Delta RMC101 - Manual (Page 204)

RMC100 and RMCWin User Manual
4-18
Axes remain in Rotational mode through all Auto Stops, Halt (H) commands, Disable Drive (K)
commands, and Set Parameters (P) commands.
Example:
To reset an axis position every 3600 position units, set the Retract Limit to 0 and the Extend Limit
to 3599. When the axis moves beyond zero in the negative direction, it will wrap around to 3599.
Notice that setting the limits to 0 and 3600 would result in 3601 position units per turn.
4.8 Spline Overview
Why Use Cubic Splines?
Some applications require that the motion controller move between a number of positions that
vary for each sequence of moves. An example of this is curve sawing. In this application a cant (a
section of a log) is scanned, and an optimizing computer determines the best path for the saws
through the cant. The motion controller then must follow this smooth path through the cant.
The most basic way to follow this curve would be to select various positions along the cant and
calculate where the saws need to be at each length on the cant. Then the programmable
controller could give commands to go to the various positions. The problem with using this
method is that for each Go (G) command, the motion controller will ramp up to a constant
velocity, and then ramp down to a stop for each point. This would not give a smooth curve
through the entire cant.
Another method would be to carefully control the speed of a move to the extend or retract limit so
that the saws follow the curve. The problem with this method is that a large number of
calculations must be done in the programmable controller.
To greatly simplify the work required by the programmable controller and also provide smooth
moves between points along a curve, the RMC has been equipped with cubic splines. When
using cubic splines, the programmable controller needs only to send the positions where the axis
should be located at various times along the curve. The RMC takes care of creating a curve that
is smooth for position and velocity and continuous for acceleration.
Basic Vocabulary
Refer to these example splines for the following definitions.
Spline Point: