FEA-Based Fatigue Life Assessment of Cycloidal Displacement Cam and Flat-Faced Follower Mechanism

Cam-followers provide reliable and controlled motions in various mechanical systems. Due to the highly fluctuating load between the cam and follower in operation, the cam-follower may be subjected to a high risk of contact fatigue failure. This paper assesses the fatigue life of a cycloidal displacement cam and a flat-faced follower under the defined loads and constraints. Computer-aided design (CAD) model of the cam-follower is developed in CATIA software and imported to ANSYS software for finite element analysis (FEA) of fatigue life. MATLAB programming is developed for determining the appropriate spring constant and pre-load force to always keep the cam and follower in contact. The fatigue life of the cam-follower has been estimated under the specified operating conditions. The analysis method can be applied to investigate the fatigue life of cams with other profiles, including the modified trapezoidal functions, polynomial functions, etc.

Investigating the characteristic delay time in the leader–follower behavior in children single-file movement

The single-file movement experiment offered a convenient way to investigate the one-dimensional leader–follower behavior of pedestrians. This study investigated the time delays of children pedestrians in the leader–follower behavior by introducing a time-dependent delayed speed correlation. A total of 118 German students from the fifth grade(aged11–12 years old) and the 11th grade(aged 17–18 years old) participated the single-file experiment. The characteristic delay time for each pedestrian was identified by optimising the time-dependent delayed speed correlation. The influences of the curvature of the experimental scenario, density, age, and gender on the delay time were statistically examined. The results suggested that to a large extent, the revealed characteristic delay time was a density-dependent variable, and none of the curvatures, the age and gender of the individual, and the age and gender of the leader had a significant influence on it. The findings from this study are variable resources to understand the leader–follower behavior among children pedestrians and to build related simulation models.

Trade credit financing for supply chain coordination under financial challenges:a multi‑leader–follower game approach

This study is designed to solve supply chain inefficiencies caused by some members’financial problems,such as capital shortages and financing restrictions in a stochastic environment.To this end,we have established a supply chain finance framework by designing two novel coordinating contracts based on trade credit financing for different problem settings.These contracts are modeled in the form of multi-leader Stackelberg games that address horizontal and vertical competition in a supply chain consisting of multiple suppliers and a financially constrained manufacturer.However,previous studies in the trade credit literature have addressed only simple vertical competition,that is,seller-buyer competition.To solve the proposed models,two algorithms were developed by combining population-based metaheuristics,the Nash-domination concept,and the Nikaido-Isoda function.The results demonstrate that the proposed supply chain finance framework can eliminate supply chain inefficiencies and make a large profit for suppliers,as well as the financially constrained manufacturer.Furthermore,the results of the contracts’analysis showed that if the manufacturer is required to settle its payments to suppliers before the end of the period,the trade credit contract cannot coordinate the supply chain because of a lack of incentive for suppliers.However,if the manufacturer is allowed to extend its payments to the end of the period,the proposed trade credit financing contract can coordinate the supply chain.Finally,the sensitivity analysis results indicate that the worse the financial status of the manufacturer,the more bargaining power suppliers have in determining the contract parameters for more profit.

Precious Scrolls of Chinese Devout Women Buddhist Followers:A Case Study of Wilt Idema’s Pitfalls of Piety for Married Women

Deeply-rooted in China’s popular culture,precious scrolls(Baojuan)are the golden material to display popular religious belief of the mass.Based on the rare texts sorted and annotated by Shang Lixin,Dutch Sinologist Wilt L.Idema continues his journey of translating precious scrolls.Focused on the theme of devoted women Buddhist followers in Ming dynasty,he explores the ethical choices of married women in facing the betrayal of servants or concubines.His translations not only add important reading material to Western readers in the field of Chinese popular literature,but also set standard for the coming translators in rendering Chinese ballads.

Multi-circular formation control with reinforced transient profiles for nonholonomic vehicles:A path-following framework

This article investigates a multi-circular path-following formation control with reinforced transient profiles for nonholonomic vehicles connected by a digraph.A multi-circular formation controller endowed with the feature of spatial-temporal decoupling is devised for a group of vehicles guided by a virtual leader evolving along an implicit path,which allows for a circumnavigation on multiple circles with an anticipant angular spacing.In addition,notice that it typically imposes a stringent time constraint on time-sensitive enclosing scenarios,hence an improved prescribed performance control(IPPC)using novel tighter behavior boundaries is presented to enhance transient capabilities with an ensured appointed-time convergence free from any overshoots.The significant merits are that coordinated circumnavigation along different circles can be realized via executing geometric and dynamic assignments independently with modified transient profiles.Furthermore,all variables existing in the entire system are analyzed to be convergent.Simulation and experimental results are provided to validate the utility of suggested solution.

Path-Following Based on Nonlinear Model Predictive Control with Adaptive Path Preview

This paper presents a Nonlinear Model Predictive Controller(NMPC)for the path following of autonomous vehicles and an algorithm to adaptively adjust the preview distance.The prediction model includes vehicle dynamics,path following dynamics,and system input dynamics.The single-track vehicle model considers the vehicle’s coupled lateral and longitudinal dynamics,as well as nonlinear tire forces.The tracking error dynamics are derived based on the curvilinear coordinates.The cost function is designed to minimize path tracking errors and control effort while considering constraints such as actuator bounds and tire grip limits.An algorithm that utilizes the optimal preview distance vector to query the corresponding reference curvature and reference speed.The length of the preview path is adaptively adjusted based on the vehicle speed,heading error,and path curvature.We validate the controller performance in a simulation environment with the autonomous racing scenario.The simulation results show that the vehicle accurately follows the highly dynamic path with small tracking errors.The maximum preview distance can be prior estimated and guidance the selection of the prediction horizon for NMPC.

A Novel Prescribed-Performance Path-Following Problem for Non-Holonomic Vehicles

The issue of achieving prescribed-performance path following in robotics is addressed in this paper,where the aim is to ensure that a desired path within a specified region is accu-rately converged to by the controlled vehicle.In this context,a novel form of the prescribed performance guiding vector field is introduced,accompanied by a prescribed-time sliding mode con-trol approach.Furthermore,the interdependence among the pre-scribed parameters is discussed.To validate the effectiveness of the proposed method,numerical simulations are presented to demonstrate the efficacy of the approach.

Environmental Impact Assessment Follow-Up of Seismic Survey Offshore Activities in Brazil

Follow-up of environmental impacts is an integral part of the Environmental Impact Assessment (EIA) process, closely related to the effectiveness of the instrument. EIA follow-up has been receiving a lot of interest from scientists and practitioners, though it is recognized as one of the weakest points of EIA systems globally. Also, EIA follow-up is influenced by the context, mainly in terms of the types of projects or activities and their related impacts on the environment. Therefore, the present paper is focused on the investigation of the follow-up stage applied to the activity of seismic survey coupled with offshore oil & gas exploitation in Brazil. Research was based on a qualitative approach that included document analysis and semi-structured interviews with analysts involved in EIA processes, and sought to generate evidence of effectiveness of the EIA follow-up as conducted by the Federal Environment Agency (Ibama) in order to situate the practice of follow-up in the broader context of international best practice principles. Based on the findings, it was concluded that, due to the peculiarities of offshore seismic survey, it is necessary to promote adaptations in the procedures for monitoring impacts in order to ensure proper alignment with the principles and conceptual foundations that guide EIA practice. Specifically, the timing of the execution of the activity imposes challenges for its integration into the “conventional” cycle that has guided the monitoring of the impacts in the EIA of projects.

Parent-Reported Reasons for Loss-to-Follow Up in Patients Hospitalized at the Neonatology Unit at Laquintinie

Introduction: Despite the known benefits of newborn follow-up clinics, attendance has historically been difficult. Infants with reported follow-up difficulty have a greater incidence of severe sensorimotor and cognitive deficits and poorer access to early intervention programs. Our objective was to determine the parent-reported reasons for loss-to-follow up in patients hospitalised at the neonatology unit of Laquintinie Hospital. Methodology: We carried out a cross-sectional study through phone interviews with parents/caregivers of patients hospitalised at Laquintinie over a 2-year period from 1st January 2021 to 31st December 2022. A non-standardised structured interview guide was used for data collection. Loss-to-follow up referred to absence to at least one visit as recorded in the neonatal follow-up chart. All necessary administrative and ethical considerations were duly respected. Results: Most neonates were born through vaginal delivery (n = 313, 69.45%). The neonates were admitted at a median gestational age of 33 weeks (Q1-Q3;32 - 35) and the median duration of hospitalisation was 12 days (Q1 - Q3;8 - 18). A total of 23 neonates had died at the time of interview giving a mortality rate of 5.1%. The three most reported reasons for loss-to-follow-up was lack of money (n = 310, 68.13%), assumption that follow-up had ended (n = 37, 8.13%), and newborn that died (n = 23, 5.1%). Conclusion: This study highlights the significant impact of financial constraints and absence of a robust follow-up system on poor uptake of neonatal follow-up post-discharge in resource limited settings like Cameroon. Our results serve as advocacy for national health insurance especially in neonates.

缺乏位置信息的视觉移动机器人leader-following编队控制

针对视觉移动机器人编队在缺乏位置信息情况下的控制问题,提出一种基于视觉的leader-following编队反馈控制方法。该方法利用leader标志物特征点在follower摄像机像平面上的坐标信息设计了观测器,对leader与follower间的相对位置进行估计,基于相对位置估计量与它们速度的关系,设计出leader-following编队反馈控制器,通过Lyapunov理论证明了闭环系统的稳定性。仿真结果表明,该控制方法能有效解决缺乏位置信息情况下视觉移动机器人编队的控制问题。

基于Leader-follower与人工势场的多移动机器人编队控制

目的提出一种基于Leader-follower法和人工势场法相结合的多移动机器人编队控制方法,从而克服传统Leader-follower法中由微分方程确定的控制率无法将队形控制与避障统一的缺点.方法确定关于参数l和φ的人工势场函数,通过控制参数l和φ,使多移动机器人保持预定队形;机器人follower通过主动避障方法躲避障碍物,确定一个总的人工势场控制队形和避障.结果算法能使多移动机器人系统成功地进行编队和避障.结论通过仿真试验,机器人系统能够顺利通过狭窄通道,躲避静态障碍物和动态障碍物,并在避障后恢复队形,顺利到达目标,算法简单,从而验证了算法的有效性.

采用Leader-follower和模糊反馈机制的机器鱼队形控制

在Leader-follower框架下的多机器鱼系统队形控制中,针对Leader和Follower相对独立及落后机器鱼离队等问题,在传统的Leader-follower队形控制算法中引入模糊反馈控制器进行反馈调节,使得领航机器鱼Leader能定时检查Follower的位置,将多机器鱼系统的队形控制问题转化为具有反馈调节的Follower跟踪Leader的位置和方向的问题,以增强多机器鱼队形控制的稳定性,更好地协同作业完成任务.仿真试验验证了所提出的方法能较好地实现多机器鱼系统的队形控制.

基于Leader-Follower的多机器鱼模糊队形控制

针对多机器鱼系统队形控制中队形发生突变,机器鱼无法快速反应的问题,本文采用模糊控制的方法对机器鱼的速度和航向角度进行控制,使跟随者快速准确的到达期望位姿。同时,以3条鱼为例,对多机器鱼队形运动进行仿真验证,仿真结果表明,当领航者直行时,跟随者与领航者的运动和速度相等;当领航者改变方向和速度后,跟随者可在较短时间内通过速度和方向挡位的改变达到期望位置,并保持规定队形。该方法可以调节运动参数,保持队形稳定,实现多机器鱼按一定队形完成规定路径,其跟随效果良好。

A Novel NeuMOS Source Follower Cell with High Precision

A novel neuMOS source follower circuit is presented.The cell can complete the s ource follower function even if the input voltage is lower than the threshold of the source follower,thus high-precision operation of the circuit is achieved. The simulation and the measurement results show that its precision is higher tha n that of other neuMOS source follower circuits.

GRACE与GRACE Follow-On重力卫星数据揭示出的黄河流域2002-2020年干旱特征

研究黄河流域干旱时空变化特征,对认知黄河流域水资源演化规律具有重要意义。本文充分利用GRACE(gravity recovery and climate experiment)与GRACE-FO(GRACE Follow-On)重力卫星在大尺度范围下监测水文信息变化中的优势,基于2002年4月至2020年7月GRACE和GRACE-FO RL06 Mascon数据,计算了黄河流域陆地水储量异常(terrestrial water storage anomaly,TWSA)及对应的水储量亏损赤字(water storage deficit index,WSDI),据此分析了黄河流域上游、中下游干旱事件及其严重性、干旱持续时间、平均与最大水储量赤字等干旱特征,并与其他4种常用干旱指数,标准降水蒸散发指数(standardized precipitation evaporation index,SPEI)、自矫正帕尔默干旱指数(self correct-Palmer drought severity index,sc-PDSI)、标准化降水指数(standardized precipitation index,SPI)和标准化径流指数(standardized runoff index,SRI)识别结果进行了对比分析。研究结果表明:在WSDI识别出的黄河流域上游、中下游分别发生的5期干旱事件及其对应的干旱等级中,存在其他传统干旱指数未识别现象;在黄河流域以往干旱事件识别中,WSDI也展现出了较其他4种传统干旱指数显著的识别优势。相比传统干旱指标多仅依赖于稀疏地表水文监测信息,基于重力卫星监测数据的WSDI干旱指标可在大尺度范围下有效识别出流域干旱特征。

Leader-following多自主体系统时变编队跟踪控制

考虑时变时延,研究了高阶leader-following多自主体系统的分布式时变编队跟踪控制问题.针对连续高阶多自主体系统,设计了基于观测器的时变编队跟踪控制协议,通过状态变换,将系统的时变编队跟踪控制问题,转变为误差系统的稳定性问题.然后利用图论及李雅普诺夫稳定定理,研究了系统实现时变编队跟踪控制的充分条件,并且指出时变编队参考函数与时变时延无关.最后,数据仿真结果证明了所设计的协议能使follower自主体实现时变编队,并且跟踪leader自主体的轨迹.

基于条件反馈机制Leader-follower多机器人队形控制

针对Leader-follower多机器人系统队形控制中,Leader和follower相对独立及落后机器人离队等问题,采用基于条件反馈机制的Leader-follower多机器人队形控制方法,建立基于条件反馈机制和Lead-follower相结合的多机器人队形控制模型。将多机器人系统的队形控制问题转化为基于条件反馈机制的follower跟踪leader的位置和方向的问题,通过实例仿真验证了方法的有效性。仿真结果表明所提出的方法是合理有效的,使多机器人系统能够有效地完成编队控制任务。

基于Leader-follower的自主车辆跟随控制器设计

为解决自主车辆的跟随控制中误差系统的稳定性问题,基于Leader-follower法设计了车辆跟随控制器。对自主车辆进行运动学建模,采用Leader-follower模型描述车辆跟随结构,用L-φ控制方法建立车辆跟随误差系统,设计跟随车辆的速度控制器,以实现跟随车辆对领航车辆的稳定跟随。通过Matlab仿真实验结果证明,该控制器使误差最终收敛到0,能达到跟随控制的目的。

基于Leader-Follower和一致性理论的多机器鱼避障控制研究

主要研究了多机器鱼队形控制的主要方法,提出了一种基于Leader-Follower框架和一致性理论的多机器鱼避障控制方法。分别分析了多机器鱼在无障碍环境和运动到障碍物区域时的队形运动。这种方法结合了Leader-Follower法和一致性理论的优点,能更好地实现多机器鱼在遇到障碍物后实现避障,从而完成整个系统的队形控制。最后仿真结果验证了该方法的可行性。

往复工作路径下Leader-follower算法的编队控制研究

多智能体编队在实际作业中,多以往复的工作路径进行,如货箱的搬运、区域的巡视监控等,如何在重复工作中确保多智能体编队的稳定性成为人们较为关注的问题。因此,利用Leader-follower控制算法理论中的l-φ法,规划follower的线速度和角速度,来保持多智能体队型的稳定性,并通过调整闭环控制系数来控制编队的收敛速度。通过MATLAB数值仿真,分别刻画了多智能体往复运动的位移时间响应图和相轨迹图等,从而验证了多智能体编队在往复工作路径任务下的稳定性。