Description of the Software Modules and Parameters
Parameter manual b maXX BM5800
Document No.: 5.16029.03
407
of 814
3
is differentiated in the RT0 cycle. Therewith, the acceleration feedforward runs synchro-
nous to the speed feedforward during both procedures. In order to reach precedence over
the speed, the speed set value must be smoothed via
Z18.33–.
If the acceleration feedforward is selected from the set value manager a constant accel-
eration value is feedforwarded per fieldbus cycle. Accordant to the interpolation proce-
dure this can come temporally before the position and/or speed (refer to Z111.6–).
With position-controlled drives having a cyclic position set value an external acceleration
can be specified additionally (refer to
Z111.8–).
To unburden the speed and position controllers, the feedforward must be timely before
the position and/or speed set values. Accordant to the interpolation procedure this is al
-
ready executed by the set value manager. Additionally, the time can be specified with
which the acceleration is supposed to arrive before the position, directly via
Z18.93–.
This is possible, only for specified combinations of the feedforward and the interpolation
method (
Z111.6–):
– Feedforward of the set value manager and the interpolation method 4
– Feedforward of the entire speed set value and the interpolation method 3 and 4
This option is activated by bit 19 of Z18.9–.
3.7.1.5 Friction compensation
This compensation consists of an additive additional torque set value (friction precontrol)
and an adaption of the P and I-parts of the speed controller (stick-slip effect countermea
-
sure).
3.7.1.5.1 Description of the friction compensation
The dynamic of a feed axis is influenced negatively from static friction (dry friction) at start
or inversion of the direction. The friction compensation enables the compensation of the
static friction by connecting an additional torque set value which is dependent on the mov
-
ing direction and speed.
Functionality
In principle the friction compensation is, that the known static friction part is compensated
via an additional torque set value and must not be balanced by the speed controller.
Thus an improvement of the controller behavior (lower position error) can be obtained es-
pecially at reversal of the moving direction. This causes an increase of the drive control’s
accuracy.
A certain compensation of the friction is achieved with the connection of a correction sig-
nal to the internal speed set value.
NOTE!
A speed controlled or position controlled operating mode must be activated (see
Z109.1–) for friction compensation.
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