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Pmac Position loop regulation


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I am a new user of turbo Pmac. I'm working with Etel motors and amplifiers for current regulation and position servo loop via Macro done by Pmac.

I read the manual and some of the post on the forum but I still don't understand how to figure out my problem.


I made my regulation loop with physical units in order to convert my gain in Pmac units


Here's the pmac position loop regulation to understand what I mean (schema is available at p. 152 of Turbo Pmac user manual)



I calculate my gain with physicals unit (wich correspond with the logic of the schema)


  • Proportionnal gain Kp (as Pmac Ixx30) [A/rad] or [A/m]
  • Derivative gain Kd (as Pmac Ixx31)
  • Integral gain Ki (as Pmac Ixx33) [1/s]


(units are: A: ampere, rad: radians, m: meters, s: second)


I am aware that Pmac units are [count] I also know:

Ixx69 the max. output current

How many count to make a motor turn (or 2 Pi rad).


I also read the units of Ixx30 (Kp) which are Ixx08/2^19 and the same logic for Ixx31 and Ixx33.

But I can't figure out the unit conversion


I hope you can understand what I mean, I would be glad to explain more If you want.

Thank you





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With the exception of the last conversions due to Ix08 and integer point implementation of the servo

algorithm in Pmac,

all of the gains in have units dacbits/cts (note that Kd multiplies the difference between current position

minus the last position, and Ki multiplies the summation of errors in cts).



For a brushless motor the physical output of the servo loop is the commanded torque producing current

Iqcmd which is an input to the current loop regulator. And the conversion from Dac bits to Ampere can be

found by Maximum ADC reading of the amplifier.


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