模糊PID复合控制在三聚甲醛生产中的应用

三聚甲醛的合成受很多因素的影响与制约,具有大滞后、强耦合、难以建立合适数学模型的特点。传统的PID控制很难达到工艺指标要求。采用模糊PID复合控制方式,通过模糊控制与PID控制的自动切换,偏差较大时采用模糊控制方式,以减小超调量并缩短调节时间;偏差较小时切换至PID控制以消除稳态误差。模糊PID控制将模糊控制动态性能好与PID控制稳态精度高的优点相结合,在生产过程中取得了明显的效果。     

基于模糊控制的螺杆挤出机温度控制系统设计

以螺杆挤出机温控系统的扰动多、非线性、时变以及大滞后的特性,研究得到了智能化的控制算法,对于现场无法充分预料的情况,这种温度控制系统能够发挥重要的作用。使用Zig Bee无线传感技术可实现温度监控的远程操作,提升检测效率和水平。对远程无线温度控制系统的硬件系统进行了设计,对CC2430射频主控芯片的外围电路、温度传感电路以及温度控制电路进行设计。针对螺杆挤出机温度控制系统进行实例分析,研究结果表明:使用常规PID控制器,在阶跃信号和脉冲干扰信号作用下,系统超调量和稳定时间不能够满足螺杆挤出机温度控制的要求。使用模糊PID控制器,相比常规PID控制器的超调量和稳定时间要明显增强。以尼龙6/Ca Cl2复合材料挤出为例,分别使用常规PID控制算法和模糊控制算法进行对比分析,研究温度控制精度对产品成型质量的影响。在模糊控制算法下,三种产品(温度设置分别为240,260,280℃)的缺口冲击强度合格率比较使用常规PID控制算法时提高了6.87%,弯曲应力合格率、断裂伸长率合格率、拉伸强度合格率分别提高了8.67%,9.33%,8.77%。     

自适应模糊滑模控制在化工过程中的应用

为有效处理多变量、非线性及非最小相位系统的复杂化工过程,提出了一种新型的自适应模糊滑模控制,该方法针对滑模控制鲁棒性好但存在抖振的问题,采用模糊控制柔化控制信号,而与滑模控制的结合可以充分利用系统信息,简化模糊控制;在此基础上提出一种新的自适应调整比例因子来进行模糊变论域,柔化了控制信号并减小了滑模控制器输出的抖振。并给出模糊滑模控制的算法和稳定性分析,得到简化后的通用模糊规则库,可通过比例因子在线调节输入量的论域,使构成的控制系统具有很强的鲁棒性、较好的自适应能力和较高的控制精度。最后对于非线性单输入单输出(SISO)和多输入多输出(MIMO)化工模型进行仿真研究,结果表明即使工况点发生大的变化或受到较大干扰时,仍具有良好的抗扰动能力和很强的鲁棒性。     

Fuzzy control of ethanol concentration for emulsan production in a fed-batch cultivation ofAcinetobacter Calcoaceticus RAG-1

A fuzzy control system was organized and applied to the control of ethanol concentration in a fed-batch cultivation process for emulsan production byAcinetobacter calcoaceticus RAG-1. The membership functions and fuzzy rules were determined by sets of data and experiences obtained from the preliminary culture experiments. The input variables, error (the difference between the set point value and the process variable) and the change of the error, were fuzzified by using the membership functions and the output variable, change of the ethanol feed rate, was inferred based on the membership functions and the given fuzzy rules. To obtain the numerical value for the output variable, the center-of-gravity method was used in the defuzzification procedure. The results showed that the ethanol concentration was well regulated around optimal level and the emulsan yield was increased compared with that of the cultivation controlled by the conventional feedback control loop.     

HEDP生产过程的智能控制

本文在分析羟基亚乙基二膦酸(HEDP)生产工艺特点的基础上,提出采用自适应模糊控制策略进行生产过程的智能控制,阐述了自适应模糊控制系统的软件设计。并模拟仿真证明其控制输出能够快速地跟踪设定值,实时控制效果良好。本文对改进现有HEDP生产控制具有参考价值。     

水泥分解炉温度控制过程的阶跃响应建模与仿真

根据从新型干法水泥分解炉温度控制过程中采集的实测数据,选取从过渡工况到动态稳定工况过程中的典型数据段,用阶跃响应法建立分解炉温度控制过程稳态工作点附近的二阶惯性加纯滞后数学模型;以分解炉出口温度偏差及偏差变化率为输入变量,尾煤变化量为输出变量,使用MATLAB的Fuzzy Logic工具箱设计二维模糊控制器,并在稳态阶...     

塑料挤出温度模糊控制系统的开发研究

介绍用于控制塑料挤出温度的模糊控制系统的开发，在硬件方面采用AT89C52为主控芯片，用带热电偶冷端补偿的专用芯片AD595进行信号放大，并用V／F变换器AD650与CD4051配合，结合软件算法进行采样。按总结温度模糊控制规则得到的模糊控制表进行控制软件的开发与实现，整个系统具有体积小、成本低、功能强、智能化等特点。     

Dynamics and Control of a Biodiesel Transesterification Reactor

Biodiesel transesterification reactors resemble the heart of any biodiesel manufacturing plant. These reactors involve a highly complex set of chemical reactions and heat transfer characteristics. The high nonlinearity inherent in the dynamics of these reactors requires an efficient process control algorithm to handle the variation of operational process parameters and the effect of process disturbances efficiently. In this work, a multi‐model adaptive control strategy is considered for achieving the goal mentioned above. In order to implement the adaptive controller, a rigorous mechanistic model of the biodiesel transesterification reactor was developed and validated with published experimental results. The validated model was analyzed for stability and nonlinearity. The analysis revealed that the system is stable. However, its high nonlinearity necessitates an advanced control strategy to be considered. The input‐output relationship between the effective process variables was studied and the control system synthesis revealed a two‐by‐two control system. Two adaptive control loops were then designed and tuned to optimize the performance of the controller. Finally, a comparison with conventional controllers revealed the superiority of the new control system in terms of set‐point tracking and disturbance rejection. The results of this work prove that an adequately designed adaptive control system can be used to improve the performance of the transesterification reactor.     

模糊推理方法在控制系统故障诊断中的应用研究

一种不依赖硬件和环境的全软件解决方案,直接利用输入信号和反馈信号的测量分析,经模糊变换获得信号特征模糊变量,通过扫描信号特征量的超限情况,调用相关推理规则运算求解得到控制系统的故障诊断信息。开发的应用软件已用于工业实际系统。     

Noncatalytic Biodiesel Fuel Production from Croton megalocarpus Oil

Biodiesel is currently considered as the most promising substitute for diesel fuel because of its similar properties to diesel. This study presents the use of the supercritical methanol method in the production of biodiesel from Croton megalocarpus oil. The reaction parameters such as methanol‐to‐oil ratio, reaction temperature and reaction time were varied to obtain the optimal reaction conditions by design of experiment, specifically, response surface methodology based on three‐variable central composite design with α = 2. It has been shown that it is possible to achieve methyl ester yields as high as 74.91 % with reaction conditions such as 50:1 methanol‐to‐oil molar ratio, 330 °C reaction temperature and a reaction period of 20 min. However, Croton‐based biodiesel did not sustain higher temperatures due to decomposition of polyunsaturated methyl linoleate, which is dominant in biodiesel. Lower yields were observed when higher temperatures were used during the optimization process. The supercritical methanol method showed competitive biodiesel yields when compared with catalytic methods.     

应用在液化石油气换热系统中的模糊PID控制

通过利用参数整定PID模糊控制器对LPG换热系统中被加热介质丙烷的出口温度进行控制。根据其动态参数和相关经验制定模糊规则,利用模糊规则对PID三个参数Kp、Ki、Kd进行调整,以改善其控制性能,应用MATLAB软件对实际系统进行仿真。结果表明,该控制方法具有超调量小、过渡时间短、适应性强、抗干扰性强等优点。最后,对照实际运行结果验证了模糊PID控制的优越性。     

采用辐射能信号的燃烧系统参数自调整模糊PI控制

针对火电厂燃烧过程中主蒸汽压力控制系统的大时滞、大惯性和非线性,采用能迅速反映燃料侧扰动的辐射能信号进行快速补偿,并设计一个参数自调整的模糊PI控制器作为主控制器。该控制器首先通过编写S函数来自动修正量化因子和比例因子,从而改善基本模糊控制器的性能;然后将模糊控制与PI控制相结合,以优化燃烧控制性能;仿真结果表明该方案显著提高了非线性、大时滞燃烧系统的控制品质。     

Implementation of Multimodel-Based PID and Intelligent Controller for Simulated and Real-Time Temperature Control of Injection Molding Machine

The proposed real-time multimodel for the injection molding process mainly contributes to the barrel temperature control. Good control of the plastic melt temperature is very important for injection molding in reducing the operator setup time, ensuring product quality, and preventing thermal degradation of the melt. The controllability and set points of the barrel temperature also depend on the precise monitoring and control of the plastic melt temperature. Motivated by the practical temperature control of injection molding, this article proposes a multimodel-based proportional integral derivative (PID) control scheme in real-time and the simulation studies of the PID, fuzzy, and adaptive neuro fuzzy inference system (ANFIS) control schemes. The injection molding process consists of three zones, and the mathematical model for each zone is different. The control output for each zone controller is assigned a weight, based on the computed probability of each model, and the resulting action is the weighted average of the control moves of the individual zone controller.     

Control of cross-direction variations in web forming machines

Web forming machines are often fitted with control actuators which can be used to produce uniform web properties across the width of the machine. A formal procedure for setting these actuators is presented. It is based on a linear incremental steady state process model and a quadratic objective function. Quadratic programming is used to determine optimum settings. It is shown that the procedure handles limited range actuators, interaction among actuators, and physical constraints on the pattern of actuation. Computing costs are seen as a potential problem when large numbers of actuators are involved.     

一种新型模糊液位控制及其应用

在连续生产过程中,工艺上通过设立缓冲容器来解决前后工序之间的物料量突变,以确保生产的平稳性,针对这类容器的液位控制,常规PID定值控制已满足不了上述要求。为解决这个问题,以长期现场实践为基础,根据操作人员的思维特性,提出了一种基于模糊控制和常规控制相结合的液位区域控制方法。该方法以液位的上下限和变化量作为输入模糊量化依据,改变了传统输入模糊量化方法,同时对于模糊输出量到控制输出采用新的转换方法,使模糊输出离散量转化为希望调节的液位量。为提高控制精确度,在实际控制输出与希望调节偏差较大时,增加了输出校正环节以减少输出误差。这种方法允许液位在给定的高低限范围内波动,以保证送出的物料缓慢平稳变化;只有液位超出高低限时,或液位在正常范围内,并且液位变化量超过给定阈值时才进行调节,以确保维持下游工序的负荷平稳。实际应用结果验证了这种方法的有效性。     

Control of pure time delay processes

The general problem of controlling a physical process with predominant time delay is analysed. An effective method of controlling such a process is proposed and successfully applied. The control scheme consists of a two-loop configuration: a fast auxiliary loop consisting of a proportional controller and a simple lag element, and a main (process) loop provided with another proportional controller operating on the process. While the auxiliary loop output acts as common feedback to both the controllers, the process output adjusts the set point of the auxiliary controller. Disturbances entering the process, for which compensation is desired, are transmitted to the auxiliary loop where a corrective action is generated even before an error appears in the controlled variable. Digital simulation study reveals that, by suitable choice of the compensator parameters, this control arrangement results in remarkably superior performance compared to other known methods of dead time control. The technique is applied to a real process having a dead time of 2·7 min to demonstrate its easy implementability and to confirm its superiority over existing control schemes.     

An enzymatic/acid-catalyzed hybrid process for biodiesel production from soybean oil

The present study is aimed at developing an enzymatic/acid-catalyzed hybrid process for biodiesel production using soybean oil as feedstock. In the enzymatic hydrolysis, 88% of the oil taken initially was hydrolyzed by binary immobilized lipase after 5 h under optimal conditions. The hydrolysate was further used in acid-catalyzed esterification for biodiesel production and the effects of temperature, catalyst concentration, feedstock to methanol molar ratio, and reaction time on biodiesel conversion were investigated. By using a feedstock to methanol molar ratio of 1:15 and a sulfuric acid concentration of 2.5%, a biodiesel conversion of 99% was obtained after 12 h of reaction at 50 °C. The biodiesel produced by this process met the American Society for Testing and Materials (ASTM) standard. This hybrid process may open a way for biodiesel production using unrefined and used oil as feedstock.     

Fuzzy logic controller implementation on a microbial electrolysis cell for biohydrogen production and storage

This work presents the implementation of fuzzy logic control (FLC) on a microbial electrolysis cell (MEC). Hydrogen has been touted as a potential alternative source of energy to the depleting fossil fuels. MEC is one of the most extensively studied method of hydrogen production. The utilization of biowaste as its substrate by MEC promotes the waste to energy initiative. The hydrogen production within the MEC system, which involves microbial interaction contributes to the system’s nonlinearity. Taking into account of the high complexity of MEC system, a precise process control system is required to ensure a well-controlled biohydrogen production flow rate and storage application inside a tank. Proportional-derivative-integral (PID) controller has been one of the pioneer control loop mechanism. However, it lacks the capability to adapt properly in the presence of disturbance. An advanced process control mechanism such as the FLC has proven to be a better solution to be implemented on a nonlinear system due to its similarity in human-natured thinking. The performance of the FLC has been evaluated based on its implementation on the MEC system through various control schemes progressively. Similar evaluations include the performance of Proportional-Integral (PI) and PID controller for comparison purposes. The tracking capability of FLC is also accessed against another advanced controller that is the model predictive controller (MPC). One of the key findings in this work is that the FLC resulted in a desirable hydrogen output via MEC over the PI and PID controller in terms of shorter settling time and lesser overshoot.     

连续反应釜温度控制系统的设计与仿真

针对连续反应釜中进行的化学反应特性,按照过程的动力学方程和能量平衡等关系,设计了一套基于西门子PCS7的连续化学反应釜(CSTR)温度控制系统。由于连续反应釜内温度的非线性、时变等特性,采用变结构模糊控制结合前馈、串级、分程等先进的控制方式,克服了传统PID算法参数调整复杂、超调量大的缺点。仿真结果表明:对温度采用变结构模糊控制能获得较好的稳态精度和动态特性,满足了反应釜内温度控制的要求。     

Smith预估-模糊控制在硝酸氧化炉自设定氨空比控制中的应用

硝酸生产氧化炉温度控制系统具有大惯性、非线性及时变等特点,采用常规控制方法对温度进行控制难以获得满意的效果。因此,提出一种新的基于模糊控制的氨空比自动设定方案,通过模糊控制器输出氨空比修正值,实现了氨空比的自动设定;同时,将Smith预估控制应用于主回路进行温度补偿,减小了时滞的不利影响。仿真结果显示:该方案自动设定的氨空比能够很好地调节氧化炉温度,较常规控制方法超调量小、调节时间短。