65
Chapter 7
Tuning of the servo system control
Figure 7-1: Servo system control block diagram
Figure 7.1 shows the servo system control block diagram. It can be seen from the figure that the servo
system generally includes three control loops: current loop, velocity loop and position loop.
The adjustment process of a servo system is used to set loop gain and filters to match the mechanical
characteristics, and finally to prevent the entire system from oscillating, to permit it to follow commands
quickly and to eliminate abnormal noise.
7.1 Auto-tuning
The auto-tuning function will try to stimulate the motor and load system by some motions, and get the
inertia of the load. If auto-tuning is successful, stiffness will be auto-set according to the inertia ratio.
Stimulate
generator
Control Loops
power module
Motor&Load
Position,Speed,Current
Autotuning
Module
Inertia, Auto-Stiffness
Figure 7-2: Auto-tuning
Cu
rr
en
t l
oo
p
PWM
Motor
Feedback
Notch filter
Observer
Lowpas
s
filter
dx/dt
+
+
+
Speed demand
analog1
analog2
Torque demand
analog1
analog2
Profile generator
Cu
rr
en
t D
em
an
d
lo
wpa
ss
F
ilte
r
Spe
ed
de
m
an
d
lo
wpa
ss
fil
te
r
Kpp
Kvff
kvp
Average filter
Profile position
Actual position
+
Kaff
-
-
+
+
+
+
+
+
Real speed
Current
feedback
DCBUS+
DCBUS-
POWER
Profile speed
kvi
+
+
+
i-limit
Acceleration feedforward
1 order
2 order
K-load
∫
dt