【文章內(nèi)容簡介】 en, put i t agai nst the wal l, and began cli mbi ng towards t he bedr oom wi ndow. I was alm ost t her e when a sar cast ic voice below sai d, 39。 I don39。t t hi nk the wi ndows need cl eaning at t hi s ti me of t he ni ght.39。 I l ooked down and near ly fel of f the ladder when I saw a pol iceman. I imm edi at ely r egr et ed answeri ng in the way I did, but I sai d, 39。I enjoy cl eani ng windows at night. 39。 So do I, 39。 answered t he pol iceman in the same tone. 39。Excuse m e inter rupti ng you. I hate t o i nt er upt a m an when he39。s busy wor king, but woul d you mind i ng wi th me to t he Wel l , I 39。d pr ef er t o st ay her e, 39。 I sai d. 39。You see, I 39。ve f or got t en m y key. He cal l ed. 39。My key, 39。 I shout ed. 39。 For t unat el y, t he shout i ng woke up m y wi f e who opened t he wi ndow j ust as t he pol i cem an had st ar t ed t o cl i m b t owar ds m e. Lesson93 A nobl e gi f t 崇高的禮物 One of t he m ost f am ous m onum ent s i n t he wor l d, t he St at ue of Li ber t y, was pr esent ed t o t he Uni t ed St at es of Am er i ca i n t he ni eent h cent ur y by t he peopl e of Fr ance . The gr eat st at ue, whi ch was desi gned by t he scul pt or August Bar t hol di , t ook t en year s t o pl et e. The 第 1 頁 共 44 頁 第一章 緒論 倒立擺系統(tǒng)的簡介 倒立擺系統(tǒng)的研究背景 及意義 倒立擺系統(tǒng)的最初分析研究開始于二十世紀(jì)五十年代，是一個比較復(fù)雜的不穩(wěn)定、多變量、帶有非線性和強(qiáng)耦合特性的高階機(jī)械系統(tǒng)，它的穩(wěn)定控制是控制理論應(yīng)用的一個典型范例 [1]。倒立擺系統(tǒng)存在嚴(yán)重的不確定性，一方面是系統(tǒng)的參數(shù)的不確定性，一方面是系統(tǒng)的受到不確定因素的干擾。通過對它的研究不僅可以解決控制中的理論問題，還將控制理論涉及的相關(guān)主要學(xué)科：機(jī)械、力學(xué)、數(shù)學(xué)、電學(xué)和計算機(jī)等綜合應(yīng)用。在多種控制理論與方法的研究和應(yīng)用中，特別是在工程中，存 在一種可行性的實驗問題，將其理論和方法得到有效的驗證，倒立擺系統(tǒng)可以此提供一個從控制理論通過實踐的橋梁。近些年來，國內(nèi)外不少專家、學(xué)者一直將它視為典型的研究對象，提出了很多控制方案，對倒立擺系統(tǒng)的穩(wěn)定性和鎮(zhèn)定問題進(jìn)行了大量研究，都在試圖尋找不同的控制方法實現(xiàn)對倒立擺的控制，以便檢查或說明該方法的嚴(yán)重非線性和絕對不穩(wěn)定系統(tǒng)的控制能力，其控制方法在軍工、航天、機(jī)械人領(lǐng)域和一般工業(yè)過程中都有著廣泛的用途，如精密儀器的加工、機(jī)器人行走過程中的平衡控制、火箭發(fā)射中的垂直度控制、導(dǎo)彈攔截控制、航空對接控制、衛(wèi)星飛行中的 姿態(tài)控制等方面均涉及到倒置問題。因此，從控制這個角度上講，對倒立擺的研究在理論和方法論上均有著深遠(yuǎn)意義。倒立擺系統(tǒng)是一個典型的自不穩(wěn)定系統(tǒng)，其中擺作為一個典型的振動和運(yùn)動問題，可以抽象為許多問題來研究。隨著非線性科學(xué)的發(fā)展，以前的采用線性化方法來描述非線性的性質(zhì)，固然無可非議，但這種方法是很有局限性，非線性的一些本質(zhì)特征往往不是用線性的方法所能體現(xiàn)的。非線性是造成混亂、無序或混沌的核心因素，造成混亂、無序或混沌并不意味著需要復(fù)雜的原因，簡單的非線性就會產(chǎn)生非常的混亂、無序或混沌。在倒立擺系統(tǒng)中含有極其豐富和 復(fù)雜的動力學(xué)行為，如分叉、分形和混沌動力學(xué)，這方面的問題也值得去探討和研究。 無論哪種類型的倒立擺系統(tǒng)都具有如下特性 [2]： (1)非線性倒立擺是一個典型的非線性復(fù)雜系統(tǒng)。實際中可以通過線性化得到系統(tǒng)Her e and t here: they had just di scovered t hat a pr isoner had escaped. At t hat mom ent , a large bl ack car wit h f our of fi cer s inside i t, stopped at t he camp gat es. The off icers got out and t he pri soner st ood to at tenti on and salut ed as t hey passed. When t hey had gone, the dri ver of t he car came t owar ds him. The man obviously want ed to t alk. He was r at her el der ly wi t h grey hair and clear blue eyes. The pri soner felt sorr y f or hi m, but t her e was nothi ng el se he coul d do. As the man came near, the pr isoner knocked hi m t o t he gr ound wit h a shar p bl ow. Then, jumpi ng into the car, he drove of f as quickly as he could. ？ Fishermen and sail or s som etim es cl ai m to have sen m onster s in t he sea. Though people have oft en laughed at stor ies tol d by s eamen, it i s now known that many of these 39。monst ers39。 which have at t imes been si ghted are si mply st range fi sh. Occasi onal y, unusual creatur es ar e washed t o t he shore, but they are r arely caught out at sea. Some ti me ago, however, a pecul iar fi sh was caught near Madagascar . A smal l f i shing boat was car r ied mi les out to sea by the power ful fi sh as it pulled on the li ne. Reali zing t hat thi s was no or di nar y f ish, t he fi sher man made ever y ef ort not to damage i t i n any way. When it was event ualy brought t o shor e, i t was found t o be over t hi r teen feet long. I t had a head l ike a hor se, big bl ue eyes, shini ng si lver ski n, and a br ight red t ail , t he fi sh, whi ch has since been sent to a museum where i t is being examined by a scienti st , is cal ed an oar fi sh. Such creature s have rar el y been seen ali ve by man as they l ive at a dept h of si x hundr ed f et. Lesson83 Af ter the el ecti ons 大選之后 The f ormer Pr ime Mini st er, Went wort h Lane, was defeated i n the r ecent elect ions. He is now reti ri ng f rom pol it ical lif e and has gone abroad. My f r iend, Cr awley, has al ways been a f anati cal opponent of Lane39。s Radi cal Progr essive Part y. Af t er t he elect ions, Crawl ey went t o the f orm er Pr im e Mi nister39。s house. When he asked i f Lane l ived ther e, t he pol iceman on duty t old hi m t ha t si nce hi s def eat , t he exPr ime Mini st er had gone abroad. On the f oll owi ng day, Cr awley went t o the house again. The same policema n was j ust walki ng slowly past the entr ance, when Crawl ey asked the same quest ion. Though a lit tl e suspici ous t his t ime, the pol i cem an gave him the same answer . The day af ter , Cr awl ey went t o the house once m or e and asked exact ly t he same questi on. This t im e, t he pol iceman l ost his t em per .39。 I tol d you yest er day and the day bef ore yesterday,39。 he shout ed, Lane was def eat ed in the electi ons. He has reti r ed f r om poli ti cal li f e and gone t o li ve 39。 I know, 39。 answer ed Cr awl ey,39。 but I l ove to hear you say i t39。 Lesson84 On st ri ke 罷工 Busmen have decided to go on str ike next week. The st ri ke is due t o begi n on Tuesday. No one knows how long i t wil l last . The busmen have stated t hat t he st ri ke wil l cont inue unt il gener al agr em ent is r eached about pay and worki ng condi tions. Most pe ople beli eve that he str ike wi l last for at least a week. Many owners of pri vat e cars are goi ng to of fer 39。f r e r i des39。 t o peopl e on t hei r way to wor k. This wi l r el ieve pressur e on t he tr ai ns to some extent. Meanwhi le, a num ber of universit y student s have vol unt eer ed to dr ive buses whi le the str ike l asts. Al l the young men are exper t dri ver s, but bef ore they dri ve any of t he buse s, t hey wil l have t o pass a speci al t est . The st