The aim of comparing the theoretical BS transfer functions to those of SR2, is to provide criteria to compare the BS measurements with those of SRs at low frequencies. This is necessary because
- The BS payload is different from the SR ones, and it's not obvious how similar or different their transfer functions should be.
- The actuators are not calibrated, therefore, we cannot compare directly the measurements with the theoretical results.
For the calculation, I used the Matlab implementation of SUMCOM, because my Mathematica license expired. I'll check the SUMCOM models once I get a license. Additionally, it should be taken into account the following:
- The parameters I currently aim to check are the TF values close to DC.
- In the Matlab implementation, the structural damping is not included in the usual mathematical way, but it's mimicked in a way that is not clear. For now, I removed those terms. Therefore, the widths and heights of the peaks should not be compared with the measured ones.
- I used an old BS model, which likely needs reviewing.
At low frequencies, the absolute values of the differences, between the BS and SR2 transfer functions, in each degree of freedom of the payload, are:
- TM-L: 5.837 dB
- TM-P: 7.8008 dB
- TM-Y: 12.5619 dB
- IM-L: 3.9148 dB
- IM-T: 3.9148 dB
- IM-V: 2.9835 dB
- IM-R: 4.8509 dB
- IM-P: 4.8524 dB
- IM-Y: 0.090293 dB
See also the plots.
These values and plots should be compared with the plots at this link (measured by Ushiba-san, but I couldn't find a klog for it).
Comments will follow in another klog.
