电动加载系统的模糊自适应PID控制研究

电动加载系统的突出优点是加载跟踪速度快,但加载过程中系统多余力能否快速消除是制约加载精度、影响加载系统动态品质的最重要因素.常规PID控制难以满足电动加载系统对高精度和快速性的要求,而模糊自适应PID控制能够解决这个难题,实验证实了系统采用模糊自适应PID算法后明显提高了加载精度和响应速度.     

电液伺服加载系统的鲁棒控制方法研究

针对舵机的主动运动对电液伺服加栽系统的强干扰所引起的多余力,设计一种鲁棒控制器并结合传统的PID控制方法来进行消除.建立数学模型并进行仿真,结果表明:动态鲁棒补偿器很好地起到了抑制外干扰的效果.     

Smooth Scheduling under Variable Rates or the Analog-Digital Confinement Game

This work considers non-terminating scheduling problems in which a system of multiple resources serves clients having variable needs. The system has m identical resources and n clients; in each time slot each resource may serve at most one client; in each such slot t each client γ has a rate, a real number ρ _γ (t), that specifies his needs in this slot. The rates satisfy the restriction ∑ _γ ρ _γ (t)≤m for any slot t. Except of this restriction, the rates can vary in arbitrary fashion. (This contrasts most prior works in this area in which the rates of the clients are constant.) The schedule is required to be smooth as follows: a schedule is Δ -smooth if for all time intervals I the absolute difference between the amount of service received by each client γ to his nominal needs of ∑ _t∈I ρ _γ (t) is less than Δ. Our objective are online schedulers that produce Δ-smooth schedules where Δ is a small constant which is independent of m and n. Our paper constructs such schedulers; these are the first online Δ-smooth schedulers, with a constant Δ, for clients with arbitrarily variable rates in a single or multiple resource system. Furthermore, the paper also considers a non-concurrent environment in which there is an additional restriction that each client is served at most once in each time slot; it presents the first online smooth schedulers for variable rates under this restriction. The above non-concurrent restriction is crucial in some applications (e.g., CPU scheduling). It has been pointed out that this restriction “adds a surprising amount of difficulty” to the scheduling problem. However, this observation was never formalized and, of course, was never proved. Our paper formalizes and proves some aspects of this observation. Another contribution of this paper is the introduction of a complete information, two player game called the analog-digital confinement game. In such a game pebbles are located on the real line; the two players, the analog player and the digital player, take alternating turns and each one, in his turn, moves some of the pebbles; the digital player moves the pebbles backwards by discrete distances while the analog player moves the pebbles forward by analog distances; the aim of the analog player is to cause one pebble (or more) to escape a pre-defined real interval while the aim of the digital player is to confine the pebbles into the interval. We demonstrate that this game is a convenient framework to study the general question of how to approximate an analog process by a digital one. All the above scheduling results are established via this game. In this derivation, the pebbles represent the clients, the analog player generates the needs of the clients and the digital player generates the schedule. Dedicated to the memory of Professor Shimon Even for his inspiration and encouragement     

基于级联多电平换流器的两级式储能系统控制策略

储能技术是构建以新能源为主体的新型电力系统的关键技术和维持微网可靠稳定运行的重要保证。国内外现有理论研究及示范工程主要集中于单级式链式储能系统,功率模块与电池系统之间无源连接,结构简单但控制自由度不高。同时,针对基于链式储能的电池荷电状态(state of charge,SOC)不均衡问题,现有的相内SOC均衡控制策略存在不同负载率适应性不足、极度不均衡时可能过调制等缺点,为此,文中基于两级式链式储能系统,研究其总体控制策略,对相间、相内SOC均衡策略进行分析,并提出一种自适应的相内SOC均衡策略,详细说明均衡控制参数的设计原则。该策略能有效地改善链式储能系统在轻载、重载等不同工况下的适应性和均衡效果。最终通过仿真验证了所提控制策略的可行性和有效性,从而为工程实施提供理论储备和技术支撑。     

Intercalative Motifs-Induced Space Confinement and Bonding Covalency Enhancement Enable Ultrafast and Large Sodium Storage

Alloying-type metal sulfides with high theoretical capacities are promising anodes for sodium-ion batteries, but suffer from sluggish sodiation kinetics and huge volume expansion. Introducing intercalative motifs into alloying-type metal sulfides is an efficient strategy to solve the above issues. Herein, robust intercalative In S motifs are grafted to high-capacity layered Bi₂S₃ to form a cation-disordered (BiIn)₂S₃, synergistically realizing high-rate and large-capacity sodium storage. The In S motif with strong bonding serves as a space-confinement unit to buffer the volume expansion, maintaining superior structural stability. Moreover, the grafted high-metallicity Indium increases the bonding covalency of Bi S, realizing controllable reconstruction of Bi S bond during cycling to effectively prevent the migration and aggregation of atomic Bi. The novel (BiIn)₂S₃ anode delivers a high capacity of 537 mAh g⁻¹ at 0.4 C and a superior high-rate stability of 247 mAh g⁻¹ at 40 C over 10000 cycles. Further in situ and ex situ characterizations reveal the in-depth reaction mechanism and the breakage and formation of reversible Bi S bonds. The proposed space confinement and bonding covalency enhancement strategy via grafting intercalative motifs can be conducive to developing novel high-rate and large-capacity anodes.     

基于真空加载的激光错位散斑干涉自动化检测系统

为满足某橡胶/金属粘接结构产品的批量化检测需求,提升检测效率和自动化水平,设计开发了一套基于真空加载的激光错位散斑自动化检测系统。该系统集成了轻量化框架和紧凑型光路,并通过检测软件和检测流程优化,得到了较为理想的散斑检测图像;同时结合产品结构特点和检测灵敏度要求,设计了基于PLC控制的真空舱和运动控制装置,实现了产品粘接质量的自动化检测应用。结果表明,该系统可检测出检测试块上预置的人工缺陷,与原有手动检测模式相比,在保证检测产品检测灵敏度要求的前提下,极大地提升了检测效率,降低了检测人员的劳动强度,具有良好的工程应用价值。     

全尺寸缝翼疲劳试验随动加载技术

缝翼及其支承结构的疲劳试验是民用飞机适航取证的一项重要工作,其难度在于需要在试验件运动过程中同步施加载荷,完成对缝翼翼面及其支承结构载荷的考验。过大的同步偏差及不当的异常处理会造成试验件的非预期损伤,是一项风险极高的地面强度试验。在试验方案中采用了控制系统与驱动系统的双驱动方式,在国内首次在翼身组合体真机环境中完成了缝翼疲劳试验,真实还原了缝翼实际运动场景,试验通过对试验运动轨迹的仿真指导随动加载框架的安装,极大地提高了活动翼面随动加载试验在翼面活动时的同步性和加载精度,同时创新的同步偏差实时监控和防错设计保障了试验的顺利运行,为该型号飞机的缝翼设计提供了更具参考价值的试验数据及试验结果。     

Disaggregating growth in future retail electricity rates

The retail rate impacts of a number of emerging trends (e.g., rapid deployment of electric vehicles and storage, transmission build-out for large-scale renewables deployment, and grid modernization) are unknown. Importantly, decision-makers are concerned about the potential future rate impacts on energy affordability and equity. We disaggregate the key drivers of retail electricity rates and assess their impacts on future rate growth considering their interactions and uncertainty. Specifically, we develop ranges of future cost growth for a generic investor-owned and vertically-integrated electric utility representing typical cost and operating characteristics. The rate driver growth rate ranges are applied in isolation and jointly to quantify the uncertainty and variability in future retail electricity rates. The results identify what rate drivers and factors may minimize and/or decrease uncertainty in retail rate growth and their linkages to industry trends.     

Evaluation of dynamic fracture toughness parameters of locomotive axle steel by instrumented Charpy impact test

The analysis of the energy of fracture of specimens from steel OSL, which is widely used for the manufacture of railway axles under shock loading, is performed. The nature and quantitative parameters of the typical stages of the processes of plastic and brittle fracture, depending on the test temperature and stiffness of the stress state at the tip of the crack‐like defect, are established. It is shown that impact loading at 20 °C leads to the formation of the local zone of plasticity and ductile–brittle fracture of the material. An increased stiffness of the stress state at the tip of the defect at ?40 °C causes brittle fracture. An approach is developed, which is based on using the size of shear lips as a quantitative parameter of fracture under normal and low temperatures, similar in its physical essence to deformation approaches of nonlinear fracture mechanics. Based on this approach and the quantitative analysis of specimen fracture zones, the physical and mechanical scheme of specimen fracture is proposed in the presence of localized plasticity and in its absence near the tip of the concentrator.     

An investigation of T‐stresses in a plate with an inclined crack under biaxial loadings

For plates with an inclined crack of wide‐range aspect ratios under biaxial loadings, T‐stress values are calculated with three‐dimensional finite element method. The results show that the normalized T‐stress is crack length and orientation dependent. A linear equation for the relationship between normalized T‐stresses and biaxility factors is proposed to describe the normalized T‐stresses for different crack lengths and crack angles under different biaxial loadings, which is more convenient and involves wider biaxility ratios compared with the existing solutions. The plate thickness effect and the trend of normalized T‐stresses along the crack front thickness are also studied for mode I and I–II mixed‐mode cracks. Based on the analyses and comparisons, it is necessary to take the thickness effect into consideration when the crack length is long enough (a/W = 7/10). When the component of mode II is significant (β > 45°), and the biaxility ratios are negative, T‐stresses near the free surface are lower than those at other positions, which are the opposite of mode I crack and most of I–II mixed‐mode crack.