Descriptions of functions
10.14 Speed controller
SINAMICS DCM DC Converter
568 Operating Instructions, 12/2018, A5E34763375A
Control and status words for encoders
An encoder interface is defined in the PROFIBUS Profile for drive technology (PROFIdrive
V4.1). This interface defines a control and status word for encoders.
They are available in the following parameters:
● r0480[0] = G1_STW encoder 1 control word
● r0480[1] = G2_STW encoder 2 control word
● r0481[0] = G1_ZSW encoder 1 status word
● r0481[1] = G2_ZSW encoder 2 status word
The bit assignments of the control and status words for the encoders can be seen in the
following function diagrams:
● FP4720 (control word for encoders 1 and 2)
● FP4730 (status word for encoders 1 and 2)
For description, refer to Chapter "Control and status words for encoders (Page 424)".
The speed controller is a PI controller with the following additional properties:
When starting the speed controller (i.e. when the controller is enabled) the I component can
start with a selectable value. This is necessary for suspended/hanging loads in order to
prevent the load from briefly sagging.
P gain and integral action time can be changed as a function of any signal (e.g. from the
actual speed value).
Droop (which can be switched in) can be implemented by feeding back the I component to
the input. As a consequence, the controller does not precisely control to the setpoint, but
permits a continuous setpoint-actual value deviation.
This is required, for example, if two drives are mechanically coupled with one another
(e.g. for a production machine where drives are coupled through the material web being
processed). In this case, the droop prevents that the two drives start to operate against one
another, although both operate with closed-loop speed control. In the case that a mechanical
connection is interrupted (e.g. if the material web breaks), then the speed of the drive
operating with droop only slightly changes.
The lead/lag element is used to improve the stability of the speed control. If required, it can
be inserted in the actual speed value channel.
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