五自由度工業(yè)機(jī)械手結(jié)構(gòu)設(shè)計(jì)【5自由度】

喜歡這套資料就充值下載吧。資源目錄里展示的都可在線預(yù)覽哦。下載后都有，請(qǐng)放心下載，文件全都包含在內(nèi)，圖紙為CAD格式可編輯，有疑問咨詢QQ:414951605 或 1304139763p 外文翻譯 現(xiàn)代機(jī)械工程,2011年,47-55 http://dx.doi:10.4236/mme.2011.12007 在線發(fā)表在2011年11月(http://www.SciRP.org/journal/mme) 設(shè)計(jì)和開發(fā)有競(jìng)爭(zhēng)力的低成本的四自由度 機(jī)械臂 Ashraf Elfasakhany1'2, Eduardo Yanez2, Karen Baylon2, Ricardo Salgado2 1Department of Mechanical Engineering, Faculty of Engineering, Taif University, Al-Haweiah, Saudi Arabia 2Tecnológico de Monterrey, Campus Ciudad Juárez, Ciudad Juarez, Mexico 郵箱: ashr12000@yahoo.com 2011年10月19日收到；2011年11月7日修訂；2011年11月15日接受 摘要 這項(xiàng)工作的重點(diǎn)是設(shè)計(jì)，開發(fā)和實(shí)施有競(jìng)爭(zhēng)力的機(jī)械手手臂的控制和粗短的成本提高。機(jī)械手手臂的設(shè)計(jì)具有四個(gè)自由度，才能完成準(zhǔn)確的簡(jiǎn)單的任務(wù)，如光材料處理，這將成為一個(gè)移動(dòng)平臺(tái)，成為工業(yè)勞動(dòng)力的助理。機(jī)械手配備有伺服電機(jī)做武器和執(zhí)行的手臂動(dòng)作之間的聯(lián)系。伺服馬達(dá)包括編碼器，所以沒有控制器實(shí)現(xiàn)。我們使用LabVIEW控制機(jī)械手進(jìn)行逆運(yùn)動(dòng)學(xué)計(jì)算，并將正確的角度對(duì)單片機(jī)的串行驅(qū)動(dòng)伺服電機(jī)改變位置的能力，速度和加速度。機(jī)械手手臂的測(cè)試進(jìn)行了驗(yàn)證結(jié)果表明，它工作正常。 關(guān)鍵詞：機(jī)械手手臂，成本低，設(shè)計(jì)，驗(yàn)證，四個(gè)自由度，伺服電機(jī)，Arduino，機(jī)械手控制，Labview機(jī)械手控制 第 11 頁 共 11 頁 1、簡(jiǎn)介 機(jī)械手實(shí)際上是術(shù)語定義為制造業(yè)研究，設(shè)計(jì)和使用機(jī)械手系統(tǒng) [1]。機(jī)械手通常被用于執(zhí)行不安全的，危險(xiǎn)的，高度重復(fù)性的，和不愉快的任務(wù)。他們有許多不同的功能，如材料處理，組裝，焊接，電阻焊接，工具機(jī)的加載和卸載功能，繪畫，噴涂等。 主要有兩種不同的機(jī)械手服務(wù)機(jī)械手和工業(yè)機(jī)械手。服務(wù)機(jī)械手是機(jī)械手操作半或全自動(dòng)履行服務(wù)的人和設(shè)備的健康有益，不包括制造過程[2]。工業(yè)機(jī)械手，另一方面，正式定義的ISO作為自動(dòng)控制、多用途的機(jī)械手在三軸以上的[1]可編程。工業(yè)機(jī)械手是用來移動(dòng)材料，零件，工具或?qū)ｉT的設(shè)備，通過各種編程動(dòng)作執(zhí)行各種任務(wù)。工業(yè)機(jī)械手系統(tǒng)不僅包括工業(yè)機(jī)械手，而且任何設(shè)備和/或傳感器所需的機(jī)械手以及測(cè)序或監(jiān)控通信接口完成任務(wù)。 在2007世界的市場(chǎng)增長(zhǎng)了3%，約114000個(gè)新安裝的工業(yè)機(jī)械手。2007年底，大約有一百萬的工業(yè)機(jī)械手的使用，估計(jì)有50000的服務(wù)機(jī)械手工業(yè)用[3]比較。 由于增加的工業(yè)機(jī)械手手臂的使用，一種進(jìn)化的主題試圖模仿人類的運(yùn)動(dòng)開始在一個(gè)詳細(xì)的模式。例如，一組學(xué)生在韓國做了一個(gè)創(chuàng)新的機(jī)械臂以舞蹈方面，賬戶重設(shè)計(jì)，書法書寫和顏色分類[4]。另一組工程師在美國開發(fā)的八自由度機(jī)械手手臂。這個(gè)機(jī)械手是能夠從一筆一球的許多形狀掌握許多對(duì)象和模擬也人[5]手。在太空，航天飛機(jī)遙控操縱系統(tǒng)，稱為SSRMS或操控，和它的繼任者是實(shí)例的多自由度機(jī)械手手臂，已被用于執(zhí)行各種任務(wù)，如檢查使用一種專門部署的繁榮的航天飛機(jī)有照相機(jī)和傳感器安裝在端部執(zhí)行器和衛(wèi)星的部署和檢索從航天飛機(jī)的貨艙演習(xí)[6]。 在墨西哥，科學(xué)家正在開發(fā)許多機(jī)械手手臂的設(shè)計(jì)，和墨西哥政府估計(jì)，墨西哥約有11000的機(jī)械臂，用于在不同的工業(yè)應(yīng)用。然而，專家認(rèn)為，機(jī)械手的手臂遠(yuǎn)不僅是高質(zhì)量的，但也準(zhǔn)確，重復(fù)性，和粗短的成本。 大多數(shù)的機(jī)械手是建立一個(gè)操作的教導(dǎo)和重復(fù)技術(shù)。在這種模式下，一個(gè)訓(xùn)練有素的操作員（程序員）通常使用的便攜式控制裝置（一種示教）教會(huì)機(jī)械手任務(wù)手動(dòng)。機(jī)械手的速度在這些編程會(huì)話是緩慢的。 目前的工作是一個(gè)兩相的項(xiàng)目的一部分，這需要一個(gè)移動(dòng)機(jī)械手能夠運(yùn)輸工具從儲(chǔ)藏室的工業(yè)電池。在這一階段的項(xiàng)目中，進(jìn)行了在蒙特雷技術(shù)大學(xué)，墨西哥，主要是設(shè)計(jì)，一個(gè)工業(yè)機(jī)械手的手臂粗短的成本的開發(fā)和實(shí)施，準(zhǔn)確和優(yōu)越的控制。這個(gè)機(jī)械手手臂的設(shè)計(jì)具有四個(gè)自由度，才能完成簡(jiǎn)單的任務(wù)，如光材料處理，這將成為一個(gè)移動(dòng)平臺(tái)，成為工業(yè)勞動(dòng)力的助理。 2、機(jī)械設(shè)計(jì) 機(jī)械手手臂的機(jī)械設(shè)計(jì)是基于一個(gè)機(jī)械手具有類似功能的一個(gè)人類手臂[6-8]。這種機(jī)械手的鏈接的節(jié)點(diǎn)允許的旋轉(zhuǎn)運(yùn)動(dòng)和操縱器的鏈接的連接被認(rèn)為是形成一個(gè)運(yùn)動(dòng)鏈。機(jī)械手的運(yùn)動(dòng)鏈的業(yè)務(wù)端稱為ARM工具末端或結(jié)束，這是類似于人類的手。圖1顯示了機(jī)械臂的機(jī)械設(shè)計(jì)的自由體圖。如圖所示，端部執(zhí)行器是不包括在設(shè)計(jì)因?yàn)樯逃脢A具的使用。這是因?yàn)?，末端是一個(gè)系統(tǒng)的最復(fù)雜的部分和，反過來，它是更容易和經(jīng)濟(jì)地使用一個(gè)商業(yè)比建造它。 圖2顯示了機(jī)械手臂的工作區(qū)。這是四自由度機(jī)械手手臂的典型工作區(qū)（4自由度）。機(jī)械設(shè)計(jì)是有限的4自由度主要是因?yàn)檫@樣的設(shè)計(jì)允許最必要的運(yùn)動(dòng)和保持成本和機(jī)械手的復(fù)雜競(jìng)爭(zhēng)。因此，關(guān)節(jié)的旋轉(zhuǎn)運(yùn)動(dòng)被限制在旋轉(zhuǎn)是圍繞兩個(gè)軸在肩、肘、腕關(guān)節(jié)周圍只有一個(gè)，見圖1。 機(jī)械手關(guān)節(jié)通常由電動(dòng)機(jī)驅(qū)動(dòng)的。伺服電機(jī)的選擇，因?yàn)樗鼈儼ň幋a器可以自動(dòng)提供反饋給電機(jī)和調(diào)整相應(yīng)的位置。然而，這些電機(jī)的缺點(diǎn)是，旋轉(zhuǎn)范圍小于180?跨度，大大減少了區(qū)域達(dá)到的手臂和可能的位置[9]。伺服電機(jī)的資格是基于由結(jié)構(gòu)和可能的負(fù)載所需的最大扭矩選擇。在目前的研究中，用于結(jié)構(gòu)材料，丙烯酸。 圖3顯示了用于負(fù)荷計(jì)算的內(nèi)力圖。計(jì) 算僅為具有最大負(fù)荷節(jié)點(diǎn)進(jìn)行的，因?yàn)槠渌墓?jié)點(diǎn)具有相同的電機(jī)，即電機(jī)移動(dòng)的鏈接沒有問題。計(jì)算中考慮了電機(jī)的重量，50克左右，除了在節(jié)點(diǎn)B電機(jī)的重量，因?yàn)樗怯蛇B接壩進(jìn)行了。圖4顯示的鏈接CB的內(nèi)力圖，其中包含的節(jié)點(diǎn)（B和C）與最高負(fù)荷（帶鏈接的直流和ED）并進(jìn)行計(jì)算如下。 用于轉(zhuǎn)矩的計(jì)算值： Wd = 0.011 kg (DE桿的負(fù)荷) Wc = 0.030 kg (CD桿的負(fù)荷) Wb = 0.030 kg (CB桿的負(fù)荷) L = 1 kg (負(fù)載) Cm = Dm = 0.050 kg (電機(jī)重量) LBC = 0.14 m (BC桿的長(zhǎng)度) LCD = 0.14 m (CD桿的長(zhǎng)度) LDE = 0.05 m (DE桿的長(zhǎng)度) 執(zhí)行在Y軸力的總和，使用荷載如圖4所示，與CY和CB解決，看到方程(1)-(4)。同樣，執(zhí)行在C點(diǎn)時(shí)刻的總和，方程(5），和B點(diǎn)，方程(6)，在B和C獲得轉(zhuǎn)矩，方程(7)和(8)，分別為。 根據(jù)計(jì)算，伺服電機(jī)被選中的是Hextronik HX12K，具有扭矩280盎司 /英寸。該電機(jī)被推薦是因?yàn)樗热魏纹渌?guī)格的汽車便宜得多。自從我們?cè)诮宇^B需要更大的扭矩，見式（8)，我們使用兩個(gè)馬達(dá)在B點(diǎn)遵守扭矩的要求；然而，一個(gè)電機(jī)是足夠的其他關(guān)節(jié)。在節(jié)點(diǎn)B使用兩個(gè)電動(dòng)機(jī)比使用一個(gè)大的電機(jī)560盎司/便宜多了。電機(jī)的相關(guān)特性，可以在圖5所示，是他們可以旋轉(zhuǎn)60度在130毫秒，他們有一個(gè)重量47.9克每。 一旦確定了機(jī)械手手臂和電機(jī)的初始尺寸，設(shè)計(jì)使用SolidWorks平臺(tái)上進(jìn)行；設(shè)計(jì)應(yīng)認(rèn)真考慮的壓克力板，碎片會(huì)被連接到每個(gè)其他方式的厚度。用于使機(jī)械手的壓克力板材1 / 8厚，薄被選中是因?yàn)樗菀准庸ぃ哂辛己玫哪土可佟? 在設(shè)計(jì)過程中，我們面臨著一些困難由于連接薄丙烯酸部分強(qiáng)烈的方式。這是燒、加入丙烯酸部分和沒有和球隊(duì)認(rèn)為基于螺釘和螺母的機(jī)械結(jié)會(huì)比其他的替代品很強(qiáng)的所需的工具，如膠為例。為了做到這一點(diǎn)，一個(gè)小的功能被設(shè)計(jì)允許緊固螺栓與螺母無須螺釘在薄的丙烯酸層。這個(gè)過程的結(jié)果如圖6所示的三維設(shè)計(jì)。 最終的設(shè)計(jì)，每一部分是印刷在全規(guī)模的厚紙板，然后驗(yàn)證這些尺寸和裝配的接口。反過來，我們建立了機(jī)械手的第一個(gè)原型。其次，機(jī)械手手臂的部分被加工從壓克力板使用圓鋸和真皮的工具。詳細(xì)的部分是在一個(gè)專業(yè)車間自做的機(jī)械手手臂的部分太小，為完成這些小的和準(zhǔn)確的削減是不容易的。 在發(fā)動(dòng)機(jī)裝配機(jī)械手的零件時(shí)，彈出幾個(gè)問題。有臨界點(diǎn)，沒有抵抗的緊固，反過來，可能會(huì)破壞；因此，考慮在這些點(diǎn)援軍。機(jī)械手手臂的最終結(jié)果如圖7所示。 3、機(jī)械手臂逆運(yùn)動(dòng)學(xué) 為了驗(yàn)證該機(jī)械臂逆運(yùn)動(dòng)學(xué)正確的定位，進(jìn)行了計(jì)算。這樣的計(jì)算是用來從一個(gè)給定的位置使用笛卡爾坐標(biāo)系統(tǒng)獲得各電機(jī)的角，如圖8所示。每個(gè)電機(jī)都有特定的功能：在Y軸電機(jī)位于聯(lián)盟最后的元素的位置，電機(jī)B和C的位置最終元件在X軸和Z軸。 問題是利用XZ平面簡(jiǎn)化，如圖9所示。在以下的已知值被定義[ 9 ]： LAB：前臂長(zhǎng)度。 LBC：手臂的長(zhǎng)度。 Z：在Z軸的位置。 X：在X軸的位置。 Y：在Y軸的位置。 利用三角關(guān)系，如圖9所示，得到電機(jī)角度θ2和θ1，如方程（9）和（10） 電機(jī)B要用θ1和電機(jī)C要用θ2。用于電機(jī)的計(jì)算從方程的角度（11）。這些計(jì)算，得到他們所采取的行動(dòng)將整個(gè)結(jié)構(gòu)的具體位置伺服電機(jī)的角。 4、末端執(zhí)行器的選擇 端部執(zhí)行器可能是一個(gè)最重要和最復(fù)雜的系統(tǒng)的一部分。明智的，它是更容易和經(jīng)濟(jì)地使用一個(gè)商業(yè)比建造它。端部執(zhí)行器的變化主要是根據(jù)任務(wù)的機(jī)械手手臂完成應(yīng)用程序；它可以是氣動(dòng)，電動(dòng)或液壓。由于我們的機(jī)械手臂的基礎(chǔ)電系統(tǒng)中，我們可以選擇末端執(zhí)行器的電氣基礎(chǔ)。此外，我們的系統(tǒng)的主要應(yīng)用是處理，因此，我們的末端執(zhí)行器的推薦式夾持器，如圖10所示。請(qǐng)注意，端部執(zhí)行器是由一個(gè)伺服電機(jī)控制，反過來，用于我們的機(jī)械手臂總伺服電機(jī)5電機(jī)，將移動(dòng)結(jié)構(gòu)。 5、機(jī)械手手臂的控制 機(jī)械手的手臂可以自動(dòng)或手動(dòng)控制。在手動(dòng)模式下，一個(gè)訓(xùn)練有素的操作員（程序員）通常使用的便攜式控制裝置（一種示教）教會(huì)機(jī)械手手動(dòng)完成其任務(wù)。機(jī)械手的速度在這些編程會(huì)話是緩慢的。在目前的工作，我們附上了兩種模式。 針對(duì)所提出的機(jī)械手手臂的控制基本上由三個(gè)層次：一個(gè)微控制器，驅(qū)動(dòng)器，和一個(gè)計(jì)算機(jī)用戶界面。該系統(tǒng)具有獨(dú)特的特性，允許靈活的編程和控制方法，它是用逆向運(yùn)動(dòng)學(xué)實(shí)現(xiàn)；另外它還可以在全手動(dòng)模式的實(shí)現(xiàn)?？刂齐娮釉O(shè)計(jì)如圖11所示。 微控制器是一個(gè)ATMEGA 368配備開發(fā)/規(guī)劃委員會(huì)命名為“伊諾”，如圖12所示。編程語言與C語言非常相似但包括幾次有助于I/O端口，控制，定時(shí)器，串行通信。該微控制器被選中是因?yàn)樗幸粋€(gè)較低的價(jià)格，這是很容易的程序，編程語言是簡(jiǎn)單的，和中斷是可以為這個(gè)特殊的芯片。 該驅(qū)動(dòng)程序使用的是一六通道微大師伺服控制板。它支持三種控制方式：USB直接連接到計(jì)算機(jī)，TTL串口用于嵌入式系統(tǒng)，如Arduino微處理器，和獨(dú)立的主機(jī)控制器的免費(fèi)應(yīng)用程序內(nèi)部腳本。該控制器，如圖13所示，包括一個(gè)0.25μ的位置、速度和加速度控制分辨率內(nèi)置。 用戶界面取決于使用的控制方法，即，逆運(yùn)動(dòng)學(xué)或全手動(dòng)模式。在下面的，是描述每個(gè)接口： 5.1、逆運(yùn)動(dòng)學(xué)控制 在這種控制方法中，用戶輸入的坐標(biāo)位置的夾持器應(yīng)。作為結(jié)果，生成的界面與LabVIEW通過可視化的用戶，如圖14所示。程序自動(dòng)執(zhí)行逆運(yùn)動(dòng)學(xué)計(jì)算獲得的角度，每個(gè)電機(jī)應(yīng)該然后發(fā)送命令到微控制器或直接驅(qū)動(dòng)，將移動(dòng)機(jī)械手到指定位置。通信與RS-232協(xié)議的執(zhí)行。在下面，你可以看到的LabVIEW用戶界面的輸入和輸出。 LabVIEW用戶界面輸入： X軸的位置。 Y軸的位置。 Z軸的位置。 夾口。 夾持器攻角。 串行端口。 LabVIEW用戶接口輸出： 電機(jī)的一角。 電機(jī)B1角。 電機(jī)B2角。 電動(dòng)機(jī)的角。 迎角。 夾持角。 這種輸出變量處理，通過適當(dāng)?shù)姆绞桨l(fā)送，使信息能以正確的方式解釋。輸出是通過串口，與控制器通信發(fā)送。當(dāng)按鈕被點(diǎn)擊“移動(dòng)”，一個(gè)過程將采取的地方，如圖15所示。這個(gè)動(dòng)作，機(jī)械手的手臂會(huì)根據(jù)輸入的值改變它的位置。此外，它已待機(jī)按鈕來停止通信控制器。 這種方法的主要優(yōu)點(diǎn)是，它使用的運(yùn)動(dòng)的一種有效方法，提供了更多的功能，可以實(shí)現(xiàn)，如位置和序列學(xué)習(xí)。一個(gè)缺點(diǎn)，另一方面，是可能的位置，擁有有效的角度后，逆運(yùn)動(dòng)學(xué)計(jì)算十分有限，因?yàn)樗欧姍C(jī)有180?約束。 5.2、手動(dòng)控制 這種類型的控制是一個(gè)額外的選擇，我們的系統(tǒng)在特定的位置上有用。在強(qiáng)制性的位置的情況下，逆運(yùn)動(dòng)學(xué)計(jì)算模式不能有效的角度，我們可以使用手動(dòng)控制代替?；旧?，手動(dòng)控制包括一系列的模擬輸入，如電位器，連接微控制器，將解釋的價(jià)值和發(fā)送指令給伺服驅(qū)動(dòng)器。為了實(shí)現(xiàn)這一點(diǎn)，一個(gè)控制板，如圖16所示，應(yīng)該建立以工作作為用戶界面?？赡艿膶?shí)現(xiàn)包括教學(xué)特點(diǎn)，單片機(jī)存儲(chǔ)位置在內(nèi)存中，通過鍵盤或一系列的開關(guān)可以回憶起這些位置。 6、測(cè)試和驗(yàn)證 進(jìn)行了測(cè)試，驗(yàn)證了機(jī)械手臂及其組件。測(cè)試涵蓋特定元素和整體的系統(tǒng)，如圖17所示。為單片機(jī)，測(cè)試是發(fā)生在發(fā)送不同的命令由軟件對(duì)單片機(jī)和檢查的變化對(duì)輸出被連接到一個(gè)伺服電機(jī)，根據(jù)命令，打開或關(guān)閉。 伺服電機(jī)是通過發(fā)送不同的直接脈沖每個(gè)伺服電機(jī)和驗(yàn)證移動(dòng)到合適的位置響應(yīng)隨后測(cè)試。我們用馬克知道初始位置在哪里，電機(jī)的最終位置是通過發(fā)送一個(gè)信號(hào)確定 用單片機(jī)和，反過來，這是解釋由伺服相比，由編碼器提供的信號(hào)，從而在旋轉(zhuǎn)到所需的位置。在這個(gè)試驗(yàn)中，伺服電機(jī)是不相符合的機(jī)械手手臂系統(tǒng)由于不正確的極化。 伺服電機(jī)的驅(qū)動(dòng)程序也使用LabVI- EW軟件發(fā)送命令發(fā)出特定的命令，其中有一個(gè)電機(jī)連接到根據(jù)推薦改變位置驅(qū)動(dòng)單片機(jī)測(cè)試。它是要注意，在項(xiàng)目的不同的伺服電機(jī)驅(qū)動(dòng)器選擇但他們和單片機(jī)之間的通信相關(guān)的幾個(gè)問題是目前開始重要的。所以我們選擇一個(gè)驅(qū)動(dòng)器，允許數(shù)據(jù)被直接發(fā)送到計(jì)算機(jī)，它只有一個(gè)USB線，因此，單片機(jī)只會(huì)用在人工控制的實(shí)施情況。 其他試驗(yàn)進(jìn)行驗(yàn)證整個(gè)系統(tǒng)的功能，如圖18所示。這些測(cè)試被介紹在LabVIEW界面的具體位置和測(cè)量參考點(diǎn)，最后一點(diǎn)，驗(yàn)證之間的距離發(fā)生：從逆運(yùn)動(dòng)學(xué)正確的轉(zhuǎn)換，指定的角度和電機(jī)的轉(zhuǎn)速之間的關(guān)系。 機(jī)械手手臂的測(cè)試和驗(yàn)證是一個(gè)需要長(zhǎng)時(shí)間的任務(wù)，因?yàn)樾枰啻蔚?。在我們的測(cè)試中，出現(xiàn)許多問題：錯(cuò)誤的角度計(jì)算，電動(dòng)機(jī)的錯(cuò)誤的校正，與物理的角度和位置的測(cè)量問題，和一個(gè)伺服電機(jī)因過載燒毀，沒有預(yù)期。 7、結(jié)果與討論 在不同操作條件下的機(jī)械手手臂，結(jié)果如下： 7.1、伺服電機(jī)的運(yùn)動(dòng)范圍 由于這種類型的電機(jī)規(guī)格包含具有小于180度的跨度得到伺服電機(jī)的極限。所有電機(jī)的實(shí)際范圍被發(fā)現(xiàn)是在范圍125 - 142度，如表1所示。這清楚地表明，機(jī)械手臂的實(shí)際操作不同于標(biāo)準(zhǔn)的情況下。 7.2、電流消耗 電流消耗取決于負(fù)載和機(jī)械手手臂的運(yùn)動(dòng)型。在目前的研究中，有4個(gè)層次的電流消耗： ?低（從0到200 mA）。這種消費(fèi)發(fā)生時(shí)，機(jī)械手是靜止的（不運(yùn)動(dòng)的情況下）。 ?正常（從200到500 mA）。當(dāng)機(jī)械手手臂移動(dòng)的能力去目標(biāo)沒有大扭矩的需要。 ?高（500～900 Ma）。這個(gè)范圍是在負(fù)載下進(jìn)入。通過克服慣性載荷的初始時(shí)刻，正常范圍內(nèi)需要的地方。 過載（電流超過900毫安）。負(fù)荷太重，電機(jī)不能移動(dòng)。在該條件下超過一分鐘，電機(jī)會(huì)燃燒，即它是不能使用。 7.3、最大載荷 使用不同的權(quán)重，得到了這些結(jié)果；一袋玉米是用規(guī)模來確定包的重量。結(jié)果進(jìn)行了通過使用機(jī)械手手臂拿起袋子，把它移動(dòng)到特定的位置。表2列出了當(dāng)前消費(fèi)在袋玉米不同的權(quán)重。從表2中，可以看出，機(jī)械手可以無負(fù)荷低于50克的問題移動(dòng)。在負(fù)載60克，機(jī)械手手臂開始有困難，經(jīng)過80克惡劣的情況電機(jī)發(fā)生不可逆煩的損傷。 7.4、最后的位置 結(jié)果表明，該機(jī)械手手臂的精度不同的移動(dòng)量（小于50克）表3給出了。如圖所示，該機(jī)械手能夠執(zhí)行移動(dòng)到指定的位置。然而，這種運(yùn)動(dòng)是不光滑的，有時(shí)電機(jī)沒有足夠的力，特別是當(dāng)負(fù)載較重時(shí)。此外，有些問題可能是由于同步兩個(gè)底部的汽車出現(xiàn)。兩個(gè)電機(jī)的步驟并不是巧合，導(dǎo)致在丙烯酸部分張力，這太多會(huì)打破部分案例。 8、結(jié)論 本文介紹了設(shè)計(jì)和發(fā)展機(jī)械手手臂，有人才來完成簡(jiǎn)單的任務(wù)，如光材料處理。機(jī)械手手臂的設(shè)計(jì)和建造的丙烯酸材料在伺服電機(jī)進(jìn)行武器和執(zhí)行的手臂動(dòng)作之間聯(lián)系。伺服馬達(dá)包括編碼器，所以沒有控制器實(shí)現(xiàn)的；然而，電機(jī)的旋轉(zhuǎn)范圍小于180o跨度，這大大降低了的胳膊和可能的位置到達(dá)區(qū)。機(jī)械手手臂的設(shè)計(jì)是有限的，由于這個(gè)設(shè)計(jì)允許最必要的運(yùn)動(dòng)和保持成本和復(fù)雜性的機(jī)械手具有四個(gè)自由度。端部執(zhí)行器是不包括在設(shè)計(jì)因?yàn)樯逃脢A具的使用，因?yàn)樗歉菀缀徒?jīng)濟(jì)地使用一個(gè)商業(yè)比建造它。 在設(shè)計(jì)過程中，我們面臨著一些困難由于連接薄丙烯酸部分強(qiáng)烈的方式。采用了一種基于螺釘和螺母的機(jī)械連接，以實(shí)現(xiàn)這一目標(biāo)，一個(gè)小的功能被設(shè)計(jì)允許緊固螺栓與螺母無須螺釘在薄的丙烯酸層。 控制的機(jī)械手手臂，三的方法來實(shí)現(xiàn)的：一個(gè)微控制器，驅(qū)動(dòng)器，和一個(gè)計(jì)算機(jī)用戶界面。該系統(tǒng)具有獨(dú)特的特性，允許靈活的編程和控制方法，它是用逆向運(yùn)動(dòng)學(xué)實(shí)現(xiàn)；另外它還可以在全手動(dòng)模式的實(shí)現(xiàn)。這個(gè)機(jī)械手手臂與別人比現(xiàn)有的機(jī)械手手臂要便宜得多，也可以控制所有電腦中的流動(dòng)，利用LabVIEW接口。 幾個(gè)測(cè)試進(jìn)行驗(yàn)證的機(jī)械手臂，測(cè)試涵蓋特定元素和整體的系統(tǒng)；在不同的操作條件，結(jié)果表明信任機(jī)械手手臂了。 9、參考文獻(xiàn) [1]操作工業(yè)機(jī)械手的詞匯，國際標(biāo)準(zhǔn)化組織標(biāo)準(zhǔn)8373，1994。 [2]工業(yè)和服務(wù)機(jī)械手，IFR國際機(jī)械手聯(lián)盟，2010。 [3]案例研究和機(jī)械手投資的收益，IFR統(tǒng)計(jì)系，2008。 [4] J.W.王、R.J.張等?！岸喙δ苤悄軝C(jī)械手的手臂”，F(xiàn)UZZ-IEEE雜志，韓國，2009八月20-24，pp.1995-2000。 [5] L.B.Duc，M.賽弗汀等?！霸O(shè)計(jì)的8自由度仿人機(jī)械手手臂”，國際會(huì)議上的智能和先進(jìn)的系統(tǒng)，吉隆坡，2007十一月25-28日，pp.1069-1074。 [6]C.R. Carignan，G.G.格夫克和B.J.羅伯茨，“太空任務(wù)設(shè)計(jì)簡(jiǎn)介：太空機(jī)械手，空間機(jī)械手研討會(huì)”，馬里蘭大學(xué)，巴爾的摩，2002日26。 [7]職業(yè)安全與健康管理技術(shù)手冊(cè)，OSHA 3167，美國勞工部，1970。 [8] B.Siciliano, L.Sciavicco, L.Villani and G.Oriolo，”機(jī)械手，建模，規(guī)劃和控制，”Springer，倫敦，2009。 [9] M.P.Groover and M.Weiss,“探索頻道的產(chǎn)業(yè)，工學(xué)，programacion Y Aplicaciones，“MC GRAW山，墨西哥城，1989。  五自由度工業(yè)機(jī)械手結(jié)構(gòu)設(shè)計(jì) [摘要]機(jī)械手是機(jī)器進(jìn)化和科學(xué)技術(shù)發(fā)展的必然結(jié)果，機(jī)械手從問世到現(xiàn)在經(jīng)過50多年的發(fā)展，在國民經(jīng)濟(jì)，科學(xué)研究以至整個(gè)社會(huì)領(lǐng)域發(fā)揮著越來越顯著的作用，成為人們生活學(xué)習(xí)中的好幫手，近十年來各種用途的機(jī)械手得到了更廣泛的應(yīng)用，如焊接、噴漆、搬運(yùn)等用于制造車間的工業(yè)機(jī)械手。 學(xué)習(xí)了機(jī)械手技術(shù)知識(shí)，查閱了大量的文獻(xiàn)資料，對(duì)國內(nèi)外機(jī)械手、主要是工業(yè)機(jī)械手的現(xiàn)狀有了比較詳細(xì)的了解。在此基礎(chǔ)上，結(jié)合本人的設(shè)想，和設(shè)計(jì)工作中需要解決的任務(wù)，本文主要研究機(jī)械手總體結(jié)構(gòu)進(jìn)行設(shè)計(jì)，主要進(jìn)行以下工作: 本體結(jié)構(gòu)設(shè)計(jì)，本機(jī)械手手臂結(jié)構(gòu)方案確定后要運(yùn)用AutoCAD把其平面裝配圖做出。 [關(guān)鍵詞]機(jī)械手、AutoCAD、機(jī)械手臂 1 Five Degree of Freedom Industrial Robot Structure Design Abstract: This paper studied and designed a five-DOF assembly processing robot, and carries on the kinematics and dynamics analysis, simulation. At last static analysis and modal analysis for the key parts of the robot by FEM, compared the analytical results .The main work was as follows: On the basis of actual situation and similar structure, Designed the kinematics and Structural programs for the five-Dof assembly processing robot, and used 3-D software to devise the structure of main part of the second proposal, at last, framed the dimensional model. Complied the assembly processing robot analytical soft and kinematics analytical; calculate the kinematic equations and the positive & reverse solutions, and used the Monte Carlo method to calculate the workspace of the robot , and used the vector product method to construct the speed Jacobian matrix of the robot. At last , according to virtual prototyping technology, simulated the positive & reverse solutions and the speed Jacobian matrix in ADAMS, and compared the simulation results with the analytical results to verify the correctness of the resolution of kinematic. Used second-class Lagrangian method to create the robot model, and deduced the robot dynamics equation. According to compiling dynamics solver program by Mat lab software , The author simulated the inverse problem of dynamics and provided the basis for the control and trajectory planning in the future. The paper studied the five-Dof assembly processing robots and established the foundation for the research of the series of robots in the future. Key words：Assembly Robots；Scheme design； Kinematic Analysis；Dynamic Analysis；Lagrange Method；Finite element method；Modal analysis. 1 目 錄 引言 1 1 工業(yè)機(jī)械手簡(jiǎn)介 2 1.1 機(jī)械手簡(jiǎn)介 2 1.2 機(jī)械手研究現(xiàn)狀及發(fā)展趨勢(shì) 2 1.3 國內(nèi)外機(jī)械手研究現(xiàn)狀 4 1.3.1 國外機(jī)械手研究現(xiàn)狀 4 1.3.2 國內(nèi)機(jī)械手研究現(xiàn)狀 4 1.3.3 工業(yè)機(jī)械手運(yùn)動(dòng)學(xué)系統(tǒng)研究現(xiàn)狀 5 1.3.4 工業(yè)機(jī)械手軌跡規(guī)劃研究的現(xiàn)狀與意義 5 1.4 本文研究的意義及主要內(nèi)容 5 2 機(jī)械手本體結(jié)構(gòu)方案的設(shè)計(jì) 7 2.1 機(jī)械手的工作要求 7 2.2 機(jī)械手機(jī)械設(shè)計(jì)的特點(diǎn) 7 2.2.1 機(jī)械手獨(dú)特的結(jié)構(gòu)特點(diǎn) 7 2.2.2 與機(jī)械手有關(guān)的概念 7 2.3 機(jī)械手手臂結(jié)構(gòu)方案設(shè)計(jì) 8 2.3.1 方案功能設(shè)計(jì)與分析 8 2.3.2 步進(jìn)電機(jī) 9 2.3.3 步進(jìn)電機(jī)選用 9 2.3.4 步進(jìn)電機(jī)型號(hào)、參數(shù)、尺寸 11 3 機(jī)械手的結(jié)構(gòu)設(shè)計(jì) 14 3.1 腕部回轉(zhuǎn)關(guān)節(jié)的設(shè)計(jì) 14 3.1.1腕部設(shè)計(jì)的基本要求 14 3.1.2典型的腕部結(jié)構(gòu) 14 3.1.3腕部回轉(zhuǎn)關(guān)節(jié)的設(shè)計(jì) 14 3.2 小臂回轉(zhuǎn)關(guān)節(jié)的設(shè)計(jì) 14 3.2.1小臂部設(shè)計(jì)的基本要求 14 3.2.2 小臂回轉(zhuǎn)關(guān)節(jié)步進(jìn)電機(jī)和減速器的選擇 15 3.3 大臂回轉(zhuǎn)關(guān)節(jié)的設(shè)計(jì) 15 3.3.1大臂部設(shè)計(jì)的基本要求 15 3.3.2 大臂回轉(zhuǎn)關(guān)節(jié)步進(jìn)及減速器的選擇 15 3.4 腰部回轉(zhuǎn)關(guān)節(jié)的設(shè)計(jì) 16 3.4.1 腰部回轉(zhuǎn)關(guān)節(jié)設(shè)計(jì)要求 16 3.4.2 腰部回轉(zhuǎn)關(guān)節(jié)步進(jìn)電機(jī)及減速器的選擇 16 3.5 氣爪的選擇 16 致謝 18 參考文獻(xiàn) 19 外文翻譯 20 第 4 頁 共 3 頁 題 目 五自由度工業(yè)機(jī)械手結(jié)構(gòu)設(shè)計(jì) 所在學(xué)院 年 月 日 ?? 任務(wù)書 ? ?? 院(系) 專業(yè)班級(jí) 學(xué)生姓名 一、畢業(yè)設(shè)計(jì)題目 五自由度工業(yè)機(jī)械手結(jié)構(gòu)設(shè)計(jì) 二、畢業(yè)設(shè)計(jì)工作自 年 月_ __日 起至 年 月 日止 三、畢業(yè)設(shè)計(jì)進(jìn)行地點(diǎn): 四、畢業(yè)設(shè)計(jì)內(nèi)容要求： （1）． 查閱國內(nèi)外文獻(xiàn)資料，了解機(jī)械手結(jié)構(gòu)的現(xiàn)狀與趨勢(shì) （2）． 熟悉計(jì)算機(jī)繪圖軟件的使用，能利用它對(duì)機(jī)械手零部件進(jìn)行建模 （3）． 確定機(jī)械手的本體結(jié)構(gòu)，并對(duì)機(jī)械手的驅(qū)動(dòng)機(jī)構(gòu)進(jìn)行設(shè)計(jì)計(jì)算 （4）． 畫出所設(shè)計(jì)的重要零件圖和裝配圖 （5）． 繪制傳動(dòng)鏈簡(jiǎn)圖 （6）． 編寫設(shè)計(jì)說明書，具體要求見《XXXX學(xué)院畢業(yè)設(shè)計(jì)論文（說明書）撰寫規(guī)范》 接受設(shè)計(jì)任務(wù)開始執(zhí)行日期 學(xué)生簽名 第 2 頁 共 2 頁 Modern Mechanical Engineering, 2011, 1, 47-55 doi:10.4236/mme.2011.12007 Published Online November 2011 (http:/www.SciRP.org/journal/mme) Copyright 2011 SciRes. MME Design and Development of a Competitive Low-Cost Robot Arm with Four Degrees of Freedom Ashraf Elfasakhany1,2, Eduardo Yanez2, Karen Baylon2, Ricardo Salgado2 1Department of Mechanical Engineering, Faculty of Engineering, Taif University, Al-Haweiah, Saudi Arabia 2Tecnolgico de Monterrey, Campus Ciudad Jurez, Ciudad Juarez, Mexico E-mail: Received October 19, 2011; revised November 7, 2011; accepted November 15, 2011 Abstract The main focus of this work was to design, develop and implementation of competitively robot arm with en- hanced control and stumpy cost. The robot arm was designed with four degrees of freedom and talented to accomplish accurately simple tasks, such as light material handling, which will be integrated into a mobile platform that serves as an assistant for industrial workforce. The robot arm is equipped with several servo motors which do links between arms and perform arm movements. The servo motors include encoder so that no controller was implemented. To control the robot we used Labview, which performs inverse kinematic calculations and communicates the proper angles serially to a microcontroller that drives the servo motors with the capability of modifying position, speed and acceleration. Testing and validation of the robot arm was carried out and results shows that it work properly. Keywords: Robot Arm, Low-Cost, Design, Validation, Four Degrees of Freedom, Servo Motors, Arduino Robot Control, Labview Robot Control 1. Introduction The term robotics is practically defined as the study, design and use of robot systems for manufacturing 1. Robots are generally used to perform unsafe, hazardous, highly repetitive, and unpleasant tasks. They have many different functions such as material handling, assembly, arc welding, resistance welding, machine tool load and unload functions, painting, spraying, etc. There are mainly two different kinds of robots: a ser- vice robot and an industrial robotic. Service robot is a ro- bot that operates semi or fully autonomously to perform services useful to the well-being of humans and equipment, excluding manufacturing operations 2. Industrial robot, on the other hand, is officially defined by ISO as an auto- matically controlled and multipurpose manipulator pro- grammable in three or more axis 1. Industrial robots are designed to move material, parts, tools, or specialized de- vices through variable programmed motions to perform a variety of tasks. An industrial robot system includes not only industrial robots but also any devices and/or sensors required for the robot to perform its tasks as well as se- quencing or monitoring communication interfaces. In 2007 the world market grew by 3% with approxi- mately 114,000 new installed industrial robots. At the end of 2007 there were around one million industrial ro- bots in use, compared with an estimated 50,000 service robots for industrial use 3. Due to increase using of industrial robot arms, an evo- lution to that topic began trying to imitate human move- ments in a detail mode. For example a group of students in Korea made a design of innovations that robotic arm take account of dancing hand, weight lifting, Chinese cal- ligraphy writing and color classification 4. Another group of engineers at USA develop eight degrees of freedom robot arm. This robot is able to grasp many objects with a lot of shapes from a pen to a ball and simulating also the hand of human being 5. In space, the Space Shuttle Remote Manipulator System, known as SSRMS or Cana- darm, and its successor is example of multi degree of freedom robot arms that have been used to perform a va- riety of tasks such as inspections of the space shuttle using a specially deployed boom with cameras and sen- sors attached at the end effector and satellite deployment and retrieval manoeuvres from the cargo bay of the space shuttle 6. In Mexico, Scientists are on track to design and de- velop many robot arms, and the Mexican government A. ELFASAKHANY ET AL. 48 estimates that in Mexico there are about 11,000 robotic arms used in different industrial applications. However, the experts think that the apogee of the robot arms is not only of higher quality, but also accurately, repeatability, and stumpy cost. Most robots are set up for an operation by the teach- and-repeat technique. In this mode, a trained operator (pro- grammer) typically uses a portable control device (a teach pendant) to teach a robot its task manually. Robot speeds during these programming sessions are slow. The present work is part of a two-phase project, which requires a mobile robot to be able to transport the tools from the storage room to the industrial cell. In this phase in the project, which carried out at Monterrey University of Technology, Mexico, the main focus was to design, development and implementation of an industrial robotic arm with stumpy cost, accurate and superior control. This robot arm was designed with four degrees of freedom and talented to accomplish simple tasks, such as light mate- rial handling, which will be integrated into a mobile plat- form that serves as an assistant for industrial workforce. 2. Mechanical Design The mechanical design of the robot arm is based on a robot manipulator with similar functions to a human arm 6-8. The links of such a manipulator are connected by joints allowing rotational motion and the links of the ma- nipulator is considered to form a kinematic chain. The business end of the kinematic chain of the manipulator is called the end effector or end-of-arm-tooling and it is analogous to the human hand. Figure 1 shows the Free Body Diagram for mechanical design of the robotic arm. As shown, the end effector is not included in the design because a commercially available gripper is used. This is because that the end effector is one of the most complex Figure 1. Free body diagram of the robot arm. parts of the system and, in turn, it is much easier and economical to use a commercial one than build it. Figure 2 shows the work region of the robotic arm. This is the typical workspace of a robot arm with four degree of freedom (4 DOF). The mechanical design was limited to 4 DOF mainly because that such a design al- lows most of the necessary movements and keeps the costs and the complexity of the robot competitively. Ac- cordingly, rotational motion of the joints is restricted where rotation is done around two axis in the shoulder and around only one in the elbow and the wrist, see Figure 1. The robot arm joints are typically actuated by electri- cal motors. The servo motors were chosen, since they in- clude encoders which automatically provide feedback to the motors and adjust the position accordingly. However, the disadvantage of these motors is that rotation range is less than 180 span, which greatly decreases the region reached by the arm and the possible positions 9. The qualifications of servo motors were selected based on the maximum torque required by the structure and possible loads. In the current study, the material used for the struc- ture was acrylic. Figure 3 shows the force diagram used for load calcu- lations. The calculations were carried out only for the joints that have the largest loads, since the other joints would have the same motor, i.e. the motor can move the links without problems. The calculations considered the weight of the motors, about 50 grams, except for the weight of motor at joint B, since it is carried out by link BA. Fig-ure 4 shows the force diagram on link CB, which con-tains the joints (B and C) with the highest load (carry the links DC and ED) and the calculations are carried out as follows. Figure 2. Work region of the robotic arm. Copyright 2011 SciRes. MME 49A. ELFASAKHANY ET AL. Figure 3. Force diagram of robot arm. Figure 4. Force diagram of link CB. The values used for the torque calculations: Wd = 0.011 kg (weight of link DE) Wc = 0.030 kg (weight of link CD) Wb = 0.030 kg (weight of link CB) L = 1 kg (load) Cm = Dm = 0.050 kg (weight of motor) LBC = 0.14 m (length of link BC) LCD = 0.14 m (length of link CD) LDE = 0.05 m (length of link DE) Performing the sum of forces in the Y axis, using the loads as shown in Figure 4, and solving for CY and CB, see Equations (1)-(4). Similarly, performing the sum of moments around point C, Equation (5), and point B, Equa- tion (6), to obtain the torque in C and B, Equations (7) and (8), respectively. gydmcmYFLWDWCC0 (1) 21.141kg 9.8m s11.18 NYC (2) 0ydmcmBBFLWDWCWgC (3) 21.171kg 9.8m s11.4758 NBC (4) 220cCDDEcDCDCDDEmCDcW LLMWLL LLDLM (5) 2202DEBBCCDDEDBCCDCDmBCCDcBCBCmBCBBLML LLLWLLLDLLWLLCLWM (6) 1.968 Nm278.6oz incM (7) 3.554 Nm503.38oz inBM (8) The servo motor that was selected, based on the cal- culations, is the Hextronik HX12K, which has a torque of 280 oz/in. This motor was recommended because it is much cheaper than any other motor with same specifica- tions. Since we need more torque at joint B, see Equation (8), we used two motors at point B to comply with the torque requirements; however, one motor is enough for the other joints. Using two motors at joint B is much cheaper than using one big motor with 560 oz/in. Other relevant characteristics of the motors, which can be shown in Figure 5, are that they can turn 60 degrees in 130 mil-liseconds and they have a weight of 47.9 grams each. Once the initial dimensions for the robot arm and the motor were defined, the design were carried out using the SolidWorks platform; design should carefully take into account the thickness of the acrylic sheet and the way that the pieces would be attached to each other. The acrylic sheet used to make the robot is 1/8 thickness and Figure 5. Servo motor. Copyright 2011 SciRes. MME A. ELFASAKHANY ET AL. 50 that thin sheet was chosen because it easier for machining and less weight with a good resistance. During design, we faced some difficulties due to the way of joining thin acrylic parts strongly. It was needed tools to burn and join the acrylic parts and that werent avail- able and the team considered that a mechanical junction based on screws and nuts would be much strong than other alternatives, such as glue for example. In order to accom- plish this, a small feature was designed which allowed to fasten the bolts with the nuts without having to screw in the thin acrylic layer. The result of this process was the tridimensional design shown in Figure 6. By end of design, each part was printed in full scale in cardboard paper and then we verified all the dimensions and the interfaces of the assembly. In turn, we built the first prototype of the robot arm. Next, parts of the robot arm were machined from the acrylic sheet using a circu- lar saw and Dermal tools. The detailing on the parts was done in a professional workshop since the parts of robot arm were too small and it is not an easy for accomplish- ing such small and accurate cuts. During assembling the robot parts with the motors, few problems pop up. There were critical points that did not resist the fastening and, in turn, may break down; hence, reinforcements in these points were considered. The final result of the robot arm is shown in Figure 7. 3. Robot Arm Inverse Kinematics To validate the right positioning of the robotic arm, in- verse kinematics calculations are carried out. Such cal- culations are used to obtain the angle of each motor from Figure 6. Robot arm 3D model. Figure 7. Robot arm complete assembly. a position given by using the Cartesian coordinate sys- tem, as shown in Figure 8. Each motor will have a spe- cific function: the motor located in the A union positions the final element in the y axis, the motors B and C posi- tions the final element in the x and z axis. The problem was simplified by using the xz plane, as shown in Figure 9. In which the following known values were defined 9: LAB: the forearm length. LBC: the arm length. z: the position in the z axis. x: the position in the x axis. y: the position in the y axis. Using trigonometry relations, as shown in Figure 9, the motor angles 2 and 1 are obtained, as seen in Equa- tions (9) and (10). 2222180arcCos2LABLBCxzLABLBC2 (9) 222122arcTanarcCos2zLABLBCxxLABxz2z(10) 0arcTanyx (11) The motor B is going to use 1 and the motor C is go- ing to use 2. The angle for the motor A is calculated as Copyright 2011 SciRes. MME 51A. ELFASAKHANY ET AL. Figure 8. Coordinate system. Figure 9. xz Plane. seen in Equation (11). With these calculations, the angles of servomotors are obtained and in turn they take the ac- tion to move the whole structure to the specific position. 4. End-Effector Selection The end effector is probably one of the most important and most complex parts of the system. Wisely, it is much ea- sier and economical to use a commercial one than build it. The end effector varies mainly according to the appli- cation and the task that the robot arm accomplishes for; it can be pneumatic, electric or hydraulic. Since our robot arm is based in an electric system, we may choose electric ba- sis of end effector. Besides, the main application of our system is handling, accordingly, the recommended type of our end effector is a gripper, as shown in Figure 10. Please note that the end effector is controlled by a servo motor and, in turn, the total servo motors used for our robot arm will be 5 motors that move the structure. Figure 10. Gripper with servo. 5. Robot Arm Control The robot arms can be autonomous or controlled manually. In manual mode, a trained operator (programmer) typi- cally uses a portable control device (a teach pendant) to teach a robot to do its task manually. Robot speeds during these programming sessions are slow. In the current work we enclosed the both modes. The control for the presented robot arm consists basi- cally of three levels: a microcontroller, a driver, and a com- puter-based user interface. This system has unique char- acteristics that allow flexibility in programming and con- trolling method, which was implemented using inverse kinematics; besides it could also be implemented in a full manual mode. The electronic design of control is shown in Figure 11. The microcontroller used is an Atmega 368 which comes with a development/programming board named “Arduino”, as shown in Figure 12. The programming language is very similar to C but includes several library- ies that help in the control of the I/O ports, timers, and serial communication. This microcontroller was chosen because it has a low price, it is very easy to reprogram, the programming language is simple, and interrupts are available for this particular chip. The driver used is a six-channel Micro Maestro servo controller board. It supports three control methods: USB for direct connection to a computer, TTL serial for use with embedded systems, such as the Arduino microcon- troller, and internal scripting for self-contained and host controller-free applications. This controller, as shown in Figure 13, includes a 0.25 s resolution for position and built-in speed and acceleration control. Copyright 2011 SciRes. MME A. ELFASAKHANY ET AL. 52 Figure 11. Electronic scheme of control. Figure 12. Arduino microcontroller board. Figure 13. Servo controller driver. The user interface depends on the control method used, i.e., inverse kinematics or a full manual mode. In the fol- lowing, each interface is described: 5.1. Inverse Kinematics Control In this control method, the user inputs the coordinate sys- tem position where the gripper should be. As consequence, interface is generated with Labview through a visual user, as shown in Figure 14. The program automatically per- forms the inverse kinematics calculations to obtain the angles that each motor should have and then sends a command either to the microcontroller or directly to the driver that will move the robot to the specified position. Communication is performed with the RS-232 protocol. In the following, you may see the Labview user interface inputs and output. The Labview user interface inputs are: x axis position. y axis position. z axis position. Gripper opening. Gripper attack angle. Serial port. The Labview user interface outputs are: Motor A angle. Motor B1 angle. Motor B2 angle. Motor C angle. Attack angle. Gripper angle. Such output variables are treated and sent by an appro- priate way, so that information can be interpreted in a correct manner. The outputs are sent via the serial port which is communicated with the controller. When the but- ton “Move” is clicked, a process will take place, as shown in Figure 15. With this action, the robotic arm will change its position according to the input values. In addition, it has a standby button that stops the communication controller. Figure 14. Labview user interface. Copyright 2011 SciRes. MME 53A. ELFASAKHANY ET AL. Figure 15. Program process. The main advantages of this approach are that it uses an efficient way of moving and offers further capabilities that could be implemented, such as position and sequence learning. A disadvantage, on the other hand, is that the possible positions that have valid angles after the inverse kinematics calculations are very limited because the servo motors have a restraint of 180. 5.2. Manual Control This type of control is an extra option for our system that useful in specific positions. In case of mandatory posi- tions that the inverse kinematics mode cannot calculate their valid angles, we may use the manual control instead. Basically, manual control consists of a series of analog inputs, such as potentiometers, that are connected with the microcontroller which will interpret the values and send a command to the servo driver. In order to imple- ment this, a control board, as shown in Figure 16, should be built to work as an interface with the user. Possible implementation includes a teaching feature where the mi- crocontroller stores positions in memory and by a keypad or a series of switches we may recall these positions. 6. Testing and Validation Several tests were carried out to validate the robot arm and its components. The testes covered both the particular ele- ments and the overall system, as shown in Figure 17. For the microcontroller, the tests are occurred by sending different commands by the software to the microcontrol- ler and check changes on the output which was connected to a servo motor that turned on or off depending on the command. The servo motors were tested afterwards by sending different direct pulses to each servomotor and verifying the response of moving to the right position. We used a mark to know where the initial position was and the final Figure 16. Potentiometer board. Figure 17. Robot arm tests. position of the motors is determined by sending a signal with the microcontroller and, in turn, it is interpreted by the servo and compared to the signal provided by the encoder, resulting in the rotation to the desired position. During this test, the servo motor was inconsistence with the robot arm system because of an incorrect polarization. The servo motor driver was also tested using the Lab- view software to send commands to the microcontroller which sent the specific commands to the driver which had one motor connected to change the position accord- ing to the commend. It is important to notice that at the beginning of the project a different servo motor driver was selected but several problems related to the commu- nication between them and the microcontroller were pre- sent. So we choose a driver that allows the data to be sent directly from the computer to it with only a USB wire, so the microcontroller would only be used in case of the implementation of manual control. Other tests were performed to verify the functionality of the whole system, as shown in Figure 18. Those tests Copyright 2011 SciRes. MME A. ELFASAKHANY