Bosch REXROTH IndraDrive Applications Manual page 67

DOK-INDRV*-MLD-APPLI**-AW02-EN-P
Rexroth IndraDrive Rexroth IndraMotion MLD Application Examples
Why "VmAxisExt"?
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Synchronous Multi-Axis Motion With Virtual Master Axis
MB_GearInPos
Declaration fbGearInPosAxis1: MB_GearInPos;
Task Activation and parameterization of the operation mode "phase syn‐
chronization" in the CCD master axis.
Slave Axis 1 (with MLD-M, always corresponds to master axis; with MLD-S,
always corresponds to local axis)
Master VmAxisExt (specification of master axis via "P‑0‑0053, Master axis
position")
MB_MotionProfile
Declaration fbMotionProfilAxis2: MB_MotionProfile;
Task Activation and parameterization of the operation mode "electronic
motion profile" in the CCD slave axis.
Slave Axis2 (corresponds to CCD slave axis [first CCD slave axis in CCD
axis group])
Master VmAxisExt (specification of master axis via "P‑0‑0053, Master axis
position")
We might ask ourselves, why apply the master axis "VmAxisExt" instead of
"VmAxisInt" to the "Master" input of the synchronous motion function
blocks"fbGearInPosAxis1" and "fbMotionProfilAxis2".
Justification: The internal virtual master axis "VmAxisInt" always refers to the
local axis. Each drive has its own internal virtual master axis (VmAxisInt). It is
our objective, however, that all drives follow the same master axis. For this
purpose, the internal virtual master axis generated in the CCD master axis must
be transmitted to the CCD slave axes. With activated MLD-M system mode,
this is automatically configured by the drive. Due to the transmission of the
master axis position to the CCD slave axes, there is a dead time of one CCD
cycle between the internal master axis (VmAxisInt) of the CCD master axis and
the secondary master (VmAxisExt) effective in the CCD slave axes. To com‐
pensate for this dead time, the CCD master axis also has a virtual CCD slave
axis. The internal virtual master axis (VmAxisInt), too, is transmitted to its own
virtual CCD slave axis. The transmitting internal virtual master axis thereby is
also available to the CCD master axis itself as an external virtual master axis
(VmAxisExt). The resulting dead time is the same as with the real CCD slaves.
Thereby, the same master axis is available to all drives in the form of "VmAxi‐
sExt".
The following paragraphs will not describe all parts of the program in detail, but
only those ones which are responsible for the actual sequence of motion.
Program section 2.3: Calling motion function blocks
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