MTS Acumen User Manual
Page 77
It is important to understand the following:
•
Load and displacement control modes are used primarily for testing.
•
The stable displacement mode is used exclusively for setup and other circumstances in which stable
system response is critical.
•
It is best practice to select stable displacement as the active control mode when positioning the actuator
to install the specimen.
Using Control Modes
When setting up your station for testing, there are situations in which you can select a control mode, and
others in which the application selects the control mode automatically.
Manual Control Mode Selection
You can select a control mode when using the Manual Command panel to position the actuator. If you
have not tuned the load or displacement control modes, it is best practice to select the stable displacement
mode. If tuning is complete, you may select any control mode.
Automatic Control Mode Selections
There are several scenarios in which the application automatically selects the stable displacement control
mode, as follows:
•
When you run inertial compensation and verification programs
•
When you run auto tune and verification programs
•
When you enter the specimen protection mode
•
When a C-Stop interlock is triggered
Also, when you start a test, you lose the ability to select control modes manually. The controller automatically
switches to the control mode selections programmed into the test procedure.
To see how control modes are used when running the example test, see
(p. 95).
Control Mode Example
Suppose you want to compress your specimen using the Manual Command panel on a properly tuned
system:
•
If you select force control, the test system will apply a compressive force to your specimen in terms of
Newtons (or pounds) of force. If you enter a 1000 Newton command and the specimen is relatively
soft, the actuator will travel several millimeters (or inches) to achieve the command. Likewise, If you
apply the same command and the specimen is relatively hard, the actuator will travel a fraction of that
distance to achieve apply the same force.
•
If you select displacement control, the test system will move the actuator in terms of millimeters (or
inches) of displacement. If you apply a 10 millimeter command to a soft specimen, the actuator may
apply only a small force to the specimen to achieve the command. If you apply the same command to
a hard specimen, the actuator will apply a much greater force to apply the same displacement.
MTS Acumen
™
| 77
Key Concepts