畢業(yè)論文基于PID的簡(jiǎn)單水溫控制系統(tǒng)設(shè)計(jì)

1、基于PID的簡(jiǎn)單水溫控制系統(tǒng)設(shè)計(jì)摘要：在工農(nóng)業(yè)生產(chǎn)和日常生活中，對(duì)溫度的檢測(cè)與控制始終有著非常重要的實(shí)際意義和廣泛的實(shí)際應(yīng)用。為了加深計(jì)算機(jī)控制理論的理解，故設(shè)計(jì)一個(gè)溫度控制系統(tǒng)，該系統(tǒng)主要由溫度信號(hào)采集與轉(zhuǎn)換模塊（傳感器DS18B20）、主機(jī)控制模塊（單片機(jī)STC89C52）、溫度控制模塊（雙向晶閘管BTA06）、液晶顯示模塊（液晶LM1602）等四部分組成，控制算法為PID算法。系統(tǒng)可實(shí)現(xiàn)穩(wěn)態(tài)誤差小于1，最大超調(diào)小于1，并且調(diào)節(jié)時(shí)間較短，恒定效果好。關(guān)鍵詞：傳感器DS18B20，單片機(jī)STC89C52，PID算法，液晶LM1602，雙向晶閘管BTA061 選題背景在現(xiàn)代工業(yè)生產(chǎn)和日常生活當(dāng)

2、中，對(duì)溫度的檢測(cè)、實(shí)現(xiàn)自動(dòng)恒溫控制有著非常重要實(shí)際意義和廣泛的應(yīng)用，例如大型火力發(fā)電站鍋爐的溫度控制、石油煉油廠油溫的控制等。一般的溫度控制系統(tǒng)其主要構(gòu)成部分有以下幾部分：被控對(duì)象、溫度信號(hào)采集與轉(zhuǎn)換模塊、顯示模塊、執(zhí)行模塊、主機(jī)控制模塊、按鍵等。關(guān)系如圖1.1： 圖1.1 溫度檢測(cè)裝備的組成結(jié)構(gòu)在此，我選擇了溫度測(cè)量及其恒溫控制作為計(jì)算機(jī)控制課程設(shè)計(jì)課題。在該控制系統(tǒng)中，控制算法不但結(jié)合經(jīng)典的PID控制算法的優(yōu)勢(shì)；還增加了死區(qū)控制，平均濾波、限幅消抖、抗積分飽和等措施抑制非正常情況的發(fā)生；此外，控制算法還采用了二維PID算法的優(yōu)點(diǎn)，加快了系統(tǒng)的動(dòng)態(tài)響應(yīng)速度。經(jīng)過實(shí)際測(cè)試，采取的措施能夠很好地

3、抑制非正常情況的發(fā)生，系統(tǒng)的響應(yīng)速度、穩(wěn)態(tài)誤差、超調(diào)量都取得了較為滿意的結(jié)果。2 方案設(shè)計(jì)及其論證2.1 溫度信號(hào)的采集及AD轉(zhuǎn)換方案一采用模擬類溫度傳感器，比如LM45、AD590、鉑電阻等。增加適當(dāng)?shù)姆糯箅娐泛虯D轉(zhuǎn)換電路以后，就可以將溫度信號(hào)送入單片機(jī)。然而，這種設(shè)計(jì)需要用到A/D轉(zhuǎn)換電路，且溫度傳感器的接線較為麻煩，制作成本較高。 方案二采用數(shù)字類溫度傳感器，比如DS18B20。DS18B20為數(shù)字式溫度傳感器，直接將溫度信號(hào)轉(zhuǎn)換為數(shù)字量，可編程的分辨率為912位,采用獨(dú)特的單總線接口，只需要一條總線就可以實(shí)現(xiàn)與單片機(jī)通信，簡(jiǎn)化了硬件電路設(shè)計(jì)，降低了設(shè)計(jì)成本。 將上述兩種方案比較，方案

4、二硬件電路設(shè)計(jì)得到簡(jiǎn)化并且設(shè)計(jì)成本降低，故采用方案二。2.2 主機(jī)控制模塊方案一采用快速單片機(jī)，比如STC12C5A32S2、ATmega16、W77E58等。以ATmega16為例，ATmega16單片機(jī)是基于增強(qiáng)的AVR RISC結(jié)構(gòu)的低功耗8 位CMOS微控制器。由于其先進(jìn)的指令集以及單時(shí)鐘周期指令執(zhí)行時(shí)間，ATmega16 的數(shù)據(jù)吞吐率高達(dá)1 MIPS/MHz，在相同晶振頻率的情況下，速度比普通快812倍。從性能上來說，該單片機(jī)是一款功能非常強(qiáng)大的單片機(jī)，然而其價(jià)格較高（15元/片），采用該單片機(jī)會(huì)使設(shè)計(jì)成本增加。 方案二采用普通單片機(jī)STC89C52。STC89C52單片機(jī)片內(nèi)有8K

5、B的EPROM和256B的RAM，程序通過串口下載，十分方便。在晶振頻率為12MHz的情況下，單指令僅需1us，完全能滿足系統(tǒng)設(shè)計(jì)要求。另外，該單片機(jī)價(jià)格便宜，僅5.8元/片。將上述兩種方案比較，方案一雖然性能上優(yōu)于方案二，但其設(shè)計(jì)成本較高，而且本系統(tǒng)不需要太快的運(yùn)行速度，故采用方案二。2.3 顯示模塊方案一采用7段式數(shù)碼管。目前，市場(chǎng)上有大量的七段式LED數(shù)碼管，價(jià)格也較為便宜，單個(gè)的數(shù)碼管僅0.8元，4位的數(shù)碼僅2.6元；不過采用數(shù)碼管作為顯示時(shí)，需要增加驅(qū)動(dòng)電路，驅(qū)動(dòng)電路的成本在8元左右，另外，數(shù)碼管只能顯示一些簡(jiǎn)單字符以及數(shù)字，而在本設(shè)計(jì)中，需要顯示較多信息，比如：實(shí)時(shí)溫度、PID參數(shù)

6、、設(shè)定溫度等，采用數(shù)碼管會(huì)大大增加程序的復(fù)雜度，并且還會(huì)對(duì)單片機(jī)的功能提出更高要求，其性價(jià)比較低。 方案二采用LM1602液晶顯示。LM1602液晶的市場(chǎng)價(jià)格在15元左右，可以與單片機(jī)直接連接，不需要增加額外的驅(qū)動(dòng)電路，它可以顯示所有的ASCII字符。另外可以同時(shí)顯示32個(gè)字符，電路設(shè)計(jì)簡(jiǎn)單、軟件復(fù)雜度低、性價(jià)比高。將上述兩種方案比較，方案一中LED數(shù)碼管雖然價(jià)格便宜，但需設(shè)計(jì)驅(qū)動(dòng)電路，而且本設(shè)計(jì)需要顯示較多系統(tǒng)運(yùn)行參數(shù)，故又增加編碼復(fù)雜度，同時(shí)對(duì)單片機(jī)性能要求提高，性價(jià)比低，方案二LM1602液晶顯示有電路設(shè)計(jì)簡(jiǎn)單，編碼復(fù)雜度低的優(yōu)點(diǎn)，故采用方案二。2.4 溫度控制模塊 方案一采用固態(tài)繼電器

7、。固態(tài)繼電器有三部分組成:輸入電路，隔離(耦合)和輸出電路。固態(tài)繼電器可以與邏輯電路兼容，耐振耐機(jī)械沖擊，安裝位置無限制，具有良好的防潮防霉防腐蝕性能，在防爆和防止臭氧污染方面的性能也極佳，輸入功率小，靈敏度高，控制功率小，電磁兼容性好，噪聲低和工作頻率高等特點(diǎn)。然而，其價(jià)格較高，電壓AC220V、最大電流5A的固態(tài)繼電器在25元左右，采用固態(tài)繼電器會(huì)使得設(shè)計(jì)成本大大增加。 方案二采用雙向晶閘管。市場(chǎng)上雙向晶閘管的種類很多，如雙向晶閘管BTA06，每片僅3.5元，可以使設(shè)計(jì)成本大大降低，配備以驅(qū)動(dòng)電路后，總體設(shè)計(jì)成本也不超過9元；另外，采用雙向晶閘管BTA06的硬件設(shè)計(jì)也較為簡(jiǎn)單。 將上述兩種

8、方案比較，方案一中固態(tài)繼電器雖然性能優(yōu)于方案二中的雙向晶閘管，但考慮固態(tài)繼電器成本遠(yuǎn)高于雙向晶閘管，故采用方案二。2.5 單片機(jī)控制方式 方案一P控制是一種最簡(jiǎn)單的控制方式。其控制器的輸出與輸入誤差信號(hào)成比例關(guān)系。當(dāng)僅有比例控制時(shí)系統(tǒng)輸出存在穩(wěn)態(tài)誤差（Steady-state error）。同時(shí)，由于水的溫度調(diào)節(jié)，可以等效于“純滯后一階慣性”，理論可推導(dǎo)其易產(chǎn)生振蕩。 方案二PI控制是在比例控制的基礎(chǔ)上加上積分作用，在積分控制中，控制器的輸出與輸入誤差信號(hào)的積分成正比關(guān)系，采用比例積分控制方式，只要有足夠長(zhǎng)的響應(yīng)時(shí)間，理論上可以做到穩(wěn)態(tài)無靜差。 方案三PID控制器就是根據(jù)系統(tǒng)的誤差，利用比例、

9、 積分、微分計(jì)算出控制量進(jìn)行控制的，也就是在比例積分控制方式下，加入微分控制，在微分控制中，控制器的輸出與輸入誤差信號(hào)的微分（即誤差的變化率）成正比關(guān)系。將上述三種方案進(jìn)行比較，由于本設(shè)計(jì)要求無靜差，被控對(duì)象慣性較大，為了加快調(diào)節(jié)速度，采用方案三即PID算法作為控制算法。3 系統(tǒng)概要設(shè)計(jì) 該系統(tǒng)能夠?qū)崿F(xiàn)測(cè)量-25125的溫度并予以顯示，精度為0.625，準(zhǔn)確度0.5。能夠?qū)崿F(xiàn)在099.9設(shè)定任一溫度保持恒定。按鍵可以設(shè)定恒溫溫度，液晶能夠?qū)崟r(shí)顯示溫度、設(shè)定溫度、偏差、占空比等基本量?？刂瞥绦蚰軌蛲瓿珊銣毓δ?，并且獲得較好的超調(diào)量、調(diào)節(jié)時(shí)間、穩(wěn)態(tài)誤差、響應(yīng)速度等量。系統(tǒng)的主要部件有7部分，分別是

10、：溫度傳感器DS18B20、STC89C52單片機(jī)、LM1602液晶、BTA06晶閘管（含光隔電路）、電爐、按鍵、電源模塊、串口通訊模塊。整個(gè)系統(tǒng)的結(jié)構(gòu)如下：圖3.1 溫度控制系統(tǒng)組成結(jié)構(gòu)系框圖4系統(tǒng)硬件設(shè)計(jì) 本設(shè)計(jì)將該電路分為四個(gè)模塊：溫度信號(hào)采集與轉(zhuǎn)換模塊（傳感器DS18B20）、主機(jī)控制模塊（單片機(jī)STC89C52）、溫度控制模塊（雙向晶閘管BTA06）、液晶顯示模塊（LM1602液晶）。4.1溫度信號(hào)采集與轉(zhuǎn)換 圖4.1 溫度信號(hào)采集與轉(zhuǎn)換原理圖如圖4.1，0.1uF電容的C19用于濾除高頻噪聲，6.8K上拉電阻用于增加數(shù)據(jù)總線的驅(qū)動(dòng)能力，DQ連接單片機(jī)的P22口，組成單總線通信系統(tǒng)，

11、用于單片機(jī)和DS18B20數(shù)據(jù)通信。4.2控制晶閘管導(dǎo)通模塊圖4.2是控制晶閘管導(dǎo)通的原理圖，MOC3022是光隔器件，單片機(jī)的P20端口和MOC3022的2腳相連接。當(dāng)P20為低電平是光隔右側(cè)的4、6引腳導(dǎo)通，進(jìn)而控制晶閘管導(dǎo)通。R13一般取2K左右。圖4.2 控制晶閘管導(dǎo)通模塊原理圖4.3液晶顯示模塊圖4.3 液晶顯示模塊原理圖4.4總系統(tǒng)原理圖圖4.4 系統(tǒng)總體原理圖5 系統(tǒng)軟件設(shè)計(jì)軟件流程圖如下：圖5.1 軟件流程圖6 設(shè)計(jì)體會(huì)及今后的改進(jìn)意見通過本次設(shè)計(jì)，提高了對(duì)計(jì)算機(jī)控制系統(tǒng)相關(guān)理論的理解，大大提升了運(yùn)用理論解決現(xiàn)實(shí)問題的能力，本課題“簡(jiǎn)單溫度控制系統(tǒng)”的設(shè)計(jì)與實(shí)現(xiàn)，從先前查相關(guān)背

12、景資料準(zhǔn)備到逐一突破的經(jīng)驗(yàn)表現(xiàn)在以下幾個(gè)面：首先，對(duì)課題牽涉到的一些器件必須加以認(rèn)識(shí)和熟練運(yùn)用。其次, 要設(shè)計(jì)某一個(gè)東西，首先要明白它是干什么的，勾畫出自己的設(shè)計(jì)思路。然后將這個(gè)問題進(jìn)行分塊，根據(jù)系統(tǒng)的指標(biāo)和功能框圖，明確各部分任務(wù)，進(jìn)行各單元電路的設(shè)計(jì)、參數(shù)計(jì)算和器件選擇。當(dāng)完成電路圖的設(shè)計(jì)后，如果有條件的話可以用某些仿真軟件進(jìn)行仿真，避免在后續(xù)進(jìn)行硬件焊接出現(xiàn)錯(cuò)誤后難以改正。最后，在設(shè)計(jì)過程中遇到一些問題能夠獨(dú)立思考從而用所學(xué)知識(shí)得以解決，真正學(xué)會(huì)了學(xué)以致用，從中增強(qiáng)了對(duì)計(jì)算機(jī)控制這門課程的學(xué)習(xí)興趣，對(duì)PID參數(shù)的調(diào)節(jié)也有了較為深入的了解。實(shí)驗(yàn)仍存在不足，比如在調(diào)節(jié)PID參數(shù)時(shí)，剛開始沒有

13、明確的方向，軟件設(shè)計(jì)不很合理等，我會(huì)以這次設(shè)計(jì)為契機(jī)，進(jìn)一步加強(qiáng)自己的學(xué)習(xí)能力，提升自己的專業(yè)知識(shí)水平。參考文獻(xiàn)1楊剛，周群. 電子系統(tǒng)設(shè)計(jì)與實(shí)踐M. 北京：電子工業(yè)出版社, 2005.2張毅剛. 單片機(jī)原理及應(yīng)用M. 哈爾濱：哈爾濱工業(yè)大學(xué)，2004.3閻石. 數(shù)字電路基礎(chǔ)M. 北京：高等教育出版社，2006.4劉金琨. 先進(jìn)PID控制及其MATLAB仿真M. 北京：中國電力出版社，2003.5康華光. 電子技術(shù)基礎(chǔ)（模擬部分）M. 武漢：高等教育出版社，2006.6王建華，黃河清. 計(jì)算機(jī)控制技術(shù)M. 北京：高等教育出版社，2003.7林敏，丁金華，田濤. 計(jì)算機(jī)控制技術(shù)及工程應(yīng)用M. 北

14、京：國防工業(yè)出版社，2008.附 錄 PID算法程序void auto_adjust(int NextPoint)Error = setPoint - NextPoint; / 偏差 if(Error > 100)open_duty =60;/全開通elseSumError += Error; / 積分dError = Error - LastError; / 當(dāng)前微分 LastError = Error;real_error = Proportion*Error+ Integral * SumError+ Derivative * dError;open_duty = (int)(re

15、al_error+0.5); void timer0() interrupt 1 /每隔50ms進(jìn)入中斷一次TH0=0x3C;TL0=0xB0;num_counter+;if(num_counter>(Sample_time*20)num_counter=0;kaitong = num_counter<=open_duty ? 0:1;鍵盤程序void key_change()static char key_num,bai=5,shi,ge;bit bai_ok = 0,shi_ok = 0,goback_to_PID = 0;key_num = keyscan();switch(

16、key_num)case 1: /進(jìn)入溫度設(shè)定界面TR0=0;/關(guān)閉定時(shí)器kaitong=1;setPosition(1,0);prints("SV: D:0.033");setPosition(2,0);prints("P :0.55 I:0.01");setPosition(1,3);inttostrr(setPoint,buffer);prints(buffer);goback_to_PID=0;while(!goback_to_PID)if(!bai_ok)key_num = keyscan();switch(key_num) case 2:/溫

17、度的十位加一bai+;if(bai=10)bai=0;bai_ok=0;break;case 3:goback_to_PID=1,bai_ok=1;break;/退出手動(dòng)調(diào)整case 4:bai_ok=1;shi_ok=1;break;/左移循環(huán)調(diào)節(jié)溫度的個(gè)位case 5: /溫度的十位減一 bai-;if(bai=255)bai=9;bai_ok=0;break; case 6:bai_ok=1;break;/右移調(diào)節(jié)溫度的個(gè)位default:bai_ok=0;break;else if(!shi_ok)key_num = keyscan();switch(key_num) case 2:/

18、設(shè)定溫度的個(gè)位shi+;if(shi=10)shi=0;shi_ok=0; break;case 3:goback_to_PID=1,shi_ok=1;break;case 4:bai_ok=0;break;case 5: shi-;if(shi=255)shi=9;shi_ok=0;break; case 6:shi_ok=1;break;default:shi_ok=0;break; else key_num = keyscan();switch(key_num) case 2:/設(shè)定溫度的小數(shù)位ge+;if(ge=10)ge=0;break;case 3:goback_to_PID=1;

19、break;case 4:shi_ok=0;break;case 5: ge-;if(ge=255)ge=9; break; case 6:bai_ok=0;break;default:break; delayl(150); setPoint = bai*100+shi*10+ge; inttostrr(setPoint,buffer); setPosition(1,3); prints(buffer); TR0=1;/重新啟動(dòng)定時(shí)器 write_com(0x01); break;default:break;g an employment tribunal claimEmployment tr

20、ibunals 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 unfairly.F

21、or 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 comp

22、ensation 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 will

23、 not usually accept it.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 or

24、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 tri

25、bunal, 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 thinki

26、ng 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 by e

27、-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 anniver

28、sary 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 experie

29、nce 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 acti

30、ons.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 life b

31、ecame 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, sudd

32、enly feel something, do it.一字開頭的年齡已經(jīng)到了尾聲?；蛟S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(duì)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 money a

33、nd 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 found th

34、at 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 pitch

35、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(chǎng)暗戀才意味著真正的成長(zhǎng)，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(zhǎng)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)的時(shí)候最

36、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(chǎng)，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(duì)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 clear,

37、 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 one

38、self 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 rained

39、. 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，天空是陰暗的

40、，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(chǎng)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 preci

41、pitation 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 the 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.aThe supersonic descent could happen as early as Sunda.The weatheThe balloon will slowly drift to the edg