Initial commit from Polytechnique Montreal

1 files changed, 45 insertions, 0 deletions

diff --git a/Donjon/src/DETFIL.f b/Donjon/src/DETFIL.f
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+*DECK DETFIL
+      SUBROUTINE DETFIL(Y,X,XL,TC,DT,N)
+*
+*----------------------------------------------------------------------
+*
+*Purpose:
+* Filters the n values of x vector for TC seconds.
+* Formulations are taken from the expression of the different
+* equation of a filter with a linear variation of x in DT time
+* step.
+*
+*Author(s): 
+* xxx
+*
+*Parameters:
+* Y   real variables Y(I) at previous time
+* X   real variables to filtered
+* XL  real variables X(I) at previous time
+* TC  filter time constant
+* DT  time step between two calculations
+* N   dimension of the vectors X,XL,Y
+*
+*--------------------------------------------------------------------
+*
+      IMPLICIT NONE
+      INTEGER  N,I
+      REAL     Y(N),X(N),XL(N),TC,DT,AA,A,B,C
+*
+*     COMPUTE PONDERATION FACTORS FOR Y,X ET XL
+*
+      AA =  - DT / TC
+      A  = EXP ( AA )
+      B  = 1. - A
+      C  = 1. - B * TC/DT
+*
+*     COMPUTE NEW Y
+*
+      DO 10 I=1,N
+*
+        Y(I)  = A * Y(I) + ( B - C ) * XL(I) + C * X(I)
+        XL(I) = X(I)
+*
+ 10   CONTINUE
+      RETURN
+      END