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HA0373T Rev Ck May 2017
Chapter 5
14)The piezos drivers will position the piezo mirror such that the laser beam is held
central within the detector array, i.e. for a 75V piezo, the X Out and Y Out values
show around 0V (37.5V piezo drive) and the spot is central within the display as
shown below.
Fig. 5.11 TARGET and VOLTS Displays Showing Values At Mid Position
15)If any positional changes occur, due perhaps to thermal drift, the position aligner
sends a signal to the piezo drivers to reposition the beam such that it is maintained
in a central position.
5.3.6
Signs Of Instability
The Control loop PID settings allow the system response to be tuned to a particular
application. Higher proportional and integral coefficients decrease the residual error
in the system and also allow the system to respond more quickly to a disturbance (i.e.
the system is a ble to dampen vibrations at a hi gher frequency range). However,
above a certain level, the system becomes unstable and the integral and proportional
coefficients will need to be decreased until the system stabilizes.
Instability in the system may be recognized by the following symptoms:
• Whistling, buzzing or similar noises from the piezo actuators
• Jumping XOut and YOut values visible on the GUI panel.
• Spot not stable in the center of the detector (i.e. spot not stable in center of Target).
