Do-More AXCONFIG/HSIO/Servo Problems

[MBAutomation]

Hello,

Currently I am running a BX-DM1E-10ED13-D PLC with a HSIO-2 Card.  I had my program running just fine, but I decided to add an encoder. TRDA-20R1N2500 RZD  (2500 PPR).  I am also using a ClearPath Servo that has  800 PPR.

The issue I am having is after I tell my servo to do a HOME function based on the encoder input counts, it goes to the limit switch than immediately starts running to the offset position. I am using encoder counts. 

I have also found that the encoder counts do not match the counts I input the servo to move.    The last time I ran my project I told it to run -100 ppr. The encoders actual value read -2000  +/-.


 Now, I have found that my issue is in the AXCONFIG.  It has something to do with the encoder check box section.  In the Do-more videos under using an encoder, it tells us to take our motor ppr/encoder ppr to make them match.   That is what I have done.   Motor PPR is 800/2500 encoder ppr =.32.  This is  where the issue is.

I think I am missing something with either my math, or my setup in the HSIO card.    When I set the card up I am using the "Quad" feature, and X4 as well.   This should be all that needs to be enabled. So, I feel it is in the math portion.

Thanks for your help in advance.

[ADC Product Engineer]

Your encoder really needs to be equal or less pulses than your Servo PPR.  You can't hit a target that is too small which is what you have now.  IE you are trying to hit a encoder count that the motor does not have enough resolution to find.

[BobO]

Your encoder really needs to be equal or less pulses than your Servo PPR.  You can't hit a target that is too small which is what you have now.  IE you are trying to hit a encoder count that the motor does not have enough resolution to find.

Or use a large enough deadband.

[MBAutomation]

Thanks guys! So I just need a smaller PPR Encoder to fix my issues?   Another question,  When using the X4, X2, X1 setup. Do I input my resolution based off of the encoder specs from AD?  For instance, if I input a X4 option do I multiply my ppr by 4 and get 10,000.
If I were to use a large Dead-band until I bought a new encoder, how would I figure that out?

[ADC Product Engineer]

Right.  Your encoder counts should always be equal to or less than your servo or stepper resolution.  Or you will need to set up deadband to make the system stable.  This is why picking a high ppr encoder doesn't gain you anything.  It's like counting by 2's, you'll never hit an odd number.  All those extra counts are well... wasted.



( PPR * multiplier / servo resolution ) * 2 to 4

I use 2 to 4 above because sometimes 2x is enough, sometimes it isn't.  Go higher with the number until it is happy.  It's one of those test it and see what you need situations.

(2500 * 4 / 800) * 2 = 25 counts dead band to start

[MBAutomation]

Perfect! Thank you so much for your help!

[MBAutomation]

Hello again,

I am having the same issue after installing a 500 ppr encoder. I forgot to mention that i'm using a wheel/timing belt pulley.  I found a write up that says when using a pulley you need to find the calibration constant.   https://www.motioncontroltips.com/faq-how-do-i-determine-the-required-pulses-per-revolution-for-an-encoder-application/.     I did this and it seems to get my numbers close.     

For a recap on what im doing.    According to the software, encoder resolution is motor ppr / encoder. 800 / 500 = 1.6 x4.  =  6.4.  I'm using a 5 for dead band.   Now, when I do this my numbers are close enough on actual on HSIO VS Encoder, but when it initially homes it hits the limit switch and just runs and doesn't stop.

Any ideas?

Thanks

[ADC Product Engineer]

Did you adjust the filter time on your limit switch?

[MBAutomation]

Yes, I have it set at 250000. Even though that's a little much for a switch.  I know its something dumb, like a simple setting.

[BobO]

Latest firmware?

[MBAutomation]

Yes sir

[MBAutomation]

So, after playing around I think I have figured it out. I do not have a why yet.    Im going to attatch pictures of my setup.  My problem lies within the Clearpath motors software.  The Accel in the Do-More software is running at 6,000,000 and the clearpath was the same, this was what worked with the 2500 ppr encoder. (this is why I am not a fan of the clear path stuff now)   Now the clear path is set at 6000 accel and the do-more is set at 600,000.  Now it runs smooth again and works fine.


Now, Question on the input of location.  I only want to move about 10".    My encoder tells me that 0=0 and 10"=2741 ppr.   But, I cannot use these numbers to move that distance.  The numbers I have to use is 0-200.    Is this because I have a 500 ppr encoder now and its 0-500 for a full revolution in a sense?

[ADC Product Engineer]

Really would need to see the project to give a good answer on the "why 200".