Direct Setpoint Input (Mdi) - Siemens SINAMICS S120 Function Manual

Function modules
8.8 Basic positioner
8.8.9

Direct setpoint input (MDI)

The "direct setpoint specification" function allows for positioning (absolute, relative) and
setup (endless position-controlled) by means of direct setpoint specification (e.g. via the PLC
using process data).
During traversing, the motion parameters can also be influenced (on-the-fly setpoint
acceptance) and an on-the-fly change can be undertaken between the Setup and Positioning
modes. The "direct setpoint specification" mode (MDI) can also be used if the axis is not
referenced in the "setup" or "relative positioning" modes, which means that "flying
referencing" (see the separate section), flying synchronization, and post-referencing are
possible.
The "direct setpoint specification" function is activated by p2647 = 1. A distinction is made
between two modes: "positioning" mode (p2653 = 0) and "setup" mode (p2653 = 1).
In "positioning" mode, the parameters (position, velocity, acceleration and deceleration) can
be used to carry out absolute (p2648 = 1) or relative (p2648 = 0) positioning with the
parameter p2690.
In the "setup" mode, using parameters (velocity, acceleration and deceleration) endless
closed-loop position control behavior can be carried out.
It is possible to make a flying changeover between the two modes.
If continuous acceptance (p2649 = 1) is activated, changes to the MDI parameters are
accepted immediately. Otherwise the values are only accepted when there is a positive edge
at binector input p2650.
Note
Continuous acceptance p2649 = 1 can only be set with free telegram configuration
p0922 = 999. No relative positioning is allowed with continuous acceptance.
The positioning direction can be specified using p2651 (positive direction specification) and
p2652 (negative direction specification). If both inputs have the same status, the shortest
distance is traveled during absolute positioning (p2648 = "1") of modulo axes (p2577 = "1").
To use the positioning function, the drive must be in the "Operation" state (r0002 = 0). The
following options are available for starting positioning:
● p2649 is "1" and positive edge on p2647
● p2649 is "0" and p2647 is "1"
– Positive edge on p2650 or
– Positive edge on p2649
An overview of the setpoint transfer / direct setpoint specification can be found in the function
diagram 3620 (see SINAMICS S120/S150 List Manual).
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Function Manual, (FH1), 04/2014, 6SL3097-4AB00-0BP4
Drive functions