Prescribed Performance Tracking Control of Time-Delay Nonlinear Systems With Output Constraints

The problem of prescribed performance tracking control for unknown time-delay nonlinear systems subject to output constraints is dealt with in this paper. In contrast with related works, only the most fundamental requirements, i.e., boundedness and the local Lipschitz condition, are assumed for the allowable time delays. Moreover, we focus on the case where the reference is unknown beforehand, which renders the standard prescribed performance control designs under output constraints infeasible. To conquer these challenges, a novel robust prescribed performance control approach is put forward in this paper.Herein, a reverse tuning function is skillfully constructed and automatically generates a performance envelop for the tracking error. In addition, a unified performance analysis framework based on proof by contradiction and the barrier function is established to reveal the inherent robustness of the control system against the time delays. It turns out that the system output tracks the reference with a preassigned settling time and good accuracy,without constraint violations. A comparative simulation on a two-stage chemical reactor is carried out to illustrate the above theoretical findings.

A frequency servo SoC with output power stabilization loop technology for miniaturized atomic clocks

A frequency servo system-on-chip(FS-SoC)featuring output power stabilization technology is introduced in this study for high-precision and miniaturized cesium(Cs)atomic clocks.The proposed power stabilization loop(PSL)technique,incorporating an off-chip power detector(PD),ensures that the output power of the FS-SoC remains stable,mitigating the impact of power fluctuations on the atomic clock's stability.Additionally,a one-pulse-per-second(1PPS)is employed to syn-chronize the clock with GPS.Fabricated using 65 nm CMOS technology,the measured phase noise of the FS-SoC stands at-69.5 dBc/Hz@100 Hz offset and-83.9 dBc/Hz@1 kHz offset,accompanied by a power dissipation of 19.7 mW.The Cs atomic clock employing the proposed FS-SoC and PSL obtains an Allan deviation of 1.7×10^(-11) with 1-s averaging time.

A Study on Student Interpreters＇ Note-Taking, Interpreting Process and Output

Interpretation, either consecutive or simultaneous, demands more advanced linguistic skills as well as higher cognitive strategies than translation. This paper investigates the characteristics of the notes taken by student interpreters in relation to the output and the process of interpretation with the purpsoe of identifying the role of note-taking in the process of interpretation, its relations with the production quality, and the factors that constrain the development of the students＇ potential as future interpreters. Statistical and qualitative analysis of the notes and think-aloud protocol reveals that students majoring in English should further improve their overall English proficiency. Note-taking, either in source language or target language, or both, should be practiced until students are able to use it expertly. Inspite of the importance of note-taking in interpretation, students should be trained to rely more on memory rather than solely on the notes.

Adaptive Optimal Discrete-Time Output-Feedback Using an Internal Model Principle and Adaptive Dynamic Programming

In order to address the output feedback issue for linear discrete-time systems, this work suggests a brand-new adaptive dynamic programming(ADP) technique based on the internal model principle(IMP). The proposed method, termed as IMP-ADP, does not require complete state feedback-merely the measurement of input and output data. More specifically, based on the IMP, the output control problem can first be converted into a stabilization problem. We then design an observer to reproduce the full state of the system by measuring the inputs and outputs. Moreover, this technique includes both a policy iteration algorithm and a value iteration algorithm to determine the optimal feedback gain without using a dynamic system model. It is important that with this concept one does not need to solve the regulator equation. Finally, this control method was tested on an inverter system of grid-connected LCLs to demonstrate that the proposed method provides the desired performance in terms of both tracking and disturbance rejection.

Achieving Given Precision Within Prescribed Time yet With Guaranteed Transient Behavior via Output Based Event-Triggered Control

It is interesting yet nontrivial to achieve given control precision within user-assignable time for uncertain nonlinear systems.The underlying problem becomes even more challenging if the transient behavior also needs to be accommodated and only system output is available for feedback.Several key design innovations are proposed to circumvent the aforementioned technical difficulties,including the employment of state estimation filters with event-triggered mechanism,the construction of a novel performance scaling function and an error transformation.In contrast to most existing performance based works where the stability is contingent on initial conditions and the maximum allowable steady-state tracking precision can only be guaranteed at some unknown(theoretically infinite)time,in this work the output of the system is ensured to synchronize with the desired trajectory with arbitrarily pre-assignable convergence rate and arbitrarily pre-specified precision within prescribed time,using output only with lower cost of sensing and communication.In addition,all the closed-loop signals are ensured to be globally uniformly bounded under the proposed control method.The merits of the designed control scheme are confirmed by numerical simulation on a ship model.

Event-triggered robust cooperative output regulation for a class of linear multi-agent systems with an unknown exosystem

This paper investigates the robust cooperative output regulation problem for a class of heterogeneousuncertain linear multi-agent systems with an unknown exosystem via event-triggered control (ETC). By utilizingthe internal model approach and the adaptive control technique, a distributed adaptive internal model isconstructed for each agent. Then, based on this internal model, a fully distributed ETC strategy composed ofa distributed event-triggered adaptive output feedback control law and a distributed dynamic event-triggeringmechanism is proposed, in which each agent updates its control input at its own triggering time instants. It isshown that under the proposed ETC strategy, the robust cooperative output regulation problem can be solvedwithout requiring either the global information associated with the communication topology or the bounds ofthe uncertain or unknown parameters in each agent and the exosystem. A numerical example is provided toillustrate the effectiveness of the proposed control strategy.

Asynchronous Learning-Based Output Feedback Sliding Mode Control for Semi-Markov Jump Systems: A Descriptor Approach

This paper presents an asynchronous output-feed-back control strategy of semi-Markovian systems via sliding mode-based learning technique.Compared with most literature results that require exact prior knowledge of system state and mode information,an asynchronous output-feedback sliding sur-face is adopted in the case of incompletely available state and non-synchronization phenomenon.The holonomic dynamics of the sliding mode are characterized by a descriptor system in which the switching surface is regarded as the fast subsystem and the system dynamics are viewed as the slow subsystem.Based upon the co-occurrence of two subsystems,the sufficient stochastic admissibility criterion of the holonomic dynamics is derived by utilizing the characteristics of cumulative distribution functions.Furthermore,a recursive learning controller is formulated to guarantee the reachability of the sliding manifold and realize the chattering reduction of the asynchronous switching and sliding motion.Finally,the proposed theoretical method is substantia-ted through two numerical simulations with the practical contin-uous stirred tank reactor and F-404 aircraft engine model,respectively.

Adaptive Optimal Output Regulation of Interconnected Singularly Perturbed Systems With Application to Power Systems

This article studies the adaptive optimal output regulation problem for a class of interconnected singularly perturbed systems(SPSs) with unknown dynamics based on reinforcement learning(RL).Taking into account the slow and fast characteristics among system states,the interconnected SPS is decomposed into the slow time-scale dynamics and the fast timescale dynamics through singular perturbation theory.For the fast time-scale dynamics with interconnections,we devise a decentralized optimal control strategy by selecting appropriate weight matrices in the cost function.For the slow time-scale dynamics with unknown system parameters,an off-policy RL algorithm with convergence guarantee is given to learn the optimal control strategy in terms of measurement data.By combining the slow and fast controllers,we establish the composite decentralized adaptive optimal output regulator,and rigorously analyze the stability and optimality of the closed-loop system.The proposed decomposition design not only bypasses the numerical stiffness but also alleviates the high-dimensionality.The efficacy of the proposed methodology is validated by a load-frequency control application of a two-area power system.

Observer Based Control for a Class of Systems with Output Deadzone Nonlinearity

In this paper, a combination of model based adaptive design along with adaptive linear output feedback controller is used to compensate for robotic manipulator with output deadzone nonlinearity. The deadzone dynamics are utilized to adaptively estimate the deadzone parameter and a switching function is designed to eliminate the error produced in the adaptive observer dynamics. The overall design of the closed loop system ensures stability in the BIBO criterion.

A 3D convolutional neural network model with multiple outputs for simultaneously estimating the reactive transport parameters of sandstone from its CT images

Porosity,tortuosity,specific surface area(SSA),and permeability are four key parameters of reactive transport modeling in sandstone,which are important for understanding solute transport and geochemical reaction pro-cesses in sandstone aquifers.These four parameters reflect the characteristics of pore structure of sandstone from different perspectives,and the traditional empirical formulas cannot make accurate predictions of them due to their complexity and heterogeneity.In this paper,eleven types of sandstone CT images were firstly segmented into numerous subsample images,the porosity,tortuosity,SSA,and permeability of the subsamples were calculated,and the dataset was established.The 3D convolutional neural network(CNN)models were subse-quently established and trained to predict the key reactive transport parameters based on subsample CT images of sandstones.The results demonstrated that the 3D CNN model with multiple outputs exhibited excellent prediction ability for the four parameters compared to the traditional empirical formulas.In particular,for the prediction of tortuosity and permeability,the 3D CNN model with multiple outputs even showed slightly better prediction ability than its single-output variant model.Additionally,it demonstrated good generalization per-formance on sandstone CT images not included in the training dataset.The study showed that the 3D CNN model with multiple outputs has the advantages of simplifying operation and saving computational resources,which has the prospect of popularization and application.

The Impact of The Three-Dimensional Cultivation Model on the Development of the Suzhou Tea Industry:Estimating Value of Output Per Acre and Diversified Sales Models

This article explores the impact of the three-dimensional cultivation mode on the development of the Suzhou tea industry,focusing on the diversified estimation of the value of output per acre and sales mode.It introduces the history and traditional cultivation practices of tea in Suzhou,as well as the current challenges and problems faced by the industry.An in-depth analysis was conducted on the overview and improvement plans of the three-dimensional cultivation mode,covering relevant technical methods.Based on this analysis,the impact of the three-dimensional cultivation on the value of output per acre was studied and predicted.Its potential and advantages were explored and compared with the effectiveness of traditional cultivation models.Additionally,the impact of the three-dimensional cultivation mode on sales was analyzed,examining its market adaptability and competitiveness,as well as its advantages in expanding sales channels and market coverage.The study also focused on the promoting effect of diversified sales models on the Suzhou tea industry,including direct consumption market development,tea processing product development and promotion,and the integration of tea culture and the tourism industry.To ensure sustainable development,the article evaluates the environmental impact,economic feasibility,social benefits,and farmer benefits of the three-dimensional cultivation model.Finally,the prospects for the development of the Suzhou tea industry were discussed,and the positioning and response strategies of the threedimensional cultivation model were proposed.

开口式移动螺旋输送关键参数的研究

封闭式螺旋输送设备产量计算公式不适应于开口式移动螺旋输送机,因此,针对螺旋输送的机壳开口角度、移速、螺旋直径和转速等关键参数进行研究。首先从原理着手分析开口式移动螺旋的输送机理,后用EDEM对开口式移动螺旋输送的过程进行了离散元仿真,从而验证理论是否可靠。由原理获得开口式螺旋输送产量与机壳开口角度、移速、螺旋直径以及转速等参数的数值关系,分析得到几个关键参数对开口螺旋输送量的显著性和影响趋势。从理论与仿真结果的对比来看,两者较为吻合,理论结果较为可靠,研究为开口螺旋输送的设计提供理论依据。

基于DEA-Tobit的综合档案馆服务效率、影响因素及提升策略

全面分析我国综合档案馆服务效率及影响因素,提升综合档案馆服务水平,促进档案事业可持续发展。以档案利用服务理论、投入产出理论为理论基础,选取最近20年《中国档案年鉴》(2001版—2020版)中的3万余条数据,基于DEA分析法,从时间(年份)和空间(省域)两个维度对我国综合档案馆服务效率进行测算,选取典型案例予以分析。基于内容分析法提出4个影响因素假设:档案开放利用程度、库藏密度、人员业务能力和档案征集能力,通过构建DEA-Tobit回归模型,对4个假设进行验证,根据验证结果,提出有针对性的综合档案馆服务效率提升策略。从基于假设验证视角出发,研究综合档案馆服务效率影响因素,为档案学领域定量研究拓展,以及档案馆服务效率影响因素分析提供了新的研究路径。

基于感知与产出视角的维吾尔语辅音/n/的教学策略探析

本文主要以二语习得理论为基础,采用实验语音学的研究方法,以零基础开始学习的新疆大学维吾尔语专业不同水平(从低年级到高年级)学生为实验对象,进行感知和产出实验的研究。感知实验主要研究实验对象对目标辅音/n/的感知能力,结合知觉同化模型(PAM),分析偏误原因,探索维吾尔语辅音/n/的听力教学策略。产出实验主要通过第二共振峰频率跟舌位的关系,分析实验者在不同元音环境下发辅音/n/的舌位位置,结合有关口语的二语习得理论,探索维吾尔语辅音/n/的口语教学策略。

时滞反馈对超磁致伸缩换能器输出的影响分析

为研究时滞反馈对超磁致伸缩换能器输出的影响规律,扩大超磁致伸缩伸缩换能器的使用范围。通过分析换能器工作原理,建立时滞反馈控制下的系统动力学模型,采用多尺度法求解得到系统在位移、速度和加速度时滞反馈控制下的输出响应。仿真分析得知:无时滞反馈控制系统的输出呈硬式非线性特性;与无时滞反馈系统相比,位移和速度时滞反馈控制的换能器通过调整控制增益或时滞可有效降低系统的振动幅值、提高系统的稳定性;加速度时滞反馈控制下的换能器能够在不改变系统振幅的条件下改变系统的谐振频率,将加速度时滞反馈控制的换能器应用于能量回收系统中,仿真发现:调整控制增益不仅能够改变能量回收系统的有效频带范围,也可以调整系统的感应电压幅值。

基于平抑风光波动的矿坑抽水蓄能电站出力与机组特性研究

由于我国能源结构的调整,现有抽水蓄能电站装机规模无法满足黄河流域的能源结构转型以及风、光资源大规模消纳的需求,同时由于采矿工作的结束,产生了大量废弃矿坑。以鄂尔多斯附近的废弃矿坑为研究对象,借助鄂尔多斯域内的黄河水资源,结合抽水蓄能电站的建设条件,选出4对符合抽水蓄能电站建设要求的矿坑。对待建抽水蓄能电站附近的风光资源数据进行采集,借助Meteonorm、Matlab以及Simulink等软件进行出力模拟,并对出力特性进行分析,证实抽水蓄能电站是风电、光伏发电的良好补充资源。由于水泵水轮机的国内外制造商没有成形的型谱系列,所以分别从抽水蓄能电站水轮机选型要点、抽水蓄能电站水轮机主要特征参数的选择、矿坑抽水蓄能电站水轮机选型实例3个角度对不同矿坑特性下的抽水蓄能机组进行合理选型。该研究对我国黄河流域抽水蓄能电站的建设、后续废弃矿坑的利用以及矿坑抽水蓄能机组的选型具有指导意义。

秦汉的粮食产量与农户生计

秦汉时期粮食的常见高产可达到每市亩产粟247公斤,秦和西汉的平均亩产范围,折合今制也在每市亩产粟74公斤至123公斤之间。正是基于这种较高水平的粮食生产能力,西汉人口才能从初期的约2000万增长到末年的约6000万。只是这一时期粮食产量的不稳定与不均衡性相当突出。这背后有着独特的历史原因,即此时的粮食产量严重依赖于土地质量和气候条件。粮食产量的不稳定和不均衡导致了小农经济的脆弱性。受限于技术,秦汉小农因抵御灾害的能力弱而容易破产,庄园经济则因其对灾害形成了“社会性对冲”,故能接替小农经济,成为中古时期的重要经济形态。

基于扰动和输入饱和限制的连续时间系统预见跟踪控制

本文研究一类带有外部干扰和输入饱和的连续时间系统的预见控制问题.为了能成功地构造出连续时间输入饱和系统的误差系统,与以往对系统方程求导不同,本文利用状态平移方法代替状态求导,使得输入饱和连续时间系统的误差系统的构造成为可能.这样原系统的预见饱和控制就转化为误差系统的标准饱和控制问题.另外,针对原系统的误差系统,分别引入状态反馈和静态输出反馈,并改写输入向量以便利用可预见信号的未来信息.利用Lyapunov函数及LMI技巧,导出了闭环系统渐近稳定的充分条件.最后仿真例子表明了本文结果的有效性.

2023/2024榨季国内外食糖市场回顾与2024/2025榨季展望

2023/2024榨季,巴西食糖生产和出口表现强劲,有效抵补了印度和泰国的供应减量,全球食糖供应过剩约500万吨,ICE原糖价格于2023年11月初创下28.14美分/磅高位后震荡回落至17.5~20.0美分/磅。国内因良种良法政策激励,以及气候适宜提振单产,产糖量恢复性增产到996.3万吨,同比增11.07%。2023年初销糖量同比大增,致使工业库存降至近年低位,累计产销率亦创近年纪录水平,而后低库存和高产销率由2024年初维持至9月份,成为整个榨季国内现货价格相对抗跌的主要支撑,基差亦整体维持在200元/吨高位。因经济复苏不及预期,抑制了含糖食品消费,涉糖行业营收普遍下降,8月和9月企业利润同比差于此前10个月的利润同比,涉糖企业通过增加糖浆预混粉等低成本替代品进口,对食糖市场形成一定挤占打压。展望2024/2025榨季,预计泰国、欧盟增产,巴西减产,幅度需持续关注含糖量和制糖比指标,印度持平可能较大,但受糖醇政策和出口政策影响仍有较大不确定,全球食糖供应过剩格局仍将持续,但过剩量将有所收窄。四季度至2025年第一季度供给宽松程度不及去年同期,若巴西产量不及预期,有可能进一步转为偏紧格局,为糖价走强提供动能。国内增产幅度约为9.4%,近期进口糖利润改善,7月和8月进口到港增加,新榨季开启,糖浆和预混粉进口数量的稳定替代,均将对国内糖价形成明显压制。此外,2024/2025榨季全球宏观经济、能源政策、强势美元和印度出口政策对食糖价格的影响明显加大。

Difference of Nitrogen Uptake and Use Efficiency in Conventional Indica Rice Cultivars with Different Nitrogen Use Efficiency for Grain Output

[Objective] The study aimed to confirm difference of nitrogen uptake and used efficiency with different nitrogen use efficiency for grain output (NUEg) types of indica rice.[Method] 88 and 122 conventional indica rice cultivars were solution-cultured in 2001 and 2002, respectively. Dry matter weight (including root system, culm and sheath, leaves, panicle), nitrogen content of different organs, yield and its components were measured. The tested rice cultivars were classified into 6 types (i.e. A, B, C, D, E and F, A was the lowest, and F was the highest) based on their NUEg level by the MinSSw method.[Result](1)Difference of NUEg of the cultivars used in this study were very large; (2) No significant difference of N content at heading stage was observed among different NUEg types of indica rice. In the cultivars with higher NUEg, however, N content in leaf, stem-sheath and entire rice plant were lower at mature stage. (3)Cultivars with higher NUEg were characterized with lower N uptake before heading and at mature stage; (4) Cultivars with higher NUEg were characterized with higher N use efficiency in biomass production and harvest index. [Conclusion] The cultivars with higher NUEg showed lower N uptake and N content, while nitrogen use efficiency was higher.