# Vector Control Q & D axis Current Loop Gain Calculation

Status
Not open for further replies.

#### jnnewton

##### Member
I tried to post this in the Robotics Section, but with no responses, maybe this is a better location. If it pleases the masses, I can delete it from the other forum, as it's not getting any action anyway.

I am trying to understand how motor parameters can be used to calculate (or at least estimate) the gains in the current PI loops (for d-axis and q-axis). The closest I have come to finding a resource on how this actually works is this AN from Freescale: http://cache.freescale.com/files/microcontrollers/doc/app_note/AN4680.pdf

They have two equations:
Kp = 2 *ζ*ω*L - R (Equation 1)
Ki = ω^2 * L (Equation 2)

Where:
Kp - Proportional Gain
Ki - Integral Gain
L - inductance (for whichever axis the loop is being applied, distinction made in Table 1)
R - Single Phase Resistance
ζ - current loop attenuation
ω - natural frequency of the current closed-loop system

1. how can I calculate or estimate the inductances Ld & Lq so i can use the proper value for Kp&Ki(d-axis) as well as Kp&Ki(q-axis)?
---1a. Can I assume that Lq = Ld = L for estimation purposes?
---1b. Is there a more accurate way of calculating those values without measuring them as shown in the AN?
2. How do i estimate current loop attenuation and natural frequency theoretically?
---2a. What motor parameters would need to be provided?
---2b. Is there an equation for this calculation that is not listed in the AN?
3. Where can I find additional relevant documentation on this matter (not Vector / FOC / motor control in general, but the estimation or calculation of these gains from standard motor nameplate & datasheet values)?

Status
Not open for further replies. 