NGHIEN Cl/U - TRAO D O I
Xay dtfng phifrfng phap dieu khien thich nghi khi phay bang dao phay
mat dau tren may phay CNC
(*) TS. HOANG VIET HONG - ThS. VU XUAN TRUCfNG
1. Bat van de
1.1. Dieu khien thich nghi AC (Adaptive control)
Da va dang difdc nhieu lmh vifc khoa hpc kl thuat tfng dung dde biet la Hnh vifc gia cdng cd khi. Trong ITnh vifc gia cdng eat gpt, dieu khien thich nghi du'dc tfng dung de nang cao hieu qua qua trinh gia cdng.
Khi tien hanh lap trinh gia cdng tren cdc may phay CNC ngifdi lap trinh thu'dng cdn ctf vao cdc dieu kien khd khan, cdc true trdc khdng the dtf doan tnfdc du'dc cd the xay ra trong qua trinh gia cdng vi mdn dung eu, vat lieu khdng ddng nhat bode rung ddng do dp ctfng vtfng Clia he thdng thay ddi,... nen thifdng chpn che dp gia cdng thap bode trung binh trong sudt qud trinh gia cdng nen khdng khai thdc bet kha ndng eua mdy, gay lang phi, keo dai thdi ban thu hdi vdn dau tif.
Dieu khien thich nghi la mdt he thdng cd kha nang nhan biet difdc cdc thay ddi eua he thdng trong qua trinh gia cdng, tren cd sd dd xtf li nhanh cdc tin hieu tif ddng dieu khien dam bao cho he thdng ludn lam viec tai trang thdi dn dinh theo yeu cau.
He thdng dieu khien thich nghi difdc chia ra 2 nhdm, mdi nhdm cd eae ddi tu'dng khdc nhau: Dieu khien thich nghi mien cifdng ACC (Adaptive Control Constraint). Vdi bd dieu khien thich nghi mien cu'dng thi tdc dp chay dao va tdc dp vdng quay true ehinh cd the thay ddi difdc, cho nen viec gia cdng d day ed the tan dung du'dc ltfc eat hay cdng suat cat Idn nhat. Cdn dieu khien thich nghi tdi ifu ACO (Adaptive Control Optimization). Vdi bd dieu khien thich nghi tdi uli, gid thanh gia cdng eho mdt bd phan du'dc tdi u\i bdi pham vi chay dao va tdc dp true ehinh.
1.2. l/u, nhrfgfc diem ciia AC - l/u diem :
-I- May ludn lam viec vdi che dp cat tdi uli nen rut ngan du'dc thdi gian gia cdng.
-1- Ludn dam bao an loan eho he thdng cdng nghe.
-I- Ludn ludn dam bao dp ehinh xdc gia cdng va chat lifdng be mat theo yeu cau.
-I- Kiem soat difdc qua trinh gia cdng.
- Nhu'dc diem:
-I- Khd dat difdc dp nhay can thiet trong pham vi rdng cua md men bode cdng suat cdt.
-I- Chi phi cho thiet bi tang, do dd phai giai bai toan kinh te - kl thuat trong dieu kien gia cdng cu the.
Z. flieu kliien thicli nghi tren may pliay CNC
2.1. X3y di/ng phi^oTng phap dieu khien thich nghi vdi tin hieu do va phan hoi la li/c cat
Cdng suat cat difdc tinh (1) Nc py
Trong dd
1020x60
: N_ - Cdng suat cat Fj - Ltfc cat tiep tuyen V - Van tdc cat
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Hinh 1: Mo hinh tong quat dieu khien thich nghi vdi tin hieu dieu khien thich nghi la life cdt
Vdi cdng suat dpng cd true chinh xdc dinh, bp dieu khien thich nghi tinh loan du'dc ltfc vdng gidi ban. Khi cdng suat eat vu'dt qud cdng suat gidi ban thi ttf phifdng trinh md ta stf anh hu'dng cua cac thdng sd che dp cdt nhif: van tdc cat V, lifdng chay dao S , chieu sau cdt B den iife cat (F = f(V, S , B)), bp i^ieu khien thich
(*) Vien May va Diing cij Cong nghiep
n TAP CHi C d KHi VIET NAM • -So U=, - Thang H nam 2009
NGHIEN Ciru • TRAO D 6 |
nghi tinh todn va dieu chinh lifdng chay dao S phu hdp cho qua trinh cdt ludn tan dung difdc cdng suat cat Idn nha't ma he thdng cdng nghe boat ddng an toan.
2.2. XSy dtfng phifdng phap dieu khien thich nghi vdi tin lii^u phan hoi la Itfdng mon
2.2.1. Dieu chinh mdy de dam bdo dq chinh xdc gia cong
Mdn dao trong qua trinh phay la dai lifdng phu thupc vao che dp cdt trong qua trinh gia cdng cQng nhif phu thudc vao thdi gian gia cdng thifc te. Khi dung cu gia cdng dat de'n tudi ben thi lifdng mdn dao dat den gid tri tdi ban. Nhieu tdc gia da xay difng difdc phifdng trinh bieu dien mdi quan he gitfa lifdng mdn dao vdi cdc thdng sd che dp cdt va vdi thdi gian gia cdng thtfc te khi gia cdng bang dao phay mdt dau:
(2) Ah = f(V, S^, B, T) Trong dd: Ah - Lifdng mdn dao
T - Thdi gian gia cdng thtfc te'
Ttf yeu cau ve dung sai kich thifdc chi tiet, thdng qua phifdng trinh Ah = f(V, S , B, T) ta xac dinh difdc khoang thdi gian can dieu chinh T^^ de Ah < 5^. Qud trinh dieu chinh cd the ttf ddng hoac bdng tay.
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inh 2: Sd do dieu chinh dao bang tay
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Hinh .3; Sd do dieu chinh tif dpng bang chifdng trinh dieu khien de dam bao dp chinh xac chi tiet gia cong.
Qud trinh dieu ehinh difdc tie'p tuc khi thdi gian gia cdng T < T (cd nghia la dao van cdn kha ndng cat). Qua irinh ndy giup giam chi phi gia cdng do da tan dung he't kha ndng cdt gpt cua dung cu tren cd sd van dam bao dp chinh xdc kieh thifdc gia cdng.
2.2.2. Dieu chinh mdy de ndng cao dQ chinh xdc gia c6ng tii'c 1^ CO h^p dung sai kich thtfdc
Qud trinh dieu chinh thu hep dtfdc 8^ thdnh 6^.. Vdi 6, < 6^ ta da thu hep du'dc dung sai ehi tiet nhif vay nang cao du'dc dp chinh xdc gia cdng.
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Hinh 4: Sd do dieu chinh tif dpng bang chifdng trinh dieu khien nang cao dp chinh xac chi tiet gia cong Qud trinh dieu chinh nay dtfng lai khi Ah > [Ah]
bode R > [R ].
Viec dieu chinh nay ddp tfng yeu cau nang cao dp chinh xdc gia cdng, xu hifdng phdt trien eua cdng nghe che tao mdy trong the ky 21, nhdm nang cao tudi ben, dp tin cay cua chi tiet.
3. Ket luan
3.1. He thdng dieu khien thich nghi giup cho qud trinh gia cdng cat gpt ndi chung va phay tren mdy phay CNC ndi rieng ludn du'dc thifc hien trong cdc dieu kien an toan ve mdy, dung eu, ngifdi tnfe tiep dtfng mdy.
Ngoai ra trong dieu kien difdc trang bi cdc cam bien day dii, vdi he thdng phan mem cd the can thiep thdng qua tinh todn ttfc thdi vdi tdc dp cao cho phep he thdng ludn du'dc gia cdng vdi che dp cat tdi im. Qua dd tie't kiem difdc thdi gian gia cdng cd ban, ndng suat cao, ehi phi thap dan den hieu qua dau tUcdc mdy gia cdng theo chifdng trinh so (NC& CNC) ed hieu qua.
3.2. Viec dieu khien thich nghi theo quan diem dam bao chat lifdng bode nang cao dp ehinh xdc gia cdng gdp phan nang cao va dam bao stf dn dinh chat lifdng cua cdc sdn pham ciia nganh cd khi. D
Tai lieu tham khao:
[1] Tran Van Dich (1997), Nghien ciJu dp chinh xac gia cong bang cac phiTdng phap thi/c nghiem. Bai giang Cao hgc va Nghien ciiu sinh Dal hpc Bach khoa Ha Npi.
[2] M. Alauddin (1997), M.A. EL Baradie. Tool life model for end milling steel (190 BHN).
Journal of materials Processing Technology.
Vol 68.
[3] V.C Vankatesh (1987), H. Chandrasekaran, Experimental techniques in metal cutting. New Dehli, Prentice - Hall of India.
[4] Prof.Dr.ha Lierath (2000), Berichte aus der Fertigungstechnik, Shaker Veriag.
[51 Eberhard Paucksch (1996), Zerspantechnik.
Braunschweig, Wiesbaden. Vieweg.
T A P C H i C d K H i V I E T N A M • ^'•' 1 i"' - Th.m.:; >; n.lm -nn'
