基于RBF神经网络陶瓷窑炉温度动态矩阵控制

陶瓷窑炉普遍具有纯滞后、大惯性、非线性、时变复杂等特点,其精确数学模型往往很难获取。针对这类系统,本文采用RBF神经网络建立被控对象模型,避免了常规控制算法建立对象精确数学模型的困难。应用动态矩阵预测算法实现对被控系统的预测控制。该控制方法具有很好的动、静态性能和强鲁棒性。以陶瓷窑炉温度为对象,与PID控制进行了比较;仿真结果证明了所提控制方法的有效性。     

制造岩棉液渣的温度常规控制

本文就液渣制造岩棉的生产过程，提出了前馈反馈温度控制方案。在这个控制方案中，导流槽出口液渣温度须进行测量，并作为主被控变量，导流槽中电极的电流也须进行测量，并作为副被控变量。在前馈回路中，要测量导流槽入口液渣温度，并作为前馈信号     

模糊预测控制在循环水加药控制中的应用

针对模糊控制和预测控制的特点.提出了一种模糊预测控制方法,利用模糊逻辑实现被控对象模糊化,解决被控对象难以建立的问题;利用预测控制,根据系统当前信息预测出系统未来的变化趋势,解决被控对象滞后问题.以火电厂循环水加药控制为例,对该控制方法进行了仿真和实际应用研究.结果表明,该系统能有效地避免纯滞后环节在控制系统中带来的振荡现象,工程应用取得了理想的控制效果,为纯滞后、大惯性、模型不确定系统的控制提供了很好的解决方法.     

基于神经网络的非线性时变对象自适应控制方法研究

针对工业控制中的非线性、时变和滞后被控对象,将神经网络辨识器和PID控制技术有机结合,构建自适应PID控制器,并引入知识先导学习算法,提高时间效率。仿真分析表明:该自适应PID控制器能够自动辨识被控对象模型、自整定控制参数,在辨识误差、响应时间及超调量等指标上均有良好表现。     

模型预测控制的应用研究

针对双容水箱液位控制系统单输入、单输出、时变、非线性、耦合和滞后的特征，以双容水箱液位为被控对象，设计基于状态方程模型的MPC预测控制器，对水箱液位进行控制。仿真结果表明：该控制器可以满足模型多输入、多输出、精确控制、抗干扰、耦合和非线性特征的控制需求，比传统PID控制器有更明显的优势。     

轮胎硫化蒸汽调节系统的设计与应用

为了设计一套控制精确的蒸汽调节系统，先对被控对象进行了特性分析，提出了设计思路，并最后设计出了完整的控制系统。经实践证明，此套系统运行可靠，可以满足工艺要求。     

基于次最优模型降阶的自整定PID控制器

针对过程工业中含有振荡环节和大滞后环节较难控制的被控对象,设计了一种基于频域辨识的自整定PID控制器.该控制器采用次最优模型降阶算法,辨识出二阶加纯滞后的模型;然后基于给定的相位裕度和幅值裕度,整定出PID参数.并通过仿真实验表明对于不同的被控对象,自整定得到的PID参数均能取得较好的控制效果.     

基于前馈-广义预测控制的篦冷机先进控制

水泥生产系统中，篦冷机具有多变量、大时间滞后、强干扰的特性，基本无法采用常规控制器实现自动控制，且手动控制效果常常不理想，因此提出一种基于前馈-广义预测控制的篦冷机先进控制方法。采用篦冷机固定板风机电流作为前馈量，可以克服篦冷机篦下压力较难控制的问题。该算法已经在某水泥厂篦冷机上成功实现并投运，极大地改善了控制品质。     

自适应控制在聚乙烯调温水系统中的应用

含有时滞的聚乙烯调温水串级控制系统是复杂的非线性时变系统,系统存在较大的纯滞后,采用模型参考自适应控制结合PID控制方法,使自适应控制器能够在线调整PID参数以匹配Smith预估器,使Smith预估器不受被控对象参数变化的影响。仿真结果表明:该控制方案有效减少了控制系统的超调量和调节时间。     

核电站蒸发器水位的二自由度模型驱动控制

针对核电站蒸发器水位被控对象的非自平衡、非线性等特性,传统PID控制难以获得期望的控制要求,设计了二自由度模型驱动PID(TDF MD PID)串级控制系统,并加入前馈控制,以克服蒸汽流量的影响。该方法通过PD反馈补偿器改善蒸发器水位对象的开环不稳定特性,使其达到稳定,然后进行控制。仿真结果表明,与传统串级PID相比,TDF MD PID结构简单,参数易于整定,具有快速的跟踪能力和很强的鲁棒性,有效地提高了系统的控制性能。     

Transient compositional effects from feeders in a starved flow modular co‐rotating twin‐screw extruder

A process dynamics model of transient output composition variations in a moduar self‐wiping twin‐screw extruder caused by input disturbances from feeders is developed. The changes of output mass flow rate and weight fraction of additives in the output stream were predicted for various time dependent input modes into a second feeder and other ports part way along the length of the machine.     

Process control of polymer extrusion. Part II: Feedforward control

A feedforward plus feedback control method (FFC) and an adaptive feedforward plus feedback control method (AFFC) were proposed in this study to control the extrudate thickness of polymer extrusion. They were tested by step changes of screw speed and feedstock, and square wave type of screw speed changes. It is found that these feedforward control methods worked very well for various load disturbances but they required a good process model and accurate on-line measurements of manipulated variables and load variables. The feedback function was necessary to compensate the over- or under-corrections of the feedforward controllers and to handle other disturbances which were not considered in the feedforward model.     

Residence time distribution of a pharmaceutical grade polymer melt in a single screw extrusion process

The residence time distribution (RTD) of a flowing polymer through a single screw extruder was studied. This extruder allows injecting supercritical carbon dioxide (scCO₂) used as physical foaming agent. The tested material is Eudragit E100, a pharmaceutical polymer. RTD was measured at various operating conditions and a model describing RTD has been developed. High screw speed or high temperature implies short residence time, but these parameters do not have the same effect on polymer flow. In the flow rate range studied, scCO₂ has no significant influence. A mathematical model consisting of a plug flow reactor in series with a continuous stirred tank reactor (CSTR) cross-flowing with a dead volume fitted well the experimental data.     

利用往复扰动螺棱强化单螺杆挤出机内混合模拟表征

提出了采用副螺棱轴向往复运动提高单螺杆挤出机混合的结构并建立了相应的数学模型。对挤出机内牛顿流体三维周期性流动和混合过程进行了数值模拟。采用有限体积方法,变量分布采用交错网格,副螺棱的周期性运动边界通过叠加网格方式实现。采用4阶Runge-Kutta方法实现流体追踪计算,得到了示踪剂界面增长及累积停留时间分布。采用Poincaré 截面揭示混沌混合存在的区域,证实了副螺棱往复运动能够产生混沌混合效应提高螺槽内的混合效果,与其位置固定时相比,缩短了平均停留时间,停留时间分布变窄。作为对比,同时分析了常规的副螺棱位置固定的单螺杆挤出机内的相应混合行为。     

Chaotic mixing in a single‐screw extruder with a moving internal baffle

A geometry in which the mixing of a single‐screw extruder was enhanced by a reciprocating baffle is proposed in this article. The effect of the baffle's amplitude on the mixing kinematics of the screw channel was investigated. A model with the baffle lower than the screw channel and the corresponding mathematical model were developed. The periodic flow and mixing performance of Newtonian fluid in such an extruder were numerically simulated. The finite volume method was used, and the flow domain was meshed by staggered grids with the periodic boundary conditions of the barrier motion being imposed by the mesh supposition technique. Fluid particle tracking was performed by a fourth‐order Runge–Kutta scheme. Distributive mixing was visualized by the evolution of passive tracers initially located at different positions. The growth of the interface stretch of tracers with time and the cumulative residence time distribution were also obtained. Poincaré sections were applied to reveal the geometrical scale of chaotic mixing patterns and the regions with embedded regular laminar flows. For comparison, the mixing performance in a conventional single extruder with fixed baffle was also investigated. POLYM. ENG. SCI., 54:198–207, 2014. © 2013 Society of Plastics Engineers     

Grafting of unsaturated acids and silanes to ethylene polymers: A kinetic model

A general kinetic model was developed to simulate the grafting of monomers such as unsaturated carboxylic acids and silanes to ethylene polymers. The polymers considered were ethylene-co-vinyl acetate (EVA), ethylene-co-butyl acrylate (EBA), and low-density polyethylene (LDPE). Grafting was assumed to proceed by a free-radical mechanism involving chain transfer. Organic peroxides having a strong tendency for hydrogen abstraction were selected as the source of primary radicals. The model simulated the grafting reaction as taking place in a single screw extruder. The residence time distribution in the extruder was experimentally determined by tracer analysis, according to which the extruder was a plug-flow reactor connected to two mixed reactors in parallel. The model is able to predict the extent of grafting in terms of predefined parameters. Comparison of model predictions with available experimental data showed slight deviations, the possible causes of which are discussed. However, the kinetic behavior expected on the basis of the input parameters was observed, and, as such, the model allowed study of the effect of process variables on grafting kinetics and provided insight into the reaction mechanism.     

Residence time in a single screw free helix extruder using a new solution to the biharmonic equation

A new analytical solution for the biharmonic equation was developed for single screw extrusion cross-channel fluid mechanical flow. This analysis led to a quantitative model for residence time distribution when combined with the historic solutions of the drag and pressure flow in the rectangular channel in the single-screw extruder. The focus of the theoretical and experimental investigation here was to examine how closely the new analytical solution correlated with experimental residence time data for a free-helix extruder. This new extrusion device was operated as both a conventional extruder and a more positive displacement device by using only helix rotation as the pump. The Moffatt eddies that occur in the quiescent corners of the rectangular channel with screw rotation were found to have a strong effect on the residence time of the extruder. Because there were no quiescent corners for the free-helix flow there was essentially no residence time tail for this mode of extruder displacement. The theoretical results for a sheet of dye spanning the screw channel width and dye “blobs” were compared with experimental results for both modes of operation. In all cases, the experiments and the theory predictions were essentially consistent.     

Isothermal transient startup of a starved flow modular co‐rotating twin screw extruder

A model for flow start‐up of a Newtonian liquid in an initially empty modular selfwiping co‐rotating twin screw extruder is developed. The changes of length of fill in front of the die and kneading disc block elements and output flow rate with time were predicted for various modular screw configurations. Experiments were also carried out on a laboratory modular machine with windows to verify predictions. Generally, good agreement with the flow analysis was found.     

Superposed hydrodynamic disturbances from feeders in a starved flow modular intermeshing co‐rotating twin screw extruder

A process dynamic model of surging in a modular self‐wiping co‐rotating twin screw extruder caused by superposed disturbances from feeders is developed. The changes of output flow rate with time (surging) are predicted for various time dependent input modes such as step function and sinusoidal function inputs into the hopper and other ports part way along the length of the machine.     

Melting performance of single screw extruders with a grooved melting zone

A novel melting model for single screw extruders with a grooved melting zone was established. The whole solid plug, which came from the grooved feed zone, was ruptured and melted mainly by continuously changing the volume of the barrel grooves and the screw channel in the grooved melting zone. A new single screw extruder platform with hydraulic clamshell barrels was constructed to investigate the melting of solid polymer with different combinations of barrels and screws. The melting model was verified by experiments. The results showed that the melting started earlier and finished in a shorter length for single screw extruders with a grooved melting zone than that for conventional single screw extruders and the melting efficiency was improved by introducing a grooved melting zone to a single screw extruder. The theoretical values are consistent with experimental results. The novel single screw extruder with grooved melting zone can dramatically increase the plasticizing efficiency and the throughput.