Note
This technote is a work-in-progress.
1 Abstract¶
Linked with: SITCOM-798
This is the technote for the settling time after a slew analysis on the TMA with M1M3. We measured the mirror cell settling time (position and rotation) after a slew.
Currently the test is PASSED but under non-nominal conditions (50% speed of slew). The IMS repeatability and precision are measured on a specific data set and the requirements for it are PASSED too.
1.1 Requirements¶
LTS-88-REQ-0051
3 SITCOM-798: M1M3 - Settling time after a slew¶
3.1 Requirement verified¶
LTS-88-REQ-0051: The positioning system SHALL be able to meet all its requirements within 3 seconds of ending a short slew (3.5 degrees in 2 seconds)
The requirement is for the system to have settled to the same (within precision) position after a short slew, within 3 seconds.
3.2 Test Case¶
Plot the settling time of the M1M3 for X, Y, Z, RX, RY, and RZ.
The data comes from the EFD: imsData. The IMS is the Independent Measurement System, a set of electronic micrometers that measure the displacement of the M1M3 mirror with respect to the cell. According to LTS-88 it has a 4 um accuracy in XYZ and 3e-5 degree accuracy in RXRYRZ.
3.3 Test Data¶
Looked for suitable cases in Rubin TV. TBD a systematic search for those cases closest to the requirement settings (3.5 degree slew at full speed, not reached yet as far as I know as of 240823).
dayObs = 2023-06-27
seqNo = 450
Duration = 5s
Azimuth only 3.5 degree slew
See RubinTV
3.4 Results¶
IMS XYZ position with azimuth and elevation reference. Vertical line denotes reference time (slew stop):
Figure 1 IMS XYZ during the slew, compared to azimuth and elevation from mount information.¶
RXRYRZ rotation with azimuth and elevation reference. Vertical line denotes reference time (slew stop):
Figure 2 IMS RXRYRZ during the slew, compared to azimuth and elevation from mount information.¶
Settling behavior from the IMS measurements. IMS values during and after slew, with RMS behavior with respect to end of the plot, with a 3 second requirement window .
Figure 3 IMS x residual compared to value at slew stop, RMS, in mm.¶
Figure 4 IMS y residual compared to value at slew stop, RMS, in mm.¶
Figure 5 IMS z residual compared to value at slew stop, RMS, in mm.¶
Figure 6 IMS rotation in x residual compared to value at slew stop, RMS, in degrees.¶
Figure 7 IMS rotation in y residual compared to value at slew stop, RMS, in degrees.¶
Figure 8 IMS rotation in z residual compared to value at slew stop, RMS, in degrees.¶
3.5 Additional verification¶
3.5.1 Requirements¶
LTS-88-REQ-0128: The IMS shall be able to measure the position of the mirror relative to the mirror cell to an accuracy of +/- 4 micro m, repeatability of +/- 2 micro m and a resolution of +/- 0.5 micro m in all three directions.
LTS-88-REQ-0129: The IMS SHALL have a minimum rotational accuracy of +/- 6 e-5 degrees, repeatability of +/- 3 e-5 degrees and a resolution of +/- 8 e-6 degrees about all three axes.
LTS-88-REQ-0131: The IMS sampling rate SHALL be at least 5 Hz.
3.5.2 Test Data¶
Looked for a sample range with visually stable behaviour between two slews.
dayObs = 2023-07-18
time between UTC 05:03:00 and 05:03:30
Duration = 30s
Motion status TBC
3.5.3 Results¶
Calculated numpy.std over all measurements in range, for the six columns. Results are:
xPosition 1.10e-03 microns
yPosition 1.94e-01 microns
zPosition 5.63e-02 microns
xRotation 7.78e-07 degrees
yRotation 1.32e-06 degrees
zRotation 7.76e-07 degrees
Which verifies the repeatability (precision) requirements 0128 and 0129. Also the sampling rate 0131 is verified with data at 40 Hz. According to data recovered from EFD, the positional data has a resolution of 0.01 micro m and 1e-6 degrees.
4 Conclusions¶
The requirement is passed in all 6 variables but in restrained conditions (50% speed) which are not nominal, so final test is TBD.
The M1M3 system IMS passes the repeatability and precision requirements.