User`s manual

8-8 Motion Mate™ DSM314 for Series 90™-30 PLCs User's Manual – January 2001 GFK-1742A
8
is ON, then the CTL bit chosen acts as a rising edge trigger to enable follower mode. After
Follower is enabled, only the PLC
Enable Follower
%Q bit controls the active state of the
following function. When the follower axis is enabled to a moving master source, some master
source counts cannot be used immediately. The master counts that accumulate during acceleration
of the follower axis are stored. When the follower axis reaches the master velocity, they will be
inserted during make-up distance correction motion. This motion has an automatically calculated
trapezoidal velocity profile determined by the
Follower Ramp Distance Makeup Time
, the
amount of accumulated counts, and the configured
Follower Ramp Acceleration.
Set the
Follower Ramp Distance Make-up Time
to the desired time in the configuration software or it
can be changed with the PLC %AQ Command 42h.
If the
Follower Ramp Distance Makeup Time
is too short then the automatically generated
velocity profile is triangular in profile. If during the distance correction velocity exceeds 80% of
the configured
Velocity Limit
, then the automatically calculated move velocity will be clamped at
80% of the limit value. Clamping the makeup move velocity at 80% of the velocity limit allows
the system some reserve velocity capacity for continued tracking of the master source velocity. In
both cases a warning message is reported and the real distance make-up time is longer than
programmed, but the distance is still corrected properly.
Setting a
Follower Ramp Distance Make-Up Time
of 0 allows the Ramp feature to accelerate the
axis without making up any of the accumulated counts. In this instance velocity will not exceed
the master velocity. For applications where lost counts do not matter, set the distance make-up
time = 0.
By default the superimposed motion profile that is automatically generated by the follower ramp
function (with non-zero makeup time) is trapezoidal using the
Follower Ramp Acceleration
and a
distance derived from the active
Ramp Makeup Time
.
The value of the
Velocity Limit
may affect functionality differently depending on the
relationships of the master source velocity. The following case examples illustrate these points.
Case 1: The master source velocity is less than 80% of the configured
Velocity Limit
and the
makeup time (Mkup Time) is a long enough interval so that the resultant velocity remains less
than 80% of the Vlim. This is the preferred operation, no errors are reported and the over speed
move of the ramp function occurs within the specified makeup time. The follower axis velocity
will not exceed 80% of the Vlim unless the master source velocity increases.
Case 2: The master source velocity is below 80% of the configured
Velocity Limit
but the makeup
time interval is too short to allow operation as in case 1. A status only error (ECh) will be
returned when the follower velocity matches the master command velocity. The makeup move
will accelerate using the active
Follower Ramp Acceleration
to 80% of the velocity limit (Vlim).
The makeup move will occur and all accumulated counts stored during initial acceleration will be
used.
Case 3: The master source velocity is greater than 80% of the configured
Velocity Limit
when the
follower velocity matches the master command velocity. A status only error (EAh) is returned
and no makeup correction move is attempted.
Case 4: At the time when the follower velocity matches the master command velocity and the
makeup move is to occur and conditions are the same as in Case 1 or Case 2 and the makeup
move has initiated, the master source increases to >80% of the
Velocity Limit
. The amount of
accumulated counts and the active makeup time value will determine if the makeup move will
complete in the specified makeup time. A status only error (F2h) will occur if the combined