Delta RMC151 - Manual (Page 791)

8 Command Reference
Description
This command starts following the position curve with the specified Curve ID. Curves can
be used for splines and profiles based on time, or for camming based on a master. For
pressure or force axes, use the Curve Start (Prs/Frc) (87) command.
For more advanced options, such as scaling or offsetting the curve, or absolute and
relative options for the master or curve alignment, see the Curve Start Advanced (88)
command.
Curve ID
Specifies which curve you wish to follow.
Master Register
This specifies whether you wish to follow the curve based on time, or based on some
master register, such as the position of another axis.
• Time-Based
To follow a curve based on time, choose _Time as the master.
If you wish to follow a curve based on time, but sometimes need to slow down or
speed up the interpolation rate, consider using a virtual axis as a master. See the
Using a Virtual Axis as a Curve Master section below.
• Master-Based
To follow a curve based on a master, choose the address of the master register, for
example, the position of another axis. When this command is issued, the Point 0 X
value is ignored. The RMC uses the position of the master at the time this command is
issued as the starting X axis position (X
0
). All the x-axis points are then computed
relative to this point. Therefore, if you want the curve to follow the master axis at the
actual x-axis values in the data, you should move the master to the starting location
before issuing the Curve Start command.
The curve will run based on the master position, even if the master changes
directions.
Cycles
Specifies the number of times to repeat the curve. The value of 1 is most common and
will run the curve once. The value 0 means the curve will repeat endlessly. Any other
value (n) means to run the curve n times. For curves with cubic interpolation that will be
repeated multiple times (Cycles is not 1), the Natural-Velocity Endpoints (+1)
Interpolation Option is not allowed.
If the y-values of the first and last points are not equal, and the curve is run for more
than 1 consecutive cycle, the curve will be automatically offset so that the first point of
the next cycle matches the last point of the previous cycle.
Starting a Curve
For the axis that you issue the Curve Start command to, the Target (Position, Pressure, or
Force) must be at the first point in the curve data (Y
0
) before issuing the command, or, a
Transition command must previously have been issued to specify how the axis should
move to get to the curve. A transition command will allow you to start a curve even
though the axis is not at the curve yet. If you want the axis to follow the curve exactly
starting from the beginning, do not use a transition; instead, make sure the axis is at the
starting point before issuing the Curve Start command.
If you are following the curve based on a master (not time), you may want to first move
the master to it's starting location. This is because the curve master positions (the curve's
x-data) will be relative to the position of the master at the time this command is issued.
The curve does not use the actual X
0
value in the curve data. Therefore, if you want the
curve to follow the master axis at the actual x-axis values in the data, you should move
the master to the starting location before issuing the Curve Start command.
Using a Virtual Axis as a Curve Master
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