Communication / PROFIBUS 09.2008
6SE7087-6QX70 (Version AK) Siemens AG
8.2-100 Compendium Motion Control SIMOVERT MASTERDRIVES
The absolute reference of the position actual value is only created in the
master (addition point "Zero offset and compensation"). The same
absolute reference is contained in the position command x
cmd
. The
control error calculated in the master x
err
thus remains free of zero
points. The drive needs to know nothing about zero points and reference
points.
In the setpoint direction two additional signals are transmitted:
1. Controller error x
err
2. Position controller gain factor k
pc
The standard telegrams 5 and 6 defined for the function Dynamic Servo
Control (DSC) are explained further in section 8.2.7.3.
If both signals x
err
or k
pc
are configured, the feedback network in the
drive is activated. If only one of the two signals is projected, it is assumed
that this serves other purposes and the feedback network is not
activated.
The position controller gain K
PC
transmitted via the Profibus has the unit
1/1000 1/s.
From the drive point of view there are two operating statuses, which can
be distinguished on the basis of k
pc
= 0 or k
pc
≠ 0 :
1. k
pc
= 0: feedback network inactive, position control circuit in the drive
opened. The master normally uses this to open the position control
circuit fully, e.g. in spindle operation or with errors. However, it can
also switch back to conventional position control in this way, without
re-configuring the drive. The drive can assume that x
err
= 0 is being
transmitted. The speed setpoint is entered via n
cmd
.
2. k
pc
≠ 0: feedback network active, position control circuit is enclosed in
the drive. Via n
cmd
a speed pre-control value is entered, which may
also be zero.
A switch between these two statuses can be made by the master at any
time. The master can also alter the value of k
pc
at any time, e.g. in order
to make dynamics adjustments in gear changes or compensation for
non-linear gears.
Feedback branch 2 must exactly simulate the action of feedback branch
2 between points A and B. Both branches must
1. work with an actual value originating from the same time and scanned
with the same frequency
2. display the same deceleration
3. contain the same fine interpolation
This is indicated by the broken arrows in the structure diagram.
The speed filter shown in the structure diagram is optional and has
nothing to do with the DSC function. It has been drawn in to make the
difference from conventional position control easier to recognize.
Interface
Operating statuses
Boundary
conditions
To Next Page
Loading...
