Danaher Motion
06/2005
Master-Slave
M-SS-005-03 Rev
E
111
In many applications, you must ensure that this quantity is precise or the
master appears to creep over time. The MC uses double-precision math (16
digits of accuracy) for cam calculations. Use the MC to calculate
mathematical expressions to obtain the greatest possible precision. For
example, if GEARRATIO=1:3, use the MC to calculate the value rather than
rounding a previously calculated value:
MasterGearRatio = 1/3
'Good: 1/3 accurate to 16 places
MasterGearRatio = 0.33333
'Poor: 1/3 accurate to 5 places
The net motion commanded to the slave is the slave position of the last
point-pair less that of the first. If you do not want net motion in the slave, you
must assign the slave positions of the first and last point-pairs to be identical.
At the point when camming is enabled, the MC takes a snap-shot of the
master position feedback, position or position external (depending on master
definition), and slave position and
offsets
all entries in the cam table for the
master and slave. Cam tables are incremental with respect to the actual
position of the axes at the time camming is started. For example, suppose a
cam table starts at (0, 0) but when the camming is enabled, the master
position is 1000 and the slave's position (
PCMD
) is -2000. Each point-pair in
the table is implicitly adjusted by (1000, -2000) throughout the cam cycle.
After each cam cycle, the offset to the master and slave is adjusted by the
MC. The cam master position is adjusted for the difference between the
master position at the starting and ending points. If the cam table has net
motion, each subsequent cycle adds the net motion to the slave-commanded
position.
Both the master and slave can be in
rotary mode
without affecting the
camming operation.
5.3.5. Cam
Cycles
One cam cycle is the operation of moving the master position feedback
through an entire cam table. Instead of using master position feedback, you
can use position or posistion external. At the end of a cam cycle, the cam
ends or transitions to the next cycle. The next cycle simply repeats the
current cam or is another cam. The number of times a cam is repeated is
controlled by
<cam>.CYCLES
. Other cams are linked in automatically with
NEXT
and
PREVIOUS
.
When the master is moving forward, the cam position feedback counts up.
The cycle ends when the master position is greater than the last entry in the
cam table. Then, the cam moves to the next cycle. Similarly, when the
master is counting down, the cycle ends when master
PFB
is less than the
first entry in the table. The cam moves to the previous cycle. It all depends
on whether the table is increasing or decreasing. If there is no
NEXT
(or
PREVIOUS
) cam cycle, camming is disabled and the slave axis stops.
Whether or not the cam cycle repeats, and the number of times it should
repeat, is specified in
<cam>.CYCLES
. You can enter
1
to indicate that the
cam runs once and does not repeat,
-1
to indicate the cam runs indefinitely,
or use a positive numberto indicate the number of times the cycle runs.
