A study on the transient characteristics of a self-regulating Joule-Thomson cryocooler

An experimental and numerical study of transient characteristics for the self-regulating Joule-Thomson (J-T) cryocooler is developed in the present work. The modelling of the bellows control mechanism and the simulation of the cooler system are developed. It is proved by experiment that the most important transient behaviours can be accurately predicted by the present numerical simulation. In order to rectify the instability problem of the bellows controlled J-T cooler, this study also proposes a revised design to improve temperature stability. The revised dual-orifice J-T cooler can effectively reduce the phenomena of unstable temperature and mass flow rate, but sacrifices the expected gas consumption rise by approximately 5 percent. Through experimental evaluation, it becomes obvious that this revised type cooler would be a better design.     

液压同步闭环控制及其应用

本文对液压同步闭环控制进行了系统的分类和比较了几种主要控制形式的特点；分析了各种控制策略及现代控制理论应用对其的影响，并对液压同步闭环控制的实际应用进行了回顾与展望。     

Closed-loop identification of wafer temperature dynamics in a rapid thermal process

Single wafer rapid thermal processing (RTP) can be used for various wafer fabrication steps such as annealing, oxidation and chemical vapor deposition. A key issue in RTP is accurate temperature control, i.e., the wafer temperatures should be rapidly increased while maintaining uniformity of the temperature profile. A closed-loop identification method that suppresses RTP drift effects and maintains a linear operating region during identification tests is proposed. A simple graphical identification method that can be implemented on a field controller for autotuning and a nonlinear least squares method have been investigated. Both methods are tested with RTP equipment based on a design developed by Texas Instruments.     

Control of pH processes based on the genetic algorithm

In this work, we propose a PID control strategy based on the genetic algorithm coupled with cubic spline interpolation method for the control of pH processes. The control scheme proposed in the present work consists of closed-loop identification based on the genetic algorithm and cubic spline method. First, we compute the parameters (K_C, Τ_I, Τ_D) of the PID controller using relay feedback and apply these parameters to control the pH Process. Then approximate linear models corresponding to each pH range are obtained by the closed-loop identification based on closed-loop operation data. The optimal parameters of the PID controller at each pH region are then computed by using the genetic algorithm. From numerical simulations and control experiments we could achieve better control performance compared to the conventional fixed gain PID control method. This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University.     

数控缠绕机闭环压力控制系统开发与研究

缠绕压力是保证复合材料缠绕制品质量的关键物理参数,在分析目前液压开环压力控制系统优缺点的基础上,结合气压传动的特点开发一套数控布带缠绕机闭环压力系统,并对其中各元器件选择原则进行研究,在实际应用中,该压力控制系统的动静态性能非常稳定,控制精度比较高.     

闭环模型测试法与计算机处理程序

模型测试是系统分析及改进机电设备的设计基础。闭环测试是一种既简单又安全的对象特性测试方法。在测试闭环衰减响应曲线的基础上，由测取若干响应曲线的特征数据，便可以求出对象模型的的阶次与结构参数，并由专用程序加以计算，仿真结果与实验数据经专用程序计算的结果完全一致，说明本方法有广泛的实用价值     

计算机辅助设计中的闭环设计方法及其实现

论述了产品的行为特性与其设计参数的关系,提出了通过构建行为特性函数利用设计结果调整设计参数的闭环设计方法。在计算机辅助设计中,应用闭环设计方法自动完成设计反复,使设计目标达到很高的设计精度,并可以进行可行性、灵敏度分析,实现优化设计。     

计算机闭环控制系统在摩擦焊接中的应用

根据摩擦焊接过程质量控制需要 ,建立了摩擦焊接过程计算机电液比例闭环控制系统 ,实现了摩擦焊接过程中轴向压力的闭环控制、滑台进给速度的开环比例控制。生产现场数据统计分析表明 ,采用电液比例计算机闭环控制系统后 ,摩擦压力与顶锻压力的平均误差小于 2 % ,变异系数接近于 0 ,摩擦焊接参数的稳定性大大提高 ,有广泛的应用前景     

自控温电伴热材料在仪表测量管线上的应用

文章就化工自动化仪表测量管线的伴热问题,介绍了自控温电伴热材料的特点、伴热设计、施工方案以及运行中的注意事项。     

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.