Fagor CNC 8055, Manual

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4.2 Control of the tandem axis
The block diagram for the application to control the tandem axis is:
The nomenclature used has the following meaning:
Torque of the tandem
master motor Is the rated torque percentage (%) reflected by the Sercos variable
TV2 of the drive that governs the master axis of the tandem. It is read
in every loop.
Torque of the tandem
slave motor Is the rated torque percentage (%) reflected by the Sercos variable
TV2 of the drive that governs the slave axis of the tandem. It is read
in every loop.
Torque distribution Gain to regularize the torques generated by the motors in order to set
a torque distribution other than a 1:1 ratio.
Pre-load Previous torque applied to both axes of the tandem in opposite
directions. This sets a traction between them in order to eliminate the
rack-and-pinion backlash when resting. It is determined as the torque
difference provided by each axis.
Pre-load filter First order filter whose purpose is to avoid the input of torque steps
(shoulders) when configuring the pre-load.
Position loop.
Applying the pre-load value involves necessarily joining the master
and the slave axes of the tandem axis mechanically. Otherwise, the
motors would move even without control command signal.