TRACKING PERFORMANCE OF CONTROL METHODS

In this work, the optimal temperature control of a styrene solution polymerization reactor with two different control algorithms is considered. DMC and PFD control mefhods are used to accomplish the optimal temperature control of the polystyrene reactor. Reactor optimal temperature profiles at different initiator initiation concentrations were obtained by applying maximum principle to the mathematical model of the free radical batch polymerization reactor lo produce polystyrene with desired conversion and molecular weight in a minimum lime. The results obtained from the experimental implementation of DMC and PID controller for the control of optimal temperature path of the polymerization reactor were compared.     

CONTROL OF MOLECULAR WEIGHT IN A BATCH POLYMERIZATION REACTOR USING LONG-RANGE PREDICTIVE CONTROL METHODS

Recently two powerful control algorithms, namely, dynamic matrix control (DMC) and extended self-tuning regulator (ESTR), have been advocated for the design of robust industrial controllers. The present paper demonstrates the application of DMC and ESTR algorithms to a bulk methyl methacrylate batch polymerization reactor operating under strong diffusional limitations of termination and propagation reactions. A realistic mathematical model is employed to simulate the strong nonlinear, time-varying dynamics of the polymerization process. The general control objective is to maintain the monomer conversion and number-average molecular weight along some desired state trajectories despite the presence of process disturbances in the total initiator concentration. It is shown that both controllers can satisfactorily control the monomer conversion and number-average molecular weight by manipulating the polymerization temperature. The similarities and the main operating features of the two controllers are examined and their closed-loop performance is directly compared to the performance of a conventional linear quadratic controller (LQC). Finally the effects of DMC and ESTR tuning parameters on the calculated control action are investigated.     

QUADRATIC PROGRAMMING SOLUTION OF DYNAMIC MATRIX CONTROL (QDMC)

QDMC is an improved version of Shell's Dynamic Matrix Control (DMC) multivariable algorithm which provides a direct and efficient method for handling process constraints. The algorithm utilizes a quadratic program to compute moves on process manipulated variables which keep controlled variables close to their targets while preventing violations of process constraints. Several on-line applications have demonstrated its excellent constraint handling properties, transparent tuning and robustness, while requiring minimal on-line computational load.     

ADAPTIVE POLE-PLACEMENT CONTROL OF A CONTINUOUS POLYMERIZATION REACTOR

A simulation of the polymerization of methylmethacrylate in a CSTR is adaptively controlled by two types of pole-placement algorithms. The strongly nonlinear polymerization process, exhibiting multiple steady states, presents difficult control problems for conventional feedback controllers. The performance of an adaptive explicit SISO controller and that of an adaptive implicit multivariable controller are compared and evaluated as applied to this process. The plant is identified by a recursive least squares estimator. Modifications made to the estimation algorithm help to maintain adequate closed-loop results. A simple warm-up procedure is introduced that successfully initializes the controller and estimator during plant start-up. Good servo and regulatory control are achieved by both pole-placement schemes.     

APPLICATION OF ADAPTIVE PID CONTROL WITH GENETIC ALGORITHM TO A POLYMERIZATION REACTOR

This article describes the application of adaptive PID control with genetic algorithm (GA) to a jacketed batch polymerization reactor. This method was used to keep the polymerization reactor temperature at the desired optimal path, which was determined by the Hamiltonian maximum principle method. The reactor was simulated and the model equations of this jacketed polymerization reactor were solved by means of Runge-Kutta-Felthberg methods. A genetic algorithm can be a good solution for finding the optimum PID parameters because unlike other techniques it does not impose many limitations and it is simple. In this research, suitability of these parameters was checked by the integral absolute error (IAE) criterion. The control parameters in the PID algorithm were changed with time during the control of a polymerization reactor. It was seen that the genetic algorithm was able to tune the PID controller used in this system in terms of higher robustness and reliability by changing the parameters continuously.     

阻燃型工程塑料的漏电起痕控制

对阻燃型工程塑料的电性能,尤其是相比漏电起痕指数（CTI）进行了描述。针对不同的阻燃分别讨论了各种能提高复合材料CTI值的合适的阻燃协效剂。     

裂解炉过热蒸汽温度控制的影响因素和控制算法的探讨

主要阐述了裂解炉过热蒸汽温度控制的影响因素和控制方案，并对蒸汽温度约束条件的非线性化问题解决方案做了初步探讨。     

具有L2增益的陶瓷取坯机械手鲁棒跟踪控制

本文对具有不确定和干扰的二自由度电动陶瓷取坯机械手系统动态模型 ,采用李雅普诺夫函数递推设计方法设计了鲁棒跟踪控制器。所设计的控制器不仅保证跟踪误差系统的稳定性而且使得由力矩干扰到跟踪误差评价信号的L2 增益小于给定的值。同时本文也给出了不用解HJI不等式设计陶瓷取坯机械手H∞ 控制器方法 ,仿真结果表明所设计的控制器具有良好的跟踪性能和较强的鲁棒性     

CONTROL OF A CONTINUOUS POLYMERIZATION REACTOR BY WIENER INPUT/OUTPUT DATA-BASED PREDICTIVE CONTROLLER WITH DIRECT INVERSE IDENTIFICATION

This article reports an experimental study for the identification and predictive control of a continuous methyl methacrylate (MMA) solution polymerization reactor. The Wiener model was introduced to identify the polymerization reactor in a more efficient manner than the conventional methods of Wiener model identification. In particular, the method of subspace identification was employed and the inverse of the nonlinear part was directly identified. The input variables in this work were the jacket inlet temperature and the feed flow rate, while the monomer conversion and the weight average molecular weight were selected as the output variables. On the basis of the identified model a Wiener-type input/output data-based predictive controller was designed and applied to the property control of polymer product in the continuous MMA polymerization reactor by conducting an on-line digital control experiment with online densitometer and viscometer. Despite the complex and nonlinear characteristics of the polymerization reactor, the proposed controller was found to perform satisfactorily for property control in the multiple-input multiple-output system with input constraints for both set-point tracking and disturbance rejection. This was also confirmed by simulation results.     

CONTROL OF A CONTINUOUS POLYMERIZATION REACTOR BY WIENER INPUT/OUTPUT DATA-BASED PREDICTIVE CONTROLLER WITH DIRECT INVERSE IDENTIFICATION

This article reports an experimental study for the identification and predictive control of a continuous methyl methacrylate (MMA) solution polymerization reactor. The Wiener model was introduced to identify the polymerization reactor in a more efficient manner than the conventional methods of Wiener model identification. In particular, the method of subspace identification was employed and the inverse of the nonlinear part was directly identified. The input variables in this work were the jacket inlet temperature and the feed flow rate, while the monomer conversion and the weight average molecular weight were selected as the output variables. On the basis of the identified model a Wiener-type input/output data-based predictive controller was designed and applied to the property control of polymer product in the continuous MMA polymerization reactor by conducting an on-line digital control experiment with online densitometer and viscometer. Despite the complex and nonlinear characteristics of the polymerization reactor, the proposed controller was found to perform satisfactorily for property control in the multiple-input multiple-output system with input constraints for both set-point tracking and disturbance rejection. This was also confirmed by simulation results.     

动态膜分离式酶反应器连续操作特性研究

在应用动态膜分离技术开发研制的新型多功能酶解反应器上进行了边反应分离的连续操作过程。通过在该反应器上进行菊粉酶等单基质酶不同操作形式的水解实验,考察了不同操作方式下反应器内流体流动的特性,并分别导出了停留时间分布函数式,从而对连续酶解过程的不同运行方式进行了研究。     

HCR工艺处理生活污水的影响因素研究

采用高效生物反应器(HCR)处理生活污水,考察了水力停留时间、容积负荷、温度和溶解氧对其去除效果的影响。结果表明,水力停留时间为3 h,DO质量浓度为3.5～4 mg/L,温度小于34℃时,HCR处理生活污水有良好的效果。和传统的活性污泥法相比,HCR工艺具有水力停留时间短、氧传递效率高和负荷高等特点。     

ADAPTIVE CONTROL OF A BATCH REACTOR

A globally stable adaptive predictive control system (APCS) is evaluated by application to a simulated PVC batch reactor. The reactor is run under APCS control with the objective of either temperature setpoint tracking or constant reaction rate. The batch nature of this system makes it possible to learn about the physical problem from successive runs. This knowledge is incorporated into the control strategy to improve the performance of the reactor. The problem of excessive manipulation of the control variable has been recognized and resolved by using control weighting. Performance of the adaptive technique is compared with previous results using self-tuning and PID control of the same reactor. APCS provides good, robust control despite the nonlinear dynamics of the system.     

The bifurcation behavior of a polyurethane continuous stirred tank reactor

In this work the open-loop nonlinear bifurcation analysis of a continuous stirred tank reactor where polyurethane polymerization reactions take place is carried out. The effect of potential manipulated, disturbance and design variables on the reactor nonlinear behavior is addressed. Moreover, the impact of cascade feedback control on the steady-state multiplicity pattern is also discussed. It is shown that cascade control introduces new nonlinearity patterns increasing closed-loop sensitivity.     

Adaptive Linear Dynamic Matrix Control applied to an integrating process

Dynamic Matrix Control (DMC) has proven to be a powerful tool for optimal regulation of chemical processes under constrained conditions. It is based on a linear convolution model derived from step-response measurements. A model predictive control algorithm optimises closed-loop performance for a nominal operating point. However, as the process moves away from this point, control usually becomes sub-optimal due to process non-linearity. As seen in this work, the DMC algorithm can be made adaptive, to establish a new local model, by recursive estimation of the local step response parameters from normal plant variations. However, when used for control of plants containing integrating process units, steady-state offsets occur for sustained changes. Thus, a novel Adaptive Linear Dynamic Matrix Control (ALDMC) algorithm has been developed and used to control a 2-input/2-output system with an integrating behaviour. Comparisons of model control and plant control with and without these features demonstrated the importance of integral compensation for integrating processes, and model adaptation in the case of plant/model mismatch. Some cross-compensation of integration by the adaptive feature was also noted. An holistic technique is demonstrated which simultaneously recognises residual integration disturbances and matrix parameter variations, whereas previous techniques which recognise only one of these will fail in the presence of the other.     

乳液聚合新方法简介——递变进料和高聚物表面活性剂

本文简要地回顾了一些非经典的乳液聚合方法,重点介绍了两种较新颖的乳液聚合技术:递变进料乳液聚合和用高聚物表面活性剂的乳液聚合。     

隔板式环流反应器研究

研究了不同宽度的隔板式环流反应器中的气含率,循环比和体积传递系数。试验结果显示随着截面结构因素 s_d/s_t 的减小,气含率相应地减少。s_d/s_t 值对液体循环比影响较大,当 s_d/s_t 值减小时,液体循环速度明显增加。同时 s_d/s_t 值减小使总塔体积传质系数也趋於减小。试验数据关联得到总塔体积传递系数(k_La)_t 与气速 u_g 和截面结构因素 s_d/s_t 的关系为:若用单位体积中输入功率为参数代替气速 u_g,则上式可改写成为:本文还对隔板式环流反应器和环隙进气环流反应器的体积传递系数进行了比较。     

BULK POLYMERIZATION OF STYRENE IN A STATIC MIXER

An experimental investigation of thermal bulk polymerization of styrene in a pilot plant will be reported. The plant is composed of a recycle tubular reactor followed by a tubular reactor. The conversion of the pre-polymerization part is in the range of 0 to 60% and at the outlet of the pilot plant up to 96%. Studies on the residence time distribution show plug-flow behaviour for a variety of different conditions with respect to viscosity and density gradient. The polymers obtained are characterized by gel permeation chromatography and compared to commercial products.     

NUMERICAL SOLUTION OF UNSTEADY CONVECTIVE DIFFUSION WITH CHEMICAL REACTION IN TIME DEPENDENT FLOWS

An earlier computer model for tubular high pressure polyethylene reactors is extended to take into account two radical generating sources, in addition to an injected initiator: a long-lived intermediate, possibly generated from the interaction of ethylene with trace amounts of oxygen, and the ethylene itself undergoing thermal polymerization. The first of these reactions can account for the smoothing of the temperature profile near the peak temperature, attributed by Lee to initiator and radical carryover; the second, whose inclusion is justified by experiments recently performed by Buback, can account for the explosive decomposition of ethylene known to occur in LDPE reactors if the temperature is allowed to exceed about 350°C, and it also can contribute significantly to polymer production at very high temperatures. The contribution of both reactions must be evaluated quantitatively, if reliable heat transfer coefficients are to be obtained from experiment.