【正文】 閥的選型主要包括閥的口徑選擇、形式選擇、閥的固有流量特性的選擇以及閥門的材質(zhì)選擇。兩個觸發(fā)器是將前置級的輸出不同極性的電壓變成觸發(fā)脈沖，分別觸發(fā) SCR1 和 SCR2。顯然，它是一個由圓盤、阻尼器和彈簧構(gòu)成的單自由度機械系統(tǒng)，其中敏感元件、轉(zhuǎn)軸和電磁鐵都有轉(zhuǎn) 動慣量；兩軸之間起密封連接作用的橡膠圈將產(chǎn)生彈簧的作用；支持測量軸運動的滾動軸承有阻尼器作用，敏感元件與多相流介質(zhì)之間的相對運動將產(chǎn)生很強的阻尼作用。 6 第 3章 系統(tǒng)硬件選擇與設計 濃度變送器的原理 力學法濃度測量原理 內(nèi)旋式濃度變送器是基于力學法濃 度測量原理而制造出來的變送器。對得到的偏差按 PID 算法進行計算，以此調(diào)節(jié)白水入口電動閥的開度，從而實現(xiàn)對紙漿濃度的調(diào)節(jié)。 增強外部故障的檢測與處理能力。造紙生產(chǎn)工藝一般包括三個工序：備料、制漿和抄紙，其中在制漿和抄紙過程中都需要用水稀釋原漿。 目前， PLC 在國內(nèi)外已廣泛應用于鋼鐵，石油，化工，電 力，建材，機械制造，汽車，輕紡，交通運輸，環(huán)保及文化娛樂等各個行業(yè)。 關(guān)鍵詞： PLC 紙漿濃度 PID 算法 II The Design of Pulp Consistency Control System Based On The S7200 PLC Abstract In the process of paper production,the pulp consistency is one of the most important physical qualities, To ajust the pulp consistency stably plays an important role in achieving the process goals and meeting the quality it can help the Enterprise to improve the economy efficiency by saving production I designed a pulp consistency control system based on S7200 PLC， the system automatically detects the pulp consistency，biase and pare with set point, and after a certain control algorithm， the output signal can control the opening of the electric valve over the water inlet,which regulates water diluted into slurry pump, and the pulp consistency in the slurry pipe changes, finally we get a stable pulp consistency. This design uses the screw type pulp consistency transducer to measure actual pulpconsistency,the consistency signal is converted into standard 420 ma signal,and then A\D conversion convert the analog signal into digital signal and feedback to the controller， and after paring with the giver value,we get the the deviation by PID algorithm， then use the result to adjust the opening of the electric valve of the water inlet,so as to realize the adjustment of the pulp consistency. use the configuration software MCGS to design manmachine interface ,so as to realize the realtime monitoring of the control this design we chose the Simens S7200,224 XP CN as the controller,and because the 224 XP CN has two analog input and one analog output interface,it can meet the requiment,so we don’t have to use analog extended module. At present,at home and abroad the PLC has been widely used in steel,petroleum,chemical industry,electric power,building materials,machinery manufacturing,automobile,light textile,transportation,environment protection and cultural entertainment,and other usege can be roughly summarized as the following categories:1,the switch quantity logic control 2,analog control 3,motion control 4,process control processing 6,’s main advantages are : high reliability,strong antijamming ,lete,fully functional,high applicability,easy to learn and easy to use,weled by engineering and technical ,small amount of work of system design and construction,maintenance is convenient,easy to transform. 5,small size,light weight,low energy consuption. KEY WORDS: PLC PULP CONSISTENCY PID ALGORITHM III 目 錄 引 言 .........................................................................................................................................1 第 1 章 緒論 ...........................................................................................................................2 論文研究背景 .....................................................................................................................2 研究背景 .................................................................................................................2 紙漿濃度變送器的發(fā)展趨勢 .................................................................................2 PLC 的發(fā)展趨勢 ......................................................................................................2 控制算法的發(fā)展趨勢 .............................................................................................2 本文研究主要內(nèi)容 ............................................................................................................3 研究意義 ............................................................................................................................3 設計思路 ............................................................................................................................3 研究工作與成果 ................................................................................................................3 第 2 章 總體技術(shù)方案 ...........................................................................................................4 紙漿濃度工藝描述及系 統(tǒng)結(jié)構(gòu)圖 ....................................................................................4 系統(tǒng)各組成模塊及控制方框圖 ........................................................................................4 方案的確定 ........................................................................................................................5 第 3 章 系統(tǒng)硬件設計 ...........................................................................................................6 濃度變送器的原理 ............................................................................................................6 力學法濃度測量原理 ...............................................................................................6 內(nèi)旋式濃度變送器的原理 .......................................................................................6 內(nèi)旋式變送器的數(shù)學模型 .......................................................................................7 執(zhí)行器的原理 ....................................................................................................................8 電動執(zhí)行器的基本原理 ...........................................................................................