Adams Car Package > Adams Car > Appendix > Special Requests > Adams Request Four Pole Filter Model

Adams Request Four Pole Filter Model

This special REQUEST allows a user to model a four pole filter within Adams. The filter operates on standard Adams output information to simulate the actual filtering of experimental test data. The filter is modeled by a set of four DIFF statements, which reduce the filter's transfer function to four first order differential equations. Therefore, four DIFF statements are required for each Adams output variable that needs to be filtered. The fourth DIFF statement for each filter model utilizes the user written DIFSUB.
Input:
DIFF/id1, IC=0, FUNC=DIF(id2)
DIFF/id2, IC=0, FUNC=DIF(id3)
DIFF/id3, IC=0, FUNC=DIF(id4)
DIFF/id4, IC=0 , FUNCTION = USER (1101,r1,r2,icd,idi,idj,idr,id1,id2,id3,id4)
REQ/id, FUNCTION = USER (1120,id1)
where:
 
 
Description
id1
=
identifier of the first DIFF statement
id2
=
identifier of the second DIFF statement
id3
=
identifier of the third DIFF statement
id4
=
identifier of the fourth DIFF statement
r1
=
the cutoff frequency of the filter to be modeled in ertz (see Notes section)
r2
=
the capacitance of the filter to be modeled in Farads (see Notes section)
icd
=
a two digit digital code used to identify the desired information, which is obtained from Adams and passed through the four pole filter. The first digit of the code identifies the type of information to be filtered (i.e. displacement, velocity, acceleration, or force). The second digit identifies the component (i.e. X, Y, Z, Ax, Ay, or Az).
icd
Type
Component
icd
Type
Component
11
disp
X
31
acc.
X
12
disp
Y
32
acc.
Y
13
disp
Z
33
acc.
Z
14
disp ang.
about X
34
acc. ang.
about X
15
disp ang.
about Y
35
acc. ang.
about Y
16
disp ang.
about Z
36
acc. ang.
about Z
21
velocity
X
41
force
X
22
velocity
Y
42
force
Y
23
velocity
Z
43
force
Z
24
velocity ang.
about X
44
force ang.
about X
25
velocity ang.
about Y
45
force ang.
about Y
26
velocity ang.
about Z
46
force ang.
about Z
 
 
Description
idi
=
identifier of the I MARKER used for requesting information, which passed through the filter
idj
=
identifier of the J MARKER used for requesting information, which passed through the filter
idr
=
identifier of the Reference MARKER used for requesting information, which passed through the filter
id
=
identifier of the Adams REQUEST statement
Request File Output
Column Number Output:
1. Filtered output of DIFF statement 1
2. (not used)
3. (not used)
4. (not used)
5. (not used)
6. (not used)
Notes on Input and Output
It is important to use consistent values for r1 and r2 for a proper functioning filter. This can be accomplished by selecting the cutoff frequency of the filter then selecting the filter capacitance corresponding the cutoff from the table below:
r1
r2
Frequency (Hz)
Capacitance (Farads)
8000
0.0010 E-6
6800
0.0012 E-6
4500
0.0018 E-6
3600
0.0022 E-6
2500
0.0033 E-6
1400
0.0056 E-6
800
0.0100 E-6
680
0.0120 E-6
450
0.0180 E-6
360
0.0220 E-6
250
0.0330 E-6
140
0.0560 E-6
80
0.1000 E-6
68
0.1200 E-6
45
0.1800 E-6
36
0.2200 E-6
25
0.3300 E-6
14
0.5600 E-6
The REQUEST statement shown above contains only one parameter in its call list (aside from the routine number). It is possible to enter up to six DIFF statement id numbers. The first DIFF id entered would cause the output of the DIFF statement to be stored in column 1 of the request file. The second id entered would place the output of the DIFF statement in the second column and so on. This allows a user to write separate filter DIFF statements for say roll angle, yaw rate, etc. but place all (up to six) in one REQUEST statement. In doing so, the size of the request output file is reduced.