bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Characterization of Polyurethane Adhesive: Independence of Environmental and Mechanical Aging
Authors: Shaafaey Mamoon , Bahrololoumi Amir , Dargazany Roozbeh
Published: February 2023

Assessment of the durability of elastomers for structural applications has been of much interest among the literary circles for quite some time. All polymeric materials undergo degradation when in contact with aggressive environmental agents like humidity, water, and temperature. This rate of degradation should increase with the growing intensity of the ambient environmental agents involved. On the other hand, during service life, these materials are also subjected to mechanical loading in one way or the other. The rate and extent of degradation can be accessed by scrutinizing the changes in constitutive behavior of material through mechanical and chemical properties. Accelerated thermal, hydrolytic, and hygrothermal aging are among the most common modes of process-related degradation, leading generally to chain scission, cross-linking phenomena, and reduced resistance to fracture stress and strain. In this experimental study, our goal is to separate the environmental degradation from mechanical damage. A polyurethane based (PUB) adhesive was aged in thermo-oxidative (0%RH), hydrolytic aging, and hygrothermal (80%RH) aging environments. The damage and decay mechanisms have been used to draw a distinction between environmental degradation and mechanical damage. Material characterization included cyclic tensile tests, gravimetric measurements to observe water-uptake, FTIR and scanning electron microscopy (SEM) tests on as-received and aged samples. Aging was conducted at three different temperatures (60°C, 80°C and 95°C) and four different exposure durations (1, 10, 30, and 90 days). This work confirms that environmental degradation is separable from mechanical damage. Data collected during gravimetric measurements indicate that during aging in desalinated water, water uptake increases linearly with the square root of the aging duration, which agrees with Fick’s second law. Increasing water uptake is proportional to decreasing tensile strength and toughness of the material. The total mechanical and environmental damage is a synergized effect of all exposure conditions and parameters involved i.e. aging time, temperature, oxygen, water, and humidity. The chemistry and mechanics of the polymer degradation were found to be in good agreement with each other.
Effect of Pyrolysis-Front Velocity on the Properties of Biochar Produced With a TLUD Reactor
Authors: Nasef Ziad , Gomez Hector , Mondal Sourov Kumar , Diaz Gerardo
Published: February 2023

Biochar is produced by pyrolysis process which is the thermal decomposition of organic material, usually at temperatures between 300 and 800°C with little to no oxygen. One technology that falls into the category of low-cost pyrolysis reactor is the Top Lit Up Draft (TLUD). It utilizes a batch process where the biomass is lit at the top. The descending pyrolysis zone eventually reaches the bottom of the fuel, completing the conversion process and resulting in production of biochar. The reactor uses a forced draft of air supplied at the bottom. An experimental approach was used in this paper to study the TLUD configuration for almond shells, where temperature profiles are shown inside the pyrolysis reactor (pyrolyzer). The correlation between primary airflow and pyrolysis front downward velocity was studied, where the effect of insulation was experimentally analyzed. The volatile gases produced were combusted using an external burner to reduce air pollution. The contribution of this paper is to correlate uniformity of the final product with ambient temperature and pyrolysis front speed. Experiments were carried out for 5, 10 and 15 Lmin−1 airflows with and without insulation. This paper creates a framework for the addition of a control scheme that may ensure uniform quality of biochar produced in TLUD configuration.
Characterizing Swimming Locomotions of an Asymmetrical Soft Millirobot in a Rotating Magnetic Field
Authors: Bagley Jake T. , Quasebarth Graham B. , Kim Dal Hyung
Published: February 2023

Millimeter-scale robots have many applications in bioengineering fields due to their ability to be actuated remotely. Certain forms of locomotion allow them to achieve high swim speeds while maintaining controllability. The corkscrew locomotions have been achieved in previous soft robot studies, but their swim speeds were much lower than those exhibited by soft robots of different locomotions. In this paper, a corkscrew swimming motion with a high swim speed was achieved with a 3D rotating magnetic field by designing an asymmetrical soft robot made of flexible polymer embedded with magnetic particles and magnetized at a specific orientation. While this robot exhibited a rolling and transient locomotion at magnetic field frequencies lower than 40 Hz, at frequencies above 40 Hz, the robot exhibited corkscrew swimming locomotion. The swimming speed peaked at a velocity of about 30 mm/s at a magnetic field frequency of 49 Hz. Beyond this frequency, the swim speed of the soft robot decreased because the rotational frequency of the robot could not match the frequency of the actuating magnetic field.
Improvement of the Sensitivity and Selectivity of Gas Molecules of Graphene-Base Gas Sensor With Carbon Nanotubes Under the Application of Strain
Authors: Hirose Yuto , Qiao Xiangyu , Fu Wangyang , Suzuki Ken , Miura Hideo
Published: February 2023

A biochemical sensor using graphene nanoribbons as a sensing element was developed for a new generation highly sensitive and compact multi-gas sensor of human’s breath for the early detection of various diseases. Even though the resistance changes of graphene appeared by adsorption of various gases, it was impossible to identify the gas molecules individually when plural kinds of gas molecules adsorbed on graphene at the same time. No selectivity was confirmed so far. In this study, to improve the sensitivity and selectivity of graphene-base gas sensor, carbon nanotubes (CNTs) were directly synthesized on graphene for increasing the area of the molecular adsorption surface. The synthesis of graphene was carried out inside a low-pressure chemical vapor deposition chamber on a copper catalyst substrate with very high purity. The grown graphene was then, transferred onto a Si/SiO2 substrate. No damage was confirmed in graphene during this transfer process. A thermochemical vapor deposition method was also applied to the production of a CNT layer directly on the GNR sensor elements. The stable ohmic contact between the synthesized CNTs and the base graphene layer was confirmed. The graphene-base gas sensor with a CNT layer showed drastic increase in the sensitivity of gas molecules comparing with a conventional single graphene-base sensor.
Numerical Study on Convective Heat Transfer Performance in Helix Lattice Sandwich Panel
Authors: Li Shulei , Zhang Shibo , Xie Gongnan , Yan Hongbin
Published: February 2023

Sandwich structures have been widely used as thermal and load-bearing materials in astronautic and aeronautic applications. owing to their advantages of high specific strength and stiffness. Among them, the X-type lattice cored sandwich panel has a superior thermal performance, with a larger pressure drop. In order to solve the disadvantage of higher pressure drop of the X-type lattice, this paper propose a new structure of helix lattice sandwich panel by modifying the structure of the X-type lattice at a similar porosity level. Forced convection of air in the helix lattice sandwich panel was numerically studied based on the validated model in available literature. The flow and heat transfer characteristics between the helix lattice and X-type lattice were compared. Results reveal that the fluid flow pattern of the helix lattice and the X-type lattice have similarities and differences. The similarity is that both of them cause a spiral type of flow and two same type of secondary flow, the difference is that compared with X-type lattice, the smaller blockage of flow area by the ligaments of the helix lattice leads to a large smooth mainstream. Besides, the overall Nusselt number of the helix lattice is slightly lower than that of X-type one with an average value of 6.69% at a certain Reynolds number, the same material thermal conductivity and similar porosity level. Although the flow pattern in the helix lattice is similar to that in X-type lattice, the smooth mainstream in the helix lattice inevitably limited the flow mixing which lead to a lower area-averaged Nusslet number on both the substrates and the ligaments relative to X-type one. However, in terms of pressure drop, the helix lattice is significantly lower than the X-type lattice due to smaller flow area blockage and smooth ligament structure, which is reduced by nearly half. The helix lattice core sandwich panel can maintain a high level heat transfer performance with little loss of pressure drop. For a given pumping power, the helix lattice outperforms X-type lattice by up to 6.65%. Furthermore, as the pumping power increases, the heat transfer performance of the helix lattice will be better than X-type lattice. Therefore, it can be considered that the helix lattice core sandwich panel solves the disadvantage of relatively high pressure drop in the X-type lattice, greatly reduced the pressure drop and the required pumping power with less heat transfer performance loss. The helix lattice core sandwich panel has a superior comprehensive heat transfer performance than X-type one.
Predicting the Hounsfield Unit (HU) of Aluminum Alloy AA2011 From the Weight Fractions of its Alloying Elements: An X-Ray Computed Tomography Study
Authors: Baydoun Ahmad M. R. , Hamade Ramsey F.
Published: February 2023

X-ray computed tomography scans are being increasingly employed as a non-destructive testing method for the detection of internal defects and material identification. However, mean Hounsfield Unit (HU) measurements for many metals and alloys are unreported in the literature due to the high HU values of metals and their alloys and also due to the wide range of possible combinations of X-ray scanning parameters. For this reason, developing a method that can accurately predict the mean Hounsfield unit value of a material given its elemental composition and mean Hounsfield measurements of its constituent elements is valuable and can help fill the gap for under-reported materials.

In this study, first, the mean Hounsfield values for AA2011 are predicted using two methods based on the mixture model. Second, the effect of the X-ray scanning parameters on the predictive accuracy of the mean Hounsfield Unit value for AA2011 is studied. To this end, X-ray CT scans are performed at three X-ray tube current levels (50, 100, and 200 mAs) and two tube voltage levels (120 and 140kVp). Also considered is the effect of scan window size (field of scan view) as represented by voxel size where three sizes (0.00287, 0.0176, and 0.0452 mm3) are utilized. The effect of sample thickness is assessed via three thickness levels (1.5, 3, and 6 mm). The findings show that both methods show good predictive ability with the second method showing greater accuracy.
An Experimental Investigation of the Mechanical Behavior of 3D Printed Structures As a Function of Manufacturing Process Decisions
Authors: Hamel Josh , Kamla Logan
Published: February 2023

When using additive manufacturing (AM) systems to fabricate functional parts built up in a layer-by-layer fashion, designers are required to make numerous decisions with respect to manufacturing processes parameters that can have significant impacts on how the resulting parts will perform under loading. One such parameter of interest is the orientation of the part within the build volume of the AM system utilized during fabrication. This parameter is important because the choice of build angle will directly impact how applied loads are transmitted to the bonded layers of the finished part. This paper presents the results of an experimental study specifically designed to explore this important factor and its effect on several key mechanical properties, including bending stiffness, ultimate strength, and toughness. This study consisted of printing and testing a large set of simple functional parts using a wide variety of build angle geometries, in addition to also considering other common process parameters focused on by previous studies. This study considered parts produced using two different AM technologies (material extrusion and vat polymerization), and multiple printing materials, in order to generate a dataset that can be used to inform the modeling and design of functional parts to be manufactured via various AM systems. The results produced show general agreement with previous similar studies, and the effects of build orientation present in the dataset generated clearly show the need for designers to consider this important parameter carefully when designing parts for AM applications. The results of this study also demonstrate the need for continued research on this critical topic to the field of AM in general.
Inhomogeneous Microstructure due to Non-Uniform Solidification Rate in NiTi Triply Periodic Minimal Surface (TPMS) Structures Fabricated via Laser Powder Bed Fusion
Authors: Hussain Shahadat , Alagha Ali N. , Zaki Wael
Published: February 2023

In recent times, interest in the fabrication of porous NiTi structures have grown significantly. Porous structures have remarkable potential to be used in the areas of tissue engineering, impact absorption, and fluid permeability. However, fabrication of NiTi structures poses challenges such as poor machinability, high work hardening, and inherent springback effects, which render them difficult to tackle through conventional manufacturing routes. Additive manufacturing (AM) can alleviate the aforementioned issues associated with NiTi shape memory alloys (SMAs). In addition, this technology can be employed for producing metallic scaffolds and porous structures of complex architectural details. Recently, a class of minimal surface topologies, known as triply periodic minimal surface (TPMS) structures has emerged as an attractive configuration for building architected constructs. Very little work can be found in the literature addressing the fabrication of NiTi TPMS structures and investigating their behaviors. The complex geometries of these structures may influence the dynamics of the melt pool in beam-based AM processes as well as the solidification rate within different regions of a product, thereby affecting the microstructures of fabricated parts. An inhomogeneity in microstructures of fabricated parts was observed, which motivated a detailed examination of these structures. The novelty of the present work lies in studying the influence of geometries of NiTi TPMS lattices along with laser process parameters.
Modeling Thermal Behavior and Residual Stress for Layer-by-Layer Rotated Scan Direction in Laser Powder Bed Fusion Process
Authors: Roney Md. Saidur Rahman , Ahsan Nazmul , Sezer Hayri , Tang Joseph , Kaul Sudhir , Ahmed Hossain
Published: February 2023

Laser powder bed fusion (LPBF) is an Additive Manufacturing (AM) process that uses a laser beam to solidify powder particles following a predefined pattern on a powder bed to build a part layer-by-layer as per a CAD model. In LPBF, the moving heat source and the rapid solidification cause nonuniform variations in temperature along the build part. This transient and moving heating and cooling process causes uneven expansion and shrinkage of the part that leads to the development of residual stresses in the part. The residual stresses depend on the thermal history of the part and may eventually lead to part distortion, crack initiation, warpage, etc. The present study represents the effect of altering the scan pattern layer-by-layer on the residual stress. Furthermore, a novel alternating double pass spiral scan pattern is introduced and compared with alternating island zigzag, alternating zigzag, regular zigzag, and spiral out-center patterns on the basis of thermal distribution and residual stress. Numerical approach is used to solve the governing equations. It is observed that residual stress greatly depends on thermal distribution. The variation in inherent residual stress is found to be lower for alternating zigzag pattern than regular zigzag pattern due to more even thermal distribution. Furthermore, the novel pattern also effectively distributes the heat which contributes to the reduction of inherent residual stress from the first layer. On the other hand, it is found that the alternating island zigzag scan pattern increases island temperature that can prevent rapid solidification. Overall, the findings of this study can be helpful in understanding the effects of altering scan directions layer-by-layer and in identifying a scan strategy that can enhance the usability of the powder bed fusion additive manufacturing technology.
Vision Based Safe Navigation of UAV for Overhead Line Inspection Enabled by Virtual Safety Bubble
Authors: Salim Rufaidah , Rezk Mahmoud , Anzil Mohammed Minhas , AlJasmi Nawal , Shukla Amit
Published: February 2023

Energy transmission systems have expanded significantly, given the increase in demand for power generation. This increase in size has led to the need of a robust inspection method. Overhead Line (OHL) systems consist of many critical components such as insulators, poles, and power lines, which need to be inspected regularly. With recent advancements, drones equipped with multiple sensors are flown, either manually or autonomously, for inspection. This paper proposes autonomous vision-based navigation of the drone over OHL. The navigation is achieved through the feedback from the camera onboard the drone. A deep learning-based model is developed for the detection of the various OHL components, which are then utilized to design the path for the drone to navigate. Furthermore, a virtual safety bubble (VSB) is developed around the drone upon the detection of the components. This VSB is part of local autonomy of the drone and ensures that a constant safe distance is always maintained from the components. This approach can help reduce the overall inspection time of OHL with less cognitive load on the operator. It also ensures the safety of the OHL installations and drone. Although the paper focuses mainly on running the experiments in a simulation environment, this could be imitated in real-life situations.
Approach for Kano-IPA Analysis of Product Attributes From Online Reviews and Product Maintenance Records
Authors: Cheng Aoxiang , Shen Mengyuan , Bi Youyi
Published: February 2023

Kano analysis and importance-performance analysis (IPA) are widely used for needs analysis, product positioning, and strategic planning in product design. Previous research uses customer surveys and online reviews as the main data sources. However, these data carry inevitable subjective bias. In contrast, product maintenance records provide objective information on product quality issues and failure patterns, which can be cross-validated with customers’ personal experience from online reviews. In this paper, we propose a systematic approach for conducting Kano-IPA analysis from online reviews and product maintenance records synthetically. An attribute-keyword dictionary is first established using keyword extraction and clustering methods from online reviews and maintenance records. After that, semantic groups including product attributes and associated descriptions are extracted by dependency parsing analysis. The sentiment scores of identified attributes are calculated by a self-supervised representation learning approach (Sentiment Knowledge Enhanced Pre-training, SKEP) from the built semantic groups. Sentiment scores and occurrence frequencies of attributes in online reviews are utilized for Kano analysis. The importance of product attributes in IPA is estimated from the impact of sentiments of each product attribute on product ratings, while the performance is estimated from the sentiment scores of online reviews or the quality statistics from maintenance records. A case study of passenger vehicles shows that integrated data can provide more comprehensive results and richer insights. The proposed approach enables automatic data processing and can support companies to make efficient design decisions with broader perspectives from multi-source data.
An Integrated Task and Path Planning Approach for Mobile Robots in Smart Factory
Authors: Liu Shuo , Feng Bohan , Yu Dan , Bi Youyi
Published: February 2023

Mobile robots are being widely used in smart manufacturing, and efficient task assignment and path planning for these robots is an area of high interest. In previous studies, task assignment and path planning are usually solved as separate problems, which can result in optimal solutions in their respective fields, but not necessarily optimal as an integrated problem. Meanwhile, precedence constraints exist between sequential processing operations and material delivery tasks in the manufacturing environment. Thus, those planning methods developed for warehousing and logistics may not simply apply to the environment of smart factories. In this paper, we propose an integrated task and path planning approach based on Looking-backward Search Strategy (LSS) and Regret-based Search Strategy (RSS). In the stage of task assignment, the real paths for mobile robots are identified based on the Cooperative A* (CA*) algorithm and the time and energy consumed by mobile robots and machining centers are calculated. Then a greedy strategy working with LSS or RSS is used to search reasonable task assignments in time-series, which can generate a joint optimal solution for both task assignment and path planning. We verify the validity of the proposed approach in a simulated smart factory and the results show that our approach can improve the operation efficiency of the smart factory and save the time and energy consumption effectively.
Experimental Study of a Novel 4 Stroke Spark Ignition Geared-Hypocycloid Engine
Authors: Nunes Alexandre , Brojo Francisco
Published: February 2023

The aim of this work was to develop a geared-hypocycloid engine to be able to determine its feasibility and performance characteristics. This was done by modifying an existing engine with a custom-designed geared mechanism to replace the conventional slider-crank mechanism (crankshaft).

The geared-hypocycloid engine design takes advantage of the hypocycloid concept, more specifically when the diameter of the inner circle is equal to the radius of the outer circle. In this specific case, the piston moves only in the longitudinal direction along the cylinder, and in a true sinusoidal motion. This motion results in reduced mechanical losses by friction of the piston head against the cylinder due to very little side forces action on the piston, as well as the piston remaining near the top-dead center, and thus in higher in-cylinder pressure, for a longer period of time. Consequently, higher torque and power output can be achieved with no increase in fuel consumption, resulting in higher efficiency. Vibrations were found to be considerably low but the geared mechanism showed high noise during operation.

The engine performance parameters such as the rotational speed, torque output and fuel consumption were measured on a dynamometer. This data allowed for power, specific fuel consumption and overall efficiency to be calculated.
Hybrid-Electric Propulsion Solutions for UAV Application
Authors: Marto Diogo , Brójo Francisco
Published: February 2023

Due to the rapid growth of the aviation industry, the concentrations of hazardous pollutants in the atmosphere are rising and the need for more environment-friendly solutions is higher than ever. This study aims to test and show the benefits of hybrid-electric propulsion systems in UAVs in two possible configurations, parallel and series. The hybrid propulsion system combines a 28-cc 2-stroke internal combustion engine with a 200-watt frameless generator. As a primary approach, the engine alone with a 16-inch diameter and 12-inch pitch propeller is characterized by its torque, power and specific fuel consumption throughout the engine’s operating range. In a second approach, the hybrid component is added and a comparison between both results taken is made. Preliminary results show that parallel configuration offers lower specific fuel consumption in comparison with the engine alone. Also, the higher load on the engine used as the primary powerplant seems to promote a more stable operation, with higher throttle control and lower vibrations. In a final remark, considerations regarding the two configurations are made. These considerations aim to establish the best points to operate each architecture and which one is best suited to be implemented on a UAV depending on the mission profile.
Study of the Influence of Different Geometries of an Organ-on-a-Chip
Authors: Carvalho Violeta , Rodrigues Nelson , Rodrigues Raquel O. , Teixeira José C. , Miranda João , Lima Rui A. , Teixeira Senhorinha
Published: February 2023

Organs-on-a-chip, OoC, have been extremely important to reduce the use of animal models allowing researchers to conduct accurate in vitro experiments with high throughput. Year after year, increasingly complex OoC platforms have been developed to better recapitulate the in vivo environment, and numerical simulations have played a fundamental role in this process. Numerical simulations in health sciences research are constantly evolving and have allowed researchers not only to better understand but also to complement and improve the in vitro experiments.

Aiming to evaluate the influence of geometry on fluid flow, in the present work, three different geometries of a single organ-on-a-chip were created, and numerical simulations were conducted by using Ansys® Fluent software. The fluid flow of the culture medium with dissolved oxygen was simulated. In terms of oxygen consumption, the influence of the geometry was noticeable in the organoid region. In terms of velocity fields, the results were not significantly affected by the geometry.
Outdoor System for Synchronous Triggering of Multiple Scientific Cameras Using Direct-Access GNSS Time Transfer
Authors: Bjelotomic Marko , Subramaniam Prashanth , Rashid Lapuz Oginne , Almaeeni Khuloud , Anzil Mohammed Minhas , Bendoukha Sidi Ahmed , Pomares Luis
Published: February 2023

Atmospheric measurement techniques often require synchronous data capturing throughout the day, at the exact moment, more than capturing it at preset points in time. The system utilizes time stamps sent from the atomic clocks on navigation satellites. Time stamps received from the satellites by the GNSS receiver are turned into a triggering impulse. Impulses are needed for triggering the repurposed low-noise scientific cameras. The cameras must be mobile in an outdoor setup with a synchronized triggering system. However, the system is not limited to low-noise scientific cameras; it can be fitted to suit other applications requiring synchronous impulse, with a timestamping option. Systems comprise a microcontroller paired with a GNSS receiver which has access to the constant, one pulse per second, stream of GNSS satellite emitted time impulses. The GNSS receiver is connected to the camera and the microcontroller unit (MCU). 1PPS pin on the GNSS module is connected to a camera acting as its external trigger. The microcontroller is connected to the GNSS module accepting the NMEA sentences. Further, MCU communicates via USB with a data storage device, providing formatted time tagging data. The satellite impulse is directly converted to the camera trigger signal, allowing an indefinite number of devices to be triggered within a 30 nanosecond gap, with the possibility of triggering multiple low-noise cameras and other trigger-needing sensors distributed hundreds of meters or kilometers apart. The microprocessor generates the time tag without influencing the moment of the time of the trigger. GNSS module independently gives synchronous triggers while parallelly sending the data to the MCU to process it before the next satellite signal, which comes every second. We evaluate the solution on three commonly available prototyping boards in search of the least time difference between their trigger pulses.
Excel® VBA for Thermal Science Applications
Authors: Jones J. H. , Eldredge T. V.
Published: February 2023

Thermal science classes require the use of a number of components to the governing equations that require the use of tables and figures in order to generate solutions to assigned problems. Examples of some of these components are thermal properties, empirical correlation results, correction factors from various textbook figures, viewfactors for thermal radiation, complicated empirical correlations, etc. The application of some of these components can be time consuming and error prone. A series of EXCEL® Visual Basic for Applications (VBA) functions were created or adapted from various internet sources to streamline thermal science analyses and allow the learners to spend more time evaluating solution behavior/sensitivity as opposed to generating results. These VBA functions have application in fluid dynamics, heat transfer, and thermodynamics courses and allow the learners to focus on understanding the concepts without the need to perform various tedious tasks.
Direct-on-Chip Microscale Jet Array Impingement Cooling With Trapezoid Diversion Columns
Authors: Yang Jingshan , Cheng Keyong , Huai Xiulan
Published: February 2023

Microscale jet array impingement cooling has been proved to be an efficient cooling technique for high-heat-flux electronics. In order to meet the current development trend of electronic components, jet impingement cooling performance needs to be continuously improved. In this work, a target surface enhancement approach for direct-on-chip microscale jet array with alternating feeding and draining jets was proposed. Trapezoid diversion columns were set regularly around inlet jets on the target surface to guide spent fluid and enhance overall performance. Besides, the inlet Reynolds number ranged from 20 to 2000 and deionized water was used as the coolant. Firstly, the impact of trapezoid diversion columns on flow and heat transfer characteristics was studied by numerical method. The results showed that the Nusselt number of current jet array was enhanced remarkably than that of convectional jet array at the almost same cost of pressure loss. Then the optimization of columns height, shape and location were carried out to improve overall performance. As a result, an optimal jet array structure with best overall performance was proposed. In the end, the maximum thermal removal capacity of optimal jet array and basic jet array was compared. It was found that the proposed optimal jet array can remove heat flux of 1950 W/cm2 when the temperature rise of heated surface was below 85 °C, which was 28.3% higher than that of basic jet array.
Adaptive Assist As Needed Control Strategy for a Lower Limb Exoskeleton
Authors: Kumbhar Shubham Shrikant , Sangwan Vivek
Published: February 2023

Robotic Exoskeletons for legs are able to act as excellent evaluation as well as training devices while reducing physical effort that a therapist needs to expend. For such exoskeletons, assist as needed control strategies are advantageous because these lead to active participation from the user. One such strategy is based on Force Fields where the controller creates a virtual force field around the foot of the user to aid the user’s leg motion. Force field controllers (FFC) presented in literature require the knowledge of parameters such as length, mass, position of center-of-mass and moment of inertia for the combined human-exoskeleton system. This paper presents an “adaptive” assist as needed control strategy that creates a virtual force field similar to the FFC without using any prior knowledge of human inertial parameters like mass, the moment of inertia, the position of COM, etc. A lyapunov stability proof for the proposed controller is also presented along with simulation results demonstrating the controller.
Automated Generation of Hybrid Probabilistic Risk Models From SysML V2 Models of Software-Defined Manufacturing Systems
Authors: Grimmeisen Philipp , Ma Yuliang , Diaconeasa Mihai A. , Morozov Andrey
Published: February 2023

The concepts of Software-Defined Manufacturing (SDM) and Digital Twins emphasize the current trend in production system development. These systems are characterized by frequent software updates to address adjustable production processes and higher system flexibility. These software-intensive systems are safety-critical and require a thorough reliability analysis. This implies the necessity to automatically re-evaluate the reliability before each software update.

In this paper, we introduce a new Model-to-Model (M2M) transformation method that enables the automatic generation of hybrid reliability models from the Digital Twin formalism based on SysML v2. The models of the Digital Twin are extended with reliability data. The method includes (i) transformation of behavioral models to Markov chains, (ii) transformation of structural models to fault trees, and (iii) the generation of hybrid reliability models based on the software and system structure. Besides, this paper describes an SDM-system, based on a robotic manipulator, that fulfills two different tasks depending on the uploaded software. This case study shows that our M2M transformation method enables continuous reliability assessment of SDM-systems.
Designing a Physical Model for the Emsworth Lock and Dam Filling and Emptying System
Authors: Doshi Nathan , Hancox Jacob , Karkhai Polakrit , Smith Cameryn , Tawakkol Adam , White Spencer , Bristow Elizabeth , Hill Aaron , McCoy Brad , Nowicki Margaret
Published: February 2023

Currently, the system of locks and dams within the United States operate where each system has a different component and needs different parts to complete the routine maintenance checks and procedures. Having unique components and parts for each lock and dam system drastically increases the costs required for the United States Army Corps of Engineers (USACE) to operate and maintain these locks and dams. One way to reduce these costs is to work towards and recommend standardized components for a lock and dam system. This process, especially for construction projects, is vital because it allows for simplification in the build and production stages of a project as well as life cycle maintenance.

Understanding hydraulic design for the inflow and outflow of a lock system was an important consideration for this design project. Reducing hawser forces while maximizing the efficiency of the filling and emptying process is the overall goal for the design. To minimize hawser forces, mitigating the effects of hydrodynamic and hydrostatic forces is essential. This research also strives to gain additional understanding of the dynamic, turbulent nature of water in a lock and dam system. In the Emsworth Lock and Dam system, the top of rock for the riverbed is significantly higher than normal presenting unique challenges for modeling and simulation, as well as physical model construction. Critical to the design of a physical model is the determination of an adequate scaling factor that will not significantly affect the natural hydraulic processes within the system. As such, it is essential that appropriate theories are applied to remain consistent with proven methods of hydraulic scaling.

Before selecting a scaling ratio, determining space limitations and a conceptual design of the model was necessary. This assisted in visualizing the model in the available spaces to ensure the design and manufacturing plan was realistic. The model contains three components: a main lock chamber, a higher elevation water reservoir, and a lower elevation water reservoir. The component that is most controlling to the design is the main lock chamber; this component cannot be altered in any way to meet the requirements of the floor space because any modifications would affect the results of the hawser force testing, and the model would not appropriately match reality. The physical model will be verified using the Froude equation — an equation that drives performance of models that are dependent on gravity. As such, when conducting any inflow or outflow of the water in the system, it is essential that the velocity is controlled such that the Froude value is consistent with that of the actual Emsworth Lock and Dam. The model must match a Froude number of 0.052 to effectively represent reality.
Economic Viability vs. Risk Mitigation: An Experimental Investigation of Project Budget Investment Decisions in Engineering Students
Authors: Midlick Mark J. , Gernand Jeremy M.
Published: February 2023

In the course of their profession, engineers must often consider not just the technical efficacy of their designs but also how their design decisions influence and are influenced by nontechnical factors. These non-technical factors can include the stated or implicit values of a company culture, the real and/or perceived social pressures from management, and individual perceptions about one’s own ethical and professional duties and responsibilities. In the field of Psychology there is a large body of research relating the internal, mental states of individuals to their external behaviors and choices. However, at this time there has been little research into how different psychological states can affect the outcome of specific engineering design decision making by individuals or teams. This study’s aim was to begin this research by conducting an experiment to simulate a common constraint in the profession of engineering: allocating a design budget to ensure the project outcome is both profitable and safe. Specifically, this study wanted to measure how the personality trait agreeableness in conjunction with a social primer consisting of a written scenario description conveying the aims of the exercise and the responsibilities of engineers related to an engineering student’s decision to favor either profit or safety in a hypothetical design scenario. A total of 141 undergraduate engineering students were recruited to participate in this experiment, which consisted of a computer-based survey and decision-making activity with a total duration of approximately 10 minutes. Results indicated that agreeableness did not relate to primer adherence in a statistically significant way; however participant beliefs about the intention of the experiment did have a statistically significant relationship with their final allocation decisions, a finding that may have implications for the management of engineering design teams, if this research can be replicated in experienced professionally practicing engineers. While not the objective of the experiment, the data show that when participants were given the opportunity to revise their selections, they most commonly revised their allocations away from profit and towards more investment in safety. Whether this is a result of simply a second attempt at the same decision with further reflection or the result of the consideration of information considered after the initial allocation remains to be determined in future research. The results of this study should serve not as conclusive evidence on the effects of trait agreeableness in engineering risk-related decision making but rather as an initial step, or model for how to investigate a potentially valuable, interdisciplinary field of inquiry. Insights from this experiment do hold useful lessons for the next phase of this research.
Autonomous Topographic Mapping of Unknown Environments by Dynamic Visual Data
Authors: Raju Vomsheendhur , Selekwa Majura F.
Published: February 2023

The simultaneous localization and mapping (SLAM) process is what makes it possible for autonomous vehicles to navigate in unknown environments. Early SLAM algorithms used and relied on ranging sensors only. In recent years, there has been an increased interest in vision-based SLAM (V-SLAM) due to the low-cost nature of digital cameras available in the market compared to ranging sensors. V-SLAM uses successive camera frames to either track features in individual frames and triangulates the position to construct a 3-D map or determine the vehicle speed by measuring the rate of change of these features relative to a known reference. This paper proposes an effective real-time method of creating a topological 3D map of the environment from a stereo vision system by using an improved stereo correspondence algorithm that minimizes errors caused by illumination and texture variation in the disparity map generation. The Cartesian world coordinates corresponding to each pixel are computed from the disparity map generated by triangulating the depth of the pixels in the reference perspective projection image to create a 3-D map of the scene as a point cloud plot. Analysis of the resulting point cloud plot indicates that the coordinates of each pixel provide the 3-D information about the scene representing a working topological map that can be used to detect the obstacles in close vicinity to the robot.
Exit Time Differences Between Gated and Open Operator Compartments in Stand-Up End-Controlled Lift Trucks With an Examination of Injury Potential in Tip-Over and Off-Dock Incidents
Authors: Martinez Jonathan , Germane Alex , Watson Richard , Gwin Lisa
Published: February 2023

Stand-up end-controlled forklifts typically have two different mechanisms for injury to the operator; injury to a limb extended outside the operator compartment or injury incurred in off-dock and tip-over type accidents. Lift truck operator compartments are designed with an open portal in compliance with current lift truck safety standards which instruct operators to egress the vehicle in the event of an off-dock or tip-over. It has been suggested that a door over the portal may be beneficial by preventing the operator from extending limbs outside the vehicle. Conversely, a door may add critical time to egress in the emergency of an off-dock or tip-over accident.

This study examined the time needed for egress with and without a door using 38 trained operators. Operators were tested in an experimental process including 151 tests with a door and 152 tests without a door. There was a statistically significant increase in the amount of time needed for egress with a door present versus without a door.

The potential for injury to an occupant that is not able to exit the cabin in off-dock and tip-over scenarios was tested using a Hybrid III 50th percentile male ATD to measure injury metrics. One tip-over and seven off-dock tests were conducted. Seven of the eight test situations resulted in serious or life-threatening injury measurements to the ATD.
Benchmarking Various Nonlinear Control Design Techniques for a Two-Link Planar Robot Arm
Authors: Ilhan Zeki
Published: February 2023

This work aims to demonstrate and benchmark different model-based nonlinear control design techniques for elementary controls education. A standard, two-link planar robot arm (Fig.1) is chosen to be the plant due to its nonlinear system dynamics and relatively simple inverse kinematics considering the math level of complexity of a typical senior-level mechanical engineering class. To facilitate model-based control design, the system dynamic model is derived through Lagrange’s equations in non-conservative form. An inverse kinematic analysis is also performed to extract the target joint variables to match for a circular motion executed in the task space. Finally, the system dynamic model is incorporated with feedback control designs based on the computed torque and sliding mode control methods. The tracking performance of the proposed nonlinear controllers are validated in closed-loop numerical simulations based on the same target trajectories to compare the performances achieved by the different algorithms.
Variation Analysis of Carbon Fibre Reinforced Polymers Light Weight Aero Engine Parts
Authors: Fernström Vilma , Lööf Johan , Frampton Andrew , Brunnacker Lena , Wärmefjord Kristina , Söderberg Rikard
Published: February 2023

In this paper the focus is on variation analysis for composite CFRP (carbon fibre reinforced polymers) parts. A detailed study of possible sources of variation in manufacturing of CFRP parts is presented. Based on the variables identified a simulation chain on how to manage and simulate this variation is described. This paper also presents a logical approach to how a digital twin for a fully automated production line of compression molded CFRP parts can be built, and to investigate and quantify how much each individual variable contributes to the final variation in the component.
Improved Accuracy of Non-Contact Respiratory Function Measurement for Patients With Severe Motor and Intellectual Disabilities
Authors: Nakahama Takumi , Kosumi Remi , Sakamoto Ryota , Kato Norihiko , Yano Ken’ichi , Iwamoto Shotaro , Tsujioka Tomohiro , Takahashi Yuya , Yamakawa Noriko
Published: February 2023

Respiratory gas analyzers to measure functions such as ventilation volume respiratory rate are expensive, and patients with severe motor and intellectual disabilities (SMID) often remove the devices, increasing contact risk and making them difficult to use in institutions. We propose here an inexpensive, non-contact method of measuring respiratory function using the depth camera introduced in our previous study. The method includes an algorithm that differentiates between body tremors, and between movements peculiar to patients with SMID and those caused by respiration, while further detecting appropriate respiration. However, the previous region of interest (ROI) was limited to a simple rectangular area from the navel to the xiphoid process, and we did not compare measurements using the geometry of the thorax and the abdomen as the ROI. In this study, we performed non-contact respiratory measurement using the geometric shape of the upper body of patients as the ROI, and investigated the improvement of measurement accuracy when the ROI was set according to the individual patient’s body. The results indicated that the values from the new method approached those of the respiratory gas analyzer more closely than the conventional method, and its measurement performance was sufficient for respiratory rehabilitation evaluation. We also found that the measured respiratory signal correlated with the ventilation rate in respiration with large ventilation rate fluctuations, and that the respiratory rhythm abnormalities associated with ventilation rate changes could be measured by the respiratory rate per min and apnea time per min evaluation indices.