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HA0303T Rev A Feb 2014
Chapter 5
5.2.8
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 able to dampen vibrations at a higher 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 pizo actuators
•
Jumping XOut and YOut values visible on the GUI panel.
•
Spot not stable in the center of the detector (i.e. center Target LED not lit
continuously).
Once the PID parameters have been adjusted, check that the system is
unconditionally stable. Tap the work surface to check that the system cannot be
provoked into instablity by vibration.
5.2.9
Troubleshooting
In summary, the 4 most common reasons why the system will not operate correctly
are:
•
A piezo controller is connected to the wrong axis - see Section 5.2.7. Item 4 or 6. or
the axes are swapped.
•
X-axis or Y-axis Position Demand Sense is set incorrectly - see Section 6.2.
•
PID constants need adjustment - see Section 6.2.
•
The ‘Drive Input Source’ parameter for the Piezo unit is set incorrectly - see Section
6.2.
Note
The default settings for the PID parameters are correct for the set up
shown in Fig. 4.9. If any of the above signs are apparent, it will be
necessary to adjust the PID settings in the Settings panel - see Section 6.2.
