# Chuong 3- DDS

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• HE THONG TON KHO XAC NH NHU CAU RI RAC( Deterministic Discrete Demand Systems )GV. ThS. Nguyen Hu PhucH BACH KHOA HQG TPHCM07/2012

• NOI DUNG Gii thieu Lo hang theo nhu cau Lng at hang theo chu ky Thuat toan Silver Meal Phng phap chi ph n v nho nhat Phng phap PPA Phng phap IPPA Phng phap WWA

• GII THIEU He thong DDS: Nhu cau trong khoang tg ri rac Phan bo nhu cau theo chu ky trong khoang tg hoach nh nhat nh Hoach nh cho vat t co nhu cau oc lap/phu thuoc. Vat t phu thuoc au ra cua he thong MRP San pham oc lap au ra cua he thong DRP

• GII THIEUNhu cau xac nh, thay oi, ri rac au chu ky(Rk)Thi gian hoach nh hu han, gom nhieu chu ky bang nhau (n)Lo hang at cho mot hay nhieu chu ky lien tiep (Qi)Khong at nhan hang au chu ky khong co nhu caun at hang au chu ky thoa man nhu cau chu ky o-Thi gian ch la 0Nhap kho ong thi, au chu kyKhong n hang chamKhong giam ga. Chi ph mua hang n v khong oi (P)Nhu cau thoa man au chu ky. Ph ton tr tnh theo chu ky(H=hP)San pham thanh phan ton tr oc lapChi ph ton kho, thi gian ch xac nh khong oiPhan tch trong thi gian hoach nh Mc ton kho ban au bang 0

• HE THONG TON KHO XAC NH NHU CAU RI RACVD: P=50 , C=100 , h=0.02 H = hP = 1 /ckh : phan chi ph ton tr trong moi chu ky(1/ck)

• Lo at hang theo nhu cau( Lot For Lot Ordering - LFL)at hang theo tng chu kyLng at hang bang nhu cau cua chu kyQk = Rk , k=1: nLFL khong co chi ph ton trLFL thch hp vi he thong :Chi ph ton tr caoChi ph at hang thapSan pham at tien San xuat lien tuc, san lng cao

• Lo at hang theo nhu cau( Lot For Lot Ordering - LFL)VD: P=50 , C=100 , h=0.02 H = hP = 1 /ck

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• LNG AT HANG THEO CHU KY(Periodic order Quantity - POQ) nh so chu ky, nhu cau c thoa man bi mot lan at hang Tng t EOQ/EOI R: trung bnh nhu cau theo chu kyLo hang la nhu cau tch luy trong moi chu ky at hang Hoach nh n hang nhan chu ky co nhu cau

• LNG AT HANG THEO CHU KY(Periodic order Quantity - POQ)VD: P=50 , C=100 , h=0.02 R = 31

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• Thuat toan SILVER-MEAL(Silver-Meal Algorithm- SMA)Thuat toan trc quan cua Edward Silver & Harlem MealCc tieu chi ph trung bnh chu ky khi so chu ky co nhu cau thoa man bi n hang tang danSMA : Ch toi u cuc bo (Local minimum)ng dung tot trong thc tienKhong dung SMA vi cac trng hp Nhu cau suy giam nhanhNhieu chu ky khong co nhu cau

• Thuat toan SILVER-MEAL(Silver-Meal Algorithm- SMA)Ph gi gia tang

Ph gi tch luy

Tong chi ph trung bnh T chu ky lien tiep:

Chi ph trung bnh trong T chu ky lien tiep:

Chon T cc tieu MVC(T) :

Lng at hang :

Thc hien lap lai ck T+1 (i=1)

• Thuat toan SILVER-MEAL(Silver-Meal Algorithm- SMA)VD: P=50 , C=100 , h=0.02

• Thuat toan SILVER-MEAL(Silver-Meal Algorithm- SMA)

• Thuat toan SILVER-MEAL(Silver-Meal Algorithm- SMA)

• PHNG PHAP CHI PH N V NHO NHAT (Least unit cost - LUC)Phng phap do tm trc quan, tng t SMACc tieu chi ph trung bnh n v khi so chu ky co nhu cau thoa man bi n v hang tang dan

• PHNG PHAP CHI PH N V NHO NHAT (Least unit cost - LUC)Ph gi gia tang

Ph gi tch luy

Tong chi ph trung bnh T chu ky lien tiep:

Chi ph trung bnh n v

Luat dng :

Lng at hang :

Thc hien lap lai cac chu ky T+1

• PHNG PHAP CHI PH N V NHO NHAT (Least unit cost - LUC)VD: P=50 , C=100 , h=0.02

• PHNG PHAP CHI PH N V NHO NHAT (Least unit cost - LUC)

• PHNG PHAP CHI PH N V NHO NHAT (Least unit cost - LUC)

• PHNG PHAP PPA (Part Period Algorithm-PPA)Phng phap trc quan, nham cc tieu chi ph tongnh lng at hang theo can bang chi ph at hang chi ph gi tch luy

Lng nhu cau kinh te:EPP = C/PhLng nhu cau tch luy

Luat dng : Max T: APP(T)EPPCai thien PPA:LA-PPA (Look Ahead PPA)LB-PPA (Look Backward PPA)

• PHNG PHAP PPA (Part Period Algorithm-PPA)VD: P=50 , C=100 , h=0.02 EPP = C/Ph = 100

• PHNG PHAP PPA (Part Period Algorithm-PPA)

• PHNG PHAP PPA (Part Period Algorithm-PPA)

• Phng phap IPPA (Incremental Part Period Algorithm)Phng phap trc quan, tng t PPAnh lng at hang theo s can bang chi ph at hang chi ph gi gia tang Lng nhu cau gia tang :IPPi = (i-1) RiLuat dng T=Max i : IPPi EPPLng at hang :

• Phng phap IPPA (Incremental Part Period Algorithm)VD: P=50 , C=100 , h=0.02

• Phng phap IPPA (Incremental Part Period Algorithm)

• Phng phap IPPA (Incremental Part Period Algorithm)

• Phng phap WAGNER-WHITIN( Wagner-Whitin Algorithm _ WWA)Phng phap toi u Cc tieu chi ph bang qui hoach ong Yeu cau hang en au chu kyThuat toanTnh ma tran chi ph bien thien tong (TVC)Xac nh chi ph cc tieu t chu ky 1 en chu ky e, vi mc ton kho cuoi chu ky e la 0:Xac nh ke hoach at hang toi u:

• Phng phap WAGNER-WHITIN( Wagner-Whitin Algorithm _ WWA)Tnh ma tran chi ph bien thien tong zcezce: tong chi ph bien thien khi at hang chu ky c, thoa man nhu cau cac chu ky ce

• Phng phap WAGNER-WHITIN( Wagner-Whitin Algorithm _ WWA)Xac nh chi ph cc tieu t chu ky 1 en chu ky e, vi mc ton kho cuoi chu ky e la 0:

• Phng phap WAGNER-WHITIN( Wagner-Whitin Algorithm _ WWA)Xac nh ke hoach at hang toi u:fn = zwn + fw-1= zwn + zv,w-1 + fv-1= zwn + zv,w-1 + + z1,,u-1 + f0n hang cuoi chu ky w, thoa nhu cau cac ck. wnn hang ke chu ky v, thoa nhu cau cac ck. vw-1n hang au ck 1, thoa nhu cau cac ck. 1 u-1

• Phng phap WAGNER-WHITIN( Wagner-Whitin Algorithm _ WWA) Ma tran chi ph bien thien tong zce

• Phng phap WAGNER-WHITIN( Wagner-Whitin Algorithm _ WWA)Xac nh chi ph cc tieu t chu ky 1 en chu ky e

• Phng phap WAGNER-WHITIN( Wagner-Whitin Algorithm _ WWA)Xac nh ke hoach at hang toi u

• SO SANH CAC PHNG PHAP