發(fā)布時間：2018-05-19 11:20

  本文選題：聚氯乙烯 + 聚合溫度��； 參考：《北京化工大學》2016年碩士論文

【摘要】：聚氯乙烯(polyvinyl chloride, PVC)在各個行業(yè)都被廣泛的應用,在國民經(jīng)濟中發(fā)揮著重要的作用,而決定PVC產(chǎn)品質(zhì)量的關鍵因素之一就是聚合裝置的反應溫度。PVC聚合反應屬于間歇的放熱反應,呈現(xiàn)出較強的非線性和大時滯特性,而PVC的生產(chǎn)對溫度有著非常嚴格的控制要求。目前,PVC生產(chǎn)過程中的聚合反應溫度通常采用PID控制,但傳統(tǒng)的PID控制器無法達到理想的控制效果,容易造成反應溫度的調(diào)節(jié)時間長,超調(diào)大,波動幅度大等問題,嚴重影響著產(chǎn)品的質(zhì)量。針對實際工業(yè)過程,本文研究了大型聚氯乙烯反應溫度的新型控制方法,主要工作如下：(1)根據(jù)聚氯乙烯生產(chǎn)工藝過程,基于聚合反應機理,分析了聚合反應各個階段的工藝過程及影響反應溫度控制的因素,并總結(jié)了整個反應溫度被控對象的控制難點。從聚合反應的動力學方程和能量物料平衡方程出發(fā),推導出反應溫度和其夾套水溫的函數(shù)關系方程式。通過最小二乘法辨識出系統(tǒng)的傳遞函數(shù),轉(zhuǎn)化為狀態(tài)空間形式,并且對辨識出的模型進行在線修正和離線驗證,證實模型的準確性和有效性,為控制器的設計奠定基礎。(2)根據(jù)聚合裝置反應溫度的不同動態(tài)特性,針對升溫段和恒溫段分別設計了最小協(xié)方差約束控制器(Minimum Variance Covariance Constrained Control, MVC3)。在預先給定被控對象的輸入方差和輸出方差的基礎上,對被控對象的綜合性能指標進行最小化,利用線性矩陣不等式進行求解出最優(yōu)的反饋控制律。然后采用單增限界的控制器切換算法對這兩個階段的控制器進行無擾切換,并運用到實際工業(yè)過程中,應用結(jié)果證實了所研究方法的可行性和有效性。(3)針對聚合反應釜存在較大的外界干擾,研究了采用線性變參數(shù)模型(Linear parameter varying, LPV)進行建模和控制。所研究方法是以外界的變量作為調(diào)度變量,描述被控對象在沿著調(diào)度參數(shù)變化的全部軌跡對應的全局動態(tài)特性。通過線性分式變換的方法設計控制器,這樣就能夠把系統(tǒng)的不確定單獨剝離出來進行考慮,用線性矩陣不等式求解控制器。這樣設計出的控制器在調(diào)度參數(shù)的變化軌跡內(nèi)都能夠很好的滿足當前的控制要求。(4)針對實際工業(yè)中難以一一直接判定控制器性能優(yōu)劣的實際情況,利用被控閉環(huán)系統(tǒng)的靈敏度函數(shù)和互補靈敏度函數(shù)判定原理,用C#語言開發(fā)了控制系統(tǒng)性能評價和參數(shù)優(yōu)化軟件,并給出了該軟件的使用方法。
[Abstract]:Polyvinyl chloride (PVC) is widely used in various industries and plays an important role in the national economy. One of the key factors determining the quality of PVC products is that the reaction temperature of the polymerization plant belongs to the intermittent exothermic reaction. PVC has strong nonlinear and large time delay characteristics, and the production of PVC has very strict temperature control requirements. At present, the polymerization reaction temperature of PID is usually controlled by PID, but the traditional PID controller can not achieve the ideal control effect, which can easily lead to the problems of long adjusting time, overshoot and large fluctuation of reaction temperature. The quality of the product is seriously affected. According to the actual industrial process, a new control method of reaction temperature of large PVC is studied in this paper. The main work is as follows: (1) according to the production process of PVC, based on the polymerization mechanism, The process of polymerization and the factors influencing the reaction temperature were analyzed, and the difficulties of controlling the reaction temperature were summarized. Based on the kinetic equation of polymerization and the equation of energy and material balance, the functional equation of reaction temperature and jacket water temperature is derived. The transfer function of the system is identified by the least square method, which is transformed into the form of state space, and the model is corrected on line and verified off-line, which proves the accuracy and validity of the model. According to the different dynamic characteristics of the reaction temperature of the polymerization device, the minimum covariance constrained controller is designed for the heating stage and the constant temperature stage, respectively. On the basis of the input variance and output variance of the controlled plant given in advance, the comprehensive performance index of the plant is minimized, and the optimal feedback control law is obtained by using linear matrix inequality (LMI). Then the controller switching algorithm with single increasing limit is used to switch the controller in these two stages without disturbance, and it is applied to the actual industrial process. The application results show the feasibility and effectiveness of the proposed method. Aiming at the large external interference in the polymerization reactor, the linear variable parameter model linear parameter varying, LPV) is used to model and control the polymerization reactor. The method is to use external variables as scheduling variables to describe the global dynamic characteristics of the controlled object along the whole trajectory of the scheduling parameters. The controller is designed by the method of linear fractional transformation, so that the uncertainty of the system can be taken into account separately, and the controller can be solved by linear matrix inequality (LMI). The controller designed in this way can meet the current control requirements very well within the changing trajectory of scheduling parameters) in view of the actual situation that it is difficult to directly judge the performance of the controller one by one in the actual industry. Based on the principle of sensitivity function and complementary sensitivity function of the controlled closed-loop system, the performance evaluation and parameter optimization software of the control system is developed with C # language, and the application method of the software is given.
【學位授予單位】：北京化工大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TQ325.3;TP273

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本文編號：1909901