實驗(yan)名稱：靜(jing)電懸浮過程的優化設計與動態控制

　　實驗目的：

　　通(tong)過(guo)多(duo)種(zhong)技術手段，對(dui)現(xian)有靜電(dian)懸(xuan)浮(fu)系統進(jin)行(xing)了多(duo)方面的(de)(de)(de)優化。從懸(xuan)浮(fu)電(dian)極的(de)(de)(de)形(xing)貌(mao)和尺寸以及定位光路考慮，實(shi)現(xian)了直(zhi)徑(jing)10mm固態(tai)(tai)金屬材(cai)料的(de)(de)(de)穩定懸(xuan)浮(fu)。通(tong)過(guo)改(gai)進(jin)控制算法(fa)，提高了熔融樣(yang)品懸(xuan)浮(fu)過(guo)程(cheng)中的(de)(de)(de)形(xing)態(tai)(tai)和位置穩定性。增加(jia)了觸發(fa)形(xing)核和液淬的(de)(de)(de)功能，豐富了材(cai)料凝固過(guo)程(cheng)研究的(de)(de)(de)手段。并且把激光加(jia)熱和測溫(wen)相耦合(he)，實(shi)現(xian)了懸(xuan)浮(fu)樣(yang)品溫(wen)度的(de)(de)(de)精確(que)控制。

　　測(ce)試設備：高壓放大器(qi)、位置敏(min)感探測(ce)器(qi)、電腦等(deng)。

　　圖(tu)1：靜電懸(xuan)浮(fu)裝置示(shi)意圖(tu)

　　實驗過程：

　　靜電懸浮中，對于直徑3mm左右的樣品，為了增加懸浮的穩定性，垂直方向一般選用半球形上電極和凹面下電極，且下電極直徑大于上電極，上下電極之間的間距一般設定為10mm。如此，對于密度7g·cm^-3直(zhi)徑3mm左右的(de)(de)樣(yang)品(pin)，實(shi)(shi)驗(yan)發現(xian)其起跳(tiao)電(dian)(dian)(dian)(dian)壓約為25kV。如(ru)果懸浮(fu)樣(yang)品(pin)的(de)(de)直(zhi)徑增大(da)(da)至(zhi)10mm，上(shang)下電(dian)(dian)(dian)(dian)極(ji)之間的(de)(de)間距(ju)需(xu)拉伸至(zhi)15mm以上(shang)，那么(me)起跳(tiao)電(dian)(dian)(dian)(dian)壓將在(zai)45kV以上(shang)。另外(wai)，對于同一(yi)樣(yang)品(pin)，實(shi)(shi)驗(yan)發現(xian)上(shang)大(da)(da)下小(xiao)型的(de)(de)垂直(zhi)電(dian)(dian)(dian)(dian)極(ji)組(zu)要(yao)比上(shang)小(xiao)下大(da)(da)型的(de)(de)電(dian)(dian)(dian)(dian)極(ji)組(zu)的(de)(de)起跳(tiao)電(dian)(dian)(dian)(dian)壓小(xiao)，因此為了(le)盡(jin)可(ke)能(neng)(neng)提高系統的(de)(de)懸浮(fu)能(neng)(neng)力(li)，需(xu)采用(yong)上(shang)大(da)(da)下小(xiao)電(dian)(dian)(dian)(dian)極(ji)組(zu)合。而且，對于上(shang)大(da)(da)下小(xiao)型電(dian)(dian)(dian)(dian)極(ji)組(zu)，電(dian)(dian)(dian)(dian)荷在(zai)樣(yang)品(pin)頂端的(de)(de)分布更(geng)彌(mi)散，如(ru)此也有效(xiao)避免了(le)因電(dian)(dian)(dian)(dian)荷太集中而導致(zhi)的(de)(de)樣(yang)品(pin)與上(shang)電(dian)(dian)(dian)(dian)極(ji)之間的(de)(de)放電(dian)(dian)(dian)(dian)。

　　圖2：靜電(dian)懸浮配電(dian)方(fang)式的改(gai)進

　　本文(wen)采用了(le)上(shang)(shang)下(xia)(xia)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)(ji)(ji)同時(shi)(shi)配(pei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)方式，如圖2所示，并進行了(le)實驗(yan)，發(fa)現給(gei)下(xia)(xia)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)(ji)(ji)接(jie)正電(dian)(dian)(dian)(dian)(dian)(dian)(dian)后，在(zai)成(cheng)功懸(xuan)浮樣品的(de)(de)同時(shi)(shi)可以減(jian)小(xiao)上(shang)(shang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)(ji)(ji)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)。這相當(dang)于把兩個高(gao)壓(ya)(ya)(ya)放(fang)大(da)器串聯(lian)起(qi)來(lai)，同時(shi)(shi)給(gei)上(shang)(shang)下(xia)(xia)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)(ji)(ji)之間提供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)。圖3為(wei)實驗(yan)測(ce)定(ding)的(de)(de)懸(xuan)浮同一樣品上(shang)(shang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)(ji)(ji)起(qi)跳電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)和懸(xuan)浮電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)隨(sui)(sui)加載在(zai)下(xia)(xia)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)(ji)(ji)上(shang)(shang)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)的(de)(de)變化。當(dang)下(xia)(xia)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)從0增大(da)到(dao)5kV時(shi)(shi)，上(shang)(shang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)(ji)(ji)起(qi)跳電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)從9.5kV降低(di)到(dao)5.8kV，而懸(xuan)浮電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)從8.2kV減(jian)小(xiao)到(dao)3.3kV，因此在(zai)下(xia)(xia)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)(ji)(ji)上(shang)(shang)加載正電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)和在(zai)上(shang)(shang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)(ji)(ji)上(shang)(shang)加載負電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)有相同的(de)(de)效果。另(ling)外，由于樣品起(qi)跳是(shi)一個比(bi)較隨(sui)(sui)機的(de)(de)過程，所以起(qi)跳電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)的(de)(de)線性度沒有懸(xuan)浮電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)好(hao)。

　　圖(tu)3：上電(dian)極(ji)起跳(tiao)電(dian)壓(ya)和懸(xuan)浮電(dian)壓(ya)隨下電(dian)極(ji)電(dian)壓(ya)的(de)變化：(a)起跳(tiao)電(dian)壓(ya)；(b)懸(xuan)浮電(dian)壓(ya)

　　實現大尺(chi)(chi)度樣(yang)品懸(xuan)浮(fu)的(de)(de)另一個(ge)關鍵點在于定(ding)位(wei)(wei)光(guang)(guang)路(lu)的(de)(de)改進。目前所使用(yong)的(de)(de)位(wei)(wei)置(zhi)敏(min)(min)感探(tan)測(ce)器(qi)(PSD)光(guang)(guang)敏(min)(min)面尺(chi)(chi)寸(cun)為(wei)(wei)11mm，定(ding)位(wei)(wei)平行激(ji)光(guang)(guang)光(guang)(guang)束(shu)直(zhi)徑(jing)(jing)(jing)為(wei)(wei)10mm，這(zhe)種組合對(dui)于實現直(zhi)徑(jing)(jing)(jing)10mm樣(yang)品的(de)(de)懸(xuan)浮(fu)是不可能的(de)(de)。懸(xuan)浮(fu)10mm樣(yang)品所需定(ding)位(wei)(wei)激(ji)光(guang)(guang)光(guang)(guang)束(shu)直(zhi)徑(jing)(jing)(jing)以及(ji)垂直(zhi)方向上下電極(ji)之間間距都為(wei)(wei)15mm，因此為(wei)(wei)了使定(ding)位(wei)(wei)激(ji)光(guang)(guang)與位(wei)(wei)置(zhi)敏(min)(min)感探(tan)測(ce)器(qi)相匹(pi)配，需通過透鏡對(dui)光(guang)(guang)束(shu)進行變(bian)徑(jing)(jing)(jing)。

　　圖4：靜電(dian)懸浮系統定(ding)位激光(guang)(guang)光(guang)(guang)路的改(gai)進

　　實驗結果：

　　如圖(tu)4所(suo)示，當定位激光(guang)(guang)通(tong)過樣(yang)品(pin)后，在(zai)(zai)其(qi)(qi)光(guang)(guang)路上放置兩個凸透(tou)鏡(jing)，二者焦距比為(wei)(wei)3：2，即可把(ba)15mm的(de)光(guang)(guang)束轉變為(wei)(wei)10mm的(de)光(guang)(guang)束，相對應(ying)樣(yang)品(pin)在(zai)(zai)位置敏感探測(ce)器(PSD)光(guang)(guang)敏面上的(de)投影(ying)直徑也縮小了1.5倍。圖(tu)5為(wei)(wei)穩定懸浮的(de)10mmTi球和Fe球，其(qi)(qi)中(zhong)Ti球的(de)質量(liang)為(wei)(wei)2.36g，Fe球質量(liang)為(wei)(wei)4.12g。

　　圖5：直徑(jing)10mm樣品的懸浮：(a)Ti；(b)Fe

　　實驗中對靜電(dian)懸(xuan)浮過程進行優化(hua)設計(ji)，改變位置定位光路和(he)配電(dian)方式，顯著提高了靜電(dian)懸(xuan)浮能力，首次成功實現(xian)了直徑10mm大尺(chi)寸(cun)金屬材料(liao)的(de)穩(wen)定懸(xuan)浮。

　　電壓(ya)放大器推薦：ATA-7050

　　圖：ATA-7050高壓放大器指標參數

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