購買設(shè)計請充值后下載,,資源目錄下的文件所見即所得,都可以點開預(yù)覽,,資料完整,充值下載可得到資源目錄里的所有文件。。?!咀ⅰ浚篸wg后綴為CAD圖紙,doc,docx為WORD文檔,原稿無水印,可編輯。。。具體請見文件預(yù)覽,有不明白之處,可咨詢QQ:12401814
機器人和電腦一體機制造
關(guān)于生成工業(yè)機器人機械手的運動
K. Kaltsoukalas, S. Makris, G. Chryssolouris
佩特雷大學(xué)實驗室制造系統(tǒng)和自動化,希臘
論文信息
文章歷史: 關(guān)鍵詞:
2013年10月17日收到初稿 路徑規(guī)劃
2014年9月19日收到修改稿 工業(yè)機器人運動
2014年10月8日通過審核 網(wǎng)格搜索
2014年10月29日網(wǎng)上資源共享
摘要
在這個研究中,提出了一個智能搜索算法定義所需的位置和工業(yè)機器人機械手的定位效應(yīng)路徑的想法。這個算法通過選擇和評估機器人的配置逐步達(dá)到所需的配置。構(gòu)造網(wǎng)格的機器人替代配置使用一組參數(shù),減少了搜索空間并減少計算時間。對于可選擇性的評價,使用多個標(biāo)準(zhǔn),用以滿足不同的要求。替代的配置重點是給機器人的關(guān)節(jié),主要影響末端執(zhí)行器的位置。網(wǎng)格的分辨率和尺寸參數(shù)的設(shè)置在期望輸出的基礎(chǔ)上,高分辨率通過對目標(biāo)位置只提供一些中間點用于平滑的路徑和一個粗略的估計。規(guī)劃的路徑是一系列的機器人配置。這種方法為一個沒有經(jīng)驗的程序員自動生成機器人路徑提供了方便,這能達(dá)到預(yù)期的標(biāo)準(zhǔn)而不必記錄中間點到目標(biāo)位置。
2014?Elsevier有限公司保留所有權(quán)利
介紹
近年來,由于能適應(yīng)不同的市場需求和產(chǎn)品結(jié)構(gòu)的變化,對柔性制造系統(tǒng)的需求日益增加。動態(tài)生產(chǎn)環(huán)境要求越來越多的裝配制造資源重新配置。自動裝配系統(tǒng),如機器人。它們的靈活性通常被制約因為高的編程工作要求機器人軌跡調(diào)整去適應(yīng)不同的裝配單元布局。經(jīng)驗豐富的機器人程序員不得不花大量時間采用常規(guī)的編程方法優(yōu)化每一個具體的應(yīng)用機器人的路徑。一種廣泛應(yīng)用的方法是演示編程,通過順序移動機器人的每個位置并記錄中間點的位置來示教。通過機器人控制器的連接記錄點產(chǎn)生機器人的最后路徑,路徑考慮到機器人的動力學(xué)約束并通過所有的約束點。機器人的最終軌跡高度依賴記錄點和程序員各自的編程經(jīng)驗。機器人自動路徑規(guī)劃提出了一個問題,在過去的幾十年里如何實現(xiàn)移動機器人從初始到最終的位置進行的研究,主要集中在路徑規(guī)劃避障。
一種運動規(guī)劃技術(shù)是通過采樣配置空間來構(gòu)建近似的模型。在過去的幾年里,已經(jīng)有很多為基于采樣的運動規(guī)劃算法進行改善的工作在進行了。在不同的類別中分類所有的規(guī)劃者很難定義一個單一的標(biāo)準(zhǔn)。經(jīng)典的分離是基于路線圖規(guī)劃者和邏輯樹規(guī)劃者之間。概率路線圖路徑規(guī)劃中引入一個計算機器人無碰撞路徑的新方法。這個方法分兩個階段進行:學(xué)習(xí)和查詢。在學(xué)習(xí)階段,一個概率圖是通過生成機器人的隨機免費配置和使用一個簡單的運動規(guī)劃連接它們建設(shè),也被稱為當(dāng)?shù)氐囊?guī)劃師。不同的方法已被用來解決各種各樣的問題,為了可變形物體的運動規(guī)劃而提出了構(gòu)建和查詢路線圖兩種不同的方法。還提出了另一個變形的技術(shù)可以應(yīng)用到生成的路徑中。介紹了障礙物的概率圖法,在生成節(jié)點的幾種策略進行了闡述并且提出了復(fù)雜三維工作區(qū)多級連接策略。通過擴展規(guī)劃無碰撞運動觸點配置的空間概率圖范例 ,隨機規(guī)劃被描述為在任意兩個多面體固體之間的CF兼容的運動規(guī)劃。這種方法的關(guān)鍵是隨機產(chǎn)生CF兼容的配置的新的采樣策略 。
引入了快速擴展隨機樹的概念,基本的想法是,初始樣品(起始組態(tài))是樹的根和新產(chǎn)生的樣本,然后連接到樹中已經(jīng)存在的樣品。兩個快速擴展隨機樹(RRTS)扎根在開始和在目標(biāo)配置中。樹的每一個探索周圍的空間,也提出了對彼此通過一個簡單的貪婪算法的使用。雖然它最初被計劃設(shè)計為人手臂的運動動作(建模為一個自由度的運動鏈),在無碰撞把握和操作任務(wù)的自動圖形動畫中,該算法已被應(yīng)用于各種路徑規(guī)劃問題。邏輯樹規(guī)劃者們已證明是處理實時規(guī)劃和重新規(guī)劃問題的一個很好的框架。為了修復(fù)快速擴展隨機樹進行更改時配置空間,一個重新規(guī)劃算法被提了出來。不是放棄當(dāng)前RRT,該算法有效地只消除了新無效部分并保持休息。在工業(yè)環(huán)境中移動機器人的動態(tài)避障已經(jīng)開始研究調(diào)查。然而,工業(yè)機器人通常被編程以執(zhí)行預(yù)定義的路徑。機器人編程的方法主要有兩大類:在線編程和離線編程。
為了用戶的互動轉(zhuǎn)化為簡單任務(wù)提出了一個在線路徑規(guī)劃支持系統(tǒng)產(chǎn)生可接受的軌跡,適用于工業(yè)機器人的編程的問題。建議得出了一種新的方法,即機器人編程使用增強現(xiàn)實環(huán)境。為現(xiàn)場的機器人編程方法所需提供靈活性和適應(yīng)性以應(yīng)對不同環(huán)境。路徑規(guī)劃方法包括生成路徑的束搜索算法。有相似的研究表明,用戶能夠執(zhí)行的操作,即通過點的選擇和修改,為了實現(xiàn)一個光滑的無碰撞路徑。一個機器人運動規(guī)劃的方法,是根據(jù)預(yù)先計算的全局配置空間(C-)的連通性提出的。運動規(guī)劃,包括離線階段和在線階段和無碰撞的路徑將通過一個多分辨率策略下使用A*算法在C-空間中搜索。
在這個研究中,提出了一種智能搜索算法去定義工業(yè)機器人機械手端部執(zhí)行器所需的位置和方向的路徑??晒┻x擇的配置的最大數(shù)量被一步步選擇和評價,直到所需的配置是接近預(yù)定的誤差范圍內(nèi)為止。替代的配置是一個聰明的方式產(chǎn)生,重視主要影響機器人的空間位置的關(guān)節(jié)角度。在配置空間上,有一個人工推導(dǎo)機器人的替代組態(tài)網(wǎng)格。一套巧妙的參數(shù)用于減少搜索空間,提高算法的性能。對于替代品的評價,使用多個標(biāo)準(zhǔn),可以提高算法拓展的靈活性,這是為了滿足不同的要求,即滿足最短路徑的要求。
封面樣式
湖 南 科 技 大 學(xué)
英文文獻翻譯
學(xué) 生 姓 名:
學(xué) 院:
專業(yè)及班級:
學(xué) 號:
指 導(dǎo) 教 師:
2015 年 5 月 30 日
2.3機械手手臂結(jié)構(gòu)的設(shè)計
按照抓取工件的要求,車床上料機械手的手臂有三個自由度,及手臂的伸縮、左右回轉(zhuǎn)和降(或俯仰)運動。手臂的回轉(zhuǎn)和升降運動是通過立柱來實現(xiàn)的,立柱的橫向移動即為手臂的橫移。手臂的各種運動有氣缸來實現(xiàn)。
2.3.1機械手手臂設(shè)計要求
機器人手臂的作用,是在一定的載荷和一定的速度下,實現(xiàn)在機器人所要求的工作空間內(nèi)的運動。在進行機器人手臂設(shè)計時,要遵循下述原則;
1.應(yīng)盡可能使機器人手臂各關(guān)節(jié)軸相互平行;相互垂直的軸應(yīng)盡可能相交于一點,這樣可以使機器人運動學(xué)正逆運算簡化,有利于機器人的控制。
2.機器人手臂的結(jié)構(gòu)尺寸應(yīng)滿足機器人工作空間的要求。工作空間的形狀和大小與機器人手臂的長度,手臂關(guān)節(jié)的轉(zhuǎn)動范圍有密切的關(guān)系。但機器人手臂末端工作空間并沒有考慮機器人手腕的空間姿態(tài)要求,如果對機器人手腕的姿態(tài)提出具體的要求,則其手臂末端可實現(xiàn)的空間要小于上述沒有考慮手腕姿態(tài)的工作空間。
3.為了提高機器人的運動速度與控制精度,應(yīng)在保證機器人手臂有足夠強度和剛度的條件下,盡可能在結(jié)構(gòu)上、材料上設(shè)法減輕手臂的重量。力求選用高強度的輕質(zhì)材料,通常選用高強度鋁合金制造機器人手臂。目前,在國外,也在研究用碳纖維復(fù)合材料制造機器人手臂。碳纖維復(fù)合材料抗拉強度高,抗振性好,比重?。ㄆ浔戎叵喈?dāng)于鋼的1/4,相當(dāng)于鋁合金的2/3),但是,其價格昂貴,且在性能穩(wěn)定性及制造復(fù)雜形狀工件的工藝上尚存在問題,故還未能在生產(chǎn)實際中推廣應(yīng)用。目前比較有效的辦法是用有限元法進行機器人手臂結(jié)構(gòu)的優(yōu)化設(shè)計。在保證所需強度與剛度的情況下,減輕機器人手臂的重量。
4.機器人各關(guān)節(jié)的軸承間隙要盡可能小,以減小機械間隙所造成的運動誤差。因此,各關(guān)節(jié)都應(yīng)有工作可靠、便于調(diào)整的軸承間隙調(diào)整機構(gòu)。
5.機器人的手臂相對其關(guān)節(jié)回轉(zhuǎn)軸應(yīng)盡可能在重量上平衡,這對減小電機負(fù)載和提高機器人手臂運動的響應(yīng)速度是非常有利的。在設(shè)計機器人的手臂時,應(yīng)盡可能利用在機器人上安裝的機電元器件與裝置的重量來減小機器人手臂的不平衡重量,必要時還要設(shè)計平衡機構(gòu)來平衡手臂殘余的不平衡重量。
6.機器人手臂在結(jié)構(gòu)上要考慮各關(guān)節(jié)的限位開關(guān)和具有一定緩沖能力的機械限位塊,以及驅(qū)動裝置,傳動機構(gòu)及其它元件的安裝。
2.3.2設(shè)計具體采用方案
機械手的垂直手臂(大臂)升降和水平手臂(小臂)的伸縮運動都為直線運動。直線運動的實現(xiàn)一般是氣動傳動,液壓傳動以及電動機驅(qū)動滾珠絲杠來實現(xiàn)??紤]到搬運工件的重量較大,考慮加工工件的質(zhì)量達(dá)30KG,屬中型重量,同時考慮到機械手的動態(tài)性能及運動的穩(wěn)定性,安全性,對手臂的剛度有較高的要求。綜合考慮,兩手臂的驅(qū)動均選擇液壓驅(qū)動方式,通過液壓缸的直接驅(qū)動,液壓缸既是驅(qū)動元件,又是執(zhí)行運動件,不用再設(shè)計另外的執(zhí)行件了;而且液壓缸實現(xiàn)直線運動,控制簡單,易于實現(xiàn)計算機的控制。
因為液壓系統(tǒng)能提供很大的驅(qū)動力,因此在驅(qū)動力和結(jié)構(gòu)的強度都是比較容易實現(xiàn)的,關(guān)鍵是機械手運動的穩(wěn)定性和剛度的滿足。因此手臂液壓缸的設(shè)計原則是缸的直徑取得大一點(在整體結(jié)構(gòu)允許的情況下),再進行強度的較核。
同時,因為控制和具體工作的要求,機械手的手臂的結(jié)構(gòu)不能太大,若僅僅通過增大液壓缸的缸徑來增大剛度,是不能滿足系統(tǒng)剛度要求的。因此,在設(shè)計時另外增設(shè)了導(dǎo)桿機構(gòu),小臂增設(shè)了兩個導(dǎo)桿,與活塞桿一起構(gòu)成等邊三角形的截面形式,盡量增加其剛度;大臂增設(shè)了四個導(dǎo)桿,成正四邊形布置,為減小質(zhì)量,各個導(dǎo)桿均采用空心結(jié)構(gòu)。通過增設(shè)導(dǎo)桿,能顯著提高機械手的運動剛度和穩(wěn)定性,比較好的解決了結(jié)構(gòu)、穩(wěn)定性的問題。
2.4機械手腕部的結(jié)構(gòu)設(shè)計
機器人的手臂運動(包括腰座的回轉(zhuǎn)運動),給出了機器人末端執(zhí)行器在其工作空間中的運動位置,而安裝在機器人手臂末端的手腕,則給出了機器人末端執(zhí)行器在其工作空間中的運動姿態(tài)。機器人手腕是機器人操作機的最末端,它與機器人手臂配合運動,實現(xiàn)安裝在手腕上的末端執(zhí)行器的空間運動軌跡與運動姿態(tài),完成所需要的作業(yè)動作。
2.4.1機器人手腕結(jié)構(gòu)的設(shè)計要求
1.機器人手腕的自由度數(shù),應(yīng)根據(jù)作業(yè)需要來設(shè)計。機器人手腕自由度數(shù)目愈多,各關(guān)節(jié)的運動角度愈大,則機器人腕部的靈活性愈高,機器人對對作業(yè)的適應(yīng)能力也愈強。但是,自由度的增加,也必然會使腕部結(jié)構(gòu)更復(fù)雜,機器人的控制更困難,成本也會增加。因此,手腕的自由度數(shù),應(yīng)根據(jù)實際作業(yè)要求來確定。在滿足作業(yè)要求的前提下,應(yīng)使自由度數(shù)盡可能的少。一般的機器人手腕的自由度數(shù)為2至3個,有的需要更多的自由度,而有的機器人手腕不需要自由度,僅憑受臂和腰部的運動就能實現(xiàn)作業(yè)要求的任務(wù)。因此,要具體問題具體分析,考慮機器人的多種布局,運動方案,選擇滿足要求的最簡單的方案。
2.機器人腕部安裝在機器人手臂的末端,在設(shè)計機器人手腕時,應(yīng)力求減少其重量和體積,結(jié)構(gòu)力求緊湊。為了減輕機器人腕部的重量,腕部機構(gòu)的驅(qū)動器采用分離傳動。腕部驅(qū)動器一般安裝在手臂上,而不采用直接驅(qū)動,并選用高強度的鋁合金制造。
3.機器人手腕要與末端執(zhí)行器相聯(lián),因此,要有標(biāo)準(zhǔn)的聯(lián)接法蘭,結(jié)構(gòu)上要便于裝卸末端執(zhí)行器。
4.機器人的手腕機構(gòu)要有足夠的強度和剛度,以保證力與運動的傳遞。
5.要設(shè)有可靠的傳動間隙調(diào)整機構(gòu),以減小空回間隙,提高傳動精度。
6.手腕各關(guān)節(jié)軸轉(zhuǎn)動要有限位開關(guān),并設(shè)置硬限位,以防止超限造成機械損壞。
2.4.2設(shè)計具體采用方案
通過對數(shù)控機床上下料作業(yè)的具體分析,考慮數(shù)控機床加工的具體形式及對機械手上下料作業(yè)時的具體要求,在滿足系統(tǒng)工藝要求的前提下提高安全和可靠性,為使機械手的結(jié)構(gòu)盡量簡單,降低控制的難度,本設(shè)計手腕不增加自由度,實踐證明這是完全能滿足作業(yè)要求的,3個自由度來實現(xiàn)機床的上下料完全足夠。具體的手腕(手臂手爪聯(lián)結(jié)梁)結(jié)構(gòu)見圖8。
圖8 車床上料機械手手指
2.5機械手末端執(zhí)行器(手爪)的結(jié)構(gòu)設(shè)計
2.5.1機械手末端執(zhí)行器的設(shè)計要求
機器人末端執(zhí)行器是安裝在機器人手腕上用來進行某種操作或作業(yè)的附加裝置。機器人末端執(zhí)行器的種類很多,以適應(yīng)機器人的不同作業(yè)及操作要求。末端執(zhí)行器可分為搬運用、加工用和測量用等。
搬運用末端執(zhí)行器是指各種夾持裝置,用來抓取或吸附被搬運的物體。
加工用末端執(zhí)行器是帶有噴槍、焊槍、砂輪、銑刀等加工工具的機器人附加裝置,用來進行相應(yīng)的加工作業(yè)。
測量用末端執(zhí)行器是裝有測量頭或傳感器的附加裝置,用來進行測量及檢驗作業(yè)。
在設(shè)計機器人末端執(zhí)行器時,應(yīng)注意以下問題;
1.機器人末端執(zhí)行器是根據(jù)機器人作業(yè)要求來設(shè)計的。一個新的末端執(zhí)行器的出現(xiàn),就可以增加一種機器人新的應(yīng)用場所。因此,根據(jù)作業(yè)的需要和人們的想象力而創(chuàng)造的新的機器人末端執(zhí)行器,將不斷的擴大機器人的應(yīng)用領(lǐng)域。
2.機器人末端執(zhí)行器的重量、被抓取物體的重量及操作力的總和機器人容許的負(fù)荷力。因此,要求機器人末端執(zhí)行器體積小、重量輕、結(jié)構(gòu)緊湊。
3.機器人末端執(zhí)行器的萬能性與專用性是矛盾的。萬能末端執(zhí)行器在結(jié)構(gòu)上很復(fù)雜,甚至很難實現(xiàn),例如,仿人的萬能機器人靈巧手,至今尚未實用化。目前,能用于生產(chǎn)的還是那些結(jié)構(gòu)簡單、萬能性不強的機器人末端執(zhí)行器。從工業(yè)實際應(yīng)用出發(fā),應(yīng)著重開發(fā)各種專用的、高效率的機器人末端執(zhí)行器,加之以末端執(zhí)行器的快速更換裝置,以實現(xiàn)機器人多種作業(yè)功能,而不主張用一個萬能的末端執(zhí)行器去完成多種作業(yè)。因為這種萬能的執(zhí)行器的結(jié)構(gòu)復(fù)雜且造價昂貴。
4.通用性和萬能性是兩個概念,萬能性是指一機多能,而通用性是指有限的末端執(zhí)行器,可適用于不同的機器人,這就要求末端執(zhí)行器要有標(biāo)準(zhǔn)的機械接口(如法蘭),使末端執(zhí)行器實現(xiàn)標(biāo)準(zhǔn)化和積木化。
5.機器人末端執(zhí)行器要便于安裝和維修,易于實現(xiàn)計算機控制。用計算機控制最方便的是電氣式執(zhí)行機構(gòu)。因此,工業(yè)機器人執(zhí)行機構(gòu)的主流是電氣式,其次是液壓式和氣壓式(在驅(qū)動接口中需要增加電-液或電-氣變換環(huán)節(jié))。
2.5.2機器人夾持器的運動和驅(qū)動方式
機器人夾持器及機器人手爪。一般工業(yè)機器人手爪,多為雙指手爪。按手指的運動方式,可分為回轉(zhuǎn)型和移動型,按夾持方式來分,有外夾式和內(nèi)撐式兩種。
機器人夾持器(手爪)的驅(qū)動方式主要有三種
1.氣動驅(qū)動方式這種驅(qū)動系統(tǒng)是用電磁閥來控制手爪的運動方向,用氣流調(diào)節(jié)閥來調(diào)節(jié)其運動速度。由于氣動驅(qū)動系統(tǒng)價格較低,所以氣動夾持器在工業(yè)中應(yīng)用較為普遍。另外,由于氣體的可壓縮性,使氣動手爪的抓取運動具有一定的柔順性,這一點是抓取動作十分需要的。
2.電動驅(qū)動方式電動驅(qū)動手爪應(yīng)用也較為廣泛。這種手爪,一般采用直流伺服電機或步進電機,并需要減速器以獲得足夠大的驅(qū)動力和力矩。電動驅(qū)動方式可實現(xiàn)手爪的力與位置控制。但是,這種驅(qū)動方式不能用于有防爆要求的條件下,因為電機有可能產(chǎn)生火花和發(fā)熱。
3.液壓驅(qū)動方式液壓驅(qū)動系統(tǒng)傳動剛度大,可實現(xiàn)連續(xù)位置控制。
2.5.3機器人夾持器的典型結(jié)構(gòu)
1.楔塊杠桿式手爪
利用楔塊與杠桿來實現(xiàn)手爪的松、開,來實現(xiàn)抓取工件。
2.滑槽式手爪
當(dāng)活塞向前運動時,滑槽通過銷子推動手爪合并,產(chǎn)生夾緊動作和夾緊力,當(dāng)活塞向后運動時,手爪松開。這種手爪開合行程較大,適應(yīng)抓取大小不同的物體。
3.連桿杠桿式手爪
這種手爪在活塞的推力下,連桿和杠桿使手爪產(chǎn)生夾緊(放松)運動,由于杠桿的力放大作用,這種手爪有可能產(chǎn)生較大的夾緊力。通常與彈簧聯(lián)合使用。
4.齒輪齒條式手爪
這種手爪通過活塞推動齒條,齒條帶動齒輪旋轉(zhuǎn),產(chǎn)生手爪的夾緊與松開動作。
5.平行杠桿式手爪
采用平行四邊形機構(gòu),因此不需要導(dǎo)軌就可以保證手爪的兩手指保持平行運動,比帶有導(dǎo)軌的平行移動手爪的摩擦力要小很多。
2.5.4設(shè)計具體采用方案
結(jié)合具體的工作情況,本設(shè)計采用連桿杠桿式的手爪。驅(qū)動活塞往復(fù)移動,通過活塞桿端部齒條,中間齒條及扇形齒條使手指張開或閉合。手指的最小開度由加工工件的直徑來調(diào)定。本設(shè)計按照工件的直徑為80--130mm來設(shè)計。手爪的具體結(jié)構(gòu)形式如圖9所示:
圖9 手爪的具體結(jié)構(gòu)
2.6機械手的機械傳動機構(gòu)的設(shè)計
2.6.1工業(yè)機器人傳動機構(gòu)設(shè)計應(yīng)注意的問題
機器人是由多級聯(lián)桿和關(guān)節(jié)組成的多自由度的空間運動機構(gòu)。除直接驅(qū)動型機器人以外,機器人各聯(lián)桿及各關(guān)節(jié)的運動都是由驅(qū)動器經(jīng)過各種機械傳動機構(gòu)進行驅(qū)動的。機器人所采用的傳動機構(gòu)與一般機械的傳動機構(gòu)相類似。常用的機械傳動機構(gòu)主要有螺旋傳動、齒輪傳動、同步帶傳動、高速帶傳動等。由于傳動部件直接影響著機器人的精度、穩(wěn)定性和快速響應(yīng)能力,因此,應(yīng)設(shè)計和選擇滿足傳動間隙小,精度高,低摩擦、體積小、重量輕、運動平穩(wěn)、響應(yīng)速度快、傳遞轉(zhuǎn)矩大、諧振頻率高以及與伺服電動機等其它環(huán)節(jié)的動態(tài)性能相匹配等要求的傳動部件。
在設(shè)計機器人的傳動機構(gòu)時要注意以下問題:
1.為了提高機器人的運動速度及控制精度,要求機器人各運動部件的重量要輕,慣量要小。因此,機器人的傳動機構(gòu)要力求結(jié)構(gòu)緊湊,重量輕,體積小。
2.在傳動鏈及運動副中要采用間隙調(diào)整機構(gòu),以減小反向空回所造成的運動誤差。
3.系統(tǒng)傳動部件的靜摩擦力應(yīng)盡可能小,動摩擦力應(yīng)是盡可能小的正斜率,若為負(fù)斜率則易產(chǎn)生爬行,精度降低,壽命減小。因此,要采用低摩擦阻力的傳動部件和導(dǎo)向支承部件,如滾珠絲杠副、滾動導(dǎo)向支承等。
4.縮短傳動鏈,提高傳動與支承剛度,如用預(yù)緊的方法提高滾珠絲杠副和滾動導(dǎo)軌副的傳動和支承剛度;采用大扭矩、寬調(diào)速的直流或交流伺服電機直接與絲杠螺母副連接,以減小中間傳動機構(gòu);絲杠的支承設(shè)計采用兩端軸向預(yù)緊或預(yù)拉伸支承結(jié)構(gòu)等。
5.選用最佳傳動比,以達(dá)到提高系統(tǒng)分辨率、減少等效到執(zhí)行元件輸出軸上的等效轉(zhuǎn)動慣量,盡可能提高加速能力。
6.縮小反向死區(qū)誤差,如采取消除傳動間隙、減少支承變形等措施。
7.適當(dāng)?shù)淖枘岜龋瑱C械零件產(chǎn)生共振時,系統(tǒng)的阻尼越大,最大振幅就越小,且衰減越快;但大阻尼也會使系統(tǒng)的失動量和反轉(zhuǎn)誤差增大,穩(wěn)態(tài)誤差增大,精度降低。故在設(shè)計時要使傳動機構(gòu)的阻尼合適。
2.6.2工業(yè)機器人常用的傳動機構(gòu)形式
1.齒輪傳動機構(gòu)
在機器人中常用的齒輪傳動機構(gòu)有圓柱齒輪,圓錐齒輪,諧波齒輪,擺線針輪及蝸輪蝸桿傳動等。
機器人系統(tǒng)中齒輪傳動設(shè)計的一些問題
齒輪傳動形式及其傳動比的最佳匹配選擇。齒輪傳動部件是轉(zhuǎn)矩、轉(zhuǎn)速和轉(zhuǎn)向的變換器用于伺服系統(tǒng)的齒輪減速器是一個力矩變換器。齒輪傳動比應(yīng)滿足驅(qū)動部件與負(fù)載之間的位移及轉(zhuǎn)矩、轉(zhuǎn)速的匹配要求,其輸入電動機為高轉(zhuǎn)速,低轉(zhuǎn)矩,而輸出則為低轉(zhuǎn)速,高轉(zhuǎn)矩。故齒輪傳動系統(tǒng)要有足夠的剛度,還要求其轉(zhuǎn)動慣量盡量小,以便在獲得同一加速度時所需的轉(zhuǎn)矩小,即在同一驅(qū)動功率時,其加速度響應(yīng)最大。齒輪的嚙合間隙會造成傳動死區(qū)(失動量),若該死區(qū)是閉環(huán)系統(tǒng)中,則可能造成系統(tǒng)不穩(wěn)定,常使系統(tǒng)產(chǎn)生低頻振蕩,因此要盡量采用齒側(cè)間隙小,精度高的齒輪;為盡量降低制造成本,要采用調(diào)整齒側(cè)間隙的方法來消除或減小嚙合間隙,從而提高傳動精度和系統(tǒng)的穩(wěn)定性。
2.3 manipulator arm structure design
According to the requirement, lathe to grab workpiece material arm has three degrees of freedom of the manipulator arm, and adjustable, turning around and drop (or pitch) movement.Turn and lifting movement of the arm is realized by pillar, column the lateral movement known as the shifting arm. Different campaigns have cylinder arm to realize.
2.3.1 manipulator arm design requirements
The robotic arm role, it is in a certain load and a certain speed, realize the work required in robot in space sport. When designing the robotic arm, follow the following principles;
1. Should as far as possible make the robotic arm each joint axis parallel; Perpendicular axis should as far as possible fellowship in a bit, so can make the robot kinematics inverse robot control simplifies, helps.
2. The robotic arm structure size should satisfy the requirements of robots work space. Working space shapes and sizes and robot arm length, arm joint rotation range have close relationship. But the robotic arm end work space does not consider the space robot wrist gesture requirements, if robot wrist gesture to specific request, it can realize space arms ends to less than the above did not consider the wrist gesture work space.
3. In order to improve the robot movement speed and control accuracy, should keep the robotic arm have enough under the condition of the strength and stiffness, as far as possible on the structure, material manage to reduce the weight of his arm. Strive to choose high intensity of lightweight materials, usually choose high-strength aluminum alloy manufacture a robotic arm. At present, in a foreign country, is also studying with carbon fiber composite materials manufacturing robot arm. Carbon fiber composite materials tensile strength, high ant-vibration sex good, small proportion (its proportion of 1/4 quite to steel, equivalent to aluminum alloy 2/3), but it is expensive, and in the performance stability and manufacturing complex shape workpiece exist problems of technology, it is not in application in practical production. At present more effective method is to use the finite element method for the optimization design of the robotic arm structure. The intensity and stiffness in ensuring the required under the weight of his arm, reduce the robot.
4. The robot of each joint bearing clearance as small as possible, in order to reduce to mechanical clearance error motion caused. Therefore, the joints should have reliable operation, easy adjustment bearing clearance adjustment institutions.
5. The robot arm relative to rotate the joints should as far as possible under the weight of the balance, the mechanical load and enhance decreases the response speed of the robotic arm movement is very favorable. In the design of robot arm, should as far as possible use in the robot of mechanical and electronic components and devices installed the weight of robotic arm to reduce weight, the unbalanced balancing mechanism when necessary to balance design remnants of unbalanced weight arm.
6. The robotic arm on the structure to consider all the joints with certain limit switches and buffering mechanical set blocks, and driving device, transmission mechanism and other components installed.
2.3.2 Design specific using scheme
Manipulator arm (arm) vertical lifting and level of arm (forearm) for linear motion telescopic movement. Linear motion realization is generally pneumatic transmission, hydraulic transmission and motor drive the ball screw to achieve. Considering the weight of carrying workpieces larger, consider the machining quality reaches the 30KG, belong to medium weight of the manipulator, and considering the stability of the dynamic performance and movement of the arm, the stiffness of safety, have higher demand. Comprehensive consideration, two arms driver all choose hydraulic drive mode, through hydraulic cylinder of direct drive, hydraulic cylinder is drive component and executive moving parts, and not to design another executive pieces; And the hydraulic cylinder realizing linear motion control simple, easy to realize the computer control.
For hydraulic system can provide great motivation, so in driving force and structural strength are relatively easy to implement, and the key is manipulator of stability and stiffness of the sports meet. Therefore the arm hydraulic cylinder of design principle is the diameter of the cylinder made great point (in overall structure's permission), then a nuclear strength.
manipulator arm cannot too big, if only by increasing the hydraulic cylinder of cylinder size to increase stiffness, cannot satisfy the system is the rigidity requirement. Therefore, in the design of the additional guide-bar mechanism, forearm add two guide bar, and piston rod together constitute an equilateral triangle section form, try to increase its stiffness; Big arms add four guide bar, a positive quadrilateral layout, to reduce the quality, each guide bar adopts hollow structure. By adding a guide bar, can significantly improve the stability and stiffness of the manipulator movement, good solve structure, reliability problems.
2.4 structure design of robot wrist
Robot arm movement (including the waist of the seat, and gives the rotary motion) robot end actuators in its working space position, which the movement in the end of the installation of robotic arm, then gives the wrist robot end actuators in the motion of its working space gesture. CaoZuoJi robot wrist is the end of the robot, and the robotic arm with exercise, realize the end of installation of wrist of actuators space with movement trajectory posture, finish the homework action needed.
2.4.1 The robot wrist structure design requirements
1. Freedom of robot wrist readings, should according to assignments need to design. The more robot wrist freedom, the number of each joint Angle, the robot wrist the greater flexibility of the robot is higher, the adaptability also rightness homework more strong. However, the increase of freedom, also will make the wrist structure more complex, robot control more difficult, costs will increase. Therefore, the wrist of freedom, should according to actual operation degree is required to determine. In meet operational requirements of the premise, should make free degree as less. General robot wrist freedom for 2 to 3 degree, some needs more freedom, and some robot wrist don't need freedom, with only the movement by the arm and waist can achieve operational requirements of the task. Therefore, to the concrete analysis of multiple layouts, consider robot, sports scheme, choose the simplest satisfy the requirements of the plan.
2. Robot wrist installed in the end of robot arm robot wrist, in the design, should strive to reduce the weight and volume to compact structure. In order to reduce the weight of robot wrist, wrist institutions drive sperating transmission. Wrist drive general installation in the arm, and do not adopt direct drive, and choose high-strength aluminum alloy manufacture.
3. Robot wrist to and end actuators connected, accordingly, want to have the standard connection to facilitate the flange, structure of loading and unloading end actuators.
4. Robot wrist institutions should have enough strength and stiffness, strength and movement to ensure the relay.
5. To have reliable transmission gap adjusting mechanism, to minimize returned empty clearance, improve the transmission precision.
6. The wrist of each joint axis rotation to limited a switch, and set limit to prevent hard out-of-gauge cause mechanical damage.
2.4.2 design specific adopts plan
Through the nc machine tools for feeding and unloading operations, considering the concrete analysis of concrete form CNC machine processing and manipulator up-down material operations in the specific requirements, and technological requirements of meet the system under the premise of improving safety and reliability of the structure of the manipulator, to make as far as possible simple, reduce the difficulty of the design and control of freedom, not to increase his wrist proved it is fully meet operational requirements of the three degrees of freedom, to realize the up-down material completely enough machine. Specific wrist (arms PAWS coupling beam) structure see figure 8.
Figure 8 . Lathe feeding manipulator finger
2.5 manipulator actuators (PAWS) structure designing
2.5.1 manipulator actuator design requirements
Robot end actuator is installed on the robot wrist used for an operation or additional device homework. Robot end, many different kinds of actuators, in order to adapt to the different assignments and operation robot requirements. End actuators can be divided into move use, processing with with and measurement etc.
Move use end actuators refers to all clamping device used to grab or adsorption transported objects.
Processing with end actuators with gun, welding torch is milling cutter, grinding wheel, such as the robot machining tool, used for additional device corresponding processing work.
With end actuator is measured with the additional head or sensors measuring device used to measuring and test operations.
In design robot end actuators, should pay attention to the following questions;
1. The robot end actuator is designed according to the operation requirement robot. A new terminal actuators occurrence, can increase a robotic new application places. Accordingly, according to the needs of the homework with people and create a new robot imagination, will continue at actuators expansion of the application field of robot.
2. The weight of the robot end actuators to grab objects and the sum of weight and operating force the load force. The robot allow Therefore, request the end-effector actuators small volume, light weight, compact structure.
3. The end-effector actuators with specificity is universal sexual paradox. Universal end actuators on the structure is complex, and even harder to achieve, for example, the universal humanoid multisensory dexterous robot hand yet practional utilization. At present, can be used to produce or those simple structure, universal sex not strong robot end actuators. Starting from the industrial application, should focus on the development of special, efficient robot end actuators, plus end actuators, in order to achieve the fast changing device of function, the robot is not advocated homework with a universal end actuators to complete variety of homework. Because this kind of everything the implementation of the structure is complex and expensive.
4. Versatility and universal sex are two concepts, universal sex machine, and refers to the multi-energy refers to the end of generality, limited actuators, suitable for different robots, which requires the end actuators have standard machine interface (such as flange), make end actuators realizes standardization and blocks digestion.
5. The end-effector actuators to facilitate installation and maintenance, easy to realize the computer control. Use computer control the most convenient is electric type actuator. Therefore, the industrial robot actuators mainstream is electric type, followed by the hydraulic and pneumatic type (in driving interface to increase electricity - liquid or electricity - air transform link).
2.5.2 robot grippers sports and drive mode
Robot grippers and machine hand claw. General industrial machine hand for double refers to how claws, PAWS. According to finger movement way, can be divided into back transformation and mobile type, press clamping way to points, within the clip type and supporting type two kinds.
Robot grippers (PAWS) drive mode basically has 3 kinds
1. Pneumatic drive mode this drive system is by electromagnetic valve to control the movement direction of the PAWS, with air regulator to adjust its movement speed. The pneumatic drive system of lower prices, so pneumatic grippers are widely used in industry. In addition, because gas compressibility, contentious hands-on claw grab motion has certain compliant sex, it is very need to grab action.
2. Electric drive mode of electric drive PAWS application also more widely. The PAWS, generally USES the dc servo motor or stepping motor, and need to get enough gear reducer driving force and torque. Electric drive mode can realize the force PAWS with position control. But this cannot be used for driving way under the condition of a explosion-proof requirements, because motor may produce sparks and fever.
3. Hydraulic drive mode hydraulic drive system transmission can achieve great stiffness.wherever continuous position control.
2.5.3 The typical structure robot grippers
1. Leveraged wedge PAWS
Using wedge block and levers to realize the pine, open PAWS, come to grab workpiece.
2. Slide groove PAWS
When the pistons forward movement, sliding channel through the pin PAWS merger, pushing produce clamping action and clamping force, when the pistons backward motion, PAWS loosen. This trip is larger, PAWS switching to grab different sizes of the object.
3. Connecting rod leveraged PAWS
The PAWS in Detroit, connecting rod and leverage thrust PAWS produce clamped to relax) movement, because (the force-magnifying function, leverage the PAWS might produce larger clamping force. Usually use a combination of and the spring.
4. Rack-and pinion type PAWS
The PAWS through the pistons pushing rack, rack driving gear rotating, produce the clamping PAWS with loosen action.
5. Parallel leveraged PAWS
Adopt parallelogram frame, so there is no need to guide can guarantee to keep the two fingers PAWS with parallel movement, the parallel rails than PAWS friction move to smaller.
2.5.4 design specific adopts plan
Combined with concrete works, this design USES the connecting rod of lever PAWS. Driven by piston, piston rod ends move, the middle rack and rack is fan rack makes the fingers open or closed. The minimum opening finger by machining diameter to the setting. This design according to the workpiece diameter of 80-130mm to design. The concrete structure form PAWS shown as shown in figure 9:
Figure 9 The specific structure PAWS
2.6 manipulator mechanical transmission design
2.6.1 industrial robot transmission mechanism design problems should be paid attention to
Robot is by multistage league stem and joint space composed of multi-degree-of-freedom sports organization. In addition to direct drive robot, robot outside each league rod and exercise is of each joint by drive through all kinds of mechanical transmission mechanism driven. Robot adopted the transmission mechanism