Danaher Motion
06/2005
Single-Axis Motion
StartType = InPosition (InPos)
When STARTTYPE = INPOS, the motion generator delays executing
the new motion command until the current move has completed and the
position error is settled to near zero.
INPOSITION
is constant equal to
2. This command is not subject to additional system delays, but any
delay associated with the command is due to user-specified parameters
for settling time.
StartType = Immediate (Immed)
When STARTTYPE = IMMED, the new move overwrites the current
move. Use this when making realtime changes to the profile such as
changing the end-point of the current move without bringing the system
to rest. For example, registration applications frequently use this
function. IMMEDIATE is constant equal to 1. This command incurs a
system delay of 5 SERCOS cycle times each execution. This time is
required to blend the previous move with the new move.
StartType = SuperImmediate (Simm)
SUPERIMMEDIATE is a variation of IMMEDIATE. The main difference
is that SUPERIMMEDIATE eliminates the 5 SERCOS cycles delay by
doing pre-calculation online, rather than offline in the motion manager.
SUPERIMMEDIATE
is constant equal to 5. The numbers of
SUPERIMMEDIATE changes at a time in the system is limited by the
load of the system and the type of move. SUPERIMMEDIATE is best
used for short, high-speed movements.
When
chaining multiple moves
which all end at zero speed, you normally
want STARTTYPE = INPOS. This forces the motion generator to wait for the
position to settle out before starting the next move. If the position profile
starts too soon on the second move, the motor may never come to rest. For
example, the next figure shows this problem when
STARTTYPE
is
incorrectly set to GCOM rather than INPOS.
As you can see, the motor speed never gets to zero because the second
move takes the velocity command positive before the velocity feedback
settles to zero.
Normally, the desired performance is for the velocity to reach zero before the
second move starts. To do this, the controller needs to wait for the axis
position error to be settled before starting the second move. This is done by
setting
STARTTYPE
to INPOS. This is shown in the following figure.
M-SS-005-03 Rev
E
93
