How many softMotion references can you create on an Interface Object

[StevenA]

I'm wondering how many softmotion references I can create on an interface object.  For example can I create a straight line move on an axis, keep that reference open then at the same time create another line move referece on a coordinate space that using that same axis?

Can I have multiple line move references open at the same time on the same axis?

Thanks,

SteveA

[PaulRB]

Hi Steve,

The short answer is yes, you can do this. However, you must be very careful that you don't start a move on both of these references at the same time. In fact, you must be sure that the move on one reference is completely finished before you start the move on the other reference. Starting both moves at the same time (or while the other one is still active) could throw an error, but it could also cause your axis to jump. This is a known limitation of SoftMotion and something that is on the roadmap for improvement.

Is there any particular behavior that you are trying to implement by using two resources with the same axis?

Thanks, 

[StevenA]

Thanks Paul,

I have noticed that the SoftMotion express vis open a reference on first call, but they never close the reference.  On my machine I will be doing regular coordinate moves and from time to time I will need to perform an Axis move.  Would it be better practice to close each reference after I perform the move?  How much overhead does it take to create a new reference?  The thought I had on keeping multiple reference open was to minimize the overhead in opening a reference.  Once my system gives a trigger to perform a move, I need it to be very responsive.

Thanks,

Steve

[PaulRB]

Hi Steve,

I did some benchmarking, and on my 9024, creating and destroying a straight line coordinate reference takes about 110usec. A better benchmark might be how much the cRIO CPU increases if you open and close references continuously.

In general, though, it is not a good idea to continuously open and close references. One simple way to do a one axis move on a coordinate space is to do a straight line move and set all of the position coordinates to 0 except the axis that you want to move. I actually use this method a lot to do one axis moves in a coordinate space.

Thanks,