MTS Series 793 - Manual (Page 32)

MTS Series 793 Tuning and Calibration
About Tuning
Introduction 32
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.
Forward Loop Filter (FL Filter)
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.
• If you observe a noisy sensor feedback signal, reduce the FL filter setting to
about 100 (providing your test does not reach 100 Hz). If additional
adjustment is needed, reduce the setting by 5 - 10 Hz at a time.
Noisy Feedback D Gain Amplifies Noise Not All Noise
is Removed