【正文】 stem design. In the design, I am control the algorithm which the author primary cognizance the design, therefore designs in the paper with to the PID algorithm mentions many. Programmable Logic Controller， PLC,it uses a programmable memory, for its internal storage procedures, the implementation of logical, sequential control, timing, counting and arithmetic operations such as useroriented instructions, and through digital or analog input / output control various types of machinery or production process. Programmable logic controller is a dedicated to the industrial control puter, and its hardware structure is basically the same with the micro puter, basic ponents: power supply, a central processing unit ( CPU ), memory, input and output interface circuit, function module, munication module. Aiming at the problem of capacious— lags in double— tanks， it was hard for the traditional PID control to the high stable constant requirements and cascade controlling could solve them. A new system based on cascade control of previous difference and PLC was investigated in industrial double— tanks. And this liquid— level control system used the previous difference algorithm of cascade controller， PLC and MCCS was designed according to the mathematical model of double tank. The this article main content includes: water tank characteristic determination and experimental curve analysis， the S7300 programmable controller hardware grasps， PID parameter installation and each parameter control performance parison ，experimental curve analysis obtains which using the PID control algorithm and overall system each part of introduction and programs using the PLC sentence controls the water tank water level. Key words: SIMATIC S7300 PLC, the controlled member characteristic, the PID control algorithm, the expansion critical ratio method, the pressure change delivering, the electrically operated regulating valve. III 目 錄 摘 要 ................................................................................................... I ABSTRACT .............................................................................................. II 1 緒論 ....................................................................................................... 1 PLC 的產(chǎn)生、定義及現(xiàn)狀 ..................................................................................... 1 過(guò)程工業(yè)控制算法的應(yīng)用現(xiàn)狀 ............................................................................ 1 PID 控制的歷史和發(fā)展現(xiàn)狀 .................................................................................. 2 論文的研究?jī)?nèi)容 .................................................................................................... 2 2 S7300 中小型 PLC 和控制對(duì)象介紹 .................................................... 3 西門子 PLC 控制系統(tǒng) ........................................................................................... 3 CPU模塊 .......................................................................................................... 3 模擬量輸入模塊 .............................................. 4 模擬量輸出模塊 .............................................. 5 電源模塊 .................................................... 6 控制對(duì)象特性 ........................................................................................................ 7 一階單容上水箱特性 .................................................................................... 7 二階雙容下水箱對(duì)象特性 .......................................................................... 10 3 PID 控制算法介紹 ................................................................................ 14 PID 控制算法 ........................................................................................................ 14 PID 調(diào)節(jié)的各個(gè)環(huán)節(jié)及其調(diào)節(jié)過(guò)程 .................................................................... 16 比例控制與其調(diào)節(jié)過(guò)程 .............................................................................. 16 比例積分調(diào)節(jié) .............................................................................................. 17 比例積分微分調(diào)節(jié) ...................................................................................... 17 串級(jí)控制 .............................................................................................................. 17 擴(kuò)充臨界比例法 .................................................................................................. 19 在 PLC 中的 PID 控制的編程 ............................................................................. 20 回路的輸入輸出變量的轉(zhuǎn)換和標(biāo)準(zhǔn)化 ...................................................... 21 IV 變量的范圍 .................................................................................................. 22 控制方式與出錯(cuò)處理 .................................................................................. 22 4 控制方案設(shè)計(jì) ...................................................................................... 24 系統(tǒng)設(shè)計(jì) ............................................................................................................. 24 上水箱液位的自動(dòng)調(diào)節(jié) .............................................................................. 24 上水箱下水箱液位串級(jí)控制系統(tǒng) ............................................................... 24 硬件設(shè)計(jì) .............................................................................................................. 25 檢測(cè)單元 ...................................................................................................... 25 執(zhí)行單元 ...................................................................................................... 26 控制單元 ...................................................................................................... 27 軟件設(shè)計(jì) .............................................................................................................. 27 5 實(shí)驗(yàn)情況介紹 .................................................................................... 30 上水箱液位比例調(diào)節(jié) ............................