Distributed Predefined-Time Control for Cooperative Tracking of Multiple Quadrotor UAVs

Dear Editor,This letter addresses the predefined-time control for cooperative tracking of multiple quadrotor unmanned aerial vehicles(UAVs)under a directed communication network.A predefined-time distributed estimator is first introduced to accurately get the reference velocity and acceleration for each UAV.

Modeling and Trajectory Tracking Control for Flapping-Wing Micro Aerial Vehicles

This paper studies the trajectory tracking problem of flapping-wing micro aerial vehicles(FWMAVs)in the longitudinal plane.First of all,the kinematics and dynamics of the FWMAV are established,wherein the aerodynamic force and torque generated by flapping wings and the tail wing are explicitly formulated with respect to the flapping frequency of the wings and the degree of tail wing inclination.To achieve autonomous tracking,an adaptive control scheme is proposed under the hierarchical framework.Specifically,a bounded position controller with hyperbolic tangent functions is designed to produce the desired aerodynamic force,and a pitch command is extracted from the designed position controller.Next,an adaptive attitude controller is designed to track the extracted pitch command,where a radial basis function neural network is introduced to approximate the unknown aerodynamic perturbation torque.Finally,the flapping frequency of the wings and the degree of tail wing inclination are calculated from the designed position and attitude controllers,respectively.In terms of Lyapunov's direct method,it is shown that the tracking errors are bounded and ultimately converge to a small neighborhood around the origin.Simulations are carried out to verify the effectiveness of the proposed control scheme.

5000 m岩心钻机司钻室人机工程设计

司钻室是岩心钻机的控制中枢,融多种功能于一体,能够显示各种钻井参数和电气参数,具有钻井控制、设备监控、通讯等功能,可为司钻人员提供安全、集中、方便、舒适、高效的工作环境。本文以H点、眼椭圆人机工程学理论为基础,对5000 m岩心钻机司钻室的座椅、仪表台、显示屏、操纵装置及空间布局进行了设计,提出了组合式、一体式、分布式三种布局,并基于人机环境和适应性等条件选择了最优方案。

Core discing characteristics and mitigation approach by a novel developed drill bit in deep rocks

Core discing often occurs in deep rocks under high-stress conditions and has been identified as an important characteristic for deep rock engineering.This paper presents the formation mechanism of core discing firstly.Then,the interaction between diamond drill bits and rock was analyzed based on numerical modeling.A novel drill bit with an inner conical crown for the mitigation of core discing was designed and verified by simulation experiments.The mitigation method was applied in the cavern B1 of CJPL-Ⅱand satisfactory results had been achieved.The percentage of core discing had been obviously decreased from 67.8%when drilling with a rectangular crown drill bit,to 26.5%when an inner conical crown drill bit had been adopted.This paper gives full insight into core discing characteristics and provides a new method for core discing mitigation;it will potentially contribute to stress measurement in deep rock engineering.

Visual Object Tracking and Servoing Control of a Nano-Scale Quadrotor:System,Algorithms,and Experiments

There are two main trends in the development of unmanned aerial vehicle(UAV)technologies:miniaturization and intellectualization,in which realizing object tracking capabilities for a nano-scale UAV is one of the most challenging problems.In this paper,we present a visual object tracking and servoing control system utilizing a tailor-made 38 g nano-scale quadrotor.A lightweight visual module is integrated to enable object tracking capabilities,and a micro positioning deck is mounted to provide accurate pose estimation.In order to be robust against object appearance variations,a novel object tracking algorithm,denoted by RMCTer,is proposed,which integrates a powerful short-term tracking module and an efficient long-term processing module.In particular,the long-term processing module can provide additional object information and modify the short-term tracking model in a timely manner.Furthermore,a positionbased visual servoing control method is proposed for the quadrotor,where an adaptive tracking controller is designed by leveraging backstepping and adaptive techniques.Stable and accurate object tracking is achieved even under disturbances.Experimental results are presented to demonstrate the high accuracy and stability of the whole tracking system.

Moving Target Landing of a Quadrotor Using Robust Optimal Guaranteed Cost Control

Dear Editor,This letter proposes a robust control strategy for the autonomous landing of a quadrotor on a moving target.Specifically,a force command that consists of a cascade dynamics estimator and an optimal guaranteed cost control law is exploited for the position-loop tracking.Then,an orientation constraint torque command is employed for the attitude-loop tracking such that the quadrotor refrains from flipping during the landing operation.

5000 m地质岩心钻机卡钻工况下瞬态动力学仿真

本文对5000 m地质岩心钻机卡钻状态的井架载荷进行了瞬态动力学仿真分析,首先分析了井架的结构特点,然后分析了井架在卡钻情况下受到的瞬态载荷,并对井架在这种特殊工况下的瞬态动力学响应进行了有限元仿真。根据仿真结果,得出了井架在卡钻这种特殊瞬态载荷作用下的危险点,对井架的结构设计及结构优化具有一定的指导意义。

基于改进应变能法的无环索弦支穹顶拉索重要性评价

基于上部网壳总应变能变化量峰值和上部网壳杆件应变能变化率标准差提出一种改进应变能法,用于评价无环索弦支穹顶不同部位的拉索重要性。改进应变能法采用上部网壳总应变能变化量峰值作为主要评价指标,其目的是表征断索后上部网壳的最不利状态且避免断索导致的下部预应力索杆体系应变能损失对以结构总应变能为指标的评价结论的干扰。改进应变能法采用上部网壳杆件应变能变化率标准差作为辅助评价指标的目的是考虑上部网壳不同部位应变能变化的分布情况。以含有三层无环索预应力索杆体系的直径100 m的无环索弦支穹顶为例。首先,建立结构有限元分析模型,通过施加预应力和外荷载得到无环索弦支穹顶的荷载态。然后,基于荷载态采用杆件瞬时移除技术完成断索模拟,采用中心差分积分模式的修正拉格朗日列式增量解法求解断后无环索弦支穹顶的杆件内力时程和节点位移时程。同时,基于杆件内力时程和节点位移时程,求得上部网壳每根杆件的应变能时程。最后,在此基础上,求得上部网壳总应变能时程和上部网壳杆件应变能变化率标准差。如果某部位断索后发生了结构连续倒塌,则该位置拉索的重要性排在首位或并列排在首位;如果未发生结构连续倒塌,则根据不同部位断索后的上部网壳总应变能变化量峰值和上部网壳杆件应变能变化率标准差为指标评价不同部位拉索的重要性。比较上部网壳总应变能变化量峰值,当断索后上部网壳总应变能变化量峰值越大,则该部位的拉索重要性越高;当上部网壳总应变能变化量峰值较为接近时,应补充比较上部网壳杆件应变能变化率标准差:上部网壳杆件应变能变化率标准差越大,拉索重要性越高。结果显示:无环索弦支穹顶的所有拉索预应力乘以相同倍数后以及所有拉索的截面面积乘以相同倍数后,采用以结构总应变能作为评价指标的拉索重要性评价结论会随预应力倍数和截面面积倍数的变化发生明显变化。这种现象的主要原因是下部预应力索杆体系应变能下降而上部单层网壳应变能上升,导致结构总应变能变化规律复杂。基于改进应变能法,采用上部网壳总应变能变化量峰值和上部网壳杆件应变能变化率标准差作为评价指标,则拉索重要性评价结论不随预应力倍数、截面面积倍数和上部网壳形式的变化而变化,避免了下部预应力索杆体系应变能下降带来的干扰,且可以有效区分不同部位的拉索重要性。研究表明:基于结构总应变能指标的拉索重要性评价方法不适用于无环索弦支穹顶,提出的改进应变能法可以有效评价无环索弦支穹顶不同部位拉索的重要性。基于改进应变能法分析发现:最外层预应力索杆体系中索力较大,断索的不对称变形导致不同部位拉索的重要性略有区别,拉索的中间段的重要性略小于其余各段;其余各层的索力远小于最外层,不同部位拉索的重要性没有明显区别。不同层预应力索杆体系之间,最外层的拉索重要性最高,向内依次降低。分析中还发现,断索部位附近的网壳杆件应变能变化较为明显,而距离断索部位较远的网壳杆件受到的影响很小;断索仅对无环索弦支穹顶的局部有影响,对结构主体的影响不大。

野生和人工饲喂条件下甘肃鼢鼠肠道细菌多样性比较

【目的】肠道微生物在宿主代谢和健康方面发挥着重要的作用,已有报道表明甘肃鼢鼠肠道菌群和地域、性别以及季节等因素有关,但对于野生和人工饲喂条件下,取食不同食物的甘肃鼢鼠肠道菌群是否存在差异尚不明确。【方法】本研究选取苜蓿、樟子松根、油松根和云杉根对甘肃鼢鼠进行分组饲喂,同时以野生个体作为对照,采用16S rRNA V3-V4高通量测序技术对野生和人工饲喂甘肃鼢鼠肠道细菌进行比较。【结果】野生和人工饲喂条件下,优势菌门均为Firmicutes和Bacteroidetes,但含量却存在显著性差异。在人工饲喂条件下,樟子松根、油松根和云杉根饲喂的三组甘肃鼢鼠肠道细菌群落结构相似度较高,而与苜蓿组和野生组之间均存在较大差异,樟子松组、油松组和云杉组甘肃鼢鼠肠道细菌多样性高于苜蓿组和野生组。【结论】野生和人工饲喂条件下甘肃鼢鼠肠道菌群组成和结构存在显著性差异。

不同因素对六盘山地区甘肃鼢鼠肠道细菌多样性的影响

【目的】研究甘肃鼢鼠肠道细菌的群落结构和多样性,探讨不同环境因素对六盘山地区甘肃鼢鼠肠道细菌多样性的影响。【方法】通过Illumina高通量测序技术,对甘肃鼢鼠的36个盲肠样品进行16S rRNA V3–V4区的高通量测序,分析了肠道细菌多样性、丰度和群落结构,探讨地域、性别和季节等因素对甘肃鼢鼠肠道细菌多样性的影响。【结果】甘肃鼢鼠肠道细菌群落主要包括3个门,其中Firmicutes门占主导地位,其次是Bacteroidetes和Proteobacteri。在属水平,优势菌属分别为Oscillospira、Ruminococcus、Coprococcus和Desulfovibrio等。不同县(区)样品中,彭阳县、隆德县和泾源县三个县的甘肃鼢鼠肠道细菌菌群结构相似度较高,海原县甘肃鼢鼠肠道细菌群落结构在组内相似度高,与其他县(区)相似度低;雌性甘肃鼢鼠肠道细菌群落结构相似性高,而雄性细菌群落结构在样品间差异较大;甘肃鼢鼠肠道细菌菌群多样性秋季显著高于春季,细菌群落结构相似度秋季高于春季。【结论】不同地域、性别和季节因素对甘肃鼢鼠肠道细菌群落结构产生显著的影响,甘肃鼢鼠肠道细菌群落结构和多样性的变化对基于食源的季节性变化具有积极的响应。

A comprehensive review of Energy Internet: basic concept,operation and planning methods, and research prospects

With the intensifying energy crisis and environmental pollution, the Energy Internet and corresponding patterns of energy use have been attracting more and more attention. In this paper, the basic concept and characteristics of the Energy Internet are summarized, and its basic structural framework is analyzed in detail. On this basis,couplings between the electric power system and other systems such as the cooling and heating system, the natural gas system, and the traffic system are analyzed, and the operation and planning of integrated energy systems in both deterministic and uncertain environments are comprehensively reviewed. Finally, the research prospects and main technical challenges of the Energy Internet are discussed.

A Miniature Video Stabilization System for Flapping-Wing Aerial Vehicles

In this paper,a miniature video stabilization system is designed to deal with the image jitter and motion blur problem for°apping-wing aerial vehicles(FWAVs).First,a light and two-axis pan–tilt(about 13 g)is built for the FWAV to counteract most of the jitter e®ect.Then,an electronic image stabilization method combined with a Micro-Electro Mechanical Systems(MEMSs)gyroscope is proposed to further stabilize the images.Finally,°ight experiment results show that the designed video stabilization system e®ectively improves the quality of aerial videos.

Voltage Profile Optimization of Active Distribution Networks Considering Dispatchable Capacity of 5G Base Station Backup Batteries

The penetration of distributed energy resources(DERs) and energy-intensive resources is gradually increasing in active distribution networks(ADNs), which leads to frequent and severe voltage violation problems. As a densely distributed flexible resource in the future distribution network, 5G base station(BS) backup battery is used to regulate the voltage profile of ADN in this paper. First, the dispatchable potential of 5G BS backup batteries is analyzed. Considering the spatial-temporal characteristics of electric load for 5G BS, the dispatchable capacity of backup batteries at different time intervals is evaluated based on historical heat map data. Then, a voltage profile optimization model for ADN is established, consisting of 5G BS backup batteries and other voltage regulation resources. In this model, the charging/discharging behavior of backup batteries is based on its evaluation result of dispatchable capacity. Finally, the range of charging/discharging cost coefficients of 5G BS that benefits ADN and 5G operators are analyzed respectively. Further, an incentive policy for 5G operators is proposed. Under this policy, the charging/discharging cost coefficients of 5G BS can achieve a win-win situation for ADN and 5G operators. As an emerging flexible resource in ADN, the effectiveness and economy of 5G BS backup batteries participating in voltage profile optimization are verified in a test distribution network.

Novel diagnostic approaches for Fanconi anemia (FA) by single-cell sequencing and capillary nano-immunoassay

Next-generation sequencing technology has been widely utilized for the diagnosis of Fanconi anemia(FA).However,mixed cell sequencing and chimerism of FA patients may lead to unconfirmed genetic subtypes.Herein,we introduced two novel diagnostic methods,including single-cell sequencing and capillary nano-immunoassay.One FA case with FANCM c.4931G>A p.R1644Q and FANCD1 c.6325G>A p.V2109I was studied.The DNA of 28 cells was amplified and eight types of cells were observed after Sanger sequencing.There were two homozygous mutations(FANCM/FANCD1).Furthermore,the capillary nano-immunoassay was conducted to analyze the expression profile of FA-associated proteins.Abnormal FANCM and FANCD1 expressions simultaneously existed.This case was thus diagnosed as FA-D1/FA-M dual subtype.Compared with mixed cell sequencing,single-cell sequencing data shows more accuracy for the FA subtype evaluation,while the capillary nano-immunoassay is a good method to detect the expression profile of abnormal or modified FA protein.

Effects of airfoil on aerodynamic performance of flapping wing

Flapping-wing aircraft(FWA)operates in a flight mode that mimics natural flyers,such as birds,bats and insects.For large scale bird-inspired flapping wings aircraft,the design of airfoil parameters is crucial to improving the aerodynamic performance.In order to study the effect of camber on the aerodynamic characteristics,we developed four different airfoils with a chord length of 12 cm.The cambers of airfoils are respectively 30 mm,25 mm,20 mm and 15 mm.A numerical investigation into the effects of camber on aerodynamic performance is carried out through COMSOL Multiphysics software using Fluid–Structure Interaction(FSI)module.In this work,the fluid–structure module employs the Navier–Stokes equations coupled with a solid stress–strain physics module and a moving mesh module.The three-dimensional(3D)flapping wing computational models with different cambers are built.The results show that certain camber of airfoil can improve the aerodynamic characteristics of flapping wing.