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近年來,伺服電機控製技術正朝著交流化、數字化、智能化三個方向發展。作為數控機床的執行機構,伺服係統將電力電子器件、控製、驅動及保護等集為一體,並隨著數字脈寬調製技術、特種電機材料技術、微電子技術及現代控製技術的進步,經曆了從步進到直流,進而到交流的發展曆程。本文對其技術現狀及發展趨勢作簡要探討。
一、數控機床伺服係統
(一)kaihuansifuxitong。kaihuansifuxitongbushejiancefankuizhuangzhi,bugouchengyundongfankuikongzhihuilu,diandongjianshukongzhuangzhifachudezhilingmaichonggongzuo,duiyundongwuchameiyoujiancefankuihechulixiuzhengguocheng,caiyongbujindianjizuoweiqudongqijian,jichuangdeweizhijingduwanquanqujueyubujindiandongjidebujujiaojingduhejixiebufendechuandongjingdu,nanyidadaobijiaogaojingduyaoqiu。bujindiandongjidezhuansubukenenghengao,yundongbujiandesudushoudaoxianzhi。danbujindianjijiegoujiandan、可靠性高、成本低,且其控製電路也簡單。所以開環控製係統多用於精度和速度要求不高的經濟型數控機床。
(二)全閉環伺服係統。閉環伺服係統主要由比較環節、伺服驅動放大器,進給伺服電動機、機ji械xie傳chuan動dong裝zhuang置zhi和he直zhi線xian位wei移yi測ce量liang裝zhuang置zhi組zu成cheng。對dui機ji床chuang運yun動dong部bu件jian的de移yi動dong量liang具ju有you檢jian測ce與yu反fan饋kui修xiu正zheng功gong能neng,采cai用yong直zhi流liu伺si服fu電dian動dong機ji或huo交jiao流liu伺si服fu電dian動dong機ji作zuo為wei驅qu動dong部bu件jian。可ke以yi采cai用yong直zhi接jie安an裝zhuang在zai工gong作zuo台tai的de光guang柵zha或huo感gan應ying同tong步bu器qi作zuo為wei位wei置zhi檢jian測ce器qi件jian,來lai構gou成cheng高gao精jing度du的de全quan閉bi環huan位wei置zhi控kong製zhi係xi統tong。係xi統tong的de直zhi線xian位wei移yi檢jian測ce器qi安an裝zhuang在zai移yi動dong部bu件jian上shang,其qi精jing度du主zhu要yao取qu決jue於yu位wei移yi檢jian測ce裝zhuang置zhi的de精jing度du和he靈ling敏min度du,其qi產chan生sheng的de加jia工gong精jing度du比bi較jiao高gao。但dan機ji械xie傳chuan動dong裝zhuang置zhi的de剛gang度du、摩擦阻尼特性、fanxiangjianxidenggezhongfeixianxingyinsu,duixitongwendingxingyouhendayingxiang,shibihuanjingeisifuxitonganzhuangtiaoshibijiaofuza。yincizhishiyongzaigaojingduhedaxingshukongjichuangshang。
(三)banbihuansifuxitong。banbihuansifuxitongdegongzuoyuanliyuquanbihuansifuxitongxiangtong,tongyangcaiyongsifudiandongjizuoweiqudongbujian,keyicaiyongneizhuangyudianjineidemaichongbianmaqi,wushuaxuanzhuanbianyaqihuocesufadianjizuoweiweizhi/ 速su度du檢jian測ce器qi件jian來lai構gou成cheng半ban閉bi環huan位wei置zhi控kong製zhi係xi統tong,其qi係xi統tong的de反fan饋kui信xin號hao取qu自zi電dian機ji軸zhou或huo絲si杆gan上shang,進jin給gei係xi統tong中zhong的de機ji械xie傳chuan動dong裝zhuang置zhi處chu於yu反fan饋kui回hui路lu之zhi外wai,其qi剛gang度du等deng非fei線xian性xing因yin素su對dui係xi統tong穩wen定ding性xing沒mei有you影ying響xiang,安an裝zhuang調tiao試shi比bi較jiao方fang便bian。機ji床chuang的de定ding位wei精jing度du與yu機ji械xie傳chuan動dong裝zhuang置zhi的de精jing度du有you關guan,而er數shu控kong裝zhuang置zhi都dou有you螺luo距ju誤wu差cha補bu償chang和he間jian隙xi補bu償chang等deng項xiang功gong能neng,在zai傳chuan動dong裝zhuang置zhi精jing度du不bu太tai高gao的de情qing況kuang下xia,可ke以yi利li用yong補bu償chang功gong能neng將jiang加jia工gong精jing度du提ti高gao到dao滿man意yi的de程cheng度du。故gu半ban閉bi環huan伺si服fu係xi統tong在zai數shu控kong機ji床chuang中zhong應ying用yong很hen廣guang。
二、伺服電機控製性能優越
(一)低(di)頻(pin)特(te)性(xing)好(hao)。步(bu)進(jin)電(dian)機(ji)易(yi)出(chu)現(xian)低(di)速(su)時(shi)低(di)頻(pin)振(zhen)動(dong)現(xian)象(xiang)。交(jiao)流(liu)伺(si)服(fu)電(dian)機(ji)不(bu)會(hui)出(chu)現(xian)此(ci)現(xian)象(xiang),運(yun)轉(zhuan)非(fei)常(chang)平(ping)穩(wen),交(jiao)流(liu)伺(si)服(fu)係(xi)統(tong)具(ju)有(you)共(gong)振(zhen)抑(yi)製(zhi)功(gong)能(neng),可(ke)涵(han)蓋(gai)機(ji)械(xie)的(de)剛(gang)性(xing)不(bu)足(zu),並(bing)且(qie)係(xi)統(tong)內(nei)部(bu)具(ju)有(you)頻(pin)率(lv)解(jie)析(xi)機(ji)能(neng),可(ke)檢(jian)測(ce)出(chu)機(ji)械(xie)的(de)共(gong)振(zhen)點(dian),便(bian)於(yu)係(xi)統(tong)調(tiao)整(zheng)。
(二)控製精度高。交流伺服電機的控製精度由電機軸後端的旋轉編碼器保證。例如鬆下全數字式交流伺服電機,對於帶17位編碼器的電機而言,驅動器每接收217=131072個脈衝電機轉一圈,即其脈衝當量為360°/131072=9.89秒。是步距角為1.8°的步進電機的脈衝當量的1/655。
(三)過guo載zai能neng力li強qiang。步bu進jin電dian機ji不bu具ju有you過guo載zai能neng力li,為wei了le克ke服fu慣guan性xing負fu載zai在zai啟qi動dong瞬shun間jian的de慣guan性xing力li矩ju,選xuan型xing時shi需xu要yao選xuan取qu額e定ding轉zhuan矩ju比bi負fu載zai轉zhuan矩ju大da很hen多duo的de電dian機ji,造zao成cheng了le力li矩ju浪lang費fei的de現xian象xiang。而er交jiao流liu伺si服fu電dian機ji具ju有you較jiao強qiang的de過guo載zai能neng力li,例li如ru鬆song下xia交jiao流liu伺si服fu係xi統tong中zhong的de伺si服fu電dian機ji的de最zui大da轉zhuan矩ju達da到dao額e定ding轉zhuan矩ju的de三san倍bei,可ke用yong於yu克ke服fu啟qi動dong瞬shun間jian的de慣guan性xing力li矩ju。 (四)速度響應快。步進電機從靜止加速到額定轉速需要200~400毫秒。交流伺服係統的速度響應較快,例如鬆下MSMA 400W交流伺服電機,從靜止加速到其額定轉速僅需幾毫秒。
(五)矩頻特性佳。步進電機的輸出力矩隨轉速升高而下降,且在較高轉速時轉矩會急劇下降,所以其最高工作轉速一般在300~600RPM。交流伺服電機為恒力矩輸出,即在其額定轉速(一般為2000RPM或3000RPM)以內,都能輸出額定轉矩。
三、伺服電機控製展望
(一)伺服電機控製技術的發展推動加工技術的高速高精化。80niandaiyilai,shukongxitongzhujianyingyongsifudianjizuoweiqudongqijian。jiaoliusifudianjineishiwushuajiegou,jihubuxuweixiu,tijixiangduijiaoxiao,youliyuzhuansuhegonglvdetigao。muqianjiaoliusifuxitongyizaihendafanweineiqudailezhiliusifuxitong。zaidangdaishukongxitongzhong,jiaoliusifuqudaizhiliusifu、ruanjiankongzhiqudaiyingjiankongzhichengweilesifujishudefazhanqushi。youcichanshengleyingyongzaishukongjichuangdesifujingeihezhuzhouzhuangzhishangdejiaoliushuziqudongxitong。suizheweichuliqihequanshuzihuajiaoliusifuxitongdefazhan,shukongxitongdejisuansududadatigao,caiyangshijiandadajianshao。yingjiansifukongzhibianweiruanjiansifukongzhihou,dadaditigaolesifuxitongdexingneng。liruOSP-U10/U100網(wang)絡(luo)式(shi)數(shu)控(kong)係(xi)統(tong)的(de)伺(si)服(fu)控(kong)製(zhi)環(huan)就(jiu)是(shi)一(yi)種(zhong)高(gao)性(xing)能(neng)的(de)伺(si)服(fu)控(kong)製(zhi)網(wang),它(ta)對(dui)進(jin)行(xing)自(zi)律(lv)控(kong)製(zhi)的(de)各(ge)個(ge)伺(si)服(fu)裝(zhuang)置(zhi)和(he)部(bu)件(jian)實(shi)現(xian)了(le)分(fen)散(san)配(pei)置(zhi),網(wang)絡(luo)連(lian)接(jie),進(jin)一(yi)步(bu)發(fa)揮(hui)了(le)它(ta)對(dui)機(ji)床(chuang)的(de)控(kong)製(zhi)能(neng)力(li)和(he)通(tong)信(xin)速(su)度(du)。這(zhe)些(xie)技(ji)術(shu)的(de)發(fa)展(zhan),使(shi)伺(si)服(fu)係(xi)統(tong)性(xing)能(neng)改(gai)善(shan)、可靠性提高、調試方便、柔性增強,大大推動了高精高速加工技術的發展。
另ling外wai,先xian進jin傳chuan感gan器qi檢jian測ce技ji術shu的de發fa展zhan也ye極ji大da地di提ti高gao了le交jiao流liu電dian動dong機ji調tiao速su係xi統tong的de動dong態tai響xiang應ying性xing能neng和he定ding位wei精jing度du。交jiao流liu伺si服fu電dian機ji調tiao速su係xi統tong一yi般ban選xuan用yong無wu刷shua旋xuan轉zhuan變bian壓ya器qi、混合型的光電編碼器和絕對值編碼器作為位置、速度傳感器,其傳感器具有小於1μs的響應時間。伺服電動機本身也在向高速方向發展,與上述高速編碼器配合實現了60m/min甚至100m/min的快速進給和1g的加速度。為保證高速時電動機旋轉更加平滑,改進了電動機的磁路設計,並配合高速數字伺服軟件,可保證電動機即使在小於1μm轉動時也顯得平滑而無爬行。
(二)交流直線伺服電機直接驅動進給技術已趨成熟。數控機床的進給驅動有“旋轉伺服電機+精密高速滾珠絲杠”和“直線電機直接驅動” 兩liang種zhong類lei型xing。傳chuan統tong的de滾gun珠zhu絲si杠gang工gong藝yi成cheng熟shu加jia工gong精jing度du較jiao高gao,實shi現xian高gao速su化hua的de成cheng本ben相xiang對dui較jiao低di,所suo以yi目mu前qian應ying用yong廣guang泛fan。使shi用yong滾gun,珠zhu絲si杠gang驅qu動dong的de高gao速su加jia工gong機ji床chuang最zui大da移yi動dong速su度du90m/min,加速度1.5g。但滾珠絲杠是機械傳動,機械元件間存在彈性變形、摩擦和反向間隙,相應會造成運動滯後和非線性誤差,所以再進一步提高滾珠絲杠副移動速度和加速度比較難了。90年代以來,高速高精的大型加工機床中,應用直線電機直接驅動進給驅動方式。它比滾珠絲杠驅動具有剛度更高、速度範圍更寬、加速特性更好、運動慣量更小、動態響應性能更佳,運行更平穩、位(wei)置(zhi)精(jing)度(du)更(geng)高(gao)等(deng)優(you)點(dian)。且(qie)直(zhi)線(xian)電(dian)機(ji)直(zhi)接(jie)驅(qu)動(dong),不(bu)需(xu)中(zhong)間(jian)機(ji)械(xie)傳(chuan)動(dong),減(jian)小(xiao)了(le)機(ji)械(xie)磨(mo)損(sun)與(yu)傳(chuan)動(dong)誤(wu)差(cha),減(jian)少(shao)了(le)維(wei)護(hu)工(gong)作(zuo)。直(zhi)線(xian)電(dian)機(ji)直(zhi)接(jie)驅(qu)動(dong)與(yu)滾(gun)珠(zhu)絲(si)杠(gang)傳(chuan)動(dong)相(xiang)比(bi),其(qi)速(su)度(du)提(ti)高(gao)30倍,加速度提高10倍,最大達10g,剛度提高7倍,最高響應頻率達100Hz,haiyoujiaodadefazhanyudi。dangqian,zaigaosugaojingjiagongjichuanglingyuzhong,liangzhongqudongfangshihaihuibingcunxiangdangchangyiduanshijian,dancongfazhanqushilaikan,zhixiandianjiqudongsuozhandebizhonghuiyulaiyuda。zhongzhongjixiangbiaoming,zhixiandianjiqudongzaigaosugaojingjiagongjichuangshangdeyingyongyijinrujiasuzengchangqi。
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