Simon

I have fitted the results of the actuation-test done on March 7th, shortly before closing IYC and evacuation.
The data were taken by the photosensors (X,Y,Z) and OpLevs (pitch and yaw) at the same time when the coil-magnet is turned off.
I attached a graph for a proper visualization.

Basically, as we already know from the measurements done by Miyo-kun, we have two main modes appearing mainly in the PS data: a dominating ~1Hz swing-mode and an additional 3.5Hz mode which is likely caused by vertical bending from the blade springs.
(It should be noted that according to the design, both swinging in X and Y direction have the same frequency).

• As can be seen from the graph, I fitted the data with five parameters per mode (the basic equation for the fit is given in the graph too).
• In case of the 3.5Hz mode, the damping is in all cases significantly smaller than for the 1Hz mode. Its amplitude is also the highest in Z-direction (not surprisingly), but relatively strong also in X; more weaker, however, in Y.
• The 1Hz mode is dominating in all sensors and is in phase in X and Y direction, but 180° shifted in Z direction.
• The same phase difference is observed for pitch and yaw (although this is just a matter of definition, especially which yaw is considered as negative or positive)
• There is, however, a small difference in the phase between the OpLev signal and the PS, and it seems that the PS reaches its minima or maxima signal slightly before the OpLev does.

Note:

• for yaw, I assumed an additional mode to cover the long path from the initial state toward the first swing-by, but this mode has an extremely high damping factor and does not play a role in the further outcome
• All graphs cover the moment from the beginning of the release toward a moment where the modes are going to be vanished by noise