仿生六足機(jī)器人機(jī)構(gòu)的設(shè)計(jì)
仿生六足機(jī)器人機(jī)構(gòu)的設(shè)計(jì),仿生六足機(jī)器人機(jī)構(gòu)的設(shè)計(jì),仿生,機(jī)器人,機(jī)構(gòu),設(shè)計(jì)
湖南農(nóng)業(yè)大學(xué)東方科技學(xué)院全日制普通本科生畢業(yè)論文(設(shè)計(jì))誠信聲明本人鄭重聲明:所呈交的本科畢業(yè)論文是本人在指導(dǎo)老師的指導(dǎo)下,進(jìn)行研究工作所取得的成果,成果不存在知識產(chǎn)權(quán)爭議。除文中已經(jīng)注明引用的內(nèi)容外,本論文不含任何其他個人或集體已經(jīng)發(fā)表或撰寫過的作品成果。對本文的研究做出重要貢獻(xiàn)的個人和集體在文中均作了明確的說明并表示了謝意。同時,本論文的著作權(quán)由本人與湖南農(nóng)業(yè)大學(xué)東方科技學(xué)院、指導(dǎo)教師共同擁有。本人完全意識到本聲明的法律結(jié)果由本人承擔(dān)。 畢業(yè)論文(設(shè)計(jì))作者簽名: 年 月 日目 錄 摘要1關(guān)鍵詞11 前言 11.1 課題背景及目的 11.2 仿生機(jī)器人研究現(xiàn)狀及發(fā)展趨勢 2 1.3 仿生學(xué)原理分析 41.4 仿生六足機(jī)器人的研究方法與思路 42 整體設(shè)計(jì)方案 52.1 工作原理分析 52.1.1 三角步態(tài)原理分析 6 2.1.2 機(jī)器人走動步態(tài)分析 62.2 機(jī)器人機(jī)構(gòu)的整體設(shè)計(jì) 72.3 電機(jī)的選擇 92.4 舵機(jī)驅(qū)動原理與控制方法12 2.4.1 舵機(jī)原理 12 2.4.2 舵機(jī)控制方法 123 零件的設(shè)計(jì)133.1 軀干的設(shè)計(jì)133.2 基節(jié)的設(shè)計(jì)143.3 關(guān)節(jié)蓋的設(shè)計(jì)153.4 脛節(jié)片的設(shè)計(jì)163.5 足的設(shè)計(jì)173.6 連接桿的設(shè)計(jì)173.7 固定片的設(shè)計(jì)184 總結(jié)19參考文獻(xiàn) 19致謝 20 仿生六足機(jī)器人機(jī)構(gòu)的設(shè)計(jì)摘 要:論文簡述了課題的背景及目的,對仿生學(xué)機(jī)器人做了簡單介紹。本文通過對仿生六足機(jī)器人的步態(tài)規(guī)劃的研究,確定了六足機(jī)器人的足的結(jié)構(gòu),采用 3 自由度分析了步態(tài)穩(wěn)定性,實(shí)現(xiàn)六足機(jī)器人直線行走和轉(zhuǎn)彎行走??傮w設(shè)計(jì)包含了六足機(jī)器人的裝配圖和零件圖的繪制,并對相關(guān)零件做了校驗(yàn),確保機(jī)構(gòu)設(shè)計(jì)的可行性。關(guān)鍵詞:仿生學(xué);六足機(jī)器人;機(jī)構(gòu)Design of Bionic Hexapod Robot Mechanism Student: Liu Liang Tutor: Sun Songlin (Oriental Science Technology College of Hunan Agricultural University, Changsha 410128)Abstract: The paper has summarized the background and the goal of its topic and has made the simple introduction of the bionic hexapod robot. Through the research of the motion of the six feet of the robot, This design has determined the foot structure,using the analysis of 3 degrees of freedom realizes the forward motion and turning motion of the robot . Picturing of the component and assembly mapping of the bionic hexapod robot as well as the inspection of related parts which ensures the feasibility of the machinery design are both included in the total design.Key words: bionics ;hexapod robot ;machinery 1 前言1.1 課題背景及目的機(jī)器人是科技和社會的發(fā)展的必然產(chǎn)物,機(jī)器人的運(yùn)用促進(jìn)了生產(chǎn)力的發(fā)展,為人類社會文明的進(jìn)步做出了巨大的貢獻(xiàn)。人工智能技術(shù)的研究使得機(jī)械向著智能化方向發(fā)展,因此機(jī)器人的研發(fā)已經(jīng)成為了各國科技競爭的一個重要方面。機(jī)器人的研制水平代表著一個國家的綜合科技實(shí)力,新型機(jī)器人更是能代表一個國家的尖端科技成果。如今,世界上機(jī)器人的應(yīng)用已經(jīng)非常普遍,機(jī)器人的種類更是繁多1。機(jī)器人從傳統(tǒng)的單一機(jī)構(gòu)向著多元化轉(zhuǎn)變,人類研究機(jī)器人也突破自身視的局限擴(kuò)展到世間萬物。機(jī)器人的研究由結(jié)構(gòu)環(huán)境的定點(diǎn)作業(yè)向著非結(jié)構(gòu)環(huán)境下的自主作業(yè)轉(zhuǎn)變,在軍事偵查、宇航、搶險(xiǎn)救災(zāi)、星球探索、搶險(xiǎn)救災(zāi)等方向顯示出廣泛的前景。機(jī)器人能在人類不能或難以到達(dá)的未知環(huán)境中工作,人們要求機(jī)器人不僅適應(yīng)原來結(jié)構(gòu)化的、已知的環(huán)境,更要適應(yīng)未來發(fā)展中的非結(jié)構(gòu)化的、未知的環(huán)境。除了傳統(tǒng)的設(shè)計(jì)方法,人們也把目光對準(zhǔn)了生物界,尋求從大自然奇妙的生物身上獲得靈感,將它們的運(yùn)動機(jī)理和行為方式運(yùn)用到對機(jī)器人的運(yùn)動和控制中,從而使得機(jī)器人既具有感覺有具有某些思維功能,并由這些功能控制動作,具有與生物或者人類相類似的智能。將仿生學(xué)原理應(yīng)用到工程系統(tǒng)的研究與設(shè)計(jì)中,為機(jī)器人的發(fā)展指出了新的方向2。仿生多足機(jī)器人是模仿多足動物運(yùn)動形式的特種機(jī)器人。據(jù)調(diào)查,地球上近一半的地面不能為傳統(tǒng)的輪式或履帶式車輛所到達(dá),但很多足式動物卻可以在這些地面上行走自如。因此,仿生多足機(jī)器人的運(yùn)動方式具有其他地面推進(jìn)方式所不具有的獨(dú)特優(yōu)越性能,仿生多足機(jī)器人的運(yùn)動方式具有較好的機(jī)動性,對不平整地面具有較好的適應(yīng)能力。多足步行機(jī)器人在不平地面和松軟地面上的運(yùn)動速度較快,而且能耗較少2?;诜律嘧銠C(jī)器人的諸多的優(yōu)點(diǎn),為了充分利用這些優(yōu)越的性能為人類服務(wù),我們有必要對其進(jìn)行深入的研究,使仿生多足機(jī)器人能在人類社會的發(fā)展歷程中發(fā)揮它的作用。1.2 仿生機(jī)器人研究現(xiàn)狀及發(fā)展趨勢仿生機(jī)器人就是通過對生物的性能和行為進(jìn)行模仿,將其結(jié)構(gòu)特征、運(yùn)動理、行為方式等應(yīng)用于機(jī)器人的設(shè)計(jì)中,研制具有某些生物的外形或機(jī)能的機(jī)器人系統(tǒng)。仿生機(jī)器人的誕生是仿生技術(shù)與機(jī)器人技術(shù)融合的結(jié)果,涉及仿生學(xué)、力學(xué)、機(jī)構(gòu)學(xué)、控制學(xué)、計(jì)算機(jī)科學(xué)、信息科學(xué)、微電子學(xué)、傳感技術(shù)、人工智能等諸多學(xué)科,從而使機(jī)器人既擁有傳統(tǒng)機(jī)器人所具有的優(yōu)點(diǎn),又將生物運(yùn)動機(jī)理和行為方式作為理論模型運(yùn)用于機(jī)器人的運(yùn)動控制,借大自然千萬年來“自然選擇”的造化之手來提高機(jī)器人的運(yùn)動能力和效率,使其突破原有理論的藩籬,大大提高了機(jī)器人的運(yùn)動特性和工作效率。仿生機(jī)器人大致可分為仿人機(jī)器人和仿非人生物機(jī)器人,仿人機(jī)器人是目前機(jī)器人技術(shù)的前沿課題和具有挑戰(zhàn)性的技術(shù)難題之一,主要是研究多自由度的關(guān)節(jié)型機(jī)器人操作臂、多指靈巧手的組合既雙足步行機(jī)器人機(jī)構(gòu);仿非人生物機(jī)器人主要是研究多足機(jī)器人、蛇形機(jī)器人、水下機(jī)器人及飛行機(jī)器人等。當(dāng)前,仿生機(jī)器人研究的熱點(diǎn)主要涉及到運(yùn)動機(jī)理仿生、控制機(jī)理仿生、信息感知仿生、能量代謝仿生和材料合成仿生。目前,已經(jīng)研制出了幾款典型的仿生多足機(jī)器人,如仿壁虎四足機(jī)器人、仿竹節(jié)蟲六足機(jī)器人、仿螳螂六足機(jī)器人、仿蜘蛛八足機(jī)器人、仿蝎八足機(jī)器人等 3。機(jī)器人的應(yīng)用范圍遍及工業(yè)、農(nóng)業(yè)、娛樂、服務(wù)和國防各個領(lǐng)域,機(jī)器人的應(yīng)用朝著多元化、多領(lǐng)域、多用途的方向發(fā)展。機(jī)器人正朝著智能化發(fā)展,將人工智能與仿生學(xué)相結(jié)合制造出類生物機(jī)器人。近年來隨著日本仿生機(jī)器ASIMO美國火星探測器等項(xiàng)目的研制成功,智能機(jī)器人的研究和發(fā)展,特別是能夠代替人在危險(xiǎn)、惡劣等環(huán)境中從事特殊任務(wù)的特種智能機(jī)器人的研究和發(fā)展,成了各國政府制定高技術(shù)計(jì)劃的一個重要內(nèi)容,支撐智能機(jī)器人的關(guān)鍵技術(shù)感知與智能控制技術(shù)已成為機(jī)器人研究領(lǐng)域的熱點(diǎn)之一1。20 世紀(jì) 90 年代初,美國麻省理工學(xué)院的教授布魯克斯在學(xué)生的幫助下,制造出一批蚊型機(jī)器人,取名昆蟲機(jī)器人,這些小東西的習(xí)慣和蟑螂十分相近。它們不會思考,只能按照人編制的程序動作。幾年前,科技工作者為圣地亞哥市動物園制造電子機(jī)器鳥,它能模仿母兀鷹,準(zhǔn)時給小兀鷹喂食;日本和俄羅斯制造了一種電子機(jī)器蟹,能進(jìn)行深??販y,采集巖樣,捕捉海底生物,進(jìn)行海下電焊等作業(yè)。美國研制出一條名叫查理的機(jī)器金槍魚,長 1.32 米,由 2843 個零件組成。通過擺動軀體和尾巴,能像真的魚一樣游動,速度為 7.2 千米/小時??梢岳盟诤O逻B續(xù)工作數(shù)個月,由它測繪海洋地圖和檢測水下污染,也可以用它來拍攝生物,因?yàn)樗7陆饦岕~惟妙惟肖。在美國,科技人員研制設(shè)計(jì)的金槍魚潛艇,其實(shí)就是金槍魚機(jī)器人,行駛速度可達(dá) 20 節(jié),是名副其實(shí)的水下游動機(jī)器。它的靈活性遠(yuǎn)遠(yuǎn)高于現(xiàn)有的潛艇,幾乎可以達(dá)到水下任何區(qū)域,由人遙控,它可輕而易舉地進(jìn)入海底深處的海溝和洞穴,悄悄地溜進(jìn)敵方的港口,進(jìn)行偵察而不被發(fā)覺。作為軍用偵察和科學(xué)探索工具,其發(fā)展和應(yīng)用的前景十分廣闊。目前,中國科學(xué)院也已經(jīng)研究出了類似仿生魚機(jī)器人。研究制造昆蟲機(jī)器人,其前景也是非常美好的。例如,有人研制一種有彈性腿的機(jī)器昆蟲,大小只有一張信用卡的 1/3 左右,可以像蟋蟀一樣輕松地跳過障礙,一小時幾乎可前進(jìn) 37 米。美國科學(xué)家研制的蜜蜂機(jī)器人,在加裝太陽能電池板和傳感設(shè)備后可自主飛行相當(dāng)長的時間。這種機(jī)器昆蟲最特殊的地方是突破了“牽動關(guān)節(jié)必須加發(fā)動機(jī)”的觀念。機(jī)器人正在向人工智能方向快速發(fā)展,仿生機(jī)器人的發(fā)展也非???。機(jī)器人的存在價值就在于它能夠做很多人類不能完成的任務(wù),人類是有生命體征的動物,對生存條件有很高的要求。而機(jī)器人是一臺機(jī)器,它沒有生命體征,只有在極其惡劣的環(huán)境中工作時才會對它機(jī)體的材料有比較高的要求。這樣就可以讓機(jī)器人代替人類去完成那些人類無法完成的任務(wù)。隨著人類研究領(lǐng)域的不斷擴(kuò)展,以及人類生活水平的不斷提高,機(jī)器人的發(fā)展也顯得越來越重要3。 自然界中的各種生物通過物競天擇和長期進(jìn)化,已對外界環(huán)境產(chǎn)生了極強(qiáng)的適應(yīng)性,在能量轉(zhuǎn)化、運(yùn)動控制、狀態(tài)調(diào)節(jié)、信息處理和方位辨別等方面還表現(xiàn)出高度的合理性。因此機(jī)器人朝著仿生方向發(fā)展是必然的。曾經(jīng)在 IEEE 機(jī)器人學(xué)與仿生學(xué)國際學(xué)術(shù)會議上,與會的機(jī)器人專家就指出:“模仿生物的身體結(jié)構(gòu)和功能,從事生物特點(diǎn)工作的仿生機(jī)器人,有望代替?zhèn)鹘y(tǒng)的工業(yè)機(jī)器人,成為成為未來機(jī)器人的發(fā)展方向1。1.3 仿生學(xué)原理分析仿生式六足機(jī)器人,顧名思義,六足機(jī)器人在我們理想架構(gòu)中,我們借鑒了自然界昆蟲的運(yùn)動原理。足是昆蟲的運(yùn)動器官。昆蟲有3對足,在前胸、中胸和后胸各有一對,我們相應(yīng)地稱為前足、中足和后足。每個足由基節(jié)、轉(zhuǎn)節(jié)、腿節(jié)、脛節(jié)、跗節(jié)和前跗節(jié)幾部分組成?;?jié)是足最基部的一節(jié),多粗短。轉(zhuǎn)節(jié)常與腿節(jié)緊密相連而不活動。腿節(jié)是最長最粗的一節(jié)。第四節(jié)叫脛節(jié),一般比較細(xì)長,長著成排的刺。第五節(jié)叫跗節(jié),一般由2-5節(jié)個亞節(jié)組成:為的是便于行走。在最末節(jié)的端部還長著兩個又硬又尖的爪,可以用它來抓住物體。行走是以三條腿為一組進(jìn)行的,即一側(cè)的前、后足與另一側(cè)的中足為一組。這樣就形成了一個三角形支架結(jié)構(gòu),當(dāng)這三條腿放在地面并向后蹬時,另外三條腿即抬起向前準(zhǔn)備替換。前足用爪固定物體后拉動蟲體向前,中足用來支持并舉起所屬一側(cè)的身體,后足則推動蟲體前進(jìn),同時使蟲體轉(zhuǎn)向。這種行走方式使昆蟲可以隨時隨地停息下來,因?yàn)橹匦目偸锹湓谌侵Ъ苤畠?nèi)。并不是所有成蟲都用六條腿來行走,有些昆蟲由于前足發(fā)生了特化,有了其他功能用或者退化,行走就主要靠中、后足來完成了。大家最為熟悉的要算是螳螂了,我們??吹襟胍粚︺Q子般的前足高舉在胸前,而是由后四條足支撐地面行走4。參考以上的昆蟲足部結(jié)構(gòu),我想出了較簡單的方式來表達(dá)。一只腳的兩個關(guān)節(jié)來主動運(yùn)動,一個關(guān)節(jié)采用左右式移擺;另一個關(guān)節(jié)則是采用偏擺式,使得腳可以提高,當(dāng)做上下運(yùn)動的一種。1.4 仿生六足機(jī)器人的研究方法與思路本次研究的仿生機(jī)器人采用六足設(shè)計(jì),而機(jī)構(gòu)設(shè)計(jì)是仿生六足機(jī)器人本次的任務(wù),也是仿生六足機(jī)器人系統(tǒng)設(shè)計(jì)的基礎(chǔ)。整機(jī)機(jī)械結(jié)構(gòu)、自由度數(shù)、驅(qū)動方式和傳動機(jī)構(gòu)等都會直接影響機(jī)器人的運(yùn)動和動力性能。同時,仿生六足機(jī)器人機(jī)構(gòu)的設(shè)計(jì)除了要滿足系統(tǒng)的技術(shù)性能外,還要滿足經(jīng)濟(jì)性能要求,即必須在滿足機(jī)器人的預(yù)期技術(shù)指標(biāo)的同時,考慮用材合理、制造安裝便捷、價格低廉以及可靠性高等問題。仿生六足機(jī)器人的機(jī)構(gòu)由軀體和腿兩部分組成,腿的數(shù)量及其配置是整體設(shè)計(jì)的主要問題?,F(xiàn)有多組機(jī)器人的足數(shù)包括三足、四足、六足、八足甚至更多,足的數(shù)目較多時適合重載和慢速運(yùn)動,而足數(shù)少時似乎運(yùn)動更加靈活。足數(shù)選擇的因素主要有:穩(wěn)定性、節(jié)能性、冗余性、關(guān)節(jié)控制性能的要求、制造成本、質(zhì)量、所需傳感器的復(fù)雜性以及可能的步態(tài)等;腿的配置是指步行機(jī)器人的足相對于機(jī)體的位置和方位的安排,確定分布形式時,還需考慮一些細(xì)節(jié)問題,如腿在主平面內(nèi)的幾何構(gòu)形和腿桿件的相對彎曲方向等。此次設(shè)計(jì)腿的分布如圖1所示。 圖 1 仿生六足機(jī)器人腿的分布示意圖 Fig 1 Bionic six foot robot leg distribution diagram綜合足數(shù)等因素,本設(shè)計(jì)的行走步態(tài)采用三角步態(tài),這也是六足機(jī)器人步行方式通常采用的。三角步態(tài)中,六足機(jī)器人身體的一側(cè)的前足和后足與另一側(cè)的中足共同組成一組。其他三條足組成另外一組。2 整體設(shè)計(jì)方案2.1 工作原理分析六足步行機(jī)器人的步態(tài)是多樣的,其中三角步態(tài)是六足步行機(jī)器人實(shí)現(xiàn)步行的典型步態(tài)。以下著重分析三角步態(tài)原理。2.1.1 三角步態(tài)原理分析“六足綱”昆蟲步行時,一般不是六足同時直線前進(jìn),而是將三對足分成兩組,以三角形支架結(jié)構(gòu)交替前行。目前,大部分六足機(jī)器人采用了仿昆蟲的結(jié)構(gòu),6條腿分布在身體的兩側(cè),身體左側(cè)的前、后足及右側(cè)的中足為一組,右側(cè)的前、后足和左側(cè)的中足為另一組,分別組成兩個三角形支架,依靠大腿前后劃動實(shí)現(xiàn)支撐和擺動過程,這就是典型的三角步態(tài)行走法。由于身體重心低,容易穩(wěn)定,所以這種行走方案能得到廣泛運(yùn)用5。2.1.2 機(jī)器人走動步態(tài)分析項(xiàng)目設(shè)計(jì)共使用18個舵機(jī)用于步態(tài)實(shí)現(xiàn)。每條腿上有三個舵機(jī),分別控制跟關(guān)節(jié)、膝關(guān)節(jié)和踝關(guān)節(jié)的運(yùn)動,其中兩個舵機(jī)安裝呈正交,構(gòu)成垂直和水平方向的自由度。由于腿具有水平和垂直平面的運(yùn)動自由度,所以考慮利用三角步態(tài)實(shí)現(xiàn)直線行走。分別給18個舵機(jī)編號(1-18),如下圖所示。AB C FED123456789101112131415161817 圖2 舵機(jī)安裝示意圖 Fig 2 Steering gear installed scheme(1)行走步態(tài)分析由1、2、3、7、8、9、13、14、15號舵機(jī)控制的A、C、E腿所處的狀態(tài)總保持一致(都是正在擺動,或者都在支撐);同樣,4、5、6、10、11、12、16、17、18號所控制的B、D、F腿的狀態(tài)也保持一致。當(dāng)處在一個三角形內(nèi)的3條腿在支撐時,另3條腿正在擺動。支撐的3條腿使得身體前進(jìn),而擺動的腿對身體沒有力和位移的作用,只是使得小腿向前運(yùn)動,做好接下去支撐的準(zhǔn)備。步態(tài)函數(shù)的占空系數(shù)為0.5,支撐相和擺動相經(jīng)過調(diào)整,達(dá)到滿足平坦地形下的行走步態(tài)要求和穩(wěn)定裕量要求7。(2)轉(zhuǎn)彎步態(tài)分析 項(xiàng)目設(shè)計(jì)的機(jī)器人采用以一中足為中心的原地轉(zhuǎn)彎方式實(shí)現(xiàn)轉(zhuǎn)彎,右轉(zhuǎn)彎運(yùn)動的過程如下:首先A、C、E腿抬起,然后A、C腿向前擺動,E腿保持不動,B、D、F腿支撐。然后A、C、E腿落地支撐,同時B、D、F腿抬起保持不動。最后A、C腿向后擺動。整個運(yùn)動過程中B、D、E、F不做前后運(yùn)動,只是上下運(yùn)動7。2.2 機(jī)器人機(jī)構(gòu)的整體設(shè)計(jì)六足機(jī)器人在步行運(yùn)動過程中將六條腿分為 2 組,以蟲體的一側(cè)的前足和后足及另一側(cè)的中足為一組,其余的三條腿又為一組。在運(yùn)動過程中,會有一組腿抬起,一組腿著地,三只著地的腿不僅保持蟲體的平穩(wěn)性,而且在擺腿的時候產(chǎn)生推動力,使蟲體能夠完成直線或轉(zhuǎn)彎運(yùn)動。本設(shè)計(jì)中采用的三角步態(tài)是將六足機(jī)器人的六條腿分為 2 組,1、3、5 號腿為一組,2、4、6 號腿為另一組。六足機(jī)器人通過控制 2 組腿交替地抬起、擺動、放下來實(shí)現(xiàn)步行運(yùn)動。抬起得每條腿從軀體上看是開鏈結(jié)構(gòu),相當(dāng)于串聯(lián)手臂,而同時著地的3條腿或6條腿與軀體構(gòu)成并聯(lián)多閉鏈多自由度機(jī)構(gòu)。步行機(jī)器人在正常行走條件下,各支撐腿與地面接觸存在摩擦不打滑,可以簡化為點(diǎn)接觸,相當(dāng)于機(jī)構(gòu)學(xué)上的3自由度球面副,再加上跟關(guān)節(jié)、膝關(guān)節(jié)及踝關(guān)節(jié)(各關(guān)節(jié)為單自由度,相當(dāng)于轉(zhuǎn)動副),每條腿都有6個單自由度運(yùn)動副。假設(shè)步行機(jī)器人任一時刻處于支撐相的腿數(shù)為n,則此時模型為具有n個分支的空間多環(huán)并聯(lián)機(jī)構(gòu),其自由度可由下式計(jì)算: (1)式中:p-運(yùn)動副數(shù),p=4n;-第i個運(yùn)動副具有的自由度數(shù),=1(i=13n),=3(i=3n+14n);L-獨(dú)立封閉環(huán)數(shù),L=n-1;-第i個獨(dú)立封閉環(huán)所具有的封閉約束條件數(shù),=6;-消極自由度數(shù),=0;和-分別為局部自由度數(shù)和重復(fù)約束數(shù),。將以上參數(shù)代入式(1),可得:F=3n+3n-(n-1)6=6由此可知,無論步行機(jī)器人有幾條腿處于支撐相,不論是3足支撐或6足支撐,整個機(jī)構(gòu)是具有6自由度的空間多環(huán)并聯(lián)機(jī)構(gòu),只是有時是3分支并聯(lián)機(jī)構(gòu),有時是6分支并聯(lián)機(jī)構(gòu)。6足步行機(jī)這樣行走,從機(jī)構(gòu)學(xué)角度看就是3分支并聯(lián)機(jī)構(gòu)、6分支并聯(lián)機(jī)構(gòu)及串聯(lián)開鏈機(jī)構(gòu)之間不斷變化的復(fù)合型機(jī)構(gòu)。同時,上式也說明,無論該步行機(jī)器人采取的步態(tài)及地面狀況如何,軀體在一定范圍內(nèi)均可靈活地到達(dá)任意的位置,并呈現(xiàn)要求的姿態(tài)。仿生六足機(jī)器人腿分布示意圖如圖3所示。 圖3 仿生六足機(jī)器人腿分布示意圖 Fig 3 Bionic six foot robot leg distribution diagram仿生六足機(jī)器人的六支腿均布在圓盤狀的機(jī)身上,根據(jù)設(shè)計(jì)要求:單腿是具有三自由度的運(yùn)動副,因此每條腿上裝配三個電機(jī)以實(shí)現(xiàn)三個轉(zhuǎn)動的自由度。電機(jī)的裝配位置為腿的跟關(guān)節(jié)、膝關(guān)節(jié)和踝關(guān)節(jié)部位。基節(jié)與機(jī)身主板連接,跟關(guān)節(jié)、膝關(guān)節(jié)與踝關(guān)節(jié)每個都有相應(yīng)的自由度來保證正常的運(yùn)動。脛節(jié)用于連接關(guān)節(jié)部位,以保證了良好的運(yùn)動性,六足機(jī)器人的足部分大致采用了仿昆蟲的足部設(shè)計(jì),具有良好的通過性、優(yōu)越的實(shí)用性以及較好的靈活性。腿在行走過程中交替地支撐機(jī)體的質(zhì)量,并在負(fù)重狀態(tài)下推進(jìn)機(jī)體向前運(yùn)動,因此必須具備與整機(jī)質(zhì)量相適應(yīng)的剛性和承載能力。項(xiàng)目設(shè)計(jì)的仿生六足機(jī)器人,采用相似的三自由度關(guān)節(jié)式腿機(jī)構(gòu),其中膝關(guān)節(jié)及踝關(guān)節(jié)分別由電機(jī)和錐齒輪共同驅(qū)動,以便用簡單的機(jī)構(gòu)獲得較大的工作空間和靈活度。通過控制相應(yīng)關(guān)節(jié)電機(jī)的運(yùn)動使機(jī)器人具備了多個自由度,能夠?qū)崿F(xiàn)機(jī)器人步行足在可達(dá)域內(nèi)任意一點(diǎn)的自由定位。在結(jié)構(gòu)上保證其能夠更有效地模擬昆蟲的行走方式以完成相對復(fù)雜的運(yùn)動。驅(qū)動系統(tǒng)在仿生六足機(jī)器人中的作用相當(dāng)于生物的肌肉,它通過轉(zhuǎn)動腿部各關(guān)節(jié)來改變機(jī)器人的姿態(tài)。驅(qū)動系統(tǒng)必須擁有足夠的功率對關(guān)節(jié)進(jìn)行加、減速并帶動負(fù)載,而且自身必須輕便、經(jīng)濟(jì)、精準(zhǔn)、靈敏、可靠且便于維護(hù)六足機(jī)器人的腿生物結(jié)構(gòu)示意圖4所示8。 圖4 仿生六足機(jī)器人腿的生物結(jié)構(gòu)示意圖 Fig 4 Bionic six foot robot leg biological structure diagram2.3 電機(jī)的選擇電機(jī)的選擇需要考慮機(jī)器人的質(zhì)量和最大扭矩。則需要有腿的質(zhì)量和尺寸,通過查閱及預(yù)算得出:上腿(股節(jié))的有效長度為 34mm,中腿(脛節(jié))有效長度為 34mm,下腿(足)有效長度 90mm。上腿 190 克,中腿 140克,下腿 150 克。對腿部進(jìn)行受力分析,做出受力簡圖5如下。 圖5 仿生六足機(jī)器人腿的受力簡圖 Fig 5 Bionic six foot robot leg force diagram仿生六足機(jī)器人以地面為 xoy 平面,仿生六足機(jī)器人的重心在 xoy 平面上的投影為坐標(biāo)原點(diǎn) O,z 軸與機(jī)身垂直。仿生六足機(jī)器人的每條腿都有三個自由度,每條腿都由上腿、中腿和下腿通過舵機(jī)連接而成。本設(shè)計(jì)中,上腿的長度為34mm,中腿的長度為34mm,下腿的長度為90mm。機(jī)體和上腿由A舵機(jī)連接,上腿與中腿由B舵機(jī)連接,中腿和下腿由C舵機(jī)連接。腿著地時,上腿與中腿間的夾角為135度,中腿與下腿間的夾角為135度,抬腿時,B舵機(jī)逆時針轉(zhuǎn)動30度。在仿生六足機(jī)器人行走過程中,未了避免腿與腿會碰到,腿擺動時需要選擇合適的角度,本設(shè)計(jì)中運(yùn)動控制時選擇的擺動角度為30度。針對仿生六足機(jī)器人支撐腿的受力狀況,其虛位移平衡方程的分析如下:首先用表示質(zhì)點(diǎn)系的廣義坐標(biāo),即有 (2),則仿生六組機(jī)器人步行足的廣義平衡方程為: (3) (4) 其中 M2、M3 為膝關(guān)節(jié)和踝關(guān)節(jié)所需扭矩,l2、l3、 m2、 m3 為脛節(jié)、足的長度和質(zhì)量。假設(shè)仿生六足機(jī)器人按“三角步態(tài)”行走,支撐相三足均勻承受負(fù)荷,則足的反力為: (5) 仿生六足機(jī)器人在實(shí)際運(yùn)動中,存在 的情況。據(jù)此,可推算出各關(guān)節(jié)所需的扭矩為:(6) (7)當(dāng)q2=90,q2-q3=30時,由公式得,關(guān)節(jié)需輸出扭矩最大值為: (8) (9)計(jì)算得出,電機(jī)的最大輸出扭矩要大于1.58 Nm。根據(jù)數(shù)據(jù)選用的伺服馬達(dá)為 TowPro 的,型號為 SG303。其主要技術(shù)參數(shù)如下: 轉(zhuǎn)速:0.23 秒30 度。 力矩:1.8Nm。 尺寸:40.4mm19.8mm36mm。 重量:37.2g。 5V 電源供電。舵機(jī)的結(jié)構(gòu)如圖6所示 圖6 舵機(jī)的內(nèi)部結(jié)構(gòu)圖 Fig 6 Internal structure of the actuator通過整體設(shè)計(jì)確定六足機(jī)器人的基本結(jié)構(gòu),通過電機(jī)的選擇確定仿生六足機(jī)器人的質(zhì)量和腿的尺寸,為后面的零件設(shè)計(jì)做了準(zhǔn)備。2.4 舵機(jī)驅(qū)動原理仿生六足機(jī)器人采用電動驅(qū)動的方式進(jìn)行驅(qū)動,驅(qū)動器采用微型直流角位移伺服電動機(jī)(舵機(jī))。2.4.1 舵機(jī)原理舵機(jī)是一種結(jié)構(gòu)簡單的、集成化的直流伺服系統(tǒng),其內(nèi)部結(jié)構(gòu)由直流電機(jī)、減速齒輪、電位計(jì)和控制電路組成。舵機(jī)采用的驅(qū)動信號是脈沖比例調(diào)制信號(PWM),即在通常為20ms的周期內(nèi),輸入以0.5-2.5ms變化的脈沖寬度,對應(yīng)的轉(zhuǎn)角范圍從0度變化到180度,脈沖寬度與轉(zhuǎn)角呈線性關(guān)系??刂菩盘柧€提供一定脈寬的脈沖時,其輸出軸保持在相應(yīng)的角度上。若舵機(jī)初始角度狀態(tài)在0度位置,那么電機(jī)只能朝一個方向運(yùn)動。所以初始化的時候,應(yīng)將所有電機(jī)的位置定在90度的位置。機(jī)器人跟關(guān)節(jié)連接的舵機(jī)轉(zhuǎn)軸為水平轉(zhuǎn)動,控制腿部前進(jìn)和后退。2.4.2 舵機(jī)控制方法標(biāo)準(zhǔn)的舵機(jī)有3條導(dǎo)線,分別是:電源線、地線、控制線。輸出轉(zhuǎn)軸電源線Vcc地線GND控制線 圖7 標(biāo)準(zhǔn)舵機(jī) Fig 7 Standard steering gear電源線和地線用于提供舵機(jī)內(nèi)部的直流電機(jī)和控制線路所需的能源,電壓通常介于4-6V,這里取5V。給舵機(jī)供電電源應(yīng)能提供足夠的功率。控制線的輸入是一個寬度可調(diào)的周期性方波脈沖信號,方波脈沖信號的周期為20ms(即頻率為50Hz)。當(dāng)方波的脈沖寬度改變時,舵機(jī)轉(zhuǎn)軸的角度發(fā)生變化,角度變化與脈沖寬度成正比。從上述舵機(jī)轉(zhuǎn)角的控制方法可看出,舵機(jī)的控制信號實(shí)質(zhì)是一個可調(diào)寬度的方波信號(PWM)。該方波信號可由FPGA、模擬電路或單片機(jī)來產(chǎn)生。采用FPGA成本較高,用模擬電路來實(shí)現(xiàn)則電路較復(fù)雜,不適合多路輸出。所以一般采用單片機(jī)作為舵機(jī)的控制器。這里主要對機(jī)構(gòu)進(jìn)行設(shè)計(jì),單片機(jī)電子部分就暫不過多研究了。舵機(jī)輸出軸轉(zhuǎn)角 輸入信號脈沖寬度(周期為20ms)0.5ms1ms1.5ms 圖8 舵機(jī)輸出轉(zhuǎn)角與輸入信號脈沖寬度關(guān)系Fig 8 Actuator output angle and input signal pulse width 3 零件的設(shè)計(jì)3.1 軀干的設(shè)計(jì)仿生六組機(jī)器人的六條腿為均布在圓盤狀得機(jī)身上,為了設(shè)計(jì)簡潔,故將機(jī)身做成圓片形,直徑為 150mm。上下各一個,中間通過加工了內(nèi)螺紋的金屬圓柱支撐,從上下用螺釘將其固定。在主板上鉆出六組通孔,每組兩個,以用來安裝六組機(jī)器人的腿。通孔的直徑因大于 M3 的開槽圓柱頭螺釘?shù)拇髲?,以便螺釘能穿過通孔??追植荚诎霃綖?5mm 的圓上,同組兩個孔相距為 25mm。為了減輕重量,在不影響結(jié)構(gòu)安全的情況下,對圓片鉆孔,十二個孔均布在半徑為 50mm 的圓上,中心同樣去一個半徑為 40mm 的圓。這樣以來就可大幅降低零件的質(zhì)量。機(jī)身主板是整個機(jī)構(gòu)最中心的地方,它承載了6只足的負(fù)荷,設(shè)計(jì)要達(dá)到滿足的載荷、強(qiáng)度要求以及適合的尺寸。以上追求了輕便化的設(shè)計(jì)還是需要強(qiáng)調(diào)它的本身及部件可靠及便于維護(hù)的特點(diǎn)。機(jī)身主板如圖9所示。 圖9 機(jī)身主板 Fig 9 Motherboard3.2 基節(jié)的設(shè)計(jì)基節(jié)作為機(jī)器人的腿的安裝位置,需考慮舵機(jī)的安裝。這里采用兩個片狀零件來構(gòu)成基節(jié)。分為上基節(jié)片和下基節(jié)片。圖10為上基節(jié)片 圖10 基節(jié)片 Fig 10 Coxal plate基節(jié)做成長片狀使得腿的安裝位置向前伸展,使得腿部空間增大,可避免兩腿的刮碰,其長度為 65mm,前端寬度為 25mm 后端基座 32mm。分上下兩塊,上基節(jié)片前端中心位置鉆一個直徑為 4mm 的通孔,為舵機(jī)的轉(zhuǎn)軸預(yù)留。以前端中心為圓心在半徑為 7.5mm 的圓上均布四個直徑為 3mm 的內(nèi)螺紋孔。通過與固定在轉(zhuǎn)動軸上的圓片連接,當(dāng)舵機(jī)轉(zhuǎn)動時,舵機(jī)的機(jī)身就會帶動與它緊固的部分轉(zhuǎn)動。這個位置可稱為仿生六足機(jī)器人的跟關(guān)節(jié)。下基節(jié)片為跟關(guān)節(jié)舵機(jī)的安放平臺,在前端半圓的中心位置裝一個半徑為10mm 的圓片,圓片的中心位置為一通孔與跟關(guān)節(jié)舵機(jī)底片的相同位置的通孔由一個圓柱銷定位。圖11為下基節(jié)片 圖11 下基節(jié)片 Fig 11 Base segment下基節(jié)片與上基節(jié)片在結(jié)構(gòu)上只有一個直徑為 4mm 的通孔的區(qū)別,其基本尺和上基節(jié)片一樣,厚度同為 3mm。3.3 關(guān)節(jié)蓋的設(shè)計(jì)關(guān)節(jié)蓋的作用是用來連接跟關(guān)節(jié)和膝關(guān)節(jié)的。其后部夾住跟關(guān)節(jié)的舵機(jī),前部套住膝關(guān)節(jié)的舵機(jī),由于在這個零件上裝載了兩個舵機(jī),考慮到穩(wěn)定性因此其長度不能太長。圖12即關(guān)節(jié)蓋 圖12 關(guān)節(jié)蓋Fig 12 Joint cover前端加工一個長 42mm 寬 21mm 的方形孔,方孔用來固定膝關(guān)節(jié)舵機(jī)由圖可知關(guān)節(jié)蓋也需兩件,后部把跟關(guān)節(jié)的舵機(jī)夾住,通過兩個螺釘固定。前端方孔的尺寸略大于舵機(jī)的同位置尺寸,將舵機(jī)放入方孔,前后各一個,兩個關(guān)節(jié)蓋相距為 20mm。因舵機(jī)本身帶有固定部。因此裝入四個 M4 的螺釘,通過上下兩個孔,與關(guān)節(jié)蓋固定。關(guān)節(jié)蓋的基本尺寸為 85mm 長、60mm 寬、厚度為 3mm。其中后部寬為 40mm。綜合兩個舵機(jī)安裝后的位置,膝關(guān)節(jié)的舵機(jī)的轉(zhuǎn)軸與跟關(guān)節(jié)舵機(jī)的轉(zhuǎn)軸的距離為30mm。這個 30mm 即為股節(jié)的長度,作為腿的最末端 30mm 的長度似乎偏短。考慮到股節(jié)短可避免相鄰兩腿的碰撞,這使得每條腿都能在一個安全的區(qū)域內(nèi)運(yùn)動。便于操控與行走,確保了機(jī)構(gòu)的可行性。3.4 脛節(jié)片的設(shè)計(jì)脛節(jié)作為膝關(guān)節(jié)和踝關(guān)節(jié)的連接部分稱之為中腿。脛節(jié)片直接與兩個舵機(jī)的轉(zhuǎn)動軸。從腿的上端往下看,脛節(jié)片的上部與膝關(guān)節(jié)的舵機(jī)相連接,當(dāng)膝關(guān)節(jié)的舵機(jī)轉(zhuǎn)動時,帶動整個脛節(jié)運(yùn)動。在脛節(jié)下端與踝關(guān)節(jié)以及足部相連接,可帶動中足、下足。從下往上看時,當(dāng)足部地面接觸踝關(guān)節(jié)舵機(jī)轉(zhuǎn)動,由于足部分與地面接觸相當(dāng)足部被固定,踝關(guān)節(jié)舵機(jī)扭矩即通過脛節(jié)片向上傳遞。傳遞上去的扭矩使仿生六足機(jī)器人的軀體運(yùn)動。在脛節(jié)的兩個脛節(jié)片中有一片需與兩個關(guān)節(jié)的舵機(jī)相連。這就有了傳動脛節(jié)片的設(shè)計(jì)。傳動脛節(jié)片的結(jié)構(gòu)圖如圖13所示 圖13 傳動脛節(jié)片 Fig 13 Femur plate transmission傳動脛節(jié)片的尺寸為長 75mm、寬 22mm、厚 3mm。在兩端的半圓的圓心位置加工直徑為 4mm 的通孔用于與舵機(jī)相連接。在中間中心線兩邊分布有兩個直徑 2.2 的通孔,加裝兩個連接桿用于兩塊脛節(jié)片的連接。連接桿的長度為 45mm。 圖14 脛節(jié)片 Fig 14 Tibia plate與傳動脛節(jié)片相對應(yīng)的另一塊脛節(jié)片用加強(qiáng)膝關(guān)節(jié)與踝關(guān)節(jié)的連結(jié),結(jié)構(gòu)如圖14所示兩塊脛節(jié)片平行裝配連接,通過中間的兩根連接桿用螺釘緊固。從而組成中腿。3.5 足的設(shè)計(jì)足作為機(jī)器人與地面相接觸的部分,由裝在踝關(guān)節(jié)上的舵機(jī)控制運(yùn)動。為了減小與地面的摩擦,足前端做成尖的圓頭狀。如圖15所示 圖15 足 Fig 15 Foot足的后部分做寬為了能夠?qū)⒍鏅C(jī)裝進(jìn)來。根據(jù)計(jì)算足的長度為 90mm,這個長度是指從足尖到裝在足上的舵機(jī)的轉(zhuǎn)軸的長度,實(shí)際的足的零件的設(shè)計(jì)長度為108mm,在保證 90mm 后還需舵機(jī)的裝配空間。足寬為 30mm。3.6 連接桿的設(shè)計(jì)為了能夠?qū)⒛承┝慵b配起來,需要加入支撐物。體積和質(zhì)量小的桿狀連接件成了設(shè)計(jì)的首選。首先作為構(gòu)成六足機(jī)器人軀干的機(jī)身主板,兩板之間的距離需按裝在跟關(guān)節(jié)上的舵機(jī)的尺寸來確定。由舵機(jī)的結(jié)構(gòu)可知舵機(jī)的寬度尺寸作為機(jī)身主板的間距的基礎(chǔ),經(jīng)計(jì)算可知軀干上的連桿需 44mm 長。通過兩頭的螺釘緊固。圖16即軀干上的連接桿。 圖16 軀干連接桿 Fig 16 Trunk connecting rod在連接桿的兩端鉆孔攻絲加工內(nèi)螺紋以便與螺釘配合。另一個是用于兩塊脛節(jié)片的連接,使得通過脛節(jié)把足和股節(jié)連接起來如:如圖17所示。 圖17 脛節(jié)連桿 Fig 17 Femur rod3.7 固定片的設(shè)計(jì)如何讓舵機(jī)的傳動軸的扭矩作用到腿的幾個關(guān)節(jié),這需要進(jìn)行相關(guān)的連接和固定,以確保實(shí)現(xiàn)機(jī)器人足部穩(wěn)定的行走以及良好的靈活性能。這需要設(shè)計(jì)專門的零件來實(shí)現(xiàn)。針對前面設(shè)計(jì)的零件設(shè)計(jì)出圓片狀的固定片。傳動連接片通過直接與舵機(jī)的傳動軸連接,再由四個螺釘與基節(jié)片或脛節(jié)片連接即可將扭矩傳遞出來。關(guān)節(jié)連接片通過裝在中心孔和舵機(jī)固定板的圓柱銷連接,用來固定舵機(jī)的位置以及給仿生六足機(jī)器人的機(jī)構(gòu)保證穩(wěn)定性。另外連接片還通過四個螺釘與基節(jié)片或脛節(jié)片相連接。在跟關(guān)節(jié)與股節(jié)片相連的過程中以及在膝關(guān)節(jié)與脛關(guān)節(jié)的連接過程中,加上脛關(guān)節(jié)與踝關(guān)節(jié)的連接過程中以及踝關(guān)節(jié)與足底根部的連接過程中都需要用到固定片與連接片,這個關(guān)鍵部位看似簡單,其實(shí)在保證整個機(jī)構(gòu)的穩(wěn)定行走的狀態(tài)中,它的作用是功不可沒的。通過具體的尺寸計(jì)算確定零件的尺寸,根據(jù)具體需要設(shè)計(jì)零件的結(jié)構(gòu),在零件設(shè)計(jì)時活學(xué)活用。如圖18和19。 圖18 傳動連接片 圖19 關(guān)節(jié)連接片 Fig 18 Driving connecting piece Fig 19 Joint connecting piece4 總結(jié)畢業(yè)設(shè)計(jì)是大學(xué)里對所學(xué)知識的一次大練兵,為我們走向即將到來的工作崗位做準(zhǔn)備。通過這次設(shè)計(jì),我看到了自己的不足,但是從最初的無從下手到后來的主動發(fā)現(xiàn)問題這一過程中,我不斷地磨練了自己。從最開始選題,覺得六足機(jī)器人很有趣。畢業(yè)設(shè)計(jì)開始后我看到任務(wù)書我在懷疑當(dāng)初的選擇是否合適,它是否適合我,我又能否適應(yīng)它。通過自己的努力慢慢的一點(diǎn)點(diǎn)的克服,從中找到了樂趣。設(shè)計(jì)的進(jìn)展也好轉(zhuǎn)了。四個月的設(shè)計(jì)即將結(jié)束。在這段時間里自己不斷地反思補(bǔ)償不足,學(xué)會了如何去做事如何提高自己。參考文獻(xiàn)1 陳懇 等.機(jī)器人技術(shù)與應(yīng)用M .北京:清華大學(xué)出版社,20062 林良明.仿生機(jī)械學(xué)M。上海:上海交通大學(xué)出版社,1991,4:21-233 王坤興.機(jī)器人技術(shù)的發(fā)展趨勢J,機(jī)器人技術(shù)與應(yīng)用,2001,3:42-454 馬惠欽.昆蟲與仿生學(xué)淺談J.昆蟲知識.2003,03:12-135 蘇軍,陳學(xué)東,田文罡.六足機(jī)器人全方位步態(tài)的研究J .機(jī)械與電子,2004,(3):48-52.6 Volker D,Josef S,Holk C. Behavior-based modeling of hexapod locomotion: linking biology and technical application J .Arthropod Structure & Development,2004, 33:237-250.7 王沫楠、楊玉春.仿生機(jī)器蟹的模型建立及優(yōu)化.哈爾濱理工大學(xué)學(xué)報(bào),2003,8(6):1-3.8 趙鐵石、趙永生、黃真.仿蟹步行機(jī)構(gòu)模型靈活度分析.中國機(jī)械工程,1998,9(3):52-54.9 王庭樹.機(jī)器人運(yùn)動學(xué)及動力學(xué).西安:西安電子科技大學(xué)出版社,1990.10 殷際英,何廣平.關(guān)節(jié)型機(jī)器人.北京:化學(xué)工業(yè)出版社,2003.11 黃真,孔憲文.具有冗余自由度的空間并聯(lián)多環(huán)機(jī)構(gòu)的運(yùn)動分析.機(jī)械工程學(xué)報(bào),2005.12 王秋麗.仿生步行機(jī)器人機(jī)構(gòu)設(shè)計(jì)建模與運(yùn)動學(xué)分析仿真D.北京:清華大學(xué)出版社,200513 ChengFT,OrinDE. Optimal force distribution in multiple chain robotic system J.IEEE Trans.onSystem,Man,and Cybernetics,1991,21(1):13-24.14 陳學(xué)東、賈文川.多足步行機(jī)器人運(yùn)動規(guī)劃與控制M,武漢:華中科技大學(xué)出版社,2006,6:78-8015 錢晉武.六足步行機(jī)靜態(tài)穩(wěn)定的必要性與充分性J.上??萍即髮W(xué)學(xué)報(bào),1992 Voll5 No4:200-203.16 爾桂花,竇日軒.運(yùn)動控制系統(tǒng)M,北京:清華大學(xué)出版社,200217 李鐵才,杜坤梅.電機(jī)控制技術(shù)M,哈爾濱:哈爾濱工業(yè)大學(xué)出版社,2002,1218 龔振邦,陳振華等.機(jī)器人機(jī)械設(shè)計(jì)M.北京:電子工業(yè)出版社,1995:312-316.19 鄒慧君,田永利,郭為忠.現(xiàn)代機(jī)構(gòu)學(xué)的形成、基本內(nèi)容和應(yīng)用前景.機(jī)械設(shè)計(jì)與研究,2002,18(2):10-12.20 蔡自興.機(jī)器人學(xué)M.北京:清華大學(xué)出版社,2000.致 謝經(jīng)過四個月的忙碌和工作,本次畢業(yè)設(shè)計(jì)已經(jīng)接近尾聲,作為一個本科生的畢業(yè)設(shè)計(jì),由于經(jīng)驗(yàn)的匱乏,難免有許多考慮不周全的地方,如果沒有導(dǎo)師的監(jiān)督與指導(dǎo),以及同學(xué)的支持,想要完成這個設(shè)計(jì)是難以想象的。在這里首先要感謝我的導(dǎo)師孫松林教授。孫老師平日里工作繁多,但在我做畢業(yè)設(shè)計(jì)的每個階段,從查閱資料到設(shè)計(jì)草案的確定和修改,中期檢查,后期詳細(xì)設(shè)計(jì),裝配彩圖等整個過程各中都予以了我悉心的指導(dǎo)。我的設(shè)計(jì)較為復(fù)雜繁瑣,但是孫老師任然悉心地糾正圖紙的錯誤。除了敬佩孫老師的專業(yè)水平外,他的治學(xué)嚴(yán)謹(jǐn)和科學(xué)研究精神也永遠(yuǎn)是我學(xué)習(xí)的榜樣,并將積極的影響我以后的學(xué)習(xí)和工作。其次要感謝同學(xué)對我的無私幫助,特別是在軟件的使用方面,正是因?yàn)槿绱宋也拍茼樌耐瓿稍O(shè)計(jì),我要感謝我的母校湖南農(nóng)業(yè)大學(xué),是母校給我提供了優(yōu)良的學(xué)習(xí)環(huán)境;另外,我還要感謝那些每位曾經(jīng)給我授過課的老師,是你們教會我專業(yè)知識。在此,我再說一次謝謝,謝謝大家。21Available online at SCIENCE DIRECTB d Journal of Bionic Engineering 3 (2006) 115-125 A Biomimetic Climbing Robot Based on the Gecko Carlo Menon, Metin Sitti Camegie Mellon University, Pittsburgh, Pennsylvania 15213-389, USA Abstract The excellent climbing performance of the gecko is inspiring engineers and researchers for the design of artificial systems aimed at moving on vertical surfaces. Climbing robots could perform many useful tasks such as surveillance, inspection, repair, cleaning, and exploration. This paper presents and discusses the design, fabrication, and evaluation of two climbing robots which mimic the gait of the gecko. The first robot is designed considering macro-scale operations on Eaah and in space. The second robot, whose motion is controlled using shape memory alloy actuators, is designed to be easily scaled down for micro-scale applications. Proposed bionic systems can climb up 65 degree slopes at a speed of 20 mms-. Keywords: gecko, robotics, biomimetics, climbing, space memory alloy Copyright 0 2006, Jilin University. Published by Science Press and Elsevier Limited. All rights reserved. 1 Introduction The locomotion, sensing, navigation, and adapta- tion capabilities in animals have long inspired humans to emulate them in robots. The purpose of this study was to determine the potential of climbing robots for both ter- restrial and extra-terrestrial explorations. Robots similar to their biological counterparts require extensive sys- tems for power, locomotion, and actuation, with com- putation, sensing, and autonomy. From animal research and current technologies, the possibility of developing biomimetic robots was analyzed. Locomotory abilities and biomimetic properties of lizards provide an advan- tage for climbing vertical surfaces. The development of climbing robots is mainly driven by the desire to automate tasks which are risky. Wall-climbing robots are used for cleaning high-rise buildings and inspection in dangerous environments such as storage tanks for petroleum industries and nu- clear power plants. Recently, there has also been in- terest in using robots which operate in a micro-gravity environment to inspect and repair space vehicles aside from helping astronauts in their risky operations. Sur- Corresponding author: Carlo Menon E-mail: menoncarlo stargatenetit face climbing and walking robots have become crucial for inspection and maintenance of space shuttles, satel- lites, nuclearplants21, pipeand buildings, search- and- rescue41 for homeland security, exploration on planets or hazardous regions, labeling oil tank volume scale, carrying high payloads, cleaning, sand blasting, painting, and microhano-scale manufacturing application-. These autonomous robots encounter mostly unstructured environments, and by legged walking and climbing lo- comotion, can overcome these obstacles easily. Climbing animals may inspire man to develop ro- bots able to access and operate in hazardous environ- ments. Many animals, e.g., cockroaches, beetles, ants21, and cricket, can climb and use mainly cap- illary forces to stay attached to surfaces. Beetles can lift a load up to 20 times heavier than their body when they are attached to a surface firmly. The geckos ability to climb surfaces, however, has attracted attention for decades. By means of compliant microhano-scale high aspect ratio beta-keratin structures on their feet, geckos manage to adhere to almost any surface with a controlled contact area41. This paper presents and discusses new gecko- inspired robots. Strategic solutions which are used by geckos for climbing are investigated and analyzed. The 116 Journal of Bionic Engineering (2006) vo1.3 No.3 paper presents the design, fabrication and test phases that the authors followed to make two robot prototypes. The first robot, called the Rigid Gecko Robot (RGR), was conceived considering operations in space. Reli- ability and robustness are the most important require- ments for the RGR. The second robot, called the Com- pliant Gecko Robot (CGR), has been conceived and designed for miniaturization. As the miniaturization of standard electric motors and pin joints, which connect rigid links of conventional robots, is intrinsically diffi- cult, a new gecko inspired flexible backbone structure actuated by Shape Memory Alloy (SMA) micro-wires was developed. 2 Problem definition The unique features of a novel climbing robot are: 0 Climbing on any surface roughness and material in any environment (on buildings, rocks and trees, in desert and space, under sea, etc.); 0 Longer operating time and range: currently, the range of autonomous micro-robots is limited by their small on board power sources. By increasing the effi- ciency with which the robots locomote by using the low power attachment and detachment of dry synthetic ad- hesives, the operating range will be increased. Fur- thermore, the self-cleaning nature of the dry adhesive material combined with the high tensile strength of the fibers allows non-degrading performance with a very long lifetime; 0 High maneuverability, speed and agility due to fast attachment and detachment in any orientation; 0 Possibility of carrying higher payloads (a gecko can carry a payload the same weight as its body while climbing a wall); 0 Accessing small areas due to their miniaturiza- tion; 0 Generating very high controlled attachment forces for realizing mechanical work during the robotic mission especially for maintenance applications; 0 Autonomous and on-line monitoring, inspection and maintenance of surfaces by integrated sensing and manipulation tools. In order to develop a vertical climbing robot with high performance, the kinematics of the most agile climbing animal, the gecko, was studied and analyzed. Kinematic data51 were analysed and modeled to simu- late the two dimensional motion of the gecko. Those simulations suggested a climbing robot having the fol- lowing characteristics: (1) Centre of mass close to the vertical surface, (2) Light structure, (3) Reliable system, (4) Robust locomotion. While reversing engineering ideas from nature, the level of biomimetic abstraction must be defined in order to design a system that is valuable from an engineering prospective. For this reason, the authors, who aimed at developing real prototypes able to climb inclined sur- faces, decided to consider only the functional charac- teristics of the gecko adhesive. Commercially available and economically convenient adhesives with good at- taching properties and repeatable behaviour were tested. These adhesives, which have the same attaching func- tionality of gecko hair and are suitable for extended testing, enabled the development of novel climbing ro- bots. We wanted to develop a robot with only the nec- essary degrees of freedom and using only essential components necessary for climbing. Therefore, the robot is not made heavier by auxiliary motors and sensors which may compromise its climbing performance. Here, the proposed designs assume relatively flat surfaces for climbing with no obstacles. 3 Robot design The gecko differs from other climbing animals in three main aspects: dry adhesive pads, foot geometry and gait. These three aspects were studied in order to design a gecko-inspired robot. In this section, the strat- egy for developing a climbing robot prototype is pre- sented and discussed. 3.1 Adhesive pads Much work has been devoted to the development of adhesion mechanisms for climbing robots. Suction ad- hesionV9101 requires the robot to carry an onboard pump to create a vacuum inside cups which are pressed against the wall or ceiling. Many grops developed Car10 Menon, Metin Sitti: A Biomimetic Climbing Robot Based on the Gecko 117 wall-climbing robots using mainly vacuum suction. However, a suction mechanism consumes high power and is relatively slow at detachment. In addition, any gap in the seal can cause the robot to fall. Last, the suction adhesion mechanism relies on ambient pressure to stick to a wall, and therefore is not useful in space applications because of the zero pressure space environment. Another common type of adhesion mechanism is magnetic Magnetic adhesion has been implemented in wall climbing robots for specific applications such as in- spection in nuclear facilities. Despite that, magnetic attachment is useful only in specific environments where the surface is ferromagnetic, so for most applications it is an unsuitable solution. Another strategy is to study passive attachment mechanisms, like those used by climbing animals. The Tokay gecko, for example, can weigh up to 300 g and reach length of 35 cm, yet is still able to run inverted and cling to smooth walls. Unique adhesive pads give the gecko incredible movement and climbing performance. Recently, nano-technology has enabled novel fabrica- tion techniques for gecko-inspired dry adhesives. Geckos have compliant micro- and nano-scale beta-keratin structures of high aspect ratio on their feet which adhere to any surface with a pressure-controlled contact area51. This adhesion is mainly due to molecu- lar forces such as van der Waals forces. Foot-hairs have a branch structure starting from the micrometer scale (stalks) and arriving in nano-scale (spatula stalks). The hairs can bend and conform to a wide variety of surface roughness. Since dry adhesion is based on van der Waals forces, surface chemistry is not of great im- portance. This means that dry adhesion will work on almost any surface. Synthetic adhesive mimicking gecko structure has been developed and exciting results are expected. Using micro-molding techniques, 4 pm di- ameter polymer micro-fibers are already available201, and high performance is possible. However, the devel- opment of a climbing robot prototype needs reliable and commercially available adhesives that could be used for a large number of tests. For this reason two commercial adhesives were tested: Silly Putty and polydimethyl siloxane (PDMS). We chose these two materials as they work on the same functional principle of the gecko ad- 13,14,17 hesive: by preloading the material against a surface, the contact area is maximized and intermolecular bonds are established. Fig. 1 shows results obtained using a customized measurement test-bed. Adhesives had a size of 95 mm2, they were loaded against a glass surface using a preload of 75 mN, an approach velocity of 0.08 mms-, and a retracting velocity of 0.4 111l11.s-l. The contact time was one second. Fig. 1 also shows that, during the one second contact phase, the preload slightly decreases caused by the plastic behaviour of the adhesive materials. During this phase, adhesives comply to surface roughness and fill nano-scale hollows. In addition, Fig.l shows that Silly Putty exerts the highest normal adhesive force and therefore this material was chosen for our robotic ap- plication. Plastic behavior 7- XiEiiq 0 Time (s) 20 I -320 Fig. 1 Silly Putty and flat PDMS adhesive force using 75 mN preload. 3.2 Foot design The adhesive pad of the climbing gecko is opti- mized for power efficiency and fast attachment and detachment cycles. In the attachment phase, the foot approaches the surface and the pad is preloaded and dragged on the surface. Thus, the pad fibers adapt to the surface roughness and maximize the contact area for high adhesion. In the detachment phase, the foot is twisted to peel the adhesive pad from its tip part. Then, the pad pops off and separates from the surface after a critical angle (about 30 degrees). Fig. 2 shows an ideal robotic foot movement. Using a compliant foot, the robot can take advantage of the properties of the adhesive pads. Fig. 3 shows the realistic solution of the attaching-detaching mechanism which was designed for our robot prototypes. Some simplifications were carried with respect to the ideal case of Fig. 2: 118 Journal of Bionic Engineering (2006) Vo1.3 No.3 Fig. 3 Foot mechanism. The adhesive is Silly Putty since tests shows that it Drag motion is not used since Silly Putty does not The approaching, preloading and peeling phases are carried out using the configuration suggested by Fig. 3. The foot mechanism is composed of an electrical solenoid motor, a rigid leg and an elastic foot material. has the highest normal force. have microhano hairs which need to be oriented. 3.3 RGR design The two-dimensional kinematic model of the RGR prototype has ten degrees of freedom (DOF), as shown in the left of Fig. 4. The first four-DOFs are used to lift the legs by means of four motors; one-DOF, in the middle of the robots back, is necessary for locomotion and it is controlled by another motor. The other five-DOFs are passive revolute joints. The right of Fig. 4 shows that the planar kinematics of the robot can be represented by a four-bar-linkage. The dynamics of the RGR, in vertical climbing mode, were studied using multi-body software (Visual Nastran Desktop 4D) and a three-dimensional model with realistic specifications. The model was 0.1 m long, 0.1 m wide and weighed 80 g. The graph on the left of Fig. 5 shows the rotation of the motor which controls the robots back displacement (number 5 in Fig. 4). This rotation is the input for the dynamic simulation. The graph on the right of Fig. 5 shows the torque output of the same motor. This torque is necessary for counterbalancing both the robot weight and dynamic forces caused by the robot motion. Fig. 4 Picture of the rigid gecko inspired robot. z30pL on the right, a schematic representa- tion of the gecko robot showing the model to be stud- ied for understanding its unstable configuration. (FL,J=Fore Left Joint; HRJ=Hind Right Joint; FRJ=Fore Right Joint; HLJ=Hind Right Joint; BRJ=Back Right Joint; MRJSMiddle Revolute Joint.) (3) Changing the position of the motor, (4) Decreasing the angle range of the BRJ rotation. For the RGR prototype, the fourth solution was chosen since a symmetrical configuration of the robot was preferred. 3.4 CGR design The CGR was designed aiming at miniaturization of climbing robots. For this purpose, an innovative compliant system has been developed. This robot has a composite frame and SMA wires which provide motion that mimics muscles. The back, Fig. 8, is flexible, and SMA wires are attached to both sides. The back is able to recover the initial length of the SMA wires during their cooling phase. Unlike revolute electronic motors and rigid links connected by pin joints used in the RGR, the flexible structure and the simple linear SMA actuators can be easily and efficiently scaled down for miniatur- ized climbing robots. The geometry of the robot was optimized both to have long robot step and amplify SMA wires force. With regard to step optimization, analytical kinematics equations were derived taking into account flexible back characteristics. Analysis was necessary to obtain AL, the step length, as a function of all the other parameters, a, b, c, and m of Fig. 8. SMA wire Fig. 8 Compliant gecko Compliant 1. Hind legs inspired robot model. Fig. 9 shows results when wires of both sides of the back are alternately contracted to perform one full step. In order to compare the effects of a and m and obtain the corresponding physical solution, the condition: a+m=constant (2) was used. In addition, the maximum contraction of the wires was limited to 4% of their length because of the inherent SMA wire characteristics. For simplicity, fore 120 Journal of Bionic Engineering (2006) voi.3 No.3 Fig. 9 Relation among L, c, (I and Ap while the variables a and m were constrained by equation a+m=constant. The SMA wire contraction was constrained to the 4% of the wire length. and hind legs were considered of the same lengths (m=b). The following considerations are deducible from the graph on the left of Fig. 9: (1) L increases with u; (2) The variation of L (a) increases with a; (3) The variation of L increases with the variation The graph on the right of Fig. 9 shows that if the length (parameter a) increases, then the step size Ap decreases (see Fig. 8). In addition, the condition a+m= constant means that the step increases with the length of the legs. The ideal robot must therefore have long legs and a short back. The second analysis focused on CGR back de- flection during the contraction of the SMA wires. Since the CGR back is fixed differently to the fore and hind legs (Fig. 4), the compliant back was modeled as a can- tilever with an external normal force, R, and a moment, M, applied to its end (Fig.10). Both R and A4 are func- tions of the cantilever deflection and their values were therefore computed in an iterative procedure during CGR back deflection. The effects of the distance spacer, s, on the distance, d, and force, F, (see Fig.10) were studied using large deflection theory221. The ffow-chart of Fig.11 shows the iterative pro- cedure which was used. Parameters ro and Fa the ap- proximated cantilever curvature and the estimated SMA constant forces respectively, represent the initial soft- ware inputs. For simplicity, the flow-chart of Fig.11 does not show all software subsystems, e.g. subsystems for computing elliptic integrals, which are involved in the cantilever large deflection computation. of c. The graph on the right of Fig. 11 shows results obtained using realistic data of the CGR prototype back, Youngs Modulus = 226 GPa; back length=lO cm, back width = 24 111111. This graph is critical for control strate- gies. In fact, the developed cantilever deflection model can be used in a feed-forward control loop. For the CGR locomotion design, weight and dynamic forces were neglected as the prototype was designed to be very light and to climb slowly. Fig. 10 Model for the SMA force analysis. The CGR can be reduced to the study of a cantilever contracted by a SMA wire. The distance spacer(s) introduces a variable moment M. 51 41 I I/ Displacement (mm) Fig. 11 On the left side: flow-chart of the software developed for the iterative computation of CGR back deflection. Large deflection theory was used. On the right side: force that the SMA wires exerted for bending the CGR back. Different curves correspond to different values of the distance spacers. 4 The prototypes and experiments In this section, actual RGR and CGR prototypes are presented. Robot specifications and characteristics are also discussed. 4.1 RGR prototype The chassis of the RGR, which was designed to operate in macro-scale and for space applications, was Car10 Menon, Metin Sitti: A Biomimetic Climbing Robot Based on the Gecko 121 built using aluminum alloy. The frame was made by folding aluminum sheets. RGR was equipped with five solenoid motors, four for lifting the legs, and one for locomotion. The maximum torque of each motor, which was amplified by a 8 1 : 1 gearboxes, was 25 Nmm ob- tained using 5 V. The RGR was controlled by a PIC 16F877 micro-controller integrated in a customized electronic board. Fig. 12 shows the control strategy used for one-full step. All five motors were controlled in sequence in order to detach one foot at a time minimiz- ing the risk of robot falling. Fig. 13 Picture of the compliant gecko inspired robot. The use of glass fiber had two different purposes: reinforce the compliant body structure; electrically iso- late the CGR frame when in contact with SMA wires. A thin layer of epoxy, obtained by the use of a spinner machine, was also spread over the composite back in order to increase the electrical insulation. Composite theory was used to compute the mechanical properties of the CGR back laminate (Table 1). Table 1 Mechanical properties of the CGR back laminate Fig. 12 Control strategy for one-full robot step: time evo- lution of the rotations of each motorized joint. 4.2 CGR prototype The fabrication of the CGR, shown in Fig. 13, was very challenging due to the use of SMA wires and com- posite material chassis. The CGR back was equipped with 50 pm diameter SMA wires with a transition tem- perature of about 90 C (Flexinol
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