电压型PWM整流器非线性控制策略综述

为提高PWM整流器的性能,国内外学者开始将非线性控制理论应用到PWM整流器控制中。介绍了几种国内外三相电压型PWM整流器非线性控制策略的研究现状,包括反馈线性化控制策略,基于Lya-punov稳定理论的控制策略,基于无源控制理论的控制策略,模糊控制策略和基于人工神经网络理论的控制策略,并进行了分析。     

异步电动机的无源性跟踪控制--转子电阻及负载转矩皆未知时变的情形

研究了负载转矩和转子电阻在一般的未知时变情形时对异步电动机期望时变电磁转矩的渐近跟踪控制问题.首先给出了转子电阻和负载转矩在时变已知的情形时无源性控制器的设计方法,然后通过设计负载转矩和转子电阻的在线估计器,得到了转子电阻和负载转矩在时变但未知的一般情形下无源性控制器的设计.仿真结果证明了这样设计的控制器具有良好的性能.     

合作机器人的被动约束特性及实验研究

合作机器人(Cobot)是在同一作业空间与人直接物理合作的机器人。为了实现Cobot与人直接合作,Cobot的关节机构必须具有被动约束特性。建立了一种基于双超越离合器的不完全约束关节机构的模型和它的控制模型,对关节机构的被动约束特性和Cobot的轨迹跟踪特性进行了实验研究。实验结果表明,不完全约束关节机构具有被动特性,并能约束Cobot关节的运动状态,并能使Cobot在不同操作力作用下跟踪期望轨迹,不会因机器人失控伤害操作者,满足Cobot与人合作的要求。具有这种关节机构的Cobot可以应用在外科手术、物料搬运和零件的装配等需要人机合作的场合。     

Investigations on the re-passivation of carbon steel in chloride containing concrete in consequence of cathodic polarisation

Although the complex changes at the steel–concrete interface due to cathodic polarisation are widely acknowledged to have a beneficial influence concerning the cathodic protection (CP) of steel in concrete, some questions concerning the repassivation of carbon steel in consequence of cathodic polarisation are still not satisfactorily clarified. In the recent literature, some indications are presented that repassivation occurs after a certain time of polarisation. Therefore, the investigations discussed in this paper aim to clarify, to what extent the re-passivation of carbon steel due to cathodic polarisation occurs, and if the ennoblement of OCP is a sufficient indication for repassivation. In a first step, the corrosion state of five nominal equal test specimens was determined by electrochemical impedance spectroscopy (EIS). After determining the initial corrosion state by evaluating the charge transfer resistance and the polarisation resistance, respectively, the specimens were polarised cathodically. Impedance data were recorded before, during and after polarisation. The impedance data were evaluated by equivalent circuit fitting with special attention to charge transfer resistances and the impact of diffusion on the corrosion and polarisation behaviour. The results indicate that the reduction of oxides and oxygen diffusion during cathodic polarisation has strong impact on the systems behaviour and that repassivation effects occur after switching off the polarisation current and during depolarisation, respectively.     

Electrochemical response of Fe65.5Cr4Mo4Ga4P12 C5B5.5 bulk amorphous alloy in different aqueous media

A bulk amorphous Fe_65.5Cr₄Mo₄Ga₄P₁₂C₅B_5.5 alloy was investigated for its electrochemical behaviour in different electrolytes. The investigations showed substantial differences in response between the rapidly quenched and cast samples of the same composition. Annealing of the cast samples improved their corrosion resistance, which was possibly due to structural relaxation processes. The alloy was found to have very good resistance to neutral and slightly acidic chloride solutions in the rapidly quenched form. The passivation observed could not be attributed to any metal/metalloid oxide and was most probably due to an adsorbed oxygen layer. No chromium or molybdenum enrichment was observed at the surface. However, a sub‐surface phosphorus enrichment was observed in rapidly quenched samples, in the as‐received state as well as after electrochemical treatments, which may be responsible for their improved corrosion resistance.     

Incorporation of Cr in the passive film on Fe from chromate solutions

The uptake of Cr species from chromate solutions by Fe has been studied using X-ray absorption near edge structure (XANES). The objective of the investigation was to compare XANES with radioactive tracer techniques used by Brasher et al. Cr(III) was detected on the passive iron surface. The amount of Cr(III) was increased by cathodic polarization and decreased by anodic polarization. This demonstrated that the uptake of Cr(III) was the result of cathodic processes and was not a direct result of the growth of the passive oxide film. Cr(VI) was only found after Fe was exposed to a saturated dichromate solutions for extended periods indicating that Cr(VI) was not strongly absorbed on the passive film.     

中立型不确定线性系统的无源滤波器设计

利用构造Lyapunov函数的方法研究了一类中立型不确定线性系统的滤波器设计问题,得到了使相应增广系统是无源系统的滤波器存在的条件和设计方法,并且将结果化成线性矩阵不等式的形式,容易求解,最后用一个示例验证了所得结论的有效性.     

Closed-form solutions of singular KYP lemma: strongly passive systems,and fast lossless trajectories

In this paper, we deal with a special class of passive systems, which possess the characteristic property of having no finite spectral zeros. We call these systems strongly passive. It is well known that, for these systems, storage functions, i.e. solutions to the linear matrix inequality (LMI) arising from the Kalman–Yakubovich–Popov (KYP) lemma, cannot be obtained by the conventional approach of algebraic Riccati equations (AREs) and Hamiltonian matrices. In this paper, we first show that a strongly passive system always admits a unique storage function. We then provide a closed-form expression for this unique storage function. Using the closed-form formula of the unique storage function we characterise the ‘lossless’ trajectories of strongly passive systems and show that such systems admit impulsive lossless trajectories on the half-line; we call them fast lossless trajectories. This adds to the existing notion that such systems do not admit any ‘slow’ lossless trajectories.     

基于互联与阻尼配置无源控制的并网逆变器电流控制技术

在分布式电源并网发电中,并网逆变器及其输出滤波器是实现电能馈送的重要环节。本文在并网逆变器中引入T型滤波器取代传统的电感滤波器以减小并网电流的谐波含量。为了克服采用T型滤波器对并网逆变器系统带来的不稳定性,本文提出了一种互联与阻尼配置的无源控制控制策略,并详细分析了该控制器的稳定性。仿真与实验结果证明采用该控制策略可以有效实现并网逆变器稳定运行,具有较好的稳态性能和动态性能。     

基于无源化方法的非线性系统自适应控制

研究了一种非线性系统的动态神经网络控制方案，利用无源化方法证明了其自适应控制系统的稳定性，并得到了动态神经网络系统的学习算法，仿真实验验证了本方法的有效性。