The controller divides the
Speed
setpoint
by the actual winding
diameter. The
Speed
setpoint
tan
either be provided by a JOG
value, an analog input terminal X8, or by the digital frequency input
X5. When
changing
the operating mode, also the operating unit or
one of the LECOM
interfaces
are available.
This procedure allows a
Pilot
synchronization
of the circumferential
Speed
of the bale to the line
Speed.
That means that the field
frequency is high for
small
diameters and low for large diameters.
9.2.2 Dancer-Position controller
The dancer has the following tasks:
l Generation of the tensile stress of the material by means of a
weight or
pneumatic
cylinder.
l
Gompensation
of eccentricities in the bale
caused
by the
rnobility of the dancer.
l
l-he
actual
Position
is detected via a
Sensor
(Potentiometer or
non-contact System).
-
The dancer-Position controller is a closed-loop control of the line
Speed.
lt compensates all deviations of the
Pilot
control channel
and the motor
Slip
which
depend on the load.
9.3
Loop or dancer-Position control for line drives
An example of loop or dancer-Position control is the drive of two
conveyor belts
which
transport material. The material forms a loop
between the two conveyor belts or
Passes
a dancer cylinder.
The dancer or the loop is
controlled
in that way that the
Position
of
the
slack
is kept
constant
and thus the
Speeds
of the two conveyor
belts are synchronized
For this purpose, the corrected dancer
Signal
is multiplied by the
value of the digital frequency. The
product
of this
multiplication
is
added to the value of the digital frequency. For
further
information
see
chapter
9.14.
9.4
Grinding or cutting-off wheel drives
If
the
surface
Speed
of the wheel has to remain
constant
in spite
of
lwear,
the motor
Speed
has to be adjusted reciprocally to the
wheel diameter. Therefore, the actual wheel
diameter
has to be
detected by a Sensor. The generated
Sensor
value is transmitted
to the controller
which
adjusts the drive to a
constant
Speed.
For
this purpose, the dancer-Position control has to be switched off
internally.
-
105
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