"Read Steps Generated" sometimes differs by factor of 4

[RWA]

This is my latest problem, and probably the best question that I've asked on this forum.

I am configuring a simple move portion of my program:

Setting operation mode to absolute position, inputting a target position (steps),  start motion, and read steps generated.  For this case, X steps into target Position yields X steps from the read steps generated.

Now, I want to try something different

So, I configure the axis for velocity mode:

Setting operation mode to velocity, inputting a velocity (steps/s),  start motion, and read steps generated.  Its difficult in this case to determine the quantitative difference between actual steps and what this is returning, but I don't feel as though they are the same.

Now for the problem:

After configuring the axis to perform as above, I now switch back into absolute position:

Setting operation mode to absolute position, inputting a target position (steps),  start motion, and read steps generated.  For this case, "X"steps into target Position yields "4X" steps from the read steps generated.

The best I can figure, this is also the difference in the velocity mode.

Does anyone know why this is?  I know its off by a factor of  4, but  the idea of a spurious 4 floating around in my program doesn't satisfy me.  And since its not constant, it may revert back to the original operation mode without knowing (or too late after a destructive test is run). and skewing my data.

[RManion]

Hey RWA,

I have two questions for you about your setup.

1) Is it always a factor of 4, regardless of how long you stay in Velocity mode?

2) Do you use a halt before changing operation mode?  In the past I've seen some weird results when the operation mode is changed without halting execution.

Robert

Message Edited by RManion on 07-13-2005 06:36 PM

[RWA]

Hi RManion

1) Is it always a factor of 4, regardless of how long you stay in Velocity mode?

It has been giving me weird results for awhile.  I made a side program to test it out.  The factor of 4 that I found was while in Absolute Postion Mode.  The output of the "read steps generated" VI, when divided by 4, equaled the target position.

2) Do you use a halt before changing operation mode?  In the past I've seen some weird results when the operation mode is changed without halting execution.

I don't believe I did.  Let me see what that does.  I've reset and reinitialized the 7344 Hardware, and its still off by 4 (not sure if it'll switch back).

Oh, and you were right about the Torque section in the user manual.  I finally found the section and it gave a pretty straightforward explaination.  It was similar to what I had been using, but I'm modifing it slightly to accomidate my needs. 🙂 

[RManion]

Hey RWA,

You do mean multiplier of 4 right?

Let me know what it does after you try changing things.  I have dealt with a situation in the past that it made a significant difference.  If you are still having trouble afterwards, I will see if I can resproduce the behavior here.

Talk to you soon,

Robert