數(shù)控車(chē)床主傳動(dòng)系統(tǒng)畢業(yè)設(shè)計(jì)外文翻譯

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1、 數(shù)控車(chē)床 在先進(jìn)制造技術(shù)領(lǐng)域最根本的觀念之一是數(shù)控（NC）。數(shù)控來(lái)臨之前，所有機(jī)床是手工操作和控制。手動(dòng)控制機(jī)床有許多限制，或許沒(méi)有比操作者的技能更突出。用手動(dòng)控制，產(chǎn)品質(zhì)量直接相關(guān)，并僅限于操作者的技能。 車(chē)床主要是為了進(jìn)行車(chē)外圓、車(chē)端面和鏜孔等項(xiàng)工作而設(shè)計(jì)的機(jī)床。車(chē)削很少在其他種類(lèi)的機(jī)床上進(jìn)行，而且任何一種其他機(jī)床都不能像車(chē)床那樣方便地進(jìn)行車(chē)削加工。由于車(chē)床還可以用來(lái)鉆孔和鉸孔，車(chē)床的多功能性可以使工件在一次安裝中完成幾種加工。因此，在生產(chǎn)中使用的各種車(chē)床比任何其他種類(lèi)的機(jī)床都多。 車(chē)床的基本部件有：床身、主軸箱組件、尾座組件、溜板組件、絲杠和光杠 件在各種速度下回轉(zhuǎn)。主軸

2、箱基本上由一個(gè)安裝在精密軸承中的空心主軸和一系列變速齒輪(類(lèi)似于卡車(chē)變速箱)所組成。通過(guò)變速齒輪，主軸可以在許多種轉(zhuǎn)速下旋轉(zhuǎn)。大多數(shù)車(chē)床有8~12種轉(zhuǎn)速，主軸箱安裝在內(nèi)側(cè)導(dǎo)軌的固定位置上，一般在床身的左端。它提供動(dòng)力，并可使工一般按等比級(jí)數(shù)排列。而且在現(xiàn)代機(jī)床上只需扳動(dòng)2~4個(gè)手柄，就能得到全部轉(zhuǎn)速。一種正在不斷增長(zhǎng)的趨勢(shì)是通過(guò)電氣的或者機(jī)械的裝置進(jìn)行無(wú)級(jí)變速 由于機(jī)床的精度在很大程度上取決于主軸，因此，主軸的結(jié)構(gòu)尺寸較大，通常安裝在預(yù)緊后的重型圓錐滾子軸承或球軸承中。主軸中有一個(gè)貫穿全長(zhǎng)的通孔，長(zhǎng)棒料可以通過(guò)該孔送料。主軸孔的大小是車(chē)床的一個(gè)重要尺寸，因此當(dāng)工件必須通過(guò)主軸孔供料時(shí)，它確定

3、了能夠加工的棒料毛坯的最大尺寸。 這個(gè)問(wèn)題導(dǎo)致了1959年自動(dòng)編程工具（APT）語(yǔ)言的發(fā)展，使用類(lèi)似數(shù)控英文語(yǔ)句來(lái)定義幾何零件，描述刀具配置，并制定所需的方案。新的APT語(yǔ)言的發(fā)展是重大的一步，推動(dòng)數(shù)控技術(shù)的進(jìn)一步發(fā)展。原來(lái)的數(shù)控系統(tǒng)廣泛使用穿孔紙，后來(lái)由磁性塑料帶代替。一個(gè)使用穿孔紙的人解釋了該機(jī)器的磁帶使用說(shuō)明作為知名的數(shù)控概念發(fā)展（DNC）解決了紙張和塑料帶與數(shù)控相關(guān)作為執(zhí)行指令的編程語(yǔ)言磁帶的問(wèn)題。在直接數(shù)字控制下，精密機(jī)床的束縛，通過(guò)數(shù)據(jù)傳輸鏈路，連接在主機(jī)和機(jī)器工具，通過(guò)數(shù)據(jù)傳輸連接需要。直接數(shù)字控制穿孔紙帶和塑料帶的應(yīng)用上是一個(gè)重大的進(jìn)步。但是，它受所有技術(shù)，在主機(jī)上卻有相同的

4、限制。當(dāng)主機(jī)出現(xiàn)故障，機(jī)器工具也會(huì)出現(xiàn)故障。這個(gè)問(wèn)題引導(dǎo)了計(jì)算機(jī)數(shù)控的發(fā)展。 關(guān)于可編程邏輯控制器（PLC）和微型計(jì)算機(jī)的發(fā)展使微處理器的發(fā)展。這兩項(xiàng)技術(shù)的發(fā)展，計(jì)算機(jī)數(shù)字控制（CNC）允許的數(shù)控系統(tǒng)。每臺(tái)機(jī)器工具，PLC或微型計(jì)算機(jī)，它為同樣的目的。這允許程序自動(dòng)輸入和存儲(chǔ)在每個(gè)機(jī)床上。數(shù)控解決相關(guān)的主機(jī)停機(jī)的問(wèn)題，但它推出了著名的數(shù)據(jù)管理的另一個(gè)問(wèn)題。同樣的程序可能會(huì)被裝上10種不同的微型電腦，它們之間沒(méi)有溝通。此問(wèn)題處理是在當(dāng)?shù)貐^(qū)域網(wǎng)絡(luò)的過(guò)程中解決的connectDigital信號(hào)處理器的。 在形成了直接數(shù)字控制（DNC）這個(gè)概念之后，可以不再采用紙帶或塑料帶作為編程指令的載體，這樣

5、就解決了與之有關(guān)的問(wèn)題。在直接數(shù)字控制中，幾臺(tái)機(jī)床通過(guò)數(shù)據(jù)傳輸線路聯(lián)接到一臺(tái)主計(jì)算機(jī)上。操縱這些機(jī)床所需要的程序都存儲(chǔ)在這臺(tái)主計(jì)算機(jī)中。當(dāng)需要時(shí)，通過(guò)數(shù)據(jù)傳輸線路提供給每臺(tái)機(jī)床。直接數(shù)字控制是在穿孔紙帶和塑料帶基礎(chǔ)上的一大進(jìn)步。然而，它敢有著同其他信賴(lài)于主計(jì)算機(jī)技術(shù)一樣的局限性。當(dāng)主計(jì)算機(jī)出現(xiàn)故障時(shí)，由其控制的所有機(jī)床都將停止工作。這個(gè)問(wèn)題促使了計(jì)算機(jī)數(shù)字控制技術(shù)的產(chǎn)生。 微處理器的發(fā)展為可編程邏輯控制器和微型計(jì)算機(jī)的發(fā)展做好了準(zhǔn)備。這兩種技術(shù)為計(jì)算機(jī)數(shù)控（CNC）的發(fā)打下了基礎(chǔ)。采用CNC技術(shù)后，每臺(tái)機(jī)床上都有一個(gè)可編程邏輯控制器或者微機(jī)對(duì)其進(jìn)行數(shù)字控制。這可以使得程序被輸入和存儲(chǔ)在每臺(tái)機(jī)

6、床內(nèi)部。它還可以在機(jī)床以外編制程序，并將其下載到每臺(tái)機(jī)床中。計(jì)算機(jī)數(shù)控解決了主計(jì)算機(jī)發(fā)生故障所帶來(lái)的問(wèn)題，但是它產(chǎn)生了另一個(gè)被稱(chēng)為數(shù)據(jù)管理的問(wèn)題。同一個(gè)程序可能要分別裝入十個(gè)相互之間沒(méi)有通訊聯(lián)系的微機(jī)中。這個(gè)問(wèn)題目前正在解決之中，它是通過(guò)采用局部區(qū)域網(wǎng)絡(luò)將各個(gè)微機(jī)聯(lián)接起來(lái)，以得于更好地進(jìn)行數(shù)據(jù)管理。 在許多情況下的模擬信號(hào)會(huì)用各種方法處理問(wèn)題，在很多方面像濾波和頻譜分析，設(shè)計(jì)模擬硬件來(lái)執(zhí)行這些職能是可能的，但已變得越來(lái)越少，由于更高的性能需求，靈活性的需求，以及需要削減減少開(kāi)發(fā)/測(cè)試的時(shí)間的需求。正是在困難時(shí)，換句話說(shuō)，是模擬信號(hào)的硬件設(shè)計(jì)分析改變了現(xiàn)狀。 抽樣一個(gè)信號(hào)是專(zhuān)門(mén)為嵌入式信號(hào)處

7、理的操作，這種處理器被稱(chēng)為數(shù)字信號(hào)處理器，是數(shù)字信號(hào)處理器的代表。今天有數(shù)百個(gè)家庭的DSP從盡可能多的制造商，每一個(gè)特定的價(jià)格/性能/使用組來(lái)設(shè)計(jì)的。大的廠家很多，像德州儀器，摩托羅拉，都提供專(zhuān)門(mén)的DSP像馬達(dá)控制或調(diào)制解調(diào)器這些領(lǐng)域的，和一般的高性能DSP處理，可以執(zhí)行廣泛的任務(wù)范圍。軟件開(kāi)發(fā)工具包也可以，也有公司做好DSP的，允許程序員可以實(shí)現(xiàn)復(fù)雜的處理算法，利用簡(jiǎn)單的“拖放和下降”的方法的軟件開(kāi)發(fā)工具。 DSP的或多或少取決于兩類(lèi)下降的基礎(chǔ)架構(gòu)的定點(diǎn)和浮點(diǎn)。定點(diǎn)設(shè)備操作一般在16位，而浮點(diǎn)器件上32-40位浮點(diǎn)操作。不用說(shuō)，定點(diǎn)設(shè)備一般比較便宜。另一個(gè)重要的結(jié)構(gòu)不同的地方是，定點(diǎn)處理器

8、往往只有一個(gè)“通用的蓄電池架構(gòu)”，這使得他們的方案很棘手，更重要的是，制造的C-編譯器固有的低效率。浮點(diǎn)DSP的表現(xiàn)更像是共同的通用CPU的寄存器文件。 在市場(chǎng)上有成千上萬(wàn)不同的數(shù)字信號(hào)處理器，找到項(xiàng)目最合適的數(shù)字信號(hào)處理器是一個(gè)艱巨的任務(wù)。最好的辦法可能是成立一個(gè)約束和心愿，并試圖針對(duì)它的最大制造商的處理器來(lái)進(jìn)行比較。 MPEG音頻解碼，數(shù)字壓縮的數(shù)據(jù)反饋到執(zhí)行的DSP解碼，解碼后的樣本，將轉(zhuǎn)換成模擬域回來(lái)，與由此產(chǎn)生的信號(hào)放大器或類(lèi)似的音頻設(shè)備。這個(gè)數(shù)字到模擬轉(zhuǎn)換（DCA）的工作由一個(gè)具有相同名稱(chēng)和不同音頻媒體的電路提供不同的性能和質(zhì)量，如THD（總諧波失真），對(duì)位，線性度，速度，

9、過(guò)濾特征和其他一些。 該TLS320family儀器由定點(diǎn)，浮點(diǎn)組成，數(shù)字信號(hào)處理器的多處理器（DSP）及foxed點(diǎn)DSP控制器。 TMS320系列數(shù)字信號(hào)處理器設(shè)計(jì)了實(shí)時(shí)信號(hào)處理具體的架構(gòu)。F/C240是C2000DSP平臺(tái)，并控制應(yīng)用而優(yōu)化。C24x的DSP控制器系列，結(jié)合這個(gè)控制器外設(shè)的實(shí)時(shí)處理能力，以創(chuàng)造一個(gè)控制系統(tǒng)應(yīng)用的理想解決方案。以下特點(diǎn)使TMS320系列正確選擇應(yīng)用廣泛的加工范圍： ---非常靈活的指令集 ---固有業(yè)務(wù)靈活性 ---高速性能 ---創(chuàng)新的并行結(jié)構(gòu) ---成本效益 一代的TMS320系列器件具有相同的CPU結(jié)構(gòu)，但不同的片上存儲(chǔ)器和外設(shè)配置不同。

10、附帶了設(shè)備使用的片上存儲(chǔ)器和外設(shè)新組合，以滿足全球電子市場(chǎng)的需求范圍。通過(guò)整合到一個(gè)單一芯片內(nèi)存和外設(shè)，TMS320系列設(shè)備降低了系統(tǒng)成本和節(jié)省電路板空間。 16位定點(diǎn)DSP的C24x核心器件模擬設(shè)計(jì)提供了數(shù)字解決方案，不犧牲精度和系統(tǒng)性能，可通過(guò)為技術(shù)先進(jìn)的控制算法，如適應(yīng)控制使用增強(qiáng)，卡爾曼濾波，和國(guó)家控制。C24x DSP控制器提供的可靠性和可編程性。模擬控制系統(tǒng)，一方面，是硬連線解決方案和經(jīng)驗(yàn)，可能因老化性能降低，元件容差和漂移。 高速中央處理單元（CPU）可處理的數(shù)字化設(shè)計(jì)，事實(shí)上，并不是與查表結(jié)果近似的算法。這些指令集的DSP控制器，它集成了信號(hào)處理指令和通用控制功能，具有廣泛

11、的開(kāi)發(fā)時(shí)間，并提供了結(jié)合傳統(tǒng)的8位和16位微控制器使用相同的環(huán)節(jié)。指令集還允許您保留您的軟件投資在其他普通C2x上，源代碼C2x代兼容，源代碼與德州儀器的數(shù)字信號(hào)處理器C5x代兼容。 在C24x架構(gòu)也非常適用于控制信號(hào)的處理。它用于存儲(chǔ)中間結(jié)果的32位寄存器的16位字，并有兩個(gè)硬件可用號(hào)碼提供給獨(dú)立的CPU。這種組合減少量化誤差和截?cái)?，以及附加功能增加進(jìn)化的能力。這些職能可能包括取消陷波器，可以在一個(gè)系統(tǒng)或一個(gè)機(jī)械共振技術(shù)，可消除系統(tǒng)狀態(tài)的傳感器。 在C24xDSP控制器考慮讓德州儀器具備快速配置不同價(jià)格/性能點(diǎn)或各種系列的成員進(jìn)行應(yīng)用優(yōu)化的外設(shè)功能設(shè)置的優(yōu)勢(shì)。這兩個(gè)數(shù)字和混合信號(hào)外設(shè)庫(kù)包

12、括： ---定時(shí)器 ---串行通信接口（SCI的，SPI） ---模擬到數(shù)字轉(zhuǎn)換器（ADC） ---事件管理器 ---系統(tǒng)保護(hù)，如低電壓和看門(mén)狗定時(shí)器 該DSP控制器外設(shè)庫(kù)是不斷增長(zhǎng)和變化的，以適應(yīng)未來(lái)的嵌入式控制市場(chǎng)。 該TMS320F/C240于的介紹是第一個(gè)標(biāo)準(zhǔn)裝置中的DSP控制器24x系列。它決定一個(gè)單芯片的數(shù)字電機(jī)控制器的標(biāo)準(zhǔn)。該C240可以執(zhí)行20 MIPS。幾乎所有的指令執(zhí)行時(shí)間為50 ns。這一高性能允許實(shí)時(shí)非常完整的控制算法，如自適應(yīng)控制，卡爾曼濾波的執(zhí)行。非常高的采樣率也可用于盡量減少循環(huán)延遲。 在240C具有高速信號(hào)處理和數(shù)字控制功能所必需的建筑特色，以及

13、它需要提供一個(gè)電機(jī)控制應(yīng)用的單芯片解決方案的外設(shè)。該240C使用亞微米CMOS制造技術(shù)，實(shí)現(xiàn)了日志的功耗等級(jí)。還包括一些掉電模式，進(jìn)一步節(jié)省功耗。 要作為一個(gè)系統(tǒng)管理員，必須有強(qiáng)大的DSP芯片上的I / O和其他外圍設(shè)備。該240事物管理器是不同于其他任何可以用一個(gè)數(shù)字信號(hào)處理器的處理器。此應(yīng)用程序優(yōu)化的周邊裝置，與高性能的DSP核心，可提供了高精確度和高效率的全變速控制的所有汽車(chē)類(lèi)型的先進(jìn)控制技術(shù)。事物管理器包括特殊的脈沖寬度調(diào)制（PWM）生成功能，如可編程死區(qū)的功能和空間矢量PWM狀態(tài)機(jī)，3相馬達(dá)，提供了完善的設(shè)施，最先進(jìn)的最高效率開(kāi)關(guān)電源晶體管。 有獨(dú)立的定時(shí)器，每個(gè)與它自己比較的寄

14、存器，支持非對(duì)稱(chēng)代（noncentered）以及對(duì)稱(chēng)（中心）的PWM波形。 開(kāi)環(huán)和閉環(huán)控制系統(tǒng) 開(kāi)環(huán)控制系統(tǒng) 這個(gè)詞意味著有一個(gè)復(fù)雜的控制系統(tǒng)自動(dòng)控制一定的數(shù)額。它通常意味著該系統(tǒng)通常是能夠適應(yīng)不同的作業(yè)條件，并能有令人滿意的回應(yīng)。然而，并非任何類(lèi)型的控制系統(tǒng)都具有自動(dòng)功能。通常情況下，自動(dòng)控制功能是通過(guò)feed來(lái)完成的。 g的反饋結(jié)構(gòu)，它被稱(chēng)為開(kāi)環(huán)系統(tǒng)，該系統(tǒng)是精確控制的一個(gè)事實(shí)，就是可能不知道確切的控制，特點(diǎn)在于最簡(jiǎn)單，最經(jīng)濟(jì)，它有一個(gè)明確的軸承溫度。這也指出了一個(gè)開(kāi)環(huán)控制系統(tǒng)的性能重要的缺餡，該系統(tǒng)不能夠適應(yīng)變化的環(huán)境或外部干擾。在此控制情況下，或許是有經(jīng)驗(yàn)的人提供了一個(gè)理想中的

15、外室溫控制，門(mén)或窗被打開(kāi)或在營(yíng)運(yùn)期間，關(guān)閉間歇性，在房子里的最后溫度不會(huì)精確的受開(kāi)環(huán)控制。 閉環(huán)控制系統(tǒng) 閉環(huán)控制缺少更準(zhǔn)確和更適應(yīng)由輸出反饋提高系統(tǒng)的輸入。為了獲得更準(zhǔn)確的控制信號(hào)必須反饋，并參考輸入，以及一個(gè)驅(qū)動(dòng)信號(hào)成比例的輸出和輸入的差異，必須通過(guò)系統(tǒng)發(fā)送而修正錯(cuò)誤。與一個(gè)或更多反饋，就像是剛才所說(shuō)的是被稱(chēng)為閉環(huán)系統(tǒng)。人類(lèi)系統(tǒng)是可能是最復(fù)雜和精密的反饋控制系統(tǒng)的存在。一個(gè)人可以被認(rèn)為是一個(gè)控制系統(tǒng)有許多輸入和輸出，開(kāi)展高度復(fù)雜的操作能力。 為了說(shuō)明人類(lèi)作為一個(gè)正反饋控制系統(tǒng)，讓我們考慮該計(jì)劃的目的是達(dá)成一個(gè)任務(wù)對(duì)象。眼睛作為傳感裝置，不斷地反饋手的位置。之間的距離和對(duì)象的錯(cuò)誤，最終

16、到零。這是一個(gè)閉環(huán)控制的典型例子。然而，如果被告知要達(dá)到目標(biāo)，然后是看不到的，只能達(dá)到對(duì)對(duì)象估計(jì)其確切位置。據(jù)國(guó)際檢索單位一個(gè)閉環(huán)控制系統(tǒng)的算例，表明了該控制系統(tǒng)基本的一個(gè)閉環(huán)控制系的圖框。如圖所示。一般來(lái)說(shuō)，一個(gè)反饋控制系統(tǒng)配置不得限制該feedback。在復(fù)雜的系統(tǒng)有可能反饋回路和元素塊過(guò)多。 Numerical Control Lathes One of the most fundamental concepts in the area of advanced manufacturing technologies is numerical control (NC).Pr

17、ior to the advent of NC, all machine tools were manual operated and controlled. Among the many limitations associated with manual control machine tools, perhaps none is more prominent than the limitation of operator skills. With manual control, the quality of the product is directly related to and l

18、imited to the skills of the operator . Numerical control represents the first major step away from human control of machine tools. Lathes are machine tools designed primarily to do turning, facing and boring, Very little turning is done on other types of machine tools, and none can do it with equal

19、 facility. Because lathes also can do drilling and reaming, their versatility permits several operations to be done with a single setup of the work piece. Consequently, more lathes of various types are used in manufacturing than any other machine tool. The essential components of a lathe are the be

20、d, headstock assembly, tailstock assembly, and the leads crew and feed rod. The headstock is mounted in a foxed position on the inner ways, usually at the left end of the bed. It provides a powered means of rotating the word at various speeds . Essentially, it consists of a hollow spindle, mounted

21、in accurate bearings, and a set of transmission gears-similar to a truck transmission—through which the spindle can be rotated at a number of speeds. Most lathes provide from 8 to 18 speeds, usually in a geometric ratio, and on modern lathes all the speeds can be obtained merely by moving from two t

22、o four levers. An increasing trend is to provide a continuously variable speed range through electrical or mechanical drives. Because the accuracy of a lathe is greatly dependent on the spindle, it is of heavy construction and mounted in heavy bearings, usually preloaded tapered roller or ball type

23、s. The spindle has a hole extending through its length, through which long bar stock can be fed. The size of maximum size of bar stock that can be machined when the material must be fed through spindle. This problem led to the development in 1959 of the Automatically Programmed Tools (APT) language

24、 for NC that uses statements similar to English language to define the part geometry, describe the cutting tool configuration, and specify the necessary motions. The development of the APT language was a major step forward in the further development of NC technology. The original NC system were vast

25、ly different from those used punched paper , which was later to replaced by magnetic plastic tape .A tape reader was used to interpret the instructions written on the tape for the machine .Together, all /f this represented giant step forward in the control of machine tools . However ,there were a nu

26、mber of problems with NC at this point in its development. The development of a concept known as numerical control (DNC) solve the paper and plastic tape problems associated with numerical control by simply eliminating tape as the medium for carrying the programmed instructions . In direct numerica

27、l control, machine tools are tied, via a data transmission link, to a host computer and fed to the machine tool as needed via the data transmission linkage. Direct numerical control represented a major step forward over punched tape and plastic tape. However ,it is subject to the same limitation as

28、all technologies that depend on a host computer. When the host computer goes down , the machine tools also experience down time . This problem led to the development of computer numerical control. The development of the microprocessor allowed for the development of programmable logic controllers (P

29、LC) and microcomputers . These two technologies allowed for the development of computer numerical control (CNC).With CNC , each machine tool has a PLC or a microcomputer that serves the same purpose. This allows programs to be input and stored at each individual machine tool. CNC solved the problems

30、 associated downtime of the host computer , but it introduced another problem known as data management . The same program might be loaded on ten different microcomputers with no communication among them. This problem is in the process of being solved by local area networks that connectDigital Signal

31、 Processors The most important of these was that it was difficult or impossible to change the instructions entered on the tape. To made even the most minor adjustments in a program of instructions, it was necessary to interrupt machining operations and make a new tape. It was also still necessary t

32、o run the tape through the reader as many times as there were parts to be produced. Fortunately, computer technology became a reality and soon solved the problems of NC associated with punched paper and plastic tape. The development of a concept known as direct numerical control (DNC) solved the pa

33、per and plastic tape problems associated with numerical control by simply eliminating tape as the medium for carrying the programmed instructions. In direct numerical control, machine tools are tied, via a data transmission link, to a host computer. Programs for operating the machine tools are store

34、d in the host computer and fed to the machine tool an needed via the data transmission linkage. Direct numerical control represented a major step forward over punched tape and plastic tape. However, it is subject to the same limitations as all technologies that depend on a host computer. When the ho

35、st computer goes down, the machine tools also experience downtime. This problem led to the development of computer numerical control. There are numerous situations where analog signals to be processed in many ways, like filtering and spectral analysis , Designing analog hardware to perform these fu

36、nctions is possible but has become less and practical, due to increased performance requirements, flexibility needs , and the need to cut down on development/testing time .It is in other words difficult pm design analog hardware analysis of signals. The act of sampling an signal into thehat are spe

37、cialised for embedded signal processing operations , and such a processor is called a DSP, which stands for Digital Signal Processor . Today there are hundreds of DSP families from as many manufacturers, each one designed for a particular price/performance/usage group. Many of the largest manufactur

38、ers, like Texas Instruments and Motorola, offer both specialised DSP’s for certain fields like motor-control or modems ,and general high-performance DSP’s that can perform broad ranges of processing tasks. Development kits an` software are also available , and there are companies making software de

39、velopment tools for DSP’s that allows the programmer to implement complex processing algorithms using simple “drag ‘n’ drop” methodologies. DSP’s more or less fall into two categories depending on the underlying architecture-fixed-point and floating-point. The fixed-point devices generally operate

40、on 16-bit words, while the floating-point devices operate on 32-40 bits floating-point words. Needless to say , the fixed-point devices are generally cheaper . Another important architectural difference is that fixed-point processors tend to have an accumulator architecture, with only one “general p

41、urpose” register , making them quite tricky to program and more importantly ,making C-compilers inherently inefficient. Floating-point DSP’s behave more like common general-purpose CPU’s ,with register-files. There are thousands of different DSP’s on the market, and it is difficult task finding the

42、 most suitable DSP for a project. The best way is probably to set up a constraint and wishlist, and try to compare the processors from the biggest manufacturers against it. Digital-to-analog conversion In the case of MPEG-Audio decoding , digital compressed data is fed into the DSP which performs

43、the decoding , then the decoded samples have to be converted back into the analog domain , and the resulting signal fed an amplifier or similar audio equipment . This digital to analog conversion (DCA) is performed by a circuit with the same name & Different DCA’s provide different performance and q

44、uality , as measured by THD (Total harmonic distortion ), number of bits, linearity , speed, filter characteristics and other things. The TLS320family consists of fixed-point, floating-point, multiprocessor digital signal processors (D[Ps) , and foxed-point DSP controllers. TMS320 DSP have an archi

45、tecture designed specifically for real-time signal processing . The’ F/C240 is a number of the’C2000DSP platform , and is optimized for control applications. The’C24x series of DSP controllers combines this real-time processing capability with controller peripherals to create an ideal solution for c

46、ontrol system applications. The following characteristics make the TMS320 family the right choice for a wide range of processing applications: --- Very flexible instruction set --- Inherent operational flexibility ---High-speed performance ---Innovative parallel architecture ---Cost effectiven

47、ess Devices within a generation of the TMS320 family have the same CPU structure but different on-chip memory and peripheral configurations. Spin-off devices use new combinations of On-chip memory and peripherals to satisfy a wide range of needs in the worldwide electronics market. By integrating

48、memory and peripherals onto a single chip , TMS320 devices reduce system costs and save circuit board space. The 16-bit ,fixed-point DSP core of the ‘C24x devices provides analog designers a digital solution that does not sacrifice the precision and performance of their system performance can be en

49、hanced through the use of advanced control algorithms for techniques such as adaptive control , Kalman filtering , and state control. The ‘C24x DSP controller offer reliability and programmability . Analog control systems, on the other hand ,are hardwired solutions and can experience performance deg

50、radation due to aging , component tolerance, and drift. The high-speed central processing unit (CPU) allows the digital designer to process algorithms in real time rather than approximate results with look-up tables. The instruction set of these DSP controllers, which incorporates both signal proce

51、ssing instructions and general-purpose control functions, coupled with the extensive development time and provides the same ease of use as traditional 8-and 16-bit microcontrollers. The instruction set also allows you to retain your software investment when moving from other general-purpose‘C2xx gen

52、eration ,source code compatible with the’C2x generation , and upwardly source code compatible with the ‘C5x generation of DSPs from Texas Instruments. The ‘C24x architecture is also well-suited for processing control signals. It uses a 16-bit word length along with 32-bit registers for storing inte

53、rmediate results, and has two hardware shifters available to scale numbers independently of the CPU . This combination minimizes quantization and truncation errors, and increases p2ocessing power for additional functions. Such functions might include a notch filter that could cancel mechanical reson

54、ances in a system or an estimation technique that could eliminate state sensors in a system. The ‘C24xDSP controllers take advantage of an set of peripheral functions that allow Texas Instruments to quickly configure various series members for different price/ performance points or for application

55、optimization. The DSP controller peripheral library is continually growing and changing to suit the of tomorrow’s embedded control marketplace. The TMS320F/C240 is the first standard device introduced in the ‘24x series of DSP controllers. It sets the standard for a single-chip digital motor contr

56、oller. The ‘240 can execute 20 MIPS. Almost all instructions are executed in a simple cycle of 50 ns . This high performance allows real-time execution of very comple8 control algorithms, such as adaptive control and Kalman filters. Very high sampling rates can also be used to minimize loop delays.

57、 The ‘ 240 has the architectural features necessary for high-speed signal processing and digital control functions, and it has the peripherals needed to provide a single-chip solution for motor control applications. The ‘240 is manufactured using submicron CMOS technology, achieving a log power dis

58、sipation rating . Also included are several power-down modes for further power savings. Some applications that benefit from the advanced processing power of the ‘240 include: ---Industrial motor drives ---Power inverters and controllers ---Automotive systems, such as electronic power steering ,

59、antilock brakes, and climate control ---Appliance and HVAC blower/ compressor motor controls ---Printers, copiers, and other office products ---Tape drives, magnetic optical drives, and other mass storage products ---Robotic and CNC milling machines To function as a system manager, a DSP must h

60、ave robust on-chip I/O and other peripherals. The event manager of the ‘240 is unlike any other available on a DSP . This application-optimized peripheral unit , coupled with the high performance DSP core, enables the use of advanced control techniques for high-precision and high-efficiency full var

61、iable-speed control of all motor types. Include in the event manager are special pulse-width modulation (PWM) generation functions, such as a programmable dead-band function and a space vector PWM state machine for 3-phase motors that provides state-of-the-art maximum efficiency in the switching of

62、power transistors. There independent up down timers, each with it’s own compare register, support the generation of asymmetric (noncentered) as well as symmetric (centered) PWM waveforms. Open-Loop and Closed-Loop Control Open-loop Control Systems The word automatic implies that there is a certa

63、in amount of sophistication in the control system. By automatic, it generally means That the system is usually capable of adapting to a variety of operating conditions and is able to respond to a class of inputs satisfactorily . However , not any type of control system has the automatic feature. Usu

64、ally , the automatic feature is achieved by feed. g the feedback structure, it is called an open-loop system , which is the simplest and most economical type of control system.inaccuracy lies in the fact that one may not know the exact characteristics of the further ,which has a definite bearing on

65、 the indoor temperature. This alco points to an important disadvantage of the performance of an open -loop control system, in that the system is not capable of adapting to variations in environmental conitions or to external disturbances. In the case of the furnace control, perhaps an experienced pe

66、rson can provide control for a certain desired temperature in the house; but id the doors or windows are opened or closed intermittently during the operating period, the final temperature inside the house will not be accurately regulated by the open-loop control. Closed-Loop Control Systems What is missing in the open-loop control system for more accurate and more adaptable control is a link or feedback from the output to the input of the system . In order to obtain more accurate bontrol, th