畢業(yè)設(shè)計(jì)基于工程設(shè)計(jì)法的雙閉環(huán)直流調(diào)速系統(tǒng)設(shè)計(jì)1

1、 第1章 引 言41.1設(shè)計(jì)目的41.2設(shè)計(jì)要求5第2章 系統(tǒng)總體設(shè)計(jì)62.1總體思路62.2總體設(shè)計(jì)6第3章 雙閉環(huán)調(diào)速系統(tǒng)設(shè)計(jì)83.1系統(tǒng)的總體框圖設(shè)計(jì)83.2 電流調(diào)節(jié)器的設(shè)計(jì)83.3轉(zhuǎn)速調(diào)節(jié)器的設(shè)計(jì)10第4章 系統(tǒng)仿真12第5章 總結(jié)14參考文獻(xiàn)15 基于工程設(shè)計(jì)法的雙閉環(huán)直流調(diào)速系統(tǒng)設(shè)計(jì) 【摘要】 本文按工程方法設(shè)計(jì)了一個(gè)直流電機(jī)的轉(zhuǎn)速和電流雙閉環(huán)調(diào)速系統(tǒng)。該系統(tǒng)設(shè)計(jì)了電流檢測環(huán)節(jié)，電流調(diào)節(jié)器以及轉(zhuǎn)速檢測環(huán)節(jié)、轉(zhuǎn)速調(diào)節(jié)器，構(gòu)成了電流環(huán)和轉(zhuǎn)速環(huán)，前者通過電流元件的反饋?zhàn)饔梅€(wěn)定電流，后者通過轉(zhuǎn)速檢測元件的反饋?zhàn)饔帽３洲D(zhuǎn)速穩(wěn)定，最終消除轉(zhuǎn)速偏差，從而使系統(tǒng)達(dá)到調(diào)節(jié)電流和轉(zhuǎn)速的目的，并通過s

2、imulink進(jìn)行系統(tǒng)仿真，分析雙閉環(huán)直流調(diào)速系統(tǒng)的特性?！娟P(guān)鍵詞】 雙閉環(huán) 電流調(diào)節(jié)器 轉(zhuǎn)速調(diào)節(jié)器 simulinkengineering design method based on double closed-loop dc motor control system design【abstract】 this project designed by a dc moter speed and current dual-loop speed control system.the system sets up the current detecting aspect,the current r

3、egulator acr and the speed detecting link,speed regulator asr,composes the current central and the speed central,the former through the feedback of the current components to level off the current,the latter through the feedback of speed detecting device to maintain the speed stably and finally elimi

4、nates the deviation of speed bias,thus allowing the system to the purpose of regulating the current and speed.simulink for system through system simulation,finally display control system model and the results of anti-truth. 【keywords】 double-loop the speed regulator the current regulator simulink第1章

5、 引 言 20世紀(jì)60年代以前，在電氣傳動(dòng)領(lǐng)域中，我們曾廣泛使用的是由機(jī)組供電的直流調(diào)速系統(tǒng)，但該系統(tǒng)需要旋轉(zhuǎn)變流機(jī)組，至少包含兩臺(tái)與調(diào)速電動(dòng)機(jī)容量相當(dāng)?shù)男D(zhuǎn)電機(jī)，還要一臺(tái)勵(lì)磁發(fā)電機(jī)，因此，該系統(tǒng)所需設(shè)備多，體積大，費(fèi)用高，效率低。1957年，晶閘管問世，晶閘管變流裝置開始取代旋轉(zhuǎn)變流機(jī)組，產(chǎn)生了晶閘管電動(dòng)機(jī)調(diào)速系統(tǒng)，大大提高了系統(tǒng)的動(dòng)態(tài)性能。但晶閘管整流裝置也有其缺點(diǎn)，由于晶閘管的單向?qū)щ娦?，不允許電流反向，給系統(tǒng)的可逆運(yùn)行造成了困難。如今，可逆脈沖寬度調(diào)制器成為直流調(diào)速系統(tǒng)的主要方法。在工程設(shè)計(jì)與理論學(xué)習(xí)中，我們會(huì)接觸到大量關(guān)于調(diào)速控制系統(tǒng)的分析、綜合與設(shè)計(jì)問題。雙閉環(huán)調(diào)速系統(tǒng)是一種當(dāng)前應(yīng)

6、用廣泛、經(jīng)濟(jì)、適用的電力傳動(dòng)系統(tǒng)。他具有動(dòng)態(tài)響應(yīng)快，抗干擾能力強(qiáng)等優(yōu)點(diǎn)。我們知道反饋閉環(huán)控制系統(tǒng)具有良好的抗擾性能，它對于被反饋環(huán)前向通道上的一切擾動(dòng)作用都能有效的加以抑制。采用轉(zhuǎn)速負(fù)反饋和pi調(diào)節(jié)器的單閉環(huán)調(diào)速系統(tǒng)可以再保證系統(tǒng)穩(wěn)定的條件下實(shí)現(xiàn)轉(zhuǎn)速無靜差。但如果對系統(tǒng)的動(dòng)態(tài)性能要求較高，例如要求起制動(dòng)、突加負(fù)載動(dòng)態(tài)速降等，就難以滿足要求。這主要是因?yàn)樵趩伍]環(huán)系統(tǒng)中不能完全按照需要來控制動(dòng)態(tài)過程的電流或轉(zhuǎn)矩。在單閉環(huán)系統(tǒng)中，只有電流截止至負(fù)反饋環(huán)節(jié)是專門用來控制電流的，但它只是在超過臨街電流值以后，強(qiáng)烈的負(fù)反饋?zhàn)饔孟拗齐娏鞯臎_擊，并不能很理想的控制電流的動(dòng)態(tài)波形。在實(shí)際工作中，我們希望用最大的

7、加速度啟動(dòng)，到達(dá)穩(wěn)定轉(zhuǎn)速后，又讓電流降下來，使轉(zhuǎn)矩馬上與負(fù)載相平衡，從而轉(zhuǎn)入穩(wěn)態(tài)運(yùn)行。因此，我們可以采用雙閉環(huán)直流調(diào)速達(dá)到這種效果。1.1設(shè)計(jì)目的為了進(jìn)一步提高對所學(xué)知識(shí)的運(yùn)用能力，以及對運(yùn)動(dòng)控制系統(tǒng)一書的深入了解，會(huì)運(yùn)用所學(xué)知識(shí)來設(shè)計(jì)一般的控制系統(tǒng)。通過設(shè)計(jì)，一方面掌握設(shè)計(jì)方法、技巧，另一方面加強(qiáng)理論結(jié)合實(shí)際及指導(dǎo)解決實(shí)際問題的途徑，以期達(dá)到理論與實(shí)際的統(tǒng)一，從而提高同學(xué)們對科學(xué)實(shí)驗(yàn)的興趣和能力。既培養(yǎng)學(xué)生基于所學(xué)知識(shí)分析和綜合典型系統(tǒng)的能力，又使學(xué)生理解典型系統(tǒng)的工程背景、在掌握基礎(chǔ)理論和方法三、提高解決實(shí)際自動(dòng)控制系統(tǒng)問題的能力。1.2設(shè)計(jì)要求按工程設(shè)計(jì)方法設(shè)計(jì)一個(gè)直流電機(jī)的轉(zhuǎn)速和電流雙

8、閉環(huán)調(diào)速系統(tǒng)。通過控制電樞電壓改變電動(dòng)機(jī)的轉(zhuǎn)速，電樞電壓由三相橋式整流電路提供。系統(tǒng)參數(shù)：電動(dòng)機(jī)的額定數(shù)據(jù)為：，電動(dòng)勢系數(shù)，主回路總電阻，允許的電流過載倍數(shù)，觸發(fā)整流環(huán)節(jié)的放大倍數(shù)。電磁時(shí)間常數(shù)，機(jī)電時(shí)間常數(shù)，電流反饋濾波時(shí)間常數(shù)，轉(zhuǎn)速反饋濾波時(shí)間常數(shù)。額定轉(zhuǎn)速時(shí)給定電壓，調(diào)節(jié)器asr,acr飽和輸出電壓，。設(shè)計(jì)指標(biāo)：穩(wěn)態(tài)無靜差，電流超調(diào)量，空載起動(dòng)到額定轉(zhuǎn)速時(shí)的轉(zhuǎn)速超調(diào)量。第2章 系統(tǒng)總體設(shè)計(jì)2.1總體思路采用pi調(diào)節(jié)的單個(gè)轉(zhuǎn)速閉環(huán)直流調(diào)速系統(tǒng)可以在保證系統(tǒng)穩(wěn)定的前提下實(shí)現(xiàn)轉(zhuǎn)速無靜差，但是，如果對系統(tǒng)的動(dòng)態(tài)性能要求較高，例如對于經(jīng)常正、反轉(zhuǎn)運(yùn)行的龍門刨床、可逆軋鋼機(jī)，要求快速起制動(dòng)，因?yàn)楸M量

9、縮短其、制動(dòng)時(shí)間是提高生產(chǎn)率的重要因素，為此，在電機(jī)最大允許電流和轉(zhuǎn)矩受限制的條件下，應(yīng)該充分利用電機(jī)的過載能力，最好在過渡過程中始終保持電流為允許的最大值，使電力拖動(dòng)系統(tǒng)以最大加速度起動(dòng)，到達(dá)穩(wěn)態(tài)轉(zhuǎn)速時(shí)，立即讓電流降下來，使轉(zhuǎn)矩馬上與負(fù)載相平衡，從而轉(zhuǎn)入穩(wěn)態(tài)運(yùn)行。因此，我們可以采用轉(zhuǎn)速、電流雙閉環(huán)調(diào)速來實(shí)現(xiàn)。為了實(shí)現(xiàn)轉(zhuǎn)速和電流兩種負(fù)反饋分別起作用，可以在系統(tǒng)中設(shè)置兩個(gè)調(diào)節(jié)器，分別調(diào)節(jié)轉(zhuǎn)速和電流，即分別引入轉(zhuǎn)速負(fù)反饋和電流負(fù)反饋，二者之間實(shí)現(xiàn)串級(jí)連接，形成轉(zhuǎn)速、電流雙閉環(huán)調(diào)速控制。2.2總體設(shè)計(jì)方案一：單閉環(huán)直流調(diào)速系統(tǒng)單閉環(huán)直流調(diào)速系統(tǒng)是由一個(gè)轉(zhuǎn)速負(fù)反饋構(gòu)成的閉環(huán)控制系統(tǒng)。在電動(dòng)機(jī)軸上裝一臺(tái)

10、測速發(fā)電機(jī)，引出與轉(zhuǎn)速成正比的電壓與給定電壓比較后，得到偏差電壓，經(jīng)放大器，產(chǎn)生觸發(fā)裝置的控制電壓，用以控制電動(dòng)機(jī)得轉(zhuǎn)速。該系統(tǒng)可以保證系統(tǒng)穩(wěn)定的前提下實(shí)現(xiàn)轉(zhuǎn)速無靜差，但是，如果對系統(tǒng)的動(dòng)態(tài)性能要求較高，就難以滿足要求。原理框圖如圖2-1 圖2-1 方案二：雙閉環(huán)直流調(diào)速系統(tǒng) 該方案主要由給定環(huán)節(jié)、asr、acr、觸發(fā)器和整流裝置環(huán)節(jié)、速度檢測環(huán)節(jié)以及電流檢測環(huán)節(jié)組成。為了使轉(zhuǎn)速負(fù)反饋和電流負(fù)反饋分別起作用，系統(tǒng)設(shè)置了電流調(diào)節(jié)器和轉(zhuǎn)速調(diào)節(jié)器，電流調(diào)節(jié)器和電流檢測反饋回路構(gòu)成了電流環(huán)，轉(zhuǎn)速調(diào)節(jié)器和轉(zhuǎn)速檢測反饋回路構(gòu)成轉(zhuǎn)速環(huán)。因轉(zhuǎn)速環(huán)包圍電流環(huán)，故電流環(huán)稱為內(nèi)環(huán)，轉(zhuǎn)速環(huán)為外環(huán)。在電路中，asr和a

11、cr串聯(lián)，把a(bǔ)sr的輸出當(dāng)作acr的輸入，再由acr的輸出去控制整流器的觸發(fā)器。為了獲得良好的靜、動(dòng)態(tài)性能。轉(zhuǎn)速和電流兩個(gè)調(diào)節(jié)器都采用具有輸入輸出限幅功能的pi調(diào)節(jié)器，且轉(zhuǎn)速和電流都采用負(fù)反饋閉環(huán)。雙閉環(huán)調(diào)速系統(tǒng)彌補(bǔ)了單閉環(huán)調(diào)速系統(tǒng)的缺點(diǎn)，能夠滿足動(dòng)態(tài)性能要求。圖2-2綜上所述，我們選用雙閉環(huán)直流調(diào)速系統(tǒng)第3章 雙閉環(huán)調(diào)速系統(tǒng)設(shè)計(jì)3.1系統(tǒng)的總體框圖設(shè)計(jì) 根據(jù)設(shè)計(jì)的要求，本文所設(shè)計(jì)的雙閉環(huán)直流調(diào)速系統(tǒng)主要包含轉(zhuǎn)速給定電路、轉(zhuǎn)速檢測電路、電流檢測電路、整流電路等幾部分，系統(tǒng)的總體框圖如下： 圖3-13.2 電流調(diào)節(jié)器的設(shè)計(jì)1.確定時(shí)間常數(shù)（1）整流裝置滯后時(shí)間常數(shù)，三相橋式整流電路的失控時(shí)間=0

12、.0017s。（2）電流濾波時(shí)間常數(shù)，三相橋式電路每個(gè)波頭的時(shí)間是3.3ms，為了基本濾平波頭，應(yīng)有=3.33ms，因此?。?）電流環(huán)小時(shí)間常數(shù)之和，按小時(shí)間常數(shù)近視處理，取。2.確定將電流環(huán)設(shè)計(jì)成為何種典型結(jié)構(gòu)根據(jù)設(shè)計(jì)要求：，而且，因此，設(shè)計(jì)成典型系統(tǒng)3.電流調(diào)節(jié)器的結(jié)構(gòu)選擇電流調(diào)節(jié)器選用pi調(diào)節(jié)器，其傳遞函數(shù)可設(shè)為式中電流調(diào)節(jié)器的比例系數(shù) 電流調(diào)節(jié)器的超前時(shí)間常數(shù)4.選擇電流調(diào)節(jié)器參數(shù)（1）電流調(diào)節(jié)器超前時(shí)間常數(shù):。（2）電流開環(huán)增益：因，故取，因此=135.1，于是電流調(diào)節(jié)器的比例系數(shù)（3）電流反饋系數(shù)：5 校驗(yàn)近似條件電流環(huán)截止頻率（1）校驗(yàn)晶閘管裝置傳遞函數(shù)的近似條件是否滿足。因?yàn)椋?/p>

13、所以滿足近似條件。（2）校驗(yàn)忽略反電動(dòng)勢對電流環(huán)影響的近似條件是否滿足?，F(xiàn)在，滿足近似條件。（3）校驗(yàn)小時(shí)間常數(shù)的近似處理是否滿足條件。現(xiàn)在，滿足近似條件。電流環(huán)結(jié)構(gòu)框圖： 圖3-23.3轉(zhuǎn)速調(diào)節(jié)器的設(shè)計(jì)1.確定時(shí)間常數(shù)（1）電流環(huán)等效時(shí)間常數(shù)為；（2）轉(zhuǎn)速濾波時(shí)間常數(shù)。根據(jù)所用測速發(fā)電機(jī)紋波情況，?。唬?）轉(zhuǎn)速環(huán)小時(shí)間常數(shù)。按小時(shí)間常數(shù)近似處理，取。2. 確定將轉(zhuǎn)速環(huán)設(shè)計(jì)成何種典型系統(tǒng)由于設(shè)計(jì)要求轉(zhuǎn)速無靜差，轉(zhuǎn)速調(diào)節(jié)器必須含有積分環(huán)節(jié)；有根據(jù)動(dòng)態(tài)設(shè)計(jì)要求，應(yīng)按典型型系統(tǒng)設(shè)計(jì)轉(zhuǎn)速環(huán)。3.轉(zhuǎn)速調(diào)節(jié)器的結(jié)構(gòu)選擇轉(zhuǎn)速調(diào)節(jié)器選用pi型，其傳遞函數(shù)為：。轉(zhuǎn)速調(diào)節(jié)器的比例系數(shù)轉(zhuǎn)速調(diào)節(jié)器的超前時(shí)間常數(shù)4.選

14、擇轉(zhuǎn)速調(diào)節(jié)器參數(shù)（1）按跟隨和抗繞性能都較好的原則取h=5，則asr超前時(shí)間常數(shù)：；（2）轉(zhuǎn)速開環(huán)增益：；（3）asr的比例系數(shù)為：（4）轉(zhuǎn)速反饋系數(shù)：5 校驗(yàn)近似條件轉(zhuǎn)速環(huán)截止頻率（1）電流環(huán)傳遞函數(shù)簡化條件（2）校驗(yàn)小時(shí)間常數(shù)的近似處理是否滿足條件。現(xiàn)在，滿足近似條件。（3）校核轉(zhuǎn)速超調(diào)量。當(dāng)h=5時(shí)，不能滿足設(shè)計(jì)要求，實(shí)際上這是按線性系統(tǒng)計(jì)算的，而突加階躍給定時(shí)，飽和，不符合線性系統(tǒng)的前提，應(yīng)該按退飽和的情況重新計(jì)算超調(diào)量。當(dāng)h=5時(shí)，；而，因此，能滿足設(shè)計(jì)要求。轉(zhuǎn)速環(huán)框圖如下： 圖3-3第4章 系統(tǒng)仿真由于本文只進(jìn)行了理論性設(shè)計(jì)，故在系統(tǒng)安裝與調(diào)試階段對控制部分進(jìn)行matlab仿真，以

15、分析直流電機(jī)的啟動(dòng)特性，采用matlab的simulink工具箱對系統(tǒng)在階躍輸入下的動(dòng)態(tài)響應(yīng)進(jìn)行仿真，系統(tǒng)仿真結(jié)構(gòu)如圖所示： 圖4-1在額定轉(zhuǎn)速和空載下，對系統(tǒng)進(jìn)行仿真得到電動(dòng)機(jī)電樞電流和轉(zhuǎn)速的仿真輸出波形。轉(zhuǎn)速波形：電流波形：控制電壓uc的波形：以上表明，利用matlab仿真平臺(tái)對直流調(diào)速系統(tǒng)理論設(shè)計(jì)與調(diào)試，使得系統(tǒng)的性能分析過程簡單。通過對系統(tǒng)進(jìn)行仿真，可以準(zhǔn)確地了解到理論設(shè)計(jì)與實(shí)際系統(tǒng)之間的偏差，逐步改進(jìn)系統(tǒng)結(jié)構(gòu)及參數(shù)，得到最優(yōu)調(diào)節(jié)器參數(shù)，使得系統(tǒng)的調(diào)試得到簡化，縮短產(chǎn)品的開發(fā)周期。第5章 總結(jié)待添加的隱藏文字內(nèi)容1經(jīng)過這次的課程設(shè)計(jì)，不僅使在書上學(xué)到的知識(shí)得到了鞏固，而且還在設(shè)計(jì)中拓展

16、了其它沒學(xué)過的知識(shí)，比如我學(xué)會(huì)了如何用公式編輯器，如何用visio進(jìn)行畫圖，如何用matlab進(jìn)行仿真，這些軟件的學(xué)會(huì)當(dāng)然少不了老師和同學(xué)幫組，也提高了我的自學(xué)能力。這次課程設(shè)計(jì)，通過查找資料，了解情況，讓我明白了課本上的知識(shí)該用到什么地方，也了解到理論學(xué)習(xí)與工程設(shè)計(jì)的區(qū)別，加深了我對所學(xué)知識(shí)的理解。參考文獻(xiàn)1 陳桂明，應(yīng)用matlab建模與仿真，科學(xué)出版社，20022 姬富德，基于matlab的矢量控制系統(tǒng)仿真，礦山機(jī)械出版社，20013 陳伯時(shí)，電力拖動(dòng)自動(dòng)控制系統(tǒng)運(yùn)動(dòng)控制系統(tǒng)，第三版，機(jī)械工業(yè)出版社，20034李發(fā)海，王巖，電機(jī)拖動(dòng)基礎(chǔ)，第三版，清華大學(xué)出版社，2005 employme

17、nt tribunals sort out disagreements between employers and employees.you may need to make a claim to an employment tribunal if:· you don't agree with the disciplinary action your employer has taken against you· your employer dismisses you and you think that you have been dismissed unfai

18、rly.for more information about dismissal and unfair dismissal, see dismissal.you can make a claim to an employment tribunal, even if you haven't appealed against the disciplinary action your employer has taken against you. however, if you win your case, the tribunal may reduce any

19、 compensation awarded to you as a result of your failure to appeal.remember that in most cases you must make an application to an employment tribunal within three months of the date when the event you are complaining about happened. if your application is received after this time limit, the tribunal

20、 will not usually accept i.if you are worried about how the time limits apply to you, take advice from one of the organisations listed under further help.employment tribunals are less formal than some other courts, but it is still a legal process and you will need to give evidence under an oath

21、 or affirmation.most people find making a claim to an employment tribunal challenging. if you are thinking about making a claim to an employment tribunal, you should get help straight away from one of the organisations listed under further help.if you are being represented by a solicitor at the

22、 tribunal, they may ask you to sign an agreement where you pay their fee out of your compensation if you win the case. this is known as a damages-based agreement. in england and wales, your solicitor can't charge you more than 35% of your compensation  if you win the case.if you are th

23、inking about signing up for  a damages-based agreement, you should make sure you're clear about the terms of the agreement. it might be best to get advice from an experienced adviser, for example, at a citizens advice bureau.  to find your nearest cab, including those that give advice

24、by e-mail, click on nearest cab.for more information about making a claim to an employment tribunal, see employment tribunals.the (lack of) air up there watch mcayman islands-based webb, the head of fifa's anti-racism taskforce, is in london for the football association's 150th ann

25、iversary celebrations and will attend city's premier league match at chelsea on sunday."i am going to be at the match tomorrow and i have asked to meet yaya toure," he told bbc sport."for me it's about how he felt and i would like to speak to him first to find out what his exp

26、erience was."uefa has opened disciplinary proceedings against cska for the "racist behaviour of their fans" during city's 2-1 win.michel platini, president of european football's governing body, has also ordered an immediate investigation into the referee's

27、actions.cska said they were "surprised and disappointed" by toure's complaint. in a statement the russian side added: "we found no racist insults from fans of cska."age has reached the end of the beginning of a word. may be guilty in his seems to passing a lot of different li

28、fe became the appearance of the same day; 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,

29、suddenly feel something, do it.一字開頭的年齡已經(jīng)到了尾聲。或許是愧疚于自己似乎把轉(zhuǎn)瞬即逝的很多個(gè)不同的日子過成了同一天的樣子；或許是追溯過去，對自己那些近乎偏執(zhí)的怪異信念的醒悟，這些天以來，思緒一直很凌亂，在腦海中不斷糾纏?？傆X得自己自己似乎應(yīng)該去做點(diǎn)什么，或者寫點(diǎn)什么。二十年的人生軌跡深深淺淺，突然就感覺到有些事情，非做不可了。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 mon

30、ey 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; junior high school, thought to have a crush on just means that the real growth, but over the past three years later, his writing of alumni in peace, suddenly foun

31、d that isn't really grow up, it seems is not so important; then in high school, think don'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 pi

32、tch he has sweat profusely, looked at his thrown a basketball hoops, suddenly found himself has already can't remember his appearance.童年時(shí)，覺得壓歲錢和新衣服是過年必備，但是隨著年齡的推進(jìn)，會(huì)越來越發(fā)現(xiàn)，那些東西根本就可有可無；初中時(shí)，以為要有一場暗戀才意味著真正的成長，但三年過去后，自己心平氣和的寫同學(xué)錄的時(shí)候，突然就發(fā)現(xiàn)是不是真正的成長了，好像并沒有那么重要了；然后到了高中，覺得非要吐露出自己的心聲才能為高中生涯里的懵懂情愫劃上一個(gè)句點(diǎn)，但畢業(yè)晚會(huì)

33、的時(shí)候最終還是被梗塞在了咽喉，后來再次站在他曾經(jīng)揮汗如雨的球場，看著他投過籃球的球框時(shí)，突然間發(fā)現(xiàn)自己已經(jīng)想不起他的容顏。originally, this world, can produce a chemical reaction to an event, in addition to resolutely, have to do, and time.原來，這個(gè)世界上，對某個(gè)事件能產(chǎn)生化學(xué)反應(yīng)的，除了非做不可的堅(jiān)決，還有，時(shí)間。a person's time, your ideas are always special to clear. want, want, line is cl

34、ear, 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

35、 oneself an arm injection, or is a self-righteous spiritual.一個(gè)人的時(shí)候，自己的想法總是特別地清晰。想要的，不想要的，界限明確，好像沒有什么可以撼動(dòng)自己。也曾經(jīng)好像已經(jīng)下定了決心去做某件事，但更多的時(shí)候是最后又打起了退堂鼓。嫌惡過自己的怯懦，最終卻發(fā)現(xiàn)有很多緣分，有很多錯(cuò)過，好像冥冥之中真的已經(jīng)注定。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。at the moment, the sky is dark, the air is fresh factor after just ra

36、ined. suddenly thought of blue plaid shirt; those were broken into various shapes of stationery; from the corner at the beginning of deep friendship; have declared the end of the encounter that haven't start planning. those years, those days of do, finally, like youth, will end in our life.此刻，天空

37、是陰暗的，空氣里有著剛下過雨之后的清新因子。突然想到那件藍(lán)格子襯衫；那些被折成各種各樣形狀的信紙；那段從街角深巷伊始的友誼；還有那場還沒有開始就宣告了終結(jié)的邂逅計(jì)劃那些年那些天的非做不可，終于和青春一樣，都將在我們的人生中謝幕。baumgartner the disappointing news: mission aborted. r plays an important role in this mission. starting at the ground, conditions have to be very calm - winds less than 2 mph, with no p

38、recipitation or humidity and limited cloud cover. the balloon, with capsule attached, will move through the lower level of the atmosphere (the troposphere) where our day-to-day weather lives. it will climb higher than the tip of mount everest (5.5 miles/8.85 kilometers), drifting even higher than th

39、e cruising altitude of commercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. as he crosses the boundary layer (called the tropopause),e can expect a lot of turbulence.the supersonic descent could happen as early as sunda.the weathethe balloon will slowly drift to the edge of space at 120,000 feet ( then, i would assume, he will slowly step out onto something