bluuebunny/crossref_metadata_2025 huggingface dataset:
Proposal for an Adaptive Bone Screw Design Based on FEA Studies Exemplified by Pedicle Screw
Authors: Seidler Alexander , Mehlhorn Lars , Sembdner Philipp , Holtzhausen Stefan , Stelzer Ralph , Drossel Welf-Guntram
Published: November 2021

This paper presents a proposal for a density-adaptive design of bone screws using pedicle screws for spinal fixations as an example. The basis is the analysis and categorization of currently available variants of bone screws, which differ in principle in their thread design because of different application areas (cortical or cancellous bone). These screw variants are investigated in FEA simulations for pullout and bending with regard to occurring stresses. A corresponding simulation model is presented for this purpose. The precise design models for these screws are generated in a CAD system using a self-developed configuration tool. Based on the FEA evaluation, the proposal for a new pedicle screw design, consisting of several thread types merged into each other, is described in detail. By integrating different thread types over the shaft, the respective properties of the bone can thus be optimally utilized.
Fourier Analysis Guided Cable Actuator Design for Coordinated Walking Assistance
Authors: Liu Chong , Hidayah Rand , Agrawal Sunil
Published: November 2021

Cable-driven exoskeletons add minimal inertia and restrictions to the user’s leg while still providing feedback and quantitative measures of the user’s performance. However, cable robots require at least n + 1 cables to control n degrees-of-freedom, i.e., they require more actuators than the leg’s degrees-of-freedom, challenging their widespread adoption as wearable technology. The state-of-the-art in this field aims to reduce the number of actuated motors.

In this paper, we design and evaluate a “single motor-driven” leg exoskeleton prototype based on the Cable-driven Active Leg EXoskleton (C-ALEX). The prototype consists of four crank-spring mechanisms and a crankshaft designed using epicycle analysis. The epicycle analysis is performed using discrete Fourier transform (DFT) and sine curve fitting (SCF). While DFT suggests the maximum number of epicycles to imitate the target waveform, a large number of nested epicycles is challenging to design and manufacture for implementation. To validate the epicycle-guided design, we constructed a simple crankshaft model using one epicycle. Our proposed simplified model predicted and produced the joint angles calculated from the inverse and forward kinematics of a cable-driven leg exoskeleton with multiple motors. To our knowledge, this is the first multi-cable driven exoskeleton powered by a single actuator that is designed to provide continuous assistance to the user.
Point-Cloud Neural Network Using Transfer Learning-Based Multi-Fidelity Method for Thermal Field Prediction in Additive Manufacturing
Authors: Huang Xufeng , Hu Zhen , Xie Tingli , Wang Zhuo , Chen Lei , Zhou Qi
Published: November 2021

Melt pool modeling is critical for model-based uncertainty quantification (UQ) and quality control in metallic Additive Manufacturing (AM). Finite element (FE) simulation for thermal modeling in metal AM, however, is tedious and time-consuming. This paper presents a multi-fidelity point-cloud neural network method (MF-PointNN) for surrogate modeling of melt pool based on FE simulation data. It merges the feature representations of low-fidelity (LF) analytical model and high-fidelity (HF) FE simulation data through the theory of transfer learning (TL). A basic PointNN is firstly trained using LF data to construct correlation between the inputs and thermal field of analytical models. Then, the basic PointNN is updated and fine-tuned using the small size of HF data to build the MF-PointNN. The trained MF-PointNN allows for efficient mapping from input variables and spatial positions to thermal histories, and thereby efficiently predict the three-dimensional melt pool. Results of melt pool modeling of electron beam additive manufacturing (EBAM) of Ti-6Al-4V under uncertainty demonstrate the efficacy of the proposed approach.
Understanding Household Energy Challenges in Himalayan Communities Using Participatory Design Approaches
Authors: Tang Lisa , Patel Arnav , Sweeney Daniel J. , Banerjee Nilanjana , Thakur Amit K. , Chaudhari Pranava , Kumar Rahul , Joshi Jyeshtharaj
Published: November 2021

Traditional biomass-burning stoves are used for cooking and heating across the globe. These stoves generate smoke that results in household air pollution, which poses a significant risk to human health. In the past decades, there have been many efforts to promote the adoption of improved cookstove designs, but uptake of improved stoves is often slow due to high costs, inconsistent supply chains, and incompatibility with local cooking practices. This paper presents survey results from rural villages in Uttarakhand, India regarding routines and attitudes on cooking and space heating. Significant findings include the dual use of liquified petroleum gas and biomass fuels, the interconnected and seasonal nature of cooking and space heating, the cultural significance of traditional cookstoves, and the prominence of locally available materials in cookstove construction and maintenance. Comparisons of these surveys’ findings to previous investigations on energy use in the Himalayan region show many common trends, but also reveal regional differences. The paper concludes that due to the significance of culture and context in cookstove design, understanding user needs and behaviors and working with local communities are integral parts the design methodology for clean cookstoves. These results provide a case study which agrees with existing literature on the importance of participatory design in global development.
Sequentially Working Origami Multi-Physics Simulator (SWOMPS): A Versatile Implementation
Authors: Zhu Yi , Filipov Evgueni T.
Published: November 2021

This work presents the underlying implementation of a new origami simulator (SWOMPS) that allows for adaptability and versatility with sequential analyses and multi-physical behaviors of active origami systems. The implementation allows for easy updating of origami properties, realistic simulation with multi-physics based actuation, and versatile application of different loadings in arbitrary number and sequence. The presented simulator can capture coupling between multiple origami behaviors including electro-thermo-mechanical actuation, heat transfer, self-stress induced folding, inter panel contact, applied loading forces, and kinematic/mechanical deformations. The simulator contains five different solvers, including three for mechanical loading, one for self-folding, and one for thermal loading. The paper presents details of this code package and uses three practical examples to highlight the versatility and efficiency of the package. Because various loadings and different origami behaviors can be modeled simultaneously and/or sequentially, this simulator is well suited for capturing origami behaviors in practical real-world scenarios. Furthermore, the ability to apply an arbitrary number and sequence of loadings is useful for design, optimization, or system control studies where an unknown set of loads are needed to fold functional active origami. The coded implementation for this simulator and additional examples are made available to encourage future expansions of this work where new sequential and multi-physical behaviors in origami can be explored.
A Block-Based Arduino Programming Platform for Developing Computational Thinking Skills for K-12 Students
Authors: Qian Binsen , Cheng Harry H.
Published: November 2021

As a critical set of skills in the 21st century, computational thinking has attracted increasing attention in K-12 education. Microcontrollers, combined with LEDs, actuators, and a variety of sensors, provide students countless real-world projects, such as autonomous vehicles, smart homes, and robotics. By solving those projects through programming, students will not only learn computational skills but also benefit from the hands-on activities to get some experience on solving real-world problems. It makes microcontroller projects a perfect tool to develop the computational thinking skills of K-12 students. Our previous work has proposed a solution for higher graders to program Arduino through Ch, a C/C++ interpreter. It is necessary, however, to develop a platform for lower graders (K-6) since most of them do not have the ability to type through the keyboard. This paper extends our previous work such that students can program Arduino on RoboBlockly, a block-based programming platform. In the paper, we will present two case studies to demonstrate how to build blocks to control the Arduino board and what concepts students will learn from those projects. In addition, the proposed platform also provides an interactive way of transitioning students from the block-based program to a text-based program in Ch.
Singularity-Free Lie Group Integration of Multibody System Models Described in Absolute Coordinates
Authors: Müller Andreas
Published: November 2021

A classical approach to the modeling of multibody systems (MBS) is to use absolute coordinates, i.e. a set of (redundant) coordinates that describe the absolute position and orientation of the individual bodies w.r.t. to an inertial frame (IFR). A well-known problem for the time integration of the equations of motion (EOM) is the lack of a singularity-free parameterization of spatial motions, which is usually tackled by using unit quaternions. Lie group integration methods were proposed as alternative approach to the singularity-free time integration. Lie group methods are inherently coordinate free and thus incompatible with any absolute coordinate description. In this paper, an integration scheme is proposed that allows describing MBS in terms of arbitrary absolute coordinates and at the same using Lie group integration schemes, which allows for singularity-free time integration. Moreover, the direct product group SO (3) × ℝ3 as well as the semidirect product group SE (3) can be use for representing rigid body motions, which is beneficial for constraint satisfaction. The crucial step of this method, which renders the underlying Lie group integration scheme applicable to EOM in absolute coordinates, is the update of the (global) absolute coordinates in terms of the (local) coordinates on the Lie group by means of a local-global transitions (LGT) transition map. This LGT map depends on the used absolute coordinates and the local coordinates on the Lie group, but also on the Lie group itself used to represent rigid body configurations (respectively the deformation field of flexible bodies), i.e. the geometry of spatial frame motions. The Lie group formulation is thus embedded, which allows interfacing with standard vector space integration methods.
Viscous Friction Effect During the Process of Tightening and Loosening of Bolted Joints
Authors: Lin Qingyuan , Zhao Yong , Sun Qingchao , Chen Kunyong
Published: November 2021

Bolted connection is one of the most widely used mechanical connections because of its easiness of installation and disassembly. Research of bolted joints mainly focuses on two aspects: high precision tightening and improvement of anti-loosening performance. The under-head bearing friction coefficient and the thread friction coefficient are the two most important parameters that affect the tightening result of the bolted joint. They are also the most critical parameters that affect the anti-loosening performance of the bolted joint. Coulomb friction model is a commonly used model to describe under-head bearing friction and thread friction, which considers the friction coefficient as a constant independent of normal pressure and relative sliding velocity. In this paper, the viscous effect of the under-head bearing friction and thread friction is observed by measuring the friction coefficient of bolted joints. The value of the friction coefficient increases with the increase of the relative sliding velocity and the decrease of the normal pressure. It is found that the Coulomb viscous friction model can better describe the friction coefficient of bolted joints. Taking into account the dense friction effect, the loosening prediction model of bolted joints is modified. The experimental results show that the Coulomb viscous friction model can better describe the under-head bearing friction coefficient and thread friction coefficient. The model considering the dense effect can more accurately predict the loosening characteristics of bolted joints.
Finding Features of Positioning Error for Large Industrial Robots Based on Convolutional Neural Network
Authors: Kato Daiki , Yoshitugu Kenya , Maeda Naoki , Hirogaki Toshiki , Aoyama Eiichi , Takahashi Kenichi
Published: November 2021

Most industrial robots are taught using the teaching playback method; therefore, they are unsuitable for use in variable production systems. Although offline teaching methods have been developed, they have not been practiced because of the low accuracy of the position and posture of the end-effector. Therefore, many studies have attempted to calibrate the position and posture but have not reached a practical level, as such methods consider the joint angle when the robot is stationary rather than the features during robot motion. Currently, it is easy to obtain servo information under numerical control operations owing to the Internet of Things technologies. In this study, we propose a method for obtaining servo information during robot motion and converting it into images to find features using a convolutional neural network (CNN). Herein, a large industrial robot was used. The three-dimensional coordinates of the end-effector were obtained using a laser tracker. The positioning error of the robot was accurately learned by the CNN. We extracted the features of the points where the positioning error was extremely large. By extracting the features of the X-axis positioning error using the CNN, the joint 1 current is a feature. This indicates that the vibration current in joint 1 is a factor in the X-axis positioning error.
Tuning Motion of Musical Saw With a Humanoid Robot for Industrial Automation Based on a Sound Feed-Back Process
Authors: Hanai Hiroaki , Miura Atsuyuki , Hirogaki Toshiki , Aoyama Eiichi
Published: November 2021

In recent years, cooperative robots have been attracting attention for their ability to work with humans. The ability to share tools is an important factor in the development of collaborative robots. In this study, we investigated the methods necessary to realize a robot that can manipulate tools. To understand the characteristics of the tools, we modeled the target tools and performed finite element analysis. Based on the analysis results, we determined the initial command values to be given to the robot. Under the constraint of the robot’s range of motion, we created a hand jig and arranged the tools to expand the control sound range. The robot uses acoustic information to judge a situation and meets different demands with its two arms. The left hand controls the generated frequency by applying a forced displacement to the instrument. With the right hand, the robot focuses on the difference in sound pressure between the main and secondary frequencies and controls the position of the blow in the plane of the instrument to increase this difference. The introduction of this control based on acoustic recognition makes it possible to teach the musical saw performance posture in real time. Using this method, we were able to demonstrate the possibility that a tool manipulating robot can work in an environment where humans coexist.
Switched Fractional Order Model Reference Adaptive Control for an Automatic Voltage Regulator
Authors: Aguila-Camacho Norelys , García-Bustos Jorge E. , Castillo-López Eduardo I.
Published: November 2021

This paper presents the design and implementation of a Switched Fractional Order Model Reference Adaptive Controller (SFOMRAC) for an Automatic Voltage Regulator (AVR). The fractional orders, adaptive gains and switching times of the controller adaptive laws are tuned offline, using Particle Swarm Optimization (PSO). The functional to be optimized contains not only parameters of the AVR response but also the control energy. The obtained controllers are compared to non switched Integer Order Model Reference Adaptive Controller (IOMRAC) and non switched Fractional Order Model Reference Adaptive Controller (FOMRAC) proposed previously for this process, showing that the SFOMRAC can improve both, the system response and the control energy used.
Combined Coulomb and Viscous Damping Estimation Using Topological Signal Processing
Authors: Myers Audun , Khasawneh Firas A.
Published: November 2021

In this work we develop a novel time-domain approach for the simultaneous estimation of the damping parameters for a single degree of freedom oscillator with both viscous and coulomb damping. Our approach leverages zero-dimensional sublevel set persistence — a tool from Topological Signal Processing (TSP) — to analyze the ring down vibration of the signal. Sublevel set persistence is used as it alleviates the need for peak selection when analyzing the time-domain of the signal and provides an alternative noise-robust method for visualizing the damping envelope. We are able to successfully estimate the damping parameters using both a direct approach and a function fitting method. We show that the direct approach is only appropriate for low levels of additive noise, but allows for a less computationally demanding estimation of the parameters. Alternatively, the function fitting method provides accurate estimates for significantly higher levels of additive noise. The results are provided through a numerically simulated example with mixed coulomb and viscous damping. We demonstrate the robustness of our method for accurately estimating both damping parameters for various levels of additive noise, a wide range of sampling frequencies, and both high and low levels of damping. This analysis includes providing suggested limitations of the method when applied to real-world signals.
Sustainability and Design Education: The Current Status of Product Design Higher Education in the UK
Authors: Delaney Emelia , Liu Wei
Published: November 2021

The aim of sustainability is to fulfil the needs of current generations without compromising the needs of future generations. It is also a rising area of concern within industry, it is therefore important that graduate designers are equipped with the skills to accommodate sustainability issues as well as demands from industry. Additionally, the product design stage during New Product Development has been identified to have the greatest impact on the sustainability of the entire product, however how educated designers are on the topic of sustainability is unclear. An initial literature review has been conducted to investigate design education on sustainability as well as teaching styles. Following this the study identifies and reviews UK Product Design courses to establish the current status of sustainability integration in higher education. The exploration into university prospectuses has found that around half of UK universities implement sustainability in some way, however there are limited courses which dedicate specific modules to sustainability. Additionally, links with industry and accreditation organizations between UK product design courses have been confirmed, but there is no definite information to suggest that the universities use this to aid in the implementation sustainability education. From this review future research directions have been outlined.
Kinematic Synthesis of Gait Correction for a Rehabilitation Machine
Authors: Pusnik Zvonimir , Nelson Carl A. , Burnfield Judith M. , Buster Thad W.
Published: November 2021

This paper outlines the synthesis process for a redesign of the intelligently controlled assistive rehabilitation elliptical’s (ICARE) pedal system to enhance replication of gait-like movement patterns while training. The synthesized mechanism overcomes some limitations identified in certain ellipticals, specifically generation of taller, more rounded foot paths compared to over-ground gait. The proposed solution minimizes the position and angle difference curves between the ICARE foot motion and normal gait.
Direct Sensitivity Analysis of Spatial Multibody Systems With Joint Friction Using Index-1 Formulation
Authors: Verulkar Adwait , Sandu Corina , Dopico Daniel , Sandu Adrian
Published: November 2021

Sensitivity analysis is one of the most prominent gradient based optimization techniques for mechanical systems. Model sensitivities are the derivatives of the generalized coordinates defining the motion of the system in time with respect to the system design parameters. These sensitivities can be calculated using finite differences, but the accuracy and computational inefficiency of this method limits its use. Hence, the methodologies of direct and adjoint sensitivity analysis have gained prominence. Recent research has presented computationally efficient methodologies for both direct and adjoint sensitivity analysis of complex multibody dynamic systems. The contribution of this article is in the development of the mathematical framework for conducting the direct sensitivity analysis of multibody dynamic systems with joint friction using the index-1 formulation. For modeling friction in multibody systems, the Brown and McPhee friction model has been used. This model incorporates the effects of both static and dynamic friction on the model dynamics. A case study has been conducted on a spatial slider-crank mechanism to illustrate the application of this methodology to real-world systems. Using computer models, with and without joint friction, effect of friction on the dynamics and model sensitivities has been demonstrated. The sensitivities of slider velocity have been computed with respect to the design parameters of crank length, rod length, and the parameters defining the friction model. Due to the highly non-linear nature of friction, the model dynamics are more sensitive during the transition phases, where the friction coefficient changes from static to dynamic and vice versa.
A Pareto Front Mechanism Optimization for Controlling an Aircraft Using a Bio-Inspired Rotating Empennage
Authors: Myszka David H. , Joo James J. , Murray Andrew P.
Published: November 2021

This paper presents a mechanism design optimization for actuating the horizontal stabilizers of an aircraft using a rotating empennage without a vertical stabilizer. Birds do not have vertical stabilizers and rotate their tail feathers to control agile maneuvers. A rotating empennage concept will mimic this motion and enable the bio-inspired flight of a fixed wing aircraft. To maintain control, the bio-inspired rotating empennage (BIRE) will incorporate three degrees of freedom: independent rotation of each horizontal stabilizer and rotation of the empennage relative to the main axis of the fuselage. The primary benefits of an aircraft without a vertical stabilizer is reduced drag and weight, which in turn results in more efficient operation.

In order to reduce inertia of the rotating empennage, the linear actuators that position the horizontal stabilizers will be placed within the fuselage. Mechanisms that couple the linear translation of the actuators with the rotation of the horizontal stabilizers ideally require a low peak force and short stroke from the actuator. With two conflicting objectives, a Pareto front optimization was conducted to determine appropriate link lengths of candidate solutions and to understand the effectiveness of alternate mechanisms. The study considers a rack & pinon, scotch-yoke, slider-crank, inverted slider-crank, Watt, and Stephenson mechanisms.
An Algorithm for Partitioning Objects Into a Cube Skeleton and Segmented Shell Covers for Parallelized Additive Manufacturing
Authors: Li Wilson , Poozhikala Thomas , Dinar Mahmoud
Published: November 2021

Despite a growing application of additive manufacturing, build volume has limited the size of fabricated parts. Machines that can produce large-scale parts in whole have high costs and less commercially available. A workaround is to partition the desired part into smaller partitions which can be manufactured in parallel, with the added benefit of controlling process parameters for each partition independently and reducing manufacturing time. This paper proposes an approach that divides a part into a cube skeleton covered by shell segments where all components can be fabricated with smaller 3D printers. The proposed algorithm first hollows out the original fully dense part to a user-specified thickness, then partitions the part into 26 surrounding regions using the six faces of the maximally inscribed cube (or cuboid). Islands, i.e., small, disconnected partitions within each region, are combined with the smallest neighbor to create up to 26 connected partitions. To minimize the number of printed partitions, the connected partitions are ranked based on their volume and combined with their smallest neighbor in pairs in descending order, while ensuring each pair fits within a pre-selected build volume of available 3D printers. The final partitioned shell segments, the cube (or cuboid) center, and the secondary layer of cubes propagated from the face centers of the maximally inscribed cube are generated by the algorithm. Results of two cases are shown.
The Effect of Membrane Load on the Usage of Berger’s Model in Electrostatically Actuated Pre-Stressed Circular Curved Micro Plates
Authors: Medina Lior , Eliasi Rami , Gilat Rivka , Krylov Slava
Published: November 2021

The effect of membrane load on the behaviour of axisymmetric bistable circular curved microplates on Berger’s based axisymmetric reduced order (RO) model, incorporating radial prestress, is studied. The model is first validated for a “mechanical” load, against a Föppl-von-Kármán’s RO model with twenty degrees of freedom (DOF), a finite differences (FD) solution and a finite elements (FE) model, serving as the reference. All solutions implement the “Riks” method to track possible unstable branches, which can swerve in due to the presence of higher buckling modes. A convergence study is carried out for the snap-through location and load, as well as for the critical elevation and prestress required for bistability. Based on validated results of the analysis, the reliability of the model for predicting the effect of prestress on the plate behaviour under nonlinear electrostatic load is then investigated while using FD solutions as the reference. The study furnishes a reliable expended RO model, which includes prestress on the as-fabricated curved plate. The resulting model can further be used to estimate the value of residual prestress, present in an electrostatically actuated curved plate, based on its response.
Analysis and Evaluation of Piecewise Linear Systems With Coulomb Friction Using a Hybrid Symbolic-Numeric Computational Method
Authors: Shahhosseini Amir , Tien Meng-Hsuan , D’Souza Kiran
Published: November 2021

A general formulation of piecewise linear systems with discontinuous force elements is provided in this paper. It has been demonstrated that this class of nonlinear systems is of great importance due to their ability to accurately model numerous scientific and engineering phenomena. Additionally, it is shown that this class of nonlinear systems can demonstrate a wide spectrum of nonlinear motions and in fact, the phenomenon of weak chaos is observed in a mechanical assembly for the first time.

Despite such importance, efficient methods for fast and accurate evaluation of piecewise linear systems’ responses are lacking and the methods of the literature are either incompatible, very slow, very inaccurate, or bear a combination of the aforementioned deficiencies. To overcome this shortcoming, a novel symbolic-numeric method is presented in this paper that is able to obtain the analytical response of piecewise linear systems with discontinuous elements in an efficient manner. Contrary to other efficient methods that are based on stationary steady state dynamics, this method will not experience failure upon the occurrence of complex motion and is able to capture the entirety of the dynamics.
Finite Element Analysis and Thick-Panel Clash Behaviour of Steel Fold-Lines
Authors: Shi Quan , Gattas Joseph M.
Published: November 2021

The structural and mechanical behaviours of most origami-inspired or folded structures is strongly dependent upon the mechanical behaviours of their constituent crease lines. Characterisation of the rotational behaviours of the steel hinges is therefore a critical step in the analysis of origami-inspired steel structures. This paper will present a numerical modelling approach for simulating the rotational response of digitally-fabricated steel hinges, over a large rotation range from 0° up to 170°. Numerical response predictions are verified against published experimental results, over a range of sheet thicknesses and fold line parameters. Models are then used to give insight into observed thick-panel clash behaviours and fold-line localised strap mechanics. The developed numerical modelling procedure provides a convenient analysis method for rapid prediction of steel hinge behaviour.
Grooved Cam With a Translating Follower Having an Added Ternary-Roller Intermediate Link
Authors: Hsu Kuan-Lun , Pan Tung-Hsin , Wu Long-Iong
Published: November 2021

The paper presents an analytical approach for designing grooved cam mechanisms with a modified arrangement of the common translating follower. That is, an extraneous intermediate link that has three rollers is added between the cam and the common follower. On the basis of an existing cam mechanism with a common roller follower, an extraneous intermediate link that has three rollers is added between the cam and the common follower. Such a cam mechanism has two set of profile and can creating multiple contact points between the cam and the follower at any instant. The two sets of profiles of such a cam mechanism can serve as the grooved types. Since the follower has three rollers that can simultaneously contact the cam at any instant, it can be positive driven along the guided groove of cam contour. The contact forces and contact stresses of such cam mechanisms are analyzed to illustrate the advantage of spreading force transmission and reducing contact stress of this uncommon follower. The obtained results indicate that the contact stress at the surface of the cam and the follower for such a cam mechanism can be reduced by 34% to 42% in comparison to those of cam mechanism with a common translating roller follower.
The Influence of Team Goal Alignment and Awareness on Human-Centered Design Team Decision-Making Strategy
Authors: Rao Vivek , Krishnan Ananya , Kwon Jieun , Kim Euiyoung , Agogino Alice , Goucher-Lambert Kosa
Published: November 2021

Design team decision-making underpins all activities in the design process. Simultaneously, goal alignment within design teams has been shown to be essential to the success of team activities, including engineering design. However, the relationship between goal alignment and design team decision-making remains unclear. In this exploratory work, we analyze six student design teams’ decision-making strategies underlying 90 selections of design methods over the course of a human-centered design project. We simultaneously examine how well each design team’s goals are aligned in terms of their perception of shared goals and their awareness of team members’ personal goals at the midpoint and end of the design process, along with three other factors underpinning team alignment at the midpoint. We report three preliminary findings about how team goal alignment and goal awareness influence team decision-making strategy that, while lacking consistent significance, invite further research. First, we observe that a decrease in awareness of team members’ personal goals may lead student teams to use a different distribution of decision-making strategies in design than teams whose awareness stays constant or increases. Second, we find that student teams exhibiting lower overall goal alignment scores appear to more frequently use agent-driven decision-making strategies, while student teams with higher overall goal alignment scores appear to more frequently use process-driven decision-making strategies. Third, we find that while student team alignment appears to influence agent- and process-driven strategy selection, its effect on outcome-driven selection is less conclusive. While grounded in student data, these findings provide a starting place for further inquiry into of designerly behavior at the nexus of teaming and design decision-making.
Analysis of Capillary Driven Flows Through Open Microchannels for Biosensing Application
Authors: Patel Hardikkumar , Yan Terry , Shavezipur Mohammad
Published: November 2021

Integrated micro-biosensors and microfluidic systems have been recently used for detection of cells, proteins, and other biomarkers for a wide range of applications. In this work, open micro-channel flows driven by capillary force designed for food safety applications are studied. The micro-channels are used to deliver the nutrients (extracts of different fresh produce) to the sensing site where pathogens reside. The presence of nutrients, simulating the condition that micro-organisms experience in real food materials, allow us to investigate their behavior in real time. Open channels studied in this work are partially covered to allow for etching of the sacrificial layer that creates the channel and use of capillary force to create a self-driven microfluidic system in which fluid flow is actuated by surface tension and wall adhesion. Numerical simulations are used to investigate the fluid flow regime in micro-channels using ANSYS FLUENT. The volume of fraction (VOF) method is used to simulate the dynamics of fluid flow in microchannels made of polycrystalline silicon with a thin layer coating of native silicon dioxide. The effects of channel size and different geometries (open channel, T-junction, and L-junction) on a flow rate of water in the channel are investigated. Our study shows that adding T- and L-junctions to the flow path would create a small delay in the fluid flow in the channel, and the number of junctions directly affect the delay, however, it does not prevent the fluid transfer by capillary force. The (partially covered) open channel geometry presented in this work is compatible with conventional surface micromachining process.
Trajectory Planning for a 3-S

P

S-U Tensegrity Mechanism
Authors: Venkateswaran Swaminath , Chablat Damien
Published: November 2021

This article presents the actuation strategy of a 2-DOF tensegrity type mechanism that employs three tension springs and a passive universal joint. This mechanism is proposed to be incorporated as an articulation unit for a piping inspection robot in order to overcome pipe bends and junctions. In the event of a junction, external actuations are required to allow the mechanism as well as the robot to follow a certain direction. Using DC-motors coupled with encoders, experiments are carried out on a test bench of the tensegrity mechanism. The actuation of the mobile platform is performed using cables that pass through each spring. By correlating the architecture to a 3-SPS-U parallel mechanism, the singularity-free workspace of the mechanism is analyzed to identify the tilt limits. A closed-loop PID controller is implemented using a microcomputer to perform a linear trajectory within the singularity-free workspace. The Inverse Kinematic Problem (IKP) is solved by passing input tilt angles to the controller. With the help of a force control algorithm, the experiments are carried out under no-load conditions for vertical and horizontal orientations of the mechanism. The error data of the joint positions and the motor torques are then interpreted for both orientations of the mechanism.
Nonlinear Control of a Transient Inductrack System Using State Feedback
Authors: Wang Ruiyang , Yang Bingen
Published: November 2021

The concept of Inductrack refers to the magnetic levitation technology achieved by Halbach arrays of permanent magnets. In an Inductrack system, the dynamic behaviors involved with transient responses are difficult to capture due to the highly nonlinear, time-varying, electromagnetic-mechanical couplings. In the literature, dynamic modeling of Inductrack systems that aims to analyze the transient behaviors has been widely addressed. However, one common issue with the previous investigations is that most of the dynamic models either partly or completely adopted certain steady-state and ideal case assumptions. These assumptions are extremely difficult to maintain in a transient scenario, if not impossible. Therefore, while providing good understanding of Inductrack systems, the previous results in dynamic modeling have a limited utility in providing guidance for feedback control of Inductrack systems.

Recently, a benchmark transient Inductrack model was created for characterizing the transient time response of the system with fidelity, which enables model-based feedback control design. In this work, based on the transient model, a new control method for the Inductrack dynamic system is developed. The proposed control method consists of a linear part and a nonlinear part. The linear part is devised based on a state feedback configuration; the nonlinear part is accomplished by fitting a nonlinear “force-current” mapping function. With this nonlinear feedback controller, the levitation gap of the Inductrack vehicle can be effectively stabilized at both constant and time-dependent traveling speed. The proposed control law is demonstrated in numerical examples. The nonlinear control design is potentially extensible to more complicated Inductrack systems with higher degrees of freedom.
Towards Transparent Motion Planning of Wearable Rehabilitation Exoskeletons via Model-Based Estimation
Authors: Wang Jiamin , Blankenship David , Barry Oumar
Published: November 2021

We propose a novel online model-based motion planning algorithm for a family of rehabilitation exoskeletons to improve transparency in user-guided operation. In this study, we assume that the short-term human movement intention can be embedded in the time-delay dimensions of motion signals. The model-based estimation is employed to obtain the interaction load between the dynamical subsystems respectively controlled by the human and exoskeleton. The objective of the proposed motion planning algorithm is to reduce the interaction load, which leads to the establishment of a least-square optimization problem. A Support Vector Regression (SVR) model, driven by the time-delayed motion data, is implemented to solve the optimization problem by generating the acceleration of tracking reference. The motion planning algorithm based on SVR can be combined with a variety of trajectory tracking controllers. To ensure the efficiency of the algorithm for online applications, we also design the SVR model so that its properties can be calculated recursively based on latest data sets. The performance and characteristics of the motion planning algorithm are then observed and discussed through the control simulations of a wearable wrist exoskeleton designed for pathological tremor alleviation. The results show that while the planned tracking reference can approximate the synthetic human movement intention, the motion planning accuracy can be limited by system disturbances, and the delay of signals caused by digital filters.
Design of Stackable Origami Structures With Elastic Deployment Capabilities
Authors: Ma Peiwen J. , Verniani Alessandro , Peraza Hernandez Edwin A.
Published: November 2021

This work presents a flexible type of origami structure that may be elastically deployed from a compact stacked form to a freeform target shape. The design process enables a target surface mesh to be converted into a compact stacked structure that may be deployed through the release of elastic energy stored in the folds. The process begins by finding a non-branching path passing once through each face in the target mesh. The edges of the target mesh not included in the path are cut and elastic smooth folds are introduced along those crossed by the path. The introduced smooth folds are folded in a sequence of ±180° along the path to create a stack. The structure transforms from the stacked form towards the target shape through the release of the stored elastic energy generated during stacking. The design framework considers the strain energy needed to sustain transformation and the required sizing of the smooth folds. The resemblance of the designed target shape with smooth folds compared to the target mesh is studied, and the significant volume saving when the structure is stowed in the stacked form is quantified. Examples showing the application of the design process to a diverse set of target meshes are provided. Proof-of-concept prototype fabrication using a 3D printer demonstrates the feasibility of the design approach. The results reflect the benefits of deployable stacked origami structures and show volumetric space savings from 50% to 90% while preserving around 80% of the target mesh area after the elastic smooth folds are introduced.
Data-Driven Customer Segmentation Based On Online Review Analysis and Customer Network Construction
Authors: Park Seyoung , Kim Harrison M.
Published: November 2021

Recently, many studies on product design have utilized online data for customer analysis. However, most of them treat online customers as a group of people with the same preferences while customer segmentation is a key strategy in conventional market analysis. To supplement this gap, this paper proposes a new methodology for online customer segmentation. First, customer attributes are extracted from online customer reviews. Then, a customer network is constructed based on the extracted attributes. Finally, the network is partitioned by modularity clustering and the resulting clusters are analyzed by topic frequency. The methodology is implemented to a smartphone review data. The result shows that online customers have different preferences as offline customers do, and they can be divided into separate groups with different tendencies for product features. This can help product designers to draw segment-based design implications from online data.
High-Dimensional Reliability Method Accounting for Important and Unimportant Input Variables
Authors: Yin Jianhua , Du Xiaoping
Published: November 2021

Reliability analysis is usually a core element in engineering design, during which reliability is predicted with physical models (limit-state functions). Reliability analysis becomes computationally expensive when the dimensionality of input random variables is high. This work develops a high dimensional reliability analysis method by a new dimension reduction strategy so that the contributions of both important and unimportant input variables are accommodated by the proposed dimension reduction method. The consideration of the contributions of unimportant input variables can certainly improve the accuracy of the reliability prediction, especially where many unimportant input variables are involved. The dimension reduction is performed with the first iteration of the first order reliability method (FORM), which identifies important and unimportant input variables. Then a higher order reliability analysis, such as the second order reliability analysis and metamodeling method, is performed in the reduced space of only important input variables. The reliability obtained in the reduced space is then integrated with the contributions of unimportant input variables, resulting in the final reliability prediction that accounts for both types of input variables. Consequently, the new reliability method is more accurate than the traditional method, which fixes unimportant input variables at their means. The accuracy is demonstrated by three examples.
Method for Generating Mechanical Linkages of Polygons That Fold Into a Similar Shape
Authors: Yamamoto Yohei , Mitani Jun
Published: November 2021

Origami techniques, as folding and unfolding, can be utilized in shrinkable structures. Especially when the crease pattern is rigid foldable, it can be treated as a mechanical linkage of rigid panels connected by hinges. Since rigid foldable crease patterns have the strong geometrical constraint of the facets not being able to stretch or bend, it is difficult to design new crease patterns, and variations of existing patterns are limited. However, it is known that there are cases where crease patterns can be made rigid foldable by adding some slits. This paper proposes a mechanical linkage that folds into a similar flat shape by adding slits. A method is presented of generating rigid foldable crease patterns in arbitrary polygons that fold smaller, and it is confirmed that structures that have a mechanism for shrinking can be generated from these crease patterns by using rigid thick panels and hinges.
Design of a Self Balancing Vehicle as a Test Rig for Safety Control Strategies Investigations
Authors: Righettini Paolo , Strada Roberto , Santinelli Jasmine
Published: November 2021

The present paper is related to a research activity concerning self-balancing vehicles, with particular reference to the interaction between driver and vehicle’s dynamics, at the aim to investigate safety management and strategies. In particular, the paper presents the design process of a self-balancing vehicle with the target to be used as a test rig for safety investigations. Besides the definition of the mechanical configuration, the design process includes also the choice of the motor/transmission unit, the design of the control system and the design of sensors related to vehicle/driver interaction. For design purposes, a simplified two dof planar model has been considered with the driver fixed with the vehicle chassis. Through a proper linearisation of such model, the dynamics of the system has been described by means of a state space approach, used to tune the controller, not only for stability but also for optimal response. In order to test the suitability of the designed vehicle for safety investigations, the paper presents also a Multibody model of the vehicle designed and of a driver with three driven joints. Such model allows to simulate the interaction between human (driver) and machine (vehicle), taking into consideration also the coupling between longitudinal motion and turn. By means of co-simulations between the multibody model (developed with MSC.Adams) and the controller (modelled with Matlab/Simulink), tests have been performed showing the possibility to detect influence of the driver’s behavior on the vehicle’s dynamics.