BECKHOFF AL2000 Application - Manual (Page 10)

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10
Positioning
LM applications require a sophisticated position and velocity feedback. A linear encoder and a servocontroller
are taken up in the positioning system. The position of the slide is detected by a measurement unit, a ruler-
probe combination. The unit’s linear encoder returns the information to the servocontroller. The accuracy of the
motor system depends strongly on this positioning system.
Most measurement units return incremental position information. So the linear motor has to do without the
absolute position of the slide. Especially when starting a motor operation this could be problematical. Herefore
the slide is activated to some minimal testmovement. This ‘magnetic alignment’ supplies the positioning system
with the required information.