Two direct Tustin discretization methods for fractional-order differentiator/integrator

This paper deals with fractional calculus and its approximate discretization. Two direct discretization methods useful in control and digital filtering are presented for discretizing the fractional-order differentiator or integrator. Detailed mathematical formulae and tables are given. An illustrative example is presented to show the practically usefulness of the two proposed discretization schemes. Comparative remarks between the two methods are also given.     

Affine formation control for multi-agent systems with prescribed convergence time

In this paper, the affine formation control problem for multi-agent systems with prescribed convergence time is investigated. Firstly, on the basis of a time-varying scaling function, a distributed continuous control algorithm is designed, under which a stationary affine formation of the nominal configuration is able to be achieved within a prescribed time. Secondly, to track a time-varying formation within the prescribed time, a distributed control protocol is proposed by employing a leader–follower control strategy. Furthermore, the boundary layer technique is adopted to avoid chattering effect. Finally, simulation examples are provided to demonstrated the effectiveness of the proposed design.     

微车FR型动力传动系扭振特性及其控制方法评述

阐述动力传动系扭振分析的三种方法（理论分析、试验测试以及 CAE 仿真）,并分析微车 FR 型动力传动系扭振特性。在此基础上,从动力学参数优化和附加减、隔振装置两方面总结动力传动系扭振控制方法,具体包括动力学参数对传动系固有特性和扭振响应的影响分析和TVD、CTD、DMF、STD的优缺点对比以及工程应用现状讨论。     

谐振式无线电能传输装置的设计

无线电能传输是一种新型的电能传输技术,文章设计了一种实用的无线电能传输装置,通过线圈将电能以无线方式传输。系统包括高频振荡电路、高频功率放大电路、发射和接收线圈、高频整流滤波电路,经过实验控制变量法优化后,确定发射端和接收端相应参数,实现了无线电能传输系统的设计优化。     

A novel mesh discretization strategy for numerical solution of optimal control problems in aerospace engineering

An effective approach is proposed for optimal control problems in aerospace engineering. First, several interval lengths are treated as optimization variables directly to localize the switching points accurately. Second, the variable intervals are usually refined into more subintervals homogeneously to obtain the trajectories with high accuracy. To reduce the number of optimization variables and improve the efficiency, the control and the state vectors are parameterized using different meshes in this paper such that the control can be approximated asynchronously by fewer parameters where the trajectories change slowly. Then, the variables are departed as independent variables and dependent variables, the gradient formulae, based on the partial derivatives of dependent parameters with respect to independent parameters, are computed to solve nonlinear programming problems. Finally, the proposed approach is applied to the classic moon lander and hang glider problems. For the moon lander problem, the proposed approach is compared with CVP, Fast-CVP and GPM methods, respectively. For the hang glider problem, the proposed approach is compared with trapezoidal discretization and stopping criteria methods, respectively. The numerical results validate the effectiveness of the proposed approach.     

数字时代下科技期刊可变式品牌设计的弹性管理方法

【目的】 提高科技期刊在数字时代的品牌影响力,增强品牌设计管理的弹性。【方法】 从视知觉认知心理学角度出发,对科技期刊品牌的可变性、一贯性、趣味性的设计方法进行分析与总结。【结果】 基于用户视觉认知模式解构与重组的可变式识别能够有效强化品牌影响力。【结论】 科技期刊品牌设计管理及方法需要密切围绕品牌核心定位展开;通过结合位置、色彩、动态等基本要素形成范畴化概念,以适应新媒体特性,实现广泛传播;其视觉语言强调基于用户形成品牌识别的多平台趣味整合。     

破解数字化重构的商业模式创新：战略柔性的力量

数字经济时代基于数字化创新的商业模式,已然取代传统的商业模式,成为企业获取并保持竞争优势的主要动力。而随着产业数字化趋势越发明显,企业如何实现数字化以及在数字化背景下如何创新商业模式与企业战略,影响其在市场上能否获得先发优势。因此,本研究旨在探讨数字化“大势所趋”下,企业如何实现数字商业模式创新以及影响企业绩效的具体路径。本研究以长三角地区的463家企业为研究样本,对理论模型进行层级回归分析,研究发现：数字化正向影响商业模式创新;战略柔性中介商业模式创新对企业绩效的影响;数字化显著调节商业模式创新与战略柔性之间的关系,也显著调节商业模式创新经由战略柔性影响企业绩效的间接效应,表现为企业的数字化程度越高,商业模式创新通过战略柔性影响企业绩效的作用就越强。研究结果表明,数字化背景下企业在进行商业模式创新的过程中,要加强战略柔性,以更好地适应动态环境,提升企业绩效。     

Load frequency composite control for multi-region interconnected power systems

This paper investigates a composite controller for load frequency control (LFC) in multi-region interconnected power systems via sliding mode observer design. State observers (SOs) and disturbance observers (DOs) are implied for the LFC based on the load variations with communication delays and quantization output measurements. A nonlinear integral sliding surface combined with a composite controller is developed to optimize control performance. Moreover, a three-area power system model is used to demonstrate the effectiveness of the proposed scheme in the illustrative example, confirming that frequency deviations can be rejected despite delays, uncertainties, and quantization during transmission.     

电力逆变器新型电流滞环控制方法研究

电力逆变器在电力行业中有着广泛的应用,在对电力逆变器控制方法进行系统研究的基础上,本文提出了一种适用于电力逆变器的电流滞环控制方法,其单个H桥采用与单极性SPWM调制相似的单极性电流滞环控制,脉冲产生简单,可以有效减少开关损耗。用类似相移SPWM脉冲产生方式来实现电流滞环控制时逆变器一相桥臂移相控制脉冲的产生。该控制方式保留了滞环电流控制响应速度快、具有内在限流能力和稳定性好等优点。通过仿真结果验证了本文所提方法的正确性。     

Model predictive control for pre-compensated power converters: Application to current mode control

Current Mode Control (CMC) is the standard approach to regulate DC-DC power converters in high performance applications, allowing to obtain a faster time-response and better closed-loop stability if compared to Voltage Mode Control (VMC). In the last decade, several algorithms have been proposed to improve standard CMC, most of them requiring to replace the original controller. However, it is common to have either analog or embedded CMC controllers which cannot be replaced easily in commercial power converters. Inspired by very recent results in the topic, this paper proposes a Model Predictive Control (MPC) external loop aimed at optimally modifying the set-point of a CMC loop to improve converter performance. The proposed configuration is directly applicable to any pre-compensated converter as it does not require changes on the already-in-place controller. Moreover, by leveraging a multi-rate implementation, the benefits of MPC are introduced in power conversion without affecting much the computational cost of the over-all control system, contrary to what would happen for a direct MPC implementation. Simulation and experimental results on a synchronous DC-DC buck converter, controlled by a standard CMC algorithm, confirm the benefits of the approach.     

网络权力与创新绩效:基于企业数字化能力视角

选取战略性新兴产业206家企业为研究样本,构建以企业网络权力以及创新绩效为变量、以数字化能力为中介的SEM模型,研究企业数字化转型下网络权力动态变化影响创新绩效的内在作用机制。结果显示,企业网络权力正向作用于创新绩效,数字化协同能力显著提升创新绩效,且在网络权力及创新绩效间发挥有效中介作用。因此,在数字转型背景下关注核心企业的网络权力有效运用,从而达到企业网络整体竞争力及创新绩效的显著提高。     

Frequency synchronization adaptive control for power grids under topological uncertainty

In this paper, an adaptive control strategy is proposed to address the synchronization issue for weakly damped generators under topological uncertainty. A singular perturbation analysis is then adopted for strongly damped generators and a compensation control scheme is subsequently given to maintain synchronization under topological changes. Theoretical proof is laid out for the validity of the proposed control scheme. Besides, a power sharing strategy is supplemented for strongly damped generators based on the designed controller. Finally, simulation studies are carried out to verify the effectiveness of the control strategies. Results show that synchronization can be swiftly restored even when the power grid suffers a fatal topological change. The power sharing property can be achieved under the given restriction with the proposed controller.     

一起功率振荡的原因分析和控制措施

某电厂600MW机组正常运行时,偶尔会出现功率小幅振荡的现象,影响了机组和电网的安全稳定运行。详细介绍了机组功率振荡的现象、原因、影响和处理方法,提出并实施了相应的整改措施。明确指出一次调频动作太灵敏是导致这一事件的主要原因,合理改进一次调频的控制逻辑、提高设备精度,优化高调门的流量特性曲线是控制该类事件的主要措施。     

Joint power control and beamforming codebook design for MISO channels under the outage criterion

This paper investigates the joint design of power control and beamforming codebooks for limited-feedback multiple-input single-output (MISO) wireless systems. The problem is formulated as the minimization of the outage probability subject to the transmit power constraint and cardinality constraints on the beamforming and power codebooks. We show that the two codebooks need to be designed jointly in this setup, and provide a numerical method for the joint optimization. For independent and identically distributed (i.i.d.) Rayleigh channel, we also propose a low-complexity approach of fixing a uniform beamforming codebook and optimizing the power codebook for that particular beamformer, and show that it performs very close to the optimum. Further, this paper investigates the optimal tradeoffs between beamforming and power codebook sizes. We show that as the outage probability decreases, optimal joint design should use more feedback bits for power control and fewer feedback bits for beamforming. The jointly optimized beamforming and power control modules combine the power gain of beamforming and diversity gain of power control, which enable it to approach the performance of the system with perfect channel state information as the feedback link capacity increases—something that is not possible with either beamforming or power control alone.     

Flatness-based adaptive fuzzy output tracking excitation control for power system generators

In this paper, a novel approach for the design of an indirect adaptive fuzzy output tracking excitation control of power system generators is proposed. The method is developed based on the concept of differentially flat systems through which the nonlinear system can be written in canonical form. The flatness-based adaptive fuzzy control methodology is used to design the excitation control signal of a single machine power system in order to track a reference trajectory for the generator angle. The considered power system can be written in the canonical form and the resulting excitation control signal is shown to be nonlinear. In case of unknown power system parameters due to abnormalities, the nonlinear functions appearing in the control signal are approximated using adaptive fuzzy systems. Simulation results show that the proposed controller can enhance the transient stability of the power system under a three-phase to ground fault occurring near the generator terminals.     

Load frequency control for multi-area power system based on Markov model

The usage of communication networks provides a backbone of integration of information technologies and load frequency control (LFC) scheme. Time delays introduced by network environments taking the new challenge for dynamic performances and even the stability of closed-loop LFC scheme. This paper focuses on the stability and stabilization of multi-area LFC schemes for power systems with the introduction of communication networks and renewable energies. Markov theory is exploited in this paper for describing the discrete time-delay mechanism. Then, by utilizing Wirtinger-based inequality, and constructing a novel Lyapunov functions, the results of robust stability and stabilization criteria are derived in terms of linear matrix inequality (LMI). Finally, simulation results are provided to demonstrate the effectiveness and superiority of developed results.     

实验验证教学方法在中职数字电路触发器中的实用分析

就我国中职电子信息专业而言,数字电路属于该专业最基础的课程,此外,其也被称为电子产品整机装配与维修、单片机原理和应用及集成电路等课程的必要前提。基于我国中职学生特点:思维方法单一、文化基础较弱、畏难情绪重及创新意识能力不强等。此外,作为中职执教教师,必须对学生实践能力、动手能力予以足够重视,并积极培养学生学习兴趣,其中,将实验验证教学方法应用于中职数字电路触发器教学中,是实现中职学生相关能力提高的重要途径。     

数控直流稳压电源的设计

文章所设计的数控直流稳压电源,只使用了数字电路中的振荡器、计数器、译码器、数码管以及模拟电路中的数/模转换器、运算放大器等常见芯片构成的常用电路,实现了数字调节输出电压大小的功能(步进和连续调节均可),且有较高的精度和可靠性。