【正文】 ll be traveling fast, so despite the distance, it will not be like diving into the deep end of a pool. It will be like he is diving into the shallow end. Skydiver preps for the big jump 本科畢業(yè)論文（設(shè)計(jì)） 23 When he jumps, he is expected to reach the speed of sound 690 mph (1,110 kph) in less than 40 seconds. Like hitting the top of the water, he will begin to slow as he approaches the more dense air closer to Earth. But this will not be enough to stop him pletely. If he goes too fast or spins out of control, he has a stabilization parachute that can be deployed to slow him down. His team hopes it39。 Have declared the end of the encounter that haven39。那些曾經(jīng)所謂的非做不可，只是青蔥年華里自己給自己注射的一支強(qiáng)心劑，或者說，是自以為是的精神寄托罷了。s time, your ideas are always special to clear. Want, want, line is clear, as if nothing could shake his. Also once seemed to be determined to do something, but more often is he backed out at last. Dislike his cowardice, finally found that there are a lot of love, there are a lot of miss, like shadow really have been doomed. Those who do, just green years oneself give oneself an arm injection, or is a selfrighteous spiritual. 一個(gè)人的時(shí)候，自己的想法總是特別地清晰。t want to give vent to out your inner voice can be in the high school children of the feelings in a period, but was eventually infarction when graduation party in the throat, later again stood on the pitch he has sweat profusely, looked at his thrown a basketball hoops, suddenly found himself has already can39。 The end of our life, and can meet many things really do? 而窮盡我們的一生，又能 遇到多少事情是真正地非做不可？ During my childhood, think lucky money and new clothes are necessary for New Year, but as the advance of the age, will be more and more found that those things are optional。 May be back in the past, to oneself the paranoid weird belief disillusionment, these days, my mind has been very messy, in my mind constantly. Always feel oneself should go to do something, or write something. Twenty years of life trajectory deeply shallow, suddenly feel something, do it. 一字開頭的年齡已經(jīng)到了尾聲。s 21 win. Michel Platini, president of European football39。s antiracism taskforce, is in London for the Football Association39。t agree with the disciplinary action your employer has taken against you ? your employer dismisses you and you think that you have been dismissed unfairly. For more information about dismissal and unfair dismissal, see Dismissal. You can make a claim to an employment tribunal, even if you haven39。目前恒壓供水系統(tǒng)正朝向集成化、自動(dòng)化的方向發(fā)展。 基于 PLC 的恒壓供水系統(tǒng)就是將四臺(tái)水泵按照順序編號(hào)，按照“先啟先?！钡脑瓌t，根據(jù)系統(tǒng)內(nèi)上限信號(hào)或下限信號(hào)的到來，循環(huán)控制四臺(tái)水泵的啟停情況，達(dá)到恒壓供水的目的 [8]。 8) 15s 后，壓力上限信號(hào)仍在，系統(tǒng)則會(huì)切斷最后一臺(tái)供水泵。如圖 77所示。仿真效果表現(xiàn)為： 0輸 出位燈滅，其余輸出位保持燈亮。如圖 74 所示。在仿真效果上來看，則表現(xiàn)為 0輸出位亮燈；如圖 72所示。此時(shí)，可將需要的輸入端子上撥（開關(guān)閉合），觀察輸出端子的指示燈的情況，與直接分析梯形圖所得結(jié)果對(duì)照，查看編寫梯形圖是否編寫正確。 S7200 CPU 模塊上有運(yùn)行狀態(tài)、輸入狀態(tài)和輸出狀態(tài)指示燈，在仿真時(shí)，通過觀察輸入、輸出指示燈的狀態(tài)可了解程序運(yùn)行效果。 6 軟件設(shè)計(jì) STEP 7Micro/WIN編程軟件 STEP 7Micro/WIN 是 S7200PLC 的編程軟件。本系統(tǒng)的泵機(jī)原理如圖 51 所示： 本科畢業(yè)論文（設(shè)計(jì)） 8 圖 51 恒壓供水系統(tǒng)泵機(jī)原理圖 圖 52 恒壓供水系統(tǒng)電氣控制系統(tǒng)主回路 本科畢業(yè)論文（設(shè)計(jì)） 9 根據(jù)系統(tǒng)在提高供水質(zhì)量和節(jié)能方面的要求和功能，采用 SIEMENS S7200 CPU222PLC 和變頻器為中心組成的恒壓供水控制系統(tǒng)。本例所描述的供水系統(tǒng)是針對(duì)上述問題設(shè)計(jì)的供水方式和控制系統(tǒng)，由主供水回路、備用回路、一個(gè)清水池及泵房組成。 2水泵 。當(dāng) P 供水 ≥ P 上限 時(shí)，則有選擇的切斷水泵，直至滿足 P 下限 ≤ P 供水 P 上限 為止。 本科畢業(yè)論文（設(shè)計(jì)） 7 2) 水泵啟停切換原則 恒壓供水系統(tǒng)主要是由 4個(gè)水泵完成對(duì)主管道供水壓力的維持，考慮到電機(jī)的保護(hù)，要求 4 臺(tái)水泵的運(yùn)行時(shí)間和頻率盡可能一致。 這個(gè)系統(tǒng)控制程序的設(shè)計(jì)利用了常用的順序控制實(shí)現(xiàn)的方法，對(duì)于順序控制設(shè)計(jì)，要認(rèn)真分析各個(gè)動(dòng)作階段的交互，選擇適當(dāng)?shù)霓D(zhuǎn)折點(diǎn)檢測信號(hào)來觸發(fā)狀態(tài)的切換。對(duì)于水泵的第一次啟動(dòng)和斷開，實(shí)現(xiàn)的邏輯主要在于對(duì)狀態(tài)信號(hào)的轉(zhuǎn)移處理。 1) 控制過程邏輯分析 在正常運(yùn)轉(zhuǎn)狀態(tài)下，對(duì)于恒壓供水系統(tǒng)，要根據(jù)兩個(gè)壓力極限信號(hào)來判斷是否需要進(jìn)行當(dāng)前狀態(tài)的轉(zhuǎn)換。將 4 臺(tái)水泵按順序編號(hào)，啟動(dòng)時(shí)按編號(hào)從小到大依次啟動(dòng)，而切斷則編號(hào)從小到大依次切斷，這樣的循環(huán)處理就可以保證是按照先啟先停的原則進(jìn)行的。 解決思路 對(duì)于恒壓供水系統(tǒng)的實(shí)現(xiàn)而言，主要的問題在兩個(gè)方面： 1) 如何實(shí)現(xiàn) 5s 內(nèi)，下一臺(tái)水泵的切換狀態(tài)。可編程邏輯控制器用于恒壓供水系統(tǒng)，可以可靠的實(shí)現(xiàn)對(duì)壓力的檢測信號(hào)處理以及對(duì)各個(gè)水泵相應(yīng)的切換。 目前，我國市場上主要 PLC產(chǎn)品 的種類 :西門子公司的產(chǎn)品施耐德公司 羅克韋爾公司（包括 AB公司） PLC 產(chǎn)品， GE 公司的 SERIES、 GE9070、 GE9030 系列產(chǎn)品；本科畢業(yè)論文（設(shè)計(jì)） 3 日 本的歐姆龍、三菱、富士、松下等公司產(chǎn)品； PLC 是專為在工業(yè)環(huán)境下應(yīng)用而設(shè)計(jì)的，具有 以下 幾個(gè)特點(diǎn)： 1) 可靠性高，抗干擾能力強(qiáng)； 2) 通用性強(qiáng)，控制程序可變，使用方便； 3) 功能強(qiáng)，適應(yīng)范圍廣； 4