Tính toán độ cứng vững máy công cụ cấu trúc song song

r ' - i i i ' ' i h i a - j w T f c n d h n t g o a c u n d c a o u c t u r u n e g s v u n o n g g m s o a n y g (*) TS BUI QUY LlTC (**) KS DINH BA DINH khdp noi cau tren mot bo phan quay tao mot hinh tarn giac deu Dong co servo duoc gan vao dau vit me, tao cho vit me chuyen dong quay, keo theo mat truot cd the tinh tien doc theo true vit me bi Cac chan ngoai kha nang di chuyen tinh tien theo mat truot, co kha nang quay quanh cac khdp cau, tao cho cum de dong (Cum true chinh) kha nang chuyen dong song phang Trong moi vi tri cua khong gian lam viec, de dong luon song song vdi de may Day chinh la uu the ciia may cong cu cau tnic song song TOM TAT Doctfng vOrng la dac tinh quan trong thong so ki thuat cua may cong cu cau true song song Thdi gian trU6c day, viec phan tich ciing cua may cong cu cau true song song chu yeu tap trung vao bieu cto cufng cua hexapods dua tren nen tang Stewar vdi cac chong Gan day, co nhieu nghien cuu de tinh toan ciing vufng cua may cong cu cau true song song bang cac rang buoc ciing Dac biet, da co phufong phap tim dugc ciing toi da va cufng toi thieu cua true dan tai cac vi tri bat ky khong gian lam viec cua may Cau true may song song giup cho may hoat dong hieu qua hon, curig vQng cao hon, ket cau nhe nhang, sirdung cac chan phu hop vdi chuyen dong cua may Bai bao diia phifOng phap xac djnh cifng vung cua mot mo hinh may cau true song song dien hinh, la may phay CNC true M O T A H E T H O N G Hinh mo ta may phay toa cau tnic song song, bao gom mot de di dong va bo phan quay, di chuyen theo chieu thang dung bang each gan vao cac than may tuong ung Trong moi ehuoi dong hoc, de di dong va cum truot duoc noi vdi bdi chong cd dai co dinh, la bp khung gian hinh binh hanh (*) Tnicmg Dai hoc Bach khoa Ha Noi (**) Cong ty TJSTHH Mot vien - Vien May va Dung cu Cong nghiep Hinh 1: Mo hinh may phay toa can tnic song song TAP CHI CO KHI VIET NAM •> So - Thang nam 2011 c P | ^ = NGHIEN CUU - TRAO DOI 2, D O N G H O C N G U O C • • • Viec tinh toan ciing cua may phay toa cau tnic song song co lien quan true tiep tdi viec nghien cuu dong hoc nguoe Doi vdi md hinh may phay toa cau tnic song song, van de chu yeu la xac dinh vi tri cua bo phan quay va khoang each cua chung vdi tarn de dong Khi chuyen dong cua ba chong duoc gan voi mot each di chuyen nhu bo tri giong hinh binh hanh, mot md hinh don gian nhu hinh 3.2, co the sir dung de tinh dong hoc Trong cau tnic may, ta gan he toa Oxyz vdi be may co dinh, he toa O ' x ' y V gan vdi de.dpng Theo ly thuyet song phang, thi O ' x ' y V luon song song vdi Oxyz (2) q = r e T t + ^{r T e,f -\r-b, Suy ra: (3) w, = (r - b, + a 0i +a \ oi + L' - qfr ) / L XAY DITNG MO HINH TINH DO ClTNG M A Y PHAY T O A D O C A U TRUC SONG SONG 3.1 Md hinh mau vd cac gid dinh Ve co ban, each xay dung mo hinh tinh toan ciing cua may cdng cu cau tnic song song duoc xem xet giong nhu each xac dinh cung tuong duong ciia he 16 xo No duoc chia lam hai budc BudcJ: Dau tien lien quan den viec phan chia cau tnic cua may hai phan lien quan vdi nhau, la co cau truyen luc va than may Cach ap dung theo phuong phap la gia dinh tat ca cac phan cau tnic cOn khac la tuyet doi cung Budc 2: Gop cac mo hinh ciing toan may tir cac mo hinh cung phan Vdi cac gia dinh duoc dua nhu sau: Bd qua cung ciia cac khdp cau Do cung ciia cac noi coi nhu la rat nho Do cung cua cum true chinh, gia mang cum true chinh va be may la cung tuyet doi 3.2 Md hinh cung cua he thong truyen ddng He thong truyen dan cua cau tnic may song song co the duoc phan hai he thong khac: V i du nhu true vit - dan hudng va chong - cum true chinh duoc ket noi bdi cac khdp lang tru Hinh 2: So dong ciia may phay toa dp cau tnic song song a Mo hinh tinh toan ciing vung cua cum vit me -dai 6c Vecto vi tri: r = (x,y,z) cua diem 0' he Oxyz co the the hien bang cong thiic: T r = b.-a + q e, + Lw vdi i= 1,2,3 Trongdo:^, =/"(cospV sin(3 O) ',a = r (cosp\ sinpVO)' la vecto vi tri ciia diem B va A_ he Oxyz va O ' x ' y V r , r la ban kinh ciia dai dao va be may j oi i a b Vdi P, = - r c / + 2(Z-1)TC 13 la vi tri gdc cua diem B., A ; q la chuyen v j thu i ling vdi cac diem h ; w , L la cac vecto luc don vi cua true cac noi va dai cua no; e = (0 1) Doi voi mot ban kinh r cho trudc, chi tieu tren ca hai mat bieu thiic cho phep £ i ; T E g TAP CHI CO KHI VIET NAM *l* S6 4-Thing4 nam2011 Hinh 3: Mo hinh cum vit me dai 6c NGHIEN CUU • TRAO OOl Viec lap rap true vit - dan hudng tuan theo trinh tu bao de cac phin ket noi cd duoc linh hoat can thiet v i du nhu true vit - dan hudng, dai 6c bi, va vong bi Goi k',, k , k la cung doc true ciia chung Ta se co phuong trinh ciing tong hop nhu sau: 1 — +— + — k k k u n f p va AZy la luc va bien dang ehuoi thii j (j=l,2,3), voi thu i (1,2,3), nen ta co: J - k AL , : AL s Trong do: ^ = lAA I, = LAAI ] 2i Khi thay doi chieu dai chong, gay chuyen vi va bien dang Luc do, phuong trinh (1) co dang : A: la dien tich mat cat ngang r + Ra =L w +q e,+b , t E: Mo dun dan hoi ij ij i i (10) vdii=l,2,3.j=l,2,3 L va L la khoang each giua dai 6c va vdng bi hai dau ?i Vi ciing doc true ciia true vit- dan hudng lap rap bien dang mot khoang A mot luc F tac dung len diem ' tren mat lam viec: (4)5A^F = £SA