Closed-loop identification of multivariable systems: With or without excitation of all references?

The accuracy of plant parameters estimated in closed-loop operation is investigated for a class of multivariable systems and for the situation where only some of the reference inputs are excited. This issue is important for at least two reasons: (i) there are control applications where it is preferable not to excite all references in order to avoid performance degradation, and (ii) it is not clear whether the results in the context of open-loop identification, where the existence of common parameters between the various transfer functions is a condition for improved accuracy with additional excitation, also hold in the closed-loop case. The paper examines the effect of the non-excitation of some reference inputs on the variance of the estimated parameters. The proposed expressions are valid for all conventional model structures used in prediction error identification. Although exciting all reference inputs is not necessary for identifiability, this work shows that, regardless of the parametrization, the excitation of all references never worsens and, in most cases, improves the accuracy of the parameter estimates. The analytical results developed in this work are illustrated by two simulation examples.     

基于螺旋理论的Delta并联机器人自由度分析

螺旋理论以其几何概念清楚,物理意义明确,表达形式简单等优势,常被用于分析机构的自由度。按照传统的G-K(Grubler-Kutzbach)公式,能较容易地计算出串联机构的自由度,而对于一些特殊机构,尤其是含有闭环子链的复杂并联机构,往往无法便捷、正确地求解其自由度。为解决以上问题,以一种拓扑结构为[3-R(4S)1-RUPU]+R型的Delta并联机器人为研究对象,对其4S闭环子链进行了等效运动副螺旋系的求解,并判别了机构的局部自由度以及公共约束;利用修正的G-K公式,分别对原机构和等效后的机构进行了自由度的验证。结果表明:两种情形下的自由度数均为4,且自由度的性质为3平移1旋转,与实际设计相符。     

具有预期闭环极点区域的稳定控制器的H∞优化设计方法

本文从工程应用角度出发,提出了一种将闭环极点设置于预期稳定区域的稳定控制器的 H∞优化设计方法,即实参数优化求解控制器的方法.这种方法综合考虑了闭环动态性能、抗 干扰、鲁棒性以及控制器本身的稳定性.实例表明,与现有的H∞设计方法相比,用本文方法 设计的控制系统在不显著增大抗干扰和鲁棒性指标情况下,具有闭环动态性能良好及控制器 稳定等优点,因此具有工程应用价值.     

焊线机超声波闭环控制

超声波是焊线机焊接过程中的重要参与元素,超声波控制效果决定着焊接的品质和速度。在分析超声换能器频率特性和电流响应的基础上,给出了频率自动跟踪和电流受控输出的闭环控制方案,提高了超声波效率,缩短了响应时间,增强了超声波输出的稳定性。实验结果表明,此方法实现了受控的上升时间和较小的超调     

提高波纹管式制冷器稳定性的设计

针对波纹管式自调节流制冷器普遍存在稳定性差的问题,通过对此类制冷器最核心的部件——波纹管自调机构的受力分析,对制冷器的预留位移量这个核心参数进行优化设计,增强了制冷器的自调能力,从设计上避免制冷器不自调或流量变化现象的发生,改善了长期困扰自调式制冷器的间歇性喷液现象,提高了制冷器的稳定性,并通过实验得到了论证。     

汇川技术HD92高压变频器在皮带机多电机功率平衡上的应用

本文介绍了汇川HD92皮带机专用高压变频器在宁夏某煤矿主井(斜井)皮带机上的应用并从电气原理、性能、节能分析等各方面对高压变频器在皮带机上的应用做总结     

基于闭环控制策略的负载谐振型臭氧发生器电源

介质阻挡放电型臭氧发生器负载呈容性,随负载外加电压的升高,间隙放电逐渐增强,其总的负载等效电容逐渐变大。针对负载的这一特点,提出了一种基于逆变器输出电流进行闭环频率跟踪控制的高频逆变电源方案,详细分析了该控制策略的特点,并研制了实验样机,进行了实验验证,得出应用该方案的电源具有结构简单、工作频率变化范围小、系统参数容易选择、可靠性高等优点。     

Research and Development in Drying: Recent Trends and Future Prospects

Drying R&D has seen nearly exponential growth over the past three decades. Initially driven by the need to conserve energy in this highly energy-intensive operation found in almost all industrial sectors, now the focus is on product quality, environmental impact, safety issues, new products, and processes etc. Drying provides challenging areas for multi- and cross-disciplinary research of fundamental as well as applied nature coupling transport phenomena with material science. An attempt will be made to summarize the new developments in drying technologies, identify recent trends and make predictions about the future trends that may be expected. Also, personal perspectives on models of research appropriate for drying technology will be presented. The need for industry-academia interaction and for a stake of industry in academic research is noted as a key step towards successful transfer of innovative drying technologies to industry. Finally, the weaknesses of the currently popular “closed loop” approach of research in academia, by academia and for academia, resulting on over-emphasis on “high impact-factor” rather than “high impact research” will be discussed. It is hoped that future IDS meetings will increase industry participation by enhancing their impact on industrial adoption of newer more efficient drying technologies. It is essential to make it a worthwhile—even essential—exercise for industry to participate in these meetings.     

激光直写设备超精密平稳驱动技术的研究

在二元光学激光直写设备中，主轴的速度稳定性是影响光刻精度的主要原因之一。提出采用机电混合滤波器消除电机的轴向振动和径向振动对系统的影响，提高主轴系统瞬时运动的平稳性。利用鉴相器输出的频差与相差和主轴电机的速度对锁相调速系统的结构进行优化。同时，利用神经网络改善锁相环系统的非线性特性，并采用模糊参数自调整方法调节控制器的参数。结果表明使用机电混合滤波器可使主轴的轴向与径向振动小于20nm，采用改进的锁相环控制可大大提高主轴的调速范围，并改善其动态性能。     

闭路净循环水系统膨胀罐的设计

本文提供了闭路净循环冷却水系统膨胀罐压力、容积、操作等设计参数．