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Thesis - Leigh Moody.pdf - Bad Request - Cranfield University

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Appendix I / Utilities / Digital Filters<br />

_ _<br />

22.8.2 Digital First Order Lead Filters<br />

D_LEAD propagates up to 50 digital leads over time interval (∆t), with time<br />

varying bandwidth (ωC).<br />

( X , ∆t<br />

, t , N , I ) ≡ ϕ ( X , 1 )<br />

y : = D_LEAD<br />

ω<br />

I<br />

22.8-2<br />

C<br />

LD<br />

I<br />

C<br />

Equation 22.8-6<br />

These filters are the discrete equivalent to the continuous transfer function:<br />

χ<br />

k<br />

: =<br />

⎛ t ⋅ s ⎞<br />

y<br />

⎜<br />

⋅<br />

1 tC<br />

s ⎟<br />

⎝ + ⋅ ⎠<br />

C ( s ) : = ⎜ ⎟ XI<br />

χ<br />

χ<br />

k − 1<br />

0<br />

⎛ X<br />

+<br />

⎜<br />

⎝<br />

I<br />

− 1<br />

( k −1<br />

)<br />

− 2 ⋅ χ<br />

∆t<br />

+ 2 ⋅ t<br />

−1<br />

C<br />

: = χ : = 2 ⋅ X<br />

k −1<br />

( k ) − χk<br />

− χk<br />

1<br />

yk : = XI<br />

−<br />

I<br />

⎞<br />

⎟ ⋅ ∆t<br />

⎠<br />

Equation 22.8-7<br />

Equation 22.8-8<br />

Equation 22.8-9<br />

Equation 22.8-10<br />

If (I := 1), and on first use, the filter is re-initialised without integration<br />

using input (XI). Each filter is identified by a unique number (N).<br />

22.8.3 Digital Lead-Lag Filters<br />

D_LEAD_LAG propagates up to 50 digital lead-lags over time interval (∆t),<br />

with time varying characteristics.<br />

y<br />

: = D_LEAD_LAG<br />

≡<br />

ϕ<br />

DLL<br />

( X , ∆t<br />

, t , t , N , I )<br />

( X , 1 ω , 1 ω )<br />

I<br />

I<br />

N<br />

N<br />

D<br />

D<br />

Equation 22.8-11<br />

These filters are the discrete equivalent to the continuous transfer function:<br />

⎛ 1 + s ⋅ t ⎞<br />

y ⎜<br />

⋅<br />

1 s t ⎟<br />

⎝ + ⋅ D ⎠<br />

N ( s ) : = ⎜ ⎟ XI<br />

Equation 22.8-12

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