Speed Int Gain Parameter; Pi Controller - Baldor 23H Series Installation & Operating Manual

Section 1
General Information

Speed Int Gain Parameter

PI Controller

6-2 Manual Tuning the Series 23H Control
The Speed Int Gain parameter located in the Level 1 Brushless Control Block may be set
to any value from zero to 9.99 Hz. See also, PI Controller later in this section.
Setting the Speed Int Gain parameter to 0Hz removes integral compensation that results
in a proportional rate loop. This selection is ideal for systems where overshoot must be
avoided and substantial stiffness (ability of the controller to maintain commanded speed
despite varying torque loads) isn't required.
Increasing values of the Speed Int Gain parameter increases the low frequency gain and
stiffness of the controller, an excessive integral gain setting will cause overshoot for
transient speed commands and may lead to oscillation. If the Speed Prop Gain
parameter and the Speed Int Gain parameter are set too high, an overshoot condition
can also occur.
To manually tune the control, the following procedure is used:
1. Set the speed Int Gain parameter = 0 (remove integral gain).
2. Increase the Speed Prop Gain parameter setting until adequate response to
step speed commands is attained.
3. Increase the Speed Int Gain parameter setting to increase the stiffness of the
drive.
Note: It is convenient to monitor speed step response with a strip chart recorder or
storage oscilloscope connected to J1–6 or –7 with Level 1, Output Block
Analog Out #1 or #2 set to ABS SPEED, 0 VDC = zero speed. See Section 3
for a discussion of analog outputs.
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
s
Output = (K * E) + (K
p i
where K is the proportional gain of the system and K
p
The transfer function (output /E) of the controller using 1/s (Laplace Operator) to denote
the integral,
Output/E = K + K / s = K
p l
The second equation shows that the ratio of K
Baldor Control, the integral gain has been redefined to be,
K = (K / K ) / (2p) Hz,
l i p
and the transfer function is,
Output/E = K (s + 2pK ) / s.
p l
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.
E dt)
(s + K /K ) /s.
p i p
/K is a frequency in radians/sec. In the
i p
is the integral gain of the system.
i
MN723