Danaher Motion
06/2005
Single-Axis Motion
M-SS-005-03 Rev
E
87
The profile must be updated at regular intervals. The MC usually updates the
profile every cycle time (1 ms
update rate
, if possible when the drive
supports this update rate). The SERCOS telegram also gets longer with
more axes. When using the MC with Pentium™ CPU board, the
recommended update time to controls 8 or fewer axes is 2 ms and 4 ms
when the MC controls 9-16 axes. When the MC is used with Pentium™III
CPU, it controls up to 32 axes at 2 ms update rate.
4.1.2. Motion
Buffering
The motion generator for each axis can process only one motion command
at a time because the axis can process only one position or velocity
command. However, you can send a second motion command to the
generator where it is held until the current motion command is complete
(motion buffering).
Motion buffering is controlled with
STARTTYPE
. If
STARTTYPE
is set to
GENERATORCOMPLETED, the buffered profile starts immediately after the
current profile is complete. If
STARTTYPE
is set to INPOSITION, the
buffered profile starts after the current profile is complete and the position
feedback has settled out to the position command. In both cases, the second
command is held in the motion generator to begin immediately after the
appropriate conditions are met.
You can also specify that the motion generator not buffer, but process the
new motion command immediately. This is useful when you want to make
realtime changes to the profile (changing the end position of the current
command). For this, set
STARTTYPE
to IMMEDIATE (IMMED) or
SUPERIMMEDIATE (SIMM).
4.1.3.
Override versus Permanent
Axes have numerous properties such as acceleration and deceleration.
These properties are normally set directly:
ConveyorAxis.Acc = 100
This setting is permanent. It persists until the next time the property is
assigned a value. For convenience, the MC also supports override values
where the property is set as part of a command. In this case, the setting is
used only for the current command.