Description of the Software Modules and Parameters
Parameter manual b maXX BM5800
Document No.: 5.16029.03
189
of 814
3
3.4.8 Autotuning of position / speed controller
The "system gain" that is determined by the complete inertia of the drive, the motor-torque
constant Kt and the magnetic flux are combined at the rated point in the Ks factor
Z18.40–.
The actual value of the "gain" is calculated in the parameter ""Ks actual value" Z155.10–.
The inverse of the "Ks actual value" Z155.10–: (1/Ks
act
), serves in the controller as a
standardization constant between the acceleration value (speed controller output) and
the torque current set value. Therefore, ideally, the parameterization of the posi
-
tion/speed controller is independent of the existing controlled system. The speed control-
ler can be parameterized with a symmetric optimum independent of the used motor and
the existing drive inertia.
The optimized values of the speed controller can not be used for all drives. For example,
a great load inertia could cause that the distortion in the torque current set value exceeds
10% of the motor nominal current. The excessive distortion is caused by the speed ripple
(dependent of the encoder type) and amplified by a (1/Ks
act
) which is too great. In this
case the encoder smoothing should be increased (to reduce the ripple) or a smoother set
-
ting of the speed controller should be made. ProDrive offers a calculating tool for a
smoother setting.
Automatic identification of controlled system
It is possible to carry out an automatic identification of the controlled system with the con-
troller. The values at the speed controller, the positioning controller Kv factor as well as
at the inertia and the Ks factor are determined. See
ZControl loop analysis– on page 198
for a detailed description.
3.4.8.1 Ks Determination
Refer to ZThe factor Ks– on page 404 for a general description of the factor Ks.
The value of the factor Ks at the nominal point, Ks factor Z18.40– can be calculated or
measured.
Ks calculation
The Ks factor Z18.40– can be calculated as follows:
with
Ks factor Parameter Z18.40– in (degree/s
2
)/A
Flux
nom
100% (according to definition of the Ks factor Z18.40–)
Kt Kt = Kt factor, in Nm/A
Kt factor Motor Kt in Nm/A Z107.44–
J Torque of the drive in kg m
2
(Attention: Torque inertia parameters of the
controller are shown in kg cm
2
!)
Ks factor
180
o
-----------
Flux
nom
[%]
Kt
J
------
=
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