Data Analysis-data Acquisition

QUY TRÌNH KHAI THAÙC DÖÕ LIEÄU

Voõ Löông Hoàng Phöôùc 04.10.07

• • • •

Noäi dung YÙ nghóa Caùc quy trình laáy maãu Caùc yeâu caàu cô baûn veà laáy maãu (sampling) Phaân tích soá lieäu soá (digital analysis)

2.Caùc quy trình laáy maãu

ςn −ς ξn = σς 1 ς= N

N

∑ς n −1

n

(

)

2⎤ ⎡ 1 σς = ⎢ ςn −ς ⎥ ∑ ⎣ N − 1 n −1 ⎦ N

1/ 2

we assume that the original wave data

K

{ς n }

can be approximated by a polynomial of order K:

ς n = ∑ bk (n∆t ) ~

k =0

k

A “least squares” fit provides a system of equations for unknown coefficients bk as (Bendat and Piersol, 1986):

K

N

∑ b ∑ (n∆t ) k =0

k

k +m

n =1

N

= ∑ ς n (n∆t ) n =1

m=0,1,2,...,K

K=1

2(2 N + 1)∑n =1 ς n − 6 ∑n =1 nς n N

b0 =

N

N ( N − 1)

12∑n =1 nς n − 6 (N + 1)∑n =1 ς n N

b1 =

∆tN (N − 1)( N + 1)

N

m

^

The corrected time series ς n

K

ς n (n∆t ) = ς n (n∆t ) − ∑ bk (n∆t ) ^

k =0

k