单电磁悬浮系统的神经网络模糊滑模控制

为实现单电磁悬浮系统悬浮气隙的精确控制,提出一种基于神经网络的模糊滑模控制方案.根据单电磁悬浮系统的动态非线性数学模型,设计使系统状态在有限时间内到达稳定点的滑模面,同时根据滑模切换状态,通过引入神经网络的模糊控制方法对滑模切换控制量的增益进行评估,实时对滑模控制量进行调整,实现切换控制信号的柔化.基于神经网络的模糊滑模控制系统不仅能很好地跟踪给定信号,而且能削弱滑模控制抖振,对外部扰动具有完全的鲁棒性.仿真结果表明,所设计的控制系统零超调,具有速度跟踪性能,对外部扰动具有很强的鲁棒性.     

段塞流的流量瞬变特性试验研究

An investigation of the characteristics of flowrate transients within slug flow was conducted in a largescale outdoor testing facility.The test section consisted of a 378m long,7.62cm diameter stainless steel pipe. Air and water were used as the test fluids.The response to a change of flowrate o either phase or two phases was measured using a series of pressure transducers and differential pressure transducers.An increase or decrease in gas flowrate caused a pressure overshoot above the value at new steady state or led to a pressure undershoot to form a temporary stratified flow.Pressure waves existed in the pipeline,spreading from the entrance to the exit.The magnitude of pressure overshoot in “up-gas”transient or of pressure undershoot and period of the temporary stratified flow in “Down-gas” transient are related to the change of gas flowrate and the distance away from the entrance.In contrast,the change in liquid flowrate was accommodated by smooth transitions between the corresponding steady states,and only one obvious change was found in the slug frequency.According to experimental results,the pressure overshoot,pressure undershoot and the pressure wave propagation were analyzed,and the phenomena were explained reasonably.Some correlations for the calculation of the pressure overshoot and undershoot were proposed.     

希尔伯特-黄变换方法的改进

希尔伯特-黄变换(Hilbert-Huang Transform,简称HHT)方法是一种自适应性信号处理方法,在处理非线性、非稳态信号方面有很大优势。但HHT分解复杂信号时存在求解结果精确不高、计算时间长等不足。针对HHT的边端效应、越界问题、停止准则和虚假低频成分过滤等问题,文章提出了相应的改进方法。为有效抑制边端效应,人为定义两个极值点,然后连接相邻极值点形成直线后平行延拓。利用信号与包络线的极限差值多次拟合包络线,初步解决了越界问题。根据虚假成分与原始信号的相关系数远小于真实信号与原始信号的相关系数,成功过滤掉虚假成分。数值算例的结果表明了所提方法的有效性。     

数控液压垫速度动态特性分析

通过对数控液压拉伸垫进行数学建模与动态仿真,对其下行速度动态特性进行分析,通过分析发现,当系统处于开环控制状态时,过大的调节时间和超调量,无法满足设计要求,必须加入加速度反馈形成闭环控制,才能达到很好的动态特性,同时满足生产的实际需要。     

一种高速低过冲电荷泵电路的设计

为了有效降低传统电荷泵电路的充放电过冲电流,提高电荷泵输出控制电压的稳定性,提出、设计并实现了一种高速低过冲的电荷泵结构,该电路适用于高速锁相环及时钟数据恢复电路.电路在电源电压为1.2 V的0.13 μm CMOS工艺下设计实现,并对版图数据进行了HSPICE模拟,其结果表明,电路在2.5 GHz的速度下能很好的工作,同时电流过冲相比传统电荷泵下降了70%.     

LED显示屏驱动技术讨论：动态响应

LED驱动芯片的动态响应特性经常被忽略,但却是相当重要的一个特性。动态响应影响LED显示屏的影像质量,如灰阶、线性度、EMI、信赖性。虽然这些特性彼此间有取舍关系．但是好的驱动芯片应该能够在这些特性中取得较佳的平衡。本文将探讨动态响应的重要性及LED驱动芯片与电路板设计技术,以协助工程师设计出影像质量良好的显示屏。     

Approach the powder contact force,voidage, tensile stress,wall frictional stress and state diagram of powder bed by simple pressure drop monitoring

The evaluation of the mechanical properties and the state of a powder bed are essential for industrial powder operations. We assume that the bed incipient yield is approximately the bed incipient fluidization, and the particle contact force, the bed voidage, the bed tensile stress and the bed-wall frictional stress can be determined by simple pressure drop monitoring when gradually increasing the superficial gas velocity from zero. A two-dimensional powder bed voidage-tensile stress state diagram at zero shear stress under anisotropic consolidation is initially prepared. For the sample powder bed, we show that the isotropic tensile stress estimated by the powder yield locus extrapolation, 340 Pa−770 Pa, from a shear tester is different from the anisotropic tensile stress evaluated, 120 Pa–180 Pa, by the pressure drop overshoot approximation.     

基于分段终端滑模的双三相电机控制系统研究

为进一步提高双Y移30°永磁同步电机调速系统控制性能,提出一种分段非奇异终端滑模控制方法。详细阐述分段非奇异终端滑模相比于非奇异快速终端滑模的优异性,分析了分段非奇异终端滑模面参数的意义,理论证明系统状态从到达滑模面至收敛到平衡点的作用时间是有限的。在此基础上设计双Y移30°永磁同步电机调速控制器,在保持系统动态性能的同时,减小超调量,提高了稳态精度。仿真和实验结果证明了方法的有效性。     

一种新的 PID 控制参数自寻优整定方法——控制品质加权法

提出了一种新的,用于ＰＩＤ控制,以两个控制品质参数（过渡时间Ｔｓ和超调量δ）等权或不等权和最小为整定准则,称为“控制品质加权法”的控制参数自寻优整定方法．多次仿真输出的图形和数据结果充分证明,采用控制品质加权法,比采用ＩＴＡＥ误差准则、ＩＳＥ误差准则和经验乘系数等各种传统方法,都能提供更优的控制参数,从而使系统的控制品质得到明显改善,并能满足对过渡时间Ｔｓ和超调量δ看重程度不同用户的不同要求     

水轮机调速系统整定参数新公式

本文推导出水轮机调速系统时域指标计算公式,并按二阶最佳设计提出了最小超调量概念及公式.从而得出一套水轮机调速系统整定参数计算的新公式。