paper identifies three unique classes of qualitative design problems for planar mechanical microstructures that can be potentially solved using this framework.