【正文】 能儀表及PLC等組成的工業(yè)控制系統(tǒng)[J].電力自動(dòng)化設(shè)備,:7376[14] 白冰,襲冰. GPRS技術(shù)在熱網(wǎng)監(jiān)控系統(tǒng)中的應(yīng)用[J]. 計(jì)算機(jī)與信息技術(shù), 2007,(12)：911[15] Wei Zhang, Michael S Branicky and Stephen M of network control systems [J].IEEE Control Systems Magazine,2001[16] Lu Weizhong, Wang Yihuai, Xi Xuefeng, Zhang on powerline munication and design of PLC modem[C].ICISE2010. 2010:6823 6826附錄主程序：熱網(wǎng)出水口溫度：流量處理：熱網(wǎng)壓力：補(bǔ)水箱液位：手動(dòng)溫度調(diào)節(jié)：手動(dòng)壓力調(diào)節(jié)：外文資料Introductions to temperature control and PID controllersProcess control systemAutomatic process control is concerned with maintaining process variables temperatures pressures flows positions, and the like at some desired operation value. Processes are dynamic in nature. Changes are always occurring, and if actions are not taken, the important process variablesthose related to safety, product quality, and production rateswill not achieve design conditions.In order to fix ideas, let us consider a heat exchanger in which a process stream is heated by condensing steam. The energy gained by the process fluid is equal to the heat released by the steam, provided there are no heat losses to surroundings, that is, the heat exchanger and piping are well insulated.In this process there are many variables that can change, causing the outlet temperature to deviate from its desired value. If this happens, some action must be taken to correct for this deviation. That is, the objective is to control the outlet process temperature to maintain its desired value. One way to acplish this objective is by first measuring the temperature T(t), then paring it to its desired value, and, based on this parison, deciding what to do to correct for any deviation. The flow of steam can be used to correct for the deviation. This is, if the temperature is above its desired value, then the steam valve can be throttled back to cut the steam (energy) to the heat exchanger. If the temperature is below its desire value, the steam valve could be opened some more to increase the steam flow (energy) to the exchanger. All of these can be done manually by the operator, and since the procedure is fairly straightforward, it should present no problem. However, since in most process plants there are hundreds of variables that must be maintained at some desired value, this correction procedure would like to acplish this control automatically. That is, we want to have equipment control variables with on requiring intervention from the operator. (This is what we mean by automatic process control.)To acplish this objective a control system must be designed and implemented. A possible control system and its basic ponents are shown in .The importance of these ponents is that they perform the three basic operations that must be present in every control system. These operations are(1) Measurement (M): Measuring the variable to be controlled is usually done by the bination of sensor and transmitter.(2) Decision (D): Based on the measurement, the controller must then decide what to do to maintain the variable at its desired value.(3) Action (A): As a result of the controller’s decision, the system must then take an action. This is usually acplished by the final control element.As mentioned, these three operations, M, D, and A, must be present in every control system.PID controllers can be standalone controllers (also called single loop controllers), controllers in PLC, embedded controllers, or software in Visual Basic or C puter programs.PID controllers are process controllers with the following characteristics:Continuous process controlAnalogue input (also known as “measurement” or “Process Variable” or “PV”)Analogue output (referred to simply as “output”)Set point (SP)Proportional (P), Integral (I), and/or Derivative (D) constantsExamples of “continuous process control” are temperature, pressure, flow, and level control. For example, we control the heating of a tank. For simple control, you have two temperature limit sensors (one low and one high) and then switch the heater on when the low temperature limits sensor turns on and then mm the heater off when the temperature rises to the high temperature limit sensor. This is similar to most home air conditioning amp。如果系統(tǒng)的給定值發(fā)生變化，系統(tǒng)不能對(duì)其作出迅速的反映。壓力報(bào)警也是在實(shí)驗(yàn)臺(tái)面板上有指示燈來(lái)顯示報(bào)警信號(hào)，在壓力過(guò)高時(shí)通過(guò)PLC發(fā)出報(bào)警信號(hào)使指示燈變亮，同時(shí)組態(tài)界面上的壓力報(bào)警指示燈變綠表示壓力過(guò)高產(chǎn)生報(bào)警。根據(jù)EM235的使用手冊(cè)選擇好輸入量程和單雙極性，設(shè)置好后就可以按照使用說(shuō)明進(jìn)行連線了，對(duì)于模塊上的驅(qū)動(dòng)正好用的是024V的電壓信號(hào)，可以用PLC模塊的電壓源直接引出就可以使用，把AIW0連到上，輸出AQW0連到05V的反饋端。圖63 實(shí)時(shí)數(shù)據(jù)庫(kù)運(yùn)行策略：通過(guò)建立運(yùn)行策略可以完成對(duì)系統(tǒng)的模擬運(yùn)行的本窗口。并能同時(shí)支持各種硬件廠家的計(jì)算機(jī)和I/O產(chǎn)品[11]。要把溫度傳感器pt100隨著溫度變化采集來(lái)的電阻轉(zhuǎn)換成相應(yīng)的溫度值，利用下面的溫度公式可以求得：T℃=(溫度數(shù)字量0℃的偏置量)/1℃數(shù)字量溫度數(shù)字量為存儲(chǔ)在PLC內(nèi)部存儲(chǔ)單元的值0℃偏置量為在0℃測(cè)出的數(shù)字量1℃的數(shù)字量為溫度每升高1℃的數(shù)字量[9]（2）壓力傳感器PTJ205PTJ205具有不銹鋼封焊的結(jié)構(gòu)，有很強(qiáng)的抗干擾能力。在PLC中，CPU 224XP數(shù)字量有14入/10出，最大可擴(kuò)展的數(shù)字量點(diǎn)數(shù)為168，模擬量點(diǎn)數(shù)為35，還有兩路模擬量輸入(10bit，177。保證系統(tǒng)既可以應(yīng)用PID進(jìn)行自動(dòng)調(diào)節(jié)，也可以通過(guò)直接控制變頻器的頻率信號(hào)來(lái)調(diào)節(jié)補(bǔ)水泵的轉(zhuǎn)速。在小區(qū)供暖系統(tǒng)中不僅要保證換熱站出水口的溫度保持在一定的范圍內(nèi)，二次管網(wǎng)的水要往居民小區(qū)輸送這就要求必須保證二次管網(wǎng)的壓力保持恒定。GPRSPLCD/A轉(zhuǎn)換調(diào)節(jié)閥溫度傳感器變送器A/D轉(zhuǎn)換圖43 自動(dòng)控制的流程圖在自動(dòng)運(yùn)行控制方式下，主要是通過(guò)PID控制器來(lái)對(duì)系統(tǒng)的溫度值進(jìn)行控制。在實(shí)際現(xiàn)場(chǎng)的應(yīng)用中換熱器出水口的溫度會(huì)因?yàn)楦鞣N原因出現(xiàn)上下波動(dòng)，而控制換熱器出口溫度主要是靠調(diào)節(jié)在一次供水管安裝的溫度調(diào)節(jié)閥的開度大小。當(dāng)需要較好的控制精度時(shí)可以選擇用PI控制方式，但是如果系統(tǒng)的慣性很大時(shí)就應(yīng)該選擇PID控制方式了。在將上面的設(shè)置完成之后就可以試著登陸網(wǎng)絡(luò)，雙擊剛才新建的撥號(hào)連接，填寫上用戶名和密碼，并進(jìn)行撥號(hào)，PPP服務(wù)器會(huì)自動(dòng)的檢測(cè)用戶名和密碼，進(jìn)行檢測(cè)后就可以對(duì)用戶的計(jì)算機(jī)進(jìn)行注冊(cè)。C H7710的DTU參數(shù)設(shè)置在主菜單(main menu)狀態(tài)下鍵入c進(jìn)入DTU參數(shù)配置，如果沒(méi)有刪除配置的密碼，就要輸入密碼進(jìn)入，宏電H711x 系列的GPRS無(wú)線DDN數(shù)據(jù)終端設(shè)備出廠的初始密碼都為：1234，輸入了正確的密碼后就可以進(jìn)入?yún)?shù)設(shè)置界面[5]。 GPRS要解決的主要問(wèn)題GPRS是一種新的技術(shù)，中國(guó)移動(dòng)通訊有限公司作為運(yùn)營(yíng)商為它提供了滿足行業(yè)應(yīng)用的數(shù)據(jù)傳輸網(wǎng)絡(luò)平臺(tái)，但要實(shí)施GPRS數(shù)據(jù)采集與管網(wǎng)數(shù)據(jù)監(jiān)控系統(tǒng)還需要解決以下主要技術(shù)問(wèn)題：（1）數(shù)據(jù)中心接入方式的選擇采用GPRS網(wǎng)絡(luò)，數(shù)據(jù)中心有公網(wǎng)接入方式和專網(wǎng)接入方式。無(wú)線電波還具有一定的局限性，抗干擾的能力也比較差。換熱站的高溫管道中的熱水與居民暖氣片中的冷水通過(guò)換熱器進(jìn)行交換熱量再將交換后的熱水送入各居室內(nèi)作為供暖用。在組態(tài)界面上主要顯示各小區(qū)換熱站的網(wǎng)管溫度、壓力、流量等參數(shù)并對(duì)其進(jìn)行控制，保證其安全可靠的運(yùn)行。（3）報(bào)警保護(hù)部分補(bǔ)水箱處于低液位或高液位換熱站出水口的溫度超過(guò)設(shè)定值5℃時(shí)產(chǎn)生報(bào)警本設(shè)計(jì)主要是要把分步在六個(gè)換熱站的管網(wǎng)溫度和壓力等參數(shù)上傳到監(jiān)控中心的上位機(jī)上，以便工作人員可以通過(guò)上位機(jī)直觀的看到各個(gè)換熱站設(shè)備的運(yùn)行情況并對(duì)其進(jìn)行參數(shù)設(shè)置，來(lái)保證系統(tǒng)的穩(wěn)定運(yùn)行。DTU是數(shù)據(jù)接收和發(fā)送模塊，在網(wǎng)絡(luò)中主要完成S7200 PLC與監(jiān)控中心的數(shù)據(jù)傳輸任務(wù)，同時(shí)也是與移動(dòng)GPRS網(wǎng)絡(luò)的工作接口。 深圳市宏電技術(shù)開發(fā)有限公司開發(fā)的H7000無(wú)線DDN系統(tǒng)為用戶提