Appendix D
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HA0165T Rev 4K Sept 2017
This LUT diameter adjustment mode allows appropriate circle diameters to be applied
on an application specific basis.
The loop gain can also effect system stability. If the gain is too high, the circle moves
erratically, whereas too low a setting results in the circle ‘floating’ around the edge of
the screen. Loop gain can be configured from the Controller GUI.
Both circle size and loop gain effect the system amplification. As a guide to manual
settings, if the scan circle moves erratically round the screen, the amplification should
be reduced, and conversely, if the scan circle movement is sluggish, the amplification
should be increased. As with any phase locked control loop, it may be necessary to
perform application-specific adjustments to optimize the speed of response and
stability.
D.2.3 Phase Offset
Theoretically, if the NanoTrak were to read the power and respond by moving the fiber
instantaneously, the power signal read in would be in p hase with the modulating
signal. In reality, the various electronic and electromechanical components (e.g.
power meters, piezo actuators) within the control loop can introduce delays which
means that the NanoTrak is always reacting to a power reading which was taken in
the past. This, in turn, can ca use a phase shift and in extreme cases can lead to
instability.
A phase offset can be introduced to compensate for any phase shifts. In the software,
a different phase offset can be specified for each axis of motion. This is particularly
useful in those mechanical systems that exhibit different delays in different directions.
