【正文】 ard E. Morley in 1968, have been widely used in industry including manufacturing systems, transportation systems, chemical process facilities, and many others. At that time, the PLC replaced the hardwired logic with softwired logic or socalled relay ladder logic (RLL), a programming language visually resembling the hardwired logic, and reduced thereby the configuration time from 6 months down to 6 days [Moody and Morley, 1999]. Although PC based control has started to e into place, PLC based control will remain the technique to which the majority of industrial applications will adhere due to its higher performance, lower price, and superior reliability in harsh environments. Moreover, according to a study on the PLC market of Frost and Sullivan [1995], an increase of the annual sales volume to 15 million PLCs per year with the hardware value of more than 8 billion US dollars has been predicted, though the prices of puting hardware is steadily dropping. The inventor of the PLC, Richard E Morley, fairly considers the PLC market as a 5billion industry at the present time. Though PLCs are widely used in industrial practice, the programming of PLC based control systems is still very much relying on trialanderror. Alike software engineering, PLC software design is facing the software dilemma or crisis in a similar way. Morley himself emphasized this aspect most forcefully by indicating [Moody and Morley, 1999, p. 110]:`If houses were built like software projects, a single woodpecker could destroy civilization.” Particularly, practical problems in PLC programming are to eliminate software bugs and to reduce the maintenance costs of old ladder logic programs. Though the hardware costs of PLCs are dropping continuously, reducing the scan time of the ladder logic is still an issue in industry so that lowcost PLCs can be used. In general, the productivity in generating PLC is far behind pared to other domains, for instance, VLSI design, where efficient puter aided design tools are in practice. Existent software engineering methodologies are not necessarily applicable to the PLC based software design because PLCprogramming requires a simultaneous consideration of hardware and software. The software design bees, thereby, more and more the major cost driver. In many industrial design projects, more than SO0/a of the manpower allocated for the control system design and installation is scheduled for testing and debugging PLC programs [Rockwell, 1999]. In addition, current PLC based control systems are not properly designed to support the growing demand for flexibility and reconfigurability of manufacturing systems. A further problem, impelling the need for a systematic design methodology, is the increasing software plexity in largescale projects. Objective and Significance of the Thesis The objective of this thesis is to develop a systematic software design methodology for PLC operated automation systems. The design methodology involves highlevel description based on state transition models that treat automation control systems as discrete event systems, a stepwise design proces。接著要連接組態(tài)，圖 62 說明了用于下載項目數(shù)據(jù)的組態(tài)計算機(jī)(PU 或 PC)與操作單元的連接。同時也可以讀取變頻器數(shù)據(jù)通過上位機(jī)進(jìn)行顯示，達(dá)到在線監(jiān)視和診斷的目的。詳細(xì)程序見附錄二?！?對應(yīng) k3001～k3012。從 DP 上讀取數(shù)據(jù)：OPN DB 5CALL DPRD_DATLADDR:=W16108 RET_VAL:=MW32RECORD:=P BYTE 8從 DP 上寫入數(shù)據(jù)：OPN DB 6CALL DPWR_DATLADDR:=W16108RECORD:=P BYTE 8RET_VAL:=MW30對于寫變頻器的數(shù)據(jù)是與變頻器的 k3001～k3016，建立對應(yīng)關(guān)系，讀變頻器的數(shù)據(jù)則是與變頻器的參數(shù) P734 建立對應(yīng)關(guān)系。接下來還可以存放諸如通訊的錯誤代碼和與變頻器有關(guān)的其它計算數(shù)據(jù)。2） 建立通訊 DB 塊一般地，讀寫數(shù)據(jù)都做在一個 DB 塊中，且最好與硬件組態(tài)設(shè)定的 I/O 地址范圍大小劃分相同大小的區(qū)域，便于建立對應(yīng)關(guān)系和管理。在PLC 和變頻器通訊方式配置時要對 PP0 進(jìn)行選擇。帶有 DP 口的 S7300/400 PLC 也可以通過 CPU 上的 DP 口來實現(xiàn)。打開編寫有主程序的塊OB1，然后選擇“調(diào)試” →“監(jiān)視”命令，程序即處于仿真模擬狀態(tài)，如圖57 所示圖 57 S7PLCSIM 仿真窗口 48）將圖 58 中單選框的 stop 模式打到 run 模式，如圖 58 所示 圖 58 S7PLCSIM 仿真窗口 59）根據(jù) I/O 點的分配和控制要求，仿真圖如圖 59 所示圖 59 S7PLCSIM 仿真窗口 6第六章 ProfibusDP 通信 ProfibusDP的變頻器的通訊 在 PROFIBUS 現(xiàn)場總線中，PROFIBUSDP 的應(yīng)用最為廣泛。如圖 56 所示圖 56 S7PLCSIM 仿真窗口 36）點擊 S7PLCSIM 工具條中標(biāo)有“I”的按鈕，或執(zhí)行菜單命令“Insert”“Input Variable”，創(chuàng)建輸入 IB 字節(jié)的試圖對象。圖 54 S7PLCSIM 仿真窗口 1在 S7PLCSIM 窗口中用菜單命令“Excuticve ” “Continuous scan”或點擊“Continuous scan”按鈕，令仿真 PLC 的掃描方式為連續(xù)掃描。點擊 STEP7 的 SIMATIC管理器工具條中的（SIMATIC on/off）按鈕，或執(zhí)行菜單命令“Options” ，打開S7PLCSIM 窗口如圖 54 所示，窗口自動出現(xiàn) CPU 試圖對象。單擊“下一個”確認(rèn)設(shè)置，進(jìn)入下一個向?qū)гO(shè)置畫面，在項目名稱欄中輸入名稱然后點“完成” ，完成一個新項目的創(chuàng)建。 圖 52 管理器向?qū)Вㄟx擇程序塊） 在圖 52 向?qū)е?，選擇組織塊 OB1，OB1 代表最高的變成層次，他負(fù)責(zé)組織 S7 程序中的其他塊，一個程序中必須要有 OB1。MPI 地址的默認(rèn)設(shè)置為 2。第五章 軟件調(diào)試在 STEP7 編程軟件中生成項目步驟：本設(shè)計軟件調(diào)試用 S7PLCSIM 調(diào)試，首先雙擊 windows 桌面上的“SIMATIC Manager”圖標(biāo)，打開 STEP7 管理界面，默認(rèn)自動向?qū)鐖D 51 所示。以下是監(jiān)控系統(tǒng)的程序梯形圖以上程序段 1～程序段 7 的總體功能：按下啟動按鈕后，系統(tǒng)開始對壓力采集，把采集到的壓力對應(yīng)的無量綱數(shù)據(jù)經(jīng)過 FC105 轉(zhuǎn)換后，可得到的實際壓力對應(yīng)的電壓值，把它與壓力上限對應(yīng)的電壓比較，當(dāng)大于上限時，并且工件完成一次壓制后，壓力報警燈亮。當(dāng)多監(jiān)控的壓力大于設(shè)定的溫度上限值時，監(jiān)控系統(tǒng)報警燈亮，同時軋鋼機(jī)完成一次壓制后停機(jī)。以下是監(jiān)控系統(tǒng)的程序梯形圖以上程序段 1～程序段 7 的總體功能：按下啟動按鈕后，系統(tǒng)開始對溫度采集，把采集到的溫度對應(yīng)的無量綱數(shù)據(jù)經(jīng)過 FC105 轉(zhuǎn)換后，可得到的實際溫度對應(yīng)的電壓值，把它與溫度上限對應(yīng)的電壓比較，當(dāng)大于上限時，并且工件完成一次壓制后，溫度報警燈亮。當(dāng)軋鋼機(jī)的溫度大于設(shè)定的溫度上限值時，監(jiān)控系統(tǒng)報警燈亮，同時軋鋼機(jī)完成一次壓制后停機(jī)。使用反向轉(zhuǎn)換時，輸出值將隨輸入值的增加而減小。如果輸入整型值小于 K1，輸出將鉗位于 LO_LIM，并返回一個錯誤。SCALE 功能使用以下等式：OUT = [ ((FLOAT (IN) K1)/(K21)) * (HI_LIMO_LIM)] + LO_LIM 常數(shù) K1 和 K2 根據(jù)輸入值是 BIPOLAR 還是 UNIPOLAR 設(shè)置。為 1 表示輸入值單極性O(shè)UT 輸出 REAL I、Q、M、D、L、P 轉(zhuǎn)換結(jié)果RET_VAL 輸出 WORD I、Q、M、D、L、P 如果指令的執(zhí)行沒有錯誤，返回值為W160000.FC105 功能SCALE 功能接受一個整型值(IN)，并將其轉(zhuǎn)換為以工程單位表示的介于、下限和上限(LO_LIM 和 HI_LIM)之間的實型值。LO_LIM 輸入 REAL I、Q、M、D、L、P 常數(shù) 以工程單位便是的下限值。以下是 FC105 參數(shù)表表 2 FC105 參數(shù)表參數(shù) 說明 數(shù)據(jù)類型 存儲區(qū) 描述EN 輸入 BOOL I、Q、M、D、L 使能輸入端，信號狀態(tài)為 1 時激活該功能ENO 輸入 BOOL I、Q、M、D、L 如果該功能的執(zhí)行無誤，輸出端信號為 1IN 輸入 INT I、Q、M、D、L 常數(shù) 欲轉(zhuǎn)換為工程單位表示的實型值。D/A 轉(zhuǎn)換器將 PLC 的數(shù)字輸出量轉(zhuǎn)換為模擬電壓或電流，再去控制執(zhí)行機(jī)構(gòu)，模擬量 I/O 模塊的主要任務(wù)就是實現(xiàn) A/D 轉(zhuǎn)換和 D/A 轉(zhuǎn)換。在本系統(tǒng)中監(jiān)控的參數(shù)輸入量是模擬量，如軋鋼機(jī)的溫度，潤滑系統(tǒng)和冷卻系統(tǒng)的壓力，必須將它們轉(zhuǎn)換為表轉(zhuǎn)量程的電流或電壓，例如 DC420mA,15V,010V,PLC 用 A/D 轉(zhuǎn)換器將它們轉(zhuǎn)換成數(shù)字量。系統(tǒng)演示等待加工完畢的工件退出，此時即可進(jìn)入下一個工件的加工。當(dāng)工件移動到限位開關(guān)