bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved evaluation of the genetic variability of Brazilian strains of Erwinia psidii with newly developed microsatellite markers
Authors: Hermenegildo Pollyane da Silva , Guimarães Lúcio Mauro Silva , Badel Jorge Luis , Marques Abi S. A. , Alfenas Acelino Couto , Velloso Ferreira Marisa A. S.
Published: January 2021

Erwinia psidii is the causal agent of bacterial blight of guava, and wilt and dieback of eucalypt in Brazil. Previous studies using repetitive sequence‐based PCR (rep‐PCR) revealed limited genetic diversity in E. psidii populations. Here, the draft genome sequence of the type strain IBSBF435 was probed for variable number of tandem repeats (VNTRs) that could be used to study E. psidii genetic diversity by multilocus variable number of tandem repeat analysis (MLVA). Eleven selected VNTRs were used to assess genetic relatedness among 108 E. psidii strains from guava (36) and eucalypt (72), of different geographic origins and years of collection. A total of 79 haplotypes were detected in the strain collection. The number of alleles per locus ranged from 3 to 15. A minimum spanning tree indicated the occurrence of nine clonal complexes, of which two contained only guava strains, five only eucalypt strains, and two contained guava and eucalypt strains. The three oldest strains collected from guava in the 1980s (IBSBF435, IBSBF454, and IBSBF493) exhibited distinct haplotypes. IBSBF435 was genetically more closely related to some eucalypt strains than to guava strains, which supports previously reported lack of host specificity. IBSBF454 grouped with guava strains more recently collected from different states, suggesting that it could have been disseminated to different Brazilian areas. The implication of the lack of differentiation between guava and eucalypt strains is discussed in relation to the detection of E. psidii affecting eucalypt more than 25 years after the first description of guava bacterial blight.
Adaptations to explosive resistance training with partial range of motion are not inferior to full range of motion
Authors: Werkhausen Amelie , E. Solberg Christian , Paulsen Gøran , Bojsen‐Møller Jens , Seynnes Olivier R.
Published: January 2021

We tested whether explosive resistance training with partial range of motion (ROM) would be as effective as full ROM training using a noninferiority trial design. Fifteen subjects with strength training experience took part in an explosive—concentric only—leg press training program, three times per week for 10 weeks. One leg was randomly assigned to exercise with partial ROM (ie, 9º) and the other leg to full ROM. Before and after training, we assessed leg press performance, isokinetic concentric and isometric knee extension torque, and vastus lateralis muscle architecture. Overall, both training modalities increased maximal strength and rate of force development. Training with partial ROM yielded noninferior results compared to full ROM for leg press peak power (+69 ± 47% vs. +61 ± 64%), isokinetic strength (4‐6 ± 6%‐12% vs. 1‐6 ± 6%‐10% at 30, 60, and 180˚s‐1), and explosive torque after 100 (47 ± 24 vs. 35 ± 22) and 150 ms (57 ± 22% vs. 42 ± 25%). The comparison was inconclusive for other functional parameters (ie, isokinetic peak torque (300˚s−1), joint angle at isokinetic peak torque, explosive torque after 50 ms, and electrically evoked torque) and for muscle fascicle length and thickness, although noninferiority was established for pennation angle. However, partial ROM was not found statistically inferior to full ROM for any measured variable. Under the present conditions, the effects of explosive heavy resistance training were independent of joint ROM. Instead, these data suggest that the distinct timing of muscle work in explosive contractions confers more influence to the starting joint angle than ROM on adaptations to this type of training.
A catalogue of PROMs in sports science: Quality assessment of PROM development and validation
Authors: Hansen Christian F. , Jensen Jonas , Siersma Volkert , Brodersen John , Comins Jonathan D. , Krogsgaard Michael R.
Published: January 2021

Choosing the most adequate PROM for a study is a non‐trivial process. The aim of this study was to provide a catalogue with analyses of content and construct validity of PROMs relevant to research in sports science, including all published local translations. The most commonly used PROMs in sports research were selected from a PubMed search “patient reported outcome measures sports”, identifying 439 articles and 194 different PROMs. Articles describing development of the 61 selected PROMs were assessed for content validity, and all articles regarding construct validity of each PROM and all published translations (in total 622 articles) were analyzed. A catalogue with assessments of the 61 PROMs was produced. The majority were of inferior validity, with few exceptions. The most common reason for this was that the PROM had not been developed by methods that ensure high content validity. Another major reason for inferior validity was that construct validity had not been secured by adequate statistical methods. In conclusion, this catalogue provides a tool for researchers to facilitate choosing the most valid PROM for studies in sports research. Furthermore, it shows for popular PROMs where further validation is needed, and for fields in musculoskeletal medicine where valid PROMs are lacking. It is suggested that a targeted effort is made to develop valid PROMs for major conditions in musculoskeletal research. The current method is easier to practice compared with assessment after COSMIN guidelines.
Detecting endometrial cancer
Authors: Jones Eleanor R , O’Flynn Helena , Njoku Kelechi , Crosbie Emma J
Published: January 2021

Key content

Endometrial cancer (EC) is the most common gynaecological cancer in the UK.

Ninety percent of women with EC present with postmenopausal bleeding (PMB), but less than 10% of women with PMB have a sinister underlying cause.

National Institute for Health and Care Excellence guidance advises that symptomatic postmenopausal women undergo urgent investigation; however, guidance is unclear for premenopausal women.

Current investigations for PMB, including transvaginal ultrasound scan, endometrial biopsy and/or outpatient hysteroscopy, have advantages and disadvantages.

Novel detection tools are in development, which combine minimally invasive sampling with genomic, proteomic and single cell technologies.

Learning objectives

To understand who is at risk of EC and who should be referred for urgent investigations.

To understand the evidence underpinning the current diagnostic pathway for EC.

To highlight unique and promising perspectives for EC detection and their potential to transform clinical care.

Ethical issues

Current diagnostics for EC are invasive and often painful. There is an urgent need for high‐quality randomised controlled trials to inform effective pain relief options.

Premenopausal women with suspected EC do not fit criteria for urgent investigations. How can we identify those at highest risk to ensure they are fast‐tracked appropriately?

Novel diagnostic tools hold promise, but they must be robustly validated before being introduced into clinical practice.
A Nondestructive Technique for the Evaluation of Thin Cylindrical Shells' Axial Buckling Capacity
Authors: Yadav Kshitij Kumar , Cuccia Nicholas L. , Virot Emmanuel , Rubinstein Shmuel M. , Gerasimidis Simos
Published: January 2021

The axial buckling capacity of a thin cylindrical shell depends on the shape and the size of the imperfections that are present in it. Therefore, the prediction of the shells buckling capacity is difficult, expensive, and time consuming, if not impossible, because the prediction requires a priori knowledge about the imperfections. As a result, thin cylindrical shells are designed conservatively using the knockdown factor approach that accommodates the uncertainties associated with the imperfections that are present in the shells; almost all the design codes follow this approach explicitly or implicitly. A novel procedure is proposed for the accurate prediction of the axial buckling capacity of thin cylindrical shells without measuring the imperfections and is based on the probing of the axially loaded shells. Computational and experimental implementation of the procedure yields accurate results when the probing is done in location of highest imperfection amplitude. However, the procedure overpredicts the capacity when the probing is done away from that point. This study demonstrates the crucial role played by the probing location and shows that the prediction of imperfect cylinders is possible if the probing is done at the proper location.
Knee Angles After Crosstalk Correction With Principal Component Analysis in Gait and Cycling
Authors: Skaro Jordan , Hazelwood Scott J. , Klisch Stephen M.
Published: January 2021

Principal component analysis (PCA) has been used as a post-hoc method for reducing knee crosstalk errors during gait analysis. PCA minimizes correlations between flexion–extension (FE), abduction–adduction (AA), and internal–external rotation (IE) angles. However, previous studies have not considered PCA for exercises involving knee flexion angles that are greater than those typically experienced during gait. Thus, the goal of this study was to investigate using PCA to correct for crosstalk during one exercise (i.e., cycling) that involves relatively high flexion angles. Fifteen participants were tested in gait and cycling using a motion analysis system. Uncorrected FE, AA and IE angles were compared to those calculated with PCA performed on (1) all angles (FE-AA-IE PCA correction) and (2) only FE-AA angles (FE-AA PCA correction). Significant differences existed between uncorrected and FE-AA-IE PCA corrected AA and IE angles for both exercises, between uncorrected and FE-AA PCA corrected AA angles for both exercises, and between FE-AA-IE and FE-AA PCA corrected IE angles for cycling. Correlations existed before PCA correction and were eliminated following PCA correction with the exception that FE-IE correlations remained following FE-AA PCA correction. Since the two PCA analyses differed only in their IE angle predictions for the high flexion exercise (cycling), IE angle results were compared to previous studies. Using FE-AA PCA correction may be the preferred protocol for cycling as it appeared to retain physiological IE angle correlations at high flexion angles. However, there exists a critical need for studies aimed at obtaining more accurate IE angles in such exercises.
Numerical Simulation of Insulin Depot Formation in Subcutaneous Tissue Modeled as a Homogeneous Anisotropic Porous Media
Authors: Zedelmair Michael , Mukherjee Abhijit
Published: January 2021

In this study, a numerical model of insulin depot formation in the subcutaneous adipose tissue of humans has been developed using the commercial computational fluid dynamics software. A better understanding of the underlying mechanisms can be helpful in the development of novel insulin administration devices and cannula geometries. Developing a model of insulin depot formation can provide faster results compared to extensive experimental studies which are typically done on porcine tissues. The injection method considered in this simulation involves an insulin pump that uses a rapid acting U100 insulin analogue. The depot formation has been studied by simulating Bolus injections ranging from 5 to 15 units of insulin, which corresponds to volumes of 50–150 μL. The insulin is injected into modeled subcutaneous tissues typically present in human abdominal regions. The subcutaneous tissue has been modeled as a fluid-saturated porous media. An anisotropic approach has been used to define the tissue permeability. The value of the porosity in parallel and perpendicular directions has been varied to modify the viscous resistance to the flow in these directions. The developed model has been validated by comparing with published experimental results, which show qualitative similarities in disk-shaped insulin depot formation. The validated model is then used to study formation of insulin depot inside the subcutaneous tissue at varying insulin flow rates involving different cannula geometries and arrays. The numerical model has been found to be an effective option to evaluate new cannula designs prior to the manufacturing and testing of prototypes, which can be rather time consuming and expensive.
Large Eddy Simulation of Microvortex Generators in a Turbulent Boundary Layer
Authors: Heffron Andrew P. , Williams John J. , Avital Eldad J.
Published: January 2021

This study investigates the flow physics on microvortex generators (MVGs) in order to improve their performance in turbulent boundary layers (TBLs). TBLs can be a challenging environment for MVGs because of the streamwise length of the generated vortex and the increased parasitic drag of the MVGs. Large eddy simulation (LES) is used to properly resolve the turbulent boundary layer of a flat-plate with a zero-pressure gradient and MVG vane. Three different vane-types are investigated (e423-Mod, triangular, and rectangular vanes) and are studied in a single vane configuration. Important flow features such as a separation bubble on the leading edge of the rectangular vanes which introduced unsteadiness into the vortex formation and degraded the MVG's efficiency was observed. The e423-Mod and triangular vanes were observed to be more aerodynamically efficient. The triangular vane was found to be the most efficient when evaluated immediately downstream of the vane. However, the vortex from the triangular vane decayed very rapidly due to it being formed very close to the wall which degraded its efficiency further downstream. The e423-Mod vane avoided this problem but its drag was very high relative to the strength of the generated vortex and its vortex experienced a brief period of rapid decay immediately downstream decreasing its efficiency. Further downstream, the vortex of the rectangular vane at 16 deg became the most efficient through a combination of low vane drag and low vortex decay in the TBL, demonstrating the need to consider a range of issues when designing an MVG.
Sensitivity of Micromilling Responses to Grain Variations in Wire Arc Additively Manufactured Aluminum Alloy 4043
Authors: Gao Zhongjia , Nowak James F. , Corbin Johnathan , Delgado Lauren , Samuel Johnson
Published: January 2021

Given the recent trend toward hybrid processing involving the integration of wire arc additive manufacturing (WAAM) and machining capabilities, this paper aims to identify and correlate microstructural variations observed in wire arc additively manufactured aluminum alloy 4043 workpieces to their specific micromilling responses. This is done with the explicit goal of assessing the feasibility of using micromilling responses to detect microstructural variations in WAAM workpieces. As part of this effort, variations in the interlayer cooling time are used to induce changes in the microstructure of a thin-wall WAAM workpiece. The microstructures are first characterized using in-process thermographic imaging, optical microscopy, polarized light microscopy, and indentation. Micromilling slotting experiments are then conducted on different regions within the workpiece. The findings suggest that cutting force signals are the premier candidate for in situ extraction of information regarding microstructural variations within WAAM workpieces. In particular, in situ analysis of the cutting force frequency spectrum can provide critical information regarding dominant failure mechanisms related to the underlying microstructure. Other key micromilling responses such as surface roughness, burr formation, and tool wear also correlate well with the underlying microstructural variations. While these early stage findings hold promise, future research efforts spanning multiple metal alloys systems and micromachining processes are needed to mature the proposed concept.
Tip Leakage Flow Instability in a Centrifugal Compressor
Authors: Cao Teng , Kanzaka Tadashi , Xu Liping , Brandvik Tobias
Published: January 2021

In this paper, an unsteady tip leakage flow phenomenon is identified and investigated in a centrifugal compressor with a vaneless diffuser at near-stall conditions. This phenomenon is associated with the inception of a rotating instability in the compressor. The study is based on numerical simulations that are supported by experimental measurements. The study confirms that the unstable flow is governed by a Kelvin–Helmholtz type instability of the shear layer formed between the main-stream flow and the tip leakage flow. The shear layer instability induces large-scale vortex roll-up and forms vortex tubes, which propagate circumferentially, resulting in measured pressure fluctuations with short wavelength and high amplitude which rotate at about half of the blade speed. The 3D vortex tube is also found to interact with the main blade leading edge, causing the reduction of the blade loading identified in the experiment. The paper also reveals that the downstream volute imposes a once-per-rev circumferential nonuniform back pressure at the impeller exit, inducing circumferential loading variation at the impeller inducer, and causing circumferential variation in the unsteady tip leakage flow.
Some Observations on the Computational Sensitivity of Rotating Cavity Flows
Authors: Hickling Tom , He Li
Published: January 2021

Across the open literature, there is no clear consensus on what the most suitable modeling fidelity is for rotating cavity flows. Although it is a widely held opinion that unsteady Reynolds-averaged-Navier–Stokes (URANS) approaches are unsuitable, many authors have succeeded in getting reasonable heat transfer results with them. There is also a lack of research into the validity of hybrid URANS/large eddy simulation (LES) type approaches such as detached eddy simulation (DES). This paper addresses these research challenges with a systematic investigation of a rotating cavity with axial throughflow at Grashof numbers of 3.03×109 and 3.03×1011. The disk near-wall layers remained laminar at both conditions, meaning that a turbulence model should not be active in these regions. The disk heat transfer was observed to affect the near-disk aerodynamics, which in turn affect the disk heat transfer: this feedback loop implies that conjugate heat transfer computations of rotating cavities may be worth investigating. On the shroud, additional eddy viscosity in URANS and DES was found to interfere with the formation of heat transfer enhancing streaks, whilst these were always captured by LES. DES exhibited a concerning behavior at the higher Grashof number. Locally generated eddy viscosity from the shroud was injected into the bulk fluid by the radial inflow. This contaminated the entire cavity with nonphysical modeled turbulence. As the radial inflow is a characteristic feature of rotating cavity flows, these results show that caution is necessary when applying hybrid URANS/LES approaches to this type of flow.
Large Eddy Simulation of a Turbulent Spray Burner Using Thickened Flame Model and Adaptive Mesh Refinement
Authors: Rezchikova Aleksandra , Mehl Cédric , Drennan Scott , Colin Olivier
Published: January 2021

The accurate simulation of two-phase flow combustion is crucial for the design of aeronautical combustion chambers. In order to gain insight into complex interactions between a flame, a flow, and a liquid phase, the present work addresses the combustion modeling for the large eddy simulation (LES) of a turbulent spray jet flame. The Eulerian–Lagrangian framework is selected to represent the gaseous and liquid phases, respectively. Chemical processes are described by a reduced mechanism, and turbulent combustion is modeled by the thickened flame model (TFM) coupled to the adaptive mesh refinement (AMR). The TFM-AMR extension on the dispersed phase is successfully validated on a laminar spray flame configuration. Then, the modeling approach is evaluated on the academic turbulent spray burner, providing a good agreement with the experimental data.
On the Accuracy of Voluntary Observing Ship’s Records
Authors: Vettor Roberto , Guedes Soares C.
Published: January 2021

A one-to-one comparison of the significant wave height reported by Voluntary Observing Ships (VOS) with the ERA-interim database is performed. A preliminary filtering procedure allows excluding reports affected by the most evident observations’ errors and removing the systematic biases in order to clean up the database. A statistical analysis confirms the previous finding regarding the goodness of the database when analyzing average values, but also highlights a large spreading of the observations. The work identifies critical areas and conditions in which the mismatch between numerical data and observations is more significant. The pattern of the differences reveals a regional consistency with VOS overestimating the significant wave height in marginal and enclosed seas as well as in the western sides of the oceans, while showing good matches in the eastern sides and offshore areas, except in the southern oceans where VOS leads to underestimations. The causes of such differences are finally discussed.
Relation Between Atmospheric Circulation Patterns in the North Atlantic and the Sea States in the Iberian Peninsula
Authors: Lucas Cláudia , Bernardino Mariana , Guedes Soares C.
Published: January 2021

A statistical analysis of significant wave height (Hs) in a location offshore Portugal continental coast, Leixões, is performed. The spectral and parametric information of sea states at this point used in this analysis was obtained from a 21-year hindcast simulation using the spectral wave model simulating wave nearshore (SWAN) forced by wind fields produced by the Weather Research and Forecasting (WRF) model forced by the ERA-Interim reanalysis. The modeling of the climatic variability of directional spectra provides information of the shape of the expected directional spectra in the various sea states at these locations, i.e., how the spectral parameters and their probability of occurrence change in the regions studied. The occurrences of spectral classes are estimated, and for each class, the variability of the spectral parameters is described by means of joint distributions. The classification of the different sea states provides important information about the wave conditions present in the target areas. A relation between the sea states and the Lamb weather types (WTs) as well as a methodology for classifying atmospheric circulation patterns is presented in this study. The results of this study provide a description of the wave climate through demonstration of the interaction between sea states and weather patterns and relating different circulation patterns to different sea states. This study provides useful information on the wave conditions that can be utilized in the design of ocean engineering structures as well as in the assessment of the operability and safety of shipping and renewable energy devices.
Numerical Investigation on the Cage-to-Cage Wake Effect: A Case Study of a 4 × 2 Cage Array
Authors: Sim Jaesub , Cheng Hui , Aarsæther Karl Gunnar , Li Lin , Ong Muk Chen
Published: January 2021

Aquaculture has been the world’s fastest-growing food producing method and grown to become the second-largest export industry in Norway during the past 40 years. Usually, the high-value fish such as Atlantic Salmon (Salmo Salar) is raised in a multi-cage fish farm, where the flow interactions between fish cages exist. In this study, the interactions between fish cages are implemented into the numerical program, FhSim, to investigate its influences on the responses of a multi-cage fish farm. Tensions in anchor lines, drag force, and cultivation volume of each cage in a full-scale 4 × 2 multi-cage fish farms under different flow directions are analyzed numerically. The discrepancies of the responses based on three cases, i.e., (i) without any wake effects, (ii) with only cage-to-cage wake effect, and (iii) with all the wake effects, are compared and discussed. The results indicate that neglecting the wake effects will overestimate the total drag force of the eight cages up to 128% and underestimate the total cultivation volume of the eight cages as much as 42%. This study can provide suggestions on how to consider the wake effects during the design of the multiple-cage system.
HapticWall: An Encountered-Type Two-Dimensional Vertical System for Virtual Reality
Authors: Li Yuwei , Kim David Donghyun , Anthony Brian
Published: January 2021

We present HapticWall, an encountered-type, motor actuated vertical two-dimensional system that enables both small and large scale physical interactions in virtual reality. HapticWall consists of a motor-actuated vertical two-dimensional gantry system that powers the physical proxy for the virtual counterpart. The physical proxy, combined with the HapticWall system, can be used to provide both small and large scale haptic feedbacks for virtual reality in the vertical space. Haptic Wall is capable of providing wall-like haptic feedback and interactions in the vertical space. We created two virtual reality applications to demonstrate the application of the HapticWall system. Preliminary user feedback was collected to evaluate the performance and the limitations of the HapticWall system. The results of our study are presented in this paper. The outcome of this research will provide better understanding of multi-scale haptic interfaces in the vertical space for virtual reality and guide the future development of the HapticWall system.
A Novel Intelligent Learning Control Scheme for Discrete-Time Nonlinear Uncertain Systems in Multiple Environments
Authors: Zhang Jingting , Yuan Chengzhi , Stegagno Paolo
Published: January 2021

In this paper, we propose a novel intelligent control scheme for a class of discrete-time nonlinear uncertain systems operating under multiple environments/control situations. First, based on the deterministic learning theory, artificial neural networks (NNs) are employed to accurately learn/identify the uncertain system dynamics under each individual environment. The learned knowledge is then utilized to: (i) achieve improved control performance by developing a family of experience-based controllers (EBCs), each of which is tailored to an individual environment; and (ii) determine real-time activation of the EBCs by developing a pattern recognition mechanism for online identifying the active control situation. In addition, a robust quasi-sliding mode controller is further designed and embedded in the overall control scheme to guarantee system stability during the transition process among multiple environments. The novelty of the proposed control scheme lies in its intelligent capabilities of knowledge acquisition and re-utilization in real-time control, enabling self-adaption to uncertain changing control environments. A simulation example is included to verify the effectiveness of the proposed results.
A Control Algorithm Framework for Time-of-Arrival and Arrival Airspeed Control
Authors: Stephens Shawn S. , Kunz Donald L. , Baker William P. , Hess Joshuah A. , Casbeer David W.
Published: January 2021

This paper documents the framework for a control algorithm which commands an aircraft to arrive at a specified final location with constraints on arrival time, airspeed, and heading in an environment with steady state wind and turbulence. The path is defined as a variable-length racetrack, allowing for an accurate estimate of the arrival time which can be quickly changed by increasing or decreasing the size of the racetrack. The arrival time is estimated using Gaussian quadrature which allows for the inclusion of steady state wind into the arrival time estimate. The time-of-arrival error between the estimated and the desired arrival time is then minimized through real-time path and air-speed control. A sensitivity study was performed which varied aircraft performance, wind speed, wind direction, arrival time and magnitude of turbulence. The results show the controller achieved a time-of-arrival error of less than one second and arrival airspeed error less than four meters per second across all simulations with moderate turbulence and wind speed less than one third the desired airspeed of the vehicle.
Nonlinear Modeling and Analysis of Power Lines With Stockbridge Dampers Under Vortex-Induced Vibrations
Authors: Malla Arun L. , Gupta Sunit K. , Barry Oumar
Published: January 2021

Vortex-induced vibrations have a considerable effect on overhead power transmission lines, often leading to fatigue-failure. While nonlinear models exist for power lines, vibration dampers, and vortex-induced vibrations, no work combines the nonlinearities stemming from the cable, vibration damper, and fluid forces in a single model. As power transmission lines are a major component of modern infrastructure, a thorough understanding of the nonlinear dynamic interactions of conductors, dampers, and wind forces is crucial. This paper examines a conductor with attached Stockbridge dampers under vortex-induced vibration. Sources of nonlinearity in this system include mid-plane stretching of the conductor, equivalent cubic stiffness of the Stockbridge damper, and fluctuating lift force modeled as a Van der Pol oscillator. The equations of motion for the resulting system are discretized using Galerkin’s method and solved using the numerical continuation method. Through parametric analysis, the effects of factors such as damper position and mass ratio on system response are determined. Insight is gained on the combined nonlinear system and a strong foundation is formed for ongoing study.
Modelica-Based Control of a Delta Robot
Authors: Okasha Ahmed , Bortoff Scott A.
Published: January 2021

In this paper we derive a dynamic model of the delta robot and two formulations of the manipulator Jacobian that comprise a system of singularity-free, index-one differential algebraic equations that is well-suited for model-based control design and computer simulation. One of the Jacobians is intended for time-domain simulation, while the other is for use in discrete-time control algorithms. The model is well-posed and numerically well-conditioned throughout the workspace, including at kinematic singularities. We use the model to derive an approximate feedback linearizing control algorithm that can be used for both trajectory tracking and impedance control, enabling some assembly tasks involving contact and collisions. The model and control algorithms are realized in the open-source Modelica language, and a Modelica-based software architecture is described that allows for a seamless development process from mathematical derivation of control algorithms, to desktop simulation, and finally to laboratory-scale experimental testing without the need to recode any aspect of the control algorithm. Simulation and experimental results are provided.
Modeling and Analysis of the Effects of Startle Reaction on Group Coordination
Authors: Mwaffo Violet , Vernerey Franck
Published: January 2021

Startle reaction is an alarm behavior observed in animal groups during anti-predatory response or fear-inducing stimulation. This behavior is characterized by spontaneous change in heading direction and increasing speed that can drastically affect group coordination. In this work, we leverage a mathematical model of fish social behavior to recreate startle reaction. Specifically, we model startle reaction through a biased jump diffusion process, where the jumps process captures sudden and fast changes of heading direction observed during this escaping behavior. Then, using extensive numerical simulations, we test their effects on group of fish including an informed individual prescribing the direction of motion and several followers by systematically varying the frequency and intensity of the sudden and fast turns introduced in the heading direction of a single individual. We demonstrate the emergence of novel form of leadership and phase transition between complete ordered states and disorganized states. In addition, we evidence that at specific range of frequencies and amplitudes, the initiation of this behavior might be utilized to divert group followers from their reference trajectory while keeping them in a synchronized state with the startling individual. Our findings offer a new paradigm to recreate the emergence of leadership applicable to divert or contain multi-vehicle systems.
Formation Control of Non-Holonomic Mobile Robots Moving on Slippery Surfaces
Authors: Mwaffo Violet , De Lellis Pietro , Humbert Sean
Published: January 2021

In this work, we analyze the decentralized formation control problem for a class of multi-robotic systems evolving on slippery surfaces. Grounded on experimental data of robots moving on a gravel surface inducing slippery, we show that a deterministic model cannot capture the uncertainties resulting from the kinematics of the robots while, instead, a model incorporating stochastic noise is capable of emulating such perturbations on wheel driving speed and turn rate. To account for these uncertainties, we consider a second order non-holonomic unicycle model to capture the full dynamics of individual vehicles where both actuation force and torque are subject to stochastic disturbances. Upon reducing the input-output dynamics of individual robot to a stochastic double integrator, we investigate the effects of these perturbations on the control input using concepts from stochastic stability theory and through numerical simulations. We demonstrated the applicability of the proposed scheme for formation control notably by providing sufficient conditions for exponential mean square convergence and we numerically determined the range of noise intensities for which team of robots can achieve formation stabilization. The promising findings from this work are expected to aid the design of robust control schemes for formation control of non-holonomic robots on off-road or un-paved surfaces.
Performance Evaluation of Suspended Energy Harvesting Backpack Using Half-Wave Mechanical Rectification
Authors: Mi Jia , Li Qiaofeng , Liu Mingyi , Li Xiaofan , Zuo Lei
Published: January 2021

Human beings are becoming more and more dependent on electronic devices, such as smart phones, smart watches, GPS, etc. This paper presents the design, modeling and testing of a novel suspended energy harvesting backpack using half-wave mechanical rectification. The proposed half-wave rectification mechanism can convert bidirectional linear vibration into unidirectional rotation with nonlinear inertia. Compared with full-wave mechanical rectification, the proposed half-wave rectification is designed only to convert the motion in one of the vibration directions while remaining idle in the other direction. Numerical simulation shows the proposed half-wave rectification based suspended energy harvesting backpack can obtain about two times of the average output power as the previous full-wave rectification design while also maintaining larger output power in the wideband frequency range. Bench test results indicate that the proposed half-wave rectification-based energy harvesting backpack can harvest 6.7 W (peak)/2.1 W (average) under 2 Hz and 6 mm excitation with a 31.8 kg payload, which is a significant improvement compared with 1.9 W(peak)/0.9 W (average) for the counterpart of full-wave rectification system. In addition, bench test results also validate the energy harvesting in wideband frequency range. Treadmill tests demonstrate an average power range of 1.2–11.0 W under walking speeds of 3.2–6.4 km/h with a 13.6 kg payload.
Physics-Informed Gaussian Process Based Optimal Control of Laser Powder Bed Fusion
Authors: Ren Yong , Wang Qian
Published: January 2021

Regulating the melt-pool size to a constant reference value during the build process is a challenging task in Laser Powder Bed Fusion additive manufacturing (LPBF-AM). This paper considers adjusting laser power to achieve a constant melt-pool volume during laser processing of a multi-track build under LPBF-AM. First, a Gaussian Process Regression (GPR) is applied to model the variation of the melt-pool volume along the deposition distance, with physics-informed input features. Then a constrained finite-horizon optimal control problem is formulated, with a quadratic cost function defined to minimize the difference between the melt-pool volume and a reference value. A projected gradient descent algorithm is applied to compute the sequence of laser power in the proposed optimal control problem. The GPR modeling of melt-pool dynamics is trained and tested using simulated data sets generated from a commercial finite-element based AM software, and the same commercial AM software is used to evaluate the control performance. Simulation results demonstrate the effectiveness of the proposed GPR modeling and optimal control in regulating melt-pool volume for building multi-track parts with LPBF-AM.
Contact-Rich Trajectory Generation in Confined Environments Using Iterative Convex Optimization
Authors: Zhao Wei-Ye , He Suqin , Wen Chengtao , Liu Changliu
Published: January 2021

Applying intelligent robot arms in dynamic uncertain environments (i.e., flexible production lines) remains challenging, which requires efficient algorithms for real time trajectory generation. The motion planning problem for robot trajectory generation is highly nonlinear and nonconvex, which usually comes with collision avoidance constraints, robot kinematics and dynamics constraints, and task constraints (e.g., following a Cartesian trajectory defined on a surface and maintain the contact). The nonlinear and nonconvex planning problem is computationally expensive to solve, which limits the application of robot arms in the real world. In this paper, for redundant robot arm planning problems with complex constraints, we present a motion planning method using iterative convex optimization that can efficiently handle the constraints and generate optimal trajectories in real time. The proposed planner guarantees the satisfaction of the contact-rich task constraints and avoids collision in confined environments. Extensive experiments on trajectory generation for weld grinding are performed to demonstrate the effectiveness of the proposed method and its applicability in advanced robotic manufacturing.
Position and Attitude Control of Underactuated Drones Using the Adaptive Function Approximation Technique
Authors: Shamshirgaran Azin , Ebeigbe Donald , Simon Dan
Published: January 2021

Despite the popularity of drones and their relatively simple operation, the underlying control algorithms can be difficult to design due to the drones’ underactuation and highly nonlinear properties. This paper focuses on position and orientation control of drones to address challenges such as path and edge tracking, and disturbance rejection. The adaptive function approximation technique control method is used to control an underactuated and nonlinear drone. The controller utilizes reference attitude signals, that are derived from a proportional derivative (PD) linear feedback control methodology. To avoid analytic expressions for the reference attitude velocities, we employ a continuous-time Kalman filter based on a model of the measurement signal — which is derived by passing the reference attitude position through a low-pass signal differentiator — as a second-order Newtonian system. Stability of the closed loop system is proven using a Lyapunov function. Our design methodology simplifies the control process by requiring only a few tuning variables, while being robust to time-varying and time-invariant uncertainties with unknown variation bounds, and avoids the requirement for the knowledge of the dynamic equation that governs the attitude of the drone. Three different scenarios are simulated and our control method shows better accuracy than the proportional-derivative controller in terms of edge tracking and disturbance rejection.
Computationally Efficient Urea-Dosing Controllers for Urea-SCR
Authors: Ganne Rajakumar , Jain Kaushal K. , Meckl Peter H. , Angre Harshil , Hiremath Jagdish R.
Published: January 2021

This paper presents two non-model-based reference-shaping and a model-based predictive urea-dosing controller for the Urea-SCR system. An ideal urea-dosing controller would minimize both tailpipe NOx and NH3 slip. However, this is not possible because of the trade-off between deNOx and NH3 slip. This trade-off is used to clearly define a control objective in terms of NH3 slip. Three controllers are then developed to meet this control objective such that they are all computationally inexpensive. The three controllers are then tested for three very different drive cycles. Simulation results show that the performance of the non-model based reference-shaping controllers is subjected to manual tuning of their variables. In contrast, the predictive controller, which is the highlight of this paper, can adapt to various drive cycles without compromising on the computational cost.
A Numerical Investigation of an Eddy Current Sensor for Detecting Small Defects in Metal Additive Manufacturing
Authors: Guo Zhengya , Lee Kok-Meng , Hao Bingjie , Xiong Zhenhua
Published: January 2021

This paper presents a parametric study of an eddy current (EC) sensor that measures the magnetic flux density (MFD) for detecting lack-of-fusion defects commonly found in metal additive manufacturing (Metal-AM). In this study, the EC-sensing system is simulated using a two-stage method that decomposes the EC-based detection of a defective conductor into two subproblems; the first analytically solves for the EC assuming no defects, and the second solves for the EC perturbation in the focused regions near the defects using a distributed current source method. Based on the proposed EC model, the effects of geometrical parameters on the sensitivity of an EC-sensing system were analyzed and verified by comparing with finite-element analysis (FEA). The study leads to the identification of two key parameters that significantly affect the sensitivity and accuracy of an EC sensor for detecting small defects, which are the locations and axes of the MFD sensors relative to the coil. The ECD distributions are simulated for two EC-sensor design scenarios: fixed at specified locations, and scanning over the entire specimen. Both DCS-based and FEA results match excellently well when images are at a fixed senor location. When scanning, DCS-based images are much smoother and require significantly less time to scan as compared to FEA that requires remeshing between steps and exhibits significant numerical noise, demonstrating the accuracy and efficiency of the proposed numerical model.
Optimal Control of a Multirotor Unmanned Aerial Vehicle Based on a Multiphysical Model
Authors: Michel Nicolas , Kong Zhaodan , Lin Xinfan
Published: January 2021

Electric multirotor aircraft with vertical-take-off-and-landing capabilities are emerging as a revolutionary transportation mode. This paper studies optimal control of a multirotor unmanned aerial vehicle based on a system-level multiphysical model. The model considers aerodynamics of the rotor-propeller assembly, electro-mechanical dynamics of the motor and motor controller, and rigid-body dynamics of the vehicle, as control based on a system-level model incorporating all these dynamics and their coupling is missing in literature. A forward flight operation is considered for time-optimal and energy-optimal control, as well as battery voltages of 25 V and 21 V. Energy-optimal control is shown to reduce the energy required for the operation by 38.5% at 25 V, while reducing the battery voltage increases the minimum operation time by 19.8%. The energy-optimal cruise velocity is also examined, demonstrating that the optimal velocity predicted without considering rotor aerodynamics uses 35.2% more energy per meter travelled than is required at the true optimal velocity.
NEMS Circular Plates Under Hard Electrostatic Excitations: Amplitude-Frequency Response of Superharmonic Resonance of Second Order to Include Casimir Effect
Authors: Caruntu Dumitru I. , Beatriz Julio , Huerta Benjamin
Published: January 2021

This work deals with the frequency-amplitude response of the superharmonic resonance of second order of electrostatically actuated clamped NEMS circular plate resonators. The NEMS system consists of a circular plate parallel to a ground plate. Hard excitations (large AC voltage) due to the electrostatic force of frequency near one fourth of the natural frequency of the plate resonator leads the plate into a superharmonic resonance of second order. Hard excitations are excitations significant enough to produce resonance although far from the primary resonance zone. There is no DC component in the voltage applied. For the partial differential equation of motion two reduced order models are developed. The first one uses one mode of vibration and it is solved using the Method of Multiple Scales (MMS), and the frequency-amplitude response is predicted. Hard excitations were modeled by keeping the first term of the Taylor polynomial of the electrostatic force as a large term. The second model uses two modes of vibration, and it is solved using numerical integration. This produces time responses of the resonator. In this work, the quantum dynamics effect such as Casimir effect is considered significant. The two branches, one unstable and one stable, with a saddle node bifurcation point are predicted. Both methods are in agreement for amplitudes up to 0.7 of the gap. The effect of damping and voltage on the frequency response are reported.
Control-Oriented Modeling of Cycle-to-Cycle Combustion Variability at the Misfire Limit in SI Engines
Authors: Maldonado Bryan P. , Kaul Brian C.
Published: January 2021

A control-oriented model is presented that can capture the prior-cycle correlation of combustion cycles during conditions with high levels of exhaust gas recirculation (EGR). Combustion events are modeled in discrete time and the dynamic evolution is captured by the residual air, fuel, and inert gas trapped in the combustion chamber. The mathematical formulation of the model is presented together with the calibration procedure to emulate a particular engine operating condition. A cycle-to-cycle system identification methodology is described which allows regressing model parameters from experimental data. Simulations are presented and compared to real engine measurements to show the modeling potential for analysis and control of combustion events.
The Effect of Simultaneous Auditory and Visual Sensing Cues in a Two-Dimensional Vicsek Model
Authors: Lemus Jeremy , Roy Subhradeep
Published: January 2021

Collective behavior refers to the group-level organization arising from interaction among individuals. To exchange information the individuals rely on their sensing modalities. Experimental studies provide evidence that the integration of information from multiple sensory modalities can influence animal navigation and social communication. In this paper, we present a modified Vicsek model with a composite sensing scheme that combines both auditory and visual sensing cues through the set of sensory neighbors. We investigate the combined effect of auditory and visual sensing on the group behavior compared to pure vision and audition using numerical simulation. We observe that taking the advantage of composite modality, the particles get access to more information that enables them to form a single large, cohesive, and perfectly aligned group using a narrow sensing region, which is possible in either vision or audition only using a wider sensing region.