Conclusion--Driving the HEPIs +- 500micro units suggests no interferences
Details--Jim unlocked the HEPIs for the ITMs yesterday and as we want to be sure of no interferences, the platforms were strokes in X Y RX & RY (X Y & Z should suffice) by 500um/urad.
The ISIs were put into DAMPED as tilting of the platform will trip on the T240s. With the HEPI ISOLATED, offsets were ramped into the isolation filters. With all the cartesian loops closed with large DC gain, interferences impeding motion will be evident in the local sensors as the loops are satisfied. Interferences will be evident with clipping and coordinated slope changes--see 40171.
The four attached plots show the ITMX first with horizontal drives and then vertical drives; ITMY are the third and 4th plots. The lower graph has the 4 local sensors and the upper shows the cartesian position. All traces indicate things are fine with no obvious clipping or slope changes. The horizontal drives on the ITMY show the peaks shifting; I'm not sure what this means if anything...will keep thinking. The positions end up at zero again. Maybe this does indicate an interference as the X drive nears the end of the drive offset but not obvious enough to clearly clip. Maybe this is worth a closer look driving further and trying open loop. Will think and look some more and will report as required.
Drove ITMY to +- 700 micrometers to check for interference and I have to say there is something. The attached is similar to above but this time, for the local sensors in the lower panel, after shifting all signals to zero before the start time, additionally now the absolute value is taken. With this, all the traces should overlay another. Certainly there is no clipping or large slope changes. The wobble seen on the first and fourth peak indicates the H3 negative stroke may be compromised though. This is actually a subtle slope change where that sensor stops moving as much and the others compensate. H3 negative drive is the common factor for reduced displacement during the 1st and 4th peaks. H1 H2 & H3 sensors are all displaced at rest pretty far from zero at ~11000+ counts, nearly half the range. This may be impacting the H3 more than others. It could also be corner3 starts to experience some additional resistance either in the actuator or within the pier but obviously is able to strain the system. Still, plenty of range for operations but I will check it out to maybe find the problem.
FRS 10607
