Tuning characteristics of control modes, Tuning characteristics of control modes 33 – MTS Series 793 User Manual
Page 33
About Tuning
MTS Series 793 Tuning and Calibration
Introduction
33
Tuning Characteristics of Control Modes
Each control mode has different tuning characteristics.
Displacement control
The displacement control mode (also called stroke control) uses an LVDT sensor
in the actuator as the controlling feedback source. The displacement control
mode typically:
•
Requires tuning only when first set up.
•
Does not require a specimen for tuning.
•
Uses a square wave when tuning an LVDT but not when tuning a
displacement gage.
•
May not yield actuator movement if P gain is set too low.
•
May yield rapid, noisy, and unstable actuator movement if P gain is set too
high.
Force control
Force control uses a force sensor (also called a load cell) as the controlling
feedback source. The force control mode typically:
•
Requires tuning between tests, whenever a specimen is changed, and
whenever changes are made to the force train.
•
Requires a specimen to be installed.
•
Uses a ramp waveform for initial tuning. However, if the desired results
cannot be achieved with a ramp waveform, a squarewave is used for tuning.
•
May yield sluggish response if P gain is set too low.
•
May yield unstable response is P gain is set too high.
Strain control
Strain control uses an extensometer or strain gage bonded to the specimen as the
controlling feedback source. The strain control mode typically:
•
Requires tuning between tests, whenever a specimen is changed, and
whenever changes are made to the force train.
•
Requires a specimen to be installed (you may choose to use a broken
specimen).
•
Uses a ramp waveform for the initial tuning.