Siemens SIMATIC S5 Manual page 62

IP 266
Closed-loop positioning
When positioning under closed-loop control, the drive's current actual position is
compared with the setpoint position computed by the setpoint generator. The
difference between these two values is fed to the position controller, which
supplies a voltage setpoint. This setpoint is proportional to the positioning speed.
During positioning, deviations are picked up and fed continually to the position
controller, thus enabling precise positioning.
Following a positioning operation, the final position is maintained. The position
controller is able to detect disturbances and compensates any positional
deviations.
IP266
S
act (t)
-
Position
controller
+
Setpoint
generator
Target position
Speed
Acceleration
Figure 4-3. Schematic Diagram for Closed-Loop Positioning
EWA 4NEB 812 6057-02
Power section (control) motor and pulse generator
Speed
Actuator
controller
Power section
Fundamentals of Positioning
M
T
4-3