Open-Loop Positioning - Siemens SIMATIC S5 Manual

Fundamentals of Positioning
A setpoint generator is required for programmable positioning operations,
regardless of whether positioning is in an open or closed loop.
The setpoint generator's output variable depends on a number of parameters:
• the difference between the current position of the axis and the target
position
• speed
• acceleration/deceleration

Open-loop positioning

When positioning under open-loop control, the setpoint generator provides a
time-dependent speed or speed setpoint V
power section. Drive movement is governed by this voltage. The setpoint
generator outputs the setpoint voltage until the drive has reached the target
position.
During positioning, the setpoint generator is not informed of the current
position. There is thus no guarantee that the drive's final position is identical to
the required target position.
Target position
Speed
Acceleration
V
(t)
setp
Setpoint
generator
4-2
. This is the voltage used to drive the
(t)
setp
V
act (t)
Speed
Actuator
controller
Power section
Figure 4-2. Open-Loop Positioning
IP 266
Measuring
transducer
V
T
M T
M: Motor
T: Tachogenerator
V : Tacho voltage
T
EWA 4NEB 812 6057-02