bluuebunny/crossref_metadata_2025 huggingface dataset:
Local Redesign for Additive Manufacturability of Compliant Mechanisms Using Topology Optimization
Authors: Koppen Stijn , Hoes Emma , Langelaar Matthijs , Frecker Mary I.
Published: November 2021

Compliant mechanisms are crucial components in current and future high-precision applications. Topology optimization and additive manufacturing offer freedom to design complex compliant mechanisms that were impossible to realize using conventional manufacturing. Design for additive manufacturing constraints, such as the maximum overhang angle and minimum feature size, tend to drastically decrease the performance of topology optimized compliant mechanisms. It is observed that, among others, design for additive manufacturing constraints are only dominant in the flexure regions. Flexures are most sensitive to manufacturing errors, experience the highest stress levels and removal of support material carries the highest risk of failure. It is crucial to impose these constraints on the flexure regions, while in others part of the compliant mechanism design, these constraints can be relaxed. We propose to first design the global compliant mechanism layout in the full domain without imposing any design for additive manufacturing constraints. Subsequently we redesign selected refined local redesign domains with design for additive manufacturing constraints, whilst simultaneously considering the mechanism performance. The method is applied to a single-input-multi-output compliant mechanism case study, limiting the maximum overhang angle, introducing manufacturing robustness and limiting the maximum stress levels of a selected refined redesign domain. The high resolution local redesigns are detailed and accurate, without a large additional computational effort or decrease in mechanism performance. Thereto, the method proves widely applicable, computationally efficient and effective in its purpose.
Towards Generalization of Intelligent Fault Detection for Roller Element Bearings via Distinct Dataset Transfer Learning
Authors: Larocque-Villiers Justin , Dumond Patrick
Published: November 2021

Through the intelligent classification of bearing faults, predictive maintenance provides for the possibility of service schedule, inventory, maintenance, and safety optimization. However, real-world rotating machinery undergo a variety of operating conditions, fault conditions, and noise. Due to these factors, it is often required that a fault detection algorithm perform accurately even on data outside its trained domain. Although open-source datasets offer an incredible opportunity to advance the performance of predictive maintenance technology and methods, more research is required to develop algorithms capable of generalized intelligent fault detection across domains and discrepancies. In this study, current benchmarks on source–target domain discrepancy challenges are reviewed using the Case Western Reserve University (CWRU) and the Paderborn University (PbU) datasets. A convolutional neural network (CNN) architecture and data augmentation technique more suitable for generalization tasks is proposed and tested against existing benchmarks on the Pb U dataset by training on artificial faults and testing on real faults. The proposed method improves fault classification by 13.35%, with less than half the standard deviation of the compared benchmark. Transfer learning is then used to leverage the larger PbU dataset in order to make predictions on the CWRU dataset under a challenging source-target domain discrepancy in which there is minimal training data to adequately represent unseen bearing faults. The transfer learning-based CNN is found to be capable of generalizing across two open-source datasets, resulting in an improvement in accuracy from 53.1% to 68.3%.
Optimal Performance Comparison of Nonlinear Energy Sinks and Linear Tuned Mass Dampers
Authors: Yegorov (Egorov) Ivan , Uden Austin , Yurchenko Daniil
Published: November 2021

This paper studies a targeted energy transfer (TET) mechanism for a two-degree-of-freedom (TDOF) model in free vibration. The model comprises a primary linear system and a secondary system in the form of an energy sink which can be nonlinear. The free vibrations are considered subject to an impulsive excitation exerted on the primary system, leading to a nonzero initial velocity. The goal is to obtain the spring parameters in the nonlinear energy sink (NES) so as to maximize an energy dissipation measure (EDM) representing the percentage of impulsive energy that is absorbed and dissipated in the NES. A global optimization algorithm is used for this purpose. The optimal performance is assessed for the purely linear, linear-cubic, and purely cubic configurations of the spring connecting the primary and secondary systems. The corresponding results are compared with each other. The optimization process is performed for the EDM averaged over given ranges of the initial impulse and natural frequency in the primary system. It is shown that the type of the optimal configuration can vary depending on these ranges.
Approximating Hinges With Multimaterial Compliant Joints
Authors: Talken Independence , Liang Zijuan , Plecnik Mark
Published: November 2021

This paper investigates the use of multimaterial compliant joints produced through additive manufacturing in order to approximate a revolute joint. Compliant joints benefit from low friction and reduced wear, but at the cost of increased joint stiffness, reduced range of motion, and a reduced ability to resist loading. In addition, they might also provide a poor approximation of the revolute joints they intend to replace. In this paper, we experiment with three multimaterial compliant joint configurations. The first joint emphasizes accurate kinematics, the second joint aims to reduce axis-aligned stiffness, and the third joint compromises between the two. Samples were fabricated on a desktop 3D printer using PLA (polylactic acid) as the rigid material and TPU (thermoplastic polyurethane) for its flexibility. Samples were measured for tensile stiffness, torsional stiffness, range of motion, and approximation of a hinge motion. Our results indicate design trade offs where joints that measure most ideal for one property will be least ideal for another. The most novel design in this paper straddles this trade off. In the end, the suitability of each joint design is determined by the loading, accuracy, and range of motion requirements posed by a given application.
Coupled Lateral and Longitudinal Control for Trajectory Tracking, Lateral Stability, and Rollover Prevention of High-Speed Automated Vehicles Using Minimum-Time Model Predictive Control
Authors: Chen Shuping , Chen Huiyan , Pletta Alex , Negrut Dan
Published: November 2021

Most controllers concerning lateral stability and rollover prevention for autonomous vehicles are designed separately and used simultaneously. However, roll motion influences lateral stability in cornering maneuvers, especially at high speed. Typical rollover prevention control stabilizes the vehicle with differential braking to create an understeering condition. Although this method can prevent rollover, it can also lead to deviation from a reference path specified for an autonomous vehicle. This contribution proposes and implements a coupled longitudinal and lateral controller for path tracking via model predictive control (MPC) to simultaneously enforce constraints on control input, state output, lateral stability, and rollover prevention. To demonstrate the approach in simulation, an 8 degrees of freedom (DOF) vehicle model is used as the MPC prediction model, and a high-fidelity 14-DOF model as the plant. The MPC-based lateral control generates a sequence of optimal steering angles, while a PID speed controller adjusts the driving or braking torque. The lateral stability envelope is determined by the phase plane of yaw rate and lateral velocity, while the roll angle threshold is derived from the load transfer ratio (LTR) and tire vertical force under the condition of quasi-steady-state rollover. To track the desired trajectory as fast as possible, a minimum-time velocity profile is determined using a forward-backward integration approach, subject to tire friction limit constraints. We demonstrate the approach in simulation, by having the vehicle track an arbitrary course of continuously varying curvature thus highlighting the accuracy of the controller and its ability to satisfy lateral and roll stability requirements. The MATLAB® code for the 8-DOF and 14-DOF vehicle models, along with the implementation of the proposed controller are available as open source in the public domain.
The Missing Link Between Project and Prototype: Teaching Student Designers to Navigate the Prototyping Process
Authors: Arndt Hansen Camilla , Eifler Tobias , Deininger Michael
Published: November 2021

It has been well established that prototyping is an important part of development projects. Prototypes are used in engineering design courses but teaching students the strategic skills needed to decide what to prototype during development projects is often not a part of the curriculum.

This paper proposes a model that uses the prototyping process to link individual prototyping activities and project goals. The proposition is that when designers work intentionally with prototyping as a process, they will be able to make strategic decisions about how and when to use prototypes.

To teach students a prototyping process mindset, a simple prototype prioritization tool, the Prototyping Target, was developed and integrated into project-based product development courses. Fifteen student teams used the Prototyping Target to decide which project questions to answer with prototypes every week over three weeks. Results show that criticality to project success is a good starting point but not the only parameter to consider when deciding what to prototype.

A comparison between prototyping plans made with and without the Prototyping Target shows that student teams selected a clearer purpose for their prototypes when they used the prioritization tool before planning specific prototyping activities.

Overall, this paper demonstrates the benefits of teaching student designers to navigate the prototyping process.
Modelling the Axis Drift of Short Wire Flexures and Increasing Their Support Stiffness Using Polymers
Authors: Daan Boris , Rommers Jelle , Herder Just L.
Published: November 2021

For steel flexures, complex geometries are required to reach high support stiffness and limit axis drift over large ranges of motion. These complex flexures are expensive and difficult to manufacture. This paper presents a method of designing short, polymer wire flexures with high support stiffness and modelling their axis drift using a novel method, the arc method. The arc method is validated against finite element methods (FEM) and physical tests, showing at least a factor 10 lower error than existing pseudo-rigid-body models (PRBM) at 70° deflection, while maintaining a simple modelling approach. The use of polymers increases support stiffness of wire flexures by a factor 7800 with respect to steel at 70° deflection, even though the material stiffness is substantially lower. This is due to the large allowed strain of polymers increasing the possible diameter by a factor 110.
Conceptual Configuration Synthesis of Line-Foldable Deployable Space Truss Structures Utilizing Graph Theory and Entropy
Authors: Wang Shoufei , Zhao Yong
Published: November 2021

From the perspective of the truss as a whole, this research presents an approach to synthesizing conceptual configurations for deployable space truss structures that are line-foldable with the help of graph theory and entropy. First, according to graph theory, the bijection between a truss and its graph model is established by defining a bijective mapping between set elements. Therefore, operations can be performed based on graph models. Second, the principle of configuration evolution is interpreted by employing Maxwell’s rule, it also discusses the necessary and sufficient condition of configuration evolution. Configurations of evolution belong to three phases: space configuration, transformation configuration, and linear configuration. And it finds that the reasonable transformation configuration plays a key role. Further, maximum clique detection depending on backtracking is used to screen out unreasonable transformation configurations. Third, it introduces entropy, and the phenomenon of entropy change in configuration evolution is revealed and induction weights of rigid links are defined. It calculates the weight value of a transformation configuration by adding up induction weights of rigid links removed, also, weight values are used to classify transformation configurations. Finally, based on the previous analysis, a procedure to synthesize transformation configurations is formed and it is verified by a truss model with 7 nodes. This research lays the foundation for geometric dimension design and engineering applications.
Autonomous Robotic Subcutaneous Injection Under Near-Infrared Image Guidance
Authors: Huang Dingliang , Hu Bin , Chen Yinna , Chen Yu , Sui Liangchen , Wang Zhaoyang , Jiang Yijun , Ren Zhongyuan , Wang Yuxuan , Cao Xu , Qi Peng
Published: November 2021

Subcutaneous injections are administered into the region beneath the skin, while avoiding puncturing the blood vessels, which gives many types of medications for various medical conditions. In this paper, a portable robotic system performing autonomous cannulation of subcutaneous injections is proposed, and it achieves to automatically locate the proper injection site by analyzing near-infrared (NIR) image sequences. The robot mainly consists of two functional modules-image processing module and motion control module. The former with a full-search algorithm processes the images obtained by the NIR equipment. The puncture point is selected in the area where there are no blood vessels and a method of “range square” is utilized. The motion control module of the robotic system employs the pulse width modulation (PWM) wave to effectively control the motors and manipulates the syringe to puncture at the selected point. The image processing algorithm was evaluated based on the real NIR images of volunteers’ hands and forearms, and the image servo control of the robot was tested on the phantom. The experimental results were analyzed by a medical professional, and the success rate of the image processing algorithm is 96.09%, while the puncture time can satisfy the clinical demand for the efficiency of puncture procedures.
Prediction of Driver’s Center of Gravity Position on a Stand-Up Type PMV Considering Intentions
Authors: Nakagawa Chihiro , Sato Kosuke , Shintani Atsuhiko
Published: November 2021

In recent years, Personal Mobility Vehicles (PMVs) have been attracting attention as a new means of transportation. They are environmentally friendly without exhausting harmful gases. These vehicle bodies are relatively smaller than cars, so they have a high affinity for pedestrian space. However, depending on the specifications of the vehicle, driver’s behaviors have great effect on the vehicle movement because the weight of the vehicle is comparatively low. In addition, applying the automatic driving on PMV will be one of the next steps to make use of PMVs. It is important to understand the dynamic behavior of drivers not only during their intentional driving but also during the automatic driving. In this study, we focused on stand-up type PMVs. We measured driver’s center of gravity and several forces on a standing PMV. From the measurements, we looked at the correlation coefficient, and used multiple regression analysis to derive the prediction equations of driver’s center of gravity position on stand-up type PMVs. These results can be applied to simulate the dynamic motion of the PMV and a driver.
In-Situ Laser-Based Process Monitoring and In-Plane Surface Anomaly Identification for Additive Manufacturing Using Point Cloud and Machine Learning
Authors: Lyu Jiaqi , Akhavan Taheri Boroujeni Javid , Manoochehri Souran
Published: November 2021

Additive Manufacturing (AM) is a trending technology with great potential in manufacturing. In-situ process monitoring is a critical part of quality assurance for AM process. Anomalies need to be identified early to avoid further deterioration of the part quality. This paper presents an in-situ laser-based process monitoring and anomaly identification system to assure fabrication quality of Fused Filament Fabrication (FFF) machine. The proposed data processing and communication architecture of the monitoring system establishes the data transformation between workstation, FFF machine, and laser scanner control system. The data processing performs calibration, filtering, and segmentation for the point cloud of each layer acquired from a 3D laser scanner during the fabrication process. The point cloud dataset with in-plane surface depth information is converted into a 2D depth image. Each depth image is discretized into 100 equal regions of interest and then labeled accordingly. Using the image dataset, four Machine Learning (ML) classification models are trained and compared, namely Support Vector Machine (SVM), K-Nearest Neighbors (KNN), Convolutional Neural Network (CNN), and Hybrid Convolution AutoEncoder (HCAE). The HCAE classification model shows the best performance based on F-scores to effectively classify the in-plane anomalies into four categories, namely empty region, normal region, bulge region, and dent region.
Topology Optimization Design of Structures Based on Eigenfrequency Matching
Authors: Giraldo-Guzmán Daniel , Lissenden Clifford , Shokouhi Parisa , Frecker Mary
Published: November 2021

We demonstrate the design of resonating structures using a density-based topology optimization approach, which requires the eigenfrequencies to match a set of target values. To develop a solution, several optimization modules are implemented, including material interpolation models, penalization schemes, filters, analytical sensitivities, and a solver. Moreover, common challenges in topology optimization for dynamic systems and their solutions are discussed. In this study, the objective function is to minimize the error between the target and actual eigenfrequency values. The finite element method is used to compute the eigenfrequencies at each iteration. To solve the optimization problem, we use the sequential linear programming algorithm with move limits, enhanced by a filtering technique. Finally, we present a resonator design as a case study and analyze the design process with different optimization parameters.
Efficient Design Principles for Designing Innovative Aerial Robots
Authors: Tan Chee How , Foong Shaohui , Hölttä-Otto Katja
Published: November 2021

The field of aerial robotics has advanced rapidly, but the design knowledge has not yet been codified into reusable design principles. Design principles have been developed for many other areas of mechanical design to both advance the field itself and help novice designers benefit from the past expert knowledge easier. We used an inductive approach and collected 90 aerial robot examples through the reviewing of recent work in aerial robotics and studying the key motivations, features, functionalities and potential design contradictions. Then, design principles are iteratively derived by identifying patterns and grouping them by the problem they solve, and the innovation made to solve it. From this, we find 35 unique design examples that can be grouped into either fourteen design principles for more sensing, battery, mission, or actuation efficient design; or six design principles to improve a desired functionality in an aerial robot such as reducing complexity or improving how the robot can interact with objects or its environment. We compared the research results with similar work in the area of mechanical design and examined the commonalities and highlighted design principles unique to aerial robots. The design principles presented in this research can support the design for future innovative aerial robots.
Design for Product Circularity: Circular Economy Indicators With Tools Mapped Along the Engineering Design Process
Authors: Saidani Michael , Kim Harrison
Published: November 2021

Monitoring the circularity potential of products and materials is key to ensure environmental savings and economic profitability of circular economy loops, such as reuse, remanufacturing, or recycling. The choices and decisions made during the product design phase have a major influence and impact on the circularity performance of products. While numerous indicators and tools have been recently developed to assess, manage, and accelerate the transition to a more circular economy, their application and usability during the early design phases of products are often overlooked. Based on a screening of several tens of circular economy indicators, the present research work identified twelve product-centric circularity indicators, each of them coming with a computational tool, to be deployed during the design process in order to improve the circularity potential of products. To help designers and engineers selecting the appropriate solution, these circularity indicators and tools are positioned on a generic five-step design process, namely: requirements definition, conceptual design, detailed design, designs comparison, product monitoring and communication. Concrete examples are given on how these indicators and their assessment framework can support the design of more circular products. Current shortcomings of available approaches are finally highlighted and discussed (such as the lack of c-indicators for the detailed design phase or linkage with computer-aided design software) for an augmented integration of such promising circularity indicators and their associated tools within the design and development process of products.
Design of a Monolithic Constant-Force Compliant Mechanism for Extended Range of Motion and Minimal Force Variation
Authors: Lo Ching-Wei , Chang Yuan , Wang Mien-Li , Lin Cian-Ru , Lee Jyh-Jone
Published: November 2021

Compliant mechanisms enable passive force control through induction of strain energy during deformation. This has been perceived as a desired factor for developing precise handling equipment of limited size where additional sensors and controls are inessential to its operation. In this paper, our objective is to design a monolithic constant-force compliant mechanism to be integrated in a constant-force gripper for extended range of bidirectional motion. A topology synthesis method has been proposed by means of domain definition, discrete parameterization, topology optimization, and nonlinear structural deformation evaluation. This article adapts a compliant topology of a homogeneous beam configuration that exhibits zero stiffness behavior over a pre-established effective region. The optimization by genetic algorithm generates discrete shaping parameters for formation of an optimal geometry. The structural deformation computation via vector form intrinsic finite element that accounts for large displacement motion quantifies an iterative series of load-displacement relations in the optimization. Results have been verified using a conventional finite element method. A conceptual gripper has been proposed with a pair of embedded constant-force compliant mechanisms. This procedure has prepared a general guideline for future development of passive compliant devices that require accurate force regulation over a wide range of motion.
Human-Centric Design Requirements and Challenges for Enabling Human-AI Interaction in Engineering Design: An Interview Study
Authors: Shergadwala Murtuza N. , Seif El-Nasr Magy
Published: November 2021

AI technologies are enabling the development of not only active tools that provide decision-support, but also interactive tools that seek human input and feedback. As interactive tools facilitate human-AI interaction, their design needs to be informed by human-centric requirements, that is, the needs of the users of such tools. In the context of engineering design, there is a gap in our understanding of designing intelligent tools that facilitate human-AI interaction. To fill this gap, the research question of this study is, What are the human-centric design requirements for the design of AI agents to enable human-AI interaction in engineering design contexts? To answer this question, we conducted an interview study with faculty members in engineering design. The faculty predominantly discussed engineers, designers, and engineering design students as the potential stakeholders who would directly benefit from human-AI interaction. For such stakeholders, we identify several human-centric design requirements and challenges in designing AI tools that facilitate human-AI interaction in engineering design. We find that the requirements focused on the need to understand the stakeholders’ cognition and the engineering design contexts. The results of our study point to the need for the theory of mind in AI agents to enable them to infer stakeholder preferences while engaging in engineering design activities.
Energy Absorption Characteristics of Passenger Car With Origami Structure
Authors: Yang Yang , Zhao Xilu , Hagiwara Ichiro
Published: November 2021

In the crash collision, the vehicle energy absorbers play an important role in the energy absorbed performance. Current vehicle energy absorbers have two defects during collision, such as only 70 % collapsed in its length and high initial peak load. It is because present energy absorbed column is the most primitive from the point of Origami structure. We developed the column so called Reversed Spiral Origami Structure; RSO which solves these 2 defects. However, for RSO, the manufacturing cost of hydroforming in the existing technology is too expensive to be applied in real vehicle structure. To address the problems, we have developed a new molding method called “Partial-heating torsion molding method”. And we have developed RTO (Reversed Torsion Origami Structure) by this new molding method at a very low cost. We show this RTO also solves the two defects of the present vehicle absorbers by not only simulation but also experiments. This structure is possible to replace conventional energy absorbers and it is expected to be widely used such as not only in automobile structures but also in building ones.
The MAIANDROS System for Random-Vibration-Based On-Board Railway Vehicle and Track Monitoring
Authors: Vlachospyros Georgios , Iliopoulos Ilias A. , Kritikakos Kiriakos , Kaliorakis Nikolaos , Fassois Spilios D. , Sakellariou John S. , Deloukas Alexandros , Leoutsakos George , Giannakis Christos , Chronopoulos Elias , Tountas Elias , Kapiris Dimosthenis
Published: November 2021

A bird’s–eye overview of the innovative, on–board and Multi–Purpose, random vibration based MAIANDROS Condition Monitoring system for railway vehicles and infrastructure is presented. The system includes Modules for Suspension Monitoring (SM), Wheel Monitoring (WM), Track Monitoring (TM) for track segment condition characterization, Lateral Stability Monitoring (LSM), and Remaining Useful Life Estimation (RULE) for critical components such as wheels. It is based on Statistical Time Series type methods and proper decision making, and aims at overcoming various challenges of current systems while pushing their performance limits. Its unique advantages include high diagnostic performance, ability to detect early–stage (incipient) faults, robustness to varying Operating Conditions, early detection of the onset of hunting, operation with a minimal number of low–cost sensors, and minimal computational complexity for achieving real–time or almost real–time operation. Its high achievable performance is demonstrated via indicative assessments using a prototype system onboard an Athens Metro vehicle and Monte Carlo simulations with a SIMPACK based high–fidelity vehicle model.
A Study of a Pendulum-Like Vibration Isolator With Quasi-Zero-Stiffness
Authors: Tian Yishen , Cao Dengqing , Wang Yan
Published: November 2021

This article introduces a pendulum element to a 3-spring vibration isolator to achieve a high-static-low-dynamic (HSLD) stiffness or even quasi-zero stiffness (QZS) around the equilibrium position. Numerical simulation is given and the harmonic balance method (HBM) is used to obtain time responses for analysis. Effects of different parameters on the isolation performance are studied and summarized. Approximation force and displacement transmissibility of the system are calculated to evaluate the isolation performance. Comparisons are made with those of an equivalent linear isolator and the typical 1 degree-of-freedom (DOF) QZS isolator. Results show that the novel vibration isolator performs better than existing isolators under selected parameters. The left bent backbone of the novel isolator demonstrates evident softening geometric nonlinearity. Therefore, it achieves a wider frequency range of isolation than the linear 1DOF isolator and typical 3-spring QZS isolator. Moreover, the transmissibility of the novel isolator is smaller at higher frequencies as the jump phenomenon occurs on the left.
Introduction and Preliminary Investigation of Buoyancy Assisted Robots That Are Cheap, Safe, and Will Never Fall Down
Authors: Williams Matthew David , Hong Dennis
Published: November 2021

We introduce and define a new family of mobile robots called BAR (Buoyancy Assisted Robots) that are cheap, safe, and will never fall down. BARs utilize buoyancy from lighter-than-air gases as a way to support the weight of the robot for locomotion. A new BAR robot named BLAIR (Buoyant Legged Actuated Inverted Robot) whose buoyancy is greater than its weight is also presented in this paper. BLAIRs can walk “upside-down” on the ceiling, providing unique advantages that no other robot platforms can. Unlike other legged robots, the mechanics of how BARs walk is fundamentally different. We also perform a preliminary investigation for BARs. This includes comparing safety, cost, and energy consumption with other commercially available robots. Additionally, the preliminary investigation also includes analyzing previous works relating to BARs. A dynamical analysis is performed on the novel robot BLAIR. This is presented to show the impacts of buoyant and drag forces on BLAIRs. Preliminary analysis with the prevalence of drag is presented with simulations using a genetic algorithm and simulations. Results show that BARs with different mechanisms prefer different styles of walking gaits such as prancing or skipping. This work lays the foundation for future research work on the gaits for BARs.
A Comprehensive Numerical Study on the Number of Identifiable Kinematic Parameters of Parallel Mechanisms
Authors: Kong Lingyu , Chen Genliang , Huang Guanyu , Song Sumian , Xie Anhuan , Zhang Dan
Published: November 2021

Kinematic error model plays an important role in improving the positioning accuracy of robot manipulators by kinematic calibration. The identifiability of kinematic parameters in the error model directly affects the positioning accuracy of the mechanism. And the number of identifiable kinematic parameters determines how many parameters can be accurately identified by kinematic calibration, which is one of the theoretical basis of kinematic error modeling. For serial mechanisms, a consensus has been reached that the maximum number of identifiable kinematic parameters is 4R + 2P + 6, where R and P represent the numbers of revolute and prismatic joints, respectively. Due to complex topologies of parallel mechanisms, there is still no agreement on the formula of the maximum number of identifiable parameters. In this paper, a comprehensive numerical study on the number of identifiable kinematic parameters of parallel mechanisms is conducted. The number of identifiable parameters of 3802 kinds of limbs with different types or actuation arrangements are analyzed. It can be concluded that the maximum number of identifiable kinematic parameters is Σ i = 1 n 4Ri + 2Pi + 6 − Ci − 2(PP)i/3(PPP1)i/(2Ri + 2Pi)(PPP)i, where Ci represents the number of joints whose motion cannot be measured and n denotes the number of limbs in a parallel mechanism; (PP)i, (PPP1)i, and (PPP)i represent two consecutive unmeasurable P joints, three consecutive P joints in which two of them cannot be measured, and three unmeasurable P joints, respectively.
Connecting Qualitative and Quantitative Analysis Through Bond Graph Modeling and System Dynamics
Authors: Suk Hailie , Hall John
Published: November 2021

Access to resources can contribute to social progress in extremely impoverished communities. The introduction of cyber-physical systems for electricity, water, and irrigation facilitates greater fulfillment of needs. Yet, the availability of resources may be inconsistent or lacking. The social dynamics of the community can provide insight into how the available resources support well-being. Thus, the cyber-physical system requires the addition of a social consideration to become cyber-physical-social systems. However, the social considerations typically include qualitative parameters. This prompts the need for integrating qualitative and quantitative information.

In this paper, we present a method for mathematically representing qualitative and quantitative relationships. This is achieved by connecting Bond Graph Modeling and System Dynamics. The Bond Graph model is used to mathematically represent relationships between qualitative and quantitative elements. These relationships are used in the System Dynamics analysis. The method is anchored in expanding cyber-physical to cyber-physical-social systems through incorporating both qualitative and quantitative information in the systems analysis.

The mathematical connectivity of qualitative and quantitative information is a key feature of this approach. A test problem in resource allocation is used to demonstrate the function and flexibility of the method. This is anchored in connecting qualitative and quantitative information in the analysis.
Integer Ratio Self-Synchronization in Pairs of Limit Cycle Oscillators
Authors: Bhaskar Aditya , Shayak B. , Zehnder Alan T. , Rand Richard H.
Published: November 2021

The existence of multiple stable states of higher order m:n locking in coupled limit cycle oscillators has been studied by prior authors in the context of injection-locking in systems driven by an external periodic force. The current work builds on this concept to study the higher order locking characteristics of pairs of limit cycle oscillators self-synchronizing under coupling forces. To this end we analyze three oscillator systems: Van der Pol oscillators using numerical analysis, a simplified model for MEMS oscillators using numerical analysis as well as perturbation theory, and a full model of thermo-optically driven MEMS oscillators using numerical analysis. For the Van der Pol system, higher order locking is observed for the strongly nonlinear case corresponding to relaxation oscillations and the transition from weak to strong nonlinearity is studied using a parameter sweep. Additionally, coupling of a different nature such as quadratic coupling is also capable of inducing higher order coupling in Van der Pol oscillators. For the MEMS systems with linear coupling, higher order locking is observed when a strong cubic stiffness nonlinearity exists. Devil’s staircase-like structures are obtained for the coupling strength-frequency ratio parameter space which suggest overlapping Arnold locking regions for m:n locks corresponding to different integers.
Hybrid Modeling of Melt Pool Geometry in Additive Manufacturing Using Neural Networks
Authors: Jones Kevontrez , Yang Zhuo , Yeung Ho , Witherell Paul , Lu Yan
Published: November 2021

Laser powder-bed fusion is an additive manufacturing (AM) process that offers exciting advantages for the fabrication of metallic parts compared to traditional techniques, such as the ability to create complex geometries with less material waste. However, the intricacy of the additive process and extreme cyclic heating and cooling leads to material defects and variations in mechanical properties; this often results in unpredictable and even inferior performance of additively manufactured materials. Key indicators for the potential performance of a fabricated part are the geometry and temperature of the melt pool during the building process, due to its impact upon the underlining microstructure. Computational models, such as those based on the finite element method, of the AM process can be used to elucidate and predict the effects of various process parameters on the melt pool, according to physical principles. However, these physics-based models tend to be too computationally expensive for real-time process control. Hence, in this work, a hybrid model utilizing neural networks is proposed and demonstrated to be an accurate and efficient alternative for predicting melt pool geometries in AM, which provides a unified description of the melting conditions. The results of both a physics-based finite element model and the hybrid model are compared to real-time experimental measurements of the melt pool during single-layer AM builds using various scanning strategies.
Combinatorial Optimization of Pre-Formed Hose Assemblies
Authors: Gustafsson Erik , Persson Johan , Tarkian Mehdi
Published: November 2021

Cable and hose routing is a complex and time-consuming process that often involves several conflicting objectives. Complexity increases further when routes of multiple components are to be considered through the same space. Extensive work has been done in the area of automatic routing where few proposals optimize multiple hoses together. This paper proposes a framework for the routing of multiple pre-formed hoses in an assembly using a unique permutation process where several alternatives for each hose are generated. A combinatorial optimization process is then used to find Pareto-optimal solutions for the multi-route assembly. This is coupled with a scoring model that predicts the overall fitness of a solution based on designs previously scored by the engineer as well as an evaluation system where the engineer can score new designs found through the use of the framework to update the scoring model. The framework is evaluated using a testcase from a car manufacturer showing a severalfold time reduction compared to a strictly manual process. Considering the time savings, the proposed framework has the potential to greatly reduce the overall routing processes of hoses and cables.
Optimal Selection of Equivalence Factors for ECMS in Mild Hybrid Electric Vehicles
Authors: Hegde Shailesh , Bonfitto Angelo , Rahmeh Hadi , Amati Nicola , Tonoli Andrea
Published: November 2021

The increasing stringent emissions regulation over the years have shifted the focus of automotive industry towards more efficient fuel economy solutions. One such solution is Hybrid electric architecture, which is able to improve the fuel economy and consequently cutting down emissions. A well known control strategy to solve optimization problem for energy management of Hybrid electric vehicles is ECMS (Equivalent Consumption Minimization Strategy). Finding the best control parameters (equivalence factors) of this strategy may become quite involved. This paper proposes a method for the selection of the optimal equivalence factors, for charging and discharging, by applying genetic algorithm in the case of a P0 mild hybrid electric vehicle. This method is a systematic and deterministic way to guarantee an optimal solution with respect to the trial and error method. The proposed ECMS is compared to a technique available in literature, known as the shooting method, which relies only on one equivalence factor for discharging. It is demonstrated that the performance in terms of pollutant emissions are comparable. However, ECMS with GA always guarantees an optimal solution even in the case of heavy accessory load, when shooting method is not valid anymore, as it does not guarantee a charge sustaining condition.
Influence of the Cyclist’s Characteristics on the Optimal Pacing Strategy for an Ascending Road
Authors: Angulo Manuel , Polanco Alejandra , Muñoz Luis
Published: November 2021

Pacing strategies are used in cycling to optimize the power delivered by the cyclist during a race. Gains in race time have been obtained when using these strategies compared to self-paced approaches. For this reason, this study is focused on revising the effect that the variation of the cyclist’s parameters has on the pacing strategy and its results.

A numeric method was used to propose pacing strategies for a cyclist riding on an ascending 3.7 km route with a constant 6.26% road grade. The method was validated and then implemented to study the effect of aerobic and anaerobic power delivery capacity, mass, and drag area on the pacing strategies and their corresponding estimated race times.

The results showed that modifying 1% of the aerobic capacity or cyclist mass value led to a change of 1% on the race time. Modifying 1% the anaerobic capacity and the drag area led to changes of 0.03% and 0.02% on the race time, respectively. These results are strongly dependent on the route characteristics.

It was concluded that for the studied route (constantly ascending), the variation of the cyclist’s aerobic capacity influences the pacing strategy (i.e., the power delivery over the distance). The anaerobic capacity and mass of the cyclist also influence the pacing strategy to a lesser extent.
Point-to-Point Path Planning Based on User Guidance and Screw Linear Interpolation
Authors: Laha Riddhiman , Rao Anjali , Figueredo Luis F. C. , Chang Qing , Haddadin Sami , Chakraborty Nilanjan
Published: November 2021

Despite the increasing number of collaborative robots in human-centered manufacturing, currently, industrial robots are still largely preprogrammed with very little autonomous features. In this context, it is paramount that the robot planning and motion generation strategies are able to account for changes in production line in a timely and easy-to-implement fashion. The same requirements are also valid for service robotics in unstructured environments where an explicit definition of a task and the underlying path and constraints are often hard to characterize. In this regard, this paper presents a real-time point-to-point kinematic task-space planner based on screw interpolation that implicitly follows the underlying geometric constraints from a user demonstration. We demonstrate through example scenarios that implicit task constraints in a single user demonstration can be captured in our approach. It is important to highlight that the proposed planner does not learn a trajectory or intends to imitate a human trajectory, but rather explores the geometric features throughout a one-time guidance and extend such features as constraints in a generalized path generator. In this sense, the framework allows for generalization of initial and final configurations, it accommodates path disturbances, and it is agnostic to the robot being used. We evaluate our approach on the 7 DOF Baxter robot on a multitude of common tasks and also show generalization ability of our method with respect to different conditions.
Reduced-Order Model With Foot Tipping Allowance for Legged Balancing
Authors: Peng William Z. , Song Hyunjong , Kim Joo H.
Published: November 2021

Tipping is an instrumental aspect of multi-phase contact situations that arise during common tasks such as the locomotion of legged systems. Despite its importance in balance recovery, tipping is often ignored in trajectory optimization due to the lack of existing methods that are able to actively plan and optimize for unspecified contacts. Trajectory Optimization based on nonlinear programming requires a priori knowledge about anticipated contact changes, such as their order and timing, in order to generate physically feasible motions. In this paper, an optimization framework with conditional constraints is established for direct collocation in trajectory optimization for legged balancing with foot tipping allowance. The proposed approach can evaluate the timing of contact phases without preplanned contact forces or sequences of events, which is not possible with conventional methods. This optimization framework is demonstrated by computing the balanced regions of two reduced-order models of a legged system, namely, inverted-pendulum-based models without and with a flywheel, and is verified with control simulations. The contribution of tipping to balance stability is quantified and compared to prior results obtained without tipping allowance. The framework presented can also be generalized to other multi-phase contact scenarios, such as rolling and sliding, where unspecified discontinuous changes in contact occur with important consequences in the performance of legged systems.
Feeling the Heat! Exploring the Relationship Between Students’ Empathy, Attitudes Towards Sustainability, and Their Identification of Problem Requirements
Authors: Prabhu Rohan , Alsager Alzayed Mohammed , Starkey Elizabeth
Published: November 2021

As global resources deplete, there has emerged a need for designers to emphasize sustainability in engineering design. Towards this end, several researchers have presented design tools to support sustainable design; however, designers must be encouraged to adopt a sustainable design mindset and actively utilize these design tools and techniques in the design process. Prior research has identified the need for interpersonal skills such as empathy among individuals to encourage an active sustainable mindset among them. While several researchers have demonstrated the relationship between designers’ empathy and their identification of problem requirements in engineering design, little research has explored this relationship in the context of sustainable design. This direction of research is particularly important as environment-focused decisions in engineering design do not always benefit the primary user of a solution, but often affect secondary and tertiary stakeholders. Our aim in this paper is to explore this research gap through an experimental study with undergraduate engineering students. Specifically, we compared the relationship between participants’ trait empathy and their attitudes towards sustainability, in the context of environmental sustainability. We then investigated the relationship between their trait empathy, attitudes towards sustainability, and their identification of problem requirements in a design task. From the results, we see that students’ intentions towards sustainable actions positively correlated with their identification of environment-focused requirements. On the other hand, students’ perspective-taking — a component of their trait empathy — positively correlated with their identification of user-focused requirements. These findings provide an important first step towards understanding the relationship between designers’ individual differences and their adoption of sustainability in engineering design.
Product Development Using Perceived Correlations Between the United Nations Sustainable Development Goals and Social Impact Categories
Authors: Johnson Gabrielle E. , Fisher Marin J. , Salmon John L. , Mattson Christopher A.
Published: November 2021

This paper discusses the perceived relations between the Social Impact Categories (SIC) and Social, Economic, and Environmental (SEE) Aspects derived from the United Nations’ Sustainable Development Goals (SDGs). Surveys showed high correlations between Health and Safety and Population Change to the majority of SEE Aspects. There were also high correlations between the SICs and economic and environmental factors. Further research will survey perceived relations between all three SEE impact categories.