Dynomotion

Group: DynoMotion Message: 10670 From: cnc_machines Date: 12/15/2014
Subject: Stepper Encoder Gain
Greetings,

I am having some math issues with my KStep running closed loop.

  1. Motor is 1.8 Degree stepper
  2. Pulley Ration 14:30
  3. Optical Encoder 1000 Counts per revolution

The encoder is attached to the big pulley, and the motor to the small one. I cant seem to figure out how to properly calculate what the input and the output gain should be.


For example:

  • Motor Steps Per Rot - 3,200
  • After the pulley reduction this makes 6857.1429 Counts per rev for the encoder pulley.
  • I thought the gain would be calculated by dividing 6857 by 1000 (encoder input) but that doesnt seem to work.

Anyone  have any suggestions?


Thanks,


Scott
Group: DynoMotion Message: 10671 From: Tom Kerekes Date: 12/15/2014
Subject: Re: Stepper Encoder Gain
Hi Scott,

Your math seems correct but not sure what you are doing with the answer, or what you are expecting, or what is happening.

Are you setting InputGain0 to 6.8571429 ?

Do the red and blue plots on the Step response match in open loop mode?

Are you off by a factor of 4? Is the encoder 1000 quadrature counts/rev or 1000 cycles/rev  ? 

Regards
TK

Group: DynoMotion Message: 10672 From: cnc_machines Date: 12/15/2014
Subject: Re: Stepper Encoder Gain
THANKS!!!

What a frustrating day.. I was trying to get the blue command and step response plots to exactly overlap. I was putting 6.85714 into the input gain location. It wasnt working.. looks like I was off by a factor of 4.