About Tuning
Model 493.02 Controller Service
Tuning
205
Acceleration
stabilization
Test systems with specimens affected by acceleration resonances can
use a mass accelerometer signal for stabilization. Acceleration
stabilization dampens the resonances (vibrations) affecting the
specimen.
Typical systems that benefit from acceleration stabilization include:
• Load units that operate at high frequencies with massive grips
• Test systems that employ swivels, linkages, and test tables
Sensor feedback is provided by an accelerometer attached to (or near)
the specimen. The controller converts this feedback into a stabilization
signal which is combined with the composite command signal (post-
PIDF correction). The “stabilized” command signal is then sent to the
valve driver.
Note Acceleration stabilization works to minimize compliances from
swivels, linkages, and test tables. Acceleration compensation is
used to correct the signal from a moving load cell. The system
software does not support acceleration compensation.
Forward loop
filter (FL)
FL filter adjustments compensate for noise in the servoloop—which
usually comes from sensor feedback. FL filter adjustments establish a
frequency bandwidth for the servo-loop command signal.
Keep in mind:
• By default, the FL filter is set to one-half the system rate.
• The minimum FL filter frequency setting is 0.01.
• Be sure the forward loop filter frequency is higher than any
frequency in the test program. (Most testing occurs below 50 Hz.)
• Systems with moving load cells or heavy grips can produce a
noisy force signal.
Noisy Feedback D Gain Amplifies Noise Not All Noise
is Removed
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