挤出机温度控制系统中PID控制器的应用

针对目前挤出机温度控制系统温度波动范围大、超调量大等缺点,本文设计了以PLC为控制核心的多回路不等温塑料挤出机温度控制系统。采用PLC中PID控制器,通过扩展模拟输出模块,控制可控硅的导通量从而实现对升温速度的控制,同时保留原来的风扇降温环节。改进过的挤出机温度控制系统,能够达到精确的温控效果。     

基于预测控制的神经网络PID在热分散温度控制系统中的应用

热分散过程中对温度的控制是非常重要的,温度控制具有非线性、慢时变、大滞后的特点,并且存在不可测的干扰,所以采用基于预测控制的神经网络PID策略,预测下一时刻的模型输出,经过反馈校正,结合最优化指标调整BP网络的权值校正PID的调节参数,实现对热分散温度控制系统的有效控制.该方法已应用在某纸业制浆控制系统中,该系统温度控制平稳,调节时间短,热分散效率明显提高,取得了较好的效果.     

汽车安全气囊标牌热风焊接的控制系统设计

针对汽车安全气囊标牌焊接作业中采用热风焊接技术存在的缺乏成熟控制系统的现状,设计了一套完善的安全气囊标牌热风焊接控制系统。控制系统采用PLC作为核心控制单元,采用K型热电偶作为温度采集传感器,并设计了控制系统的控制程序和人机交互界面。控制算法采用优化的PID算法实现了出风口处的温度的精确控制。重复性温度采样分析的实验结果表明,应用该系统进行控制后的温度偏差在±1℃之内,温度控制精度较高,明显优于传统的控制方式。     

基于MATLAB的热力除氧器模糊PID控制仿真研究

针对热力除氧器系统大滞后、大惯性、非线性以及难以建立精确的动态数学模型等特点,本文采用模糊控制算法与传统的PID控制算法相结合,设计了热力除氧器温度控制系统。为了检测所设计的温度控制系统的性能,采用仿真软件MATLAB的模糊工具箱结合Simulink动态仿真分别对模糊PID控制算法和PID控制算法进行了仿真试验。试验结果表明,模糊PID控制系统能较好地满足除氧工艺要求,提高了热力除氧器温度控制系统的精度和工作效率。     

粒子群优化模糊PID在燃烧器温度控制中的应用

针对燃烧器温度控制系统是一个时变、大延迟和非线性的控制系统,无法建立准确数学模型,难以进行精确控制的问题,常使用模糊PID算法实现对此类系统的控制.但模糊PID算法需要专家给出模糊规则并调节参数,且参数调节过程中存在误差,控制性能较差.本文采用粒子群优化模糊PID算法中的量化因子Ke、Kec和比例因子Ku,快速整定模糊...     

基于PLC的内燃机专用清洗设备控制系统

为了实现内燃机专用清洗设备的实时监测与控制,采用了三菱FX2N可编程控制器及其A/D模块作为控制器件,完成了该设备控制系统的硬件和软件设计,实现了对设备作业的自动控制和清洗液温度的控制.实际应用结果表明,该控制系统能准确控制清洗液温度,并提高了作业的质量和效率.     

基于模糊理论的除氧器温度控制系统设计

针对发电厂的除氧器温度控制系统中被控对象具有大滞后、大惯性、非线性等特点,以及其精确的数学模型难以建立的实际情况,采用模糊控制策略,设计了发电厂除氧器的模糊温度控制系统.同时,根据输入量误差及误差率的变化,设定了一个修正因子以调整模糊控制器的控制规则.从而很好地改善了系统的动态特性,提高了稳态精度.     

基于AVR单片机的炉温控制系统

各种大功率的电阻炉均具有大惯性、长滞后时间等特性,采用常规PID控制器难以取得较好的控制效果.提出一种基于AVR单片机的炉温控制系统设计方案,该系统控制器采用大林算法.硬件以AVR单片机ATmega8515作为微控制器,用单总线DS18B20芯片采集温度,交流过零触发型固态继电器驱动输出,具有4×4键盘和HS12864-12液晶显示器.该系统易于扩展成分布式多点温度控制系统.实验结果显示了该方案的有效性.     

基于模糊PID的电烘箱温度控制系统设计与实现

电烘箱温度具有非线性、大惯性、大滞后等特点,往往难以建立精确的数学模型。目前在工业生产中普遍采用的传统PID控制方式精度不高,难以取得较好的控制效果。为了提高电烘箱温度的控制效率和控制精度,以模糊自适应PID控制算法为基础,研究基于模糊PID的电烘箱温度控制技术,开发一种基于模糊PID的电烘箱温度控制系统。     

熔模精密铸造温度模糊控制方法研究

铸造温度是一种典型的具有时滞、大惯性和参数时变特性的控制对象,且其干扰源较多,而采用常规且成熟的PID控制方法很难达到理想的控制效果。因此,提出了一种模糊Smith智能温度控制方法,即在模糊控制理论的基础上将PID控制与模糊Smith预估控制相结合。仿真结果表明,该方法可以有效改善温度控制系统的品质,从而进一步提高温度控制系统的抗干扰能力和鲁棒性。     

常减压装置加热炉过程控制不稳定分析及改造

该文就炼油厂常减压装置中加热炉扩容改造中出现的物料出口温度控制不稳定的问题进行了分析，指出了旧的前馈一负反馈控制系统存在的问题，针对加热炉扩容后出现的控制大滞后问题提出了解决办法。选用霍尼韦尔可编程调节器，采用前馈一增益自适应的Smith预估补偿控制算法，满足了工艺要求，使加热炉出口温度的控制平稳，达到了预期的效果。     

Study on low pressure evaporation of fresh water generation system model

A low pressure evaporation fresh water generation system is designed for converting brackish water or seawater into fresh water by distillation in low pressure and temperature. Distillation through evaporation of feed water and subsequent vapor condensation as evaporation produced fresh water were studied; tap water was employed as feed water. The system uses the ejector as a vacuum creator of the evaporator, which is one of the most important parts in the distillation process. Hence liquid can be evaporated at a lower temperature than at normal or atmospheric conditions. Various operating conditions, i.e. temperature of feed water and different orifice diameters, were applied in the experiment to investigate the characteristics of the system. It was found that these parameters have a significant effect on the performance of fresh water generation systems with low pressure evaporation.     

Nonlinear model-based control algorithm for a distillation column using software sensor

This paper presents the design of model-based globally linearizing control (GLC) structure for a distillation process within the differential geometric framework. The model of a nonideal binary distillation column, whose characteristics were highly nonlinear and strongly interactive, is used as a real process. The classical GLC law is comprised of a transformer (input-output linearizing state feedback), a nonlinear state observer, and an external PI controller. The tray temperature based short-cut observer (TTBSCO) has been used as a state estimator within the control structure, in which all tray temperatures were considered to be measured. Accordingly, the liquid phase composition of each tray was calculated online using the derived temperature-composition correlation. In the simulation experiment, the proposed GLC coupled with TTBSCO (GLC-TTBSCO) outperformed a conventional PI controller based on servo performances with and without measurement noise as well as on regulatory behaviors. In the subsequent part, the GLC law has been synthesized in conjunction with tray temperature based reduced-order observer (GLC-TTBROO) where the distillate and bottom compositions of the distillation process have been inferred from top and bottom product temperatures respectively, which were measured online. Finally, the comparative performance of the GLC-TTBSCO and the GLC-TTBROO has been addressed under parametric uncertainty and the GLC-TTBSCO algorithm provided slightly better performance than the GLC-TTBROO. The resulting control laws are rather general and can be easily adopted for other binary distillation columns.     

SCADA system for oil refinery control

A Supervisory Control and Data Acquisition (SCADA)/Programmable Logic Control (PLC) system is always used to control small industries like water treatment stations; electric power stations and irrigation systems. Oil and gas refineries generally rely on a Distributed Control System (DCS) to provide all process and equipment control functionality. In this paper, a SCADA/PLC system is used to control a whole oil refinery instead of the conventional control through DCS. The design and specific implementation method of a SCADA/PLC real system in an oil refinery process is introduced. It consists of four main units: a crude oil storage unit, a crude oil pretreatment unit, a distillation unit and products storage/dispatch unit. The output products from crude oil refinery process are Liquefied Petroleum Gas (LPG), Naphtha, Gasoline, Kerosene and Diesel that have a great usage in our daily life. The reason for using the Multipoint Interface/Decentralized Peripherals (MPI/DP) connection in main control loop instead of Ethernet connection is that MPI/DP speed is 185 kbps and Ethernet connection speed is 10/100 kbps, which increases the speed of transfer data through the system. Displacer level transmitters and automatic servo level gauging transmitters are used for measuring levels in the crude oil refinery process. Also differential pressure flow transmitters are used for measuring flow rate. Temperature transmitters with thermocouple temperature elements are used for temperature control. Constructing a highly stable and reliable SCADA/PLC system instead of DCS must realize automatic management and control of oil refinery process in order to avoid the waste of manpower, physical resources, and also to increase the safety of workers.     

基于径向基函数神经网络和NLJ优化算法的精馏塔控制

精馏塔是一个非常重要的操作单元,具有较强的非线性和时变性,很难进行基于机理建模分析的实时优化控制.通过对精馏塔的相关过程变量进行主元分析确定了5～6个关键变量作为神经网络的输入,建立了精馏塔多个质量指标的RBF神经网络的软仪表模型,实现了这些质量指标的在线估计.选取其中部分软仪表模型作为优化控制系统中的约束条件函数模型和目标函数模型,采用NLJ优化算法(变收缩系数的随机搜索算法)获取最优的决策变量设定值,从而得到了满足生产质量要求的精馏塔产品的最大采出,实现了精馏塔的卡边优化控制.     

基于纯滞后补偿技术的镁合金熔炉温控系统设计与实现

针对镁合金熔炉的纯滞后特性,采用smith预估器对系统进行补偿.根据镁合金熔炉的结构和特性,建立了以PID和smith预估器为核心的温度控制系统模型;然后设计了硬件系统和软件控制流程;再通过simulink仿真比较了普通PID控制和simth预估控制模式.结果表明,smith预估控制系统可以消除系统的静态误差,减小超调,缩短调节时间,提高控制精度,使得系统运行稳定,性能明显优于普通的PID控制系统.     

氨水吸收式制冷系统性能与精馏性能试验分析

基于性能高效、结构紧凑的理念,研制一套氨水吸收式制冷试验系统,在部分回流、全回流工况下对系统进行性能试验。结果表明:部分回流工况下,发生器电加热功率要与进料量相匹配;通过降低冷凝器中的冷却水温度和减小冷却水量来降低精馏塔操作压力,提高系统性能;全回流工况下,回归得到适用于精馏塔板操作范围内的精馏板效率关联式,反映了精馏板效率与操作工况、氨水物性以及结构因素中主要变量的影响关系。     

主蒸汽温度的BP神经网络PID控制系统的研究

针对火电厂主蒸汽温度系统大惯性、大迟延、非线性的特点,常规串级PID控制难以取得满意的调节效果,为了改善常规PID控制的不足,文章在研究BP神经网络的基础上,把BP神经网络PID控制应用到主汽温控制系统中。运用matlab仿真,结果表明,与传统控制相比BP神经网络PID控制算法有效减小了系统的超调量,提高了系统的响应速度,在主汽温控制系统中具有很好的控制效果。     

Tribological performance of distilled biomass oil from rice straw by pyrolysis process

The biomass oil pyrolysed from rice straw was refined through distillation process under one atmosphere pressure. Four distilled fractions were obtained in the temperature ranges of 54–64, 72–80, 84–92 and 96–100 °C respectively. Their chemical components and special group structures were analysed by gas chromatography‐mass spectrometry (GC‐MS) and Fourier transform infrared spectroscopy. The tribological performances of the prepared fractions were evaluated by MQ‐800 four‐ball tribometer as well. The results showed that both density and acid number of the biomass oil increased with the distillation temperature and that the total distillation yield was 55.7%. Every distillation fraction had different anti‐wear and friction reduction. Their average friction coefficients were 0.185, 0.227, 0.179 and 0.293 in 30 minutes, and the average wear scar diameters were 1.035, 0.958, 0.870 and 0.983 mm under a rotation speed of 1450 rpm respectively. It was found that the fraction distilled in the temperature range of 84–92 °C showed better friction reduction and wear resistance. Copyright © 2008 John Wiley & Sons, Ltd.