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The bearing is designed to be virtually friction- free, so that it moves under the smallest of forces. Even extremely
small manufacturing variations in the bearing can be sufficient to make it rotate. Therefore, to ensure that the
bearing rotation is steady throughout a full 360°, a process called Rotational Mapping, which is explained in
the next section, is carried out.
Rotational Mapping
As explained previously, any real air bearing will have small variations in behavior around one revolution of
the shaft.
By combining the absolute angular position data from the optical encoder with microprocessor control of the
motor, these small variations can be mapped automatically and stored, since the variations are consistent over
time, unless changes occur in the air bearing.
The microprocessor can allow for these automatically by carrying out a baseline correction of the torque. This
results in a very wide bearing operating range, without operator intervention; i.e., a confidence check in bearing
performance.
Instructions for performing the rotational mapping can be found in the Rheology Advantage™ online help.
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AR 2000 Operator's Manual
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