bluuebunny/crossref_metadata_2025 huggingface dataset:
Preliminary Simulation Study Combining Operational Modal Analysis and a Two Step Parameter Identification Method on 6-SPS Parallel Manipulator for Machining Purposes
Authors: Ringgaard Kasper , Balling Ole
Published: November 2018

Machining of large components, such as multi-megawatt wind turbine parts, is currently done using large expensive CNC machines. Using small parallel kinematic machines can provide an economical attractive alternative. Optimization of the conditions for a stable and accurate machining process is necessary. Knowledge of position dependent dynamic response is key when performing such optimization. This contribution is a part of current research striving towards efficient parameter identification for dynamic models of 6-SPS parallel kinematic manipulators for machining purposes. Stiffness and damping are updated for a small set of manipulator poses using Operational Modal Analysis and a two step parameter identification routine. The model obtained contains information of the dynamic response for all poses in the workspace. In this study a six degree of freedom 6-SPS model is derived and operational modal analysis experiments are simulated. The obtained modal parameters are used for parameter identification. It is concluded that the operational modal analysis performs well in estimating frequencies and mode shapes of the symmetric structure, but damping estimates are poor. Parameter identification routine performance is satisfactory, but the poor damping estimates from modal analysis causes incorrect and uncertain parameter identification.
Synthesizing Designs With Inter-Part Dependencies Using Hierarchical Generative Adversarial Networks
Authors: Chen Wei , Jeyaseelan Ashwin , Fuge Mark
Published: November 2018

Real-world designs usually consist of parts with hierarchical dependencies, i.e., the geometry of one component (a child shape) is dependent on another (a parent shape). We propose a method for synthesizing this type of design. It decomposes the problem of synthesizing the whole design into synthesizing each component separately but keeping the inter-component dependencies satisfied. This method constructs a two-level generative adversarial network to train two generative models for parent and child shapes, respectively. We then use the trained generative models to synthesize or explore parent and child shapes separately via a parent latent representation and infinite child latent representations, each conditioned on a parent shape. We evaluate and discuss the disentanglement and consistency of latent representations obtained by this method. We show that shapes change consistently along any direction in the latent space. This property is desirable for design exploration over the latent space.
Improving Organization Design by Clustering Project Actors
Authors: Khoriaty Anthony , Jaber Hadi , Yassine Ali A.
Published: November 2018

This paper proposes to cluster project actors (i.e., members) to form complementary teams based on their interactions and interdependencies with each other. First, the Design Structure Matrix (DSM) is used to model the interactions between project members, which are based on the number of deliverables exchanged between them. Then, an agglomerative clustering technique is proposed to place the project members into groups. The algorithm permits management to impose certain restrictions on team formations, such as the number and maximum size of the teams, which members must be placed together, and which members must be kept apart. Most importantly, the algorithm allows cyclic information exchanges (i.e., loops) to be inserted into team clusters. It produces as output the recommended team formations, as well as the percentage of the total number of interactions that occur within the clustered teams. The proposed clustering method is illustrated using data collected from a vehicle development project at a large European automotive company.
Design of a Micro-Positioning Stage Using Corrugated Flexure Beam With Cubic Bézier Curve Segments
Authors: Wang Nianfeng , Zhang Zhiyuan , Zhang Xianmin
Published: November 2018

The paper introduces an analytical stiffness matrix method to model a new type of corrugated flexure (CF) beam with cubic Bézier curve segments. In order to satisfy particular design specifications, shape variation for limited geometric envelopes are often employed to alter the elastic properties of flexure hinges. In this paper, cubic Bézier curves are introduced to replace the axis of CF unit to rebuild the CF beam and the micro-positioning stage. Mohr’s integral method is applied to derive the stiffness matrix of the cubic Bézier curve segment. Modeling of the CF unit and the CF beam with cubic Bézier curve segments are further carried out through stiffness matrix method, which are confirmed by finite element analysis (FEA). Discussions about the two control points of the cubic Bézier curve segments are then conducted through search optimization, which highlights the off-axis/axial stiffness ratio and the axial compliance on the position of the two control points, to enable the micro-positioning stage both achieving high off-axis/axial stiffness ratio and large axial compliance. The derived analytical model provides a new option for the design of the CF beam.
Kinematic Analysis of Mechanisms Based on Parametric Polynomial System
Authors: Arikawa Keisuke
Published: November 2018

Many kinematic problems of mechanisms can be expressed in the form of polynomial systems. Gröbner Bases computation is effective for algebraically analyzing such systems. In this research, we discuss the cases in which the parameters are included in the polynomial systems. The parameters are used to express the link lengths, the displacements of active joints, hand positions, and so on. By calculating Gröbner Cover of the parametric polynomial system that expresses kinematic constraints, we obtain segmentation of the parameter space and valid Gröbner Bases for each segment. In the application examples, we use planar linkages to interpret the meanings of the algebraic equations that define the segments and the Gröbner Bases. Using these interpretations, we confirmed that it was possible to enumerate the assembly and working modes and to identify the geometrical conditions that enable overconstrained motions.
A Vibration Damping Analysis Method of Turbine Blade Shroud Dampers Based on a Given Eigen-Mode
Authors: Jiazhe Zhao , Yanrong Wang , Yanbin Luo , Xiaojie Zhang
Published: November 2018

High cycle fatigue damage caused by resonance and forced vibration can significantly affect the life and reliability of turbine rotor blades in aero-engines. The friction damper has been widely used to reduce the resonant stress of blades, on which the turbine blade shroud dampers are highly used.

In order to solve the problems of vibration damping analysis and design of shrouded blades dampers, an analytical method without complex and time-consuming nonlinear vibration response has been proposed based on a given eigen-mode in this paper. For the serrated shrouded damper, two typical friction models, namely macro-slip model, and micro-slip model, have been introduced. Additionally, a complete set of damping analysis method has been introduced by the energy method, based on the vibration dynamics principle and eigen-mode analyzed by finite element method. Combined with the analysis of the natural vibration characteristics of the shrouded turbine blade, the law of the damping ratio with the relevant design parameters, such as the vibration stress, the pre-twist angle, the friction coefficient and the nodal diameter, was obtained through a calculation example. The method can also provide an important reference for the parameterized design of dampers.
Influence of Upstream and Downstream Stator Blades on the Rotor Blade Flutter Characteristics
Authors: Xiaojie Zhang , Yanrong Wang , Le Han , Jiazhe Zhao , Yanbin Luo
Published: November 2018

One of the important issues in turbomachinery flutter analysis is the intra-row interaction effects. The present work is aimed at a systematic research of the adjacent rows effects on aerodynamic damping. Three models, the isolated rotor, the IGV-rotor and the rotor-stator model, are performed to identify the upstream and downstream stator effects on the rotor blade. It is found that the aerodynamic damping from the stage flutter simulations are quite different from that from isolated rotor. In addition, the mixing-plane method is also applied to calculate the stage flutter characteristics and its accuracy of flutter predictions is compared with the time-marching method. It is indicated that the main difference of aerowork density between MP and TM is in the tip area, and in some cases the result from MP method can be misleading. Furthermore, study with different axial gaps illustrates that there is a nonmonotonic relationship between the rotor blade aerodynamic damping and the gap in the rotor-stator model, while the rotor blade aerodynamic damping monotonically increases with the gap in the IGV-rotor model.
Integrative Design, Build, Test Approach for Biomedical Devices With Lattice Structures
Authors: Egan Paul F. , Bauer Isabella , Shea Kristina , Ferguson Stephen J.
Published: November 2018

Advances in 3D printing are enabling new rapid prototyping strategies for complex structures, such as mechanically efficient tissue scaffolds. Here, we have developed an integrated methodology with Design, Build, and Test phases to characterize beam-based lattices for bone tissue engineering. Lattices were designed with 50% and 70% porosity with beam diameters of 0.4mm to 1.0mm fabricated with polyjet printing. Build accuracy was validated with microscopy that demonstrated overall lattice dimensions were at most 0.2mm different from design and beam diameters were at most 0.15mm different. Quasi-static compression testing showed lattice elastic moduli ranged from 28MPa to 180MPa and decreased with higher lattice porosity but increased with larger beam diameter sizes. Scaffold cages for vertebral bone fusion were prototyped using 50% and 70% porous lattices with 0.8mm diameter beams with added central voids for improved nutrient transport, reinforced shells for increased mechanics, or both. Cage stiffnesses ranged from 1.7kN/mm to 7.2kN/mm and suggests the strongest cage prototypes are suitable for carrying typical spinal loads of up to 1.65kN. The study demonstrates the value in using integrated rapid prototyping approaches for characterizing complex structures and designing novel biomedical devices.
Fatigue Life Prediction of Vortex Reducer Based on Stress Gradient
Authors: Luo Yanbin , Wang Yanrong , Zhong Bo , Zhao Jiazhe , Zhang Xiaojie
Published: November 2018

The effects of stress gradient and size effect on fatigue life are investigated based on the distributions of stress at notch root of the notched specimens of GH4169 alloy. The relationship between the life of the notched specimens and the smooth specimens is correlated by introducing the stress gradient effect factor, and a new life model of predicting the notched specimens based on the Walker modification for the mean stress effect is established. In order to improve the prediction precision of life model with the equation parameters having a definite physical significance, the relationships among fatigue parameters, monotonic ultimate tensile strength and reduction of area are established. Three-dimensional elastic finite element (FE) analysis of a vortex reducer is carried out to obtain the data of stress and strain for predicting its life. The results show that there is a high-stress gradient at the edge of the air holes of the vortex reducer, and it is thus a dangerous point for fatigue crack initiation. The prediction result of the vortex reducer is more reasonable if the mean stress, stress gradient and size effect are considered comprehensively. The developed life model can reflect the effects of many factors well, especially the stress concentration. The life of the notched specimens predicted by this model give a high estimation precision, and the prediction life data mainly fall into the scatter band of factor 2.
Improvement of the Balancing Accuracy in Gravity Compensators Based on the Inverted Slider Crank Mechanism
Authors: Arakelyan Vigen , Zhang Yang
Published: November 2018

The static balancing of mechanical systems is an important issue because it allows significant reduction of torques. However the literature review shows that in many cases the gravity balancing of mechanical systems is carried out by neglecting the masses of auxiliary links associated to the principal mechanism. For many balancing schemes it is the source of errors.

This paper deals with an improved solution for gravity compensators based on the inverted slider crank mechanism considering the masses of the rocker and the spring. For this purpose, the torques due to auxiliary links are determined. Then, they are introduced into the balancing equation for minimization of the residual unbalance. In this way, a more accurate balancing of gravity compensators is achieved. The efficiency of the suggested approach is illustrated by numerical simulations.
Design, Modeling, and Experimental Drag Characterization of a Bio-Inspired, Shape-Adapting Underwater Vehicle
Authors: DeVries Levi D. , Kutzer Michael D. M. , Richmond Rebecca E. , Bass Archie C.
Published: November 2018

Autonomous underwater vehicles (AUVs) have shown great promise in fulfilling surveillance, scavenging, and monitoring tasks, but can be hindered in expansive, cluttered or obstacle ridden environments. Traditional gliders and streamlined AUVs are designed for long term operational efficiency in expansive environments, but are hindered in cluttered spaces due to their shape and control authority; agile AUVs can penetrate cluttered or sensitive environments but are limited in operational endurance at large spatial scales. This paper presents the prototype testbed design, modeling, and experimental hydrodynamic drag characterization of a novel self-propelled underwater vehicle capable of actuating its shape morphology. The vehicle prototype incorporates flexible, buckled fiberglass ribs to ensure a rigid shape that can be actuated by modulating the length of the semi-major axis. Tools from generative modeling are used to represent the vehicle shape by using a single control input actuating the vehicles length-to-diameter ratio. By actuating the length and width characteristics of the vehicle’s shape to produce a desired drag profile, we derive the feasible speeds achievable by shape actuation control. Tow-tank experiments with an experimental proto-type suggest shape actuation can be used to manipulate the drag by a factor between 2.15 and 5.8 depending on the vehicle’s operating speed.
Study and Design of Sustainable Packaging for Household Hoods
Authors: Landi Daniele , Postacchini Leonardo , Cicconi Paolo , Ciarapica Filippo E. , Germani Michele
Published: November 2018

In industrialized countries, packaging waste is one of the major issues to deal with, representing around 35% of the total municipal solid waste yearly generated. Therefore, an analysis and an environmental assessment of packaging systems are necessary. This paper aims at analyzing and comparing the environmental performances of two different packaging for domestic hoods. It shows how, through a packaging redesign, it is possible to obtain a reduction of the environmental impacts. This study has been performed in accordance with the international standards ISO 14040/14044, by using attributional Life Cycle Assessment (LCA) from Cradle to Gate. The functional unit has been defined as the packaging of a single household hood. Primary data have been provided by a household hood manufacturer, while secondary data have been obtained from the Ecoinvent database. LCA software SimaPro 8.5 has been used to carry out the life cycle assessment, and ReCiPe method has been chosen for the life cycle impact assessment (LCIA) stage. The results have shown the new packaging model being able to cut down the environmental impacts of approximately 30%. These outcomes may be used by household manufacturers to improve performances and design solutions of their different packaging.
A 3D-Printed Needle Driver Based on Auxetic Structure and Inchworm Kinematics
Authors: Pfeil A. , Barbé L. , Wach B. , Bruyas A. , Geiskopf F. , Nierenberger M. , Renaud P.
Published: November 2018

Linear actuation is a basic need in robotized manipulation of surgical instruments, that must comply with a challenging environment in terms of safety, compactness and now often compatibility with imaging modalities like CT or MRI. In this paper, we focus on needle manipulation for interventional radiology. We propose a needle driver, i.e. a linear actuator for needle insertion, based on the inchworm principle combined with pneumatic energy. Our first contribution is to propose, model and implement the device using a so-called auxetic structure. Its use increases achievable displacement under pressure and provides sufficient off-axis stiffness to use the actuator without additional guidance. Simplified modeling is introduced for the actuator synthesis. Our second contribution is to implement the actuator with multimaterial additive manufacturing combining rigid and flexible materials to increase compactness. As a third contribution, initial assessment of component sterilization and compatibility with X-ray and MRI imaging modalities is presented.
Sequential Accelerated Life Testing Design for System Reliability Analysis With Untestable Components
Authors: Hu Zhen , Mourelatos Zissimos P.
Published: November 2018

Testing of components at higher-than-nominal stress level provides an effective way of reducing the required testing effort for system reliability assessment. Due to various reasons, not all components are directly testable in practice. The missing information of untestable components poses significant challenges to the accurate evaluation of system reliability. This paper proposes a sequential accelerated life testing (SALT) design framework for system reliability assessment of systems with untestable components. In the proposed framework, system-level tests are employed in conjunction with component-level tests to effectively reduce the uncertainty in the system reliability evaluation. To minimize the number of system-level tests which are much more expensive than the component-level tests, the accelerated life testing design is performed sequentially. In each design cycle, testing resources are allocated to component-level or system-level tests according to the uncertainty analysis from system reliability evaluation. The component-level or system-level testing information obtained from the optimized testing plans are then aggregated to obtain the overall system reliability estimate using Bayesian methods. The aggregation of component-level and system-level testing information allows for an effective uncertainty reduction in the system reliability evaluation. Results of two numerical examples demonstrate the effectiveness of the proposed method.
Coupled Multi-Material and Joint Topology Optimization: A Proof of Concept
Authors: Florea Vlad , Shah Vishrut , Roper Stephen , Vierhout Garrett , Kim Il Yong
Published: November 2018

Over the past decade there has been an increasing demand for light-weight components for the automotive and aerospace industries. This has led to significant advancement in Topology Optimization methods, especially in developing new algorithms which can consider multi-material design. While Multi-Material Topology Optimization (MMTO) can be used to determine the optimum material layout and choice for a given engineering design problem, it fails to consider practical manufacturing constraints. One such constraint is the practical joining of multi-component designs.

In this paper, a new method will be proposed for simultaneously performing MMTO and Joint Topology Optimization (JTO). This algorithm will use a serial approach to loop through the MMTO and JTO phases to obtain a truly optimum design which considers both aspects.

A case study is performed on an automotive ladder frame chassis component as a proof of concept for the proposed approach. Two loops of the proposed process resulted in a reduction of components and in the number of joints used between them. This translates into a tangible improvement in the manufacturability of the MMTO design.

Ultimately, being able to consider additional manufacturing constraints in the Topology Optimization process can greatly benefit research and development efforts. A better design is reached with fewer iterations, thus driving down engineering costs. Topology Optimization can help in determining a cost effective and efficient design which address existing structural design challenges.
Design of a Wheelchair Robot for Active Postural Support
Authors: Murray Rosemarie C. , Ophaswongse Chawin , Agrawal Sunil K.
Published: November 2018

This paper describes the design and control architecture of a novel Wheelchair-mounted Robot for Active Postural Support (WRAPS). The WRAPS is a robotic exoskeleton that allows limited degrees-of-freedom (DOFs) of the trunk relative to the pelvis. There are three DOFs in the sagittal plane of the human body and one in lateral bending. The work is motivated by the needs of individuals with impaired trunk motor control, who currently rely on the use of passive and predominantly static supports to maintain a static posture. These devices can be overly restrictive and inhibit the user in their activities of daily living (ADLs). The WRAPS is capable of supporting a human user within their active range of torso motion. It has the potential to assist users in their ADLs while encouraging a dynamic range of healthy postures.
Input Shaping for Vibratory Systems Using Deadbeat State Feedback Control
Authors: Sinha Alok
Published: November 2018

A general algorithm is developed for input shaping on the basis of the deadbeat state feedback control theory in discrete-time. This algorithm is easily extended to generate input sequence robust to parametric uncertainties in a flexible structure. Numerical results are presented for systems with one and two vibratory modes.
Semi-Active Damping for Off-Road Bicycle Suspension: An Experimental Study
Authors: Pierce R. Scott , Whitener Caleb , Kaul Sudhir
Published: November 2018

This paper presents experimental results from the testing of a semi-active damping system in an off-road bicycle (bike). Magnetorheological dampers are being increasingly used in automotive applications to enhance damping capability of a suspension system or to mitigate the trade-off between ride comfort and handling. A magnetorheological (MR) damper requires a relatively low amount of energy to control damping characteristics, and behaves as a passive damper in the absence of any power input. This study investigates the use of a semi-active magnetorheological damper for the rear suspension of a mountain bike. The performance of this damper has been compared to the current shock absorber on the bike. All testing has been performed on a shaker table and the performance of the damper has been evaluated by comparing the input acceleration at the hub of the rear wheel to the acceleration at the seat of the bike. The main aim of this study is to investigate the viability of using an MR damper in a mountain bike suspension system. Test results indicate that the performance of the semi-active MR damper is comparable to the current shock absorber. Furthermore, the MR damper lends itself to hands-off control that will be investigated in a future study. Therefore, it can be concluded from preliminary testing that an MR damper can be used in a mountain bike to effectively control damping.
Understanding Ecological Efficiency and Robustness for Network Design Using Thermodynamic Power Cycles
Authors: Panyam Varuneswara , Dave Tirth , Layton Astrid
Published: November 2018

Ecology has acted as a source for sound design principles and studies of ecosystems have examined how ecological principles can enhance sustainable human network design. Engineered systems are often designed for maximum performance, but in many cases, robustness is lost due to unwanted variations in inputs or efficiency. Taguchi’s signal to noise ratio and other quality engineering principles are well known fundamentals in the field of robust design. In this paper, we will introduce flow-based metrics from ecological network analysis (ENA) for robustness, efficiency, and redundancy. Ecosystem robustness is related to the balance between flow path diversity and system delivery efficiency. Systems with diverse flows are more resilient to a disturbance since there are redundant pathways, but are inefficient because they contain many flow paths with the same endpoints. Efficient systems are better able to transfer material and energy, but this is at the cost of fewer pathways so the system is brittle. Thus to survive a disturbance, an ecosystem system balances redundancy with efficiency. Thermodynamic power cycles are used to understand the relationship between energy efficiency, measured using first law efficiency, and ecological robustness and an ecological balance of efficiency to redundancy (as measured by ascendency vs development capacity). The result highlights the importance of understanding differences in the meaning of efficiency between two fields, and that from an engineering standpoint robustness does not have to be sacrificed to obtain energy efficiency.
Torsional Tip Motion of Double Beam Atomic Force Microscopy
Authors: O’Donnell John , Zargarani Anahita , Mahmoodi S. Nima
Published: November 2018

This paper investigates the vibration of a coupled microcantilever beam structure, in which a rigid body at their free end connects the two beams. The coupled beams are under equal and out-of-phase forces applied by piezoelectric films, which result in overall torsional motion. The equations describing the motion of the structure as well as the boundary conditions are developed using the Hamilton principle under the assumption of the structure being an Euler-Bernoulli beam. Two equations for each beam are realized: bending and torsional equations, which are combined in one torsional equation. The equation is solved using Galerkin approximation. The effects of dimensional parameters and input parameters are investigated including height, width, thickness, beam arrangement, applied voltage, input frequency, and mass of the tip. Geometry and mass were found to have significant effects on the angle, while input voltage was found to have a small linear effect. The overall sweeping motion was found to have an angle well below one degree in general. This shows that while the piezoelectric actuators can generate torsional sweeping, the effect is at a small angle that depends more on design than actuation force.
Analysis of the Spinning Motion and the Orientation Description Methods for 2-DOF RMs
Authors: Kai Liu , Jingjun Yu , Xianwen Kong
Published: November 2018

In this work, two degree-of-freedom rotational mechanisms (2-DOF RMs) also called 2-DOF pointing mechanisms are discussed systematically about their motion characteristic and orientation description methods. Based on the graphical approach, 2-DOF RMs are divided into three types in term of the features of their instantaneous rotational freedom lines, and the models of the spinning motions for all the three types of 2-DOF RMs are built respectively by constraint conditions. According to the spinning motion models, the orientation description methods suitable for the three types of 2-DOF RMs are introduced in detail severally to simplify the kinematic equations in succedent work. Then the correctness of the spinning motion models is verified via the virtual prototype simulation with several examples. Finally, the methods suitable for describing the orientation of these mechanisms are proposed. Conclusions would facilitate the analysis of kinematics of 2-DOF RMs and exhibit the motion characteristics of 2-DOF RMs expressly.
Concept of an Automatic Integration of Parts Measurement Data Into Feature-Based CAD Models
Authors: Weber Martins Thiago , Niemczik Lars , Anderl Reiner
Published: November 2018

This paper introduces a concept to integrate measurements data into feature-based 3D CAD models. The concept focuses on its application in the measurement of bifurcated sheet metal profiles. For that, an interface to read and import this data into the CAD system is developed. Since the measurement data is stored as a point cloud, further data processing (reverse engineering) is necessary to recreate the work piece shape in the CAD system. If the measured work piece model and the CAD model of the design piece are available, an automated comparison of the defined dimension takes place. The result is a notification in the CAD model indicating which dimension deviates from the target values. Use-cases are elaborated for integrating the concept in the product development process. To implement this concept, an experimental setup is built up consisting of a measurement system and 3D CAD system. The COPRA ProfileScan Desktop is used to measure the profile. Siemens NX 11 is the chosen CAD system. Based on this setup, the concept is validated on a manufactured profile.
An Assembly Information Model for Rapid Assembly Modeling
Authors: Lv Zhuo , Zhang Xu , Wang Haoqi , Ming Wei
Published: November 2018

The purpose of this paper is to develop a novel assembly information model, hierarchical assembly pair (HAP), as the basis of rapid assembly modeling, which aims to refine the current product-modeling paradigm and forms an advanced product-modeling framework. Apart from the geometry level, this model expresses the designer’s assembly design intent (ADI) at the feature level and part level, thus forming three sub models. Based on the model, some new technologies in the field of CAD can be integrated to promote the ADI’s automatic transformation at different levels and efficient transmission between structure-similar part models. Moreover, as the carrier of ADI, HAP can be embedded into the part models at part modeling stage and instantiated to assemble the parts at assembly modeling stage, thus reducing numerous tedious and error-prone operations such as picking up geometry elements and inputting constraint commands. The example of machine vice proves the validity of the model.
Variable Step Size Kalman Filter Using Event Handling Algorithm for Switching Systems
Authors: Bakhshande Fateme , Söffker Dirk
Published: November 2018

This paper presents a novel variable step size Kalman Filter by augmenting the event handling procedure of Ordinary Differential Equation (ODE) solvers with the predictor-corrector scheme of well-known discrete Kalman Filter (KF). The main goal is to increase the estimation performance of Kalman Filter in the case of switching/stiff systems. Unlike fixed step size Kalman Filter the sample time (ST) is adapted in the proposed approach based on current estimation performance (KF innovation) of system states and can change during the estimation procedure. The proposed event handling algorithm consists of two main parts: relaxing ST and restricting ST. Relaxing procedure is used to avoid high computational time when no rapid change exists in system dynamics. Restricting procedure is considered to improve the estimation performance by decreasing the Kalman filter step size in the case of fast dynamical behavior (switching behavior). The accuracy and computational time are controlled by using design parameters. The effectiveness of the proposed approach is verified by simulation results using the bouncing ball example as a switching system.
CTRNN Computing Realization Through Network of Coupled MEMS
Authors: Tesfay Mehari K. , Hasan Mohammad H. , Alsaleem Fadi , Rafaie Mostafa
Published: November 2018

With enormous data being generated every day from countless applications and sensor networks, the need for efficient computing devices to process and make use of this data continues to grow and is projected to increase in the future. The idea of analog computing has been redeemed recently and is poised as the future computing paradigm in these applications due to its powerful computing power and lower energy consumption. This work presents a mechanism where MEMS devices are coupled together resulting in dynamic behaviors that qualitatively resemble that of the biologically-inspired Continuous-Time Recurrent Neural Networks (CTRNNs). Moreover, interesting oscillations behaviors and limit cycles attributed to various weight manipulations and excitation input levels have been observed.
Three Approaches for Managing Stiffness in Origami-Inspired Mechanisms
Authors: Yellowhorse Alden , Howell Larry L.
Published: November 2018

Ensuring that deployable mechanisms are sufficiently rigid is a major challenge due to their large size relative to their mass. This paper examines three basic types of stiffener that can be applied to light, origami-inspired structures to manage their stiffness. These stiffeners are modeled analytically to enable prediction and optimization of their behavior. The results obtained from this analysis are compared to results from a finite-element analysis and experimental data. After verifying these models, the advantages and disadvantages of each stiffener type are considered. This comparison will facilitate stiffener selection for future engineering applications.
Towards the Design of Resilient Waste-to-Energy Systems Using Bayesian Networks
Authors: Mak W. H. Jonathan , Cardin Michel-Alexandre , Ziqi Liu , Clarkson P. John
Published: November 2018

The concept of resilience has emerged from various domains to address how systems, people and organizations can handle uncertainty. This paper presents a method to improve the resilience of an engineering system by maximizing the system economic lifecycle value, as measured by Net Present Value, under uncertainty. The method is applied to a Waste-to-Energy system based in Singapore and the impact of combining robust and flexible design strategies to improve resilience are discussed. Robust strategies involve optimizing the initial capacity of the system while Bayesian Networks are implemented to choose the flexible expansion strategy that should be deployed given the current observations of demand uncertainties. The Bayesian Network shows promise and should be considered further where decisions are more complex. Resilience is further assessed by varying the volatility of the stochastic demand in the simulation. Increasing volatility generally made the system perform worse since not all demand could be converted to revenue due to capacity constraints. Flexibility shows increased value compared to a fixed design. However, when the system is allowed to upgrade too often, the costs of implementation negates the revenue increase. The better design is to have a high initial capacity, such that there is less restriction on the demand with two or three expansions.
Predicting Manufactured Shapes of a Projection Micro-Stereolithography Process via Convolutional Encoder-Decoder Networks
Authors: He Yusen , Fei Fan , Wang Wenbo , Song Xuan , Sun Zhiyu , Baek Stephen
Published: November 2018

Projection micro-stereolithography (P-μSLA) processes have been widely utilized in three-dimensional (3D) digital fabrication. However, various uncertainties of a photopolymerization process often deteriorates the geometric accuracy of fabrication results. A predictive model that maps input shapes to actual outcomes in real-time would be immensely beneficial for designers and process engineers, permitting rapid design exploration through inexpensive trials-and-errors, such that optimal design parameters as well as optimal shape modification plan could be identified with only minimal waste of time, material, and labor. However, no computational model has ever succeeded in predicting such geometric inaccuracies to a reasonable precision. In this regard, we propose a novel idea of predicting output shapes from input projection patterns of a P-μSLA process via deep neural networks. To this end, a convolutional encoder-decoder network is proposed in this paper. The network takes a projection image as the input and returns a predicted shape after fabrication as the output. Cross-validation analyses showed the root-mean-square-error (RMSE) of 10.72 μm in average, indicating noticeable performance of the proposed convolutional encoder-decoder network.
A Cloud Service Framework for Virtual Try-on of Footwear in Augmented Reality
Authors: Chu Chih-Hsing , Cheng Chih-Hung , Wu Han-Sheng , Kuo Chia-Chen
Published: November 2018

This paper presents a cloud service framework for design evaluation of personalized footwear in augmented reality (AR) via networks. The service allows users to ubiquitously perceive themselves trying on 3D shoe models in a video stream. They upload a clip of feet motion recorded by a commercial depth camera to the cloud. A new clip is generated to display the try-on process and made available to specified receivers via video streaming on a mobile device. The framework design emphasizes making most use of open-source software and off-the-shelf technologies commercially available. A prototyping cloud system implementing the framework demonstrates the practical value of virtual footwear try-on as AR as a Service (ARaaS). This research realizes the idea of human-centric design evaluation in modern e-commerce. The cloud framework may provide a feasible solution to improve the usability for real-time applications of augmented reality.
Influence of Bias Angle on Output Performance of Nonlinear Asymmetric Energy Harvesters: Experimental Investigation
Authors: Wang Wei , Cao Junyi , Zhang Ying , Bowen Chris R.
Published: November 2018

In recent decades, the technique of piezoelectric energy harvesting has drawn a great deal of attention since it is a promising method to convert vibrational energy to electrical energy to supply lower-electrical power consumption devices. The most commonly used configuration for energy harvesting is the piezoelectric cantilever beam. Due to the inability of linear energy harvesting to capture broadband vibrations, most researchers have been focusing on broadband performance enhancement by introducing nonlinear phenomena into the harvesting systems. Previous studies have often focused on the symmetric potential harvesters excited in a fixed direction and the influence of the gravity of the oscillators was neglected. However, it is difficult to attain a completely symmetric energy harvester in practice. Furthermore, the gravity of the oscillator due to the change of installation angle will also exert a dramatic influence on the power output. Therefore, this paper experimentally investigates the influence of gravity due to bias angle on the output performance of asymmetric potential energy harvesters under harmonic excitation. An experimental system is developed to measure the output voltages of the harvesters at different bias angles. Experimental results show that the bias angle has little influence on the performance of linear and monostable energy harvesters. However, for an asymmetric potential bistable harvester with sensitive nonlinear restoring forces, the bias angle influences the power output greatly due to the effect of gravity. There exists an optimum bias angle range for the asymmetric potential bistable harvester to generate large output power in a broader frequency range. The reason for this phenomenon is that the influence of gravity due to bias angle will balance the nonlinear asymmetric potential function in a certain range, which could be applied to improve the power output of asymmetric bistable harvesters.
Investigating the Use of Reinforcement Learning for Multi-Fidelity Model Selection in the Context of Design Decision Making
Authors: Chhabra Jaskanwal P. S. , Warn Gordon P.
Published: November 2018

Engineers often employ, formally or informally, multi-fidelity computational models to aid design decision making. For example, recently the idea of viewing design as a Sequential Decision Process (SDP) provides a formal framework of sequencing multi-fidelity models to realize computational gains in the design process. Efficiency is achieved in the SDP because dominated designs are removed using less expensive (low-fidelity) models before using higher-fidelity models with the guarantee the antecedent model only removes design solutions that are dominated when analyzed using more detailed, higher-fidelity models. The set of multi-fidelity models and discrete decision states result in a combinatorial combination of modeling sequences, some of which require significantly fewer model evaluations than others. It is desirable to optimally sequence models; however, the optimal modeling policy can not be determined at the onset of SDP because the computational cost and discriminatory power of executing all models on all designs is unknown. In this study, the model selection problem is formulated as a Markov Decision Process and a classical reinforcement learning, namely Qlearning, is investigated to obtain and follow an approximately optimal modeling policy. The outcome is a methodology able to learn efficient sequencing of models by estimating their computational cost and discriminatory power while analyzing designs in the tradespace throughout the design process. Through application to a design example, the methodology is shown to: 1) effectively identify the approximate optimal modeling policy, and 2) efficiently converge upon a choice set.
Bifurcations of Periodic Orbits of a One-Dimensional Pre-Compressed Granular Array
Authors: Acar Gizem Dilber , Balachandran Balakumar
Published: November 2018

Bifurcations of periodic orbits of a one-dimensional granular array are numerically investigated in this study. A conservative two-bead system is considered without any damping or external forces. By using the Hertzian contact model, and confining the system’s total energy to a certain level, changes in in-phase periodic orbit are studied for various pre-compression levels. At a certain pre-compression level, symmetry breaking and period doubling occur, and an asymmetric period-two orbit emerges from the in-phase periodic orbit. Floquet analysis is conducted to study the stability of the in-phase periodic solution, and to detect the bifurcation location. Although the trajectory of period-two orbit is close to the in-phase orbit at the bifurcation point, the asymmetry of the period-two orbit becomes more pronounced as one moves away from the bifurcation point. This work is meant to serve as an initial step towards understanding how pre-compression may introduce qualitative changes in system dynamics of granular media.
Development and Validation of a Lithium-Ion Polymer Battery Cell Model for 12V SLI Battery Applications
Authors: Liu Yiqun , Liao Y. Gene , Lai Ming-Chia
Published: November 2018

An intuitive and comprehensive lithium-ion polymer battery cell model is developed in the Simulink environment. The developed model has capability of transient function in the Thevenin-based model, AC-equivalent function in the impedance-based model, and runtime prediction in the runtime-based model. Several model parameters are determined through five experimental discharging currents (6.67A, 10A, 20A, 30A, and 40A). The model is correlated and validated with other three continuous discharging currents (4A, 15A, and 50A) and two pulse discharges (20A and 30A). The validation indicates a less than 7% discrepancy between model simulation and experiment. The model is currently effective for lithium-metal-oxides polymer battery cell with capacity between 18Ah and 22Ah (20Ah +/− 10%). For other capacity battery cell, the parameters of series resistors need to be adjusted in the model. These parameters can be determined using three to five continuous constant current discharging tests. It is intended to make the developed cell model scalable and accurate in a wider ranges of battery specifications. Expending the developed cell model to a 12 voltage Starting-Lighting-Ignition (SLI) battery used in the start-stop or 48 voltage battery pack for mild hybrid electric vehicle is an example.
Molecular Dynamics Simulations on the Tensile Deformation and Failure of a Polyethylene/Copper Interface
Authors: Liao Lijuan , Meng Changyu , Huang Chenguang
Published: November 2018

In this study, a microscale interface consisting of amorphous polyethylene (PE) chains with the united-atom (UA) model and face-centered cubic (FCC) crystal copper as the substrate was established. Moving the copper layer with a given rate, the damage evolution of the interface during the tensile deformation was examined by molecular dynamics (MD) simulations. The stress-strain relationship was obtained to capture the evolution of tensile deformation. The distribution of the temperature field was adopted to predict the damage initiation and the failure mode. The phase diagram of the failure mode with respect to the thickness of the PE layer and the loading rate was provided. The results show that the PE layer with smaller thickness brings higher load-bearing capacity with larger yield strength. As for the rate-dependence, a rate-hardening followed by a rate-softening of yield strength was observed. In addition, the failure modes evolves from cohesive failure to interfacial one as the loading rate of tension increases progressively. It can be assumed that the control parameter on the failure mode changes from pure material strength of PE to the bonding strength between PE and copper. Furthermore, a larger thickness of PE layer leads to the cohesive failure with higher probability under a narrow range of loading rate with small values. However, the thickness-dependence of failure mode attenuates gradually and diminishes ultimately under higher loading rate, which leads to the transformation from mixed mode to interfacial one.
Investigation of Planet Gear Motion in a Planetary Gear Train With Direct High Speed Monitoring
Authors: Fukuda Tomoki , Nakagawa Masao , Matsui Syota , Hirogaki Toshiki , Aoyama Eiichi
Published: November 2018

Planetary gear trains (PGTs) are widely applied in various machines owing to their advantages, such as compactness, low weight, and high torque capacity. However, they experience the problems of vibration due to the structural and motional complexities caused by planet gears. In a previous study, it was shown that high speed monitoring is effective for evaluating the motion of planet gears under steady conditions and transient conditions including the influence of backrush. However graphical investigation was conducted manually, and improvement in accuracy is required. In this report, an improved method is proposed, which includes lighting conditions and measurement conditions. Throughout these improvement processes, instant center of rotation is calculated automatically with detected coordinates using software. This makes it possible to estimate the transient response of PGTs with planet gear motion.
Mechanical Design for Accuracy of Linkage Servo Press for Near-Net Shape Forming
Authors: Tao Jing , Qian Huanan , Yu Suiran
Published: November 2018

The accuracy of machine is important to achieving highly accurate shapes. This paper is focused on mechanical design of highly accurate mechanical linkage servo press applicable to (near-)net shape forming. The effects of geometric errors, deformations under heavy loads and ram tilting are analyzed. A top-down design for accuracy approach is proposed: First, accuracy model for identification of inaccuracy-causing factors and their interlinking relations is developed. Then, based on this model, top accuracy index are decomposed and translated into structure design specifications at component level. Both analytic and simulation methods are employed for design for accuracy in aspects of dimensional and geometric tolerance allocation, stiffness synthesis and anti-eccentric load capability. A case study of mechanical design for accuracy of a six-linkage mechanical servo press is also presented to demonstrate and test the proposed design approaches.