• DOK-DIAX02-DDS02.1*ANA-ANW1-EN-E1,44 • 12.96
86
7. Commissioning the functions of the digital AC servo drive
7.13. Velocity Loop
Fig. 83: Block diagram of the velocity loop
Matching of the digital servo drive to the machine mechanics is done by
activating the velocity loop parameters stored in the motor feedback (see
Section 6.3 "Setting the gain parameters". These are the standard
parameters for the servo drive. If the machine axis tends to become
unstable during operation even after the standard values have been
activated, this may be due to the following:
– backlash between the motor shaft and the machine
– the machine construction is not rigid enough.
– unfavourable matching of mass moments of inertia
(the ideal case is a 1 : 1 ratio for rotor mass moment of inertia to the
external mass moment of inertia).
These factors can cause:
– poor surface quality of the workpieces
– increased wear on the machine mechanics
and must therefore be avoided.
In cases where these symptoms cannot or can only partly be eliminated,
the digital intelligent INDRAMAT AC servo drive offers the possibility of
adjusting the gain parameters. The functions of the gain parameters are
illustrated in Fig. 83.
Changing the standard settings of the velocity loop should not
be undertaken by anyone other than personnel with sound
knowledge of control engineering.
If changes to the standard settings do not achieve the desired result,
consult the INDRAMAT Service Department.
ENA3A-Abb53/InbetrDDS
ω
actual
I
command
ω
command
K DI
K
I
1)
K DP
K
P
ω
:
Velocity loop
proportional gain
T
GL
:
Smoothing time constant
K
DP
: Velocity loop derivative/proportional gain
T
N
:
Velocity loop integral reaction time
K
DI
: Velocity loop derivative/integral gain
K
PI
:
Current loop proportional gain
K
I
: Integral gain
2) : Unit integrator
3) : Current limitation
w
command
: Command value motor speed
w
actual
:
Actual value motor speed
I
actual
: Actual value motor current
I
command
:
Command value motor current
I
actual
K PI
1)
K
I
=
––––––
K
P
ω
T GL
T
N
2)
3)
KP
ω
Functions of the
speed controller parameters
