【正文】 PLC 的內(nèi)部電源是指將外部輸入的交流信號(hào)經(jīng)過(guò)整流、濾波、穩(wěn)壓等處理后轉(zhuǎn)換成滿足內(nèi)部電路工作需要的直流電源或電源模塊。 PLC 的生產(chǎn)廠家、種類(lèi)如此繁多，不同種類(lèi)之間的功能設(shè)置差異又非常大， 這在選擇 PLC 機(jī)型上帶來(lái)了一定的難度。 根據(jù) PLC I/O 節(jié)點(diǎn)使用原則，即預(yù)留出 25%左右的 I/O 點(diǎn)以做擴(kuò)展時(shí)使用，4 層電梯有 32 個(gè)輸入信號(hào)和 27 個(gè)輸出信號(hào)，本系統(tǒng)選用的 PLC 為三菱 FX2128MR，這種機(jī)型的 I/O 點(diǎn)數(shù)均為 64，但其編輯指令可超過(guò) 1000 條，有 2021 步的程序內(nèi)，并配有相應(yīng)的編程軟件 MEDOC。 控制直流電動(dòng)機(jī)所需的 I/O 點(diǎn)數(shù) 本設(shè)計(jì)針對(duì)電梯控制，因此我 們根據(jù)實(shí)際情況可知，要控制電梯的升和降， 需要一個(gè)可逆運(yùn)行的直流電機(jī)。 內(nèi)存估計(jì) 一般程序所需內(nèi)存容量主要和下面幾個(gè)因素相關(guān)：內(nèi)存利用率、開(kāi)關(guān)量輸入 輸出點(diǎn)數(shù)、模擬量輸入輸出點(diǎn)數(shù)、用戶的編程水平 。對(duì)于同一程序來(lái)說(shuō)，高利用率可以縮短掃描時(shí)間，提高系統(tǒng)的響應(yīng)速度，還可以降低內(nèi)存的使用量。 一般的經(jīng)驗(yàn)計(jì)算公式如下： 如果只有模擬量輸入時(shí)：內(nèi)存字?jǐn)?shù) =模擬量點(diǎn)數(shù) *100，即 400 如果模擬量輸入 /輸出共存時(shí)：內(nèi)存字?jǐn)?shù) =模擬量點(diǎn)數(shù) *200，即 800，大概所占 內(nèi)存 40KB，基于實(shí)際考慮，在本設(shè)計(jì)中不存在此情況。系統(tǒng)響應(yīng)時(shí)間 =掃描的周期 +輸入濾波的時(shí)間 +輸出濾波的時(shí)間。 輸入輸出模塊的選擇 PLC 輸入 模塊的主要作用是檢測(cè)設(shè)備的輸入信號(hào)，然后變成 plc 可以?xún)?nèi)部處理的電平信號(hào)。 PLC 輸出模塊的主要功能 是內(nèi)部輸出電平 ，外部負(fù)載設(shè) 備控制信號(hào)在輸出之前進(jìn)行轉(zhuǎn)換。我們選用交流 220V 作為電梯系統(tǒng)的曳引電機(jī)的工作電壓，選用交流 220V 作為轎箱門(mén)開(kāi)關(guān)控制電機(jī)的工作電壓，選用 24V 作為指示燈工作電壓 泰山學(xué)院本科畢業(yè)論文 17 確定 PLC 機(jī)型 由上述條件可知 ，三菱的 FX 系列是最佳選擇。 泰山學(xué)院本科畢業(yè)論文 18 4 軟件設(shè)計(jì) 程序流程圖 上電電 初始化 確認(rèn)本層與目標(biāo)層 目標(biāo)層為本層？ 電梯選向 電梯啟動(dòng) 高速運(yùn)行 樓層檢測(cè) 是否目標(biāo)層？ 電梯減速 平層檢測(cè) 電梯制動(dòng) 開(kāi)門(mén) 延時(shí) 電梯加速 關(guān)門(mén) 是否停止運(yùn)行 停止 等待 N Y N Y N 門(mén)廳呼叫？ 轎箱呼叫？ Y N Y Y N 圖 3 程序流程圖 泰山學(xué)院本科畢業(yè)論文 19 開(kāi)關(guān)門(mén)控制 開(kāi)門(mén)控制 本層開(kāi)門(mén)是指電梯在停車(chē)狀態(tài)和非檢修條件下，轎廂所在層樓有廳外召喚時(shí)，電梯自動(dòng)開(kāi)門(mén)。 圖 4開(kāi)門(mén)控制 開(kāi)門(mén)控制 正常情況下，開(kāi)門(mén)的條件 有以下幾種 :本層開(kāi)門(mén)、停車(chē)狀態(tài)按轎內(nèi)開(kāi)門(mén)按鈕、正常運(yùn)行換速平層停車(chē)自動(dòng)開(kāi)門(mén)。停止關(guān)門(mén)或不關(guān)門(mén)的條件：關(guān)門(mén)到位、有開(kāi)門(mén)信號(hào)、開(kāi)門(mén)繼電器吸合。對(duì)于信號(hào)的登記通常使用自鎖原理，無(wú)論電梯上往行或下行，當(dāng)轎廂運(yùn)行至有內(nèi)指令的樓層時(shí)，均要換速停車(chē)，并清 除原來(lái)的信號(hào)，不需反向信號(hào)。如有人想到三層時(shí)，按下三層的內(nèi)指令按鈕，則 X15 為 ON。當(dāng)轎廂到三層時(shí) M503 為 OFF，起消號(hào)作用。 當(dāng) M121 或 M122 為 ON 時(shí)，分別進(jìn)行上召喚和下召 喚信號(hào)的直駛和反向運(yùn)行保號(hào)，如當(dāng)下行時(shí)， Y2 為 ON，則 M122 為 ON。分別記憶上升或下降信號(hào)。而且在直駛過(guò)程中只在內(nèi)選層停車(chē)，當(dāng)電梯運(yùn)行方向和外召喚指令具有相同的方向時(shí)電梯換速后停車(chē)，即順向的截車(chē)。 泰山學(xué)院本科畢業(yè)論文 22 圖 9 到層指示圖 故障報(bào)警 報(bào)警的條件有幾種情況：電機(jī)出現(xiàn)故障、轎箱超出上 下限位。 圖 10 故障報(bào)警 泰山學(xué)院本科畢業(yè)論文 23 結(jié) 論 通過(guò)本次設(shè)計(jì)，我的知識(shí)領(lǐng)域得到進(jìn)一步擴(kuò)展，專(zhuān)業(yè)技能得到進(jìn)一步提升，同時(shí)增強(qiáng)了分析和解決工程實(shí)際的綜合能力。另外，也培養(yǎng)了自己嚴(yán)肅認(rèn)真的科學(xué)態(tài)度和嚴(yán)謹(jǐn)求實(shí)的工作作風(fēng)。當(dāng)然，設(shè)計(jì)中肯定還有其他不足 之處，懇請(qǐng)各位老師指正。在此，同時(shí)感謝在本次設(shè)計(jì)中給予我?guī)椭母魑活I(lǐng)導(dǎo)、老師和同學(xué)。 最后，對(duì)各位老師審閱我的論文深表感謝，很愉快能和老師領(lǐng)導(dǎo)們完成本次設(shè)計(jì)，同時(shí)，并渴望老師們給予批評(píng)指正。本次論文與設(shè)計(jì)的完成對(duì)我是一個(gè)巨大的激勵(lì)，使我在今后的學(xué)習(xí)和工作中充滿信心，更為我今后的學(xué)習(xí)與工作提供了寶貴的經(jīng)驗(yàn)。 disdain for this taxation without representation (socalled because the colonies had no voice in the establishment of the taxes) gave rise to revolts such as the Boston Tea Party. However, even after the Revolutionary War and the adoption of the . Constitution, the main source of revenue for the newly created states was money received from customs and excise taxes on items such as carriages, sugar, whiskey, and snuff. Ine tax first appeared in the United States in 1862, during the Civil War. At that time only about one percent of the population was required to pay the tax. A flatrate ine tax was imposed in 1867. The ine tax was repealed in its entirety in 1872. Ine tax was a rallying point for the Populist party in 1892, and had enough support two years later that Congress passed the Ine Tax Act of 1894. The tax at that time was two percent on individual ines in excess of $4,000, which meant that it reached only the wealthiest members of the population. The Supreme Court struck down the tax, holding that it violated the constitutional requirement that direct taxes be apportioned among the states by population (pollock v. farmers39。 trust, 158 . 601, 15 S. Ct. 912, 39 L. Ed. 1108 [1895]). After many years of debate and promise, the sixteenth amendment to the Constitution was ratified in 1913, providing Congress with the power to lay and collect taxes on ine without apportionment among the states. The objectives of the ine tax were the equitable distribution of the tax burden and the raising of revenue. Since 1913 the . ine tax system has bee very plex. In 1913 the ine tax laws were contained in eighteen pages of legislation。s new deal, imposed a five percent excise tax on dividend receipts, imposed a capital stock tax and an excess profits tax, and suspended all deductions for losses (June 16, 1933, ch. 90, 48 Stat. 195). The repeal in 1933 of the eighteenth amendment, which had prohibited the manufacture and sale of alcohol, brought in an estimated $90 million in new liquor taxes in 1934. The social security act of 1935 provided for a wage tax, half to be paid by the employee and half by the employer, to establish a federal retirement fund (Old Age Pension Act, Aug. 14, 1935, ch. 531, 49 Stat. 620). The Wealth Tax Act, also known as the Revenue Act of 1935, increased the maximum tax rate to 79 percent, the Revenue Acts of 1940 and 1941 increased it to 81 percent, the Revenue Act of 1942 raised it to 88 percent, and the Individual Ine Tax Act of 1944 raised the individual maximum rate to 94 percent. The postWorld War II Revenue Act of 1945 reduced the individual maximum tax from 94 percent to 91 percent. The Revenue Act of 1950, during the korean war, reduced it to percent, but it was raised the next year to 92 percent (Revenue Act of 1950, Sept. 23, 1950, ch. 994, Stat. 906). It remained at this level until 1964, when it was reduced to 70 percent. The Revenue Act of 1954 revised the Internal Revenue Code of 1939, making major changes that were beneficial to the taxpayer, including providing for child care deductions (later changed to credits), an increase in the charitable contribution limit, a tax credit against taxable retirement ine, employee deductions for business expenses, and liberalized depreciation deductions. From 1954 to 1962, the Internal Revenue Code was amended by 183 separate acts. In 1974 the employee retirement ine security act (ERISA) created protections for employees whose employers promised specified pensions or other retirement contributions (Pub. L. No. 93406, Sept. 2, 1974, 88 Stat. 829). ERISA required that to be tax deductible, the employer3