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3 換刀機(jī)械手的總體方案設(shè)計(jì)
3.1 設(shè)計(jì)任務(wù)
本次設(shè)計(jì)的主要任務(wù)是：自動(dòng)換刀機(jī)械手，實(shí)現(xiàn)數(shù)控鏜銑床的自動(dòng)換刀，需要換的刀具主要是BT40型刀柄，需要實(shí)現(xiàn)的工作是抓刀—換刀—松刀的動(dòng)作。
主要技術(shù)參數(shù)：刀具最大重量6kg，雙臂回轉(zhuǎn)式換刀，刀臂數(shù)量和長度以及直徑主要依據(jù)配套刀庫的設(shè)計(jì)要求。換刀時(shí)間2.5S。
3.2機(jī)械手的平穩(wěn)性
工業(yè)生產(chǎn)要求機(jī)械手工作速度快，運(yùn)動(dòng)平穩(wěn)，定位精度高。應(yīng)注意其影響因素，設(shè)計(jì)合理結(jié)構(gòu)，以滿足要求。
3.2.1、影響平穩(wěn)性以定位精度的因素
1、 慣性力的影響
圖 3.1 慣性曲線
機(jī)械手速度突變，加（減）速度不連續(xù)，會(huì)產(chǎn)生巨大的慣性沖擊力，以至使工件滑動(dòng)、部件松動(dòng)、零件破裂。定位時(shí)，大的減速度使臂部往復(fù)振動(dòng)，直接影響定位精度。因此，應(yīng)根據(jù)機(jī)械手的運(yùn)動(dòng)特性，選擇適宜的控制系統(tǒng)，使加（減）速度按所需的運(yùn)動(dòng)歸路變化，同時(shí)，在保證剛度的前提下，減輕機(jī)械手運(yùn)動(dòng)件的重量。
2、結(jié)構(gòu)剛度的影響
零件結(jié)構(gòu)剛度性差，配合間隙大及整機(jī)固有頻率低時(shí)，受較小慣性沖擊，就發(fā)生振動(dòng)。不但降低定位精度，而且降低機(jī)械手壽命。應(yīng)選擇合理結(jié)構(gòu)，提高機(jī)械手固有頻率及承受慣性載荷的能力。
3、定位方法的影響
常用的定位方法中，電氣開關(guān)的定位精度最低，伺服定位較高，機(jī)械擋塊的定位最高。
4、控制系統(tǒng)的影響
電控系統(tǒng)的誤差，閥類泄漏，檢測元件失靈，擋塊偏移等會(huì)降低定位失靈。
5、驅(qū)動(dòng)源的影響
液壓、氣壓、電壓及油溫波動(dòng)都會(huì)降低平穩(wěn)性及定位精度，必要時(shí)，用蓄能器等穩(wěn)定液壓、氣壓、電壓，用加熱器和冷卻器控制油溫。
3.2.2 機(jī)械手的運(yùn)動(dòng)特性
深入分析機(jī)械手的運(yùn)動(dòng)特點(diǎn)，有利于根據(jù)工作條件選擇適宜的運(yùn)動(dòng)特點(diǎn)。下面為我們所選工業(yè)機(jī)械手所具有的運(yùn)動(dòng)規(guī)律，在減速較大時(shí)的情形。
圖 3.2 運(yùn)動(dòng)特性曲線
按上圖的運(yùn)動(dòng)，機(jī)械手的速度變化呈等加速或不等加速運(yùn)動(dòng)，其減速過程亦分為等減速運(yùn)行和不等減速運(yùn)行，在呈等加速運(yùn)行，而不等減速運(yùn)行時(shí)，由于速度行程短，故有利于提高機(jī)械手的工作速度。
特點(diǎn)：速度變化基本上連續(xù)，運(yùn)動(dòng)中不會(huì)產(chǎn)生沖擊，可以滿足高速、平穩(wěn)和定位精度高的要求。
3.3機(jī)械手運(yùn)動(dòng)特性的分類
氣動(dòng)機(jī)械手：氣動(dòng)機(jī)械手的加速或調(diào)節(jié)系統(tǒng)采用氣路節(jié)流調(diào)速系統(tǒng)，控制系統(tǒng)采用氣缸端部節(jié)流緩沖裝置、氣路節(jié)流緩沖回路、液壓緩沖氣等。定位系統(tǒng)采用機(jī)械擋塊或多點(diǎn)定位幾機(jī)構(gòu)定位精度。
液壓機(jī)械手：液壓機(jī)械手的加速或調(diào)節(jié)系統(tǒng)油路節(jié)流調(diào)速系統(tǒng)，控制系統(tǒng)采用油缸端部節(jié)流緩沖裝置及緩沖回路、減壓節(jié)流繼續(xù)能緩沖系統(tǒng)、伺服系統(tǒng)等。定位系統(tǒng)采用關(guān)閉電磁換向閥定位精度、機(jī)械擋塊定位精、伺服系統(tǒng)定位精度度等。
電動(dòng)機(jī)械手：電動(dòng)機(jī)械手的加速或調(diào)節(jié)系統(tǒng)采用電路節(jié)流調(diào)速系統(tǒng)，控制系統(tǒng)采用反接制動(dòng)電路、減速電路、凸輪或連桿機(jī)構(gòu)等。定位系統(tǒng)采用電磁制動(dòng)器、脈沖電路定位精度、機(jī)械擋塊定位精度等。
機(jī)械聯(lián)動(dòng)機(jī)械手：機(jī)械聯(lián)動(dòng)機(jī)械手的加速或調(diào)節(jié)系統(tǒng)采用凸輪連桿機(jī)構(gòu)，控制系統(tǒng)采凸輪曲線和連桿機(jī)構(gòu)。定位系統(tǒng)采用凸輪基圓及凸輪頂點(diǎn)、連桿極限位置。
3.4開關(guān)型機(jī)械手的速度及位置控制
用電氣開關(guān)、換向閥、節(jié)流閥和機(jī)械擋塊等來控制的機(jī)械手稱為開關(guān)型機(jī)械手。
液壓機(jī)械手的速度控制：開關(guān)型液壓機(jī)械手一般采用截流減速方法，少數(shù)采用蓄能器或溢流閥減速方法，也可以幾種方法一起采用。
氣動(dòng)機(jī)械手的速度控制：氣動(dòng)機(jī)械手有很多優(yōu)點(diǎn)，但氣動(dòng)的壓縮性大，阻尼效果差。符合大的氣動(dòng)機(jī)械手采用液壓緩沖回路。
一般采用的裝置是氣動(dòng)-液阻裝置。
開關(guān)型機(jī)械手的定位系統(tǒng)：定位系統(tǒng)與速度控制系統(tǒng)有密切的關(guān)系，但他們都有其獨(dú)立性，例如，節(jié)流減速后既可以發(fā)出指令關(guān)閉油路定位，也可以壓在擋塊上而定位。
電氣開關(guān)定位：電動(dòng)機(jī)械手一般采用電磁制動(dòng)器定位。當(dāng)機(jī)械手運(yùn)動(dòng)到定位點(diǎn)時(shí)，行程開關(guān)發(fā)出信息給電控系統(tǒng)，激勵(lì)電磁制動(dòng)器而定位。
特點(diǎn)：結(jié)構(gòu)簡單，工作可靠，維修方便，但定位精度低。
機(jī)械擋塊定位：一般是在減速后，驅(qū)動(dòng)壓力將運(yùn)動(dòng)件壓在機(jī)械擋塊上或驅(qū)動(dòng)壓力將活塞壓靠缸蓋而定位，定位精度較高。可分為單點(diǎn)定位或多點(diǎn)定位的擋塊機(jī)構(gòu)。
3.5機(jī)械傳動(dòng)型機(jī)械手速度及位置控制
為了便于控制機(jī)械手的速度及位置，一些專用機(jī)械手采用凸輪機(jī)構(gòu)和連桿機(jī)構(gòu)進(jìn)行驅(qū)動(dòng)。
特點(diǎn)：工作速度可以提高而且與主機(jī)同步工作而不產(chǎn)生誤動(dòng)作。
通過以上論述和比較，選用液壓緩沖器和油缸端部緩沖的方式，定位選用機(jī)械擋塊定位。
3.6 機(jī)械手類型確定
根據(jù)以上的介紹，通過比較我確定選用電動(dòng)機(jī)械手。這樣選擇的原因主要是根據(jù)精度和成本的原因。由于是個(gè)單獨(dú)的部件大量生產(chǎn)，成本是非常主要的原因，氣動(dòng)和液壓機(jī)械手的制造精度要求非常高，成本也就高，而電動(dòng)機(jī)械手作為發(fā)展得最為完善的機(jī)械手，在精度滿足需要的同時(shí)，成本是最低的，所以選擇了電動(dòng)機(jī)械手。
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4 總體結(jié)構(gòu)設(shè)計(jì)
4.1 手爪部分設(shè)計(jì)
機(jī)械手手爪部分的作用是抓住和放開工件，并且要保證在抓刀后的換刀過程中保證刀具不會(huì)重手爪中飛出。
目前的加工中心換刀機(jī)械手的手爪種類繁多，可以說每個(gè)廠家都推出自己的獨(dú)特的換刀機(jī)械手，目前使用最多的有4種機(jī)械手，分別是單臂單手式機(jī)械手，回轉(zhuǎn)式單臂雙手機(jī)械手，雙手式機(jī)械手和多手式機(jī)械手。
單臂單手式機(jī)械手的特點(diǎn)是機(jī)械手只做往復(fù)直線運(yùn)動(dòng)，主要用與刀具主軸和刀庫刀座的軸線平行的場合，機(jī)械手的插、拔刀運(yùn)動(dòng)和傳遞刀具的運(yùn)動(dòng)全都是直線運(yùn)動(dòng)，因?yàn)闆]有回轉(zhuǎn)運(yùn)動(dòng)所產(chǎn)生的離心力，因?yàn)闊o回轉(zhuǎn)運(yùn)動(dòng)所產(chǎn)生的離心力，所以機(jī)械手的握刀部分可以比較簡單，只需要兩個(gè)彈簧卡銷卡住刀柄即可。但是換刀各動(dòng)作均需順序進(jìn)行，時(shí)間不能重合，所以換刀時(shí)間較長。例如在轉(zhuǎn)塔頭帶刀庫的換刀系統(tǒng)中，不工作主軸的換刀時(shí)間與工作主軸的加工時(shí)間重合，可使用這類機(jī)械手。
回轉(zhuǎn)式單臂雙手機(jī)械手的兩手部成180°，手型種類很多，常見的有固定式雙手、可伸縮式雙手、剪式雙手等。這類的機(jī)械手可以同時(shí)抓住可拔、插位于主軸和刀庫（或運(yùn)輸裝置）里的刀具，與單臂單手式機(jī)械手相比，可以縮短換刀時(shí)間。這類機(jī)械手應(yīng)用最廣泛，形式也最多。
雙手式機(jī)械手的手臂運(yùn)動(dòng)方式有2種，一種是機(jī)械手只做往復(fù)直線運(yùn)動(dòng)的，這樣的機(jī)械手有雙手平行式和雙手交叉式，這樣的機(jī)械手可起運(yùn)輸裝置的作用，使用于容量大、距主軸較遠(yuǎn)的、特別是分置式的刀庫和換刀。還有一種是機(jī)械手有回轉(zhuǎn)運(yùn)動(dòng)的。這2種機(jī)械手向刀庫還回用過的刀具和選用新刀，均可在主軸正在加工時(shí)進(jìn)行，所以換刀時(shí)間較短。
多手式機(jī)械手的各個(gè)機(jī)械手順次使用，可以用語單主軸機(jī)床（機(jī)械手和刀庫為一體），和帶雙刀庫的雙主軸轉(zhuǎn)塔頭機(jī)床。這類機(jī)械手的使用者最少。
根據(jù)以上的分析，手爪部分的結(jié)構(gòu)我選擇了回轉(zhuǎn)式單臂雙手機(jī)械手，而夾刀的部分我選用了鉤手的結(jié)構(gòu)，這樣選擇的原因是鉤手具有結(jié)構(gòu)簡單，安裝拆卸方便，不需要額外的驅(qū)動(dòng)，抓刀方式簡單等特點(diǎn)。結(jié)構(gòu)如圖4.1所示。
圖4.1 鉤手結(jié)構(gòu)示意圖
如圖4.1所示，當(dāng)機(jī)械手旋轉(zhuǎn)的時(shí)候，鉤手與刀柄先接觸，由于機(jī)械手繼續(xù)旋轉(zhuǎn)，刀柄對(duì)頂柱有擠壓作用，頂柱的后面是彈簧，并且定位頂柱沒有鎖定，所以頂柱收縮到機(jī)械手臂內(nèi)，刀柄順利進(jìn)入鉤手內(nèi)，旋轉(zhuǎn)結(jié)結(jié)束，頂柱通過彈簧的彈力恢復(fù)原位，定位頂柱鎖頂，頂柱不能移動(dòng)，卡住刀具，抓刀結(jié)束。
刀具重量的范圍，由于溝手結(jié)構(gòu)的刀爪抓刀后，刀具的重量集中在刀爪內(nèi)圈的突起上，頂柱受力不到刀具重量的1/10，所以當(dāng)?shù)蹲ψサ逗螅啥ㄎ豁斨峁┑耐屏h(yuǎn)遠(yuǎn)大于頂柱所受到的力，所以肯定能把刀具固定住，而不用擔(dān)心刀具會(huì)在機(jī)械手旋轉(zhuǎn)的時(shí)候掉下來。
4.2 機(jī)械手手臂的設(shè)計(jì)
機(jī)械手工作中運(yùn)動(dòng)速度較高，在結(jié)構(gòu)位置應(yīng)保證運(yùn)動(dòng)平穩(wěn)，這樣可以提高機(jī)械手運(yùn)動(dòng)的平穩(wěn)性，可以提高機(jī)械手適用的可靠性，并提高使用壽命。
4.2.1臂部要防止偏重
通常臂部處于懸臂的工作狀態(tài)，在設(shè)計(jì)臂部、腕部和手部結(jié)構(gòu)時(shí)，盡量使其總的重心在支撐中心，防止對(duì)支撐中心的偏重。一但偏重，將會(huì)產(chǎn)生附加的彎矩，引起導(dǎo)向裝置不均勻的磨損。在回轉(zhuǎn)運(yùn)動(dòng)中，偏重對(duì)回轉(zhuǎn)軸附加有動(dòng)壓力，其方向不斷變化，特別是高速及速度突然變化時(shí)更加明顯，這些都將引起機(jī)械手的振動(dòng)，嚴(yán)重的會(huì)造成卡死。
預(yù)防的措施：
1.減輕腕部、手部的重量，并盡量減少偏心載荷?？刹捎娩X合金制造腕部和手部。
2.合理分布臂部上各部件重量和增加平衡重，使臂部平衡。
3.某些機(jī)械手結(jié)構(gòu)上無法避免偏重，則應(yīng)加強(qiáng)導(dǎo)向支撐，盡量減輕偏重對(duì)運(yùn)動(dòng)的影響。
4.2.2加強(qiáng)臂部剛度
提高臂部剛度是減少手部顫動(dòng)的關(guān)鍵，有利于提高定位精度，故常采用導(dǎo)向形式來加強(qiáng)定位。
4.2.3改進(jìn)緩沖裝置和提高配合精度
機(jī)械手的緩沖裝置是保證運(yùn)動(dòng)平穩(wěn)和減少振動(dòng)的主要措施。
機(jī)械沖擊，它是在臂部運(yùn)動(dòng)中與定位裝置相碰撞而產(chǎn)生的。它可用緩沖裝置來消除。
4.2.4采取的措施：
1.提高部件的配合精度，減少間隙，有利于運(yùn)動(dòng)平穩(wěn)，特別是高速運(yùn)動(dòng)的機(jī)械手更需要保證加工精度和提高配合。
2.機(jī)械手的緊固件在運(yùn)動(dòng)中受變載荷的作用必須采用防松措施。
綜合以上所述，我在設(shè)計(jì)機(jī)械手手臂的時(shí)候采用了完全中心對(duì)稱的機(jī)構(gòu)，并且通過調(diào)整螺栓來調(diào)整機(jī)械手手臂的水平。因?yàn)檎w的尺寸很小，所以機(jī)械手換刀臂的軸的直徑比較小，并不適合采用鍵連接來傳動(dòng)，所以采取了脹縮環(huán)這一個(gè)標(biāo)準(zhǔn)件來連接機(jī)械手換刀臂和機(jī)械手換刀臂的軸。脹縮環(huán)具有非常好的對(duì)中性，并且能夠傳遞非常大的轉(zhuǎn)距，結(jié)構(gòu)簡單，非常適用在機(jī)構(gòu)尺寸小的結(jié)構(gòu)中。機(jī)械手換刀臂的結(jié)構(gòu)簡圖如圖4.2所示。
這個(gè)手臂的形狀，完全按照中心對(duì)稱的方式設(shè)計(jì)，但是為了適應(yīng)不同型號(hào)的刀柄，兩邊的刀爪是可以拆卸調(diào)換的。
圖4.2機(jī)械手換刀臂的結(jié)構(gòu)簡圖
4.3機(jī)械手傳動(dòng)結(jié)構(gòu)的設(shè)計(jì)
根據(jù)第2章的介紹，我選擇凸輪換刀裝置作為傳動(dòng)方案。
凸輪機(jī)械手換刀裝置是目前加工中心常用的機(jī)構(gòu)之一，與傳統(tǒng)的氣動(dòng)、液壓換刀機(jī)構(gòu)相比，它具有換刀速度快、換刀可靠、運(yùn)動(dòng)平穩(wěn)的特點(diǎn)。近年來加工中心得到了廣泛的應(yīng)用。凸輪機(jī)械手換刀裝置通常由2個(gè)凸輪以及相應(yīng)的機(jī)構(gòu)組成，其中，一個(gè)平面凸輪通過連桿機(jī)構(gòu)，用來完成“裝刀”與“ 拔刀”動(dòng)作；另一個(gè)弧面凸輪帶動(dòng)凸輪分度機(jī)構(gòu)，用來實(shí)現(xiàn)機(jī)械手的轉(zhuǎn)位，完成“抓刀”和“換刀”動(dòng)作。
圖4.3 凸輪機(jī)械手換刀機(jī)構(gòu)原理圖
1—驅(qū)動(dòng)電動(dòng)機(jī) 2—減速器 3—錐齒輪 4—平面凸輪
5—弧面凸輪 6—連桿機(jī)構(gòu) 7—機(jī)械手 8—滾動(dòng)盤 9—電氣信號(hào)盤
凸輪換刀裝置的結(jié)構(gòu)原理如圖1所示，它主要由驅(qū)動(dòng)電動(dòng)機(jī)1、減速器2、平面凸輪4、弧面凸輪5、連桿6、機(jī)械手7等部件構(gòu)成。換刀時(shí)，驅(qū)動(dòng)電動(dòng)機(jī)1連續(xù)回轉(zhuǎn)，通過減速器2與凸輪換刀裝置連接，提供裝置的動(dòng)力；并通過平面凸輪、弧面凸輪以及相應(yīng)的機(jī)構(gòu)，將驅(qū)動(dòng)電動(dòng)機(jī)的連續(xù)運(yùn)動(dòng)轉(zhuǎn)化為機(jī)械手的間歇運(yùn)動(dòng)。
圖4.3中，平面凸輪4通過錐齒輪3和減速器2連接，在驅(qū)動(dòng)電動(dòng)機(jī)轉(zhuǎn)動(dòng)時(shí)，通過連桿機(jī)構(gòu)6，帶動(dòng)機(jī)械手7在垂直方向作上、下運(yùn)動(dòng)，以實(shí)現(xiàn)機(jī)械手在主軸上的“拔刀”、“裝刀”動(dòng)作?；∶嫱馆?和平面凸輪4相連，在驅(qū)動(dòng)電動(dòng)機(jī)回轉(zhuǎn)時(shí)，通過滾動(dòng)盤8（共6個(gè)滾珠）帶動(dòng)花鍵轉(zhuǎn)動(dòng)，花鍵軸帶動(dòng)機(jī)械手7在水平方向上作旋轉(zhuǎn)動(dòng)作，以實(shí)現(xiàn)從機(jī)械手轉(zhuǎn)位，完成“抓刀”和“換刀”動(dòng)作。電氣信號(hào)盤9中安裝有若干開關(guān)，以檢測機(jī)械手實(shí)際運(yùn)動(dòng)情況，實(shí)現(xiàn)電氣互鎖。
弧面凸輪轉(zhuǎn)角
平面凸輪轉(zhuǎn)角
圖4.4 平面凸輪和弧面凸輪的運(yùn)動(dòng)過程
平面凸輪與弧面凸輪的動(dòng)作配合曲線如圖4.4所示。
在驅(qū)動(dòng)電動(dòng)機(jī)的帶動(dòng)下，弧面凸輪在7.5°～57.5°的范圍內(nèi)，完成機(jī)械手80°的轉(zhuǎn)位動(dòng)作。在57.5°～72.5°的范圍內(nèi)弧面凸輪、平面凸輪均不產(chǎn)生機(jī)械手運(yùn)動(dòng)，用于松開刀具。
當(dāng)凸輪繼續(xù)轉(zhuǎn)動(dòng)到72.5°～137.5°的范圍內(nèi)，平面凸輪通過連桿機(jī)構(gòu)帶動(dòng)機(jī)械手進(jìn)行向下運(yùn)動(dòng)；其中，在72.5°～117.5°范圍內(nèi)，只有平面凸輪帶動(dòng)機(jī)械手作向下的運(yùn)動(dòng)，機(jī)械手同時(shí)拔出主軸、刀庫中的刀具；在117.5°～137.5°的范圍內(nèi)，因刀具已經(jīng)脫離主軸的刀座，兩凸輪同時(shí)動(dòng)作，即：在機(jī)械手繼續(xù)向下的過程中，已經(jīng)開始進(jìn)行180°轉(zhuǎn)位，以提高換刀速度。
在凸輪轉(zhuǎn)動(dòng)到117.5°～242.5°的范圍內(nèi)，弧面凸輪帶動(dòng)機(jī)械手進(jìn)行180°轉(zhuǎn)位，完成主軸與刀庫的刀具交換；當(dāng)進(jìn)入222.5°～242.5°的范圍時(shí)，兩凸輪同時(shí)動(dòng)作，平面凸輪已經(jīng)開始通過連桿機(jī)構(gòu)帶動(dòng)機(jī)械手進(jìn)行向上運(yùn)動(dòng)，以提高換刀速度。
從222.5°起，平面凸輪帶動(dòng)機(jī)械手向上運(yùn)動(dòng)，機(jī)械手同時(shí)將主軸、刀庫中的刀具裝入刀座；這一動(dòng)作在222.5°～287.55°范圍，完成“裝刀”動(dòng)作。接著的287.55°～302.5°范圍內(nèi)，弧面凸輪、平面凸輪均不產(chǎn)生機(jī)械手運(yùn)動(dòng)，機(jī)床進(jìn)行刀具的“夾緊”動(dòng)作，這一動(dòng)作由機(jī)床的氣動(dòng)或液壓機(jī)構(gòu)完成。
在302.5°～360°的范圍內(nèi)，弧面凸輪完成機(jī)械手80°反向轉(zhuǎn)位動(dòng)作，在機(jī)械手回到原位，換刀結(jié)束。
3 for the sword overall design of manipulator
3.1 design task
The design of the main task is to: automatically change the manipulator, realize the sword of nc boring and milling machine automatically change the knife, need to change tool is mainly BT40 the style of work, need to achieve is to hold knife knife--in--the action of the sword. Loose
The main technical parameters: tool maximum weight 6 kg, arms rotary change knife, the knife arm number and length and diameter of main basis supporting knife library design requirements. Change the tools time 2.5 S.
3.2 the smoothness of manipulator
Industrial production requirements manipulator speed, smooth movement, high precision positioning. Should pay attention to the impact factors, rational structure design to meet the demand.
3.2.1, influence factors of position precision to stability
1,Effect of inertia force
Figure 3.1 inertia curve
Manipulator, add (reduce speed mutations) speed discontinuous, can have a huge impact, to make the work and inertia sliding, components and parts broken loose. Positioning, big reducing speed make brachial ministry reciprocating vibration, directly influence the positioning accuracy. Therefore, should be based on the characteristics of the manipulator movement, selecting the appropriate control system, make add (minus) according to the speed of movement of change, at the same time, in the way that the premise of stiffness, reduce the weight of the manipulator moving parts.
2, the influence of the structure stiffness
Parts structure stiffness sex differences and, together with the big gap and the inherent frequency low, smaller impact by inertia vibration that happened. Not only reduce the positioning accuracy, and reduce the manipulator life. Should choose reasonable structure, improve the natural frequency of the manipulator and bear inertial load capacity.
3 and the influence of the localization method
The location of the commonly used method, electrical switch positioning accuracy of servo positioning, lowest, high mechanical stop the positioning of the highest.
4, the influence of the control system
The error of the electric control system, the kind of leak, the test components failure, block piece of migration will reduce positioning failure.
5, driving sources
Hydraulic, pneumatic, voltage and the oil temperature fluctuations will reduce the stability and precision, when necessary, use the accumulator, hydraulic and pneumatic, voltage stability, with heater and cooler control the oil temperature.
3.2.2 manipulator the motion characteristics
In-depth analysis of the manipulator, which is beneficial to the sport characteristics according to the working conditions of the appropriate choice movement characteristics. Below we chose for industrial robots is the motion law of the slowdown, in the situation. Larger
Figure 3.2 movement characteristics curve
According to the movement, the speed of the manipulator is accelerating or changes such as ranging movement, the deceleration process accelerated also divided into operation and slow down, a slowdown in running range and speed up and running, ranging from running, due to slow down the speed, the short trip to improve the speed of work of the manipulator.
Characteristics: speed change, movement of continuous basically won't impact, can satisfy the high speed, stable and positioning precision requirements.
3.3 the classification of the manipulator movement characteristics
Pneumatic robot manipulator acceleration or adjust the pneumatic system adopt pneumatic throttling speed regulation system, the control system adopts cylinder ends throttling buffer device, pneumatic, hydraulic buffer circuit throttling buffer gas, etc. Positioning system adopts mechanical block piece or more positioning a few institutions positioning accuracy.
Hydraulic manipulator of the manipulator: hydraulic acceleration or adjusting system throttle control system, the control system by oil cylinder ends throttling buffer device and buffer circuit, the reduced pressure throttling continue buffer system, servo system, etc. Positioning system adopts closed directional control valve positioning precision electromagnetic, mechanical stop piece of positioning precision, positioning accuracy servo system is spent etc.
Electric manipulator: electric manipulator acceleration or regulation system of the circuit throttling speed regulation system, the control system using reverse connect braking circuit, deceleration circuit, CAM or linkage mechanism, etc. Positioning system by electromagnetic brake and pulse circuits positioning accuracy, mechanical block piece of positioning accuracy, etc.
Mechanical linkage manipulator: machinery of the manipulator acceleration or adjust the linkage system, adopt CAM link mechanism, and control system adopt CAM curve and the linkage mechanism. Positioning system adopt CAM and CAM, connecting rod and round vertex limit position.
3.4 switch type of the manipulator speed and position control
Use electrical switch, reversing valves, throttle valve and mechanical stop to control of the manipulator called switch type manipulator.
Hydraulic manipulator speed control: switch type hydraulic manipulator generally USES the closure slowdown, a few accumulator or the way the overflow valve slowdown method, may also several methods used together.
Pneumatic manipulator speed control: pneumatic manipulator has a lot of advantages, but pneumatic large compressibility, damping effect is poor. Accord with large pneumatic hydraulic buffer circuit using manipulator.
General use of the device is pneumatic-fluid resistance device.
The switch of the manipulator type positioning system: positioning system and speed control system has the close relation, but they all have its independence, for example, can not only after a slow throttling instructions close, also can pressure oil positioning in block block and positioning.
Electrical switch orientation: general electric manipulator using electromagnetic brakes positioning. When manipulator movement to anchor point, travel switch to send messages of electronic control system, incentive electromagnetic brake and positioning.
Features: simple structure, reliable, easy maintenance, low but positioning accuracy.
Mechanical stop piece of positioning: general is slowing down, drive after pressure will be moving parts in mechanical stop block pressure or driver pressure will be the piston and cylinder pressure on location, location accuracy is higher. Can be divided into the single point positioning or more positioning of the block piece of institutions.
3.5 mechanical transmission speed and the position control of manipulator
In order to facilitate control the speed of the manipulator, some special manipulator and position of the CAM mechanism and the linkage mechanism driven.
Features: the speed of work can improve and and host synchronous work and do not produce false action.
Through the discussion above and comparison, choose hydraulic buffer and oil cylinder at the end of the location selection, buffer way mechanical block piece of positioning.
3.6 determined manipulator type
According to the introduction of the above, through the comparison I select electric manipulator. Such are the main reasons why choose according to the precision and the cause of the cost. Because a single components of mass production, the cost is very main reasons, pneumatic and hydraulic manipulator in manufacturing precision require very high, high cost, and electric manipulator as the most complete development manipulator, precision to meet demand in at the same time, cost is the lowest, and the choice of the electric manipulator.
4 overall structure design
4.1 PAWS part design
The role of the manipulator PAWS part is to capture and let go of the workpiece, and in ensuring that the change of knife knife after the catch in the process of cutting tool will not guarantee ChongShou claw fly out of.
The current processing center for the sword of the manipulator PAWS sort is various, can say that each manufacturer to launch their own unique change the tools at present use most manipulator, there are four manipulator, respectively is a single hand arm of robot arm, rotary hands hands of robot manipulator, and more hands of robot.
A single hand arm of robot is characteristic of the manipulator only do reciprocating linear motion, basically use and tool spindle and knife knife a library of parallel axis of the occasion of the manipulator, plug, sports and transfer tool youth movement is all linear motion, because no rotary motion produces the centrifugal force, because there is no rotary motion produces the centrifugal force, so of the manipulator hold a knife parts can be quite simple, just two spring card pin stuck to the handle. But in every action sword all need to order, time can't overlap, so in knife the time is long. For example in turn with the sword of the library tower head change cutters system, not to work with the change of time and sword spindle work the axis of processing time overlap, can use this kind of manipulator.
Rotary arm of the manipulator hand into two hands 180 °, hand model is a lot of more phyletic, common have fixed the hands, but the telescopic hands, scissor hands, etc. This kind of robot can at the same time holding can pull out, main shaft and knife inserted in library (or transportation device) of knives, and a single hand arm of robot can shorten the sword, compared in time. This kind of manipulator, form is also the most widely used the most.
Both hands of robot arm movement there are two ways, one is only do reciprocating linear motion manipulator, such manipulator has hands parallel type of ideas and hands, such manipulator can be up the role of transportation device, used in large capacity, far away from the main shaft, especially in the separation of the library and the change of knife knife. Still another kind is a manipulator of the movement of the rotary has. The two kinds of manipulator to knife library of cutting tools and recycle also choose new knife, all can in the spindle is processing and so in a relatively short time sword.
More hands each of robot manipulator, can use language followed single spindle machine (manipulators and knife library as one), and take double the library tower head turned double spindle of machine tools. This kind of manipulator users at least.
According to the above analysis, the structure of the PAWS part I chose the rotary arm manipulator, and hands nipped dao part I choose the hook of the hands of the structure, this is the reason for the choice of the hook is simple in structure, convenient installation remove, do not need additional drive, catch a knife way of simple features. Structure is shown in figure 4.1.
Figure 4.1 the hook structure schematic drawing
As shown in figure 4.1 shows, when manipulator turns, the hook and the first contact, as a result, the type of handle continues to rotate manipulator blind have extrusion action, the back of the blind is spring, and locating the blind not lock, so blind to the mechanical arm contraction in the handle into the hook, smooth, rotating and, in the end by spring elastic recovery blind in situ, the orientation lock top blind blind, can't move, cutting tools, catch a knife stuck over.
The range of tools, because the weight of the structure of the hand knife knife after the claw, cutting tool of the weight of the focus on the sword of the inner ring claw bumps, force of the cutting tools weight not blind 1/10, so when the knife knife after the claw, provided by the positioning of the blind thrust far greater than by blind strength, and so you can put the tool to fix, and not be worried about the tool will be in the fall when rotating manipulator.
4.2 the design of manipulator arm
Manipulator movement in the high speed work, the structural position should guarantee the smooth movement, so that it can improve the stability of the movement of the manipulator, can improve the reliability of the manipulator applicable and improve the service life.
2 the brachial ministry to prevent lay particular stress on
Usually the arm in the working state of the cantilever, in the design department, the wrist and hand arm structure, make its overall focus in support of the support center, prevent the center of lay particular stress on. A but lay particular stress on, will generate additional bending moment, cause orientation device uneven wear. In the rotation movement, attention to move additional pressure to rotate, its direction changes, especially in high speed and speed suddenly change more apparent, which will cause the vibration of the manipulator, serious can cause jammed.
Prevention measures:
1. Reduce the wrist, hand weight and reduce eccentric load. Can use aluminum alloy manufacture of wrist and hand.
2. The reasonable distribution of each component of weight on the arm and increase the balance weight, make brachial ministry balance.
3. Some structure can't avoid manipulator of lay particular stress on, should be strengthened, and try to reduce guide support to the influence of lay particular stress on sports.
4.2.2 strengthen brachial ministry stiffness
Improve the brachial ministry is to reduce the hand trembling stiffness key, help to improve the precision, reason often used to strengthen the guidance form positioning.
4.2.3 improvement and improve the buffering devices with precision
The buffering devices is to guarantee the manipulator smooth movement and reduce vibration of the main measures.
Mechanical impact, it is in the movement of the arm and positioning device collide and of generation. It is used to eliminate the buffering devices.
4.2.4 take measures:
1. Raise the parts with precision, reduce gap, be helpful for the smooth movement, especially the movement of the manipulator needed to ensure that more machining accuracy and improve coordination.
2. Of the manipulator in sports change by fastener load role against pine measures must be adopted.
Comprehensive above mentioned, I in the design of the manipulator arm when completely symmetrical institutions, and center by adjusting bolt to adjust the manipulator arm level. Because the overall size is small, so the manipulator arm of the shaft of the sword in relatively small diameter and is not suitable for the key link to drive, so take the bilge shrink rin