bluuebunny/crossref_metadata_2025 huggingface dataset:
Cyber-Physical Infrastructures for Advancing Pyrolysis Conversion Process: A Case Study of Biochar Production
Authors: Hersh Benjamin , Mohajeri Amir , Mirkouei Amin , Xian Min
Published: November 2020

Biomass-based products (bioproducts) have been introduced as a means to address food-energy-water nexus challenges. However, the existing approaches have not been integrated to convert biomass into market-competitive bioproducts (e.g., biochar and bio-oil). Pretreatment and conversion processes represent the most substantial portion of the total bioproduct cost. This study proposes a portable conversion process for high-quality biochar and bio-oil production, using mixed reactors and advanced cyber-physical infrastructures to promote cross-cutting technological and commercialization opportunities. The proposed portable process converts biomass to bioproducts near the collection sites, which can address collection, staging, and logistics challenges. The fundamental novelty of this study lies in utilizing cyber-physical technologies for advancing pre-/post-conversion processes and crossing the boundaries to meet the market needs. A case study for biochar production from various biomass feedstocks is used to demonstrate and verify the application of the conversion process and the cyber-based advances. The results indicate that the integrated cyber-physical conversion pathway can increase process yield and quality. It is also found that biomass properties and conversion process configurations play a crucial role in determining the process yield and biochar quality in terms of the physical-chemical structure.
Cable-Suspended Robot for Algae Harvesting
Authors: Williams Robert L. , Pagan Jesus
Published: November 2020

This paper presents a novel application for a portable 4-cable-suspended point end-effector robot, that of algae harvesting from large (1–4 acres) outdoor circulating pond systems. Algae, used as an alternative energy crop to produce biofuels (and other consumer products), still remain too expensive. One of the greatest expenses in processing algae is the harvesting process. To replace the typical energy-intensive pumping of the entire pond water through algae filters, we propose using a cable-suspended robot to collect algae, which largely then drains while the robot translates the product to a collection point. An additional benefit of our concept, in additional to lower harvesting cost, is that the algae still growing in the pond is not shocked as in the current pumping process, leading to better, healthier yields.
The Stability and Stiffness Analysis of a Dual-Triangle Planar Rotation Mechanism
Authors: Zhao Wanda , Pashkevich Anatol , Klimchik Alexandr , Chablat D.
Published: November 2020

The paper deals with the stiffness analysis and stability study of equilibrium configurations for dual-triangle tensegrity mechanism, which is actuated by adjusting elastic connections between the triangle edges. For this mechanism, the torque-deflection relation was obtained as a function of control inputs and geometric parameters. It was proved that the mechanism can has either a single or three equilibrium configurations that can be both stable and unstable. Corresponding conditions of stability were found allowing user to choose control inputs ensuring the mechanism controllability. The obtained results are confirmed by the simulation examples presented in the paper.
Systems of Systems Engineering to Improve Resilience: A Case Study Comparison of Biologically Inspired and Traditional Approaches
Authors: Watson Bryan C. , Weissburg Marc J. , Bras Bert
Published: November 2020

Systems of Systems (SoS) are networks of systems that operate together synergistically. The response of these SoS to unexpected constituent system failures can undermine their effectiveness. One potential solution is to increase the SoS’s hard (physical design) or soft (human intervention) resilience. The costs and demands on humans increase greater than linearly as SoS scale increases. These limitations require a novel approach to improve SoS resilience. We hypothesize that Biologically Inspired (BID) network design can improve SoS resilience. A systems dynamics model of a Forestry Industry is presented and an optimization search over potential hard and soft resilience approaches is compared to a BID network improvement. SoS resilience is measured through the newly developed SoSRM. Results provide evidence that BID network design provides an approach to increase SoS resilience beyond hard and soft resilience improvements alone (SoSRM increased from .922 to .926). Secondly, this work provides evidence that incorporating detrital actors increases SoS resilience (SoSRM increased from .909 to .926). Third, this paper documents the first case study that uses the new SoSRM metric to justify a design decision. Finally, we provide a counter-example to the theory that increased sustainability always results in increased resilience.
Design of a Compliant Hinge Based on Closed Form Pressure Balancing
Authors: Gomes Robin F. P. , Nijssen Joep P. A. , van Ostayen Ron A. J.
Published: November 2020

Compliant mechanisms consist of a monolithic body and obtain motion through elastic deformation. Multiple compliant flexure designs are known but their translational to rotation stiffness ratio is often limited. This work introduces a novel compliant hinge design with increased stiffness ratio compared to the state of the art compliant hinges. The hinge functions by having an encapsulated fluid medium that contributes to high normal stiffness, but doesn’t influence the rotational stiffness. A 2D design model is presented that shows the effect of the geometry on the stiffness ratio performance. Subsequently, a computational 3D analysis is performed and the resulting design is realized as a demonstrator. The performance is compared to conventional compliant hinges based on the stiffness ratio. This shows an increase of at least a factor 30 on the stiffness ratio.
Mechanical Redesign of a Transtibial Prosthesis With Active and Passive Components and a Four-Bar Mechanism
Authors: Plata Devon K. , Thayer Jessica B. , Voglewede Philip A.
Published: November 2020

This paper proposes a redesign of a four-bar mechanism for an active transtibial prosthesis created by Bergelin 2010 and modified by Klein 2009. Bergelin utilized a four-bar mechanism, motor, and spring to match the prosthesis ankle moments to the ankle moments of a healthy ankle. Bergelin’s prosthesis did succeed in matching ankle moments closely, but with excessive motor energy expenditure when the prosthesis was in a neutral position. Klein proposed a redesign of the mechanism to change the motor-spring connection from parallel to series to eliminate the energy requirement when the device is in neutral position, which allowed for the application of impedance control of mechanism. This paper proposes a reoptimization of the series motor-spring mechanism configuration proposed by Klein, which further reduces the energy input configuration of the active prosthesis.
Two-Dimensional Team Lifting Prediction With Different Box Weights
Authors: Arefeen Asif , Xiang Yujiang
Published: November 2020

A novel multibody dynamics modeling method is proposed for two-dimensional (2D) team lifting prediction. The box itself is modeled as a floating-base rigid body in Denavit-Hartenberg representation. The interactions between humans and box are modeled as a set of grasping forces which are treated as unknowns (design variables) in the optimization formulation. An inverse-dynamics-based optimization method is used to simulate the team lifting motion where the dynamic effort of two humans is minimized subjected to physical and task-based constraints. The design variables are control points of cubic B-splines of joint angle profiles of two humans and the box, and the grasping forces between humans and the box. Two numerical examples are successfully simulated with different box weights (20 Kg and 30 Kg, respectively). The humans’ joint angle, torque, ground reaction force, and grasping force profiles are reported. The joint angle profiles are validated with the experimental data.
Finite Element Models for Flexible Cosserat Solids
Authors: Bauchau Olivier A. , Shan Minghe
Published: November 2020

The application of the finite element method to the modeling of Cosserat solids is investigated in detail. In two- and three-dimensional elasticity problems, the nodal unknowns are the components of the displacement vector, which form a linear field. In contrast, when dealing with Cosserat solids, the nodal unknowns form the special Euclidean group SE(3), a nonlinear manifold. This observation has numerous implications on the implementation of the finite element method and raises numerous questions: (1) What is the most suitable representation of this nonlinear manifold? (2) How is it interpolated over one element? (3) How is the associated strain field interpolated? (4) What is the most efficient way to obtain the discrete equations of motion? All these questions are, of course intertwined. This paper shows that reliable schemes are available for the interpolation of the motion and curvature fields. The interpolated fields depend on relative nodal motions only, and hence, are both objective and tensorial. Because these schemes depend on relative nodal motions only, only local parameterization is required, thereby avoiding the occurrence of singularities. For Cosserat solids, it is preferable to perform the discretization operation first, followed by the variation operation. This approach leads to considerable computation efficiency and simplicity.
Developing Training Tools for Clinicians in LICs: Using Hidden Markov Modeling to Study the Decision-Making Strategies of Expert and Novice Prosthetists
Authors: Saravanan Pratima , Walker Michael , Menold Jessica
Published: November 2020

Approximately, 40 million amputees reside in the rural parts of Low-Income Countries (LICs), and 95% of this population do not have proper access to prosthetic devices and rehabilitation services. A proper prosthetic prescription requires a clear understanding of the patient’s ambulation, goals, cultural and societal norms, locally available prosthetic materials, etc., which can be accomplished only by a local prosthetist. However, due to the lack of prosthetic schools and training centers in LICs, the rural parts lack well-trained amputee care providers. Hence there is a need to educate the prosthetists and prosthetic technicians in the LIC, specifically in the rural regions. To accomplish this, the current research proposes a decision-support tool to aid decision-making during prescription and educate prosthetists. A controlled study was conducted with expert and novice prosthetists to compare effective decision-making strategies. Results suggest that experts leverage distinct decision-making strategies when prescribing prosthetic and orthotic devices; in comparison, novices exhibited less consistent patterns of decision-making tendencies. By modeling the decision-making strategies of expert prosthetists, this work lays the foundation to develop an automated decision support tool to support decision-making for prosthetists in LICs, improving overall amputee care.
Only As Strong As the Strongest Link: The Impact of Individual Team Member Proficiency in Configuration Design
Authors: Brownell Ethan , Cagan Jonathan , Kotovsky Kenneth
Published: November 2020

Prior research has demonstrated how the average characteristics of a team impact team performance. Individual characteristics of team members and individual team member behavior have been largely ignored, especially in the context of engineering design. In this work, a behavioral study was conducted to uncover whether the most or least proficient member of a configuration design team had a larger impact on overall performance. It was found that a configuration design team is most dependent on the proficiency of its most proficient member and results suggest that replacing the most proficient member with an even more proficient member can be expected to have a more positive impact than replacing any other member with a higher proficiency member of the same change in proficiency. The most proficient member had a significant positive effect on how quickly the team reached performance thresholds and that the other members of the team were not found to have the same positive impact throughout the design study. Behavioral heuristics were found using hidden Markov modeling to capture the differences in behavior and design strategy between different proficiency members. Results show that high proficiency and low proficiency team members exhibit different behavior, with the most proficient member’s behavior leading to topologically simpler designs and other members adopting their designs, leading to the most proficient member driving the team design and team performance.
Novice Designers’ Approaches to Justifying User Requirements and Engineering Specifications
Authors: Loweth Robert P. , Daly Shanna R. , Sienko Kathleen H. , Hortop Amy , Strehl Elizabeth A.
Published: November 2020

User requirements and engineering specifications represent important criteria that engineering designers use to define their design problems and evaluate the suitability of their solution concepts. Novice designers frequently develop user requirements and engineering specifications as part of curricular design projects; however, few studies have explored how novice designers justify the user requirements and engineering specifications that they develop. This preliminary study analyzed the design reports of capstone design teams to determine how novice designer participants justified their user requirements and engineering specifications. Teams frequently used “Sponsor interactions” and “Perceptions of user needs” as justifications for user requirements but gathered limited data directly from users. As such, the user requirements developed by teams may have been based on team assumptions rather than actual user needs. Teams frequently used “Sponsor interactions,” “Technical research,” and “Prior work” as justifications for engineering specifications. However, teams also developed several engineering specifications without clear justifications. Our findings suggest that as novice designers develop their design skills, they may need scaffolding and support tools to guide the development of user requirements and engineering specifications that accurately reflect user needs.
A Novel Gripping System for Delivery of Packages via Unmanned Aerial Vehicles
Authors: Maroo Trigun Dinesh , Wright Andrew B.
Published: November 2020

An Unmanned Aerial Vehicle (UAV) can carry packages to locations that are unreachable by a ground vehicle using a gripper that can handle standard sized packages. This paper presents a UAV-mounted system for grasping corrugated boxes. The proposed gripping system uses two pairs of end effectors which are arranged perpendicular to each other. All four grippers are geared so that they can be actuated by a single control input. The mechanism is designed to handle position and orientation errors of the box relative to the gripper. The gripper was experimentally validated using a test box that was misaligned in position and orientation.
Examine the Bending Stiffness of Generalized Kresling Modules for Robotic Manipulation
Authors: Kaufmann Joshua , Li Suyi
Published: November 2020

Via analytical modeling and experimental validation, this study examines the bending stiffness adaptation of bistable origami modules based on generalized Kresling pattern. These modules, which are the building blocks of an octopus-inspired robotic manipulator, can create a reconfigurable articulation via switching between their stable states. In this way, the manipulator can exhibit pseudo-linkage kinematics with lower control requirements and improved motion accuracy compared to completely soft manipulators. A key to achieving this reconfigurable articulation is that the underlying Kresling modules must show a sufficient difference in bending stiffness between their stable states. Therefore, this study aims to use both a nonlinear bar-hinge model and experimental testing to uncover the correlation between the module bending stiffness and the corresponding origami designs. The results show that the Kresling origami module can indeed exhibit a significant change in bending stiffness because of the reorientation of its triangular facets. That is, at one stable state, these facets align close to parallel to the longitudinal axis of the cylindrical-shaped module, so the module bending stiffness is relatively high and dominated by the facet stretching. However, at the other stable states, the triangular facets are orientated close to perpendicular to the longitudinal axis, so the bending stiffness is low and dominated by crease folding. The results of this study will provide the necessary design insights for constructing a fully functional manipulator with the desired articulation behavior.
A Novel Single-Step Unconditionally Stable Numerical Integration Scheme With Tunable Algorithmic Dissipation
Authors: Zhang Huimin , Zhang Runsen , Zanoni Andrea , Masarati Pierangelo
Published: November 2020

A novel single-step time integration method is proposed for general dynamic problems. From linear spectral analysis, the new method with optimal parameters has second-order accuracy, unconditional stability, controllable algorithmic dissipation and zero-order overshoot in displacement and velocity. Comparison of the proposed method with several representative implicit methods shows that the new method has higher accuracy than the single-step generalized-α method, and also than the composite P∞-Bathe method when mild algorithmic dissipation is used. Besides, this method is spectrally identical to the linear two-step method, although being easier to use since it does not need additional start-up procedures. Its numerical properties are assessed through numerical examples, and the new method shows competitive performance for both linear and nonlinear problems.
Optimizing Support for Heat Dissipation in Additive Manufacturing
Authors: Wang Cunfu , Qian Xiaoping
Published: November 2020

The paper presents a formulation for support optimization to maximize heat dissipation in additive manufacturing. To simulate heat transfer from the part to the supports, a boundary-dependent heat flux is applied on the part/support interface. Since the density-based topology optimization does not involve explicit boundary, the heat flux is implicitly imposed through a domain integration of a Heaviside projected density gradient. As such, this formulation also supports simultaneous optimization of support and parts in additive manufacturing. Self-supporting supports are obtained by controlling the anisotropic thermal conductivity of the supports. Three different objective functions related to heat dissipation efficiency are investigated. Numerical examples are presented to demonstrate the validity and efficiency of the proposed approach.
An Optimization Method for the Static Balancing of Manipulators Using Springs
Authors: Wang Jieyu , Kong Xianwen
Published: November 2020

This paper discusses a novel optimization method to design statically balanced manipulators. Only springs are used to balance the manipulators composed of revolute (R) joints. Since the total potential energy of the system is constant when statically balanced, the sum of squared differences between the two potential energy when giving different random values of joint variables is set as the objective function. Then the optimization tool of MATLAB is used to obtain the spring attachment points. The results show that for a 1-link manipulator mounted on an R joint, in addition to attaching the spring right above the R joint, the attachment point can have offset. It also indicates that an arbitrary spatial manipulator with n link, whose weight cannot be neglected, can be balanced using n springs. Using this method, the static balancing can be readily achieved, with multiple solutions.
A Sliding-Mode Control Algorithm to Enhance In-Hand Motion Capabilities
Authors: Kumar Rajesh , Mukherjee Joyjit , Mukherjee Sudipto
Published: November 2020

This paper reports a method for regulating the internal forces during in hand manipulation of an unknown shaped object with soft robotic fingers. It is known that for the case of multifingered manipulation, a part of the forces applied by the fingers result in the motion of the object, whereas the other part is considered to be an internal force. The internal forces do not result in the motion of the object but are used to improve the grip on the object. For an object with unknown shape, the internal forces are regulated to ensure that the object does not slip off during manipulation. It is shown that if soft fingers show bounded conformity and the finger-object interface does not have relative slip (or a bounded slip), then the relative angular velocity between the object and the fingertip frame in contact is bounded. The proof is used to define of a new metric of relative slip. The metric is used to design a sliding mode control algorithm. The robotic fingers are assumed to be under virtual rigidity constraint, that is, the distance between the fingers do not change. The control algorithm is attractive as it skirts requirement of information of the shape of the object or to solve optimization problems. The control algorithm developed controls the internal forces and does not require the knowledge of the shape of the object. The methodology is simulated for the case of one spherical object and one conical object.
Optimized Design and Performance Study of High Speed Five-Axis Machine Tools
Authors: Chan Tzu-Chi , Yang Jyun-Sian
Published: November 2020

With the development of machine tools trending toward high precision, intelligence, multi-axis, and high speed, the improvement of the processing performance and rigidity of the machine is considerably important.

The objective of this study is to design of a high-speed five-axis moving-column machine tool and perform structural analysis and optimization. We study the static and dynamic characteristics of the five-axis machine tool, design and improve the mechanical structure, and optimize the structural configuration of the machine. The entire machine structure is further analyzed and enhanced to improve its static and dynamic characteristics, including static rigidity, modal, transient, and spectral response characteristics. The static and dynamic characteristics of the machine structure directly affect the machine processing performance, and further affect the work piece precision machined by the tool. Through this study, the design technology for speed, accuracy, and surface roughness of the machine tool are further improved.
Compliant Interface in Component Mode Synthesis
Authors: Masarati Pierangelo , Darbas Fanny , Wander Israël
Published: November 2020

Substructuring, or component mode synthesis, requires components to share interface regions. When components modeled with rather different, often incompatible levels of refinement need to be connected, correctly defining the interfaces may be important. This work proposes the definition of the reduction of interface regions to the equivalent rigid-body motion which minimizes the strain energy in the structural component. The proposed formulation provides a natural and physically sound solution for the connection of detailed structural components within coarse, multi-rigid-body and 1D flexible models.
Natural Frequency Based Topology Optimization of an Aircraft Engine Support Frame
Authors: Warwick Braden T. , Mechefske Chris K. , Kim Il Yong
Published: November 2020

The multi-stage design space refinement (MSDSR) technique increases the likelihood of convergence of topology optimization (TO) with large volume fraction constraints. This work considers MSDSR TO of an aircraft engine support frame with a natural frequency-based objective function. The problem statement maximized the first natural frequency, effectively maximizing the stiffness to mass ratio of the frame. The problem statement considered natural frequency constraints, which eliminated all natural frequencies within 5% of the engine excitation frequency times a safety factor of two. The design space did not consider the initial geometry; therefore, allowing for the determination of the optimal stiffener location on the initial geometry. The results of this work increased the first natural frequency of the engine support frame by 25.9%, eliminated all natural frequencies within 11.3% of the engine excitation frequency, and added only 0.253 kg of mass to the frame. The results of this work further demonstrate the advantages of MSDSR TO and the impact that it can have on the aerospace industry. Specifically, the design space considered in this work allows for the structural reinforcement of a pre-existing design, which is easier to implement and easier to regulate than similar results from the literature.
Integrated Strategy for Automatic Lane-Changing Decision and Trajectory Planning in Dynamic Scenario
Authors: Ren Meng , Wu Guangqiang
Published: November 2020

Automatic lane change is a necessary part for autonomous driving. This paper proposes an integrated strategy for automatic lane-changing decision and trajectory planning in dynamic scenario. The Back Propagation Neural Network (BPNN) is used in decision-making layer, whose prediction accuracy of the discretionary lane-changing is 94.22%. The planning layer determines the adjustable range of the average vehicle speed based on the size of the “lane-changing demand”, which is obtained based on the data of hidden layer in neural network, and then dynamically optimizes the lane-changing curve according to the vehicle speed and the current scenario. In order to verify the rationality of the proposed lane-changing architecture, simulation experiments based on a driving simulator is performed. The experiments show that the vehicle’s maximum lateral acceleration under the proposed lane-changing trajectory at a speed of 70km/h is about 0.1g, which means the vehicle has better comfort during lane-changing. At the same time, the proposed lane-changing trajectory is more in line with the human driver’s lane-changing trajectory compared with that of other planning strategy. Meanwhile, the planning strategy can also support the lane-changing trajectory planning on a curved road.
Comparison of Soft Curved Crease Surrogate Hinges
Authors: Klett Yves , Middendorf Peter , Muhs Fabian , Tachi Tomohiro
Published: November 2020

The use of compliant hinges as integral elements of origami-based and origami-inspired structures can provide significant benefits compared to other hinge concepts, namely ease of integration, durability and tunable stiffness, range and target positioning of the hinge. So far, mostly classical straight-crease constructions have been used for the application of such hinges. Curved-crease geometries impose new constraints on the application of compliant elements in the crease region due to the implicit surface curvature in every non-flat folding state. This paper introduces a new, simple surrogate hinge based on angled slash arrays, and compares their behavior to classical lamina-emergent surrogate hinges.
Temperature Control to Increase Inter-Layer Bonding Strength in Fused Deposition Modelling
Authors: Kumrai-Woodruff Raoul , Wang Qing
Published: November 2020

Fused Deposition Modelling (FDM) provides opportunities for new development in numerous areas. Z-directional anisotropic strength caused by weak inter-layer bonding has been recognized as the reason for limited industry adoption of FDM. This paper aims to investigate increasing the Z-directional strength of Acrylonitrile Butadiene Styrene (ABS) using a temperature controlled print environment. The ambient temperature during printing was increased to reduce heat transfer from the print, thereby encouraging more polymer chain inter-diffusion between layers. Dogbone specimens were printed at ambient print temperatures between 24.8°C and 71.2°C and tensile tests were performed. A thermal camera was used to identify heat loss in the FDM process. Ultimate tensile strength was found to increase by a maximum of 104% compared to open enclosure printing. A stylus profiler and scanning electron microscopy were used to compare the quality of the inter-layer bonds, suggesting that additional polymer inter-diffusion occurred at hotter ambient temperatures. A weak positive relationship was found between ambient air temperature and inter-layer part strength. Further experimentation could provide scope to determine an ideal ambient print temperature that is likely to be dependent on print settings and the printer used.
The Influence of Heat Exchanges on Friction in Robotic Joints: Theoretical Modelling, Identification and Experiments
Authors: Pagani Roberto , Legnani Giovanni , Incerti Giovanni , Beschi Manuel , Tiboni Monica
Published: November 2020

This paper presents a model that describes the effect of heat exchange on dynamic friction in the joints of an industrial robot. As concern the modeling of friction as a function of the rotation speed of the joint, a third degree polynomial is used. The coefficients of the polynomial, which depends on the temperature, are estimated by means of a suitable identification procedure. The proposed technique is simple to implement and economically convenient. Experimental tests have shown that the method here proposed, despite its simplicity, can estimate with good reliability the variations of friction that occur during the operation of an industrial robot due to thermal effects. Possible fields of application are the improvement of the friction compensation algorithms used for robot control systems and the prediction of energy consumption.
Design Science Meets Data Science: Curating Large Design Datasets for Engineered Artifacts
Authors: Ramnath Satchit , Haghighi Payam , Ma Jiachen , Shah Jami J. , Detwiler Duane
Published: November 2020

Machine learning is opening up new ways of optimizing designs, but it requires large data sets for training and verification. The primary focus of this paper is to explain the trade-offs between generating a large data set and the level of idealization required to automate the process of generating such a data set. This paper discusses the efforts in curating a large CAD data set with the desired variety and validity of automotive body structures. A method to incorporate constraint networks to filter invalid designs, prior to the start of model generation is explained. Since the geometric configurations and characteristics need to be correlated to performance (structural integrity), the paper also demonstrates automated workflows to perform finite element analysis on 3D CAD models generated. Key simulation results can then be associated with CAD geometry and fed to the machine learning algorithms. With the increase in computing power and network speed, such datasets could assist in generating better designs, which could potentially be obtained by a combination of existing ones, or might provide insights into completely new design concepts meeting or exceeding the performance requirements. The approach is explained using the hood frame as an example, but the same can be adopted to other design components.
3D Additive Lattice Topology Optimization: A Unit Cell Design Approach
Authors: Hanks Bradley , Frecker Mary
Published: November 2020

Non-stochastic lattice structures are patterned after the unit cell topology and are of interest to the research and design communities for improving stiffness to weight ratios and/or metamaterial design. While additive manufacturing (AM) increases design freedom, it remains difficult to design or select an appropriate unit cell topology. In this work, a ground structure topology optimization approach is developed for unit cell design. Using a multi-objective evolutionary algorithm, this framework incorporates a library of different objectives, constraints, and penalties. The Additive Lattice Topology Optimization (ALTO) approach generates novel lattice structures for AM from the selected design objectives. A key purpose of this framework is incorporating AM process considerations into the optimization through objectives, constraints, and penalty functions for improved manufacturability. Two case studies presented in this work demonstrate ALTO’s ability to generate novel lattice structures with specific functionality while accounting for AM process constraints for laser powder bed fusion. Case Study 1 is an example of generating a lattice structure for heat sink applications. Case Study 2 demonstrates creation of three novel lattices with different stiffness properties, each with the same volume fraction. Using ground structure topology optimization and incorporating AM process considerations, ALTO is a unique approach for improved lattice structure design.
316L Stainless Steel Sensitization in Carbon Nanotube CVD Growth for Bacterial Resistance
Authors: Voss Sterling , Mecham Bret , Bowden Lucy , Monroe Jacquelyn , Bowden Anton E. , Jensen Brian D.
Published: November 2020

Physically altering the micro-topography of a surface can dramatically affect its capacity to support or prevent biofilm growth. Growing carbon-infiltrated carbon nanotubes on biomedical materials is one such approach which has proven effective. Unfortunately, the high temperature and carbon-rich gas exposure required for this procedure has proven to have deleterious effects. This paper proposes a kinetic model to explain the rusting phenomenon observed on 316L stainless steel substrates which have undergone the chemical vapor deposition process to grow carbon-infiltrated carbon nanotubes. The model is derived from Fick’s Second Law, and predicts the growth of chromium carbide as a function of temperature and time. Chromium carbide formation is shown to be the mechanism of corrosion, as chromium atoms are leeched from the the matrix, preventing the formation of a passivating chromium oxide layer in place of problematic iron oxide (rust) formation. The model is validated using experimental methods, which involve immersion in bacteria culture, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX).
Comfort-Oriented Design of Model Predictive Control in Assisted and Autonomous Driving
Authors: Luciani Sara , Bonfitto Angelo , Amati Nicola , Tonoli Andrea
Published: November 2020

This paper presents a method based on a Model Predictive Control (MPC) aiming to optimize the passenger comforts in assisted and autonomous vehicles. The controller works on the lateral and longitudinal dynamics of the car, providing front wheel steering angle and acceleration/deceleration command. The comfort is evaluated through two indexes extracted from the ISO 2631: an equivalent acceleration aeq and a Motion Sickness Dose Value (MSDV) index. The MPC weighting parameters are designed according to the values assumed by these indexes. Specifically, each weighting parameter is changed until the most satisfying comfort evaluation and the maximum vehicle performances, in terms of lateral deviation, tracking velocity and relative yaw angle, are reached. The controller is tested numerically on a simulated scenario resulting from real GPS data obtained in a highway. The method is compared with an alternative control strategy based on the combination of a PID and a Stanley control for the longitudinal and lateral dynamics, respectively. The results demonstrate the effectiveness of the approach, leading to a low percentage of passengers can experience motion sickness.
A Novel Compliant Bistable Mechanism Incorporating a Fixed-Guided Flexural Member
Authors: Joo James J. , Myszka David H.
Published: November 2020

This paper presents the design of a novel compliant bistable mechanism. Bistable mechanisms are commonly used in switches and other devices that operate in two distinct modes. This mechanism is a single monolithic structure with simple geometry and does not require external components or post-manufacture assembly. As such, the design is ideally suited for additive manufacturing at large, or micro, scales. The design features a fixed-guided flexural member with surrounding geometry. When a load is applied to the mechanism in a stable configuration, the flexural member exhibits an inflection point that enables bifurcated behavior. As a result, the mechanism snaps between two stable positions in an on-off operation mode. This paper describes the mechanism geometry and its operation. Preliminary design modeling equations are formulated. A finite element simulation is presented that verifies the design equations. Lastly, a prototype is presented to confirm the operation and facilitate force and displacement measurements.
A Mobility Determination Method for Parallel Platforms Based on the Lie Algebra of SE(3) and its Subspaces
Authors: Sánchez-García A. J. , Rico J. M. , Cervantes-Sánchez J. J. , López-Custodio P. C.
Published: November 2020

This contribution presents a screw theory-based method for determining the mobility of fully parallel platforms. The method is based in the application of three stages. The first stage involves the application of the intersection of the subalgebras of Lie algebra, se(3), of the special Euclidean group, SE(3), associated with the legs of the platform. The second stage analyzes the possibility of the legs of the platform generating a sum or direct sum of two subalgebras of the Lie algebra, se(3). The last stage, if necessary, considers the possibility of the kinematic pairs of the legs satisfying certain velocity conditions; these conditions allow to reduce the platform’s mobility analysis to one that can solved using one of the two previous stages.
A Computational Framework Enabling Comparative Analysis of Progressive Damage Models for Composite Materials
Authors: Apetre N. A. , Michopoulos J. G. , Iliopoulos A. P. , Steuben J. C. , Phan N.
Published: November 2020

The present work is motivated by the need for an efficient and quantifiable assessment of how various strain- or stress-based composite materials failure criteria and damage evolution models that capture the load-induced material degradation, along with their intrinsic parameters, can affect our understanding of material behavior and facilitate suitability decisions of such criteria. The difficulty of performing comparative analysis among many of these criteria and models has been a significant impediment to the composite materials design and material certification communities. In response to these needs, the present work describes the development, verification and validation of such a general computational framework. This framework enables not only increasing the user’s understanding of the effect of parameters associated with models under consideration on the model predicted results but also allowing the user to address more advanced problems such as material design, optimization and potentially certification. The framework implemented into “COMSOL Multiphysics” utilizes symbolic algebra to automatically generate the required expressions to be used in the respective computational modules. Two strain-based models for two distinct specimen geometries are used to show the framework capabilities: one model is described by three damage modes and a second one is given by four damage modes. The first geometry is that of a unnotched coupon whereas the second is that of an open hole specimen in tension. The theoretical predictions are compared with the experimental ones in terms of load-strain responses. The results indicate that by proper selection of specific input parameters, these models can accurately predict the structural response of composite laminate structural systems up to failure.
A New Approach to Solution of Time-Independent One-Dimensional Schrödinger Wave Equation
Authors: Sinha Alok
Published: November 2020

A new approach has been developed in this paper to solve time-independent Schrödinger wave equation for any arbitrary potential and space varying mass as well. The method is based on the state transition matrix used in the analysis of linear time-varying systems, and can determine both bound states and reflection and transmission coefficients associated with scattering problems. Numerical examples for the computation of eigenvalues and eigenmodes associated with bound states are presented for quadratic potential, quartic potential, constant potential well and arbitrary potential well with both constant and space-varying or position-dependent masses. Similarly, transmission coefficients for scattering problems without any infinite potential, and time delays for scattering problems with an infinite potential are computed for arbitrary potential wells.
Measured Data Alignments for Monitoring Metal Additive Manufacturing Processes Using Laser Powder Bed Fusion Methods
Authors: Feng Shaw C. , Lu Yan , Jones Albert T.
Published: November 2020

The number and types of measurement devices used for monitoring and controlling Laser-Based Powder Bed Fusion of Metals (PBF-LB/M) processes and inspecting the resulting AM metal parts have increased rapidly in recent years. The variety of the data collected by such devices has increased, and the veracity of the data has decreased simultaneously. Each measurement device generates data in a unique coordinate system and in a unique data type. Data alignment, however, is required before 1) monitoring and controlling PBF-LB/M processes, 2) predicting the material properties of the final part, and 3) qualifying the resulting AM parts can be done. Aligned means all data must be transformed into a single coordinate system. In this paper, we describe a new, general data-alignment procedure and an example based on PBF-LB/M processes. The specific data objects used in this example include in-situ photogrammetry, thermography, ex-situ X-ray computed tomography (XCT), coordinate metrology, and computer-aided design (CAD) models. We propose a data-alignment procedure to align the data from melt pool images, scan paths, layer images, XCT three-dimensional (3D) model, coordinate measurements, and the 3D CAD model.
Analysis of High Fidelity Modeling of Drone Dynamics and Aerodynamics for Reduced Energy Consumption
Authors: Hoang Samantha , Marsh Laurel , Aliseda Alberto , Shen I. Y.
Published: November 2020

This paper studies the effect of rotor blade aerodynamics and rotor grouping on the accuracy of open-loop simulations with respect to generated trajectories and energy consumption for multi-rotor drones. To examine these effects an 18-rotor high performance drone carrying a 30 kg payload is used. The effect of the rotor blade aerodynamic model on simulation results is examined by comparing roll, pitch, yaw, and vertical motion trajectories produced when using blade element theory model with trajectories produced when using a lumped blade model. The results show a 20% difference between the maximum roll and pitch angle achieved, a 58% difference in maximum altitude achieved, and a 91% percent difference in the maximum yaw angle achieved. These results indicate that the choice of aerodynamic model for the rotor blades has a significant effect on the simulated trajectories and in the calculated energy consumption of those trajectories. The effect of rotor groupings on energy consumption is examined by comparing two different rotor groupings for the 18-rotor drone. Roll, pitch, and yaw motions are simulated for both groupings and the resulting energy calculation shows a 4–5% difference in energy with a motor efficiency curve and a 8–9% difference with a motor efficiency curve included in the power calculation. These results indicate that rotor grouping is important in over-actuated drones for reducing the overall energy consumption of the drone, and thus increase its endurance. This energy reduction may become especially important when closing the loop with a control system or in extreme flight conditions such as stall or strong gusts.
Orthogonal Distance Fields Representation for Machine-Learning Based Manufacturability Analysis
Authors: Balu Aditya , Ghadai Sambit , Sarkar Soumik , Krishnamurthy Adarsh
Published: November 2020

Computer-aided Design for Manufacturing (DFM) systems play an essential role in reducing the time taken for product development by providing manufacturability feedback to the designer before the manufacturing phase. Traditionally, DFM rules are hand-crafted and used to accelerate the engineering product design process by integrating manufacturability analysis during design. Recently, the feasibility of using a machine learning-based DFM tool in intelligently applying the DFM rules have been studied. These tools use a voxelized representation of the design and then use a 3D-Convolutional Neural Network (3D-CNN), to provide manufacturability feedback. Although these frameworks work effectively, there are some limitations to the voxelized representation of the design. In this paper, we introduce a new representation of the computer-aided design (CAD) model using orthogonal distance fields (ODF). We provide a GPU-accelerated algorithm to convert standard boundary representation (B-rep) CAD models into ODF representation. Using the ODF representation, we build a machine learning framework, similar to earlier approaches, to create a machine learning-based DFM system to provide manufacturability feedback. As proof of concept, we apply this framework to assess the manufacturability of drilled holes. The framework has an accuracy of more than 84% correctly classifying the manufacturable and non-manufacturable models using the new representation.
Improving Linearity of Circular Capacitive Pressure Sensor by Using a Dimple Mask
Authors: Bhuiyan Md Ebrahim Khalil , Shavezipur Mohammad
Published: November 2020

A new design concept for MEMS capacitive pressure sensors is presented that can be used to improve the linearity of the capacitance-pressure (C-T) response of the sensor. The sensor uses an extra dimple mask and etching step in the fabrication process of the device to create small bumps under the pressure sensitive and flexible membrane. Different designs, including a conventional sensor, are modeled and simulated using FEM coupled-field multiphysics solver in ANSYS®. Polycrystalline silicon is used as the structural material in the simulations. Coefficient of linear correlation between device capacitance and ambient pressure is used as the linearity factor to quantitatively compare the performance of different sensors. The finite element analysis show that the linearity factor improves from 0.938 for a conventional design to 0.973 for a design with a central bump. For a design with five bumps (one at the center of membrane and four off-center) the linearity factor increases to 0.997 for bumps of 1.5 μm thickness for wide pressure range of 0.0–4.0 MPa. The proposed design can be tailored for different applications that require certain sensor materials or different pressure ranges by using optimized sensor dimensions.
Back and Forth: Using Conversation Analysis to Explore Dialogues of Sharedness of Mental Models
Authors: Yi Sue , Damen Nicole B. , Toh Christine A.
Published: November 2020

Shared mental models have been shown to enhance team performance. However, research has not observed the different types of sharedness of mental models that may uniquely impact the design process. Therefore, this study examines the types of sharedness of mental models that occur in design teams using Conversation Analysis on data collected from two design teams that performed activities in the early design process in a controlled lab environment. Designers were asked to develop an agreed upon list of ranked design principles, and then generate one or two solutions using the list. These design activities allow for the examination of the varying ways that designers share knowledge, negotiate, and reach understanding. Through our analysis, we identify characteristics of conversation that designers used to build shared understanding. Our results also show how team mental models are built from patterns of conversation that are evident during open-ended and unstructured design discussions. This work sets a foundation for future research to gain a deeper understanding of how designer mental models are shared in unstructured conversations that take place during design practice.