ADLINK PCI-8158 - Manual (Page 59)

Operation Theory 49
The S-curve profile motion functions are designed to always pro-
duce smooth motion. If the time for acceleration parameters com-
bined with the final position don’t allow an axis to reach the
maximum velocity (i.e. the moving distance is too small to reach
MaxVel), then the maximum velocity is automatically lowered (see
the following Figure).
The rule is to lower the value of MaxVel and the Tacc, Tdec,
VSacc, VSdec automatically, and keep StrVel, acceleration, and
jerk unchanged. This is also applicable to Trapezoidal profile
motion.
This kind of speed profile could be applied on velocity mode, posi-
tion mode in one axis or multi-axes linear interpolation and two
axes circular interpolation modes.
4.2.5 Velocity mode
Velocity mode means the pulse command is continuously output-
ting until a stop command is issued. The motor will run without a
target position or desired distance unless it is stopped by other
reason. The output pulse accelerates from a starting velocity to a
specified maximum velocity. It can be followed by a linear or S-
curve acceleration shape. The pulse output rate is kept at maxi-
mum velocity until another velocity command is set or a stop com-
mand is issued. The velocity can be overridden by a new speed
setting. Notice that the new speed could not be a reversed speed
of original running speed. The speed profile of this kind of motion
is shown below: