77
K-Cube Stepper Motor Controller
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.
E.3
Error Correction
E.3.1
Backlash correction
The term
backlash
refers to the tendency of the stage to reach a different position
depending on the direction of approach.
Backlash can be overcome by always making the last portion of a move in the same
direction, conventionally the positive direction. Consider the situation in Fig. E.6, a
positive
move, from 10 to 20 mm, is carried out as one simple move, whereas a
negative
move, from 20 to 10 mm, first causes the stage to overshoot the target
position and then move positively through a small amount.
Fig. E.6 Backlash correction
The particular stage selection will usually have this type of ‘backlash correction’
enabled as its default mode of operation, but it can be overridden if the overshoot part
of the move is unacceptable for a particular application.
See Chapter 6 Software Reference, Move/Jogs Tab for details on setting the
backlash correction.
negat ive move
positive move
10mm
20mm
position