Synchronised trigger output

[Tieval]

Hi all,

 

Currently, we obtain a 5V trigger generated using a virtual axis which is synchronised with a moving axis in the same coordinate system. We're obtaining a trigger approximately every 0.5mm that the axis moves.

 

The trouble is, it is not accurate enough and as speed settings are altered, there are issues with synchronisation. I assume that this is because, despite being in the same coordinate system, the PMAC still treats them independently. Does anyone have any suggestions as to how I could generate a pulse? Perhaps an output every given number of counts?

 

Thanks

[curtwilson]

What mechanism are you using to generate the trigger? Software commands or hardware output (position compare) from the ASIC?

 

Can you generate a hardware position compare output from the feedback of the real motor? This is what the people who need the highest accuracy use.

[Richard Naddaf]

Have you tried using the position compare feature? This is a built-in function which does exactly what you are trying to do manually, but at much higher precision and speed.

You can learn about it in the "Using the Position-Compare Feature on Turbo PMAC" section in the Turbo PMAC User Manual.

[Tieval]

Hi Curt and Richard,

 

Thanks for this. I'm currently trying to set up a position compare output as described in the Turbo PMAC user manual. I've checked I4902 and I4903 for the presence of DSPGATE2 IC. They are $3 and $1 respectively which I believe indicates the presence of 2 IC's, one of which is a DSPGATE2 IC. Do I68n1/I69n1 need to be set?

 

Using "Position compare examples" and the "Using the Position-Compare Feature on Turbo PMAC" I have established that register:

 

M108->Y:$078007,0,24,S ; Position compare A value (counts)

M109->X:$078007,0,24,S ; Position compare B value (counts)

 

However, my motion program is unable to change these from a set value of -1. I have also tried to alter these values manually in the M-Variables but they revert back to -1. I imagine I'm missing something very simple here.

 

Many thanks

[Richard Naddaf]

It sounds like you are pointing to the wrong addresses. Which Turbo PMAC hardware do you have?

[Tieval]

Currently I'm using the Turbo PMAC2 Ethernet Ultralite, although we do also use the PCI card as well.

[Tieval]

Sorry, I should also have mentioned that I am using ABB Drives. I fear this may make position compare impossible? Are there any other methods of generating a precise trigger based on the movement of the Y axis? Or, perhaps a method of improving the precision of our virtual motor?

[steve.milici]

This feature over MACRO is supported through MSn, MI-variables: MI921, MI923, MI925, MI926, MI928 and MI929. There is a very good description in the Turbo PMAC User’s Manual starting on page 362 (specifically page 364 for MACRO). I don’t believe the F-MAC module supports position compare. It only supports position capture for homing.

 

A compiled PLC 0 looking at the position register will probably be your best altaernative.

[Tieval]

Thanks for everyone's help. Have managed to get a PLCC 0 working as a trigger.