Gemini GV6K and Gemini GT6K Programmer's Guide

product of master travel and average ratio. Because the slave travel is not specified explicitly,
it is possible for arithmetic round-off errors to cause actual slave travel during a ramp to differ
from theoretical calculations. For applications in which slave distance is important, preset
segments should be used.
A preset (MCØ) Following segment will also start with the final ratio of the previous segment,
but may end in one of two ways. FOLRNF specifies the final ratio of a preset Following
segment. The only valid value for FOLRNF is zero (0). If FOLRNFØ is given before the
GOBUF, the resulting motion segment will be constructed exactly as preset Following moves
are outside of compiled profiles. In this case, the starting ratio must be zero, the final ratio
will be zero, and the maximum intermediate ratio will be given by FOLRN and FOLRD. The
relationships between ratio, master distance, and slave distance for this case are given on page
192 under the heading Master and Follower Distance Calculations. The FOLRNF command
affects only the immediately subsequent preset Following segment, and must be given
explicitly for each preset segment which is to end in zero ratio.
If FOLRNFØ is not given before the GOBUF, the segment will end with the ratio given by
FOLRN and FOLRD, and need not start with zero ratio. This type of motion segment is
constrained, however, to intermediate ratios which fall between the starting and final ratios.
Compiled profiles are built from motion segments created with the GOBUF command. That
is, the motion segments may be all Following or all non-Following, but not a mixture of
Following and non-Following.
The GOBUF command builds the appropriate type of motion segment based on the values of
FOLMAS and FOLEN during compilation. These parameters may not be changed inside a
compiled program after a GOBUF. The choice of zero or non-zero FOLMAS must be the same
during PRUN as during PCOMP (if non-zero, the value can be changed, but still must be nonzero).
If a non-zero FOLMAS is given, the value of FOLEN must be the same during PRUN as
during PCOMP.
Distance
Calculations For
Compiled
Following Moves
The graph below shows 6 possibilities of ratio change profiles for preset segments, with legal
FOLMD and “D” values constrained by the requirement that the average ratio (given by
“D”/FOLMD) is between R1 and R2. If the distance is outside these ranges, in the profile used
to get from R1 to R2 over FOLMD (covering “D” slave distance), an error message will be
generated during the PCOMP command. For the graphs shown, the constraints are expressed by:
(R1 * FOLMD) = “D” >= (R2 * FOLMD) if R2 < R1
The two graphs above show the cases of R1R2, but the distance calculations of the
ramp and constant ratio portions are the same for the two cases. For each graph, the heavy
lined profile (first case) of these mimics the shape of the corresponding preset velocity change
Chapter 6. Following 143