PI Controller
Both the current and rate control loops are of the Proportional plus Integral type. If “E” is defined to be the error signal,
E = Command – Feedback
then the PI controller operated on “E” as
Output = (Kp * E) + (Ki s E dt)
where Kp is the proportional gain of the system and Ki is the integral gain of the system.
The transfer function (output /E) of the controller using 1/s (Laplace Operator) to denote the integral,
Output/E = Kp + KI / s = Kp (s + Ki/Kp) /s.
The second equation shows that the ratio of Ki/Kp is a frequency in radians/sec. In the
Baldor Series 22H AC Vector Control, the integral gain has been redefined to be,
KI = (Ki / Kp) / (2p) Hz,
and the transfer function is,
Output/E = Kp (s + 2pKI) / s.
This sets the integral gain as a frequency in Hz. As a rule of thumb, set this frequency about 1/10 of the bandwidth of the control loop.
The proportional gain sets the open loop gain of the system, the bandwidth (speed of response) of the system. If the system is excessively noisy, it is most likely due to the proportional gain being set too high.
MN722 | Manual Tuning the Series 22H Control |
