2002 td tensions vs td positions,platform temp, platform hght, and fits
feb,2003
links to plots:
avgTotKips,temp,platformhght,and
Difference in cable tensions for 2002
Cable
tension differences at constant temperature.
fit
residuals for totalKips(temp,platformHght) using all the data.
fit
residuals for totalKips(temp,platformHght) using 6am to 8pm.
fit
residuals for totalKips(temp,platformHght) using 8pm to 6am.
fit
residuals for totalKips(temp,avgTdPos) using all the data.
the
TotalTension2000TotalTension2002
Sections:
The
measured data for 2002.
Fitting totalTension(temp,platformHght):
Fitting totalTension(temp,avgTdPos)
Fitting tension1Td(temp,tdpos[3],az,za)
Comparing the tensions for
2000 and 2002.
Intro
The platform height and tempurature is recorded once every two minutes.
The tiedown position and tensions are recorded once a second. This data
set is interpolated to integral minutes and recorded (see looking at platform
position, temp, and tensions). The data for 2002 is shown below.
The following fits were done:

totalTension(temp,hght)=c0 + c1*(temp 74.)+ c2*(platformHght1256.35Ft)

totalTension(temp,avgTdPos)=c0 + c1*(temp74.) + c2*(avgTiedownPosition)

for tiedownX (X=12,4,8) let azTdx=azimuth of tdX, and cosAz=cos(azazTdX)
then
tensionTdX(temp,tdPos,az,za) =c0 + c1*(temp) +c2*tdPos12+c3*tdPos4+c4*tdPos8+c5*cosAz*sin(za)+
c6*cosAz*cosZa
The fits have been added to the idl routines in ~phil/idl/prf (@prfinit)

kipsTot=kipstemphght(temp,platformhght)

kipsTot=kipsTempTdPos(temp,avgTdpos)
kips1Td=kipstd(az,za,temp,tdpos[3])
The measured
data for 2002.

avgTotKips,temp,platformhght,and
Difference in cable tensions for 2002
Bad data points were removed (temp<50F, hght<1255 feet). The
data was smoothed to 60 minutes and then decimated. The upper plot is the
total tension and the platform temperature. The center plot is the platform
height (in feet above sea level). We keep the average height at 1256.35
feet. The lower plot shows the tension difference between the two cables
at each tiedown. The nonzero values are calibration errors in the loadcells.
The tension in cable1 td8 had 1.5 kips added to is from jan1 to 30may because
there was a dc offset.

Cable
tension differences at constant temperature.
The plot shows the difference in tensions for the pairs of cables at
each tiedown (at constant temperature and tension). The 3 colors are tensions:15Kips,
30Kips, and 45Kips (both cables summed). The bottom plot is td8 which had
the most problems. It was recalibrated on 31may02 and 3oct02. There is
not a large drift between the tensions. When recalibrating , the
major error was a dc offset so there is probably a dc drift with time.
Fitting the tensions..
The data used for fitting met the following criteria:
temp gt 60 and less than 95
platform position within .4 feet of 1256.35
tension in 1 cable gt 4 kips and less then 65 kips (when calibrating).
A linear ramp was removed from td8_1 for may through oct.
Fitting totalTension(temp,platformHght):
Fits were done for all day, 6am to 8pm, and 8pm to 6am.
The plots show the fit residuals versus date,hour,hght,and temperature.

fit
residuals for totalKips(temp,platformHght) using all the data.

fit
residuals for totalKips(temp,platformHght) using 6am to 8pm.

fit
residuals for totalKips(temp,platformHght) using 8pm to 6am.
totalTension(temp,platformHght)
time 
constant (kips)
@74F,hght=1256.35

kips/
degF

kips/
PlatformInch

rms(kips)

npts

allday 
122.7

5.11

8.78

5.8

274400

6am8pm 
120.9

5.03

8.67

6.0

166945

8pm6am 
129.4

3.66

9.12

2.8

107407

Fitting totalTension(temp,avgTdPos)
A fit was done with all the data using the temperature
and the average tiedown position.

fit
residuals for totalKips(temp,avgTdPos) using all the data.
totalTension(temp,avgTdPos)
time

constant(kips)
T=0F,tdPos=0

kips/
degF

kips/
avgTdInch

rms(kips)

npts

allday

245.4

2.74

6.90

3.90

274562

The temperature dependence varies in the two fits
because different things are being meausured. The temperature variation
of the first fit is when the platform is held constant. The 2nd temperature
dependence is at constant tiedown jack position but the platform is allowed
to move.
Fitting tension1Td(temp,tdpos[3],az,za)
The tension in each pair of tiedowns was fit for the
az,za,temp, and position of the 3 tiedowns. The fit residuals (for the
tension on 1 block) were 1.5,1.7, and 2.2 kips for td12,td4, and td8.
Comparing the
tensions of 2000 with 2002.
The previous model for tension(temp,hght) and tension(temp,tdPos)
was made with data from april,may 2000. During this period we were not
actively tracking the average platform height with the tiedowns.
The plot shows the
TotalTension2000TotalTension2002 using the models of Kips(temp,platformhght)
and kips(temp,tdAvgPosition). The fits were evaluated at the temp and hghts
measured for 2002. The black line is the difference of the fits totKips(temp,platformHght).
The red line is the difference in the fits for kipsTot(temp,avgtdpos).
The difference of 15 to 20 kips would occur if additional weight was added
to the platform. Increasing the weight would decrease the tension needed
to maintain the platform at a particular height.
processing: x101/td/model/2002/doplot.pro,yr2002FitGetDat.pro, year2002FitDat.pro
home_~phil