NGHIEN CUfU TRAO D O I
NGHIEN Cifu VA THIET KE MAY PHAY CNC
RESEARCH AND DESIGN OF CNC MILL MACHINE
KS.TrUtfng Van Hpi, TS. Nguyen Trpng Doanh Viin Co khi, TrUdng Dai bpc Bach khoa Ha Noi.
TOM TAT
Viec thiet ke mdy CNC tgi Viet Nam dd vd dang Id vdn dequan trgng cdn phdi nghien cdu, bdi vi cdc nghiin cdu trong linh vUc ndy chUa dap dng dUdc viec ldm chu cong nghe CNC. Cot loi cua mdy CNC Id cdc true chuyen dgng, bao gom cdc hi ddn dgng vd he thdng diiu khien CNC. Thiet ki'mdy CNC chinh la thiet kehe thong dieu khien cho cdc true chuyen dgng chinh cua mdy. Bdi bdo ndy de cap din nhdng van di cd bdn trong thiet ke mdy phay CNC phuc vu nghien cdu vd ddo tgo.
ABSTRACT
Design of CNC machine tools in Vietnam is a very important problem for research, because the actual research in this field are not answered to requirements for mastering of CNC technology. The core of CNC machine is composed of actionners and CNC system. This paper deals with main problems in designing of milling machine for research and education goal.
I.GICflTHIEU
Miy phay CNC Ii m i y phay dUpe diiu khien tU dpng bang h i thong dii'u khii'n so CNC.
Chung dupe sd dung rpng rai trong gia eong cic be mat dinh hinh phdc tap, doi hoi cd dp ehinh xac cao. Trin cP sd ve kich thUde, hinh ding cua sin pham, eo the lap trinh bang tay hay lip trinh tu dpng de tao ra cac dudng ehuyen dao. Chuyen sang thinh quy dao chuyen dpng tren khong gian 3 chieu. Cau tao chung cua m i y phay CNC bao gom toi thii'u 3 true chuyen dpng tao n i n b i mat 3D vi mpt true ehuyen dpng cua dao. True chuyen dpng cua dao dUpe diiu khii'n vdi toe dp xac dinh, nin he thdng dii'u khiin khong q u i phdc tap. Ba true chuyen dpng X, Y v i Z l i ba true quyet dinh den chat lupng v i dp chinh xic cua m i y CNC.
Hai chuyen dpng X, Y dupe thUe hien bdi ban hai
tpa dp X, Y, tao ehuyin dpng eua ban miy theo hai phupng \ai6ng gde vdi true dao. True Z con lai la true dUa dau dao tiin lin hay ha xuong theo yiu ciu cua be mat gia eong. M6 hinh mot true cbuyi'n dpng cua b i n m i y dUpe bii'u dien tren hinh 1.
1, DODECOSWO
[I]Heti»og(to
Hinh I. Cdu tgo mgt true chuyen o cita mdy phay CNC.
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NGHIEN CUfU-TRAO D 6 I
2. MO HiNH D O N G LVC HOC CUA TRUC Z Chuyen dpng quay cua true chinh dUpe thUc hien bdi dpng cP servo 1 chieu, hop so va true mang tai. Mo hinh dong lUc hpe cua true nay dupe bii'u dien tren hinh 2. Bin may dUpc dieh chuyen bdi true vit me - bi. Gia thiet r i n g khdp noi gifla dpng ep va vit me - bi hoan toan edng va ehuyen dpng hai chiiu khong co khe hd. Can thiet phii xiy dUng cic phUPng trinh dpng lUe hpe cho true chinh eua miy. Cae phUOng trinh nay the hien ban ehat vit ly eua mpt true ehuyen dpng.
Chung se giup viee dii'u khii'n chinh xae tdc dp v i vi tri cua true de thUe hiin viec gia eong ehinh xac cic biin dang can thiit.
Hop gidm tdc
vk c =
(3) (4) (5) Vdi T^ - mo men keo eua dpng ep, C^
- he so c i n eiia dpng ep, - toe dp quay cua true dpng CP, 0) - m o men truyen sang true mang tai, J^- Mo men quan tinh eua true dpng cP, 6_^- vi tri gdc cua true dpng eP, M_.- mo men eat, N- d so truyen cua hop giam toe, to - toe dp true mang
Ham truyen phan d i i n eua dpng cP dupe dpn giin hda do hang so thdi gian T nhd:
F„(s) --
j }
(6) Vdi R - d i i n trd thuan eua ro to, Kt la hang so m o men keo cua dpng cd, T - hang so thdi gian cua mach diin.
Hinh 3. He thong dieu khien toe do dUdi tdc dgng nhiiu Mc Ham truyen cua thiet bi dieu khien:
Fpw(s)= k^+kj.s-\-ko/s (7) Hmh 2. Mo hinh dgng luc hoc cua true quay Ham truyen cua he thong vdi dau vao thiJ
nhat la: . , h.-. ,
H i thdng die'u khien servo cho true chinh f " i i w - 7— , %(^ . ^ y°i nay eo dang nhU tren hmh 3 vOi Me la tae dpng
nhieu. Ham truyin eua he thong vdi dau vao thii Gia thiet la he thong dan dpng eo dp cdng hai (nhieu): ^ r >. _ I'-j.^'^
vdng eao, vi mo men can ti le vdi toe dp gde, thi *" ~ i-Fp.r)(sj^F._is) (^' ta si cd eae phupng trinh dong lUe hpe nhU sau:
: ~c .CO -T =1 d (1) Toe dd cua true mang tii:
T^.N-c. uj,=J..9,^M^ (2) aJi(ir) = F i i ( s ) . t J , „ ( 5 ) + ^ F i 2 ( s ) . M , ( s ) ^^^^
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3. MO HINH DONG LlTC HOC CUA TRUC X Mo hinh dpng lUc hpe cua true mang b i n miy X hay Y d i u tUong tU nhau, n i n ta chi xet mpt trUdng hpp l i du. C i c phUPng trinh cP bpc bao gom:
i„,r-Cm-<Om-T^=Jrr,.e^ ( H ) r , . . V - c ^ . a ; , = ; , . e , + M, (12)
Van tdc tren dau ra cua he n i y dupe xac dinh nhu sau:
i-.(5) = F2i(s).y,„(s) + F22(5)./v(s) (17) Trong do:
F21U) = \KD f"K^S'K::k\S:':
Wc 2^
(13)
_ Sb , (14) F, -771.^.X, = 0 (15) Tuong tu nhu phan trin ta eo h i m truyen
eua phan eP Idii:
•:KS s--fi"p5-A;j.A-rf:i>.:
(18) (19)
F2(s)-- (16)
Thong thudng trong cie h i thong diiu khien so, tie dpng cua nhiiu dupe xem la rat nho v i khdng dUpc quan tam. NhUng thUc te trong bii toin may nay ta thay nhilu d day cbinb l i lUc cit.
Tuy nhien, tie dpng nay ehi ed anh hUdng trong thdi gian rat ngin khi ehuyen td trang thai chUa eat sang trang thai eat. Dap dng trin dau ra la tde dp ed bi anh budng nhUng sau do se dn dinh den toe dp yiu eau vi ta sd dung bp die'u khii'n PID cd k h i ning chdng nhieu rat tdt.
4. MOT SO KET QUA MO PHONG Hinh 5 md ta kit qua md phdng ve d i p dng cua true X trong trUdng hpp chuyen dpng khong tai.
Htnh 4. He thongdieu khien servo toe do cua (rue tinh hen
: * _ j i ) . » « j . , : j : c ^ r
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Hinh 5. Ddp iing cua he truyen ddng Ichi tin hieu Id hinh bdc thang vd hinh sin.
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Td hinh vi ta thay h i dieu khii'n b i c 2 vdi he khong vUpt qua ngUdng cho phep. Neu khong xd ly dupe van d i niy, m i y gia cong se khong dat dupe dp ehinh x i e y i u eau.
so can nho hpn 1 Iuon ed dap dng nhU hinh 5.a.
Tuy nhien, d dayed dp qua la dieu khong mong muon doi vdi may CNC. Chlnh vi de Ioai bd anh hudng nay, ngoai h i thong dii'u khien PID eon phii sd dung bp han ehe ngUdng, sao eho d i p dng
Tren hinh 6 l i kit qua m o phong cua dap dng khi chuan v i o la h i m xung v i ham tang.
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1 - - ; - - . ... ..;..
1
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1
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:" 1
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1
Hinh 6. Ddp dng cua he diingPID khi tin hieu Id hdm xung vd hdm tuyen tinh.
10 phorg loc ao dong
Hinh 7. Mo phong toe do dong cd.
Trin hinh 7 la thay doi eua toe dp eua d i p dng khi dau vao l i h i m b i e thang.
Dpng CP diin mpt chieu diiu khii'n toe dp ed ham truyin la he cap 1 dang 0. Chinh vi viy thiet bi dieu khii'n PID sd dung trong trUdng hpp niy la dieu kien de dam bao dp chinh xic cao nhat. Do be thong dieu khii'n d trUdng hpp nay chi la h i eap 2, n i n h i Iuon dn dinh, duy chi chu y la dap dng cua he thong la h i m dao dpng
hay khong m i thoi. Khi dieu chinh eic h i so ti l i K , h i so tich p h i n K, va h i so vi p h i n K^ theo phUPng phap Ziegler - Nichols ta s i thu ddpc he vdi toe dp dap dng yeu eau v i ed the giim hay lo?i bd han tie dpng cua dao dpng. Ta quan t i m duy nhat den sai so dii'u khien, trong trUdng hpp nay la sai sd toe dp:
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NGHIEN CUU - TRAO D O I
e„ = l i m , , „ e f = l i m „ „ s . E ( s ) = l i m 5 ^ [ u , „ ( s ) - M , ( S ) ] (20)
Khi ham vao la ham bac thang don vi, thi sai lech tinh se bang 0, tiJc la khong co sai so ve toe do. Tuong tii nhu vay cho true tinh tien sai so toe do dieu khien cung se tien tdi 0. Nhil vay toe do dieu khiln se dap iing duoc yeu cau ve do ehinh xae.
4. KET LUAN
Nghien ciJu nay da xay dung duoc mo hinh dong lue hoc cua may phay CNC, tinh toan cong suat dong CO va thiet ke he thong dieu khien. Mo hinh toan hoe xay dung dUOc co the sir dung de mo phong va danh gia chat luong ciia may tren co sd tinh toan va thiet ke. Tuy nhien, de viec thiet ke may phay CNC dugc tot can phai nghien ctiu them nhieu van de nhu npi suy. do ciing viing ciia may, khe hd trong eac bo truyen CO khi. I h e m vao do, can thiet phai che tao t h i de kiem nghiem thiic te va danh gia miie dp anh hudng cHa dp ehinh xac gia cong phan co khi len dp chinh xae eua may do cung la hudng phat trien va han che eua bai bao, •!•
Ngay nhan bai: 15/12/2012 Ngay phan bien: 15/01/2013
Ngiidi phan bien: PGS, TS. Vu Ngoc Pi, TrUdng Dai hpe Ky thuat Cong nghiep, Dai hpe Thai Nguyen.
Tai li^u tham khao:
[1]. Riels M. Linear Control Systems Engineering, McGraw-Hill International Edition, 1995.
[2]. W.; Chen J: Yang).- Design of servo system for 3-axis CNC drilling machine based on XPC target, Computing, Communication, Control, and Management, 2009. CCCM 2009. ISECS International Colloquium on 8-9 Aug.
2009.
[3]. Tert P.F: Computer numerical controlled drilling machine interfaced toa computer aided design package.
PhD Thesis 1996- Cape Peninsula University of Technology.
[4]. Nguyen Trpng Doanh, Nguyen Dilc Minh, Thiet ke may cat ranh soin CNC trong 16 sau. Tap chi Co khi Viet Nam so 5/2012.
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