User guide

198 6000 Series Programmer's Guide
Define the
Slave-to-Master
Following Ratio
(
FOLRN & FOLRD)
The FOLRN and FOLRD commands establish the goal ratio between the slave and master
travel, just as the V command establishes the goal velocity for a typical non-Following move.
The FOLRN command specifies the ratio's numerator (slave travel), and the FOLRD command
specifies the ratio's denominator (master travel). If the denominator (FOLRD) is not specified,
it is assumed to be 1.
FOLRNF may be
used to define a final
ratio for compiled
Following profiles
(see page 166).
FOLRN and FOLRD are specified with two positive numbers, but the resulting ratio applies to
moves in both directions; the actual slave direction will depend on the direction commanded
with the D command and master direction. Numeric variables (VAR) can be used with these
commands for slave and/or master parameters (e.g., FOLRN(VAR1) : FOLRD3). The
maximum value of the resulting quotient is 127 to 1.
For a preset Following move (MCØ mode), the FOLRN/FOLRD ratio represents the maximum
allowed ratio. For a continuous move (MC1 mode), it represents the final ratio reached by the
slave.
Example ☞ As an example, assume the slave-to-master ratio is set to 5-to-3 for an axis (FOLRN5 :
FOLRD3). The first parameter (5) is scaled by the SCLD value to give slave steps. The
second parameter (3) is scaled by the SCLMAS value to give master steps. If the SCLD setting
is 25000 and the SCLMAS setting is 4000, the slave-to-master step ratio would be 5 ∗ 25000
to 3 ∗ 4000, or 125 slave steps for every 12 master steps.
Define the
Master Distance
(FOLMD)
The “master distance” for moves in the Following mode (FOLEN1) is analogous to the move
time for normal time-based moves with Following disabled (FOLENØ). For time-based
moves, the time required to ramp to a new velocity (MC1 mode) or move to a new position
(MCØ mode) is determined indirectly by the acceleration (A), deceleration (AD), and velocity (V)
command values. For Following mode moves, a ramp to a new ratio (MC1 mode) or a move
to a new position (MCØ mode) takes place over a specific master distance, not over a specific
time. This distance is defined directly by the user with the FOLMD command.
In other words, the FOLMD command defines the master distance over which a preset slave move
will take place, or the master distance over which a continuous slave move will change from its
current ratio (including zero) to the commanded ratio (ratio established by FOLRN and FOLRD).
By carefully specifying a master distance (FOLMD), a precise position relationship between
master and slave during all phases of the profile is ensured.
☞ HINT: If the slave is in continuous mode (MC1) and the master is starting from rest,
setting FOLMD to Ø will ensure precise tracking of the master's acceleration ramp.
If scaling is enabled (SCALE1), the FOLMD value is scaled by the SCLMAS parameter.
Examples and more information on this topic can be found below in the section titled Slave
vs. Master Move Profiles.
Enable the
Following Mode
(FOLEN1)
When an axis is configured as a slave with the FOLMAS command, it will continuously
monitor the position and motion of its master, even if the slave is at rest. This allows
subsequent motion to be related to the motion of the master via ratios (FOLRN/FOLRD) and
ramping over master distances (FOLMD). Such moves are done with Following enabled
(FOLEN1).
It is also possible, and sometimes desirable, to have the slave motion independent of master
motion, yet still “aware” of master position. For example, a move may need to start at a
specified master position, yet finish in a fixed time, independent of the master speed. This
move would be performed with Following disabled (FOLENØ).
Following may be enabled or disabled between moves, as needed, without affecting the
monitoring of the master.
If a move is performed with Following disabled, its motion profile is determined by the
acceleration, deceleration, and velocity specified with the A, AD, and V commands. Its motion
is the same as if the axis were not configured as a slave, but the axis does monitor the master.
If a move is performed with Following enabled, its profile is determined by the specified
master distance (FOLMD) and Following ratio (FOLRN/FOLRD). The next section describes
such profiles.