65
T-Cube Stepper Motor Controller
E.2.4
Minimum and Maximum Positions
These positions are dependent upon the stage or actuator to which the motors are
fitted, and are defined as the minimum and maximum useful positions of the stage
relative to the ‘Home’ position - see Fig. E.4.
The distance from the Minimum position to the Maximum position is the ‘useful travel’
of the stage. It is often the case that the Minimum position is zero. The Home and
Minimum positions then coincide, with movement always occurring on the positive
side of the Home position.
Rotary stages have effectively no limits of travel. The Minimum and Maximum
positions are conventionally set to 0 and 360 degrees respectively. When the position
of a rotary stage is requested, the answer will be reported as a number between 0 and
360 degrees, measured in the positive direction from the Home position.
Fig. E.4 Minimum and Maximum Positions
E.2.5
Power Saving
The current needed to hold a motor in a fixed position is much smaller than the current
needed to move it. When a stepper motor is at rest it is advisable to reduce the phase
(holding) currents so that the motor does not overheat. Furthermore, this heating can
cause thermal movements through expansion of the metal of the stage.
For this reason, power saving is implemented by default from the software drivers.
When a motor is moving, the ‘Move Power’ is applied. When a motor is stationary, the
‘Rest Power’ is applied. See ‘Phase Powers’ in Section 6.3.3.
Stage/Axis Tab
for
more details on these power settings.
Trave l
Min. position (zero)
(home)
Max. position
Offse t
-ve limit switch
SW positive limit
SW negative limit
Содержание TST001
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