ElmoMC SimplIQ Digital Servo Drives-Bell Getting Started - Manual (Page 69)

The SimplIQ for Steppers Getting Started & Tuning and Commissioning Guide
MAN-BELGS (Ver. 1.1)
69
Figure 61: Test results for maximum KP for KI/KP=3
Adjust the speed command for optimal tuning. The speed command should be as
large as possible to minimize friction effects and information delay effects
9 .
When the gains increase, the friction is less apparent, but the current
consumption for the same reference speed increases. You will have to reduce the
speed command until the current waveform does not saturate. Let us denote the
final KI and KP by KI
0
and KP
0
, here KP
0
=40 and KI
0
=120.
Remark: The speed command should be large enough to minimize friction
effects, which decreases our ability to evaluate the test results. Friction is
considered high if the speed response depends significantly on the reference
magnitude. In extreme cases we observe the current increasing while the motor
speed stays fixed below its destination. See an example in Figure 59. Increasing
the velocity command helps to minimize the friction effect. The steady state
current (0.1 Ampere in one direction and 0.1 Ampere in the other direction) is a
measure of the amount of friction.
2. Fix KP=KP
0
/1.3, which in our example gives 40/1.3=30, then perform step
response tests while increasing KI by a factor of 1.3 at a time, from the initial
value of KI
0
. Continue increasing KI until the system exhibits overshoot of about
30%. In our example the final values are KP=30 and KI=8000, see the results in
Figure 62, which includes several tests of increasing KI in the range given in the
following table and marked on the plot.
9 Friction will cause the response to behave differently as a function of speed. Information delay is
explained in the "Fixed vs. Gain Scheduled Controllers" section above.
0.1 0.12 0.14 0.16 0.18 0.2
-1.5
-0.9
-0.3
0.3
0.9
1.5
x 10
4
C
ount
s
/s
e
c
.
Tim e (sec.)
K I=120,K P =40
K I=90,K P =30
K I=60,K P =20
K I=30,K P =10
Reference
0.1 0.12 0.14 0.16 0.18 0.2
-0.5
-0.1
0.3
0.7
1.1
1.5
Am
p
e
re
Tim e (sec.)
K I=120,K P =40
K I=90,K P =30
K I=60,K P =20
K I=30,K P =10