工業機器人的驅動機構和驅動系統
一(yi)、工業機器人(ren)的驅動機構
工(gong)業機器人的驅(qu)動機構(gou)(gou)分為直(zhi)線驅(qu)動機構(gou)(gou)和旋轉(zhuan)驅(qu)動機構(gou)(gou)。下面簡單(dan)介(jie)紹(shao)一下這兩種驅(qu)動機構(gou)(gou)。
1.直線驅動機(ji)構
1. 1齒(chi)輪齒(chi)條裝置
通常,齒(chi)條是固定不動的(de)，當齒(chi)輪(lun)傳動時, 齒(chi)輪(lun)軸連同拖板(ban)沿齒(chi)條方向做直線運(yun)(yun)動, 這樣, 齒(chi)輪(lun)的(de)旋轉(zhuan)運(yun)(yun)動就轉(zhuan)換成為拖板(ban)的(de)直線運(yun)(yun)動, 如圖(tu)1.1所示。拖板(ban)是由導(dao)桿或導(dao)軌支承的(de)。該裝置(zhi)的(de)回差較大。
圖1.1齒輪齒條裝置
1.2普通絲杠(gang)
普(pu)通(tong)絲(si)杠(gang)驅動(dong)是由一(yi)個旋轉的精(jing)密絲(si)杠(gang)驅動(dong)一(yi)個螺母沿絲(si)杠(gang)軸向移動(dong)。由于(yu)普(pu)通(tong)絲(si)杠(gang)的摩擦力較大(da), 效率(lv)低(di), 慣性大(da), 在(zai)低(di)速時容易(yi)產(chan)生爬行現象, 而(er)且精(jing)度低(di), 回差大(da), 因此在(zai)機器人上很(hen)少采用(yong)。
1.3滾珠絲杠
在機器(qi)人上經(jing)常采用(yong)滾(gun)珠(zhu)絲杠(gang), 這(zhe)是(shi)因為滾(gun)珠(zhu)絲杠(gang)的(de)(de)(de)摩擦(ca)(ca)力很小且運(yun)動(dong)響應速度(du)快(kuai)。由(you)于滾(gun)珠(zhu)絲杠(gang)在絲杠(gang)螺母的(de)(de)(de)螺旋槽里放置了許多滾(gun)珠(zhu),傳動(dong)過程中所受的(de)(de)(de)摩擦(ca)(ca)力是(shi)滾(gun)動(dong)摩擦(ca)(ca), 可(ke)極大(da)地(di)減小摩擦(ca)(ca)力,因此傳動(dong)效率高,消除(chu)了低速運(yun)動(dong)時(shi)的(de)(de)(de)爬行現象。在裝配(pei)時(shi)施加(jia)一定(ding)的(de)(de)(de)預(yu)緊力,可(ke)消除(chu)回(hui)差。
如(ru)圖1.2所示, 滾珠絲杠里的(de)(de)滾珠從(cong)鋼套管(guan)(guan)中出(chu)來, 進(jin)入經過研磨(mo)的(de)(de)導槽(cao), 轉動(dong)(dong)2～3圈以后(hou), 返回鋼套管(guan)(guan)。滾珠絲杠的(de)(de)傳動(dong)(dong)效(xiao)率(lv)可以達到(dao)90%, 所以只需要使用極(ji)小(xiao)的(de)(de)驅動(dong)(dong)力(li), 并采用較小(xiao)的(de)(de)驅動(dong)(dong)連接(jie)件就(jiu)能夠傳遞(di)運動(dong)(dong)。
圖(tu)1.2滾球絲杠副
2.旋(xuan)轉驅動機構
2.1齒輪鏈
齒(chi)輪鏈是由兩(liang)個(ge)或兩(liang)個(ge)以(yi)上的(de)齒(chi)輪組(zu)成的(de)區(qu)驅(qu)動機構。它不但可(ke)以(yi)傳(chuan)遞(di)運(yun)動角(jiao)位移和角(jiao)速度, 而且可(ke)以(yi)傳(chuan)遞(di)力和力矩。
使(shi)用齒(chi)輪(lun)(lun)鏈機構應注意兩個(ge)問(wen)題。一是(shi)(shi)齒(chi)輪(lun)(lun)鏈的(de)(de)引(yin)入會改(gai)變系(xi)統(tong)的(de)(de)等效轉(zhuan)(zhuan)動(dong)慣量, 從而(er)使(shi)驅動(dong)電機的(de)(de)響應時間(jian)減小, 這樣伺服系(xi)統(tong)就更加容易控制。輸出(chu)軸(zhou)轉(zhuan)(zhuan)動(dong)慣量轉(zhuan)(zhuan)換到驅動(dong)電機上, 等效轉(zhuan)(zhuan)動(dong)慣量的(de)(de)下降與輸入輸出(chu)齒(chi)輪(lun)(lun)齒(chi)數的(de)(de)平方成(cheng)正(zheng)比。二是(shi)(shi)在引(yin)入齒(chi)輪(lun)(lun)鏈的(de)(de)同(tong)時, 由于齒(chi)輪(lun)(lun)間(jian)隙誤差, 將會導致機器人手(shou)臂(bei)的(de)(de)定(ding)位誤差增加; 而(er)且, 假如不采取一些補(bu)救措施, 齒(chi)隙誤差還會引(yin)起伺服系(xi)統(tong)的(de)(de)不穩定(ding)性。
通常， 齒(chi)(chi)(chi)輪(lun)(lun)(lun)鏈轉(zhuan)動(dong)有以(yi)下(xia)幾種類型(xing)， 如(ru)圖2.1所示。其中圓柱齒(chi)(chi)(chi)輪(lun)(lun)(lun)的(de)傳(chuan)動(dong)效(xiao)(xiao)(xiao)率(lv)約(yue)(yue)為(wei)(wei)(wei)(wei)90%，因為(wei)(wei)(wei)(wei)結構簡單，傳(chuan)動(dong)效(xiao)(xiao)(xiao)率(lv)高(gao)，圓柱齒(chi)(chi)(chi)輪(lun)(lun)(lun)在機(ji)器人設計(ji)中最(zui)常見；斜齒(chi)(chi)(chi)輪(lun)(lun)(lun)傳(chuan)動(dong)效(xiao)(xiao)(xiao)率(lv)約(yue)(yue)為(wei)(wei)(wei)(wei)80%，斜齒(chi)(chi)(chi)輪(lun)(lun)(lun)可以(yi)改變輸(shu)出(chu)軸方向；錐齒(chi)(chi)(chi)輪(lun)(lun)(lun)傳(chuan)動(dong)效(xiao)(xiao)(xiao)率(lv)約(yue)(yue)為(wei)(wei)(wei)(wei)70%，錐齒(chi)(chi)(chi)輪(lun)(lun)(lun)可以(yi)使輸(shu)入軸與輸(shu)出(chu)軸不(bu)在同一個平(ping)面(mian)，傳(chuan)動(dong)效(xiao)(xiao)(xiao)率(lv)低(di)(di)；蝸(gua)輪(lun)(lun)(lun)蝸(gua)桿(gan)傳(chuan)動(dong)效(xiao)(xiao)(xiao)率(lv)約(yue)(yue)為(wei)(wei)(wei)(wei)70%，蝸(gua)輪(lun)(lun)(lun)蝸(gua)桿(gan)機(ji)構的(de)傳(chuan)動(dong)比大，傳(chuan)動(dong)平(ping)穩，可實現(xian)自鎖，但(dan)傳(chuan)動(dong)效(xiao)(xiao)(xiao)率(lv)低(di)(di)，制造成本(ben)高(gao)，需要潤滑；行星輪(lun)(lun)(lun)系(xi)傳(chuan)動(dong)效(xiao)(xiao)(xiao)率(lv)約(yue)(yue)為(wei)(wei)(wei)(wei)80%，傳(chuan)動(dong)比大，但(dan)結構復(fu)雜(za)。
圖(tu)2.1齒(chi)輪鏈機構
2.2同步皮帶
同(tong)(tong)(tong)(tong)步(bu)(bu)(bu)皮(pi)(pi)(pi)帶(dai)(dai)(dai)(dai)(dai)類似于工(gong)廠的(de)(de)(de)風(feng)扇皮(pi)(pi)(pi)帶(dai)(dai)(dai)(dai)(dai)和其他傳(chuan)動(dong)皮(pi)(pi)(pi)帶(dai)(dai)(dai)(dai)(dai), 所不(bu)同(tong)(tong)(tong)(tong)的(de)(de)(de)是這(zhe)種皮(pi)(pi)(pi)帶(dai)(dai)(dai)(dai)(dai)上具(ju)(ju)有(you)(you)(you)許多(duo)型齒(chi), 它們和同(tong)(tong)(tong)(tong)樣(yang)具(ju)(ju)有(you)(you)(you)型齒(chi)的(de)(de)(de)同(tong)(tong)(tong)(tong)步(bu)(bu)(bu)皮(pi)(pi)(pi)帶(dai)(dai)(dai)(dai)(dai)輪(lun)齒(chi)相嚙(nie)合。工(gong)作時(shi), 它們相當于柔軟(ruan)的(de)(de)(de)齒(chi)輪(lun), 具(ju)(ju)有(you)(you)(you)柔性(xing)好(hao), 價(jia)格便宜(yi)兩大優點。另(ling)外(wai), 同(tong)(tong)(tong)(tong)步(bu)(bu)(bu)皮(pi)(pi)(pi)帶(dai)(dai)(dai)(dai)(dai)還被用(yong)(yong)于輸(shu)入軸(zhou)(zhou)和輸(shu)出軸(zhou)(zhou)方(fang)向不(bu)一致的(de)(de)(de)情況。這(zhe)時(shi), 只要同(tong)(tong)(tong)(tong)步(bu)(bu)(bu)皮(pi)(pi)(pi)帶(dai)(dai)(dai)(dai)(dai)足夠(gou)長,使(shi)皮(pi)(pi)(pi)帶(dai)(dai)(dai)(dai)(dai)的(de)(de)(de)扭角誤差(cha)不(bu)太大, 則同(tong)(tong)(tong)(tong)步(bu)(bu)(bu)皮(pi)(pi)(pi)帶(dai)(dai)(dai)(dai)(dai)仍能夠(gou)正常工(gong)作。在(zai)伺服系統中(zhong), 如果輸(shu)出軸(zhou)(zhou)的(de)(de)(de)位置采(cai)用(yong)(yong)碼(ma)盤測量, 則輸(shu)入傳(chuan)動(dong)的(de)(de)(de)同(tong)(tong)(tong)(tong)步(bu)(bu)(bu)皮(pi)(pi)(pi)帶(dai)(dai)(dai)(dai)(dai)可(ke)以(yi)(yi)放在(zai)伺服環外(wai)面, 這(zhe)對系統的(de)(de)(de)定位精度和重(zhong)復性(xing)不(bu)會(hui)有(you)(you)(you)影響, 重(zhong)復精度可(ke)以(yi)(yi)達到1 mm以(yi)(yi)內。此外(wai), 同(tong)(tong)(tong)(tong)步(bu)(bu)(bu)皮(pi)(pi)(pi)帶(dai)(dai)(dai)(dai)(dai)比齒(chi)輪(lun)鏈價(jia)格低得多(duo), 加工(gong)也容(rong)易得多(duo)。 有(you)(you)(you)時(shi), 齒(chi)輪(lun)鏈和同(tong)(tong)(tong)(tong)步(bu)(bu)(bu)皮(pi)(pi)(pi)帶(dai)(dai)(dai)(dai)(dai)結合起(qi)來(lai)使(shi)用(yong)(yong)更為方(fang)便。
2.3諧波齒輪(lun)
雖然諧波(bo)(bo)齒(chi)(chi)(chi)(chi)(chi)輪(lun)(lun)(lun)已(yi)問世多年, 但直到(dao)最近人(ren)們才(cai)開始廣泛地使(shi)用它。目前, 機(ji)器(qi)(qi)人(ren)的旋轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)關(guan)節(jie)有60％～70％都(dou)使(shi)用諧波(bo)(bo)齒(chi)(chi)(chi)(chi)(chi)輪(lun)(lun)(lun)。諧波(bo)(bo)齒(chi)(chi)(chi)(chi)(chi)輪(lun)(lun)(lun)傳動機(ji)構由剛(gang)性(xing)(xing)(xing)(xing)(xing)(xing)齒(chi)(chi)(chi)(chi)(chi)輪(lun)(lun)(lun)、諧波(bo)(bo)發生(sheng)(sheng)器(qi)(qi)和柔(rou)性(xing)(xing)(xing)(xing)(xing)(xing)齒(chi)(chi)(chi)(chi)(chi)輪(lun)(lun)(lun)三(san)個主要零件組成, 如圖2.2所(suo)示。工作時(shi), 剛(gang)性(xing)(xing)(xing)(xing)(xing)(xing)齒(chi)(chi)(chi)(chi)(chi)輪(lun)(lun)(lun)固定安(an)裝, 各齒(chi)(chi)(chi)(chi)(chi)均布于圓(yuan)(yuan)周, 具有外齒(chi)(chi)(chi)(chi)(chi)形的柔(rou)性(xing)(xing)(xing)(xing)(xing)(xing)齒(chi)(chi)(chi)(chi)(chi)輪(lun)(lun)(lun)沿(yan)剛(gang)性(xing)(xing)(xing)(xing)(xing)(xing)齒(chi)(chi)(chi)(chi)(chi)輪(lun)(lun)(lun)的內齒(chi)(chi)(chi)(chi)(chi)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)動。柔(rou)性(xing)(xing)(xing)(xing)(xing)(xing)齒(chi)(chi)(chi)(chi)(chi)輪(lun)(lun)(lun)比剛(gang)性(xing)(xing)(xing)(xing)(xing)(xing)齒(chi)(chi)(chi)(chi)(chi)輪(lun)(lun)(lun)少(shao)兩個齒(chi)(chi)(chi)(chi)(chi), 所(suo)以柔(rou)性(xing)(xing)(xing)(xing)(xing)(xing)齒(chi)(chi)(chi)(chi)(chi)輪(lun)(lun)(lun)沿(yan)剛(gang)性(xing)(xing)(xing)(xing)(xing)(xing)齒(chi)(chi)(chi)(chi)(chi)輪(lun)(lun)(lun)每轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)一圈就反方向(xiang)轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)過兩個齒(chi)(chi)(chi)(chi)(chi)的相應轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)角(jiao)。 諧波(bo)(bo)發生(sheng)(sheng)器(qi)(qi)具有橢圓(yuan)(yuan)形輪(lun)(lun)(lun)廓, 裝在諧波(bo)(bo)發生(sheng)(sheng)器(qi)(qi)上(shang)的滾珠用于支承柔(rou)性(xing)(xing)(xing)(xing)(xing)(xing)齒(chi)(chi)(chi)(chi)(chi)輪(lun)(lun)(lun), 諧波(bo)(bo)發生(sheng)(sheng)器(qi)(qi)驅動柔(rou)性(xing)(xing)(xing)(xing)(xing)(xing)齒(chi)(chi)(chi)(chi)(chi)輪(lun)(lun)(lun)旋轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)并使(shi)之(zhi)發生(sheng)(sheng)塑性(xing)(xing)(xing)(xing)(xing)(xing)形。轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)動時(shi), 柔(rou)性(xing)(xing)(xing)(xing)(xing)(xing)齒(chi)(chi)(chi)(chi)(chi)輪(lun)(lun)(lun)的橢圓(yuan)(yuan)形端部只(zhi)有少(shao)數齒(chi)(chi)(chi)(chi)(chi)與(yu)剛(gang)性(xing)(xing)(xing)(xing)(xing)(xing)齒(chi)(chi)(chi)(chi)(chi)輪(lun)(lun)(lun)嚙合(he), 只(zhi)有這樣, 柔(rou)性(xing)(xing)(xing)(xing)(xing)(xing)齒(chi)(chi)(chi)(chi)(chi)輪(lun)(lun)(lun)才(cai)能相對于剛(gang)性(xing)(xing)(xing)(xing)(xing)(xing)齒(chi)(chi)(chi)(chi)(chi)輪(lun)(lun)(lun)自由地轉(zhuan)(zhuan)(zhuan)(zhuan)(zhuan)過一定的角(jiao)度。
假設剛性齒(chi)(chi)輪(lun)有100個齒(chi)(chi), 柔性齒(chi)(chi)輪(lun)比它少2個齒(chi)(chi), 則(ze)當諧波發生器轉(zhuan)50圈(quan)時, 柔性齒(chi)(chi)輪(lun)轉(zhuan)1圈(quan), 這樣只占用很小的空間(jian)就可(ke)得(de)到1∶50的減(jian)速(su)比。 由于同時嚙合的齒(chi)(chi)數較(jiao)多, 因此諧波發生器的力矩傳遞能力很強。在3個零件(jian)中(zhong), 盡管任何2個都可(ke)以(yi)選為輸(shu)入元件(jian)和輸(shu)出元件(jian), 但通常總是(shi)把諧波發生器裝(zhuang)在輸(shu)入軸上(shang), 把柔性齒(chi)(chi)輪(lun)裝(zhuang)在輸(shu)出軸上(shang), 以(yi)獲得(de)較(jiao)大的齒(chi)(chi)輪(lun)減(jian)速(su)比。
圖2.2諧(xie)波齒輪驅動
二、工業機器(qi)人的驅(qu)動系統
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