電大機械控制工程基礎試題及答案5

1、專業(yè)好文檔一、 填空題(每空1分，共20分)1. 傳遞函數(shù)的定義是對于線性定常系統(tǒng),在初始條件為零的條件下，系統(tǒng)輸出量的拉氏變換與輸入量的拉氏變換之比。2. 瞬態(tài)響應是系統(tǒng)受到外加作用激勵后，從初始狀態(tài)到最終或穩(wěn)定狀態(tài)的響應過程。3. 判別系統(tǒng)穩(wěn)定性的出發(fā)點是系統(tǒng)特征方程的根必須為負實根或負實部的復數(shù)根，即系統(tǒng)的特征根必須全部在復平面的左半平面是系統(tǒng)穩(wěn)定的充要條件。4. i型系統(tǒng)在單位階躍輸入下，穩(wěn)態(tài)誤差為 0 ，在單位加速度輸入下，穩(wěn)態(tài)誤差為 。5. 頻率響應是系統(tǒng)對正弦輸入穩(wěn)態(tài)響應，頻率特性包括幅頻和相頻兩種特性。6. 如果系統(tǒng)受擾動后偏離了原工作狀態(tài)，擾動消失后，系統(tǒng)能自動恢復到原來的工

2、作狀態(tài)，這樣的系統(tǒng)是(漸進)穩(wěn)定的系統(tǒng)。7. 傳遞函數(shù)的組成與輸入、輸出信號無關，僅僅決定于系統(tǒng)本身的結(jié)構(gòu)和參數(shù)，并且只適于零初始條件下的線性定常系統(tǒng)。8. 系統(tǒng)的穩(wěn)態(tài)誤差與輸入信號的形式及系統(tǒng)的結(jié)構(gòu)和參數(shù)或系統(tǒng)的開環(huán)傳遞函數(shù)有關。9. 如果在系統(tǒng)中只有離散信號而沒有連續(xù)信號，則稱此系統(tǒng)為離散(數(shù)字)控制系統(tǒng)，其輸入、輸出關系常用差分方程來描述。10. 反饋控制系統(tǒng)開環(huán)對數(shù)幅頻特性三頻段的劃分是以c（截止頻率）附近的區(qū)段為中頻段，該段著重反映系統(tǒng)階躍響應的穩(wěn)定性和快速性；而低頻段主要表明系統(tǒng)的穩(wěn)態(tài)性能。11. 對于一個自動控制系統(tǒng)的性能要求可以概括為三個方面：穩(wěn)定性、快速 性和精確或準確性。二

3、設有一個系統(tǒng)如圖1所示，k1=1000n/m, k2=2000n/m, d=10n/(m/s)，當系統(tǒng)受到輸入信號 的作用時，試求系統(tǒng)的穩(wěn)態(tài)輸出。(15分)解： 然后通過頻率特性求出 三一個未知傳遞函數(shù)的被控系統(tǒng)，構(gòu)成單位反饋閉環(huán)。經(jīng)過測試，得知閉環(huán)系統(tǒng)的單位階躍響應如圖2所示。(10分)問：(1) 系統(tǒng)的開環(huán)低頻增益k是多少？(5分)(2) 如果用主導極點的概念用低階系統(tǒng)近似該系統(tǒng)，試寫出其近似閉環(huán)傳遞函數(shù)；(5分)解：（1），(2) 四已知開環(huán)最小相位系統(tǒng)的對數(shù)幅頻特性如圖3所示。(10分)1. 寫出開環(huán)傳遞函數(shù)g(s)的表達式；(5分)2. 概略繪制系統(tǒng)的nyquist圖。(5分)1 2

4、五已知系統(tǒng)結(jié)構(gòu)如圖4所示, 試求：(15分)1. 繪制系統(tǒng)的信號流圖。(5分)2. 求傳遞函數(shù)及。(10分)六系統(tǒng)如圖5所示，為單位階躍函數(shù)，試求：(10分)1. 系統(tǒng)的阻尼比和無阻尼自然頻率。(5分)2. 動態(tài)性能指標：超調(diào)量mp和調(diào)節(jié)時間。(5分)1 2 七如圖6所示系統(tǒng)，試確定使系統(tǒng)穩(wěn)定且在單位斜坡輸入下時，k的數(shù)值。(10分) 由勞斯判據(jù)： 第一列系數(shù)大于零，則系統(tǒng)穩(wěn)定得 又有：2.25 可得：k4 4k54八已知單位反饋系統(tǒng)的閉環(huán)傳遞函數(shù)，試求系統(tǒng)的相位裕量。(10分)解：系統(tǒng)的開環(huán)傳遞函數(shù)為，解得一. 填空題(每小題2分，共20分)1 對控制系統(tǒng)的基本要求一般可以歸納為穩(wěn)定性、快速

5、性 和準確性。2 按系統(tǒng)有無反饋，通?？蓪⒖刂葡到y(tǒng)分為 開環(huán)控制系統(tǒng) 和 閉環(huán)控制系統(tǒng) 。3 在控制工程基礎課程中描述系統(tǒng)的數(shù)學模型有微分方程 、傳遞函數(shù)等。4 穩(wěn)態(tài)誤差反映出穩(wěn)態(tài)響應偏離系統(tǒng)希望值的程度，它用來衡量系統(tǒng)控制精度的程度。5 一階系統(tǒng)的單位階躍響應的表達是。6 有系統(tǒng)的性能指標按照其類型分為時域性能指標和頻域性能指標。7 頻率響應是線性定常系統(tǒng)對正弦輸入的穩(wěn)態(tài)響應。8 穩(wěn)態(tài)誤差不僅取決于系統(tǒng)自身的結(jié)構(gòu)參數(shù)，而且與輸入信號的類型有關。9 脈沖信號可以用來反映系統(tǒng)的抗沖擊能力。10. 階躍信號的拉氏變換是 1/s 。二 圖1為利用加熱器控制爐溫的反饋系統(tǒng)（10分）圖1 爐溫控制結(jié)構(gòu)圖

6、 試求系統(tǒng)的輸出量、輸入量、被控對象和系統(tǒng)各部分的組成，且畫出原理方框圖，說明其工作原理。解答：輸出量：爐溫。輸入量：給定電壓信號。被控對象：電爐。 系統(tǒng)包括：電位器、放大器、電機、減速器以及自藕調(diào)壓器、熱電偶。 原理方框圖：三如圖2為電路。求輸入電壓與輸出電壓之間的微分方程，并求出該電路的傳遞函數(shù)。（10分）圖2解答：跟據(jù)電壓定律得四、求拉氏變換與反變換 1 求解答：2 求解答：=六、 化簡框圖，并求出閉環(huán)傳遞函數(shù)圖4解：g1g2 g3h2h1/g3xi(s)xo(s)_+h1/g3xi(s)xo(s)_xi(s)xo(s)七、圖示機械系統(tǒng)由質(zhì)量m、阻尼系數(shù)c、彈簧剛度k和外力組成的機械動力

7、系統(tǒng)。圖(a)中是輸出位移。當外力施加3牛頓階躍力后，記錄儀上記錄質(zhì)量m物體的時間響應曲線如（b）圖所示。試求：1）該系統(tǒng)的微分方程數(shù)學模型和傳遞函數(shù)；(4分)2）該系統(tǒng)的彈簧剛度質(zhì)量m、阻尼系數(shù)c、彈簧剛度k；（3分）3）時間響應性能指標：上升時間、調(diào)整時間、振蕩頻數(shù)、穩(wěn)態(tài)誤差（5分）。圖(a) 機械系統(tǒng) 圖（b）響應曲線解答：解：1）對于該系統(tǒng)有： 故 2）求k 由laplace變換的終值定理可知： 而=1.0，因此k=3. 求m， 由得： 又由式求得=0.6 將0.6代入中，得=1.96。再由求得m=0.78。 求c 由，求得c=1.83.3）求 2.55 (取=0.05時) 3.40

8、(取=0.02時) 求 0.91 2.323 求n 取=0.05時，=0.64 取=0.02時， =0.85 求 當輸入為階躍信號時，系統(tǒng)的穩(wěn)態(tài)誤差為： 對于0型系統(tǒng) ，代入式中求得： =0.5八、已知某系統(tǒng)是單位負反饋系統(tǒng)，其開環(huán)傳遞函數(shù)，則該系統(tǒng)在單位脈沖、單位階躍和單位恒速信號作用下的分別是多少？（8分）解答：該系統(tǒng)為單位負反饋且為0型系統(tǒng)，k=11, 所以該系統(tǒng)在單位階躍和單位恒速信號作用下的分別是、。在單位脈沖信號作用下的穩(wěn)態(tài)誤差為九、設有如圖所示的反饋控制系統(tǒng)，試求根據(jù)勞斯判據(jù)確定傳遞函數(shù)k值的取值范圍解答：系統(tǒng)的特征方程：可展開為：列出勞斯數(shù)列：k0,30-k00k30if we

9、 dont do that it will go on and go on. we have to stop it; we need the courage to do it.his comments came hours after fifa vice-president jeffrey webb - also in london for the fas celebrations - said he wanted to meet ivory coast international toure to discuss his complaint.cska general director rom

10、an babaev says the matter has been exaggerated by the ivorian and the british media.blatter, 77, said: it has been decided by the fifa congress that it is a nonsense for racism to be dealt with with fines. you can always find money from somebody to pay them.it is a nonsense to have matches played wi

11、thout spectators because it is against the spirit of football and against the visiting team. it is all nonsense.we can do something better to fight racism and discrimination.this is one of the villains we have today in our game. but it is only with harsh sanctions that racism and discrimination can

12、be washed out of football.the (lack of) air up there watch mcayman islands-based webb, the head of fifas anti-racism taskforce, is in london for the football associations 150th anniversary celebrations and will attend citys premier league match at chelsea on sunday.i am going to be at the match tomo

13、rrow and i have asked to meet yaya toure, he told bbc sport.for me its about how he felt and i would like to speak to him first to find out what his experience was.uefa hasopened disciplinary proceedings against cskafor the racist behaviour of their fans duringcitys 2-1 win.michel platini, president

14、 of european footballs governing body, has also ordered an immediate investigation into the referees actions.cska said they were surprised and disappointed by toures complaint. in a statement the russian side added: we found no racist insults from fans of cska.baumgartner the disappointing news: mis

15、sion aborted.the supersonic descent could happen as early as sunda.the weather plays an important role in this mission. starting at the ground, conditions have to be very calm - winds less than 2 mph, with no precipitation or humidity and limited cloud cover. the balloon, with capsule attached, will

16、 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 strat

17、osphere. as he crosses the boundary layer (called the tropopause),e can expect a lot of turbulence.the balloon will slowly drift to the edge of space at 120,000 feet ( then, i would assume, he will slowly step out onto something resembling an olympic diving platform.below, the earth becomes the conc

18、rete bottom of a swimming pool that he wants to land on, but not too hard. still, hell 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 jumpwhen 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 completely.if he goes too fast or spins out of control, he has a